CORNELL UNIVERSITY LIBRARY ENGINEERING s-s-,-.^';^;.^,;^ L-.r^ivrsrsitv Library TH 7222.C29 1902 Heating and ventilating buildings.A manu 3 1924 003 891 391 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003891391 WORKS OF PROF. R, C. CARPENTER PUBLISHED BY JOHN WILEY & SONS. Heating and Ventilating: of Buildings. 8vo, XV + 562 pages, 277 figures, cloth, $4.00, Experimental Engineering. For Engineers and for Students in Engineering Laboratories. 8vo, xix + 843 pages, 335 figures, cloth, $6.00. HEATING AND VENTILATING -BUILDINGS. A MANUAL FOR HEATING ENGINEERS AND ARCHITECTS. BY ROLLA C. CARPENTER, M.S., C.E., M.M.E., Professor Experimental Engineering, Cornell University. Past President American iyecze/y fi'eaim^ and Ventilating Engineers- Member American Society Mechanical Engineers, FOURTH EDITION, REVISED AND ENLARGED. FOURTH THOUSAND. NEW YORK: JOHN WILEY & SONS, London: CHAPMAN & HALL. Limited. 1906 Copyright, 1895, 1902, BY ROLLA C. CARPENTER, BOBEET DRUMMOND, PRINTER, NEW YORK. PREFACE TO FOURTH EDITION. The first edition of this work was published in 1895, since which time three complete editions have been printed and sold. The fourth edition has been very largely re-written and con- siderable new matter added ; the size of the book as compared with the first edition being increased by nearly one-third. Three new chapters have been added : one relating to the fan or blower for moving air, another to the general subject of mechanical systems of heating and ventilating and a third to schoolhouse heating and ventilation. It is believed that the book in its present form describes the latest improvements in the art of heating and ventilating; it also gives directions for the construction and installation of all the various systems of heating and ventilating now in use. The writer is under obligation for assistance and material in preparing the fourth edition of this book to Prof. Homer Woodbridge, of the Massachusetts Institute of Technology, to the various heating engineers who have taken active part in the American Society of Heating and Ventilating Engineers, to the technical papers devoted to the subject of heating and ventilation, and to Prof. Herman Diederichs, of Ithaca, N. Y. Ithaca, N. Y., July i, 1902. EXTRACTS FROM PREFACE OF FIRST EDITION. The art of heating and ventilating buildings is that branch of engineering which is devoted to a practical application of the general physical laws of heat, of pneumatics, and of hydraulics to the construction of heating and ventilating apparatus. The object of the present book is to present to the reader, in as concise a form as possible, a general idea of the principles which apply, and of the methods of construction which are in use at the present time, in various systems of heating and venti- lating. In preparing the present book, the writer has endeav- ored to present, in as clear and concise a manner as possible, first, a statement of the general principles of pure science which apply; second, a discussion of data and results of important tests showing the relation of theoretical principles to practical con- struction ; third, a description of the various practical methods which are in use in heating and ventilating buildings ; fourth , a description of the methods of designing various systems of heating and ventilating ; fifth, a collection of useful tables for practical application of the principles stated. The writer has endeavored to arrange the matter so that it can be understood by any person possessing a thorough and practical knowledge of English and arithmetic. Algebraic demonstrations and formulas, when introduced, are usually printed in smaller type ; and if a general conclusion is deduced by algebraic methods it is restated in the form of a rule of practice. It has been the desire of the writer to arrange the work in a scientific manner, and to give no methods or rules of practice Vlll EXTRACTS FROM PREFACE OF FIRST EDITION. which were not based on the results of good, sound theory — the theory to be modified by such co-efficients as have been obtained by actual tests or experience. In the case of nearly every system of heating this has been possible. It is believed in this respect that the book will be an improvement over any- thing which has preceded it. The book generally presents such information as the writer has found in an extensive practice in the erection and operation of heating apparatus to be that "which is required by contractors and by engineers in charge of the erection of plants. For the literary part of the work obligation is due to nearly every writer who has preceded him. In nearly every case special credit has been given, but in the back part of the book will be found a complete list of authorities. The writer has had the cordial assistance of many noted heating engineers, many manufacturers of heating apparatus, and all the publish- ers of current literature devoted to this subject. The principal portion of the practical part of the book is devoted to construction of gravity-heating systems, using steam and hot water, but systems of heating with hot air, with or without a blower, with exhaust steam and with electricity, are considered, and practical directions for construction are given. The general character of the contents will be best seen by con- sulting the table which follows. Ithaca, N. Y., October i, 1895. TABLE OF CONTENTS. CHAPTER I. NATURE AND I'ROPERTIBS OF HEAT. AaTICLiEi paqb 1. Demand for Artificial Heat 1 2. Magnitude of the Industry of Manufacturing and Installing Heat- ing Apparatus 1 3. Nature of Heat 2 4. Measure of Heat — Heat-unit 4 5. Relation to Mechanical and to Electrical Units 4 6. Temperature — ^Absolute Zero -. 6 7. Thermometer Scales 7 8. Special Forms of Thermometers 9 9. Pyrometers and Thermometers for High Temperatures 11 10. Maxima and Minima Thermometers 12 11. Use of Thermometers 13 12. Specific Heat 14 13. Latent Heat '. 15 14. Radiation 15 15. Reflection and Transmission of Radiant Heat ' 16 16. Diffusion of Heat , 17 17. Conduction of Heat 18 18. Convection, or Heating by Contact 19 19. Systems of Warming 20 CHAPTER II. PRINCIPLES or VENTILATION. 20. Relation of Ventilation to Heating 21 21. Composition and Pressure of the Atmosphere 21 22. Diffusion of Gases 24 23. Oxygen 24 24. Carbonic Acid or Carbon Dioxide, CO2, and Carbonic Oxide, CO. . . 25 ix X TABLE OF CONTENTS. ARTICLE PAGE 25. Nitrogen — Argon 27 26. Analysis of Air 27 27. Determination of Humidity of the Air 32 28. Amount of Air Required for Ventilation 34 29. Influence of the Size of the Koom on Ventilation 37 30. Force for Moving the Air 38 31. Measurements of the Velocity of Air 40 32. The Flow of Air and Gases 46 33. The Effect of Heat in Producing Motion of Air 51 34. Distribution of Air - 55 35. The Outlet for Air 58 36. Ventilation-flues 59 37. Summary of Problems of Ventilation 60 38. Dimensions of Registers and Flues 62 CHAPTER III. AMOUNT OF HEAT EEQUIKED EOE WAEMING. 39. Loss of Heat from Buildings 64 40. Loss of Heat from Windows 64 41. Loss of Heat from Walls of Buildings .■ . . . 65 42. Heat Required for Purposes of Ventilation — Total Heat Required. . 69 CHAPTER IV. HEAT GIVEN OFF FROM RADIATING SURFACES. 43. The Heat Supplied-by Radiating Surfaces 80 44. Heat Emitted by Radiation 81 45. Heat Removed by Convection (Indirect Heating) 83 46. Total Heat Emitted 84 47. Heat Transmission Varies with Circulation 87 48. Methods of Testing Radiators 89 49. Measurement of Radiating Surface 93 50. Effect of Painting Radiating Surfaces 94 51. Results of Tests of Radiating Surface 95 52. Tests of Indirect Heating Surfaces 103 53. Conclusions from Radiator Tests 112 54. Probable Efficiency of Indirect Radiators 115 55. Temperature Produced in a Room by a gi,ven Amount of Surface when Outside Temperature is High 115 CHAPI'ER V. PIPE AND FITTINGS USED IN STEAM AND HOT-WATER HEATINS. 56. General Remarks 117 57. Cast-iron Pipes and Fittings 117 TABLE OF CONTENTS. xi ARTICLS p^gj, 58. Wrought-iron and Steel Pipe 119 59. Pipe Fittings 122 60. Valves and Cocks 128 61. Air-valves 132 62. Expansion Joints 135 CHAPTER VI. EADIATOES AND HEATING SURFACES. 63. Introduction 137 64. Radiating Surface of Pipe 137 65. Vertical Pipe Steam Radiators 139 66. Cast-iron Steam Radiator 140 67. Hot- water Radiator 142 68. Direct-Indirect Radiator 146 69. Indirect Heaters 146 70. Proportion of Parts of Radiators 149 CHAPTER VII. STEAM-HEATING BOILEBS AND HOT-WATEB HEATERS. 71. General Properties of Steam — Explanation of Steam Tables 150 72. General Requisites of Steam-boilers 151 73. Boiler Horse-power 152 74. Relative Propoitions of Heating to Grate Surface 153 75. Water Surface in Boiler — Steam and Water Space 156 76. Requisites for Perfect Steam-boiler 157 77. Classification of Boilers 158 78. Horizontal Tubular Boiler 160 79. Locomotive and Marine Boilers 161 79a. Vertical Boilers 162 80. Water-tube Boilers 163 81. Hot-water Heaters 165 82. Classes of Heating-boilers and Heaters 166 83. Heating-boilers with Magazines 171 84. Heating-boilers for Soft Coal 172 CHAPTER VIII. SETTINGS AND APPLIANCES, METHODS OF OPERATING. 85. Brick Settings for Boilers 173 86. Setting of Heating-boilers 177 87. Tlie Safety-valve 179 88. Appliances far Showing the Level of Water in Boiler 182 89. Methods of Measuring Pressure 183 XU TABLE OF CONTENTS. ARTICLE FAOS 90. Thermometers 186 91. Damper Regulators 186 92. Blow-off Cocks or Valves 187 93. Expansion Tank 188 94. Form of Chimneys 190 95. Size of Chimneys 191 96. Chimney-tops 192 97. Grates 193 98. Traps 194 99. Return-traps 197 100. General Directions for the Care of Steam-heating Boilers 199 101. Care of Hot-water Heaters 201 102. Boiler Explosions 201 103. Explosions of Hot-water Heaters 206 104. Prevention of Boiler Explosions 206 CHAPTER IX. VARIOUS SYSTEMS OP PIPING. 105. Systems Employed in Steam-heating 208 106. Definitions of Terms Used ,...208 107. Systems of Piping 210 108. Systems of Piping Used in Hot-water Heating 215 109. Combination Systems of Heating 218 110. Pipe Connections, Steam-heating Systems 221 111. Pipe Connections, Hot-water Heating Systems 223 112. Position of Valves in Pipes 225 113. Piping for Indirect Heaters 226 114. Comparisons of Pipe Systems 227 115. Systems of Piping where Steam does not return to the Boiler 227 116. Protection of Main Pipe from Loss of Heat 227 CHAPTER X. DESIGN OF STEAM AND HOT-WATEK SYSTEMS. 117. General Principles 231 118. Amount of Heat and Radiating Surface Required for Warming. . . . 232 119. The Amount of Surface Required for Indirect Heating 239 120. Summary of Approximate Rules for Estimating Radiating Surface. 245 121. Flow of Water and Steam 247 122. Size of Pipes to Supply Radiating Surfaces 252 123. Size of Return Pipes, Steam-heating 1 . . . 259 124. Size of Pipes for Hot-water Radiators 260 125. Size of Ducts and Ventilating Flue for Conveying Air 264 126. Dimensions of Registers 267 TABLE OF CONTENTS. XUl ARTICLE PAGE 127. Summary of Various Methods of Computing Quantities Required for Heating 268 128. Heating of Greenhouses 268 129. Heating of Workshops and Factories 277 CHAPTER XI. HEATING WITH EXHAUST STEAM. NON-GRAVITY RETUKN SYSTEMS. 130. General Remarks 282 131. Systems of Exhaust Heating 282 132. Proportions of Radiating Surface and Main Pipes Required in Ex- haust Heating 283 133. Systems of Exhaust Heating with Less than Atmospheric Pressure. 285 134. Combined High- and Low-pressure Heating Systems 297 135. Pump Governors 298 136. The Steam Loop 299 137. Reducing Valves 300 138. Transmission of Steam Long Distances 302 CHAPTER XII. HEATING WITH HOT AIB. 139. General Principles 310 140. General Form of a Furnace 312 141. Proportions Required for Furnace Heating 314 142. Air-supply for the Furnace 317 143. Pipes for Heated Air 318 144. The Areas of Registers or Openings into Various Rooms 320 145. Circulating Systems of Hot Air 322 146. Combination Heaters 323 147. Heating with Stoves and Fireplaces 323 148. General Directions for Operating a Furnace 324 149. Practical Arrangement of Furnaces 324 150. Rules for Furnace Heating 330 151. Abstract for Furnace Specifications 330 CHAPTER Xni. MECHANICAL VENTILATORS. 154. General Conditions 333 155. Centrifugal Ventilators 334 156. Propeller or Disc Fans 341 157. Volume or Positive Blowers 341 158. Theoretical Work of Moving Air 343 XIV TABLE OF CONTENTS. ARTICLE FAGB 150. M'ork of Moving Air through Pipes. — Dimensions of Pipe-lines for Air .' 345 160. Murgue's Theory of the Centrifugal Ventilator 349 161. Author's Fan Theory. — Maximum Pressure Produced by Fan or Blower. — Work Required to Run a Fan 356 162. Application of Theory. — Rule for Capacity. — Rule for Power. — Tests to Verify Rules 364 163. Relative Efficiencies of Fans or Blowers and of Heated Flues 368 164. Disc aijd Propeller Fans 372 165. Measurement of Air Supplied a Room 373 CHAPTER XIV. MECHANICAL SYSTEJIS OF HEATING AND VENTILATING. 166. General Remarks 377 167. Various Forms of Mechanical Ventilating and Heating Systems.. . 377 168. Volume or Regulating Dampers 381 169. Form of Steam-heated Surface „ 381 170. Ducts or Flues. — Registers 384 171. Blowers or Fans 388 172. Heating Surface Required 389 173. Size of Boiler Required ."390 174. Practical Construction of Hot-blast System of Heating 391 175. Description of Mechanical Ventilating Plant 397 176. Systems of Ventilation without Heating 404 177. Heating with Refrigerating Machines : 405 178. Cooling of Rooms 405 CHAPTER XV. ; HEATING WITH ELECTEICITT. 179. Equivalents of Electrical and Heat Energy 407 180. Expense of Heating by Electricity 407 181. Formulae and General Considerations 410 182. Construction of Electrical Heaters 412 183. Connections for Electrical Heaters! 415 CHAPTER XVI. TEMPEBATUEE REGULATORS. 184. General Remarks 416 185. Regulators Acting by Change of Pressure 417 186. Regulators Operated by Direct Expansion 421 187. Regulators Operated with Motor. — General Types 422 188. Pneumatic Motor System 424 TABLE OF CONTENTS. XV ARTICLE pj^QB 189. Saving Due to Temperature Kegulation.— Construction of Pneu- matic Thermostat 427 CHAPTER XVII. SCHOOLHOUSE WARMING AND VENTILATION. 190. General Remarks 430 191. Complex Character of Problem 430 192. Three Objects Sought 431 193. Relation of Pure Air to Vitality ^ 431 194. Limitations to the Supply of Pure Air 432 195. Draughtiness in Large Halls 432 196. Means for Reducing Draughtiness 433 197. Little Draughtiness in Outflowing Currents 435 198. Air-supply for Schoolroom ; . , 435 199. Cost : 436 200. Boiler Power 438 201. Power for Moving Air through Ventilating System 439 202. Gravity Ventilation 440 203. Mechanical Ventilation 441 204. Fuel for Air Warming 443 205. Skilled Attendance Required 444 206. Successive Ventilation 445 207. Supply of Air for Rooms not Frequently Occupied 446 208. Course of the Air-supply 447 209. Quick Preparatory Warming 449 210. Warming by Rotation 449 211. Heat Commonly Wasted 450 212. Solar Heat 451 213. Automatic Control of Temperature 452 214. Double Glazing 453 215. Double Sashing 453 216. Waste of Heat at Night 454 217. Plenum and Vacuum Methods 454 218. Location of Inlets 454 219. Location of Outlets 456 220. Local Ventilation 456 221. Air Filtration 457 222. Air Humidity 458 223. Method of Warming 459 CHAPTER XVIII. Bt-EOirlCATION PBOPOSALS AND BUSINESS SUGGESTIONS. 224. General Business Methods • 462 225. General Requirements 463 XVI TABLE OF CONTENTS. ARTICLE FAOS 226. Form Proposed by the National Association of Manufacturers of Heating Apparatus 466 227. Form of Uniform Contract 476 228. Specifications for Plain Tubular and Water-tube Boilers 480 229. Protection from Fire — Hot Air and Steam-heating 484 230. Duty of the Architect 487 231. Methods of Estimating Cost of Construction 487 232. Suggestions for Pipe-fitting 488 APPENDIX. liteeatxjee and references 493 Explanations of Tables 497 Tables 499 Index 543 HEATING AND VENTILATING BUILDINGS. CHAPTER I. INTRODUCTION. NATURE AND PROPERTIES OF HEAT. 1. Demand for Artificial Heat. — The necessity for artifi- cial heat depends to a great extent upon the climate, but to a certain extent on the customs or habits of the people. In all the colder regions of the earth artificial heat is necessary for the preservation of life, yet there will be found a great difference in the temperature required by people of different nations or races living under the same circumstances. On the continent of Europe, 15 degrees centigrade, corresponding to about 59 degrees F., is considered a comfortable temperature ; in America it is the general practice and custom to maintain a temper- ature of 70 degrees in dwellings, offices, stores, and most work- shops, and a heating apparatus is considered inadequate which will not maintain this temperature under all conditions of weather. 2. Magnitude of the Industry of Manufacturing and In- stalling Heating Apparatus. — The industry connected with the manufacture and installation of the various systems for warming is a great one and gives employment to many thou- sand workmen. The manufacture of heating apparatus is not only of great magnitude, but it is varied in its nature ; all kinds of apparatus for heating — as, for instance, the open fireplace built at the base of a brick chimney, the cast-iron stove with its unsightly piping, the furnace and appliances for warming 2 HEATING AND VENTILATING BUILDINGS. air, apparatus for heating by steam and also by hot water — can be readily bought on the market in almost every form, from that of the simplest to that of the most complicated design. The exact amount of capital invested in this industry could not be ascertained by the author, but in twenty cities, selected in alphabetical order from a list of one hundred and sixty-five cities of the United States containing over twenty thousand inhabitants, the total amount invested in the business of erect- ing and installing heating apparatus as given in the Census Report by the U. S. Government for 1890 was $12,910,250, and the yearly receipts for 1890 from this business in the same cities was $5,592,148. The aggregate population of these cities was 1,573,508 people. This would indicate an invest- ment of $8.20 and a yearly expenditure of $3.52 for each inhabitant. Reckoning on the same basis for the cities of the United States which contain over 25,000 inhabitants each, we should have an invested capital of over $io6,ooo,ooo and a yearly expenditure of over $46,000,000. These numbers are probably less than the amount actually invested, but they serve to give an idea of the magnitude of the industry connected with the supply of apparatus for artificial warming. 3. Nature of Heat. — Before consideration of the methods of utilizing heat in warming buildings a short discussion of the nature and scientific properties of heat seems necessary. Heat is recognized by a bodily sensation, that of feeling, by means of which we are able to determine roughly by com- parison that one body is warmer or colder than another. From a scientific standpoint heat is a peculiar form of energy, similar in many respects to electricity or light, and is capable, under favorable conditions, of being reduced into either of the above or into mechanical work. We shall have little to do with the theoretical discussion of its nature, but, as it is well to have a distinct understanding of its various forms and equivalents, we will consider briefly some of its important properties. Heat was at one time considered a material substance which might enter into or depart from a body by some kind of con- duction, and the terms which are in use to-day were largely founded on that early idea of its material existence. The theory that heat is a form of energy and is capable of INTROD UCTION. 3 transformation into work or electricity is thoroughly established by fact and experiment. It probably produces a molecular motion among the particles of bodies into which it enters, the rate of such motion being proportional to the intensity of the heat. Heat has two qualities which correspond in a general way to intensity on the one hand and quantity on the other. The intensity of heat is termed temperature — this can be measured by a thermometer ; but, except in scientific discussion, no name has been applied to designate the unit-quantity of heat,* and there is no method of measuring it directly, although it is of as much importance as temperature. It is a fact which will appear from later statements that the amount of heat contained in two bodies of different kinds, but of the same weight and temperature, may be essentially different, A familiar analogy might perhaps be seen in the case of the dimensions and weight of men. The weight would depend on the general dimensions, height, breadth, etc., and it would probably be the case that two men having equal heights would have quite different weights. In a similar manner the amount of heat depends upon the temperature and also upon the property of the body to absorb heat without showing any effects which may be measured on a thermometer. This latter property in itself depends upon the nature of the body and also upon that peculiar quality of heat to which reference has been made. Under every -condition heat must be quite differ- ent in nature from temperature. Note that heat is equivalent, not to mechanical force, but to mechanical work. Work, defined scientifically, is the applica- tion of force in overcoming some resistance ; it is the result of a force acting through a certain distance ; the distance moved through having as much effect on the result as the force acting. The work done is proportional to the product of the force exerted, multiplied by the space passed through. In English measures the unit of this product is 2. foot-pound, which signifies one pound raised to a height equal to one foot ; it is itself a complex quantity resembling heat in this respect. Heat can be transformed into work. *The term entropy is now applied' in scientific discussions to this property, 4 HEATING AND VENTILATING BUILDINGS. 4. Measure of Heat — Heat-unit. — As explained heat can- not be measured by the thermometer ; it can, however, be measured by the amount that some standard is raised in tem- perature. The standard adopted is water, and heat is univers- ally measured by its power to raise the temperature of a given weight of water. In English-speaking countries the heat-ttnit is that required to raise one pound of water from a temperature of 62 to 63 degrees, and this quantity is termed a British thermal unit ; this will be referred to in this work, by its initial letters B. T. U., or simply as a heat-unit. The amount of heat re- quired to change the temperature of one pound of water one degree is not the same at all temperatures ; the variation, how- ever, is slight and for practical purposes can be entirely disre- garded. The unit of heat used by the French and Germans, and for scientific purposes generally, is called the calorie ; it is equal to one kilogramme (2.20 pounds) of water raised one degree centigrade (1.8 degrees Fahrenheit) and is equal to 3.9672 B. T. U. The calorie is referred to water at a temper- ature of 15-16° Centigrade (60 degrees Fahrenheit). 5. Relation to Mechanical Work and to Electrical Units.- — The relation of heat to mechanical work was accu- rately measured by Joule in 1838 by noting the heating effects produced in revolving a paddle-wheel immersed in water. The wheel being revolved by a weight falling a given distance, the mechanical work was known ; this compared with the rise in temperature of the water enabled him to determine that the value of one heat-unit estimated from 39° to 40° F. was equiv- alent to 772 foot-pounds. Later investigation has slightly in- creased this result, so that when reduced to a temperature of 62 degrees F., and for this latitude, it is 6 foot-pounds greater, so that at present the work equivalent of one heat-unit is generally regarded as 778 foot-pounds. This signifies that the work of raising i lb. 778 feet is equivalent to the energy re- quired to change the temperature of i lb. of water, at 62° F. in temperature, i degree. The equivalent value of heat and mechanical work is now thoroughly established, and under favorable conditions the one can always be transformed into the other. As illustrations of the transformation of heat into work we have only to consider INTROD UCriON. 5 the numerous forms of steam-engines, gas-engines, and the like. A transformation from mechanical work into heat is shown in the rise of temperature accompanying friction in the use of machines of all classes. 'The heat produced in the perform- ance of any mechanical work is exactly equivalent to the work accomplished, 778 foot-pounds of mechanical work being per- formed in order to produce a heating effect equivalent to rais- ing I lb. of water 1° Fahr. The term horse-power has been used as the m.easure of the amount of work. It has been fixed as 33,000 foot-pounds per minute. This is equivalent to 42.42 B. T. U. per minute, or to 746 watts in electrical measures. For the work done in one second the above numbers should be divided by 60 ; for that done in one hour they should be multiplied by do. In all English-speaking countries the capacity of engines and ma- chinery in general is expressed in horse-power, so that it is necessary to become familiar with this term and its equivalents in heat and electrical units. The electrical units are all based on French measures, the centi- metre (0.3937 inch) being the standard of length, the gramme (15.432 grains) the standard of mass, and the second the unit of time ; the system being generally denominated the C. G. S. system. In this system the unit of force, the dyne, is i gramme moved so as to acquire a velocity of one centimetre per second. As the force of gravity in lati- tude of Paris is 32.2 feet = 981 cm., the dyne is equal to the weight moved, expressed in grammes divided by 981, for latitude of Paris. The unit of work and of energy is called an erg and is equal to the force of one dyne acting through one centimetre, or to a gramme-centi- metre divided by 981. One million ergs is equal to 0.0738 foot-pound. One watt is equal to 10 million ergs per second, or 738 foot-pounds per second. One calorie is 42,000 million ergs, one minor calorie 42 million ergs. One B. T. U. is 10,550 milHon ergs. Expressed in work we have the following equivalents : One horse-power = 746 watts =550 foot-pounds per second = 0.707 B. T. U. per second. = 0.1767 calories per second = 176.7 minor calories per second = 7460 millions of ergs per second. (See full table of equivalents in back of book.) P HEATING AND VENTILATING BUILDINGS. 6. Temperature — Absolute Zero. — One of the properties of heat is called temperature ; this property can be measured by a thermometer and is proportional to the intensity of the heat. All our knowledge of heat, as obtained by the gensatioft of feeling, deals only with the temperature, and the terms in common use by means of which bodies are compared and denominated hot, hotter, hottest, have reference, not to the heat actually in the different bodies, but to the temperature. There is always a tendency for heat to flow through inter- vening mediums from a hotter to a colder body, and there is no tendency for heat to flow from a cold to a hot bpdy, although the relative amounts of heat in the two bodies might be different from that indicated by the thermometer. Thus, as an illustration, a pound of water requires about eight times as much heat to raise it one degree in temperature as a pound of iron, and hence when equal weights of both of these materials are at the same temperature the water contains eight times as much heat as the iron, although in common parlance the two bodies would be equally hot. The tendency for the hotter body to cool off and give up its heat to surrounding objects is characteristic of all materials, and if no other heat were supplied all bodies would come sooner or later to one common temperature. This temperature, when finally reached by all bodies in the universe, will represent the ultimate limit of all cooling and almost the entire absence of heat. It will be near absolute zero for all thermometric scales, and no greater cold will be possible or even conceivable. The inter-planetary space is believed by many to be very nearly at this limit, at the present time. Scientific men have made very careful determinations to ascertain what such a temperature must be, compared with the ordinary thermometric scales. A perfect gas which remains under constant pressure will contract in volume an amount directly proportional to the change of temperature when reckoned from the point of great- est cold, which point is known as the absolute zero. By experi- ment it is found that when air is at a temperature of 32 degrees its volume is reduced one part in 492 each time that the tem- perature is lowered one degree. From this fact it has been concluded that the absolute zero is 492 degrees on the Fahren- INTROD UCTION. heit scale or 273 degrees on the Centigrade scale, below the freezhig-point of water. Strictly speaking there is no perfect gas, yet the results obtained with different gases by different ob- servers are so nearly in accord that there is no question but that the results as given above are for all practical purposes correct. 7. Thermometer Scales.— The thermometer is an instru- ment used to measure temperature. The effect of heat is to expand or to increase the volume of most bodies. For perfect gases the amount of this expansion is strictly proportional to the change of temperature ; for liquids and solids the expansion, while not exactly proportional to the increase of temperature, is very nearly proportional to it, and these bodies can be used for an approximate and even a close measure of difference of temperature. In nearly all thermometers the temperature is measured by the expansion of some body, mercury, alcohol, or air being commonly used as the thermometric substance. The first thermometer was probably made by Galileo before 1597. It consisted of a glass bulb containing air, terminated ^-^l' wm below in a long glass tube which dipped into a vessel I containing a colored fluid. The variations of volume f of the enclosed air caused the fluid to rise or fall in the tube, the temperature being read by an arbitrary scale. Alcohol thermometers were in use as early as 1647, being made by connecting a spherical bulb with a long glass stem, on which graduations were made by beads of blue enamel placed in positions correspond- ing to one thousandths of the volume. Fahrenheit, a German merchant, in 1721 was the first to make a mercurial thermometer, and the instru- ment which he designed, with certain modifications, has been retained in use by the English-speaking people up to the present time. Fahrenheit took as fixed points the temperature of the human body, which he called 24 deo-rees, and a mixture of salt and sal-ammoniac, which he supposed the greatest cold possible, as zero. On Ordinary this scale the freezing-point is 8 degrees. These ^°^\'J,jj°^ degrees were afterwards divided into quarters, and al Ther- later these subdivisions themselves, termed degrees, "^^'eter. On this modified scale the freezing-point of water becomes 32 Fig. I. 8 HEATING AND VENTILATING BUILDINGS. degrees, blood-heat 96 * degrees, and the point of boiling water at atmospheric pressure 212 degrees. Unscientific as this thermometer is, it has been retained by two of the principal nations of the world, the English and the American ; it is awkward to use, it was borrowed from a foreign nation which had itself adopted a more scientific instrument, and except for the fact that it has been long in use it has not a single feature to recommend it. In 1724 Delisle introduced a scale in which the boihng- point of water was called zero and the temperature of a cellar in the Paris Observatory was called 100 degrees. This ther- mometer was used for many years in Russia, but is now obso- lete. In 1730 Reaumur made alcohol thermometers in which the boiling-point of water was marked 80 degrees. This thermometer is still in use in Russia. Celsius adopted a centesimal scale in 1742 on which the boiling-point was marked zero and the freezing-point of water 100 degrees. This instrument is not now in use, although the centigrade scale is often called after Celsius. The botanist Linnaeus introduced the centigrade thermometer, in which the freezing point of water is marked zero and the boiling- point of water 100 degrees. This themometer is now adopted for ordinary use by the nations of continential Europe and for scientific use by every nation in the world. The relative values of the degrees on the different ther- mometers used by various nations are given in the following table : THERMOMETRIC SCALES. Degrees between freezing and boiling.. Temperature at freezing-point Temperature at boiling-point Comparative length of degree H if (I (( Countries where used Fahren- heit. Centigrade. Reau- mur. 180 100 80 32 212 100 80 I 5/9 9/5 I 9/4 5/4 England France Russia and and America Germany Celsius. ICO 100 O 9/5 I Not in use * As determined later, this should be 98°. INTROD UCTION. 9 In all thermometric scales as given above, fixed points are determined by reference to the freezing and boiling points of water, with barometer at 29.92 inches, and all thermometers are constructed by marking these two points and then subdi- viding into the required number of degrees. The boiling- point of water changes with the atmospheric pressure and with the purity of the water. The greater the pressure the higher the boiling-temperature. A table in the Appendix of this book shows the relation between the barometer pressure and the temperature of boiling water at atmospheric pressure. Mer- cury, alcohol, liquids and solids generally do not expand uniformly for each degree of temperature, or, in other words, they are not perfect thermometric substances. The error, however, is slight and is of more scientific than practical im- portance. Any perfect gas, however, does expand uniformly and is a perfect thermometric substance, but gas varies in volume with slight change in barometric pressure, and, while of great value as material for a scientific thermometer, is too bulky and awkward for ordinary use. It is at the present time considered doubtful if there is any perfect gas in exist- ence, or one which cannot be liquefied by intense cold or great pressure. Air, hydrogen, and nitrogen act like perfect gases at ordinary temperatures ; the same is true in a slightly less degree of oxygen. Yet oxygen is a liquid whose boiling- point is 119 degrees centigrade (182 degrees Fahrenheit) below zero. Nitrogen and air are liquids boihng at a temper- ature of 193 degrees centigrade (315 degrees Fahrenheit) below zero. Pictet and Cailletet have reduced the temper- ature to 200 degrees C. below zero, finding air at that tempera- ture to be a liquid as limpid as water and, like water, having a decided blue tint when seen by transmitted light. 8. Special Forms of Thermometers. — The mercurial ther- mometers, as ordinarily constructed (Fig. i), consist of a bulb of glass joined to a capillary glass tube filled so as to leave a vacuum in the upper part of the glass stem, above the mer- cury; they cannot be used for any temperature higher than that of the boiling-point of mercury, which is about 575° F. More recently these thermometers have been filled with nitro- gen or carbonic dioxide in the upper part of the glass stem, lO HEATING AND VENTILATING BUILDINGS. which by pressure prevents the mercury boiling. Thermom- eters constructed in this way can be used safely in temperatures as high as the melting-point of ordinary glass, say to iocx)° F. Mercurial thermometers are made in various ways ; the cheaper ones have graduations on an attached frame of wood or metal, Fig. i, but the more accurate and better grades have the graduations cut directly on to the glass stem, Fig. 2. It has been found that the glass from which these thermometers are made changes volume slowly for many m.onths after construction, so that it is necessary to fill the thermometer with mercury a long time before graduation. In the better grade of thermometers the graduations are obtained by comparing point by point with an accurate standard ; in the cheaper ones by sim- ply subdividing into equal parts between freezing and boiling points. At very low temperatures ( — 38° F.) mer- cury solidifies and its rate of expansion changes ; alcohol or spirits of similar nature are not so affected, and hence are better suited for use in thermometers for measuring extremely low temperatures. Air thermometers, while rather difficult to use and of somewhat clumsy construc- FiG. 2 tion, are accurate through any range of temperature. These are made either by confining the air in a constant vol- ume and measuring the increase in pressure (Fig. 3), or else by maintaining the pressure constant and noting the increase in volume. If the volume be maintained constant, the pressure will increase directly propor- tional to the increase in absolute tem- perature. In the air thermometer (Fig. 3) the volume is kept constant and the increase in pressure is measured by the rise of mercury in the tube OC above the line AB. That is, in passing from the freezing to the boil- ing point of water, the barometer being fig. 3. - Air Ti^ome- at 29.92, the pressure will increase '^'^^^ 180/492, as expressed on the Fahr. scale, or 100/273 on the Cen. scale. V^ A — £■ C IN TROD UCTION. II The determination of temperature with the air thermometer, even if the instrument is calibrated to read in degrees, needs a correction for barometer-reading, since the height to which tlie mercury will rise in the tube will depend on the pressure of the air. The directions for using the instrument would be: ist. Find the constant of the instrument by putting the bulb in melting ice, and dividing the absolute temperature, 492, by the sum of barometer-reading and reading of tube of the ther- mometer; 2d. To find any temperature, multiply the (rf;w/««^ as found above by the sum of barometer-reading and reading of thermometer, and subtract from this product 460°. Note. — In using the instrument always keep the mercury at or near point A, so as to keep volume of air constant. 9. Pyrometers and Thermometers for High Temper- atures. — Most metals have rates of expansion which differ sensibly from each other, and this fact has been utilized in the construction of thermometers. Metallic thermometers are frequently used for high temperatures and have often been called pyrometers. If two bars of metal with unequal rates of expansion be fastened together at one end and heated, the difference of extension of the two ends can be utilized in moving a hand over a dial graduated to show change of temperature (Fig. 4). The metal may also be bent into the form of a helix, in which case the heating will tend to change the curvature and thus move a hand which can be used to measure -the temperature. A thermometer consisting of an iron bulb and a dial, very much like the metallic pyrometer in appearance, is made by filling the bulb with ether or hydro- carbon vapor, and constructing it on the same principle as gauges used to register pressure on boilers. The vapor has a temperature corresponding to a given pressure, so that the dial can be calibrated to read in degrees of temperature instead of pounds of pressure. Fig. 4. Metallic Pyrometer. 12 HEATING AND VENTILATING BUILDINGS. These instruments are extremely convenient and answer admirably for temperatures not exceeding 1000° F. Calorimetric Pyrometers. — The principle of operation used in determining specific heat, Art. 13, can, if the specific heat is known, be employed to ascertain the temperature of any hot body. Temperature by the Color of Incandescent Bodies and by Melt- ing-points. — Pouillet, as the result of a large number of experi- ments, concluded that all incandescent bodies have a definite and fixed color corresponding to each temperature. This color and temperature scale was given as follows : Color. Temp. C. Temp. F. 525 700 800 900 1000 1 160 1200 1300 1400 1500 977 1295 1652 1652 1932 1850 2192 2372 2552 2732 Dark red , Faint cherry Cherry Bright cherry Dark orange Bright orange White heat Bright white Da'zzling white This scale applies only to bodies that shine by incandescent light and not from actual combustion. A pyrometer making practical application of this scale has been invented by Noel, and consists of a telescope with polarizing attachment and a scale so fixed as to read the angle through which a part of the instrument turns while a sudden transition of color takes place. Temperature by the Melting-points of Bodies. — The melting- points of bodies often provide an excellent means of deter- mining temperature. The temperature is obtained by using metallic alloys having known melting-points, it being higher than those which have melted, but lower than those which remain unmelted. A table of temperature of melting-points is given in the Appendix. In Germany a carefully prepared set of alloys can be purchased for temperature determinations in this manner. 10. Maxima and Minima Thermometers. — The ordinary method of making a thermometer for recording the highest temperature is by introducing a small piece of steel wire about INTROD UCTION. 13 half an inch in length and finer than the bore of the thermom- eter into the tube above the mercury, in a mercurial thermom- eter. The thermometer is placed with its stem in a horizontal position, and the steel index is brought into contact with the extremity of the column of mercury. Now when the heat increases and the mercury expands the steel wire will be thrust forward ; but when the temperature falls and the mercury contracts the index will be left behind, showing the maximum temperature. For showing minimum temperature a spirit thermometer prepared in a similar manner is used, as the spirits in contracting draw the index with the alcohol because of the capillary adhesion be- tween the alcohol and the glass; but when the alcohol expands it passes by the index, without displacing it, so that its position shows the lowest temperature to which the in- strument has been subjected. II. Use of Thermom- eters. — In the use of ther- mometers for determining the temperature of the air, they should be exposed to unob- structed circulation in a dry place and in the shade. Any drops of moisture on the bulb of the thermometer tend to evaporate and lower the tem- perature. For determining the temperature of steam or water under pressure thermometers are set into a brass frame so that they will screw directly into the liquid (Fig. 5) without per- mitting leakage. In other cases the thermometer can be in- serted into a cup made as shown in Fig. 6. Cyhnder-oil or mercury is put into the cup, and the reading of the thermom- eter will then indicate the temperature of the surrounding i= Fig. 5. — Steam- thermometer. Fig. 6. — Ther- mometer-cup. 14 HEATING AND VENTILATING BUILDINGS. fluid. When the thermometer is inserted into a cup some time will be required to obtain the correct temperature. The temperature of steam-pipes or hot-water pipes cannot be obtained accurately by any system of applying the thermometers externally to the pipes, and in , case ther- mometers are used they should be set deep into the current of flowing steam or water, not placed in a pocket where air can gather. 12. Specific Heat. — The capacity which bodies have of absorbing heat when changing temperature varies greatly; for instance, the same amount of heat which would raise one pound .of water one degree in temperature would raise about 8 pounds of iron i degree in temperature or would raise i pound 8 degrees in temperature. The term used to express this property of bodies is specific heat, which is defined as follows: Specific heat is the quantity of heat required to raise the temperature of a body one degree, expressed in percent- age of that required to raise the same amount of water one degree, or in other words with water considered as one. Specific heat can always be found by heating the body to a given temperature, cooling it in water, and noting the increase in temperature of water. Thus if i pound of iron in cooling 8 degrees heats one pound of water one degree, its specific heat is ^ = 0.125. ^ table of specific heats of the principal materials is given in the back of the book, from which it will be seen that the specific heat of water is greater than that of any other known substance. A knowledge of the specific heat of various materials is of considerable importance in the design of heating apparatus, since it indicates the capacity for absorbing heat without in- crease of temperature. The heat which is absorbed in raising the temperature of a body is all given out when the body cools, so that although there is a difference in the amount absorbed, there is no difference in the final result due to heating and cooling. The total heat which a body contains is equivalent to the product obtained by multiplying difference of temperature, specific heat and weight. The results will be expressed in heat-units or in capacity of heating one pound of water. INTROD UCTION. 1 5 The specific heat of bodies in general increases sh'ghtly with the temperature, the values in the table being true from 32" to 212°, 13. Latent Heat. — When heat is applied to any liquid the temperature will rise until the boiling-point is reached, after which heat will be absorbed ; but the temperature will not change until the entire process of evaporation is complete, or until the liquid is all converted into vapor. The heat ab- sorbed during evaporation has been termed latent, since it does not change the temperature and its effects cannot be measured by a thermometer. In the evaporation of water about five and one-half times as much heat is required to evap- orate the water when at 212 degrees, into steam at the same temperature, as to heat the water from the freezing to the boiling point. Heat stored during evaporation is given out when the vapor condenses, so that there is no loss or gain in the total operation of evaporating and condensing. A similar storage of heat takes place when bodies pass from the solid to the liquid state, but in a less degree. Although similar in some respects, latent heat differs in nature from specific heat. In both cases, heat not measured by the ther- mometer is stored ; when the temperature is lowered the stored heat is given up in both cases : in the first it represents a change in the physical condition, as from a solid to a liquid or a liquid to a gas ; in the second the condition remains unchanged. ' 14. Radiation. — Heat passes from a warmer body to a colder by three general methods, each of which is of consider- able importance in connection with the methods of heating. These methods are radiation, conduction, and convection. The heat which leaves a body by radiation travels directly and in a straight line until it is intercepted or absorbed by some other body. Radiant heat obeys the same laws as hght, its amount varying inversely as the square of the distance, and with the sine of the angle of incHnation. The amount of radiant heat which is emitted or which is absorbed depends largely, if not altogether, upon the character of the surface of the hot and cold body ; it is found by experiment that the power of ab- sorbing radiant heat is exactly the same as that of emitting i6 HEATING AND VENTILATING BUILDINGS. it. The relative amount of heat emitted or absorbed by different surfaces is given in the following table. RELATIVE EMISSIVE POWERS AT THE BOILING TEMPERATURE. Lamp-black loo White-lead lOo Paper gS Glass go India ink 85 Shellac 72 Steel 17 Platinum 17 Polished brass 7 'Copper 7 Polished gold 3 Polished silver 3 Radiant heat passes through gases without affecting their temperature or being absorbed to any appreciable extent. It is probably true that a very large body of air, especially air containing watery vapor, does absorb radiant heat, for it is known that the earth's atmosphere intercepts a sen- sible proportion of the heat radiated from the sun. 15. Reflection and Transmis- sion of Radiant Heat. — Radiant heat, like light, may be reflected and sent in various directions by materials of various kinds. Thus in Fig. 7 heat radiated from K is re- flected to L, and vice versa. The following table shows the proportion of radiant heat which would be reflected by various substances : Fig. 7. — Reflection of Heat. REFLECTING POWER. Silver-plate 97 Gold gj Brass , g3 Speculum-metal 86 Tin 85 Polished platinum 80 Steel 83 Zinc 81 Iron -J-] Radiant heat also possesses the property of passing through certain substances in very much the same manner that light will pass through glass. This property is called diathermancy. The following table gives the diatheimanous value of various substances, the heat being obtained from a lamp. The trans- mission power varies with the source of heat. INTROD UCriON. 17 PER CENT OF HEAT TRANSMITTED THROUGH DIFFERENT SUBSTANCES. WHEN RECEIVED FROM AN ARGAND LAMP (dESCHAUD's PHYSICS). Solids. Colorless Glass 1.88 mm. thick. Flint-glass from 67 to 64;^ Plate-glass 62 to 59 Crown-glass (French) 58 Crown-glass (English) 49 Window-glass 54 to 50 Colored Glass 1.85 mm. thick. Deep violet 53 Pale violet 45 Very deep blue 19 Deep blue 33 Light blue 42 Mineral-green 23 Apple-green 26 Deep yellow 40 Orange 44 Yellowish red 53 Crimson 51 Liquids g.21 mm. thick. Colorless Liquids. Distilled water \\ 1 ^:^^L^^^^^fe^f^^^B T"™*^^^" Fig. 22. — Inlet near Top, Discharge near Bottom. 35. The Outlet for Air. — The outlet for air should be as near the bottom of a room as possible, and it should be con- nected with a flue of ample size maintained at a temperature higher than that of the surroundinsf air, unless forced circula- PRINCIPLES OF VENTILATION. 59 tioH is in use, in which case the excess of pressure in a room will produce the required circulation. If the temperature ill a room is higher than that of the surrounding air, and if the flue leading to the outside air can be kept from cooling and is of ample size and well proportioned, the amount of air which will be discharged will be given quite accurately by the tables referred to. These conditions should lead us to locate vent- flues on the inside walls of a house or building, and where they will be kept as warm as possible by the surrounding bodies. If for any reason the temperature in the flue becomes lower than that of the surrounding air the current will move in a re- verse direction, and the ventilation system will be obstructed. The conditions as to size of the outlet register are the same as those for the inlet ; the register should be of ample size, the opening should be gradually contracted into the flue, and every precaution should be taken to prevent friction losses. 36. Ventilation-flues. — The size of ventilation-flue will depend to a great extent upon the character of system adopted, but will in all cases be computed as previously explained. A prac- tical system of ventilation gener- ally is intimately connected with a system of heating, and the vari- ous problems relating to the size and construction of ventilating ducts will be considered later. In eeneral the ducts should be of such an area as not to require a high velocity, since friction and eddies are to a great extent due to this cause. The size of the ventilating duct can be computed, knowing its rise, length, and the differ- ence of temperature by dividing the total amount to be discharged by the amount flowing through one square foot of area of the Hue under the same conditions. (See Table XVI, paye 531 ) Fig. 23.— Ventilation-flue. 6o HEATING AND VENTILATING BUILDINGS. In introducing heated air into a room, it is very much bet- ter to bring in a large volume heated but slightly above the required temperature of the room rather than a small volume at an excessively high temperature. If the temperature of the air entering be 25 degrees above that of the air in the room^ the discharge in a flue one square foot in area would be, in cubic feet per second, 5.7 for a height of 10 feet, 9.0 for a height of 25 feet, 11.4 for a height of 40 feet, if no loss from friction, as given in Table XVI, page 531. The actual dis- charge can be safely taken as 50 to 60 per cent of the theo- retical. As the difference of temperature of the air In the rodm and outside may usually be taken as 20°, the velocity in feet per second for heights corresponding to the distance of floor to roof in a building of 3 stories would be about as follows :. 1st floor, 5; 2d floor, 4; attic or top floor, 3, — or about one half the theoretical. For air entering, the order of the velo- cities would be reversed on the particular floors. The area of the flue would be found by dividing the total air required per second by these numbers. The general arrangement for heating the air and introduc- ing it into a room is shown in Fig. 23. In this case the cold air is drawn in at D and delivered into the chamber C, whence it passes through the heater, thence into the flue, entering the room at the register B. The vitiated air enters the ventilating flue at E. 37. Summary of Problems of Ventilation. — From the foregoing considerations it is to be npted that the practical prob- lems of ventilation require the introduction, first, of thirty or more cubic feet of air per minute for each occupant of the room, and in addition sufUcient air to provide perfect combus- tion for gas-jets, candles, etc., which are discharging the prod- ucts of combustion directly into the room. Second, the prob- lem requires the fresh air to be introduced in such a manner as to make no sensible air-currents, and to be in such quanti- ties as to keep the standard of contamination below a certain amount. This problem can be solved by either, first, moving the air by heat, in which case the motive force is very feeble and likely to be counteracted by winds and adverse conditions ; second, by moving the air by fans or blowers, in which case. PKINCIPLES OF VENTILATION. 6 1 the circulation is more positive, and less influenced by other conditions. The methods for meeting these conditions will be given under appropriate heads in later articles. It will generally be found much more convenient to esti- mate the air required, not in cubic feet per minute for each person, but by the number of times the air in the room will need to be changed per hour. If the number of people who ■occupy a room be known, and each one requires 30 cubic feet of air per minute or 1800 cubic feet per hour, one can easily compute the number of times the air in a room must be changed to meet this requirement. Thus a room containing 1800 cubic feet, in whicli five people might be expected to stay, would need to have the air changed five times per hour in order to supply the required amount for ventilation purposes. By consulting the table Properties of Air, No. X, it will be seen that one heat-unit contains sufiScient heat to warm 55 cubic feet of air, at average pressures and temperatures, one degree ; so that practically to find the number of heat-units re- quired for warming the air one degree we must simply divide by 55 the number of cubic feet to be supplied,. If the cubic contents of the room is to be changed from five to ten times per hour, we can very readily make the necessary computations by knowing the volume of the room. Even in the case of direct heating, where no air is purposely supplied for ventilation, there will be a change by diffusion of the air in a room, this the writer has found practically met by an allowance equal to one to three changes in the cubic contents per hour. The heater must supply heat for ventila- tion purposes in addition to that transmitted by the walls. The number of times that air will need to be changed per minute in a given room will depend upon its size as com- pared with the number of occupants. If we take the smallest size of rooms, in which we allow only 400 cubic feet of space per occupant, a supply of 30 cubic feet per minute would change the air in this space in 13^ minutes, or at the rate of 4^ times per hour. If 600 cubic feet are supplied per occupant, the air of the room would be changed once in 20 minutes, or at the rate of 3 times per hour. The following table may be 62 HEATING AND VENTILATING BUILDINGS. of practical value, as it shows the number of changes per hour required to supply each person with 30 cubic feet per minute when the space supplied is as given in the table: Space to each Person. Number of Times Air to be Cubic Feet. Changed per Hour. 100 18 200 9 300 6 400 4-5 500 3.6 600 3 700 2.6 800 2.25 900 2 38. Dimensions of Registers and Flues. — The approxi- mate dimensions of registers and flues can be computed from consideration of the limiting velocity of entering air. For residence heating the velocity in flues is likely to be as follows, in feet per second : Warra-air Duct. Ventilating Duct. Entering Air at Register. Discharpe Air at Register. First story Strt'iTuI Story 2.5 to 4 5 6 7 6 5 4 3 3 3 3 3 4 4 3 24 Attic floor The velocity per hour being 3600 timn e" e'" \ J/ =(/-/'): ^-^ + -^ + ^ + g^j (3) If the temperatures of the surfaces could be exactly known, it would be possible to calculate the amount of heat transmitted ; but while it is possible to measure the temperature of the air in contact with the plates, it is not possible to measure the actual temperatures of the surfaces of the plates themselves. Denote the temperature of the air inside an apartment by Tand that outside by T . It is evident that heat will flow from the warm room to the cooler air outside, and that the inner surface of the wall will be cooler than the air of the room, and the outer surface will be warmer than the outside air. It will be possible to obtain three values of M in terms of the coefficient of conductivity C, that of radiation K, and that of convec- tion K', since the amount of heat received by the inner surface is equal to that conducted through the wall and discharged from the outer sur- face. In forming these equations it is assumed that the heat transmitted is in every case proportional to tlie difference of temperature, which, although not quite exact, is sufficiently near for practical purposes, espe- * Translated from Traite de la Chaleur by the author. :74 HEATING AND VENTILATING BUILDINGS. cially for small differences of temperature. We have three equations -as follows: M = ''^^~^'^ , M =(K ^■ K'){T- i), M={K + K'){f — 7*); ■ by combining these equations and substituting Q =i K + K', we have _ T(C + Qe) + CT' '- ^CTQe (4) _ T\c + g^) + rc 2C + 2^ ^^' If j2« is relatively so small with reference to 2C that it may be neg- lected in the last formula, we have M = IQ{T-T') (7) in which case the heat transmitted is independent both of the thickness of the material and its conductibility. As an example consider several plates of glass varying in thicicness and with a conductivity in metric measures as given in various tables in this book as follows: C = 0.75, Q = K + K' = 2.91 + 2.20 = 5.10, from which 2C + <2^ = 1.50 + 5.10^. Taking ^ equal to the following values, we have e meters 0.00 1 0.002 0.003 0.004 0.005 e inches 0.04 0.08 0.012 0.016 0.02 2C + Qe 1.5005 I. 50102 1.501503 1.502013 1.502523 The above calculation indicates that within practical limits 2C + Qe remains constant, and that the heat transmitted through glass is inde- pendent of the thickness and the coefficient of conductivity. If, on the other hand, the coefficient of conductivity C is very small and the thickness c is very great, we can neglect 2C in the value of M, .^giving us as a consequence ^^CQiT-j:, (8) As the value of C is never less than Q for any except the poorest con- ductors, such as hair felt and filamentary bodies, it is necessary to have AMOUNT OF HEAT REQUIRED FOR WARMING. 7$ the thickness ^ very great in order to have the conditions as above prac- tically realized. If there are 'two walls built in close contact and without air-space •between them, with a temperature of x at tlie junction surface and a thickness e, e", and coefficients of conductibility C, C, we shall find as 'before several values of M as follows : M = ^^i^^\ M= ^^^7^'\ M=Q{T-/). M=Q{t'-TX ■from which can be obtained the following value of Afintermsof T'and T': M= g(^-^') , (9) 2 + 2 ^*i) If there are several walls in contact without an air-space between ithem, the value of the heat transmitted would be, with notation as before, 0(T— T') + 2(^ + ^+^j The foregoing computation, as stated by Peclet, applies to apartments hi which exposed walls are not opposite to each other, it being assumed that heat is radiated to an exposed wall by an inner unexposed wall of the same tempeiature as the room. For the condition where all the walls are exposed the temperature of each wall will be less than that of the room and there will be no reciprocal radiation. In considering this 'Case mathematically we shall have to substitute in the last set of equa- tions K' the coefficient of convection for g = /^T + K' , since, in accord- ance with this hypothesis, /s' becomes equal to o. This hypothesis gives lower values than in the preceding case as will be shown by example. There is little doubt but that the mathematical conclusion drawn by .Peclet follows from the hypothesis adopted, viz., thai all the radiant heat passing through the exposed walls must be reciprocally radiated from the interior walls. In most modern examples of heating, however, ^radiant heat is probably supplied the outside walls from furniture and theaters situated in the room to such an extent as to make the actual amount of heat transmitted practically as much in the one case as in the o:her, and in the tables already given the condition which gives the greatest transfer of heat only has been considered. As explaining the use of the formulas we take the following example •from Peclet. Assume a wall lo meters (32.8 ft.) in height formed of !Stone masonry, with coefficient of conductivity C = 1.7 (see first column 76 HEATING AND VENTILATING BUILDINGS. Table, p. 78, slightly smaller than limestone). Coefficient of radiation K = 3.60 (see Article 46, p. 84) and coefficient of convection A" = 1.96 for a wall 10 meters high (see last formula Article 45). Assume tlie interior temperature T = 15° C. (60°. 5° F.) and the exterior temperature T' = 6° C. (43.4° F.) as corresponding with mean conditions in Paris. From this j2 = /£" + A" = 3.60 + 1.96 = 5.56. Substituting these various values in equations (4), (5), and (6), and assuming different values of the thickness {e) as follows, we have for a single exposed wall : Thickness {e) meters . ... o.io 0.20 0.30 0.40 0.50 0.60 0.70 0.80 o.go i.oo " Winches 3.9 7.9 12.8 15.7 19.7 23.6 27.6 31.5 35.4 39.4 Temperature inside face of wall (0 deg. C 11.15 II. 6 12 12.3 12.56 12.77 12.96 13. i 13.2 13.3 Temperature outside face of wall (/') i^eg. C ... 10 9.7 9.4 9.2 9.0 8.8 8.7 8.6 8.5 8.4 Calories per square meter per hour, jT/ .... .. ., 25.4 22.3 Tg.8 17,9 16.2 15.0 13.8 12.8 12.0 11.2 B.T.U. per sq ft. per hr. . 9.3 8.2 7.4 6.6 5.9 5.5 5.1 4.7 4.4 4.1 For the case when all the walls are exposed we have : t deg. C. (inside face) ... 8.9 9.3 9.7 10 10.3 10.6 10.8 11. o 11.2 11. 9 <' deg. C. (outside face)... 8.2 8.0 7.9 7.7 7.6 7.5 7.4 7.4 7.3 7.3 Calories per square meter per hour, ^ 12 11. « 10.4 9.7 9.1 8.6 8.2 7,8 7,4 7.0 B.T.U. per sq. ft. per hr.. 4.4 4.1 3.8 3.6 3.3 3.1 3.0 2.8 2.7 2.6 For walls with air-spaces, having a temperature of x and x' at the re- spective sides of the air-space, we shall find without sensible error that the heat transmitted through the space is by radiation and convection, of which the coefficients are K + K" = Q. The heat transmitted through each space can be represented by Q{z — x'). The value of the heat transmitted will be expressed by substituting 7. + 7^ in equa- tion (9) for -- . Preserving the same notation, we shall have walls with two air-spaces: M= 77 — ; — 7 — ; — >T ('o) Je I / I t!'\' If the walls are « in number and each of the same material, it follows that __e(r-ro__ If the construction consisted of several thin walls or parts without an air-space of the same total thickness of the wall with air-spaces as above, we should have ti— i parts filling the air-spaces and n parts constituting AMOUNT OF HEAT REQUIKED FOR WARMING. 77 the remaining part of the wall. By substituting in equation (lo) the heat transmission will be for this case : Q(T-T) Q{T-T^ 2 + «^ + ' g/^ 2 + =^{in — I) By finding the ratio in the above equations Peclet proves that a wall with air-spaces 0.02 m. (.8 incli) thick, as compared with the same wall with the spaces filled with baked clay, transmits the following proportion of heat : Number of walls or parts of walls 2 3 4 5 10 Proportion of heat transmitted in wai: with air-space 0.75 0.64 o.S'/ 0.53 0.43 He shows that the thickness of the air-space should always be sucfi that e is less than . , e The heat transmitted through the solid walls is by conduction, that through the airspace principally by radiation and convection, which latter quantity may under the same conditions with thick spaces be so large as to overbalance the gain due to the air-space. This demonstration shows what has been found to be practically correct : that the less the radiation from the surfaces of the walls the more efficient will the air- spaces prove to be. Transmission of Heat through Glass. — As already explained in con- nection with equation (7), the heat transmitted through glass when one side only is exposed to the air can practically be represented by the ■equation M = \Q{T-T'). It also follows that if x be the mean temperature of the glass, M=(.T-x)Q, M={x-T')Q, whence x = \{T-^T'). . (13) When the entire enclosure is surrounded with glass Peclet states that the heat transmission will be somewhat less, because of the reduction in the temperature of the glass due to the lack of reciprocal radiation, and that the following equations apply : M = {T- x)K\ M = Q{x — r\ irom which we obtain K'T+QT' . .. QK'(T-r) , ^ ^= Q + K' ^"'^ ^== Q + IC ■ ■ ■ • ('4) Peclet calculates the heat transmitted by the above formulas with the following results : 78 HEATING AND VENTILATING BUILDINGS. Height of windows, meters. 12 3 4 5 feet 3.28 6.56 9.84 1 3.1 16.4 Value of AT' (coefRcient of convection), ) „ J. > 2.4 2.21 2.1 •? 2.08 2.0? one exposure j ^ ^ • -> Heat transmission per hour per de- \ c ^ ^ gree C. per square meter, calories., p-^5 2.56 2.52 2.496 2.479 Ditto per degree F. per square foot, \ 0^3 0.945 0.93 0.92 0.91 B.T. U \ Room surrounded with glass. Heat transmitted per hour per degree) J 65 j , C. per square meter, calories j ■' r^'^to^ per degree F. per square foot, ( 608 ^ jgg ^ 55 „ ^^^ 0.535. It is quite probable that the hypothesis from which the equations are derived when the room is entirely surrounded with glass is erroneous. By neglecting the thickness e in the general formula it can be shown that the heat transmitted by multiple glass will bear the following pro- portion to that transmitted by a single thickness: Number of glass 1234 n 212 2 Proportion of heat transmitted i — — — • ^ 3 2 5 I + « The following tables of the coefficients for the thermal conductivity of poor conductors are taken from Peclet's work and are included here for reference. The results will be found essentially the same as given by various authorities in the table in the appendix. CONDUCTION OF HEAT FOR ONE DEGREE DIFFERENCE OF TEMPERATURE PER HOUR. Material. Gray marble, fine-grained White marble, coarse-grained Limestone, fine-grained (mean of three samples).. Limestone, coarse-grained (mean of two samples). Plaster of Paris Brick Per Degree Cent. Powdered brick, coarse-grained...., Fir at right angles to the fibres Fir parallel with fibres Walnut at right angles to the fibres. Walnut parallel with fibres Cork Glass Sand Wood ashes Powdered charcoal Powdered coke Cotton, raw or woven Paoer Per Square Meter I Meier Thick. Calories, 3.48 2.78 1.82 1-3 0,44 .69 •139 ■093 ■17 .10.3 .174 .143 ■75 .27 .06 .079 .160 .040 .034 Per Degree- Fahr. Per Sq. Ft., T Inch Thick. B. T, U, 28 22. 5 14. 8 10-.'; 3-6 5-0 i.i 0.75 1.4 0.83. 1.4 1-15, 6 2.2 0.5 0.65 1-3 0.32^ 0.27 AMOUNT OF HEAT REQUIRED FOR WARMING. 79^ The following table for coefficient of convection K, as calculated from the last formula, Article 45, is taken from Peclet's work : TABLE GIVING VALUES OF K' FOR VARIOUS HEIGHTS IN METERS FOR A PLANE VERTICAL SURFACE. Heights, K>. Heights, K>. Meters. Meters. O.IO 3.848 2 2.21 0.20 3-186 3 2.13 0.30 2.926 4 2.08 0.40 2.770 5 2.05 0.50 2.66 10 i.g6 0.60 2.585 15 1.92 1. 00 2.400 20 1.90 The table shows a decrease in the coefficient of convection with in- crease in height in a vertical wall as explained in Article 45. This de- crease is calculated from the hypothesis that the air which is heated rise* while remaining in contact with the body, and for this reason has its capacity diminished for absorbing heat. This hypothesis is doubtless- true in the case of absorption of lieat by air-currents from radiators or heated bodies, but is probably considerably in error for walls of build- ings, and may be entirely neutralized by the fact that the air against th& interior wall is likely to be much warmer near the top, thus making aft increasing temperature difference. CHAPTER IV. HEAT GIVEN OFF FROM RADIATING SURFACES. 43. The Heat Supplied by Radiating Surfaces. — The heat used in warming is obtained either by directly placing a heated surface in the apartment, in which case the heat is said to be obtained by direct radiation, or else by heating the air which is to be used for ventilating purposes while on passage to the room, in which case the heating is said to be by indi- rect radiation. As air is not heated appreciably by radiant heat, this latter term is very clearly one which is used in a wrong sense. In this treatise we shall use the terms direct heating or radiation and indirect heating. Direct heating is performed by locating the heated surface directly in the apartment : this surface may be heated by fire directly, as is the case with stoves and fireplaces ; or it may receive its heat from steam or from hot water warmed in some other portion of the premises and conveyed in pipes. The general principles of warming are the same in all cases, but for the case of stoves the temperature is greatly in excess of that for steam or hot-water heating surfaces. The heat is carried away from the heated surface partly by radiation, in which case the heat passes directly in straight lines and is absorbed by people, furniture, and objects in the room, without warming up the intervening air directly, and also by particles of air coming in contact with the heated surface, which may be the radiating surface, or the people and objects in the room which have been warmed by radiant heat. The sensation caused by radiant and convected heat is quite different: the radiant heat has the effect of intensely heating a person on the side towards the source of heat, and of producing no warming eflect whatever on the opposite side. The heat which has passed off by convection is first utilized in warming the air, and the sensation produced on any person is that of lower temperature-heat equably distributed. Radiant and con- 80 HEAT GIVEN OFF FROM RADIATING SURFACES. 8 1 vected heat are essentially of the same nature : in the one case it is received by the person directly from the source of heat, and at a high temperature; in the other case it is received from the air, which is at a comparatively low temperature. The heat in passing through any metallic surface raises its temperature an amount whicTi depends upon the facility w'ith which heat is conducted by the body and discharged from the outer surface. The phenomena of the flow of heat through any metallic substance can be I ^ i ]■ illustrated by the sketch in Fig. 25. *g \i E represents the source of heat, and ABCD a section of a metallic wall sur- c rounding, the flow of heat takes place Fig. 25. into the metallic surface, then through the solid metal, and finally through the outer surface. It is noted that the heat meets with three distinct classes of resistances: first, that due to the inner surface; second, that due to the thickness of the material; and third, that due to the outer surface. The first and third resistances are due to change of media, and when the material under consideration is a good conductor, constitute the principal portion of the resistance to the passage of heat. ' If the resistance on the inner surface AB is small and that on the outer surface CD is great, the temperature of the metal- lic body will approach that of the source of heat, for the reason that the heat will be deUvered to the surface CD faster than it is discharged. In this case the thickness of the material is of little or no importance, and the rate at which heat will pass will depend entirely upon the rapidity with which it can be discharged from the outer surface. 44.. Heat Emitted by Radiation. — Heat emitted by radia- tion, per unit of surface and per unit of time, is independent of the form and extent of the heated body, provided there are no re-entrant surfaces which intercept the rays of radiant heat. The amount of heat projected from a surface of such form as to radiate heat fequally in all directions, depends only on the nature of its surface, the excess of its temperature over that of the surrounding air, and the absolute value of its tem- perature. 82 HEATING AND VENTILATING BUILDINGS. Radiation of heat was stated by Sir Isaac Newton to be in exact proportion to the difference of temperature of the heated surface and the surrounding media, but this law was found to be inaccurate by Dulong and Petit. They found that the radiation increased at a greater rate than the difference in tem- perature, and for high temperature, was much in excess of that given by the law of Newton. From a large number of experi- ments on the cooling of bodies they were able to determine the following law : " The rate of cooling due to radiation is the same for all bodies, but its absolute value varies with the nature of the surface." It is represented by the formula V=ma\a' - i), in which m represents a number depending on the nature of the surface of the body, a represents a constant number, which for the centigrade thermometer is equal to 1.0077 and for the Fahrenheit above 32° to I.OOI96, d the temperature of the sur- rounding air, and t the excess of temperature of the body over tliat of the surrounding space. Peclet found that if the radiant heat be received by a dull surface the value of m becomes equal to a constant 124.72 mul- tiplied by K, a coefficient which depends on the nature of the surface. A table giving the rapidity of cooling for different values of difference of temperature in both Fahrenheit and metric units is given on page 84, and the value of the coeffi- cient K for different surfaces, which is to be multiplied by the numbers which express the relative rates of cooling, is given in a subsequent table. The results of the experiments by Pdclet accord very well with recent experiments made in testing radiators for steam and hot-water heating. For these cases either wrought or cast iron is used, and the difference in radiating power is im- material. The construction of the ordinary form of radiator is such as to present very little free radiating surface, as all the heat which impinges from one tube on another is reradiated back, and consequently not of' use in heating the apartment. The greater portion of the heat removed is no doubt absorbed HEAT GIVEN OFF FROM RADIATING SURFACES. 83 by the air which comes in contact with the radiator, or, in other words, it is removed by convection. 45. Heat Removed by Convection (Indirect Heating). — The heat removed by convection is independent of the nature of the surface of the body and of the surrounding absolute tem- perature. It depends on the velocity of the moving air, and is thought to vary with the square root of the velocity. It also depends on the form and dimensions of the body and of the ex- cess of temperature over that of the surrounding air. We are indebted to P^clet for exact experiments giving us the value of the loss from this cause. Pdclet's experiments were, however, made in ordinary still air, and if the velocity is increased should be multipHed by factors which will be given later. The formulae which P6clet found as applying to bodies of different form were as follows, the results below being given in heat-units per square foot per hour. The general formula for loss by convection is, in metric units, The values of K' depend upon the form and surface of the body and are as follows : For a sphere, radius r, K'= 1.778 + 0. 1 3/r. For a vertical cylinder, circular base, radius r, height A, K' = (0.726 -}- 0.0345 / ^fr){2.^i + 0.8758 ^h). For horizontal cylinder, radius r, K' — 2.058 + 0.0382/r, For vertical planes, height h, K' = 1.764 + 0.636/4^^. Numerical values of these various quantities are given in tables, Art. 46. 84 HEATING AND VENTILATING BUILDINGS. 46. Total Heat Emitted. — The amount of heat given off by radiation and convection for various differences of tempera- HEAT-UNITS PER HOUR. Radiation. Convection. Excess of Temperature. Total Radiation. Per Degree ence Differ- Total. Per Degree Dif- ference. Deg. Cent Fahr Calories B. T. U. Calories B . T. U. Calories B.T.U. Calories B. T. U. per Sq. per per Sq. per Sq. Metre per 'per Sq. per Metre. Sq. Ft. Metre. S q. Ft. Sq. Ft. 1 Metre. Sq. Ft. 10 18 11.2.S' 4.1 A- 1. 12 AT 228 .AT 9.4 A-' 3-4 -Sr'o.g4 K' .189 K' 20 36 23.2 *' 8.6 " 1. 16 " 239 " 22.2 8.2 " I. II '* .228 " 30 54 36.1 " 13.2 " 1.20 " 243 " 36.6 " 13 5 " |l.22 " ■245 " 40 72 50 I " 18.5 ; 1. 25 " 257 ' 52.2 K 19.2 " 1.30 .265 ■' 50 90 63.3 " 24.2 1.3. " 269 " 68.6 " 25-3 '1 1-37 '' .284 " 60 108 81.7 •' 30.2 1.36 '■ 281 " 86.0 " 3"-8 ' 1-43 ' 295 " 70 126 99-3 " 36.6 " 1.42 '■ 291 " 104.0 " 38,4 " 1.49 " .306 " 80 ■44 118. 5 " 43-7 " 1. 48 " 304 " 122.6 " 45-0 " 1-53 " .311 " 90 162 138.7 " 51.2 1-54 317 141. 7 " ^^■'^ I! '-F !! .32 ' 100 180 161. 3 " 59-5 ' 1. 61 " 33 161,5 59.5 I. 61 •33 110 ig8 185.3 •' 68.5 " ..69 " 305 '• 181. 5 " 67.0 11.64 ' -334 .. 120 216 2U.3 ' 78.0 " 1.76 • 361 " 202.1 " 75-S 1.68 " ■345 ■' 130 234 239-3 " 88.3 " 1.83 377 " 223.1 " 8z.2 " 1.72 " •35 ' 140 252 269,5 " 99 " 1.92 395 '' 244.4 , go.o ' 1-74 355 " 150 270 302.1 " 112 " 2.01 " 416 " 366.1 '• 98.0 " 1.76 ' •3« !! 160 288 339.0 " 125 " 2 12 *' 435 " 288.1 ■' 106 " I 79 •365 " 170 306 37" 4 '39 .! 2.22 " 454 310-5 " 115 " 1.82 " 372 '' 180 324 418. s '■ IS5 2.32 " 478 " 333-2 ' 123 1. 8s " •38 igo 342 463.2 " ^11 !1 2-43 503 3SD-I 132 t.87 ' 384 200 360 511.2 188 " 255 523 ' 379-4 ' 140 1.89 " •39 210 378 563.1 " 208 " 2.68 ~' 553 402.9 149 " 1. 01 " 394 220 396 619.0 229 " 2.81 " 573 ' 426.7 157 " 1.93 " 40 230 414 679-5 " "55 ,. 2 95 " 0:7 ;' 450.4 " 166 " 1.95 ■•"I !. 240 432 744.8 " 27s 3-10 665 '• 475-0 175 " 1.97 406 " 250 45° 848.7 " 314 3-39 " 700 " 498.6 " 184 " 1.99 " 408 " FACTOR TO DETERMINE RADIATION LOSS FROM VARIOUS SURFACES. Value of Coefficient K. Polished silver 0.43 Silvered paper 0.42 Polished brass 0.258 Gilded paper 0.23 Red copper 0.16 Zinc 0.24 Tin 0.215 Polished sheet iron 0.45 Sheet lead 0.65 Ordinary sheet iron 2.77 Rusty sheet iron 3 ■ 36 Cast iron, new 3- 17 Rusty cast iron 3.36 Glass 2.gl Powdered chalk 3-32 Powdered wood 3.53 " charcoal 3-42 Fine sand 3.62 Oil painting 3.71 Paper 3.71 Soot 4.01 Building stone 3.60 Plaster 3.60 Wood 3.60 Calico 3 . 65 Woollens 3.68 Silk 3.71 Water 5.31 Oil 7 . 24 Note. — To find the total heat emitted by radiation, tnultiply the value of JST as given in the above lable by the numbers corresponding to radiation due to difference of tempi rature as in the preceding table. HEAT GIVEN OFF FROM RADIATING SURFACES. 85 ture and from any surface when K or K' is unity is given in the first table on p. 84, as computed from P^clet's experiments. The total heat emitted by any surface will be obtained by multiplying the results given in the first table by the factor of radiation and convection for the required conditions. This table is exact for the surrounding air at 15° Centigrade or 59° Fahrenheit. FACTOR TO DETERMINE CONVECTION LOSS FROM BODIES OF VARIOUS DIMENSIONS. Value of Coefficient A". Diameter, i Horizontal Cylinder. Vertical Cylinder, Height in Metres and Feet. Metres. Indies. o.s m. 1.64 ft. I m. 3.28 ft. h 2 m. 6.56 ft. h 3 m. 9.84 It. h 4 m. ij. izft. h 5 in. 16.4 ft. h 10 m. 32.8 ft. 0.025 0.05 O.IO 0.20 0.40 0.60 0.8 10 0.984 1.968 3-94 7.88 15-74 23.62 31-50 39-38 63.0 ■6:9" 4-38 3-08 2.43 2.10 5-114 3-59 2.82 2-44 2.25 2.18 2.15 3-55 3.22 3.05 2-93 2.88 2.85 2.83 3-2 2.9 2.75 2.65 2.60 2.57 2.55 2.95 2.68 2-54 2-45 2.40 2-37 :..36 2.84 2.57 2-44 2.35 2.31 2.28 2.26 2.79 2.52 2-39 ^.30 2.26 2.23 2.22 2.73 2.48 2.35 2.26 2.22 2.20 2.18 2.62 2.38 2.26 2.17 2.13 2. II 2.09 1.94 ratio — a 20 20 20 15 I3i 12.5 20 The table on p. 86 gives the total loss from various forms of direct radiating surfaces in still air, calculated by P6clet's coefficients, sHghtly modified by recent experiments. The loss of effective surface due to rays of radiant heat im- pinging on hot surfaces can be calculated as follows: D Fig. 26. TTTT Fig. 26(7. 86 HEATING AND VENTILATING BUILDINGS. Thus in Fig. 26, supposing pipes equally hot, occupying the relative positions of Cand B, the effective radiating sur- FiG. 27. face of C will be diminished by that portion of the circumfer- ence intercepted by the lines CD and CE. The angle DCB HEAT-UNITS EMITTED PER HOUR PER SQUARE FOOT FROM VARIOUS SURFACES, DIRECT RADIATION, STILL AIR. Differ- ence of of Tempera- ture. Deg. F. 10 20 30 40 50 60 70 80 90 100 no 120 130 140 150 160 170 180 190 200 225 250 275 300 325 350 Coefficient or Difference Amount per Degree of Temperature. Horizontal Pipe, Diameter. 6 iti. 4 in 2 in. I in. 40 m. Massed Surface. 0.55 I . II 1. 18 1.24 l.2g 1-33 1.36 1.40 1-43 1.47 1.51 1-54 1-57 1. 61 1.64 1.66 1 .69 1.72 1-75 1.78 1.87 1.97 2.07 2.17 2.27 2-37 Radiator, Height. 40 in. 24 in. Tliin. Massed. 0.62 0.66 1.25 1.32 1-34 1.42 1.40 1.48 1.46 1-54 1.50 1.58 1-54 1.63 1.58 1.67 1.63 1.72 1.66 1.76 1. 71 1.80 1.74 1.84 1.78 1.88 1.81 1. 91 1.84 1.94 X.87 1. 97 1. 91 2.02 1.94 2.05 1.98 2.09 2.01 2.12 2.12 2.24 2.23 2.35 2.34 2.47 2.45 2. =8 2.55 2 70 2.67 2.82 12 in. Tliin. 0.85 1.72 1.84 1. 92 2.01 2.06 2.12 2.18 2.24 2.28 ^■34 2.39 2.44 2.48 2.53 2.57 2.62 2.65 2.71 2.76 •^.91 3.06 3.22 3-37 3-50 3.66 Total per Square Foot per Hour.* Horizontal Pipe, Diameter. 6 in. 4 in. Radiator, Height. 40 in. Massed Surface. 5-50 20.2 35 49.6 • 64.5 79.8 95.2 I 12 128 147 166 184 203 223 2'44 265 286 307 330 356 420 493 563 654 740 835 40 In. 24 in. Thin. Massed. 6.7 6.6 24.9 26.4 39-7 42.7 56.2 59-0 73 77 90 95 108 113 127 133 147 153 167 175 188 198 208 219 230 242 252 266 276 291 300 316 324 341 348 367 375 393 403 415 477 500 557 587 637 670 742 780 840 882 945 995 T2 in. Thin. 8.5 34-4 55.2 77 100 124 148 173 199 22S 257 287 318 346 378 410 443 475 512 552 650 762 872 1020 II 50 1295 * Results divided by loco give approximate weight of steam condensed per ho .r. " HEAT GIVEN OFF FROM RADIATING SURFACES. 87 has for its sine DB/BC. DB is the external radius of the pipes, BC the distance between the centres, which is usually not far from two diameters. In Figs. 26a, 27, and 28 the shaded Fig. 28. areas show the position of surface, by which the radiant heat coming from a single pipe or a single section is intercepted and reradiated to its source. Supposing the distance apart to be as given above, the fol- lowing table gives the percentage of reduction in amount of heat transmitted due to this cause, compared with single pipe : Amount of Surface Probable Reduc- Rows of from which no Radi- tion in Heat Tubes. ation takes place. transmitted. Per cent. Per cent. I 16 8 2 42.7 21 .3 3 55 27.5 4 66 33 5 73 36.5 6 79 39-5 47. Heat Transmission Varies with Circulation. — Prof. A. W. Richter made a series of experiments under the gen- eral supervision of the author for determining the rate of transmission ofi heat through plates of different thickness and of different materials from steam to water. From these experiments it was shown that the total heat transmitted from steam to water was a quantity which varied with the velocity of the water in contact with the plate, the thickness 88 HEATING AND VENTILATING BUILDINGS. of the plate, and with the difference of temperature of the steam and water, so that, other conditions being neglected, the heat transmitted per degree difference remained uniform. Thus if we denote by y the heat transmitted per square foot per degree difference of temperature, by x the number of pounds of water flowing in contact with the plate per square foot per hour, by r the thickness of the pla,te in inches, by A, B, and D constants dependent on .the material, then will y '.+■)= D A{r + B) {X + A). The values of the constants as determined by experiment are as follows : Material. A B D D/A Mild steel, very smooth surface 6900 9000 7000 8500 0.675 0.675 0.623 0.91 285 285 312 285 0.0413 0.0317 0.0447 0.0335 Cast iron, clean surface not machined. The total heat transmitted per square foot per hour is to be found by multiplying the values as obtained from the formula by the difference in temperature of the water and steam. (See table on opposite page.) Experiments made by Adams and Gerry* show substan- tially the same results for the transmission of heat through iron or steel plates from steam to water. When, however, the hot medium was one that parted with its heat slowly, as oil or air, the rate of transmission was found to vary much more rapidly than the difference in temperature between the two media, and to be practically independent of the rate of circulation of the cooler medium ; this is doubtless explained by the fact that the rate of transmission was limited to the rate of delivery of heat fiom the heated body. This in the case of air or oil *See Transactions of American Society of Heating and Ventilating Engineers, vol. I. HEAT GIVEN OFF FROM RADIATING SURFACES. 89 TRANSMISSION OF HEAT, STEAM TO WATER, IN B. T. U. PER SQUARE FOOT PER DEGREE DIFFERENCE OF TEMPERA- TURE PER HOUR. Weight of Water per ' Square Foot Mild Steel, Very Smooth Surface. Thickness, Inches. Cast Iron. Thickness, Inches. per Hour, Pounds. O.OI O.I 0.5 1.0 O.OI 0.1 0.5 1.0 1000 2000 3000 4000 417 476 536 597 656 368 422 475 527 582 242 277 312 347 383 171 195 220 245 269 252 288 324 360 397 228 261 294 327 363 164 187 212 236 259 121 139 156 174 191 Mild Steel, Rough Surface. Thickness, Inches. Brass. Thickness, Inches. O.OI O.I 0.5 I.O O.OI 0.1 o.S 1.0 1000 2000 3000 4000 416 462 509 55S 610 368 409 450 491 532 243 26g 297 324 350 170 189 208 227 24s 487 557 629 700 772 427 489 551 613 675 274 314 353 393 431 190 218 246 274 301 is so small as to render insignificant the extra resistance caused by different kinds of metals, such as cast iron or wrought iron of different thicknesses. 48. Methods of Testing Radiators. — So far as the writer knows, no standard method has been adopted for use in the testing of radiators, and while numerous tests have been made by different engineers and experimenters, they are often not concordant either as to the method of testing or as to the re- sults obtained. The results in the testing of radiators are greatly affected by small variations in temperature, by irregu- lar air-currents, and by the amount of moisture contained originally in the steam. Obscure conditions of little apparent importance and often disregarded greatly influence the results. The heat emitted by the radiator is in all cases to be computed by taking the difference between that received and that dis- charged. This result is accurate, and easily obtained. This heat is utilized in warming the air and objects in the room, and to supply losses from various causes, which take place constantly; it is diffused so rapidly, and used in so many 90 HEATING AND VENTILATING BUILDINGS. ways, that it is practically impossible to measure it, although it is, of course, equal to that which passes through the radiator. The radiating surface is almost invariably heated either by steam or by hot water. In the case of a steam radiator the heat received may be determined, by ascertaining the number of pounds of dry steam condensed in a given time, multiplying this by the heat contained in one pound of steam, and deduct- ing from this product the weight of condensed water, multi- pHed by its temperature. To make a test of this kind with accuracy requires, first, a knowledge of the amount of moisture contained in the original steam ; second, the pressure of the steam or its temperature; third, an arrangement for permitting Fig. 29. — Radiators Arranged for Testing. water of condensation to escape from the radiator without the loss of steam, and means of accurately weighing this water, and also of determining its temperature. The radiator can be located in any desired position in the room, on the floor, or slightly elevated therefrom. The temperature of the room during the test should be maintained as nearly constant as possible, and no test should be less than from 3 to 5 hours in length. The method adopted by Mr. George H. Barrus in making a radiator test is shown in Fig. 29. The one adopted by the author, in many respects similar, is shown in Fig. 30. In some recent tests of steam radiators made at Sibley College * the author adopted the following plan of operation * See Transactions vol. i., American Society Heating and Ventilating En gineers. HEAT GIVEN OFF FROM RADIATING SURFACES. 91 for measurement of the heat discharged and for operating the radiators : First, the steam supplied to the radiator to be passed through a separator and a reducing-valve to remove entrained water and maintains a constant pressure during any given run. Second, the amount of moisture in the steam to be measured by a calorimeter, and corrections made to the result for the entrained water. Third, the pressure and temperature of the steam in the radiator to be measured by accurate gauges and thermometers. Fourth, the amount of heat passing through the radiator to be obtained by weighing the condensed Fig. 30.— Radiator Arranged for Testing Steam, measuring its temperature, and computing by this means the heat discharged. Fifth, the air from the radiator to be effectually removed. Large errors are caused by leaving varying amounts of air in the radiator. The ordinary air-valve is often very unsatisfac- tory for this purpose ; if used, it must be closely watched, of the results may be seriously affected. . The heat supplied was computed by knowing the weight, the percentage of moisture, and the heat contained in one pound of steam. Various methods were tried for drawing off the condensed watefr : in some tests a trap was used, but better results were obtained by employing a water-column with gauge- glass and drawing off the water of condensation by hand, at 92 HEATING AND VENTILATING BUILDINGS. such a rate as to maintain a constant level in the glass. To prevent loss by evaporation, this water needs to be received either into a vessel containing some cold water, or else into one with a tight cover, the latter being generally preferred. Methods of Testing Indirect Steam Radiators. — For this case the general methods of testing should be the same as those previously described, and in addition the volume of air which passes over the radiator should be measured; also, its temperature before and after passing the radiator. For meas- uring the velocity of air the most accurate instrument at present known is the anemometer, which has been described and illustrated in Article 30, page 40. In measuring the veloc- ity the anemometer should be moved successively to all parts in the section of the flue, and the average of these results should be used. The velocity in feet per minute multiplied by the area of section in square feet should give the number of cubic feet. The number of cubic feet of air heated can also be computed, as ex- plained in Article 30, page 40, by dividing the heat emitted by the radiator by the prod- uct of specif7C heat of air and increase in temperature. The heat which is ab- sorbed by the air can be com- puted by multiplying that required to raise one cubic foot one degree, as given in Table X, by the total num- ber of cubic feet warmed mul- FlG. 31.— Et.EVATION OF APPARATUS. 4.- r J U tU • ■ l. •^ tiplied by the mcrease in tem- perature. Fig. 31 shows an arrangement adopted by the author in testing indirect radiators, the air-supply being measured by an anemometer not shown. Testing Hot-water Radiators. — The amount of heat trans- mitted through the surfaces of a hot-water radiator can be determined in either of two ways : first, by maintaining circula- HEAT GIVEN OFF FROM RADIATING SURFACES. 93 tion at about the usual rate, measuring the temperature of the water before entering and after leaving the radiator; also, measuring or weighing the water transmitted. The heat trans- mitted would be equal in every case to the product of the weight of water, multiplied by the loss of temperature. In making these tests the same precautions as to removing the air from the radiator must be adopted as in testing steam radiators. These radiators can also be tested by filling with water at any desired temperature and noting the time required for the water to cool one or more degrees. In this case the iron which composes the radiator would cool the same amount, and a correction must be added. The easier way to correct for the metal composing a radiator is to consider the weight as that of the water increased by that of the iron multiplied by its specific heat. The specific heat of wrought iron is, practically, i di- vided by 9; that of cast iron, i divided by 8; hence for a cast- iron radiator the effect would be the same as though we had an additional amount of water equal to -J of the weight of the radiator. In the practical operation of this test the water in the radiator must be kept thoroughly agitated by some sort of stirring device. 49. Measurement of Radiating Surface. — The amount of radiating surface is usually expressed in square feet, and the total surface is that which is exposed to the air, and includes all irregularities, metallic ornaments, etc., of the surface. Where the surface is smooth and rectangular or cylindrical it is easily measured, but where it is covered with irregular projections the measurement is a matter of some difficulty and uncertainty. The only practical method of measuring irregu- lar surface seems to be that of dividing it up into small areas and measuring each one of these areas separately by using a thick sheet of paper or a bit of cord, and carefully pressing it into every portion of the surface. The sum of all the small areas is equivalent to the total area. This method is at best only approximate, and even when exercising the utmost care different observers are likely to differ three or four per cent in their results. The writer has tried several other methods of measuring surface, but so far without 94 HEATING AND VENTILATING BUILDINGS. marked success. One method, which promised good results, was to cover the whole surface with a thin paint and compare the weights with that required for covering one square foot of plain surface. This method proved even more approximate than the other, and had to be abandoned, as the paint was not of equal depths on all portions of the surface. The total contents of the radiator in cubic feet can be easily determined by filling it with a weighed amount of water of a known temperature and dividing the result by the weight of one cubic foot. The volume displaced by the whole radiator can be determined by immersing it in a tank whose cubic contents can readily be measured. The difference between the cubic contents when the radiator is in the tank and when taken out is the volume of the radiator. For this test the openings in the radiator must be tightly stopped. The same method applied with the radiator immersed in both cases ; but in one case with the radiator filled with air and the other with water would give as a result the, water displaced by the metal actually used in the construction, or, in other words, the cubic volume of the metal. This could no doubt be more accurately obtained by dividing the weight of the metal by the weight of one cubic inch or cubic foot. These methods give accurate means of measuring the total external and internal volume of the radiator, but not the surface. 50. Effect of Painting Radiating Surfaces. — In the ex- periments of P^clet which have been given in Article 46 the effect of different surfaces has been fully considered. From these experiments it would appear in a general way that the char- acter of the surface affects the heat given off by radiation only, and not that given off by convection. In ordinary cases of direct radiation, because the surfaces are closely massed to- gether, the radiant heat does not probably exceed on an aver- age 40^ of the total emitted, and is nothing in indirect heating. From the experiments quoted, on page 84, it would appear that if we consider the radiant heat given off as 100 from a new sur- face of cast iron, that from wrought iron would be 87, from a surface coated with soot or lampblack 125, from a surface with a lustre like new sheet lead 20J, from a polished silver surface \l^. These results make very much less difference, when ap- HEAT GIVEN OFF FROM RADIATING SURFACES. 95 plied to total heat emitted, since the total radiant heat is only a small portion of the whole heat given off. Calling the radiant heat as 40^ of the total, we should have the following numbers as representing the heat emitted from various surfaces : Cast iron, new 100 Rusty surface 102 Wrought iron 93 Bright iron surface 72 Dull lampblack 106 White lead, dull 106 The writer had some experiments made in Sibley College, the results of which showed that the effect of painting was to increase the amount of heat given off. It was found that two coats of black asphaltum paint increased the amount 6^, two coats of white lead 9^. Rough bronzing gave about the same results as black paint. On the other hand a coat of glossy white paint reduced the amount of heat emitted about 10^. 51. Results of Tests of Radiating Surface. — The results of the experiments of P^clet have been given quite fully, and they will be found to agree well with best modern tests when the conditions are similar. The radiating surface ordinarily employed for steam or hot-water heating consists of a number of pipes closely grouped together so as to occupy as little space as possible. In some instances long coils or series of parallel rows of pipe are employed arranged horizontally, but ordinarily the pipes are vertical, and grouped together in two to four rows. The usual height of radiator is 36 to 40 inches with the bottom placed about 3 inches from the floor, making the actual height of radiating surface about 3 feet. In some instances radiators are lower, in which case the results per unit of surface are considerably increased. The value of a radiator in which the surface is grouped so as to prevent the free escape of radiant heat will depend largely upon the effectiveness with which the air-currents strike the heating surfaces. There is a tendency for heated air to move in a vertical current in contact with the radiator surface, and thus to keep the upper portion in a very hot atmosphere, which has the effect of materially lessening its efificiency. The prac- tical effect of these restrictions is to reduce the heating power of radiators which are composed of a large amount of surface 96 HEATING AND VENTILATING BUILDINGS. closely grouped. The following summary of a series of radi- ator tests made by J. H. Mills shows that with very small radiators the results are in practical accordance with those of Peclet's experiments, but as the radiators increase in size they fall off about in proportion to the loss of effective radiat- ing surface. B. T. U. per Sq. Ft. per Hour per Degree Difference of Temperature. Sq. Ft. of Radiating Surface. Difference of Temperature. Peclet's Formula. Actual. lO 155 1.86 2.10 20 150 1.84 2.08 30 158 1.87 2.06 40 175 1.92 1-75 50 155 1.86 1-73 60 165 1.89 1.67 The following experiments were made by Tredgold * for the time of cooling of water in vessels of various kinds. The writer has reduced the results to heat-units given off per square foot of surface per hour. SUMMARY OF TREDGOLD'S EXPERIMENTS. Material Cooling^. Material of Radiator. ■0 "o % % I' Sis Heat-units Emitted per Sq. Ft. per Hour. Total Heat- units. Per Deg. Diff. Temp. By Peclet's Formula. Hot water.. Tinned iron cylinder 180 SS-5 124.5 255 1.43 1. 17 Hot water... 11 (. Glass Wrought-iron block Rusly wrought iron — ■ 180 180 180 56-5 S7 57 123-5 123 123 426 434 486 2.37 2 41 2.70 2.36 2.36 2-5 Prof. C. L. Norton, Boston, Mass., reported in Transactions of American Society of Mechanical Engineers, 1898, that the heat transmitted from a body of hot oil was proportional to the following numbers : Coated with cylin- der oil 116 Painted dull black 120.5 Painted glossy " 101 Wew pipe 100 Fair condition 115 Rusty and black. ... 118 Cleaned with caustic ' potash 1 18 Painted dull white 115 Painted glossy " 100.4 Cleaned with pot- ash 115 * Tredgold's Warming and Ventilating of Buildings, second edition, pages 56 to 60. HEAT GIVEN OFF FROM RADIATING SURFACES. 97 The following table is abstracted from one published in " Warming and Ventilation of Buildings," by J. H. Mills: to i-i < w < f-i •z u ...» -- O a o O 5 Id W M K < < H 2 I W f a: So cfl oj o ■jiy puB toEajg Oi w « » moo -*- N 13. t> *O00 VO m (V ■* m t> M BiQ aajSaa _^0O-^'* \OCT\ONtn tsOO "O VO O-OO ut£. « -ifOCO 0>O t^t^t, row jad s)iun-)Baxi ci « ei H H M M M H H M ciHMcicHMciciHciHMHMHMC) •JH Jad ■J.i bg jad pasnapuo3 (^ -j- fo rrj « « « m « N c* « rrmmrn^ci N mrow rO« «n « M Mm aajEja JO sqT • OS ' NW« «««NNMN« « CO N 00 m moo m 00 c 00 m >■- "*oo moo oo Q 3"* "* ■* "^ ■*■«■■*■*■* •"! .0 li .»o ^ ^O ^o vo i/i u^ m m^o \Q 10 10 10 m m 3 tj g 1- uRg-g. R8.g.g.g.g.g.a 000 iN»n«ot^O« OtnrO'+OmO 1 < O OS t- t^« vo \o \o vo tN t^ ^N two "O t^ t>. o. r- t>. B NMN (N«C)NClP4(HCj woo 000 Ooooooooooo ooooooooooooo e« f^^NN nSmNNWNC^ (M«mrO«m«MNNNm«NWNNN s ««W(S«NN««NNn«CTW m ■w ii .§.-2 .s -s Sm s S l= = a J2 c +J a 8 V u^^ io\o a 4;^ S rt W M W C wi ja i> 1 S V T3 C ,d°- - s i^^i a i" ^A ^ 1 : X %'. : "T' 0?" o « u ^^^ 4j 1 a 1 ^ ^-^ 5 5 3 '^J-r- ; 1^ - H « fO ".2 c'xS 05 pipej i", loo' in a single 3" diameter outside, 5' lo ipe, S. Williams ; core 3" linders _ _ r TJ art u 0- oj ^ y u '• 1 "^ c ' h circulatior 4- branch ci y diam., 2 diator i" di or, Walwor c, 29" high ing Iron Co iator, 10 sec if c II! c t-iron pipe 3" diam., in single 3Hght-iron pipe 3" diam., in sii =1 pipe 4" diam., in single line ss i" horizontal pipe ; 4-branc! 3Ught-iron, i" horizontal pipe, in brass vertical tube-radiator rugated brass vertical tube-ra tical wrought-iron tube-radiat nion " radiator, cast iron, 6 se. riumph '* radiator, A. A. GrifB rce '* Excelsior " cast-iron rad rt " radiator, cast iron, 6 pane roit Radiator Exeter Machine grle bar of Gold^s Pin Indirect ivard Oxbow Radiator, 2 loops cription of heati n wrought-iron n cast-iron pipe bed cast-iron pi cylinders, i" cy bed cast-iron pq n cast-iron pipe bed " 'f ved rib cast-iroi -radiator, cast i tical cast-iron ri c3ti:iJ2iJ3o5 PH'S<- 5.S0 z> 981 >D 3S BN"I ^■i " '8 S8 I * SI I! n 1 4 •f 98 HEATING AND VENTILATING BUILDINGS. The following table gives the abstract of a large number of radiator tests made under the supervision of the author : * Name or Kind of Radiator. W. I. vertical pipes W. I. vertical pipes, Nasoo . W. I, hot water, Western No, 2. W. I. steam. Western No. z Steel, hot water. Western No. 1 . Steel, steam. Western No. x Cast iron, Bundy " " Bundy filite «C (1 (t " " Reed., Royal Union,, Perfection Steam Perfection Hot Water. Ideal Steam " " " Hot Water " " National Steam " " Whittier Ex. Surface. " " Michigan Indirect 2-inch pipe, single, horizontal . , i-inch pipe, single, horizontal., Dimensions. 53-6 47-94 41.19 43-33 45-13 79 41.8 48.7 49,12 52.81 49-9 48.17 40,2 48 40 38.65 58.2 Tests of Kelsey & Jackson. o u v.- sgfS s e «; 94 90 146.6 9' 89 150 91 140 ) Fntering- steam \c) Condensed water , (4) Inside radiator (e) Outside radiator Steam-pressure, absolute, pounds Degfree of superheat (degrees Fahr.) Total heat per lb. of steam, B. T. U *' " *' condensed water,B.T.U. " " " radiated, B. T, U " radiated, B. T. U '* " per hr.per deg., B. T. U. " persq. ft., B. T. U .. 29-59 86.75 216.3 216.3 87.60 248.4 218.8 211. 1 213.2 207.5 16.01 208.3 16.8 liTg.i 29.6 1162.8 J84.9 187.5 934-2 539° 975-3 5580 4I-5S 34-74 . I •4°5 ■ .173 91.46 277-4 221.4 213.2 209.6 17-65 56.0 [176.3 190. [ 986.2 5585 30.0 1. 014 91.80 307-7 219.8 217.0 213.6 17.14 87.9 1191.0 188.5 1002.5 5295 24-5 0.82- 87.90 326.0 221.1 218.6 213-7 17.56 104.9 1199.5 189.8 1009.7 5760 24.22 0.819 96.0 346.2 221.9 219. z 213.2 17.85 124.3 1209.1 190.7 1018.4 S432 21.7 0-734 The above table shows the results of a series of carefully- conducted tests made by the author, giving the results of sup- * Test by Denton & Jacobus, July, 1894. lOO HEATING AND VENTILATING BUILDINGS. plying steam of different degrees of superheat to a cast-iron radiator containing 29.6 square feet of surface. The entering steam was superheated by a gas-furnace as desired. By com- parison of the degree of superheat with the final results it will be noted that the heat transmitted per degree difference of temperature fell off materially with increase of the degree of superheat. Temperature readings taken from a thermom- eter inserted immediately inside the radiator (^) indicated no superheat, although the small condensation warrants the opinion that the steam in the central portion of the radiator was superheated. A thermometer {/) was fastened in contact with the outer surface of the radiator and protected as much as possible from loss of heat by hair felt. This thermometer read about 3.5 to 5.5 degrees less than the inside one, thus indicating an error in that method of taking temperatures of a radiator surface, as it is probable that the surface was at the same temperature both inside and outside. The following tests made on cast-iron steam-radiators of different dimensions by the author are interesting as showing that the heat transmission is lessened by increasing the height or the thickness o-f the radiator, and increased by diminishing the distance between the sections or parts. TESTS OF CAST-IRON STEAM RADIATORS WITH DIFFERENT DIMENSIONS. Number of columns Thickness of radiator, Inches Height of radiator, inches Distance between sections, inches Actual surface, square feet Rated surface, square feet Barometer, inches Tetnperature^ degrees Fahr, (rt) Adjacent air, degrees (<5) Entering steam, degrees (£) Condensed water, degrees \d') Difference between steam and air, deg. Steam-pressure, absolute, pounds Quality of steam, per cent Steam condensed per hour, pounds Ditto and per square foot, pounds Total heat radiated per hr., B. T. U Ditto and per square foot Ditto and per degree (actual) B. T. U Ditto and per degree (rated) B. T. U TB 29.60 30.00 29.59 86.75 216.3 216.3 129-5 16.01 97 5-77 ■195 5390 182 1.405 1-385 35 A 39.82 42.50 29.37 86.27 221 .20 22 1. 20 134-9 17.60 99 g.8i -245 9320 232 1-733 1.624 35 3-4 51-73 55.00 28 94 89-53 222.28 222. 28 132-74 1797 98-5 12-54 .242 11,840 . 229 1.725 1.622 14 3-8 36-59 50.00 29.93 81.77 224.59 224.59 132.82 18.79 99 7.92 .217 7515 207 1.549 1. 132 36 1.2 49-9 52.00 28.94 79.6 223.7 180.3 144. 1 18.4 97-9 10. s .21 10,308 207 1.43 1.38 «-5 36 li 49.1 49-5 28.94 79-3 223.8 184. 1 144.6 18.5 96.7 12.4 - -253 12,282 250 1.72 1.71 HEAT GIVEN OFF FROM RADIATINC SURFACES. lOI W IT) O CO o vnoo N C« T^ m ^ lo en C<^ -j-OO CO i-H M M QioO M O ^ O to 00 00 in M to « O « lO t** en Tj- m CO CO oraoo OMio^cf) wt^cno mmo^mto c* M M M M at o^ t^ c< c^ o o o O CT- N CT>00 H. vo cnoo OO c> cn e* o i-i M O 00 o^vD m m W W M Qi N M li^ N CO r>. O ^00 CO ^ CO en Ttco r^ M iH H o^ r^ w O r^ H M o O O M N IH VO •^o en CO C>OD 00 tH CO lO N O vO 4oO -^ -^vO M CO W O^ CO W -^ 1-1 OO CO d Tl- M CO W •^ C^ Tl- O i-i H M M o^ a« M H H PI W O eO CO M t-^ CO CO O r^ t^ r^ N c^ in w w M o CO M J3 f"^ •o £ 3 ba o c a. 3 lu o U g HI ^ 15 o In w aJ bfi U 3 U L, L- n 4-1 " 'r'r'2 4J «i C tH V :^ w '^H 1 C"* bet: be etf ^ rt J3 > QJ << > 1 o o < (4 (d - o u O ol cS u 3 3 J3 a" C ^ to ui V u o - EH ft " J^ 2 2 S o ■- -- HQQ n to " o T3 >r) S-O rt C I- d O u . CIS -w M-t *«-l iH . 3 cr w en .— I o « m p (U (1> nl M-i u 3 n! [A a ,__ cr C^J M ■-I u o C J) ■- u 3 3 S " o N <-> IH .S d C •3 2 •a 4-1 4-J .3 "^ T3 m rt a. >- o 0.0 o £ t* . c c'> p cS CT3 B 2 •a c ■a y - O g o-O o 9 nl (rt " O. a. " T3 « "^ 1 3 .™ cn iH — 3 c4 (n 3 „ « 2 11 rt " 3 M O- bo bJS .5 > J, "1 cfl C .2 d n; o d o o 01 1-. s - o S c.i: •« 1- «■ bo C4 o::; ■ JL (J w C I02 HEATING AND VENTILATING BUILDINGS. The wall radiator, which gives the highest results in the above series of tests, was placed about four inches from a wall and was about 21 inches in height by 54 inches in length. Its efficiency is about the same as horizontal pipe surface. The following table is of value as showing the relation be- tween coal consumption and temperatures of water and air in a hot-water heating system. CONDITIONS OF TEMPERATURE, CIRCULATION, AND COST OF WARMING WITH A DIRECT WATER-HEATING APPARA- TUS AT DRAPER HALL, ABBOT ACADEMY, ANDOVER, MASS., 1890, BY J. H. MILLS. .\verage Temperatures Fahre nheit for 24 Hours. Cost of Coal for at $6 per ton of 24 Hours, 2000 lbs. Date, 1890. Diff.Air Outside Inside. Flow Return Mean Loss. and Lbs. Coal per Per 1000 Water. Water. Water. Day. Cu. Ft. Feb. 24 36° 7-"' 187° ISO" 168° 37° 97° 1600 $4.80 8.6 mills " =5 39 71 196 162 '79 34 108 1250 3-75 6.8 " " 26 39 70 133 -36 159 47 89 1550 4.65 8.4 " " =7 40 71 ■83 14s ,64 38 93 '45° 4-35 '•9 !. " 28 39 6, 172 124 148 43 79 ITOO 33° 6.0 " Mar. I 39 70 175 1S3 164 42 94 I I 50 3-45 6.2 " " 2 26 64 169 131 150 38 86 I I 00 3-3° 6.0 " 3 20 69 188 153 170 35 101 1650 4 95 9° 'i 4 21 68 178 141 159, 37 9' 1500 4.50 8.1 " 5 37 69 181 147 164 34 95 1400 4.20 7.6 ■' " 6 20 66 187 150 168 37 102 1650 4-95 9.0 " " 7 II 63 191 150 170 41 >07 I goo 5 -70 I cent 8 i3 65 183 145 164 38 99 1850 5-55 I " !' 9 22 57 157 138 147 '9 90 1050 3-'5 5.7 mills 10 24 67 172 135 163 37 96 1400 4.20 7.6 ■• *' II 39 70 1S2 144 '63 38 93 1300 3.90 7.0 " " 12 40 70 157 127 142 3° 72 900 2.70 S.o " !! '3 42 ^3 157 120 138 37 75 750 2.25 4.° ! 14 40 65 161 131 145 28 80 750 2.25 4.° " ! '1 37 57 155 125 l^o 30 S3 650 '•95 3-5 !! " 16 34 60 15° 114 132 36 72 700 2.10 3-* " '7 19 6t 172 141 156 3' 95 1050 3-'5 5.7 " " 18 35 61 156 123 '39 33 78 1200 3.6° 6-5 " '' 19 =S 61 168 128 148 40 87 1400 4.20 7.6 " 20 28 ^3 160 127 '43 33 80 1200 - 3.60 6.3 " *' 21 34 69 157 127 142 30 73 goo 2.70 50 " ** 22 37 67 155 125 140 30 73 900 2.70 5-0 " 23 35 67 155 130 132 25 6s 600 I 80 3.2 " 24 =4 60 156 129 '37 37 77 J200 3.60 "i774~ 6-5 " Average ~^" 65° 170° 136° 153° 34° 87° I2IO 6.8 mills The building is of brick, four stones above the basement, and contains g6 sleeping- and study-rooms, 12 music- and 24 public rooms; total, 132, besides basement. Contains 553,000 cubic feet space; exposed wall, 17,478 square feet, and 5236 feet glass. The heating apparatus consists of two Mills 14-section No. 5 boilers set in battery. Com- bined fire-surface, 936 square feet, with 25 square feet of grate. Third boiler runs dynamo. Heating-surface to boiler, i to 7J. Distance from boiler to last radiator, 385 feet. Main supply-pipe, 7 in. ; vertical supply-pipes, ij in.; connections to radiators, \ in. Radiating surfaces— one hundred and forty Royal Union radiators = 5000 square feet; indirect Golds' pin, 450; pipe surface, 1550; total, 7000. Radiating surface to space warmed, I to 79. HEAT GIVEN OFF FROM RADIATING SURFACES. IO3 RESULTS OF RADIATOR TESTS WITH SUPERHEATED STEAM. Radiator No. i. Height, 18". Measured surface, 38.6 sq. ft. Least distance between sec- tions, i inch. iJo. of Pressure. Temperature Air. Degrees. Temperature Steam. Degrees. Degree B. T. U. per Hour Pounds of Sieara Con- Test. Lbs. Superheat. per Sq. Ft. per Degree. densed per Hour. 6 2 71.3 217.0 1.48 6.25 5 2 77.1 217. 1 •13 1.50 8 13 4 2 74.0 252.8 35.83 1. 16 7 88 7 5 70.2 239.0 13.10 1.41 9 18 3 5 75-5 252.7 24.10 1-23 8 3« 2 10 72.5 264.7 20.70 1.24 9 18 8 10 75.8 238.4 ■30 1.50 9 25 I 30 74-1 274 5 I. 10 1.83 14 07 Radiator No. 2. Height, 38". Measured surface, 49.1 sq. ft. Least distance between sec- tions, \ inch. 6 2 73-5 217.0 1.88 - 13.00 5 2 80.3 217. 1 •13 1.92 12.75 4 2 77.0 252.8 35-83 1. 41 12.75 7 5 73-5 239.0 13.10 1.74 14.16 3 5 76.7 252.7 24.10 1.45 13-12 2 10 74.2 264.7 26.70 1.62 15.00 8 10 77-3 238.4 •30 1. 91 15.16 I 30 76.8 274.5 1. 10 1.97 18.94 52. Tests of Indirect Heating Surfaces. — The tests which have been made on indirect heating surfaces show very great difference in results, varying from those given by Peclet for the loss due to convection alone, to results which are 8 or ID times as great. This difference in result is no doubt due in each case to the velocity of air which comes in contact with the surface. When the indirect radiators are not freely sup- plied with air, or the velocity is low, the amount of heat which is discharged is small ; when the velocity of the air is high, the amount of heat taken up is proportionally greater. According to experiments made by the writer, the coefficient of heat transmission increases as tke square root of the velocity of the air. The amount of air passing over a given surface of the radi- ator can be estimated quite accurately by the amount of heat given off, which we can rea.sonably suppose in this case to be I04 HEATING AND VENTILATING BUILDINGS. all utilized in warming the air. At a temperature of about 60 degrees, I heat-unit will warm 55 cubic feet of air i degree (see Table X), so that the number of cubic feet of air warmed is equal to 55 times the total number of heat-units given off from i square foot of heating surface per hour, divided by the difference of temperature of entering and dis- charge air. NOTE- — Let T = temperature discharge air, f that of entering air, H = total number of heat-units given off per square foot of surface, a the number of square feet of surface- Thien, Cubic feet'of air per square foot heating surface = -r^^^ — -pr . The following tests, made under the direction of the writer, give actual results obtained in testing steam-pipes in a current of air moving at different velocities : SUMMARY OF RESULTS.— TEST OF 2" STEAM-PIPE WITH BLOWER- Steam- pressure by Gauge - Average Difference of Temperature of Steam and Air of Room. Velocity of Air Passing over Pipe. Feet per Second. Heat Transmis- sion in B. T. U. per Square Foot per Hour for each Degree of Temper- ature. Increase in Temperature of Air, Deg. Fahr. Cubic Feet of Air per Sq. Fl. per Hour. Cubic Feet of Air per Sq.Ft. per tain- 4-45 5-09 5-38 5.86 5-27 5-15 123.72 120.30 113.68 113.44 119.32 116.20 9.8 9.4 4.1 4.5 6.7 5-5 6.32 6.37 4.29 4-72 5.46 5-46 26.7 28-4 42.0 42-4 34-9 37-4 148 142 63 69 102 83 27 25 11 12 16 15 5-20 117.77 12-48 13-70 I2-IO 12-25 13-73 13-55 134.29 132.73 127.84 125.75 125.93 122.87 7.1 6.7 6.0 5-5 4-3 4.4 5.53 5-19 5.24 5-19 4.53 4-99 35-9 37-3 40.9 43-1 48-3 51-4 112 10 1 91 83 65 66 19 17 15 14 11 II 12-97 128.24 25-35 27.10 27.54 28-21 27.10 26-70 157.05 158.27 153-70 153-28 146-68 147-19 8-6 9-1 6-7 6-3 4-3 4.6 5-67 5.91 5-36 5.41 4.20 4.61 37.1 37-7 44-8 45-4 52-6 53-7 130 136 lOI 100 65 70 22 23 17 17 II 12 26-97 152.69 HEAT GIVEN OFF FROM RADIATING SURFACES. IO5 EXPERIMENTS ON INDIRECT RADIATORS. «■ Names of Radiators, En^ineers^ and Dates of Experiments. jT Tempera- DiSE. h 3 tures Temp. tX ■0 c r< ■3 u a S 5< I 2IS 160 160 215 I 215 ■56 156 2I,S I 215 13s 135 215 I 21 S 147 147 215 60 10 2sg 71 168 Q7 I6B 60 lO 239 7' 170 q8 .67 70 .1 222 42 145 103 180 40 S 227 31 142 lOQ IQ4 60 5 227 78 162 84 139 CO Ott- rtTJ o 4J o Units of Heat. f Gold's pin C. B. Richards,; Novelty 1873-4. 1 G. Whittier.... [pipe coil W. J. Baldwin, J Gold's pin 1885. ( Compound coil. W. Warner, 1S80, Gold's pin J. H. Mills, J Walworth 1879. (Mills. 5 44 509 100 Cubic Feet of Air per Foot per Hour. Average. 5.00 4.08 1.58 1.48 1.28 1.42 1.42 1-43 1.60 1. 61 1. 71 1.50 Dr. Gray, 1875, Gold's pin. J. R. Reed, 1875, -i hittier fGold's pin. C. B. Richards, J Novelty ... 1873-4. I G. Whittier. l,Pipe coil . .. 90 20 2,9 33 12, 92 226 68 3 222 45 129 84 177 I 215 139 139 2IS I 215 132 132 215 I 21, 102 102 215 I 215 106 106 215 6.54 5-°9 9 15 8.70 6.66 6.98 200 Cubic Feet of Air per Foor per Hour, Average. J. R. Reed, i875. Whittier G. Whittier Gold's pin fGold's pin C. B. Richards, 1 Novelty 1873-4. I G. Whittier [Pipe coil J. H. Mills, 1876, Gold's pin W. J. Baldwin, J Gold's pin Nov., 1885. I Compound coil.. 68 3 222 .52 no S8 170 5 68 3 ■^22 .';2 114 62 170 5- 58 3 222 S2 127 75 170 7 I 21., 129 129 215 12 I 21, 121 121 215 ri 1 21, 87 87 215 8 I 21, 89 8q 215 8 76K TO 239 Si 159 78 1,8 8 60 5 227 82 i=;o 68 145 8 60 5 227 82 ■52 70 145 8 300 Cubic Feet of Air per Foot per Hour, Average. 336 1. 81 1. 8a 2.66 2-53 1.94 2.03 2.13 2.1s 2.91 3.68 3.46 2.48 2 SI 3-36 3.52 3-52 2.96 J. H. Mills, 1876 W. J. Baldwin, 1885. C. B. Richards, _ 1873-4- Gold's pin Gold's pin Compound coil. Gold's pin Novelty G. Whittier ,Pipe coil 76?^ 10 239 90 158 67 148 60 227 7° 137 67 1,8 60 227 70 13s ('5 158 215 121 121 215 215 III IIS 215 21'; 77 77 215 215 76 76 215 8.91 8.93 8.40 15-92 14 86 10.14 10.02 376 3-55 3-34 4-63 4.32 3.95 2.91 400 Cubic Feet of Air per Foot per Hour, Average. J. H. Mills, J Gold's pin., 1876. I Walworth . , 77 6 230 67!^ 6 230 70 142 10.04 142 54 142 8.88 500 Cubic Feet of Air per Foot per Hour, Average. J. H. Mills, ( Walworth . * ' ( Gold's pin. 1876. 85 20 259 go 160 70 169 13.69 20 259 go l66 76 169 15.16 600 Cubic Feet of Air per Foot per Hour, Average. 643 I. H. Mills, ( Walv 1876. I Gold s pin,. 8S 76!^ 142 52 132 II. 61 145 55 132 12.54 3.64 4.42 3.gl 5.06 5 61 5-50 5-94 700 Cubic Feet of Air per Foot per Hour, Average. T. H. Mills, ( Gold's pin I 77 I 5 227 94 145 51 13313.43 1876. tNason I 85 I 7m 23 3 I 79 135! 56 I iS4i,'i-3° ~ 800 Cubic Feet of Air per Foot per Hour, Average. * From John H. Mills' work on Heat, by permission. 6.31 6.21 6.26 io6 HEATING AND VENTILATING BUILDINGS. Q < o < »— I Q < H u Id . p: Q < Pi W H O in O a, O o ,ti 4J at .3=8 1, OJ 0) ^ fe ■ ■l^?oi o h u USQ OIJOJ •D3S Jad Id ■JiV WH JO Xl 100(3 A WE 5f^ ■3 -J •aiv ■JIV PIOD pnE JO mB3is 2| a ■ B •aoEjjng JO 133jI ajBnbg fe cd u ■"" cx •o « a g-S 3 Q- ,0 ■ '<, « aj ." rt >»<; j3 •a s > I- u I- *j o S.S. t«tM rt ^ o j; a: 8 N\0 n r^ « m T^oo r- O-O^ t^ " " " " " N "" " N M t> 8 (T. H « w k>j W T O-CO -O t^CO ■* M I r- M PI H ■-• .oo m I m in i>,^o f- S 3 31 ^j = ■0 .. O O t" c "^ O O S'O o , ^ i 2 ^ o oi « Ml iSC^.E U CU »_ - — c a OS CQ 00 S 10^ « __, -ooi— ^ -§so .00 M .00 00 mmmo (^. h _. ooominOOC? O >n O tv'O 000 rooo cnt» m ■^r o "«i- w lo M fn r«. M \0 N vo 0> t«. * r^ ^ in "^ 00 in m m "^ s OCO 0.CO o>oo i a's. 00 fn 11 N IsqjCojCajn v o ^s» \ a V '^ V ^ V I S (/) > M P «J 15 E 'S-a oooo.S.S M.5 Si, SbSSSCOBSK < S 9 flj 3 , •3Dll3J3ja'a joj -CM t- uTO ^~oo O* ' I m * mvo (^00 Oi HEAT GIVEN OFF FROM RADIATING SURFACES. lO/ Tests of Blower Systems of Heating. — The heat given off from an indirect radiator over which the air is forced by a blower or fan varies with the difference in temperature be- tween the steam in the pipe and the surrounding air, with the velocity of air, and with the number of rows of pipes over which the air passes. A series of tests were made under supervision of the author by blowing air over an indirect heater, consisting of eight sections, each section containing four rows of one-inch pipe and 180.85 square feet of heating surface, and arranged so that one or more sections could be employed as desired. During each test air was drawn by suction through the heater or radiator by a blowing-fan hav- ing a wheel 4 feet in diameter, driven by an engine. The principal portion of the test was made with the fan revolving 400 turns per minute, and so as to give a peripheral speed to the tips of the fan-wheel of 5026 feet per minute. The speed of the air approaching the heater was for the most part 473 feet per minute, but between the coils its speed was about 1250 feet and in the discharge-duct 2900 feet per minute ; its temperature on entering was about 70° Fahr. The tables following give the data and results of the various tests expressed in B. T. U. per square foot per hour per degree difference of temperature between the steam and the entering air and between the steam and the mean temperature of the air. The tables also give the probable B. T. U. per square foot per hour for the entering air at 0° Fahr., this amount being calculated from the results of the test by application of the well-known physical law that the heat transmitted varies almost exactly with the difference of temperature. By divid- ing this latter quantity by the number of heat-units latent in one pound of steam, as shown in a steam-table for the required pressure, the weight of steam that would be condensed per square foot of heating surface per hour is obtained as given in the tables which follow. A general table given on page 1 10 was computed from the average results of the tests by application of well-established physical laws. io8 HEATING AND VENTILATING BUILDINGS. vD u^ l^ « vO in & in H 00 m CO O 88S C- (N N vC en I^ M O 6 H. 6 w cno o en en "^ 4 O IH m O^ . M •rt \Ci O ■* u. I^ H O^ Tj- r^ O u^ tn en n" \r, cnsO •^ ■^ -* * w N vO xn ? 00 m en m if* 3 m 00 W N ^ O H w en en iH N oo r-Tj-q 1^ oo ■* m ■* M vO O . M "* cnoo a* Qi t-. w O en M i-^ o ■;; o CO cn N in N »n o^ w -^ 'I- ~' w IH vO o « "o" in •a 00 O m oo in in en 88^ ts. N N -^ in in H vO rt N en 00 en q >-( (M in O w IH m a> . M ■rj- i-i -(^ r^ oo r^ H O' en r^ o „; r-^ in M en n" XT, N m a^ •^ ^ ^ "' M •^ r^ 1-^ T£- CO N 1 o f> r^ O O o o in o oS, « OO M r- w M M C| cnvo o « t^ ■7^ o CO w in vO m M >o o» . \0 u^ o ^ W r- o O en »> <^ in ■^ M C*^ M c i t M en m" H en N ^ •^ -^ ■* w M 3 r^ h-. en r^ »n c^ r- r-^ m in l-l O en o o o CO en 88^ •* 00 M cno 00 H O M N so M en o q. m C^ o r^ en IH in o^ . ^a M ';J- u-1 •"• r^ O OO en r^ O u; r-. vn H en ci en N -* i-T M -t '^ M M in 00 ^S C^ « en o M o oo 8 m en % o oS m in u^ m ■^ O "* « O M ^ m Tj- in O r^ •^° o r^ O r^ oo M •O O . cc »n O C^ l-l vO 00 r^ c* t-- O ^ en N en N M en en _ ^ Tl- "^ w M H »n oo »n in o^ e^ in in o en CO vn in 8^?; ts Th o "^ O ^w ^ \n en ^too en o o. in o ■o VO vO M m O^ . CO cnoo a, H O CO r~~ >~* h-l r^ o lo HI en N M N M 't Ti- M « U-1 N CO O M m N m "o" ITi H a- in C7V M 88^ w Tt O N t-t en M t^ m N en r^ en O o C> CO' r^ r^ vq_ M in a^ , CO 11 r^^O ^ vO 00 r-* H r^ O ,n r> o IH en N w W N ■^ ■* M IH • E : s : 6 oj u ■ u C . 4-1 4-» . *-l Eh . r- tA .in : fe .«tL, bcrt bfl D (i, S J; c " M 4) — ' M-. .if « 1^ 6 « OJ ' a. o tn u OJ j^ -13 dj . " - . w vh to o n:^ cr > QJ _' nj o o " ■= -S rt s c " Is G 1) 1) E . a '^ o! ?i CL -' ill ^^ v o [/i o £ o-a . > „ 10 O *J OJ c a. B 0) an ' : wg. ■ I) ^ .:: be o OJ ;- *J u ?] u I- ~ 1) CL 4J CU ^ 4_l c4 OS Oh 2« 2 sj y N 4-. > o _3_0 _ w en T^ mo r^oo c^ o m e>» en -rj- HEAT GIVICN OFF FkOM RADIATING SURFACES. IO9 a • CO Tf • to « O^N*^ \oO O CO O t^ M o* «*^ iH CO u-»^Q r-^ Ul o CO C^ ^So ' a» t^ M o "1 J e«^ 00 MM ^ '^ : o N [ ^tn o°vO cnMc«^J^ O O . CO Qo ... in 'T CO ^ CO M O^ . Qsco \0 N CO ^_ irj w O M H u^C^^_^0"^^^':J-MvO h'~*Ou-> W l> M M ^ Tj- « « « CO en N O CO C^ c«TO O O cnr--N 0^l>^. enO O «o^ r^ MM ^Tt" ■S^O O CO w .CT'r^coO'O M f^O in Q% M M ■'^ '^ o rt--<:ra'r^MM o O o o-'^r^TfO. a* «o^ o^ MM ■7^r^ ;i o o"?; O Thcnm-^O 00 r^'^O ^, coo N O M '^O OvO cnO>int_i^O CT» w r>. CO M -"^ '^ m *^ "' MM 0) en en : [xh 0) t^H — t- j3 u u 2 . > a = -g 3 " it «; ^■ ■a .^ : B . CIS 0) u 01 " ii u 3 m ,S C ex aj u a u JS ■ IS ts ca ■ <« 3 O M Syuoo«xiO PJ2 S u " S ^ j; M rtl *^ ^ ^ *-' ,a ._ - a— S • a. Ertc«Bi5jiHg 3 u u u o H . u C O 53 l- !fl _, '-^ *;^ U 4-1 " - - a' m w ■■ it: : w iTS . S if o .5 c o H -^ E c tJ - ^ c o Z n ■a o 1- si tii a; v^ _ b/) 1- . - •a o . «j (U ajj a; ; o. o SI 3 ■ «J o 3 „-j: 2 1" "' ■"»,■*" «■, D _vh cr 3 1- n u 1J (L) n) o " u u = S c e : « g .„ bo o aj ^^ *^ o nj i_ 0) ^ -^ rt . .. _ " a. '^ E 4! D.^ ^H^ oi p ts ■5 i;-5 For actual conditions, {x - t")B = c'{T - x)R. (2) Dividing (i) by (2), t'-t = c{T-t') x-t" c\T-x) ^^' When /' = 70, 7" = 220, ^ = o, and c = 1.8, we have T .(If^) . 3.S6. The coefficient of heat transmission c' grows less as the tem- perature in the room becomes higher, as already shown in Art. 46 ; so the equations can only be solved in an approximate manner. The following table gives the temperatures in column 4, whic-h a room would have for various tempera- ii5 HEATING AND VENTILATING BUILDINGS. tures outside, provided there was sufficient radiating surface to heat the room to 70 degrees in zero weather. The tempera- ture of the radiator in all cases is assumed to be that due to 3 pounds pressure of steam by gauge, or 220 degrees. TABLE.* Coefficient. + Total Heat per ResuUiDg Difference Temperature Heat per Square Foot pei Hour Square Foot Temi-erature Temperature Oulside Air. per Hour. of Room. Radiator and per Degiee Room. — 10 ..S5 288 64.7 155-3 1.8 270 70 150 10 1-75 253 75-1 144-9 20 1-7 236 St 139 30 1.65 218 86.5 133.5 40 1.6 203 93.1 128. 50 1-55 188 98-7 122.5 6a 1-5 172 104.7 116. 5 70 1.45 15« iro.5 ioy.5 80 1.4 142 117.1 102.9 go 1-35 130-5 123.5 9f>.5 100 '•3 117 130.3 89.7 Example showing Application of Table. — To determine by a test of the apparatus, when weather is 60°, whether a guarantee to heat to 70° in zero weather is maintained, operate the apparatus as though in regular use and note the average temperature of the room. If the room has a temperature equal to or in excess of 104.7° f^-> ■' would have a temperature of 70° in zero weather, ^11 other conditions, such as wind, position of windows, etc., being the same as on the day of the test. * This table, although calculated for steam with radiator at temperature of ■320° F. , is practically correct for hot-water radiation or for steam at any pressure and temperature. f Value of 6 6 74 32 32 14 2000 1400 .16 36 3 10 1/4' 1/4 5/'6: 3/8 8j 10 30I V 3! 3 239: 310 15; 17 2700 3100 1600 1800 9/^2 3/S 10 40 3 385 4000 zroo 9/32 3/8 462 4600 2200 9/32 3/8 12 52 3 600 24 5600 2800 5/. 6 .3/8 26 7000 5200 5/16 3/8 8o3o 5400 60 16 "/3» 1/2 16 83 3 1206 32 10500 7200 66 16 3/8 1/2 16 104 3 1504 37 12500 7500 Fifteen square feet of surface to each horse-power. 79. Locomotive and Marine Boilers. — Boilers of the horizontal tubular type with a fire-box entirely enclosed and surrounded by heating surface are usually termed locomotive boilers from the fact that such construction is common on locomotives. Boilers of this style are sometimes used for sta- l62 HEATING AND VENT/LACING BUILDINGS. tionary power purposes, and possess the advantage over the plain tubular boiler of requiring no brick setting. They are not, however, as strong in form as the plain tubular, since large flat surfaces have to be used over the fire-box. Marine Boilers. — A cylindrical boiler with an internal cylin- drical fire-box is principally used on large boats. The fire-box Fig. 115. — Locomotive Boiler. is often corrugated. This form of boiler is very strong and efficient, but because of cost of con- struction has been little used for station- ary purposes. 79. Vertical Boilers. — Vertical boil- ers of large size are made in every respect like the horizontal tubular boiler, but are set so that the flame plays di- rectl)' on one head and the heated gases pass up through tubes. These boilers are generally provided with a water-leg which extends below the lower crown sheet and is intended to receive deposits of mud, etc., from the boiler. They are usualh' made so that the heat passes directl}' out of the top of the flue, but in some cases the heat is made to pass down a portion of the length of the ex- ternal shell before beine discharged. They are economical in the use of fuel and occupy very small amount of floor-space; they require, Fig, it6. — Upright Tubu- lar Boiler. S TEAM-HEA TING ROILERS.—HOT- WA TER HEA TERS. 163 however, a great deal of head-room, are very easily choked up with deposits and sediment, very difficult to clean, and very likely to leak around the tubes in the lower crown-sheet, and consequently have a short life. Vertical boilers with horizontal radial tubes projecting outward with ends closed, known as porcupine boilers, are also on the market, and quite recently a vertical boiler of the water-tube type has been constructed. 80. Water-tube Boilers. — The water-tube boilers, which are used for power purposes, are designed to withstand great pressures, and can be purchased in sizes ranging from 60 to 500 horse-power per boiler. The general construction of these boilers is such as to have the water on the inside of the tubes and the fire with- out. There are two gen- eral forms : first, those with straight tubes, and second, those with curved tubes. In all cases they have large steam-drums at the , . V t J <. Fig. 117. — Babcock & Wilcox Boiler. top, which are connected to ' the heating-surface by headers filled with water. In the Bab- cock & Wilcox, Heine, and Root the tubes are inclined and parallel, and are connected at the end with headers, the fire being applied in each case under the elevated portion of the inclined tube, so as to insure circulation uniformly in one direction. In the Babcock & Wilcox boiler, cast-iron zigzag headers are used ; in the Root boiler, the tubes are connected together by external U-shaped bends; in the Heine boiler (Fig. 120), the tubes are connected to large, flat-stayed surfaces. In the Babcock & Wilcox and Heine boilers, feed-water is supplied at the lower part of the top drums ; while, in the Root boiler, it is supplied to a special drum in the down-circulation tubes at the back end of the boiler. The Stirling boiler has three hori- zontal drums at the top connected by curved tubes to a single lower drum at the back end of the boiler ; the Hogan has one drum at top and two at bottom, which are parallel and 164 HEATING AND VENTILATING BUILDINGS. connected by curved tubes, and also a series of down-circu- lating tubes connecting the same drums, but not exposed to the heat of the fire. In the Stirling boiler, the feed-water is intro- FiG. 118. — Root Boiler. duced in the top drums ; in the Hogan boiler, into a special heater and purifier arranged as a part of the downward circu- lation. Fig. 119. — Stirling Boiler. The Harrison boiler consists of an aggregation of spheres of cast iron or steel connected by necks, fcg-ming what is to be considered rather as a sectional, than a water-tube boiler. These STEAM-HEA TING BOILERS— HO T- WA TER HEA TERS. 1^5 spheres are held in place by bolts, which will stretch and act as safety-valves in case of excessive pressure. In addition to the water-tube boilers for power purposes which have been mentioned here, there are many others which cannot be described in the space at our command, but of which we may name the National, Campbell & Zell, and the Caldwell as worthy of notice. All the water-tube boilers are provided with mud-drums, which are usually cast-iron cylinders removed from the circu- FiG. I20. — Heine Boiler. lation and intended to receive any deposits of scale or material which is loosened in the process of circulation. 8i. Hot-water Heaters. — Hot-water heaters differ essen- tially from steam-boilers, principally in the omission of a reservoir or space for steam above the heating surface. The steam-boiler might an- swer as a heater for hot water, but the large capacity left for the steam would tend to make its operation slow and quite unsatisfactory. The passages in a hot-water heater need not extend so directly from bottom to top as in a steam-heater, since the problem of providing for the early liberation of the steam- bubbles does not have to be con-' sidered. In general, the heat from the furnace should strike the surfaces Fig. 121.— Vertical Magazine ,1 Hot-water Heater. in such a manner as to increase the natural circulation, and not act to produce a backward circula- tion. This may be accomphshed in a certain measure by ar- 1 66 HEATING AND VENTILATING BUILDINGS. ranging the heating-surface so that a large proportion of the direct heat will be absorbed near the top of the heater. There is a great difference of opinion as to the relative merits of horizontal and vertical heating-surfaces for this pur- pose, but the writer cannot find that any experiments have been made which satisfactorily decide this question. Where the sur- face is very much divided, and the fire is maintained at a high temperature, considerable steam is likely to be formed, and this always acts in a certain measure to increase circulation in the heating-pipes and diminish it in the heater ; it is likely also to produce a disagreeable crackling noise. Practically, the boilers for low-pressure steam and for hot water differ from each other very little as to the character of the heating-surface, and in describing the general classes which are in use no attempt will be made to make any distinction as to whether the apparatus will be used for hot-water or steam heating. If designed for steam-heating, a reservoir or chamber connected with the circulating system is in every case pro- vided, containing water in its lower part and considerable steam capacity above the water-line, also sufficient area of water-surface to permit the separation of the steam from the water without noise and violent ebullition. 82. Classes of Heating-boilers and Hot-water Heaters — Plain-surface Boilers. — There are probably no boilers or heaters built at the present time with a plain surface, either spherical or cylindrical, since the expense of a given amount of surface in that form would practically preclude its use. Extended-surface Heaters (Figs. 122 and 123). — Heaters of this class with extended and irregular surface, are used quite extensively in hot-water heating, and with the addition of domes are used to some extent in steam-heating. In these heaters the water is received at the lowest point, as at A, and is heated as it gradually rises, receiving the effect of the fire at various projections, and is finally discharged at B. The grate is at G, the smoke being discharged at S. The smoke and heated gases move in nearly a direct line in Fig. 122, and in a sinuous course in Fig. 123. A form which is in extensive use, and in which water and smoke are each grouped in one body, is shown in S TEA M-HEA TING B OILERS. —HO T- WA TER HE A TERS. 1 67 Fig. 124. In this case the extended surface is produced by the wedge-shaped hollow prisms extending over the fire-space. The heated gases have a return circulation around the lower portion of the heater, and also come in contact with a top dome from which the heated water is drawn off. Fig. 122. — Extended-surface Heater. Fig. 123. — Extended-surface Heater. Fig. T24. — ExTF.NDF.D Surface, Vekitcal Prisms. Fig. 125. — Radial and Curved WITH Extended Surface. Heaters belonging to the extended-surface class made with vertical cylinders, into which are connected either straight hori- zontal tubes with closed end, as shown on the right-hand side of Fig. 125, or U-shaped projections of pipe either horizontal or slightly inclined, are in use for both water- and Steam-heat- 1 68 HEATING AND VENTILATING BUILDINGS. ing. In case they are used for steam-heating the water-line is carried at sufficient distance from the top of the cylinder to give the required steam-space, and the heater is supplied with both pressure- and water-gauges. The heated gases pass around the cylindrical part of the boiler and may be made to circulate among the projections by means of baffle-plates. Tubular Boilers. — Heating-boilers with fire-tubes and with a steel shell similar in construction to the horizontal and vertical tubular boiler described in Articles 76 and 78, are in use for heating to considerable extent in the forms already de- scribed. Modifications of these, with return flues arranged so that the heat passes both upward and downward, and also with two or more short cylindrical shells connected together by tubes filled with water, are in extensive use. Very few hori- zontal tubular boilers, or boilers of the locomotive type, are used for the heating of small buildings. Water-tube Boilers. — Water-tube boilers of all classes and Various modifications are in extensive use for heating. The tubes are made of either cast-iron or wrought-iron pipe. The pipe-boilers which are in the market are arranged with nearly Fig. 126. — Field Tube. every form of heating-surface ; some are built with heating- surface in the form of the pipe-coil, as shown in Fig. 92, page 108, and others in the form of a manifold coil, as shown in Fig. 93, page 108. Still other boilers have the pipe arranged in the form of a spiral connecting with a receiving-drum below and a steam-drum above. The heated gases are arranged to move STEAM-HEA TING BOILERS.— HO 7 - WA TER HE A TERS. 169 in some cases parallel with the surfaces, and in other cases at right angles. The Field tube is used extensively for the purpose of in- creasing the heating-surface ; in its original form it consisted of a tube with a closed end projecting downward and expanded into the boiler-shell ; into this extended another tube which did not reach quite to the bottom, and was held in position by an internal perforated support, as shown in Fig. 126. This is used in heating-boilers with various modifications both pro- jecting downward and horizontally. When used projecting downward, it is termed a drop-tube, and is supplied either with an internal tube, as shown, or a partition ; when used hori- zontally the internal tube is frequently supplied from a com- partment separated from that to which the external tube is attached. Fig. 127 illustrates a type of heating-boiler which is quite extensively used for both hot water and steam, and is built by different manufacturers, either of steel or cast iron. The heater consists of a cylindrical drum, the lower surface of B B ^rf^ DROJTUBE Fig. 127. — Drop-tube Surface. Fig. 128. — Drop-tube and Coil-heater. which is covered with tubes of the type described which pro- ject downward. The tubes directly over the fire and over the fire door are short, while those around the fire are sufificiently long to form the external walls of the heater. The return water is received in one of the long pipes near the bottom of the heater, and the steam or heated water is taken off at the top. The drum in one of these heaters is provided with a baffle-plate connected to the diaphragm in the drop-tube, so I/O HEATING AND VENTILATING BUILDINGS. that the circulation must take place in a vertical direction in the tube. Fig. 128 shows a heater in which the surface is made up partly of pipe-coils and partly of drop-tubes. The return water is received in the lower concentric drum, and as it is warmed passes to the top drum of the heater, from which it flows to the building ; a type of heater in many respects similar is made without drop-tubes, the whole surface being obtained by use of pipe-coils, made either with return bends or with branch tees. Sectional Boilers. — The greater number of cast-iron boilers are made by joining either horizontal or vertical sections. These sections are joined in some instances by a screwed nipple, in other cases by a packed or faced joint, and are held in place with bolts. The sections generally contain water and B B B B B Oo ■ c Oo . : ( ; c 1 Oo Oo „-_ p)-an of seotiojj Fig. 129. Fig. 130. Boiler WITH Horizontal Boiler with Horizontal Sections. Sections. steam, and the heated gases circulate around the sections in flues provided for that purpose. The joints in the flues are usually made tight enough to prevent the escape of smoke by the use of an asbestos or similar cement. STEAM-HEA TING BOILERS.— HOT- WA TER HEA TERS. I^I Horizontal Sections. — Fig. 129 represents a type of heater in which the various sections are horizontal, the surface being in- creased to any amount by adding sections. This form is used extensively in a number of hot-water heaters. Fig. 130 shows another form of boiler made in a similar manner, but with the sections of such form as to produce both an up and down circulation within the heater. The up circulation takes place over the hottest portion of the fire, the down circulation in special external passages which are not heated. Vertical Sections. — Boilers with vertical sections are made in the same manner in many respects, the sections being united by internal or ex- ternal connections. When united by ex- ternal connections, screwed nipples con- necting the sections to outside drums, of the general form as shown in Fig. 131, are usually employed. In this case the return-water is received into horizon- tal drums AA, which extend the full length of the heater, and flows into the lower part of each section. The steam or hot water is drawn off from a similar drum, B, which extends over the top of -^_ the heater and is connected with each section by a screwed nipple. Fig. 130 shows methods of attaching steam- and ^'°- '3i- water gauges. This form is used quite extensively in steam- heating and to some extent for hot-water heating. 83. Heating-boilers with Magazines. — Nearly all of the heating-boilers are manufactured as required with or without a magazine to hold a supply of coal. The magazine in most cases consists of a cylindrical tube opening at or near the top of the heater and ending eight to twelve inches above the grate. The magazine is filled with coal, which descends as com- bustion takes place at the lower end, and provides fuel for further combustion (see Fig. 121). The magazine works suc- cessfully with anthracite coal, which is that ordinarily employed in domestic heating, but it takes up useful space in the heater, decreases the effective heating surface for a given size, and in 172 HEATING AND VENTILATING BUILDINGS. that respect is objectionable. The writer's own experience would lead him to believe that the magazine heater, except in very small sizes, requires as much attention as the surface burner, and consequently has no special advantage.* 84. Heating-boilers for Soft Coal. — It is quite probable that no furnace, either for power or heating boilers, has yet been produced which will consume soft coal without more or less black smoke. This smoke is due principally to the imper- fect combustion of the hydrocarbons contained in the coal. The hydrogen burning out after the gases have left the fire leaves solid carbon in the form of small particles, which float with and discolor the products of combustion. The amount of loss as found by experiment in Sibley College,f even when dense black smoke is produced, seldom reaches one per cent, and is of no economical importance. The sooty matter produced in the combustion of this coal is likely to adhere to the water-heating surfaces, and if these are minutely divided it will be certain to choke the passages for the gases of combustion. For the combustion of soft coal those heaters have been the most successful which have a grate with small openings, and with an area 50 to 70 per cent as large as that needed for anthracite coal, also with the heating-surface of comparatively simple form and arranged so as to be easily cleaned. It is considered im- portant that the air-flues be so arranged as to keep the products of combustion as hot as possible. This coal is likely to swell when first heated, and cannot be fed successfully by a maga- * Magazine heaters have been constructed with a magazine set obliquely- above and to the side of the grate, and In that position are not open to all the objections stated. t See Table XIV, page 529. CHAPTER VIII. SETTINGS AND APPLIANCES -METHODS OF OPERATING BOILERS AND HEATERS. 85. Brick Settings for Boilers. — Hoiizontal tubular boilers and a few heating-boilers require to be set in brickwork, of which the general arrangement is shown in Fig. 132. The horizontal tubular boiler is usually supported from cast-iron flanges which are riveted to the sides of the shell, and which rest Fig. 132. — Perspective Vnav of Tubular Boiler Sei in Hrickwokk directlv on the walls of brickwork, or are supported b-\- sus- pension-rods from above. In some instances the boiler-lugs rest on cast-iron columns embedded within the brick-work, and of such a length that all the brickwork above the grates can be removed without affecting the setting. In setting the boiler 173 1/4 HEATING AND VENTILATING BUILDINGS. the back end should be sh'ghtly lower than the front, in order that the entire bottom of the boiler may be drained at the blow- off pipe. One of the lugs of the boiler on each side should be anchored in the brickwork ; the others should rest on rollers, which in turn rest on an iron plate embedded in the brick o walls. This permits expansion due to heating and cooling to take place without straining the boiler. If the boiler is not over 14 feet in length, two lugs on a side will be sufficient to sustain it, but if it is of greater length, more lugs will need to SETTINGS AND APPLIANCES. 175 be supplied. The brickwork surrounding the boiler is more durable if built with an air-space, as shown in Fig. 134. It must be thoroughly stayed, by means of cast-iron braces, con- nected with tie-rods at top and bottom of wrought iron to Fig. 134. — Sectional View of Boiler-setting. prevent transverse or longitudinal motion. The top may be arched over so as to leave a passage for the hot gases directly over the shell, as in Fig. 132, or made to rest directly on the boiler, and the hot gases taken away at the front end by means of a flue, usually termed a breeching, which extends to the chimney. The practice of taking the heated gases from the front end of the boiler is rather more common than that of returning them to the back end over the top, and there are many engineers who believe that the hot gases injure the boiler when coming in contact with the shell above the water-line. Figs. 133, 134, and 135 show longitudinal and transverse sections of a boiler-setting, with smoke-pipe or breeching in front, which can be highly commended as representing the best practice. The depth of foundation to be used in boiler-setting will: depend upon the character of the soil and the weight of the boiler. For large tubular and water-tube boilers it should gen- erally be not less than 3 feet. Fire-brick of the best quality 176 HEAriNG AND VEXTILATING BUILDINGS. should be used to line the brick walls for a height equal to that from the grate to the water-line of the boiler, and these should be arranged so that if necessary they can be relaid without disturbing the outer brickwork. In the setting shown in Figs. 133-134 the top of the boiler is covered with a coating of some good, non conducting material, for which magnesia, asbestos, or mineral wool may be recommended, put on while in a plastic condition to tlie depth of 2 inches with a mason's SETTINGS AND APPLIANCES. 17/ Fig. 136. Brick-set Magazine Boiler. trowel. Brickwork is often used ; but it is heavier, and quite liable to crack from the effects of heat. 86. Setting of Heating-boilers. — If heating-boilers are to be set in brickwork, the special directions which have already been given can be applied, with such modifications as may be needed for the boiler in ques- tion. Nearly all heating-boilers are now set in what is called a portable setting, in which no brick whatever is used. Some of the heaters are ,made by the system o'f manufacture adopted so that no outside casing is re- quired, as in Fig. 138; others require a thin casing of galvan- ized or black iron which is lined with some non-conducting ma- terial, as magnesia, asbestos fibre, or rock wool, which is placed outside the heater and arranged so as to enclose a dead-air space, as in Fig. 137. These coverings are nearly as efficient in preventing the loss of heat as brickwork, and they form a more cleanly and neater appearing job. The slight amount of heat which escapes from such a setting is seldom more than that required to warm up the basement or room in which the heater is located. The boiler must in all gases be provided with a steam- gauge, safety-gauge, and damper regulator, all of which are specially described later. The steam-gauge should be either connected below the water-level or else provided with a siphon to prevent dry steam entering the interior tube. A safety- valve of the single-weighted type is preferable and should be connected at the top of the heater. The damper regu- lator usually consists of a rubber diaphragm which is acted on by pressure so as to open and close the dampers as required. It will prove more durable, generally, if connected below the water-line and located about on a level with the top of the heater, as this will insure the contact of water against the rubber diaphragm. Fig. 137 represents a boiler with portable setting 178 HEATING AND VENTILATING BUILDINGS. with external iron casing and equipped with all appliances, and Fig. 138 represents a portable setting without enclosing case. Hot-water heaters are set in the same general manner as steam-boilers. Each should be provided with thermometers showing both the temperature of the flow and the return water, * Fig. 137. — Heating-boiler with Portable Setting. Fig. 138. — Heating-boiler with Portable Setting. and with a pressure-gauge graduated to show pressure of water in feet and sufficiently large to show any variation in height in the open expansion tank. The dampers to a hot-water heater Fig. 139. — Section of Lever Valve, Old Form. cannot be opened and closed by variation in pressure, but reliable thermostats are now on the market which will operate the dampers by change of temperature in the various rooms of the building. SETTINGS AND APPLIANCES. 179 87. The Safety-valve. — The safety-valve has been used since the earliest days of boiler construction for reducing the pressure when it reached or exceeded a certain limit. It has been built in various forms, but in every case has con- sisted essentially of a valve opening outward and held in place by a weight or a spring. One form in common use con- sists of a valve held in place by a weight on the end of a lever, shown in Fig. 139 in section and in Fig. 140 in elevation. In this form of safety-valve the force required to lift the valve Fig. 140. — Lever Safety-valve, Modern Form. can be regulated by sliding the weight to different positions on the lever. The form shown in Fig. 141 consists of a single weight suspended from the valve and hanging in the upper Fro. 141. — Dead-weight Safety-valve — Weight Inside of Boiler. part of the boiler. This form is to be commended, since it cannot be adjusted without opening the boiler. A form used very extensively for low-pressure heating- boilers consists of a single weight resting on a valve, as shown in Fig. 142 ; its principle of operation is the same as that of the i8o HEATING AND VENTILATING BUILDINGS. other valves. A form much used on power-boilers, and frequently called, from the suddenness with which it opens, a pop-valve consists of a very quick-opening valve held in place with a spring, one form of which is shown in Fig. 143. y=^ Fig. 142. — Externally Weighted Fig. 143. — Section of Spring or Pop Safety-valve. Safety-valve. It is desirable that the safety-valve be made in such a manner that the engineer or attendant to the boiler cannot manipulate it at pleasure so as to maintain a higher pressure on the boiler than prescribed. Serious accidents have been caused by excessive weighting of the safety-valve through ignorance or carelessness on the part of the attendants, and for this reason a class of valves should be selected which cannot be tampered with. Some of the safety-valves are provided with an external case which can be locked, and others are provided with internal weights, as already described. The lever safety-valve offers the most temptation for extra weighting and should rarely be used. The area of a safety-valve must be sufficiently large to effectually reduce the boiler pressure when the valve is open and when a brisk fire is burning on the grate. It may be computed from the following considerations : The steam which will flow through one square inch of open- ing in one hour of time was found by Napier* to equal in ■ Raiikine's '' Steam Engine.'' SETTINGS AND APPLIANCES. )»I pounds nearly 50 times the absolute pressure of the steam ; further, it has been found by experiment that the safety- valves in ordinary use open only to such an extent as to make \ of the total area of the valve effective in reducing the press- ure. From these considerations it will be seen that the area of the safety-valve in inches should be -^^ the weight of steam generated per hour, divided by the absolute pressure. Considering that lOO lbs. of steam can be generated from each square foot of grate per hour, this would be equivalent to the following rule: The area in square inches is equal to 18 times the grate surface in square feet, divided by the absolute pressure. The following table gives the area of safety-valve in square inches per square foot of grate required on marine boilers by the English Board of Trade : Boiler Pressure. Area in square inches for each sq. ft. grate. Boiler Pressure. Absolute, Pounds per sq. inch. Above atmos- phere. Absolute. Above atmos- phere. Area in square inches for each sq. ft. grate. 15 20 25 30 35 40 45 50 5 10 15 20 25 30 35 1-25 1.07 0.94 0.83 0.75 0.68 0.625 0.576 60 70 80 90 100 no 120 130 45 55 65 75 85 95 105 115 0.50 0.44 0.40 0.36 0.33 0.30 0.277 0.258 The following formula gives results very closely in accord with the English Board of Trade table. Let A = area of safety-valve in square inches, P = absolute pressure = gauge pressure plus 15, (9 = number of square feet of grate surface. Various rules quite different from the above are given in treatises on boiler construction, but it is believed that the above table represents the best practice of to-day and forms a safe guide for estimating the size of safety-valves. Safety-valves are liable to stick fast to the seat, through corrosion, in which case they fail to raise with excess of press- IS2 HEATliYG ANV VENTILATING BUILDINGS. ure ; for that reason tliey should be periodically lifted from their seats and otherwise inspected. In case the area of the valve required is greater than 4 inches in diameter, two safety-valves should be provided for each boiler. 88. Appliances for showing Level of Water in the Boiler. — In the first boilers constructed floats were used, and such appliances are still common on European boil- ers. In this country water-gauge glasses and tr)'-cocks are now used, to the exclusion of all other devices. The water-gauge (see Fig. 144), consists of two angle-valves, one of which is screwed into the boiler above the water line; the other is screwed about an equal distance below, and these are connected by means of a glass tube usually -g to {- inch external diameter and strong enough to withstand the steam-press- ure. When both angle- valves are open the water will stand in the gauge-glass the same height as in the boiler, but if either valve is closed the water-level shown in the glass will not accord with that in the boiler. Three try-cocks are usually put on a boiler in addition to the water- gauge. The try-cocks are made in various forms, one kind being shown in Fig. 145, these are located so that one is above, the other below, and the third at about the mean posi- tion of the \\'ater-line. When the top one is opened, it should show steam ; when the bottom one is opened it, should Glass Fig. 144, Water-gauge Fig. 145. — Register Gauge-cock. show water. Both try-cocks and gauge-glasses should usually be put on boilers, so that the reading as shown in the water- gauge glass can be checked from time to time. This is neces- sary, because if dirt should get in the angle-valves or passages SETTINGS AND APPLIANCES. 183 leading to the gauge-glass the determination would be inac- curate. Water-columns attached to the boiler by large pipes, both above and below the water-line, and fitted with try-cocks and water-gauge as shown in Fig. 146, are often provided. These columns frequently contain floats (Fig. 147), so arranged that steam is admitted into a small whistle if the water falls below or rises above the required limits, and thus gives an alarm. Fig. 146. — VV ATtR-COLUMN. JriGS. 147. — Rkliance Alarm Watlr-column. 89. Methods of Measuring Pressure. — The excess of pressure above that of the atmosphere is measured by some form of manometer or pressure-gauge. Where the pressure is small in amount, a siphon, or U-shaped tube filled with some liquid is a very convenient means of measur- ing pressure. The method of using a simple manometer of this character is shown in Fig. 148, in which a U-shaped tube, G F E D, has one branch attached to the vessel containing the fluid whose pressure is to be measured ; the other, as at D, is open to the air. If water, mercury, or other liquid be placed in the U-shaped Fig. 148. — U-SH,APED Ma- nometer. 184 HEATING AND VENTILATING BUILDINGS. tube it will be forced down on the side of the greater pressure and upward on the side of the less, a distance proportional to the pressure. The height of the fluid in one side in excess of that on the other will be a measure of the difference of pressure be- tween that of the atmosphere and that in the vessel. Various forms of manometers are used, of which several are shown in Fig. 149. For very low pressures water is the liquid generally employed ; for mod- erate pressures up to 15 or 25 pounds mercury is very convenient, and often used ; while for high pressures a pressure- gauge (Fig. 150), as described later, is commonly employed. The Bourdon pressure-gauge is or- dinarily used. This consists of a tube of elliptical cross-section bent into a circular form. The free end of the tube is attached by gearing to a hand which moves over a dial. Pressure on the interior of the tube tends to straighten it, and Fig. 149. — U SHAPED Manometer Tubes. Fig. 150. — Bourdon Gauge moves the hand an amount proportional to the pressure. Fig. 150 shows the interior of a pressure-gauge of this char- SETTINGS AND APPLIANCES. 185 acter with the dial removed. In place of the tube a corrugated diaphragm is sometimes employed. A section of such a gauge is shown in Fig. 151. In the use of gauges of the character just described it is necessary to protect them from extreme heat. For this purpose when they are connected to a steam-boiler a Fig. 151. — Diaphragm Gauge. siphon or U-shaped form of pipe is to be used in the connec- tion, so that water and not steam will be forced into the inte- rior of the gauge. The manometers and gauges described in every case measure the pressure above or below that of the atmosphere. If they measure a pressure lower than that of the atmosphere they are commonly called vacuum-gauges, but the principle of construc- tion is the same as described. The relations of various units used in measuring pressure can be readily determined from the following table of equiva- lents : I inch of mercury = 13.619 inches of water = 1. 134 feet of water = 0.49101 pound = 399.51 feet of air at 60 degrees Fahrenheit and barometer pressure 30 inches. The pressures are usually taken as acting on one square inch of a body. lo6 HEATING AND VENTILATING BUILDINGS. 90. Thermometers. — The methods of constructing various kinds of thermometers have been described in Articles 8 to 12. In any hot-water heating system it is quite important to know the temperature of the water leaving the heater, and in many cases also that of the return. This information, while not so vital to the safety of the heater as that given by a pressure-gauge on a steam-heat- ing system, is of the same character, and will prove to be equally valuable in indicating the work done by the heater, and the heat absorbed by the system. Any of the suitable forms described in Chap- ter I can be used, but special forms in which the thermometer-bulb sets in a cup of mercury (Fig. 152) are often used, the cup being screwed into the pipe whose temperature is required. These thermometers should be set so as to ex- tend deep into the current of flowing water, and there should be no opportunity for air to gather around the bulb ; otherwise the readings will not be the true temperature. 91. Damper-regulators. —Nearly all steam- boilers are provided with an apparatus for open- ing or closing the dampers and draft-doors to the boiler as may be required to maintain a con-stant steam-pressure. For low-pressure steam-heating plknts the regulator consists in nearly every case of a rubber diaphragm (Fig. which receives the steam-pressure on one side, and acts against a counter^weight resting on a plate on the opposite side. The plate is connected by a rod to a lever pivoted to the external case, which in turn is connected to the various drafts by means of chains, and so arranged that if the pressure rises the lever is lifted and the drafts closed, while if the press- ure falls the lever also falls, and the drafts are opened. By means of weights on the lever the regulator can be set to operate at any pressure. The regulator should be connected to the boiler below the water-line, or by means of an U-shaped pipe, arranged so that the part of the vessel below the dia- FiG 152. — Ther- MuMETIiR FOR H or ■ WATER HliATING. IS3) SETTINGS AND APPLIANCES. 187 phragm will remain full of water ; otherwise the heat in the steam will cause the rubber to deteriorate rapidly. The form shown in Fig. 153 is so arranged that the diaphragm must in every case be in contact with water. While rubber diaphragms are usually durable for low-pres- sure steam-regulators, still they occasionally are ruptured. In order to prevent accident from such a cause, the Nason Manu facturing Co. have devised a form of such a character that the draft-doors will close, instead of open, in case of rupture. This is done by using a link in the connecting-chain to the draft- doors of some metal that will be fused at a temperature below that of boiling water, and arranged so that in case of rupture the escaping steam and hot water will impinge upon and melt it ; the damper will be closed by its own weight when the link breaks. Damper-regulators for high-pressure steam are constructed so as to operate on the same principle as those described, but instead of a rubber diaphragm either a metallic diaphragm or a piston working in a cylinder, and operated by water-pressure, is employed. The following cut shows the external appearance of one of the many forms in use. Fig. 153. — Diaphragm Damper-regulator. Fig. 154. — Piston Damper-regulator. 92. Blow-ofif Cocks or Valves. — Every steam-boiler should be provided with an appliance for emptying all of the water at any time. This may be done by leading a pipe from the lowest part of the boiler and providing a cock or valve so that it can be discharged at pleasure. The pipe leading from the boiler should have a visible outlet, so in case there is any leak it can i88 HEATING AND VENTILATING BUILDINGS. Fig. 155. — Packed Plug cock. be seen and stopped. The writer prefers a cock (Fig. 155) to a valve for use on the blow-off pipe, since it is less likely to be stopped by scale or sediment from the boiler. In case the water of condensation from the heating coils is not returned to the boiler it is necessary to blow off some of the water very frequently in order to lessen the deposition of scale or dirt on the bottom of the boiler. 93. Expansion-Tank. — An expansion- tank will be needed in hot-water heating systems. With increase of temperature from 40° F. to the boiling-point, water expands 4.66 parts in 100, or nearly 5 per cent. The force of expansion is nearly irresistible, and the increase in volume due to it must be provided for, so as not to produce a dangerous press- ure. The method ordinarily adopted con- sists in the use of a vessel called an expansion-tank, whose cubical contents must be somewhat greater than one twentieth of the total cubical contents of heater, pipes, and radiators. It must be connected to- the heating sys- tem in such a way as to receive the in- crease in volume, and should be placed on a level somewhat above that of the highest radiating surface. If there is to be no sensible increase in pressure due to expansion the tank is connected with the outside air by a vent-pipe, and in this case the pressure inside will be atmospheric ; the pressure ' on the heating system will depend on the distance from the water-level in the tank, each foot corresponding to 0.435 pounds per square inch (2.4 feet being equivalefit to one pound of pressure at 212° F.). PIPE Fig. 156. Expan- sion-tank. SETTINGS AND APPLIANCES 189 In case a pressure in excess of the atmosphere is required, the vent pipe is closed and a safety-valve attached which will open when the pressure reaches the desired point. By increas- ing the pressure on the system the boiling temperature of the water will be much increased, and hence it will be possible to maintain a higher temperature throughout the system. As showing the increase in temperature of the boiling point with excess of pressure, the following table is inserted : Pressure. Temperature of Pounds Boiling- Point per sq. in. Equivalent Head, (degrees F.). above in Feet. Atmosphere. 212 5 12 22S 10 24 240 15 36 250 20 48 259 25 60 267 30 72 274 35 84 280 40 96 287 45 108 292 50 120 297 55 132 302 60 144 307 70 168 316 80 192 324 go 216 332 100 240 338 125 300 352 150 360 365- 175 420 378 200 480 388 Pressure systems of hot-water heating were used at one time to a considerable extent in England, under what was known as the Perkins* system, in which small pipes and exceedingly high pressures and temperatures were used. It has also been used to some extent in this country in the Baker system of car-heating. The advantages of the pressure system are those which are due simply to the use of higher temperatures and smaller radi- ating surfaces ; the disadvantages are the danger of an explosion * Hood's " Heating and Ventilating of Buildings.' igO HEATING AND VENTILATING BUILDINGS. which would be likely to happen were the safety-valve inoper- ative, or did any part of the apparatus give way. The sudden liberation of a considerable body of water having a temperature above the boiling point would result in the instantaneous pro. duction of a large amount of steam, which might produce dis- astrous results. With the open expansion-tank it seems hardly possible that any serious accidents could result even from the most careless management, since the escape of steam from the top of the expansion-tank would prevent the accumulation of pressure. To prevent accident the expansion-tank should be connected to the heater by a pipe protected from frost and without stop or valve, so as to render it impossible to increase the pressure on the system by stoppage of the connection. It is desirable to provide the expansion-tank with a glass water-gauge showing the depth of water, and a connection to the supply-pipe for adding water to the system. In case the expansion-tank occupies a cold location where it might freeze in extreme weather, a small pipe connected with the circulating system, in addition to those described, should be run to the tank and connected at a higher level than the ex- pansion-pipe, so as to insure circulation of warm water. 94. Form of Chimneys. — The form and size of the chim- ney is of great importance in connection with the satisfactory operation of a heating plant, and it should in every case receive the closest inspection before guarantees of capacity are made. It will be found that for a specified area a round chimney will have the most capacity, but in ordinary building construc- tion such a chimney is difificult to construct and is not ordi- narily built. A square chimney of the same area has some- what more friction, and one with a rectangular narrow flue very much more, so that an increase in area proportional to ex- cess of perimeter should be made for such cases. The chimney should be as smooth as possible on the inside in order to pre- vent loss of velocity by friction, and, if of brick, the flue should in every case be plastered. In the construction of chimneys it is better that the inside be made with a thin wall not con- nected in any way with the outside, both in order to permit SETTINGS AND APPLIANCES. IQI free expansion of the inner layer of the chimney with the heat and also to secure the advantage of the non-conducting power of an air space between the inside and outside walls. Such a construction is common for chimneys for power purposes^ but is not ordinarily applied to those used in buildings. 95. Sizes of Chimneys. — The area of cross-section required for a given chimney will depend upon its height and also upon the amount of coal to be burned. The conditions which affect chimney draft are so numerous, and so difficult to consider in any theoretical discussion, that empirical or practical formulae derived from the study of actually existing plants are prob- ably more satisfactory than those obtained from purely theo- retical computations. Of the various formulae which have been given for the capacity of chimneys the writer prefers that of William Kent, from which the accompanying table is com.puted. Kent's formula is computed on the assumption that the chimney shall have a diameter two inches greater than that required for passage of the air, in order to compensate for friction. The following is his formula : E = — ^ = A—Q.t iTT. Vh ^'^' H = 3.33E Vl; .5= 12 V£ + 4; in which A = actual area in square feet of the chimney, E = effective area, A = height in feet, S = side of the square in inches, 11= horse-power of plant. If we let J? = number of square feet of radiating surface to be supplied, then. Article 73, page 153, ir= looP; 3oi? from which E = — -^' The table gives the diameter of round or side of square chimneys in inches for various heights computed from the above formulae, with the diameter in- creased by 2, to allow for friction. A square chimney is considered the equivalent of the inscribed round one. 192 HEATING AND VENTILATING BUILDINGS. DIAMETER OR SIDE OF CHIMNEY IN INCHES REQUIRED FOR VARYING AMOUNTS OF DIRECT STEAM-RADIATING SURFACE. Height of Chimney in Feet 20 SO 40 60 60 80 100 120 Square Feet of Steam Ra- Horse- diation. power. 250 2.5 7-4 7.0 6.7 6.4 6.2 6.0 6.0 6.0 500 5-0 9.6 9.2 8.8 8.2 8.0 6.6 7-3 7.0 7£0 7-5 11.3 10.8 10.2 9.6 9-3 8.8 8.5 8.2 1,000 10.0 12.8 12.0 II. 4 10.8 10.5 10. 9-5 9.2 1,500 15.0 15-2 14.4 13-4 12.8 12.4 II-5 II. 2 10.8 2,000 20.0 17.2 16.3 15-2 14-5 14.0 13-2 12.6 12. 1 3,000 30.0 20.6 18.5 18.2 17.2 16.6 15.8 15.0 14.4 4,000 40.0 23.6 22.2 20.8 ig.6 19.0 17.8 17.0 16.3 5,000 50.0 26.0 24.6 23.0 21.6 21.0 19.4 18.6 18.0 6,000 60.0 28.4 26.8 25.0 23-4 22.8 21.2 20.2 19.5 7,000 70.0 30.4 28.8 27.0 25.5 24.4 23.0 21.6 20.8 8,000 80.0 32.4 30.6 28.6 26.8 26.0 24.2 23-4 22.2 9.000 90.0 34-0 32.4 30.4 28.4 27.4 25.6 24.4 23-4 10,000 100.0 37-0 34.0 32.0 30.0 28.6 27.0 25.4 24.6 15,000 150.0 38.4 36.2 35.0 33-0 31.0 29.2 20,000 200.0 .... 43.0 42.0 41.0 37-0 35-0 34-0 30,000 300.0 50.0 48.0 46.0 43.0 41.0 For other kinds of heating multiply the radiating surface by the following factors : Hot- water heating 1.5, indirect steam 0.7, hot-blast heating 0.2. 96. Chimney-tops. — The draft of a chimney is influenced to a great extent by the conditions of the surrounding space. If other buildings exist in the vicinity of such a form as to de- flect the currents of air down the chimney, the draft will be impaired and may be entirely destroyed. The objects which tend to produce downward air-currents may sometimes be situated a considerable distance from the chimney and thus ren- der the specific cause of poor draft very difificult to determine. The remedy for a smoky chimney is sometimes difficult to ap- ply, but usually the draft will be improved, first, by increasing the height of the chimney ; second, by adopting some form of chimney-top which utilizes the force of horizontal currents to aid by induction in increasing the draft. The writer found that curved trumpet-shaped tubes located with the small ends projecting into the chimney in an upward direction increased the draft materially when the wind was blowing into the openings, and there is little reason to doubt but that a chimney-top may be constructed in such a manner as to materially increase the draft. SETTINGS AND APPLIANCES. 193 97- Grates. — For supporting the fuel during its combus- tion in such a manner as to allow a free passage of air, a per- forated metallic construction of some sort is required. For burning very fine coal the perforation must be small and close together ; for burning larger sized coal the perforations may be. larger and further apart. The area of the air-spaces compared with the total area of the grate should be about 50 per cent in order to secure best results, but they will more generally be found to be 30 to 40 per cent. The grates are usually con- structed of cast iron and in a very great variety of forms, as shown in Figs. 157 and 158. In some instances a series of parallel bars is used ; in others the grates are made in one solid Fig. 157. Different Forms of Grates. Fig. 158. casting. This latter practice is never one to be recommended. The solid grate is likely to break from expansion strains due to heating unless made in such form that the various parts are free to expand independently. Nearly all heating-boilers, hot-water heaters, and furnaces are supplied with some form of shaking- and dumping-grate. Many of these grates are known from experience of the writer to give most excellent satisfaction, and doubtless all present points of merit. The various shaking-grates operate in nearly every way, and it is hard to conceive. either a form of grate-bar or a method of shaking which is not exemplified in some of these grates. Some of the bars are flat or rectangular in shape, and are operated by shaking backward and forward ; others are triangular and are continually rotated so as to pre- sent successively new surfaces to the fire each time they are shaken. The shaking-grate will, in general, be found much superior to the fixed one, and a furnace fitted with such grates 194 HEATING ANx} VENTILATING BUILDINGS. is more easily managed and more cleanly than one with a fixed grate of any description. 98. Traps. — In all systems of gravity steam-heating, the water of condensation returns directly to the boiler, and no appliance either for maintaining a water-line in the building or returning the condensed steam to the boiler is required. But there are cases in which it is necessary to maintain the water- line at a certain definite height, and also to prevent the escape of steam without interfering with the discharge of condensing water. For this purpose a steam-trap is re- quired. One form of a steam-trap which has always been used to a greater or less extent for this purpose is a siphon made in the shape of a U bend, or its equivalent of pipe and fit- tings, as shown in Fig. 159. It consists of two legs, AB and BC, which may be close to- gether or any distance apart, but the length of which must be sufficiently great to prevent pressure acting through the pipe FA forcing the water out of BC. CE is a vent-pipe ex- tending to the air ; D is the discharge for the condensed water. In ordinary operation the leg CB is filled with water which is constantly overflowing, and AB with steam and water ; the total pressure in both legs being in each case equal. The siphon-trap may be open to the objection that it will require a great deal of vertical room if the pressure is great ; B Fig. 159. Siphon-trap. Fig. 160. — Float-trap. for this reason traps with mechanical movements of some kind are usually preferred. The simplest of these traps contains a float (Fig. 160) which rises and falls with change of level of the SETTINGS AND APPLIANCES. 195 water in the vessel. Rising above a certain point, it opens a discharge-valve ; falling below, it closes it. Traps of this class are made of a great many designs. In some instances traps are made as in Fig. 161, in which a weight W\?, used instead of Fig. 161. — Counter-weighted Trap. a float and is nearly counter-balanced by the weight D. As the water rises in the trap it tends to lift the weight J^an amount proportional to its volume, thus opening a discharge- valve at^. When the water falls, the valve is closed. It is noted that the counter-weight D is always above the water-line P. A large number of traps are made with a hollow metallic float or bucket, so arranged as to open a valve when the bucket is full of water. One form is shown in Fig. 162, in which the water ent-ers the trap at A, filling the space 5 between the bucket and the walls of the trap. This causes the bucket to float, and thus to close an orifice in the discharge-pipe V. When the water rises above the edges of the bucket it flows into it and causes it to sink, which opens the discharge-valve at V. The water is forced out through the pipe B by the steam pressure acting on the surface 55. The bucket traps are made in great variety, both as to form of valve, guides for bucket, etc. Fig. 163 shows cvne of the traps which is in common use, with all details of con- struction. Another extensive class of traps are made so as to be closed by the expansion due to increase in temperature. These traps differ from each other very much in form ; the principle, how- Fig. 162. — Bucket Trap. 196 HEATING AND VENTILATING BUILDINGS. ever, is in all cases the same. Thus in the diagram, Fig. 164, steam is supplied at^ and discharged at B.. The bent springs 5 are prevented by guides from moving laterally, so that the expansion due to heat causes a motion which closes the orifice in the discharge-pipe B. When the water in the traps cools Fig. 163. — Bucket Trap. the valve opens. The materials used for traps of this class can be metallic or some composition of material like that em- ployed for air-valves. The discharge can be arranged to take place from the bottom or, as shown in the diagram, from the side. Fig. 164. — Expansion-trap. Traps which combine one or more of the principles of operation as described are on the market. Thus Fig. 165 rep- resents a trap with two valves in which one valve is opened by expansion, the other by a float. The bucket traps have generally proved the most reliable and less likely to be injured by use. The float-traps have been liable to failure because of leakage of the float, but recent improvements in manufacture render this accident quite im- SETTINGS AND APPLIANCES. 197 probable. All traps need periodical inspection, as the valves are likely to become more or less. choked up, in which case the trap may fail to operate. All of the traps described Fig. 165. — Combined Float- and Expansion-trap. will discharge the water to a height which corresponds to the steam-pressure in use, and hence when used with high-pressure steam will lift water to a considerable distance ; but in no case will they return the water into the boiler from which the steam was received. For this purpose a trap of considerable more complexity, known as a return-steam trap, must be used. 99. Return-traps. — Traps which receive the water of con- d-ensation and return it to a boiler having considerably higher- pressure steam than that acting on the returns, are known as ^ ^ -^ Fig. 166.— Diagram Showing Action of Return-trap. return-traps. They are made in quite a variety of forms, but the general principle of operation is shown by the diagram Fig. 166. In this figure D represents the boiler and AB'Caz trap, 198 HEATING AND VENTILATING BUILDINGS. which is located above the boiler and is supplied with steam from the lioiler at A. It is connected with the return system by a pipe leading from the tank or drum P, and pipe dis- charging into the trap at E. A pipe leads from the bottom of the trap B and connects below the water-line with the boiler. Check-valves are located at C and C, which permit the flow to take place toward the boiler only. The essential method of operation of the trap is as follows : First, water flows into the trap from the return P, until it reaches a certain level, when it acts on the float B so as to open a balanced steam-valve, Fig. 167, — BT7CKET Return-trap. called an equalizing-vavle, connected to the main pipe.(4. This permits steam from the boiler to enter the trap, which equal- izes the pressure of steam in the trap and boiler. The water in the trap, because of its greater density, then commences to flow out through the pipe B, and need only cease when the level becomes nearly the same as in the boiler. The dis- charge of the water causes the float B to fall, which closes the equalizing valve, and the operation as described is again re- peated. Instead of a float a bucket may be used to operate the SETTINGS AND APPLIANCES. 199 equalizing-valve, acting in a manner similar to that described for the ordinary bucket trap. A section of such a trap is shown in Fig. 167. .The bucket is probably superior to the float for this pur- pose, since it is less likely to be affected in its operation by change in density or pressure of the steam. Various other systems for opening and closing the equaliz- ing-valve have been adopted, of which one, shown in Fig. 168, Fig. 168. — Gravitating Return-trap. consists in mounting the trap so that it will move into one position when empty and into another when full, the motion so obtained being used to open and close the equalizing-valve. A different construction for accompHshing the same pur- pose is shown in Fig. 169. Return-trap. 100. General Directions for the Care of Steam-heating Boilers.— Special directions will be no doubt supplied by the 200 HEAT/NG AND VENTILATING BUILDINGS. maker for each kind of boiler, or for those which are to be managed in a peculiar way. The following directions are gen- eral and should always be observed, regardless of the kind of boiler employed : 1. Before starting the fire see that the boiler contains water. Its surface should stand a distance of from one third to one half the height of the gauge-glass. 2. See that the smoke-pipe and chimney-flue are clean and that the draft is good. 3. Build the fire in the usual way, using a quality of coal which is adapted to the heater. 4. In operating the fire keep the fire-pot full of coal and shake down and remove all ashes and cinders as often as the state of the fire requires it. If a magazine heater is used it must be kept full of coal. 5. Hot ashes or cinders must not be allowed to remain in the ash-pit under the grate-bars, but must be removed at stated intervals to prevent burning out of the grate. 6. To control the fire, see that the damper regulator is properly attached to draft-doors and damper; then regulate the draft by weighting automatic draft-lever as required, lightly or not at all in mild weather, but increasing as the weather be- coming colder. 7. Should the water in the boiler escape, by means of a broken gauge-glass or other mishap, it will be safer to dump the fire and let the boiler cool before letting in cold water. In no case should an empty boiler he filled when hot. If the water gets low, but not but of sight, in the gauge-glass, extra water may be added at any time by the means provided for this purpose. 8. Occasionally lift the safety-valve from its seat to see that it is in good condition. 9. Clean the boiler, if used in a gravity system of circulation, once each year by filling with pure water and emptying through the blow-off pipe. If the steam is used largely for power, the boiler rnust be cleaned at frequent intervals. In case the boiler should become foul or dirty it can be thoroughly cleaned by adding a few pounds of caustic soda and allowino- it tO' stand one day, then emptying and thoroughly rinsing. Kero- sene oil will loosen boiler scale and not injure the boiler, but; SETTINGS AND APPLIANCES. 20I its odor win be quite likely to penetrate the whole building in which the heating system is located. 10. During the summer months the writer would recom- mend that all the water be drawn off from the system and that air-valves and safety-valves be opened, to permit the heater to dry out and remain so. Good results are, however, obtained by filling the heater full of water, driving off the air by boil- ing slowly, and allowing it to remain in this condition until needed in the fall. The water should then all be drawn off and fresh water added. 1 1. Keep the fire surfaces of the boiler clean and free from soot. For this purpose a brush is provided with most heaters. 12. In case any of the rooms are not heated, look out for the steam-valves at the radiators. If a two-pipe system, both valves at each radiator must be opened or closed at the same time, as required. See that the air-valves are in proper condi- tion. If a one-pipe system, one valve only has to be opened or closed. 13. If the building is left unoccupied in cold weather, draw all the water out of the system, which can only be done by opening blow-off pipe, all radiators, and air-valves. lOi. Care of Hot-water Heaters. — The general direc- tions for. the care of steam-heating boilers, Article 100, apply in a general way to hot-water heaters as to the methods of caring for the fires and for cleaning and filling the heater. The special points of difference only need to be considered. All the pipes and radiators must be full of water and the expansion-tank should contain some water, as shown by the gauge-glass or by the pressure-gauge; and this condition should be determined before building a fire and whenever visiting the heater for the pur- pose of replenishing the fuel. Should any of the radiators not circulate, see that the radiator valve is open then open air- valve until the water runs out, after which it must be closed tight. Water must always be added at the expansion-tank when for any reason it is drawn from the system. 102. Boiler Explosions. — Boiler explosions sometimes occur with disastrous results. They are not limited to boilers in which high-pressure steam is employed, but also occur in some instances with low-pressure boilers employed in heating. 202 HEATING AND VENTILATING BUILDINGS. The cause of a steam-boiler explosion is in every case an excess of pressure above that of the strength of the boiler. The effect of this is primarily to rupture a part or portion of the boiler, relieving the pressure on the side of the rupture. This leaves unbalanced all the pressure acting on the opposite side of the boiler, which usually is sufficient to project the boiler into the air with considerable velocity. As showing the amount of force which exists even with small pressures we would have for each square foot of the boiler with lo pounds pressure above the atmosphere a force of 1440 pounds per square foot of surface, applied to move it as a projectile-. If the pressure were ten times as great the force would be ten times greater, and the effect many times worse. The disaster caused by the explosion would depend largely upon the sud- denness with which this force was applied ; if it were applied gradually no bad results might follow; if applied instantly the results might equal the explosion of a large amount of dyna- mite. Boilers sometimes explode because of defective mate- rial, poor construction, or overheating of parts ; they also some- times explode because of defects in the safety-valve or in the appliances for showing the true level of the water; but in all cases the immediate cause of the explosion is over-pressure. The causes which lead to the formation of steam with a pres- sure in excess of that of the strength of the boiler are vari- ous ; one of them is the practice of permitting the water in the boiler to get low and then supplying feed-water, which because of the highly heated condition of the surfaces is rapidly converted into steam, causing the pressure to become exces- sively high. It is not necessary to suppose that boiler explosions are caused by any mysterious force which is suddenly developed in the boiler. On the other hand, the amount of force which is stored in the hot water and steam is sufficient to produce at any time a terrific explosion, provided the necessary opportunity is presented. Dr. R. H. Thurston has computed the energy stored in vari®us classes of boilers under the ordinary conditions of working, and the following table shows some of the principal results of that calculation and will give some idea of the enor- mous force stored in heated water and steam : SETTINGS AND APPLIANCES. 20^ STORED ENERGY OF STEAM-BOILERS.* 4.S" % Maximum nT - /PO- Total Energy Ht.of Initial Type. i! , Stored Energy Available. per lb. of Boiler. Proj't'n of Boiler. Velocity. Total, t- Foot-lbs. Feet. I. Plain cylinder. . . 100 10 47,281,898 18,913 18,913 606 2. Cornish cylinder. 30 60 58,260.060 3.431 3,431 2go 3. Two-flue cylind'r 150 35 82,949.407 12,243 1-2,243 625 4. Plain tubular. . . . 75 60 51,031,521 5,372 5,372 430 5. Locomoiive 125 525 54,044,971 2,786 2,786 375 6. " 125 650 71,284,592 2,851 2,851 379 7- 125 600 66,218,717 3,219 3,219 397 8. '■ 125 425 65,555.591 4,677 4,677 455 9. Scotch marine. .. 75 300 72,734,800 2,687 2,687 348 10. 75 350 109,724,732 2,889 2,889 356 II. Flue and return.. 30 200 92,101,987 1,644 1,644 245 12. " " " .. 30 180 104.272,264 1,862 1,862 253 13. Water tube 100 250 i74.56£>38o 5,067 5,067 445 14. " ■' 100 250 230,879,830 5,130 5,130 450 15- " " 100 250 109,624,283 2,030 2,030 323 * "Steam-boiler Explosions, in Theory and Practice," by R. H. Thurston. Considering the total number of heating-boilers in use in the United States the number of explosions is very small, so that if we suppose no improvement in construction over the ordi- nary methods, the risk which any person would run is very slight ; and it seems quite probable that if one were to use a heating-boiler as safe as the average boiler, the chances would be that if he did not die until killed from this cause he would live to be 10,000 years old. That is, estimating from the total number of boilers in use for heating, as compared with the number of explosions of such boilers, the chances are that one per year in ten thousand would explode. Some disastrous explosions of heating-boilers have, how- ever, occurred in the United States, of which may be mentioned that at the Central Park Hotel, Hartford, Feb. 17, 1889, in which fifteen people were killed and the hotel entirely de- stroyed ; also the boiler explosion at St. Mary's Church, Fort Wayne, Ind., in which the church and priest's house were nearly torn down, which occurred Jan. 13, 1886; another at Dell Brown's Hotel, Eagle Bridge, N. Y., Dec. 20, 1888, in which several people were injured and the building badly wrecked. Also various other explosions doing less damage. It would seem, from a study of the boilers which are in- jured by explosions, that no boiler is entirely free from the dis- 204 HEATING AND VENTILATING BUILDINGS. astrous effects of an explosion when it is badly managed; but on the other hand it also appears that the sectional boilers, or boilers in which the wateroccurs in small quantities, are subject to injuries which are comparatively slight and generally easily repaired. So far as the writer can find from a study of all the explosions recorded in the United States, the water- tube boilers, or those with small masses of water, are singu- larly exempt from disastrous explosion. They are, however, quite likely to have some part broken away, in which case the pressure on the boiler is relieved quickly enough to avert a serious explosion. The worst accidents which usually happen to the sectional boilers are those due to the burning out of a tube or some easily replaceable part. This results ordinarily in a very severe leak, which can, however, be repaired. The total number of boiler explosions for the United States for all classes of boilers average about 255 per year, and, as re- ported by the Locomotive, they have been as follows for the . last ten years : BOILER EXPLOSIONS IN THE UNITED STATES. Total Injured. Year. Total No. E.xplo- sions. Station- ary, etc. Portable. Saw- mills. Railway Locomo- tives. Steam- boats. Total Killed. 1884 1885 18S6 1887 1888 1889 1890 1891 1892 1893 1894 152 155 185 198 246 . 180 226 257 269 48 80 88 67 104 85 94 115 122 18 16 16 20 30 21 16 35 24 245 56 33 45 73 69 56 75 68 79 15 10 14 23 15 25 22 33 15 16 14 14 20 13 l6 17 II 254 220 254 264 331 304 244 263 298 220 261 288 314 388 505 433 351 371 442 151 The following table gives the total number in Great Britain for the same time : BOILER EXPLOSIONS IN GREAT BRITAIN. Explosions, 77 72 Years. Explosions. KiUe 1882-83 45 35 1883-84 41 18 18S4-85 43 40 1885-86 57 33 1886-87 37 24 1887-88 61 31 1888-89 67 33 Years. 18S9-90 1890-91 1891-92 1892-93 72 Total 660. Ratio 482 Killed. 21 32 23 20 313 SETTINGS AND APPLIANCES. 205 This table would seem to indicate that the explosions in this country were more disastrous, so far as taking life is concerned, as in this country two people were killed for about every three ex- plosions, whereas in Germany and Great Britain we have about twice as many explosions as deaths. This is probably due to the fact that the statistics in this country classify as boiler explosions only those which are markedly disastrous, whereas in France and Germany every leak or break which appears from this cause is recorded as an explosion. As showing the disastrous effects often produced by a boiler explo- sion, the following is abstracted from Thurston's Manual of Steam- boilers. Fig. 170 shows the boiler- room before the explosion. The boiler was made of -^^ iron, was 3 feet in diameter, and was 7 feet high ; the upper tube-head was flush with the Fig. 170. The Boiler before Explosion. '^-^'^-^ "/ ,« ^ "^ 5&^ 4- r%Aj, liiB'ii, nfflnl ^^ ^mM^^'i"- ■■ imnininmiiiriGTT ^Eff^ li^^^^s "^^mss&^^m ^^^^w^^ in ^^M^^^^^^^Z Fig. 171. — Path taken by the Boiler. top of the shell, the lower forming the crown of the fur- nace, which was about 2 feet above the grates and the base 206 HEATING AND VENTILATING BUILDINGS. of the shell, and was flanged upon the inner surface of the furnace. There was a safety-plug in the lower tube- head which was not melted out. The working pressure was 60 pounds per square inch, and the explosion probably took place at or a little below this pressure, throwing the boiler through the roof and high over a group of buildings and a tall tree close by, finally burying itself half its diameter in the frozen ground. There had been a leak in the lower head which Fig. 172. had reduced by erosion the thickness of InCrs^f RrT^ro": the tubes and the lower head, so that the pressure was sufficient to force the lower hestd down away from the tubes, opening fifty or more holes 2 inches in diameter from which the fluid contents of the boiler issued at a high velocity, relieving the pressure below and converting the whole boiler into a great rocket weighing about 2000 pounds. 103. Explosions of Hot-water Heaters. — While hot- watpr heaters provided with an open expansion-tank are to a great extent free from the dangers of explosions, still it is quite possible that extreme carelessness in erection, the freez- ing up of connections to expansion-tank, or other mishaps, might render the apparatus fully as dangerous as the steam- boiler under its most unfavorable conditions. Some very dis- astrous explosions have occurred of hot-water heating plants when operated under the Perkins or high-pressure system,. and it seems quite probable that such a system, even under the most favorable conditions, is more dangerous than the steam- heating system. The hot-water heating system .should be constructed so that the connection between the expansion- tank and heater cannot by any possible means be closed. The placing of a valve in this connection was the cause of a very disastrous explosion in a residence in New York City quite recently, and emphasizes the necessity for caution in this respect. 104. Prevention of Boiler Explosions.— Boiler explo- sions are probably preventable in every single case by using, first, boilers properly designed, and constructed of excellent SETTINGS AND APPLIANCES. 20/ material and with good workmanship ; and second, by seeing that all appliances, as safety-valves, blow-off cocks, feeding apparatus, etc., are in excellent order; and third, by providing skilled and intelligent attendance. Disastrous results are usually almost entirely prevented by the use of sectional boilers, and for heating purposes there are at the present time comparatively few of any other kind in use. As a rule heating-boilers, especially those of small sizes, are not under close supervision, but are attended to and visited only at comparatively long intervals. For this reason automatic appliances for feeding the boiler and for regulating the pressure, opening and closing the dampers, are usually supplied ; hence the person erecting the plant should exercise the utmost care to see that such appliances are in excellent order and of such character as are Hkely to prove durable and rehable. While it is quite certain from our statistics that not one boiler out of ten thousand is likely to explode per year, yet nevertheless the contractor should always bear in mind that a steam-boiler is in every case a magazine of stored energy, and if badly constructed, poorly erected, or carelessly managed may do an immense amount of damage. CHAPTER IX. VARIOUS SYSTEMS OF PIPING. 105. Systems employed in Steam-heating. — There are- two systems of heating, in the first of which, known as the Gravity Circulating System, the water of condensation from the various radiators fiows by its own weight into the boiler at a point below the water line ; in the second the water of con- densation does not flow directly into the boiler, but is returned by some special machinery or, in some cases, wasted. The second system is often called the High-pressure System, be- cause steam of any pressure can be produced in the boiler, a por- tion of which may be employed in operating engines, elevators, etc. It is very seldom, however, that this high-pressure steam is used in radiators, low-pressure steam being obtained directly from the boiler by throttling or passing through a reducing- valve, or, in some instances, indirectly by using the exhaust- steam from engines or pumps. In this chapter we shall discuss only the systems of piping used with gravity circulating systems of heating, reserving for a later chapter a description of the methods employed in the other system of heating, although there is in the arrange- ment of pipe lines very little which pertains to either system exclusively. 106. Definitions of Terms used. — Certain terms have been adopted which are always used to describe definite parts in a system of piping, as follows : The main or distributing pipe is the pipe leaving the boiler or heater and conveying the heated products to the radiating surfaces. In steam-heating this is termed the main steaiii-pipc, and in hot-water heating the main floiv-pipe. It maybe car- ried from the boiler without branches to the top of the build- 208 VARIOUS SYSTEMS OF PIPING. 20g ing (Fig. 173), where the distributing-pipes are taken off, or it may run in a horizontal or vertical direction from the heater, and branch pipes taken off as required. The pipes in which the flow takes place from the radiating surface toward the boiler are called return-pipes. The pipes which extend in a vertical direction are termed risers ; when the flow in these pipes is downward they are called return-risers. A relief or drip is a small pipe run from a steam-main, so as to convey any water of condensation to the return ; it must be employed at all points where water is Hkely to gather. For illustration of use see Fig. 176. Pitch is the inclination given to any pipe when running in nearly a horizontal direction. In general the inclination or pitch of a supply-pipe should, in steam-heating, be downward from the boiler, and arranged so that the water of condensa- tion will move in the same direction as the current of steam. In hot-water heating the pitch should be upward from the boiler. In all return-pipes the inclination should be down- ward, toward the heater or boiler. A relay is a term sometimes used to describe a sudden change of alignment, or " jumping up," of a horizontal pipe. This is often necessary in a long line of piping to keep the pipe near the ceiling and preserve the necessary pitch. At such , points a drip or relief must permit water of condensation to flow into the return. Water-line is a term used to denote the height at which the water will stand in the return-pipes. It is usually very nearly the same as the level of the water in the boiler, being higher only in case there is considerable reduction in pressure due to friction. In heating with high-pressure steam it is desirable to have all the relief-pipes discharge into a return filled with water, so that circulation of steam shall be continuously in one direction ; this is of less importance with low-pressure steam, provided the water which gathers in returns can move freely and quickly to the boiler. The term siphon is applied to a bend below the horizontal ; it is sometimes used in the main return to hold water at a dif- ferent level from that in the boiler. This is done by admitting steam to the top part of the bend on the boiler side by a relief 2IO HEATING AND VENTILATING BUILDINGS. from the main steam-pipe. It is similar to the siphon-trap, F'g- IS9> Article 98. If the relief were not connected to the top of the bend the water would pass over by suction into the boiler. Steam-traps are vessels designed with valves which open automatically so as to preserve the water-level in the re- turns at any desired point. Various kinds are described in Chap. VIII, Article 98. Water-hammer is a term applied to a very severe concus- sion which often occurs in steam-heating pipes. It is caused by water accumulating to such an extent as to condense some of the steam in the pipe, thus forming a vacuum which is filled by a very violent rush of steam and water. The water strikes the side of the radiators or pipes with great force, and often so as to produce considerable damage. In general a water-hammer may be prevented by arranging the piping in such a manner that the water of condensation will immediately drain out of the radiator or pipes. A bend in the return of a steam- or water-heating system, when convex upward, will frequently accumulate air to such an extent as to prevent circulation in the system. This is designated as an air-trap. When bends of this character must be used a small pipe for the escape of the air should be con- nected with the highest portion of the bend and led to some pipe which will freely discharge the entrapped air. An air-valve is not ordinarily to be recommended for such situations. 107. Systems of Piping. — The systems of piping ordinar- ily employed provide for either a complete or a partial circulat- ing system, each consisting of main and distributing pipes and returns. Several systems of piping are in common use, of which we may mention : First, the complete-circuit system, often called the one-pipe system, in which the main pipe is led directly to the highest part of the building ; from thence distributing-pipes are run to the various return-risers, which in turn connect with the radiat- ing surface and discharge in the main return. The supply for the radiating surface is all taken from the return-risers, and in VARIOUS SYSTEMS OF PIPING. 211 some cases the entire downward circulation passes through the radiating system. This system was employed by Perkins in his method of high- pressure hot-water heating, and is mentioned by P^clet as in use in France in 1830. In this country it seems to have been introduced into use by J. H. Mills, and is often spoken of as the Mills system of piping. The system is equally well adapted for either steam 'or hot-water heating, and on the score of posi- tiveness of circulation and ease of construction is no doubt to 212 HEATING AND VENTILATING BUILDINGS. be commended as superior to all others. It is principally ob- jectionable because the horizontal distribution-pipes have to be run in the top story of the building instead of the basemenl; which may or may not be of serious importance. b yvvy^vv.^^^;^^^ ^^\.\\\\\v\\^gti;t^;;!^i^^^^vt^ Second, a partial-circuit system, in which the main flow-pipe rises to the highest part of the basement by one or more branches, from whence the distributing-pipes run at a slight incline, often nearly around the basement, and finally connect with the boiler below the water-line. The radiators are con- VARIOUS SYSTEMS OF PIPING. 213 nected by risers which carry both flow and return from and to the distributing pipes, as shown in elevation in Fig. 174 and in plan in Fig. 175. This method of piping is employed exten- sively for steam-heating, and is perhaps less open to objection than any other. ^w ' •T 1 M 1 >. D 3 C3 [c 5] fi^ •3 J g *T3 3 1 H 1 Third, a system of circulation in which each radiator is pro- vided with separate flow- and return-pipes (Fig. 176). In this case the riser and distributing pipes are run as before, but are connected to the return by a drip-pipe ; the return is located 214 HEATING AND VENTILATING BUILDINGS. below the water-line of the boiler. The supply-riser from each radiator is taken from the main flow-pipe, and the return-riser is connected to the main return below the water-level. In case two connections are made to a radiator, one for supply and the other for the return, it is quite important that the connection bdk\^N\\\\\\V^k^V\V\V\V\V^^^ >iyvVvSXxVys.'~~Xxsji Ja- of the return-riser to the main return be made below the water- level of the boiler, in order to prevent steam flowing from two directions to the radiator. Such a condition is certain to cause VARIOUS SYSTEMS OF PIPING. 21 5 water-hammer, as the radiator will retain water of condensa- tion. Various modifications of this third system have been used from time to time with greater or less success. For instance, each radiator has in some cases been connected to a separate flow and return riser, and in other cases simply to a separate return riser. These modifications are unimportant and hardly worthy of notice. 108. Methods of Piping Used in Hot-water Heating. — A system of hot-water heating should present a perfect system of circulation from the heater to the radiating surface and thence back to the heater through the returns ; an expansion-tank being provided, as explained, to prevent excessive pressiire due to the heating and the consequent expansion of the water. The direct-circuit system, as described for steam-heating. Fig. 173, is well adapted for hot-water heating, and has been used to a limited extent. When this system is employed for hot-water heating two connections are usually taken off from the return riser at different levels for each radiator, as shown in Fig. 103, page 114; although in some cases a single connection is made and a radiator of ordinary form employed, otherwise the method of piping is exactly similar to that described for steam- heating. The system of piping ordinarily employed for hot-water heating is illustrated in Fig. 177. In this system the mains and distributing pipe have an inclination upward from the heater; the returns are parallel to the main and have an inclina- tion downward toward the heater, connecting at its lowest part. The flow-pipes are taken from the top of the main and supply one or more radiators. The return-risers are connected with the return-pipe in a similar manner. In this system great care must be taken to produce nearly equal resistance to flow in all the branches leading to the different radiators. It will be found that invariably the principal current of heated water will take the path of least resistance, and that a small obstruction, any irregularity in piping, etc., is sufficient to make very great dif- ferences in the amount of heat received in different parts of the same system. For instance, two branch pipes connected at opposite ends of a tee, which itself is connected by a centre 2l6 HEATING AND VENTILATING BUILDINGS. opening to a riser, are almost certain to have an irregular and uncertain circulation. z a o Q Z O ^ !S M PQ O E o b C5 Z in 2 The method of piping generally adopted for the closed or high-pressure system is that of the complete-circuit or one-pipe system, as illustrated in Fig. 173. This system when now employed is used only for moderately low pressures, and a safety-valve is provided on the expansion-tank to prevent excessive pressure. In this system, or, in fact, in any of the systems for hot-water heating, the level of the return-pipe can VARIOUS SYSTEMS OF PIPING. 217 be carried below that of the heater without bad results. The method of applying this system is shown in Fig. 178, which is D > z > o "x ^ t-S^ similar in many respects to that used in the Baker system of car-heating. The expansion-tank must in every case be connected to a line of piping which cannot by any possible means be shut off from the boiler. It does not seem to be a matter of im- portance whether it is connected with the main flow or with 2l8 HEATING AND VENTILATING BUILDINGS. the return. The form of expansion-tank and the different kinds of fittings have been described in Art. 93, page 158. Single-pipe systems for hot-water heating have been used to some extent. In this case there is a gradual flow of the heated water to the top, and the consequent settlement of the colder water to the bottom. The form of piping would be essen- tially the same as that shown in Fig. 173 or 174. The writer erected such a system at one time as an experiment, and found that it worked well after the water had once become heated. Where there is no objection to a system which heats slowly, this would probably do well on a small scale, but could not be recommended for an extensive job. 109. Combination Systems of Heating.^Several methods have been devised for using the same system of piping alter- nately for steam or hot water as the demand for higher or lower temperature might change. The object of this is to secure the advantages which pertain to the hot-water system of heating for moderate temperature and to steam-heating for extremely cold weather. As less radiating surface is re- quired for steam-heating, there is the advantage due to reduc- tion in first cost. This may be of considerable moment, since a heating system must be designed of such dimensions as to be satisfactory in the coldest weather, and this involves the ex- penditure of a considerable amount for surfaces which are needed only at rare intervals. The combination system of hot-water and steam heating must require, first, a heater or boiler which will answer for either purpose ; second, the construction of a system of piping which will permit the circulation of either steam or hot water; third, the use of radiators which are adapted to both kinds of heating. These requirements will be met in the best manner by using a steam-boiler provided with all the fittings required for steam- heating, but so arranged that the damper regulator may be closed off from the heater by means of valves when the system is needed for use in hot-water heating. The addition of an expansion-tank is required, which must be arranged so that it can be closed off when the system is required for steam- heating. VARIOUS SYSTEMS OF PIPING. 219 Of the different systems of piping, that designated as the complete-circuit or one-pipe system (Fig. 173) is the only one which is equally well adapted for both hot water and steam. In case that system cannot be conveniently installed, the one shown in Fig. 177 for hot water will be found to give fairly good results, it being objectionable in steam-heating only because of the fact that the condensation in the main pipe flows against the current. The radiators and connecting pipes should be of the form required for hot-water heating, but the proportions and dimensions the same as for steam-heating. While this system has many advantages in the way of cost over the complete hot-water system, yet the labor of changing from steam to hot water will in some cases be troublesome, and should the connections to the expansion-tank not be opened, serious results would certainly follow. A combination hot-air furnace and hot-water system has been employed to considerable extent. In such a case the water-heating surface is obtained by inserting a coil of pipe or suitable vessel into the hot-air furnace, and certain rooms and portions of the house are warmed by the heated air directly from the furnace, while other parts are heated by the circula- tion of hot water. This system is an admirable one from every point of con- sideration, theoretically ; but practically it is a very difficult one to design and construct in such a manner that the supply of heat to the different rooms shall be positive and well dis- tributed. Fig. 179 shows the arrangement of such a system.* In this case the hot-air furnace supplies heat to the lower floors and the hot-water circulating system to the upper floors. Any system of piping suitable for hot-water heating can be employed for this purpose : the one shown is that of the com- plete-circuit or one-pipe system, the heated water being taken directly to the top of the building and all radiating surface supplied by the descending current. As the writer knows from experience, it is very difficult indeed to proportion the heating surface in the furnace and the radiating surface in the room so as to give in all cases satisfactory results without an * An admirable series of articles were written on this subject by J. W. Hughes, and appeared in Metal Worker, February, 1895. 220 HEATING AND VENTILATING BUILDINGS. irregular and uncertain distribution of heat. It will generally be found that the fire maintained in a hot-air furnace is mi-ch more intense than that in a steam or hot-water heater ; and further, the heating surface which is usually employed is sub- jected to the full heat of the fire, consequently a smaller amount of heating in proportion to radiating surface must be Fig. 179. — Combination System, Hot-air Furnace and Hot Water. employed. Whereas in the ordinary hot-water heater one foot of heating surface supplies from 8 to 10 of radiating surface, in this system i foot of heating surface will supply 25 to 35 feet of radiating surface in coal-burning furnaces and 50 to 75 in wood-burning furnaces. Similar combination systems of hot air and steam are also used, but in such cases the heater must be very much like a steam-boiler, and possess all its appliances and also storage capacity for steam. In the case of the hot-water and hot-air system the heater is substantially a hot-air furnace, to which is added a coil of pipe or vessel of suitable form, which serves as the heating surface for the hot water, so that the change in construction is very slight ; but for steam-heating the change of construction must be more marked, and is likely to be more expensive and complicated. VARIOUS SYSTEMS OF PIPING. 221 iio. Pipe Connections, Steam-heating Systems. — The manner in which branches are taken off may have great effect on the results obtained in any heating system, since any in- crease in friction in any part of the system will cause the flow to be sluggish in that portion, and require more press- ure to induce circulation. The size of pipes required in order that resistances may not exceed a certain amount are given in the next chapter ; but it should be noted that bad workman- ship may defeat the opeiration of a steam-heating plant having the best proportions possible, and that great care is needed, (i) to secure the alignment of every part, (2) the absence of air- traps or any obstructions whatever which would reduce the circulation or make it irregular or uncertain. Some details which are to be considered rather as suggestions than as formal directions are given. In general, pipe connections should be made so as to afford as little resistance as possible to the flow of steam, and in such a manner as not to interfere with the expansion of the main pipes. The line of piping should present the freest possible channels of circulation for the steam ^s it leaves the boiler and for the water of condensation as it returns. The expansion, which is not essentially different from if inches for each 100 feet in length, can usually be well provided for by the use of two or more right-angled el- bows substantially as shown in Fig. 180. No general rule can be laid down for all cir- cumstances and conditions. The following examples and illustrations from Heating and Ventilation show the methods of piping commonly employed in setting steam-radiators with Fig. 180. — Connection to Radiator „„^^i.;r^„o T<\cr 1 8/-, from Steam Main. one-pipe connections, i'lg. I80 illustrates the method where the radiator is set close to the main and no special drip is required. 222 HEATING AND VENTILATING BUILDINGS. The method often employed in connecting a riser to a horizontal steam main and running a special drip-pipe for con- densed water to the return main is shown in Fig. i8i. Fig. i8i. — Connection to Riser from Main and Return. The method often employed in connecting radiators to risers is shown in the upper portion of Fig. 182. The lower portion illustrates an essentially different method from that shown in Fig. 181 of connecting the riser to the main, and the drip-pipe to the return. This method, however, does not allow for expansion of the steam main ; hence this must be provided for in some other portion of its length. The area of the main pipe must in every case be equivalent in carrying capacity to that of all the branches taken off ; it consequently may be reduced as the distance from the heater becomes greater and as more branches are supplied. Table XXII, Appendix, gives the equivalent capacity of pipes of different diameters, and can be used in determining the rela- tive number of branches of a given size, and also the reduction in pipe area which may be made after a certain number of branches have been connected. It will, however, in general be found, except when large pipes are used, less expensive to run the main full size than to use reducing fittings. VARIOUS SYSTEMS OF PIPING. 223 III. Pipe Connections, Hot-water Heating Systems.— If the system of circulation adopted is the complete-circuit system, as in Fig. 173, in which the heating main is first taken directly to the top of the building and thence run horizontally Fig. 182. — Connection of Radiator to Riser. to the various lines of return risers, the system of construction would be essentially the same as that described for a steam- heating plant. The main riser should connect into a drum, from the top of which the distributing-pipes leading to the return risers are taken. The size of the distributing-pipes should be proportional to the amount of radiating surface, and the various distributing-pipes should be arranged so that the resistance in each will be substantially equal. The flow connection for each radiator should be taken off at a point about level with the top of the radiator, as in Fig. 103, 224 HEATING AND VENTILATING BUILDINGS. page 1 14, and the return should enter the same pipe at a point below the radiator. A valve affording as little resistance as possible is to be put in each connection. Hot-water heating systems have been erected in which the radiators are joined to the riser by one connection only ; and while this system seems to be somewhat slower in heating than that with two connec- tions, it is otherwise quite satisfactory. In the system commonly employed the main and distribut- ' ing pipes are erected in the basement, as shown in Fig. 177. An offset from the main to the foot of the riser has usually to be made, which should be done as from the steam main in Fig. 180, and in such a manner as to take the flow from the upper part of the pipe ; such a connection is also shown in No. 3, Fig. 183. The connection to the main return may be made on Fig. 183. — Connections to Mains, Hot-water Heating. the side or at the top, as convenient. In some instances a tee turned at an angle and a 45-degree elbow can be used with good results, as shown at No. 2, Fig. 183. The method of connecting shown at No. i should only be employed in case the room is not sufficiently high for connections, as shown at No. 3, as its use is attended with doubtful success in many cases. In taking off branches from the top of a riser a tee should seldom or never be employed, since it will be found that if for any reason the current becomes established in one direction it will be very difficult to induce it to flow in the other. When branches running in opposite directions have to be taken from the main riser, long-radius tees, as shown in Fig. 52, p. 125, should be employed ; but unless the riser is long it will in general be better to erect a separate line for each branch. Precautions should be taken in every case that the junction of two currents shall not exert an opposing force which will im-. pede the circulation. VARIOUS SYSTEMS OF PIPING. 225 The connections to radiators for this system need to be made in such a way that the horizontal branches which are taken off from the risers will receive a strong current of water. There is a tendency for water to flow directly in the line of motidn, and to the highest radiators in the system. This renders it necessary to increase the resistance in the riser beyond the branch a greater or less amount in order to induce circulation into the side connections. This may be done in several ways, as shown in Fig. 184: (i) by connecting I ■ I ra MtHATQII Fig. 184. — Connection to Radiators, Hot-water Heating. the radiator to an elbow placed on the main pipe and con- tinuing the main pipe from the side opening of a tee or Y, as shown at A and B; or (2) by using a reducing fitting, as shown at C, and continuing the riser with a reduced diameter. The return connections can be made in a similar manner, but they will in every case iX'ork well if the return riser be run in a direct line and the connection be made into the side opening of aY. 112. Position of Valves in Pipes.— If a valve has to be used on a horizontal pipe it should be located so as to afford the least possible obstruction to the flow of water in the required direction. If a globe valve be used with the stem, set vertically, Fig. 185, it will form an obstruction sufficient to fill the pipe very nearly full of water ; if the stem be placed in a horizontal direction the flow ot water will be less impeded. Globe valves form a great obstruction to the flow in water-heating pipes, and under no circumstances should they be used for that work. In the case of steam-heating they are less objectionable, provided they are located in such a manner as to permit free drainage 226 HEATING AND VENTILATING BUILDINGS. of the pipes. In general, angle or gate valves can be used, however, in every place with better satisfaction. For hot-water heating special valves have been designed, Fig. 185. — Illustration of Water Held by Globe Valve. which when open offer no special impediment to the flow, and which close sufficiently tight to prevent circulation, although not sufficient to prevent leaks. See page 13 1. 113. Piping for Indirect Heaters. — Indirect radiators have been described and methods of setting them illustrated in Article 69, page 146, These radiators are gen- erally set in a case or box which is suspended from the basement ceiling and made of matched boards lined with tin. Fig. 186. The sides of the casing should be removable for repair of the radiator. The system of pipes which supply the indirect radiators are generally most conveniently erect- ed, like those shown in Fig. 175 or 177 for steam-heating, and like that shown in Fig. 179 for hot- water heating. The heater should be located above the water-line of the boiler a sufficient distance to afford ready means of draining off the water of con- densation. In case this is impossible, a style of radiator should Fig. 1S6. — Indirect Surface. VARIOUS SYSTEMS OF PIPING. 227 be adopted which can be heated by water circulation. An automatic air-valve should be connected to the heater, and every means should betaken to obtain perfect circulation to and from the boiler. The chamber which surrounds the indirect surface is to be supplied with air from the outside by a properly constructed flue. The air passes up through or over the heater and into the rooms by means of special flues, the sizes of which are given in Chapter X. 114. Comparisons of Pipe Systems. — As to the best sys- tem of piping to be adopted little can be said in a general way- The circuit-system. Fig. 173, no doubt gives the freest circula- tion and is applicable to either hot-water or steam heating. In some respects it is simpler to construct, and it seems quite probable that small errors of alignment, minute obstructions, and error in proportioning the pipes would not be so fatal to the perfect operation of this system as of the others. It requires, however, that distributing pipes be placed in the top story of a building, and this in many cases will be so objection- able that it cannot be used. Regarding other systems there is little to be said. For steam-heating there seems to be little or no use in making more than one connection to any radiator ! and this practice, which is now common, will I think become universal. 115. Systems of Piping where Steam does not Return to the Boiler. — For such systems the method of piping and of making connections would be in every case essentially as described ; and usually this can be done with less care because of the fact of greater difference of pressure between the supply and the return. Such systems are not often employed except in connection with use of exhaust steam, which is considered in Chapter XI. 116. Protection of Main Pipe from Loss of Heat. — The loss of heat which takes place from an uncovered main steam or hot-water pipe is, because of its isolated position, considerably greater than that which takes place from an equal amount of radiating surface. Unless this heat is actually required it will cause an expenditure of fuel the cost of which is likely to be in a few seasons many times that of a good cover- ing. 228 HEATING AND VENTILATING BUILDINGS. The heat lost per square foot of surface from a small un- covered pipe is from 375 to 400 heat-units per square foot per hour in steam-heating, or an amount equal to that required for the evaporation of 0.4 pound of steam. Computing this loss for 100 square feet for a day of 20 hours and for a season of 150 days, it will be found equivalent to the coal required to evaporate 120,000 pounds of steam ; this would not be less than 12,000 pounds of coal, which at $5.00 per ton would cost $30.00. The cost per square foot per annum will be found on the above basis to be 30 cents, of which 75 to 80 per cent would have been saved by using the best covering. The loss from hot-water pipes would be about two thirds of the above. The best insulating substance known is air confined in minute particles or cells, so that heat cannot be removed by convec- tion. No covering can equal or surpass that of perfectly still and stagnant air; and the value of most insulating substances depends upon the power of holding minute quantities in such a manner that circulation cannot take place. The best known insulating substance is a covering of hair felt, wool, or eider- down, each of which, however, is open to the objection that, if kept a long time in a confined atmosphere and at a temperature of 150 degrees or above, it becomes brittle and partly loses its insulating power. A covering made by wrapping three or more layers of asbestos paper, each about -^^ inch thick, on the pipe, cover- ing with a layer of hair felt f inch in thickness, and wrap- ping the whole with canvas or paper, is much used. This covering has an effective life of about 5 years on high-pressure steam-pipes and 10 to 15 years on low-temperature pipes. There are a large number of coverings regularly manufactured for use, in such a form that they can be easily applied or removed if desired. There is a very great difference in the value of these coverings ; some of them are very heavy and contain a large amount of mineral matter with little confined air, and are very poor insulators. Some are composed entirely of incombustible matter and are nearly as good insulators as hair felt. In general the value of a covering is inversely pro- portional to its weight — the lighter the covering the better its VARIOUS SYSTEMS OF PIPING. 229 insulating properties ; other tilings being equal, the incombus- tible mineral substances are to be preferred to combustible material. The following table gives the results of some actual tests of different coverings, which were conducted with great care and on a sufficiently large scale to eliminate slight errors of observation. In general the thickness of the coverings tested was I inch. Some tests were made with coverings of different thicknesses, from which it would appear that the gain in jn sulating power obtained by increasing the thickness is very slight compared with the increase in cost. If the material is a good conductor its heat-insulating power is lessened rather than diminished by increasing the thickness beyond a certaia point. PERCENTAGE OF HEAT TRANSMITTED BY VARIOUS PIPE- COVERINGS, FROM TESTS MADE AT SIBLEY COLLEGE, CORNELL UNIVERSITY, AND AT MICHIGAN UNIVERSITY.* Relative Amount Kind of Covering. of Heat Transmitted. Naked pipe.... • 100. Two layers asbestos paper, i in. hair felt, and canvas cover 15.2 Two layers asbestos paper, i in. hair felt, canvas cover, virapped writh manilla paper 1 5 • Two layers asbestos paper, i in. hair felt 17 . Hair felt sectional covering, asbestos lined 18.6 One thickness asbestos board 59-4 Four thicknesses asbestos paper. .. 50.3 Two layers asbestos paper 77-7 Wool felt, asbestos lined 23.1 Wool felt with air spaces, asbestos lined 19.7 Wool felt, plaster paris lined 25.9 Asbestos molded, mixed with plaster paris 31.8 Asbestos felted, pure long fibre 20. i Asbestos and sponge 18.8 Asbestos and wool felt > 20.8 Magnesia, molded, applied in plastic condition 22.4 Magnesia, sectional 18. S Mineral wool, sectional 19.3 Rock wool, fibrous 20. 3 Rock wool, felted 20 . 9 Fossil meal, molded, f inch thick 29 . 7 Pipe painted with black asphaltum 105 . 5 Pipe painted with light drab lead paint 108 . 7 Glossy white paint 95. o * These tests agree remarkably well with a series made by Prof M. E. Cooley of Michigan University, and also with some made by G. M. Brill, Syracuse, N. Y., and reported in Transactions of the American Society of Mechanical Engineers, vol. xvi. 230 HEATING AND VENTILATING BUILDINGS. The following table translated from Pdclet's Traite de la Chaleur gives in a general way the amount of heat transmitted through coverings of various kinds and of different thicknesses ; the loss from a naked pipe is taken as lOO. LOSS OF HEAT THROUGH VARIOUS PIPE-COVERINGS. Thickness, in inches. 0.4 0.8 1.6 4.0 6.0 Relative Loss of Heat. Kind of Covering. 0.04 0.08 o. 16 0.32 0.64 1.28 2.56 5.12 10.00 29 20 18 13 II 7 43 32 29 23 20 13 Sb 48 45 ,38 35 25 66 63 62 58 55 44 7.3 73 73 72 71 70 77 83 85 92 96 102 78 87 91 103 110 130 79 90 95 109 118 149 100 100 ICO 100 100 100 6 II 22 41 68 109 150 180 100 Eider down, loose wool, hair felt, etc. Powdered charcoal. Wood across fibres. Sand. Clayey earth. Stone, rock. White marble. Solid gas carbon. Naked, or unprotected surface, iron. CHAPTER X. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 117. General Principles. — The general problem of design includes the proportioning of, first, the amount of radiating surface which will be located directly in the rooms to be heated in all systems of direct heating, and in the air-passages or flues leading to the rooms in all cases of indirect heating ; second, the size of the pipes which are to convey the heated fluids to the radiating surfaces ; and third, the proper size of boiler or heater. The question of the system or method of heating which is to be adopted will usually depend upon considerations of cost or of personal preference on the part of the proprietor. The various systems of heating, whether by steam, hot water, or hot air, as commonly practised in this country, do not often come in direct competition. Hot-air heating, where the air is moved by natural draft, is adapted only to the smaller sizes of dwelling-houses, and where heat does not need to be carried any considerable distance horizontally. It is generally found that if the horizontal distance exceeds 15 or 20 feet the supply of heat becomes uncertain in amount. With steam and hot- water heating there is no such limitation as to distance ; the first cost is, however, considerably greater than that of hot air, but heat can be supplied with certainty to all parts of the sys- tem under all atmospheric conditions. Regarding the relative merits of systems of steam and hot-water heating, little can be said. It will generally be found that the first expense of steam-heating is considerably less, and that there is considerable difference of opinion regarding the relative economy of oper- ation of steam an"d hot-water heating plants. The tests which liave been made have generally shown somewhat in favor of 231 232 HEATING AND VENTILATING BUILDINGS. water.* The difference, however, is not great, and may be due to local conditions, but is probably due to the fact that the temperature of the discharged gases may be somewhat lower for the hot-water heater than for the steam-boiler, and also to the fact that in comparatively mild weather the fire in the hot-water heater may be regulated somewhat closer, to meet the demand for heat. The hot-water system in general requires rather better workmanship in the erection of pipe lines than steam-heating, and more care must be taken in pro- portioning the various pipes and fittings. The heat from hot- water radiators is somewhat less in intensity and more pleasant than that from steam-radiators, and the temperature can be regulated by simply throttling the supply-pipe of the radiators^ which is not the case with steam. Whether direct or indirect heating shall be used will de- pend also on circumstances. It will be found that in general the surface required for indirect heating is one third to one half greater than that for direct, and it will give off 50 per cent more heat per square foot, so that the operating expense is practically twice that of direct heating. Indirect heating as- sures excellent ventilation, and it is advisable to use it for certain rooms of residences because of that fact. 118. Amount of Heat and Radiating Surface required for Warming. — The amount of heat required for buildings of various constructions has been considered quite fully in Chapter III. From which it may be seen (page 70) that in ordinary building construction the amount required in heat- units, for each degree difference between inside and outside temperature, is approximately equal to the area of the glass surface plus one fourth the area of the exposed wall surface plus one fifty-fifth of the number of cubic feet of air required for ventilation. The air required for ventilation will vary with the con- ditions ; but in direct heating it seems necessary to allow for three changes per hour in halls, two in rooms on first floor, and one in rooms on upper floors. * See Transactions American Society Mechanical Engineers, vol. x, paper by the author. See also Report Massachusetts Experimental Station No 8.. 1890. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 233 The amount of heat given off by one square foot of radiat- ing surface, as determined by a great number of experiments, is given in Chapter IV, from which it is seen (pages 84 and 113) that for the ordinary radiating surface, with a temperature of 150 degrees above the surrounding air, 1.8 heat-units will be given off per square foot of surface per degree difference of temperature per hour, and when the temperature is no above the surrounding air about 1.7 heat-units are emitted. The total heat emitted from radiating surfaces of different characters, corresponding to the average results of experiments is shown on the diagram, Fig. 187, in which the horizontal distances correspond to the mean difference of temperature between the air in the room and the radiator, while vertical distances, the value of which is read on the scale at the left, correspond to the total heat-units transmitted per square foot per hour. To use the diagram assume the difference of temperature between the air of the room and the radiator, then look on vertical line until intersection with the line representing the desired condition is found, thence read results on the left. Thus, for instance, if the difference of temperature is 150 de- grees the intersection of the line from this point with that representing direct ordinary radiation corresponds to 275 heat- units, and with that representing i-inch horizontal pipe, 375 heat-units, as read ort the scale at the left. The dotted lines in the diagram give the heat transmitted from various indirect surfaces for different velocities of the moving air. The results are to be found as for direct radiation, but the difference of temperature is that estimated from the mean of the surround- ing air and the radiator. Having the total heat required for warming and that which is given offfrom one square foot of radiating surface, it is quite evident that the surface required may be computed by the process of dividing the former by the latter. Expressing results algebraically we can produce a formula from which the radiating surface may be calculated quickly and easily as follows : Let R equal the total radiating surface required, t the required tem- perature of the room, /' the temperature of the outside air, T the tem- 234 HEATING AND VENTILATING BUILDINGS. V 109 125 150 176 .200 Mean Difference of Temperature Fig. 187. — Diagram of Heat from Radiating Surfaces. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 235 perature of the radiating surface, C number of cubic feet in the room, G the number of square feet of glass, IV the external wall-surface, a the heat given off per square foot of radiating surface per degree difference per hour.« the number of times the air is to be changed per hour. We have, first, the heat required for one degree difference of tem- perature as explained, pages 68 and 70, which is approximately I/=o.o2nC+ G + ilV. (I) Second, the radiating surface is H multiplied by difference of temperature between room and outside air divided by that given off from one square foot. Hence we have i - f t — flr \ ^ = (r^r^.^=(r37).t5'' + '' + *^} • • " ^^^ The heat required per degree difference of temperature between room and outside air, as expressed in equation (i), must becomputed for every given case. The other quantities which constitute a factor to be multiplied in the above are readily computed and expressed in the table on p. 236, which is calculated for a great variety of conditions. From this table it is seen that we need to multiply the area of the glass, plus \ the wall surface, plus .02n of the cubic feet of air supplied per hour, by factors which are approximately as follows : If we are to heat to 70 degrees in zero weather with steam of 10 pounds pressure, multiply by ^ ; if we are to heat to 60 degrees, multiply by ^ ; if we are to heat to 50 degrees, multiply by \. As the steam pressures increase, these factors are reduced. As a method of applying the rule consider a room 20 feet by 12 feet floor surface, and 10 feet high, contain- ing 2400 cubic feet, in which the air is to be changed twice per hour. Suppose that it has 320 square feet of exposed wall surface and 48 square feet of glass. The heating surface re. quired will be found by taking the area of the glass, 48, \ the exposed wall, 80, and .02 the cubic contents, which is equal to 87 ; the total heating surface required would be (48 -|- 80 4- 87) 215, multiplied by the factor given in the table, which ih about \, so that the radiating surface required equals 5^ square feet. In this case there is about one square foot of heating surface to 44 cubic feet of space. 236 HEATING AND VENTILATING BUILDINGS. FACTORS FOR PROPORTIONING DIRECT RADIATORS FOR DIF- FERENT TEMPERATURES ROOM AND OUTSIDE AIR. Number of Colu 1 2 3 4 5 Coefficients for S.6 '•7 1.8 1.9 Temperature Temperature Air. Room. — 10° 100° .61 • 54 .43 .31 .19 100 .55 •49 .40 ,28 •17 + 10 100 .50 • 44 •36 .25 .16 — 10 80 .42 .38 •31 .23 .145 80 •38 • 33 .275 .20 .13 + 10 80 •33 .30 .24 .18 .11 — 10 70 .35 .32 .262 .19 .122 70 •32 .28 •23 .17 .109 + 10 70 .26 .24 .20 .14 .092 — 10 60 .29 .26 .22 .16 .104 60 .25 .22 .19 .14 .089 + 10 60 .21 .18 •15 .12 ■075 — 10 50 • 23 .23 .18 .15 .087 50 .20 .19 .15 .12 .072 + 10 50 .16 .14 .12 .10 .058 Usual conditions of steam-heating correspond to a mean of columns two and three. HOT WATER. f^Coejfficient 1.6.) Temperatures water 140° i6o» i8o» 200» „ - 10° 80° •93 •70 •56 ■ 47 •42 80 .83 .62 .50 .42 •38 + 10 80 •73 •54 ■435 • 36 •33 — 10 70 •71 •55 •45 .38 • 35 70 .62 •47 .40 •333 •32 + 10 70 .53 •41 ■34 .28 .26 — 10 60 .54 .44 .41 ■ 31 .28 60 .47 • 37 .36 • 27 • 23 + 10 60 •39 • 31 •31 .27 .21 — 10 50 .41 .33 .25 •25 • 255 50 •38 .28 •30 .20 .196 + 10 50 .275 .225 .20 •175 .156 The radiating surface is in each case found by multiplying heat as required to supply loss from building per degree difference of temperature inside and outside by factor as given in the table. This factor is -7-; in formula (2). ( / t)0' DESIGN OF STEAM AND HOT-WATER SYSTEMS. 237 For a room with the same dimensions but on the second floor the quantities will be computed in the same way, except that we will take -^-^ of the cubic contents to supply that re- quired by ventilation, so that the total heat required for one degree difference of temperature would be 48 -|- 80 -|- 44 = 172. One fourth of this quantity gives the radiating surface for low- pressure steam-heating, which in this case would be 43, or one square foot of heating-surface to 55 cubic feet in the room. For hot-water heating the method of computation would be exactly the same, but the factor would be 0.4 instead of \. The radiating surface would then be, for the case considered, 0.4 of 216, which is 86, or one to 28 cubic feet for a room on the first floor, and 0.4 of 172 or 69 square feet, which is in ratio of i to 35 cubic feet for the second floor. Many designers of heating apparatus compute the amount of radiating surface required by approximate " rules-of-thumb " which are in current use in their localities. These rules differ in many cases very greatly from each other, and often have to be modified materially in order to give satisfactory results. In the application of the more scientific rules which have been given there will still always be an opportunity for applying judgment and the results of experience and practice, since it is quite impossible that any table of coefficients, no matter how extensive, could be given which would apply to all cases of building construction and to all exposures. Allowance for un- usual conditions are given by Mr., Wolff as follows (see page 69): The amount of radiating surface as given should be in- creased respectively as follows : Ten per cent where the exposure is a northerly one and winds are to be counted on as important factors. Ten per cent when the building is heated during the daytime only and the location of the building is not an exposed one. Thirty per cent when tlie building is heated during the daytime only, and the location of the building is exposed. Fifty per cent when the building is heated during the winter months intermittently, with long intervals (say days or weeks) of non-heating. Certain allowances, in addition to the above, the amount of which must be determined by the judgment or experience of 238 HEATING AND VENTILATING BUILDINGS. CRUDE ESTIMATE OF SPACE HEATED BY i SQ. FT. OF DIRECT 5r£^iI/-HEATING SURFACE. Authority.. Dwellings. First floor Second floor. . . Average Living rooms. , 1 side exposed. 2 sides ' ' Halls and bath-rooms. Sleeping rooms Public Buildings. Offices \ Banks School-rooms -j Factories Stores, wholesale. . . . " retail " dry -goods. . . . " drugs Assembly halls Auditoriums Churches Large hotels A. 35 to 6o 50 to 80 50 to 80 35 to 60 50 to 80 35 to 60 75 to 100 75 to TOO 75 to 100 125 to 200 125 to 200 B. 60 to 80 ■ 60 to 80 ■ 60 to 80 100 75 75 to 100 75 to 100 150 to 200 35 to 50 50 to 75 D. 50 70 70 150 125 80 70 200 125 50 50 45 40 40 to 50 60 to 75 50 to 75 60 to 80 80 to 100 80 to 100 100 to 150 TOO to 150 the engineer, should be made for unusual construction of the building, either good or bad. The rules which have been given for determining the amount of radiating surface are exceedingly numerous. Some of these rules require the proportioning of radiating surface, as in Tredgold's * and Hood's f works, by the amount of glass, others by the amount of glass and exposed wall surface, :j: but the great majority by the number of cubic feet of space in the room. The discussion which has been given is sufficient to show that the amount of heat required is a function of the exposed surfaces, so far as the loss from the walls is concerned, and of the cubic contents, so far as the supply of air for venti- * " Warming and Ventilating Buildings," Tredgold, 1836. f "Warming Buildings," Hood, 1855. X John J. Hogan in Metal Worker, Nov. 10, 1888. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 239 CRUDE ESTIMATE OF SPACE HEATED BY i SQ. FT. OF DIRECT HOT-WATER HEATING SURFACE. Authority.. Dwellings.. First floor Second floor. .. Average Living rooms. . I side exposed.. -x sides "■ Halls and bath-rooms Sleeping rooms . . . Public Buildings : Offices Banks School-rooms.. Factories. Stores, wholesale . . . " retail " dry-goods.. . " drugs Assembly halls Auditoriums Churches F. 25 to 35 35 to 40 20 to 30 15 to 25 30 to 60 30 to 60 45 to 70 45 to 70 45 to 70 80 to 100 80 to 100 80 to 100 A. 25 to so -j J 20 to 50 ( 20 to 40 30 to 50 ( 20 to 50 I 25 to 50 i 20 to 50 [ 25 to so 45 to 65 I 35 to 65 I 45 to 65 [ 35 to 65 45 to 65 35 to 65 70 to 130 Soto J 25 70 to 130 80 to 125 High Temp. 50 to 70 Low Temp. } 30 to 50 S 50 to 70 30 to 50 50 to 70 30 to 50 65 to 90 65 to go j- 65 to 90 > 130 to 180 j- 130 to 180 20 to 30 30 to 40 25 to 40 30 to 50 30 to 50 35 to 50 35 to 50 40 to 60 40 to 60 75 to 130 75 to 130 H. 30 28 25 20 to 30 30 to 40 30 to 50 30 to 50 50 to 70 50 to 70 80 to 100 80 to 100 E. 28 25 20 to 30 30 to 40 30 to 40 40 to 50 50 to 60 50 to 60 75 to 100 75 to 100 latioh, but both of these quantities must be considered in order to give results which are even approximately correct. In any locality it would seem that the rules which are in common use when modified as to the condition of buildings in which they have been successfully applied would be of con- siderable value ; for that reason the preceding tables are given showing the relation of radiating surface to cubic feet of space to be heated as stated by various authorities ; it will be noticed, however, that there is such extreme* variation in the amount of heating surface required for the same conditions that the results are almost valueless, and indicate that wide variation is common in the practice of different designers, 119. The Amount of Surface Required for Indirect Heating. — For this case the heat received by the rooms is all supplied by air which passes over the radiating surfaces and is heated by convection. A large number of tests have been quoted of these heaters, both with natural and mechanical draft 240 HEATING AND VENTILATING BUILDINGS. (see Article 52, page 103). From these experiments it is seen that the amount of heat given off by one square foot of surface varies with the velocity of the air, as shown by the table on page 1 14 and also in the diagram Fig. 187, the use of which has been explained. From the table on page 1 14 it will be noticed that with natural circulation the velocity in feet per second will vary from 2.97 for a height of 5 feet to 8.4 for a height of 50 feet, and the corresponding convection expressed in heat-units per degree difference of temperature per square foot per hour, which in the preceding table is termed the coefficient, varies from 1.7 to 2.8. In indirect systems of heating the warm air enters at a temperature 30 to 60 degrees above that in the room and passes out either through the vent-flues or by other means of egress at a temperature practically that of the room. In cool- ing to the temperature of the room it must surrender sufficient heat to balance that lost through the walls and windows. Neglecting the slight change in volume due to change in temperature, the amount required can be readily computed ! thus if the entering air be about 100 degrees F., one heat-unit (B. T. U.) will raise 58 cubic feet one degree (see Table X) ; hence one cubic foot in cooling thirty degrees will surrender 30/58 parts of a heat-unit. Since we require approximately to balance the building loss, heat-units equal to the product of the difference of the temperature of the room and the outside air, multiplied by the glass surface, plus one fourth that of the exposed wall, we can find the volume of air required by divid- ing the result by 30/58 for the above case. The extent of heating surface in square feet in the radiator can be obtained by dividing the total number of cubic feet of air as obtained above by the number of cubic feet which may be heated the required amount by one square foot of heating surface. These results are better expressed in shape of formulas from which tables suited for practical application may be computed. Let / equal the temperature of the room, t' that of the outside air, /" that of the mean temperature of the air surrounding the heating surface, T' that of the heated air, 7" that of the radiating surface, H the heat required per hour per degree difference of temperature to supply loss from the room, a the DESIGN OF STEAM AND HOT-WATER SYSTEMS. 24 1 heat given off from i sq. ft. radiating surface per degree difference of temperature. We have the following formula : Loss from the room per hour {t — t')H =(t — t')(G + ilV) nearly; (i) Heat brought in by i cu. ft. of air i/58( T —t); {2) Heat given off from i sq. ft. of radiating surface per hour ^a{T-n; . (3) Cubic feet of air required per hour = ——- — ~ ; ..... (4) Cubic feet of air heated by i sq. ft. of radiating surface per hour a{r—i") = 77^8(r^L"7J (see Article 31. page39);. (5) U i')(T' i')/f Radiating surface = Atr — 1^ = (Factor as in table) H; . (6) The table,* page 242, computed from the above formulae for various conditions gives a series of factors which, multiplied into the building loss H per degree difference of temperature, will give the radiating surface required ; it also gives the num- ber of cubic feet of air heated the required amount per square foot of radiating surface per hour. To use the table, we need simply to know, in addition to temperatures, the probable coefficient of heat transmission, all other conditions being given. For ordinary indirect heat- ing, first floor, the velocity of air can be considered as 2 to 4 feet per second, and the corresponding value of this co- efficient as 2. For higher floors the velocity is higher, and co- efficients may be taken as 3. (See page 1 14 ) ' As an example, assume outside temperature zero, inside temperature 70°, and the air leaving the indirect at 100', the factor with which to multiply the building loss to obtain radiating surface is 0.69. This is practically 3.00 times that for direct heating. Com- puting the radiating surface required for the same room as that considered in the case of direct heating (page ,235), in which there was 48 square feet of glass and 320 square feet of exposed wall surface, and in which the total loss of heat per degree difference of temperature was 128 heat-units, the indi- rect surface required would be this quantity multiplied by the factor 0.69, which is 88 square feet, or about one half more than . required in the calculation for direct heating. For the * In the table the terrr> "-^efficient is used for the heat transmitted per degree 242 HEATING AND VENTILATING BUILDINGS. TABLE OF FACTORS TO OBTAIN INDIRECT HEATING SURFACE AND OF CUBIC FEET OF AIR HEATED PER SQUARE FOOT OF SURFACE PER HOUR. Temperatures. B. T, U.-Total Heat per Sq. Ft. Heater. Factors for Heater Surface.* Cu. Ft. Air per Sq. Ft. Heat. Surf, per Hour. Air Entering- Room. m Mean Differ- ence Air and Radia- tor. c l—hI7- , ^ V-' ' + W ^ = 37.70^^^^. ^=0.167^ ^_ The friction caused by bends and by passing through valves and into entrance of pipes is of considerable amount, and often requires consideration. It can be considered as producing the same resistance to flow as though the pipe had been increased in length certain distances as follows : 90-degree elbow is equivalent to increase in length of the pipe 520 diam- eters, globe valve 700 diameters, entrance of a pipe in tee or elbow 60 diameters, entrance in straight coupling 20 diameters. The flow of steam in pipes presents some problems slightly different from that of flow of air (Articles 31 and 32), but in many respects the two cases are similar. There is a tendency for the steam to condense, which changes the volume flow- ing and affects the results greatly. The effect of condensa- tion and friction is to reduce the pressure in the pipe an amount proportional to the velocity and also to the distance, and these losses are greater as the pipe is smaller. There DESIGN OF STEAM AND HOT-WATER SYSTEMS. 249 are at the present time exact data regarding the steady flow of steam in pipes, yet it has been customary for writers to assume that the same laws which apply to the flow of water hold true for steam also, and that the same methods can be used in com- puting quantities. These results are certainly safe, although no doubt giving sizes somewhat larger than strictly necessary for the purposes required. In estimating the size of steam-pipe for power purposes it is customary to figure the area of cross-section, such as giving a velocity of flow not exceeding 100 feet per second. This velocity is generally accompanied by a reduction of pressure in a straight pipe of about one pound in 100 feet. For steam- heating purposes the general practice is to use a much larger pipe and lower velocity, so that the total reduction in pressure on the whole system is much less ; the effect of a drop in pres- sure of one pound will cause the water to stand in the return pipe in a gravity system 2.4 ft. above the water-level in the boiler. The velocity of water and steam in a gravity system of heating is due to a different cause from that in the case just considered, for the reason that the pressure upon the heater acts uniformly in all directions, and exerts the same force to pre- vent the flow into the boiler from the return, as to produce the flow into the main. For such cases the sole cause of circula- tion must be the difference in weight of the heated bodies, hot water, or steam in the ascending column and the cooler and heavier body in the descending column. The velocity induced by a given force will be reduced in proportion as the mass moved is greater. In the case of steam-heating the difference between the weight in the ascending and descending column is so great that the velocity will not be essentially different from that of free fall, provided correction is made for loss of head due to friction, etc., as explained, but in case of hot water the theoretical velocity produced will be found very small. The case is very similar to the well-known problem in mechanics in which two bodies A and B of unequal weights are connected by a cord passing over the frictionless pulley C (Fig. 190). 250 HEATING AND VENTILATING BUILDINGS. The heavier body B in its descent draws up the lighter body A. In this case the moving force is to the force of gravity as the difference in the weights is to the sum of the weights, and the velocity is the square root of twice the force into the height. In other words, if/ equals the moving force, we have by proportion f:g::B-A:B-^A, from which B~A ^ "^ B + A' which, substituted in place of / in formula v = the following as the velocity : / 2 ^(^ - A-)A B + A ' /i being the height fallen through. In applying this to the case of hot-water heating we have, instead of the descent and ascent of two solids of different weights, the descent and ascent of columns of water connected as shown in Fig. 191, the heated water rising in the branch AI^ and the cooler water descending in the branch BC. The force which produces the motion is the difference in weight of water in the two columns; the quantity moved is the sum of the weight of water in both columns. This is equal to the difference in weight of I cubic foot of the heated and cooled water divided by the sum, multiplied by the total height of water in the system, so that if fFi represents the weight of i cubic foot in the column BC, a.nd IV represents the weight of i cubic foot in the column A/'", and A represents the total height of the system, then the velocity of circulation will be, in feet per second. V'^ h{W, — W) {IV, + IV) Fig. 191. — Circulation IN Hot- WATER Pipes. In this formula no allowance whatever is made for friction, consequently the results obtained by its use will be much in excess of that actually found in pipes. The amount of fric- tion will depend upon the length of pipe and its diameter. As result of experiment the writer found considerable variation DESIGN OF STEAM AND HOT-WATER SYSTEMS. 25 1 in different measurements of velocity, but in no case did he find a velocity greater than that indicated by the formula. The following table is calculated from the formula without allowance for loss by friction. The computation is made with the colder water at 160 degrees F., although little difference would be found in calculations at other temperatures. VELOCITY IN FEET PER SECOND IN HOT-WATER PIPES. d . ?'■■ Difference of Temperature. ^.u 2 4 2.6 2.7 3-0 4.0 500 1.6 1.9 2.2 2.2 2 6 2.8 3.0 3.2 4.2 600 1.8 2.0 2.4 2.5 2 8 3.0 3-2 3-5 4-5 800 2.0 2-3 2.6 2.7 3 2 3.-I 3.6 3-9 5-0 1,000 2.2 2.5 2.9 3-0 3 4 3-7 3-9 4-3 5.5 1,400 2.5 2.8 3-3 3-4 3 9 4.2 4.£ 4.9 6.5 1,800 2-7 3-2 3-6 3.8 4 4 4-7 5-0 5-4 7.0 2,000 2.g 3.3 3.8 3-9 4 5 4.9 5-2 5-6 7.2 3,000 3.4 3-9 4-4 4.6 5 3 5.8 6.1 6.6 8.5 4,000 3.8 4.3 5-0 5-2 6 6.5 6.8 7-5 9-7 6,000 4-1 4-7 5-4 5-7 6 5 7-1 7-4 8.2 10.5 8,000 4-4 5-0 5.8 6.0 7 7.5 7.9 8.7 "•3 10,000 4-7 5-3 6.1 6.4 7 4 8.0 8.4 9.2 II. 9 * The table is computed by formulae for d, see below, in which h = 318.6, ^ = 9.2, cu. ft. of steam per minute for 100 sq. ft. radiating surface. The table is computed for straight pipes with water-level in returns 6 inches above that in boiler. In case there are liends or obstructions consider the length of pipe increased as follows : Right-angle elbow 40 diameters ; globe-valve 125 diameters ; entrance to tee 60 diameters, For other resistances and steam- pressures multiply the diameters as given above by the following factors : Water-level in return above boiler 2 in. 12 in. 18 in. Multiply by 1.25 0.88 0.80 Steam-pressure above atmosphere 0.5 lbs. 2 lbs. 5 lbs. Multiply by 1.22 1.16 1.09 For obtaining the diameter of steam-main to be used in case there is a separate return multiply the above results by 0.82. For indirect heating without separate return multiply above results by t.4, with separate return use the results in the form given. 5/^27 ' d = 0.5374 1/ — , in which Q = cubic feet per minute, d = diameter in inches, / = length in feet, A = equivalent net head in feet. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 257 The following table will be found convenient for obtaining the size of a steam-main for low-pressure steam-heating, single- pipe system, for various lengths. The table is computed from same formulae as those on page 256, but for a lower steam- pressure, and results are given in commercial sizes of pipes, COMMERCIAL SIZES OF STEAM-MAINS FOR A SINGLE PIPE, (System of heating by direct radiation : pressure 0.5 lbs.; friction resistance 3 inches of water for lengths 100 feet and under ; 6 inches of water for greater distances.) Radiating^ Surface. Square Feet. Length of Steam-main in Feet, 40 8a 100 1 200 300 I Diameter of Pipe in Inches 600 20 40 60 80 100 200 300 400 500 600 800 1000 1400 1800 2000 3000 4000 6000 8000 .10000 I20CO 14000 16000 18000 20000 I I ij li li li li 'i li li -H li li li '■ ^k li li 14 14 14 li 14 2 2 2 2 2 2 2 2 24 24 2 24 24 3 24 24 3 3 H 3 34 34 3 34 34 4 34 34 4 4 4 4 4 4 4 4 4 44 4* 44 44 5 5 5 5 6 54 54 6 7 54 54 6 7 6 6 6 7 6 7 7 7 7 7 7 8 7, 8 8 9 8 8 8 9 9 9 9 10 14 2 2 24 3 3. ^\ 4 4 4^ 4i 5 6 7 7 9 9 10 II li li 2 2^ 3 '3 3 34 4 4| 5 5 6 7 7 9 10 II II li Ij ^^ I:j- i^ ij I5 I^ 2 2t 2i 3 3 3 34 3J 3 3i 4 4 4 4* 44 5 5 6 5 6 6 7 7 7 7 8 8 9 9 10 10 II 10 12 II 12 II 12 12 14 2 3 34 4 4 44 5 6 6 7 7 3 9 10 II 12 12 14 14 14 16 in using the above table take the equivalent length as explained on page 256, 258 HEATING AND VENTILAl ING BUILDINGS. TABLE FOR THE CAPACITY OF STEAM-PIPES 100 FEET IN LENGTH WITH SEPARATE RETURNS. By A. R. Wolff. Diameter of Diameter of Return. Inches. 2 Lbs. Pressure. S Lbs. Pressure. Supply. Inches. Total Heat Transmitted. B. T. U. Radiating Surface. , Squsre Feet. Total Heat Transmitted. B. T. U. Radiating Surface. Square Feet. 1 li I* 2 2i 3 3i 4 4i 5 6 7 8 9 lO 12 14 i6 I I li 2 2i 2* 3 3 3i 34 4 4 4i 5 6 7 8 9000 18000 30000 70000 132000 225000 330000 480000 690000 930000 1 500000 2250000 3200000 4450000 5800000 9250000 13500000 19000000 36 . 72 120 280 528 900 1320 1920 2760 3720 6000 9000 12800 17800 23200 37000 54000 76000 15000 30000 50000 I 20000 220000 375000 550000 80COOO I I 50000 1 5 50000 2500000 3750000 5400000 7500000 9750000 15500000 23OOOOCO 32500000 60 120 200 480 880 1500 2200 3200 4600 6200 10000 15000 21600 30000 39000 62000 92000 130000 In above table each square foot of radiating surface is assumed to transmit 250 heat-units per hour, a safe and con- servative estimate, as will be seen by consulting Chapter IV. For pipes of greater length than 100 feet multiply results in the above table by the square root of lOO divided by the length. In all cases the length is to be taken as the equivalent length in straight pipe of the pipe, elbows, and valves, as given on page 248. For other lengths multiply above results by following factors: Length of pipe in feet. . 200 Factor '. . . o. 7 1 300 400 0.58 0.5 500 600 700 800 900 1000 0.45 0.41 0.38 0.33 0.33 0.32 For example, the capacity of a pipe 8 inches in diameter and 800 feet lorlg would be 0.35 of 12800 sq. ft. of radiating surface = 4480 sq. ft. It will be noted that the size of return specified by Mr. Wolff is about one pipe-size greater than be- lieved to be necessary by the author, but sizes of main steam- pipe are in substantial agreement with tables on pp. 256 and 257. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 259 Unless otherwise impracticable the author would always advise the use of the table of commercial sizes of steam-mains in proportioning pipe sizes. In using the table, first find the size of the branch pipes from single radiators, and then the size of the mains which will be increased with amount of radiation carried, as shown in the table. 123. Size of Return-pipes, Steam-heating.— The size of return-pipes, if figured from the actual volume of water to be carried back, would be smaller than is safe to use, largely because of air which is contained in the steam-pipes, and which does not change in volume when the steam is condensed. For this reason it is necessary to use dimensions which have been proved by practical experience to be satisfactory. When the steam-main is large, the diameter of the return-pipe will prove satisfactory if taken one size less than one half that of the steam-pipe ; but if the steam-maiii is small, for instance, 5 inches or less, the return-pipe should be but one or two sizes smaller. The return-pipe should never be less than i inch, in order to give satisfactory results. The following table suggests sizes of returns which will prove satisfactory for sizes of main steam-pipes as given : Diameter Diameter Diameter Diameter Steam-pipe. Return-pipe. Steam-pipe. Return-pipe. inches. inches. inches. inches. 1* li 5 3 2 li 6 3* 2i 14 8 4 3 2 9 > 4i 3i 24 10 4i 4 2J 12' 5 The size of return-pipes, if computed on basis of reduction in volume due to condensation of the steam, supposing the steam to have a gauge-pressure of 40 pounds and that one half its volume is air, would be, neglecting friction, about one sixth of that of the main steam-pipe, which is much smaller than would be considered safe in practice. *■ Van Nostrand's Science .Series, No. 68. 26o HEATING AND VENTILATING BUILDINGS. Main and Return-pipes for Indirect Heating Surfaces. — The indirect heating surfaces require about twice as much heat as the same quantity of direct radiating surface, and hence, for same re- sistance in the pipe, the area should be twice that required in di- rect heating. It will usually be sufificiently accurate to use a pipe whose diameter is 1.4 times greater than that for direct heating. Reliefs and Drip-pipes. — The size of drip-pipes necessary to convey the water of condensation from a main steam to a return cannot be obtained by computation, as there is much uncertainty regarding the amount of water that will flow through, under the conditions which exist. As the flow through the relief tends to increase the press- ure in the return, it may also serve to lessen the velocity of flow beyond the point of junction, provided the size is greater than necessary to carry off the water of condensation from the steam-main. Drip-pipes should be united to the return in such a manner as to re-dnforce rather than impede the circula- tion, which result can usually be attained by joining the pipes with 60 or 45 degree fittings. The writer would recommend the employment of the fol- lowing sizes of drip-pipes as ample for usual conditions ; DIAMETER OF DRIP-PIPE FOR STEAM-MAINS OF VARIOUS LENGTHS. Length of Steam-main in Feet. Diameter of to 100. 100 to 200. 200 to 400. 400 to 600. Steam-main, Inches. Diameter of Drip-pipe in Inches. OtO 2 \ i i 1 3 h i 1 I 4 i f I li 5 i I li I* 6 I li li H 124. Size of Pipes for Hot-water Radiators.— Method of computation of the velocity with which circulation will take place in a hot-water heating-system without friction has been considered in Article 121, page 250. In some instances this DESIGN OF STEAM AND HOT-WATER SYSTEMS. 26 1 velocity is increased by bubbles or particles of steam which pass up the main risers and reduce the specific gravity of the water in the ascending pipes to such an extent that the actual velocity produced is much in excess of what would have been possible had no steam formed. This condition is undesirable, as it is usually accompanied with more or less noise and a very high temperature in the boiler, and should not serve as a basis for designing main-pipes to be used in hot-water heating ap- paratus. It should not be ^■ecommended that heaters be run in such a manner as to produce steam in any part of the circulation. The heat which is given off from radiating surfaces of va- rious kinds has already been considered (page 234"), and as each thermal unit given off by the surface is obtained by the cooling of one pound of water one degree in temperature, it is easy to compute from the data already given (i) the weight of water required, and (2) the number of cubic feet needed to heat each square foot of radiating surface. The following table gives the data necessary for computing the volume of water required to supply radiating surface for various conditions likely to occur in heating : HOT-WATER HEATING. Data Used in Computation of Tables. o o Temperature outside air o o o Temperature water in radiator. . 140 160 180 200 220 Heat-units per degree diff. tem- perature per square foot per hour 1-4 1-45 1-5 i-6 1.8 Weight of cu. ft. water, pounds.. 61.37 60.98 60.55 60.07 59-64 Total heat-units per square foot per hour : Room 60° per sq. ft 113 145 180 224 288 70° 98 130 165 208 270 Culiic feet of water required to supply one sq. ft. per hour. Radiator cooled 5°— Room 70° 0.316 0.426 0.546 0.686 o.go2 60° 0.396 0.472 0.592 0.740 0.970 70° 0.158 0.213 0.273 0.343 0.451 60° 0.183 0.236 D.296 0.37 0.483 70° 0.138 0.142 0.182 0.228 0.339 60° 0.132 0.157 0.131 0.247 0.361 70° 0.079 0.107 0.137 0.172 0.226 60° o.ogi 0.118 U.148 0.175 0.241 Radiator cooled 10° — Radiator cooled 15° — It << Radiator cooled 20° — By dividing the number of cubic feet to be supplied per hour by the velocity with which the water moves per hour we obtain the area of the pipe in square feet. 262 HEATING AND VENTILATING BUILDINGS. The general case from which practical tables may be com- puted can best be considered by the use of formulae, as fol- lows: Let w equal the weight of water per cubic foot, let H equal total heat per square foot per hour from radiator, R total radiating surface, Q number of cubic feet of water per hour, A area of pipe in square feet, a area of pipe in square inches, v velocity in feet per second as given in table, page 251, F equal velocity in feet per hour, 7" loss of temperature of water in radiator. We have the following formulae: (i) a = 144A. (2) V = 360CW , > HR _ ( Total heat divided by heat given off by i "-* wT ~ ^ ( cu. ft. equals total number of cubic feet. (4) -^= , = yi = — — . From which ^^' V 36CKW 144 (5) Q=z2t,av. Equate (3) and (5), and <6) i?= '^ (7) HR ■ 2^wvT By taking special values corresponding to temperatures of water and of surrounding air we can reduce these formulae to simple forms. Thus, if the temperature of the radiator is 180° and of the room 70°, the total heat-units given off per hour, H, will be 165. If we further assume that the water in the radiator cools during the circulation a certain amount, say 10 degrees, T will equal 10, weight of water ze/ will equal 60.5 pounds, and we shall have formulae 8 and 9 : (8) R = gzaw R (9) ^=^ For the above condition the radiating surface is equal to 92 times the area of the main pipe in square inches times the velocity of the water in feet per second ; and further, the area in square inches is equal to the radiating surface divided by 92 times the velocity. The velocity in feet per second will depend upon the height, the difference of temperature, and amount of friction. The following table gives relations of radiating surfaces to areas of main pipes, friction neglected. For distances less than 200 ft. suflficient allowance for friction will be made by making the main one size larger than required by table. DESIGN OF STEAM AND HOT-WATER SYSTEMS. 263 AREA AND DIAMETER OF HOT-WATER HEATING-MAIN, DIRECT RADIATION.* DiFFEREN'CE OF TEMPERATURE, 10 DEGREES. (1) (2) (3) Multiply each (4) Multiply Square Root Radiating (5) Height, Velocity Water 100 Square Feet Equivalent Head Jfeet. Feet per Second. Radiating- Surface for Area Main by Surface for in Feet. Diameter by I • 0.335 3-26 0.205 0.0015 5 - 0.750 1.45 ' 0.133 0.0081 10 1.06 1.03 0.II3 0.017 15 1.28 U.85 0.104 0.025 20 1-5 0.723 o.ogs 0.035 25 1.67 0.65 o.ogi 0.044 30 1.83 0.595 0.087 0.052 40 2.12 0.513 o.oSi 0.072 50 2.37 0.46 0.076 0.088 6o 2-59 0.42 0.072 0.105 8o 3.00 0.362 0.068 0.142 lOO 3-35 U.324 0.064 0.176 In the above table column (i) gives the height in feet ; column (2) the velocity corresponding to the head for a reduc- tion in temperature of lo'' F.; column (3) is the area in square inches, neglecting friction, for each 100 square feet of radiating -surface ; column (4) is the corresponding diameter of pipe required for each square foot of surface, and is to be multiplied by the number of square feet of radiating surface to give the diameter for any given case ; the actual diameter should be one pipe size greater- column (5) is the equivalent head which would produce the same velocity if falling freely in the air. The preceding table is in the same form as that given for diameters of steam-main. If we consider 10 feet as the aver- age height or head producing circulation for the first floor, it will be seen that we shall need, neglecting friction, one square inch in area in our main pipe for each 100 square feet of radia- tion, or the diameter of our pipe would be found for this case * As illustrating the use of the table, compute the area of main pipe needed to supply 350 square feet of direct radiation situated 25 feet above the .heater. The area is obtained by multiplying 3.5 by 0.65, which will equal 2.28 square inches. The diameter can be found from this, or it may be obtained from column (4), by multiplying thesquare root of 350 by 0.091. The square root of 350 is 18.7, the product is 1.7. The pipe used, if the distance is about 200 feet, should be i\ inches in diameter. 264 HEATING AND VENTILATING BUILDINGS. as equal approximately to \ of the square root of the radiating surface in square feet. If the temperature of the water be supposed to change 20° in passing through the radiators, the required area of the main would be one half of that given by the table ; if 15°, two thirds, etc. In hot-water heating the return-pipe must have the same diameter as the supply-pipe, since there is no sensible change in bulk between the hot and cold water. We may take as a practical rule, applicable when less than 200 feet in length : The diameter of main supply- or return-pipe in a system of direct hot-water heating should be one pipe-size greater than the square root of the number of sqtiare feet of radiat- ing surface divided by gfor the first story, by 10 for the second story, and by 1 1 for the third story of a building ; for indirect hot-water multiply above results by 1.5. The table given for commercial sizes of steam-mains in a single-pipe system of heating applies with accuracy to systems of hot-water heating and is easily and quickly applied. The table is to be used as explained for steam-heating. 125. Size of Ducts for Air-supply and Ventilation.^ An approximate method of computing the sizes of air-flues would evidently be that of dividing the total amount of air which is required in a given time by that delivered or dis- charged through a flue one square foot in area. A table is given for capacity of ventilating-pipes, see Appendix, Table XXV. The air required can be found as explained in Article 119, or by consulting the table, page 243. As an illustration, consider the same problem as in previous cases, viz., that of a room with 48 square feet of glass surface and 320 square feet of exposed wall surface, and from which the heat loss per degree difference of temperature is 128. Supposing air in room to be 70" F. and that suppHed by flue to be 100° F., we see by table page 265 that for every heat-unit as above there will be required 135 cubic feet of air per hour, and for this case we will require 135 X 128 = 17,280 cubic feet per hour. If excess of temperature of air in flue over that out- side be considered as 50°, and height of flue as 10 feet, the dis- charge per square foot of flue (see table in Appendix) will be 242 feet per minute or 14,520 per hour. Hence the required area of the flue will be 17,280 divided by 14,520 = 1.19 square feet DESIGN OF STEAM AND HOT-WATER SYSTEMS. 265 = 171 square inches. Areas of flues may be computed by the following table, making suitable allowance for friction. As the velocity of flow increases with difference of tem- perature between outside air and that in the flue, and is lessened when this difference is small, it is better to assume a mean difference of temperature so low that the computation will certainly afford plenty of air for ventilation. THEORETICAL AREA OF FLUE IN SQUARE INCHES REQUIRED TO SUPPLY A GIVEN AMOUNT OF HEAT. (Excess of temperature is 30"; allowance for friction, o.) ■& 5 Sot Height or Head of Flue in Feet. tH) SiSfe ■1* •0 • II IS. JO a 5 10 15 20 30 40 so 60 80 100 Area of Fl Je in Sqi are Fee H « B.T.U. B.T.U. 700 10 12 8.5 7 5-5 4.6 4.1 3-5 3-3 3 2.7 1400 20 24 17-5 14 II 9.2 8.2 7-' 6.6 6.1 5-5 aioo 30 36 26 21 i6.5 14 12.5 10.5 9-7 9.1 8.1 2800 40 48 35 28 22 .8.4 16.4 14 13.2 12.2 10.9 3500 50 60 43 35 27 23 21 18 16.3 15.2 13.6 5250 75 90 l" 58 41 35 V 27 24 23 21 7000 100 120 87 71 55 46 41 35 33 31 27 6750 125 150 108 83 68 57 51 44 41 38 34 X0500 150 180 129 116 82 ^ 61 S3 48 46 41 12225 175 210 151 123 95 81 r 62 57 |3 48 14000 200 240 173 141 109 93 82 71 66 61 55 17500 250 300 216 157 ,36 115 102 87 81 76 68 21000 300 360 258 212 164 138 122 105 98 152 82 28000 400 480 346 244 21S ,84 .63 141 '30 124 109 35000 500 600 432 315 273 231 204 175 163 '53 136 52500 750 900 645 530 412 347 306 263 243 229 204 70000 1000 1200 865 715 545 462 403 352 326 306 273 10500 1500 1800 1290 io6o 825 693 612 527 457 458 408 14000 2000 2400 1730 1410 1090 925 818 705 65s 612 545 175000 2500 3000 2160 1760 1360 1150 1018 870 820 765 68 1 21000 3000 3600 2580 2120 1640 1380 I2l3 'OSS 980 9>5 817 Table is computed by finding air required to supply heat by formula 4. page 241, when outside air is 0°. inside air 70°. and heated air 100°, and dividing this by the air supplied by a flue one square foot in area for the given height and a difference of temperature of 30°, as obtained in Table 16. Actual flues should be talcen 1 inch larger in each dimension to allow for friction. Ventiiating-flues for a given height should be taken one quarter larger than the values given in the table. It should be noted that this table gives the area of flue without allowance for ioss due to friction, and in piactice the results must be increased to give satis- factory service. ♦ See page 70. t Approximately equal to area of glass plus one fourth the exposed wall-surface. 266 HEATING AND VENTILATING BUILDINGS. The preceding table is computed by the method explained for different heights of flue and for a difference of temperature of the air in the flue over that in the space into which it discharges of 30° F. For difference of temperature other than 30° multiply results in the table by the following factors to obtain the area of the flue : Difference Temperature, Degrees. Factor. Difference Temperature, Degrees. Factor. 10 20 40 1.74 1.22 0.87 50 60 70 0.775 0.71 0.655 For usual conditions of residence heating in which the air in the supply-flue is 30° above the temperature of the air in the room, and that in the ventilating-flue 20°, we may compute the approximate area in square inches of the supply- and venti- lating-duct, by multiplying each heat-unit per degree difference of temperature lost from the walls by a series of simple factors which are easily memorized. TABLE OF FACTORS FOR AREA OF AIR-FLUES. Supply-duct. Ventilating-duct. Story of Building. Approxi- mate Head in feet. Velocity in feet per sec. Factor for Area, sq. in. Approxi- mate Distance to Roof. Velocity in feet per sec. Factor for Area, sq. in. First Floor Second " Third " Fourih " (1) 5 28 40 50 (2) 2.8 6.8 8.1 9- (3) :i.40 0.95 0.82 0.71 (4) 47 32 20 10 (5) 5-5 4.2 3-6 2.6 (6) 0.93 1.27 1.33 2.17 As an example, find the required area of heat- and venti- lating-ducts for a room with 200 square feet of exposed wall- surface and 30 square feet of glass : 30 plus one fourth of 200 is 80, the approximate building loss per degree. This quantity multipHed by factors in columns (3) and (5) gives respective areas of flues in square inches with sufficient exactness for ordinary requirements. The factors afford a ready means of computation in the absence of an extended table, similar to that on page 265. DESIGN OF Sl^EAM AND HOT-WATER SYSTEMS. 267 In some instances the amount of air can be computed as a function of the cubic contents of the room, especially when required for ventilation alone. For ventilation purposes the problem of proportioning the air-passages is solved simply by computing, first, the air required, on the basis of 1800 cubic feet per hour for each person who will occupy the room ; second, the number of times the air will be changed per hour, by dividing this result by the volume of the room. This method is considered fully in Article 38, page 62, and a table is given for computing the area of the flue ill square inches for different velocities of the moving air. In applying this method to practical problems, it is best to proportion the ducts so that in no case will the required velocity of the c\ir in the flue exceed 12 feet per second or 43,200 feet per hour, an amount not. likely to be reached without a fan or blower, and one which corresponds to a pressure of nearly o.i inch of water. 126. Dimensions of Registers. — The registers should be so proportioned that the velocity of the entering air will not be sufficient to produce a sensible draft ; that is, the area must be such that the velocity shall not exceed 3 to 5 feet per second or 10,800 to 18,000 lineal feet per hour. The writer thinks that very excellent results are obtained by proportion- ing the registers 'for first floor so as to give velocity of 2\ feet per second, and those of higher floors and at entrance to ventilating-shafts 3 feet per second.* The results above, ex- cept for entrances to ventilating-shafts on the top floor, are less than is usually produced by natural draft, so that the area computed by dividing the total amount of air required by the number which expresses the velocity gives satisfactory results. The above rules are for effective or clear opening, and this will be found in each case to be about two thirds of the nomi- nal or rated size of the register as shown in the table given in Article 144. By computing, from the data given, the number of changes of air per hour in room, the table page 63 can be used as explained to determine the effective area in square inches required for each 1000 cubic feet of space. * See Article 38. 268 HEATING AND VENTILATING BUILDINGS. As an example illustrating use of this table, suppose, in a room containing 2500 cubic feet, air to be changed four times per hour, and that velocity in air-flue be 6 feet per second, in ventilating-shaft 4 feet, through fresh-air register 2.5 feet, through ventilating-register.3 feet. The table on page 53 gives the net area for each 1000 cubic feet of space, so that for above conditions the results as found in the table must be multiplied by 2.5. We should have, taking 2.5 times the tabulated values, the following results: Net area supply-flue 67.5 sq. in.; ventilating-shaft 100 sq. in.; fresh-air register 166 sq. in.; ventilating-register 136.5 sq. in. The nominal area of the register to be used should be about 50 per cent greater than the net area ; it may be taken from the table given in Article 144. The velocity correspond- ing to 2.5 feet per second is taken as the mean of that given in the table for 2 and 3. It is best to make flue dimensions about one inch greater than obtained by calculation, to allow for surface friction. 127. Summary of Various Methods of Computing Quan- tities Required for Heating.' — The following table gives the required size of steam^pipes and of steam-boiler or hot-water heater, for various amounts of radiating surface. The propor- tions given will apply to residence heating or where the length of main pipe is not over 200 feet. The value given for the steam-main is that for the single-pipe system when no return is needed. For the system of separate steam- and return-pipes the diameter of the steam-main should be taken f of that given, that of the return as in table page 259. The cubic space heated is given if the ratio to radiating surface be known ; this is an approximation only, although it may often serve a use- ful purpose when experience has been gained of heat required in constructions of similar nature in the same locality. About two thirds as much air is warmed by hot-water as by stearn radiators, and flues should be about two thirds as large as given in the table on page 270. 128. Heating ol jreenhouses. — Greenhouses and con- servatories are heated in some cases by steam and in other cases by hot water, and there is quite a difference of opinion held by florists respecting the relative merits of these two DESIGN OF STEAM AND HOT-WATER SYSTEMS. 269 D \0 (^ N t^ C (Tj m in N N ~ 8 ?--8j fo d" d in ' S'°"'81 O O in if m t^ iH e <" J^ O M M M a •- u rt ^ 2 2 2 §•1111 a as ^nj O "^ d , y • a; u flj « ^ S rt g o S "m 3rt s":: &ou "? j; 1- u^ ^ I o o f^. o { m m in m m O O I t^ iNio m m o t 10 o O fo 1 \d \d in»o 00 ( m o »n H I min^mt^ioQ o ( 5ri6 oB O 10 o ot in m fo o ■+ « m « m o < in o n O W M H VD 1 in m N m ) h' M H vo m c .«■ — ^ ^ b>»r»4J ■ . 41 S v- t- u 4-* aj2 o c rt OJ „ *""'«») 2,— ^ - bMiMcn„fc--,_ ■^- - u "' 3 ■7 S V. 4J v, L, ij 01 ill — -d 5° c.S a 8is c rt a. "SB > u 11 3| December . . January February. . . March, 17 days 34-99° 33-27 32.04 29-75' 41-52° 44-35 43-67 39-94 57° 62.48 65-96 58-83 47-59' 51-41 52-54 4^-44 1505 2304 1704 1085 40.21° 42.72 42.42 39-16 51-69° 61 66.32 58.11 46.39° 49-45 51-01 46-73 2350 3202 2540 1692 Averages. . . 32-51° 42-37° 61.06° 49-74° Total 659S 41.12° 59-28° 48-39° Total 9784 276 HEATING AND VENTILAriNG BUILDINGS. Summary for Hot-water Boiler. Total coal consumed from December i, 1889, to March 18, 1890, 6598 lbs. Average daily temperature for the time, 49.74°. Summary for Steam-boiler. Total coal consumed from December i, 1889, to March 18, 1890, 9784 lbs. Average daily temperature for the time, 48.39°. A saving of fuel in favor of hot water of about 33 per cent. Similar tests were made under tlie ^en°ral direction of the author for the Michigan Experiment Station and are to be found reported in full in a paper by the writpr, read before the American Society of Mechanical Engineers, Volume XI. For this test two houses were used, each of the same size and of the same grade of construction. The houses were equally exposed to the heat of the sun, but the hot- water house was rather more exposed to the wind. The general method of testing was essentially the same as that described, and the results show substantially the same difference. The heaters used were cast- iron of the drop-tube form, quite different from those used in Massachusetts, but well adapted for the work. The following table gives a summary of the results : SUMMARY OF RESULTS OF TEST OF HOT WATER AND STEAM. Year. 1889 1890 Months. December. 10 January. February. March. April. Days of Experiment, 3t 28 20 30 a a •a i ai 2799 90.3 27.7 38 27.2 54-1 £4.8 4 a •X. a a n V 55 1800 60 36.2 42 38 51.8 54-9 5.9 Total coal . Average coal per day. . Average outside temper- ature, 6 a.m Average outside temper- ature 4P M 1025 93.2 31.8 38.5 35-1 53.9 54-9 825 75 31.8 38.5 35-1 54-9 60.3 13 3475 112. 1 27-7 38 27.2 52.5 53.8 4.4 34CO 121. 4 22 33.8 27 54-1 53-5 4.3 2ns 99.1 22 33-8 27 54-4 56 4.2 2714 114. 4 19.2 29.2 22.0 53-3 55.7 2288 135-7 19.2 29.2 22.0 54.3 57 ■ 1800 60 36.2 42 38 58.4 60.2 4-3 Average outside temper- ature, 9 p.M Average inside temper- ature, 6am Average inside temper- ature, 9 p.M Extreme variation DESIGN OF STEAM AND HOT-WATER SYSTEMS. 277 .During the month of April, 1890, the same amount of coal was burned in both heaters in order to see what the effect would be on the resulting temperature of the two houses. The results gave a temperature which averaged 8.5 degrees higher in the hot-water house than in the steam-heated house. Experiments were made by Prof. L. H. Bailey, of Cornell University, in 1891 with houses which were not similar either as to exposure or methods of piping, the results of which were in general somewhat more favorable to steam than to hot water. In 1892 Prof. Bailey arranged the same room so that it could be alternately heated with steam and hot water. The results of this last test so far as economy is concerned were also somewhat in favor of the steam-heat. The general conclusions which Prof. Bailey drew from this test were as follows : Conclusions. Under the present conditions the following results can be deduced. It will be observed that they confirm several of the conclusions of last year. 1. Hot water maintained a slightly greater average difference between the minimum inside and outside night temperature than steam. 2. There was practically no difference in the coal consumption under the two systems. 3. With a small plant like this the fluctuations under both systems are much greater than in larger ones, and neither proved very satis- factory. 4. The utility of slight pressure in enabling steam to overcome un- favorable conditions is fully demonstrated. 5. The addition of crooks and angles is decidedly disadvantageous to the circulation of hot water and of steam without pressure, but the effect is scarcely perceptible with steam under low pressure. 6. In starting a new fire with cold water, circulation commences with hot water sooner than with steam, but it requires a much longer time for the water to reach a point where the temperature of the house will be materially affected. 7. The length of pipe to be traversed is a much more important con- sideration with water than with steam. 8. A satisfactory fall towards the boiler is of much greater importance with steam than the manner of placing the pipes. 129, Heating of Workshops and Factories. — Work- shops or factories where counter-shafts and belting are running which keeps the air in agitation can be heated satisfactorily by 2/8 HEATING AND VENTILATING BUILDINGS. erecting coils of pipe for radiating surface near the ceiling of the room. Coils made with branch-tees, as described in Article 64, page 137, may be used, with the pipes placed in a hori- zontal plane and parallel to each other. In such a position the radiating surface is very efficient, and the heat given off as shown by experiment is a maximum. In a coil located near the ceil- ing the temperature of the room in the upper portion will be come very high and will not be evenly distributed unless the air is mechanically agitated, so that the overhead system of piping is only satisfactory in shops and places where there are moving belts or other means for agitating the air. The method of proportioning supply-pipes and radiating surface for this case has already been considered. Mr. C. J. H. Woodbury gives, in Vol. VI, page 861, " Transactions of American Society Mechanical Engineers," considerable useful data relating to this method of heating. It is the favorite method for heating cotton-mills, about one foot in length of i^inch pipe being used for 90 cubic feet of space. Summary of Approved Methods for Design of Steam and Hot-water Systems of Heating. — For convenience of applica- tion the following concise summary of approved methods of computation for radiating surface dimensions of pipes and grate surface are here given : A. Compute area of windows and outside doors, G, and one-fourth the exposed wall surface, \W, for each room. In computing exposed surface estimate ceilings and partitions adjacent to unheated rooms as 30 to 50 per cent exposed. Denote this result by A. B. For direct radiation. Compute 2 per cent of the cubic contents of each room. For residence heating take once this quantity for second- and third-floor rooms, twice this quantity for first-floor rooms, three times this quantity for halls; for office, store, or bank rooms, twice this quantity; for large assembly-rooms, lecture-halls, churches, etc., one half this quantity under usual conditions. Denote this result by ^. DESIGN OF STEAM AND HOT-WATER SYSTEMS, ^jg C. For radiating surface, direct heating, multiply the sum of the results A and B by one fourth for steam-heating ; multiply this last quantity by five thirds for direct hot-water heating. D. For dimensions of piping, direct heating, use the tables given. The table computed for one-pipe systems of steam- heating, commercial sizes of pipes, will apply with accuracy for dimensions of pipes for hot-water heating, both return- and flow-pipe being of dimensions shown in the table. For two- pipe systems of steam-heating use the special table for steam- and return-pipes, or use the table referred to above for steani- pipes less than 3 inches, taking the main one pipe-size smaller than tabulated when above 3 inches in diameter. Take in all cases the diameter of return from the special table. In applying tables, in all cases, find first the diameter of branches to each radiator; second, the diameter of sub-main ; and third, the diameter of main and return, corresponding in each case to total area of radiator and the equivalent length of pipe. The equivalent length of pipe is the actual length increased by allowance for elbows and bends as explained. E. For radiating surface, indirect heating, multiply the result A ^^ G -\- \W by the following factors for steam- heating,: for the first floor, by 0.7; for the second floor, by 0.6; for the third floor, by 0.5. For hot-water heating multiply each result as above by five thirds. F. For dimensions of piping, indirect heating, use the table given for one-pipe system of steam-heating, for finding the diameter of the steam-pipe in steam-heating and for the diame- ter of flow- and return-pipes in hot-water heating. Take the diameter of return-pipe for steam-heating from special table. Tables to be used as explained. G. Size of air-flues, indirect heating, should be computed on the basis of a cross-sectional area for each square foot of surface in the radiator as follows, steam-heating: 1.5 to 2.0 square inches for the first floor, i.oto 1. 2 5 square inches for the second floor, and 0.9 to i.o square inch for the third and higher floors. The cold-air flue supplying any radiator should 28o HE AIDING AND VENTILATING BUILDINGS. have 0.8 the area of cross-section of that of the hot-air flues. The vent-flues from the room should have an area equal to that of the hot-air flues on the first floor, and lo to 20 per cent greater for the higher floors. For hot-water indirect heating area of flue may be two thirds as great, reck- oned from area of radiating surface. H. Dimensions of register for supplying air should be such as to give a net area not less than one and two-thirds to twice that of the section of the hot-air flue ; for ventilation purposes the net area should be 50 per cent greater than cross- sectional area of hot-air flue. I. To compute heating surface in boiler or heater, divide total radiating surface, in which is included the surface of all uncovered pipe, by 6 to 8 for the area of heating surface in a steam-heater, and by lo to 12 for area of heating surface in a hot-water heater. To compute area of grate divide total radiating surface obtained as before by 120 to 2O0 for steam-heating, and by 200 to 300 for hot-water heating. J. To compute area of smoke-flue first find total radiating surface as explained ; if for steam, obtain diameter of flue as explained in Article 95 ; if for a hot-water heating system, multiply by 0.6 to reduce to equivalent steam-radiation j then proceed as before. CHAPTER XI. EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 130. General Remarks. — Steam after being employed in an engine contains the greater portion of its iieat, and if not condensed or utilized for other purposes it can usually be em- ployed for heating without materially affecting the power of the engine. The systems of steam-heating which have been described are those in which the water of condensation flows directly into the boiler by gravity. In other systems in use high-pressure steam is carried in the boilers, high- or low- pressure steam in the heating-mains and radiators, and the return-water of condensation is received by a trap and de- livered either into a tank from which it is pumped into the the boiler or in some instances wasted. The exhaust steam may need to be supplemented by live steam taken directly from the boiler, which may be reduced in pressure either by passing, through a valve partly open, or a reducing-valve, as described in Article 137. It will often be found that little attempt is made to utilize the heat escaping in the exhaust steam from non-condensing engines, and consequently a good opportunity exists for con- struction of systems which will save annually many times their first cost. 131. Systems of Exhaust Heating. — The exhaust steam discharged from non-condensing engines contains from 20 to 30 per cent of water, and considerable oil or greasy matter which has been employed in lubricating. When the engine is freely exhausting into the air, the pressure in the exhaust-pipe is, or should be, but slightly in excess of that due to the atmos- 281 282 HEATING AND VENTILATING BUILDINGS. phere. The effect of passing exhaust steam through heating- pipes is likely to increase the resistance and cause back press- ure which will reduce the effective work of the engine. The engine delivers steam discontinuously, but at regular intervals at the end of each stroke. The amount is likely to vary with the work done by the engine, since the engine-governor is always adjusted to admit steam in such amount as is required to preserve uniform speed; if the work is light very little steam will be admitted to the engine. For this reason the supply available for heating varies within wide limits. The general requirements for a successful system of exhaust- steam heating must be, first, the arrangement of a system of piping having such proportions as will make little or no increase in back pressure on the engine and will provide for using an intermittent supply of steam ; second, provision for removing the oil from the exhaust, since this will interfere materially with the heating capacity of the radiating surfaces ; third, provision against accidents by use of a safety or back- pressure valve so arranged as to prevent damage to the engine by sudden increase in back pressure. These requirements can be met in various ways. To pre- vent sudden change in back pressure due to irregular supply of steam the exhaust-pipe from the engine should be carried directly to a closed tank whose cubic contents should be at least 30 times that of the engine and as much larger as practi- cable. This tank can be provided with diaphragms or baffle- plates arranged so as to throw all or nearly all the grease and oil in the steam into a drip-pipe, from which it is removed by means of a steam-trap, as described in Article 98, page 194. To this tank may be connected a relief-pipe leading to the back- pressure valve, and also a supplementary pipe for supplying live steam. The supply of steam for heating should be drawn from the top of the tank. Any system of piping may be adopted, but extreme care should be taken that as little resistance as possible is introduced at bends or fittings. The radiating surface employed should be such as will give the freest possible circulation. In general, that system will be preferable in which the main steam-pipe is carried directly to the top of the building, the distributing- EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 283 pipes run from that point, and the radiating surface is supph'ed by the down-flowing current of steam (Fig. 173). It is desir- able to have a closed tank at the highest point of the system, from which the distributing-pipes are taken, and provided with drips leading to a trap so as to remove, before it can reach the radiating surface, any water of condensation or oil which has been carried to the top of the building. 132. Proportions of Radiating Surface and Main Pipes Required in Exhaust Heating. — The size of exhaust pipe required for an engine of given power, in order that the back pressure shall not exceed a certain amount, may be computed, the only data required in addition to that already given for heating with live steam, being that relating to the steam re- quired by engines. The amount of steam used by engines will depend upon the workmanship and class to which they belong, but we can assume with little error that non-con- densing engines will require the following weights of steam per horse-power per hour : simple with throttling-governor 40 pounds, with automatic governor 35 pounds, with Corliss valves 30 pounds ; compound using high-pressure steam 25 pounds. In order that the pipes may be sufficiently large it is better to proportion the systems for the more uneconomical type. TABLE OF DATA FOR COMPUTATION. Steam-pressure from Atmosphere o Absolute 14 , 7 Temperature of steam, F Temperature of air Difference _■ ■ -, Heat per min. from 100 sq. ft. radiation in B. T. U. equal 3 times' difference Total heat of steam above 212° Latent heat steam B. T. U Cubic feet steam per lb Cubic feet steam to weigh ?^ lb Cubic feet steam required each min. to supply 100 ft. rad. sur. , air 70° Weight of I cubic foot steam lbs. CThrottlingr „ ,, . - XT T» J Automatic Radiating surface per H. P \ Corliss [Compound Head of steam in feet equal i foot water of water column I 2 3 10 — 2 14.7 iS-7 .6.7 18.7 24.7 12.7 212 216 219 222 239 204 70 70 . 1° 70 70 70 142 146 149 152 169 134 426 4^8 447 456 507 402 966 967 967 967 973 962 966 90., 960 957 946 970 26.4 24 6 23-3 21.0 16.2 303 17. b 16.4 15.5 14.0 10.8 20.2 II. 6 11.25 10.85 ID. I 8.8 12.6 0.0379 .0403 .0427 047s .0640 .0326 J52 14b 143 139 126 162 134 129 127 122 112 146 114 IIO 107 104 95 122 95 91 90 87 79 102 1669 158s 1455 I317 lOIO 1902 -5 9-7 192 70 122 366 958 978 .39 <• 26.0 II. 5 .0257 179 158 134 112 2440 In the following discussion the dimensions of piping are computed for an engine using 40 pounds of steam per horse-power per hour (f pound per minute), and exhausting 284 HEATING AND VENTILATING BUILDINGS. against a back pressure above or below atmosphere as stated.* The preceding table gives properties of steam, also radiating surface supplied per horse-power by engines of various classes. The computation of the size of exhaust-pipes can be made by the following algebraic process : Let V equal velocity of the steam in feet per second ; V, velocity in feet per minute; /, length of pipe in feet; D, diameter of pipe in feet; d, diameter in inches; A, area of pipe in square feet; Q, cubic feet of steam discharged per minute ; k, back pressure above atmosphere ex- pressed in feet of steam ; p, back pressure expressed in pounds per square inch ; HP, horse-power of engine ; c, number of cubic feet in one pound of steam. From the formulae, page 248, we have, for velocity in feet per second „J~~hD ,/h ^ = 481/^-^:^5^ = nearly sof^i?; ....(.) from which by reduction the velocity in feet per minute V = yaooy jD = 866 yjd. (2) The discharge in cubic feet per minute Q = AV= zoooA\ jD = 4.723|/^ hpaf-pr. The air from the svstem can be exnelled bv 296 HEATING AND VENTILATING BUILDINGS. pressure through the mercury seal, which, however, acts to prevent its return to the system when the pressure falls, thus maintaining any vacuum produced by condensation. In the operation of the systems which have been described for circulating steam at less than atmospheric pressure, the valves or checks which prevent the return of the air must in all cases be so constructed as not to leak ; since any leakage of air into the system at any point would destroy the vacuum. The problem of constructing every valve or fitting of an entire system so as to remain perfectly tight, especially when below atmospheric pressure, is a difficult one, consequently all the above systems are likely to become inoperative for these reasons. To overcome the effect of slight leaks of air into the system Andrew G. Paul has designed and patented a system which in many respects is similar to that described, but/fn which the air is removed from each radiator positively by/an air-exhaust- ing device controlled by a thermostatic air-valve similar to that already described as in use in the Paul system. The Johnson system of hermetic heating, designed by W. S. Johnson of Milwaukee, consists of an air-valve attached to a radiator which is constructed in such a manner that when the air is once forced out it cannot return. In this case the air-valve and also the supply-valve are operated by pneumatic pressure controlled by a thermostat located at any convenient point in the room, as in the Johnson system of temperature regulation. It is intended to be used in connection with the Johnson system of heat regulation, and is arranged to produce any desired vacuum, by condensation, and consequently any desired temperature in the radiator to which it is attached. The Van Auken system of circulation is similar to the Paul system as already described, in that it has an exhausting device attached to a thermostatic air-valve in essentially the same manner. The thermostatic movement, however, is regulated by change of temperature in the room and operates both admission- and air-valve for each radiator, as in the Johnson system. The air- valve is so constructed that it admits air to the radiator when the temperature of the room is too high and discharges it through the exhauster when the temperature is too low, thus controlling the temperature by varying the amount of air in the radiator. EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 2g2 134. Combined High- and Low-pressure Heating-sys- tems. — In nearly all systems of heating with exhaust steam it is necessary to arrange the piping so that at times live steam may be admitted in any amount required, as substantially described in Article 130. In some instances high-pressure steam is carried in the boiler and may possibly be use.d in a few radiators, while the principal part of the building is heated with low-pressure steam which is drawn directly from the boiler, and is reduced in press- 298 HEATING AND VENTILATING BUILDINGS. ure by passing through a reducing-valve. In this case the return-water of condensation passes to a tank or chamber at the lowest portion of the system, and is fed into the boiler by means of a return-trap or steam-pump. The principal elements of such a system is shown in Fig. 199, as designed by the Albany Steam Trap Company, and forms a useful illustration of the method of piping essential. To start the pump automatically and to keep it moving at the proper speed a pump-governor (Article 135) is used. 135. Pump-governors. — In non-gravity systems of heating the water of condensation is returned to the boiler by return- traps, as described in Article 98, page 194, or by steam-pumps. The trap is automatic, and when in good order will operate without attention, but the ordinary steam-pump needs to be started and stopped, as required, to remove the water. To render the pump automatic a device termed a pump-governor is often employed. Many forms are used, but they con- sist in nearly every case of a tank containing a float or equiv- alent device, connecting with levers to the valve which admits steam for operating the pump. The tank is connected to the suction and located above the pump. When the tank is full of water, the steam-pump is put in operation by the rising of the float, which opens the steam-valve. When the tank is empty, the float falls, closing the steam-valve and thus stopping the pump. A pump-governor consist- ing of a float-trap with outside connections to a steam-valve, as described by F. Barron,* is shown in Fig. 200. A steam-pump with attached governor is shown partly in section Fig. 201. In this case the float is of the bucket form, the valve for supplying steam to the pump is flat with a single Fig. 200. — Pump-governor with Outside Levers. * Heating and Ventilation, March, 1894. EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 299 port, and is connected by an internal lever to the bucket in such a manner that when the tank is filled the valve will be opened and the pump will operate, and when the tank is empty the valve will be closed, and the pump will stop. The pump-governors are frequently set some little distance Fig. 201. — Internal Connected Pump-governor. from the pump, but attached in every case so as to produce the results described. 136. The Steam-loop. — A device which has been used quite extensively for returning water of condensation to the boiler when the pressure has been reduced only a few pounds is called a steam-loop, the construction and principle of operation of which, as described by Walter C. Xerr, is as follows : The figure shows the loop returning the water, from a separator attached to an engine-main, to a boiler above the separator level. " From the separator drain leads the pipe called the ' riser,' which at a suitable height empties into the horizontal. This runs back to the drop-leg, connecting to the boiler anywhere under the water-line. The riser, horizontal, and drop-leg form the loop, and usually consist of pipes varying in size from three quarters of an inch to two inches, and are wholly free from valves, the loop being simply an open pipe. 300 HEATING AND VENTILATING BUILDINGS. giving free communication from separator to boiler. (Stop- and check-valves are inserted for convenience, but take no part in the loop's action.) " Supposing, for example, the boiler- pressure to be loo pounds and the pressure at the separator reduced to 95. " The pressure of 95 pounds at the separator extends (with even further reduction) back through the loop. Fig. 202. — The Steam-loop. but in the drop-leg meets a column of water (indicated by the broken line) which has risen from the boiler, where the pressure is 100 pounds, to a height of about 1 1 feet, that is, to the hydro- static head equivalent to the 5' pounds difference in pressure. Thus the system is placed in equilibrium. Now the steam in the horizontal condenses, lowering slightly the pressure to 94 pounds, and the column in the drop-leg rises 2.3 feet to balance it; but meanwhile the riser contains a column of mixed vapor, spray, and water, which also tends to rise to supply the horizontal, as its steam condenses, and being lighter than the solid water of the drop-leg it rises much faster. By this proc- ess the riser will empty its contents into the horizontal, whence there is a free run to the drop-leg and thence to the boiler." 137. Reducing-valves. — The reducing-valve is a throttling- valve arranged to be operated automatically so as to reduce the pressure and also to maintain a constant pressure on the steam-mains. A great many forms of these valves are in common use. In one a diaphragm of metal or rubber is em- ployed, as in Fig. 203. The low-pressure steam acts on .one side of the diaphragm, a weight or spring which may be set at any desired pressure on the other side. This diaphragm is EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 30I connected with a balanced valve which is moved to or from its seat as less or more steam is required to preserve constant pressure. Since the pressure in the main steam-pipe does not Fig. 203. — Holt's REDUCiNG-VAiTE. effect the motion of the valve, its position will depend upon the pressure on the two sides of the diaphragm. The pressure on one side is that due to the steam which has passed through the valve, and that on the other to a weight or spring which can be set at any desired point. Another form of reducing-valve with differential piston and diaphragm is shown in Fig. 204, and is described as follows : Steam from the boiler enters at side " steam inlet" and, passing through the auxiliary valve K, which is held open by the tension of the spring S, passes down the port marked " from auxiliary to cylinder," underneath the differential piston D. By raising this piston D the valve C is opened against the initial pressure, since the area of C is only one half of that of D. Steam is thus admitted to the low-pressure side, and also passes up the port XX underneath the phosphor-bronze diaphragm 00. When the low pressure in the system has risen to the required point, which is determined by the ten- 302 HEATING AND VENTILATING BUILDINGS. sion of the spring S, the diaphragm is forced upward by the steam in the chamber, the valve K closes, no more steam is admitted under the piston D. The valve C is forced onto its seat by the initial pressure, thus shutting ofi steam from the low-pressure side. This ac- tion is repeated as often as the low pressure drops below the re- quired amount. The piston D is fitted with a dash-pot E, which prevents chattering or pounding. In another style of construction a piston acted on by the low- pressure steam serves to open or close a balanced valve an amount sulificient to maintain the steam- pressure constant. 138. Transmission of Steam Long Distances. — It is fre quently necessary to transmit steam long distances under- ground, and in many cases this method gives better financial returns than the construction and operation of a large num- ber of small and isolated plants. A number of plants, in which steam has been conveyed long distances in pipes laid under- ground, have been constructed for the purpose of heating portions of cities, and also various buildings belonging to the same public institution. The system of heating from a common boiler-plant has not generally proved successful financially in cities, as out of a large number which have been erected the writer knows of only one which is now in use. In the heating of various build- ings which belong to the same public institution this system of construction has proved a great improvement in many respects over that of separate heating-plants, although it is doubtful if in a single case it has ever resulted in the lessening of expense for fuel. Fig. 204. — Mason's Reducing- VALVE. EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 303 The three important requisites in the construction of such plants are, first, a removal of all surface-water so that it cannot possibly come in contact with the steam-pipe ; second, provision for taking up expansion of pipe and keeping it in proper alignment ; and, third, insulation of the pipe from heat losses. The first condition, which is the most important of all, is also the most likely to be overlooked, and many failures to secure economic transmission have been caused by allowing the surface-water to come in contact with the heated pipes. This water can be removed by the construction of a drain beneath or by the side of the pipe-system, provided with proper outlets. A perfect drainage-system for the soil is in every case an essential requisite for success. Provision for expansion may be made by the use of expan- sion-joints, as already described in Article 62, page 135, or by the use of elbows and right-angled offsets arranged to partly turn as the line expands. The writer has had experience with various forms of these joints, and found nothing equal to the straight expansion-joint, Fig. 90, which should, however, be constructed so that it cannot by any possible accident be pulled apart ; this may be done either by use of an internal lug or external brace. These joints should be thoroughly anchored, so that they will stay in position, and should be placed suf- ficiently close together to take up all expansion without strain on the pipe-line. If the ordinary slip-joints are used, they will need to be placed at distances of about 120 feet apart. The pipe between the joints should rest on rollers or connect- ing hangers which permit its free motion. If elbows and off- sets are employed to take up expansion, there will be an abrupt change in grade, and if any part dips below the main steam-Hne it should be drained by a pipe connecting to a trap or to the return. If bends convex upward are necessary, means must be provided for removing the air. In general, in systems where the steam is transmited long distances the best results will be possible only when the boiler- plant can be located on lower ground than the buildings to be heated, so that the water of condensation may be returned by gravity. This cannot always be done, and in many cases it will only be possible to return the water of condensation by j04 HEATING AND VENTILATING BUILDINGS. a pump located in one of the buildings to be heated, and regulated by a pump-governor. This in some Cases may in- volve more expense than will be warranted by the saving due to returning the water of condensation. For the insulation of the pipe many methods have been adopted, of which we may mention first the wooden tube and concentric air-space surrounding the pipe, Fig. 205. The Fig. 205. — Pipe with Woodkn-tube Insulation. tube is usually made by sawing out the interior portion of a log, leaving a shell or wall about two inches thick. Each length is provided with a mortise and tenon joint, and the dif- ferent lengths are joined together by driving. These wooden tubes are slipped over the steam-pipe as it is laid, the pipe being held in a central position by collars, so as to leave an air- space about one inch thick surrounding the pipe. This pipe is usually strongly banded with hoop-iron, and the joints can be made water-tight when laid, but checks soon form in the wood-pipe and make crevices through which the soil-water can reach the steam-pipe. Recently a form of tube made of two layers of inch board separated by tarred felting has come into use and is in general to be preferred to the solid tube as hav- ing superior insulating qualities. A view of such tubing partly in section is shown in Fig. 206. Fig. 206. — Wyckoff Built-up Wood Tubing. The wooden-tube system of insulation is objectionable, principally because it does not protect the pipe from ground- EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 30S water, its durability, as proved by experience, is not great, .and leaks in the steam-pipe are very difficult to locate and repair. A modified plan of the construction described has been em- ployed, in which both steam- and return-pipes were covered with asbestos and hair-felt and placed in a box made of 2-inch plank; the box was laid on a concrete bottom three inches thick, and after the pipes were laid it was completely surrounded with concrete. This was arranged so that the steam-pipes would not be disturbed by decay of the wood. The concrete would in that event support the steam-pipes and constitute a protecting tube. The heat insulation proved on trial to be much superior to that of the solid wooden tube, while its cost was somewhat less. Similar constructions in which the wooden tube has been replaced by sewer-pipe are in use and are of superior durability, In one case familiar to the writer a wooden tube lined with sewer-pipe was laid outside the steam- pipe, the whole being covered with earth ; such a construction replaced one shown in Fig. 205, but in practice its heat-insula- tion properties have not proved to be better. The best system of transmitting steam long distances, but probably also the most expensive, is to be obtained by build- ing a conduit lined with brick or masonry laid in cement and sufficiently large for inspection and repairs. The pipe should be carried in it on proper hangers and thoroughly wrapped with insulating material, as described in Article 116, page 200. Every required condition can be easily met in this construc- tion. The loss of heat from systems protected by a simple wooden tube is considerable, rising in many cases to from 30 to 40 per cent of that from the bare pipe. This is, however, due to the poor system of insulation used, since it should not exceed in any case 20 per cent of that from naked pipe (see page 2 30).' The 'loss from the underground system of piping at Cornell University, which is somewhat over one half mile in length, and in which the steam-pipes are laid inside of sewer-pipe, with a wooden tube outside the sewer pipe, the whole covered with about 4 feet of earth, causes the consumption of about two and one half tons of coal per day, which is about 10 per cent of the total coal consumption when the plant is working at normal 306 HEATING AND VENTILATING BUILDINGS. capacity. This heat loss is very nearly a constant amount and cannot be expressed as a fixed percentage of the total steam used, for the reason that when the steam consumption is large this percentage of loss is small and vice versa. High-pressure steam for power purposes is also sometimes transmitted in this manner and engines operated at a great distance from the boiler-plant. The losses from such a system of transmission are often serious, especially if a long pipe-line has to be kept hot, and if the engine is operated only a part of the time or only at partial capacity. Where the engine is worked to its full capacity, the loss is usually less than by any other system of transmission. The following paragraph gives a careful estimate, based on actual experiment, of the loss ex- perienced in transmitting constant power by various methods a distance of looo feet. The loss in transmitting power by any system is principally constant, and hence when the power is greatly increased the percentage is correspondingly reduced. The following estimate is based on the transmission of lOO horse-power lOOO feet : Percentage Method of Transmission. of Loss. Line shafting: Loss by friction (average 32) 25 to 40 Electricity : Loss in transforming from mechanical to electri- cal, and vice versa 20 to 30 Line loss 2 to 5 Total loss, electrical transmission 22 to 35 Conveying steam : Naked steam-pipe (still air) 37 to 45 Pipe covered with solid wood and earth 11 to 13 For operating machinery which is required occasionally or at intervals electricity is no doubt the most economical medium, since when the demand for power ceases the expenditure on account of transmission also becomes nothing, which is rarely the case either with line-shafting or steam. The diagram, Fig. 207, gives the summary of the results of a test of the Lehigh Coal-storage Plant, South Plainfield, N. J., EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 307 made by the writer to determine the heat lost in supplying an ensjine situated 740 feet from a boiler-house, the connecting He iJlz _0! sbetv| ee^ B >ile 'h ouse 8 nd Engini D / \ , -N / ) \ / 2000 lbs / \ To al 3t6 am pe H 3yi Ut ed on Lj. ^ Lbs s, 1 / \ y •V / / \ N — — / \ j ^ -^ ' 80 lbs T tal W eiK ht f (j on den sec St ear n p ir Koi r Lbs, 75 lbs . %-f- - ^ 5 ^ "S =- / s ''4V - £-w I s ;^i-^ => 100 lbs. // \ ID L^ci'iD 5 cb ^ ^ to H :^p* fri / / u z F^^: : CO .J / \ J (D li tA m '/ 1\ ^ |« ^ ; ■* r^ ^ / / \\j 3 .- -p a. ._ / V \ * n Mg CD oi // \ H i-ft 3)4=1'-' 80 J.bs. \ % •"l < '- CO 3 // L°Lffi_i_» sP. — \ y \ \c T / / 3) _ J ' ■V 70 lbs. \ \^ r-. r / ' ,e| ri / 1^. \ / / '^ / "} s£_ -/- 1/ ~ 60 lbs. t\ / / \ / V l^o c«" <>% V^ / \ s — s^y / 50 V N / > V ~ \ yq, ^ _ . ^ T sm Der atL re )f [ ="g ne Po Dm ^ ' 30" Baro ne er 20° 15° — — — — — — T jm Den Vtu ■e c •fA r ^ — / •^ . ^ \ /' J / I 35( / \ / \ / \ — . V- \ M aist jre f Ste am at tn gin e P \ Uer t 1 N / \ 2* ' / \ 1 'v. ^ \ 1 H ~ ~" V loistu re- T e ite 'in Is U rn F ey Ce It - \ ^ ^ >- ^ V " \ ^ ■ — ^ _ |V / _ __ _ _ _ 12 4, 6 8 10 12 14 16 18 20 22 24 .25 2» Fig. '207.— Diagram showing Results of Test to oetekmtnk. Heat Losses jn Underground Pipe. pipe-line consisting of 250 feet of 6-inch, 106 feet of 5-inch, and 391 feet of 4-inch pipe, having a total radiating surface of 1057.5 square feet. 308 HEATING AND VENTILATING BUILDINGS. The engine was 12-inch diameter, i6-inch stroke, running with a piston speed of aboift 600 feet a minute, thus producing, when cutting off at one third stroke, a velocity of steam of about 60 feet per second in the 4-inch supply-pipe. As this pipe was 391 feet long, more reduction in pressure was antici- pated than was actually found. As shown by the summary which follows, the actual reduction varied from 5 to 7 pounds, averaging 6 pounds. The general method of testing adopted was such as to give information, first, of the amount of water in the steam as it entered the steam-pipe ; second, the amount of water in the steam as it reached the engine ; third, the amount of water collected at intervening drips ; fourth, the total amount of steam used ; fifth, the fall in pressure between the boilers and engine. These determinations were made as follows : The amount of water in the steam was determined by a throttling calorimeter, the sample of steam being drawn in each case from a vertical pipe located close to a bend from a horizontal, and collected by a half-inch nipple extending past the centre of the vertical pipe. The drip was caught at places which had been provided in the pipe, and was weighed from time to time. The barometer readings were taken with an aneroid which had been compared with a mercurial barometer. The cor- rected readings are given in the summary as well as in the dia- gram. Simultaneous observations of the quantities given in the summary were taken every ten minutes. A study of the summary shows that the loss was sensibly constant during the run. This is clearly shown by noting the fact that any increase in the amount of steam flowing through the line had the effect of decreasing the percentage of moisture at the engine. The total heat loss per hour was equivalent to that required to evaporate (36 -)- 45.1 =) 81.1 pounds of water from a tempera- ture of 314° F., to a pressure of 70.1 pounds by gauge. This is equal to {81. i X 893 = ) 72,322 B. T. U. The average steam-pressure was 70. i pounds by gauge, its temperature 313.6° F., the average outside temperature 16.6° F.; hence the difference of temperature was 297°. The loss for each de- gree difference of temperature between that of outside air and that of steam becomes (78,342 -=- 297 = ) 243.7 B- T. U. per EXHAUST AND VACUUM STEAM-HEATING SYSTEMS. 309 hour. The total radiation surface was 1057.5 square feet; hence the loss in B. T. U. per square foot per hour was 0.229 per degree difference of temperature. This for a difference of temperature of 150° corresponds to 0.17 B. T. U. per degree difference per squcire foot per hour, an amount about 10 per cent of that which would have been given off from a naked pipe. (See page 86.) The loss by condensation varied from 3 to 8 per cent, the loss of pressure and consequent ability to do work about 6 per cent. The total loss was not far from 10 per cent from both these causes ; if this had been proportional to length, it would have been 13.5 per cent for a line 1000 feet in length. The diagram shows variations in the observed quantities as they occurred from time to time. It is to be noted that as the demand for steam at the engine was large the moisture in the steam delivered was correspondingly reduced. CHAPTER XII. HEATING WITH HOT AIR. 139. General Principles. — The general laws which apply- to hot-air heating have already been considered in the articles relating to Ventilation and to the Methods of Indirect Heat- ing with Steam or Hot Water.* The method of heating with hot air, as usually practised, consists in first enclosing a suit- able heater, termed a furnace, in a small chamber v.'ith brick or metallic walls, which is connected to the external air by a flue leading to its lower portion and to the various rooms to be heated by smaller flues leading from the upper part. In operation the cold air is drawn from the outside, is warmed by coming in contact with the heated surfaces of the furnace, and is discharged through the proper flues or pipes to the various rooms. The rapidity of circulation depends entirely upon the temperature to which the air is heated and the height of the flue through which it passes ; the velocity will be in every case essentially as given in the table on page 531. In order that a system of circulation may be complete flues must be pro- vided for the escape of the cooler air from the room to be heated, otherwise the circulation will be very uncertain and the heating quite unsatisfactory. Registers and flues for the escape of the air from the room are often neglected, although fully equal in importance to those leading to the furnace. Regarding the relative merits of hot-air heating by furnace as described and of the various systems of steam or hot-water heating, little can be said in a general way, since so much de- pends on circumstances and local conditions. It is rarely that these systems come in direct competition. The force which * See pages 52 and 239. 310 HE A TING WITH HOT AIR. 3 1 1 causes the circulation of the heated air is a comparatively feeble one and may be entirely overcome by a heavy wind ; consequently it is generally found that the horizontal distance to which heated air will travel under all conditions is short ; i, hence the system is in general not well adapted for large buildings. When properly erected and well proportioned, this system gives, in buildings of moderate size, very satisfactory results. It may be said, however, that, in erecting a hot-air system of heating, competition has been in many cases so sharp as to induce cheap, rather than good, construction. Small fur- naces have been used in which the temperature of the ex- terior shell had to be kept so high, in order to meet the demands for heat, that the heated air absorbed noxious gases from the furnace and entered the room in such condition as to impair, rather than to improve, the ventilation. Ventilation- ducts for removing the air from the rooms have often been neglected, and hence the results obtained have been far from satisfactory. Such faults are to be considered, however, as those of design and construction rather than as pertaining to the system itself. In order that the hot-air system should be satisfactory in every respect, the furnace should be sufficiently large, and the ratio of heating surface to grate such that a large quantity of air may be heated a comparatively small amount rather than that a small quantity shall be heated a great amount. As air takes up heat very much more slowly than steam or water, it would seem that the relative ratio of heating surface to grate surface should be more than that commonly employed in steam-heating. By studying the proportions which have already been given for steam-heating boilers (page 125) it will be seen that the ratio of heating surface to grate surface for the steam-boiler varies between 20 and 45, averaging about 32. From a study of the results in catalogues of manufacturers of furnaces the ratio of air-heating surface to grate surface in hot- air furnaces seems to vary from 20 to 50 as extremes. These proportions are essentially the same as used in steam-heating and are much too small for the best results in hot-air heating. It is quite evident that since air cannot be heated by radiation, 312 HEATING AND VENTILATING BUILDINGS. and is warmed only by the contact of its particles against the heated surface, that the exterior form of the furnace should be such as will induce a current of air to impinge in some por- tion of its course directly against the surface. Regarding the economy of this or any other system of indirect heating, it is simply a question of perfect combustion and rela- tive wastes of heat. If the fuel is perfectly burned and all the heat which is given off is usefully applied, the system is per- fect. The waste of heat in any system of combustion is that due to loss in the ashes, to radiation, and to escape of hot gases into the chimney. If the furnace is properly encased and if the hot-air pipes are well covered, there is no reason why losses from imperfect combustion and from radiation should not be a minimum. The chimney loss depends largely upon the temperature of the surface of the heater : if this is high, the loss will be large. In general, it may be said that the larger the heating surface provided the lower may be its temperature, and the greater the economy. It should be noted, however, that this or any system of indirect heating requires the consumption of more fuel than when the heating surfaces are placed directly in the room, and for that reason the operating expense must be considerably greater than that of direct systems of hot-water and steam heating. (See page 234-) Furnaces, or in fact heating-boilers of any kind, are un- economical if operated with a deficient supply of air. In this case the product of combustion will contain carbon monoxide,* an extremely poisonous and inflammable gas, which is quite likely to take fire and burn, on coming in contact with air, at the base or top of the chimney. 140. General Form of a Furnace. — The principles which apply in furnace construction are not essentially different from those already given in Chapter VII for steam and hot-water boilers. In the case of a hot-air furnace the fire and heated products of combustion are on one side of the shell and the air to be warmed on the other. In the case of steam or hot- water boilers the water and steam occupy the same relative * See Article 24, page 26. HEATING WITH HOT AIR. 313 positions as the air in the case of the hot-air furnaces. The types and forms of furnaces which are in use may be classified exactly the same as heating-boilers, Articles "jj and 82, as having plain or extended surface, and as being horizontal or vertical, tubular or sectional ; it may be said that the forms which are in use are fully as numerous as those described for steam-heating and hot-water heating. The material which is employed in construction is usually cast iron or steel, and there is a very great difference of opinion as to the relative merits of the two. It seems quite probable that cast iron, because of its rough surface, may be a better medium for giving off heat than wrought iron or steel, but it is quite certain that at a very high temperature, some carbon from the cast iron will unite with the oxygen from the air forming carbonic acid. When very hot it may be slightly permeable to the furnace gases. Such objections are, how- ever, of little practical importance, since the temperature of a furnace never should, and never does if properly proportioned, exceed 300 or 400 degrees Fahr., and for this condition the difference in heating power of cast iron and steel is very slight. It is of great importance that the shell of the furnace be tight, so that smoke and the products of combustion can- not enter the air-passages. Furnaces can be purchased with or without magazine feed, but the demand of late years is principally for those without the magazine, since it has not been proved to present any special advantages. Furnaces are often set in a chamber surrounded with brick walls, as explained for steam-boilers, but they are more fre- quently set inside a metallic casing, this latter being termed a portable setting ; this casing varies somewhat as constructed by different makers, but usually consists of two sheets of metal, the outer of galvanized iron, with intervening air-space empty or filled with asbestos. The casing is placed at such a distance from the furnace as to provide ample room for the passage of air. Some form of dumping or shaking grate which can be readily and quickly cleaned is almost invariably employed. The draft-doors which admit air below the grate and check- dampers in the stovepipe are usually arranged so they can be 314 HEATING AND VENTILATING BUILDINGS. opened or closed from some convenient place on the first floor of the house by means of chains passing over guide-pulleys. A pan in which water may be kept is added to every fur- nace for the purpose of increasing the moisture in the air; this is of importance, since the heated air requires more moisture than cold to maintain a comfortable degree of satura- tion, as explained in Article 27, page 32. 141. Proportions Required for Furnace Heating.— The proportion of the area of heating surface in the furnace to that of the grate cannot be computed from any data accessible to the writer, and the proportions given are assumed to be twice those which have been found to give best results in steam-heat- ing ; these apparently agree well with the best practice. The tables which are given are computed for a maximum tempera- ture of 120° F. for the air leaving the furnace, which is 50 degrees in excess of the ordinary temperature in the house. No doubt better practice might require the introduction of more air at a lower temperature, but considering the fact that this high temperature only has to be maintained when the outside weather is extremely cold, it seems quite doubtful if the expense of a furnace large enough for this additional duty, would be warranted. The ratio which the grate surface of the furnace should bear to the glass and exposed wall surface of the room can be com- puted with sufficient accuracy from known data relating to the heat contained in coal and to the probable efficiency of com- bustion. The heat given off from the walls of a room for each degree difference of temperature between the inside and out- side has been shown on page 59 to be approximately equal to the area of the glass plus one quarter the area of the exposed wall surface, which we will in this place denominate as the equivalent glass surface. One pound of good anthracite coal will give off about 13,000 heat-units in combustion. One pound of soft or bituminous coal will give off in combustion from 10,000 to 15,000 heat-units, depending on the kind and quality. Of this amount a good furnace should utilize 70 per cent.* The amount of coal which is burned per square foot * It is quite probable that the efficiency of combustion in an ordinary fur- nace is much less than the above, often as low as 50 percent. HEATING WITH HOT AIR. 315 of grate surface per hour will depend very much upon the character of attendance ; in ordinary furnaces used in house heating, and where it is expected to replenish the fires only two or three times per day, this amount is low, being not greatly in excess of 3 pounds. If the air is 120 degrees in temperature, nearly 60 cubic feet will be required, when heated one degree, to absorb one heat-unit (see Table X), and if such air is delivered 50 degrees above that of the air in the room, each cubic foot will bring in \ of one heat-unit. The velocity of air in feet per minute with ample allowance for friction is given in a table on page 1 14, from which it is seen that it will be safe to assume velocities of 4, 5, and 6 feet respectively, per second in the flues or stacks leading to the various floors. The velocity of the air passing the register may be assumed as 3 feet per second in every case ; this lower velocity is obtained by making the area of the register somewhat larger than that of the pipe leading to it. Tlie following mathematical discussion gives these various consid- erations in general and algebraic terms, as follows : Let F = square feet in grate, C = weight of coal burned per square foot of grate per hour, r = heat-units per pound of coal, E = efficiency of furnace, h = heat-units per hour, T— temperature of air leaving fur- nace, /' = temperature outside air, / = temperature of room, G = area of glass in room, IV = area of exposed wall surface, // = heat lost by room for one degree difference of temperature, Ar= cubic feet of air heated by furnace per hour, K' = cubic feet air required to warm room. We have, as explained, /i = CFEr = total heat given off by furnace, equal to that re- quired for all the rooms (i) _eoCFEr^ _ ^^j^.^ jggj. ^j ^j^ heated per hour by furnace. . . (2) T - t' ^' _ (-(5: + J f^)(/ _/')=: total heat-units to warm the room. . , (3) V I - (>oiG + \W ){l - I') ^ ^^j^j^ fggj ^f jjjj. ^Q ^^^^ jjjg j.QQ^_ ^ ^4) ~ T-t For average conditions substitute in above, as explained, T= 120, t = -JO, t' = o, C =^ .70, r — 13,000, Cr = 9100, and we have ^ = 9iooCi^ = 2^-. (5) K = ASSoCF = o.^h (6) K' = ^A{G + IW) (7) When^=A". C^= 5-^1^; whence 3, i^ = %-y^. • • (8) h' = yo{G + ilV) (9) 3l6 HEATING AND VENTILATING BUILDINGS. For computing areas of leader-pipes and stacks, for resi- dence heating, assume velocities which can safely be taken as follows : First floor, 4 feet per second or 240 per minute ; second floor, 5 feet per second or 300 per minute; third floor, 6 feet per second or 360 per minute. (See table, page 115.) Through a cross-section of the flue equal to one square inch 100 cubic feet will pass in one hour when the velocity is 4 feet per second, 125 when the velocity is 5 feet per second, 150 when the velocity is 6 feet per second, 252^ when the velocity in feet per second is represented by v. Denote area of flue in square inches by L ; then from equa- tion (7) ^_K' _ 84(g + i^) _ 3-36(g + i^) _ _ ,jo^ 257^ 251/ V. ' ' \ I From this, by transposition, we have V L 3-36 (^ + iW^)=^ 00 If for first-floor rooms z/ = 4. G-\-\W= 1.19L. If for second-floor rooms z' = 5, If for third-floor rooms v = 6. G-\-iW= 1.78Z. (Also see table on page 53.) The following table gives the relative values of these vari- ous quantities, computed for the conditions as explained : HEATING WITH HOT AIR. 317 PROPORTIONS REQUIRED IN FURNACE HEATING. Equivalent glass surface * . . . 2S 5° 75 100 125 150 200 250 500 750 1000 Cu. ft. air to be heated per hr. 2100 4200 6300 8400 10,500 12,600 16,800 21,000 42,000 63,000 84,000 Grate area, square inches . . . 22 43 64 85 107 127 170 212 425 640 850 Equivalent diameter round grate, inches Heating surface, square feet. 7-5 4 8.5 6 't n.5 10 iz.s 12 13-5 15 15 22 17 27 7 4200 =4 8400 29 80 33 100 Diameter smoke-pipe, inches 3^6 xo iz,6oo II Approximate cubic feet 1 space j 420 840 1260 ieso 2100 2520 16,800 52s T050 1570 2100 2625 3150 4200 5250 2100 15,750 21,000 Area stack— ist floor (vel. 4) sq. in. 21 42 63 84 T05 126 168 2tO 420 630 840 2d " (vel. s) " 17 33 SI 68 85 102 135 170 345 500 670 3d " (vel. 6) " 14 28 42 55 70 84 112 140 280 420 560 Diameter leader-pipe— t ist floor.. 7 7-5 9 10.5 II. 6 12.7 14-7 16.5 19 23.2 26.7 2d " 7 7 8.2 9-5 lo.s "■5 13.2 14.7 21 25.2 29.2 s"*- " •■ 7 7 7-5 8.5 9-5 10.4 12 13 4 19 23.2 26.7 Net area register, sq. in. — 1st floor (vel. 3)... 28 56 84 110 210 168 224 280 560 840 1 120 2d " and above 21 42 63 84 105 126 168 210 420 630 840 Area ventilating flue 21 42 63 84 105 126 168 210 420 630 840 Net area ventilating register . 17 33 51 68 8S 102 135 170 345 500 670 * This quantity is defined page 314. f For pitch of one inch per foot. Use larger pipe for less pitch. Note. — The proportions in the above table agree very well with those given by the Excelsior Steel Furnace Co. for the condition of changing the air in each room four times per hour, which can be talcen as representing the average amount required to bring in the heat. Tiie grate surface is computed for combustion of 3 pounds per square foot per hour, with an efficiency of 70 per cent, or a greater amount at less efficiency. The heating surface given in above table is much larger than ordinarily found in furnaces, but not too large for best results. 142. Air-supply for the Furnace. — The air-supply for the furnace is usually obtaine(i by the construction of a passage- way or duct of wood, metal, or masonry leading from a point beneath the furnace casing or near its bottom to the outside Fig. 208. — Hot-air Furnace with Cold-air Box below Celiar Bottom. air, essentially as shown in section Fig. 208. This duct or pipe is usually termed the cold-air box and is often constructed of 3l8 HEATING AND VENTILATING BUILDINGS. wood. In all cases there should be a screen over the outer end to keep out vegetable matter or vermin, and doors should be arranged so that it can be cleaned periodically. A damper is usually desirable, arranged so that it can be partly or entirely opened to regulate the admission of the cold air. The cold- air box should be made perfectly tight and in a workmanlike manner, so that air cannot escape into or be drawn from the cellar or basement. This should join onto the furnace casing at as Iowa point as the character of the cellar bottom will per- mit. In some instances it is desirable to erect two cold-air boxes, opening to the air on opposite sides of the house, so that the supply may be drawn from either direction as re- quired to obtain the help of wind-pressure, to aid in the cir- culation of the air over the furnace. The cross-sectional area of the cold-air box is proportioned, by different authorities, from 66 to lOO per cent of the sum, of the areas of all pipes taken from the furnace. If this were proportioned so that its area should be in ratio to the re- spective volume of cold and heated air, the sectional area of the cold-air box should be about 8o per cent, of the sum of the areas of the various stacks. To avoid frictional resistances it would seem to be advisable when practicable to make its area equal to that of the sum of the areas of the stacks. 143. Pipes for Heated Air. — The pipes for heated air are of two classes : first, those which are nearly horizontal and are taken from near the top of the furnace casing — these are usually round and made of a single thickness of bright tin, and if possible erected with an ascending pitch of one inch to one foot, and are termed leader-pipes ; second, rectangular verti- cal pipes or risers, termed stacks, made in such dimensions as will fit in the partitions of a building and to which the leader-pipe connects. The bottom of the stack is enlarged into a chamber termed a boot, which is made in various forms and provided with a round collar for connection to the leader-pipe. The top part of the stack may be provided with a similar boot from which horizontal rectangular stacks are taken, or it may be connected to a rectangular chamber into which the register may be fitted and which is known as the register box. The stacks usually pass up or near the woodwork of partitions, HEATING WITH HOT AIR. 319 and for lessening the fire risk as well as preventing loss of heat should be made with double walls separated by an intervening air-space. The register boxes should also in every case have double walls. The general form of a stack in position in a partition, with boot attache;^<^ bottom for leader-pipe and with round connfection for register box, is shown in Fig. 209. The leader-pipes and stacks, boots, and register boxes are now a standard article of manufacture by several firms. I am indebted to the Excelsior Steel Furnace Company of Chicago for the table of capacity and dimensions of various forms ^ of stacks and leader-pipes, given on page \ if - 320. iliLi, Ill n It will be found profitable in nearly every case to wrap the leader-pipes with two or more thicknesses of asbestos paper \ •s. o H H O pa -«l O O OQ •sA o < H -<: a z o H < O o a o <: >-) & o M OS Fig. 210. — First-floor Outside Register Box with Collar At- tached. and mineral wool in order to prevent loss of heat. It is desirable to locate the stacks in the inside partition-walls of the building, or where they will be protected as much as possible from loss of heat, since any loss affects the rapidity of circulation. It is generally necessary to have the leader- pipes not over 15 feet in length, otherwise the circulation will be uncertain in amount and character. 320 HEATING AND VENTILATING BUILDINGS. 144. The Areas of Registers or Openings into Various Rooms. — Registers are made regularly in various forms, square or round, and arranged for use either in the floor or side walls * TABLE OF SIZES AND DIMENSIONS OF SAFETY DOUBLE HOT- AIR STACKS. •6 Hi I ■5 OJ N 3 B in V -•2 C V la p u .S a c ■0 c 0) Is aoj a. 2-,? «■« = ..2 !l c S— XI J3 u u 11 a m s. -a a g -a OJS Si V •&= u » u ubic Feet of Space (approxi- mate) that can be Heated with each Stack with Pipe and Registers of size given. J3 s tin °B |£ 1/1 2 n S-. £0 Is gs OT3 ■£52 tn < , ^1 68.8x6 Auditorium and balcony 4)3700 925 to 4Xit Reported by R. C. Carpenter, Ithaca, N. Y. All cast iron; indi- rect draft. Inside cast- ng; aSyCar- ton 9-5 t6,oo4 2-story wooden house; ceilings 9 ft., 8 ft. Ex- posed 1850 11 HEA7TNC WITH HOT AIR. ACTUAL FURNACE WORK. 329 ^ . (/} rt" V 111 rt 3 CP SI ■^ol ■ i (i 0) > 'fi U J3 « c a Q, S e^ t/} s V u hn mi 2 a a 0^ St; i 1 9 1 1) Q 4i 1 9 K Cli 5 Equivalent Glass Sur equals the Glass Sui ter of the Difference Surface and the Gia »*-■ N •0 c u s p E '(5 a " " " (double) U.4 " o.^D , Width of wheel at outer circumference 0.25Z) 0.3ZJ " " " " inlet " o.sZ* 0.4 to o.^D Length of blade radially 0.25/? 0.2 to 0.3Z) * Proceedings of Institute of Mechanical Engineers in 1847, MECHANICAL VENTILATORS. 335 The air enters the fan-wheel through the opening in the casing adjacent to and surrounding the axis ; it is then thrown outward and compressed by the centrifugal force produced by the rapidly revolving blades ; this causes a difference of pres- sure between the centre and circumference of the wheel, which in turn produces a continuous flow of air from the centre out- ward. If the chamber leading to the inlet is restricted and the delivery opening unrestricted, the pressure at the centre may be less than that of the atmosphere, in which case the fan is said to act by suction or as an exhaust fan ; if the outlet passage in the casing is restricted, more or less pressure will be produced, in which case the fan will be considered to act as a pressure fan. It should be noted that the blades or vanes in the wheels of the centrifugal blowers vary greatly in shape as made for different purposes and by different designers, and that, although the centrifugal fan has been used practically for more than two centuries, engineers are as yet not in agreement as to the best proportions and best forms of the working parts. A number of examples of different design will be shown later in the chapter. Fig. 224. — Casing for Ventilating-fan. The casing or framework surrounding the fan-wheel should be constructed so as to first permit or direct the flow of air to the centre of the fan-wheel, and second to receive the discharge of the fan and direct it as desired; from which it is evident that the form of the casing may be varied greatly to suit different con- ditions. The forms of casing usual in centrifugal ventilators 336 HEATING AND VENTILATING BUILDINGS. for buildings are those with plain sides, having a periphery or scroll which is spiral in form and which contains considerable room or clearance in excess of that required for the fan-wheel. The clearance space in the casing is essential for noiseless operation and efficient results, as will appear later. The fol- lowing clearances or distances between wheel and casing, expressed in proportional parts of the diameter of the fan- wheel, D, are common in the best practice of fan construction: Least radial distance from wheel to casing. . o.oZD to O. i6Z>. Maximum radial " " " " " .. o-SoZ* to i.ooZ?. Least side " " " " " .. 0.05 to 0.0% D. The inlet opening, C, Fig. 224, to the fan-casing is usually circular in form, concentric with the axis of the fan-wheel, located in either or both sides of the casing as circumstances may permit, and with dimensions as given in a preceding table. The outlet or discharge opening in the fan -casing often extends for exhaust-fans completely around the periphery, but in case of pressure-fans delivering into conduits or pipes the periphery is closed except at the opening for discharge, which should be constructed so as to permit delivery with the least possible shock. As will be shown later, the exhaust-fan is more efficient when discharging into an expanding conduit or chimney of proper shape than when delivering freely into the air. The ordinary forms of casing differ from each other prin- cipally in the position of the discharge opening, as shown in Figs. 225 to 227; thus in Fig. 225 the discharge is horizontal and at the bottom, in Fig. 226 it is horizontal and at the top, and in Fig. 227 it is vertical and at the top. The casings are made with discharge at any angle or position desired, and single or double as required. The inlet opening, which is not shown in the figures referred to, is usually located in the side of the casing opposite the motor or driving-wheel and is always concentric with the axis of the wheel. The centrifugal fan may be driven by any convenient type of motor, and several types are suggested in the various figures referred to; thus in Fig. 223 is shown a fan-wheel adapted for a belt; in Figs. 225 and 227 are shown fans driven by direct MECHANICAL VENTILAl^ORS. 337 connection to a steam-engine; while in Fig. 226 is shown a fan driven by direct connection to an electric motor. The Guibal chimney or distharge-tube, invented about fifty years ago by M. Guibal, is extensively used in connection with fans for mine ventilation, and would doubtless prove equally beneficial for ventilating work; it is in effect a continuation of the casing at the point of delivery, so as to form a trumpet- shaped or expanding tube through which the air is discharged without shock and with a gradual reduction of velocity. It Fig. 225.— Bottom Hori- Fig. 226.— Top Hori- zontal Discharge. zontal Discharge. Fig. 227. — Top Vertical Discharge. has been found that an expanding discharge-tube with gradual curves in the general form of the vena contracta adds greatly to the efficiency, for the reason that the reaction due to shock at delivery is largely overcome, and the full momentum is utilized in moving the air. The Guibal fan as used in connection with the chimney is constructed in a variety of ways; it is generally of large diameter, carrying six to twelve vanes, which are sometimes plane and sometimes curved, but are usually curved so as to meet and guide the current of incoming air at the inlet end, and are straight and radial at the outer extremity, of a form similar to that shown in Fig. 228, in which the blades have that shape which gives the highest efficiency by Murgue's theory. The Guibal fan is constructed in such a variety of forms by different designers, the only essential characteristic being the expanding chimney, that no special description is possible. A fan- wheel of this type having a diameter of 5.8 metres, as used 338 HEATING AND VENTILATING BUILDINGS. for ventilating a mine in England, is shown in Fig. 229; in this case the blades are not curved near the inlet as required by the theory of Murgue for highest efficiency. Fig. 228. — The Guibal Chimney and Fan. Fig. 229. — The Guibal Fan and Chimney, A modified form of the Guibal chimney and fan, combined- with a spiral scroll having considerable clearance, is shown in MECHA NICA L VENTILA TORS. 339 Figs. 230 and 231, as designed by Professor Ser of Paris. It consists of a circular plate fixed on a shaft and carrying on each side thirty-two curved vanes, each of which is a portion of a cyHndrical surface whose generatrices are parallel to the shaft and whose transverse section is circular; the width of the vanes is constant, and they are so arranged that inflow takes Fig. 230. — Elevation of the Ser Ventilator. Fig. 231. — Section through Ser Ventilator. place without shock and that the air is discharged from the fan in the direction of 45° with the tangent to the outer periphery. The air enters the fan on both sides, and after passing through it enters a volute which conducts it to an expanding chimney, from which it escapes into the atmosphere. The volute is so designed that there is as little loss of energy as possible at entry from the fan and while passing through it; the sides of the chimney are inclined at not more than i to 8 in order to avoid the loss due to the sudden enlargement of passage. The Capell fan, which at one time had an excellent repu- tation in Europe for mine ventilation, is shown in Fig. 232. It is formed of two fans, one outside the other, having the same axis and revolving at the same angular velocity. The first consists of a drum of steel plate which may be open on one or both sides to receive the air at the centre, the opening being equal to its inner diameter. The cylindrical surface of the inner drum contains six openings, in general rectangular, and spaced at equal intervals, whose area is less than the cylindrical surface of the drum and equal to that of the open- 340 HEATING AND VENTILATING BUILDINGS. ing. On the inner side of the drum and ending at one of the sides of the openings are arranged six vanes of steel plates curved in a direction opposite to that of the rotation. The second wheel is larger than the first and is completely closed Fig. 232. — The Capell Fan. at the sides by steel plates, between which are arranged six curved vanes as shown in the figure. The fan is surrounded with a spiral casing and connects with a rapidly expanding chimney. The fan shown in Fig. 233 has vanes tangent at the inlet Fig. 233. — The Rankine Fan. and radial at the discharge, being so arranged as to meet the air with least resistance at the inflow and direct it into the fan with the least possible shock ; they then curve backwards, but end in a radial direction at the outer periphery, so as to give least loss at discharge, being of a form suggested by Professor MECHANICAL VENTILATORS. 34 1 Rankine in 1857 as likely to give the highest efficiency. In this fan a spiral casing is employed instead of a chimney. In addition to the fans shown numerous forms have been designed which have not proved to be of great practical im- portance and which, for want of space, cannot be considered more in detail. A form of centrifugal fan or blower, shown mounted in a brick casing in Fig. 234, is often used where the conditions are not favor- able for the form shown in Fig. 222. It is known as the ccne blower, for the reason that a cone-shaped guide is used to direct the entering air from the centre toward the cir- cumference. In construction it con- sists of a plate mounted on a shaft to which are connected the cone guides and the various vanes required to give the centrifugal motion to Fig. 234.— The Cone Fan or the air; its principle of operation is lower. identically the same as that of other forms of centrifugal blowers. 156. Propeller or Disc Fans. — The name is applied to a class of fans which move the air forward by impact as well as by centrifugal force. In general these fans are mounted in a cylindrical casing and have a number of vanes or blades which are arranged with a diminishing pitch from the centre to the circumference somewhat similar to the blades of a propeller. Three forms are shown, one with plane blades. Fig. 235, one with curved blades driven by a motor, Fig. 236, and one with helix-shaped or screw blades, P'ig. 237, into which the air is guided by fixed vanes. The fans in this class are useful for moving large volumes of air with comparatively low pressures and velocities. They are as a rule not adapted for use where there is any great resistance to be overcome. 157. Volume or Positive Blowers.^ — This name is appli- cable to that class of blowers which deliver a fixed volume of air at each revolution and which are positive in their action 342 HEATING AND VENTILATING BUILDINGS. and prevent the return of compressed air, not by uniform action of centrifugal force, but by use of valves or by contact of the Fig. 235. — Propeller Fan with Plane Blades. Fig. 236. — Propeller Fan with Curved Blades. Fig 237. — Rateau Screw Fan and Wheel. rotating parts. A great variety of blowers have been con- structed that could be put in the above classification, "but the Fig. 238. — Section of the Root Positive Blower. only ones at present in extensive use are piston blowers and tw:o forms of rotary blowers shown in Figs. 238 and 239- MECHANICAL VENTILATORS. 343 Blowers in this class ar; will adapted to move small volumes of air at high pressures and are extensively used for blast- furnaces and similar work. They are not well adapted for ventilators or for any other purposes requiring large quantities of air at comparatively low pressures. Fig. 239.— Section of the Connessville Positive Blower. 158. The Theore iral Work of Moving Air.— The work performed by the ta? is made up of the resistance due to moving and compressing a definite amount of air, and can always be considered as equivalent to moving a given weight of air through a height or head which is equivalent to the sum of the velocity and pressure heads _ expressed in feet of air at the density corresponding to the air after being compressed. These results, neglecting all resistances, can be expressed in the shape of formulas, as follows : Thus let Q equal the volume of the air at atmospheric pressure, Q its volume at delivery pressure, c the weight per cubic foot at atmospheric pressure, d the weight at delivery pressure, \V weight of air delivered per second, d density at atmospheric pressure, and d' at the delivery 'pressure, v the velocity of the air in feet per second, i^the velocity of the periphery of the fan, m and r coefficients, Farea of cross-section at point of measurement of velocity, h the sum of pressure-head and velocity l;ead as measured at the same point expressed in feet of air at atmospheric pressure, K the same quantity expressed in feet of air at delivery pressure, p the same quanticj' eixpressed in ounces per square inch, il/work in foot- pounds per secofid, P work in horse-power ; then we have also Q^^p^Q , Q = mi/ A, (I) (2) 344 HEATING AND VENTILATING BUILDINGS. and h' = rv''' (3) d d' lV=Q'd = Q-c^ = Qc (4) d d Fvi> M= work = Wh' = Wk-j-, = Qch-j, = Qch! = mrcv'' = -~. (5) M Fvp ^ = ^=88^ (6) From equations (2), (3), and (5) it is noted that, first, the volume of air delivered varies with the speed of the fan ; second, that the difference of pressure varies with the square of the speed of the fan ; and third, the work done varies with the cube of the speed of the fan. Table No. XXIV in Appendix, which is computed from equation (6), gives the theoretical power required to move a given volume of air, expressed in cubic feet per minute, at any- desired velocity, expressed in feet per second, when the air is at a temperature of 70° F. When at any other temperature, t, the results must be multiplied by the ratio of the densities as given in Table No. X, or as expressed by the formula 460 + 70 ^ 530 460 -\- t ~ 460 -(- t' The efficiency of a fan is the ratio of that theoretically necessary for moving a given volume of air to the actual work required; that is, the theoretical work efficiency = — -. -. . actual work If the efficiency of a fan or blower is known , the actual work can be obtained by dividing the theoretical work, as given in the table, by the efficiency. The efficiency of fans or blowers will usually be found greater as the head increases up to the equivalent of one ounce per square inch, and will vary within the limits of 1 5 and 40 per cent, averaging under usual conditions of ventilating work not far from 30 per cent. As an example, find the actual horse-power required to drive a fan delivering 10,000 cubic feet of air per minute at a velocity of 50 feet per second when MECHANICAL VENTILATORS. 345 the efficiency of the fan is 25 per cent. The theoretical work is 4.42 horse-power as given by Table No. XXIV ; the actual will be for the case considered 4.42 divided by 0.25, which is equal to 17.68. 159. Work of Moving Air through' Pipes — To the work needed for moving the required volume of air at the desired velocity must be added that which is necessary to overcome the resistance in the fan and in the various pipes or flues. As already explained, the loss of head due to friction in a circular pipe can be expressed by the formula in which h = loss of head in feet of air, d = diameter in feet, / ^ length in feet, v = velocity in feet per second. Let/ = loss of head expressed in ounces per square inch; d' = diameter in inches; 2^ = 64.32; 4.S = 0.025. We have A = 115/ at 50° F.; ^ - z ~ 24646^' ~ 2jo66d" ^'^^'^^y' (2573 X "5) — which is the formula representing the loss of pressure in a pipe of galvanized iron, carefully made and erected, with all internal laps extending in the direction of the air movement, assumed in the work on "Mechanical Draft" published by the B. F. Sturtevant Co., Boston. The work done in overcoming friction, expressed in foot- pounds per second, is equivalent to the resistance, expressed in pounds, multiplied by the space passed through in one second of time. If F denote the area of cross-section, / the resistance per Fp square inch in ounces, then will —^ equal the total resistance in pounds ; if v denote the velocity in feet per second, it will equal space passed through in one second. Hence the work Fpv done in one second will equal —g-; this result divided by 550 will equal the horse-power, P: Fpv ~ ?8oo' 346 HEATING AND VENTILATING BUILDINGS. From these two formulas can be calculated the drop or loss in pressure in ounces in a given pipe-line, and also the horse- power required to overcome the resistance of moving air at the given velocity through the given pipe. Table No. XXIII in the Appendix gives such values for the principal pipe sizes and for a length of pipe equal to lOO feet. For any other length multiply the results in the table by J^ the square root of the given length in feet, for the reason that the work required varies as the square root of the length. Dimensions of Pipe-lines for Air. — Formulas for comput- ing the flow of air through a pipe under various conditions have been fully discussed. For practical use Table No. XXV in Appendix has been computed, which gives the diameter of circular pipe, also the corresponding side of a square pipe, for a given discharge in cubic feet per minute and a given length, with a drop in pressure equal to an inch of water-column (0.58 ounces per square inch) and a temperature of 100° F. The relation of the discharge to the diameter of a circular pipe is also shown in the diagram Fig. 240, in which the ordinates give the diameter of pipe corresponding to a given discharge repre- sented as abscissa; the varying lengths of pipe-lines being distinguished by different lines. The scale on the left corre- sponds to the lines inclined upward to the right and to the upper scale at the bottom, that on the right to the lines inclined upward to the left and to the lower scale at the bottom. To use the diagram, suppose it be required to find the diameter of a circular pipe whose length is 500 feet and whose capacity must be 20,000 cubic feet of air per minute; find intersection of vertical line from 20,000 with upper line marked 500, thence horizontally to the scale at the left, which is intersected at a point corresponding to the required diameter, which by inter- polation is found to be 38.5 inches. If the capacity is to be 90,000 cubic feet per minute and length 100 feet, find the intersection of vertical from 90,000 with lower line marked 100, and read diameter on right, which will be found to be 52 inches. The flow of air through other than circular pipes has not been discussed in this work; it is known, however, that for any pipe the resistance to the flow varies as the mean hydraulic MECHANICAL VENTILATORS. 347 348 HEATING AND VENTILATING BUILDINGS. radius, a quantity equal in every case to the area of cross-sec- tion divided by the perimeter which is subjected to friction; 11" ::: W'' :4:::: : ::: S3H0h ji ^allllllllH^ f *^*tj| : 1- ■f ITT"" _| o : ■*:::: it -r-i — i: r- ■■wf-^-- ilHh c ' t|-- til ::;ij-:: — t-t--- UfcJri" f#f1i [;;;:::;; 1 t#-t tw :::p:: g;||:; i^^^^^^p^ii^ ^■S'^-^^ :::: ::::: ■ j- ■ ■ c i 1 1 n1 :::: :::: i = " X" ' c 1 rr4r WW -f+T + i #F^^^±i t™ IP ij :: : ! hhttfh: ■-■■■fF -If- ^t^^ -t-|-[ — ^M- -^ -Li- \i ( JU-U- . I, , -f-f tt +-r g J-; li- ,A+- - +- ^ H tc — 1 - i[: - " Iftr -t: — Ttf ' V*" "Tt*" "^ E-E - -- ^ -- ■i-H-L+^ E:::::j:: ::: S j JT. . 1\" -U: IJii: ";A 1 -i-Ui-Xl "ij" 1 j I -1 cStJ 3 Ij 1 ^-Mv- \f-- 4k{44w TjSslill ipsli dr^i !#^ ; 444--1- g:::i|| tt 1 1 ^^i 4#i 6«^l -HI -14 H il:::::fj '1 1 ill '1 t: '^ 1- 1 iif:::^::: 1 lulllllljlj i rt :: :3 ::: ir w ." !: 1 --- o ■-■- 2 .... -ff-1 t D |[j rtrP lU 3. :::::: 1. :::;:: :> : :t:: 2 - -Tt c :::::: J ±j 1- r ■ ■ tt z of :o .J+U.-- i: ':!! l\' ;i\ h iiliiM lAL iiril m T"^ ;: E: :: c m :::: ±D j c 3 3 t > D :::::: cc J : :;±: - -i-P- " 1 5 :::±: a ■ Si □ : ::fl - i-p \ ■ s Fj:S:: : : i: C > :::4 ; iiiil ill Mrilhiu h' ffftf f'll !, .1. \ : i : : : jc 1 o 1- ■- oc:: ^m pS^ " S3H0NI "OEH ^^^:^Ji i \"-rt \ H o H z; 3 c w u K H So- [14 for a circular pipe this becomes one-fourth part of the diameter, for other cases it must be computed. From this relation we have constructed a diagram or chart, MECHANICAL VENTILATORS. 349 Fig. 241, which enables a designer to select a rectangular pipe having dimensions which give a carrying capacity equal to a known circular pipe, it being supposed that one of the required dimensions of the rectangular pipe is known. In the diagram Fig. 241 the diameter of the known circular pipe is given as ordinate, corresponding to the scale at the left; one of the dimensions of the equivalent rectangular pipe is given as abscissa, the other is denoted by a series of lines corresponding to the scale at the right. Thus to find a rectangular pipe with the same carrying capacity as a 30-inch circular pipe, one dimension of which shall be 40 inches, we find the intersection of the horizontal line from 30 on the scale at the left with the line marked 40 on the scale at the right ; the result read on the bottom scale is 19, which indicates that a rectangular pipe with dimensions of 19 by 40 inches is equiva- lent in capacity to a circular pipe with a diameter of 30 inches. 160. Murgue's Theory of the Centrifugal Ventilator. — The first satisfactory theory of the centrifugal ventilator was published by Daniel Murgue, engineer to the Colliery Com- pany of Besseges in 1872. This theory is given here in full, as it is believed to be of essential importance. Murgue assumes, first, that all the air delivered to a fan flows through an orifice in a thin plate with a velocity due to the difference of pressure or actual head, h, produced by the operation of the fan; this he terms the equivalent orifice and denotes its area by a; second, that all the air flows through a similar orifice, which he calls the orifice of passage, with a velocity due to the head representing the resistance or loss of head, h^, the area of which he represents by 0. He proves that the theoretical depression or reading of a water-gauge due to the speed of the periphery, u, is in a perfect fan equivalent to twice the height of column necessary to generate such velocity in a falling body; that is, if u equal the velocity in feet per second and H the maximum difference of pressure or initial depression produced, H = — . o The mathematical demonstration given by Murgue is as follows; Let Q equal volume of air delivered per second, Hi the difference of pressure produced by the fan or blower when completely ciosea, which is termed 35° HEATING AND VENTILATING BUILDINGS. the initial depression, kt, the loss in pressure through the fan, and h the effective or actual difference of pressure. Then we shall have h-H-h, (I) If the flow through an orifice be taken as 0.65 of that due to the product of velocity and area which is practically true in a round orifice, we shall have Q = o.6^a\/2gk (2) Q = 0.65(7 |/2^/4o. . (3) By division we have ho _ a' Substitute the value of ho in equation (i) and reduce, we have This value substituted in equation (2) gives e=°^^5!£M. (5, /-:-: From the latter formula it is noted that the initial depression /f is a function of the square of the volume delivered. The area of the equivalent orifice a is supposed to be known and depends upon the resistance to the passage of the air on the suction side of an exhaust fan and on the delivery side of a pressure fan ; the equivalent orifice of passage o depends upon the internal resistance, and hence on the dimen- sions and arrangement of the ventilator. In the determination of the initial depression the ideal ventilator only is considered in which there is no loss by friction or shock. Two cases are considered : first, when the suction wheel or exhaust fan is revolving without a casing, and, second, when the wheel is provided with the Gui- bal casing and chimney. Denote the radius of the inlet by r ; that of the external circumference hy R: tne angular speed of rotation in feet per second by oa ; the absolute speed of the extremities of the vanes by ooR ; the tangential speed by u. Supposing that the air before entering the fan is motionless and that it traverses the inlet with the speed of v, , we should then have a nega- tive head corresponding to the pressure -^ (6) MECHANICAL VENTILATORS. 3SI The interval between two consecutive vanes forms an hjasde canal which the air enters with a certain speed, z/i, and leaves with a less speed, Vi. This slowing action produces, according to Bernouille's theory, a gain of pressure expressed by the difference ■ ■ — (7) The speed of entry vi is the resultant of two speeds : the one, z/o, being radial, the other, oar, being tangential, and if there is no shoclc or loss, vi' = v^ + oaV^ Substituting this value of v^. in the preceding equation we have ^<±^J^ ■2.g ■^g ^ ' Supposing a prismatic element of the air passing through the fan at a distance x from the centre, having a radial height dx and a base 5 in a perpendicular direction, and a density 5, we shall have for the mass of this element , 8Sdx -T- (^> The centrifugal force developed by its rotation dScix „ dF oa'x . (lo) By dividing the above by SS, we have the pressure expressed per unit of area in the column of air as follows : OD^xdx dh = (II) g .Integrating this last between the limits x =. r and x = R, we shall have a total difference of pressure from the inlet to the outside of the vanes co'K' — coV" , , h = (12) ^g Adding the results in equations (6), (8), and (12) together and sub- stituting u = (23) in which Ha is the theoretical depression, go the corresponding volume, and Tp the work to overcome the passive resistance. 354 HEATING AND VENTILATING BUILDINGS. As the difference of pressure increases with the square of the speed of rotation, and the volume with the speed of rotation, it follows that the work required varies with the cube of the number of turns. A summary of the discussion of Murgue's demonstration proves that the maximum depression or difference of pressure is " g The actual or effective difference of pressure is Ku^ h^ ^ + ^ (i8) (19) or h^H^MQ, (22) and the volume of air delivered is o.6i)au^2K Q = V^' (20) All of which propositions have been amply demonstrated as practically true. Murgue's theory shows the relation that exists between the difference of pressure, the volume discharged, and the area of equivalent orifice in such a manner that if any two of these quantities are given the others can be computed. It also enables us to represent the manometric power of a fan by the simple equation h = H — MQ^, (22), by means of which fans of various forms and sizes can be readily compared. As illus- trating the application of Murgue's theory, a table is given showing the observed and calculated depression caused in a mine at Besseges by a Guibal ventilator: Number. Equivalent Orifice, Square Feet. Speed of Rotation. Volume per Second, Cubic Feet. Observed Depression, Inches. Calculated Depression, Inches. I 3.921 76-39 187.32 1-1795 I ■ 3042 2 7-455 " 364-79 1.2779 1.2763 3 20.714 " 951-05 1.0665 i.o68i 4 25-521 ** IU4.00 0.9827 0.9764 5 29-343 it 1225.15 0.8996 0.9059 MECHANICAL VENTILATORS. 355 The results of the tests indicate that the difference of pres- sure of this fan can be expressed as follows : /^ = 1. 3 1 37 in. — 0.00000027Q2. The objections to Murgue's theory when applied to ventilat- ing-fans is the practical difficulty arising from the fact that the equivalent orifice does not correspond to any dimension of the fan, and, further, that this theory does not readily produce practical methods for determining the capacity and efficiency of any fan, although the general results as to the best shape of vanes hold true in every case. It is quite certain that the casing surrounding the fan may be made of such shape that it will perform to a great extent the same function as the Guibal chimney by affording an opportunity for the gradual transformation of velocity into pressure without sensible loss of energy in shock. This result is accomplished by constructing the outer periphery of the casing of a spiral form and at a distance from the circumference of the fan-wheel, which, under usual conditions, is made to vary from one half the radius of the fan-wheel to the full radius of the same at the point of discharge. The casing should be connected to the discharge-pipe with a smooth curve, so as to present the least possible opportunity for loss of energy. The clearance-chamber between the casing and the wheel should be of such form as to receive and transmit the air without shock, and should have maximum volume at the point of discharge. The table on page 356 gives the theoretical maximum difference of pressure which may be produced by different velocities of periphery in feet per second, corresponding to H in Murgue's theory. Professor Rateau has modified the Murgue theory by substituting Q/ Vgk for the value of the equivalent orifice (2/.65 V2gk, this being done in order to simplify the inter- mediate computations, the results except for the value of the coefficients being otherwise the same. Rateau also used a " reduced orifice " {b) as equal to the equivalent orifice divided by the square of the external radius, r, of the fan inlet; that is l> =■ — ^=. He uses the term " manometric power," M, 356 HEATING AND VENTILATING BUILDINGS. MAXIMUM PRESSURE DUE TO SPEED OF FAN. Speed of Difference Speed of Difference Speed of Difiference Periphery of Pressure, Periphery of Pressure, Periphery of Pressure, of Fan, Inches of of Fan, Inches of of Fan, Inches of Ft. per Sec. Water. Ft. per Sec. Water. Ft. per Sec. Water. 49-21 1.08 77.10 2.66 98.75 4-36 50.19 I-I3 78.41 2-75 100.08 4-48 52.82 1-25 80.05 2.87 IOI.71 4-63 55-12 1.36 82.02 3.00 103.02 4-75 58.07 1-51 83.01 3- 08 104.33 4.87 60.04 1.61 85.30 3.26 105.30 5-05 62.67 1.76 86.62 3-36 107.28 5-15 , 64.96 1.89 88.58 3-51 108.27 5-24 66.93 2.00 90.55 3-66 109.58 5-37 70.21 2.20 91.86 ' 3-77 110.89 5-50 72.50 2.35 94-49 3.99 112.53 5-63 74.80 2.50 96.13 4-13 113-85 5-76 75-79 2.57 97-77 4.27 114.50 5-87 as equal to gh/u^, in which u is the peripheral velocity of the fan. In accordance with Rateau's notation a fan may be represented by an equation of the following form, where s, t, and 11 are constants depending upon the construction I If so -\- —^ -\- to^ -\- U = O. In a series of tests made by Mr. Brian Donkin the follow- ing values of these constants were found : Value of Constants. Number of Fan. s t » VIII u. 136 14.18 1.690 VI 0.192 5-85 1.666 X 2.43 13-55 1-755 XI 10.05 126.4 3-51 The characteristic curve of the Rateau fan, Fig. 237, is shown in Fig. 242, which gives the manometric power and various efficiencies for a series of reduced orifices. 161. The Author's Fan Theory. — Murgue's theory of the fan, while evidently satisfactory for mining purposes, is not well MECHANICAL VENTILA TORS. 357 adapted for ventilating -fans, for the reason that the results depend less on actual dimensions of the fan than on area and resistances of the connecting air-ducts; that part, however, relating to the shape of vanes is applicable without change to fans employed for every service. From the author's theory practical rules are deduced for the delivery of the fan from the 1.0 0.9 0.8 0.7 0.6 05 0.4 0.3 0.2 ^ / * s-*^ / / / N, \ r^ H -hV> AL( NE / / ^ N '"f ^j ^ A \ \ /, f /' N \ s /' / ,0 f ^ s f/ / \ 1 f / ; / / [/ 0.4 0.6 0.8 1.0 REDUCED ORIFICER- FiG. 242. — Characteristic Curves of Rateau Fans. dimensions of the fan-wheel and casing, although external resistances due to the flow of air through a pipe are not con- sidered. For convenience denote the various quantities as follows: External radius of fan-wheel = 7i'. Internal radius of fan-wheel = r. External diameter of fan-wheel = D. Internal diameter of fan blades = =2R, v' = iv, d =z 2r. To prove that the velocity of the flow of air varies as the velocity of the tips of the vanes, note that a particle is moved outward between two vanes by the centrifugal force produced by the rotation, which varies as the velocity generated in a unit of time. Denote the time of revolution by t; then the centrifugal force of a particle, dx, of the fluid at the distance, X, from the centre will be ' 27tx\^dx ^Tt^xdx -r)^ = —t^ (^) The integral of this quantity is the centrifugal motive force of the column, x, and equals —[^ (2) If ;tr = a, the full length of the column between the vanes, this becomes 2Ti^a^ "^' (3) which is the entire centrifugal motive force of the air between the vanes. The pressure of a column of length a is ga, in which ^ = 32.16 = force of gravity, from which it would appear that the length of a column of air, h, whose pressure is equal to that produced by the centrifugal force would be the result in column (3) divided by {g)\ from which 271^ c? ^--W ^4) This would produce a velocity, provided there were no resist- ances, equal to that acquired by falling through a height or MECHANICAL VENTILATORS. 359 head equivalent to that expressed in equation (4). That is, the velocity would be ♦'37J=v'^^^*=\/*-=?=^" (s) From which it would appear that the theoretical velocity of the issuing air would vary inversely as the time for one revolu- tion or directly as the peripheral velocity of the tips of the vanes. In practice the velocity of the discharge of air, v, will seldom or never equal that of the tips of the vanes, u, and is usually less, but under certain conditions of discharge it may exceed the value of u. If we denote the ratio oi v to u by e, then we shall have V ^^ e .u (6) Maximum Pressure Produced by a Fan or Blower. — This quantity corresponds to the initial depression in Murgue's theory and is obtained only at the time when the work imparted to the fan is all utilized in overcoming resistances, as, for instance, in a pressure fan when the discharge opening is entirely closed. For this case, if there is no loss of energy due to eddies or other resistances, we shall find, since the work done is equal to the weight moved or the pressure H overcome in one second multiplied by the space, that from which u H=W-. g But W =^ cFu, hence I? H = ^F-, g and we have for unity of volume and area, since Q and F each = I, -=7 '« From the last equation it is noted that the maximum pres- sure produced may be equal to twice that due to the head producing the same velocity which is the same result as ob- tained by Murgue. 360 HEATING AND VENTILATING BUILDINGS. In general the increase in pressure produced will always be less than the theoretical, if we denote the coefficient indi- cating this ratio by K. Then for the case when velocity of discharge is zero, we have rr KU^ "=^ W The actual increase of pressure produced will be lessened by increasing the velocity of discharge, as indicated by the formula, h^ (9) For dimensions of outlet, F, less than or equal to those of the inlet, F^, we have as nearly true ^ = Ku\. - ^J. Substituting this value in the preceding equation, we have for- the resultant pressure-head in feet of air , Ktt^ I FV For the pressure expressed in any other units the results must be divided by the ratio of the weight of the unit desired to that of one foot of air. Call this ratio d ; then will we have for maximum pressure in the desired unit ^=^ C") The table on page 361 gives values of relative, density S expressed in feet and inches of water, the barometer being 29.92 inches. The value of the coefficient^ will depend upon the construction of the fan, the casing, and chimney ; but, as shown by Murgue, its value for an uncovered exhaust fan can- not exceed 50 per cent. Its value varies greatly with different fans and with the area of discharge opening ; it was found by experiments by Buckle to have an average value, for ventilating- fans, of 0.617, in which case the equation (8) becomes I/= 0.617- (8') MECHANICAL VENTILATORS. RELATIVE WEIGHT OF WATER AND AIR. 361 h in the Formula. Tampe rature. Weight per Cubic Foot. Feet of Air Balanced by Water- column of Degrees Degrees Water. Air. Fahrenheit. Centigrade. I Foot. 1 Inch. 32 62.42 0.0864 722,4 60.2 41 5 62.42 0.0793 789.3 65.8 50 10 62.41 0.0771 801.2 66.7 59 15 62.38 ' 0.0765 815,5 67.9 68 20 62.33 0.0752 828.8 69.1 77 25 62.26 0.0740 841.3 70.1 86 30 62.17 0.0728 854-0 71.2 95 35 62.38 0.0717 865.8 72.2 104 40 61.97 0.0704 880.2 73-3 "3 45 61.85 0.0693 894.2 74-5 122 50 61.70 0.0682 904.7 75-4 131 55 61.54 0.0672 975.8 81.3 Considering the weight of one cubic foot of air as .08 pound, the following equations will show the relation of the velocity of the tips of the blade to the pressure in Buckle's formula : When/ = pounds per square inch, u = 3ioV/>. When /j = ounces per square inch, u =. SoV/j. When h^ = inches of mercury, u =, 220V h^ When h^ = inches of water, u = 6oi^A^. The table on page 362 shows the relation of the peripheral velocity of the fan to the pressure produced, computed from the formulas as given above. The table will be found to give lower pressures than the maximum actually produced with most fans when the outlet is closed, hence it can be considered a safe one to use. It is to be noted that this table gives the pressures only when the fan is operating to deliver a small volume of air. To deter- mine the pressure when the outlet has an area F and the inlet an area /^^ , multiply the tabular results by 1.62(1 — p- j ■ The effect of varying the area of discharge outlet is shown in the diagram Fig. 243, which shows the pressure in inches of water produced by a speed of 500 revolutions per minute in three different fans, each having a fan-wheel 4 feet in diameter and an inlet 22 inches in diameter. In one case the blades were radial, in another case bent forward, and in a third case 362 HEATING AND VENTILATING BUILDINGS. PR^SURE CORRESPONDING TO VARIOUS PERIPHERAL VELOCITIES OF FAN. (Buckle's Formula.) Allowance made for Increased Density of Air. Peripheral Velocity. Pressure Produced. Feet per Second. Feet per Minute. Ounces per Square Inch. Inches of Water. I 60 0.000156 0.000269 5 300 0.0039 0.0068 10 600 0.0156 0.0269 15 900 0.035 o.o6l 20 1,200 0^062 0.107 25 1,500 0.098 U.167 '30 1,800 0.140 0.281 40 2,400 0.250 0.430 50 3,000 0.38 0.65 60 3,600 0.52 0.89 70 4,200 0-73 1.26 80 4,800 0.96 1.65 90 5,400 1. 21 2.08 100 6,000 1.49 2.57 no 6,600 1. 73 3-07 120 7,200 ii.ii 3-63 130 7,800 2.46 4.24 140 8,400 2.83 4.87 150 9,000 3-23 5-57 160 9,600 3-67 6.32 170 10,200 4.16 7.14 180 10,800 4.70 8.09 190 11,400 5-29 9-15 200 12,000 5-93 10.20 210 12.600 6.59 "•34 220 13,200 7.27 12.51 230 13,800 7-97 13-78 240 14,400 8.69 14.97 250 15,000 9.41 16.19 260 15,600 10.17 17.49 270 16,200 10.95 18.84 280 17,000 11-75 20.25 290 17,600 12.56 21.61 300 18,000 13-39 23.04 bent backward. It will be noted that the highest readings obtained when the outlet was closed agreed very closely with the results given in the table by Murgue, H = —, and are 6g considerably greater than in Buckle's table given above. The Velocity and Volume. — The velocity of air in feet per second discharged from fan will be, in accordance with the notation used, V iz^ eu =z zneRn = TtDen, MECHANICAL VENTILA TORS. 363 and that entering v' = iv =:eiu = 2TtRein = nDein. . . (11) The cubic feet of air supplied per second will equal cir- cumferential inlet velocity multiplied by area of cross-section of fan inside of the vanes : Q = v'b'nd = ivb'nd = eiub'nd = einDb'ndn — {7t'^ei){Ddb')ji. (12) o.Ur £ .6 £ 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 ABEA OF OUTLETr SQUARE FEET Fig. 243.— Relation of Pressure to Area of Outlet. 3.0 Work Required to Run a Fan.— The work is equal to the square of the velocity as expressed in (ii) multiplied by the mass moved, which in turn is equal to the weight divided by twice the force of gravity {2g). That is, Useful work in foot- ) ^_ ^j^^-i _ pounds per second j 2g ~ 2g -v^ = Substituting in above Q - : eiub'nd, cin b'de'w' (13) Substituting in above u = nDn, we have T^-^bdD^e^n^ (14) From which it would appear that the work to drive a fan will increase with the cube of the number of revolutions. 364 HEATING AND VENTILATING BUILDINGS. 162. Application of Theory. — The equations which have been given are general ones applying to all centrifugal fans regardless of form of blade or of entrance and admission passages. From equation (11) it is noted that the velocity of the discharge-air varies with the velocity of the tips of the blades. The value of the coefificient e depends on the pressure which opposes the delivery of the air, the velocity of the fan, and probably also on the form of blades. For fans working against a pressure of about i ounce per square inch or about 1.73 inches of water this coefficient seems from practical data to be about 0.32, increasing to 0.4 or 0.5 with free delivery. In the ordinary construction of ventilating-fans the width b' and inlet diameter d are usually taken in a fixed proportion to the external diameter of the fan- wheel D, as noted in the table of proportions, and so that the product of b'd will equal 0.2 to o.2 5Z'^. Substituting in equation (12) the following values for the coefficients : ;r^ = 9-94 = nearly 10; e = 0.4, average velocity of discharge air to periphery velocity ; i = 0.6, coefficient of supply to inlet; db' = o.2D\— Q=--.4sn' (IS) By actual experiment this coefficient is found to vary with change in resistance, as explained later, from 0.3 to 0.6. If we substitute the value of the above coefficients in equa- tion (14), and also the value of c = 0.8, and divide by 550, we have, as a value of work performed reduced to horse-power, 7^= 0.0000 12 (i^'w^) very nearly. . . . (16) The above results are for a fan working with a moderate resistance, and in practice the last coefficient will vary, being less as the resistance is greater ; it is approximately correct when the delivery pressure is one ounce per square inch, and decreases for higher pressures and increases for lower pressures, being in both cases essentially as expressed in the following rules : Practical Rule for Capacity. — By referring to formula (12) it is noted that the capacity is equal to the product of three constants multiplied by width of wheel, diameter of inlet, and MECHANICAL VENTILATORS. 365 by diameter of fan-wheel into the number of revolutions. Since, in accordance with common practice, the last three proportions are varied together, we shall have as a practical rule for determining the capacity of fans with proportions similar to above the following Rule. — The capacity of fans, expressed in cubic feet of air delivered per minute, is equal to the cjibe of the diameter of the fan-wheel in feet multiplied by the number of revolutions, mul- tiplied by a coefficient having the following approximate value : For fan with single inlet delivering air without pressure, 0.6; delivering air with pre.ssure of i inch, 0.5; delivering air with pressure of i ounce, 0.4. For fans with double inlets the coefficient should be increased about 50 per cent. For prac- tical purposes of ventilation the capacity of a fan in cubic feet per revolution will equal 0.4 the cube of the diameter in feet. Practical Rule for Power. — The delivered horse-power required for a given fan or blower is equal to the fifth power of the diameter in feet, multiplied by the cube of the number of revolutions per second, divided by one million, and multiplied by one of the following coefficients : For free delivery jo, for delivery against one' ounce of pressure 20, for delivery against two ounces of pressure 10. As an example showing application of rules, find the capacity in air delivered and horse-power required for a blower working against a pressure of i ounce and provided with a wheel 5 feet in diameter and of usual proportions, running at 300 revolutions per minute, or 300/60 = S per second. The capacity equals (5 X 5 X S)(o-4)(30o) = 15,000 cubic feet per minute. The horse-power equals (5 X 5 X 5 X 5 X 5)(2o)(3oo X 300 X 300) ^ - gj 1,000,000 60 X 60 X 60 If the speed should be doubled, the horse-power needed would be increased eight times, provided the relative resistance remained the same. It should be noted that the horse-power as given by the above rule is that delivered to the fan, and in reckoning the amount to be supplied, it should be increased an amount sufficient to cover any loss by friction in the motor and transmission mechanism. 365 HEATING AND VENTILATING BUILDINGS. Tests which Verify the Rules. — This extremely simple rule for capacity agrees very closely with an extensive series of experiments made on different fans, with proportions approximately those given. Thus, for instance, in a test made of a fan-wheel 5 feet diameter, running at 300 revolu- tions per minute at Wheeling, W. Va., the air discharged was 16,446 cubic feet per minute against a pressure of about i.o inch. By the rule just stated the discharge would be 0.4 X 125 X 300= 15,000, an amount 10 per cent less but still within the limits of error of measurement of air. In another test a fan of 4 feet 6 inches diameter when running at 310 revolutions gave a discharge of 11,651 cubic feet per minute under working conditions. The rules as stated above would give a delivery of 11,284 cubic feet per minute. In another case the test of an American blower-fan 18 inches diameter, working against a pressure of i.i inches of water, delivered 1368 cubic feet per minute; by the rule given it should deliver 1394 cubic feet per minute. The simple rule stated for capacity, while approximate and applying only to fans of essentially the same proportions as those mentioned and when working under the conditions described, will still be found very useful. For fans of materially different proportions working under higher pressures the rule will not apply even approximately. Experiments by the author with a fan 4 feet in diameter give the following coefficients for capacity and horse-power: Pressure above Atmosphere per Square Inch. Coefficient for Capacity. Coefficient for Horse-power. Inches of Water. Ounces. (a) (i) 0.60 0.30 0.5 0.29 .56 .27 1.0 0.59 .50 ■25 1.72 1.0 .40 .20 2.0 1. 18 .35 .16 3-74 2.0 •30 .10 In a test of three fan-wheels, with inlet opening on one side equal in diameter to one half the fan-wheel, the following results were obtained: MECHANICAL VENTILA TORS. 1^7 Pressure. CoefBcient for Capacity. Coefiticient for Power. Inches of Water. Ounces. («) (*) O 0.50 30 0.5 0.29 •45 28 I.O 0.59 .40 26 1.72 1. 00 • 30 20 2.0 ];.i8 .27 18 3-74 2.00 .10 10 The following table gives results of tests of two fans used in heating the Veterinary Building at Cornell University: Diameter of wheel, inches Width at center, inches Diameter inlet, inches Discharge opening, inches Diameter engine cylinder, inches Length of stroke, inches Heating surface, lineal feet, total " " " " heater " " " " tempering coil ... . Lineal feet per cubic foot heated Cubic feet of air per minute ■ . Lineal feet of pipe in heater, per cubic foot of air Pressure in ounces Revolutions engine per minute Revolution of fan Indicated horse-power Delivered horse-power, actually found Steam pressure, pounds Temperature outside air Temperature of room Temperature of warm air Heat supplied per minute B. T. U Heat per lineal foot of pipe, B. T. U. per hour. . Pounds of steam, per square foot of heating sur- face per hour Cubic feet of space heated Changes of air per hour RESULTS COMPARED WITH CAPACITY AND Cube of diameter in feet Coefficient for capacity Capacity by rule ■ Fifth power of diameter in feet D*n^ -i- J, 000,000 Factor for horse-power Horse power by rule Large Fan. Small Fan 36 54 40 X 42 19 8 4.770 3,816 954 12.7 21,000 4-5 0.875 220 200 8.6 5-5 22 34 70 80 4.560 58.8 0.17 121,724 10. 1 28 034 18 28 22 X 22 6 8 1,980 1:584 396 28.02 5,180 3 o 201 402 2-5 i.5i 22 34 70 136 5.180 195.6 0.61 56,732 5-5 POWER RULES. 343 0.3 22,028 16,807 0.179 30 5.36 49 • o. ,250 663 o. 30 1. 2 5 053 16 368 HEATING AND VENTILATING BUILDINGS. 163. Relative Efficiency of Fans or Blowers and of Heated Flues. — Fans or blowers are usually driven by steam- engines of a medium or poor grade, and as they must be considered in connection with the motive power for a fair comparison, they do not present the most efficient method of transforming heat into mechanical work. The very best engine constructed would develop about a horse-power for a consumption of 1.25 pounds of coal per hour under the boiler, which would correspond to an efficiency of transformation of heat into work of about 1 2 per cent. The engine ordinarily employed for driving blowers is of the simple non-condensing type, using about 40 pounds of steam per horse-power hour and requiring per horse-power from 5 to 8 pounds of coal to be burned under the boiler per hour ; its thermal efficiency is from 2 to 4 per cent, perhaps averaging not far from 3 per cent. Peclet, in his Traite de la Chaleur, gives a number of effi- ciency tests of blowers, the results being, in the various cases cited, respectively 15, 16, 18, 20, 25, 17, 20, and 10 per cent. Professor Woodbridge of the Massachusetts Institute of Tech- nology obtained the following results in a series of tests of different pressure-blowers and of exhaust-fans when operating under a working pressure 0.05 of an inch: Tests of Blowers. Tests of Disc Fans. Speed. Numbfer. Speed. Number. 300 Soo 500 700 Efficiency, Per Cent. Efficiency, Per Cent. I 14.9 13-4 6 13.7 16.4 2 4.6 5-7 7 13-5 15-3 3 15.6 15-1 3 16.4 19-5 4 15-7 17.3 9 II. I 12.9 5 14.8 14.6 10 14.4 15-2 Quite an extensive series of experiments on different fans and blowers have been conducted by the author in ' Sibley College, Cornell University; these have shown that the efficiency of fans under usual conditions may vary between 10 MECHANICAL VENTILATORS. 369 and 40 per cent, and under best conditions may rise to 50 per cent. A blower with an efficiency of 10 per cent, operated by an engine having an efficiency of 3 per cent, would constitute a plant with a joint efficiency of 0.3 of i per cent; this may be considered as the poorest ease likely to be found in practice. The joint efficiency of engine and blower would probably be about f of I per cent in average practice, and about 1.25 per cent in the best cases likely to be found. In many cases all the steam exhausted from the engine may be used for heating or other useful purposes, which would make the joint efficiency from twenty to thirty-three times that mentioned above. The following mathematical principles may be applied. Thus let r equal that percentage of heat in the coal burned under the boiler which is converted into mechanical work by the engine, /"that percentage of the indicated horse-power of an engine which is utilized in moving the air, R thp total available heat in B.T.U., 7" and T' the absolute temperature, inside and outside the chimney. The total useful work performed by a fan or blower will then be W^=T/%rfR, (I) in which the efficiency of the engine and blower combined is denoted by rf. The ratio of the useful work done by the same coal in operating an engine and a fan to that done by heating a chimney for discharging air at the top will be found by divid- ing the above equation by the mechanical work done in a chimney (see equation (c), page 53, in which c = .238): Rh ^'^=^ (^) Wy 77%crrf 185 .2 rr/ ^f- Wj^ h - h • • • • v3; 1st. Consider ^/= 0.003 = the assumed lowest value, the outside temperature = 60°, so that T — 60 ■\- 460 = 520 in all cases; then r. 280 R,= -j- ...... (4) 370 HEATING AND VENTILATING BUILDINGS. 2d. Take r/"= 0.0066, the average value; then 620 , . ^f='k (5) 3d. Take rf=- 1.25 per cent, the highest value when the exhaust steam is not used ; then ^.= ^' (^) 4th. For the case when the exhaust steam may be utilized or the fan can be driven by shafting, r may equal 80 per cent, /= i6f per cent, and r/'=ii.3 per cent, for which case T> 10,600 ^/=-F- (7) From the above formulas it is noted that the relative efficiencies of fan and blower would be about equal for the case of the most inefficient fan and engine were the chimney 280 feet high; for the average case they would be equal when the chimney was 620 feet high, and for the best case when the chimney was 1203 feet high. From this it appears that the fan and engine under average conditions are from three to twelve times as efficient as a chimney lOO feet high. In all the above cases the delivery of air from the top of the chimneyis considered. A fan is frequently used to draw air by suction as well as to deliver it by increase of pressure ; and as the air entering the fan is seldom heated to any great extent, the work of a fan under usual conditions is fairly comparable with that of delivering cold air into a chimney. For this case the ratios of efficiencies will be found by dividing formula (i) by formula RhT (e), page 54, for supply of air to a chimney, W^ = cT '2 ^--^;- hT ~ Jt ■ • • ^^> When the outside temperature is 60°, T equals 520°, which will be used in all cases. Substituting ?/= 0.0003, we have for the most inefficient fan and engine 0.00 1 06 ■5 7"'' R^= T^~ (8) MECHANICAL VENTILATORS. 371 Substituting other values of r/"as before, values may be found for the average and best quality of fan and engine. For these last conditions the relative efficiency depends upon the square of the absolute temperature directly and on the height of the chimney inversely. Attention has already been called to the extremely waste- ful results which characterize the movement of air by heat, as in a chimney. From this it may be deduced at once that any mechanical appliance, even with a moderate efficiency, would be many times more economical for moving air than a chimney. This is rather more remarkable since mechanical appliances for moving air at low pressures, as is usually required in ventilation, have a comparatively low efficiency and seldom make use of more than 25 per cent of the power applied. Even, however, considering the case when the efficiency is very low, we shall still find the mechanical appli- ance usually much less wasteful for moving air than when heat is applied directly in a chimney. Thus considering the case when the total efficiency of the heat applied to drive a steam- engine and all the intermediate machinery for mechanically moving the. air to be .6 of i per cent, we shall have the mechanical method of ventilation as many times more econom- ical than the chimney as shown in the table on page 372. The foregoing discussion shows that mechanical ventilation as usually conducted is much more efficient than that which may be obtained with heat applied directly to a chimney; consequently the cost of obtaining ventilation by mechanical means is many times less than by use of a heated chimney. It may be remarked in this connection that many results have been published showing higher efficiencies of a fan or blower than quoted in this work. Very high results are generally to be attributed to errors in measurement of the air discharged, or by neglecting to measure velocities in all portions of the dis- charge-flue, or by use of incorrect apparatus. An efficiency of 35 per cent is to be considered high for fans working under the light pressures which are common in ventilating work. While the truth of the conclusions regarding the relative efficiency of ventilation by mechanical means or by a chimney cannot be questioned when fuel has to be burned for this 372 HEATING AND VENTILATING BUILDINGS. TABLE SHOWING NUMBER OF TIMES MECHANICAL VENTILA- TORS ARE MORE EFFICENT UNDER AVERAGE CONDITION THAN A CHIMNEY DISCHARGING AIR FROM A ROOM. Temperature of Chimney. Fahr. 80° 100" 150° 200* 25°° 300° 400" 4;o° Height of Ratio of Efficiencv Chimney, Feet. lo 68.4 73-4 87.3 102 118 I3'5 173 194 20 34 2 36-7 43-6 51 59 67 86 97 30 22 8 24-5 29.1 34 39 45 57 65 40 17 1 18.3 21.8 24 29 34 44 48 50 13 7 ]4-7 15-4 20 24 27 35 39 60 II 4 12.2 14.5 17 19 22 28 32 70 9 8 10.5 12.8 15 17 19 25 28 80 8 5 9-2 10.9 12 15 17 22 24 90 7 6 8.1 9-7 II 13 15 17 21 100 6 8 7-3 8.7 10 12 13-5 15-3 19.4 125 5 4 5.9 7.0 ' 8.1 9-5 10 13-9 15-5 150 4 6.1 5'i 6.7 8.0 9.0 II. 7 13 175 3 9 4.2 5.0 5-8 6.7 7-7 9.9 II. I 200 3 4 3.6 4.4 5-1 6.0 6.7 8.6 9-7 250 2 7 2.9 3-1 4-1 4-7 5.4 6.9 7.8 300 2 3 2.4 2 9 3-4 3 9 4.5 5.7 6 ■; special purpose, yet it should be noted that in many cases a heated chimney is available without extra cost or, from the character of the building, is the only kind of ventilation per- missible; for such cases it is to be adopted as preferable to mechanical ventilation. 164. Disc and Propeller Fans. — The same general for- mula which have been quoted for centrifugal fans also apply to the disc or propeller fans. In this case the air is delivered from the entire edge of the blade and with a velocity propor- tional to the velocity of the blade at that point. An extensive series of tests of fans of this character were made by W. G. Walker of London, Eng., and published in Engineering, August, 1 897. The results of the test show that the efficiencies under the best conditions are essentially the same as those for pressure-blowers as quoted. These fans developed, according to the experiments made, a volumetric efficiency in some cases greater than unity; this can only be explained by the fact that the velocity of the air-particles must under some conditions have been greater than that of the blade, a condition some- times found true in tests of propellers for steam-boats. MECHANICAL VENTILATORS. 373 The rule for capacity as given for blowers of the radial-flow type would seem by the tests to also apply closely to propeller fans, while that quoted for horse-power required does not apply. The capacity would be expressed by the following formula, in which « = a constant varying from .06 to .50 per cent, dependent upon the resistance : Q = aiy'n. The horse-power would be expressed by a formula, in which ^ = a constant to be determined: H.P. = bDht^. 165. Measurement of Air Supplied a Room. — Specifica- tions for ventilating apparatus generally require as a condition of acceptance the delivery of a specified amount of air into a room, and it is important that accurate measurements of such air be made. Air is generally delivered into a room through the grill of a register, and it will be found in nearly every case that there is considerable variation in velocity in the air delivered from different portions of the register. The results would also vary considerably with the position of the anemometer, which is the best instrument for such measurements. An approved method of measuring the air discharged from a register requires the use of a temporary pipe or tube of the size of the register frame, which is extended into the room for a distance of about two feet, and is subdivided into small sections, each from 4 to 8 inches in size, by fine wires. The average velocity if taken in each section with the anemometer will represent accurately the velocity of the entering air, and this quantity multiplied by the area of cross-section of the temporary tube will give the volume suppHed. If the anemometer is held close to the face of the register, there may be considerable error in obtaining the average velocity and also the actual area of cross-section of the incom- ing air, both of which quantities are essential. 166. Introduction of Air into Rooms. — The principal difificulties experienced in mechanical ventilation are those relating to an equable distribution of air in the rooms to be ventilated. It is a comparatively easy matter to force any 374 HEATING AND VENTILATING BUILDINGS. required amount of air through a given duct into a room pro- vided there be suitable discharge-flues or openings leading to the air, but it is a very difficult matter to supply this air in such a manner that it will be thoroughly and perfectly dis- tributed. In all cases of mechanical ventilation there must be erected ducts or pipes for conveying the air to the room, and also suitable ducts or passages for removing the air from the room, and these may be arranged in various ways with refer- ence to each other. Air may be introduced into rooms through registers either in the floor or ceiling or in the side walls at various heights, and each system has certain advantages and disadvantages. In introducing the air through floor-registers, any sweepings, dirt, or contamination falling to the floor is likely to be carried by the entering air into a position where it might be respired and thus become a medium for spreading or communicating disease. Where warm air is introduced for ventilation, as is likely to be the case during the cold months, there is a tendency for this air to rise, thus causing a natural circulation, which assists the artificial one due to pressure. On the other hand natural circulation tends to increase the air-currents in local positions, and especially in the lines between the supply- and discharge-registers, and this prevents that equable distribu- tion which might otherwise be obtained. This system, which we may term the up-draft system, has been extensively used in the past, and is at the present time frequently employed for the ventilation of large auditoriums, as, for instance, the House of Parliament in London, Eng., the Senate Chamber at Wash- ington, D. C, and various theatres and opera-houses. In the House of Parliament, London, Eng., the air is introduced throughout the whole floor-area through small perforations covered with matting, and is removed through registers in the ceiling. Professor S. H. Woodbridge constructed a system of ventilation, in 1896, for the Senate Chamber at Washington, in which the air is introduced through perforations located in the fixed furniture, and discharged in the ceiling. The introduction of the fresh air through registers or per- forations in the ceiling and its discharge from the floor-line would seem to be supported by the best theoretical reasons. MECHANICAL VENTILATOKS. 375 since it naturally presents the best methods for an equable dis- tribution, provided the air-currents are not of sufficient intensity to cause a sensible draft. This system has not, however, been as extensively used as that with the up-draft currents, but has been applied successfully to a few large auditoriums. The introduction of air from the side walls is perhaps more extensively practised for the ventilation of rooms of moderate height and extent than any other, and is doubtless the best suited for the ventilation of such rooms as are usually found in school buildings. For such cases the best results are obtained by locating the supply-register on an inner wall of the room and about three or four feet from the ceiling, and the discharge- or vent-register in the same wall and near the floor-line diagonally opposite the supply-register. This arrangement of registers is found to give a fairly equable distribution of the air with rooms from I2 to 14 feet in height when not exceeding 30 to 40 feet in floor dimensions. The introduction of air at two or more registers under similar conditions is likely to cause cross-currents and eddies, thus producing irregular ventilation. In all systems of ventilation, as previously mentioned, the fresh air should be introduced in such a manner as not to produce sensible drafts ; where it enters in such a position as to impinge directly on the people, the velocity should, for best results, not exceed 3 feet per second ; but where it is delivered in the upper portion of the room and into a larger body of nearly still air the velocity may be 6 to 10 feet per second without producing serious inconvenience to the occupants. Mechanical ventilation may be performed by forcing the required amount of air into a room and allowing it to discharge through suitable flues or by exhausting the air from a room, fresh air being supplied by suitable connections to the outside; or it may be performed by a combination of forcing and exhausting methods. The system of forcing the required amount of air into a room is as a rule more positive than that of exhausting the air from a room, since in the first case leaks in the flues or conduits have less influence on the results than in the other ; this system is also generally more cheaply con- structed. The exhaust system would necessarily be used in cases where noxious gases need to be removed from a room 37^ HEATING AND VENTILATING BUILDINGS. without the possibility of spreading into adjacent rooms. The combination of the two systems is frequently employed; in which case the air is delivered into the room by force or under a slight pressure and is removed from the room by action of an exhaust-fan placed in the discharge-flue. In this latter case the exhaust fan is virtually used as a substitute for a chimney. CHAPTER XIV. MECHANICAL SYSTEMS OF HEATING AND VENTILATING. i66. General Remarks. — In the systems of hot-air heat- ing which have been described the circulation of air is caused by expansion due to heating, which is a feeble force and is likely to be overcome by adverse wind currents, by badly pro- portioned pipes, or by friction ; by employing a fan or blower of some character for moving the air the circulation will be rendered positive and so strong as to be unaffected by these causes. This system can be employed where power is available, and in many cases will be found to present an economical and satisfactory system of heating, comparing well with any that has been devised, especially when the amount of ventilation provided is considered. The cost of heating a large quantity of air is, however, in every case one of considerable amount, so that it is quite probable that in expense of operation no system of indirect heating, whether by furnace or steam-pipes, can compare with that of direct hot-water or steam radiation. The system of mechanical ventilation is in almost every case employed in connection with steam-heated surfaces, but in some instances the system has been applied successfully with furnace-heated surfaces.* 167. Various Forms of Mechanical Ventilating and Heating Systems. — A mechanical system of ventilation is much more economical than one which depends upon the use of a heated flue for the reasons already given, and in connec- * The Metal Worker, May 25, 1895, gives an interesting example show- ing the successful use of a blower and furnace for heating a church. 377 378 HEATING AND VENTILA7UNG BUILDINGS. tion with a method of warming it may also form a convenient and economical system of heating. In general it will be necessary to warm the air which enters for ventilation purposes in cold weather in order to prevent uncomfortable sensations of chilliness; this may be done to a sufficient extent to provide all the heat needed for warming or to an amount sufficient only to prevent a sensation of chilliness, which may be perhaps to 72" to 7 5*^. A mechanical system of circulation can be employed for the purpose of heating only, by driving air over heated surfaces and thence into the rooms to be warmed, and many successful plants of this kind have been erected for heat- ing shops or other places where direct radiation was objection- able; it is most successfully used, however, in buildings where ventilation is necessary by introducing a constant volume of air which is heated more or less as may be necessary to provide a uniform temperature in the room. Systems of mechanical ventilation and heating have been used in the art for more than a century, but until within the last decade they have not been extensively or systematically installed. As erected at present we have the following general methods of installation in use. First, systems which supply a constant volume of air which is warmed sufficiently to provide all the heat required ; the air may be warmed (A) by concen- trating the heating surface near the fan and providing a flue or passage over it for hot air and another around it for cool air; these two flues or pipes are kept separate for some distance, but join at the bottom of a vertical flue leading to the room to be heated, where they are controlled by a regulating damper, which is arranged to open one flue as it closes the other; this system is generally known as the double direct system, and is the one in most extensive use. All the air before reaching the fan is usually warmed to 70° or 75° by a coil of steam-pipe, termed the tempering-coil. The air is warmed in the second way (B) by separate radiating surfaces arranged as for indirect heating with steam; at the base of the vertical flues leading to the various rooms to be warmed, a by-pass pipe around the heater permits the cool or tempered air to enter a room in any desired amount, being regulated by a damper. In this latter MECHANICAL VENTILATING SYSTEMS. 379 system the heating surface is subdivided, but only one air-pipe has to be erected from the fan to each heater. A third system (C) has been recently used to a consider- able extent, in which the air driven into the room by the fan is vv^armed only to a temperature of 72° to 75°, or sufficient to prevent a sensation of chilliness, and the remaining heat needed is supplied by direct radiation. For this latter case sufficient direct radiation must be used to balance the loss from the walls and windows, or in other words, the steam-radiating surface for each room in square feet must equal in which G = area of the glass in square feet, /^equals the area of the exposed surface of the wall. The system employed for heating and not for ventilation would need the same amount of radiating surface and piping or ducts for supplying hot air, but would not need the pipes for supplying cool or tempered air. In all these systems a fan or blower, as described in the previous chapter, is located in a convenient place, but usually in the basement; it can be arranged to draw by suction or to force the air over the heating surface as desired, but for the ventilating systems with double ducts or heaters at the base of the flues, it is in general more convenient to force the air over the main heater or heaters and draw the air by suction through a steam-coil situated between the fan and the outside air, known as a tempering coil and of sufficient extent to warm the entering air to 70° in the coldest weather. The usual arrangement of fan and heating surface, when the heater is concentrated at one place, is shown in Fig. 244. The entering air is first drawn through a filter to remove any dust, if necessary, thence through a tempering coil, which is not shown in the drawing. It then passes through the fan and is thence in part forced through the heater and then into a hot-air chamber, from which hot-air pipes lead to vertical flues leading to the various rooms; a part flows into the passage beneath the fan and thence into the cold or tempered air-pipe, which in the system shown is directly below the hot-air pipe, although in other systems the position may be reversed. In 380 HEATING AND VENTILA7VNG BUILDINGS. Fig. 245. — Arrangement of Blower and Heater. MECHANICAL VENTILATING SYSTEMS. 381 Fig. 245 is shown another style of blower and heater in which the cold-air flue is located above the hot-air flue. 168. Volume- or Regulating-dampers. — These dampers are used at the place where the horizontal flues for hot and cold air join a vertical flue leading to the room to be warmed. These dampers are made in a variety of ways, but in such a manner that one flue will be opened -as the other is closed, so as to provide the discharge of a constant volume of air. One form of damper is shown in Fig. 246, consisting of two planes or disks mounted at right angles on the same shaft and so connected that the hot-air pipe will be closed as the cold-air pipe is opened and vice versa. The damper in the figure is shown as operated by a thermostat, but it could readily be arranged to be operated by hand from the room to be warmed. Fig. 246, — Regulating DAMPERS. Fig. 247. — Volume- dampers. Another form of volume damper is shown in Fig. 247, of the same general character as that in Fig. 246, and operated in the same manner and so as to secure the same results. 169. Form of Steam-heated Surface.— The heating sur- face is generally built of inch pipe, set vertically into a square cast-iron base, connected at top with return-bends, although the box coil. Fig. 94, page 139, or any form of indirect radiat- ing surface could be used. 382 HEATING AND VENTILATING BUILDINGS. Figs. 248, 249, and 250 show forms of heating surface built up of one-inch pipe in use in the blower system of heating. Fig. 248. — Heater for Mechanical System. The heaters are especially designed to afford free circulation of the steam and to permit a ready removal of the water of condensation and air. Fig. 249. — Details of Heater Shown in Fig. 248. The heating surface, as will be seen by referring to tests, page 109, will emit 600 to 1000 B.T.U. per square foot per MECHANICAL VENTILATING SYSTEMS. 383 hour and should average one square foot for every 13 to 15 cubic feet of air heated from 0° to 120° F. per minute. To Fig. 250. — Heater for Mechanical Systems of Heating. account for inefficiency of heating surface there should be about 10 per cent excess or one square foot of heating surface for 12 cubic feet of air heated. This heating surface for convenience is usually estimated in lineal feet of one-inch pipe, and on this basis there should be one foot in length of one-inch pipe for 4 cubic feet of air heated per minute, which agrees well with the average practice; the increase in temperature of air being as shown in the diagram. Fig. 251, as the results of tests previously referred to. The fan is either arranged 100 200 300 K» 600 600 70O 800 900 1000 1100 1200 IGOO 1400 1500 - HEATING SURFACE SQUARE FEET Fig. 251. — Diagram showing Relation between Temperature of Dis- charged Air and Heating Surface. 384 HEATING AND VENTILATING BUILDINGS. Cast-iron radiators have been used only to a limited extent in connection with blowers or fans. During the year 1905 a few sectional cast-iron heaters were installed by the American Radiator Co., which gave good results both as to efificiency and capacity. Cast iron possesses the advantage over steel or wrought iron of being more durable and less expensive, and if successful it will doubtless be employed extensively in future installations. Fig. 251. — Blower Connected to Engine. 170. Ducts or Flues — Registers.- — The dimensions of the ducts or flues leading from the heater should be such that the required amount of air may be delivered with a low pressure and velocity, so as to avoid excessive resistances due to friction. The velocity which will be produced by various pressures in excess of that of the atmosphere is given in Table XXVI, from which it is seen that a drop in pressure sufficient to balance \ inch of water (0.29 ounce per square inch) will produce a ve- locity of 30 feet per second in a pipe 100 feet long and i foot in diameter; this is generally considered to be the maximum velocity which should be pemitted in any of the pipes or pas- sages. In proportioning apparatus in this system of heating it is generally required that sufficient air shall be brought in to change the cubic contents of the room four times per hour. By consulting the table on page 63, it will be seen that for this condition, and without allowance for friction, it will require a MECHANICAL VENTILATION SYSTEMS. 385 flue with 5.7 square inches of area for each 1000 cubic feet of space in the room. By adding two inches to the diameter obtained as above, a fair allowance for friction will be made. A more accurate method of proportion area of ducts is by use of Table XXV, which gives the diameter of a round pipe or side of a square pipe required to discharge a given volume of air at a known distance and with a drop in pressure of one inch of water. The author would advise the use of this table in proportioning ducts for supply of air in its use. It is first necessary to determine the air required for each room, and the length of the pipe-line. This table, together with that given in Art. 163, will give the dimensions. The pipes are usually made of galvanized iron or bright tin and should have tight joints and be protected from loss of heat by some good covering (see page 229). Flues of briqk or masonry cause more friction than those of galvanized iron, and if used should generally be about two inches larger in diameter than provided for by this table. As branch pipes for various apartments are taken off, the main pipe can be reduced in size ; this shouldnever be done abruptly, but only by the use of taper- ing tubes, the angle of whose sides measured from the line of the main pipe should rarely be greater than 1 5 degrees. In a double-duct system of heating the area of the hot-air duct should be sufificient to carry 90 per cent of the total air ; that of the cold-air duct sufificient to carry 40 to 50 per cent. The area of the cold-air duct or passageway leading to the fan should be as great as possible in order to keep the velocity of entering air low ; if the area of cross-section is equal to the sum of the areas of all the ducts leading from the heating surface, the velocity will probably be about three quarters of that in the hot-air pipes, and may draw in considerable dust and dirt from outside. The flues which convey air to the rooms should discharge near the upper part of the room substantially as described on page 59 and shown in Fig. 23. The friction in small pipes is greater than in large ones, being relatively pro- portional to the circumference or perimeter; hence the sum 386 HEATING AND VENTILATING BUILDINGS. of the areas of the branch pipes should be considerably greater than that of the main,* The table on opposite page gives the number of small pipes which provide an area equivalent to that of one large pipe of similar cross-section ; in case no table is at hand the same re- sults may be obtained by dividing the larger diameter by the smaller one and taking the square root of the fifth power of the quotient. The following table gives the actual amount discharged with constant resistance, and with pressure equal to one half inch of water column in round pipes, as computed from Unwin's formulae, page 47 : (also see Table XXV in Appendix) : VELOCITY AND QUANTITY OF AIR DELIVERED IN PIPES OF DIFFERENT DIAMETERS, EACH 100 FEET LONG, WITH AN AIR-PRESSURE EQUAL TO \ INCH OF WATER COLUMN. Diameter of Velocity of Air. Cubic Feet of Diameter of Velocity of Air. Cubic Feet of Pipe. In. Ft. per Sec. Air per Min. Pipe. In. Ft. per Sec. Air per Min. I 8.7 2.6 16 . 35.6 3.024 2 12.4 16 18 36. S 4.032 3 15-0 45 20 38.1 5,184 4 17-3 90 22 40.6 6,480 5 19.4 160 24 42.4 8,208 6 21.3 253 26 44.2 9,936 7 23 380 28 46.0 11,952 8 24-5 515 30 47-4 14.256 9 26.1 720 36 52.0 23,040 10 27.4 900 42 56.x 33,120 II 28.6 1 190 48 61.0 46,080 12 30.5 1440 54 63.6 61,920 13 31.3 1620 60 67.0 80,640 14 32.4 2160 *The velocity of flow of air is given in formulae on page 47 ; the amount discharged is equal to the area of the pipe multiplied by the velocity, and will be equal in every case to the square root of the fifth power of a constant multi- plied by the diameter of the pipe. If we denote diameter of larger pipe by D, of smaller pipe by d, and the number of smaller pipes required to make one of area equivalent to that of larger by n, -=a To find diameter of round pipe, d, which shall be equivalent in carrying capacity to a rectangular pipe with dimensions a and b, we would have FORCED-BLAST SYSTEMS. 387 0, o H Id < Id a: H o z < a o M J OQ < § -S - o >> c -g a .s •5 £ — s.- S u " 3 ° " S- C " C vO o ".i:Ti . • O c ,s tun rt ■" " '5 .- a « S g o g „ « „ o. 1 ■* ^7 1 10 «• 1 QQ c<^ao 1 ■* M M ^ M W « rt u 5Q in i-i CO vo , I CO >-H N_M_cn_ I CO i-i w en -^ m qq^nO^co CO w r>. 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M N M « W CO ■^ inQ CO *viM moo >-■ -^co WO mr-^ o co 0^0 co « coo w*J... i-icicOTtin « w PI to CO ' ^ ino CO CT- ^ w TOO «0 O-^O^i^r^OO n M N c< W CO CO "d- ' Q coo cr-cooo Nco coo r^N Ot- pH i_i M M M C4 CO CO -^ in ut r^co Od , cor^O moo « OM^ii N N CO CO ■+ ■* xi^-^ t^ O^ y W TT r-> O w r^O CO m I « CO ■^O CO i-< CO r>. N CO -fd- -> CO t^-^ r^co O^ _ fyv - COO CT> coco CO cooo a* ■^ **'^ iiciNeO'^^i'^o r-co cT"" tH i-iei ci -^ocoi-. m Tto^rfiioo t->.r^i>.oc^ t- ^ N cOcO"^inO r>-CT''- O w -too N r^ CJ 00 O 00 coo »n i-< cj c» CO coo 00 « O >H CD , ji-HQOvOinr^O^coo^ _ _ __ 1-1 coo CO O O N 0*00 o 00 O^ O c» « co-d-inooo cr»i-« w w n w m coco-rr^noo mco -1- - « CO O to N CO r-* H M « CO T^ in r- o^ I coo 00 Hi ^co cj M O « -too O* in PJ M «H M w N W CO'stUlOr-'.CO coOoo w c* « CO 00 M r^vo O^ -t O^ 30 O^ CO Tf_ ^o 00 O r^ to grj . . . •NO0OM0^^>.OlnO000T^u-)00^^nu-»^>.0'-l( "n eomco m i-< « n coto^mo i^co o •-" -^co ^ o ^ CTitoco> M M H<-.ciN co-^r^o r>. 1^*00 O cow c^O i-ico r^o^N Oco O^in cooo coinin-::fi-i o c-i coo* (jn ■ . •i-iMco^mr*«ooON«nooOcor^— O^0i0c»00 0^»nr^ *Nu-)0^ Mi-iF^MC^Nc^coco TO r^co CO O r^ r-oo 1- W CJ CO Tt 1-^0 WOOD CT-O "i-l^N HI CO r^O O r^ino I->.-f-f'*>n coco 00 CT> O co • HI comoo Moo -t- *-> o O I-I cor^c^ or^co oco tor-^oo -icoooo — m M M cj CO -1- ino r>.co O — comr^c^co -^1- Oco T o m o ■ MWMi-.-ifqcieo^Tr^^'n—r-- -_'-i « M •saqouj ai adid-:sR|a UT'E]/^ JO HNW'^lOCOC^XaaOrHlMCO^lOCOC^QOOSOtM^COQOOCOClCO^O iHrHiHiHi-t^iH(HiHiHCsINNNNC0C0T( ■ S 0. > ■ S cu > ■ S (L > ■ S 0< > ■ S Oi Q u. =1*1 K OS aS a « ofi K OS 3V, a OS 3 In X ■ 1 U 0. u 0- ■u a U 0. 70 42 214 10336 312 14628 1.3 377 17928 1.6 428 20700 3-7 607 29352 10.5 80 48 18S 12584 ■> 2b, 17809 1.6 32s 2i827| 2.4 367 25202 4 5 530 3573S 12. 8 90 S-; 167 16150 7 236 22856 2.0 289 28012 3.7 333 32343 5-7 472 45860 .6.4 100 bo ISO 20723 ■) 212 29329 2.b 260 35945' 48 300 41503 7-4 425 58850 21. 1 no 66 n7 24548 I I IQ3 34741 3-1 236 4=579' 5-7 273 49162 8.8 387 6971 1 25.0 120 72 I2S 30165 I 1 177 42678 3.8 217 52304 7.0 250 60392 10.7 354 85«34 30.7 140 84 107 40465 I 8 152 57268 S.I 186 70188 9.4 214 81040 14 4 304 114913 4" -3 160 96 94 51344 2 3 <33 72264 6.4 163 89057 .1.5 152 102807 iS-3 260 145806 52.4 TABLE OF DIMENSIONS.* Fan with Steel-plate Housing. (fl „■ Size of J3 G ii n S3 Inlet, Outlet. Engine Cylinder Weights. "0 a u aj ij B .2 Size of Pulley. In. a t u V B gcr Size. In. B _4| g Fan Only. Single Engine. Double Engine. S5 « Q P < < cJ5 u 70 42 ^r% 14 X 8,^ 26 530 24 X24 576 4x4 3x3 1000 1290 1330 80 48 2-^ 16 X 81^ 30 706 26J^X26H 702 4x4 3x3 1300 1590 1630 90 54 2-]^ 18 X loVi 34 907 30 X30 900 5x5 4x4 1650 2150 2190 100 bo 2^ 20 X loj^ 38 1134 34 X34 1156 6xb ,5x5 2000 2640 2850 no 66 2-^jl 22 X lo!-^ 42 1385 37 X37 1369 6xb 5x5 2500 3140 3350 120 72 2^:3 24 X 12!^ 46 Ib6r 41 X41 1681 7x7 bxb 3000 3870 4300 140 84 ^I'S 28XI2H 53 2206 47^x47^^ 225b 7x7 4000 5600 5700 160 96 31^ 32 X 12J4 bo 2827 53^ X 531,^ 2862 7x7 5200 6800 6900 * Catalogue American Blower Co. MECHANICAL VENTILATING SYSTEMS. 395 The i20-inch fan has a wheel 6 feet in diameter, as shown by the table of dimensions. By consulting the table of powers it will be seen that this fan, running with a speed of 200 revolutions per mmute, requires less than 7 horse-power to drive the blower. The capacity, as given under the same head, is that for a fan working with free inlet and outlet, and, as before remarked, is about 10 per cent greater than the capacity when delivering into conduits. To totally close off either inlet or discharge of the blower causes the air to move around with the fan ; this removes so much load from the engine that unless it is provided with an excellent governor it will speed up to a very great rate and may run away. This fact that an increase of resistance diminishes the power required at different speeds is not considered in the tables given; consequently these powers are somewhat in ex- cess of those actually required. The excess of power would depend upon friction and other resistances; consequentl}?^ no allowance can be made which would be accurate for all con- ditions. Dimensions of Horizontal Conduits. — We now come to the question regarding dimensions of horizontal conduits that con- vey the air from the blower to various parts of the building. There is a great difference of opinion as to the proper velocity of the air through such conduits, and circumstances have a great deal to do with this question. In my opinion the easier you make it for the air to travel the more successful will be the plant. In no plants, in public-buildings, do we advocate a velocity of air that exceeds 3^ leet per second, or 1800 feet per minute ; 1200 feet, or even 400 feet, is better, although in an extensive plant the conduits might be so large as to be un- sightly and interfere with the convenience of the building. Vertical flues in the walls leading to the various apartments should be so large that the velocity of the air will not exceed 15 feet per second, or 9CX) feet per minute. Maximum Velocity of Air. — From an economical and efficient standpoint air should never enter a room through a register, screen, or grille at a velocity exceeding 400 feet per minute (6.6 feet per second). A greater velocity is liable to create 39^ HEATING AND VENTILATING BUILDINGS. such a rapid movement of the air as will stir up the dust in the room and create serious throat affections. Again, air coming in contact with the screen at a very high velocity will cause a low whirr or whistle often proving very annoying. Better ventilation, or perhaps we should say better circulation of the air, takes place when introduced at a moderate velocity than at a high velocity, because in that case the air enters gently and is distributed by gravitation, due to the cooling of the air in contact with cold walls, and the whole body of air is thus kept in slight motion and the entering air is more evenly distributed. If the air is forced in at high velocity, it creates swift currents and counter-currents, which will completely prevent the equitable distribution of the fresh air. Introduction of Air. — My method of introducing air into a room is from a register about 8 feet above the floor, connected with a flue located in an inside wall, and discharging the cur- rent of air in the direction of an outside wall. The vent regis- ter should be located in the same wall as the fresh-air register, but at the opposite side and in the warmest corner of the room. General Remarks. — Architects very often combat such ar- rangements on the ground of interfering with their plans or of taking up too much room, and very often seriously object to making even the slightest alteration. This often leads to sorry arrangements for heating and ventilating plants, which will probably always continue so long as competiting manufacturers design those to be installed in certain buildings. It may be said generally that while the method of design- ing, followed by different manufacturers, may be essentially different from that given here, yet the experience of the writer has shown that the quantities, as computed by various manu- facturers when submitting plans in competition for the same building, are essentially the same as those stated here. MECHANICAL VENTILATING SYSTEMS. 397 175. Description of Mechanical Ventilating Plant. — The plant erected in the New York State Veterinary College in 1896 is described, not because it has any peculiar points of merit or is to be-regarded as a model of its kind, but principally for the reason that the author has in his possession data regarding details of construction, and has had careful tests made of the efficiency of the plant. The buildings are arranged as follows: A main building three stories in height, in which are located the offices, lecture- rooms, museum, laboratories, and, in the basement, the heating and ventilating plant; the north wing to this building, one story in height, containing the anatomical theatre, labora- tory, preparation room, locker, and lavatory; a mortuary build- ing located in the rectangle formed by the main building and north wing at two sides; an operating shed east of the mortuary; and the stables and the isolated wards for con- tagious diseases, which are located to the east and south, and not heated from the main plant. The operating shed is built of wood; all other buildings are of buff brick and of slow- burning construction, viz., all the inner walls are finished in brick and painted, the timbers are ail extra heavy and exposed to view, the flooring and sheeting on the roof is laid over plank, the ceilings are of narrow pine, and in general no enclosed spaces are left. The roofs are all covered with tin and the trimmings in the interior of the main building are of oak. The building is lighted, except in the north wing and operating shed, through side windows; in the former the prin- cipal light comes through skylights in the roof. Except on the three stories of the main building, all floors are of concrete. A vault in the rear of this building and on a level with the basement contains the boilers, crematory, and cold storage. The exposure of walls and windows to the weather is about as follows: Main Building. Brick Wall. Glass. On the north about 3366 sq. ft 644 sq. ft. " " '• south 3366" " 644" ' " " " east 9339" " 1546" ' " " " west 9504 " " 1572 " " Surfaces covered by tin roof 6074 " 398 HEATING AND VENTILATING BUILDINGS. North Wing-. Brick Wall. Total exposed wall surface 6069 sq. ft. " roof surface 4875 " '' Skylight surface 552 " " Window surface 170 " " The essential dimensions are as given in the annexed table : DIMENSIONS OF PRINCIPAL ROOMS AND FLUES. Room First Ftoor. No. I' No. 2* No. 3* No. 4 Museum. . . . South Hall.. North Hall. No. s Second Floor. No. 8 ... No. *. . . No. II*.. No. 12*. . Museum Lecture-room. South Hall North Hall and Temp. ) Third Floor. No. 13 * No. 14 * No. 15 No. 16 No. 17 * No. 18 North wing, first floor.... No. 6 Closets and lockers, No. 7 Cubic Contents, Cu. Ft. Number of Persons. 4,920 3,600 4,920 3,600 39,366 7,200 7,200 10 10 10 12 10 20,800 - ] 5>9o4 12 5,904 5,904 5>904 10 10 10 34.992 3,600 3,600 5,904 10 10 5,904 20,892 10 13,488 40 ] 5,904 10 ■ 5,904 10 39,600 40 10 Air-flue, Dimensions Inches. (8X7* H "|6X7^T 3(8X24 I H 3(6X24 I T |8X7iH UX7iT i3X7i I6X7} J8X81 °(8X6) J8X8) °(8X8) 8X7^ 6X7i 3(16X24) 3(16X20) Air- register, Inches. 10X15 10X15 10X15 10X15 4(21X29) 14X20 12X20 14X20 j- 14X20 14X20 ( 2(20X24) f 2(18X24) - 12X24 14X20 3(16X24) 3(16X20) 2(10X16) Vent- register, Inches. 8X15 8X15 8X15 8X15 2(24X24) 2(24X16) 10X20 10X20 10X20 10X20 10X20 12X20 2(18X21) i 18X20 1 18X21 12X20 12X20 3(16X20) 3(20X24) 10X16 Direct Radiat- ing, Sq. Ft. 40 40 40 240 no ICO 40 40 40 40 40 100 40 40 400 * Offices and studies assumed as containing o people. Description of Plant. — The ventilating plant is located in the basement, and as shown on plan and sectional views, con- sists of two independent heating and ventilating plants con- nected to different portions of the building. These plants were installed so that if one portion of the building only was in use, the other portion need not be ventilated. A system of direct heating was put in for the halls and museum and some rooms MECHANICAL VENTILATING SYSTEMS. 399 when no ventilation was required for supplying heat. It was also put into a number of other rooms to be used after school hours, when the ventilating system would not be in operation. This system, although shown on the drawings, is of no especial interest and was only erected because of the peculiar conditions which existed. The cold air enters the building through two windows; from these it is carried to the cold-air rooms shown on base- ment plan, and before entering which it is passed through fine 400 HEATING AiVD VENTILATING BUILDINGS. wire screens to remove any large particles of dust which might be drawn in. Air from the museum, which is usually unoccu- pied, can also, when desired, by the opening of certain registers, be drawn into each cold-air room and mixed with air from the outside. From the cold-air rooms it is drawn into the fans through a coil of steam-piping known as the ' ' temper- ing coil," the office of which is to warm or temper all the air entering the building to between 65" and 70"; in case the entering air is already near this temperature, the damper is so adjusted that the entering air passes underneath the tempering coil and through the by-pass. The air-pipe from each fan, and through which the air is forced, is separated into two pipes, one above the other. The upper and larger one contains a chamber in which is placed a number of steam-coils similar to the tempering coil. This is called the heater, its duty being to raise the temperature of the air passing through the warm-air pipe from 65° or 70° to 100° or 150°. The general arrangement of the system is shown in Fig. 259, from which it is seen that air is taken in from the outside, is passed through or under the tempering coil T, depending LONGITUDINAL ELEVATION Looking at Front Wall Fig. 260. — Elevation showing Direct Radiation. on the position of the damper. This damper may be regulated as desired, either by a thermotsat or by hand. The blower is placed as shown, and serves to draw in the air from the out- side, also to force it over the heating surface and into thf. MECHANICAL VI'NTILAIUNG SYSTEMS. 4°! ^'arm-air chamber, also through an opening in front of tlie -heater and into the cool-air chamber. From the v/arm-air chamber and also from the cool-air chamber pipes are led to a vertical flue (which we will term the mixing flue), connecting with the rooms to be heated. These pipes are controlled by a single damper, operated by a thermostat which is so adjusted that either the warm-air pipe or the cold-air pipe can be opened as desired, but the total supply of air cannot be changed by any motion of the damper. A complete test of this plant was described by the author -in Vol! IV of the "Trans. American Society Heating and Ventijating Engineers," from which the following data and results are taken. The heating surface consisted of inch pipe screwed into cast-iron bases or manifolds, arranged in five sections for eich fan. Each section had four tiers of pipe, and contained for the large fan 954 feet of inch pipe and for the small fan 396 feet. One of these sections was arranged as a tempering coil, to warm the air when required before reaching the fan, the •other four sections were set in the heater coil. The total heating surface expressed in lineal feet of one-inch pipe, 4770 for the large fan and 1980 for the small fan. The following table gives the principal dimensions of machinery : Large Fan. Small Fao. Diameter of wheel, inches 84 44 Width at centre, inches 36 18 Diameter of inlet, inches 54 28 Discharge opening, inches 40X42 22X22 Diameter engine cylinder, inches 19 6 Length of stroke, inches 8 8 Heating surface, lineal feet 4770 1980 " " heater, lineal feet 3816 1584 " " tempering coil, lineal feet ... . 954 396 Lineal feet of pipe per cubic foot 12.7 28.2 -Dimensions of flues from fan : Tempered air, inches 40X20 42X10.5 Warm air, inches ■ 72X28 42X14.25 -Area of flue in square feet : Tempered air 5-56 3.o6 Warm air 11.66 4.04 402 HEATING AND VENTILATING BUILDINGS. Velocity of air, feet per miuute by measurement: Large Fan. Small Fan. Feb. 13 888 1186 Tempered air Feb. 25 1400 1073 Feb. 13 1000 601 Warm air Feb. 25 1218 411 Temperature outside air 32°, Feb. 13, 1897: Tempered air 60 63 Warm air gi.5 100 Fig. 261. — Speed, Horse-power, and Weight ok Air, Large Fan, Feb. 25, 1897. 05 / WERAG E TEMP ERATUR riDING A.M. OIR CTRAE lATION ON UN IL8:i5 J. 30000 ^' \ 25000 20000 B.T. Ml U. FEB lUTE i s^X"^ -\ ^ 16000 10000 SEH BO T TO JMS 1 'i5 Q- \ 10 ■MPER/ TUBEC F AIR II COLD AIR CH. M8ER )F SMAI L FAN ' 1 ,^ ~^ s_ ^vtipzjn ^TURE DFAIR^ / ^ 1 t COLD OF AIR CHAireER ARQE FAN "^ ^^ A.M. ,, I > 1 } ■ I I . . P.M. Fig. 262. MECHANICAL VENTILATING SYSTEMS. 40J. The graphical results of tfie test on February 25 are shown in the two diagrams, Figs. 261 and 262. The results of a test were as follows : Large Fan. Small Fan. . Cubic feet of air per minute 2i,ooo 5,i8o Lineal feet of pipes per cubic foot per minute 4.5 3.28 Pressure in ounces 7/8 1/32 devolutions per minute 220 201 Delivered engine horse-power 5.5 i.oi Indicated " " 8.6 1.5 Steam pressure, pounds 22 22. Temperature outside air, degrees 34 34 " entering air " 80 136 " of rooms supplied, degrees 70 70 Heat supplied per minute 4560 5180- Heat per foot lineal pipe, B. T. U. per minute o.gS 3.26 Pounds of steam condensed per square-foot heating surface per hour 0.17 o.6jl Cubic feet of space heated 121,724 56,732^ Changes of air per hour 10. 1 ' 5.5 COMPARISON OF RESULTS WITH CAPACITY AND POWER RULES. Cube of diameter of fan in feet 343 4g 2 Coefficient for capacity rule 0.3 0.5 Capacity by rule 22,028 5,250! Fifth power of diameter in feet 16,807 663 D'N^ -r- 1,000,000 0.179 0.053. Factor for horse power by rule 30 20 Horse-power by rule 5.37 1,16 It will be noted that the heating surface for the large fan. is apparently less efficient than for the small fan; this is- explained by the action of the thermostat, which regulated the relative amount of hot and tempered air to maintain a uniform temperature, and merely indicates that only a portion was. utilized at the time of the test. It will also be noted that the temperature of the air delivered by the small fan was higher and the pressure less than was the case with the large fan ; this in large part was due to the fact that the small fan was only run at about two thirds its rated speed. The necessity for ventilation was also less in that portion of the building heated by the small fan. The practical operation and use of the building has proved that better results would have been pro- duced had one fan and heating system been employed instead of two. 404 HEATING AND VENTILATING BUILDINGS. 176. Systems of Ventilation without Heating. — Where large quantities of air are required, especially in seasons when heat is not needed, systems of ventilation may be constructed which are independent from the systems of heating. The cir- culation of the air through the building may be produced either by exhausting or rarefying the air in the discharge-ducts, or by ■delivering fresh air to the rooms under pressure, as described for hot-blast heating. The air may be rarefied in the discharge-flue by heating eitiier with steam or hot-water radiators, with an open fire- place or a stove. When circulation is produced by heat, the amount of air moved will depend upon the height of the chim- ney or di.scharge-duct and its temperature, and will be essen- tially as that given in the table on page 531. The air may also be exhausted from the building by induction, for which may be used a jet of steam, water, or compressed air which is de livered from a nozzle into a convergent pipe of somewhat larger diameter and with both ends open. A very strong draft can be produced in this way, although at the expense of more energy than that required to operate exhaust fans or blowers. The air may also be exhausted by means of a fan located in the main flue. In case any of these means for producing drafts by exhausting or rarefying the air in the discharge-ducts is employed, every precaution that has been mentioned in regard to chimney-tops (page 192) should be observed, otherwise a considerable portion of the force may be required to over- come adverse wind currents. The general remarks regarding inechaiiicailieati'.ig-systems and also the tables of dimensions apply equally well to this case. The tables on page 63 will be useful in proportioning areas of flues and registers for the discharge of a given amount of air ; as an allowance for friction add one inch to each lineal dimension. The blower system of ventilation has been fully described in the preceding chapter together with the theory of fans, and tables of capacities of various fans given which are applicable to this case. In this system, as well as in the mechanical system of heating, especial care should be tak-en that the resistances in pipes and flues are as small as can be made, that bends are MECHANICAL VENTILATION SYSTEMS. 405 made with a long radius, and that the reduction in size in pass- ing from one pipe to another is as gradual as possible. 177' Heating with Refrigerating Machines. — The refrig- erating machine is virtually a pump which removes heat from a body at one temperature and discharges it at a higher tem- perature. Reckoned on the basis of heat transmitted, it is a very efificient machine, as it may move from a lower to a higher temperature lo to 20 times as much heat as the mechanical equivalent of the work performed ; in all respects this machine is the converse of the steam-engine. By utilizing the heat which is discharged from a machine of this character in warm- ing a building, and also that in the exhaust steam from the engine working the compressor pump, there is a possible efifi- ciency many times greater than that which can be obtained by burning the coal directly, which is, however, purely theo- retical. The practical arrangement of such a machine, if using air as the working fluid, would be such as to draw in air from the outside, compress it to such a point that its temperature would be very high, pass it through circulating pipes and radiating- surfaces when still under pressure, and discharge into a cham- ber from which the pressure has been removed, or in the out- side air after being cooled. If the exhaust steam could be used for heating, such a system would be very economical,, although it would be costly and take up considerable room. An ammonia refrigerating machine might be used, in which case the heat in the compressed ammonia could be removed by water, which would thus become heated and could be circulated for the purpose of warming. The scheme of using the re- versed heat-engine or refrigerating machine as a warming machine was pointed out first by Lord Kelvin in 1852,* and although it presents great advantages economically, the writer has no data showing that it has ever been put to practical use. 178. Cooling of Rooms.— The converse operation of cool- ing rooms, although at the present not undertaken except in the case of 'cold-storage plants and warehouses, bids fair to be at some time an industry of considerable importance. Rooms. * Proc. of the Phil. Soc. of Glasgow, Vol. Ill, p 369. 406 HEATING AND VENTILATING BUILDINGS. imay be artificially cooled by a system constructed similar to that described for hot-blast heating. The coils or radiating surface, however, would need to be replaced by ice or con- structed in such a manner that ammonia or some liquid at a very low temperature could be circulated. Over these the air could be driven, its heat would be absorbed, and it could be reduced in temperature to any point desired. In lowering the temperature of the air, a considerable amount of moisture might be precipitated, and some means should be provided for artificially removing it without heating, otherwise the rooms would be made damp. It may be remarked that ordinary pipe-fittings cannot be used with safety for ammonia circula- tion, and that special fittings are manufactured for this purpose. CHAPTER XV. HEATING WITH ELECTRICITY. 179. Equivalents of Electrical and Heat Energy. — Electrical energy can all be transformed into heat, and as there are certain advantages pertaining to its ready distribution, it is likely to come into more and more extended use for heat- ing, especially where the cost is not of prime importance. The valuje of mechanical and electrical units has been given on page 5, from which it will be seen that one watt for one hour, which is the ordinary commercial unit for electricity, is equal to 3.41 heat-units ; for one minute it is 1/60 and for one second it is 1/3600 this amount. Electricity is usually sold on the basis of 1000* watt-hours as a unit of measurement, the watts being the product obtained by multiplying the amount of cur- rent estimated in amperes by the pressure or intensity esti- mated in volts ; on this basis 1000 watt-hours is the equivalent of 3410 heat-units. We have considered in Chapter HI the amount of heat required per hour for the purpose of warming. This amount divided by 3410 will give the equivalent value in kilowatt-hours which would need to be supplied for the re- quired amount of heat. 180. Expense of Heating by Electricity. — The expense of electric heating must in every case be very great, unless the electricity can be supplied at an exceedingly low price. Much data exists regarding the cost of electrical energy when it is obtained from steam-power. Estimated f on the basis of * One thousand watts is called a kilowatt. f The mechanical energy in one horse-power is equivalent to 0.707 B. T. U. per second or 2545 per hour. One pound of pure carbon will give ott 14,500 heat-units by combustion, which if all utilized would produce 5.7 horse-power 407 4o8 HEATING AND VENTILATING BUILDINGS. present practice, the average transformation into electricity does not account for more than 4 per cent of the energy in, the fuel which is burned in the furnace ; although under best, conditions 15 per cent has been realized, it would not be safe to assume that in commercial enterprises more than 5 per cent could be transformed into electrical energy. In transmit- ting this to a point where it could be applied losses will take place amounting to from 10 to 20 per cent, so that the amount of electrical energy which can be usefully applied for heating would probably not average over 4 per cent of that in the fuel. In heating with steam or hot water or hot air the average amount utilized will probably be about 60 per cent, so that the expense of electrical heating is approxi- mately as much greater than that of heating with coal as 60' is greater than 4, or about 15 times. If the electrical current can be furnished by water-power which otherwise would not be usefully applied, these figures can be very much reduced. The.above figures are made on the basis of fuel cost of the electrical current, and do not provide for operating, profit, interest, etc., which aggregate many times that of the fuel. With coal at $3.30 per ton this cost on above basis is about .97 cent per thousand watt-hours. The lowest commercial price quoted, known to the writer, for the electric current was 3 . cents ; per thousand watt-hours the ordinary price for lighting current varies from lO to 20 cents. It may be said that for lighting purposes 10 cents per thousand watt-hours is con- sidered approximately the equivalent of gas at $1.25 per thou- sand cubic feet. It may be a matter of some interest to consider the method of computation employed for some of these quantities. The ordinary steam-engine requires about 4 pounds of coal for each horse-power developed; on account of friction and other losses about 1.5 horse-power are required per kilowatt, or in other for one hour, in which case one horse power could be produced by the combus- tion of 0.175 lb. of carbon. The best authenticated actual performance is one horse-power for 1.2 lb., corresponding to 14.6 per cent efficiency. The usual, consumption is not less than 4 to 6 pounds per indicated horse-power, or from 3 to 5 times the above. A kilowatt is very nearly ij horse-power, but liecause- of friction and other losses requires an engine of i,; indicated horse-power. HEATING WITH ELECTRICITY. 409. words 6 pounds of coal are required for each thousand watts of electrical energy. In the very best plants where the output is large and steady this amount is frequently reduced 20 to 30- per cent from the above figures in cost. The cost of 6 pounds of coal at $3.33 per Xon is one cent. To this we must add transmission loss about 10 per cent, attendance and interest 20. per cent, making the actual cost per kilowatt 1.3 cents per hour. As one pound of coal represents from 13,000 to 15,000 heat-units, depending upon its quality, and one kilowatt-hour is equivalent to 3415 heat-units, if there were no loss whatever in connection with transformation of heat into electricity, one pound of coal should produce 4 to 5 kilowatts per "hour of electrical energy. This discussion is sufificient to show that at cost prices electrical heating obtained from coal will amount under ordinary conditions to 15 to 20 times that of heating with steam or hot water, and at commercial prices which are- likely to be chaiged for current its cost will be from 2 to 10 times this amount. The following table gives the cost of a given amount of heat^ COST OF HEAT OBTAINED FROM ELECTRICITY. Cost per kilowatt hour, cents. Heat- units. - I 2 3 4 5 6 7 ' 8 9 ■ 10 B. T.U. ' Cost of heat obtained, cents. 10.000 2.93 5-86 8.78 11. 71 14.64 17.57 20.50 23.42 26.3; 29.28 20.000 s.ss 11.68 17.57 23.42 29.28 35.13 40.99 > 46.84 52.70 58.56. 30,000 8.78 17-57 26.35 35.14 43.92 52.70 61.49 70.28 79.06 87.84 40,000 II. 71 22.42 35.14 46.84 58.56 70.28 81.98 93.68 105 .40 117.12 50,0C0 14.64 29.28 43.92 58.56 73-20 87.84 102.48 117.12 131.86 146.40. 6o,oco 17.S7 35-14 52.70 70.28 87.84 105.40 122.98 140-56 158.12 175.68 70,000 20.50 40.99 61.49 81.98 102.48 122.98 143.47 163.96 184.46 204.96- 80,000 23.42 46.84 70.28 93.68 117. 12 140.56 ■63.97 187.36 210.80 234-24 go. coo 26.35 S2.70 79.06 105.4? 131.76 158.10 184.46 210.84 237.17 263 52 100,000 29.28 58.56 87.84 117. 12 146.40 175.68 204 . 96 234.24 263.52 292.80. jJq-j-j;. — 10,000 heat-units is equal to two thirds the heat coniained in one pound of the best coal, and is very near the average amount that can be realized per pound in steam or hot-water heating, hence the table can also be considered as showing the relative price of electricity and coal for the same amount of healing. For instance, if 5 cents per kilowatt hour is charged for electric current, the expense would be the same as that of good coal at 14.64 cents per pound, which is at rate of I392.80 per ton. 410 HEATING AND VENTILATING BUILDINGS. if obtained from the electric current, furnished at different prices. Thus 30,000 heat-units if obtained from electric current furnished at 8 cents per kilowatt hour would cost 70.28 cents per hour. The amount of heat needed for various buildings can be determined by methods stated in Chap. III. There are some conditions where the cost is not of moment and where other advantages are such as to make its use desir- able. In such cases electricity will be extensively used for heating. For the purposes of cooking it will be found in many cases that electrical heat, despite its great first cost, is more econom- ical than that obtained directly from coal. This is due to the fact that of the total amount of heat, which is given off from the fuel burned in a cook stove very little, perhaps less than one per cent, is applied usefully in cooking: the principal part is radiated into the room and diffused, being of no use what- ever for cooking, while the heat from the electric current can be utilized with scarcely any loss. 181. Formulae and General Considerations. — The fol- lowing formulae express the fundamental conditions relating to the transformation of the electric current into heat f C=^. . . . . (I) W=CE=aii (2) ^=|f (3) H = o.2AaR (4) hi = .000000095 C'i?. (S) ^a = 3415 f^ = 3.4isC»A' = 2.4iSC£. (6) In which the symbols represent the following quantities: £, electro- motive force in volts ; C, intensity of current in amperes ; R, resistance of conductor in ohms ; I, the length in metres ; w, the area of cross-sec- tion in square centimetres; k, coefficient of specific resistance; VV, kilo- watts ; H, the heat in minor calories, and hv in B. T. U. per second, h^ the heat in B. T. U. per hour. The amount of heat given off per hour is given in equation (6), and is seen to be dependent upon both the resistance and the current, and apparently would be increased by increase in either of these quantities. , The effect, however, of increasing the resistance as seen by equation (i) will be to reduce the amount of current flowing, so that the total heat supplied BE ji TING WITH ELECTRICITY. 41 I would be reduced by this change. On the other hand, if there were no resistance no heat would be given off, for to make ^ = o in equation (6) would result in making h^ = o. From these considerations it is seen that in order to obtain the maximum amount of heat, the resistance must have a certain mean value dependent upon the character of material used for the conductor in the heater, its length and diameter. For purposes of heating, a constant electromotive force or voltage is maintained in the main wire leading to the heater. A very much less voltage is maintained on the return wire, and the current in passing through the heater from the main to the return drops in voltage or pressure. 'This drop provides the energy which is transformed into heat. The principle of electric heating is much the same as that involved in the non-gravity return system of steam-heating. In that system the pressure on the main steam-pipes is essen- tially that at the boiler, that on the return is much less, the reduction of pressure occurring in the passage of the steam through the radiators ; the water of condensation is received into a tank and returned to the boiler by a steam-pump. In a system of electric heating the main wires must be sufficiently large, to prevent a sensible reduction in voltage or pressure between the dynamo and the heater, so that the pressure in them shall be substantially that in the dynamo. The pressure or voltage in the main return wire is also constant but very low, and the dynamo has an office similar to that of the steam- pump in the system described, viz., that of raising the pressure of the return current up to that in the main. The power which drives the dynamo can be considered synonymous with the boiler in the other case. All the current which passes from the main to the return current must flow through the heater, and in so doing its pressure or voltage falls from that of the main to that of the return. Thus in Fig. 263 a dynamo is located at D, from which main and return wires are run, much as iii the two-pipe system of heating, and these are so proportioned as to carry the re- quired current without sensible drop or loss of pressure. Between these wires are placed the various heaters ; these are arranged so that when electric connection is made, they 412 HEATING AND VENTILATING BUILDINGS. draw current from the main and discharge into the return wire. Connections which are made and broken by switches take the Diagram of Electric Heating. place of valves in steam-heating, no current flowing when the switches are open. The heating ^ect is proportional to the current flowing,. and this in turn is affected bjr the length, cross-section, and relative resistance of the ma- terial in the heater. The resist- ance is generally proportioned such as to maintain a constant temperature with the electro- motive force available, and the amount of heat is regulated by increasing the number of con- ductors in the heater. 182. Construction of Elec- trical Heaters. —Various forms of heaters have been employed. Some of the simplest consist Fig. 264.— Electric Heater at the merely of coils or loops of iron Vaudeville Theatre, London, ^jre arranged in parallel rows so that the current can be passed through as many wires as are needed to provide the heat required. In other forms of HEATING WITH ELECTRICITY. 413 these heaters the heating material has been surrounded with fire-clay, enamel, or some relatively poor conductor, and in other cases the material itself has been such as to give consid- erable resistance to the current. It is generally conceded that Fig. 265.— Office or House Heater. the most satisfactory results are obtained with electrical as with other heaters by regulating the resistance, by change of length and cross-section of the conductor, to such an extent as to keep the heating coils at a moderately low temperature. Some of 414 HEATING AND VENTILATING BUILDINGS. the various forms which have been used are shown in the cuts, Fig. 264 represents a portable form of electrical heater used in the Vaudeville Theatre, London. Fig. 265 shows the interior of an office or house heater made by the Consolidated Car Heating Co., of Albany. The electrical heating surface is made in the latter by a coil of wire wound spirally about an incom- bustible clay core. The casing is like that for an ordinary Fig. 266. —Car Heater of Consolidated Co. c X^AI"? lo|- 121 141 Fig. 267. — American Car Heater. stove, and is built so that air will draw in at the bottom and pass out at the top. The electrical heaters at the present time are used almost exclusively in heating electrical cars, where current is available and room is of considerable value. These heaters are generally located in an inconspicuous place beneath the seats, their gen- eral form being shown in Figs. 266 and 267. HEATING WITH ELECTRICITY. 415 183. Connections for Electrical Heaters. — The method of wiring for electrical heaters must be essentially the. same as for lights which require the same amount of current. The details of this work pertain rather to the province of the electrician than to that of the .steam-fitter or mechanic usually employed for installing heating apparatus. These wires must be run in accordance with the underwriters' specifications, so as not, under any conditions, to endanger the safety of the building from fire. CHAPTER XVI. TEMPERATURE REGULATORS. 184. General Remarks. — A temperature regulator is an automatic device whicli will open or close, as required to pro- duce a uniform temperature, the valves which control the supply of heat to the various rooms. Although these regula- tors are often constructed so as to operate the dampers of the heater, they differ from damper-regulators for steam-boilers, as described in Article 91, by the fact that the latter are un- affected by the temperature of the surrounding air, although acting to maintain a uniform pressure and temperature within the boiler, while the former are put in operation by changes of temperature in the rooms heated. The temperature regulator, in general, consists of three parts, as follows : First, a thermostat which is so constructed that some of its parts will move because of change of tempera- ture in the surrounding air, the motion so produced being used either directly or indirectly to open dampers or valves, and thus to control the supply of heat. Second, means of transmitting and often of multiplying the slight motion of the parts of the thermostat produced by change of temperature in the room, to the valves or dampers controlling the supply of heat. Third, a motor or mechanism for opening the valves or dampers, which may or may not be independent from the thermostat. In some systems the thermostat is directly connected to the valves or dampers, and no independent motor or mechanism is employed ; in this case the power which is used to open or close the valves regulating the heat-supply is generated within the thermostat, and is obtained either from the expansion or contraction of metallic bodies, or by the change in pressure 416 TEMPERA TURE REGULA TORS. 4U caused by the vaporizing of some liquid which boils at a low temperature. The force generated by slight changes in tem- perature is comparatively feeble, and the motion produced is generally very slight, so that when no auxiliary motor is em- ployed it is necessary to have the regulating valves constructed so as to move very easily and not be liable to stick or get out of order. In most systems, however, a motor operated by clock- work, water, or compressed air is employed, and the thermostat is required simply to furnish power sufificient to start or stop this motor. The limits of this work do not permit an extended historical sketch of many of the forms which have been tried. The reader is referred to Knight's Mechanical Dictionary, article "Thermostats," and to Peclet's "Traite du la Chaleur," Vol. II, for a description of many of the early forms used. Those which are in use may be classified either according to the general character of the thermostat or the construction of the motor employed to operate the heat-regulating valves as follows : Thermostats. Moved by expansion or contraction. Moved by change of pressure. No auxiliary motor. Temperature Regulators. Expansion or contraction. Pressure. Motor. f Clockwork. Water. Compressed air. 185. Regulators Acting by Change of Pressure. — A change of temperature acting on any liquid or gaseous body causes a change in volume, which in some instances has been utilized to move the heat-regulating valves so as to maintain a constant temperature. Fig. 268 represents a regulator in which the expansion or contraction of a body of confined air is utilized to control the motion of the dampers to a hot-water heater. It consists of a vessel containing in its lower portion a jacketed chamber connected to the hot-water heater at points of different elevation so as to secure a circulation from the heater through the lower portion or jacket of the vessel from 2 to 3. Above this is a second chamber which is covered on top with a rubber diaphragm, and which contains a funnel- shaped corrugated brass cup. The opening to the cup is in 4i8 HEATING AND VEA'TILATING BUILDINGS. the lower portion of the chamber, the top and hirger surface resting against the rubber diaphragm. Enough water at atmospheric pressure or alcohol is poured into the upper chamber through the opening marked i to seal the orifice in Fig. 268. — Lawler Hor-wAiER Damper-kegulator. the inverted cup and confine the air it contains. The reg- ulator acts as follows: The warm water from the heater mov- ing through the lower chamber communicates heat to the water or alcohol in the upper chamber, which in turn warms the air in the inverted cup, causing it to expand. This moves the rubber diaphragm and connected levers leading to the dampers substantially as in the damper-regulator for steam- heaters, already described. The Powers regulator for hot-water heaters (see Fig. 269) is sor" e described, but acts C- I'ill vaporize at a lower ; heater is placed in the vessel communicating wilu luc uiapuragm, in which case considerable pressure is generated before the water in the heater reaches the boiling-point. As the water in the heater is usuall)- under a pressure of 5 to 10 pounds per square inch, its boiling temperature is from 225 to 240 degrees, water of at- mospheric pressure which boils at 212° can be used in the closed vessel, and will generate considerable pressure before that in. the heater boils. TEMPERA rURE REG ULA TORS. 419 The method of construction is shown at the right, in Fig. 269,33 applied to a hot-water heater. The diaphragm employed consists of two layers of elastic material with compartments be- tween and beneath ; the lower one is connected to the chamber I 2 3 Fig. 269. — The Powers Thermostat for Hot-water Heaters. A, which is filled with water at atmosplieric pressure and is sur- rounded by the hot water flowing from the heater. The water in chamber A, being under less pressure, will boil before that in the heater, and will produce sufficient pressure to move the diaphragm and levers so as to close the dampers, before the water in the heater reaches the boiling-point. The compart- ment between the two diaphragms f, f is in communication with a vessel D, which in turn is connected by a closed pipe E with a thermostat, which may be placed at any point in the house and so arranged that if the temperature becomes too high in that room, the dampers of the heater will be closed. With this apparatus the dampers are closed either bj^ excessive temperature of water at the heater or too great a heat in any room. The intermediate compartment is only required when the dampers are to be operated by change of temperature in the rooms. The thermostat employed in this apparatus consists of a vessel 2, Fig. 269, separated into two chambers by a diaphragm ; one of these chambers, B, is filled with a liquid which will boil at a temperature below that at which the room is to be maintained; the other chamber, yi, is filled with a liquid which 420 HEATING AND VENTILATING BUILDINGS. does not boil, and is connected by a tube to a diaphragm damper-regulator which moves the dampers through the me- dium of a series of levers. Fig. 269, 2, shows a transverse section and i an elevation with parts broken away of a thermostat, and Fig. 270 an ele- vation with attached ther- mometer. The vapor of the liquid in the chamber B pro- duces considerable pressure at the normal temperature of the room, and a slight increase of heat crowds the diaphragm over and forces the liquid in the chamber A outward through a con- necting tube which leads to the damper - regulator, one form of which has been Fig. 270.— Elevation of Thermostat- , ., , described. The damper-regulator as applied to a steam-heater is pro- vided with a single rubber diaphragm with the parts arranged as shown in the sec- tional view Fig. 271. In this case the liquid pressure is applied above the diaphragm, its weight being coun- terbalanced by springs and weights, attached to the levers. The liquid used in the thermostat may be any which has a boiling temperature somewhat below that at which the room is to be kept. Many liquids are known which fulfil this condition, of which we may mention etheline, bromine, various petroleum distillates, anhy- drous ammonia, and liquid carbonic acid. The liquids em- ployed in the Powers thermostat are said to give pressures as follows at the given temperatures : Fig. 271. — Diaphragm Damper-regulator. TEMPERATURE REGULATORS. 42 T. At 60° I pound to the square inch. 65° 2^ " 70° 4 " " " " 75° ••••• 5i " 80° 7 " " 90° 10 " " " " 100° 13 " " " " 186. Regulators Operated by Direct Expansion. — Metals of various kinds expand when, heated and contract when cooled, and this fact has often been utilized in the con- struction of temperature regulators. A single bar of metal expands so small an amount that it is- of little value for this purpose unless very long, or unless its expansion is multiplied by a series of levers. Several forms have been used, of which may be mentioned : a bent rod with its ends confined so that expansion tends to change its curva- ture ; a series of bent rods of oval form resting on each other with the ends confined between two fixed bars ; two metallic bars having different rates of expansion arranged parallel and the variation in length multiplied by a series of connecting levers an amount sufificient to be available in moving dampers ; two strips of metal of different kinds bent into the form of an arc and fastened together so as to form a curved bar, with, the metal which expands at the greater rate on the inside, so that expansion tends to straighten it when heated ; the differ- ence in expansion between an iron rod which is not heated and the flow-pipe of a hot-water heater multiplied by means of a series of levers. The constructions described above have all been tried for the purpose of moving the dampers of heaters or for opening and closing valves. In general, how- ever, they have not proved satisfactory, because of the slight motion caused by expansion, and the uncertainty of operation obtained with multiplying devices. Certain organic materials have the property of bending or curling when heated, and this has been utilized in the construction of the Howard regulator. This regulator consists o'f a ther- mostat in the form of a plaque of triangular form 11 inches long and 9 inches wide (Fig. 272), which is located in any 422 HEATING AND VENTILATING BUILDINGS. living-room. As the temperature of the room increases the plaque bends. It is connected by means of cords running over pulleys to a very light and easily moved cylinder damper arranged so as to regulate both fire and check drafts. The damper used in connection with this thermostat consists of a slotted cylinder rotating on the inside of a tube which leads in one direction to the ash-pit and in the other to the smoke-pipe. A parti- tion separates the two parts of the tube, and the slots in the cylindric damper are so arranged that when the connection for air to the furnace is open the other is closed, and vice versa, a very slight motion serving to completely open or close the damper. The cylinder damper is con- nected to the plaque by a cord, and is so arranged that the drafts are opened by the motion of the thermostat and closed by gravity. The direct expansion of a liquid or of a gas in a confined vessel has also been utilized to move a diaphragm or piston which is connected by levers to the dampers of heaters, in a manner similar to that described in the preceding article. The writer at one time constructed a regulator for a hot-water system in which the expansion of water in a closed vessel sur- rounding the return-pipe was employed to operate a damper- regulator similar to those used in steam-heating, page 156. P^clet describes, regulators in which the expansion of air was employed to move a piston connected by cords and pulleys to the dampers. 187. Regulators Operated with Motor — General Types, — The regulators which have been described in the preceding articles operate the regulating valves with a feeble force acting through a considerable range, or with a considerable force act- ing through a short distance. They are consequently liable to be rendered inoperative by any accident to the levers or connecting tubes, or by any cause which renders the valves difificult to operate. To overcome such difficulties several Fig. 272. — Howard Thermostatic Plaque. TEMPERATURE REGULATORS. 423, systems have been devised in wliich the power for operating the dampers should be obtained from an independent source, and in which the work required of the thermostat would be simply that of starting and -stopping an auxiliary motor. In the first systems of this kind the motor employed was a system of clockwork which had to be wound at stated intervals in order to supply the force required for moving the dampers. In recent systems electricity, water, or compressed air is employed to generate the power required, and in some instances regulators are arranged to operate not only the valves which supply heat to the rooms, but also the various dampers for sup- plying hot or cold air in the ventilating system. In all of the early forms of this kind of regulator the thermostat consisted of a tube of mercury or a curved strip,, made of two metals of different kinds soldered together and arranged so that a given change of temperature would pro- duce sufficient motion to make or break electric contact. A current was obtained from a battery, and connecting wires led to the motor and to the various terminals. When electric con- tact was made at a position corresponding to the highest' temperature, the current would flow in a certain direction and cause a magnet to release a pawl which would start a motor revolving in the proper direction for closing the valves. When the temperature fell below a certain point, the thermo- stat would make electric connections so that the current would flow in the opposite direction and cause the motor to reverse its motion, thus opening the valve. If the motor was operated by water, the electric current would open ahd close a valve in the supply-pipe ; if the motor was operated by electricity, the current from the battery would move a switch on the wires leading to the motor. The valves for regulating the heat-supply are made in a great variety of ways. Dampers for regulating the flow in chimneys or flues are generally plain disks, balanced and mounted on a pivot, so that they may be turned very easily; globe- or gate-valves are usually employed in steam-pipes and must, to give satisfactory service, either be closed tight or opened wide. A system in which steam-valves are oper- ated requires much more power than one in which dampers 424 HEATING AND VENTILATING BUILDINGS. Many systems of heat-regulation employing motors are in use and are doubtless worthy an extended notice, but space will only permit a short description of the one in most ex- tensive use in the larger buildings of this country, namely, the Johnson system of temperature regulation. l88. Pneumatic Motor System. — In the Johnson system of heat-regulation the motive force for opening or closing the ■valves which regulate the heat-supply is obtained from com- pressed air which is stored in a reservoir by the action of an automatic motor. The thermostat acts with change of tem- perature to turn off or on the supply of compressed air. When the air-pressure is on, the valves supplying heat are ■closed ; when off, they are opened by strong springs. The detailed construction of the parts are as follows : The compressed air is supplied by an automatic air-com- pressor which is operated in small plants by water-pressure and acts only when the supply of compressed air has fallen be- low the limit of pressure. The ■external form of the air-com- pressor is shown in Fig. 273. It ■consists of a vessel divided into two chambers by a diaphragm ; one chamber is connected to the water-supply, the other to the atmosphere. The water enter- ing on one side crowds the dia- phragm over until a certain position is reached when the supply-valve is closed and a discharge-valve is opened, after which the diaphragm returns to its original place. The motion of the diaphragm backward and forward serves to draw in and "yiq, discharge air from the other chamber in a manner similar to the operation of a piston-pump, valves being provided on both inlet- and discharge-pipes! 273- — External View Small Air-compressor. OF TEMPERATURE' REGULATORS. 42! When the air-pressure reaches a certain amount, the pump ceases its operation. An air-pipe leads from the air-compressor to the thermostat, and another from the thermostat to the diaphragms in con- nection with valves or dampers. " The action of the thermo- stat, as already explained, is simply to operate a minute valve for supplying or wasting, as necessary, compressed air in the pipe leading from the thermostat to the diaphragm-valves. Fig. 274 is a sectional view of the diaphragm-valve, the Pig. 274. — Sectional View of Diaphram- VALVE. Fig. 275-— Damper FOR Hot- AND Cold-air Flue. •compressed air being admitted above the valve and acting merely to close it. It can also be closed if necessary by hand. The compressed air can also be made to operate dampers of ■which various styles are used, and these may be placed in ven- tilating flues, hot-air pipes, or smoke-flues, and so arranged as to admit either warm or cold air alternately to a room, as may be required to maintain a uniform temperature. Fig. 275 shows a damper for two round flues, one for cold air, the other 426 HEATING AND VENflLATING BUILDINGS. for hot, connected to a diaphragm and arranged so that when one is open the other will be closed. This system of heat-regulation has been brought to a very high degree of perfection, and if sufificient heat is supplied the temperature of a room is maintained with certainty within one degree of any required point. Farther than that, the system is so arranged that after all the rooms of the house reach the desired temperature the heat-regulator then acts to close the furnace-dampers. The apparatus is in extensive use for regulating temperature in the hot-blast system of heating. Fig. 276 shows the method adopted of applying a damper- regulator to a stack for indirect heating which is so arranged as to admit either warm or cool air as necessary to maintain a uniform temperature. ^ Fig. 276. — Double Damper in Brick Duct. 189. Saving Due to Temperature Regulation. — The ex- pense of constructing a perfect system of heat-regulation is met in a short time by the saving in fuel bills. The writer recently examined the records of the fuel consumed in a build- ing when heated for a series of years without, and afterwards with, the heat-regulating system. He also examined the records showing the coal consumed in two buildings of exactly the same size and class, in the same city, and as nearly as possible with the same exposure. In both these* cases the saving was somewhat over 35 per cent annually of the cost of the regu- lating apparatus. The saving in any given case must, of course, depend upon TEMPERA TURE REG ULA TORS. 427 conditions and how carefully the drafts are regulated under ordinary systems of operation. Usually, when the temperature is regulated by hand, the rooms are allowed to become alter- nately hot and cool, but a greater portion of the time 'they are much warmer than is necessary, and frequently windows are opened for the escape of the extra heat. The maintenance of a uniform temperature for such cases means a saving of fuel by utilizing the heat better, and usually, also, by a more perfect combustion of fuel. It would seem from these considerations that a reasonable estimate of the saving obtained by the use of a perfect temperature regulator, as compared with ordinary regulation, would run from 15 to 35 per cent of the fuel bills per year. Construction of Pneumatic Thermostat. — The following diagram and explanation will render the principle of action of ^^ RESERVOIR a THERMOSTAT b Fig. 277. — Diagram Illustrating the Pneumatic Thermostat. the pneumatic thermostat as employed in the Johnson system of heat regulation intelligible. Fig. 277 shows to different scales the reservoir for com- pressed air, a diagram of the thermostat and of a diaphragm 428 HEATING AND VENTILATING BUILDINGS. -for operating dampers. The thermostat is drawn relatively to a very large scale. The temperature regulator as a whole con- sists first of an air compressor, as shown in Fig. 273, or one of similar construction, and arranged so as to maintain a constant pressure in air reservoir R or in the pipes of the building. The principle of operation of the thermostat is illustrated by the diagram, although the details of construction of the act- ual instrument are quite different. Compressed air from the reservoir or air-pump passes through the pipe A to the cham- ber B, thence, if the double valve ab is open, it will pass out through the pipe C to the chamber V above the diaphragm. Its pressure then causes the end X' of the lever X' X to move downward. This lever is connected to the damper in such a manner as to close ofT the supply of heat when in the lowest position. If the room becomes too cold, mechanism to be hereafter described moves the valve ab into such a position as to close the corhmunication to the compressed air in the cham- ber B and open communication with the atmosphere at b. This permits the air to escape from the chamber F, through the pipe C and opening b, into the air, the diaphragm in the lower part of the chamber f^ being moved upward by a spring or weight not shown in the sketch. Thus it is seen that by mov- ing the double valve ab the chamber f^isput in communication with the compressed air and the damper moved to close off the heat, or with the outside air, in which case the pressure in the •chamber Fis lessened and the damper is moved by action of a weight or a spring so as to admit the warm air. The mechanism for moving the valve ab consists of a thermostat T, which may be made of any two materials having a different rate of expansion, as rubber and brass, zinc and brass, etc. Connected to the thermostatic strip is a small valve K, so adjusted that when the room is too warm the valve will be opened and when too cold it will be closed by the ex- pansion and contraction of the thermostatic strip. Suppose the room too warm and the valve K open, air then flows through the chamber B, through the filtering cotton in the lower part of B' , thence through the small tube ^and the valve K to the air. The small tube d connects with an expansible chamber D and opens back of a small diaphragm. When the TEMPERATURE REGULATORS. 429 •it Vaive K is open the spring 5 forces the diaphragm into the ■contracted or collapsed position, causing the lever GF to move the valve ab so as to put the chamber B in communication with chamber V and permit the air-pressure to close the damper ■connected to the lever X'X. If, however, the room becomes too cold, the thermostat T moves so as to close the valve K; this stops the escape of air from the pipe (3? and causes sufficient pressure to accumulate under the diaphragm at D to move the lever FG, so as to move ab to the left, thus cutting off the sup- ply of compressed air from the chamber J^and permitting the air to escape at b. It will be noted that air is continually ■escaping at A" during the time the room is too hot, but this is •a very short interval as compared with the entire time, and moreover the orifice at K is exceedingly small, so that the loss ■of air is quite insignificant. It will also be noted that with this apparatus the damper is quickly moved from a position fully open to shut, or vice versa, and that it will not stand in an intermediate position fully open or fully shut. The manufacturers of the Johnson thermostat have quite recently designed an instrument which will move the adjusting ■damper connected to the line XX' slowly and will hold it in any intermediate position as desired. This is considered an advantage for systems of ventilation in which it is always de- sired to admit the same volume of air, but in which the relative amounts of hot and cold air are varied to maintain the desired temperature. CHAPTER XVII. SCHOOLHOUSE WARMING AND VENTILATION. 190. General Remarks. — The warming and ventilation of school buildings constitutes one of the most important applica- tions of the art and involves in some one of the varied classes a practical exposition of all the scientific principles relating to the subject. The best general discussion of this application of the science of heating and ventilation is to be found in a treatise written by Professor S. H. Woodbridge of the Massa- chusetts Institute of Technology for the Board of Education of the State of Connecticut in 1898, and which by permission is here reprinted. 191. Complex Character of the Problem. — The principles of warming and ventilation are essentially the same for all types of buildings in common use in cold climates. The problems connected with their application are, however, so many and so varied that they present almost every possible form of treatment. This chapter, though nominally only a brief discussion of the principles of warming and ventilation as applied to schoolhouses, thus necessarily includes the wider aspects of the subject. What the respiratory system is to an animal the ventilating system is to a building. As the habits of an animal determine the type of respiratory system most appropriate to it, so the type and use of a building are the principal factors in deter- mining the characteristic features of the ventilating system best adapted to it. The large and modern high school build- ing presents a complex type far removed from the simpler patterns found in the dwelling-house, the office building, the 430 SCHOOLHOUSE WARMiNG AND VENTJLATION. 43 1 audience-hall, the church, or even the theatre. It presents an jnvolved combination of rooms designed for widely -different purposes, each room requiring an equipment adapted to its special use, and the building as a whole demanding a treat- jnent with proper reference to its periodic use and its peculiari- ties of arrangement and exposure. Between the complex problem peculiar to such a building and the simple one pre- sented by the one-room schoolhouse at a country cross-road there exists a range of type completely filling the interval, each step of the gradation necessitating a corresponding modi- fication in the method of, and means for, ventilation. . 192. Three Objects Sought. — Three ends are to be ■sought in warm'ng and ventilating work as it relates to the maintenance of vital energy at its best by wasteless and ^effective means. These ends are hygienic, economic, and mechanical. The hygienic side of such a study is highly important, and deserves more than the passing notice to be -here accorded. Both ventilation and warming of buildings are necessary chiefly for hygienic reasons. The economy and the :mechanical efficiency of warming and ventilating methods are -relatively minor and even inconsequential matters. If, there- fore, less space is here given to the topic of first importance than to those which are secondary, it is because, in discussions to be found elsewhere, the hygienic side has been pressed upon public and professional notice, and the economic and mechan- ical aspects of the problem have been given minor attention. 193. Relation of Pure Air to Vitality. — Air is as essential to the products of physical and dependent mental energy as it is to the intensity and brilliancy of a candle-flame. The physical energy of the body is as much the product of the oxidation of carboii within it as the energy of the engine is the product of oxidation in the fires under the boilers. The normal brilliancy of a candle-flame is obtained only in the purest air. The engine develops its greatest energy only when its fires are freely fed with air. A withdrawal of oxygen from the air in quantity equal to 1/500 of the volume of the -air reduces by 1/20 the luminosity of a candle-flame burned -within it. The quantity and intensity of vital energy suffer a corresponding, if not an equal or even greater, change when 432 HEATING AND VENTILATING BUILDINGS. protractedly exposed to abnormal atmospheric conditions. The breathing of impoverished air results of necessity in the dulling of the vital fires of the body and of the keen edge of the intellect. It means a weakened body and a dulled mind. A lowered vitality of the body, besides exposing it to an increased liability to communicated, contracted, or constitu- tional disease, also impairs its effectiveness as a vital mechan- ism. The aggregate of physical and mental vitality lost through ignorant or indifferent regard, and even culpable disregard, of the exact and delicate dependence of the activities, of body and mind on the maintenance of a normal, including atmospheric, environment, surpasses all common conception or belief That air quality is fully as important as food quality in the production of vital energy is a conception which has yet to be borne in upon the public, if not the professional, belief and conscience. 194. Limitations to the Supply of Pure Air. — A rule which may be safely insisted upon for general adoption and application is that pure air should be supplied to enclosures in the maximum rather than in the minimum quantity tolerable. Only two considerations should be allowed to limit the quantity of air-supply: air-draughts and bank-drafts. Draughtiness in air-currents is more dangerous to health than the ordinary vitiation of air in badly ventilated enclosures. On the other hand, the warming and, under some circum- stances, the moving of air in large quantities for ventilating- work is far from costless. Both draughtiness in air movement and costliness in the warming of air put, therefore, a deterring" limit on air quantities to be used in practical ventilating work. 195. Draughtiness in Large Halls. — With a given hourly per capita air-supply, the danger from draughtiness within an enclosure increases, approximately, inversely as the per capita, space. Fortunately, however, the necessity and importance of ventilation are not the same for crowded as for sparsely occupied rooms, being of least account in rooms intermittently- occupied, and of greatest account in those most continuously used. The length of time for which a person is exposed to- the confined air of an enclosure is, therefore, an essential factor in determining the proper rate of its ventilation. The harmful' SCHOOLHOUSE WARMING AND VENTILATION. 433: effects of short exposure to impure air once a week are small when compared with those incurred by frequent and prptracted exposure to such air. It is, of course, in crowded audience- rooms which have a small per capita space, and to which a large per capita air-supply cannot be furnished without dan- gerous risk of draught, that the most impure air must of necessity be found. On the other hand, such rooms are least continuously occupied. If, therefore, danger is directly pro- portionate to the time of exposure to impure air, the sensibly close air of a poorly ventilated church, lecture-hall, concert- hall, or theatre may not be productive of such harm as the purer air of a better ventilated, but more frequently and longer- occupied, schoolroom. By helpful coincidence, therefore, the most difficult rooms to ventilate freely are those least requiring such ventilation, inasmuch as they are least used, and when used are occupied for only short periods. In effect, the time of actual occupancy varies with the provided per capita space •; and, for equal hygienic results, the per hour and per capita air- supply required also vary in the same manner. Considering only permanent effects on health, and individual air-supply of lOOO cubic feet per hour furnished to a crowded audience-hall having but lOO cubic feet space per capita, may, therefore, be regarded as equally good ventilation with 3000 cubic feet per capita supply of air per hour furnished to a schoolroom having 300 cubic feet per capita space. For the ventilation of crowded rooms the air-volumes usuable are limited by draught dangers; and for ventilating less and the least crowded rooms, the quantities are limited by the cost. It is the office of the architect and the engineer to provide for the rooms of the first class a maximum air-supply with a minimum of draught ; and for rooms of the second class the freest ventilation consistent with reasonable expense. To produce for crowded rooms, ventilation which shall be abundant and yet draughtless, and for other rooms a general ventilation which shall be effective and inexpensive, are among the most important, and often the most difficult, heating and ventilating engineering services to be rendered. 196. Means for Reducing Draughtiness. — The audience- halls and larger lecture-rooms of schoolhouses cannot gen- 434 HEATING AND VENTILATING BUILDINGS. erally be provided for as perfectly as can similar rooms having fixed seats or desks, the usual or specially provided surface of which may be utilized for a diffusive entrance of large quantities of air. The floors of these large rooms must at times be cleared for drill, dancing, and social occasions. Danger from draughts must, therefore, be reduced by dividing the inflow into as many and small and slow-moving currents as practi- cable, and by giving to the inlets such positions and formations as shall deliver the air in directions least liable to produce sensible draughtiness. The animal heat yielded by a crowded audience is frequently more than that lost through walls, windows, and other means. The effect of that heat is to raise the temperature of the auditorium air and to necessitate a tem- perature of air-supply lower than the temperature of the room. Because of the need of this low temperature, it is desirable to. give to the entering currents of air a direction which shall as much as possible prevent their dropping floorward, at least in concentrated form. If the air-supply must be admitted through wall apertures, they should be elevated, unless they are made so large as to reduce the rate of inflow to or below a linear rate of 30 feet per minute. Even when the wall openings are elevated, the currents should be given an initial upward direc- tion. They will thus take a longer path before reaching the floor, and will, therefore, mix more thoroughly with the warm air of the room by being longer in contact with it, and by flowing more diffusively through it. If the air-inlets to a room of this character can be placed in the floor and protected from infalling dirt, that position is preferable to a wall location. In general it may be said that wall inlets through which air issues with rapid or even moderate movement and at temperatures from 100° downward should be elevated well above the head plane for the purpose of giving the currents a location in the unoccupied parts of a room. By means of chutes of solid or open material, the entering air may be given a slight or sharp upward course. B)^ completely covering the inlet with a semi-cylindrical surface of fine wire gauze or other impervious material, of any size desired, the entering air may be made to move radially from the inlet in a more or less horizontal plane, and with a velocity varying with the extent of the diffusing SCHOOLHOUSE WARMING AND VENTILATION. 435 surface, and with the volume of air issuing through it. By deflecting plates or blades set to separate the current and to throw the entering air in divergent directions, the inflow may be given a radial direction from the inlet, both laterally and vertically if desired. Blades are preferable to gauze, as the meshes of the latter fill, and, even when clean, offer sensible resistance to air-flow. Blades are as effective in breaking up the larger current into a number of divergent ones, and produce a quicker and more thorough diffusion of air throughout a room. The form of diffuser must be chosen with reference to the location and surroundings of the inlet. Properly made and used, diffusers make impossible a processional of air from inlet to outlet that does no effective ventilating work. The rapidity of air-flow through supply-flues has obviously no necessary effect upon draughtiness within rooms. By the use of suitable diffusing means, air, although brought to the diffusers with a relatively high velocity, may yet by them be given such reduced velocity and dispersed movement as to remove all danger from this cause. 197. Little Draughtiness in Outflowing Currents. — For the protection against draught due to outward movement of air from rooms less precaution is needed. The movement of escaping air is slowly accelerative toward the location of the discharge, the velocity of the movement toward that point decreasing inversely as the square of the distance from it. The air-movement, therefore, being convergent for a wide range, is the reverse of the divergent inflow produced by the use of deflecting plates or "diffusing surfaces, and is wholly unlike the concentrated and continuous current projected from a supply-register. It is necessary only that the area of the outlets should not be too large, the volume of air-movement too great, the final velocity of air-approach too rapid, and that permanent sittings should not be placed too near the out- lets. 198. Air-supply for Schoolroom. — In the case of a schoolroom, the per capita floor and cubic space is generally from two to three times that common in well-filled audience- halls. To such a room, having a cubic space of from 11,000 to 12,000 feet, and seating from forty- five to fifty scholars, it 436 HEATING AXD VENTILATIXG BUILDINGS. is practicable to supply without draughtines's and without the use of exceptional precautionary means for preventing it, from 2000 to 2500 cubic feet of air per hour to eacn occupant, or a. total hourly quantity of from 100,000 to 125,000 cubic feet, the larger quantity being more than one sixth of the contents of the room per minute. When special means are provided for a draughtless entrance and removal of air these quantities may be largely increased. Between 90 and 1 00 cubic feet per minute for each sitting have been passed through the class- rooms of a schoolhouse equipped in accordance with modern methods, and there was no complaint of draughts. Usually, however, the limit of immunity from draughts is reached when the rate of air-supply is brought up to an equivalent of ten changes per hour. 199. Cost. — The expense of ventilation properly includes the cost of all special building arrangements and construction provided; of all special equipment for heat production and air warming ; of power for moving, distributing, and removing the air; of fuel for warming; and of specially skilled attendance required above that called for in ordinary heating work. In reference to the first of these items it may be said that the cost of adapting a building to a rigid system, or to a pre- cise method or theory of ventilation, is generally greater than that of adapting a ventilating system to a building planned with reasonable regard to heating and ventilating requirements. Flexibility and elasticity belong more appropriately to a single feature of a building than to the fundamental plan. If the plan and the ventilating system are concurrently and har- moniously developed, it is generally possible to provide at moderate cost an effective arrangement for ventilating work. If the entire scheme of the building and its system of ventila- tion are subordinated to rigidity in ventilating methods,, theories, or notions — such as those that fix the exact and only location for fresh-air inlets and outlets, the sizes of airways,, the means for air-movement, the type, whether plenum or vacuum, of the ventilating system — the owner may pay large sums for a slight gain or even an actual loss in the efficiency of warming and ventilating work. In general it may be said of this item of cost, as also of the efficiency in operation of the . SCHOOLHOUSE WARMING AND VENTILATION. 437 ■whole system of ventilation and warming, that simplicity of arrangement and compactness of plan are the characteristics most favorable to economy. The second item named as chargeable to the cost of venti- lation is the increased power of the furnace, steam, or other type of plant above that required for heating alone. Limiting, for the sake of brevity, the present discussion to the use of steam for warming and ventilating purposes, it is evident that boiler capacities must be larger for warming and ventilating work than for warming alone. It is important, however, to note the fact that the needed increase in boiler power is not usually proportional to the amount of heat given to the air used for ventilating work. The fuel cost of warming and ventilation is not correctly computed by adding the cost of heating without ventilation to that of ventilation without heating. The sum thus obtained is greatly in excess of the actual cost when the heating and the ventilating arrangements are designed and operated as parts of one system. There is commonly a waste in heating alone which may be much reduced by proper and effective ventilation. By the ordinary and crude methods of heating, both the individual rooms and the different stories of a building are unequally warmed. The upper parts of rooms, especially of those in the first story, are overheated when the lower parts are at a normal temperature. The upper stories of- buildings are overwarmed when the lower stories are com- fortably warmed. The average temperature of the building is thus raised above what would be required if the temperature ia each room and throughout the building were uniform. The heat lost by transmission through walls is proportionally increased. As a further result, the normal loss of heat by air- leakage through the top of the building is rapidly increased, both because of the higher temperature of the escaping air and because of the increased volume of leakage due to the greater pressure producing the leakage movement. Windows in the upper stories of overheated buildings are generally open, and this tends seriously to increase the rate of leakage loss. Such outflow of superheated air at the top of the building produces a corresponding inflow of cold air on the lower floors. This, in turn, necessitates an increased use of heat for the proper 43^ HEATING AND VENTILA7VNG BUILDINGS. warming of these floors. All such excessive heat loss is reduced in proportion as uniformity of temperature throughout the building is approached. The tendency of free and well- planned ventilation is to produce such uniformity both in indi- vidual rooms and throughout the building. By maintaining a plenum condition in the lower rooms without increasing that common in the upper stories, the inward leakage of cold air is reduced. If the heat required to warm a building to a uniform temperature is computed on the basis of theoretical loss by transmission through walls and by normal leakage, it will be found that the quantity required for continuous and generous schoolhouse ventilation alone is from three to four times that theoretically needed for warming alone. In practice, however, the gain made by effective ventilating work is not uncommonly such that the heat used for the combined warming and ventilat- ing work during school hours exceeds that required for actual heating alone by not more than from fifty to seventy-five per cent. In some exceptional cases the fuel burned for the com- bined work has been found to vary but little from that pre- viously required for heating alone. 200. Boiler Power. — It is thus evident that the increase in the amount of fuel required when ventilating and warming are combined is much less than it would be if they were treated as separate items in the cost of a building's use. In the same proportion the additional boiler power lequired is also con- siderably less than might be expected. Assuming an average of 2|- boiler horse-power, for each classroom, as necessary for warming alone — the equivalent in classrooms of other parts of the building being also included — then the average required for combined heating and ventilating may safely be taken as 5 horse-power for each classroom and its equivalent. The additional cost of ventilating equipment used for air-warming, or for indirect radiating surface, varies greatly with the mode of such warming. A square foot of the most effective form of such surface when exposed to rapid currents of cold air passed over it, such as may be obtained by the use of a fan, may be made, to yield from six to eight times the heat available from the same surface when exposed to the quiet air of a room. If, therefore, warming is entirely accomplished by SCHOOLHOUSE WARMING AND VENTILATION. 439 heat carried to rooms by the ventilating air as a vehicle, it is possible to effect a very considerable saving in the heating surface, and also to make the heating system so compact as to avoid the use of long and costly runs of supply and return piping. Thus, by the indirect method, the amount chargeable to heating work is considerably reduced. On the other hand, in proportion as direct heat is used and the temperature of ventilating air is reduced to that desired for rooms, the heating surface made necessary merely for air- warming becomes charge- able to ventilating work. If air is passed at 70° into rooms which are kept at that same temperature, the heat given to the rooms by direct means must be not less than the theoretical quantity required for their warming under the conditions of heat loss attending uniform temperature. In general, in the matter of cost of equipment, it is true that while the plan of dealing with heating arid ventilation as parts of one system undoubtedly increases the cost, it does not do so to the extent that might be supposed. 201. Power for Moving Air through Ventilating System. — Air is moved through a building and its ventilating system only by some form of power expenditure. When unconfined air is warmed, approximately one third of the heat imparted to it has no effect in raising its temperature, and is expended in the work of expanding the air. That work put into and stored in the air is, in part at least, available for ventilating purposes. It is that which makes ventilation by gravity methods possible, and, under conditions designed with reference to that end, wholly inexpensive so far as the mechanical side of the problem is concerned. The working pressure which is due to differences in temperature and in weight between the air inside and the air outside of a building varies through a wide range. Even where that pressure is greatest it is yet so small that a close and dust-filled cobweb can resist it and arrest air-flow. When the differences in tem- perature between inside and outside air are trifling, and when the height of ventilating shafts is moderate, the actuating pres- sure becomes so small that, if full air-quantities are under such conditions to be moved through them, either excessively large airways must be provided, or else the air of the shaft must be 44° HEATING AND VENTILATING BUILDINGS. heated to give it the required lightness for inducing the neces- sary flow. When this latter practice becomes necessary, the economical use of heat and the greatest mechanical effect are secured when the air is heated at the lowest practicable point in the flue, and when heat is imparted by means which least obstruct the freedom of air-flow. To heat large volumes of air while they are on the way of escape from a building is mani- festly wasteful. The practice of continuously warming the air in discharge-flues in order to insure sufficient flow in cool and moderate weather, and of placing the means to secure this beyond either the control or the neglect of janitors or engineers, is a costly proceeding. In the usual practice the increased velocity actually gained by such means is small when measured by the heat expended. To change in 50^ weather the rate of air-flow from 2 50 to 400 linear feet through a flue 2 feet square and 49 feet high would require an increase of 30'' in the tem- perature of the flue air. To move 100,000 cubic feet of air per hour through that flue by such an increase in temperature would necessitate the burning of 7 pounds of coal, or approxi- mately 50 pounds of coal per school day for each classroom, and all equivalent ventilating work. Such a method con- tinuously used would increase the fuel account for the building from 25 to 30 per cent above the cost of warming the building and warming the air supplied for ventilating work. A method involving this expense is not consistent with economy. In cases, however, where a necessary contraction, contortion, or exceptional cooling of flues may jeopardize draught effects, or where for special reasons it is desired to strengthen the local draught, the heating of flue air for accelerating draught action may, in the absence of better means, become economically advisable. 202. Gravity Ventilation. — In planning a gravity method of ventilation, both supply- and discharge-flues should be made large enough to move the required volume of air when outside temperatures range from 40° to 50°, and when the temperature of the discharge air is 70°. The cross-sectional area of such flues should be governed by the temperature of the air in the supply-ducts ; the highest outside temperatures for which the vent-ducts are provided; their cross-sectional forms; the SCHOOLHOUSE WARMING AND VENTILATION. 44I straightness and smoothness of flues; the height of the flue system ; the favorable or unfavorable exposure of discharge-flue tops ; the freedom of air-supply to the supply-flue system ; and the presence or absence of means for securing accelerating, rather than retarding, effects of wind action. Since flues con- structed in accordance with all these requirements would prove excessively large as well as costly in cold-weather use, means for reducing and controlling air-flow in such weather should be provided. For this purpose throttling-dampers should be placed at the top of vent-shafts, or at room connections with such shafts, and also at fresh-air intakes for the fresh-air system of flues. No general rule for fixing the flue sizes for gravity work in schoolhouses of two and three stories can be given. Under the most favorable circumstances the conditions which necessarily affect flow rate are many and varied. For supply- flues an area ranging from 3^ square feet in upper stories to 5 square feet in lower stories is recommended, and for vent- flues an area ranging similarly from 4^ to 6 square feet. Flues of these sizes will be found better fitted for effecting desired air-movement and for economic work than flues of smaller or much larger areas. 203. Mechanical Ventilation. — The superiority of the so-called mechanical, as compared with the gravity, method of ventilation appears in the relatively small space needed for flues, both supply and discharge ; in the sureness and uniformity of ventilating action through all variations of weather ; and in the low cost of moving air through a ventilating system. Air- ways in gravity methods must be made from two to three times larger than those required in well-arranged mechanical methods, unless the rate of flow through the flues by the gravity method is greatly accelerated by heat used for that purpose. The mechanical, and, therefore, the money, waste inherent in such a method appears from the fact that when escaping air is raised 30° in temperature, each cubic foot of that air carries outward more than one half a thermal unit — in work equivalent, approximately 400 foot-pounds. In a well- designed mechanical system the average requirement of work expended on each cubic foot of air is less than 10 foot-pounds. Under these latter conditions the maximum power expenditure 442 HEATING AND VENTILATING BUILDINGS. would be one horse-power for each 200,000 cubic feet of air moved per hour, or one-half horse-power per classroom and its equivalent in other air-supply throughout the building. If air is propelled through a ventilating system by steam-driven fans, and if the engine steam is condensed by the ventilating air which it serves to warm, the cost of the motive'power used is negligible. If the exhaust steam is wasted, the cost in fuel per classroom would be 2 pounds per hour. If the exhaust steam is utilized for warming purposes, the fuel cost would be reduced from one-fifth to one-sixth pounds per hour per class- room, as against the 7 pounds above found necessary for heat- ing the discharge air in vent-flues through a range of 30° in temperature. The reduction of fanwork to a minimum is not, under the circumstances, important as a matter of economy. The main duct velocities may easily be carried to and beyond 1000 linear feet per minute, and the flow through distributing and uptake flues to 750 linear feet. Between the mains and the branches a velocity of from lOOO to i 500 linear feet can be provided for the purpose of insuring an evenness of supply to rooms under the ordinary varying conditions of air-pressure in them due to wind action. The yearly fuel cost per room for moving air by efficient fan power is, in round numbers, 150 pounds of coal, and the yearly cost amounts to three fourths of a cent per year per capita. That cost may be largely increased by a malarrangement of system, by a contraction and contortion of airways, and the consequent necessity for high air velocities or pressures, or by the needless multiplying of fans. One fan well placed and well proportioned, obtaining and delivering air through generously sized channels, may do effective work in the supply and removal of air for a school building of from 1,000,000 to 1,500,000 cubic feet internal capacity. When the system is planned for such work it is essential that the flues, whether discharge or supply, in that part of the system with which the fan is not directly connected should be given sizes but little under those required for gravity work. Neither the plenum nor the vacuum condition pro- ducible in rooms by a fan connection through one set of flues, either supply or exhaust, can be sufficient to produce in the complementary flues the velocities maintained in those im- SCHOOLHOUSE WARMING AND VENTILATION. 443 mediately connected with the fan. The interposing of a room between the two systems of flues has the effect of greatly reducing the pressure available for producing air-flow through that system of flues with which the fan or other motive agency is not connected. The pressure-drop between the two systems not infrequently reaches 3 5 per cent of the initial amount, and the resulting velocity of air- flow through the complementary flues falls to 60 per cent of that through the fan-flues. If the system is plenum, the areas of discharge-flues should, there- fore, be made from 70 to 100 per cent larger than the supply- flues, according to the plenum condition desired within the affected rooms. 204. Fuel for Air-warming. — The cost of fuel for air- warming, though large in the aggregate, is small in the indi- vidual accounts. The cost depends on the manner in which fuel is burned, on the degree of completeness of the transfer of heat from combustion gases to air, on the effectiveness or wastefulness with which air is used, and on the quantity of air supplied. If fuel is so used that 8500 thermal units per pound of fuel are made available; approximately 500,000 cubic feet of air can be warmed one degree by each pound of coal burned. When, therefore, 2400 cubic feet of air an hour are furnished to each person for six hours during each school day, and for the one hundred and sixty school days per year, when artificial ventilation is required, the total per capita yearly supply of air reaches 2,304,000 cubic feet. This quantity would be warmed through one degree by 4.6 pounds of coal. The mean tem- perature of the New England climate during the time that artificial ventilation is required (from November 1st to June 1st) is nearly 35", and the average increase of temperature to be given the air during that time to bring it to 70'', or to the tem- perature required for ventilating work, is, therefore, 35". The fuel required for that purpose would be 163! pounds, costing approximately 4 1 cents. This sum, therefore, represents the yearly per capita cost of generous schoolroom ventilation. There is nothing of vital necessity or benefit which can be had in such large return for so small an outlay, and there is nothing for which the average citizen and the general public so grudg- ingly part with money. The yearly fuel consumption for a 444 HEATING AND VENTILATING BUILDINGS. schoolroom seating fifty, when the room is freely ventilated for six hours each day, should be approximately four tons. The cost of warming such a room without ventilation, prac- tically through fifteen hours a day through the school year, would be between five and six tons. The same would be true for all equivalent work in a school building outside the class- rooms. Experience has demonstrated the fact that, by the use of methods designed with reference to greatest economy, and by the employment of a capable engineer who is interested in rightly using the system given to his charge, the yearly fuel account per classroom and its equivalent may be reduced to between six and seven tons. 205. Skilled Attendance Required. — There remains to be noticed under the general head of the costs of ventilation the necessity for better skilled and higher-priced service for ventilating than for simple heating work. In the heating and ventilating account the expense for fuel is the one of large proportion. The amount of that item is largely dependent on the effective or wasteful use of coal. The skilled fireman who makes 10 pounds of steam from each pound of coal burned uses only six tenths as much coal as is heaped up under the boilers by the mere shovelman who makes only six pounds of steam from each pound of coal. It is the cheap and wasteful man who, in the long run, is costly. Well-paid efficiency is here, as always, in the line of profitable economy. Further- more, a man to whom is to be committed the duty of maintain- ing those atmospheric and thermal conditions upon which freshness of physical and mental activity are largely dependent, should be chosen with care and paid commensurately with the importance and value of his service. So to minimize that trust as to commit it to incompetence on the specious plea of economy is to invite failure and insure loss. Up to this point in the discussion of the subject of warming and ventilation the general items of cost have been dealt with. It is now intended to set forth in detail various opportunities for economy in methods as illustrated by the special charac- teristics of schoolhouses. The several means for special economy in the warming and ventilating of schoolhouses will accordingly be discussed under the following heads: successive SCHOOLHOUSE WARMING AND VENTILATION. 445 ventilation; quick preparatory warming; warming by rotation; heat commonly wasted; solar heat; automatic control of tem- perature; double glazing; double sashing; waste of heat at night; plenum and vacuum methods; location of inlets and outlets. 206. Successive Ventilation. — The first suggestion made in the interest of economy relates to a method for the succes- sive use of one and the same volume of air, first for the free ventilation of the least occupied parts of a school building, and then for the ventilation of those rooms in which the vitiation of air is either excessive or else of obnoxious quality. The parts of buildings, especially in those designed for use as high or normal schools, which are not closely occupied, frequently aggregate as much in space as the classrooms themselves. Such parts of a building are generally continuously ventilated, though perhaps infrequently occupied. No amount of instruc- tion or training of janitors and engineers is likely to result in a continued practice of opening and closing dampers or registers, according to the occupied or unoccupied condition of rooms. However carefully such precautions may be taken at first, they are likely to be eventually abandoned, and the ventilation of the entire building to become continuous during school sessions. It is this continuous ventilation of large parts of the building outside of classrooms which greatly increases the apparent cost of classroom ventilation, and which justifies the use of economic methods for the ventilation of rooms not continuously occupied. Besides the provision to be made in school buildings of higher grade for such rooms as audience- halls, lecture-rooms, recitation and class rooms, gymnasiums, and laboratories — all of which, when in use, require, in the order given, increasingly large per capita suppHes of air — are the coat, lunch, bath, lavatory, and sanitary rooms, and the private and retiring rooms, each requiring its own appropriate treatment. Unquestionably, a generous and continuous flush- ing of all these apartments with the purest air would prove hygienically advantageous and financially disastrous. In every case there is at some point of ventilating work a balance between hygienic gain and financial loss. The gain to be derived from ventilating work is not directly proportional to 446 HEATING AND VENTILATING BUILDINGS. the air-quantities employed. When no air is furnished for breathing purposes, death is immediate. An air-supply of one cubic foot per minute would barely, but uncertainly, support life; five cubic feet per minute continuously furnished would advance such existence into the region of sustained but low vitality; ten cubic feet would insure more vigorous but yet curtailed vitality ; thirty cubic feet would advance it to vigor and stability; while fifty cubic feet would round it into a robustness which, if the energizing effects of the gaseous make-up of air are alone considered, would be little improved by still larger supplies of air. Only in cases of special impuri- ties or of abnormal or disease-producing contents given to, and carried in, the air of an enclosure, or in cases of prostrated vitality requiring the utmost opportunity for recovery, is there commensurate gain in providing more than 50 cubic feet of air per capita per minute for breathing purposes, provided, of course, that such air is effectively used. For ordinary school- room work even that quantity cannot be safely urged unless assurance is given of the purpose and ability of its users to make ventilation draughtless. 207. Supply of Air for Rooms not Frequently Occupied. — The quantities of air which should be furnished by ventilat- ing means cannot be safely based solely on the number of those to occupy the rooms to be provided for. For reasons 'already noted, the smaller the per capita space, the less the per capita air-supply must necessarily be made. On the other hand, the larger the per capita space, the greater the per capita supply required to maintain the agreeable if not the wholesome quality of the air. The most active and dangerous impurity in the air of occupied enclosures is the matter of organic nature, called effluvia, thrown off by the body through its pores. That matter rapidly changes in character, passing through a fermenting and decomposing to a putrescent condi- tion. The longer it is retained within a room, the worse its odor becomes and the more morbific its condition. The aims of ventilation should be, as far as practicable, to limit atmos- pheric impurities to the location of their origin, and to reduce the quantity and the time of retention of such impurities within an enclosure to a minimum. In proportion as the per capita SCHOOLHOUSE WARMING AND VENTILATION. 44^ space of an enclosure is greater, the quantity of such matter contained in it is large, the time of its retention longer, and its character more offensive and harmful. It follows, therefore, that the more sparsely occupied rooms of a building are those to which the largest per capita supply should be furnished. Laboratories in which gas is burned and in which vapors, fumes, ,and gases are generated in any considerable amount outside of hoods also belong to the class of rooms needing more air per occupant than do classrooms. The same is true of gymnasiums, physical-training rooms, and playrooms, for vigorous physical exercise produces a condition of the body calling for a larger air-supply than the condition of repose demands. 208. Course of the Air-supply. — The ventilation of corri- dors should be sufficiently free to fill them with air suitable for passage to, and use in, class or other rooms. The continuously or frequently open doors or transoms between corridors and rooms make the continuous or occasional mingling of corridor air with that of rooms probable and almost inevitable. The passage from such an accidental to an intentional use of hall- ways for fresh-air reservoirs and channels is both legitimate and proper. Playrooms, lunch-rooms, gymnasiums, and other rooms of their 'general type, though intermittently occupied and sometimes crowded, belong, because of their average con- dition, to the sparsely occupied class of rooms. Continuously and separately to ventilate them, on the basis of the largest or the ordinary numbers occasionally occupying them would require great volumes of air. Such rooms and parts of build- ings may, however, be ventilated in series, or by a successive method, which will meet the requirements pf their shifting groups of occupants, and yet require the use of relatively small volumes of air. Coat, bath, lavatory, and sanitary rooms need no independent supply of purest air. Air pure enough for breathing purposes in schoolrooms is certainly suitable for airing wraps hung in coat-rooms. The air which passes out from schoolrooms through discharge-flues is, generally speak- ing, as pure as that surrounding the occupants of the rooms. Stigmatized as foul only as a matter of convenience to distin- guish it from the air-supply, it is popularly supposed to become 448 HEATING AND VENTILA7VNG BUILDINGS. SO by virtue of its entrance into the way of the outcast. Lavatory, bath, and sanitary rooms are, from a hygienic point of view, most suitably treated when they are atmospherically isolated from other parts of a building, as when ventilated by strong aspirating currents which cause air to move toward and into them from adjacent apartments, and prevent air-movement from such rooms to those apartments. Classrooms may be vented, in part at least, through their coat-rooms. Lavatory, bath, and sanitary rooms may take their air from the supply which has done its partial ventilating work in the hallways, playrooms, and other permanently or periodically occupied rooms. For that purpose air may be continuously supplied in generous quantities to playroooms, lunch-rooms, physical- training rooms, or gymnasiums, which are in the basement, and which are occupied but a small fraction of the time. From these rooms the air may be sent to ventilate the corridors of the building, rather than being immediately thrown away. The corridors are by this means flushed with fresh air which should find egress, not through the roof nor through outlets or windows on the upper floor, but rather through the lavatories and sanitaries. If the air-supply is generous enough, as it may be made to be, it may be sent from the corridors to the class- rooms, and thence to the coat- rooms. Thus in successive ventilation the movement of air must be from locations of lesser to those of greater vitiation, as from playrooms to corri- dors, from classrooms to coat-rooms, or as from the corridors through playrooms to sanitary rooms. When at recess scholars leave classrooms for play- or lunch- rooms the conditions described above are in part temporarily reversed. The crowds are then in the basement, and the corridor air contains impurities brought from the crowded basement rooms. Meanwhile, however, the vacated class- rooms are being flushed by their independent and uninterrupted air-supply, and at the same time the large volume of corridor air is so diluting the impurities carried upward from the base- ment that they become imperceptible, if, indeed, they are at all noticeable even in the basement rooms themselves. In this successive method, then, basement rooms and corridors, sanitary rooms, and coat-rooms may be effectively ventilated SCHOOLHOUSE WARMING AND VENTILATION. 449 by moderate quantities of air as compared with the volume that would be required if each part were as effectively and contin- uously ventilated by independent means. 209. Quick Preparatory Warming. — The heat quantity necessary for the preparatory warming of a building varies greatly with the methods used. In the first place, the heat expenditure is approximately proportional to the time given to the warming process. The quicker the process, the less the fuel required. During the process of warming, heat is lost by its transmission through walls and by air-leakage. For rapid heating the production and distribution of heat must be large and quick. A heating apparatus of low power, although economical in its first cost, is, in the end, expensive, because it is unequal to such a demand. A heating system successfully planned with reference to maintaining both an internal tem- perature of 70° against an outside temperature of zero, and also a generous ventilation at such times, is equal to the demands of such work. The continuous work which is demanded in the raising of large volumes of air from zero to 70°, besides fur- nishing heat to compensate for loss through walls and by air- leakage, is no more than the work of raising that same air, when in rotation, from 45" to 115°. The heating surface which will raise 1,000,000 cubic feet of air an hour from zero to 70° will not, however, if filled with steam at the same pres- sure, raise that quantity of air from 45"" to 115". To accom- plish that, either an increased steam-pressure in the battery or an extension of the battery surface would be necessary. 210. Warming by Rotation. — Next in importance to the quantity of heat produced is the method in which it is used. Relatively little heat and time are required to warm the air of a building as compared with the heat and time needed for warming walls, floors, ceilings, and contents. The surfaces about and within a room may be cool or even cold, while its air is warm and comfortable. Of the heat yielded by direct radiation, approximately one half is given to walls and other surfaces by radiation, and one half to air by convection. Heat brought into the rooms by inflowing air warms the air first, and the warmed air then raises the temperature of walls and other surfaces by its contact with them. The same heat 45° HEATING AND VENTILATING BUILDINGS. quantity, therefore, if delivered to a room by air-currents will produce a comfortable temperature sooner than if it were yielded to the room by a radiating surface. The larger and hotter the air-currents are, the more rapid the warming process becomes. The warmer the air entering the heating battery, the higher its temperature is on leaving it, and the amount of heat required to bring that air to a given temperature is corre- spondingly less. A considerable gain is, therefore, made when, for the purpose of warming a building, air is taken from the building itself, rather than from the colder outside supply. The method of warming a building in this way is one of rota- tion: the air is taken from the building, heated, distributed to the rooms, and, after yielding considerable of its heat to the room surfaces, is brought back to the heating battery either by means of a special arrangement of flues, or by the use of the corridor-ways and stairwells. Warming by rotation should, of course, cease and ventilation should begin before a building is occupied. The rotary method of warming may be made possible in any warming and ventilating system by suitable provision for it in the building plans and heating arrangements. Its economic value may be roughly stated as 2 pounds of coal, for every degree of difference between inside and outside air temperatures, and for every 1,000,000 cubic feet of air used in rotation. Since the mean temperature of the outside air in the early morning is much lower than the daily average of tem- perature, the gain to be made by rotation is manifestly large. If, for example, 35° represents the average daily temperature, then 25° may represent the average early morning tempera- ture. If the average indoor temperature at the same hour is 50°, the gain made by warming inside rather than outside air is thus 25". The saving of coal under these circumstances would be 50 pounds for every 1,000,000 cubic feet of air rotated. Thus, if 3,000,000 cubic feet each hour were rotated for two hours, 300 pounds of coal would be saved. 211. Heat Commonly Wasted. — A continuous saving of heat commonly wasted may be made by utilizing that given off by boiler walls, the smoke-flue, hot-water tanks, traps, pumps, engines, and other parts of the apparatus which are steam-hot. The total heat available from such sources is SCHOOLHOUSE WARMING AND VENTILATION. 45 1 sometimes large, and, in exceptional cases, has been found to be more than lo per cent of the average heat quantity required for warming and ventilating work. If objections are made to the husbanding and utilization of this heat because of volatile and offensive oils about engines and pumps, slovenly care of such apparatus, faulty setting of boilers, and unsuitable methods of draught control, such objections have not sufficient weight to oiifeet the advantages gained from saving this heat usually wasted. If correct methods are employed, and if janitors are made to attend to their duties, this saving can easily be made and is of considerable value. Another form of heat usually wasted is the spare heat of boiler-gases escaping through the smoke-pipe. This may be used for strengthening draughts through vent-stacks, and thus the making of heat especially for that purpose is rendered unnecessary. This spare heat may also be made available for strong ventilation of sanitary rooms or any other equally important work. For this purpose the chimney and the ventilating-stack about it should be designed with reference to the transfer of the needed amount of heat from the combustion gases to the vent-flue air. In all such work care should be taken not to reduce the tem- perature of the combustion gases so as to jeopardize the chimney-draught. Still another form of heat usually wasted is that of fires banked for the night, this heat being generally expended in useless steam-making in closed boilers. Such steam may be used in limited and subordinate parts of the heating system, as in the foot- warmers, hallway coils, heaters in sanitary rooms for the protection of fixtures against freezing, and for other like work. Provision for these uses may be made in any steam system through suitable supply- and return-pipe connections with the boiler. 212. Solar Heat. — Solar heat is a. factor to be regarded in the planning of a warming and ventilating system. It may be demonstrated by a properly protected thermometer that the average day temperature of air is higher on the south than on the north side of a building. The difference often reaches io°. An average of 5" would make it highly advantageous to take the air for ventilating work from the south rather than from the north side of a building. If an average rise of 35" is 452 HEATING AND VENTILATING BUILDINGS. needed in the air temperature in ventilating work, then one seventh of the heat required for that rise could be gained by choosing a south as against a north location for the inlet. Such a location is possible only when mechanical ventilation is used, for in gravity work it is necessary to place the inlet on the side of the building toward the prevailing winds of winter. 213. Automatic Control of Temperature. — From a hy- gienic point of view the close regulations of the temperature of a building is important; and from an economic point of view it is even more important, when the air-volumes used are large. Such regulation cannot be safely entrusted to teachers who, absorbed in their work, fail to note a change in temperature until it becomes sufficiently extreme to extort notice. A radical and speedy change being then called for, windows and doors are resorted to until rooms become chilly. The inevi- table results of such methods of regulating the temperature are wasteful escape of heat and disastrous catching of colds. The heating surface for the warming of a building must be made sufficient for the demands of the severest weather. At other times only fractional parts of the heat producible from it are needed. The quantity of heat yielded by such surfaces may be closely regulated by automatic means which control either the flow of steam or hot water into the heaters, or the propor- tions in which cold and hot air are mixed to produce the tem- peratures required. Such control is as essential to the evenness of temperatures furnished by a heating system and to the economy of its working as is a governor to th*' steadiness and the economy of the working of an engine. The importance and reliability of the control in these essential particulars are fully established. That reliable results are obtainable with the best forms of apparatus properly installed, cared for, and used, has been abundantly demonstrated. At the present time the cost of such apparatus for buildings of twelve rooms and more should be estimated at one twelfth of the cost of installing the entire warming and ventilating system. Aside from the undoubted value of a reliable system for control of temperature in protecting health and in sustaining vigor, its service in economizing fuel is important. If pneumatic pressure is used SCHOOLHOUSE WARMING AND VENTILATION. 453 for the automatic operation of valves and dampers, it will often be found highly advantageous to employ that means for actuating remote and scattered valves and dampers. That operation may be effected from some convenient point by switch-valves, three-way cocks, or other means. Vent-shaft dampers located at different points at the top of a building may be opened and closed by the turning of a controlling-valve or three-way cock in the basement. Steam-valves controlling different parts of the distributing system may be similarly operated, and also dampers for directing air-flow through flues common to several rooms or parts of a building. Remoteness, difficulty of access, number of points to be reached, and a seeming complication of arrangement are often responsible for the disuse of important parts of an apparatus. In the method described, the nearness of means and the simplicity of use of the means make it more likely that the desired results will be secured. 214. Double Glazing. — As heat loss through the glass of windows is generally about four times that through equal areas of walls, a double glazing in windows is advantageous. The two panes, thoroughly clean, can be puttied in, one on the outside and one on the inside of a sash, with a space between them of from one fourth to one half of an inch. If the work is reasonably well done, the inside surfaces of the panes will remain clean indefinitely. Double glazing stands between cold temperature on the outside of a building and the desired temperature on the inside, and so is as effective upon one side of a building as another. If day and night are included, the differences in temperature between the north and south side are not great. The saving in heat by double glazing can be made to approximate 33 per cent of the heat escaping through single-glazed windows; the saving in fuel approximates 2 pounds per hour for every looo square feet of windows. 215. Double Sashing. — Double windows are more effective than double glazing in preventing heat waste. They protect against both inside and outside differences of temperature, and also against the inward leakage of cold air resulting from pressure due either to inside ai^d outside temperature differences or to wind action. They are, therefore, doubly serviceable. 454 HEATING AND VENTILATING BUILDINGS. They are more effective on the prevailing windward side of a building than on its leeward side. 2i6. Waste of Heat at Night. — To carry over from one day to another as much as possible of the heat of a building, some of which is stored in its air and much more in its walls, the building should be closed as tightly as practicable when not in use. The in-leakage of air through walls and windows is far more rapid than is usually supposed. Recent experi- ments made in a building of ordinary schoolhouse construction indicate that in ' mildly cold and quiet weather such leakage equals the cubic contents of a room or building approximately once in each ninety minutes. In sharply cold weather it is greater, and still more so in windy weather. Air-leakage is the unknown and most disturbing factor in estimating the required power of heating-plants. Unless such leakage is to be relied upon as a factor in ventilation, it should be made as small as possible. To reduce loss of heat at night, and when- ever the building is closed, the vent flues or shafts should be closed by dampers at their tops. 217. Plenum and Vacuum Methods. — For the same reason discharge ventilation should not be made in excess of the supply. The supply should, on the other hand, be in sufficient excess of the discharge to produce a slight pressure or plenum condition, particularly within the lower rooms of a building. A vacuum condition within rooms augments the inward movement of cold air through walls and windows, and tends to cold floors and chilly rooms. In cold climates the proper warming of buildings in which the ventilation is Strongly or even slightly vacuum is rendered more costly and more difficult than is justifiable on any other ground than that of a blindly consistent adherence to the vacuum method of ventila- tion. 218. Location of Inlets. — The efficiency of a ventilating system has an important bearing on the cost of obtaining the results for which it is provided. The air-quantity used does not determine the thoroughness of the ventilating work it effects. As the Gulf Stream goes through the Atlantic, so air often goes through schoolrooms, its ventilating effectiveness ranging as low as from 36 per cent to 40 per cent out of a SCHOOLHOUSE WARMING AND VENTILATION. 453 possible lOO per cent. The location of outlets and the con- centrated or diffused movement of air through rooms are the chief determining factors in the problem. The natural trend of air-currents within a room is downward over the cooling surface of outside walls and windows. The movement of that slightly chilled air is then over the floor toward the inner and warmer walls. The trend of the ceiling air is toward the outer walls and the falling currents. The location of the fresh and warm air inlet is of less moment than that of the outlet. It is wholly unnecessary to carry the entering air by flues to the vicinity of the outer walls. No matter from what point it enters the room its warmth keeps it at the ceiling, and the ceiling currents carry it with certainty to the outer walls. If^ as this air in its turn drops down those walls and then takes its course over the floor, its movement is to be even, it must from its entrance move concordantly with the ceiling currents of the room. To that end it should become a part of those currents and be thoroughly mixed with them before it i-eaches the outer walls. For this reason the best location for the inlet is upon the inner wall at a point that shall be central with reference to the outside wall or walls. The best treatment of the inflowing currents is to diffuse them by means of the fixtures described on page 435. To place the inlet in such a position that it shall throw its unbroken current athwart the cooling wall and windows, and then impinge upon the opposite inside or outside wall, tends to leave a section of the room under the overhead current and between it and the outlet doubtfully pro- vided for. Any arrangement ©f in-put or out-take producing a circling of air about the perimeter of a room from the point of entrance to that of escape is to be avoided as wasteful, how- ever picturesque the course, as seen in smoke, may be. When ventilation is free, the volume of air used must be large and its temperature low. Under such circumstances it becomes necessary to provide an entrance for the air which shall not expose the-occupants of rooms to draughts. For this reason it is advisable and generally necessary to place the inlet at such an elevation that currents produced in the rooms shall be in their upper parts. A further advantage gained is that, when the inlet is in this position, it prevents the entering air 4S6 HEATING AND VENTILATING BUILDINGS. from passing through the lower strata of air, which are gen- erally less pure than the upper strata, and from carrying a considerable portion of such air into recirculation. On the other hand, when the ventilating work is light, the air-volume small, and the temperature of the inflowing air high, or when the work of warming takes the precedence of ventilation, the fresh-air inlet should be placed near the floor and the entering air be given a horizontal, rather than a vertical, direction of flow. 219. Location of Outlets. — If the outlet is at the floor-line and directly beneath the windows or the cooling walls, the falling currents of cooled but purest air in a room are with- drawn before their most effective ventilating work can be done by their passage over the floor. If, however, that air is made to traverse the lower part of the room before its escape, it is brought .into a position for effecting the largest ventilating work. The outlet should therefore be on the inner or warmer wall side or sides of the room. It should be placed near or in the floor in order to remove as effectively as possible the air which traverses the lower part of the room in the floor cur- rents, and in order to prevent its rise at the inner wall and its re-entrance into the ceiling current of warmer and purer air. If there is only one outlet, it should be located with reference to the most even movement of the ventilating current over the entire floor. In rooms having but one outside exposure, two outlets, so located as to insure floor-ventilating currents which shall actively affect the inner corners of the rooms, are prefer- able to a single vent centrally located. There remain to be considered certain matters relating to the ventilating and warming of schoolhouses which are of sufficient economic or hygienic importance to warrant a brief discussion in this chapter. They are special local ventilation, air filtration, air humidity, and methods of warming. 220. Local Ventilation. — Strong local exhaust is required in certain parts of schoolhouse ventilation. Where ventilation can be effected by the immediate removal of atmospheric im- purities, a great gain is made by doing so. Completely to remove the smoke of an open fire buraed in a brazier placed in the middle of a room would require a hundred or a thousand SCHOOLHOUSE WARMING AND VENTILAriON- 457 times more air than if that fuel were burned in a fireplace. The air of a chemical laboratory may be kept as clear as that of a classroom and with no greater per capita supply, if all fuming work is done under hoods. If such work is generally done in the open rooms, ten times that volume of air passed through them might not clear the air. The discharge from such rooms should be largely, if not chiefly, through the hoods ; and the airways through and from the hoods should be designed and furnished with reference to that purpose. So also the general ventilation of sanitary rooms should be largely by means of strong local discharge through the fixtures of both closets and urinals. If the discharge ventilation is not effected by mechanical means, the vent-flues of lavatories, sanitary rooms, and hoods of lunch-room ranges should be made warmer than the flues of other rooms. In this way a move- ment of air toward and into the rooms which are to be locally ventilated is produced, counteracting and overcoming any conflicting pull of flues which discharge air from other parts of the building. The location of chemical laboratories, of kitchen schoolrooms, and of other rooms of similar character should be on the top floor, since the trend of air, especially in cold weather, is upward through a building. When guch rooms are thus situated, fumes, gases, and odors generated within them are more completely confined to the place of their origin (see page 447, lines 6 to lo) than was ever possible when these rooms were placed, as was formerly the custom, in the base- ment. 221. Air Filtration. — The importance of filtering air sup- plied to school buildings varies with local conditions. In dusty or smoky localities such filtering may be essential to the cleanliness of a building and to the protection of its contents. As a hygienic measure it is not generally, if ever, necessary or important. Thoroughly to clear the air-supply of microbic dust by any ordinary means of filtration would be impossible in a large school building ; to do so by any means whatever would be impracticable. To remove even the larger particles of dust from such large quantities of air by the ordinary or dry method of filtration makes necessary such excessively large areas of filtering-cloth, or else so much fan power to force the 458 HEATING AND VENTILATING BUILDINGS. air through the filters, that resort to the method can be advo- cated only with hesitancy. If such filtering is to be attempted with any thoroughness greater than that required to quiet vague apprehension or disturbiftg imagination, so large an area of filtering-cloth should be provided that the entire quantity of air may be filtered through it with a flow rate of not more than 2 or 3 cubic feet per minute through each square foot of the filtering surface. By doubling the air-pressure produced by the fan, the surface quantity may be reduced nearly one half. In order to filter the air of a building accommodating six hundred scholars, the filtering surface to be furnished should be, under the conditions first assumed, 8ooo square feet for schoolrooms and some 4000 square feet for other parts of the ventilation. Any filtering device used must necessarily be made so that a compact arrangement of the surface is secured, and so that the material may be easily removed for cleansing. 222. Air Humidity. — The moisture contained in outside air in winter weather is small. When such air is warmed to 70° without increasing the moisture which it contains, the capacity of the warm air for absorbing additional moisture is large, and evaporation from all moist surfaces becomes rapid. The skin and the mucous membranes of the mouth, throat, and nose, and the moist surfaces of the eye and the ear, are more or less affected, in some persons with irritating' and even serious results. Except for such consequences, dry air is hygienically advantageous, because of its effect in retarding the development and reducing the vitality of microbes, and also because it retards the decomposition and decay of organic matter. The generally fine physical appearance and evident good health and comfort of the thousands whose school life is spent in the relatively dry air of well-ventilated buildings, and the general absence of complaint from_ them, must be accepted as evidence of the irrational position assumed by humidity hobbyists. Water cannot be evaporated either rapidly or slowly except by heat expenditure. For each pint of water evaporated at low temperatures looo heat-units must disappear in the process. To give an out-of-door June humidity to 1,000,000 cubic feet of air warmed through the average range of temperature required for winter ventilation would make SCHOOLHOUSE WARMING AND VENTILATION. 459 necessary the evaporation of 400 pounds of water and the burning of some 50 pounds of coal. The warming of that quantity of air through the average range of 3 5° of temperature would require the burning of 75 pounds of coal. The cost of moistening air to that degree through the school year would therefore range from one half to two thirds of the cost of warming it. The comforting assurance indulged in by some persons that the perspired moisture given to the air of well- iiUed rooms sufficiently satisfies hygienic demands, overlooks both the quality of that moisture as dermal sewage, and also its quantity, which is but little more than one tenth of the assumed standard requirement. The delightful and invigorat- ing character of ideal June conditions of the atmosphere cannot be questioned. It by no means follows, however, that such conditions artificially maintained would be either healthful or satisfactory. The more moist the air, the larger the quantity needed both for comfort and for health. With outside air at 70° 'and at normal moisture, the supply of 2400 cubic feet of air, which is generous in winter weather, would be intolerably meagre. Such humidity to be endurable demands the open windows and the out-of-door abundance of air that belong to June. 223. Method of Warming. — ^The amount of heat required for schoolhouse work is fixed in each case. That quantity remains the same, by whatever simple or complicated form of apparatus it is" generated, and by whatever form of surface it is transferred to the air of the building. Invariably that form of apparatus by which each pound of fuel can be made to produce and yield the most heat, and that arrangement of apparatus which will insure the most effective and therefore the least wasteful use of heat, is the type of highest economy. Such considerations must, however, be balanced against those of the first cost of the apparatus itself, the cost of its maintenance, and the cost of the floor-space and arrangements in the base- ment and in other necessary places. In this light steam-plants or mechanical methods of ventilation for a one-room school- house become incongruous, as also do jacketed stoves for a building of twelve or more rooms. In a general way, furnaces are preferable to stoves for buildings of more than one or two 460 HEATING AND VENTILATING BUILDINGS. rooms, and steam apparatus is to be recommended rather than furnaces for buildings of more than six or eight rooms. The economical advantage of mechanical ventilation begins when the building is large enough to make the use of steam advis- able. So far as the effective and economical production and transfer of heat is concerned, it may be said that the best types of furnaces are equal to the best forms of steam apparatus. Such furnaces should have an effectively arranged heating sur- face not less than fifty, and, if possible, one hundred, times larger than the grate surface. The "powerful heaters," with their common ratios of one of grate to twenty or thirty of heating surface, produce shell temperatures which are inversely proportional to the ratios of the grate and shell areas. Such heaters overheat the air, cook, char, or burn its dust, thus sensibly and harmfully affecting its quality, and give in return only doubtful hygienic benefits in the way of germicidal results. When steam or hot water is used, the warming may be either wholly indirect or partly or entirely direct. The indirect method has the advantages of restricting all heating surfaces and piping to the basement; of compacting the heating system; of reducing the heating surface required, when mechanical ventilation is used, to less than half that needed for obtaining the same heat by direct radiation ; of clearing the upper floors of piping and heating surface; of protecting floors, ceilings, and walls of the upper stories from damage by water-leakage ; and of issuing air into rooms at a temperature which tends to reduce harmful draught effects. Direct radiation, on the other hand, when the air is warmed only for ventilation, and for this purpose is given a temperature of from 2" to 4° above that desired for rooms to prevent its falling floorward with draught effect, has the advantages of furnishing heat with sureness where wanted; of providing that heat without ventilation; of reducing the cost of maintaining the warmth of rooms when ventilation is not required ; of furnishing more ready means for temporarily warming single or isolated rooms without running fans or other ventilating mechanism for the purpose ; of pro- viding compensating, radiant, and sentient heat for the heat lost by occupants by radiation to cold window and wall sur- faces ; and of counteracting the often too sharply chilled air- SCHOOLHOUSE WAKMING AND VENTILATION, 461 currents from windows and wall surfaces, and so reducing their tendency to chill floors. Of these two methods the direct is to be preferred chiefly for reasons of working economy, and the indirect on aesthetic grounds and on account of the lower cost of its installation. CHAPTER XVIII. SPECIFICATION PROPOSALS AND BUSINESS SUGGESTIONS. 224. General Business Methods. — Nearly all heating- plants are constructed by contractors, who agree for a specified sum to install a heating-plant in accordance with certain speci- fications, or, in absence of specifiations, one which is guaranteed to fulfil certain stipulations as to warming and ventilating in any stress of weather. Specifications are prepared either by a disinterested third party who is thoroughly familiar with the subject, or by the party submitting the proposal. The first method, although not common except in the case of large buildings, is, when the specifications are properly drawn, satis- factory both to the owner and the contractor. With proper specifications estimates can be obtained from different bidders on work of the same class and quantity, and this is likely to result in a better quality of work, and often in lower prices. Where each contractor bids on his own specifications and arranges for apparatus in accordance with his own judgment, there will be a very, great difference in the quality and method of construction proposed, which is likely to result to the advan- tage of an unscrupulous bidder, who would, if possible, use cheap material and the least possible quantity of heating and radiating surface. It is for these reasons to the advantage of all concerned that full and complete specifications should be provided which will show, accurately, the character, amount and quality of the required work. The specifications may be written as a part of the tender for the work, or as an independent document to which reference is made in the proposals. The specifications are often accompanied with drawings which show the location of all the principal parts of the heat- ing apparatus and frequently many details of construction ; the 462 SPECIFICATION PROPOSALS— SUGGESTIONS. 463 drawings are considered in every case a portion of the specifica- tions and are equally binding on the contractor. After the bid has been accepted a contract is drawn which should contain a full statement of the agreement between con- tractor and owner, and of all conditions relating to the method of payment, penalties, time of completion of work, etc. J. J. Blackmore and J. G. Dudley, New York, acting as a committee appointed by the National Association of Manu- facturers of Heating Apparatus, have given the matter relating to uniform specifications much study, and we are indebted to them for the following discussion, and also for the copy of the uniform proposals here submitted. 225. General Requirements.* — " It is not within the scope of a work such as this, nor have the trade conditions in the heating business advanced to such a point, that all the details of any or every system can be provided for. The following proposed form for uniform standard specifications, however, covers the ground as fully as can be done at this time, as is shown by the recommendation by the National Association of Manufacturers of Heating Apparatus, and if generally accepted by heating contractors, manufacturers, architects, investors, and the laymen installing steam or hot-water heat- ing apparatus, would result in a higher standard of excellence. Much trouble now exists in securing best results, due to ignorance on part of owner, architect, or contractor, as well as to unfair competition or unauthorized substitutions of 'cheap' materials. " Any specification should set forth unequivocally and in detail (as far as feasible) all that the contractor is to furnish and exactly what is to be accomplished by his guarantee, which should embody a standard of economy as well as one of efficiency. The function of the owner or architect is to stipulate what results must be accomplished according to standards in accepted use, and to give the consulting engineer (when char- acter of heating-plant demands one) or the contractor proper latitude as to methods to be pursued. Further than this, it is' the office of owner or architect, in justice to himself and to competing bidders, as well as to the successful contractor, to * Written for this work by J. J. Blaclimore and J. G. Dudley, 464 HEATING AND VENTILATING BUILDINGS. see that the provisions of the specifications are carried out, and that the quantity and character of material agreed upon are actually furnished and used. Certificates to that end should be demanded and given, if it is deemed necessary, since much injury is done to a legitimate and beneficial calling by what is termed ' skinning the job,' that is, agreeing to furnish certain things and then by taking advantage of ' lay ' ignorance sub- stituting inferior goods or omitting them outright. "As already shown, the attainment of certain results follows from, and is accomplished by, scientific and mathematical proc- esses, whether actually figured and reasoned out, or arrived at by ' rule of thumb,' as many really excellent contractors are known to do. " In illustration, imagine a country residence in course of erection after plans by, and under supervision of, a competent architect, and note how a proper heating-plant is installed. To begin with, the owner should learn from his architect or from any other properly informed person that the desired efficiency, sufficiency, and results to be procured by the heating system depends more on amount of investment than on anything else. For instance, the same results can be achieved by employ- ing either steam or water. The first cost, however, is less with steam, while, it is contended by many, the running and ultimate cost is less with water. The reason for this is that with the hot-water system as usually installed, with an open tank for expansion of water, the temperature of the heating medium ranges from 150° to 200° F., while with steam it ranges from 212° to 240° F.; as a consequence more radiating surface is needed for the former than for the latter. " To continue the illustration, let the owner select steam, and also suppose that he elects to have indirect heating on ground-floor, to obtain extra ventilation (for be it understood that some ventilation, accidental or otherwise, is absolutely necessary to obtain right heating results), while on the upper floors he chooses direct heating. This done, it then devolves on the engineer, contractor, or architect to determine the respective amounts of heating surfaces required to warm the several rooms to the indicated temperature according to an accepted standard. Much harm at present results from de- SPECIFICA riON PROPOSALS— SUGGESTIONS. 465 manding and permitting the several bidders to estimate on different amounts of heating-surface for exactly the same work. The minimum amount should be determined by some one individual, who should be recompensed for this service, and he alone held responsible for this estimate. The owner or archi- tect should indicate on the building plans where surfaces shall be placed, bearing in mind always the room required in the allotted spaces and also the requirements of the system. This is necessary for the contractor to know, since on it depend the number of his riser-lines and the amount of piping in his boiler-room. " When feasible, the owner or architect should indicate all the ' specialties ' desired in the apparatus, and each bidder should be compelled to figure as nearly as possible on exactly the same set of specifications. This method is just to those who estimate in good faith, and usually closer and lower figures will be obtained by the owner. The contractor, with these data before him, takes dimensions either from the architect's plans or from the measurements of the building itself ; he then com- putes the quantity and cost of all materials which will be used in the completed apparatus ; the method of computation varying from that of pure guesswork or shrewd 'estimating' to that of painstaking measurement and actual figuring out of the exact amount of stock required, together with its purchasable cost from the trade catalogues and price-lists. "To the net cost for material, including boiler, radiators, pipe, fittings, valves, vents, floor- and ceiling-plates, registers, ducts, covering, painting, bronzing, smoke-pipe, freight and cartage, boa^rd, car-fares, labor, and incidentals, is added such a margin of profit as the contractor considers his experience, reputation, and workmanship are entitled to. " In justice to the bidders the Conditions of the award should be clearly set forth beforehand, and it should be stated whether this work will go to the lowest bidder, or whether a ' preference ' (often justified) is to be given a certain con- tractor. When it is known that the preparation of a set of specifications and of an estimate of cost is an expense, and often not a small one, to each and every bidder, the injus- tice of requiring all to bear this instead of having it done 466 HEATING AND VENTILATING BUILDINGS. once and for all is too evident for argument. It is for this reason that a uniform standard specification is recommended by the National Association of Manufacturers of Heating Apparatus. " Suppose now the award be made to the lowest bidder, bids having been made on the same set of specifications which embody full statements in regard to requirements of the completed plant. The owner (or architect) and the contractor are then to execute a proper contract for the performance of the work and for the payments therefor. Then each should be required to fulfil the conditions of said contract. The National Association of Master Steam and Hot-water Fitters has adopted a uniform standard contract which seems to meet the requirements and is quite generally accepted in such cases. The form is given below and may be obtained of the secretary of that association. 226. Form Proposed by the National Association of Manufacturers of Heating Apparatus. — For a steam-heat- ing plant. UNIFORM STANDARD SPECIFICATION FOR A COMPLETE LOW-PRESSURE STEAM OR HOT-WATER HEATING APPARATUS. Note.— All clauses and terms in this type and enclosed in brackets [] apply only to hot water. All clauses and terms in this type and enclosed in parenthesis () apply only to steam. Words in italics are to be supplied in each contract. TO BE INSTALLED AND ERECTED COMPLETE IN the three-story stone and frame residence OWNED BY /. N. Vestor, No. 75 Broadway, New York City, LOCATED AT N. W. Corner of State and Hudson Streets, Yonkers, N. Y. THE HEATING SYSTEM shall be erected according to the single pipe method of (steam) [water] heating, the (steam) [water] to circulate (under a press- ure) [at a temperature] never exceeding (three (j) pounds to the square inch at) [ degrees F. in the flow-pipes of] tlie boiler, SPECIFICATION PROPOSALS— SUGGESTIONS. ^6-J conveyed to heating surfaces by a system of piping so erected that all water (of condensation) in the system shall be freely eturned to boiler by gravity alone. (steam generator.) [water heater.] The (steam) [water] shall be (generated) [heated] by one No. 2 Vertical Tubular Sectional Boiler, manufactured by C. Iron & Co.,N. Y. City, and by them guaranteed free from all flaws and defects. Said boiler to have a grate area of 700 square inches, capable of burning all kinds of coal 2,% fuel, and guaranteed by makers to be capable of supplying (steam) [water] to 750 net square feet of direct radiation without " forcing " ; boilers to be certified by manufacturer to be able to stand a cold-water pressure of 80 pounds to the square inch. An opening not less than two {2) feet by five (5) feet into the building and boiler-room shall be provided by owner. BOILER SETTING. Boiler to be placed as near smoke-flue as possible, upon a level concrete or other equally solid foundation provided by owner. The top to be not less than six — feet from ceiling of boiler-room. All necessary excavating to be done at expense of contractor. 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O 3 °- t % O ° Z o 5 O rt s ^ 5 ■6S!. -a o n a; ° c o •5 o c 4) •a c •a" d e ° S = e oa ^ 3 -^ =s o 3 o ^ ° 3 ^ 5 v^H -■" 2 E u I ■a OJ 3 ^ s I ° t/l oj 4-1 3 J5 in !3 — 1- ^ > ■a o 4) O 3 1- ■u u cd 4J 3 O J3 Im ■M 3 & O O 73 (1) C u ■a ° TO C "ft o ^ E cd 1- c o C 3 E =S o ^ o is J2 O 11 cu „ J2 O u c o 4-1 D & U & E-s rt O t- ■(-» O. 4) to 1) E o 482 HEATING AND VENTILATING BUILDINGS. Riveting for a Working Pressure of 100 lbs, — Horizontal seams double- staggered riveted, lap-joint ; pitch of rivets 3" longitudinally and 2i" diagonally. Circular seams single-riveted, lap-joint ; pitch of rivets ■2\". Flange seam and vertical seam of dome double-staggered riveted ; pitch of rivets 3" longitudinally and 2i" diagonally. Circular seam at dome head single-riveted ; pitch of rivets 2^". For a Working Pressure of 125 lbs. — Horizontal seams triple-riveted ; lap-joints required except for boilers exceeding 66" diameter, when hori- zontal seams shall be made with butt-joint, with inside and outside lap strips covering the joint, these strips same thickness as plate in shell of boilers ; three rows of rivets each side of joint; pitch of rivets on triple lap-joints 3i" longitudinally, 2" diagonally, 2f" transversely. Pitch of rivets on butt-strapped joints 3i" and 6J" longitudinally, 2" diagonally, and 2f " transversely. Circular seams single-riveting, lap-joint ; pitch of rivets 2J"- Flange seam, od, dome triple-riveting staggered ; pitch of rivets 3" longitudinally and 2" diagonally ; vertical seam of dome double-staggered riveting ; pitch of rivets 3" longitudinally and 2\" diagonally. Circular seam at dome head single-riveting ; pitch of rivets 2J"- Bracing. — All braces to have a sectional area of i\ square inches and to be of the solid crowfoot style, and riveted to heads and shell with two rivets in each end ; pitch of rivets 4" On heads of boiler these braces to be set radially and spaced about 7" centres, and to lead from head to shell and to be at least 3 ft. in length and preferably longer. Braces in dome to lead from shell of dome to shell of boiler, spaced about 18" centres, two rivets in each end spaced 4" centres ; braces as long as height of dome will permit. Head of dome may be convex and without braces. Tube Setting.— '^uhe.s to be set in straight horizontal and vertical rows, one inch apart each way, and no tube nearer shell than three inches. Distance from top of upper row of tubes to shell not less than one third the diameter of boiler. Tubes to extend through heads, and be carefully expanded and beaded to the heads. Calking. — Calking edges of each seam to be bevelled by machine be- fore plates are put together, and calking tool driven straight. Manholes. — A suitable manhole in top of shell, having an internal opening 1 1" x 15", reinforced with strong internal frame of forged iron. Manhole to be provided with suitable plate, bolt, guard, and gasket. For large boilers a manhole shall be left in front head beneath the tubes. Hand-holes.—h. suitable hand-hole, \\" x 6", in each head under tubes, provided with suitable plate, bolt, guard, and gasket. Outlets.— Outlet for steam should be on top of the dome, the opening into dome to be reinforced with wrought-iron flange properly threaded and riveted to the head ; the safety-valve to be attached to this opening. The opening for blow-off should be in the back head at the side of hand-hole. The opening for surface blow shall be in the top of the shell, SPECIFICATION PROPOSALS—SUGGESTIONS. 483 and provided with pipe having a trumpet shaped mouth ending at water- line. The opening for feed connection should be in the top of shell and reinforced. The feed-pipe is to be extended downward below the water- line, and at least four feet horizontally. The upper connection for water-column should be in front head near top. The lower connection for water-column should be in front head, about on the centre line of the boiler. Wall-brackets. — There should be two heavy cast-iron wall-brackets riveted to each side of shell for supporting boiler on masonry. These brackets should be at least 9 inches wide with foot 12 inches long, and 14 inches on the boiler and i\ inches thick, with heavy rib through the centre. These, and all other castings riveted to the shell, to conform to the shape of same and fit accurately without linings of any kind. Testing. — For a working pressure of 100 lbs. the boiler should be tested to a hydrostatic pressure of 150 lbs. per square inch, and for a working pressure of 125 lbs. it should be tested to a hydrostatic pressure of 200 lbs. per square inch, and should be perfectly tight under each test. Castings. — The boiler should be provided with a cast-iron front at least J" thick, with double flue, fire and ash-pit doors swinging right and left. Fire-doors should be provided with perforated liners and air-reg- isters. Provide heavy cast-iron dead-plate, arch-plate over fire-door, and cast-iron plates at each side of fire-door opening, to protect the fire-brick- The grates* should equal in width the full diameter of the boiler, and should be in two lengths, with necessary bearing bars ; the entire length of the grate surface should equal about one third the length of the tubes. The air-space in the grates for soft coal should be from y to f", and for hard coal from |' 'to ^' . Two heavy cast-iron arch bars for supporting brick at rear of boiler. One back door and frame of cast iron, to provide access to rear of the setting. All necessary anchor-bolts for holding front and back doors in posi- tion, and at least four long tie-bolts extending full length of the setting^ with cast-iron washers for rear end. Four heavy cast-iron buck-stays with rods, extending crosswise of the setting, for supporting side walls. Four cast-iron wall-plates with rollers for supporting brackets to rest upon. Fittings.— Ont. steam-gauge inches diameter. One lever safety- valve. One water-gauge fitted to cast-iron water-column, with three gauge-cocks. One steam-cock for blow-oflf. One globe-valve, and one check-valve for feed-pipe connections. One set of fire tools, slice- bar, and rake. One damper with suitable handles and with auto- matic regulator. * If rocking gates are desired, name of manufacturer should be specified. 484 HEATING AND VENTILATING BUILDINGS It is generally desirable to provide two independent methods of feeding, so that an accident will not affect the supply of feed- water ; but specifications for the feed-pumps are not often in- cluded with those for the boiler. 229. Protection from Fire — Hot Air and Steam Heating. —Where hot-air stacks or steam-pipes pass up through parti- tions near woodwork there is considerable danger of fire, and for this reason certain requirements have been made both as to the position of hot-air pipes in furnace-heating and steam pipes in steam-heating. The following digest, compiled by H. A. Phillips, of the municipal laws relating to hot pipes in buildings, in force in some of the principal cities of the United States, appeared in the American Architect and Building News, Feb. 1893, and is useful in preparing specifications. They are as follows : Boston. — I. Hot-air pipes shall be at least i inch from woodwork. (This may be modified by inspector in first-class buildings.) 2. Any metal pipe conveying heated air or steam shall be kept i inch from any woodwork, unless pipe is protected by soapstone or earthen tube or ring, or metal casing, Baltimore. — I. Metal flue for hot air may be of one thickness of metal, if built into stone or brick wall. 2. Otherwise it must be double, the two pipes separated by i-inch air-space. 3. No woodwork shall be placed against any flue or metal pipe used for conveying hot air. Chicago. — I. Hot-air conductors placed within 10 inches of wood- work shall be made double, one within the other, with at least \ inch air-space between the two. 2. All hot-air flues and appendages shall be made of IC or IX bright tin. 3. Steam-pipes shall be kept at least 2 inches from woodwork, unless protected by soapstone, earthen ring or tube, or rest on iron supports. Cincinnati.— ^o pipes conveying heated air or steam shall be placed nearer than 6 inches to any unprotected combustible material. All subject to approval of inspector. Cleveland.—!. Hot-air conductors placed within 10 inches of wood- work shall be made double, one within the other, with at least \ inch air-space between the two. 2. No pipes conveying heated air or steam shall be placed nearer than 6 inches to any unprotected combustible material. Z?^«j/^r.— Metal flue for hot air may be of one thickness of metal, if SPECIFICATION PKOPOSALS— SUGGESTIONS. 485 built into stone or brick wall ; otherwise it shall be made double or wrapped in incombustible material. Detroit. — No metal pipe for conveying hot air shall be placed nearer than 3 inches to any woodwork. Such pipes over 15 feet long shall be , safely stayed by wire or metal rods. District of Columbia. — i. Hot-air pipes shall be at least i inch from woodwork. 2. Pipes passing through stud or wooden partitions shall be guarded by double collar of metal, " giving at least 2 inches air-space, having holes for ventilation, or other device equally secure, to be approved by inspector." 3. Metal pipe double, with the space filled with i inch of non-com- bustible, non-conducting material, or a single pipe surrounded by i inch of plaster of Paris or other non-conducting material between pipe and timber. Kansas City. — i. Any metal pipe conveying heated air or steam shall be kept i inch from any woodwork, unless pipe is protected by soap- stone or earthen tube or ring, or metal casing, or otherwise protected to satisfaction of superintendent. 2. No wooden fine or air-duct for heating or ventilation shall be placed in anyTsuilding. Memphis. — i. All stone or brick hot-air flues and shafts shall be lined with tin pipes. 2. No wooden casing, furring, or lath shall be placed against or over any smoke-flue or .metal pipe used to convey hot air or steam. 3. No metal flues or pipes to convey heated air shall be allowed unless inclosed with 4 inches thidkness of hard, incombustible material, except horizontal pipes in stud partitions, which shall be built in the following manner: The pipes shall be double, one inside the other, and \ inch apart, and with 3 inches space between pipe and stud on each side; the inside faces of said stud well lined with tin plate, and the out- side face with iron lath or slate. Where hot-air pipe passes through partition shall be at least 8 feet from furnace. 4. Horizontal hot-air pipes shall be kept 6 inches below floor-beams or ceiling. If floor-beams or ceiling are plastered or protected by metal shield, then distance shall not be' less than 3 inches. 5. Where hot-air pipes pass through wooden or stud partition, they shall be guarded by double collar of metal with 2-inch air-space and holes for ventilation, or by 4 inches of brickwork. 6. No hot-air flues or pipes shall be allowed between any combus- tible floor or ceiling. 7. Steam- pipe shall not be placed less than 2 inches from woodwork unless wood is protected by metal shield, and then distance shall not be less than i inch, 8. Steam-pipes passing through floors and ceilings or lath-and-plaster 486 HEATING AND VENTILATING BUILDINGS. partitions shall be protected by metal tube 2 inches larger in diameter than pipe. 9. Wooden boxes or casings inclosing steam-pipes and all covers to recesses shall be lined with iron or tin plate. Milwaukee. — i. Hot-air conductors placed within 10 inches of wood- work shall be made double, one within the other, with at least \ inch air-space between them. 2. All hot-air flues and appendages, shall be made of IC or IX bright tin. Nashville. — ^i. Sheet-iron flue running through floor or roof shall have a sheet-iron or terra-cotta guard at least 2 inches larger than flue. 2. Steam-pipes shall be kept at least 2 inches from woodwork. 3. All steam and hot-air flues and pipes must be suspended by iron brackets. Newark. — i. Hot-air pipes shall be set at least 2 inches from wood- work and the woodwork protected with tin. 2. Such pipes placed in lath-and-plaster partitions must be covered with iron, tin, or other fire-proof material. New York. — (Same regulations as noted under heading of " Mem- phis.") No hot-air flue or pipe allowed between combustible floor or ceiling. Omaha. — i. Steam-pipe shall not be placed less than 2 inches from woodwork unless wood is protected by metal shield ; and then distance shall not be less than i inch. 2. Steam-pipes passing through floors and ceilings, or lath-and- plaster partitions, shall be protected by metal tube 2 inches larger in diameter than pipe. 3. Wooden boxes or casings inclosing steam-pipes and all covers to recesses shall be lined with iron or tin plate. 4. Stud partitions in which hot-air pipes are placed to be at least 5 inches wide, and the space between studs at least 14 inches. 5. Hot-air pipes shall not be placed between floor-joists unless same are doubled and the joists 14 inches apart. 6. Bright tin shall be used in construction of all hot-air flues and appendages. Providence. — i. Hot-air pipes shall be at least i inch from' wood- work, unless protected by soapstone or earthen ring, or metal casing permitting circulation of air around pipe. 2. Steam-pipes must be kept at least i inch from woodwork, or sup- ported by incombustible tubes or rest on iron supports. St. Louis. — I. Hot-air pipes shall be at least i inch from woodwork, unless protected by soapstone or earthen ring or metal casing permitting circulation of air around pipe. 2. Steam or hot-water pipes carried through wooden partition or between joists, or in other close proximity to woodwork, shall be SPECIFICATION PROPOSALS— SUGGESTIONS. 487 inclosed in clay pipe or covered with felting or other non-conducting material. San Francisco. — i. Metal flue for hot air may be of one thiciiness of metal, if built into stone or brick wall ; otherwise double, one pipe within the other, i inch apart, and space filled with fire-proof material. 2. No woodwork shall be placed against any flue or metal pipe used for conveying hot air. 3. Steam-pipes shall be placed at least 3 inches from woodwork, or protected by ring of soapstone or earthenware. Wilmington. — Metal pipes to carry hot air shall be double, one inside the other, ^ inch apart ; or, if single, have a thickness of 2 inches of plaster of Paris between pipe and woodwork adjoining same. 230. Duty of the Architect. — The heating system is an essential part of the building in this latitude, and it should be the duty of the architect to provide building designs of such character that it can be readily and economically installed. The architect's specifications for the buildings hould provide for the construction of ventilating, heating, and smoke i!ues, and his plans should show the location, including pipe-lines, of every- essential part of the heating apparatus. All responsibility re- garding flues and the general adaptability of the heating sys- tem to the building should be assumed by the architect, and: not shifted to the contractor. If the heating system is designed at the same time as the building, slight changes can be made in arrangements of details, partitions, doors, etc., that will tend to cheapen construction, and will add to the efificiency of opera- tion and the general appearance of the heating apparatus. If steam or water pipes are required to be erected out of sight, conduits should be provided, so that they will be readily accessible for inspection and repairs. 231. Methods of Estimating Cost of Construction. — In estimating the cost of construction of any system of heating apparatus the contractor must depend largely upon his own experience and knowledge. No general directions can be given, but a few suggestions are offered which may aid in adopting a systematic method of proceeding. Determine first the amount and character of radiation to be placed in each room by the methods which have already been given fully in Chapter X. Second, determine the position and sizes of pipes leading from 488 HEATING AND VENTILATING BUILDINGS. the heater to the various radiating surfaces by methods given in Chapter XI. To facihtate the above work, a set of floor drawings of each story should be obtained, and on these there should be carefully laid out the position of all radiators, flues, pipe-lines, etc. After determining the amount required, a schedule of material should be made and the cost should be computed. The manufacturers have adopted a price, which is changed very rarely, for all standard fittings, pipes, etc., and from which a discount is given which varies with the condition of the market, cost of material, labor, etc. The discount is usually large upon cast-iron' fittings and brass goods, being seldpm less than 70 per cent, and sometimes 80 per cent and even greater. The discount on piping, especially the smaller sizes, is much - less, ordinarily ranging from 40 to 70 per cent. The cost of labor will vary greatly in different localities, so that no general method of estimating can be given. It must be determined largely by experience in each locality and with a given set of men. The cost of heaters of any given type, with fittings, etc., can only be determined accurately by correspond- ence with manufacturers. Table XXIVa may frequently be useful, as it gives the list- price of the principal standard fittings, pipes, and valves (see appendix to book). 232. Suggestions for Pipe-fitting. — Certain suggestions are here made relating to the actual work of pipe-construction which may be useful to those not having an extended experi- ence. In the actual construction of steam-heating or hot-water heating systems it is usually customary to send a supply of pipe and fittings to the building somewhat greater than is required, and the workman, after receiving plans of construction which show the location and sizes of the various pipes to be erected, makes his own measurements, cuts the pipes to the proper length in the building, threads them, and proceeds to screw them into place. In some rare instances all lengths of pipe are purchased the proper length, and the workman has merely to put them in the proper position. The skill required for pipe-fitting may seem to the novice to be easily acquired : SPECIFICA TION PROPOSALS— SUGGESTIONS. 489 this is not' true, as it is a trade requiring as much training and experience as any with which the writer is familiar. The tools belonging to this trade consist of tongs or wrenches for screwing the pipe together, cutters for cutting, taps and dies for threading the pipe, and vises for holding it in position while cutting or threading. A very great variety of tongs and wrenches is to be found on the market, some of which are ad- justable to various sizes of pipe, and others are suited for only one size. For rapid work no tool is perhaps superior to the plain tongs, and one or more sets especially for the smaller sizes of pipes should always be available. For large pipes, chain tongs of some pattern will be found strong and convenient, and can be used with little danger of crushing the pipe. A form of adjustable wrench known from the inventor as the Stilson wrench has proved a very excellent and durable tool, and is well worthy a place in the chest of any fitter. Other wrenches of value are also on the market, one with a triangular head and projecting teeth being especially valuable for small pipes. The wrenches or tongs which are used for turning the pipe in most cases exert more or less lateral pressure, and if too great strength is applied at the handles there is a tendency to split the pipe. It is an advantage to have the tongs or wrenches catch on the outer circumference of the pipe with as little lateral pressure as posible, and to this end the projecting edges should be kept sharp and clean. The cutter ordinarily employed for small pipe consists of one or more sharp-edged steel wheels, which are held in an ad- justable frame, the cutting being performed by applying pres- sure and revolving it around the pipe. With this instrument the cutting is accomplished by simply crowding the metal to one side, and hence burrs of considerable magnitude will be formed both on the outside and inside of the pipe. The outside burr must usually be removed by filing before the pipe can be threaded. The inside burr forms a great obstruction to the flow of steam or water, and should in every case be removed by the use of a reamer. Workmen quite often neglect to remove the inside burr. A cutter consisting of a cape chisel set in a frame is more diflfrcult to use and keep in order, although it makes cleaner cuts; it can be had in connection with some 49° HEATING AND VENTILATING BUILDINGS. of the adjustable die-stocks, but is rarely used. Pipes, es- pecially the larger sizes, are sometimes cut by expert workmen with diamond-pointed or cape chisels, but this process requires too much time to be applicable to small pipes. The hack-saw is coming into use to some extent for cutting pipes, and is an excellent instrument for this purpose, as it does not tend to burr or crush the pipe, and is quite as rapid as the wheel-cutter. The dies for threading the pipes are of a solid form, each die fitting into a stock or holder with handles, or of an adjust- able form, the dies being made of chasers, which are held where wanted and can be set in various positions by a cam. The adjustable dies can be run over the pipes several times, and hence work easier than solid ones ; but in their use great care should be taken that the exterior diameter of the pipe is not made less than the standard size. The cutting edges of the dies should be kept very sharp and clean, otherwise perfect threads cannot be cut. In the use of the dies some lubricant, as oil or grease, kept on the iron will be found to add materi- ally to the ease with which the work can be done, and will tend to prevent heating and crumbling of the pipe and injury to the threads. Taps are required for cutting threads in openings or coup- lings into which pipes must be screwed — an operation which the pipe-fitter seldom has to perform, unless a thread has been in- jured. The vises for holding the pipe should be such as will: prevent it from turning without crushing it under any circum- stances. Adjustable vises with triangular-shaped jaws on which, teeth are cut are usually employed. In the erection of pipe great care should be taken to pre- serve the proper pitch and alignment, and the pipes should, to appear well, be screwed together until no threads are in sight. Every joint should be screwed six to eight complete turns for the smaller sizes, 2" and under, and eight to twelve turns for the larger sizes, otherwise there will be danger of leakage. It is a good plan to test the threads on all pipes before erection by unscrewing the coupling and screwing it back with the ends reversed. It is also advisable to look through each length of pipe and see if it is clear before erect- SPECIFICATION PROPOSALS— SUGGESTIONS. 491 ing in place ; serious trouble has been caused by dirt or waste in pipes, which would have been removed had this precaution been taken. In screwing pipes together, red or white lead is often used ; the writer believes this practice to be generally objectionable, and to be of no especial benefit in preventing leaks. The lead acts as a lubricant, and consequently aids by reducing the force required to turn the pipe. It will generally be found, however, that linseed or some good lubricating oil will be equally valuable in that respect, and will have the advantage of not discoloring the work. If possible, arrange the work so that it can " be made up " with right and left elbows, or right and left couplings. Packed joints, especially unions, are objectionable, and likely to leak after use. Flange-unions, packed with copper gaskets, should be used on heavy work. Good workmanship in pipe-fitting is shown by the perfec- tion with which small details are executed, and it should be remembered that bad workmanship in any of the particulars mentioned may defeat the perfect operation of the best-de- signed plant. APPENDIX CONTAINING REFERENCES AND TABLES. LITERATURE AND REFERENCES. The literature devoted to the subject of warming and ven- tilation is quite extensive, dating back to a treatise on the economy of fuel and management of heat by Buchanan in 1815. A most excellent compilation of this literature was made by Hugh J. Barron of New York, in a paper presented to the American Society of Heating and Ventilating Engineers at its first meeting in January, 1895, from which the following list of books has been copied : A Treatise on the Economy of Fuel and Management of Heat. Robertson Buchanan, C.E. Glasgow, 181 5. Conducting of Air by Forced Ventilation. Marquis de Chabannes. London, 181 8. The Principles of Warming and Ventilating Publib Buildings, Dwell- 'ing-houses, etc. Thos. Tredgold, C.E. London, 1824. Warming, Ventilation, and Sound. W. S. Inman. London, 1836. The Principles -of Warming and Ventilating, by Thos. Tredgold, with an appendix. T. Bramah, C.E. London, 1836. Heating by the Perkins System. C. J. Richardson. London, 1840. Illustrations of the Theory and Practice of Ventilation, with Re- marlcs on Warming. David Boswell Reid, M.D. London, 1844. A Practical Treatise on Warming by Hot Water. Chas. Hood, F.R.S. London, 1844. History and Art of Warming and Ventilating. Walter Bernan, C.E. London, 1845. Warming and Ventilation. Chas. Tomlinson. London, 1844. Walker's Hints on Ventilation. London, 1845. Practical Treatise on Ventilation. Morrill Wyman. Boston, 1846. Traite de la Chaleur. E. Peclet. Paris. First edition, 1848; sec- ond edition, 3 vols, 1859. ' 493 494 APPENDIX CONTAINING REFERENCES AND TABLES. Practical Method of Ventilating Buildings, with an appendix on Heating by Steam and Water. Dr. Luther V. Bell. Boston, 1848. Warming and Ventilation. Chas. Tomlinson. London, 1850. Practical Ventilation. Robert Scott Burns. Edinburgh, 1850. Ventilation and Warming. Henry Ruttan. New York, 1862. A Treatise on Ventilation. Robert Richey. London, 1862. American edition of Dr. Reid's Ventilation as Applied to American Houses, edited by Dr. Harris. New Yorlc, 1864. A Treatise on Ventilation. Lewis W. Leeds. Philadelphia, 1868; New York, 1871. Observations on the Construction of Healthy Dwellings. Capt. Douglas Galton. Oxford, 1875. Practical Ventilating and Warming. Jos. Constantine. London, 1875, Warming and Ventilation. Chas. Tomlinson. London, 1876. Sixth edition. Mechanics of Ventilating. Geo. W. Rafter, C.E. New York, 1878.. Ventilation. H. A. Gouge. New York, 1881. Ventilation. R. S. Burns. Edinburgh, 1882. American Practice in Warming Buildings by Steam. Robert Briggs, Edited by A. R. Wolf, with additions. New York, 1882. Steam-heating for Buildings. W. J. Baldwin. New York, 1883. Thirteenth edition published in 1893. The Principles of Ventilation and Heating. John S. Billings, M.D. New York, 1884. Heating by Hot Water. Walter Jones. London, 1884. A Manual of Heating and Ventilation. F. Schuman. New York, 1886. Ventilation. W. Butler. Edited by Greenleaf. New York, 1888. Steam-heating Problems from the Sanitary Engineer. New York, 1888. Metal Worker Essays on House Heating. New York, 1890. Heat — Its Application to the Warming and Ventilation of Buildings. John H. Mills. Boston, 1890. Ventilation and Heating. T. Edwards. London, 1890. Ventilation — A Text-book to the Art of Ventilating Buildings. Wm. Paton Buchan. London, 1891. The Ventilating and Warming of School Buildings. Gilbert B. Mor- rison. New York,- 1892. Hot-water Heating. Wm. J. Baldwin. New York, 1893. Ventilation and Heating. John S. Billings, M.D. New York, 1893. Warming by Hot Water, Chas. Hood, C.E. Edited by F. Dye. London, 1894. In addition to this list of books a large number of pam- phlets have been printed containing valuable articles on spe- cial subjects. The scope of this work does not permit any APPENDIX CONTAINING REFERENCES AND TABLES. 495 historical review of the Hterature or of progress and improve- ments in the art of heating. CURRENT LITERATURE OF THE DAY. The current hterature relating to this subject is extensive, and consists mainly of magazines and papers published weekly or monthly, and devoted to the whole or to special parts of the industry. In these journals are to be found from time to time descriptions of new apparatus and complete drawings of plants recently constructed which will prove invaluable in the study of this art. The American Society of Heating and Ventilating Engi- neers, formed soon after the publication of the first edition of this book, has contributed greatly to advance the scientific and practical knowledge of the art of heating and ventilating. Much information for the fourth edition of the work has been obtained from the Transactions of that society, which are the most valuable books of reference yet published for engineers. LIST OF TABLES IN BODY OF BOOK. Air delivered from pipes of dif- ferent diameters 386 Area for each 1000 cu. ft. of space 63 Air required per person for vari- ous standards of purity 35 Blower systems, tests.. 108, 109, no Boilers, dimensions of 161 Boiler explosions 204 Boilers, proportions of 156 Boiler specifications, table 481 Boilers, stored energy in 203 Boiling temperature and barom- eter 22 Building loss 64, 66, 67 Chimney dimensions 192 Conduction of heat 78 Direct hot-water heating, di- mensions 269 Direct radiation, space heated, steam heated 238 Direct radiation, space heated, water heated 239 Direct radiation, table of factors 236 Direct steam-heating, dimen- sions 269 Drip-pipes, sizes 260 Efficiency of fans and heated flues 368, 372 Electric heating, cost 409 Equalization of pipe diameters. 387 Exhaust heating, data 2S3 Exhaust heating, radiating sur- face and dia. of exhaust-pipe.. 285 Fan capacities • 394 Fan dimensions 394 Fan proportions 334 Fan tests 366, 367 Fan velocity and pressure 36a Flue areas 62, 265 Flue areas, table of factors 266 Flues, hot-air and ventilating... 270 Furnace heating, proportions... 317 Furnace work, actual propor- tions 328, 329 Greenhouse heating, hot water. 273 Greenhouse heating, steam 273 Greenhouse heating, tests., 275, 276 Heat emitted, radiation and convection 84 Heat loss through pipe-cover- ings 230 Heat transmission, steam to water 89 Heat transmitted through differ- ent media I7 Heat units from direct radiation. 86 Heat units per sq. ft. of surface. 113. "4 Hot-water mains, dimensions. .. 263 49^ APPENDIX CONTAINING PEFERENCES AND TABLES. House-heating boilers, tests.... 155 Indirect hot-water heating, di- mensions 269 Indirect radiation, space heated, steam heated 244 Indirect radiation, space heated, water heated 245 Indirect radiation, table of fac- tors 242 Indirect steam-heating, dimen- sions - 269 Pipe-coverings, tests 229 Pipe sizes 121 Power transmission, loss in ... . 306 Pressure due to fan speed 356 Radiation loss for various sur- faces 84 Radiator proportions 149 Radiator tests, hot-water 102 Radiator tests, indirect 105, 106 Radiator tests, steam-heatedsur- faces. .97, 98, 99, 100, loi, 103, 104 PAGE Register areas 322 Relation between pressure and temperature 189 Relation between velocity and force of air 55 Relative conducting powers. .. . 18 Relative emissive powers 16 Relative reflecting powers 16 Relative weight of air and water 361 Return pipes, sizes 259 Safety-valve, area 181 Size of room, influence on ven- tilation 37 Stack areas 320 Steam-mains, dimensions ... 253, 256, 257 Steam-pipes, capacity 258 Temperature by color of incan- descent bodies 13 Thermometric scales 8 Tredgold's experiments 96 Velocity in hot-water pipes 251 LIST OF TABLES IN APPENDIX. Table No. I. Reduction Table United States and Metric Systems. II. Equivalent Value of Units British and Metric Systems. III. Reduction Table — Ounces to Inches of Water. IV. Properties of Gases. V. Properties of Circles, Squares, and Cubes. VI. Circumferences and Areas of Circles. VII. Logarithms of Numbers. VIII. Properties of Familiar Substances. IX. Coefficients of Strengths of Materials. X. Properties of Air. XI. Relative Weights of Water and Air. XII. Moisture Absorbed by Air. Xlla. Relative Humidity of Air. XIII. Properties of Saturated Steam. XIV. Composition of Various Fuels in United States. XV. Barometer Corrections for Freezing-points. XVI. Theoretical Velocity of Air in Flues. XVII. Thermal Conductivities. XVIII. Standard Dimensions of V/rought-iron Pipe. XIX. Weight of Water at Different Temperatures. XX. Reduction Pressure per Square Inch to Feet of Water. XXI. Contents of Pipes in Cubic Feet and Gallons. XXII. Equalization of Pipe Areas. XXIII. Horse-power Lost in Friction of Air. XXIV. Theoretical Horse-power required to move a Given Volume of Air. XXV. Diameter of Pipe to Discharge Given Volume of Air. XXVI. Velocity of Air Flowing in a Pipe. XXVII. Temperature of Various Localities. APPENDIX CONTAINING REFERENCES AND TABLES. 497 EXPLANATION OF TABLES. Of the tables which have been given a few only need special explanation in order to fully understand their use. These are as follows : Table No. VII, Logarithms of numbers. This table will be found of very great convenience in facilitating any operation involving multiplication and division. Thus it will be found in every case that the sum of two logarithms is the logarithm of a number equal to the product of the two num- bers whose sum was taken, and the difference of two logarithms is the logarithm of the quotient obtained by dividing one by the other. Every logarithm consists of two parts : a decimal part, which is given in the table, and an index or characteristic, which must be prefixed. The index or characteristic is a whole number and is one less than the number of integral places ; for a decimal number it is negative and one more than the number of ciphers between the decimal point and the first significant figure. Thus, to find the logarithm of 254, a number containing 3 integral places, the index is 2, the decimal part of this logarithm found opposite 25 and under 4 in the table is 4048, making the full logarithm 2.4048. If the number had been 25.4 the index would have been i, the decimal part as be- fore. If the number had been 0.0254, the index would have been minus 2, the decimal part the same as before. As an illustration showing how to multiply by logarit>'ms, multiply 254 by 2.48. We have : The logarithm of 254 = 2.4048 " 2.48 = 0.3945 Log. of product = 2.7993 The sum of these two logarithms, which is the logarithm of the product, is equal to 2.7993. The index, or number 2, is of use in showing that there are three figures or integral places in the result. To find the logarithm, look in the table for the number next smaller than 7993 ; in this case the result is exact and is found opposite 63 in the column marked zero, indicating that the product is 630 ; the actual product of these numbers is slightly less than this, the difference, however, being scarcely ever of any practical importance. Had our number been 7994, it would have been one greater than 7993 and 6 less than the logarithm of the next number. In that case our number would 498 APPENDIX CONTAINING REFERENCES AND TABLES. have been 630^, which, reduced to a decimal, would have been the number to consider as the product. The logarithm of a power can be found by multiplying the logarithm by the num- ber which represents the power and the logarithm of a root by dividing by the index of the root. Thus, to raise 368 to the fifth power, we have : Log. 368 = 2.5658 Multiply by 5 Log. 5th power = 12.8290 No. = 674!^ expanded to 13 places = 6745000000000, To extract 5th root : 368 : — Log. 368 = 2.5658 Divide by 5 = 0.51316 = log. of root Root = 3.259 In general the table will be found to afford an easy method of dividing or multiplying, and it will be well worth while to become master of its use. The table which is printed in the book is correct for 4 places of figures only, but tables of 7 and even 13 places have been printed. The four-place table can be used with confidence for all operations not requiring extreme accuracy. It will in almost every case be found sufficiently accurate for all practical prob- lems of designing. The method of using Tables Nos. XII and Xlla: to deter- mine the amount of moisture in the air has been quite fully ex- plained on p. 32. The method of using Table No. XIII (prop- erties of saturated steam) has been fully explained on p. 150. The reader should note that the steam-pressure tabulated is that above a vacuum, and not the reading of a pressure-gauge. The pressure-gauge reads from the atmosphere, which is generally 14.7 pounds above zero ; hence, in order to use the table, add 14.7 pounds to the steam-gauge reading for the pressure above zero. The other quantities will be quite readily understood. The table for equalization of pipe areas has been quite fully explained on page 387. The number of pipes of the size, as shown in the side column, required to give an equivalent area to the one in the top column is given by the numbers. Thus 14.7 pipes I inch in diameter have a carrying capacity equiva- lent to that of one pipe 3 inches in diameter. APPENDIX CONTAINING REFERENCKH AND TABLES. 499 t/i u t« g I/) IS" < ui tn cj h . Q g ^^ f^ z tn a U z Hg . 0^ M rt-^O CO M '^QO « \0 M m O^ coco 00>-i>-<»-'CIC4C. -T M. o^O CO r^ -^ CO r^o Tj- CO N 1-1 c^co cor>i-i ino^eor^O T « O^inwoo Tj-'-t r^ M CO -^O CO 0» M CO •:}■ II II II II II II II II II M « CO TT iDvO r^co (4 < 3 r-rft-i rN.TriHCO in« Th o^ Tfco coco « r>. c^ OO^MINNCOCO-i- ■^00 MOO ^00 W 00'-i'-t««NCOCO Square Yards to Square Metres. woo -^H i^cooin coo incOM 0000 U-) w w CO -^ in ino r^ Square Ft. to Square Deci- metres. Ow(H„(MC^NCOCO CT-oo r^o in Th CO w 1- c< moo w -^ r^ COO cr«co r^ r>o m m -^ co t-< « CO Tt mo r>-co c &Z 9 N CO m r^co '- CO m ino mO ini-iO <-o Tf 0^ coco w r>. iH t°^l N O^mMco iniico i-« f N eocorl-mm II II II II II II II II II 11 M CO -^ ino r^co < g tn U ija XT) ly T:t 0^ TtCO COOO W coo CO r^ -^ f^ *-t oco 00 r>.o in -^ Tj- '- IN en ^ mo r>.co oco Tl-OO CJOD Tf w CO -^O CO O^ -1 HH w Ti- in r-^oo '-' « a»co r^o in -J- "^ CO w "-I W CO Tt mo t^CO 2" IS i-tiHMc*co-^-rl-mm 000000000 coo ^c^ 0000 Th« ^ -t -tco coco CO OOMMMWCOCO-^ coo O' w mco »H -^ r>. 000'Hi-.0 «mr>.0 « l-l HH 1- M W « 1 II II II II II II II II II (A -a a coo CO r^ 1- r^ w OO1HI- — C<«MCO r*" " a ■H M CO ■^ inO r--co 0^ M ci CO ^ mo r^co Oi 00 COO w inco M -"^f- r^ >-H K- 1-. .coo^mi~( r>.co Avoird pois Pounds Kilo- erramra inoO-iONi^wco h X n ■<3- 0^ coco « r^ w OOMwNNCOCOTf Avoirdu- pois Ounces to Grammes. mi-o "-"Ocir^c^ r> 0^ O^co CO t^ r^o m ■*ON-'* III coo cor>.o Tfr>.M coo mcoi-t Ocoo u) N mco M Th t^ o^ n in M Ht H. •-. C4 c* O^'co~3o"l-Co~m -rt Thlo 2 oi g-=a O' O' 0* O' O' u^ 0* fj^ u^ r-.mcoi-« CTT^incotH & •=^O^T^c^eoQ0 coco co « Omcico mwco >-i i-i « coco-^min II II II II II II 11. II II i-H w CO ^ mo r^oo 0^ TtOO C^ TTCO W TTOO CO r^ W in 0^ in PI r^ P) CO coco S 2i 30 r^ in rt w M 0*00 t^mcOM CM-^'tc* CO r^ w inco « ^ M M M « M CO to OC^CO-^OOMCO-* w ui m 1-^ rtco '-' inco « OW O^mi-co TtOr» >< h <; 0. cfl S ^ •rt COCO CO r^ M r^ - S a O'co 00 r^ i>o mm '1 N corrmo i^oD m.i . r^ m N r^ -^ w 00 Fluid Ounce to Mill litres in HI r-. COOO ^ m Hi d^ O^QO 00 r-* r> r^o o CI >noo M ^ i^ coo ,u M W M M « M d sto tres Gen- res. r^eoo r^rj-pH.Qo mw - 1= s-a CO r^ w ■^00 N m ©vco *2=tja M M M N « « CO QSg-= 1 II II II II 11 M II II II 1 M M CO 'i- mo r^oo o* « Si's m fl ;> ■s bfl c<; ^ Si at T 5 £" _m u £h U ^ g rt y nkn son V. Surve yard, .s of u mpari S-SffS M §3-°ti ^£o.S autho ms to t autho or a St Iso der S-.01 to c 0^ rt &i The ar. CO The suita nd w u< s-g f^ ss. 500 APPENDIX CONTAINING REFERENCES AND TABLES. 8 S ^ O w m < ■^ h 3? = SuS WSo> coo rhe* OoOvO •*« O "-• N en rj- -^ uiO f> cr,o ow inao M ^ r^ 1- M c*^ ino r^ ff' O I- N ^ m r^oo O ^ en -H hH I-. N w M c*^ cnr->.o enr^o c*^r^o OOOOIHIHHIHM O «co Tj-OO woo -^ H M M cocn-^*^m OO'-'-'i-i^CJfNCN HI N C*^ -^ uTO 1^00 O \OWOO -^OO WOO TT O w M « cocn"^^m 000000000 II II II II II II II II II 3 h CI is M Ttr>.o« ■^1-^00 O tNOO -^OO WOO "* N en "i- in r>.oo o o r-inc* Ooo u^cn^-( 000000000 \nO vnO w^O mO vn in I- o CN r^ cnao ■^ o^ M cn-^o r^o^o w en 000000 II (I II II II II II II II »-< C-) en *:t- \rt\o r-co o^ r^ -^ M CO in N 0^0 en cnr^i-. Tj-oo « inc>en w N ■^ invO 00 O O M N TtO CO O W -^ r^ 0^ O Nco -^i-i i^cno^in O M I « en CO -^ Tt in H « en ^o r> i-" « en t in\o \0 W 00 Tf O vO en t-> O -^00 M 0^co CO l~^0 O O M M en T^f in 00 a^ o r-^oo O N 00 in inao w in ^ -^ N en'^invo r^oo o^ en r^ O en r^ o CO O in en Hi o O HI N en Tf in CO >0 ■* M O 00 w inoo HI Tfvo en r^ O 00 vO in ino r> o ■^- w CT- N in eno o* cno o^ e S" OOOOQOOOO 000000000 r^ -t HI CO in c» Q^O en cnr-M -fi-oo-w mc^en 000 00 r^o o in ^ '^t- cnt-^H. ino^enr^Hi in M M M w M en en I II II 11 II II II II II II I H M en 'T UHO l-^QO O^ asos 5 of- H C .Sis 3 > mO u^O »nO »rtM\0 ■I en Tj-vo t>. ^ o M en M T]-\0 00 O CJ in r^ CT» enO O^ M O O^ W moo OOOh«hih(N«c< 000000000 O Nco TtO-O NCO t:J- '^ O^ enoo en r-* N vD ■- OOHiMMMcncnri- N -H-^ 00 O N TtO CO N Ttooo HI cnlnr-.o^ OOHtHWWenen^ C4 ';^0 00 O N •^'O oo M rro 00 HI en in r- o^ II II II II II 11 II (I s 2 2n « -Tf-o o^M cnmr-^o O Nco -fHj r^cno^m ■rfoenco cnr-^NO h< OOHfHioicjcncn-^ N ■^O CO O N '^J-O CO saasS Ills- u S ^ rt ° %%h. •a cj " ni cd N Tl-\0 CO . en »n r-^ O^ ^co N O O ^00 N O r-^ ^ N c r-* -r — o^o N inoo o cno o^ -« -^ inO innt-O hivO c»r> «io — 3 c ci rj- r-^ O HI ^vo CO cno c7>c^o o^o^ incTi ■^co w r^ H« in O ■^co in O O M r- w CO enoo HI en Tho r>. o^ O N en eno O cno o eno o^ ■^co en r^ 1-1 in o ^cz inoo Hi r^c^co enoo M en -^o r-> O^ O « en OOOOOOhim 000000000 d en '^ ino r^oo o> in m in m in t^ in in ■^ r> o^ N in M HI M HI N W r^ TJ- hi 00 in N 0^^ en en ino CO Hi en in TtCO N in o^ en r^ ^ M M a IT N 00 '^ HI t-s. Qh M N in r>. en moo M en = ^ HI HI W « N . i>- ■* r^ -d- HI 00 Ti- M "JS en M I~^ tN S M HI HI N N en en -^ m 3a y-i N cn T^ ino r^co • '?_ » CjO t:J- N M Ooo en ■3"S S r^ HI m Cen litres Flu Ounc d d w eno en r- H HI W N N en S-ri »• tres Cen es to r^ Tt- w 00 in « 00 en moo eno 00 HI Tf Millil Cubic litr Fluid M M M M W M II II II II II II II II II tH « en ^ mo r>.QO C7» •5! « OJ .= u -- S-Q .- ^aajjs SI'S'!* «§&c.2 a^H V I- t5 £ S « c rt a; 7^ U nJ U u a »gft •sis V B U 'O O A) 2 ■■-'. • .a r" d iSac-a'tx Qj 5 -^ ^ ^ •c ?•= "SB < 3 3 •O rt .- 3 ,'- . fJ o 1 £— u B ii aj 2 rt c!S 3 'a_ ri 9 c > 2i m « ^ c u V . - *J 6.S 3 J* rt M E« «■■ 4J I- >< * d = « S G ■c'S 1^ vi •°ff •o rt LI La 5S ? » -a sa p 3 ^ 3 ■D g "•■Saf.S'l-SjjSM :;ofeiigo^sSv^ 2 °-s-i--2 lass's iif?? o u ^•^ I/] TT^ -o "7 -a ^5 " ■; ■^■i: e:S-5 4J S n A c " rt" '^"""•a-rtl 5. 1^^ H « ..'o C'" ? o ao ^ o^-s s o „-y E § p Oj (^ H g J3 rt a.3 iJ 3 O"; " "^ -" •" >l V Z vi£ >i S .•OJ5J3 hxJ3 «•- "S " 61-!' ^ S - go APPENDIX CONTAINING REFERENCES AND TABLES. SOI Table No. II. EQUIVALENT VALUE OF UNITS IN BRITISH AND METRIC SYSTEMS. One foot = 12 inches = 30.48 centimetres = 0.3048 metre. One metre = 100 centimetres = 3.2808 ft. = 1.936 yd. One mile = 5280 ft. = 1750 yd. = 1609.3 metre. One foot = 144 sq. in. = 1/9 sq. yd. = 929 sq. centimetres = .0929 sq. metre. One sq. metre = loooo sq. centimetres = 1.1960 sq. yds. = 10.764 sq. ft. One cubic foot = 1728 sq. in. = 2832 cu. centimetres = 0.02832 cu. metres. One cubic metre = 35.314 cu. ft. = 1.3079 cu. yds. One pound adv. = 7000 grains = 16 oz. = 453.59 grains = 0.45359 kilograms. One kilogram = 1000 grams = 2.2046 lbs. = 15432 grains = 35.27 oz. adv. COMPOUND UNITS. One foot-pound = 0.13826 kg.-mt. = 1,3826 gr.-c. = 1/778 B. T. U. One horse-power = 33000 ft. -pound per minute = 746 Watts. One kilogram-metre = 7.233 ft.-lb = 723.300 gr.-c. = 1/426 calorie. One gram-centimetre = i/iooooo kg.-mt. = .00007233 ft.-lb. One calorie =426.10 kg.-mt. = 3.9672 B. T. U. = 42000 million ergs per second = 42 Watts. One B. T. U. = 778 ft.-lbs. = 0.2521 cal. = 10820 mil. ergs. =» 107.37 kg.-m. One calorie per sq. metre = 0.3686 B. T. U. per sq. ft. C. G. S. SYSTEM. One .dyne = one gram /981 = 0.00215 lb. One erg. = i dyne X i cent. = 0.0000707 ft.-lb. One Watt = 10 mil. ergs, per sec. = 0738 ft.-lbs. per sec. = h. p. /746. One h. p. --. 746 Watts. 502 APPENDIX CONTAINING REFERENCES AND TABLES. Table III. — reduction table. HEIGHT OF WATER-COLUMN IN INCHES TO CORRESPOND TO VARIOUS PRES- SURES IN OUNCES PER SQUARE INCH. TEMPERATURE JO FAHR. P-es9ure inUz. Dcim:!! Farts of an Ounce. per Sq. In. ■ •" •' ■-' -3 ■ 4 -5 .6 .7 .8 -9 o 0.17 0-35 0.52 0.69 0.87 1.04 1.21 1.38 1-56 1 1-73 1.90 2.08 2.25 2.42 2.60 2.77 2.94 3-" 3-29 2 3.46 3-63 3.8. 3-98 4. IS 4-33 4-50 4-67 4-84 S-oi 3 S-I9 5-36 5-54 5-71 5 88 6.06 6.23 6.40 6.57 6-75 4 6.92 7.09 7.27 7-44 7.61 7-79 7.96 ^■\\ 8. 30 8.48 S 8.65 8.82 9.00 9.17 9 34 9-5= 9.09 9.86 10.03 10.21 6 10.38 10.55 10.73 10.90 II 07 T1.20 11.43 11.60 11.77 11.95 7 12. II 12.28 12,46 12.63 12.80 12.97 13-15 "3-3= 13 49 13.67 8 13.84 14.01 14.19 14-^6 "4-53 14.71 14.88 '5-05 15.22 15-40 9 15-57 15-74 15.92 16. og 16.26 .6,45 16.62 16.79 16. 96 17.14 PRESSURES IN OUNCES PER SQUARE INCH CORRESPONDING TO VARIOUS HEADS OF WATER IN INCHES. Deci Head in Inches. .0 •' .2 •3 -4 -5 .6 •7 .8 -9 0.06 0.t2 0.17 0.23 0.29 0.35 0.40 0.46 0.52 I 0.58 0.63 0.69 0.75 0.81 0.87 0.93 0.98 1.04 1.09 2 1. 16 1.2[ 1.27 '-33 1.39 1-44 1.50 1-S6 1.62 1.67 3 1-73 1.79 1.85 i.gi 1.96 2.02 2.08 2.14 2.19 2.25 4 ''•V- = -37 2.42 2.48 = •54 2.60 2.66 2.72 2-77 2.83 5 2.89 2-94 3.00 3-c6 3-12 3.18 3.24 3-29 3-35 3-41 6 3-47 3-52 3-s8 3-6l 3.70 3 -75 3.81 3-87 3-92 3-98 7 4.04 4.10 4.16 4.22 4.28 4-33 4-39 4-45 4-50 4-56 8 4.61 4.67 4-73 4-7S) 4-»s 4.91 4-V7 5-03 5-08 5-H 9 _S.2o 5.26. 5-3- 5-37 5.42 5.48 5-54 .S-60 5.66 5.72 Table IV. table of properties of gases. Element or Compound. Oxygen Nitrogen Hydrogen Argon Carbon Phosphorus Sulphur Silicon Air Water vapor Ammonia Carbon monoxide. . . . (Carbonic oxide) Carbon dioxide (Carbonic acid) Olefiant gas Marsh gas Sulphurous acid Sulphuretted hydrogen Bisulphuret of carbon. Ozone Symbol by Volume. 79N O N H C P S Si + 21O H2O NHs CO C02 CH, CH4 SO2 SHi S,C Os Atomic Weights. 16 14 I 19 12 31 32 14 18 17 28 44 14 16 64 34 76 24 Cubic feet per lb. at 62°. n.88 13-54 189-7 15-84 6.iig 5-932 13-55* 13 14 21.07 22.3 13-6 8.64 13-587 23-757 6.463 5.582 2.487 7-97 Weight per. cu, ft. at 62°. Lbs. 0.0814 0-0738 0.00527 O.63131 0.16337 O.16861 0-07378 0.0761 0.04745 0.0448 0.07364 O.I1631 0.0736 0.04209 0.15536 O.17918 0.40052 0.12648 Specific Gravity at 62°. Water = : 001 350 001 185 0000846 001607 OOIOI3 0026221 002705 001184 001 22 I 0007613 001 18 002369 0.00187 o. 001 181 0.000675 0.002493 0.002877 0.00643 o 00203 Relative Density. ,10563 97137 06926 3118 82323 1877 2150 01032 0000. 6253 5892 9674 1. 52901 0.967104 0.55306 1-54143 2.3943 5-3007 64656 ■ by this table there would be 12.75 cubic feet of air at 32" per pound. APPENDIX CONTAINING REFERS-NCES AND TABLES. 503 Table No. V. TABLE OF CIRCLES, SQUARES, AND CUBES. H «ir TT 4 tfl «3 v; 3 Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. I.O 3.142 0.7854 1. 000 1. 000 1 . 0000 I . 0000 l.I 3-456 0.9503 1. 210 I -331 1.0488 1.0323 1.2 3 -770 I.1310 1.440 1.728 1.0955 1.0627 1-3 4.084 I 3273 1.690 >:.I97 I . 1402 I. 0914 1.4 4-398 1.5394 1.960 2.744 I. 1832 1.1187 1-5 4.712 1.7672 2.250 3-375 1.2247 I. 1447 1.6 5.027 2.0106 2.560 4.096 I . 2649 I. 1696 1-7 5-341 2.2698 2.890 4.913 1.3038 I. 1935 1.8 5-655 2.5447 3.240 5-832 I. 3416 I. 2164 1.9 5-969 2.8353 3.610 6.859 1-3784 1.2386 2.0 6.283 3-1416 4.000 8.000 I. 4142 1.2599 2.1 6.597 3-4636 4.410 9.261 I. 4491 1.2806 2.2 6.912 3-8013 4.840 10.648 1.4832 1.3006 2.3 7.226 4.1543 5-290 12.167 J. 5166 1.3200 2.4 7-540 4-5239 5.760 13-824 I . 5492 1-3389 2.5 7-854 4.9087 6.250 15.625 i.;8ti 1.3572 26 8.168 5.3093 6.760 17-576 1.6125 I. 3751 2-7 8.482 5-7256 7-290 19.683 1.6432 1.3925 2.8 8.797 6.1575 7.840 21.952 J 6733 1.4095 2.9 9. Ill 6.6052 8.410 24.389 I . 7029 1.4260 3.0 9.425 7.0686 9.00 27.000 I. 7321 1.4422 3-1 9-739 7-5477 9.61 29.791 1.7607 1.4581 3.2 10.053 8.0425 10.24 32.768 1.7889 1.4736 3-3 10.367 8.5530 10.89 35.937 1.8166 1.4888 3-4 10. 681 9.0792 11.56 39 304 1.8439 1.5037 3-5 10.996 9.6211 12.25 42.875 1.8708 I. 5183 3.6 II. 310 10.179 12.96 46.656 1.8974 1.5326 3-7 11.624 10.752 13.69 50.653 1.9235 I . 5467 3.8 11.938 11.341 14 44 54.872 1.9494 t.5605 3-9 12.252 11.946 15.21 59-319 1.9748 1.5741 4.0 12.566 12.566 16.00 64.000 2.0000 1-5874 4-1 12.881 13-203 16.81 68.921 2.0249 1.6005 4-2 13.195 13-854 17.64 74.088 2.0494 I. 6134 4-3 13 509 14-522 18.49 79-507 2.0736 I. 6261 4-4 13-823 15.205 19.36 85.184 3.0976 1.6386 4S 14-137 15-904 20.25 91.125 2.1213 I. 6510 4.6 14.451 16.619 21.16 97.336 2.1448 I. 6631 4.7 14.765 17-349 22.09 103.823 2.1680 I 6751 504 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND C\J'&'£.'S,— Continued. n tlK jr 4 »' «3 r„ a Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 4.8 15.080 18.096 23.04 110.592 2 . 1909 1.6869 4.9 15-394 18.857 24.01 117.649 2.2136 1.6985 5.C 15 • 708 19-635 25.00 125.000 2.2361 I. 7100 5-1 16.022 20.428 26.01 132.651 2.2583 1.72:3 5.2 16.336 21.237 27.04 140.608 2.2804 1-7325 5-3 16.650 22.062 28.09 148.877 2.3022 I - 7435 5-4 16.965 22.902 29.16 157-464 2.3238 1-7544 5-5 17.279 23.758 30.25 166.375 2.3452 1-7652 5-6 17-593 24.630 31.36 175-616 2.3664 1-7758 5-7 17.907 25.518 32-49 185.193 2.3875 1-7863 5-8 18.221 26.421 33-64 195-II2 2.4083 I . 7967 5-9 18.535 27.340 34.81 205-379 2.4290 I . 8070 6.0 18.850 28.274 36.00 216.000 2.4495 1.8:7: 6.1 19.164 29.225 37-21 226.981 is. 4698 :.8272 6.2 19.478 30.191 38-44 238.328 2.4900 1-8371 6.3 19.792 31-173 39.69 250.047 2 . 5 100 1.8469 6.4 20.106 32.170 40.96 262.144 2.5298 1.8566 6.5 20.420 33.183 42.25 274.625 2.5495 : . 8663 6.6 20.735 34-212 43-56 287.496 2.5691 1.8758 6.7 21.049 35-257 44-89 300.763 2.5884 1.8852 6.8 21.363 36-317 46.24 314.432 2.6077 1.8945 6.9 21.677 37-393 47.61 328.509 2.6268 I . 9038 7.0 21.991 38.485 49.00 343-000 2.6458 :.9:29 7-1 22.305 39-592 50.41 357-9" 2.6646 1.9220 7.2 22.619 40-715 51.84 373.248 2.6S33 1.9310 7-3 22.934 41.854 53-29 389-017 2.7019 1.9399 7-4 23.248 43-008 54-76 405.224 2.7203 1-9487 7-5 23.562 44.179 56.25 421.875 2.7386 1-9574 7.6 23.876 45-365 57-76 438.976 2.7568 I. 9661 7-7 24.190 46.566 59-29 456.533 2-7749 1-9747 7.8 24.504 47-784 60.84 474-552 2.7929 1.9832 7-9 24.819 49-017 62.41 493 - 039 2.8107 :.99:6 8.0 25-133 50.266 64.00 512.000 2.8284 2.0000 8.1 25-447 51-530 65.61 531-441 2.846: 2.0083 8.2 25-761 52.810 67.24 551-468 2.8636 2.0165 8.3 26.075 54.106 68.89 571-787 2.8810 2.0247 8.4 26.389 55-418 70.56 592-704 2.8983 2.0328 8.5 26 . 704 56-745 72.25 614.125 2.9155 2 . 0408 8.6 27.018' 58.088 73-96 636.056 2.9326 2.0488 ^7 27-332 59-447 75-69 658.503 2.9496 2.0567 8.8 27.646 60.821 77-44 681.473 2.9665 2.0646 8.9 27.960 62.211 79.21 704.969 2.9833 1S.0724 APPENDIX CONTAINING REFERENCES AND TABLES. S05 CIRCLES, SQUARES, AND Z\i'S^%— Continued. n mt IT 4 «» «' V7, Vn Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 9 28.274 63.617 81.00 729.000 3.0000 2.0801 9.1 28.588 65.039 82.81 753-571 3.0166 2.0878 9.2 28.903 66.476 84.64 778.688 3 0332 2.0954 9-3 29.217 67.929 86.49 804.357 3-0496 2.1029 9-4 29.531 69.398 88.36 830.584 3-0659 2. 1 105 9-5 29.845 70.882 90.25 857-375 3.0822 2.1179 g.6 30.159 72.382 92. 16 884.736 3.0984 2.1253 1 9-7 30.473 73-898 94.09 912.673 3- "45 2.1327 1 9-8 30.788 75.430 96.04 941.192 3 1305 2.1400 9-9 31.102 76-977 98.01 970.299 3.1464 2.1472 10.0 3i-4r6 78.540 100.00 1000.000 3.1623 2.1544 10. 1 31-730 80.119 102.01 1030.301 3-17S0 2.1616 10.2 32.044 81.713 104.04 1061.208 3-1937 2.1687 10.3 32.358 83.323 106.09 1092.727 3.2094 2.1757 10.4 32.673 84.949 108.16 1124.863 3-2249 2.1828 10.5 32.987 86.590 110.25 1157.625 3 ■ 2404 2.1897 10.6 33.301 88.247 112.36 1191 .016 3-2558" 2.1967 10.7 33-615 89.920 114.49 1225.043 3.2711 2 . 2036 10.8 33-929 gl.609 116.64 1259.712 3 2863 2.2104 10.9 34-243 93-313 118.81 I2g5.02g 3-3015 2.2172 II. 34-558 95-033 121.00 1331.000 3.3166 2.2239 11. 1 34-872 96.769 123.21 1367.631 3-3317 2.2307 II. 2 35-186 98.520 125.44 1404. g28 3.3466 2.2374 11-3 35 ■ 500 100.29 127.69 1442.897 3-3615 2.2441 11.4 35-814 102.07 129.96 1481.544 3-3764 2.2506 II. 5 36.128 103.87 132.25 1520.875 3-3912 2.2572 II. 6 36.442 105.68 134-56 1560.896 3-4059 2.2637 II. 7 36.757 107.51 136. Sg 1601.613 3-4205 2.2702 II. 8 37.071 109.36 139.24 1643.032 3-4351 2.2766 II. 9 37-385 III. 22 141. 61 1685.159 3.4496 2.2831 12.0 37.699 113. TO 144.00 1728.000 3.4641 2.2894 12. 1 38.013 114.99 146.41 1771.561 3-4785 2.2957 12.2 38 327 I 16. go 148.84 1815.848 3.4928 2 3021 12.3 38.642 118.82 151.29 1860.867 3 5071 2 . 3084 12.4 38-956 120.76 153-76 1906.624 , 3-5214 2.3146 12-5 39.270 122.72 156.25 1953-125 3-5355 2 . 3208 12.6 39-584 124.69 158.76 2000.376 3 - 5496 2.3270 12.7 39-898 126.68 161.29 2048.383 3-5637 2.3331 12.8 40.212 128.68 163.84 2097.152 3-5777 2.3392 ia.9 40.527 130.70 166.41 2146.689 3-5917 2-3453 13.0 40.841 132.73 169.00 2197.000 3 6056 2.3513 13.1 41-155 134-78 171. 61 2248.091 3-6194 2-3573 13.2 41.469 136.85 174.24 2299.968 3.6332 2.3633 So6 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND ZVi'SE.^— Continued. n 1 nit «> «3 v; 3 Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 13-3 41.783 138.93 176.89 2352.637 3.6469 2.3693 13-4 42.097 141.03 179-56 2406.104 3.6606 2-3753 13-5 42.412 143.14 182.25 2460.375 3.6742 2.3811 13.6 42.726 145-27 184.96 2515.456 3.6S78 2.3870 13.7 43-040 147.41 187.69 2571-353 3.7013 2.3928 13-8 43 -.■'54 149-57 190.44 2628.072 3.7148 2.3986 13.9 43-668 151-75 i93-2t 2685.619 3-7283 2.4044 14.0 43.982 153-94 196.00 2744.000 3-7417 2.4101 14.1 44.296 156.15 198.81 2803.221 3-7550 2.4159 14.2 44.611 158.37 201.64 2863.288 3-7683 2.4216 14-3 44-925 160.61 204.49 2924.207 3.7"i5 2.4272 14.4 45-239 162.86 207.36 2985.984 3-7947 2.4329 14-5 45-553 165.13 210.25 304S.625 3.8079 2.4385 14.6 45.867 167.42 213. 16 3112.136 3.8210 2.4441 14.7 46.181 169.72 216.09 3176.523 3.8341 2-4497 14.8 46.496 172.03 219.04 3241.792 3-8471 2-4552 14-9 46.810 174 -37 222.01 3307.949 3.8600 2.4607 15.0 47-124 176.72 225 . 00 3375- 000 3-8730 2.4662 15. 1 47.438 179.08 228.01 3442.951 3-8859 2.4717 15.2 47-752 181.46 231.04 3511.80S 3.8987 2.4772 15-3 48.066 183.85 234-09 3581.577 3.9115 2.4825 15-4 48.381 186.27 237.16 3652.264 3.9243 2.4879 15.5 15.6 48.695 188.69 240 25 3723.875 3.9370 2-4933 49.009 191. 13 243 . 36 3796.416 3-9497 2.4986 15-7 15-8 49-323 193-59 246.49 3869.893 3.9623 2 . 5039 49-637 196.07 249.64 3944-312 3-9749 2.5092 15-9 49-951 198-56 252.81 4019.679 3-9875 2.5146 16.0 50.265 201.06 256.00 4096.000 4-0000 2.5198 2.5251 16. 1 50.580 203.58 259.21 4173.281 4.0125 16.2 50.894 206.12 262.44 4251-528 4.0249 2.5303 16.3 51.208 208.67 265.69 4330.747 4.0373 2-5355 16.4 51-522 211.24 26S.96 4410.944 4.0497 2.5406 16.5 51-836 213-83 272.25 4492.125 4.0620 2.5458 16.6 52.150 216.42 275.56 4574.296 4-0743 2.5509 16.7 52.465 219.04 278.89 4657-463 4.0866 2.5561 16.8 52.779 221.67 282.24 4741.632 4.0988 2.5612 16.9 53-093 224.32 285.61 4826.809 4. mo 2.5663 17 53-407 226 98 289.00 4913-000 4.1231 2.5713 17. 1 53-721 229.66 292.41 5000.211 4.1352 2.5763 17.2 54-035 132.35 295.84 5088.448 4-1473 2.5813 17-3 54-350 235.06 299.29 5177.717 4-1593 2.5863 2.5913 17-4 54-664 237-79 302.76 5268.024 4.1713 APPENDIX CONTAINING REFERENCES AND TABLES. S^/ CIRCLES, SQUARES, AND ZM'S^?,— Continued. n n-n 4 «« B» -Tn 3 Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 17.5 54-978 240.53 306.25 5359-375 4.1833 2.5963 17.6 55-292 243.29 309. 76 5451.776 4.1952 2.6012 17-7 55-606 246.06 313.29 5545.233 4.2071 2.6061 17.8 55-920 248.85 316.84 5639.752 4.2190 2.6109 17-9 56-235 251.65 320.41 5735.339 4-2308 2.6158 18.0 56.549 254-47 324-00 5832.000' 4.2426 2 . 6207 18. 1 56.863 257.30 327.61 5929 741 4.2544 2.6256 18.2 57-177 260.16 33t-24 6028 . 568 4.2661 2 . 6304 18.3 57-491 263.02 334-89 6128.487 4.2778 2.6352 18.4 57-805 265.90 338.56 6229.504 4.2895 2 . 6401 18.5 58.119 268.80 342-25 6331.625 4.3012 2 . 6448 18.6 58.434 271.72 345-96 6434.856 4.312S 2.6495 18.7 58.748 274-65 349.69 6539.203 4.3243 2 . 6543 18.8 59-062 277-59 353-44 6644.672 4.3359 2.6590 18.9 59-376 .280.55 357-21 6751.269 4-3474 2.6637 19.0 59 690 283.53 361.00 6859.000 4-3589 2.6684 19. 1 60.004 286.52 364.81 6967.871 4-3703 2.6731 19.2 60.319 289.53 . 368.64 7077.888 4-3818 2.6777 19-3 60,633 292.55 372-49 7189.057 4-3932 2.6824 19-4 60.947 295.59 376.36 7301-384 4.4045 2.6869 19-5 6r.26i 298.65 380.25 7414-875 4.4159 2.6916 19.6 61.575 301.72 384-16 7529-536 4-4272 2 . 6962 19-7 61.889 304.31 388.09 7645-373 4-4385 :i.7008 19.8 62.204 307-91 392-04 7762.392 4-4497 2.7053 19.9 62.518 311.03 396-01 7880.599 4.4609 2 . 7098 20.0 62.832 314.16 400.00 8000.000 4.4721 2.7144 20.1 63.146 317.31 404.01 8120.601 4.4833 2.7189 20.2 63.460 320.47 408.04 8242.408 4-4944 2.7234 20.3 63-774 323.66 .412.09 8365.427 4-5055 2.7279 20.4 64.0S8 326 85 416.16 8489.664 4.5166 2.7324 20.5 64.403 330.06 420.25 8615.125 4-5277 2.7368 20.6 64.717 333-29 424.36 8741.816 4-5387 2.7413 20.7 65.031 336.54 428.49 8,869.743 4-5497 2.7457 20.8 65.345 339-80 432.64 8989.912 4-5607 2.7502 20.9 05-659 343.07 436.81 9129.329 4-5716 2-7545 Si.o 65-973 346.36 441.00 9261.000 4.5826 2-7589 21. 1 66.288 349.67 445.21 9393-931 4-5935 2.7633 21.2 66.602 352.99 449-44 9528.128 4.6043 2.7676 21.3 66.gi6 356.33 453.69 9663.597 4.6152 2 . 7720 21.4 67.230 359.68 457.96 9800.344 4.6260 2.7763 21-5 67.544 363.05 462.25 9938.375 4.6368 2.7806 21.6 67.858 366.44 466.56 10077.696 4-6476 2.7849 • 21.7 68.173 369.84 470.89 10218.313 4.6589 2.7893 S08 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CM'Q^?,— Continued. n nw IT «' n' ♦'; Diam, Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 21.8 68.487 373.25 475.24 10360.232 4.6690 2.793s 31.9 68.801 376.69 479-61 10503.459 4-6797 2.7978 22.0 69.115 380.13 484 . 00 10648.000 4 . 6904 2 . 8021 22.1 69.429 383.60 488.41 10793.861 4.7011 2.8063 22.2 69-743 387.08 492.84 10941.048 4.7117 2.8105 22.3 70.058 390-57 497-29 11089.567 4.7223 2.8147 22.4 70.372 394.08 501.76 11239.424 4.7329 2.8189 22.5 70.686 397-61 506.25 11390.625 4-7434 2.8231 22.6 71.000 401.15 510.76 I1543.176 4-7539 2.8273 22.7 71.314 404-71 515-29 11697.083 4-7644 2.8314 22.8 71.268 408.28 519-84 11852.352 4-7749 2-8356 22.9 71.942 411.87 524.41 12008.989 4-7854 2 8397 23.0 72.257 415-48 529.00 12167.000 4.7958 2.8438 23.1 72.571 419. 10 533-61 12326.391 4.8062 2.8479 23.2 72.885 422.73 538-24 12487.168 4.8166 2.8521 23-3 73-199 4-26.39 542.89 12649.337 4.8270 2.8562 23.4 73.5I3 430.05 547-56 12812.904 4-8373 2.8603 23-5 73-827 433-74 552.25 12977.875 4.8477 2.8643 23.6 74.142 437-44 556.96 13144.256 4-8580 2.8684 237 74-456 441-15 561.69 13312.053 4-8683 2.8724 23.8 74-770 444.88 566.44 13481.272 4.8785 2.8765 23.9 75-084 448.63 571.21 13651.919 4.8888 2.8803 24.0 75-398 452.39 576 00 13824.000 4.8990 2.8845 24.1 75-712 456.17 580.81 13997.521 4.9092 2.8885 24.2 76.027 459-96 585.64 14172.488 4-9193 2 . 8925 24-3 76.341 463.77 590.49 14348.907 4.9295 2.8965 24-4 76.655 467.60 595-36 14526.784 4.9396 2 . 9004 24.5 76.969 471-44 600.25 14706.125 4-9497 2.9044 24.6 77-283 475.29 605.16 14886.936 4-9598 2.9083 24.7 77-597 479.16 610.09 15069.223 4-9699 2.9123 24.8 77.911 483-05 615.04 15252.992 4-9799 2.9162 24.9 78.226 486.96 620.01 15438.249 4.9899 2 . 9201 25.0 78.540 490.87 625.00 15625.000 5.0000 2.9241 25-1 78.854 494-81 630.01 15813.251 5-0099 2.9279 25-2 79.168 498.76 635.04 16003.008 5-0199 2.9318 25-3 79-482 502.73 640.09 16x94.277 5-0299 2.9356 25-4 79.796 506.71 645.16 16387.064 5-0398 2.9395 25-5 80. Ill 510.71 650.25 16581.375 5.0497 2.9434 25.6 80.425 514-72 655.36 16777.216 5.0596 ■ 2.9472 25-7 80.739 518.75 660 . 49 16974-593 5.0695 2.9510 25.8 81.053 522.79 665.64 17173-512 5.0793 2-9549 25.9 81.367 526.85 670.81 17373-979 5.0892 2.9586 APPENDIX CONTAINING REFERENCES AND TABLES. 509 CIRCLES, SQUARES, AND CXi'SZ?,— Continued. n HIT 4 «» K« •Tn 3 V7, Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. a6.o 81.681 530.93 676.00 17576.000 5-0990 2.9624 46.1 81.996 535 -02 681. 21 17779.581 5 . 1088 2 . 9662 26.2 82.310 539-13 686.44 17984-728 :-ii85 2.9701 26.3 82.624 543-25 691.69 18191.447. 5-1283 2.9738 26.4 82.938 547-39 696.96 18399.744 5.1380 2.9776 86.5 83.252 551-55 702.25 18609.625 5-1478 2.9814 26.6 83.566 555-72 707-56 18821.096 5-1575 2.9851 26.7 83.881 559-90 712.89 19034. 163 5.1672 2.9888 26.8 84-195 564.10 718.24 19248.832 r . 1768 2 . 9926 26.9 84.509 568.32 723-61 19465 . 109 5.1865 2.9963 27.0 84.823 572-56 729.00 19683.000 5.1962 3.0000 27-1 85-137 576.80 734-41 19902.511 5.2057 3.0037 i-1.2 85-451 581.07 739-84 20123.648 5-2153 3-0074 27.3 85-765 585-35 745-29 20346.417 5.2249 3.OIII 27.4 86.080 589-65 750.76 20570.824 5.2345 3-0147 27-5 86.394 593 96 756-25 20796.875 5.2440 3-0184 27.6 86.708 598.29 761.76 21024.576 5-2535 3.0221 27-7 87.022 602.63 767.29 21253.933 5.2630 3-0257 27.8 87 336 606.99 772-84 21484.952 5-2725 3.0293 27.9 87.650 611.36 778.41 21717.639 5.2820 3.0330 28.0 87-965 615-75 784.00 21952.000 5-2915 3.0366 28.1 88.279 620. 16 789.61 22188.041 5-3009 3-0402 28.2 88.593 624.58 795-24 2242. .768 5-3103 3-0438 28.3 88.907 629.02 800.89 22 65.187 5-3197 3-0474 28.4 89.221 633-47 806.56 22906.304 5-3291 3-0510 28.5 89-535 637-94 812.25 • 23149.125 5-3385 3.0546 28.6 89.850 642.42 817.96 23393.656 5-3478 3.0581 28.7 90 164 646.93 823.69 23639.903 5-3572 3-0617 28.8 90.478 651.44 829.44 23887.872 5-3665 3-0652 28.9 ,90.792 655-97 835-21 24137.569 5-3758 3.0688 29.0 91 . io6' 660.52 841.00 24389.000 5-3852 3.0723 29.1 91 .420 665.08 846.81 24642.171 5 - 3944 3-0758 29.2 91-735 669.66 852.64 24897.088 5-4037 3 0794 29.3 92.049 674.26 858-49 25153-757 5-4129 3.0829 29-4 92.363 678.87 864.36 25412.184 5.4221 3.0864 29 5 92.677 6S3.49 870.25 25672.375 5-4313 3.0899 29.6 92.991 688.13 876.16 25934-336 5-4405 3-0934 29.7 93-305 692 . 79 882.09 26198.073 5-4497 3.0968 29.8 29.9 93.619 697-47 888.04 26463.592 5-4589 3.1003 93-934 702.15 894.01 26730.899 5.4680 3-1038 30.0 30.1 94.248 706.86 900.00 27000.000 5-4772 3.1072 94.562 711.58 906.01 27270.901 5-4863 3-I107 30.2 94.876 716.32 912.04 27543.608 5-4954 3-II4I S'O APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND QV'SK?,— Continued. n ntr IT ""4 »' «s ■ v;. 3 Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 30.3 95.190 721.07 918.09 27818.127 5-5045 3.1176 30.4 95 ■ 505 725-83 924.16 28094.464 5-5136 3.1210 30-5 95.819 .730.62 930.25 28372.625 5.5226 3-1244 30.6 96.133 735-42 936.36 28652.616 5.5317 3-1278 30.7 96.447 740.23 942.49 28934.443 5.5407 3-1312 30.8 96.761 745.06 948 . 64 29218. 112 5.5497 3-1346 30.9 97-075 749.91 954-81 29503.629 5.5587 3.1386 310 97-389 754-77 961.00 29791.000 5-5678 3.1414 31 i 97.704 759.65 967.21 30080.231 5.5767 3.1448 31.2 98.018 764.54 973-44 30371.328 55857 3.1481 31-3 98-332 769.45 979-69 30664.297 5 - 5946 3.1515 31.4 98.646 774.37 985.96 30959.144 5-6035 3-1548 31-5 98.960 779-31 992-25 31255.875 5.6124 3-1582 31.6 90-274 784.27 998.56 31554.496 5.6213 3.1615 31-7 99.588 789.24 1004 . 89 31855-013 5.6302 3 - 1648 31.8 99-903 794-23 1011.24 32157-432 5.6391 3.1681 31.9 100.22 799 23 1017.61 32461.759 5.6480 3-1715 320 100.53 804.25 1024.00 32768.000 5-6569 3.1748 32.1 100.85 809.28 1030.41 33076.161 5-6656 3-1781 32.2 loi. 16 814-33 1036.84 33386.248 5-6745 3-1814 32.3 101.47 819.40 1043.29 3369S.267 5-6833 3-1847 32.4 101.79 824.48 1049.76 34012.224 5.6921 3-i88o 32-5 102.10 829.58 1056.25 34328.125 5-7008 3-1913 32-6 102.42 834.69 1062.75 34645-976 5-7096 3-1945 32.7 102.73 839.82 1069.29 34965.783 5-7183 3.1978 32.8 103.04 844 . 96 1075.84 35287.552 5.7271 3.2010 32.9 103 . 36 850.12 1082.41 35611.289 5-7358 3.2043 330 103.67 855-30 1089.00 35937.000 5.7446 3-2075 33-1 103.99 860.49 1095.61 36264.691 5.7532 3.2108 33-2 104.30 865.70 1102.24 36594.368 5.7619 3-2140 33-3 104.62 870.92 1108.89 36926.037 5.7706 3-2172 33.4 104.93 876.16 1115.56 37259-704 5.7792 3 - 2204 33-5 105.24 881.41 1122.25 37595-375 5.7S79 3-2237 33-6 105.56 886.68 1128.96 37933.056 5.7965 3.2269 33-7 105.87 891.97 1135.69 38272.753 5.8051 3-2301 33-8 106.19 897-27 1142.44 38614.472 5.8137 3-2332 33-9 106.50 902.59 1149.21 38958.219 5.8223 3-2364 34.0 106.81 907.92 1156.00 39304.000 5.8310 3.2396 34- 1 107-13 913.27 1162.81 39651.821 5-8395 3-2428 34-2 107.44 918.63 1169.64 40001 . 683 5.8480 3.2460 34-3 107.76 924.01 1176.49 40353.607 5.8566 3-2491 34-4 108.07 929.41 H83.36 40707 . 584 5.8651 3-2524 4PPENDIX CONTAINING REFERENCES AND TABLES. S 1 1 CIRCLES, SQUARES, AND CXi'QYJS,— Continued. n 711T IT 4 k' »' ^« s Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 34-5 108.38 934-82 1190.25 41063.625 5-8736 3-2554 34-6 108.70 940.25 1197.16 41421.736 5.8821 3-2586 34-7 109.01 945.69 1204.09 41781.923 5.8906 3.2617 34-8 109.33 951-15 1211.04 42144.192 5.8991 3 - 2648 34-9 109.64 956.62 I218.OI 42508.549 5 ■ 9076 3-267q 35-0 109 . 96 962.11 1225.00 42875.000 5.9161 3.2710 35-1 110.27 967.62 1232.01 43243-551 5-9245 3.2742 35-2 110.58 973-14 1239.04 43614.208 5-9329 3.2773 35-3 iio.go 978.68 1246.09 43986.977 5.9413 3-2804 35-4 III. 21 984.23 1253.16 44361 . 864 5-9497 3-2835 35-5 "I-53 989 . 80 1260.25 44738.875 5-9581 3.2866 35-6 III. 84 995-38 1267.36 45118.016 5.9665 3-28'97 35-7 112. 15 1000.98 1274.49 45499.293 5-9749 3-2927 35-8 112.47 1006.60 1281.64 45882.712 5-9833 3-2958 35-9 112.78 1012.23 1288.81 46268.279 5.9916 3.2989 36.0 113.10 1017.88 1 296 . 00 46656 000 6 . 0000 3 • 3019 36.1 113.41 1023.54 1303.21 47045.881 6.0083 3-3050 36.2 113-73 1029.22 1310.44 47437-928 6.0166 3.3080 36.3 114.04 1034.91 1317.69 47832.147 6.0249 3-31" 36.4 114-35 1040.62 1324-96 48228.544 6.0332 3-3141 39-5 114.67 1046.35 1332.25 48627.125 6.0415 3-3171 36.6 114.98 1052.09 1339-56 49027.896 6.0497 3.3202 36 7 115.30 1057.84 1346.89 49430.863 6.0580 3.3232 36.8 115-61 1063.62 1354-24 49836.032 6.0663 3 3262 36.9 115.92 1069.41 I361.61 50243.409 6.0745 3-3292 37-0 116.24 1075.21 1369.00 50653.000 6.0827 3-3322 37-1 "6.55 1081.03 1376.41 51064.811 6 . 0909 3-3352 37-2 116.87 1086.87 1383-84 51478.848 6.oggi 3-3382 37.3 ,117.18 1092.72 1391.29 51895.117 6.1073 3-3412 37-4 117.50 1098.58 1398.76 52313.624 6-115,5 3-3442 37-5 117.81 1104.47 1406.25 52734-375 6.1237 3-3478 37-6 118. 12 1110.36 1413.76 53157-376 6.1318 3-3501 37-7 118.44 IH6.28 1421.29 53582.633 6.1400 3-3531 37.8 118.75 1122.21 1428.84 54010.152 6.1481 3-3561 37-9 119.07 1128.15 1436.41 54439-939 6.1563 3 ■ 3590 38.0 119-38 II34-" 1444.00 54872.000 6.1644 3 . 3620 38.1 119.69 1140.09 1451.61 55306.341 6.1725 3.3649 38.2 120.01 1146.08 1459.24 , 55742-968 6.1806 3-3679 38.3 120.32 1152.09 1466.89 561S1.887 6.1887 3-3708 38.4 120.64 1158.12 1474.56 56623.104 6.1967 3-37.37 38.5 120.95 1164.16 1482.25 57066.625 6 , 2048 3-3767 38.6 121.27 1170.21 1489 . 96 57512.456 6.2129 3-3796 38.7 T21.58 1176.28 1497.69 57960.603 6.2209 3-3825, 512 APPENDIX CONTAINING REFERENCES AND TABLES. CIRCLES, SQUARES, AND CXi^'E'S,— Continued. ft mr TT "'4 k' ,1' Vn 3 Diam. Circumf. Area. S^iuare. Cube. Sq. Root. Cub. Rt. 38.8 121.89 1182.37 1505.44 58411.072 6.2289 3.3854 38-9 122.21 1188.47 I513-21 58863.869 6.2370 3.3883 39.0 122.52 1194.59 1521.00 59319.000 6.2450 3.3912 39-1 122.84 1200.72 1528.81 59776.471 6.2530 3.3941 39.2 123.15 1206.87 1536-64 60236.288 6.2610 3.3970 39.3 123.46 1213.04 1544-49 60698.457 6.2689 3.3999 39.4 123.78 1219.22 1552.36 61162.984 6.2769 3.4028 39-5 124.09 1225.42 1560.25 61629.875 6.2849 3.4056 39.6 124.41 1231.63 1568.16 62099.136 6.2928 3.4085 39.7 124.72 1237.86 1576.09 62570.773 6 . 3008 3.4114 39-8 125.04 1244. 10 1584.04 63044.792 6.3087 3.4142 39.9 125.35 1250.36 1592.01 63521.199 6.3166 3.4171 40.0 125.66 1256.64 1600.00 64000 . 000 6-3245 3.4200 40.1 125.98 1262.93 1608.01 64481.201 6.3325 3.4228 40.2 126.29 1269.23 1616.04 64964 . 808 6.3404 3.4256 40.3 126.61 1275.56 1624.09 65450.827 6.3482 3.4285 40.4 126.92 1281.90 1632.16 65939.264 6.3561 3.4313 40.5 127.23 1288.25 1640.25 66430.125 6,3639 3.4341 40.6 127.55 1294.62 1648.36 66923.416 6.3718 3.4370 40.7 127.86 1301.00 1656.49 67419.143 6.3796 3 4398 40.8 128.18 1307.41 1664.64 679II.3I2 6.3875 3.4426 40-9 128.49 1313.82 1672.81 68417.929 6.3953 3-4454 41.0 128.81 1320.25 1681.00 68921.000 6.4031 3-4482 41. 1 129.12 1326.70 1689.21 69426.531 6.4109 3.4510 41.2 129.43 1333.17 1697.44 69934.528 6.4187 3-4538 41-3 129.75 1339-65 1705.69 70444.997 6.4265 3-4566 41-4 130.06 1346.14 1713.96 70957.944 6.4343 3-4594 41-5 130.38 1352.65 1722.25 71473-375 6.4421 3 . 4622 41.6 130.69 1359.18 1730.56 71991.296 6.4498 3.4650 41-7 131.00 1365,72 1738.89 725II.7I3 6-4575 3.4677 41.8 131.32 1372 28 1747.24 73034.632 6.4653 3.4705 41.9 131.63 1378.85 1755.61 73560.059 6.4730 3.4733 42.0 131-95 1385.44 1764.00 74088.000 6.4807 3.4760 42.1 132.26 1392.05 1772.41 74618.461 6.4884 3.4788 42.2 132.58 1398.67 1780.84 75151-448 6.4961 3-4815 42.3 132.89 1405.31 1789.29 75686,967 6.5038 3 - 4843 42.4 133.20 1411.96 1797.76 76225 ,024 6.5115 3-4870 42.5 133-52 1418.63 1806.25 76765-625 6.5192 3-4898 3-4925 3-4952 3.4980 42.6 133-83 1425.31 1814.76 77308.776 6.5268 42.7 134-15 1432.01 1823.29 77S54-483 6-5345 42.8 134.46 1438.72 1831.84 78402.752 6.5422 42.9 134-77 1445-45 1840.41 7S953-5S9 6.5498 3-5007 APPENDIX CONTAINING REFERENCES AND TABLES. SI3 CIRCLES, SQUARES, AND ZVi'&'^'i— Continued. n «7r 4 Area. «= «» ^/n 3 Ciam. Circumf. Square. Cube. Sq. Root. Cub. Rt. 43 -o 135-09 1452.20 1849.00 79507.000 6.5574 3-5034- 43- i 135.40 1458.96 1857.61 80062.991 6.5651 3-5061 43-2 135-72 1465-74 1 866. 24 80621.568 6-5727 3-5088 43-3 136.03 1472-54 1874.89 81182.737 6.5803 3-5115 43-4 136-35 1479-34 1883,56 81746.504 6.5879 3.5142 43-5 136.66 1486.17 1892.25 82312.875 6.5954 3-5169 43-6 136-97 1493 01 1900.96 82881.856 6 . 6030 3-5196 43-7 137.29 1499.87 1909.69 83453-453 6.61C6 3.5223 43-8 137-60 1506.74 1918.44 84027.672 6.6182 3-5250 43-9 137-92 1513.63 1927.21 84604.519 6.6257 3-5277 44.0 138.23 1520.53 1936.00 85184.000 6.6333 3-5303 44.1 138.54 1527-45 1944.81 85766.121 6.6408 3-5330 44.2 138.86 1534-39 1953.64 86350.888 b.6483 3-5357 44-3 139-17 154^-34 1962.49 86938.307 6.6558 3-5384 44-4 139-49 1548-30 1971-36 87528.384 6.6633 3 5410 44-5 139.80 1555-28 1980.25 88121.125 6.S708 3-5437 44.6 140.12 1562.28 1989.16 88716.536 6.6783 3 • 5463 44-7 140.43 1569.30 1998.09 89314.623 6.6S58 3 - 5490 44.8 140.74 1576.33 2007 . 04 89915.392 6.6933 3-5516 44-9 141.06 1583-37 2016.01 90518.849 6 . 7007 3-5543 45.0 141.37 ■ 1590-43 2025.00 91125.000 6.7082 3-5569 45 I 141.69 1597-51 2034.01 91733.851 6.7156 3-5595 45-2 142.00 1604 . 60 2043.04 92345. 40S 6.7231 3-5621 45-3 142.31 1611.71 2052.09 92959.677 6.7305 3.5648 45-4 142.63 1618.83 2061.16 93576.664 6.7379 3 ■ 5674 45-5 142-94 1625.97 2070.25 94196.375 6.7454 3.5700 45.6 143.26 1633.13 2079 . 36 94818.816 6.7528 3.5726 45-7 143-57 1640.30 2088.49 95443.993 6.7602 3.5752 45-8 143-88 1647.48 2097 . 64 96071.912 6.7676 3-5778 ■ 45-9 144.20 1654.68 2106.81 96702.579 6.7749 3-5805 1 ' 46.0 144-51 1661. go 2116.00 97336.000 6.7823 3-5830 46.1 144-83 1669.14 2125.21 97972.181 6.7897 3 5856 46.2 145 . 14 1676.39 2134.44 98611.12S 6.7971 3.5882 46-3 145.46 1683.65 2143.69 99252.847 6.8044 3-5908 46.4 145-77 1690.93 2152.96 99897.344 6.8117 3-5934 46-5 146.08 1698.23 2162.25 100544.625 6.8191 3.5960 46.6 146.40 1705-54 2171.56 101194.696 6.8264 3-5986 46.7 146.71 1712.87 2180.89 101847.563 6.8337 3.60U 46.8 147-03 1720.21 2190.24 102503.232 6.8410 3-6037 46.9 147-34 1727-57 2199.61 103161.709 6.8484 3-6063 47.0 147-65 1734-94 2209.00 103823.000 6.8556 3.6088 47.1 147-97 1742.34 2218.41 104487. Ill 6.8629 3.6114 47.2 148.28 1749-74 2227.84 105154.048 6.8702 3.6139 514 APPENDIX CONTAINING REFESENCES AND TABLES. CIRCLES, SQUARES, AND CM^'ES,— Continued. n nrr 4 «» «» ^'n 3 Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 47-3 148.60 1757-16 2237.29 105823.817 6-8775 3.6165 47-4 148.91 1764 60 2246.76 106496.424 6.8847 3.6190 47-5 149.23 1772.05 2256.25 107171.875 6.8920 3.6216 47.6 149-54 1779-52 2265.76 107850.176 6.8993 3.6241 47-7 149-85 1787.01 2275.29 108531.333 6.9065 3 6267 47-8 150.17 1794 51 2284.84 109215.352 6.9137 3.6292 47 9 150.48 1802.03 2294.41 109902.239 6 . 9209 3.6317 48.0 150.80 1809.56 2304 . 00 110592.000 6.9282 3.6342 48.1 151. n 1817.H 2313-61 111284.641 6.9354 3-6368 48.2 151.42 1824.67 2323.24 111980.168 6 . 9426 3-6393 48.3 I5I-74 1832.25 2332.89 112678.587 6.9498 3-6418 48.4 152.05 1839-84' 2342.56 113379-904 6.9570 3-6443 48.5 152-37 1847-45 2352.25 114084.125 6.9642 3.646a 48.6 152.68 1855.08 2361.96 114791-256 6.9714 3-6493 48.7 153.00 1862.72 2371-69 115501.303 6.9785 3-6518 48.8 153-31 1870.38 2381.44 I16214.272 6.9857 3-6543 48.9 153-62 1878.05 2391.21 116930.169 6.9928 3-6568 49.0 153-94 1885.74 2401.00 117649.000 7.0000 3-6593 49.1 154-25 1893,45 2410.81 118370.771 7.0071 3.6618 49.2 154-57 1901.17 2420.64 119095.488 7-0143 3.6643 49-3 154.88 1908 . 90 2430.49 119823.157 7.0214 3.6668 49-4 155-19 1916.65 2440.36 120553.784 7.0285 3.6692 49-5 155-51 1924.42 2450.25 121287.375 7.0356 3-6717 49.6 155-82 1932.21 2460.16 122023.936 7 0427 3-6742 49-7 156.14 1940.00 2470.09 122763.473 7.0498 3-6767 49.8 156.45 1947.82 2480.04 123505.992 7.0569 3-6791 49.9 156.77 1955-65 2490.01 124251.499 7.0640 3.6816 50.0 157-08 1963.50 2500.00 125000.000 7.0711 3.6840 51.0 160.22 2042 . 82 2601.00 132651.000 7.1414 3.7084 52-0 163.36 2123.72 2704.00 140608 . 000 7.2111 3-7325 53-0 166.50 2206.19 2809.00 148877.000 7.2801 3.7563 54.0 169.64 2290.22 2916.00 157464.000 7-3485 3 • 7798 55-0 172.78 2375-83 3025 . 00 166375.000 7.4162 3-8030 56.0 175 93 2463.01 3136.00 175616.000 7-4833 3.8259 57-0 17907 2551.76 3249.00 185193.000 7-5498 3-8485 58.0 182.21 2642.08 3364.00 195112.OCO 7.6158 3 - 8709 590 185-35 2733.-7 34SI.00 205379.000 7.6811 3.8930 60.0 188.49 2827.44 3600 . 00 216000.000 7 - 7460 3-9149 61.0 191.63 2922.47 3721.00 226981.000 7.8102 3-9365 62.0 194-77 3019.07 3844.00 23S328.OOO 7.8740 3-9579 63.0 197.92 3117-25 3969-00 250047.000 7-9373 3-9791 64.0 201.06 3216.99 4096 . 00 262144.000 8.0000 4.0000 65.0 204.20 3318.31 4225.00 274625.000 8.0623 4.0207 66.0 207.34 3421.20 4356.00 287496.000 8.1240 4.0412 APPENDIX CONTAINING REFERENCES AND TABLES. 5 1 5 CIRCLES, SQUARES, AND CXiS^S—Contimied. n «T tfl kS >/n a Diam. Circumf. Area. Square. Cube. Sq. Root. Cub. Rt. 67.0 210.48 3525.66 4489.00 300763.000 8.1854 4.0615 68.0 213-63 3631-69 4624.00 314432.000 8 2462 4 0817 6g.o 216.77 3739-29 4761.00 328509.000 8 3066 4 1016 70.0 219.91 3848.46 4900 . 00 343000.000 8 3666 4 1213 71.0 223.05 3959.20 5041 .00 357911.000 8 4261 4 1408 72.0 226.19 4071.51 5184.00 373248-000 8 4853 4 1602 73.0 229.33 4185.39 5329.00 389017.000 8 5440 4 1793 74.0 232.47 4300.85 5476.00 405224.000 8 6023 4 1983 75.0 235.62 4417-87 5625.00 421875.000 8 6603 4 2172 76.0 238.76 4536-47 5776.00 438976.000 8 7178 4 2358 77.0 241.90 4656-63 5929 00 456533 000 8 7750 4 2543 78.0 245.04 4778-37 6084.00 474552-000 8 318 4 2727 79.0 248.18 4901 -68 6241.00 493039.000 8 S882 4 2908 80.0 251.32 5026-56 6^00.00 512000.000 8 9443 4 3089 81.0 254-47 5153-01 6561.00 531441.000 9 0000 4 3267 82.0 257-61 5281-03 6724.00 551368.000 9 0554 4 3445 83.0 260.75 5410.62 6889.00 571787-000 9 1 104 4 3621 84.6 263.89 5541-78 7056.00 592704.000 9 1652 4 3795 85.0 267.03 5674-50 7225.00 614125.000 9 "195 4 3968 86.0 270.17 5808.81 7396.00 636056 . 000 9 2736 4 4140 87.0 273-32 5944- 6g 7569.00 658503.000 9 3274 4 4310 88.0 276.46 6082.13 7744-00 681472.000 9 3808 4 4480 89.0 279 . 60 6221.13 7921.00 704969.000 9 4340 4 4647 90.0 282.74 .6361.74 8100.00 729000.000 9 4868 4 4814 91.0 285.88 6503.89 8281.00 753571-000 9 5394 4 4979 92.0 289.02 6647.62 8464.00 778688.000 9 5917 4 5144 93.0 292. 17 6792.92 8649 . 00 804357.000 9 6457 4 5307 94.0 295-31 6939-78 8836.00 830584.000 9 6954 4 5468 95-0 298.45 7088 . 23 9025.00 857375-000 9 7468 4 5629 96.0 301.59 7238.24 9216.00 884736.000 9 7980 4 5789 97.0 304-73 7389-83 9409 . 00 912673.000 9 8489 4 5947 98.0 • 307-87 7542.98 9604 . 00 941192.000 9 8995 4 6104 99. 311.02 7697.68 gSoi.oo 970299.000 9 9499 4 6261 lOO.O 314-16 7854.00 10000.00 1000000.000 10.0000 4.6416 5l6 APPENDIX CONl'AINING REFERENCES AND TABLES. Table No. VI. CIRCUMFERENCES AND AREAS OF CIRCLES.* Diam. Circum Area. Diam. Circum. Area. Diam. Circum, Area. I 3.1416 0.7854 65 204.20 3318 31 129 130 405.27 13069.81 2 6.2832 3.1416 66 207.34 3421.19 408.41 13273.23 3 9.4248 7.0686 67 210.49 3525.6s 131 411-55 13478.22 4 12.5664 12.5664 68 213.63 3631.68 132 414.69 13684.78 5 15.7080 '9-635 69 216.77 3739-28 133 417.83 13892.91 6 18.850 28.274 70 219.91 3848.45 134 420.97 14102.61 7 21.991 38-485 7' 223.0s 3959-19 135 424.12 14313.88 t' 25-133 50.266 72 226.19 4071.50 136 427.26 14526.72 Q 28.274 63-617 73 229.34 4185.39 137 430,40 14741.14 10 31.416 78 S40 74 232.48 4300.84 138 433-54 14957.12 11 34-558 95-033 75 235.62 4417.86 139 436.68 15174.68 12 37-699 113.10 76 238,76 4536.46 140 439.82 15393.80 '3 40.S41 132 73 77 241.90 4656.63 141 442.96 15614.50 14 43.982 '53.94 78 245-04 4778.36 142 446 11 15836.77 i=i 47 124 176.71 21 248.19 4901 67 143 449.25 i6o6u.6i i6 50.265 201.06 80 251-33 5026.55 144 452.39 16286.02 ■7 53.407 226.98 81 254-47 5153.00 145 455-53 16513.00 i8 56.549 254-47 82 257-61 5281.02 146 458.67 16741,55 10 59.690 283-53 83 260.75 5410.61 147 461.81 16971,67 20 62.832 314-16 84 263 . 89 5541-77 148 464.96 1 7203 , 36 21 65-973 346.36 85 267.04 5674.50 149 468.10 17436,62 22 69.115 380.13 86 270.18 5808 . 80 150 471.24 17671-46 23 72.257 415.48 87 273-32 5944 68 151 474 -.38 17907 86 24 75.398 452 . 39 88 270.46 6082.12 152 477-52 18145,84 25 78.540 490-87 h 279 60 6221 .14 153 480.66 18385,39 26 8i.68i 530-93 90 282.74 6361,73 154 483.81 1 8^26, 50 27 84.823 572-56 91 285.88 6503 , 88 155 486 95 1 8S69 . 19 28 87.965 615,75 92 29. 03 6647.61 156 490.09 I9113.45 11 91.106 660.52 93 292.17 6792.91 IS7 493 - 23 19359,28 94 - 248 706.86 94 295 31 6939.78 158 496.37 19606. 68 31 97-389 754.77 95 298.45 7088.22 159 499.51 19855.65 32 100.53 804.25 96 301-59 7238.23 160 502 65 20106.19 33 103.67 855.30 97 304.73 7389.81 161 505.80 20358.31 34 106.81 907.92 98 307-88 7542 . 96 162 508.94 20611.99 35 109.96 962.11 -.kl 311.02 7697-69 163 512-08 20867.24 ■36 IT3-10 1017.88 100 314.16 7853-98 164 515 22 21124.07 37 116.24 1075.21 101 317.30 Sou 85 i6s 518.36 21382.46 3S 119.38 1134.11 102 320.44 8171.28 166 521,50 21642.43 11 122.52 1194.59 103 321.58 8332.29 167 524 6s 21903.97 22167.08 125 66 1256.64 104 326-73 8494.87 168 527.79 41 128.81 1320.25 'OS 329-87 8659.01 169 530.93 22431,76 42 '31 95 1385.44 106 333.01 8824.73 170 534 07 22698.01 43 135-09 1452.20 107 336.15 8992-02 171 537.21 22965 . 83 44 138-23 '520.53 108 339.29 9160.88 172 540 35 23235.22 45 '41-37 '590.43 lr>9 342.43 9331 -32 173 543 50 23506,18 46 144-S1 ' 66 1 . 90 HO 345.58 9503.32 174 546.64 23778.71 47 147-65 ■734.94 III 348-72 9676.89 '75 549-78 24052.82 48 150 80 1809 56 112 351 86 9852.03 176 552.92 24328 49 49 '53 94 '885.74 "3 355.00 100-28.75 177 556.06 24605.74 24884.56 25164.94 25446.90 25730.43 50 157.08 1963 50 114 358.14 10207 03 178 559-20 51 ifio.22 2042.82 "1 361.28 10386.89 'ill 562.3s 52 163.36 2121!. 72 116 364.42 10568.32 565.49 53 166.50 169 65 2206.18 117 .167.57 10751.32 181 568.63 54 2290.22 118 370.71 1093s 88 182 571.77 26015 53 26302,20 26590.44 55 172.79 237.';. 83 12^ 373.85 11122.02 183 574-91 56 ^75.93 246^.01 376-99 11309-73 184 578-05 ^l 179-07 2551.76 121 380.13 11499.01 185 581.19 26880-25 27171.63 27464.59 27759.11 28055.21 28352,87 28652,11 28952.92 58 182.21 2042.00 122 383 27 11689.87 186 584.34 il '85.3s 188.50 191.64 2733-97 2827.43 123 124 3S6.42 389.56 11882.29 12076.28 187 188 587-48 590.62 61 2922.47 125 392 70 12271.85 189 593-76 62 1Q4.78 3019.07 126 395.84 12468.98 190 596.90 63 197.92 3"7.25 127 398.98 12667.69 191 600,04 64 201 .06 3216.99 128 402.12 12867.96 192 603.19 * From Kent's Poclcet-book for Mechanical Engineers. APPENDIX CONTAINING REFERENCES AND TABLES. "JI/ Table No. VII. LOGARITHMS OF NUMBERS. No, 1 2 S 4 5 6 7 S 9 10 0000 0043 oo«6 0128 0170 0212 0253 0294 0334 03M II 0414 0453 0492 0531 0569 0607 0645 0682 0719 0755 12 0792 0828 0864 0899 0934 0969 1004 1038 1072 1 106 13 "39 '"73 1206 1239 1271 1303 1335 1367 1399 1430 14 1461 1492 1523 1553 1584 1614 1644 1673 1703 1732 IS ,1761 1790 i8i8 1847 187s 1903 1931 1959 1987 2014 16 2041 2068 2095 2122 2148 2175 2201 2227 2253 2279 ^ 2304 2330 2355 2380 2405 2430 2455 2480 2504 2529 2553 2577 2601 2625 2648 2672 2695 2718 2742 2765 19 2788 2810 2833 2856 2878 2900 2923 2945 2967 2989 20 3010 3032 3054 307s 3096 3"8 3139 3160 3181 3201 21 3222 3243 3263 3284 3304 3324 3345 3365 3385 3404 22 3424 3444 3464 3483 35°2 3522 354' 3560 3579 3598 23 3617 3636 3655 3674 3692 37" ■3729 3747 3766 3784 24 3802 3820 3838 3856 3874 3892 3909 3927 3945 3962 25 3979 3997 4014 4031 4048 4065 4082 4099 41 16 4133 26 4150 4166 4183 4200 4216 4232 4249 4265 4281 4298 27 4314 4330 4346 4362 4378 4393 4409 4425 4440 4456 28 4472 4487 4502 4518 4533 4548 4564 4579 4594 4609 29 4624 4639 4654 4669 4683 4698 4713 4728 4742 4757 30 4771 4786 4800 4814 4829 ■4843 4857 487-1 4886 4900 31 4914 4928 4942 4955 4969 49S3 4997 501 1 5024 5038 32 5051 5065 5079 5092 Si°5 5"9 5132 5145 5159 5172 33 S«85 5198 5211 5224 5237 525° 5263 5276 5289 5302 34 5315 5328 S340 5353 5366 5378 5391 5403 5416 5428 35 5441 S4S3 5465 5478 5490 5502 5514 5527 5pg 5551 36 5563 5575 5587 5599 5611 5623 .5635 5647 5658 5670 37 56S2 5694 S7°5 5717 5729 5740 5752 5763 m\ 5786 38 5798 5809 5821 5832 5843 5855 5866 Hi 5888 5899 39 59" 5922 5933 5944 5955 5966 5977 5988 5999 6010 40 6021 6031 6042 6053 6064 6075 60S5 6096 6107 6117 41 6128 6138 6149 6160 6170 6180 6191 6201 6212 6222 42 6232 6243 6253 6263 6274 6284 6294 6304 6314 6325 43 6335 6345 6355 6365 6375 63S5 O395 6405 6415 6425 44 6435 6444 6454 6464 6474 6484 ■6493 6503 6513 ^522 45 6532 6542 6551 6561 6571 6580 .6590 6599 6609 6618 46 6628 6637 6646 6656 6665 6675 6684 6693 6702 6712 47 6721 6730 6739 6749 6758 6767 6776 6785 6794 6803 48 6812 6821 6830 6839 6848 6857 6866 6875 6884 6893 49 6902 691 1 6920 6928 6937 6946 6955 6964 6972 6981 50 6990 6998 7007 7016 7024 7033 7042 7050 7059 7067 51 7076 7084 7093 7101 7110 7118 7126. 7'35 7143 7'52 52 7160 7168 7177 7185 7193 7^02 7210 7218 7226 7235 7316 7396 53 7243 7251 7259 7267 7275 7284 7292 7300 7308 54 7324 7332 7340 7348 7356 7364 7372 7380 7388 No. 1 2 3 4 5 6 7 8 9 Sl8 APPENDIX CONTAINING PEFERENCES AND TABLES. Logarithms of Numbers — Continued. No. 1 2 3 4 5 7 8 9 55 7404 7412 7419 7427 7435 7443 745' 7459 7466 7474 56 7482 7490 7497 7505 7513 7520 7528 7536 7543 755' 57 7559 ■7566 7574 7582 7589 7597 7604 7612 -4^619 7627 58 7634 7642 7649 7&S7 7664. 7672 7679 7686 .7694 7701 59 7709 7716 7723 7731 7738 7745 7752 7760 7767 7774 eo 7782 7789 7796 7803 7Sro 7818 7825 7832 7839 7846 61 7853 7860 7868 787s 7882 7889 7896 7903 7910 7917 62 7924 7931 7938 7945 7952 7959 7966 7973 7980 7987 63 7993 8000 8007 8014 8021- 8028 8035 8041 8048 8055 64 8062 8069 8075 8082 8089 8096 8102 8109 8116 8122 65 8129 S136. 8142 8149 8156 8162 8169 8176 8182 8189 66 S195 8202 8209 8215 8222 82i8 8235 8241 8248 8254 67 8261 8267 8274 8280 82S7 8293. .8299 8306 8312 8319 68 8325 8331 8338 8344 8351 8357 8363 837° 8376 8382 69 8388 8395 8401 8407 8414 8420 8426 8432 8439 8445 70 8451 8457 8463 8470. 8476 8482 8488 8494 8500 8506 71 8513 8519 8525 8531 8537 8543 8549 8555 8561 8567 72 8573 8579 8585 8591 8597 8603 8609 8615 8621 8627 73 !533 8639- 8645 8651 8657 8663 8669 8675 8681 8686 74 8692 8698 8704 8710 8716 8722 8727 8733 -8739 8745 75 ^X^l 8756 8762 876S S774 8779 8785 8791 8797 8802 76 8808 8S14 8820 8825 8831 8837 8842 8848 8854 8859 77 8865 8871 8876 8882 8887 8893 8899 8904 8910 8915 78 8921 ^^V 8932 8938 8943 8949 8954 8960 8965 8971 79 8976 8982 8987 8993 8998 9004 9009 9015' 9020 9025 .80 9031 9036 9042 9047 9053 9058. 9063 9069 9074 9079 81 9085 9090 9096 9101 9106 9112 9117. 9122 9128 9>33 82 9138 9143 9149 9154 9159 9165 9170 9175 9180 9186 83 9I9I 9196 9201 9206 9212 9217 9222 9227 9232 9238 B4.. 9243 9248 9253 9258 9263 9269 9274 9279 9284 9289 85 9294 9299 9304 9309 93^5 9320 9325 9330 9335 9340 86 9345 9350 9355 9360 9365 937° 9375 9380 9385 9390 87 .9395 9400 9405 9410 9415 9420 9425 9430 9435 9440 88 9445 9450 9455 9460 9465 9469 9474 9479 9484 9489 8fl 9494 9499 9504 9509" 95'3 9518 9523 9528 9533 9538 90 9542, "9547 9552 9557 9562 9566 9571 9576 9581 9586 91 9590 9595 9.600 9605 9609 9614 9619 9624 9628 9633 92 9638 9643 9647 9652 9657 9661 9666 9671 967s 9680 93 9685 9689 9694 9699 9703 9708 9713 97 '7 9722 9727 94 9731. 9736 9741 9745 9750 9754 9759 9763 9768 9773 95 9777 9782 9786 9791 9795 9800 9805 9809 9814 ■9818 ■96 9823 9827 9832 9835 9841 9845 9850 9854 9859 9863 97 9868 9872 9877 9881' 9886 9890 9894 9899 9903' 9908 98 9912 9917 9921 9926 9930 9934 9939 9943 9948 9952 9? 9956 9961 9965 9969 9974 9978 9983 9987 9991 9996 No. 1 2 3 4 5 6 7 8 9 APPENDIX CONTAINING HHFJiJiJiNCJiS AND TABLES. 519 Table No. VIII. IMPORTANT PROPERTIES OF FAMILIAR SUBSTANCES. Meta\s from 32° to 212°- Aluminium Antimony Bismuth . Copper Iron, cast Iron, wroug-ht.. Gold,... Lead Mercury at 32°. Nickel Platinum Silver Steel ,.... Tin Zinc Stones — Chalk Limestone Masonry Marble, gray . . Marble, white. Woods — Oak Pine, white Mineral substances — Charcoal, pine Coal, anthracite, . . Coke Glass, white , Sulphur Liquids — Alcohol, mean. Oil, petroleum. Steam at 212°.. Turpentine Water at 62°... Solid- Ice at 32* Gases — Air at 32° Oxygen Hydrogen. .... Carbonic acid.. Specific Gravity. Water, i. .61 102.65 6.712 9-823 8.1 7.5 7-744 19.258 ".352 13 598 8 800 16.000 10.474 . 7.834 7.291 7. 191 2.78^ 3-156 2.240 2.686 2.650 .86 .55 .44 t-43 1. 00 Specific Heat. Water, 1, Absorbing and Radiat- ing Power of Bodies in Units of Heat per Square Foot for Dif- ference of 1°. •9 .88 .0006 .87 .922 .OOT22 .00127 .000089 .00198 .212 .0508 .0308 • °!J39 .092 .1298 .1138 .0324 .0314 • 0333 .1086 .0324 .056 .1165 .0562 •°953 .2149 .2174 .2 .2694 .2158 ■57 •65 .241S .2411 .203 ■ 1977 •3> •847 .416 1.000 .23B .2412 3 -=936 .2210 Conducting Power in Units 01 Heat per square Foot of Sur- face witli Difference of 1°. .049 .0327 .648 .566 .1329 .0265 .0439 .049 .6786 ■735 ■735 • 735 ■735 ■73 ■73 ■5948 1.480 1.0853 515D 103.0 103.0 5-6 4.4 0.4 •17 Weiglit in Pounds Melting Points. Degrees Fahr. Per cu. in 0.0956 0.2428 0.3533 0.2930 0.3I79 0.2707 0.2801 0.696s 0.4106 0.4918 0.3183 0.5787 0.3788 0.2916 0.2637 0.26 Per cu. ft, 174.0 197.0 140.0 168.0 165.0 54.0 34-6 27.5 88.7 62.5 180.7 127.0 57-5 55^o .050 54-37 62 ■as .0807 •00559 .1234 81a 476 1692 1996 2250 3700 2590 608 -39 3700 2000 4000 446 680 520 APPENDIX CONTAINING REFERENCES AND TABLES. Table No. IX. COEFFICIENTS, STRENGTH OF MATERIALS. Cast-iron Average American ordnance Repeatedly melted Wrought-iron — Finest Low- ( with grain moorplates: I across " r> 'J • \ with " Bridfire-iron: \ ,, ° { across " Bars, finest Bars, ordinary Bars, soft Swedish Wire Steel— Mild-steel plates Axle and rail steel Crucible tool- " Chrome " Tungsten " Steel wire Piano-wire. Copper — Cast Rolled Wire, hard drawn Brass Wire Gun-metal , . Phosphor bronze Zinc, cast .. Zinc, rolled Tin Lead Timber- Oak ,. White pine Pitch-pine Ash.. Beech Mahogany Stone — Granite Sandstone , . Limestone Brick Ultimate Strength. Tons per Square Inch. Tension. 54-10* 7 14 15-20 27-29 24 22 19 27-29 25 19-24 25-50 26-32 30-45 40-65 80 72 70 150 10-14 15-16 28 8-13 22 11-23 15-26 2-3 7-10 2 0.9 3-7 14-34 4 4-7 4-6 4-7 Com- pression. 25-65 42 36-58 60-75 Shearing. 35 5 4 24 2-4 4 24-5 14-24 14-3 i-6 9-13 II Moduli. Tons per Sq. Inch. Elasticity. 10-14 5000 to 6000 12,000 to 13,000 12,000 \ to I 13.000 13,000 7000 8000 5500 6400 4500--6000 6000 5500 1000 800 600 950 750 Rig. Es 650 1300 to 2500 5000 5000 to 5200 2800 1500 2200 1700 2400 From Vol. XXII., Encyc. Britannica. APPENDIX CONTAINING REFERENCES AND TABLES. 521 Table No. X. PROPERTIES OF AIR. Of the Weights of Air, Vapor of Water, and Saturated Mixtures OF Air and Vapor of Different Temperatures, under the Ordi- nary Atmospheric Pressure of 29.921 Inches of Mercury. ■^^i •3a °^ 13 *- g £3| Mixtures of Air sat Lirated with Vapor. ij V. 1 S .Si H 3 > £^ a 15 oj "■3 G Elastic Weight of a cubic foot of the mixture. t • aJ *j d ^Q a III w Force of the Air in tlie mixture of Air and Va- por in inciies of Mercury. 9 t a a Weight of the Air in pounds. Weight of the Vapor in pounds. Total weipht of mixture in pounds. 1 2 3 4 s 6 7 8 0° ■935 .0864 0.044 29-877 .0863 .C00079 .086379 12 .960 .0842 .074 29.849 .0840 .000130 .084130 22 .980 .0824 .118 29.803 .0821 .C00202 .C82302 32 1. 000 .0807 .181 29.740 .0802 .COC304 .080504 42 1.020 .0791 .267 29.654 .0784 .000440 .07S840 52 1.041 .0776 .388 29-533 .0766 .00C627 .077227 60 1-057 .0764 .522 29.399 -0751 .CC0830 .075252 62 1. 061 .0761 .556 29.365 .0747 0CC881 .075581 70 1.078 .0750 -754 29,182 .0731 .001153 •073509 72 1.082 -0747 .785 29.136 -0727 .001221 .073921 82 I.I02 -0733 1.092 28.829 .0706 .001667 .072267 92 1. 1 22 .0720 1-501 28.420 .0684 .002250 .070717 100 1. 139 .0710 1.929 27-992 .0664 .002848 .C69261 102 1. 143 -0707 2 036 27.885 .0659 .002997 .068897 112 1. 163 .0694 2.731 27.190 .C631 .003946 .067042 122 1. 184 .0682 3.621 26.300 • 0599 .C05142 .065046 132 1.204 .0671 4-752 25-169 -0564 .006639 .063039 .T42 1.224 .0660 6.165 23-756 .0524 -C0S473 .of 0873 152 1.245 .0649 7-930 21.991 .0477. .010716 .058416 162 1.265 .0638 10.099 19.822 -0423 .013415 .055715 172 1.285 .0628 12.758 17-163 -0360 .016682 .052682 182 1.306 .0618 15.960 13-961 .0288 .020536 .049336 192 1.326 .0609 19.828 10.093 .0205 .025142 .045642 202 1-347 .0600 24.450 5-471 .0109 •030545 .041445 212 1.367 .0591 29.921 000 .0000 .036820 .036820 522 APPENDIX CONTAINING REFERENCES AND TABLES. Table No. X. — Continued. PROPERTIES OF AIR. Mixture of Air satu- rated witil Vapor. rbed by one Dry Air per ttJT3 c i V ■Si! ^1 Si s. u It 11 a " V E ss ■^2 3 c iX •50 a H 3 «J s^.g< |g« H PS b! u CO m (J U 1 9 10 11 12 IS 14 IS 0° .00092 1092.4 > • t • .02056 .02054 48.5 48.7 12 .00115 646.1 .02004 .02006 50.1 50.0 22 .00245 406.4 .01961 .01963 5I.I 51.0 32 .00379 263.81 3289 .01921 .01924 52.0 51.8 42 .00561 178.18 2252 .01882 .01884 53.2 52.8 52 .00819 122.17 1595 .01S47 .01848 540 53.8 6o- .01251 92.27 1227 .0181S .01822 55^o 54-9 62 .01179 84.79 "35 .oi8ir .01812 56.2 55.7 70 .01780 64.59 882 .01777 .01794 57-3 56.5 72 .01680 59-54 8ig .01777 .01790 58.5 56.8 82 .02361 42.35 600 .01744 .01770 57-2 56.5 92 .03289 30.40 444 .01710 .01751 58.5 57.1 100 ■04495 23.66 356 .01690 •01735 59.1 57-8 102 •04547 21.98 334 .01682 .01731 59-5 57-8 112 .06253 15.99 253 .01651 .01711 60.6 58.5 122 .08584 11.65 194 .01623 .01691 61.7 59.1 132 .11771 8.49 151 .01596 .01670 62.5 59.9 142 .16170 6.18 1.18 .01571 .01652 63.7 60.6 152 .22465 4-45 93-3 .01544 .01654 65.0 60.5 162 .31713 3-15 74-5 .01518 .01656 62.2 60.4 172 .46338 2.16 59.2 .01494 .01658 67.1 60.3 182 .71300 1.402 48.6 .01471 .01687 68.0 59-5 192 1.22643 .815 39-8 ■01449 68.9 202 2.80230 .357 32-7 .01466 > . • • 68.5 . . . ■ 212 Infinite .000 27.1 .01406 71.4 ,... Table XL RELATIVE WEIGHTS OF WATER AND AIR. Temperature. Temperature. Relative Weight. Weights. Degrees F. Degrees C. Degrees F. Degrees C. 32 722.4 86 3° 854.0 • 41 5 789.3 95 35 865.8 50 10 801.2 104 40 880.2 13 15 815.5 "3 45 894.2 68 20 828.8 122 5= 904.7 77 25 841.3 131 55 915.8 APPENDIX CONTAINING REFERENCES AND TABLES. 523 Table No. XII. MOISTURE ABSORBED BY AIR.* The Quantity of Water which Air is Capable of Absorbing to the Point of Maximum Saturation, in Grains per Cubic Foot FOR Various Temperatures. Degrees Grains in a Degrees Grains in a Fahr. Cubic Foot. Fahr. Cubic Foot. — 20 0.219 55 4.849 — 10 0.356 57 5-191 - 5 0.450 60 5-744 0.564 62 6.142 5 0.705 65 6.782 10 0.873 67 7.241 15 1-075 70 7.980 20 1. 321 72 8.508 25 1. 611 75 9-356 30 1.958 77 9.961 32 2.H3 80 10.933 35 2.366 85 12.736 40 2.849 90 14.791 45 3-414 95 17.124 50 4.076 100 19.766 52 4-372 105 , 22.751 Table No. XIIa. relative humidity of the air.* Difference of Temperature, Wet and Dry Temperature of the Air. Bulb. 33° F. 70° F. 90° F. 0.5 95 98 98 I 90 95 96 2 79 90 92 3 69 86 88 4 59 81 85 5 50 77 81 6 40 72 78 7 31 68 75 8 21 64 71 9 12 60 68 10 3 55 65 12 14 48 40 59 53 16 33 47 18 20 26 19 41 36 22 13 32 24 7 26 • From Weather Bulletin No. 127, U. S. Dept. of Agriculture, 1897, te barometer 92.4. 524 APPEADIX CONTAIAING KEfEKENCES ANE> TABLES. Table No. XIII. PROPERTIES OF SAiURAlED STEAM. [From Charles T. Porter's treatise on The Richards Steam-ctigine Indicator.'] Press- Sensible Heat Total Heat Weight of ure above iiero. Temperatnre. above zero Fahr. Xntent Heat. above zero Fahr. One C'ubia Foot- Xbs. per , eq. in. Fahr. Beg. B.T.U. B.T.U. B.T.U. Lbs. 1 103.00 102.08 1042.96 1145.05 .0030 s 136.36 126.44 1026.01 1153.45 .0058 8 141.63 141.87 1015.25 1167.13 .0085 4 153.07 153.39 1007.23 1160.63 .011? 5 163.33 162.73 1000.72 1163.44 .013V 6 170.13 170.57 995.24 1165.83 :016S 7 176.91 177.42 990 47 1167.89 .0189 8 183.91 183.48 986.34 1169.72 .0314 9 188.31 188.94 983.43 1171.37 .0239 10 193.24 193.91 978.95 1173.87 .0361 11 197.76 198.49 975.76 1174.25 .0289 18 201.96 202.73 973.80 1175.53 .0313 13 205.88 206.70 970.03 1176.73 .0337 14 209.56 210.43 967.42 1177.85 .0363 15 213.03 213.93 964.97 1178.91 .0387 16 216 29 217.25 963.65 1179.90 .0413 17 219.41 220.40 960.45 1180.85 .0437 18 222.37 223.41 958.34 1181.76 .0463 19 225.20 236.28 956.34 1183.63 .0487 20 227.91 229.03 954.41 1183.45 .0511 - £1 230.51- 231.07 953.57 1184.24 .0536 22 233.01 234.21 950.79 1185-.00 .0561 23 2S5.43 236.67 949.07 1185.74 .0585 24 237.75 239.03 947.43 1186.45 .0610 25 240.00 241.31 945.83 1187.13 .0634 26 242.17 243.53 944.27 1187.80 .0653 27 244.28 245.67 943.77 1188.44 .0083' 28 246.32 247.74 941.32 1189.06 .0707 29 248.31 249.76 939.90 1189.67 .0731 30 250.24 251.73 938.93 1190.26 .0755 81 252.12 253.64 937.18 1190.83 .0779 33 853.95 255.51 935.88 1191.39 .0803 83 255.73 257.33 934.60 1191.93 .0837 84 257.47 259.10 933.30 1193.46 .0851 35 259.17 260.83 933.15 1192.98 .0875 36 260.83 263.53 930.96 1193.49 .0899 87 262.45 204.18 929.80 1193.98 ."0922 88 264.04 265.80 928.07 1194.47 .J0946 89 265.59 267.38 937.56 1194.94 .0970 40 267.12 268.93 926.47 1195.41 .0994 41 268.61 270.46 935.40 1195.86 -1017 42 270.07 271.95 934.35 1196.31 1041 43 . 271.50 273.41 923.33 1196.74 1064 ^4 272.91 374.85 922.33 1197.17 .1088 45 274.39 276.26 921.33 1197.60 .1111 46 275.65- 377.65 930.36 1198.01 .1134 APPENDIX CONTAINING REFERENCES AND TABLES. 525 Properties of Saturated S'V's.am— Continued. Fress. Sensible He.it Total Hcnt Weighted' One Cubic ure above zero. Temperature. above Latent Heat. above zero Falir. zero Fahr. Foot. Lba,per eg. in. Fahr. Deg. B.T.U. B.T.U. B.T.U. Lbs. 47 276.98 279.01 919.40 1198.43 .1158 48 278.29 280.35 918.46 1198.82 .1181 49 279.58 281.67 917.54 1199.21 .1204 50 280.85 282.96 916.63 1199.60 .1237 61 28^.09 284.24 915.73 1109.98 .1251 S2 £83.32' 28."). 49 914.85 1200.35 .1274 S3 284.58 2S6.73 912.98 1200.72 .1297 54 285'. 72 287.95 913.13 .1201.08 .1330 55 286 89 289.15 912.29 1201.44 .1343 56 288.05 290. S3 911.46 1201.79 .1368 67 289.11 291.50 910.64 1202.14 .1388 58 290.31 298.65 909.83 1203.48 .1411 59 291.4a 293.79 909.03 1203.82 .1434 60 292.52 294.91 908,24 1203.15 .1457 61 293.59 296.01 907.47 1203.48 .1479 62 294.66 297.10 906.70 1203.81 .1502 63 295.71 298.18 905.94 1204. IS .1524 64 296.75 299.-24 905 20 1204.44 .1547 65 297.77 300.30 904.46 1204.76 .1569 66 298.78 301.33 903.73 1205.07 .1592 67 299.78 302.36 908.01 1205.37 .1614 68 800.77 303.37 902.29 1205.67 ;i637 69 301.75 304.38 901.59 1205.97 .1659 70 302.71. 305.37 900.89 1206 ..26 .1681 71 303.67 306.3.1 900.21 1206.56 .1703 73 304.61 307.32 899.52 1206.84 .1725 73 305.55 308.27 898.85 1207.13 .1748 74 306.47 309.22 898.18 1207.41 .1770 75 307.38 310.16 897.53 1207.69 ,1793 76 308.29 311.09 896.87 1207.96 .1814 77 309.18 313.01 890.23 1308.24 .1836 78 310.06 313.92 895.. 59 1208.51 .1857 79 310.94 313.82 894.95 1208.77 .1879 ' 80 811.81 314.71 894.33 1209.04 .1901. 81 83 83 84 85 86 87 88 89 90 312.67 315.59 893.70 1209.30 .1933 313.52 314.36 315.19 316.02 316.83 317.65 318:45 319.24 320.03 316.46 317.33 318.1^ 319.04 319. 8ff 320.71 331.54 322.36 323.17 893.09 893.48 891.88 891.28 890.69 890:10 889.53 888.94 888.37 1209.56 1209.82 1210.07 1210.33 1210.57 1210.83 1311.06' 1311.31 -1311.55 .1967 ,1988 .2010 .2032 .2053 .20T5 .2097 .2118 91 82 93 94 95 i 320.83 331.59 322.36 323.12 333.88 323.98 ' 324.78 325.57 326.35 327.13 887.80 887.34 886.68 888.13 885.68 1211.79 1212.02 1212.36 1313.49 1212.73 .213?. .2160 .2182 .2204 .2224 52G APPENDIX CONTAINING REFERENCES AND TABLES. Properties of Saturated Steam — Continued, ■ Press- ■ Sensible Heat Total Heat Weight of ure above ^ zero. Temperature. above Latent Heat. above One Cubic zcm Fahr. zero Fahr, .Foot. Lbs.pcr 6q. 111. Fahr. Deg. B.T.t7. B.T.U. B.T.U. Lbs' S6 324.63 327.90 885.04 1213.95 .3245 97 325.87 328.67 S84.50 1218.18 .3266 98 326.11 329.43 8i83.97 1213.40 .2288 99 326.84 330.18 883.44 1313.63 .2309 100 327.57 880.93 883.91 1213.84 .2330 101 328.29 831.67 882.39 1214.06 .2351 103 839.00 383.41 881.87 3314.28 .2371 103 829.71 338.14 881.35 1314.50- .2392 104 330.41 333.86 880.84 1214.71 .2415" 105 831.11 834.58 880.34 1214.93 .3434 106 831.80 335.30 879.84 1315.14 .2464 107 832.49 336.00 879.34 1215.35 .2475 108 883.17 386.71 878.84 1215.55 .2496 109 383.85 337.41 878.35 1215.76 .8516 110 831.52 838.10 877.88 1215.97 .2537 111 335.19 838.79 877.37 1216.17 .2558 113 335.85 339.47 876.89 1318.37 .2578 113 336.51 340.15 876.41 1316.67 .2599 114 387.16 340.83 875.94 1216.77 .2619 115 337.81 841.50 875.47 1318.97 .2640 116 338.45 342.16 875.00 1317.17 .2661 117 339.10 342.83 874.53 1317.36 .2681. 118 839.78 343.48 874.07 1817.58 .2702 119 340.36 344.14 873.61 1217.75 .2720 120 340.99 344.78 873.15 1217.94 .2743 lai 841.61 345.43 872.70 1318.13 .2768 123 843.33 «46.07 872.25 1318.33 .3783 123 342.85 346.70 871.80 1218.51 .3803 • 124 843.46 347.34 871.35 1218.69 .3822 125 844.07 847.97 870.91 1218.88 .2848 126 344.67 848.59 870.47 1219.06 .2888 127 345.27 849.31 870.03 1319.25 .2883 128 845.87 849.88 869.59 1219.43 .2903 129 846.45 350.44 869.16 1219.61 .2928 130 847.05 851.05 868.73 1219.79 .2943 131 347.64 351.68 868.30 1219.97 .2961 133 348.22 352.36 867.88 1220.15 .2981 133 348.80 853.86 867.46 1220.83 .3001 134 849.38 853.46 "W.OS 1220.50 .3020 135 349.95 854.05 b66.62 1220.67 .8040 136 850.52 '864.64 866.30 1330.85 .8060 137 351.08 855.38 868.79 1321.03 .3079 138 351.75 355.81 665.38 1231.19 .3099 139 362.31 358.89 864.97 1231.36 .3118 140 863.76 856.98 864.56 1331.53 .3188 141 353.81 357.64 864.16 1231.70 .3158 143 353,86 358.11 863.76 1221.87 .8178 143 854.41 358.67 863.86 1222.03 .3199 144 354.96 359.34 862.96 1222.20 .3219 APPENDIX CONTAINING REFERENCES AND TABLES. 527 Properties of Saturated Steam — Continued. Presd- Sensible Heat Total Heat 'Vt'eightof, atove rero. Temperature. above Ltttefit Heat. above One Cubic zero Fahr. , zero Fahr. .Foot. 'il}^^. Fahr. Deg. B.T.TT. ■B.T.U. b.t;tj.- Lbs. 145 355.50 359.80 862.56 1333.36 .8239 146 1I7 356.03 360.85 863.17 1333.53 .3859 356.57 360.91 , 861.78 ; 333.69 : 233.85 .3279 M^ 357.10 361.46 861.39 .3299 149> 357.63 862.01 881.00 1233.01 .3319 150 358.16 363.55 860.62 J323.18 .3340 151 858.68 363.10 860.23 1833.33 .3358 1.53 359.20 363 64 859.85 1223.49 .3576 153 359.73 364.17 859.47 1883.65 .3394 154 360.23 364.71 859.10 1283.81 Mn 155 360,74 365.24 858. 7S 1223.97 .3430 156 361.36 365.77 858.85 12i4.12 .3448 157 361.76 366.30 857.98 1324.28 .3466 158 362.37 368.83 857.61 1824.43 .3484 159 303.77 367.34 857.24 1884.58 .3503 180 363.37 367.86 856.87 1834.74 .8530 161 363.77 368.38 856.50 1834.89 .3539 162 364.27 368.89 856.14 1235.04 .3558 163 364.76 369.41 855.78 1285.19 .3577 164 865.25 869.92 855.42 1225.34 .3596 165 865.74 370 43 855.06 1225.49 .3614 166 366.23 870.93 854.70 1825.64 .3633 167 368.71 371.43 854.35 1225.78 .8652 168 367.19 371.93 853.99 1225.93 .3671- 169 367.68 373.43 853.64 1226.08 .3690 170 368.15 373.93 853.29 1226.23 .3709 171 368.63 373.43 853.94 1236.37 .3727 173 389.10 373.91 853.59 1226.51 .3745 173 369.57 374.40 853.25 1286.66 .3763 174 370.04 874.89 851.90 1226.80 .3781 175 370.51 3X5.38 851.56 1226.94 .3799 176 370.97 875.86 851.23 1-^27.08 .3817 177 371.44 876.34 850.88 1227.23 .3835 178 371.90 -376.83 850.54 1287.37 .3853 179 372.36 377.30 850.20 1327.51 .-3871 180 373.82 8t7.78 849.86 1237.65 .3889 181 373.27 378,25 849.53 1237.78 .3907 isa 873.73 878.72 849.20 1327.93 .3925 183 374.18 879.19 848.86 1238.06- .3944- 184 874.63 379.66 848-. 53 1238.20 .3903 185 375.08 380.13 848.80 1328.33 .3980 186 375.53 880.59 847.88 1228.47 .3999 137 375.97 381.05 847.55 1223.61 .4017 188 376.41 381.61 847.23 1828.74 ,4035 189 376 85 381.97 846.90 1228.87 .4053 190 877.29 382.43 846.58 1239.01 .4072 191 877.72 382.88 816.26 1839.14 .4089 193 378.16 383.33 845,94 1229.27 .4107 193 378.59 883.78 845.62 lfe89.41 .4125 52S APPENDIX CONTAINING REFERENCES AND TABLES. Properties of Saturated Steam — Continued. Pressure Sensible Heat Total Heat Weight of above Zero. Temperature. above Zero Fahr. Latent Heat. above Zero Fahr. One Cubic Foot. Lbs. per sq. in. Fahr. Deg. B.T.U. B.T.U. B.T.U. Lbs. 194 379.08 384.23 845.30 1229.54 .4143 195 379.45 384.67 844.99 1229.67 .4160 196 379.97 385.12 844.68 1229.80 .4178 197 380.30 385.56 844.36 1229.93 .4196 198 380.72 386.00 844.05 1230.06 .4214 199 381.15 386.44 843.74 1230.19 .4231 SOO 381.57 386.88 843.43 1230.31 .4849 201 381.99 387.32 843.12 1230.44 .4866 20i 383.41 387.76 842.81 1230.57 .4283 203 382.82 388.19 842.50 1230.70 .4300 204 383.24 388.62 842.20 1230.82 .4318 203 383.65 389.05 841.89 1230.95 .4335 206 384.06 .389.48 841.69 1231.07 .4352 20r 384.47 389.91 841.29 1331.20 .4369 208 384.88 390.33 840.99 1331.32 .4386 209 385.28 390.75 840.69 1231.45 .4403 210 385.67 391.17 840.39 1831 .67 .4481 QUANTITIES OF HEAT CONTAINED IN ONE POUND OF WATEB AT VAKIOUS TEMPERATURES, RECKONED FROM ZERO, FAHRENHEIT. [From Charles T. Poi-ter's treatise on The Richards' Steam-Engine Indicator.'] Tempera- ture. Heat con- tained above Zero. Tempera- ture. Heat con- tained above Zero. Tempera- ture. Heat con- tained above Zero. Fahr. Deg. B.T.U. Fahr. Deg. B.T.U. Fahr. Deg. B.T.U. 35 35.00 155 155.33 275 276.98 40 4(1 00 160 160.37 280 882.09 45 45.00 165 165.41 2S5 287.21 50 50.00 170 170.45 290 292.32 55 ,55.00 175 175.49 896 297.45 60 60.00 180 180.54 300 302.58 65 65.01 185 185.69 306 307.71 70 70 02 190 190 61 310 318.84 75 73.02 195 195.69 316 .317.98 80 80.03 200 200.75 330 323.13 86 85.04 205 205.81 385 328.28 90 90.05 210 810.87 330 333.43 95 95.06 215 215.93 336 338.69 100 100.08 880 221 .00 340 343.75 105 103.09 825 286.07 345 348.92 110 110.11 230 231.15 3.50 354.10 115 115.18 235 236.23 355 359.88 120 120.14 240 241.31 360 364.46 125 123 16 245 246.39 365 369.65 130 1.30.19 250 251.48 370 374.84 135 135.21 255 856.57 375 380.04 140 140.24 260 361.67 380 385.24 145 145.27 266 266.77 385 390.45 150 150.30 270 271.87 390 396.67 APPENDIX CONTAINING PEFERENCES AND TABLES. 529 Table XIV. COMPOSITION OF VARIOUS FUELS OF THE UNITED STATES. Mine or Name. Mount Pleasant Exeter (Rice) Exeter Coxe's No. I. . ,.. No. II Forty-foot . . . York Farm (Bkwt) . . Jermyn Cayuga Manville Shalt Avondale Oxford Continental Woodward* Cumberland Eureka Antrim Long- Valley New Rtver Pocahontas Cardiff Union New Castle (Lump). Mt. Olive (Lump)... Big" Muddy Streator (Lump)... . . Gillespie Ladd (Lump) . Wilmington (Lump). Indiana Block New Pittsburgh . Vanderpool (Lump). Wills Creek Jackson Hii! , Hocking Valley Brier Hi;i..r Weilsville Goshen Hastings Turtle Creek Youghiogheny Trotter Reynoldsvilie Pittsburgh Summer Hill (Slack). Monongahela Leisenring, Canne'l , Cooperstown Locality. Coal as Received. Fixed C. Vol. Matter. Scranton, Pa . . . Pittston, Pa Scranton, Pa.. Slate out. ... Scranton. Pa Schuylkill Co., Pa... Pottsviile, Pa . ..... Scranton, Pa Maryland Pennsylvania Towanda. Pa West Virginia Wales ".'.". Jerome Park, Colo. . New Castle, Colo.. . Illinois Streator, 111 lilinois Wilmington. I'l — Brazil, Ind Indiana Block Kentucky , . Ohio Nebraska . . . Monongahela R., Pa. Pennsylvania . . ... Conne])svjiIe,Pa. . . Pennsylvania Monongahela R.. Pa, Connellsville. Pa — Peyton. W. Va... ... Nova Scotia 80.54 7Q.41 74 73 87.96 83.98 75 29 81 68 84.46 85.70 86.68 91.45 83.13 79 23 75 5° 70 47 69 30 67.3' 72.90 68.88 67.45 52.86 50.80 44.10 53.80 44 30 49 55 42.45 ^9.90 53 7<-^ 40. 40 =14.60 46 f5 55. 5*^ 48 90 56 30 49'5=' 49 83 60.88 59 45 54 oc 58 go 59 04 53 30 6.21 0° 12.38 12.42 12.22 13.13 13.05 13 12.77 12.90 12-37 13-49 13 54 13-57 >3-7i 13.91 14.20 14.72 BITUMINOUS COAL— AVERAGE TABLE OF RESULTS.* Mine. Locality. re 1 < a u ■a V X E > s y ■§£• &■- en Heat-units per Pound of Dry Coal. Lbs. of Water Evaporated from and at 212°. Percentage f Combustible Matter in Black Smoke. Gillespie Auburn Screeningrs. LittlePittsburg,Va. Bernmont Gillespie, 111 Sugar Creek, 111 viorgantown, W. Va. Monongahela R., Pa. New Blossburg, Pa.. Clearfield Co., Pa -. Monongahela R., Pa, No. 2 Slope. U. S . Reynoldsville, Pa Connellsville. Pa,... New River, Va Nova Scotia 36.26 37-5 37-5 ^l 18.54 23-79 34-95 32.38 24.67 29.26 17.84 30.75 "■33 15.2 6.6 8.04 It. 30 5.82 4-33 4. II 5-37 6.25 3-72 4.09 51-41 47-3 55 -9^ 59.96 70.16 70.39 60.72 63.61 69.96 64.49 78.45 65.16 1.26 1.275 1.42 1.28 1. 31 1-34 1-34 1-255 1-345 io,go2 11,200 12,800 13,424 13.695 13,897 14,450 15,324 15,134 15.285 15.283 15,435 11.28 II. 6 W-3 13-9 14 18 14.39 14.96 15-86 15.67 15 82 15.82 15-98 0.56 1.04 0.27 0.43 0.30 0.27 0-33 0.92 0.2 o.S Euieka Turtle Creek Nova Scotia Reynoldsville Leisenring-. Pocahontas Cooperstown * From experiments made by Flory and Gilbert at Sibley College, Cornell University. The heat-units are given per pound of dry coal. Coal in ordi- nary conditions contains from 3 to 10 percent of moisture, and the results must be reduced accordingly. Seventy per cent of the theoretical heating value represents the average results obtained in practice. APPENDIX CONTAINING REFERENCES AND TABLES. S3 I Table No. yAN.—Conti ANALYSES OF ASH. Specific Color ciu„ Alum- Oxide , ^ Grav. of Ash. =""=*• ina. Iron. ''""*■ Loss.s^i^ PeiiDsylTania Anthracite, " Bituminous. Welsh Anthracite Scotch Bituminous Lignite Reddish Buff. Gray. 45.6 76.0 40.0 37-6 19.3 42-75 21.00 44-8 52.0 II. 6 .60 12.0 3-7 23-7 trace I.I 2.6 Table No. XV. FOR REDUCING BAROMETRIC OBSERVATIONS TO THE FREEZING-POINT. Reading of Ba- Correction at Correction at Correction at Correction at rometer.' 10° Fahr. 40° Fahr. 70° Fahr. 90° Fahr. Inches. Inches. Inches. Inches. Inches. + 27 0.045 0.028 O.IOO 0.148 27.5 0.046 0.028 0.102 0.I5I ■28.0 0.047 0.029 0.104 0.153 28.5 0.048 029 0.106 0.156 29 0.049 C30 0.108 0.159 29.5 0.050 0.030 0. log 0.162 30.0 0.051 0.031 0. Ill 0.164 30.5 0.052 0.032 O.I13 0.167 31-0 0.053 0.032 O.I15 0.170 Table XVI. THEORETICAL VELOCITY OF AIR, IN FEET PER SECOND, DUE TO NATURAL DRAFT. Height of Excess of Temperat ure in Flue above External .'\ir. Feet. 5° 10'' 15° 20° =5° 3°° 50° too" 150° I 0.8 i.i 1.4- 1.6 T.8 2.0 ^■5 3 6 4.4 5 1.8 2.5 3-t 3 6 4 4-5 5.6 8.1 9.9 10 2.6 3.fi 4-4 .■; 1 5 7 6.6 8.1 II. 4 14.0 IS 31 4-4 5-4 6 ■H 7 V 9-9 14.0 17. 1 so ' 3.6 5-I 6.3 7 2 8 I 8.3 II. 4 19.8 =5 4.0 S-7 7-1 8 r 9 9 9 12.8 18.0 19.8 22. 1 10 4-4 6.3 7.8 8 8 9 TO. 8 14.0 24.2 35 4.8 6.8 8.4 9 S TO 7 II. 7 15-1 22.3 26.1 40 51 7-3 8.9 10 2 II 4 12. s 16. 1 27.9 45 5-4 7-7 9.4 TO 8 12 I '3-3 17. 1 24.2 29.6 50 5-7 8 I 9.9 II 4 12 8 14.0 18.0 25-5 31. 1 60 6.3 8.8 10 8 12 6 14 15-3 19.8 27.8 33-3 70 6.8 9-5 11.7 13 6 'S 2 t6.s 21. 4 30.0 .36.1 So 7*3 TO. 2 13. 5 14 4 16 2 18.7 22.9 32.2 38.9 90 7-7 10.8 13,3 IS 1 17 2 t8.8 24-3 34.2 41.6 100 8.1 II. 4 14.0 16 2 17 8 19.8 25.6 36.0 4:-2 125 91 12.3 15.6 18 I 20 I 22.1 28.7 403 49-3 150 9.9 14.0 17.2 19 8 22 2 24. 3 31.4 44-3 54-3 532 APPENDIX CONTAINING REFERENCES AND TABLES, Table No. XVII. THERMAL CONDUCTIVITIES. PER DEGREE DIFFERENCE OF THE SUBSTANCE. Substances. Copper Iron Zinc Lead Air, ■) Oxygen, I _ Nitrogen, [ Carbonic oxide, J Carbonic acid Hydrogen Glass Porphyritic trachyte. Marble Underground strata Limestone Sandstone of Craig- | leith Quarry S ' ' Trap-rock of Calton Hill. Sand of experimen- I _ _ tal garden j ' " " Water , Fir across fibres " along fibres Walnut across fibres . . . " along fibres... . Oak across fibres Cork Hempen cloth, new.. . " old. ... Writing paper, white.. . Gray paper, u n sized ... . Calico, new, of ) all densities ) Wool, carded, of ) all densities j- • • • • Finely carded cotton-wool Eider-down Indian rubber Brick dust Wood ashes Coke Thickness, one metre. Calories per sq. metre. 326 57-5 56 28 0.0177 0.0137 0.0125 0.82 2.12 3-13 1.8 1.82 3-84 1-5 0.94 0.72 0.093 0.169 .0.105 0.173 0.212 0.105 0.052 0.043 0.043 0.0337 0.05 0.044 0.04 0.039 0.17 0.15 0.06 4.96 Thickness, one foot. B. T. U. per sq. ft. per hr. 594 104 102 50.5 0.323 0.0249 0.0227 1.49 3.86 5.67 3-29 3-31 7.0 2.73 1.72 1.82 0.169 0.308 0.192 0-315 0.387 0.192 0.095 0.078 0.078 0.0515 0.91 0.08 0.073 0.017 0.308 0.272 0.109 9.01 Authority, Clausius and Maxwell, accord- ing to kinetic theory. Do. do. do. Do. do. do. P6clet. Aryton & Perry, Phil. Mag., 1878, first half year, p. 241. P6clet. Forbes and Wm. Thomson. Do. Do. Do. do. do. do. do. do. do. J. P. Bottomley. Pfeclet in Everett's Units and Physical Constants. Do. Do. Do. Do. Do. Do. Do. Do. Do. Do. Do. Do. Do. do. do. do. do. do. do. do. do. do. do, do. do. do. ao. do. do. do. do. do. do. do. do. do. do. do. do. APPENDIX CONTAINING REFERENCES AND TABLES. 533 Oh a! < Q o < u H O H a ij w O n o D O y a Nominal Weight per Foot. en T3 C 9 O P- H OS t^ moo ■*«) oi O'ci M in « « M t^ M imo lo m m Tj-N tnm>-vo -^t^O romoo ^0»O t^t-^O'O noon cum ot^ MMNWfnir)t>.(>o'N 4oo* rooo' en d inoo rn t>. t^ « m Length of Pipe Containing One Cubic Foot. _rnN^qo«iSo^HmE^^g„'SS-?gg'5^3"aP;S.s >n fO i>. ^ « "I ^4 Is 1 m moo M CO w in h- o^eo f% 1^oo t>. « <>. ooo oo oo tn m - ■* t-. M \D vo t^ moo lo N o>oo t>.vS u^■<^'^-fOcnm«N ««« ■^ d t>.'0 -^moNMMHM •* St: (L> ^n^vl>.^^■^^H oooo w ino>-*t^t^H (T'^-.^n»no^m^no^lnN ^r^m-^roo O h o « cmo -i-'O oo h-o -^cmon ot^mmw h ■* "o mvo a> m vo tn ooo p-\o mm-^fncnroN n « « m n ot>.\n- cj inoo t^ Thoo m c?i ^ -tiHO -*«3 vo T^ h o* h r^ N 'O -^ en o^O Ot^-o ^r>.^^^>.MOo nco mw O t-^mrow -^^ -■ M M m Ti->o tNO t^Nvo H\o mtnchno o\-a-vo t^ ^ moo 15 u B cr en m o ro'd o^ f. moo oo oo mvo ooo en 't m ro rr ooo oo -d- ^ m M H m moo ^ m t-. tnoo t-* c^ o-oo t^ o r-oo o co ^ o « vo M N tn ■»!- r-» 3> « mo^ooco o woo mtnt-ot-^in m M h- -^ N n invD t^o\i- (n moo h m 1 H M H « « N O ooo rHO CO -^ m « M VD -^ mvo N -^vo rfl -^ t^oo m N N m m\Q m'O fnroorivD mo t>-vo n'O'O mt^mMvow t>- M « m moo m H oo ^h ^\o m c^« m tvo Th t> t^ ti-\o cm-, o o- ^ M N N -^-vo 0\ N m o ■^^ xf inoo N o eg f-. mvo " \o -nH 'e- mvo vd oo n o- >*• mio "o t^oo \o oo Th -^ in moo c m^o o» m m ti- tho -^ m'O r-«-r^t— m noconh DO-mcT.mNmo-* t~Nvo -vof-ooOOOO-*m Cv'o r^. ■^i- m ■*■ H M H « m -*- m'O t^cr.M m ^mtj-N moo h ■<^ t^ h -^oo m ^ 1 is 1 o c N\0"VO« -« o-^oosmi-i !>. ^00 oo N f-O-O O. M N t tn MMNNm^mmc^oocj^-mr^omtj-om^om^O^mvo u 1 c oooo^-o•m■<^ mTh-i- i>.vo t-vo o h « T^>o m m m m ■* ^'??2S?2-2-»>8SSff?S5"S as, SI'S, KRSS PI'S nS s n lE 85 u c Sr m 9vc a mvo ^ o Soiooooo-o-oOOMW-f^m -'*■ ^HH««rom-4-.4- m'O t^ t^co " « fo .^^ in\£3 b- 1| lU a ' * M w H M ei n m ■<*- -^ m mvo' t^od o o h « ^ mvo t^m 11 |5 (A U •s ^XeSvrSrt^ ^ ^^ p^ -J; ^^ ^-5 mvo »>oo OS H « en jj- m-o tj. 534 APPENDIX CONTAINING REFERENCES AND TABLES. Table No. XIX. WEIGHT OF WATER PER CUBIC FOOT FOR VARIOUS TEM- PERATURES.* Weight of Water per Cubic Foot, from 32° to 212° F., and Heat- units PER Pound, Reckoned Above 3?° F. . per square inch, .433 X 144 = 62.352 lbs. per cubic foot. Head, 6 ■Feet. I 2 3 4 5 7 9 0-433 0.866 1.299 1,732 2,165 2.598 3,031 3 404 3-897 10 4- 330 4-763 5-196 5,629 6.062 6.495 6,928 7.361 7.794 8-227 20 8.660 9-093 9-526 9-959 10.392 10.825 11,258 11.691 12.124 12-557 30 12.990 13-423 13.856 14-289 14,722 15-155 15-588 16.021 16.454 16.887 40 17.320 17-753 18.186 18,619 19,052 19,485 ig gi8 20 351 20.784 21.217 50 21.650 22.083 22,516 22-949 23.382 23.815 24-248 24.681 25.114 25-547 60 25.980 26.413 26.846 27-279 27.712 28-145 28,578 29,011 29,444 29,877 70 30.310 30.743 31.176 31 609 32 042 32-475 32-908 33-341 33-774 34-207 80 34.640 35 073 35-506 35-939 36.372 36,805 37.238 37-671 38,104 38-537 90 38.970 39-403 39- 836 40,269 40.702 41-135 41-568 42.001 42.436 42.867 HEAD IN FEET OF WATER, CORRESPONDING TO PRESSURES IN POUNDS PER SQUARE INCH. J lb. per square inch = 2.30947 feet head, i atmosphere = 14.7 lbs. per square inch = 33.95 feet head. Press- ure. I 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90 23.0947 46.1894 69 2841 02.3788 "5-4735 1.38-5682 161 .6629 184.7576 207.8523 2.309 25-404 48-499 94,688 117.78 140 88 163.97 187.07 210.16 4.619 27-714 50-808 96.998 120.09 143.19 166.28 189.38 212.47 6.928 30 023 53,118 76,213 99-307 122.40 145.50 168.59 191,69 214-78 9.238 32.333 55.427 78.522 101.62 124-71 147-81 170 90 194-00 217-09 11.547 34.642 57.737 80 831 103-93 1Z6.02 150.12 173.21 196.31 Z19.40 13-857 ,36-952 60,046 83.141 106.24 129-33 152.42 175-52 198.61 221. 71 16.166 39.261 62.356 -"5 450 J08.55 131.64 154-73 177-83 200-92 224.02 18.476 41-570 64-665 87.760 110.85 133-95 157.04 180-14 203.23 226.33 20.785 43.880 66.975 50.069 113.16 136.26 159-35 182.4s 205.54 228.64 * Kent's " Pocket-book.' 536 APPENDIX CONTAINING REFERENCES AND TABLES. Table No. XXI. CONTENTS IN CUBIC FEET AND U. S. GALLONS OF PIPES AND CYLINDERS OF VARIOUS DIAMETERS AND I FOOT IN LENGTH.*- 1 gallon = 231 cubic inches, i cubic foot = 7.4805 gallons. is Fori Foot in c For I Foot in e For I Foot in Length. SI'S Length. is Length. *l 1 i = Cu. Ft , U.S. Cu. Ft., 1 U. S. i5 Cu. Ft., U.S. Q also Area Gals., 231 also Area Gals., 231 (5 also Area Gals., 231 in Sq. Ft. Cu. In. in Sq. Ft. Cu, In. in Sq. Ft. Cu. In. i .0003 .0025 6M .2485 1-859 '9,^ 1.969 14-73 A .0005 .004 7 .2673 1-999 19H 2.074 15-31 A .0008 •o°S7 7^ .2867 2.14s 20 2.182 16.32 .001 .0078 .3068 2.295 20!^ 2.292 17-15 k .0014 .0102 iVa .3276 2.45 21 2.40s 17-99 A .0017 .OT2g 8 .3491 2. 611 21^ 2.521 18-86 1 .0021 .0159 8^ .3712 2.777 22 2.640 19-75 « .0026 .0193 ■3941 2,948 22!^ 2.761 20.66 i .0031 .0230 8% .4.76 3-125 ''3 , 2.88s 21,58 H .0036 .0269 9 -4418 3-3°S ^i\i 3.012 22-53 \ .0042 .0312 9^ .4667 3.491 24 3-142 23.50 w .0048 •03.S9 .4922 3.682 25 3-4°9 25.50 I .0055 .0408 9M .5185 3-879 26 3-687 27-58 'S .0085 .0638 10 •5454 4.0B 27 3-976 29-74 .0123 .0918 io!4 ■5730 4.286 28 4.276 31-99 M .0167 .1249 loH .6013 4-498 29 4-587 34-31 2 .021B .1632 10% .6303 4.715 30 4-909 36-72 2/4 .0276 .2066 II .66 4 937 31 5-241 39.21 2^ .0341 ■2550 II^ 11J4 .6903 5.164 32 ■ 5-585 41.78 2% .0412 •3°8s .7213 5-396 33 5-940 44-43 3 .04QT .3672 i.M ■7530 5-633 34 6.30s 47.16 .0576 .4309 12 .7834 5-875 35 6.681 49.98 .0668 .4998 "1^ .8522 6-375 36 7.069 52.88 3M .0767 •5738 '3,, .921S 6-895 37 7.467 55-86 4 .0873 .6528 13K •994 7 436 38 7.876 58.92 4!4 • 098s .7369 '■•, - 1.069 7 997 39 8.296 62.06 4ii .1134 .8263 ■4!^ 1. 147 8.578 40 8-727 65.28 4% .1231 .9206 'S,, 1.227 9.180 41 9-168 68 58 5 .1364 1.020 js!^ 1.3:0 9.801 42 9-621 71 97 sM •1503 1. 125 16 1.396 10.44 43 ia-085 75-44 sH .1650 1-2.34 i61^ 1-485 II, II 44 10-559 78.99 5% .1803 1-349 '7,, 1.576 11,79 45 11.04s 82.62 6 .1963 1.469 17)4 1.670 12,49 46 II. 541 86.33 6jl .2131 1-594 18 1.768 13.22 47 12.048 90 13 .2304 1.724 i81^ 1.867 13-96 48 12.566 94.00 To find the capacity of pipes greater than the largest given in the table look in the table for a pipe of one half the given size, and multiply its capacity by 4; or one of one third its size, and multiply its capacity by q, etc. To find the weight of water in any of the given sizes multiply the capacity in cubic feet by 62J4 or the gallons by 8)4, or, if a closer approximation is required, by the weight of a cubic foot of water at the actual temperature in the pipe. Giv^n the dimensions of a cylinder in inches to find its capacity in U. S. gallons : square the diameter, multiply by the length and by .0034. U d = diam. / = length, gallons = o'^X .7854 X/ .„, i—=^ = .0034 a^(. 231 * Kent's " Pocket-book.*' appendix containing references and tables. 537 Table No. XXIL equalization of pipe areas.* Sizes Nu"bcr of small pipes required to make area equivalent to one larger pipe, witli allowance for friction. of Pipe. in. in. I in. in. in. 2 in. in. i^. 3J^ in. 4 in. 4?^ in. 5 m. 6 in. iS. 8 in. 5^ in I ' ch I 2.0 I 3-7 1.8 I 7.6 3-7 a.o I "•3 5-4 3-1 1-5 I 19 9.2 5-1 2.6 1-7 1 ?6'.7 9-3 4-5 3-1 1.83 I SS 2S-S 14-7 7-3 4-7 2.9 1-7 I 80 39 27 10.6 7-1 4-1 2-5 i-S I TOB 53 30 ■4-7 9.8 5-8 3-5 2.4 1.4 I 146 70 . 39 19-5 13.4 7.8 4-7 2.7 1.8 I 3 I i33 90 53 16. B 9.9 5-9 3-5 2.5 1-7 1.25 z 290 143 80 11 16 9.3 5-4 3-7 2.7 2 1.6 I 427 2 10 117 57 38 23 13-7 7-7 5-8 4-1 3-3 2-5 1-5 I 595 295 i6S 80 , 54 32 19 2^ ; .... 7.6 5-5 4.1 . 3-2 1 8 1.4 * Especially computed. Table XXIII. HORSE-POWER LOST IN FRICTION OF AIR PER 100 FEET OF PIPE. 50^ F. Velocity of Air, Feet per Second. Diame- ter of Pipe, Inches. 5 10 15 2<. 25 3° 40 5° 75 100 Horse-power Lost in Friction, 15 18 24 30 36 42 48 54 60 0001 .0011 .0036 .0086 .0167 .0289 .0685 ■1339 .4518 0003 .0021 .0072 .0171 •0335 .0578 ■■37' .2677 .9036 0004 .0032 .0108 ,0256 .0502 .0867 .2056 .4016 1.3554 0005 .0043 .0145 0343 .0669 .1156 .2741 ■5.354 1.8072 0007 .0053 .0182 .0430 ■0835 .1445 • 3425 .6695 2.2590 0008 .0064 .0217 .0512 .1004 •1735 .4112 .8031 2.7158 0008 .0075 ■0253 .0602 .1169 .2023 ■ 4795 •9373 3.1626 OOII .0086 .0289 .0685 ■1339 .23^3 .5483 I 0708 3.6144 00 J 4 .0107 .0361 .0857 •1673 2891 .6855 1.3388 4 5180 0016 .0128 •0434 .1024 .2008 • s-fSg .8224 1.6062 ';.42i6 0019 .0150 .0484 .1204 .2:138 .4046 .9590 1.8,46 6,5252 0021 .0171 .0578 •1371 .2677 .4626 1.0965 2.1416 7.2288 0024 .0193 .0648 .1548 .3006 .5202 1.2330 2.4102 8.1324 0027 .0214 .0723 .1713 -3346 .5782 I 3706 2.6771 9.0360 I .0710 2.T416 ;• 125 4.2833 4.3390 b 4249 7.4970 8 5666 10 7 01 12.849S 1 4 . 9900 17. '.331 19.2780 21.4164 •5 18 24 36 42 48 54 60 Pressure Lost, Ounces per Square I ich. .033 •'33 .300 •533 ■ 833. 1.200 2.133 3.333 7.500 .017 .067 .150 .267 .417 .600 1.067 1.667 3.750 .011 .044 .100 .178 .278 .400 .711 I. Ill 2.500 .008 .033 ■ 075 •133 .208 .300 •533 .833 1.875 .007 .027 .060 .106 .166 .240 .427 .667 1.505 .006 .022 .050 ,089 .139 200 .356 .556 1.250 .005 .019 .043 .076 .119 .172 • 305 .476 1.071 .004 .017 .037 .067 .104 .150 .267 .417 •9.37 .003 .013 .030 • 053 083 . 120 .213 .333 •750 .003 .oil .025 .044 .069 .loo .178 .278 .625 .002 .C09 .022 .038 .060 .086 .152 .238 .536 .002 .oo3 .019 , .033 .052 .07, •133 .208 .469 .002 .007 .016 .030 .046 .066 .118 .185 .417 .002 .007 .015 .027 .042 .060 .107 ..67 ■375 I3^333 6.667 4-444 3-333 2.666 2.222 1.905 1.667 1-333 I. Ill •952 •833 .741 .667 538 APPENDIX CONTAINING REFERENCES AND TABLES. Table XXIV. THEORETICAL HORSE-POWER REQUIRED TO MOVE A GIVEN VOLUME OF AIR, AT 70° F., AT A GIVEN VELOCITY. Velocitj of Air, Feet per Second Cu. Ft. of Air perMin., 5 10 '5 20 =S 30 40 SO 75 100 Temp. 70° F. i.Theoretical Horse-power. 1,000 .0009 .0035 0080 .0141 .022I .0318 .0566 .0884 .1987 ■3S3S 2,000 .0018 .0071 0.59 .0283 .0442 .0636 .1131 ..1768 ■ 3973 .7070 3,000 .0026 .0106 0239 .0424 ■°S$3 ■09S5 .1697 .2651 .5960 1.0605 4,000 .003s .0141 0318 .0566 .0884 .1273 .2262 ■3535 .7946 1.4140 5,000 .0044 .0177 0398 .0707 .1105 .1591 .2828 ■4419 ■9933 1.767s 10,000 .0088 •0353 0795 .1414 .2209 .3182 .5656 .8838 1.9866 3-5350 20,000 .0176 .0706 1590 .2828 .4418 • 6364 1.1312 1.7676 3 9732 7.0700 30,000 .0264 .1059 238s .4242 .6627 • 9546 1.6968 2.6514 5.9598 10.6050 40,000 ■ 0352 .1412 3180 .5656 .8836 1.2728 2.2624 3 5352 7.9464I 14.1400 50,000 .0440 .1765 3975 .7070 I. 1045 1.5910 2.8280 4.4190 9.933o| 17.6750 75,000 .0660 .2647 5962 I. 0605 1.6567 2.3865 4.2.(20 6.6285 14.7990' 26.5120 100,000 .0880 •3530 7950 I. 4140 2 . 2090 3.1820 5.6560 8.B380 19.8660' 35.3500 125,000 .noo .4412 9937 1.767s 2.7612 3-9775 7.0700 11.0475 24.7320' 44.1870 150,000 .1320 •5294 I 1924 2.1210 3.3'34 4.77.30 8 4840 13.2570 ^9-5980 53.0240 175,000 .1540 .6177 I 3912 2.4745 3-8657 S.5685 9.8980 14 4665 34.6650 61.8620 aoo,ooo .1760 . 7060 I 5900 2.8280 4.4180 6.3640 11.3120 17.6760 30.7320 7O.7O>0 For any other temperature, /, multiply by — (/ —32). 492 APPENDIX CONTAINING REFERENCES AND TABLES. 539 A u H < ^ fa O K u z t-t w z o fa o w « D yi en W tti a, H ►— t fa H o EC r/1 ^ t/i w O B< J •T-t X < fa h- (5- o w o < fa Pi D H IE o fa w fa fa o VI o in Iz; fa S 1 (A U u .5 s: K O* O *M II "^ 1 .2 en ;-< i II ""l p-jHico w M-o Tfc*ii- N cnr^o^o O « wocoi-'cnoor-* c<^co co o tn o o m C) '^ vo Nr^ococo Hr^c,! ou->cnM o mo Cl NO O^N Tj-M « c>mO M a*r--ena-in 8 ■^ r^M d-l-w\0 N Ten r^vo r^ O u^ in t-^ O •'i-'O oo o vo u-j M o O a>o cnco en i>- q ino O inintnino OinO O O O Om t^ino (N w N r-^u-)Or^»ninmmO r^ M inco o N Oco ini-finmcnOO NO M M M N N N COTtiOinOr^COOD OO 8 ^ trii^Ooo Nooco Nco r>.co cncoco cn^t- ON mO O^cohi t-^H me<^0 tnO mO ^MHtHiNcncn-^Tj- u-)0 o t-^ r^ i^ C| O0000'n000mu->0000"^ u-)0»ninoNOOONNin»nOON u O "*0 OO O O in HI O O CT>0 N CO en r^ H iH 1-1 w tM N en•T■^u^mor>^~coco [L. ^ cncnenni mwo 0"^Hioo H m cno r^ O^ N tj-o r-^cnO »nO ■^hioo cnoo n o iH Hi HI M N cnm^TTininoo r^r^ o c^ mu-iinininomo O O OO OinO tn N Nr^r-.Nu-ir»inmwiO O O N o N O cnuir^O^xncnO'^oo t-^ThO mo 't' M HI r-i H. H( N cncnrj-Tfmor^t^ooco 1 X ooo o -^oo N M mo cno x>-oo en Tj- N OO M e*-imo N O^Tj-co n CT>mO mOen HI M H M N N encn'T'^mooor^ Cl mOOOOOmOOOOmOOO»n r^O O OwimN O u-immN O 0"^r>. o^cnmr^co-tNQO NO -^M r^NO o H H( M M N enen-^^inoo r>.r^oo s. '^ Tj-w CT'ino^O^O inenr^co eneni-^uiM 00 M N -Tt-vnor^Nm OO N r^ hi m o H M M HI N N cnenen^tmrnooo c; inmmO O O O mO mOmmOmin N N N omO»nr-^Of^"^t-^w ONN O- N rfO r^enO mO enni t-^ cnoo N O H, HI HI H. N encn'^Tj-mmOOX-^t^ § i; t-.N o ■^r'-enTj-oo t-^N enoo or^r^ r^O N cn-^o^mo cno enoo no O en i_,iHHMHiNencnen'^'^.NNOOOinmNNt^r^N OO HI m rj-o Ht OO en r^ r^ enco c<^o O M HI HI H. N N cncn'>T'*"^lnoo^- s, ^ O O^ -^O r^oo Hi O m O O N O -TO O ooo o '-' NO cninoN r^NO on m ^^ S M M HI NN NenenTtTt-Tj-mm d mmomo O OmOmmOmOOin N r^mr^O mvnr>.\nN N ini>.mo N r^OM N -i-Qomoo NmMO O -i-co m K M M M N N cnen^rrrmmmo O ^j 1- 8888888888888888 o o o o o q_ o_ q o_ o^ o^ o_ o q q_ q_ M N en 'tt- vn O* o" d d" O" m o" m O in O HI N enTj-mt-^o w u-tr->o ,1. HI M M N 54° APPENDIX CONTAINING KEFEKENCES AND TABLES. Table XXVI. VOLUME OF AIR DISCHARGED AT VARIOUS PRESSURES THROUGH PIPE ONE FOOT IN DIAMETER, 100 FEET LONG, AT 60° F. Difference of Pressure. Velocity in Feet per Second. Inches of Water. Ounces per Square Inch By Unwin's Formula. Pipe I Ft. in Diam., By Approximate Formula. 100 Ft. long. r = .7 '^^igh- O.OI 0.006 4-3 4.6 0.05 0.030 9.6 9-5 O.I 0.058 14-5 14.5 0.2 O.I16 19.4 20.5 0.3 0.174 23.6 25-1 0.4 0.232 27.4 29.1 0.5 0.289 30.5 32.5 0.6 0.347 34.0 35.2 0.7 0.405 36.0 ■ 38.3 0.8 0.463 39-2 40.7 0.9 0.512 41.0 43-7 I.O 0.579 43-0 45-7 2.0 1. 158 61. 1 65.2 3.0 1.303 78.6 78.^ 4.0 2.316 85.3 91. 1 5.0 2.895 86.2 103.3 6.0 3-474 104.0 II3-3 7.0 4-053 114. 122. 1 8.0 4.622 121. 130.6 g.o 5.221 128.0 138.8 10. 5.790 136.0 I4S-7 II. 6.369 142.0 I53-0 12.0 6.948 148.0 159-6 For pipes of different diameters, d' , and lengths, /', multiply results in the above table by a/z-—. For different temperatures, ^, multiply results in table by i A^" + ' . r S20 APPENDIX CONTAINING REFERENCES AND TABLES. 541 Table No. XXVII. TEMPERATURES OF VARIOUS LOCALITIES. Compiled from Observations of the Signal Service, U. S. A., and Blodgett's " Climatology of the United States." Note, — In the United States the comfortable temperature of the air in occupied rooms is generally 70 degrees when walls have the same temperature. Station. No. of months fire is required. Albany, N. Y Baltimore, Md Boston, Mass Buffalo, N. Y Burlington, Vt . . . . Chicago, 111 Charleston, S. C. . . Cincinnati, O Cleveland, O Detroit, Mich Duluth, Minn Indianapolis, Ind. . Key West, Fla Leavenworth, Kan. Louisville, Ky Memphis, Tenn.. . Milwaukee, Wis.. . New Orleans, La. . New York, N. Y. . Philadelphia, Pa.. Pittsburg, Pa Portland, Me Portlrnd, Ore San Francisco, Cal St. Louis, Mo. ..'. . St. Paul, Minn.... Washington, D. C. Wilmington, N. C. Mean temp, of cold months. 7 6 7 8 7 7 3 7 7 7 8 7 o 6 6 5 8 o 7 7 7 8 6 4 5 7 5 4 35 39 37 35 32 35 52 42 38 35 28 41 o 37 42 39 37 o 40 40 39 33 43 53 37 25 40 50 Av. No. of deg. temp, to be raised. 35 31 33 35 38 35 18 28 32 35 42 29 o 33 28 31 33 o 30 30 31 37 27 17 33 45 30 20 Max. No. deg. temp, to be raised. 87 72 81 83 90 90 47 77 83 90 loS 88 26 90 80 68 95 44 76 75 82 82 67 34 86 102 73 55 Minimum tempera- ture F°. — 17 — 2 — H — 13 — 20 — 20 + 23 — 7 — 13 — 20 -38 — 18 + 44 — 20 — 10 + 2 — 25 + 26 — 6 — 5 — 12 — 12 + 3 + 36 — 16 -32 + 3 + 15 INDEX. Absolute Zero U Air, Amount for Ventilation 3 j 35 Air, Analysis of 27 Air and Gases, Flow of 47 Air, Bacteria in 23 Air, Changes per Hour 72 Air Circulation, Furnace Heating 311 Air, Cost of Moistening 459 Air Delivered by Pipes 386 Air, Dimensions of Pipe Lines for 346 Air Discharged from Fan 362 Air, Distribution of .■ 55 Air, Dry, Advantage of 458 Air, Effect of Heat on 38, 51 Air-filter 388 Air-filtration, Importance of 457 Air-filtration, Surface Required for 458 Air-flues, Indirect Heating 279 Air, for Various Standards of Purity, Tables 35, 36 Air, Force Required for Moving 38 Air, Humidity. 458 Air, Impurities in 23 Air-inlet, Location for 56 Air, Introduction into Rooms, Experiments 56 Air, Introduction of, into Rooms 373 Air-leakage, Rapidity of 454 Air, Measurement of Velocity 40 Air, Moisture Absorbed by 523 Air-outlet, Location for 58 Air, Properties of 521 Air, Relation between Force and Velocity 55 Air Required, Mechanical Ventilation 391 Air-space in Grate ^" Air Supplied a Room, Measurement of 373 543 544 INDEX. FAOB Air-supply for Furnace 317 Air-supply for Rooms Not Frequently Occupied 446 Air-supply for Schoolroom 435 Air-supply, Limitations 432 Air, Theoretical Work of Moving 343 Air Thermometer, Constant for _ 11 Air Thermometers 10 Air-trap 210 Air-valve, Automatic 134 Air-valve 132 Air-valve, Thermostatic ; 290 Air- valve, Moigan 295 Air, Velocity by Computation 43 Air, Velocity due to Natural Draft 531 Air, Velocity in Pipe, Ledoux' Formula 50 Air, Velocity in Pipe, Unwin's Formula 49 Air, "Velocity of Entering 50 Air Velocity on Different Floors 60 Air, Velocity through Heating 52 Air Warming, Fuel Consumption 443 Air, Work of Moving through Pipes 345 Air, Work in Heating 53 Allowance for Gas-burners in Ventilation 30 Analysis of Air 27 Anemometer, Calibration of •. . . 43 Anemometer,, Description of 40 4ngle Valve 130 Architect, Duty of 487 Area Cold-air Duct -. 247 Area of Flue for Given Amount of Heat, Table 265 Area of Grate 280 Area Hot-air Duct, Indirect Heating 247 Area of Pipe, Steam Heating 222 Area Smoke Flue 280 Area of Steam Main 253 Areas of Registers, Tables 320, 322 Areas of Stacks 321 Argon 23, 27 Artificial Heat, Demand for 1 Artificial Heat, Necessity for 1 Ash, Analysis of 531 Atmosphere, Composition and Pressure of 21 Atmosphere, Weight of 22 Attendance, Skilled, Required in Heating and Ventilating Plant 444 Back-pressure Valve 282, 288 Bacteria in Air 23 INDEX. 545 PAGE Bath-rooms, Ventilation of 44g Blowers or Fans in Mechanical Ventilation 388 392 Blowers, Volume or Positive 34j Blow-off Cocks or Valves 187 Boilers, Actual Power j53 Boiler, Babeock & Wilcox jg3 Boilers, Care of 199 Boiler, Computation of Heating Surface 280 Boiler Construction 100 Boiler, Dimensions, Table 161 Boiler Domes 161 Boiler Explosions 201 Boiler Explosions, Prevention of 206 Boilers, Fire-tube 158 Boiler Foundations 175 Boiler, Harrison 163 Boilers, Heating, Classification 160 Boiler, Heine 163 Boiler, Hogan 163 Boiler, Horizontal Tubular 160, 168 Boiler, Horse-power 152 Boiler, House-heating 154 Boilers, Locomotive and Marine 161 Boiler, Plain Surface 166 Boiler Power, Schoolroom Ventilation 438 Boiler Proportions, Table 156 Boiler, Rating of : 153 Boiler, Root 163 Boiler, Sectional 170, 171 Boiler, Setting for 173 Boiler, Size in Mechanical Ventilation 390, 392 Boiler Specifications 480 Boilers, Steam, General Requisites 151, 157 Boiler, Stirling 103 Boilers, Stored Energy in. Table 203 Blower Systems of Heating, Tests and Tables 107, 108, 109, 110 Boilers, Vertical 162 Boilers, Water-tube : 158, 163, 168 Books, List of, on Heating and Ventilating 493 Bourdon Gauge 184 Box Coil 139 Branch Pipes, Areas of 386 Branch Tees. 126 Breeching 1 ' ^ Brick Setting for Furnace ^31 British and Metric Systems, Equivalent Values 501 Bucket Trap 1^5 546 INDEX. PAGE Buckle's Proportions for Centrifugal Ventilators 334 Calibration of Anemometer 43 Capacity and Power of Fans 36G Capacity of Rectangular Pipes 349 Capacity, Practical Rule for Fan ' 364 Capell Fan, Description of 339 Carboeidometer, of Wolpert 29, 30 Carbonic Acid, Amount in Air 21, 25, 26 Carbonic Acid, Methods of Determining 28, 29, 30, 31, 32 Carbonic Oxide 26 Carpenter, R. C, Tests of Radiating Surfaces 98, 99, 104 Carpenter's Theory of Centrifugal Ventilators 356 Casing for Indirect Heatei's 147 Casings for Fans 336 Cast-iron Pipes and Fittings 117 Ceiling and Floor Plates 128 Centigrade Thermometer , 8 Centrifugal Ventilators, Author's Theory 356 Centrifugal Ventilators, Description of 334 Centrifugal Ventilator, Murgue's Theory of 349 C. G. S. System 5 Changes of Air per Hour 72 Check Valve 132 Chimney, Guibal 337 Chimney, Guibal, Effect of 352 Chimney Dimensions, Table •. 192 Chimney, Form of 190 Cliimney, Size of 191 Chimney Tops 192 Circles, Squares, and Cubes, Tables 503 Circulation Affecting Heat Transmission 87 Circulation in Gravity Systems 249 Circulation in Hot- water Pipes 250 Circumference and Area of Circles, Table 516 Class-rooms, Ventilation of 448 Coal per Square Foot of Grate 154 Coat-rooms, Ventilation of 448 Cocks 131 Cocks, Blow-off 187 Cocks, Try 182 CoefEcient of Heat Conduction, Defined 18 Coil Connections 138 Cold-air Box 317 Cold-air Duct, Area 247, 385 Combination Heaters 323 Combination Systems of Heating 218 INDEX. 547 PAGE' Combustion of Fuel, Efficiency 315 Complete Circuit System of Piping 210 Condenser, Siphon 286 Conducting Power for Heat, Table 18 Conduction of Heat 18, 78 Conductivities, Thermal 532 Conduits, Horizontal 395 Cone Blower, Description of 34I Constant for Air Thermometer , n Contents of Pipe in Gallons and Cubic Feet 536 Convection, Heat Removed by 83 Convection Loss from Different Bodies 80 Convection of Heat I9 Cooling of Rooms 405 Corner Coil 138 Corner Vsilve 131 Corridors, Ventilation of 447 Cost of Construction, Methods of Estimating 487 Cost of Electric Heating, Computations 407 Cost of Electric Heating, Table 409 Cost of Mechanical Ventilation 442 Cost of Moistening Air 459 Cost of Ventilation 436 Coupling, Reducing 122 Coupling, Right- and Left-hand 123 Coupling, Wrought-iron Pipe 122 Cross Valve 131 Cubic Space and Changes' of Air, Table 02 Damper Regulator, Connection for 177 Damper Regulators 186, 418, 420 Dampers, Volume or Regulating 381 Diaphragm Gauge 185 Diaphragm Valve 425 Diathermancy, Defined 16 Diathermanous Values, Tables 17 Diffusion of Gases ' 24 Diffusion of Heat 17 Direct Hot- water Heating Surface, Space Heated by 239 Direct-Indirect Radiators ; 146 Direct Steam-heating Surface, Space Heated by 238 Direct Radiation 80, 86 Disc and Propeller Fans, General Formulse for 372 Distributing Pipe 208 Double Sashing, Effect of 453 Double Windows 453 Draughtiness 432 54^ INDEX. PAGE Draughtiness in Outflowing Currents 435 Draughtiness, Means for Reducing 433 Drip-pipe 209 Drop Tube , 170 Dry Air, Advantage of 458 Ducts for Air Supply and Ventilation 264 Ducts or Flues, Dimensions 384 Economizer 293 Economy in Heating Systems 312 Efficiency of Combustion 315 Efficiency of Fan 344 Efficiency of Indirect Radiators, Tables 114 Efficiency, Relative, of Fans or Blowers 368, 371 Efficiency, Relative, of Heated Flues 368, 371 Elbows and Bends 118, 124 Electric Heater Connections 415 Electric Heaters, Construction of 412 Electric Heating, Cost of 407 Electric Heating, Diagram 412 Electric Heating, Formulae and General Considerations 410 Electric Heating, Principle of 411 Electrical Units, Relation to Heat 4 Emission of Radiant Heat 16 Equalizing Pipe Diameters, Table 387 Equalizing Valve 198 Equalization of Pipe Areas, Table 537 Equivalent Glass Surface 314 Equivalent Orifice, for Fan 349 Evans & Almirall, Heating System 292 Exhaust Fan 335 Exhaust Steam-heating 281 Exhaust Steam-heating, Paul System 290 Exhaust Steam-heating, Webster System 288 Exhaust Steam-heating, Williams' System : . . 287 Exhauster, Paul System 290 Expansion Joints 136 Expansion of Pipe 136 Expansion Plate 128 Expansion Tank 188 Expansion Trap 196 Extended Surface Heater 166 Extended Surface Radiator 142 Factory Heating 277 Fahrenheit Thermometer 7 Fan and Heating Surface, Arrangement of 379 INDEX. 549 PAGK Fan Capacity 3g^ Fan, Capell, Description of ; 33(j Fan Casings ggg Fan Dimensions 394 Fan Efficiency 34^ Fan, Maximum Pressure Produced by , 359 Fan, Practical Rule for Capacity 334 Fan, Rankine, Description of 34O Fan, Rule for Power 355 Fan, Tlieoretical Horse-power of • 344 Fan, Work Required to Run 353 Fan Tiieory, Application of 364 Fans, Disc or Propeller, General Formulse for 372 Fans, Propeller or Disc 341 Fans, Capacity and Power of 3Qg Fans or Blowers, Relative Efficiency of 368, 371 Field Tube 169 Filtration of Air, Importance of 457 Filtration dl Air, Surface Required for 458 Fire Protection 484 Fire-tube Boiler I57 Fittings, Cast-iron 122 . Fittings, Malleable Iron 122 Flange Unions 124 Float-trap 194 Flow of Air and Gases 47 Flow of Air through Orifice, Unwin's Formula 47 . Flow of Air through Orifice, Weisbaeh's Formula 47 Flow of Steam through Pipes 51 Flow of Water and Steam 247 Flow of Water through Pipes 51 Flue Area for Given Amount of Heat, Table 265 Flue Radiators 142 Flues, Heated, Relative Efficiency of 368, 371 Flues, Hot-air, Table 270 Flues and Registers, Dimensions of 62 Flues, Ventilating, Table 270 Foot-pound, Defined 3 Friction, Allowance for, in Case of Bends and Elbows 248 Fuel Consumption, Air Warming 443 Fuel Saved by Double Glazing 453 Fuels, Composition of 529, 530 Furnace 310, 312 Furnace Heating, Computations for 315 Furnace Heating, Proportions for 312, 317, 328, 329 Furnace Heating, Rules for 330 Furnace Heating, Specifications 330 SSO INDEX. PAGE Furnace Operation' 324 Furnaces, Practical Arrangement 324 Gas-burners, Allowance for, in Ventilation 30 Oases, Diffusion of 24 Gases, Properties of 502 Gate-valve 128 Gauge, Diaphragm 185 Gauge, Bourdon 184 Glazing, Double, Eflect of 453 Globe Valve 128 Governor for Pump 298 Grate Area 280 Grates 193 Gravity Circulating System, Steam-heating 208 Gravity Systems, Cause of Circulation in 249 Gravity Ventilation 440 Greenhouse Heating 268 Guibal Chimney 337 Guibal Chimney, Effect of ■ 352 Guibal Fan and Chimney, Modified Form, Description of 338 Guibal Fan, Description of 337 Head of Water Corresponding to Various Pressures 535 Head, Loss of, in Pipes 345 Heat Absorbed by Heating Surfaces 154 Heat, Conduction of 18, 78 Heat Contained in Water at Various Temperatures 528 Heat, Convection of 19 Heat, Difl'usion of 17 Heat Emitted by Radiation 82 Heat from Radiating Surfaces, Diagram 234 Heat, Intensity of 3 Heat, Its EfTect on Air 38, 51 Heat, Latent 151 Heat, Latent, Defined 15 Heat Loss from Buildings 64 Heat Loss from Pipes 305 Heat Loss from Pipes, Protection Against 228 Heat Loss in Underground Pipes, Tests 307 Heat Loss through Walls 06 67 Heat, Nature of 2 Heat Loss from Windows 65 Heat, Quantity of 3 Heat, Radiant, Defined 15 Heat, Relation to Electrical Lfnits 4 Heat, Relation to Mechanical Work 4 INDEX. 551 PAOB Heat Removed by Convection 83 Heat Required for Ventilation 69 Heat Required for Warming 232 Heat, Saved by Double Glazing 453 Heat, Solar, Effect of 45I Heat, Specific, Definition of 14 Heat, Total, by Radiation and Convection 84 Heat, Total, in a Body 14 Heat Transmission Affected by Circulation 87 Heat Transmission through Glass 65 77 Heat Transmitted in Blower Systems, General Equations Ill Heat Unit, British Thermal Unit 4 Heat Unit, Calorie 4 Heat Units from Different Surfaces, Direct Radiation 86 Heat Waste at Night 454 Heat Wasted 45O Heated Flues, Relative Efficiency of 368, 371 Heaters, Care of 201 Heaters, Combination 323 Heaters, Electric, Construction of 412 Heater, Extended Surface 16(5 Heater, Vertical Magazine 165 Heaters, Hot-water ■ 105 Heaters, Indirect 146 Heating and Grate Surface, Relative Proportions 153 Heating and Ventilating Systems, Methods of Installation 378 Heating Apparatus, Magnitude of Industry of Manufacture 1 Heating Boiler for Soft Coal ■ 172 Heating Boilers. . . .' 151) Heating Boilers with Magazine 171 Heating Boilers, Setting for 177 Heating by Contact, Convection 19 Heating by Exhaust Steam 281 Heating, Combination Systems 218 Heating, Hermetic, Johnson System 290 Heating, Hot-blast System 391 Heating, Mechanical Systems 377 Heating of Greenhouses 268 Heating Surface 151 Heating Surface, Form of 382 Heating Surface in Boiler 280 Heating Surface Required in Mechanical Ventilation 389, 391 -Heating System, Evans & Almirall 292 Heating System, Morgan 295 Heating System, Osborne •. • • ■ 294 Heating System, \' an Auken : 296 Heating System, Yarian 294 552 INDEX. FAQE Heating Systems, Combined Higli and Low Pressure 297 Heating Systems, Comparison 231 Heating, Tests of Blower Systems '07 Heating with Electricity ' 407 Heating with Exhaust Steam under Vacuum 285 Heating with Hot Air 310, 314 Heating with Refrigerating Machines 405 Heating with Stoves and Fire-places 323 Heating, Workshops and Factories 277 Hermetic Heating, Johnson System 296 High-pressure System, Steam-heating 208 Horizontal Tubular Boiler 160 Horse-power 5 Horse-power Boiler 152 Horse-power Lost in Friction in Pipes 537 Horse-power Required to Move Air 538 Horse-power, Theoi-etical, of Fans 344 Hot-air Circulating System 292, 322 Hot-air Duct, Area in Indirect Heating 247 Hot-air Flues, Table 270 Hot-air Heating 310, 314 Hot- and Cold-air Ducts, Relative Areas 385 Hot-water Damper Regulator, Lawler 418 Hot- water Heaters 165 Hot-water Heaters, Explosion of ' 206 Hot-water Heating, Connections to Mains 224 Hot-water Heating, Direct, Proportion of Parts, Table 269 Hot-water Heating, Greenhouses 273 Hot-water Heating, Indirect, Proportion of Parts, Table 269 Hot- water Heating Main, Direct Radiation 263 Hot-water Heating, Perkins' System 189, 211 Hot-water Heating, Pipe Connections 223 Hot-water Heating, Pressure System 189 Hot-water Heating, Return Pipe 264 Hot-water Heating, Rule for Size of Pipe 264 Hot-water Heating Systems, Summary of Methods for Design 278 Hot-water Pipes, Circulation in 250 Hot-water Radiator 142 Hot-water Radiators, Size of Pipe for 260 House-heating Boiler 154 House-heating Boilers, Tests of 155 Howard Regulator 421 Humidity of Air 458 Humidity of Air, Determination of 32 Humidity of Air, Influence on Ventilation 34 Humidity of Air, Table 33 Impurities in Air 23 INDEX. 553 Indirect Heater Piping 226 Indirect Heaters -.ar Indirect Heating Surface, Main and Return Pipes for 260 Indirect Heating, Surface Required 239 Indirect Heating Surface, Tests of 1q3 Indirect Hot-water Heating Surface, Space Heated by 245 Indirect Radiation ^ gQ gg Indirect Radiators, Efficiency, Tables X14 Indirect Steam-heating Surface, Space Heated by 244 Influence of Thickness of Material on Heat Transmission 81 Inlet Opening to Fan 33(5 Inlets, Location of 454 Introduction of Air into Rooms 373 Introduction of Air into Rooms, Experiments 56 Introduction of Air, Mechanical Ventilation 396 Johnson System of Hermetic Heating 296 Joule ; 4 Kent's Formula, Size of Chimney 191 Kinealy, Prof. J. H., Radiator Tests 113 Lap Welding Process 119 Latent Heat, Defined 15 Lavatory, Ventilation of 448 Leader Pipes 318 Leakage of Air, Rapidity of 454 Ledoux's Formula for Velocity of Air in Pipes 50 Local Ventilation .^. . . 456 Location of Inlets 454 Location of Outlets 456 Locomotive and Marine Boilers 161 Lock-nut and Nipple , 124 Logarithmic Tables 517 Long-distance Tiansmission of Steam 302 Loss in Transmitting Power 306 Loss of Effective Surface, Radiant Heat 86 Loss of Head in Pipe 345 Loss of Head or Pressure 48 Loss of Heat from Pipes 305 Main and Return Pipes for Indirect Heating Surface 260 Main Connections, Hot-water Heating 224 Main Flow-pipe, Steam-heating 208 Main Pipe, Steam-heating. . '. 208 Manifold Coil 137 Manometer 183 554 INDEX. PARE Manometer, Description of 41 Marine and Locomotive Boilers 161 Maximum and Minimum Thermometers 12 Maximum Velocity of Air, Mechanical Ventilation : 395 Measurement of Air Supplied in Room 373 Measurement of Radiating Suif ace 93 Mechanical Systems of Heating and Ventilating 377 Mechanical Ventilating Plant, Description 397 Mechanical Ventilation, Cost of 442 Mechanical Ventilation, Superiority of 441 Mechanical Ventilators, General Conditions 333 Mechanical Work, Relation to Heat 4 Mercurial Thermometers 10' Mill's System of Piping 211 Mills, J. H., Tests of Radiating Surfaces 97, 102, 105, 106- Mitre Branch Tee Coil 138- Mixing Dampers 381 Moisture Absorbed by Air 523 Moisture, Amount in Air 21 Morgan, Air- valve 295 Morgan, Heating System 295 Moving of Air, Force for 3S iMurgue's Theory of Centrifugal Ventilator 349 Murgue's Theory, Rateau's Modification of , ■ . ■ 355 Murgue's Theory,^ Summary of 354 Nature of Heat 2 Nitrogen 27 Noel Pyrometer 12 Offset 126 One-pipe System 210 One-pipe System, Hot-water 218 One-pipe System, Steam-heating 253 Orifice of Passage, for Fan 349 Osborne Heating System 294 Outlet Opening to Fan 336 Outlet Register, Size 5!^ Outlets, Location of 456 Oxygen in Air 24, 25 Ozone 21, 25 Painting Radiating Surface 94 Partial Circuit System of Piping 212 Paul System, Exhaust Steam-heating 290 Pficlet's Formulae for Loss of Heat , 73 Perkins' System, Hot-water Heating 189, 211 INDEX. 555 PAGE Petticoat Pipe jqj Pipe Area, Steam-heating 222 Pipe Boot 3jg Pipe Connections, Hat-water Heating 223 Pipe Connections, Steam-heating 221 Pipe Covering 228 Pipe Covering, Tests of. Table 229, 230 Pipe Dimensions for Given Discharge of Air 539 Pipe, Double-extra Strong 119 Pipe, Expansion of 136 Pipe, Extra Strong 1 ] <> Pipe-fltting, Suggestions 488 Pipe Fittings 122 Pipe Junctions, Tee's, Y's, etc 125 Pipe-lines for Air, Dimensions of 340 Pipe Eadiating Surface 137 Pipe, Relief and Drip 260 Pipe Sizes 12] Pipe, Standard Grade 110 Pipe, Steam, Computation for 252 Pipe System, Steam Not Returned to Boiler 227 Pipe Systems, Comparisons 227 Pipe Systems, Hot-water 215 Pipe, Table of Standard Dimensions 533 Pipe, Wooden Tube, Insulation for 304 Pipe, Wrought-iron and Steel 119. 121 Pipes and Fittings, Cast-iron 1 ] 7 Pipes for Hot Air 318 Piping, Arrangement of Cold and Hot Air 325 Piping, Complete Circuit System 210 Piping, Exhaust Heating 283, 285 Piping for Greenhouses 270 Piping for Hot-water 215 Piping Indirect Heaters 220 Piping, Indirect Heating 279 Piping, Mill's System 211 Piping, One-pipe System 210 Piping, One-pipe System for Hot-water 218 Piping, Partial Circuit System 212 Piping Systems. . . '. ""' Piping, Two-pipe System • • • • -^^ Pitch in Pipes 2"" Pitot-tube ^^' ^2 Plates, Ceiling and Floor 128 Plenum Method of Ventilating 454 Pop-valve 1^" Portable Setting for Furnace 331 556 INDEX. Portable Setting far Heating Boilers 177 Power and Capacity of Fans 366 Power Boiler 158 Power Boilei-s, Eating of 153 Power for Moving Air through Ventilating System 439 Power Required, Mechanical Ventilation 394 Power, Kule for Fan 365 Power's Regulator 418 Preparatory Warming 449 Pressure, Fan 335 Pressure, Head 41 Pressuie, Maximum, Produced by Fan or Blower 359 Pressure of Water for Different Heights 535 Propeller or Disc Fans 341 Properties of Familiar Substances 519 Properties of Gases 502 Proportions of Centrifugal Ventilation 334 Protection from Fire 484 Pump Governor 298 Pyrometer, Noel 12 Pyrometers, Description of 11 Radiant Heat, Defined 15 Radiant Heat, Emission of 16 Radiant Heat, Reflection and Transmission of 16 Radiating Surface, Allowance for Unusual Conditions 237 Radiating Surface, Eflfeet of Painting 94 Radiating Surface, Exhaust Heating 283, 285 Radiating Surface, Greenhouses 271 Radiating Surface, Grouping of 95 Radiating Surface, Heat from. Diagram 234 Radiating Surface, Indirect Heating 239, 279 Radiating Surface, Measurement of 93 Radiating Surface, Pipe 137 Radiating Surface Required for Warming 232 Radiating Surface, Rule for Computing 235 Radiating Surface, Rules for Estimating 245 Radiating Surface, Tests of 95 Radiation 15 Radiation and Convection, Total Heat Lost by 84 Radiation, Direct '. 80, 86 Radiation, Heat Emitted by 82 Radiation, Indirect 80 Radiator, Cast-iron, Sectional 140 Radiator, Cast-iron, Standard 139 Radiator, Cast-iron, Tests of 100 Radiator Connections, Hot-water 225 INDEX. 557 PAGE Eadiator Connections, Steam 221 Eadiator, Extended Surface ]^42 Eadiator, Flue j42 Eadiator, Hot-water 242 Eadiator Testing, Direct Steam 89 Eadiator Testing, Hot-water 92 Eadiator Testing, Indirect Steam 92 Eadiator Tests, Conclusions H2 Eadiator Tests with Superheated Steam IO3 Eadiator Valve I3 j Eadiator, Vertical Pipe X40 Eadiators, Direct-Indirect j4(3 Eadiators, Height of 95 Eadiators, Hot-water, Size of Pipe for 260 Eadiators, Proportion of Parts 149 Eankine Fan, Description of 34O Eapidity of Inleakage of Air 454 Eate of Cooling Due to Eadiation 82 Eateau Screw Fan 342 Eectangular Pipes, Capacity of 349 Eeducing Valve 300 Eeflection and Transmission of Eadiaut Heat 16 Eegister Area 388 Eegister Area, Tables 320, 322 Eegister Box 318 Eegister Details 327 Eegister, Size of 267, 280 Eegisters 384 Eegisters and Flues, Dimensions of 62 Eegisters, Floor and Wall, Merits of 321 Eegulator, Howard .'. . 421 Eegulator, Lawler, foi- Hot Water 418 Eegulator, Power's 418 Eegulator, Temperature 416 Eelation of Air to Vitality 431 Eelation of Ventilation to Heating 21 Eelative Tests, Hot-water and Steam-heating Plants for Greenhouses. . 274 Eelay 203 Eelief- and Drip-pipes, Size of 260 Eelief-pipe 209 Eeturn Bend 126 Eeturn Branch Tee Coil 138 Eeturn Pipe, Hot-water Heating 264 Eeturn Pipes, Steam-heating, Size of 259 Eeturn Eiser, Steam-heating 209 Eeturn Trap 197 Eiser, Steam-heating 209 5S8 INDEX. PAGE Root Positive Blower 342 Rule for Computing Radiating Surface 235 Rule for Fan Power 3G5 Rule for Size of Steam-pipes, Babcock's 254 Rule, Practical, for Fan Capacity 364 Rules for EJstimating Radiating Surface 245 Rules for Furnace Heating 330 Rust Joint 118 Safety-valve, Computation for 181 Safety-valve, Description 179 Safety-valve, Size, Table 181 Sanitary Rooms, Ventilation of 448 Sashing, Double, Effect of 453 Schoolhouse, Method of Warming, General Discussion 459 Sehoolhouse Warming and Ventilation, Character of Problem 430 Schoolroom Air-supply 435 Sectional Boilers 170, 171 Setting for Boilers 173 Setting for Indirect Heaters 148 Siphon 209 Siphon Condenser .' 286 Siphon Traps 194 Smoke-flue Area 280 Solar Heat, Eflfeet of 451 Space Heated by Direct Hot- water Heating Surface, Table 230 Space Heated by Direct Steam- heating Surface, Table 238 Space Heated by Indirect Hot- water Heating Surface, Table 245 Space Heated by Indirect Steam-heating Surface, Table 244 Specific Heat, Definition of 14 Specifications for Furnace Heating 330 Specifications, Form of Contract , 476 Specifications, General Business Methods 462 Specifications, General Requirements 463 Specifications, Heating Apparatus 466 Specifications, Tubular and Water-tube Boilers 480 Stack Areas 321 Stacks 318 Stacks, Indirect Heating 146 Standard Weights and Measures 499 Steam-boilers, General Requisites 151, 157 Steam Condensed in Heating 113 Steam, Flow of 248 Steam, Flow through Pipes 51 Steam-gauge, Connection for 177 Steam-heating Boilers, Care of 199 Steam-heating, Direct, Proportion of Parts, Table 269 INDEX. 559 PAQE steam-heating, Gravity Circulating System 208 Steam-heating, Greenhouses 273 Steam-heating, High-pressure System 208 Steam-heating, Indirect, Proportion of Parts, Table 209 Steam-heating, Pipe Connections 221 Steam-heating Systems, Summary of Methods for Design 278 Steam-loop .- 299 Steam-main, Area 253 Steam-pipes, Capacity 258 Steam-pipes, Size by Babcock Rule 254 Steam-pipes, Size of, in Direct Radiation, Tables 256, 257 Steam-piping, Computation 252 Steam, Properties of 524 Steam-radiator, Cast-iron, Sectional 140 Steam-radiator, Cast-iron, Standard 14U Steam-radiator, Vertical Pipe 139 Steam-space in Boilers 156 Steam-tables, Explanation of 150 Stone Walls, Heat Loss through 67 Strength of Materials, Coefficients 520 Stuffing-boxes 130 Successive Ventilation 445 Systems of Warming 20 Systems of Heating, Comparison 231 I Tables in Appendix, Explanation of 497 Tables in Appendix, List of 496 Tables in Body of Book, List of 495 Temperature 6 Temperature, by Color, Table 12 Temperature, by Melting Points ■. 12 Temperature Control, Automatic 452 Temperature, Defined 3 Temperature of Various Localities 541 Temperature Produced in Room when Outside Temperature is High. . . 114 Temperature Regulation 422, 424 Temperature Regulation, Saving Due to 426 Temperature Regulators. . . . .' 416 Tests of House-heating Bailers 155 Tests of Radiating Surface 95 Thermometer 18^ Thermometer, Centigrade 8 Thermometer Cup 13 Thermometer, Fahrenheit 7 Thermometer, Wet and Dry Bulb 32 ThermometerSi Air I*' Thermometers, Construction and Forms of 9 560 INDEX. PAOB Thermometers, Maxima and Minima 12 Tliermometers, Mercurial 10 Thermometers, Methods of use 13 Thermometric Scales, Tables 8 Thermostat 416 Thermostat, Johnson System 427 Thermostat, Pneumatic, Construction of 427 Thermostatic Valve, Webster 290 Thermostats 178 Transmission of Heat through Glass 65, 77 Transmitting Power, Loss in Different Systems of / . . . . 306 Transmission of Steam, Long-distance , 302 Trap, Bucket 195 Trap, Combined Float and Expansion 197 Trap, Counter-weighted 195 Trap, Expansion 196 Trap, Float 194 Trap, Return '. 197 Traps, Siphon 194 Tredgold, Experiments on Radiating Surface 96 Try-cocks 182 Two-pipe System 214 Underground Pipes, Heat Loss in 307 Un win's Formula for Flow of Air through Orifice 47 Unwin's Formula for Velocity of Air in Pipes 49 Vacuum Circulating System 294 Vacuum-gauge 185 Vacuum Heating System 285 Vacuum Method of Ventilating 454 Valve, Air 132 Valve, Angle.- 130 Valve, Automatic Air 134 Valve, Back-pressure 282, 288 Valve, Check 132 Valve, Corner 131 Valve, Cross 131 Valve, Diaphragm 425 Valve, Equalizing 198 Valve, Gate 128 Valve, Globe 128 Valve, Reducing 300 Valves and Cocks 128 Valves, Position in Pipes 225 Van Auken System of Heating 296 Volume of Air Discharged from Fan 362 INDEX. 561 PAOE Volume of Air Discharged through Pipes at Various Pressures 540 Volume or Positive Blowers 34I Volume or Regulating Dampers 381 Velocity Head 41 Velocity in Hot-water Pipes, Table 251 Velocity of Air by Computation 43 Velocity of Air by Heating 52 Velocity of Air Discharged from Fan 362 Velocity of Air Due to Natural Draft 531 Velocity of Air, Maximum in Mechanical Ventilation 395 Velocity of Air, Measurement of 40 Velocity of Air on Different Floors 60 Velocity of Air, Questions Relating to its Measurement 45, 46 Velocity of Entering Air 56 Vent-pipee 327 Ventilating Flue, Size 59 Ventilating Flues, Table 270 Ventilating, Mechanical Systems 377 Ventilating Plant, Test of 403 Ventilation, Amount of Air for 34, 35 Ventilation and Heating, Relation between 21 Ventilation by Gravity 440 Ventilation by Heating of Air 38, 39 Ventilation by Mechanical Means 39 Ventilation, Centrifugal, Murgue's Theory of 349 Ventilation, Centrifugal, Description of 334 Ventilation, Centrifugal, Proportions of 334 "Ventilation, Cost of 436 Ventilation, Heat Required for 69, 70 Ventilation, Influence of Humidity on 34 Ventilation, Influence of Size of Room on 37 A'^entilation, Local ^^^ Ventilation, Mechanical, Air Required 391 Ventilation, Mechanical, Power Required 394 Ventilation, Mechanical, Superiority of 441 Ventilation of Classrooms 448 Ventilation of Coat, Bath, Lavatory, and Sanitary Rooms 447 Ventilation of Corridors 447 Ventilation, Plenum Method 454 Ventilation, Size of Ducts 264 Ventilation, Summary of Problems 60 Ventilation, Successive 445 Ventilation, Vacuum Method 454 Ventilation without Heating 404 Vertical Boilers • ^^^ Walls, Heat Loss through 6^' ^'^ S62 INDEX. FAOE Warming by Eotaticm 449 Warming Closets 141 Warming, Quick Preparatory 449 Warming Schoolhouses, Method of, General Discussion 459 Warming, Systems of 20 Waste of Heat at Night 454 Water Column 183 Water, Flow of , 247 Water, Flow through Pipes 51 Water-gauge 182 Water-hammer 210 Water-heaters, Care of 201 Water-leg 1G2 Water-line, Steam-heating 209 Water-space in Boilers 156 Water Surface in Boilers 156 . Water-tube Boilers 158, 163, 168 Webster System, Exhaust Steam-heating 288 Webster Thermostatic Valve 290 Weight of Air ■ 22 Weight of Water per Cubic Foot at Various Temperatures 534 Weisbach's Formula for Flow of Air through Orifice 47 Wet- and Dry-bulb Thermometer 32 Williams's System, Exhaust Steam-heating 287 Windows, Double 453 Windows, Heat Loss from 65 Wood Tubing for Pipe Insulation 304 Work, Defined 3 Work Done in Heating Air 53 Work of Moving Air through Pipes 345 Work Required to Run Fan 363 Workshop Heating 277 Work, Theoretical, of Moving Air 313 Wrought-iron and Steel Pipe 119, 121 Wyekoff Built-up Wood Tubing 304 Yaryan Heating System 294 INDEX TO ADVERTISEMENTS American Blower Company 2 American Radiator Company 5 Buffalo Forge Company 3 HEEENDJiiEN MANUFACTURING COMPANY, ThE „ 5 Johnson Temperature Regulating Company . . » . . . . » 1 Nason Manufacturing Company 4 Stuetevant Company, B. F 7 Webster & Company, Warren 0...0... 6 5'i:^^:=:eJ?^^tf^^5S==:^S33'j^^'c£^^S=SJ^^^(i^^SS^::^^^'^ TEMPERATURE REGULATION. ^ ra ^ ^ THE JOHNSON SYSTEM THERMOSTAT. OF TEMPERATURE REGULATION has been in public use since 1883 with ever-increasing favor, and is now used in all classes of buildings where heating is required. This is the original and perfectly developed system and is applicable to every kind of heat- ing device. ( THE HUMIDOSTAT controls the humidity of rooms within Ml 2i, thus securing health, comfort, and p economy. The only device made ^ securing these results. Address Johnson Temperature Regulating Company, 240 FOURTH AVENUE, NEW YORK CITV. HUMIDOSTAT. ?em m^c ^- "A B C " Kan System OK Heating and Ventilation PROVIDES A UNIFORM DECREE OF HEAT. FURNISHES AMPLE VENTILATION. FIRST COST AND OPERATING EXPENSES LOW. SUITABLE FOR FACTORIES, CHURCHES, SCHOOLS, HOSPITALS, THEATRES, IN FACT, LARGE BUILDINGS OF ALL TYPES. THE MOST COMPLETE LINE OF HEATERS AND FANS ON THE MARKET. CATALOGUES ON REQUEST. Buffalo Fan System OF Heading ©end Ventil acting. For Schools, Churches, Theatres, and all Public and Industrial Buildings. BuffeiLlo Forge Con\pa.ny ENGINES ' For Electric Light arvd PoNver Service. Simplicity of Design. Durability of Construction. Close Regulation. Smooth Cool Running- at Sustained High Speed. Horizontal, Vertical, Simple, Compoxirvd, Belted, Direct- Connected. Buffalo Forge Company, BUFFALO. N. Y.. U. S. A. NASON SIDELUG " STEAM TRAP "Nasoii" Steam Traps for Pressures to 70 lbs. "Sidelug" Steam Traps for Pressures 70 to 150 lbs. Nasoii " Wrought Tube Radiators for Working Steam , Pressures to 250 lbs. fl. \L "Equator" Steam House Heater. |. "Gulf Stream" Hot Water House Heater. |f |i» "Nason" Ammonia Valves and Fittings ^ for Ice and Refrigerating Plants. ^ Pressure Regulating Valves for Steam, Water, ^ Gas, Air, Etc. STEAM PUMPS, AIR COMPRESSORS, FANS, BLOWERS, AND ENGINEERING SUPPLIES, AND SPECIALTIES OF EVERY DESCRIPTION. SEND FOR OUR 1902 CATALOGUE. NASON MANDFACTDRING COMPANY 71 Fulton Street, New York. I* I- 4 ^"Ji. sis^-^"<^-^.^*„^ FURMAN BOILERS. Made in Portable Brick-Set and Sectional Styles. Embracing 150 Different Sizes. Guaranteed Fully up to Tlieir Ratings. Capacities up to 8,000 Square Feet Radiating Surface. " In my experience there is no Boiler equal to tlie Furman New Sectional." — Gf.o. F. Bakbkk, Architect, Kno.wille, Tenn. Let us send ^'ou free a copy of our catalo,t;ue. Illustrating and Describing fully our Large and Complete line of Loilers. .\lso one of our 1 )raughtsniaii"6 Rules. Address : THE HERENDEEN MFG. CO. (DEPT. C B), GENEVA, N.Y. IDEAL BOILERS and AMERICAN RADIATORS. Lar";est Makers. Largest Assortment. Largest Value.^. Best Service. Send tor our Profusely Illustrated CATALOGUES.^ Ide-\l Premier EoiLEr Naiiokal Radiator. A MERICAN R ADIATOK C OMPANY General Offices, Chicago. Boston, New York, PHiLAijELi'Hi.\, r,i_!in-Ai.o, Si. L(ti;s, IVIinneaiolis, IJek\'er, Lonuon. THE ARCHITECT OR ENGINEER who fails to investigate claims to surpassing merit made by any apparatus entering into his work constantly runs the risk of remain= ing ignorant of something he would most gladly know of. The "Webster System" of Steam Circulation for Heating Purposes lays claims to an efficiency and economy which, if vindicated, con- stitute that system a class by itself. If the steam heating of a large and important building is a problem you must shortly solve, we shall be pleased to have you write us. WARREN WEBSTER & CO., CAMDEN, N. J. STURTEVANT Blowers of all Descriptions. steam Hot Blast Apparatus for Positive Ventilation and Heating. Generating Sets for General Lighting and Power Requirements. Steam Traps and other Sundries required for the Complete Equipment of Heating and Ventilating Installations. B. F. STURTEVANT CO. BOSTON, MASS. New York, Philadelphia, Chicago, London. SHORT-TITLE CATALOGUE OF THE PUBLICATIONS OF JOHN WILEY & SONS, New York. London: CHAPMAN & HALL, Limited. ARRANGED UNDER SUBJECTS. Descriptive circulars sent on application. Books marked witli an asterisk (*) are sold at net 'prices only, a double asterisk (**) books sold under the rules of the American Publishers' Association at net prices subject to an extra charge for postage. All books are bound in cloth unless otherwise stated. AGRICULTURE. Armsby's Manual of Cattle-feeding i2mo, Ji 75 Principles of Animal Nutrition 8vo, 4 00 Budd and Hansen's American Horticultural Manual: Part I. Propagation, Culture, and Improvement i2mo, i 3° Part II. Systematic Pomology i2mo, i 50 Downing's Fruits and Fruit-trees of America 8vo, 5 00 Elliott's Engineering for Land Drainage i2mo, i 50 Practical Farm Drainage i2mo, i 00 Graves's Forest Mensuration 8vo, 4 00 Green's Principles of American Forestry i2mo, i 50 Grotenfelt's Principles of Modern Dairy Practice. (WoU.) i2mo, 2 00 Kemp's Landscape Gardening i2mo, i 50 Maynard's Landscape Gardening as Applied to Home Decoration i2mo, i 50 * McKay and Larsen's Principles and Practice of Butter-making 8vo, i 50 Sanderson's Insects Injurious to Staple Crops i2mo, i so Insects Injurious to Garden Crops. (In preparation.) Insects Injuring Fruits. (In preparation.) Stockbridge's Rocks and Soils 8vo, 2 so Winton's Microscopy of Vegetable Foods. 8vo, 7 50 Woll's Handbook for Farmers and Dairymen i6mo, i 50 ARCHITECTURE. Baldwin's Steam Heating for Buildings i2mo, 2 so Bashore's Sanitation of a Country House i2mo, 100 Berg's Buildings and Structures of American Railroads 4to, 5 00 Birkmire's Planning and Construction of American Theatres 8vo, 3 00 Architectural Iron and Steel 8vo, 3 so Compound Riveted Girders as Applied in Buildings 8vo, 2 00 Planning and Construction of High Office Buildings 8vo, 3 so Skeleton Construction in Buildings 8vo, 3 00 Brigg's Modern American School Buildings 8vo, 4 00 ] Carpenter's Heating and Ventilating of Buildings Bvo, 4 00 Freitag's Architectural Engineering 8vo» 3 SO Fireproofing of Steel Buildings 8vo, 2 30 French and Ives's Stereotomy 8vo, 2 so Gerhard's Guide to Sanitary House-inspection i6mo, i 00 Theatre Fires and Panics i2mo, i 50 *Greene's Structural Mechanics 8vo, 2 50 Holly's Carpenters' and Joiners' Handbook i8mo, 7S Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 00 Kidder's Architects' and Builders' Pocket-book. Rewritten Edition. r6nio, mor., s 00 Merrill's Stones for Building and Decoration 8vo, 5 00 Non-metalUc Minerals: Their Occurrence and Uses 8vo, 4 00 Monckton's Stair-building 4to, 4 00 Patton's Practical Treatise on Foundations 8vo, 5 00 Peabody's Naval Architecture 8vo, 7 50 Rice's Concrete-block Manufacture 8vo, 2 00 Richey's Handbook for Superintendents of Construction i6mo, mor., 4 00 * Building Mechanics' Ready Reference Book. Carpenters* and Wood- workers* Edition i6mo, morocco, i 50 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 00 Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, i 50 Snow's Principal Species of Wood 8vo, 3 so Sondericker's Graphic Statics with AppUcations to Trusses, Beams, and Arches. 8vo, 2 00 Towne's Locks and Builders* Hardware i8mo, morocco, 3 00 Wait's Engineering and Architectural Jurisprudence 8vo, 6 00 Sheep, 6 so Law of Operations Preliminary to Construction in Engineering and Archi- tecture 8vo, s 00 Sheep, s So Law of Contracts 8vo, 3 00 Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .8vo, 4 00 Woicester and Atkinson's Small Hospitals, Establishment and Maintenance, Suggestions for Hospital Architecture, with Plans for a Small HospitaL i2mo, I 25 The World's Columbian Exposition of 1893 Large 4to, i 00 ARMY AND NAVY. Bemadou's Smokeless Powder, Nitro-cellulose, and the Theory of the Cellulose Molecule i2mo, 2 so * Bruff's Text-book Ordnance and Gunnery 8vo, 6 00 Chase's Screw Propellers and Marine Propulsion 8vo, 3 00 Cloke's Gunner's Examiner gvo, i 50 Craig's Azimuth ^to, 3 so Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 00 * Davis's Elements of Law 8vq^ 2 50 * Treatise on the MiUtary Law of United States 8vo, 7 00 Sheep, 7 so De Brack's Cavalry Outposts Duties. (Carr. ) 24mo, morocco, 2 00 Dietz's Soldier's First Aid Handbook i6mo, morocco, 1 25 * Dredge's Modern French Artillery 4to, half morocco, is 00 Durand's Resistance and Propulsion of Ships 8vo, s 00 * Dyer*s Handbook of Light Artillery. i2mo, 3 00 Eissler's Modern High Explosives 8vo, 4 00 * Fiebeger's Text-book on Field Fortification Small 8vo, 2 00 Hamilton's The Gunner's Catechism i8mo i 00 * Hoff's Elementary Naval Tactics 8vo, i so 2 Ingalls's Handbook of Problems in Direct Fire 8vo * Ballistic Tables 8vo' * Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II. . 8vo, each' * Mahan's Permanent Fortifications. (Mercur.) 8vo, half morocco' Manual for Courts-martial i6mo, morocco,' * Mercur's Attack of Fortified Places ; iimo * Elements of the Art of War 8vo' Metcalf's Cost of Manufactures— And the Administration of Workshops. ,8vo! * Ordnance and Gunnery. 2 vols i2mo' Murray's Infantry Drill Regulations i8mo, paper' Nixon's Adjutants' Manual ' j-n,,,' Peabody's Naval Architecture g^g' * Phelps's Practical Marine Surveying ', gyg' Powell's Army Ofllcer's Examiner . , i2moi 4 00 Sharpe's Art of Subsisting Armies in War i8mo, morocco! i So * Tupes and Poole's Manual of Bayonet Exercises and Musketry Fencing. 24mo, leather, 50 * Walke's Lectures on Explosives gvo 4 00 Weaver's Mihtary Explosives g^o ' 3 ^^ * Wheeler's Siege Operations and Military Mining 8vo', Winthrop's Abridgment of MiUtary Law i2mo,' Woodhull's Notes on MiUtary Hygiene i6mo Yoi-ng's Simple Elements of Navigation i6mo, morocco! 4 00 I 50 6 00 7 SO I 50 2 00 4 00 5 00 5 00 10 I 00 7 SO 2 so 00 so SO 00 ASSAYING. Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. * i2mo, morocco, i so Furman's Manual of Practical Assaying 8vo, 3 00 Lodge's Notes on Assaying and Metallurgical Laboratory Experiments 8vo, 3 00 Low's Technical Methods of Ore Analysis 8vo, 3 00 Miller's Manual of Assaying , i2mo, i 00 Cyanide Process i2mo, t 00 Minet's Production of Aluminum and its Industrial Use. (Waldo.) i2mo, 2 50 O'DriscoU's Notes on the Treatment of Gold Ores 8vo, 2 00 Ricketts and Miller's Notes on Assaying 8vo, 3 00 Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 4' 00 Ulke's Modern Electrolytic Copper Refining 8vo, 3 00 Wilson's Cyanide Processes i2mo, i so Chlorination Process i2mo, i so ASTRONOMY. Comstock's Field Astronomy for Engineers 8vo, 2 50 Craig's Azimuth 4to, 3 50 Doolittle's Treatise on Practical Astronomy 8vo, 4 00 Gore's Elements of Geodesy 8vo, 2 so Hayiford's Text-book of Geodetic Astronomy 8vo, 3 00 Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 so '* Michie and Harlow's Practical Astronomy 8vo, 3 00 •* White's Elements of Theoretical and Descriptive Astronomy i2mo, 3 00 BOTANY. Davenport's Statistical Methods, with Special Reference to Biological Variation. i6mo, morocco, i 25 Thomi' and Bennett's Structural and Physiological Botany i6mo, 2 25 Westernraier's Compendium of General Botany. (Schneider.) 8vo, 2 00 3 CHEMISTRY. Adriance's Laboratory Calculations and Specific Gravity Tables i2nio, i 25 Alexeyefi's General Principles of Organic Synthesis. (Matthews.) 8vo» Allen's Tables for Iron Analysis 8vo, Arnold's Compendium of Chemistry. (Mandel.) Small 8vo. Austen's Notes for Chemical Students i2mo, Bernadou's Smokeless Powder. — Nitro-cellulose, and Theory of the Cellulose Molecule i2mo» * Br'owning's Introduction to the Rarer Elements 8vo, Brush and Penfield's Manual of Determinative Mineralogy. 8vo, Claassen's Beet-sugar Manufacture. (Hall and Rolfe.) 8vo, Classen's Quantitative Chemical Analysis by Electrolysis. (Eoltwood.). .8vo, Cohn's Indicators and Test-papers i2mo, Tests and Reagents 8vo, Crafts's Short Course in Qualitative Chemical Analysis. (Schaeffer.). . .i2mo, Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von Ende.) i2mo, Drechsel's Chemical Reactions. (Merrill.) i2mo, Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, Eissler's Modern High Explosives 8vo, Effront's Enzymes and their Applications. (Prescott.) 8vOj Erdmann's Introduction to Chemical Preparations. (Dunlap.) i2mo, Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. i2mo, morocco, Fowler's Sewage Works Analyses i2mo, Fresenius's Manual of Qualitative Chemical Analysis. ("Wells.) 8vo, Manual of Qualitative Chemical Analysis. Part I. Descriptive. (Wells.) 8vo, System of Instruction in. Quantitative Chemical Analysis. (Cohn.) 2 vols 8vo, Fuertes's Water and Public Health i2mo, Furman's Manual of Practical Assaying 8vo, * Getman's Exercises in Physical Chemistry i2mo> Gill's Gas and Fuel Analysis for Engineers i2nio, Grotenfelt's Principles of Modern Dairy Practice. (Woll.) i2mo, Groth's Introduction to Chemical Crystallography (Marshall) i2mo, i 25 Hammarsten's Text-book of Physiological Chemistry. (Mandel.) 8vo, 4 00 Helm's Principles of Mathematical Chemistry. (Morgan.) i2mo, i 50 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco» 2 50 Hind's Inorganic Chemistry 8vo, 3 ty * Laboratory Manual for Students i2m:0, i 00 Holleman's Text-book of Inorganic Chemistry, (Cooper.) 8vo, 2 50 Text-book of Organic Chemistry. (Walker and Mott.) 8vo, 2 50 * Laboratory Manual of Organic Chemistry. (Walker.) i2mo, i 00 Hopkins's Oil-chemists' Handbook 8vo, 3 00 Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, i 25 Keep's Cast Iron 8vo, 2 50 Ladd's Manual of Quantitative Chemical Analysis i2mo, i 00 Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 00 * Langworthy and Austen. The Occurrence of Aluminium in Vegetable Products, Animal Products, and Natural Waters 8vo, 2 00 Lassar-Cohn's Practical Urinary Analysis. (Lorenz.) i2mo, i 00 Application of Some General Reactions to Investigations in Organic Chemistry. (Tingle.) i2mo, i 00 Leach's The Inspection and Analysis of Food with Special Reference to State Control 8vo, 7 50 Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 3 00 Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. .. .8vo, 3 00 Low's Technical Method of Ore Analysis 8vo, 3 00 Lunge's Techno-chemical Analysis. (Cohn.) i2mo i 00 4 3 00 3 00 3 so I 50 2 SO I 50 4 00 3 00 3 CO 2 00 3 00 I so 2 SO I 25 4 00 4 00 3 00 I 2S I SO ^ 00 5 00 3 00 12 50 I SO 3 00 2 00 I 2S SO SO 6o GO 2S SO 00 oo oo so so oo oo so 50 5 oo 2 oo 2 00 I so 2 00 so S oo 1 so * McKay and Larsen's Principles and Practice of Butter-making 8vo Handel's Handbook for Bio-chemical Laboratory i2mo * Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe. . i2mo. Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 3d Edition, Rewritten 8yq Examination of Water. (Chemical and Bacteriological.) i2mo, Matthew's The Textile Fibres gvo, Meyer's Determination of Radicles in Carbon Compounds. (Tingle.). . i2mo, Miller's Manual of Assaying i2mo Cyanide Process i2mo, Minet's Production of Aluminum and its Industrial Use. (Waldo.) . . . . i2mo, Mixter's Elementary Text-book of Chemistry i2mo, Morgan's An Outline of the Theory of Solutions and its Results i2mo, Elements of Physical Chemistry i2mo, * Physical Chemistry for Electrical Engineers i2mo, Morse's Calculations used in Cane-sugar Factories i6mo, morocco, Mulliken's General Method for the Identification of Pure Organic Compounds. Vol. I Large 8vo, O'Brine's Laboratory Guide in Chemical Analysis 8vo, O'Driscoll's Notes on the Treatment of Gold Ores 8yo, Ostwald's Conversations on Chemistry. Part One. (Ramsey.) i2mo, " " " Part Two. (Turnbull.) i2mo, * Penfleld's Notes on Determinative Mineralogy and Record of Mineral Tests. 8vo, paper, Pictet's The Alkaloids and their Chemical Constitution. (Biddle.) 8vo, Pinner's Introduction to Organic Chemistry. (Austen.) i2mo.- Poole's Calorific Power of Fuels 8vo, Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- ence to Sanitary Water Analysis i2mo, i 25 * Reisig's Guide to Piece-dyeing 8vo, 23 00 Richards and Woodman's Air, Water, and Food from a Sanitary Standpoint. .8vo , 2 00 Ricketts and Russell's Skeleton Notes upon Inorganic Chemistry. (Part I. Non-metallic Elements.) 8vo, morocco, Ricketts and Miller's Notes on Assaying gvo, Rideal's Sewage and the Bacterial Purification of Sewage 8vo, Disinfection and the Preservation of Food 8vo, Riggs's Elementary Manual for the Chemical Laboratory 8vo, Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, Rostoski's Serum Diagnosis. (Bolduan.) i2mo, Ruddiman's Incompatibilities in Prescriptions 8vo, * Whys in Pharmacy i2mo, Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo, Schimpf's Text-book of Volumetric Analysis i2mo, Essentials of Volumetric Analysic i2mo, * Qualitative Chemical Analysis 8vo, Smith's Lecture Notes on Chemistry for Dental Students 8vo, Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco. Handbook for Cane Sugar Manufacturers i6mo, morocco, Stockbridge's Rocks and Soils 8vo, * Tillman's Elementary Lessons in Heat 8vo, * Descriptive General Chemistry 8vo, Treadwell's Qualitative Analysis. (Hall.) 8vo, Quantitative Analysis. (Hall.) 8vo, Turneaure and Russell's Public Water-supplies 8vo, Van Deventer's Physical Chemistry for Beginners. (Boltwood.) i2mo, * Walke's Lectures on Explosives 8vo, Ware's Beet-sugar Manufacture and Refining Small 8vo, cloth, Washington's Manual of the Chemical Analysis of Rocks 8vo, 5 3 00 3 SO 4 00 I 25 4 00 I 00 2 oc I oa 3 00 2 SO 2 SO I 23 r 25 2 SO 3 00 3 00 2 SO I so 3 00 3 00 4 00 5 00 I SO 4 00 4 00 2 00 Wassermann's Immune Sera : Haemolysins, Cytotoxins, and Precipitins. (Bol- duan.) i2mo, t oo "Weaver's Military Explosives 8vo, 3 00 "Wehrenfennig's Analysis and Softening of Boiler Feed-Water 8vo, 4 00 Wells's Laboratory Guide in Qualitative Chemical Analysis 8vo, i 50 Short Course in Inorganic Qualitative Chemical Analysis for Engineering Students lamo, i 50 Text-book of Chemical Arithmetic i2mo, i 25 Whipple's Microscopy of Drinking-water 8vo, 3 50 Wilson's Cyanide Processes i2mo, i 50 Chlorination Process 121110, i 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 V/ulling's Elementary Course in Inorganic, Pharmaceutical, and Medical Chemistry i2mo, 2 00 CIVIL ENGINEERING. BRIDGES AND ROOFS- HYDRAULICS. MATERIALS OF ENGINEERING, RAILWAY ENGINEERING. Baker's Engineers' Surveying Instruments i2mo, 3 00 Bixby's Graphical Computing Table Paper igi X 24^ inches. 25 ** Burr's Ancient and Modern Engineering and the Isthmian Cana .. (Postage, 27 cents additional.) 8vo, 3 so Comstock's Field Astronomy for Engineers 8vo, 2 50 Davis's Elevation and Stadia Tables 8vo, i 00 Elliott's Engineering for Land Drainage i2mo, i 50 Practical Farm Drainage i2mo, i 00 *Fiebeger's Treatise on Civil Engineering 8vo, 5 00 Flemer's Phototopographic Methods and Instruments 8vo, 5 00 Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 00 Freitag's Architectural Engineering. 2d Edition, Rewritten 8vo, 3 50 French and Ives's Stereotomy 8vo, 2 50 Goodhue's Municipal Improvements i2mo, i 75 Goodrich's Economic Disposal of Towns' Refuse - 8vo, 3 50 Gore's Elements of Geodesy 8vo, 2 50 Hajrford's Text-book of Geodetic Astronomy 8vo, 3 00 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Howe's Retaining Walls for Earth i2n:o, i 25 * Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. 25 Ives and Hilts's Problems in Surveying i6mo, morocco, i 50 Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 00 Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 00 Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . i2mo. 2 00 Hahan's Treatise on Civil Engineering. (1873.) (Wood.) 8vo, 5 00 * Descriptive Geometry 8vo, 1 50 Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 Merriman and Brooks's Handbook for Surveyors i6mo, morocco, 2 00 Nugent's Plane Surveying 8vo, 3 50 Ogden's Sewer Design i2mo, 2 00 Parsons's Disposal of Municipal Refuse 8vo, 2 00 Patton's Treatise on Civil Engineering 8vo half leather, 7 50 Reed's Topographical Drawing and Sketching 4to, 5 00 ■ Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 3 50 Siebert and Biggin's Modern Stone-cutting and Masomy 8vo, i 50 Smith's Manual of Topographical Drawing. (McMillan.) 8vo, 2 50 Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 8vo, 2 00 6 Taylor and Thompson's Treatise on Concrete, Plain and Reinf orcea 8vo, s o» * Trautwine's Civil Engineer's Pocket-hook i6mo, morocco, 5 oo Venable's Garbage Crematories in America 8vo, 2 00 Wait's Engineering and Architectural Jurisprudence Svo, C co Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture 8vo, 5 oo Sheep, s 50 Law of Contracts Svo, 3 00 Warren's Stereotomy — Problems in Stone-cutting Svo, 2 50 Webb's Problems in the Use and Adjustment ci Engineering Instnmients. l6nio, morocco, i 25 Wilson's Topographic Surveying Svo, 3 50 BRIDGES AND ROOFS. Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .8vo, 2 00 ♦ Thames River Bridge 4to, paper, s 00 Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and Suspension Bridges Svo, 3 so Burr and Falk's Influence Lines for Bridge and Roof Computations Svo, 3 o» Design and Construction of Metallic Bridges Svo. 5 oo Du Bois's Mechanics of Engineering. Vol. II f mall 4to, 10 00 Foster's Treatise on Wooden Trestle Bridges 4to, s 00 Fowler's Ordinary Foundations Svo, 3 50 Greene's Roof Trusses Svo, i 2S Bridge Trusses Svo, 2 50 Arches in Wood, Iron, and Stone Svo, 2 so Howe's Treatise on Arches Svo, 4 00 Design of Simple Roof-trusses in Wood and Steel Svo, 2 00 Symmetrical Masonry Arches Svo, 2 so Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of Modern Framed Structures Small 4to, 10 00 Merrlman and Jacoby's Text-book on Roofs and Bridges: Part I. Stresses in Simple Trusses Svo, 2 so Part II. Graphic Statics Svo, 2 50 Part ni. Bridge Design Svo, 2 so Part IV. Higher Structures Svo, 2 so Morison's Memphis Bridge 4to, 10 00 Waddell's De Pontibus, a Pocket-book for Bridge Engineers . . i6mo, morocco, 2 00 * Specifications for Steel Bridges i^nio, so Wright's Designing of Draw-spans. Two parts in one volume Svo, 3 5°. HYDRAULICS. Barnes's Ice Formation °'^°' Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from an Orifice. (Trautwine.) 8vo, Bovey's Treatise on Hydraulics ^™, Church's Mechanics of Engineering 8™, Diagrams of Mean Velocity of Water in Open Channels paper. Hydraulic Motors ^™' Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, Flather's Dynamometers, and the Measurement of Power i2mo, Folwell's Water-supply Engineering 8vo, Frizell's Water-power ™' 7 2 00 s 00 6 00 I SO 2 00 2 SC' 3 00 4 00 S 00 4 00 S 00 4 00 S oo 6 00 5 oo 5 00 10 00 I so 4 oo 3 00 2 so 3 oo Fuertes's "Water and Public Health » . i2mo, i 50 Water-filtration Works i2mo, 2 50 Ganguillet and Kutter's General Formula for the Uniform Flow of Water in Rivers and Other Channels. (Hering and Trautwine.) 8vo, 4 00 Hazen's Filtration of Public Water-supply 8vo, 3 00 Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50 Herschers 115 Experiments on the Carrying Capacity of Large, Riveted, Metal Conduits 8vo, 2 00 Mason*s Water-supply. (Considered Principally from a Sanitary Standpoint.) 8vo, Merriman's Treatise on Hydraulics Svo, * Michie*s Elements of Analytical Mechanics 8vo, Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- supply Large Svo, ** Thomas and Watt's Improvement of Rivers CPost., 44c. additional.) 4to, Turneaure and Russell's Public Water-supplies 8vo, Wegmann's Design and Construction of Dams 4to, Water-supply of the City of New York from 1658 to 1895 4to, Williams and Hazen's Hydraulic Tables 8vo, Wilson's Irrigation Engineering Small Svo, Wolff's Windmill as a Prime Mover Svo, Wood's Turbines Svo, Elements of Analytical Mechanics Svo, MATERIALS OF ENGINEERING. Baker's Treatise on Masonry Construction Svo, Roads and Pavements Svo, Black's United States Public Works Oblong 4to, * Bovey's Strength of Materials and Theory of Structures Svo, Burr's Elasticity and Resistance of the Materials of Engineering Svo, Byrne's Highway Construction Svo, Inspection of the Materials and Workmanship Eijiployed in Construction, i6mo. Church's Mechanics of Engineering Svo, Du Bois's Mechanics of Engineering. Vol. I Small 4to, ^Eckel's Cements, Limes, and Plasters Svo, Johnson's Materials of Construction Large Svo, Fowler's Ordinary Foundations Svo, Graves's Forest Mensuration 8vo, * Greene's Structural Mechanics Svo, Keep's Cast Iron 8vo, Lanza's Apphed Mechanics Svo, Marten's Handbook on Testing Materials. (Henning.) 2 vols Svo, Maurer's Technical Mechanics. 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