MC-NRLF 075 UNIVERSITY OF CALIFORNIA ANDREW SMITH HALLIDIC: 1868^^^, 19O1 THE ENGINEERING RECORD SERIES STEAM HEATING AND VENTILATION BY WILLIAM S. I^ONROE, M. E. Member American Society of Mechanical Engineers. Member American Society of Heating and Ventilating Engineers. Member Western Society of Engineers. NEW YORK THE ENGINEERING RECORD 1902 f. ' r Draln. J >Wr f tvet 0nm-* 0c//er in ttoilv. Figure 2. The Two-pipe System. ly of large size and given a very decided fall toward the boiler from all directions. Two-pipe system. The more usual system of piping, and that first employed, is known as the "two-pipe system," and is repre- sented in Figure 2. In this, each radiator has one pipe for supply- ing steam and another to remove the water of condensation. The only object in the two-pipe connection is to provide a freer and more positive flow of steam and condensed water, but this is a STEAM HEATING AND VENTILATION. 15 very important consideration. In a one-pipe system, such as indi- cated by Figure 1, the water of condensation flows from the radia- tors back to the boilers against the current of steam, falling through the steam in the vertical pipes and flowing along the bot- tom of the horizontal pipes. Such a simple system as this, shown in Figure 1, might be employed, and to a considerable extent, if the pipes are of ample size, and also if there are no valves on the radiators, so that steam can be turned on the entire system at all times. In this case there would be a constant and practically uniform flow of water through the pipes, and, if these were prop- erly laid out, the system might give perfect satisfaction. But it is impracticable to have all the radiators of a system turned on at one time, and the difficulty with such a system is made evident the minute steam is turned into a cold radiator. When the steam comes in contact with a perfectly cold radiator a large amount is condensed at once in heating the cold iron, and as soon as the pressure becomes adjusted this bulk of water flows out of the radia- tor connection at one time and drops down the vertical pipe. When it reaches the horizontal main in the basement it is picked up by the current of steam and carried to other parts of the system, filling up the pipes in places; and as it is relatively much colder than the steam, the latter, in trying to get by it, is suddenly con- densed, disturbing the equilibrium of pressure, as we might say, and producing the disagreeable crackling and pounding noises which are always encountered in poorly constructed heating sys- tems, and which are commonly known undei the name of water- hammer. This noise, besides being very annoying to the occupants of the building, interferes with the circulation of steam and also produces undue strains in the piping. The two-pipe system to a certain extent does away with these difficulties ; that is, in using the two-pipe connectioL it is generally easier to avoid the water-hammer and other annoyances incident to imperfect circulation; but unless the pipes are properly propor- tioned and properly drained the sarrnj difficulties will be encoun- tered. The simple one-pipe system, indicated in Figure 1, is there- fore, as before stated, rarely, if ever, used, but there are a number of modifications of it which are used with decided success, and in some of the largest installations. One-pipe system with separate return main. The simplest one- pipe system usually employed is represented in Figure 3. In this 16 STEAM HEATING AND VENTILATION. the horizontal steam main in the basement is pitched so as to drain away from the boiler, and at its extreme end a return pipe is con- nected and led back to the boiler, entering it below the water-line. In this way the flow of steam and water of condensation is in the same direction in the mains, and upon the sudden condensation of considerable steam, as will occur when turning steam into a cold radiator, the water falls down the risers against the current of steam; but in the main it is propelled along in the same direction as the steam current. If the mains are extensive they can, more- over, be drained at several different points. This system is exten- sively used for residences and buildings of only a few stories in height, and it has also been used in larger installations. The Chi- cago Athletic Club, a building ten stories in height, is heated by O .Oar. Figure 3. A Common Type of One-pipe System. exhaust steam with this system of piping with a pressure of not over 2 pounds in the coldest weather, and with little, if any > difficulty with water-hammer. In such a plant the risers as well as the mains must be of ample size, and the latter must have suffi- cient pitch and be thoroughly drained. The consideration of these questions as affecting the size of the pipes will be taken up in a subsequent chapter. Mills' system. The only system of single-pipe connection which has been very extensively .used in high buildings, such as the mod- ern office building, is that known as the one-pipe overhead, or Mills' system, and is indicated diagrammatically in Figure 4. In this system the steam is conducted through a large main supply pipe to the attic of the building, or to the ceiling of the top floor. STEAM HEATING AND VENTILATION. 17 and from this the mains extend around the building to supply the risers. The risers are connected to the return mains in the base- ment. It will be seen that in this system the current of steam and water of condensation is everywhere in the same direction ex- cept in the connections to the radiators, and the risers should be sufficient in number so that these connections may be compara- tively short. This arrangement has the very decided advantage over the ordinary upward-supply one-pipe system that the water of condensation that falls down the risers from the radiators does not, when it reaches the horizontal pipe at the bottom, encounter the main current of steam, as the horizontal pipe is only a drain pipe, in which there is practically no steam current, and which is designed solely to dispose of this water. a a a cr cr Floor. L//.r SL^w* Q noon a a a a a ^n ^ -a cr a * | cr a a OLflto: _Jasemenr. a a . .. ffeturri. 3H r Rttvrn. ~f C- - Figure 4. The Mills System. Two-pipe, overhead system. The principle of the two-pipe system is much the same in all cases, but special adaptations of it are made to meet special conditions. There is, for example, a two-pipe over- head system in which steam mains are in the attic as well as in the one-pipe overhead, but there is a separate set of return risers which connect with the return mains in the basement. But each supply riser should also be drained into the basement returns. The arrangement has been but very little used. Drainage of pipes. It must be remembered that in any system 18 STEAM HEATING AND VENTILATION. there is always a certain amount of water in the supply mains and risers due to the radiation from the pipes themselves. If the pipes are thoroughly covered with a good non-conductor of heat there is but very little water from this cause ; but little as it is, the mains must be so run that it will flow to certain points, where it must be drained into the return or into proper receptacles. If the steam pipes are arranged so that water can accumulate at any point, trouble is sure to follow. It is a fundamental principle in steam heating that pipes shall be so graded that water of conden- sation will tend, by the action of gravity, to flow with the current of steam to certain points, where it can be properly drained off. The various systems of piping are sometimes more or less com- bined in the same installation, and when radiators are of very large size they should, if possible, be given both a supply and return con- nection, as the principal advantage of the double connection lies in the internal circulation which tends toward the more rapid removal of air and water. More will be said on the subject of radiator connections in a subsequent chapter on radiators. Gravity systems. In the preceding discussion and the accom- panying diagrams we have assumed that the water of condensation returns through the return pipes directly to the boiler, there to be re-evaporated into steam by the fire on the grate. This is what is known as the "gravity system" of steam supply, and is self-regulating as to water consumption, except for such small amounts of steam and water as may be lost by leaks. It is but one of the many methods of steam supply, though the one now most employed where the plant is used only for heating and there is no steam power. In the gravity system the water stands in the return pipes and risers at practically the same level as that in the boiler, though in the remote parts of the system it rises above the boiler level by a height equivalent to the pressure required to effect the circula- tion through the system. For this reason gravity systems should l>e designed for free circulation, with pipes of ample size, the dif- ference of pressure required between the steam mains and the most extreme point of the returns never exceeding a pound or two per square inch. Gravity systems are therefore generally run at very low pressures, though frequently in very cold weather as much as 15 pounds is carried for the sake of the higher temperature of steam. The operation of this system is the same at any pressure. STEAM HEATING AND VENTILATION. 19 The gravity system is a comparatively recent development, the earliest steam-heating systems being generally auxiliary to a steam- power plant. In these the steam was taken direct from the boiler supplying the engine, and the return water was run through a steam trap into an open tank, from which the water supply was taken for the boilers. This method is still employed in many old plants. Exhaust steam heating. The greater economy in high-pressure steam for engines, however, gradually increased the boiler pressure used for steam power, and with this increase in pressure it be- came difficult to heat a building directly from the same boiler that supplied steam to the engines, as steam heating at high press^ ure was found unsatisfactory for many reasons, principally on ac- count of the very high temperature of the radiators and the lia- bility to leaks and the increased danger from water-hammer. And furthermore, the same desire for greater economy which had in- creased engine pressures drew the attention of steam users to the value of the latent heat in exhaust steam for heating purposes. A brief study of the steam engine shows us that not much over 12 per cent, of the heat energy supplied to an engine is transformed into mechanical work, and by far the major part of the wasted heat escapes in the latent heat of the exhaust steam. This heat, though it has been thus far impossible to transform it into mechanical energy, is readily available for heating purposes; but a generation ago, when it was first proposed to use exhaust steam for heating, the problem involved the then serious question of back pressure on the engines. Heating systems at that time were built to ac- commodate the high pressure then in use and with what would now be called very small pipes, and admitting exhaust steam into such a system required a considerable pressure on the exhaust side of the engine to force steam through the piping and radiators and the water of condensation out through the returns. The back pressure necessary frequently amounted to 10 or 15 pounds per square inch, and certainly made a decided reduc- tion in the economy of the engine. It at once became a question whether the saving by using exhaust steam exceeded the loss on account of the back pressure on the engine. If the back pressure was very high in comparison to the mean pressure in the engine cylinder there might be difficulties in the practical operation of the engine ; but as far as the theoretical consideration of the coal 20 STEAM HEATING AND VENTILATION. pile goes, it is more economical to use exhaust steam even at a high back pressure. As heating systems are now designed, one which requires a pressure of 5 pounds to ensure a good circulation is defective in design, and 2 pounds is more than ought to be required in most cases. A back pressure of this amount on an engine running at 50 pounds mean effective pressure would increase the coal con- sumption but a fraction of 1 per cent., while taking the heating power that is available in the exhaust steam directly from the boiler would increase the coal consumption over 60 per cent. Another consideration enters, however, into the question of cir- culation in a steam-heating apparatus. Besides merely forcing the steam and water through the radiators and piping, it is necessary to force out the air which accumulates, and to do this the S3 r stem must carry a pressure somewhat above that of the atmosphere, unless a vacuum system, which will be described later, be used. Theoretically it would be possible to operate a simple gravity system below the atmospheric pressure if the whole system was per- fectly air tight and the air was all boiled out of the water and forced out of the system in the first place. In such a case if the fires were put out and the system allowed to become cold, the con- densation of steam would leave a perfect vacuum, and on starting up the fire, steam could be carried at any pressure below or above the atmospheric, according to the intensity of the fire. But if it be attempted to run much below atmospheric pressure the slightest leak anywhere in the system will rapidly break the vacuum and allow air to accumulate. It is, however, impossible to make a system theoretically air tight, and steam invariably contains some air from the feed water, as water will absorb sev- eral times its own volume. Air in the radiators and piping is, therefore, an evil that cannot be avoided, and it rapidly accumu- lates in the radiators or ends of pipes where the flow of steam is slowest. Consequently an air valve is- almost a 'necessity on every radiator, and those which are now almost universally used are au- tomatic ; that is, they close as soon as the hot steam comes in con- tact with them, and open if air accumulates and they become cold. To some extent these automatic air valves enhance the air prob- lem, inasmuch as when the radiator is cold it entirely fills with air at atmospheric pressure. In any case the result of the presence of air is that the pressure of steam in the system must be sufficient STEAM HEATING AND VENTILATION. 21 to force the air out, though for this purpose a fraction of a pound above the atmospheric should suffice; and frequently better re- sults are obtained with such a slight excess than with a greater pressure. A subsequent chapter on radiators will discuss the action of air and position of an air valve. Arrangement of exhaust heating systems. This brings us to a discussion of the methods by which low-pressure exhaust steam is employed for heating. The simplest method, and the one usually employed in exhaust-steam heating, consists in dividing the main exhaust pipe, which receives the exhaust steam from all engines and pumps about the steam plant, into two branches, one leading to the atmosphere, the other being connected to the heating sys- tem. On the pipe to the atmosphere is placed a back-pressure valve, the object of which is to automatically maintain a uniform pressure upon the exhaust and upon the heating system, so that FiG.SA Fio.SB Forms of Back-Pressure Valve. the steam may flow into the heating system as fast as it condenses in the radiators. Two forms of back-pressure valves are shown in Figure 5, A and B, the essential feature consisting of a disk that is weighted so that when the pressure on the inlet side exceeds a certain amount the disk rises and allows sufficient steam to escape to the atmosphere. The water formed by the condensation of steam in the heating system is carried back through the main return pipe to some kind of receiver, and is pumped into the boil- ers. It is generally arranged to pass through some kind of an 22 STEAM HEATING AND VENTILATION. exhaust-steam feed-water heater on its way to the boiler. The pump is also usually operated automatically, as will be discussed later. The feed-water heater is an essential in all steam plants, and its purpose is to utilize as much as possible of the heat in the exhaust steam in heating the water fed to the boiler. As, however, not more than 18J per cent, of the exhaust steam can in any case be required to heat the coldest feed water to the full temperature of the exhaust steam, 212 degrees Fahr., there is always a con- siderable quantity left, which can be utilized in heating the build- ing; and furthermore, as the hot return water is always in one way or another fed back to the boiler, the more steam that is re- quired for the building the more return water there is and the less steam is needed to heat cold feed water. If the heat in the exhaust steam is not thus used in heating the feed water or heating the building, or both, it would be wasted, and its equivalent in coal would have to be used under the boiler to replace it. There are two distinct classes of exhaust-steam feed-water heat- ers; the closed or pressure heaters, and the open heaters. In the former the feed water is pumped through the heater against the boiler pressure; the exhaust steam passing into an inlet chamber,, and generally through a series of tubes into the outlet chamber,, the tubes being set in wrought-iron plates, which divide the inlet and outlet chambers from the water space around the outside of the tubes. In a water-tube heater the position of the steam and water is reversed. In the open heater the water and steam are practically together in the same chamber, the water flowing in from some source against only the pressure of the exhaust steam. The suction of the feed pump is connected to the heater and the delivery direct to the boilers. With the closed heater cold water is pumped through the heater to the boiler, while with the open heater hot watei from the heater is pumped direct to the boiler. The scheme of steam supply described is represented in Figure 6, and is, with various modifications of detail, almost universally employed in heating systems in which exhaust steam is used. It will be noticed that in the figure the pipe to the heating system is provided with a live-steam connection. This is necessary in a great many plants where, in extremely cold weather, the exhaust steam is not sufficient to heat the building. In modern practice such a connection is always provided with a reducing-pressure STEAM HEATING AND VENTILATION. 23 valve. These valves, one of which is represented by Figure 5 C, are of such construction that they can be set for any desired differ- ence between the highland low-pressure sides. The reducing valve must always be set for a pressure somewhat lower than that at which the back-pressure valve opens, as otherwise some live steam from the reducing valve might pass through the back-pressure valve to the atmosphere and thus be wasted. Figure 7 shows an arrangement with a press- ure heater which is much employed in steam- heating systems. The exhaust steam enters the bottom of the heater and goes out at the top. The connection is also provided with a by-pass so arranged that in case it is necessary to shut out the heater for repairs or cleaning,, the valve B in the by-pass may be opened and the valves A and C closed, so that the steam will pass around the heater. In ordinary use the valve B in the by-pass is closed and A and C opened. The arrangement of the supply to the heat- ing system, which is connected to the outlet of the heater, and. * -Free Exhaust, y Back-Pressure Valve. Figure 6 Exhaust Steam-Heating Supply Connections. the back-pressure valve on the free exhaust, is the same as indi- cated in Figure 6. The main return pipe is run into a cylindrical receiving tank, from which the water is pumped through the heater. Attached, to the receiving tank is an automatic pump governor, which, by means of a float operating on the steam sup- /& /ir -. I UNIVERSITY , 24 STEAM HEATING AND VENTILATION. ply to the pump, regulates the level of water in the receiving tank. As soon as the water in the tank rises above the proper level the pump is started by the float, and when it falls below this level the pump is stopped. Figure 8 represents an arrangement with an open heater. The steam connection is precisely similar in principle, but a different arrangement of details is indicated, the valves being lettered to correspond with those in Figure 7. The returns are run into a receiving tank similar to the other arrangement, but this tank t free Exhaust to Open Air. Back- Pressure Valve. Main Supply to Heating System. Water Level in Returns. I \ Main Return Glass. {Receiving Figure 7 Arrangement with Pressure Heater. is connected directly to the heater, and practically forms a part of it. The automatic float which controls the operation of the pump is generally, in such cases, connected directly on to the heat- er, as indicated in the governor marked D. In Figure 8, on the left of the heater, is indicated another float governor, E, which is frequently attached to heaters of this charac- ter. This operates on the cold-water supply. In this connection it will be noted that frequently in moderate weather only a portion of the exhaust steam is needed to heat the building, the remainder escaping through the back-pressure valve. In such cases it is neces- sary to make up the loss of water by taking a certain amount from the city mains or other source of supply. With the open type of STEAM HEATING AND VENTILATION. 25 heater this is generally run directly into the heater and sprayed through the current of exhaust steam. It is for the control of this cold-water supply that the governor, E, is provided. In this case the governor on the cold-water supply should be set for a level of water a few inches below the level which operates the feed pump. Otherwise the cold water might be let into the heater while the pump was running and when it was not needed. The open heater should in all cases be provided with an overflow connected to a low-pressure trap. This outlet should be a few inches above live Steam. Supply to' Heating System. W////^///yM^///y//^ Figure 8 Arrangement with Open Heater. the water-line, but should be low enough to prevent the possibility of a sudden inflow of return water flooding the exhaust pipes. With the arrangement shown in Figure 7 the cold water may be supplied by a pipe running direct to the receiving tank, and it may be regulated by hand, according to the level of the water, shown by the gauge glass, or by a float governor similar to the one indi- cated on the open heater in Figure 8. In large plants also there are frequently two or more feed pumps, one of which has a suction connected to the cold-water supply, or the boilers are provided with injectors. Further details of piping will be discussed in a subsequent chapter. It will be seen that, in connection with the open heater, the re- 26 STEAM HEATING AND VENTILATION. ceiving tank is merely a part of the heater, forming an additional reservoir for the return water. It is possible to do away with the tank entirely, connecting the returns direct into the water cham- ber of the heater, but as the water space of the heater is generally comparatively limited, the water level in such cases is subject to more or less extreme fluctuations, due to the fact that the return water does not always come back with a uniform flow. This is especially the case with large office buildings, when the building is being heated in the morning and a number of cold radiators are apt to be turned on at nearly the same time. In the same way it is possible also to do away with the receiving tank represented in Figure 7, but this is subject to the same objection as in the other case, only to a more extreme degree, as the small governor pro- vides scarcely any reservoir volume for the return water and the pump is subject to sudden changes in speed. In the arrangement shown in Figure 7 the main return pipe is generally connected at the point, F, and not directly to the tank. The writer has installed a number of large plants with open heaters and no receiving tanks whatever which have given perfect satisfaction; and recently installed a plant having over 16,000 square feet of radiating surface with practically the same arrange- ment as indicated in Figure 7, but without any receiving tank. This system requires rather careful attention, especially in the early morning, but it was impracticable on account of local condi- tions to put in a receiving tank, and the system has given thorough satisfaction. It should be noted here that the system represented in Figure 8 is practically a gravity system, the heater and tank taking the place of the boiler represented in Figures 1 to 4, and acting both as steam-producing chamber and reservoir for return water, both being at this point under precisely the same pressure. The water level in the return pipes and return risers will stand at a higher level than in the heater or boiler in the case of Figures 1 to 4, by a distance representing the difference in pressure required to force the steam through the system, just as in the ordinary gravity sys- tem. As a matter of fact, also, it is found that in the system shown in Figure 7 the pump operates much more smoothly and ;uniformly if the system is made a gravity system by connecting a small equalizing steam pipe between the main steam supply of -the heating system and the top of the receiving tank and governor. STEAM HEATING AND VENTILATION. 27 If the plant referred to operates without a tank this equalizing pipe is found to be practically a necessity. In any case an equaliz- ing pipe above the water line between the heater and its tank, or the heater and the governor, is necessary to maintain the same, pressure upon the water in the tank as exists elsewhere in the re- turn-water reservoirs. The water-line of the heating system sometimes becomes an important consideration,, especially when it is desired to place radiators in the basement of a building. If these are set so low that the return water is liable to rise above the connections, the radiators will fill with water when turned on, which will prevent the steam from circulating into the radiator and will be sure to give trouble from water-hammer. Besides this, with anything except the overhead-supply systems, the water from the returns will back through the radiator and run down the supply riser, and it is therefore generally necessary to set radiators several feet above the water-line, according to the maximum pressure which is necessary to create circulation of steam through the system in coldest weathp* If the system is designed for very low pressure, 1 or 2 pounds, the radiator may be placed within 4 feet of the water-line, but should never be lower than this, especially in parts of the building far removed from the heater. For this reason basements are usually heated by steam coils suspended from the ceiling or placed on the walls, near the ceiling, although radi- ators are sometimes put on brackets attached to the walls; fre- quently, in order to lower the water-line, the pump, governor, and heater also, when the open heater is used, are placed in a pit. There are, however, special arrangements of radiator connections which, may be used with safety, even though they are set below the water line. These are discussed in the chapter on radiators. There are many combined automatic pumps and receivers de- signed for taking care of the return water which are very satis- factory, but all work on the same principle of a tank with a float governor to operate the pump. There are also automatic traps de- signed to return the water of condensation from the exhaust-steam heating systems, without using a pump, direct to a high-pressure boiler by means of an ingenious combination of float valves, traps, reservoirs and check valves, and some of these work with consid- erable satisfaction if carefully watched and kept in good repair. In many mills and factories which use condensing engines, and 28 STEAM HEATING AND VENTILATION. in which, consequently,, exhaust steam is not readily available for heating, steam for this purpose is taken direct from the boilers through a, reducing pressure valve and used in the heating system at a pressure of 5 to 20 pounds per square inch. In such systems the water is generally returned to the boilers by an automatic pump and receiver, or by one of the special styles of traps referred to, which for operating at such pressures can be made much simpler than when used for the extremely low pressure of the ordinary exhaust systems. Vacuum systems. As a refinement of exhaust-steam heating there has been developed within the last decade what is known as vacuum systems of steam heating, the object of these being to ex- haust the air from the system by artificial means so that circulation may be effected at atmospheric pressures with absolutely no back pressure on the exhaust pipes from the engines. There are two distinct forms, one known as the Paul system, the other as the Webster. The former system provides each radiator with an auto- matic air valve of special construction and connects a very small pipe, usually | inch, to each of these valves, bringing them together in pipes of proper size in the basement of the building, and con- necting to a special exhauster, which maintains a constant suc- tion on the entire system of air piping. The steam and return pipes for this system are entirely independent of the air pipe and it may be installed on any of the systems previously mentioned. The Webster system operates on an entirely different principle, in that it employs an automatic air-and-water valve at the return outlet of the radiator. This thermostatic valve, as it is called, is constructed on a principle much like the automatic air' valve, but is of larger proportions. It is adjusted so that it closes automati- cally when it comes in contact with the steam temperature, and opens when water or air collects about it, and the temperature is reduced. The system is necessarily a two-pipe system, the returns being connected to these thermostatic valves, but no other air valves or air piping are used. The return pipes are connected in the basement to a vacuum pump which puts a strong suction on the returns, and by means of which both air and water are drawn through the thermostatic valves, the water being delivered by the vacuum pump to an open heater or receiving tank, while the air is separated by an automatic device. The return pipes of this system are very small, just sufficient to take care of the water, no STEAM HEATING AND VENTILATION. 29 steam being allowed to circulate in them. The steam mains, where necessary, are drained into the return pipes through thermostatio valves. The return mains being under suction, and having 110 direct connection with the steam pipes, can, a certain extent, be run independent of the usual necessity of draining by gravity, in some cases the water being lifted out of radiators placed below the return -mains. In the Union Depot at Columbus, Ohio, which is equipped with this system, the radiators in the basement are about 13 feet below the supply and return mains, which run parallel along the base- ment ceiling, and the return water is drawn up out of the radiators without any water-hammer or other inconvenience. A modification of the Paul system was recently installed in a large office building in Chicago which has given decided satisfac- tion. Instead of the air valve on each radiator, a small tee with an aperture only 1/16 inch in diameter was screwed into the air hole of the radiator, and these connected together into a system of small air pipes running to an air pump or exhauster. This maintains a constant suction on the air holes. Although there is apparently a continual leakage of steam in this system,, it is not more than with the automatic air valves, as the latter are seldom maintained in perfect adjustment. The tees were made w r ith a plug on the outside which could be removed for the purpose of cleaning the pin-hole by means of a wire. Plants equipped with vacuum systems frequently operate slight- ly below the atmospheric pressure, and besides entirely doing away with back pressure on engines and removing the air from the system, there are many incidental advantages in the operation of plants of this character which will lead to a very extended adoption. The principal objection to vacuum systems lies in the fact that the exhausters or vacuum pumps take considerable live steam to operate them, and almost as much in moderate weather as on very cold days. The recent development of vacuum pumps, however, has been of great value to steam-heating work. Pumps of this class are now made which will not run away when all the water is pumped out of the suction, the water end of the pump receiving only air and steam. They will run along slowly under such conditions, taking care of the water as it comes. If a pump of this descrip- tion is connected to the lower point of the main return from 30 STEAM HEATING AND VENTILATION. e heating system, it can be made to maintain what is now called a dry return. This is in some cases valuable, as it obviates the necessity of considering the water-line, as before mentioned, in placing radiators in basements. Vacuum pumps used in this way are especially valuable in cases where return water is to be brought l>ack from a heating system at some distance from the source of steam supply. CHAPTEE III. STEAM-HEATING APPARATUS. Boilers. The questions of boiler design, construction, setting, etc., involve so many considerations requiring careful scientific study, that the entire problem is omitted from this work and the reader is referred to the valuable treatises devoted exclusively to the subject. There is, however, one kind of boiler which should be given some special mention- in this place. This is the self-contained cast-iron sectional boiler which is used only for small, low-pressure gravity-heating systems in residences. These boilers are built up in sections of various shapes bolted together, the joints being kept tight merely by the pressure caused by the bolts. On account of their material, as well as the method of construction, they are not adapted for anything but very low pressures. For the larger plants in which cast-iron boilers are used, it is better to install two small ones than to attempt to use one large one, as it gives better economy in operation, and there is less danger of accident to small boilers than to those with large castings. In selecting these boilers it should always be borne in miud that the demands of commercial competition cause them to be very generally overrated by their makers, so that in choosing sizes from catalogues it is advisable to make considerable reduction from the rated capacities. Mr. James R. Willett, in a pamphlet on the heating and ventilating of residences, gives the accompanying table for the sizes of cast-iron boilers. Where boilers of the kinds used for steam power are employed in simple heating plants of large size of which there are to-day but few there is an old rule for proportioning the size, to the effect that there must be 1 square foot of boiler surface to 10 square feet of radiating surface. This rule when applied to a boiler with a well-designed furnace, stack and setting should be very conservative. It is much better to estimate the steam consumption of the entire plant (see Chapter V., page 60 for steam consumption of radiation) and calculate the boiler requirements according to the rules of boiler design. The designs of the cast-iron heating boilers are innumerable and 32 STEAM HEATING AND VENTILATION. can only be selected by the careful judgment of the engineer. The- chief points to be considered -are efficiency of heating surface and capacity of grate in proportion to surface, strength of parts, tight- ness of joints, ease of cleaning and effectiveness of circulation there should be no "dead ends" where the water is not kept in circulation by the heat of the fire. Willett's Table of Cast-iron Boiler Capacities. Radiators; Area of boiler Radiators; Area of boiler total sq. ft. grate in sq. in. total sq. ft. grate in sq. in. 400 500 1,600 1,420 500 580 1,800 1,560 600 650 2,000 1,700 700 740 2,250 1,880 800 820 2,500 2,020 900 890 2,750 2,230 1,000 970 3,000 2,400 1,200 1,120 3,500 2,770 1,400 1,270 4,000 3,120 There might also be classed under the head of steam-heating apparatus the various traps, automatic receivers and other special 4pt iiiliiiHaa Fio.9 FiG.IO FIG. II One, Two and Three Column Radiators. appliances which are used especially in connection with exhaust heating for returning the water of condensation to the boiler, and which were described in the preceding chapter. But besides these the only apparatus pertaining to a heating system without STEAM HEATING AND VENTILATION. 33 mechanical ventilation are the radiators, and in the design of the system the rtmost consideration should be given to their selection and proportioning. Radiators. Radiators are made either of cast or wrought iron and are classified according to kind of heating for which they are used into direct, direct-indirect, and indirect radiators. A few years ago wrought-iron pipe made up with bends and headers into coils of various sizes and shapes was used very largely for radia- tors, and especially for indirect radiators; but on account of their greater economy of construction, cast-iron radiators are rapidly supplanting the wrought-iron pipes for all purposes. To-day FIG. 12 wrought-iron pipe coils are used in direct heating where very large radiators are required spread over a large area of wall surface., such as in factory rooms or warehouses, where a series of long^ pipes connected into headers at each end are run along the walls-, either over'or under the windows, preferably under. Pipe coils are- also used for large indirect radiators, but in this case, as a rule, , only in connection with ventilating fans, as will be described in subsequent chapters. The styles and kinds of cast-iron radiators 'are innumerable.. They are made in sections or loops, which are fastened together 34 STEAM HEATING AND VENTILATION. by pipe nipples of various kinds, with a paper or thin metal gasket between the faced surfaces of the joint. These nipples are some- times threaded and screwed up tight by special wrenches, but what is known as the push-nipple is extensively used. These nipples are not threaded but are turned to a close fit with the holes in the loops, at the joint, which are bored out perfectly true, and they are driven tight by pressure with jacks or presses made for the pur- pose. Cast-iron radiators are classified according to the kind of sur- face, into plain-surface and extension-surface radiators, and ac- cording to their style of construction into open and flue radiators, &nd of the open one, two, three and four column type, according to the formation of the loops. The different classifications will be better understood from inspection of the accompanying illustra- tions. The extension-surface radiators, Figures 14 and 18, as the name implies, have extensions of various kinds in the form of ridges or pins cast on to the otherwise plain surface, and are used principally for indirect radiators. The flue radiators, Figure 1C, are used extensively for direct-indirect radiation, but for such pur- pose are provided with shields and provision of some kind for con- nection with the outer air. Flue radiators, such as shown in Fig- ures 12 and 13, are sometimes spoken of as veiled-surface radiators. Most low radiators of considerable width in proportion to the lieight are of the flue type. The radiator that has been used for direct radiation much more widely than any other is the two- column plain-surface radiator, such as is shown in Figure 10, but the numerous other forms are being more and more extensively introduced. . Most radiators for steam heating have all the loops connected by only one steam passage through the bottom, but some are also connected at the top as well. Such radiators are adapted to steam heating from hot-water heating practice, as they are the only kind that can be used in the latter, and are hence known as the hot-water type. See Figure 20. Almost all low and wide steam radiators are made in this way, and by some authorities this con- struction is preferred in all kinds. Further discussion of this sub- ject will be taken up later. Measuring radiators. Eadiators are universally rated by the number of square feet of surface which they contain. This, at the present time, is for many reasons a very arbitrary method and STEAM HEATING AND VENTILATION. holds chiefly for want of a better. The main difficulty lies in the great difference in the value of the various kinds of surfaces, no distinction being made in such rating between plain, extension or veiled surface. The variation is enhanced also by the fact that radiators are to a large extent overrated, especially in the less com- mon sizes and styles; and owing to the difficulty of accurately measuring the surface, this fact is very generally overlooked. A number of methods have been proposed and tried for measuring the surface of radiators which are made in ornamental design and with all kinds of irregular surfaces. In the course of a large ex- perience with radiators of all kinds, the author tried many different methods and finally devised one which he has found comparatively ; Fio.15 Direct FIG. 16 Indirect Radiators. FIG. 17 THE ENGINEERING simple and very reliable. By this method all irregular surfaced are measured by covering them with very thin flexible paper which must be carefully turned and folded into all irregularities of the surface. After being thus fitted, the paper should be rubbed by blackened fingers. They are generally sufficiently soiled for the purpose from handling the radiators. In this way when the paper is spread out, the part that was folded under can be readily distin- guished, and the actual area of the surface can be determined by measuring the blackened parts with a planimeter. In lieu of a planimeter, thin cross-section paper can be used and the areas de- termined by counting the small squares. In measuring up a ra- diator loop, it is best to divide the surface by thin lines of white chalk or paint and measure each division separately. The parts 36 STEAM HEATING AND VENTILATION. that have a uniform cross-section, as the columns of most direct radiators, can be measured by determining the actual circumfer- ence of the surface by fitting a paper around it and multiplying this by the length of the column. It was once objected to this method that it does not take into account the effect of the raised ornamentation on a radiator. This is not the case, or at least any ornament that it does not take into account would not increase the total surface to an appreciable degree. Measurements of ra- diators by this method by different observers acting independently have been found to check within less than I per cent. FlO.18 Indirect Radiator. Action of radiators. Before proceeding further in the discussion of radiators, it may be well to consider some of the principles which govern their operation in practical use. The fundamental prin- ciple of their, operation is undoubtedly the axiomatic theory that there is a universal tendency toward the equalization of tempera- ture; in other words, that hot bodies give up their heat to the colder ones which surround them. In general this is accomplished by three different processes, namely: conduction, convection and radiation, the word radiation being used here in the special sense of -radiant heat. These may best be defined by illustrations. When one part of a rigid body is in contact with a warmer body heat passes or flows from the latter through the former to its cold por- STEAM HEATING AND VENTILATION. 37 lions as long as there is any difference of temperature. This is conduction of heat, and the rate of flow under the same conditions of temperature varies as a factor known as the heat conductivity of the body concerned. The heat conductivity of fluids, liquids and gases is very low, practically zero, but heat is transferred in them by convection. The particles in direct contact with the source of heat are heated above the temperature of the rest, and an increase in temperature of any liquid or gas invariably decreases p ujy FIG. 2O Hot- Water and Steam Pipe Loops. THE IKCJNttHIHQ BAQ, its specific gravity and causes an upward current of the hot parti- cles, which brings the colder particles in turn in contact with the hot body, thus maintaining a circulation which tends to raise the temperature of the entire mass. Eadiation or radiant heat is en- tirely different from either of -these in its action. It is a wave motion and travels through air and all transparent bodies with the velocity of light without heating them, and only appears as sensible heat when its course is interrupted by opaque bodies by which it is absorbed.* *Some bodies which are quite opaque to light waves are more or less transparent to heat waves, and vice versa, and nothing except the im- material ether is absolutely transparent to them. The earth's atmos- phere absorbs a considerable amount of the radiant heat from the sun. 38 STEAM HEATING AND VENTILATION. A radiator gives out its heat to its surroundings by radiation to the walls and objects and by convection to the air. What propor- tion is given out in each way it is difficult to measure in any case and depends principally on the construction of the radiator and the way it is set, but also more or less upon the conditions of tem- perature, nature of surface, etc. Peclet, the great French physi- cist, in the middle of the century, fully investigated the laws of ra- diant heat as well as those of convection in still air. The formulas which he deduced are applicable only in a limited degree to ra- diator practice. His investigations, as well as those of others since that time, showed that for a single iron pipe in still air* under conditions of temperature which prevail in radiator practice, the heat given off as radiant heat is just about equal to that given out by convection. t But radiators are invariably built of clusters of pipes or sur- faces, and as radiant heat travels only in straight lines and per- pendicular to the surface of its source, a large proportion of the surface is wasted so far as radiant heat is concerned, due to what may be called the mutual interception of the rays. In the ordi- nary one-column cast-iron radiator, the proportion of surface from which no radiant heat takes place is nearly 20 per cent., in the two-column, 45 to 55 per cent, and in the three-column, 55 to 65. Assuming that the radiant heat amounts to one-half the total, the reduction of heat emitted would be one-half of these percentages. Another fact which further reduces the radiant heat is that ra- diators are usually set very close to a wall which becomes heated to a comparatively high degree and consequently radiates back a large portion of the heat to the wall side of the radiator. This is true to an extreme degree in the case of indirect radiators which are enclosed in boxes of wood or sheet metal and are not located in the room they are to warm. With these the heating is accom- plished entirely by convection, while with direct radiators the ra- diant heat rarely amounts to 40 per cent., generally not over 30, and often in practice considerably less. For a radiator in any par- ticular location the radiant heat is constant for the same conditions *By "still air" in this sense is meant the air of a room in which there are no currents except those created by a column of hot air rising from the heated surface. tFor a complete account of Peclet's experiments and his results see "A Treatise on Heat" by Thos. Box; London: E. & T. N. Spon. STEAM HEATING AND VENTILATION. 39> of temperature of the radiator and surrounding objects, and is in- dependent of currents of air. This is by no means the case with the convected heat, which is increased greatly by a slight draft from any extraneous source. In this connection it is very remark- able what a great effect an almost imperceptible draft will have on the heat given out by a radiator. This is partly due to the lower- ing of the temperature of the air between the loops, but also to the fact that with the same temperatures any increase in velocity in- creases the amount of heat the air absorbs. Radiator tests. Numerous tests of radiators have been made since those of Mills, Eichards and others in the early '70's, bur there is a wide variation in the results obtained, due partly to the different kinds of radiators tested and partly to the different meth- ods of testing. As yet, no standard means of testing radiators has been adopted. The steam radiator as a heat-using device is theo- retically perfect; that is, all of the heat that is put into the ra- diator by the latent heat of the steam condensed is given out to the air and objects surrounding. Its efficiency is therefore 100 per cent. The question of practical efficiency is, therefore, more strictly speaking, only one of effectiveness of surface. That is, of two radiators under exactly the same conditions of tempera- ture and surroundings, that one which has such an arrangement of its surfaces as to give out the most heat per square foot is the most effective, usually called the most efficient. In all tests of radiators, the heat given off is measured by connecting them so that the steam which condenses can be accurately weighed, its pressure, quality and temperature being determined at the same time. The results are generally reduced to British thermal units given off per square foot per hour per degree difference of tem- perature between the air of the room and the steam of the ra- diator. Tests of radiators have been made in various ways by Mr. George H. Barrus, by Profs. Denton and Jacobus of the Stevens Institute, by Prof. R. C. Carpenter, of Sibley College, Cornell University, and by the author. The results of Prof. Carpenter's tests are pub- lished in detail in his valuable work on "Heating and Ventilation of Buildings.'' In these tests the radiators were located in sepa- rate compartments, 7 xlO feet, built together in a large room, and as shown in Figures 21 and 22. In order to allow some circulation of air so that the temperature of air of the compartments might 40 STEAM HEATING AND VENTILATION. not get as high as that of the radiators, small openings were made in each at the bottom and top. In 1895 and 1896 the author had occasion to make comparative tests of a large numher of radiators of various kinds and types, and the arrangement used by him for testing is shown in Figures 23 to 25. The two test rooms were built in the main floor of a large warehouse, and each was 15 feet by 11 feet 8 inches, and extended to the ceiling, 15 feet 5 inches high. The walls of the test rooms were built of matched and beaded pine and lined with lapped courses of heavy building paper. The warehouse room in which the test rooms were located was Fl G. 2 1 Prof. Co rpente r's Arrangement for Testing Radiators. about 85 by 50 feet, with brick walls on both sides and wood and glass partitions at each end. Neither end of this large room, how- ever, was open to the outside air and the side walls were party walls. Every effort was made to keep the air of the test rooms free from all drafts except those induced by the column of hot air rising from the radiators and to otherwise make the conditions as nearly as possible those of actual practice. To permit some cir- culation in the test room, so that the air would not get too hot, an opening 4 inches long and 1 8 inches high was cut in the front STEAM HEATING AND VENTILATION. 41 wall at the floor, and to prevent direct drafts on the radiators, those openings were surrounded inside by a wooden screen, 2 feet 8 inches high. The front partition was also opened 18 inches at the ceiling. The piping, as shown in Figure 25, was arranged so that the steam was supplied to the radiators on what is known as the one-pipe overhead system. Steam was supplied to the separator at a pressure of 2 or 3 pounds above atmosphere through a 2-inch pipe from a small heating boiler. The pressure carried at tho boiler was slightly in excess of that on the separator, it being throttled at the latter. By this means and by leaving the drip on the separator slightly opened, the steam was supplied free from all entrained moisture. The piping, separator, etc., were all care- fully covered. The heat given off was measured by drawing off the condensed steam from the drip pots into cold water and accurately weighing it. FlG. 22 Prof Carpenter's Arrangement of Each Radiator and Compartment Removed In practically all of the tests made in this plant, one radiator was used as a standard and all the others tested and compared with it In each test the radiators were connected and a preliminary run made with open air-valves until the conditions became con- stant and uniform, and a test run made for two to three hours. The radiators were then interchanged and the test repeated. Even with these precautions it was only by exercising the greatest care that it was possible to obtain results which checked closely. It is very remarkable what a decided effect can be created by a very 42 STEAM HEATING AND VENTILATION. slight motion of the air from an external source. Opening a door at one end of the warehouse room, although, as before stated, these doors did not open outdoors, made a decided difference, and if a strong wind was blowing outside, the radiator to the windward side Ceiling of Wardroom. . to- f || Opening for Air. Door Opening for Air. Door. '///v//////////////////////////////////////////////////////////// /////. FIG. 23 Front Elevation of Testing Rooms. Brick Wail of Wareroom. ty//////////////////////////////////////////////////////////////////. Radiator Room A. , Partition 2'8"Hiqh in front ( of Opening at Floor. \^\ \ Radiator. ^ so Room B. I FIG. 24- Plan of Testinq Rooms. Twe EnoOiUniMO P (Partition between Rooms. Floor of Testing Room . rio.25 Elevation of Piping.Radiator Tests Dnp Pot-^ 4'Pipt. IG'Lony. had some advantage, although no draft would be perceptible. However, with due care, the two tests for each comparison were made to check with fair accuracy. STEAM HEATING AND VENTILATION. 43 The radiator used as the standard on these tests was an ordinary cast-iron two-column steam radiator, 38 inches high, with but little ornamentation. The writer believes that this is the only way of accurately testing radiators, and the adoption of any one definite make of radiator as a universal standard of comparison would do much to extend the knowledge of the comparative effect and value of radiators. Tests of radiators made in different ways or in dif- ferent locations are valueless for accurate comparison. But all comparative tests made against the same standard if accurately and carefully carried out, could be compared in percentages of the heating effect of the standard used. The writer found that under tne conditions in his testing plant the 38-inch two-column cast- iron radiator used as a standard gave out 1.60 British thermal units per square foot per hour per degree difference of temperature with an average steam temperature of 224 degrees Fahr., and aver- age temperatures of the rooms of 76.5 degrees. The average difference of temperatures was 147.5 degrees. This cofficient of 1.6 B. T. U. per square foot per hour per de- gree difference of tempt ra~u~"2 between the steam and air is some- what lower than that which Prof. Carpenter obtained for a ra- diator of almost the same size and design. Assuming that the ra- diators were exactly alike, such variation as there was can be due to two causes: 1, a variation in the difference of temperature be- tween the steam and the surrounding room; and 2, the mode of setting and the consequent freedom of air circulation around the radiator. In regard to the first cause, all tests of radiating sur- faces from Peclet down show that the coefficient is greater, the greater the difference of temperature, and for extreme variations in the difference of temperature, the coefficient is very much great- er than in the limits of ordinary radiator practice, with steam tem- peratures from 212 to 230 and mean air temperatures from 40 to 70; within which range the variation in the coefficient from this cause is less than 9 per cent. In regard to the second cause the freedom of the air-circulation around the radiator this is by far the. chief cause of difference in action of radia- tors. Profs. Denton and Jacobus of the Stevens Institute of Technology made some comparative tests of radiators, published in The Engineering P n cord of September 8, 1894, with a plant very similar to that used by the author, except, besides having an open- ing at the top, there was in each of the test rooms an outside win- 44 STEAM HEATING AND VENTILATION. dow, "which was opened a certain amount during the tests" a dangerous way, the author believes, to test radiators with the ex- pectation of jbtaining checking results although "a screen was placed between the radiators and windows to prevent direct drafts from striking the radiators/' These tests were unquestionably carefully made and were checked by reversing the position of the radiators, so that the comparative results obtained may be taken as reliable; but the coefficients were in the neighborhood of 20 per cent, higher than that obtained by the writer on similar radiators, due entirely to the greater freedom of air-circulation from the open windows. This is a matter of great importance in practice and in consequence the results obtained in radiator tests depend largely upon the setting of the radiator. It is this fact also which makes a radiator to some extent automatic or self -adjustable. Take for example, an ordinary room say with a north exposure and one direct radiator set, as they generally are and always should be, under the window. On a moderately cold day with the ther- mometer outside at 20 degrees and the wind from the south or east, the radiator will be turned on the entire time. On another day with the thermometer outside at zero and the wind from the north, the radiator very probably keeps the room at the same mean temperature with practically the same temperature of steam. The reason is that in the latter case the cold air which leaks in through the walls and around the window casing, besides keeping the air immediately in contact with the radiator at a lowpr mean temperature, causes a much more rapid circulation around the rad- iator, with the result that it gives out more heat units per square foot. It is for this reason, too, that one may put down for a posi- tive and infallible rule in radiator design that the radiator which has the most open space around its surfaces and the most inter- rupted exposure to the surrounding air will give out the most heat per square foot under the same conditions of setting. In compliance with this rule, other things being equal, narrow radiators are more effective than wide ones, and low ones than high ones; but the effect of width and height can more than be offset by a slight in- crease in the distance between the loops; for example, the author found that a four-column 38-inch radiator gave out exactly the same heat per square foot of measured surface as a two-column 38-inch radiator, because the former had a mean distance between the loops about 16/100 of an inch greater than the latter; also a STEAM HEATING AND VENTILATION. 45 38-inch flue radiator was improved 7 per cent, in heating effect by separating the loops % inch. It is largely for this reason of freer circulation around the sur- face that the ordinary wall coils of 1 or l^-inch wrought-iron pipe, which are extensively used in factories, are much more ef- fective than cast-iron radiators. Some careful tests by Prof. M. E. Cooley of the University of Michigan showed that a single layer coil of horizontal pipes gives out 40 per cent, more heat per square foot than a two-column cast-iron radiator under the same condi- tions of setting. It may be further stated in compliance with the same rule that the hot-water type of radiators is somewhat less effective than the steam type on account of the obstruction offered by the loop con- nection at the top, and also that flue radiators are less effective than the ordinary open type. Just how much less effective the flue types are depends upon the kind and design, but the wide low flue radiators, not considering extension-surface types, are some- times over 23 per cent, less effective than the ordinary two-column radiators of the same height. It may also be stated that there is a greater difference between the high and low radiators of the flue type than of the open types. One make of two-column cast-iron radiator proved 6^ per cent, more effective in the 20-inch height than in the 38-inch, and another make nearly 10 per cent., while an 8-inch wide flue radiator showed over 20 per cent, improvement in the 20-inch over the 38-inch. Condensation at different pressures. Mr. W. J. Baldwin made some tests some years ago to determine the relative heating effect of radiators under different steam pressures, with the same con- ditions of setting. Taking the condensation at 1 pound steam pressure as 100, he found the condensation at other pressures to be represented by the following figures : 1 Ib. pressure 100 1 15 Ibs. pressure 126 5 Ibs. pressure 108 j 20 Ibs. pressure 134 10 Ibs. pressure 118 | Extension-surface radiators. In regard to what is known as ex- tension-surface radiators, they are generally made in the flue form, and numerous tests show they are never as effective per square foot of actual surface as are the radiators which have no extension sur- face. Profs. Denton and Jacobus made some tests to illustrate this point. They tested two forms of extension-surface flue ra- 46 STEAM HEATING AND VENTILATION. diators and then planed off the extensions and re-tested them. They found that with one radiator, which had 43 per cent, more surface in the first condition than in the second, gave only about 17 per cent, more heating effect. This, however, is not exactly a fair comparison on the grounds of extension surface alone, as the radiators had a much more effective proportioning of air-space design with the extensions planed off. Surface of radiators. There are other considerations which alter the effectiveness of a radiator besides the design and setting, notably the condition of the surface. Radiators are rarely used with the natural iron surface, but are painted in all possible ways. The nature of the surface has practically no effect on the con- vected heat, but a very decided effect on the radiant heat; but as the latter is generally less than 35 per cent, of the whole, the effect on the total heat emitted is not so marked. Furthermore, usually only the top and outside surface of one side is painted at all. In general the dark and lustreless paints are the most effect- ive, and may even improve the heating power, while the bright shiny metallic paints may reduce the effect quite decidedly. But few tests as to the effect of paints have been made. Prof. Carpenter found that two coats of black asphaltum increased the total heating effect by 6 per cent., two coats of white lead 9 per cent., rough bronzing about 6 per cent., while a coat of glossy white paint reduced it by 10 per cent., although the kind of ra- diator considered is not mentioned. The author found that two coats of ordinary "radiator japan paint" had but little, if any, effect, but in one case, on a 38-inch flue radiator, three coats of gold bronze reduced the heating power by over 12 per cent. This loss was probably due partly to the reduction in radiant heat from the polished surface and also to the fact that the convected heat was somewhat reduced by the heavy coating of paint acting as a non-conductor. This is doubtless sometimes the effect with old radiators which have been painted several times. Location of radiators. As before stated, the setting of the ra- diator has a decided effect on its heat-giving power, and no two conditions can be considered exactly alike in this regard. For di- rect radiators, the best place to set them is unquestionably under a window. The reason of this is that the greatest leaks of cool air from outside are around the window frames and the greatest loss of heat by radiation is from the glass. There is in conse- STEAM HEATING AND VENTILATION. 47 quence a decided downward current of cold air at the window which, if the radiator is on the opposite side of the room, rushes across the floor and is accelerated by the upward current of hot air from the radiator. Such a condition tends very decidedly to make cold currents along the floor. If the radiator be placed under the window the cold drafts are interrupted and the heat more diffused moreover, the upward current from the radiator, the downward current from the window and the leakage drafts, all combine to make a resultant draft of cold air against the side of the radiator which lowers the temperature between the loops and altogether tends to increase the effectiveness of the surfaces very considerably over what would be found in still air. Direct radiators are often put in recesses under windows and low radiators are sometimes placed under window seats. Such settings, while highly desirable from an aesthetic consideration, de- cidedly change the effectiveness of the radiator both by shutting off the radiant heat and by lessening the free convection. From some rough experiments the author is led to believe that the or- dinary marble top, which is often placed on radiators, will reduce the heating effect from 6 to 15 per cent., depending on the size, kind and height of the radiator; but this is not stated on the au- thority of a careful comparative test. CHAPTER IV. INDIRECT RADIATORS. The preceding chapter comprised mainly a discussion of the principles involved in the action of radiators in giving out their heat to the air and objects surrounding, but was confined almost entirely to direct radiation. Many of. the deductions as to the relative value of different kinds of surface may be applied to indi- rect radiators as well, but a theoretical discussion of the latter re- quires some entirely different considerations from those presented in the last chapter on direct radiation. The indirect radiator is. located below and outside of the room to be heated; it is enclosed by a casing, which has an air connection to the outside of the building, and a hot-air flue to the room to be heated. In this dis- cussion it should be stated that the term indirect radiation is often applied to radiators or heating coils which are used in connection with a fan whjch creates a forced draft. In the author's opinion this is a mistake, as the element of forced draft involves still other considerations, and such radiators are merely heating coils for mechanical ventilation and should be discussed separately as such. The indirect radiator proper depends entirely upon the draft ac- tion of the heated column of air above it for its ventilating effect,, and also for a means of communicating its heat to the room above. Theory of indirect radiator. The theory of the indirect radiator may be illustrated by the accompanying Figure 26, in which R is the radiator set in a box, B, and provided with a cold-air connec- tion, C, to the outside air (generally having a damper, d), and a hot-air duct, D, to the room to be heated, with a register, r, in the floor or wall of the room. Steam is supplied to the radiator by the pipe, p, through the casing. The heat of the radiator causes a column of hot air to rise through D, and the current is main- tained by the excess of pressure of the column of cold air outside over that of the column of hot air in D. The exact pressure which creates this current is found in the excess weight of a column of cold air of height H over that of a column of the same height and of the temperature of the air in D. This may be calculated as follows, since the weight of a cubic STEAM HEATING AND VENTILATION. 49 4 foot of a gas of any temperature is inversely proportional to its. absolute temperature, which is the temperature in degrees Fahren- heit + 460, or W = c -h (t -f- 460), where W is the weight per cu- "bie foot, t the temperature in degrees Fahrenheit, and c a constant, different for each gas and which, for air, equals approximately 40.. If t be the temperature of the cold air and T be that of the air in D, then the pressure per square foot due to a column of cold air of height H feet would be p = 40 H -r- (t + 460) and the pressure Figure 26. Diagram of Indirect Apparatus. due to a column of hot air of the same height would be P = 40 H -T- (T + 460). The difference of pressure which creates the flow of air then is 40 H 40 H 40H(T t) t + 460 T + 460 (t + 460) (T + 460) The head, h, which creates the velocity of flow, is equal to the height of a column of air of temperature T which would give the pressure p, or h = H(T t) 40 t + 460 By the laws governing the flow of fluids the theoretical velocity 50 STEAM HEATING AND VENTILATION. with which the current of air would move through D is v = j/ 2gh where h is, as above, the head producing the flow. This would be the velocity produced in D by the difference in pressure p were it not for the resistance to the flow caused by the friction of the air in passing through the radiator and ducts and past dampers, regis- ters, etc. This resistance often reduces the velocity to less than half of the theoretical velocity. Mr. Alfred E. Wolff, however, recommends that 50 per cent, of the theoretical velocity be taken in the case of ventilating flues which depend on a heated column for their action. The practical application of this theory is, however, one of con- siderable difficulty. In an indirect radiator in a given situation we do not know the temperature of the heated column, and, what is most important, we do not know the resistance of the air pas- sages. What we do know is that we have a radiator of so many square feet surface located in a certain system of boxing, ducts, etc., and supplied with steam, or hot water, at a certain tempera- ture. The temperature of the air outside being also known, or assumed for extreme conditions, the question is how much air will be delivered by this radiator to the room and also to what degree it will be heated. The amount of heat given off to the air depends upon the ve- locity and upon the difference between the temperature of- the steam in the radiator and the mean temperature of the air around it; and the velocity depends, again, upon the difference of tem- perature between the entering and out-going air as well as upon the air resistance as embodied in the arrangement of ducts, struc- ture of radiator, etc. All of these make a complicated system of variables which it is impossible to apply in theoretical formulas and anticipate what the actual result will be. In practice, a given ra- diator in a given setting, and with given temperatures of steam and outside air, condition of wind being constant, will deliver a definite amount of air heated to a definite degree and the velocity and final temperature adjust themselves until there is an equality between the temperature head acquired and the velocity head plus the head necessary to overcome the resistance. But exactly how this com- bination will adjust itself it is wellnigh impossible to say before- hand, inasmuch as the air resistance is a quantity very difficult tc predetermine, it being very greatly affected by a slight change in the arrangement. STEAM HEATING AND VENTILATION. 51 Mills' test of indirect radiators. For these reasons, all rules thus far deduced for installing indirect radiators are entirely empirical. But very few tests have been made upon indirect radiators with a view to establishing the relation between any of the variables in- volved; but SQme valuable results might be obtained by a thorough series of experiments carefully and systematically carried out. Mr. J. H. Mills, in his work on Heat, published in 1883, presents the collected results of a number of tests on several indirect radiators of different types. These tests were made on various radiators at various times and by several different experimenters. The writer has taken from the Mills table the results given for the two radiators upon which the greater number of tests were :made and has endeavored by plotting some diagrams from them to determine something of the relationships between the existing variables. The results published by Mr. Mills on the Gold pin radiator and the Whittier radiator are presented in the accom- TESTS ON GOLD'S PIN INDIRECT RADIATOR. Tempera- Diff. Temp.^ % $ tures. . . , a rt a t: OT Experimenter. C. B. Richards.... 1873-4 W. J. Baldwin.... 1875 W. Warner ....... 1880 Dr. Gray ......... 1875 C. B. Richards.... 1873-4 J. R. Reed ......... 1875 C. B. Richards.... 1873-4 J. H. Mills ........ 1876 W. J. Baldwin ____ 1885 J. H. Mills ........ 1876 W. J. Baldwin.... 1885 C. B. Richards.... 1873-4 J. H. Mills ........ 1876 J. H. Mills ........ 1876 J. H. Mills ........ 1876 J. H. Mills ........ 1876 4 j 1 ' w bfi a |: p I H W w O <5 PQ 215 160 160 215 5.44 111 340 60 239 71 168 97 168 3.83 128 239 70 222 42 145 103 180 4.60 145 288 90 259 33 125 92 226 6.54 231 400 215 139 139 215 9.15 214 572 58 222 52 127 75 170 7.92 343 495 215 129 129 215 12.65 319 791 76 239 81 159 78 158 8.49 354 531 60 227 82 150 68 145 8.16 290 510 76 239 90 158 67 148 8.91 433 557 60 227 70 137 67 158 8.93 433 558 215 121 121 215 15.92 428 995 77 230 88 158 70 142 10.04 467 628 76 259 90 166 76 169 15.16 649 948 76 222 90 145 55 132 12.54 741 784 77 227 94 145 51 133 13.43 855 839 TESTS ON G. WHITTIER'S INDIRECT RADIATOR. C. B. Richards.... 1873-4 J. R. Reed 1875 . B. Richards.... 1873-4 J. R. Reed 1875 J. R.- Reed 1875 C. B. Richards.... 1873-4 ..215 135 135 215 68 222 45 129 84 177 ..215 102 102 215 68 222 52 110 58 170 .. 222 52 114 62 170 215 87 87 215 4.40 106 275 5.09 197 318 6.66 212 416 5.50 308 344 5.86 307 366 8.53 319 533 C. B. Richards.... 1873-4 215 77 77 215 10.14 428 634 STEAM HEATING AND VENTILATION. panying table. In the accompanying diagrams, Figures 27 and 28, the relation between the British thermal units given off per hour per square foot of radiator and the cubic feet of air per square foot of radiator per hour has been plotted from these results. This last quantity is,, of course, a measure of velocity and is the only one which is of practical value in the comparison of different radiators.* The author has -marked each of the points on the diagrams with the difference of temperature between the steam and the entering air. At first inspection there seems to be but little uniformity in the arrangement of points, but a little study shows that for those representing the same difference of tempera- ture the relation between the heat units per squa-re foot and the cubic feet of air per square foot may be represented by a fairly uniform curve. . DI200 El 100 Approximate Eq turye for 2/5 of icmperciti. ~ H-8.28A a79 uaTipnc Differen re,. f ;e / S x 8 0) IVAAI O.900 800 O" 700 ,-M^ '% Act rip. - p JJX

/ 1^ J 600 O BOO S/ SL^Sr ^^ | . r ?y "* cy g. 400 \/ ? ' ^ 5? ^ -j tvv _; 300 /, r 10 200 / ^ ft qyres at Points art Differences "Ttmperature Between Steam id Entering Air. 100 // 3 in r . s: AAir in Cub. Ft. per Hour per Sq. Ft. of Radiation . Figure 27. Tests of Gold Pin Radiator. On the diagram of the tests of the Gold pin radiator are plotted the curves representing the relation for a difference of tempera- ture of 215 degrees Fahr., and also approximately that for a difference of 150 or 160 degrees. On the diagram for the Whit- tier radiator are plotted only the curve for tests at a difference of temperature of 215 degrees. There are some points, which are marked by a cross on the diagram, that seem to be decidedly out of place; that is, for the difference of temperature the ratio be- tween the British thermal units per square foot and the cubic feet of air per square foot is too low. Considering the fact, however, * Mr. Mills gives a diagram somewhat similar to these, but tue au- thor cannot find that the points given are taken directly from the tests which he produces. STEAM HEATING AND VENTILATION. 53 that the tests under discussion were made on radiators of different sizes, and several years apart, by different men, and under very dii ? - ferent conditions of setting, the uniformity of the curves is very striking, and the few points which are evidently out of place are doubtless due either to some error of observation or in some marked difference in the way of taking measurements. Inasmuch as in practice we are most concerned with extreme conditions, the curves for the difference of temperature of 215 de- grees are of most value, as they may be taken to represent an initial air temperature of degree and low-pressure steam at 215 degrees. It will be noticed that the 215-degree curve for the Gold pin radiator is quite different from that for the Whittier. As these curves show for a constant difference of temperature, the relation between the cubic feet of air per square foot of radiator, which is a measure of the velocity of air flow, and the heat given off per 1- I3UU 1200 ^ 1100 1000 Approx mate Equation ofCurvz y Difference of Temperat M oga r form - H=m jre ft: 9 800 (0 TOO | ^- ' fe cno !P ^ 3^ -500 H 400 o & 8 H 1. West ,.., 2. N. & W.. 118 3 N 1 ^ & E. 4. NE. u W u a g d S_j 3 * m s p Q PH ~ 59 160 3360 54.5 47 51 44 49 46 .18 312 2150 85 86 76 81 97 84 8.5 420 4070 85 84 87 82 85 80 59 129 1730 44.5 42.5 40 46 47 40 STEAM HEATING AND VENTILATION. 69 gaged to design the heating system, and for which the heating surface has been figured out according to Mills', Willett's, Carpen- ter's and the author's formulas, and also according to Mr. Bald- win's formula taking 65 per cent, of the glass equivalent surface. The table also gives the amount of surface which was installed in .each of the four rooms, and which has given perfect satisfaction throughout two or three severe winters. The radiator used was the two-column cast-iron radiator, 32 inches high, except in room 2, which had a 26-inch flue radiator. The radiation in room 2 was made slightly less than the amount calculated, because a large por- tion of the wall surface was a 25-inch brick wall, for which tho multiplier for W might be taken about 0.15 instead of 0.25. It might be stated that in using the formula given, i l is to be taken 10 degrees above the lowest recorded temperature, and the factor, J, should be taken from 1.05 to 1.15 for severe exposures, and may also be increased 0.1 for ordinary brick buildings with wooden floor joists, and 0.2 for wooden buildings. The factor a is to be taken at 1.7 for ordinary conditions of exhaust-steam heat- ing. It may be increased somewhat for heating at higher press- ures and for buildings with low-pressure heating and no power, in which steam pressure of 10 or 15 pounds may be carried, it may be made equal to 1.8. In such cases, also, the temperature, T, may T^e taken at 235 degrees. The factor a should be decreased where the radiators are of an unfavorable pattern or are unfavorably lo- cated, according to their relative heat-giving power, under such conditions as has been pointed out in Chapter III. The last part of the formula need be calculated but once for each building. The factor a may be taken as high as 2.8 in some greenhouses and in some factories in which wrought-iron pipe coils are used, which are quite an effective type of surface. Unless the coils are espe- cially favorably located, however, the factor should be somewhat less than 2.8. In the general application of the formula given above it will be noted that the expression (t t x ) (1.3 G + 0.25 W + 0.008 C) rep- resents the total heat given off by the room, and it is equal to K (T t) a, which is the heat given off by the radiation surface. Mr. Wolff in his practice calculates the heat lost per hour from each room according to his diagrams previously given, with the allowance for exposure as shown thereon. He then (divides this amount by the number of British thermal units given off per 70 STEAM HEATING AND VENTILATION. square foot of radiator per hour, which he takes as 250 for a two- column radiator (bronzed) set under the window, but this factor varies within wide limits, as before described, according to the kind of surface used and the nature of the setting. Indirect radiation. With indirect radiation the heat lost from the glass and wall surface must be made up by the heated air com- ing in from the indirect radiator, and to accomplish this the en- tering air must, in cold weather, have a temperature considerably above the mean temperature desired in the room. The total heat lost by the room is (t t t )' h where h is the expression (1.3 G-f- 0.25 W + 0.008 C) and the volume of air required in cubic feet per hour is V= (t 1 1 ) h X 58 -=- (T t) where T is the temperature of the air leaving the radiator. Now it is necessary for the in- direct radiator to heat all of this air from the outside temperature to the temperature T, and the total heat required to be given off by the radiator is U = V(T ^^58 = ^ tOCT yh-r-CT t). It will be seen that both U and V vary rapidly with a change in T, decreasing as T is increased. If t 70 degrees and tj = 10 degrees for extreme conditions, and if T = 150, V will be one-half and U two-thirds of what they would be if T were taken at 110. It is this fact that makes the indirect radiator quite a flexible de- vice, for in extreme weather it is possible, by partially shutting off the air supply, to maintain easily the required inside temperature at the sacrifice of a small amount of ventilation. If T = 120, U=:20Sh, and V = 93h; and with T 130, U = 18G h, and V = 77 h. As a rule, it is safe to assume from 450 to 500 British thermal units per hour per square foot of surface for an indirect radiator, as will be seen by reference to the tests as described in the last chapter, and taking the former figure, with T = 120, E = 0.46 h, and with T = 130, E = 0.415 h. Inasmuch as it has been found that for the same conditions of inside and outside temperatures E for direct radiation = 0.325 h, it will be seen that according to this calculation from 28 to 40 per cent, more heating surface is required for indirect heating than for direct. The author has in his practice used these proportions for indirect radiators, usually installing about 30 per cent, more than for direct; although in some cases, where an exceptional de- gree of ventilation is desired and the room has a comparatively STEAM HEATING AND VENTILATION. 71 large amount of glass surface, more radiating surface is neces- sary. In such cases, and especially where a large amount of ven- tilation is desired, it is necessary to see that the quantity V, tis obtained above, is equal to the amount of air required for ven- tilation. It will be found sufficient in all ordinary cases to change the air four times per hour, which is generally satisfactory for private houses; but where much entertaining is to be allowed for, six times per hour is better. In designing indirect radiators it is necessary to be very careful in the proportion of flues, but such details of construction will be considered in the next chapter. In proportioning direct-indirect radiators the same rules apply as for the indirect type, although their action as direct radiators may be counted on to some extent. Where this kind of radiator is used in connection with an exhaust ventilating system very good results are obtained by using the author's formula for direct ra- diators, with an addition to the 0.008 C of 2/3 K -f- 55, where K is the cubic feet of air per hour required for ventilation. This gives additional surface necessary to heat 2/3 K cubic feet of air from the outside temperature to that of the room. The author figures on 2/3 K (in some cases f ), as in extreme weather the de- gree of ventilation may be somewhat reduced. For these ra- diators also, the factor a in the formula may be taken as 1.9 or 2. CHAPTER VI. PIPING AND CONSTRUCTION DETAILS. Having selected the system of heating to be employed accord- ing to the needs of the building in hand, and having proportioned the radiator surface according to the requirements of the various rooms, it then remains to lay out the system of piping and arrange the various details of construction. In regard to piping connections, it should be stated at the out- set that the flow of steam through any system of piping depends primarily upon the difference in pressure between that at the sup- ply end and that at the delivery or return end, and without any difference of pressure no flow of steam can exist. In exhaust heat- ing or low-pressure gravity systems, this difference of pressure is very slight, and consequently for such systems the pipes have to be larger than for high-pressure heating or vacuum systems in which the pressure in the returns is reduced by connecting them to a vacuum pump. Again, in most systems of steam heating there is another consideration which affects the sizes of pipes ; that is, the water of condensation from the radiators. If the steam cir- culation were uniform and continuous and the water of condensa- tion kept separate from the steam supply, as in properly arranged two-pipe systems, the pipes might be very small; but it is neces- sary to allow for sudden opening of radiator valves, so as to take care of the momentary demand for steam which this causes, as well as the rush of water of condensation which accompanies it. For exhaust and low-pressure gravity systems, it may be laid down as a general rule that pipe sizes should be larger for the 'simple one-pipe system than for any other arrangement. They may be smaller for the one-pipe overhead, or Mills system, and still smaller for the two-pipe systems. A description of various systems of steam distribution was given in Chapter II. Baldwin's rule for pipe sizes. In the early days of steam heat- ing, pipe sizes were proportioned by various empirical rules, the usual basis of which was the principle of being sure to get the pipes large enough; and such rules are, to a large extent, blindly followed to-day. Mr. William J. Baldwin, in his earlier work on STEAM HEATING AND VENTILATION. 73 steam heating, gave a rule for proportioning steam pipes which is very convenient and has been very widely used. This rule states that in the sectional area of the pipe there should be allowed the area of a 1-inch pipe for every 100 square feet of radiator surface. Inasmuch as the areas of circles are proportional to the square of their diameters, this means a 1-inch pipe for 100 square feet, 2- inch pipe for 400 square feet, 3-inch pipe for 900 square feet, 8- inch pipe for 6,400 square feet, etc. These sizes are none too large for many cases, although in plants with the system care- fully arranged so that the circulation is all in one direction and the water of condensation does not have to flow back against the current of steam, pipes can be very considerably decreased below the sizes given by this rule. Mr. Baldwin also gives a diagram of minimum sizes for short horizontal supply mains from which few branches are taken, which give sizes very much smaller than the rule above quoted. [See Table I.] Mills' rule for pipe sizes. Mr. J. H. Mills gives a diagram for the sizes of mains for one-pipe overhead system? of which he is the originator. This diagram gives sizes somewhat smaller than those obtained by Mr. Baldwin's rule. In the accompanying table are given the maximum square feet of radiation on pipes of each size according to the rules of Baldwin and Mills, as well as Mr. Bald- win's sizes for return pipes. In regard to his figures for minimum sizes for mains, Mr. Baldwin states that they represent minimum conditions for lengths of 50 feet or thereabout, but that for large buildings one size larger should be used. Monroe's rule for pipe sizes. In his own practice the author has divided mains and risers of steam-heating systems into the follow- ing classifications: (a) Supply mains for one-pipe systems, which carry all water of condensation, but in the direction that the steam flows. TABLE I. PIPE SIZES FOR STEAM HEATING ACCORDING TO BALD- WIN AND MILLS. SQUARE FEET OF HEATING SURFACE. Size of pipe in inches.. 1 23 45 6 8 10 A. Mills Supply mains and risers ....;...... ... 900 1,750 2,500 3,300 4,000 7,250 10,500 B. Baldwin Supply mains and risers..,.. 100 400 9001,600 2,5003,600 6,40010,000 C. Baldwin Minimum for mains 1.700 3,000 5,500 8,700 16,000 22,000 D. Baldwin Returns 1,650 3,700 6,200 10,000 (b) Mains for two-pipe or one-pipe overhead systems, into which there is no water of condensation from the radiators. 74 STEA:J HEATING AND VENTILATION. (c) Supply risers for ordinary one-pipe systems which carry all the water of condensation and in a direction opposite to the flow of steam. (d) Risers for one-pipe overhead systems which carry all the water of condensation but in the same direction as the flow of steam, the lowest part of riser below last radiator being solely a return pipe. (e) Supply risers for two-pipe systems which carry no water condensation,, except that due to the pipes themselves. In addition to these the following classification is made for re- turn pipes : (f) Return mains for two-pipe and overhead systems which are above the water-line of the system. (g) Horizontal return mains for two and one-pipe systems which are below the water-line. (h) Return risers for two-pipe systems. Table II. herewith gives the maximum amount of radiation to be put on each size* of pip'e for the different classifications: TABLE II. PIPE SIZEb FOR HEATING SYSTEMS (MONROE). (a) (b) (c) (d) (e) (f) (g) (h) fl So 2" ? i of 02 i of -1 F 9 .2 9 ^ I _d ^ C3 c? Lri 9 1 M Ctf OJ ^ ft IP.-' 03 . 3J. PH a> .2 w 1| II gS, ft ft _S ft ft V H 4-1 !>> a > o *" *f >> o S aJ do - gd> O "a "a ^ > ! gJl "ft ^ ^ o i* ~* m d^ O> (Q ftQ ftHO ' ^-> PQ S S^- 1 ''I. W d a 02 03 n K M S 1 70 .... 50 60 80 400 400 250 150 120 150 200 900 900 700 2 300 *400 250 300 400 1,600 1,600 1,200 2^2 500 650 400 500 700 2,600 3,500 2,000 3 750 1,200 700 900 1,200 3,800 8,000 3,000 4 1,400 2,000 1,500 1,800 2,000 7,000 14,000 . . . . 5 2,400 3,500 2,500 2,600 3,600 12,000 26,000 6 4,000 5,500 3,600 4,200 .... 16,000 .... .... 7 5,500 8,000 30,000 g 7*000 12*000 10 12*000 16,000 12 18.000 25^000 The table here given represents the conditions which are to be met with in ordinary buildings, and exceptional conditions will have to be met with by the judgment of the engineer conducting the work. It will be noted in general that this table gives less STEAM HEATING AND VENTILATION. 7 radiation on the small pipe sizes and more on the large than that by either Baldwin's or Mills' rules. In small plants, or in plants, where a large number of small radiators are supplied from the risers, the number of radiators on a given riser may affect its size irrespective of the amount of radiation. Eisers less than 1 inch in size are rarely used on a two-pipe system, or less than 1J on *n ordinary one-pipe system, unless perhaps for only one small ra- diator. In an overhead system the height of the building and the consequent number of radiators on the riser affect the size, espe- cially at the lower end. In such a system it must be borne in mind that all the water of condensation from the higher radiators is falling down the pipe, passing the connections to the lower ra- diators. For such systems in high office buildings it is therefore well to make the risers fairly large toward the bottom while the upper portion can be proportioned according to the sizes given in column (d). For buildings about ten stories high, the lower part of the riser should be not less than 2 inches, and if the amount of' radiation on the riser is large or the building is over 15 stories high, this may better be 2^ inches. The table given is intended for low-pressure gravity systems and exhaust heating where not more than 2 or 3 pounds back pressure can be carried on the- engine. For high-pressure systems working at 20 or 30 pounds pressure,, such as are used sometimes in factories, when engines are used with a condenser, the pipe sizes may be somewhat smaller than those given in columns (e) and (h), although for the smaller connections it is not advisable to reduce them on account of the possibility of water from the radiators backing into the supply pipes. Pipes for vacuum systems. In vacuum systems in which the vacuum is maintained on the return side, pipe connections may be- reduced very materially, and Table III, given herewith, shows sizes recommended by Messrs. Warren Webster & Company for mains, risers and radiator connections for the vacuum systems which they install. As already described, their system is in prin- ciple an ordinary two-pipe system with a vacuum pump on the re- turns, but also having the special feature, of an automatic thermo- static valve on the return connection, which valve closes auto- matically when it is heated to steam temperature and opens when it becomes cooler. From the author's experience he would 76 STEAM HEATING AND VENTILATION. sider the sizes given in this table somewhat too small and would in general recommend about one pipe size larger. TABLE III. PIPE SIZES WEBSTER VACUUM SYSTEM.. Sizes of supply pipes, in % 1 iy 2 2 3 4 5 6 8 10 Maximum sq. ft. on runs not over 50 ft 100 150 400 900 2,000 4,000 8,000 12,000 30,000 60,000 Sq. ft. surf, for long runs, 300 to 400 ft. 40 100 300 600 1,500 3,000 6,000 10,000 22.000 40,000 Minimum for re- turn for above, in % % V 2 % 1 1% l x /4 1% 2 2% With vacuum systems which have a vacuum only on the air-valve connection, such as the Paul system, it is impracticable to reduce much the sizes of the steam pipes below those given in Table II, as the only feature of this system is that it keeps pipe and ra- diators perfectly free from air, and does not greatly affect the flow of steam and water of condensation. Radiator connections. The connections from the risers to the radiators are always made somewhat larger in proportion than the mains and risers, and Table IV gives sizes which represent good practice for low-pressure systems. TABLE IV. RADIATOR CONNECTIONS. One-pipe Systems. Two-Pipe Systems. r Max. surf. ' Max. surf. in rad. Supply. Returns. in rad. in. sq. ft. in. in. sq. ft. % 25 % K 40 1 50 1 % 75 1% 85 1% l 120 1% 130 1% l 180 Carpenter and Sickles' rule for steam pipe sizes. In designing piping for large systems it must be borne in mind that there are many things which affect the flow of steam in a piping system, and special cases must have special consideration. Elbows, bends and valves greatly increase friction in the pipes. According to the recent investigation of Professor Carpenter and Mr. E. C. Sickles, as given in a paper before the American Society of Mechanical Engineers, Volume XX, a single 90-degree elbow is equal in frictional resistance to a length of pipe equal to about 520 times the diameter, while the resistance of a globe valve is equal to a length of 706 times the diameter, and a good gate valve STEAM HEATING AND VENTILATION. 77 does not add any practical resistance. They gave the following approximate formula for diameters of pipes, which they say is practically accurate for sizes over 2J inches: d = 0.184 y w* L H- pD in which d equals the diameter in inches ; w, the weight of steam, to be delivered in pounds per minute; L, the length of the pipe in feet; D, the density or weight in pounds per cubic foot, and p, the difference in pressure in pounds per square inch between the ends of the pipe. Transposed, this formula becomes : w= V pDd 6 -5- 0.00021 L. From this it will be seen that, other things being equal, the de- livery is proportional to the square root of the fifth power of the diameter. The accompanying table, Table Y, is calculated from this for- mula, assuming p = 1 pound per square inch difference of pressure and D = 0.04, which is the density of steam at a pressure of about one pound above the atmosphere. In this table allowance is made also for two globe valves and two elbows to each length of pipe. The square feet of surface each pipe would supply, allowing 0.30 pound of steam per square foot per hour (0.005 pound per minute), which is very liberal for direct radiation, is also given in the table. This table is chiefly interesting when compared with Table II> but may be of value for long mains where the building to be heated is at a distance from the plant. It should be noticed, how- ever, that the greatest resistance is due to the elbows and valves. For example, the 8-inch pipe, 600 feet long, with two elbows and TABLE V. CAPACITIES OF STEAM PIPES. w wt. of steam delivered per min. per 1 Ib. difference of pressure. R = sq. ft. of radiation supplied at 0.005 Ib. per sq. ft. per min. Diameter, Length of pipe allowing for 2 valves and 2 elbows, in. feet. 3 w 3 R 4 w 4 R 6 w 6 R 8 w 8 R 10 w 10 R 12 w 12 R ) 200 400 600 1,000 8.1 > 7.7 6.9 6.3 5.5 ,70< ) 1,540 1,380 1,22 1,100 15.( ) 14.2 12.9 12. lO.b' 00( ) 2,840 2,580 2,400 2,120 33. 31. 29. 26.2 6,600 6,200 5,800 5,240 59.5 56.5 54. 49. 11,900 11,300 10,800 9,800 95. 90.4 87. 81. 19,000 18.080 17,400 16,200 138. 132. 128. 120. 27,600 26,400 25,600 24,000 78 STEAM HEATING AND VENTILATION. two valves is equivalent to 2,240 feet of straight pipe, and the -addition of another elbow would be equivalent to 350 feet of straight pipe and would reduce the delivery in the ratio of V2,240 -f- 2,590. Draining pipes. In laying out the piping system for a heating plant, besides the proper size of pipes there are two points which must 'be very carefully considered : (1) That pipes as well as radia- tors are properly drained so that the water of condensation will flow off easily and uniformly to its proper receptacle; and (2) that proper provision be made for the expansion of pipes, so that such expansion shall not interfere with the flow of steam or water or disturb the setting of the radiators. Pipes for an ordinary one-pipe system, which are run around the basement of a building, should be pitched toward the extreme ends, from which the return connection should be taken and run back to the receiver below the water-line. If the mains are very long they should be drained at intervals into this pipe. In a two-pipe system in which the mains are similarly run, they should be drained into the return pipes, and in making these drip connections care should be taken that the return pipes into which they drain are lower than the supply mains, so that there will be no opportunity for water to flow from the returns into the supply mains. The return pipes are generally, where possi- ble, run under the basement floor, and should be lower than the supplies. Figures 31 and 32 represent typical connections from mains to risers. Where, on account of economy of space, it is necessary to run the supply and return mains on nearly the same level, as in Figure 32, the supply main must be dripped into a separate pipe run back under the floor or along the wall and con- nected into the principal return main below the water-line of the system. In two-pipe systems where the supply mains are short and properly covered, so that there is not much condensa- tion, they may be given a slight rise from the boiler or source of supply and the water of condensation allowed to flow back. Riser connections should be taken out of the top of the mains so as to prevent any water of condensation that may be in the mains from getting into the risers. In the one-pipe overhead system there is always a main supply riser running to the branch mains in the attic, and this should have a drain pipe from its lowest point extending back to the receiving ISTEAM HEATING AND VENTILATION. 19 tank. The attic mains are drained directly into the supply risers, which drop from the bottom of them. In connecting up radiators on a one-pipe system they should be set so as to pitch slightly toward the connection from the riser, and the connection should always pitch toward the riser. Con- nections which, on account of carelessness in workmanship, were pitched in the opposite way, are a very fertile cause of water- hammer. Eadiators set on two-pipe systems should be pitched slightly toward the return connection, which should not be con- nected from the same end as the supply. There are a number of plants in which radiators connected on two-pipe systems have both the supply and return connections at the same end of the radiator, but in the opinion of the author this is a very bad prac- tice, as the radiator might very much better be connected on the one-pipe system. In fact, when radiators with such connections are in operation, unless the return connection is lower than the supply, which is not generally the case, the water of condensation is just as apt to Tun down the supply connection as down the re- turn. Furthermore, when such radiators are turned on, if the sup- ply valve is opened first, any water which may be in the radiator runs out of this connection, as well as the large amount that is formed by the first contact of steam with the cold radiator; and if the return valve is opened first, the water in the return pipe backs up into the radiator, so that when the supply valve is opened, a large amount of it will run out to the supply connec- tion. At this point it should be stated that in turning on radia- tors with two-pipe connections the supply valve should always be opened first; and the fact that the uninformed occupants of rooms frequently do not know which is the supply valve is one of the objections of two-pipe systems. Expansion of pipes. The expansion of pipes is an important consideration in any case, and where there are long mains or in high office buildings, which consequently have long vertical risers, it becomes a consideration of vital importance. The coefficient of expansion of wrought-iron pipe is 0.000007 per degree Fahr. This amounts to about 1.5 inches in a 100-foot length for low-pressure steam pipes. In horizontal mains this can be gen- erally taken care of by making turns or offsets in the mains in every 50 or 75 feet of pipe, the expansion being taken up by the spring of the pipe. All connections from mains or risers should 80 STEAM HEATING AND VENTILATION. be made with sufficient length of horizontal connection to allow for this expansion. In Figures 31 and 32 the expansion of the mains and risers is taken up in the spring of the arms, AB. An old rule for the length of such expansion arms is that the length in feet should be equal to twice the diameter in inches. This, is a fair rule in most cases, but much depends on the amount of expansion to be taken care of, and no set rule can be given. The most serious difficulties on account of expansion are met with in the long vertical risers of the modern high office buildings. In such cases any considerable movement of the riser is apt to re- sult in trouble, as the radiator connections are generally short. Pipe Elevation. p |O 32 Section. Provisions for Drainage and Expansion of Piping. Various means are employed to overcome this. In buildings over ten stories in height it can generally be taken care of by anchor- ing the risers rigidly in the middle so they expand in both direc- tions, and allowing for the expansion, by the connections to the supply main in the attic and to the returns in the basement. The radiators on the upper and lower floors, where most of the ex- pansion takes place, must have connections sufficiently long to allow for it, and they must have sufficient pitch, so that they will not be trapped by the expansion of the risers. The author is fa- miliar with one building 14 stories high in which expansion is en- tirely? tak^-iir care of in this way. Radiators on the extreme floors STEAM HEATING AND VENTILATION. 81 Radiator. are made with extra high legs, and the connection from riser is- as shown in Figure 33. In another case, in a 14-story building,, an offset was made in each riser over the windows of the seventh floor, the upper part running on the opposite side of the tier of windows from the lower part, the spring of the pipe in this offset- taking care of the expansion at this, point. The risers were an- chored rigidly in the center of each section. Arrangements of this kind are frequently used, and the chief objection is that un- less they are concealed the offsets make an unsightly appearance, and it is frequently very inconvenient to put them in on account of the arrangement of the building. In one large 16-story building with which the author is ac- quainted, a loop, as indicated in Fig- ure 34, was made with each riser and sealed in the seventh floor; but he would not recommend this arrange- ment, inasmuch as leaks are most apt to occur at the points marked C when the expansion and contraction works on the threads of the joint. Besides this, the framing of the building and extra construction details in the floor necessary to conceal these offsets are difficult and expensive. The expansion of such risers is frequently taken care of by means of expansion joints, a dia- gram of which is shown in Figure 35. The author has used these joints to a large extent, and although in some localities there is a prejudice against them, he thinks this rather unwarranted. By proper ar- rangement the expansion risers in any building not over 12 or 14 stories high .can be taken care of with one set of expansion joints. In a 14-story building heated on the overhead system the author installed an expansion joint in each riser above the radiator connection at the seventh floor. The risers were an- chored rigidly to the beams of the fifth and twelfth floors so that expansion was in both directions from these points. This gave about f inch expansion downward at the first and eighth floors and about f inch upward at the seventh and fourteenth. Ead- iator connections on the eighth floor were long enough to admit of 82 STEAM HEATING AND VENTILATION. STEAM HBZfING AND VENTILATION. 83 this expansion, and on the first floor they were connected as in Figure 33. If the radiator connections were very short, two joints would have been put on each of these risers. In laying out large systems, valves should be placed on each riser so that each one can be shut off independently of the others in case of leaks or in case of repairs or changes to be made on any of the radiators. Gate valves should be used preferably on account of the fact that they interpose infinitely less resistance to the flow of steam or water than do globe valves. Furthermore, in such cases provision should be made for changes in the arrange- ment of rooms and consequent changes in the location of radiators. It is a very good practice to put tees on each riser at each floor whether or not, in the first instance, a radiator connection is re- quired, as subsequent changes in the arrangement of rooms may make it desirable to change the radiators. Figure 36 shows the arrangement of piping in the attic of the Ellicott Square, a large 10-story building in Buffalo, N. Y., which is heated by direct radiation on the overhead system. The figure illustrates the method of connecting the overhead mains to the risers, and also the way in which expansion of the mains is pro- Tided for by bends and offsets. In this instance the piping was rigidly anchored at four points marked D, and the expansion al- lowed in all directions from these four points. It may be noted here that branch mains were taken off at points marked E and F, instead of connecting each riser to the main 10-inch pipe at these points. This was done for the purpose of saving the expense and 'the delay to the work of connecting each riser into the 10-inch pipe. Valves. Much care should be used in placing valves on a piping system. Gate valves should always be used on mains. If globe valves are used anywhere, the stems must be placed horizontally, as otherwise they form a water pocket. Thermostatic valves, so- called, are often used on radiators, being connected with an auto- matic device which opens the valve when the temperature falls, -and closes when it rises. Location of risers. In laying out the floor plans for the heating system of a large office building it is a mistake to try to reduce the number of risers to a minimum. It is much better to put in risers enough so that a radiator can be placed under any window in the building without too long a connection from the riser, for 84 STEAM HEATING AND TENTTLATION. in such buildings one can never know what changes in the arrange- ment of rooms or in the location of radiators may ultimately be desired. Figure 37 shows the t} r pical floor plan of the heating diagrams for a fourteen-story building in Chicago, showing the location of risers and radiators. This building is exceptional on account of the large number of bay windows and large amount of "glass surface. Furthermore, the risers were all concealed in the columns in the manner shown in Figures 38 and 39, the building being framed with Gray columns, built as indicated. An expan- Figure 37. Plan Showing Location of Risers and Radiators. sion joint was placed on each riser, above the radiator connection at the eighth floor, with flange unions above and below the joint. At these joints a removable wooden panel was placed over each riser, as indicated at Figure 38, but otherwise they were enclosed by the wire-lath and plaster forming the ordinary finish of the columns. Figure 39 shows a section of the column at the four- teenth floor. The radiator connections were exposed above the floor and run about as indicated on the floor plan. This building is heated on the one-pipe overhead system. It contains 11,000 square feet of radiation, supplied by an 8-inch main to the attic. The typical floor has 1,055 square feet of glass surface, STEAM HEATING AND VENTILATION. 85 square feet of wall surface and 47,400 cubic feet of space, includ- ing corridors, and is heated by 18 radiators containing 787 square feet of surface. By the author's formula given on page 68 the amount of surface required amounts to 730 square feet> but the exposure of the upper stories of this building is unusually severe. It is frequently a very difficult matter to conceal risers in fire- proof buildings on account of the floor plates of the columns and the beams, which frequently interfere with placing the risers very close to them. Figure 40, however, represents the manner in which they were enclosed in a building which was framed with ~box columns.. In this case the tile fireproofing was put on over both column and riser. In concealing risers in the walls of wooden buildings it is necessary to protect the pipes carefully from imme- diate contact with the woodwork. In hanging risers in buildings Fio.38 FiG.39 FiG.4O Methods of Running Risers in Columns. great care must be taken that the pipe be cut to the proper lengths so that the fittings for the radiator connections will come exactly in the proper place. Riser anchors. As previously stated, risers are usually, espe- cially in large buildings, anchored rigidly at certain points so that expansion shall be in both directions from these points. This should be carefully done so that the pipe will not slip, and the method to be employed to accomplish this depends largely upon the local conditions. Figures 41 and 42 show two methods of ac- complishing this, the latter being especially adaptable where the riser can be run close to the floor beam, but to make it perfectly rigid it should be made strong and shrunk in place. The method indicated by Figure 41 can be adapted to anchoring the pipe to a column instead of to the floor beams. In some cases risers are also secured at the other floors so as to allow expansion, but at 86 STEAM HEATING AND VENTILATION. the same time maintain proper alignment ; but this is not generally necessary, as the rigidity of the piping and connections is gener- ally sufficient to keap the pipes property in line. Protecting pipes. Where risers or other pipes run through the floors or walls they are generally protected by floor sleeves with floor and ceiling plates. These are usually made of galvanized iron in a telescopic form so as to fit any thickness of floor. In buildings with wooden floors they are necessary so as to give an air space around the pipe and prevent immediate contact of the steam pipe with the woodwork. In fireproof buildings they ara FiG.4t Types of Riser Anchors. frequently omitted, but it is preferable to use them, as they make a better finish around the pipe at the ceiling and prevent the ex- pansion of the pipe from disturbing the flooring or plaster. Floor and ceiling plates should be used in any case. Eadiator connections are frequently encased in the floor, but it is generally difficult to accomplish this in fireproof buildings, as the space between the floor level and the top of the iron beams is not generally sufficient to box in the connections and make proper allowance for the vertical movement of these connections due to riser expansion. It can be done in some cases, however, but the connections should always be enclosed in a galvanized-iron box and the flooring should be so laid that a strip over the pipes can be easily removed. Supporting pipes. Horizontal pipes are almost invariably sup- STEAM HEATING AND VENTILATION. 87 ported from the ceiling above by means of some kind of an expan- sion hanger, two common types of which are shown in Figures 43 and 44, the two shown in each case being, one for wooden beams and the other for iron. The rods can be cut to the length desired after the pipe is in place. There is sufficient movement of the rod at the top to allow for the small play of the pipe due to expan- sion. A simple and cheap form of hanger frequently used for small pipes in buildings with wooden floors is made of a piece of light chain looped under the pipe and hung from the nails in the floor beams. The chain can be cut to length with wire nippers. In case of very large pipes in the basement of buildings, they are FiG.43a. Fio.43b Ti Expansion Pipe Hangers. sometimes supported by some kind of a standard erected from the floor. Arrangement of pipes. In laying out the main piping connec- tions of the power plant of a large building great care must be taken to arrange the pipes as systematically as possible so that they take up no more room than necessary, and also to properly provide for the drainage of all pipes into proper receptacles. This- is frequently a difficult matter, but one can hardly give too much consideration to the subject, as the successful operation of a plant depends largely upon the way piping connections are arranged. It is impossible to give any detailed rules, as each plant is a prob- 88 STEAM HEATING AND VENTILATION. STEAM HEATING AND VENTILATION. 89 lem in itself, and is entirely subject to local conditions. The main, connections to the heating system must be laid out in connection with the exhaust and live-steam pipes of the power plant, accord- ing to the principles established in Chapter II. Simplicity in n piping system is always primarily desirable, but sufficient valves and by-passes should be installed, so that if any accident occurs to one part of the system that part can be shut off without crip- pling more than a small section. Figure 45 shows the arrangement of the main piping connec- tions in a large office building in Syracuse, N. Y., in which, on account of the extreme difference in floor levels and the crowded condition of the machinery, a really systematic arrangement of piping it was impossible to obtain. (The Engineering Record of November 5, 1898.) The main valves controlling the heating sys- Fis.44a. tern are indicated at A, B, C and D. During the heating season the valve, D, is opened and the back-pressure and reducing-press- ure valves put into service, while during the summer months the valve, D, is closed entirely, shutting off the heating mains, and the 10-inch back-pressure valve is opened wide. Ordinarily, both in winter and summer, the valve, A, is closed, so that all exhaust steam from the pumps and engines goes through the muffler tank and heater; but in case it is necessary to' open these for cleaning, the valves B and C are closed and the valve, A, opened, so that the exhaust steam may go directly either into the free exhaust or the heating system, as the case may be. The building in ques- tion contains about 15,000 square feet of radiators and is heated on a two-pipe system with basement mains. The returns come back to the two automatic governors which control the 6x4x6-' 90 STEAM HEATING AND VENTILATION. inch pumps. These deliver the return water through the closed heater into the boilers. There are three pumps used for this pur- pose, and so connected that any one can be used on the governors separately or together, and any one can be used to pump cold water through the heater. The feed pipe has a by-pass around the heater, to be used when the heater is being cleaned. Eeturn pipes should be given as much pitch as possible except where they are below the water-line of the system. In running these below basement floors they should be put in trenches, prefer- ably of brick or concrete, and with movable covers. If there is danger of water underground the trenches must be arranged so that they can be kept dry, and no better trench can be made than one of good concrete. Pipe coverings. All the piping connections should, as far as. possible, be covered with some kind of non-conducting pipe cov- ering, of which there are innumerable varieties made. In some cases risers and other pipes are left uncovered so as to utilize the- heating effect, but the disadvantage of this is that heat is given out from such pipes whether it is wanted or not, and it is much better practice to cover the risers and depend on the radiators, for heating. One of the greatest sources of fuel waste is found in uncovered mains in basements of buildings where heat is noth- ing but an inconvenience, and in order to dispel it in moderate weather windows are opened, which greatly increase the wasteful condensation. A good pipe covering will save from 65 to 80 per cent, of the heat which would ordinarily be wasted from the pipes. Coverings of which 85 per cent, is carbonate of magnesia, certain molded forms of pure asbestos fiber, and molded forms of mineral wool are the best kinds of protection for steam pipes to reduce condensation. Some coverings which show very good results when new, deteriorate rapidly, due to the charring effect of the pipes and to disintegration. Pipes and flues for indirect radiators. "We come now to the con- sideration of certain details of construction which are especially requisite in indirect heating. In this class of steam heating the piping connections are subject to much the same rules for run- ning pipes as those for direct radiators, but indirects are almost invariably located in the basement of buildings and the pipes run- ning to them are horizontal. Furthermore, the condensation per square foot of indirect radiator is from 25 to 50 per cent, more STEAM HEATING AND VENTILATION. 91 than that per square foot of direct radiatpr, so that the piping connections are generally made about a size larger, and, except in rare cases, connected on two-pipe systems. Indirect radiators are usually hung from the beams of the first floor, and various methods, which are dependent upon the local conditions, are adopted for supporting them. A frequent form of support is in- dicated in Figure 46, the radiator resting on short pieces of pipe which are hung by rods bolted to the floor joists, or hung from a pipe over them. Indirect radiators are always encased in some kind of a metal box, either of galvanized iron or tin, or of wood lined with tin. These boxes connect directly with the hot-air flues which run to the rooms above and which are of heavy tin or sheet iron. Both the flues and boxes should, of course, be as nearly air tight as possible. In regard to sizes of hot-air flues, an loor L ire i / Pipz doorf 1 WrJoists- 1 1 c Fadiator. \ /'Floor Line. % j) : ( Joists. n Radiator. Pipe about 2." / Figure 46. Indirect Radiator Support. 10 1.2 15 1.0 20 0.85 25 0.75 old rule gives 1 square inch of flue area to 1 square foot of radia- tor. This is very satisfactory in most cases, but the following table, which gives the sizes recommended by Prof. J. H. Kinealy, is to be preferred, as the size of flue should depend upon its height : SIZES OF FLUES FOR INDIRECT RADIATORS. Height in feet from center of radiator to center of register 5 Sq. in. of flue area for 1 sq. ft. radiation 1.7 The indirect-radiator boxes must, of course, have a fresh-air inlet. This should always be run from the outside and from a lo- cation removed from the possibility of contamination to the in- coming air; and it is preferable that the cold-air inlet be located at least a few feet above the ground. Cold-air supply connections from the outside to indirect boxes should be made as short as pos- sible; 1 square inch area per 1 square foot is generally sufficient, STEAM HEATING AND VENTILATION. although if the flues a:ce of considerable length or are winding, a larger ratio should be given. If a number of radiators receive air from the same cold-air flue, the flue may be somewhat smaller. In buildings in which there are a considerable number of indirect radiators there are two general methods of con- necting the fresh-air flues, which are illus- trated in Figures 47 and 48. Figure 47 represents the cellar plan of a large Massachusetts residence (The Engineering Bec- ord, August 5, 1893; Mr. A. A. Sanborn, Boston, heating contractor), in which there are seven large clusters of indirect radiators which supply about 30 hot-air flues ris- ing to the rooms above, the hot-air pipes run- ning horizontally from the radiator boxes, in some cases for 50 feet, to the vertical flues. radiators in this are all Gold's Pin in 16-foot sections.) In the Philadelphia resi- dence shown in Figure 48 (The Engineering Eecord, December 15, 1894), there is, on the contrary, a long main cold-air duct which sup- plies a large number of indirect radiators, one for each of the vertical flues, the radiator in all cases being located directly under the vertical flues. In the opinion of the author this is much the preferable method, (The building STEAM HEATING* AND VENTILATION. 93 as a much more positive circulation of air to the separate rooms can be secured than by the other method. The system shown in Figure 48 is interesting also on account cf the construction of the main cold-air duct and the connections from it to the radiator boxes. These are well illustrated in Figure 49, the main duct, it will be noted, being of brick, and underground. In the author's opinion there is one particular in which the system shown in Figure 48 might have been much improved. The colcl- air duct is long and winding, and had it been more uniform in size Figure 48. The Indirect System in a Philadelphia Residence. and supplied with another cold-air connection on the side of house opposite the existing one, it would have insured a more posi- tive circulation to all the radiators. The reason of this is that in cases, such as shown in Figure 48, where there is only one cold- air connection for a number of radiators, when there is a strong wind blowing against the side of the house opposite the fresh-air inlet it is sometimes very difficult to get a good draft in the flues, especially in those most removed from the cold-air inlet, as the force of the wind (which, with the best constructed houses, blows through the walls to a great extent), seriously opposes the current 94 STEAM HEATING AND VENTILATION. of air in the ducts. If there are two fresh-air connections, each provided with dampers, the one on the leeward side of the build- ing can be closed and the one on the windward side opened to give a proper amount of cold air. It is, moreover, desirable to put a tight damper in the duct to each radiator. Setting direct-indirect radiators. In regard to the setting of di- rect-indirect radiators, the piping connections are made according to precisely the same rule as for directs, although in cases of large radiators of this kind it may be desirable to increase slightly the pipe sizes on account of the somewhat increased condensation. A Plan first floor Register, Indirect Radiator: Elevation. Cellar Floor. Brick Duct. F.G.49 THE ENGINEERING RECORD. frequent form of fresh-air connection for this kind of radiator is indicated in Figure 50, and the connection to the outside air should in all cases be provided with an easily adjusted damper. One trouble with direct-indirect radiators is that when a strong wind is blowing against the outside wall it is difficult to prevent objec- tionable drafts, due to sudden gusts of wind, which, in cold weath- er, will make frequent cold waves across a room notwithstanding the average temperature may be about right. Figure 51 represents a special form of setting for large radiators of this kind adopted % Mr. Alfred E. Wolff, in the Singer Building, New York City. (The Engineering Record, September 3, 1898.) It will be seen that the effect mentioned is here avoided by making the cold-air STEAM HEATING AND VENTILATION. 95 Iiilet to the radiator somewhat tortuous, so that, as far as possible, the draft is due only to the hot air from the radiator. The same effect is accomplished in the United States Government method Inlet Damper. ~~ -___ "TMS ENOINECRINO RECORD. Figure 50. A Direct-Indirect Radiator. Fie. 51 Types of Direct-Indirect Radiator Casings. of setting indirects in the Detroit Post Office, which is shown in Figure 52. Mr. Henry Adams, of Baltimore, Md., was the engineer for this work. (The Engineering Eecord, August 7, 1897.) CHAPTER VII. MECHANICAL VENTILATION- GENERAL PRINCIPLES. Need of proper ventilation. It may be stated as an undeniable truth that no system of ventilation is adequate to give proper results at all times and in all kinds of weather, unless it is a me- chanical system. As has been seen in a previous chapter, the air discharge of an ordinary ventilating flue with the gravity system depends upon the difference in temperature between the air in the flue and the outside air, so that its discharge is very different in moderate from what it is in very cold weather. Very satisfactory results are in many cases obtained from indirect radiators, but the same is true of these as of an ordinary ventilating flue. And every one now knows of the precarious nature of ventilation by open doors and windows, since in cold weather the occupants of rooms invariably prefer warm and bad air to that which is cold and fresh. Yet those who have been interested in the subject, for as long as a decade, can readily recall the days when such means of ventila- tion were considered entirely sufficient even for schools, churches and other densely-peopled buildings. It is part of the marvelous scientific development of the close of the nineteenth century that there has been such an advance in the popular appreciation of the necessity and value of good ventilation, that a very fair percent- age of school-houses now erected, even in the smaller communities, boasts of a complete ventilating plant. There are, however, many such plants that are in reality not the perfect ones they are made to appear, and the problems con- nected with the proper distribution of an adequate volume of air to and through buildings and rooms of various kinds are more varied and complicated than is ordinarily supposed. Only those who have had much experience with them and who have met with failures in some of their cherished schemes of ventilation, realize that air is a very subtle medium of control. It is a comparatively simple matter to obtain a large blower and connect it by a system of ducts to the rooms to be ventilated, but to admit the air into the rooms in sufficient volume without drafts and make it circu- late where it is needed is a different proposition. The air currents STEAM HEATING AND VENTILATION. 97 have an exasperating way of going around the ceiling instead of across the breathing line; or of running down walls and out of doorways instead of across the room and out of properly-prepared vent openings. Another source of tribulation is the fact that in winter the temperature of the fresh air blown in is in most cases warmer than the average temperature of the room; while in sum- mer it is somewhat cooler, so that in the former case the incom- ing air tends to go to the ceiling., and in the latter to the floor. There are a few old-time fallacies,, vestiges of which still linger to a surprising degree in the minds of many who appreciate the necessity of good ventilation. Among these are the ideas that fresh air must be cold and that it must be admitted through win- dows, and the foul air be drawn off through vent flues-. But the worst of all is one of the carbonic-acid theories, which is to the effect that exhaled air is laden with carbonic-acid gas (C0 2 ), which, being heavier than pure air, sinks to the floor, and may be tapped off by putting an outlet anywhere at the floor-level. This notion seems to be firmly grounded into the minds of many, who cling to it steadfastly. It is difficult to explain to these unfortunates that the air exhaled by man contains ordinarily 'less than 5 per cent, of carbonic acid, which would not affect the specific gravity to an appreciable degree; and that furthermore there is an indis- putable natural law known as the diffusion of gases, in accordance- with which two gases in 'contact tend to form a perfect mechan- ical mixture. The carbonic-acid gas in the air of rooms is, however, an impor- tant consideration, as it serves as an accurate index of the degree of vitiation. It must be understood, of course, that the carbonic- acid gas in itself is not injurious and is merely an index. The air of the stuffiest lecture room that one ever goes into does not con- tain more than 50 parts in 10,000, and air that contains as much as 15 parts in 10,000, due to being repeatedly breathed, is of a, very unhealthy quality. Notwithstanding this, in soda-water fac- tories the air frequently contains as much as 150 or 200 parts of; C0 2 to 10,000, and is in no way injurious. In air that contains as, much as 10 or 15 parts of C0 2 in 10,000, due entirely to exhala-. tions from the body, it is not so much the C0 2 that constitutes the obnoxious element, as it is the organic matter and the germ-laden moisture that accompanies it not necessarily disease germs, but all kinds of natural germs, which are more or less injurious, and 8 STEAM HEATING AND VENTILATION. which, together with the organic matter given off in the moisture of the breath, gives to confined air that oppressive and stuffy ef- fest which is at once disagreeable and exceedingly unhealthful. It is not intended here to go into detail in regard to the ill effects of breathing vitiated air and the hygienic value of good ventilation. The absurdity of expecting to develop bright and healthy children by sending them day after day to shut-up school rooms, or of ex- pecting inspiring results from sermons or lectures delivered in close and stuffy halls, or of having popular reading rooms or thea- ters where the air is laden with the peculiar aroma of a mixed and varied populace, is rapidly being better and better understood, and more and more widely appreciated. There is no doubt but that in a large room which is occupied for some length of time by a crowded assembly it is impossible to se- cure air of the same purity as that outside, as the breath from the occupants vitiates the incoming air as well as that which is already in the rooms. In other words, it is impossible for the occupants of a room to inhale pure incoming air and exhale it so that it will pass out by a vent shaft without a portion of it com- ing in contact with anyone else. If this were the case it would only be necessary to supply from 12 to 15 cubic feet of air per person per hour, which is about the rate of breathing of adults, in order to insure perfect ventilation. As a matter of fact, however, the best we can do is to dilute the vitiated air as much as possi- ble, and it has been found that to accomplish this to a satisfactory degree requires from 100 to 200 times the amount of air above mentioned per person per hour. Pure air is found by investigation to contain very close to 4 parts of C0 2 in 10,000. The opinions of many able hygienists agree that when the proportion of C0 2 exceeds 6 parts in 10,000 the bad effects of poor ventilation begin to be noticeable, and when 8 parts in 10,000 are found, the characteristic odor of an ill-venti- lated room is apparent; and to those who remain in such an at- mosphere for any length of time there comes a feeling of close- ness, lassitude and dullness. It is therefore universally agreed that when the carbonic acid is formed entirely by the breathing of the occupants, the quantity should not exceed 6 parts in 10,000, though 8 parts may in some cases be permitted for short periods, and that anything in excess of this figure indicates poor ventila- tion. STEAM HEATING AND VENTILATION. 99 Air required for ventilation. The amount of fresh air required depends upon the number of people and the amount of carbonic- acid gas given off by each individual in breathing. This last factor is exceedingly variable, depending upon the weight, age and physi- cal, as well as mental, condition of the person. Pettenkofer, a very painstaking scientist, gives the following figures for the aver- age amount of carbonic-acid gas given off per hour by adults per pound of weight: In repose 0.00424 cubic feet. In general exercise 0.00591 cubic feet. In hard work 0.0122 cubic feet. In sleep, about 0.00320 cubic feet. He also adds that the amount given off by young children is nearly twice as much per pound of weight as for adults. Some diseases, such as fever, increase the amount, and others decrease it. Pet- tenkofer's figures would make the average for persons in repose about as follows: Males (160 pounds weight) 0.68 cu. ft. per hr. Females (120 pounds weight) 0.51 cu. ft. per hr. Children (80 pounds weight) 0.68 cu. ft. per hr. Parkes, in his work on hygiene, gives as the amount of carbonic- acid gas given off during repose the following: Males (160 pounds weight) 0.72 cu. ft. per hr. Females (120 pounds weight) 0.60 cu. ft. per hr. Children (80 pounds weight) 0.40 cu. ft. per hr. Average mixed community 0.6 cu. ft. per hr. These figures show some variation from Pettenkof er's ; but cer- tainly for adults the variation is not more than might be found in two sets of individuals. It is very generally accepted by hygienists that 0.6 cubic foot per hour represents a very fair average for such mixed assemblies as are found in theaters, lecture rooms, churches, etc. The amount of air required per person per hour to maintain the air of a room at a certain standard of purity may be worked out by a simple algebraic calculation, as follows : Let V be the volume of air required per person per hour for continuous occupation: N, the number of persons in the room; E, the number of parts of C0 2 gas to be allowed per 10,000, the number of parts in the fresh incoming air being 4; 100 STEAM HEATING AND VENTILATION. C, the total number of cubic feet of C0 2 acquired by the air of the room per hour; 10,000 C Then R = - , VN VIST X 4 But C = -- h 0.6 N, 10,000 VN X 4 + 6,000 N" So that E = - - . VN Solving this equation with N = 1, we find V = 6,000 -f- (R 4). For R = 6, we have V = 3,000; f or R = 7, V = 2,000; while if we allow R = 8, we have V = 1,500. Now if the room is of large volume and is only to be occupied for a short period, and before occupancy the air is brought to the- same standard of purity as the outside air, then a less amount of air is required. For example, if the room contains 500 cubic feet of space per person and is to be occupied but one hour, then ob- viously 3,000 500 = 2,500 cubic feet will have -to be supplied the first hour to have the air within the standard of 6 parts of carbonic acid gas per 10,000. We may reduce this to algebraic form as follows: Let V be as already given ; v, the volume per person per hour for a short occupancy, H, the number of hours to be occupied, and Y, the cubic feet of space in the room per person. Y Then v = V -- . H From this formula Table No. 1 is calculated. TABLE NO. 1. THE VOLUME OF AIR TO BE SUPPLIED PER PERSON PER HOUR THAT THE PURITY OF THE AIR AT THE END OF THE OCCUPANCY WILL NOT EXCEED THE AMOUNT GIVEN. Number of hours to be occupied. space in Parts of CO 2 in 10,000 not to be exceeded at end of occupancy, room per 67 8 678 67 person. Cubic feet to be supplied per person per hour. 100 2,900 1,900 1.400 2,950 1,950 1,450 2,970 1,970 1,470 200 2,800 1,800 1,300 2,900 1,900 1,400 2,935 1,935 1,435 300 2,700 1,700 1,200 2,850 1,850 1,350 2,900 1.900 1,400 400 2,600 1,600 1,100 2,800 1,800 1,300 2,870 1,870 1,370 600 2,400 1,400 900 2,700 1,750 1,250 2,800 1,800 1,300 900 2,100 1,100 800 2,550 1,550 1,050 2,700 1,700 1,200 STEAM HEATING AND VENTILATION. 101 Prom the figures given it will be seen that the quantity of air to be supplied per person depends upon the size of the room and the length of time it is occupied as well as the standard of purity de- manded. The standard of purity to be required depends somewhat upon, the nature of the room. Some rooms, such as churches, lecture rooms, theaters, libraries, and some reading rooms, are occupied by widely varying numbers of people, being sometimes very crowded and sometimes but partially filled; while others, school rooms and hospitals in particular, are occupied almost always by about the same number. Of the former class, if the cubic feet of air required is based upon the maximum crowded capacity, we may allow between 7 and 8 parts carbonic acid gas per 10,000 at the end of the period of occupancy, inasmuch as they are crowded only on rare occasions, and are also assumed to be thoroughly ven- tilated before occupancy, as of course should be the case, the pro- portion of carbonic acid gas reaching the maximum only toward the end of the occupancy period. In schools and hospitals we -should never allow over 6 parts in 10,000, and as these are occu- pied for long periods fully 3,000 cubic feet of air should be allowed per person per hour, and in many hospitals, on account of the condition of the occupants, much more. Churches, theaters and lecture rooms, besides being occupied by a variable number, are occupied for from one to three hours at a time, while libraries and reading rooms may be said to be occupied continuously. An inspection of the table and formulas already given, with proper allowance for the considerations here cited, will warrant the use of Table No. 2. TABLE NO. 2. AMOUNT OF AIR TO BE SUPPLIED PER PERSON PER HOUR IN BUILDINGS OF VARIOUS KINDS. Hospitals 3,600 to 5,000 cu. ft. per hour Barracks 3,000 cu. ft. per hour Schools 2,500 to 3,000 cu. ft. per hour Libraries based on crowded capacity 2,000 cu. ft. per nour Reading rooms based on crowded capacity 2,200 cu. ft. per hour Churches based on crowded capacity 1,400 cu. ft. per hour Lecture rooms based on crowded capacity 1,500 cu. ft. per hour 'Theaters based on crowded capacity 1,400 cu. ft. per hour For the latter, based on maximum seating capacity : Churches 1,400 cu. ft. per hour Lecture rooms 1,800 cu. ft. per hour Theaters 1,600 to 1,800 cu. ft. per hour 102 STEAM HEATING AND VENTILATION. No room which is occupied for more than five hours continuously by a definite number of adults is adequately ventilated with a less, allowance than 2,400 cubic feet per hour per individual, and 3,000 should be given. CHAPTEE VIII. SYSTEMS OF MECHANICAL VENTILA- TION. In the last chapter were discussed the general principles on which depend the volume of air necessary to give good ventilation ; the next point for consideration is the method by which this air is to be supplied and distributed. In the earlier days of me- chanical ventilation two general systems of air distribution were considered, the plenum or pressure system, and the exhaust sys- tem. In the former the fresh air is drawn from the outside and forced by the fans into the rooms to be ventilated, and finds its way out again through flues provided for t e purpose. In the ex- haust system, flues or ducts are provided for the inlet of the air, but the fans are connected to the outlets and the circulation of air is maintained by drawing out the vitiated air and allowing the fresh air to take its place. The plenum system is generally considered more direct and posi- tive, but this idea arises largely from the fact that when the ex- haust system has been used alone the fans are connected to flues in the top of the room, and the inlets, if provided at all, are small and poorly located, so that most of the incoming air comes from doors and windows and passes out of the flue without coming much in contact with the occupants. Theoretically, either system is effi- cient if it is properly designed and arranged, but the best results are, generally obtained in practice, especially for large halls or rooms, by a combination of both systems. Some years ago many rooms were ventilated on the principle that if a sufficient quantity of fresh air were forced into a room, it could find its way out through doors and windows. This was soon found to be a mis- take, as in winter all windows and doors would be closed on ac- count of cold and the outside winds ; and it is impossible to force air into a room unless an adequate outlet is provided. In the opinion of the author, the distribution of the air supply is even more important to the success of a ventilating system than the volume, and there is much that might be written on what not to do. It is difficult to lay down general rules, as each separate 104 STEAM HEATING AND VENTILATION. ease requires careful study, with proper consideration of the local conditions. The use to which the room is to be put, the arrange- ment of the occupants (whether the seats are fixed or movable), the duration of occupancy, the method of heating, the kind and extent of the outside exposure and the height of the room must all be taken carefully into account in determining the location of inlets and outlets. The point that must be borne constantly in mind is that the most perfect ventilation is desired not at the top of the room, or along the floor, but at the breathing line, which, as a rule, is about 4 feet above the floor level. There are very many rooms, unfortunately, which are much better ventilated at the ceiling than at the breathing line. Upward versus downward ventilation. There is one question which enters more or less into every problem of ventilation, but especially into that of theaters, churches and other large halls, which is a source of continual and arduous discussion among archi- tects and ventilating engineers that is, the respective value and merits of upward and downward ventilation, the former referring to supplying the fresh air at the floor and drawing the vitiated air out at the top, and the latter to the reverse of this method. The upward method is decidedly the natural one, as the temperature of the air is normally about 30 degrees lower than the temperature of the body, and the latter gives off enough heat when in repose to raise the temperature of 1,800 cubic feet of air per hour 10 de- grees. A person, therefore, standing in an open space, creates an upward current which naturally carries the exhalations from the body away from it. The downward method of ventilation must necessarily be opposed to the tendency of the individual currents from the bodies of the occupants of the room, and carries the breath back upon them, requiring a larger volume of incoming air to effect proper dilution than the upward method. In rooms which are heated entirely by the incoming air, the temperature of the latter is frequently much higher than the aver- age temperature near the occupants, and in cold weather is fre- quently higher than that of the body. In this case the air loses its heat, as the air descends, and to a large extent the natural cir- culation is downward. But in such cases the chief loss of heat is due to outside walls and windows, and the consequence is that there is a strong current downward at the windows, and along the floor to the outlets, while a large part of the breathing line STEAM HEATING AND VENTILATION. 105 escapes with what ventilation conies from a meager degree of dif- fusion. Prof. S. H. Woodbridge, in his admirable report to the Committee on Rules of the United States Senate (rendered De- cember 14, 1895), on the Heating and Ventilation of the Senate Wing of the United States Capitol at Washington, has an interest- ing discussion of this subject, especially in reference to large halls, and contains the following summary of his views upon the sub- ject : "Especially when the walls of the auditorium are inside walls and warm, the air supply does not then have to carry surplus heat to compensate for loss through cold outer walls and windows. It must generally enter the room cooler than the air of the room be- cause of the animal furnaces within it, each occupied chair repre- senting approximately the heating effect of a burning candle. In legislative halls the temperature of the air supplied is generally from 2 to 5 degrees lower than the air of the room. In crowded auditoriums, as theaters, the temperature of the supply has been known to have been held for hours from 10 to 15 degrees lower than the auditorium temperature, the per capita hourly supply being in excess of 1,200 cubic feet. "When air cooler than the air of a room enters it in large quan- tities, the most rational, as also the safest, way of admitting it is in a quiet and well-diffused manner through the floor. It then finds itself in its natural position of stable equilibrium. Because cooler, it is also heavier than the air of the warmer room, and it is at once in its normal position at the floor, where it envelops the breather, or is ready for easy, short and direct movement to the user. The warmer and polluted air is above, and in its own natural position or stable equilibrium, and ready for the shortest and easiest escape through the ceiling vent. "Ventilation by removal is the most perfect of all methods, both in the completeness of its work and in the economy of its opera- tion. The nearest possible approach in practice to ventilation of occupied rooms by the removal method is found when one is sur- rounded by cool, pure, quiet and abundant air which the heat of the body can freely move in an approaching and enveloping and ascending current about and from the body. That is upward ven- tilation. If the conditions are reversed, the fresh air entering at the ceiling and the spent being withdrawn at the floor, the fol- lowing results seem inevitable : 106 STEAM HEATING AND VENTILATION. STEAM HEATING AND VENTILATION. 107 "First, the entering air being cooler and more dense than that within the room, it must be entered in greatly diffused form to escape the production of drafts, since its weight must cause its precipitation ; and if it falls either by the swooping down en masse, now here and now there, or by continuous flow from large and scattered wall or ceiling inlets, the effects will vary from the an- noying to the intolerable, according to the momentary or continu- ous action of such down-flowing drafts. The condition of stable equilibrium is reversed by such a procedure, and nature's effort to restore that equilibrium must necessarily result in disturbance. "Second, the mass movement of air being downward, is in direct conflict with the individual currents, which are upward. The indi- vidual currents rise, as may be shown by experiment, and as may be also seen by the ascent of smoke entangled in the breath, with a movement varying from 20 to 40 feet per minute. To turn these individual currents downward, and to insure their moving from the nostrils and body floorward would require a mass downward movement of the air over the entire area of the Chamber of about 30 feet per minute, which would be equivalent to a per-minute supply for the floor alone of 129,000 cubic feet of air. The ascend- ing individual currents average from 40 to 50 cubic feet per min- ute, under favorable conditions of supply of fresh air to the body, and of rise of vitiating air from it. To completely reverse this air flow, about twenty-five times such quantities in mass movement would be required. "Unless such a complete reversal is effected, the occupant must, in downward ventilation, breathe air which contains his own and others exha 1 1 breath and dermal vapors turned back upon him. He is in the p^Jtion of a candle burning at the bottom of an open pipe through which the air current is being unnaturally forced downward. He is at the discharge end of the ventilating system rather than at the supply end. He is breathing a dilution of com- posite eliminations. The effect on gas flames distributed and burning at the floor of a chamber, to which the controlled air supply was admitted in diffused form, showed that by the down- ward method of supply the luminosity of flame is less than 5 per cent, of that obtained when the same air quantity is used with upward ventilation, the quantity of air used being a little more than sufficient to bring the flames to a maximum luminosity by up- ward ventilation. The life of the flame seemed even then to de- 108 STEAM HEATING AND VENTILATION. pend on the local down drafts of fresh and cool air, which was denied admission at the bottom of the Chamber, the place of its natural entrance. "Upward movement makes necessary the use of only enough air to supply the individual upward currents, in order to envelop the occupant in the purest air it is possible to provide by artificial ventilation methods. In crowded theaters it has recently been found that with a well-diffused air supply of 1,200 cubic feet per capita per hour the air below the breathing line can be kept with- in 1 part in 10,000 of carbonic-acid increment. F'O-58 U F.G.59 THC EMGMtcnt Types of Diffusers for Theaters. "The contrast between results of upward and downward audi- torium ventilation with equal air quantities can perhaps be best imagined by considering the effects on a theater floor crowded with smokers. "Third. In the case of the Senate Chamber, the galleries, fre- quently occupied with persons of varying degrees of cleanliness, become an important factor. To so ventilate as to carry the gal- lery air downward through the Chamber floor would be a piece of professional malpractice. STEAM HEATING AND VENTILATION. 10i> "The only logical reason to be advanced in favor of downward ventilation is cleanliness; that is, if the air passages of the floor are foul, then downward ventilation does not bring a contamina- tion due to that foulness into the Chamber. Practically, however, it is exchanging a seen and relatively harmless offense for the un- seen menaces of vitiated airs. Moreover, the only vestige of a reason for downward ventilation disappears when air is draftlessly moved through the floor and through channels and chambers so constructed and cared for as to insure cleanliness. In this con- nection it should be said that a thorough investigation of the supply chambers made at the close of the .last Congress and before any cleaning had been done, revealed a condition of cleanliness which was as gratifying as it was surprising, because of much that has been said and also because of my own preconceptions to the contrary." This is a strong argument in behalf of the upward system for ventilating halls of such a character. In the writer's opinion, the argument is unassailable and the success of Prof. Woodbridge's work in the Senate Chamber makes it especially forceful. The argument that is frequently made against the upward method is that it is difficult to secure a proper distribution of the incoming- air without causing disagreeable drafts on the feet and legs of the occupants. With the upward system the inlets must be dis- tributed among the seats, since, if the air is admitted through large registers in the aisles, it ascends straight to the ceiling with but little effect on the occupants. Air inlets and outlets. When the air is admitted by small open- ings under the seats the creation of drafts is difficult to avoid. Dif- ficult it is, but by no means impossible. The inlets must be so large that the incoming air has a low velocity (not over 150 feet, or at the most 200 feet per minute) and so arranged that the air does not strike directly against the legs of the occupants. The trouble in most cases of the kind is that the inlets are not nearly large enough. If in a theater, for example, we are going to have 1,800 cubic feet per person per hour, and this is to come in at a velocity of 150 feet per minute, it will be seen that a register about 6 inches by 5 inches or 2| inches by 48 inches will be re- quired under every seat in the house. Furthermore, this inlet should not be right in the floor, but should be raised up a few inches. Figures 53, 54, 55 and 56 show some forms of "diffusers" 110 STEAM HEATING AND VENTILATION. recommended by Prof. Woodbridge for the Senate Chamber, and Figures 57, 58 and 59 some other practical forms for theaters. For churches it is easy to contrive simple forms for long narrow inlets along the pews. It will be seen that all of these arrange- ments requires that the inlets be connected to a large plenum cham- ber underneath or that the arrangement of ducts be such as to give a perfectly uniform distribution of the air to the numerous inlets. F.e.60 Infet: Fio.61 A little reflection will show that in a large theater, for example, if the downward ventilation is employed, it is quite as necessary to have the outlets well distributed as with the reverse method. The Chicago Auditorium, a very large theater, is ventilated on this scheme. The outlets are under the seats, but are small and not frequent. The consequence is that most of the air, coming down from above, goes out the exits, which are numerous, and the large outlets back of the boxes, leaving a pocket in the middle of the house which frequently becomes very close. For smaller rooms, such as school rooms, small churches, lee- STEAM HEATING AND VENTILATION. Ill ture and reading rooms, there are many methods of air distribution which have proved successful in accomplishing the desired result of ventilating along the breathing line. Figure 60 shows a method which is much used in schoolhouses, and in rooms not over 30 feet wide it is very suc- cessful. If the rooms are of much greater width there should be inlets and outlets on both sides. Figure 61 is another method much used in school houses. Figure 62 is a very practical ar- rangement for small churches, but it obvi- ously requires that, especially in winter, the roof and windows be very tight. These three figures show vertical sections through the rooms. Figure 63 shows a very wasteful method of ventilation which is employed in the read- ing rooms of a large library. Most of the air in this case (especi- ally in mild weather) goes down the walls and out without af- fecting the breathing line. An improvement Figure 64. Ventilation in a Syracuse Bank. could be effected by putting inlets at the point A. There is always a tendency of air currents to cling to wall surfaces and this should always be taken into consideration. Figure 64 shows a diagram of the ventilation of the large bank- Plan. 112 STEAM HEATING AND VENTILATION. ing room of the Onondaga County Savings Bank at Syracuse, N. Y. The arrangement is very successful, and, on account of the fact that the clerks are employed at the windows all day long, may be preferable to a reversed arrangement of inlets and outlets; but with the system employed, the air supply is very ample in propor- tion to the number of regular occupants. Air velocities through inlets and outlets. As to the size of inlets and outlets for large registers for ventilating schemes of this kind, standard practice allows a velocity of about 300 feet per minute through the gross area of the register. Naturally a rule of this kind is dependent upon circumstances, and if an inlet has to be where air will blow directly on any of the occupants, the velocity should be slower. Mr. Wolff states that when air enters at or near the floor, the velocity should not exceed 120 feet per minute. The author has taken 180 feet per minute as a maximum in such cases. This figure may be used if diffusers are arranged so that the air will not blow directly on the feet and ankles of the occupants. Where the inlets are removed from the danger of direct drafts on the occupants, a velocity of 300 feet per minute may be used with safety. In hospitals and similar institutions, the inlets and out- lets should be very carefully placed to meet the requirements of the particular arrangement of beds, and velocities should be low. The velocities through outlets may range from 400 to 600 feet per minute. There is another consideration which should be discussed at this point, as it seriously affects the question of air distribution. That is the question of heating by means of the ventilating air. In the opinion of the author, this is never desirable in a room of what we have called the densely peopled character. Especially where there is any considerable amount of glass or exposed wall surface, there should be heating coils in the room sufficient at least to counteract the loss of heat from such surfaces; otherwise the in- coming air must in cold weather have a temperature of about 130 degrees or more and is very hard and dry. In such cases the inlets must be very high, so as not to be near the occupants. Besides this, such a great difference in temperature between the incoming air and the average of the room creates currents which interfere with the uniform circulation desired, in addition to making it very difficult to maintain a uniform temperature throughout the room. CHAPTEE IX. VENTILATING DUCTS. Theory of the flow of air in ducts. Any flow of air is created only by an inequality in the pressure of the air at two different points, and it follows that the primary requisites for a ventilating system are a means for creating the required difference in pressure and a means for distributing the flow of air to required points. As accessory to the first of these there is generally required some means for heating the air and frequently for washing it. The theoretical laws which govern the flow of air are very dif- ficult of direct application to ventilating conditions, and yet a clear FIG. 65 FiQ.66 Fio.67 understanding of the principles governing the air flow is necessary to the successful understanding of the way in which air can be handled in a ventilating system. Consider the simplest case : a pipe or duct, AB, Figure 65, of in- definite length, in which a flow of air is created from A to B. This flow can only be kept up by maintaining the air pressure at A in excess of that at B; and the greater this excess, the greater will be' 'the velocity of air in the duct. Let us denote this excess, or difference, of pressure by p. It can be measured in pounds per square inch, ounces per square inch or in the height of the water 114 STEAM HEATING AND VENTILATION. column which it will balance. In ventilating work, since p is gener- ally small, it is measured in one of the two latter units; and a column of water 1 inch high is equivalent to 0.579 ounce per square inch. The pressure p has two functions to perform; it must create the velocity (v) of air in the duct and it must overcome the fric- tional resistance to the passage of the air. X ow, if it were not for the friction of the air in the pipes, the velocity could be expressed by the familiar formula v = 1/Tgh in which v is given in feet per second and h is the height in feet of a column of air, the weight of which would give the pressure p which creates the flow. If p is expressed in inches of water column, h = [67.7 + (t -f- 520)] p, where t is the temperature of the air; and as g = 32 (approximately) in the foot-pound-second fiystem of units, the formula becomes: t \ (1) As already stated, this represents the theoretical velocity that would be attained if there were no frictional resistance to be over- come. This formula is not absolutely accurate even for the theo- retical velocity without friction, on account of the compressibility of air, but with the pressures attained in ventilating plants, the factor of correction would amount to a very small fraction of 1 per cent. But as it is, the actual velocity (v 1 ) may be anything irom 0.2 v to 0.7 v, and under the conditions of most ventilating plants it is from 0.3 v to 0.6 v. Or, v 1 being the actual velocity, we may put where c is a coefficient which will vary from 2.4 to 5 according to the nature of the resistance to be overcome, its maximum value teing 8 for the theoretical velocity without friction. Prof. Unwin gives a formula for the flow of air in round pipes which is as follows : = / V T d 4ml p o s in which k = 53.15; T = absolute temperature of air; g = 32.2; STEAM HEATING AND VENTILATION. 115 d diameter in feet; 1 = length in feet; m = a coefficient of fric- tion; p = the greater absolute pressure and p x = the lesser press- ure. The difficulty, however, with any such formula as this is that in any ventilating system with a complicated arrangement of ducts, containing, as it must, bends and branches, dampers, rectangular pipes and round, registers, heating coils, etc., it is beyond the pos- sibility of theoretical calculation to obtain any adequate value for a coefficient of friction. The pressures employed in ventilating systems do not usually exceed 1 ounce per square inch, nor the velocity 50 feet per sec- ond, or 3,000 feet per minute. The accompanying table gives the velocity v 1 as obtained by formula (2), already stated, for air at 60 degrees Fahr. and various values of c and different pressures, p. This table is rather TABLE OF AIR VELOCITIES TEMPERATURE 60 DEGREES FAHR. ., p x , v 1 in feet per second * Inches Oz. per water. sq. in. c = 2.4 c = 3. c = 4. c = 5. 0.01 .006 2.0 2.5 3.3 4.1 0.05 .030 4.4 5.6 7.4 9.2 0.10 .058 6.2 7.8 10.4 13.0 0.20 .116 8.8 11.0 14.6 18.4 0.40 .232 12.5 15.6 20.8 26.0 0.60 .347 15.1 18.8 25.2 31.5 0.80 .463 17.4 21.8 29.2 36.4 1.00 .579 20.0 25.0 33. 41.2 2.00 1.158 28.2 34.8 46.4 57.8 3.00 1.737 34.6 42.7 56.9 71.2 4.00 2.316 40. 49.5 66.2 82.5 difficult to apply practically, but it is the writer's experience tha j ; in a well-proportioned system a coefficient of 5 can be used. If the ducts are very long or tortuous, or contain many dampers, a smaller one should be used. It will be seen from this table, as well as from formulas (1), (2) and (3) that p is proportional to v 2 . (In formula (3), p p x is equivalent to the p of the table and of the other formulas, and for small values of p, p + p x would be practically a constant.) On this account, in a given system of ventilating ducts, any increase in velocity can be obtained only by increasing the pressure created by the fan, proportionally to the square of the velocities. And as the power required to move the air is practically proportional to the product of the pressure, area and velocity, the power re- quired, exclusive of that used by the friction of fan and engine or motor, is proportional to the cube of the velocity. These laws 116 STEAM HEATING AND VENTILATION. should be thoroughly understood by all who have anything to do- with ventilating systems. They would be still more important were it not that the pressures employed in ventilating systems are always small, rarely exceeding 1 inch of water column, equal to 0.579 ounce per square inch. Velocity of air in ducts. From what has been said it may be gathered that the design of a system of ventilating ducts is largely a matter of velocities. The velocity in the main ducts may vary from 30 to 65 feet per second, the latter figure being somewhat excessive if the ducts are of any considerable length. For branch ducts the velocities must be lower the smaller the duct the lower the velocity in order to maintain'the proper distribution through- out the system. This seems rather indefinite, and so it is, but there is no branch of engineering which is more strictly dependent upon empirical rules and the experience and study of the designer, than the design of a ventilating system. We may take 35 to 40 feet per second as a standard velocity for air in the main ducts, from a fan delivering from 20,000 to 40,000 cubic feet of air per minute. In the branch ducts the velocity should be reduced, ac- cording to the size of the ducts, as low as 20, or even 15 feet per second in small ducts (8 x 10-inch or 6 x 12-inch) supplying indi- vidual registers in small rooms. The velocity through the registers should not exceed 5 feet per second through the gross area, except through large ones so- located that there is no possibility of a direct draft on the occu- pants of the room. If these proportions are carried out, the neces- sary pressure at the fan to force air through the ducts will not generally exceed 0.3 ounce per square inch, but it must be borne in- mind that additional pressure is required for heating coils and other similar obstructions. This will be more particularly consid- ered in a subsequent chapter. The pressure necessary will in- crease rapidly as velocities are increased, and must be made up by increased capacity of fans and increased power. Branch ducts. In laying out ducts the utmost ingenuity should be exercised in arranging the branches, dampers, etc. All short bends and T-branches should be carefully avoided, as they greatly reduce the flow of air. A frequent specification in regard to bends is that the inside radius of the bend must be equal to the diameter, or equivalent, of the pipe. This should certainly be a minimum and twice that radius would be a preferable minimum. The air STEAM HEATING AND VENTILATION. 117 -will frequently pass right by a right-angle branch, as in Figure G6. The velocity in the branch being but a small percentage of that in the main, such connections should be made as in Figure 67. Dampers. Dampers are a necessary evil, as they certainly im- pede the flow. They should be used with caution, and the duct system should be laid out in the first place with as few dampers as possible, and in the second place with the idea that under nor- mal conditions the system should be run with all dampers wide open. There is a common practice when laying out a complicated sys- tem of ducts with numerous branches and sub-branches of put- ting a damper on every branch, the idea being that if one branch gets more than its share of air it can be "throttled down" by means of its damper, so .that the other branches will get more. The author has hardly found a case in practice where dampers were used in this way but that, in the course of practical experi- ment on the part of an ignorant attendant to proportion the air supply, most, if not all, of the dampers were more or less closed, thus diminishing the air supply and throwing a greater load on the fan. It is not alone the velocity in the ducts that we must look after, but also that at the dampers; a few half-closed damp- ers will have a decided effect upon the pressure required at the fan. Dampers should only be put in at or near the registers, and in many cases the system is better off without them even there. The branches must be systematically laid out, and with reasonable care they can be properly proportioned without adding dampers to act as a safeguard on the designer. The ordinary butterfly damper, hung by the rod in the middle, is the type most employed. They should be firmly attached to the rod, so that they cannot work loose. The damper should fit loose in its duct and should always be provided with a substantial attachment by which its position can be set and secured from the outside. Arrangement of ducts. In large plants the ducts usually radiate from the fan to the registers in a tree-like pattern; but in the opinion of the author, although apparently the simplest, this is in reality the most complicated possible way to lay out a ventilat- ing system; and it is his firm opinion that much better results can be obtained by a system of mains and feeders, to borrow elec- 1 118 STEAM HEATING AND VENTILATION. trical phraseology. The idea of the first system is indicated in Figure 68, and that of the second in Figure 69. The diagram in each case represents the basement of a building, VW being ver- tical flues which it is necessary to supply with air. In Figure 69 M may be called the mains and F the feeders. In the "tree" sys- tem of Figr.re 68 it is difficult indeed to prevent the ducts near- est the fan ifrom taking most of the air, and a much more uniform distribution is obtained by the other system, especially if the mains are made large so that the velocity is low. The feeders can then. ENGINEERING RECORD. Types of Duct Arrangement. be proportioned for a comparatively high velocity (45 to 60 feet per second for large systems) without loss. The connection to the vertical flues should, of course, be curved upward from the mains, or the connection made very free. In this system the object is to make the mains something of a plenum chamber in which the velocity is slow and the pressure uniform throughout. In a large system, where several fans are used, the best results will be obtained by locating two or three plenum chambers, as mains or as centers of distribution, at central points, from which STEAM HEATING AND VENTILATION. 119 the ducts can radiate, and to each of which feeders from the fans can be conducted. A large library building in the Middle West is a case in point. It is ventilated by an elaborate system with five large supply fans and as many exhaust fans. The ducts radiate from the fans on the "tree" system, each fan connecting to its own independent system of ducts. The ducts are large and long and ramify through the basement so as to render useless a large amount of valuable space. As the system stands, it is very difficult to adjust the air supply to the different ducts and the pressures on the different fans are very unequal. If two plenum chambers had been located in the center of each end of the building and each of the supply fans connected into one or the other, it would have greatly simplified the air distribution, taken up much less space and equalized the pressure and the load on the different fans, some of which at present are considerably overloaded, while others are the reverse. Figure 70 shows the basement plan of a building taken from The Engineering Eecord. The following description of the ar- rangement of ducts accompanied the plan: Fresh air enters through windows at the northeast corner of the basement, where the fan is located. In cold weather the air passes through the windows of a tempering chamber provided with tempering coils,, but in moderate weather this chamber is shut off and windows in. the fan room adjoining are opened to allow the air to pass di- rectly to the fan. By means of an 8-foot blower the air is de- livered into a plenum chamber about 10 x 17 feet in size adjoin- ing the fan room. From this the air is forced to three indirect heating chambers, constructed of brick, located at convenient points in the basement, from which both heated and tempered air may be uniformly distributed by the double duct system to the base of the heat flues. One of these heating chambers is built within the plenum chamber, while the other two are located at, distant points and connected with it by galvanized-iron ducts.. The heating chambers are numbered 1, 2 and 3 in the drawing.. Number 1 is located inside of the main plenum, while the other- two are located at distant points of the basement, as shown. It will be seen that in this plant the vertical ducts are sup- plied from the three chambers, which are practically three centers of distribution, but, in the opinion of the author, the system could have been improved by locating four main ducts at M, N, 0, P, and 120 STEAM HEATING AND VENTILATION. STEAM HEATING AND VENTILATION. 121 supplying these by feeders from the fan at points about at the middle of the mains. The four mains would supply the vertical flues in the four sections of the building and they could be con- nected together by a small equalizing duct forming a sort of ring system around the building. Of course there may be objections to such a system on account of the constructional features of the building, or the special use of certain rooms, and in the case un- der consideration the engineer wished to place a heating coil in each of his centers of distribution; but this being the case, it would have been better to locate four centers of distribution; for example, at D, E, F and G, the object being to make the connec- tions from them to the vertical flues as short and direct as pos- sible. In this case they should each have a feeder from the fan and could be profitably connected by an equalizing duct from which the stray vertical ducts between them could be connected. The question of the distribution of heat- ing coils in ducts will be further considered in a subsequent chapter. Figure 72 represents another building in which three centers could have been very advantageously located at A, B and C. The ducts shown, it may be pointed out, form the ex- haust system of a downward ventilating apparatus installed in this building. In regard to vertical flues, they should, if possible, be separate for each outlet; and the longer the duct, the slower the velocity to be allowed. The author is familiar with one building in which some of the vertical flues supply three registers. Each outlet is provided with an adjustable swing damper, as indicated in Figure 71, and it is exceedingly difficult to adjust them so as to give anything like a uniform distribution to the three outlets. Materials for ducts. As to the material for the construction of ducts, they are usually made of galvanized iron, in which case they should be soldered at the joints, as it is very essential that they be made air tight. Large ducts are frequently made of sheet iron, and these should be close riveted; and when they are painted, the joints should be thoroughly doped with an asphalt or other simi- lar paint. Underground ducts should be made of brick. Wood is objec- tionable in any case, and especially so unless the ground is very Fie.71 V V 122 STEAM HEATING AVZ) VENTILATION. STEAM HEATING AND VENTILATION. 123 dry, and they should be lined with tin or galvanized iron to make them tight. Brick ducts should be plastered inside and out all around with a f-inch coat of rich cement mortar, or, preferably, asphalt. There is, among some engineers, but more particularly among ventilating contractors, an opposition to underground ducts. The author has thought this originated with the latter largely from the fact that there is less profit for the ordinary ven- tilating contractor in building brick ducts than there is in iron. The objection is raised that they are liable to become damp and dirty. This is not at all the case if they are properly made. In fact, from the standpoint of cleanliness, they are preferable to iron, as any duct will become very dirty in time, and brick ones can be easily arranged so as to be washed out with a water stream from a hose. Underground ducts must, of course, as a rule, be laid out before the building is built, and it is not generally prac- ticable to put very small ones underground; but with a system designed with centers of distribution and feeder ducts, as sug- gested, the latter could, in most cases, be put underground with great advantage. In the building first referred to, not only the feeder ducts, but the centers of distribution as well, might have been put underground, and at less expense than the existing sys- tem, if the work had been laid out at the proper time. There is an objection to blowing heated air through underground ducts, but this will be considered in the following chapter. CHAPTEE X. VENTILATING FANS AND OTHEE APPA- EATUS. Types of fans. There are but two kinds of fans commonly used in ventilating plants. These are the centrifugal fan, or blower, and the propeller,, or disk fan. The distinctive characteristics of the two types are well shown in Figures 73 and 74. Figure 73. The Centrifugal Fan. The centrifugal fan consists of a wheel with several vanes mounted on a horizontal shaft, as shown in Figure 75, where the covering or casing is removed. It is always mounted in this cas- ing, which may be of wood, brick or iron, but usually the last, although for large fans the bottom part is generally of brickwork and the top of iron. The air enters through an opening in the STEAM HEATING AND VENTILATION. 125 center and is forced to the outlet by the centrifugal action due to the rapid revolution of the fan wheel. The disk fan is mounted in an opening in a wall, or in the end of a pipe, and drives air by means of its screw-like action. The disk fan is only used against very light pressures, and consequent- ly, when ducts are very short and openings large and few, the disk fan loses in efficiency rapidly as the pressure rises. Centrifugal fan capacities. There is no manufactured machine about which there are so many varying data as there is in connec- Figure 74. The Disk Fan. tion with ventilating fans. The makers' claims as to capacity are generally too high. Mr. Alfred E. Wolff, in his very excellent pamphlet on "The Ventilation of Buildings," publishes the accompanying table, Ta- ble I, for centrifugal fans. This table, like everything else from Mr. Wolff's pen on the subject, is very valuable, although the ex- perience of the author in testing some large fans would indicate that even the capacities here given are somewhat too liberal. Mr. M. C. Huyett, an ex-fan manufacturer of extended experi- ence, has published a valuable table of centrifugal fan capacities which is given in Table II. Mr. Huyett's table is based on the 126 STEAM HEATING AND VENTILATION. s ra- in 3 g O i i fa s fc H O U g O g i O5O'-HrH TH o o as t as c i i - y. o -i ^CaCCOO O ! 9 M* t W 00 U> MB IO WJO IO O O O ^ *** *O ^ O *O fH O 00 f STEAM HEATING AND VENTILATION. 127 velocity of the fan-wheel periphery multiplied by the "blast area" of the fan. The blast area being practically the area of the blade, is taken as the width of the wheel multiplied by one-third of the diameter. As Mr. Huyett points out, it will be seen that this rep- lesents a maximum velocity for the air, as it is impossible to give to it a velocity greater than that of the wheel rim. The table may, therefore, be taken as representing practically a free air discharge, and checks very close with the author's tests made on fans working under low velocities or free delivery in the ducts. TABLE I. QUANTITY OP AIR SUPPLIED BY BLOWERS OF VARIOUS SIZES AGAINST A PRESSURE OF ONE OUNCE PER SQUARE INCH. (ALFRED R. WOLFF.) Diam. Revs, per H.-P. to Cubic ft. wheel, ft. minute. drive blower. per minute. 4 350 6. 10,635 5 325 9.4 17,000 6 275 13.5 29,618 7 230 18.4 42,700 8 200 24. 46,000 9 175 29. 56,800 10 160 35.5 70,340 12 130 49.5 102,000 14 110 66. 139,000 15 100 77. 160,000 The theoretical calculation of fan discharge is very compli- cated, and, so far as the author's experience goes, is very unreliable on account of the difficulty of obtaining accurate values for the coefficients. In a paper in the "Transactions" of the American Society of Heating & Ventilating Engineers, for 1899, Prof. R. C. Car- penter deduces a formula in which the fan "capacity is equal to the product of three constants multiplied by the width of wheel, diameter of inlet, and by diameter of fan wheel into the number of revolutions." He states also that since, by common practice the three first factors are now always made proportional to one another, the formula becomes q = c n d 3 , by which q is obtained as cubic feet per minute, d being the diame- ter in feet of the fan wheel, n the number of revolutions per min- ute, and c a coefficient, the value of which Prof. Carpenter gives as 0.6 for single-inlet fans under free discharge, 0.5 with a press- ure of 1 inch of water, and 0.4 with a pressure of 1 ounce per square inch. "For fans with double inlets the coefficient should be increased 50 per cent." For practical work on ventilating 128 STEAM HEATING AND VENTILATION. plants Prof. Carpenter recommends c = 0.4. This coefficient gives capacities which are about 10 per cent, less than those of Mr. Wolff's table, and is very reliable where duct velocities are employed such as the author recommends in the preceding chap- ter, with 45 to 55 feet per second in the main duct; but where heating coils and other similar resistance are interposed in the air passages, as is generally the case, a coefficient of c = 0.35 is much safer. Prof. Carpenter also gives a formula for the power required to drive centrifugal fans ("Transactions" Am. Soc. Htg. & Vent. Engrs., Vol. V., p. 237), which is: HP = b d 5 n 3 -T- 10 6 , in which H P is horse-power delivered to the fan; d, the diameter Figure 75. Centrifugal Blast Wheel. in feet; n, the number of revolutions per second, and b a coeffi- cient, which should be taken as 30 for free delivery and 20 for de- livery against 1 ounce pressure. This formula, with a coefficient of 20, gives results almost identical with those of Mr. Wolff's table, and may be taken as very reliable for practical work. It is. interesting to note that according to Prof. Carpenter's coefficient,, the power required for free delivery is 50 per cent, greater than when working against a pressure of 1 ounce. This is in accord- ance with experience, as well as theory, but is, of course, due to the fact that the volume of air delivered under free discharge is much greater than under 1 ounce pressure. Disk fans. Disk fans, as stated above, are not generally used Diam. Revs, per H.-P. to wheel, ft. minute. drive fan. 2.0 600 0.50 2.5 550 0.75 3.0 500 1.00 3.5 500 2.50 4.0 475 3.50 5.0 350 4.50 6.0 300 7.00 7.0 250 9.00 STEAM HEATING AND VENTILATION. 129 where large capacity is required, except where the delivery is very free. They are usually employed where exhaust fans are required on roofs, or in other elevated positions where it is impracticable to set the large foundation which the centrifugal fan requires. It is the opinion of the author that the field of usefulness of the disk fan is larger than is generally considered, and that its de- livery is not as much reduced by increasing the resistance under which it works as is usually supposed. The disk fan seems to be used much more in Europe than it is in America. Mr. Wolff gives some valuable data upon disk fans in Table III. TABLE III. QUANTITY OF AIR MOVED BY APPROVED FORMS OF EXHAUST FAN DISCHARGING DIRECTLY INTO AT- MOSPHERE. (ALFRED R. WOLFF.) Cubic ft. per minute. 5,000 8,000 12,000 20,000 28,000 35,000 50,000 80,000 In an article in the "Transactions" of the American Society of Heating & Ventilating Engineers, 1899 (See Vol. V, p. 128;, Prof. J. H. Kinealy gives the following formula for disk fans with, straight vanes set at an angle of 40 or 45 degrees: Q = d 3 n -h 3,050, where d is the diameter in inches; n, the revolutions per minute;, and Q, the number of cubic feet per minute. He also gives for the Blackman fan (which has a blade constructed with a peculiar curve) : Q = d 3 n -r- 1,880. Prof. Kinealy states that the proper velocity for a fan is given by the formula n = 21,000 -a- d, where d is again the diameter in inches. The formula is based! on a velocity at the rim of 90 feet per second. Prof. KinealyV. formula for the Blackman fan corresponds quite closely with the> figures given in Mr. Wolff's table, and may undoubtedly be ac- cepted as reliable for free delivery. If the disk fan is used on a complicated system of ducts the author would favor multiplying Prof. Kinealy's formulas by a coefficient of 0.65; and if heating 130 STEAM HEATING AND VENTILATION. coils and other similar resistances are added, this coefficient should be made not greater than 0.5. Ventilation ~by gravity. There is one method of creating a cir- culation of air which may properly be discussed in connection with other apparatus for the purpose, and which is frequently of great value. This is the heated flue. In Chapter IV the au- thor discussed the effect produced by heating the column of air in an open flue, and the formula was derived for the theoretical velocity in feet per second (with- out friction) obtained in the flue, where T is the temperature to which the air in the duct is heated, and t is external temperature, H being the height of the flue, and g the acceleration of gravity = 32.2. Mr. Alfred R. "Wolff is of the opinion that 50 per cent, must be deducted from the formula for friction of air in ducts, etc., in order to get the actual velocity that can be attained, and he re- duces the formula to the following* form : V = (T - t) 492 in which V is the velocity in feet per minute. Mr. Wolff also gives the following table calculated from this formula : TABLE IV. VELOCITY OF AIR, IN FEET PER MINUTE, THROUGH A VENTILATING DUCT (THE EXTERNAL TEMPERATURE OF THE AIR BEING 32 DEGREES FAHR. Excess of Temperature of Air in Vent Duct Above Height of Vent- Duct in ft. 5 10 77 that of External Air, 10 15 20 25 108 133 153 171 133 162 188 210 153 188 217 242 171 210 242 271 188 230 265 297 203 248 286 320 217 265 306 342 230 282 325 363 242 297 342 383 Degrees Fahr. 30 50 100 188 242 342 230 297 419 265 342 484 297 383 541 325 419 593 351 453 640 375 484 656 398 514 726 419 541 766 150 419 514 593 663 726 784 838 889 937 15 94 20 108 25 121 30 133 35 143 40 153 45 162 50.. 171 It will be seen from this table that the velocities obtained are small, and as V is proportional to the square root of (T t) and also to the square root of H, it is necessary to multiply one of these factors by four in order to double the velocity. It is, there- STEAM HEATING AND TENTILATiON. 131 fore, necessary to have a very considerable difference in tempera- ture, or a great height of flue, or a large area, in order to produce the volume of flow that would be required in a moderate ventil- ating plant. The cost of heating a large volume of air to the required temperature is excessive in comparison with the cost of fan power. There are many special cases, such as the ventilation of the toilet rooms, where continual circulation is desired, and especially where cheap gas is available, in which the heated flue is a valuable means to be employed. In many cases a vent shaft can convenient- ly be located around a metal chimney, from which sufficient heat is obtained to produce a decided draft. Figure 76. A Type of Heating Coil. Heating coils. In the latitudes of most of the United States it is necessary to provide heating coils for all fans which take air from the outside and blow it into buildings for ventilating pur- poses. These coils are of many kinds and forms. They are usually located either between the air intake and the fan, or just at the outlet of the fan, but frequently separate coils are placed at the base of the vertical flues to each room; and often, indeed, a tem- porary coil for use in very cold weather is placed at the fan and additional ones at the separate vertical flues. Figure 76 shows one form of heating coil for a fan, the casing being removed. Figures 132 STEAM HEATING AND VENTILATION. 77 and 78 show fan and coil together, in the former the heater being on the suction side, and in the latter on the blast side. The heating coils are generally made of loops of 1-inch pipe, and the rules for proportioning them are very conflicting. The same general theories apply to them as to indirect radiators, as given in a preceding chapter of this series. In a brief article in the issue of May 13, 1899, The Engineering Eecord gives some valuable data from the authorship of Mr. W. S. Blessed of the American Blower Company. The data refers to> coils similar to that shown in Figure 76, each section of which con- tains four rows of 1-inch pipes set 2f inches center to center, and give the final temperature attained by the air under different "mean velocities" through the coil. With air at an initial "tem- perature of 30 degrees Fahr. passing through the coils at a mean velocity of 1,600 feet per minute, a common velocity with a cen- trifugal fan, the air will be raised to the temperature shown in the following table, with the steam pressures and number of coils, in use as mentioned : Steam, 5 Ibs. Pressure. Steam, 75 Ibs. Pressure. Final Temp. Final Temp. Number of Air. Number of Air. of Sections. Deg. Fahr. of Sections. Deg. Fahr. 4 74 4 92 5 88 5 117 6 100 6 137 7 110 7 143 8 117 8 156 "With a mean velocity of air of 900 feet per minute the rise in temperature of the air will be : Steam, 5 Ibs. Pressure. Steam, 75 Ibs. Pressure. Final Temp. Final Temp. Number of Air. Number of Air. of Sections. Deg. Fahr. of Sections. Deg. Fahr. 4 85 4 125 5 110 5 158 6 130 6 186 7 147 7 210 8 160 8 230 \ , "With 5 pounds pressure about 1,720 B. T. U. are given off per hour per square foot of heating surface, and with 70 pounds press- ure about 2,520 B. T. U." Commenting further on this subject, in response to an inquiry, The Engineering Eecord of June 3, 1899, says: "It may be well to describe how the manufacturers of this ap- STEAM HEATING AND VENTILATION. 133 paratus usually determine the size of hot-blast coils necessary to do a certain amount of work. It is manifest that the amount of heat which can be transferred from one substance to another, as from the steam-heated pipes of a hot-blast coil to the air which is being blown past them, is proportional, in a measure, to the time that the air is subject to the heating influence of the steam pipes. Consequently, hot-blast coils must be large enough in a plane perpendicular to the direction of the moving air; or, in other words, Figure 77. Heater on Suction Side. Exhaust. ', i Live Steam Figure 78. Heater on Blast Side. they must be a sufficient number of pipes wide, and the pipes must be of such a length that the combined area of the openings be- tween the pipes will be sufficient in size to insure the proper veloc- ity of the air to be forced through them. "For instance, if the mean velocity of air through the coils is to be 1,600 feet per minute, which is not an uncommon one with cen- trifugal blowers, and it is desired to put 16,000 cubic feet of air j)er minute through the coils, the area of the openings between the 134 STEAM HEATING AND VENTILATION. pipes should be 16,000 -4- 1,600 = 10 square feet. Makers of hot- blast coils know the area of the openings between the pipes of coils of various sizes, and select the size which will give them the clear opening needed. With the data given in the note referred to, it is possible to calculate the rise in temperature of the air which will occur with various rows of pipes and with steam of 5 and 75 pounds pressure. "The mean velocity of air should be explained. If 16,000 cubic feet of air at a temperature of say 120 degrees are to pass through the registers of a ventilating plant in a minute, this air, when at zero degrees, will have a volume of about 12,800 cubic feet. Con- sequently, as the air expands as it is heated in passing through the 200 190 .180 >I50 1 130 "!oo I 90 O Of) tn 80 70 60 50 100 300 500 700 900 1100 BOO 1500 1700 Velocity of Air passing over Heater Coils Figure 79. Influence of Velocity of Air in Heaters. coils, its velocity must increase, and its mean velocity is the one upon which most calculations are based. If the 12,800 cubic feet is expanded to 16,000 cubic feet its mean volume is (12,800 + 16,000) -f- 2 = 14,400 cubic feet. Then 14,400 ~ 1,600 (the mean velocity assumed) = 9 square feet, the area of the clear opening between the coils that would be needed." Mr. Walter B. Snow, of the B. F. Sturtevant Company, in a lecture delivered before various technical colleges, gives some dia- grams which, taken in connection with the data given above, are of great value in proportioning heatinsr coils. These diagrams give only the relative effects of varvinor velocities through the free area of the coils, as well as the relative effect of different depths. of coils. The diagrams are given in Figures 79 and 80, and aa STEAM HEATING AND VENTILATION. 135 quoted from The Engineering Record of April 21, 1900, Mr, Snow gives the following explanation: "The effect of varying velocities* and of different steam press- ures is shown in the accompanying curves drawn from the results of tests of Sturtevant heaters used in connection with fans. The relative condensation increases with both of these factors, but, as indicated by the third curve, the relative temperature increment with a given steam pressure decreases with the velocity. This is the natural result of moving a larger volume of air across the heating surface, and decreasing the time of contact. Disregard- ing the expansion by heat, the volume is proportional to the ve- 150 140 130 #120 60 > I 50 2 O m a>S "'J3 O o * g Q a> o. ll I I -I I dl * I- PH w H gU fc < By-pass Open. 102 110 .144 137 152 .259 157 .086 .173 1,230 .... 6.2 65 .086 .230 1,430 1,330 18,700 8.6 65 .115 .302 1,700 1,580 22,300 13 65 .144 .403 1,870 1,740 24,500 17.3 65 .144 .403 1,920 1,780 25,100 20.6 65 By-pass Closed. 77 .151 .029 .180 621 580 8,180 2.9 65 77 .165 .007 .172 650 605 9,500 3 130 77 +.180 .015 .165 690 640 9,010 '2.9 160 144 .072 .310 1,120 1,040 14,650 12 65 164 .334 .086 .420 1,420 1,320 18,670 19.2 65 STEAM HEATING AND VENTILATION. TABLE VI. Test of Fan F. Diam. wheel, 78 inches; width blades, 45 diam. inlet, 54 inches; net area, 13.1 sq. ft. Main duct, 45x45 inches 14.1 sq. ft. Gross area heating coil, 40 sq. ft.; surface, 7,200 sq. ft. pj Pressure of Air Velocity of Air. in oz. per sq. in. Ft. per min. a fe A a a d Is f 1 ; 1 i 1 di S H ~ 3 137 inches.; ; area, <3 -*j 1 By-pass Open. (No steam on coil.) 73 .040 .026 .065 788 730 10,320 . . . 86 .054 .032 .086 945 830 12,380 3.36 100 .068 .040 .108 1," Q 3 1,020 14,320 5.16 114 .123 .053 .176 1,240 1,150 16,250 7.11 123 ... .061 I,o50 1,255 17,680 8.88 139 ... .075 1,520 1,415 19,900 12.1 143 ... .075 ... 1,580 1,470 20,650 13.5 By-pass Closed. (No steam on coil.) 76 .071 , .011 .072 554 7,260 3.05 141 .043 .257 1,075 .... 14,080 11. A comparison is also given between the air deliveries and power required'f or both open and closed by-pass in Table VII. It should l)e noted here that the values in columns (2), (3), (5) and (6) were obtained from Tables V and VI, but in some cases by interpola- TABLE VII. EFFECT ON AIR DELIVERY AND POWER OF CLOSING BY-PASS. (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) * 02 1 y - t 1 i f-4 -t ** * " 03 d fl ! | .a 1 * 5 Pi g p, ^co a, ' A a w '*"' g< '"'do? m fs C-2 C<1 -1 o ^ o S g5g 00 g - "c3 pi to ^"^ fl 02 02 V 'jj t* o. 1 4 ' Q JH % [ fl C^ 02 |> d i5 i .j. ^> ^ O!M ^ o . CO 3 P. a h p, Pi OJ ^ GJ >> ^s a > B fa Q 'w <3 > ' > $3 O o ^ <5 2- Fan E. 77 935 621 66.3 3.2 2.9 91. ... 65 77 935 650 69.5 3.2 3.0 94. ... 130 77 935 690 74.0 3.2 2.9 91. 160 144 1,800 1,120 64.0 15.5 12.0 77.5 4.9 2.44 70 164 2,050 1,420 69.1 23.8 19.2 80.6 8.4 2.3 70 Fan' F. 76 850 554 65.1 2.9 141 1,550 1,075 69.0 12.5 11.0 88.0 4.7 2.35 70 tion, so as to obtain for comparison the values corresponding to the same number of revolutions per minute of the fan for open and closed by-pass. 138 STEAM HEATING AND VENTILATION. STEAM HEATING AND VENTILATION. 13$ The following comments on the results of these tests were made, and they have a valuable bearing on practical installations : "It will be seen that the air delivery was decreased from 21 Scale o/ i' r ?' * Figure 82. Elevations of the Hot-Blast Unit. to 36 per cent, merely by closing the by-pass. Two tests on fan E, with part of the heater turned on, and a high temperature through the fan, gave a somewhat less reduction. But even with the by-pass closed, and as high a temperature as 160 degrees, the 140 STEAM HEATING AND VENTILATION. delivery was 20 per cent, less than with the by-pass open. The only tests at these high temperatures were made with very low fan speeds, and the test of 160 degrees showed a negative pressure on the blast side of the fan, due to the draft of the hot air in the vertical ducts. The author regrets that it was impossible to repeat these temperature tests at higher fan speeds, but they do not have much bearing on practical results, as temperature in air ducts of much over 100 degrees would not be good practice anywhere. It will be noted also that whereas the delivery of air is reduced about 24 per cent, by closing the by-pass, the power required (for same speed of fan) is reduced only from 9 to 22 per cent., while it will be seen that for equal air deliveries the power was increased from 2.3 to 2.44 times by closing the by-pass. "Attention should also be called at this point to the fact, as shown by the pressure observations in Tables V and VI, that even with the by-pass wide open the resistance due to intake and pas- sages through and around the heater or, in other words, the total resistance on the inlet of the fans was in all cases quite considerably more than the total resistance of the delivery ducts, dampers and registers. This was a matter of considerable sur- prise, as the intake seemed to be of ample size, and area of the by-pass large. It was probably due, however, to the height of intake [about 40 feet], and as such resistances are very often but little considered, it will be valuable to note their importance in this case." In regard to the fan capacities obtained by these tests it will be interesting to note that those on fan E, with by-pass open, cor- respond very closely with those given by Mr. Huyett's table, and also correspond with Prof. Carpenter's formula (Q = end 3 ) using a coefficient c = 0.57, while with by-pass closed the coefficient for Prof. Carpenter's formula is c = 0.43. The velocities in the de- livery duct, however, even the highest attained, were rather low, the maximum being about 30 feet per second (1,780 per minute), which would indicate a very free delivery. Arrangement of heating coils in air ducts. The possible arrange- ments of heating coils in ducts are limitless, but thoroughly sat- isfactory ones, which operate with perfect success in all kinds of weather, are by no means easy to obtain. Figure 81 shows the arrangement of air ducts, fan and heating coils adopted for a schoolhouse in a large city, and Figures 82 and 83 show a detail STEAM HEATING AND VENTILATION. 141 of the arrangement of fan and heaters. It will be seen that there is a separate duct for each room in the building, each emanating from the central distributing point, and each provided with a mixing damper. Front Elevation of Heater Showing SteamGonnections. ciHNO RECORD. flush. Airim.i Fresh Air Met.**, Figure 83. Plan of One of the Hot-Blast Units. The system shown is a good example of a method sometimes used to distribute air through long ducts of small size. The author believes, however, that it is open to criticism, as the large number of long, small ducts cannot fail to greatly increase the 142 STEAM BEATING AND VENTILATION. frictional resistance to the flow of air, thus either diminishing the fan capacity or, for a given capacity, greatly increasing the power required to run the fan. Besides this, the air in the ducts opposite the center of the fan will unquestionably have a higher velocity than those at the sides. It would have been much bet- ter to locate centers of distribution convenient to the vertical ducts at each end of the building and at each bicycle room, and Figure 84, Figure 85. locate the heating coils with mixing dampers at these points with "feeder" ducts (underground, perhaps) from the fans to the cen- ters of distribution. In this connection it is well to state that it is not advisable to run heated air through underground ducts, for the reason that they rapidly absorb heat in cold weather. Where mixing dampers are employed, however, with coils located at a distance from the fan, it is not generally necessary to temper the air with a coil at STEAM HEATING AND VENTILATION. 143 the fan; but all the required heating surface can be placed at the centers of distribution. Mixing Dampers. There are innumerable arrangements for constructing mixing dampers, the idea being to provide a cold-air and a hot-air connection to the vertical flue to each room,, the temperature of the air to the room being regulated by the posi- tion of the mixing damper. They usually consist of a double damper, one in the cold-air connection and one in the hot-air connection, fastened together so that when one is entirely closed the other is entirely open, and vice versa. Three types of mixing dampers, selected at random, are shown in Figures 84, 85 and 86. Thermostats. Mixing dampers are frequently arranged to be operated by automatic thermostats, which regulate their position Room. Figure 86. by the temperature of the room being heated. The principal diffi- culty is that they frequently throw the dampers to the extreme "cold-air position" when the temperature rises, and to the extreme "hot-air position" when it falls again. It is very difficult to obtain a thermostat which will move a mixing damper gradually through its arc by means of a small range of temperature at the thermo- stat, and this is the most important requirement. Air purification.- There is much auxiliary apparatus employed in ventilating systems besides the heating coils, and among these may be mentioned especially means for cleaning and purifying the air. In our large cities, especially for hospitals, something of this kind is very essential. The air is frequently blown through loose cloth screens. The most effective way of cleaning the air, how- ever, is to blow it through a spray of water or through wire screens 144 STEAM HEATING AND VENTILATION. over which water is kept running, or over shallow trays of water. Care must be taken to provide against the annoyance due to freez- ing, and the formation of icicles in winter. In summer the water will lower the temperature of the air somewhat,, but the danger from the washing process lies in making the air too damp. Mr. K. H. Thomas, of Chicago, a ventilating contractor of wide THE ENGINEERING I Figure 87. Plan of Air- Washing Apparatus. experience, has recently patented a dirt "eliminator," represented in the accompanying cuts, Figures 87 and 88, which has proved very effective in severa, -^e ventilating plants. The air is blown through a special form o .pray and the eliminator proper collects the dirt and removes the excess of moisture from the air. Air cooling. Trays of ice are sometimes used, and refrigerating coils also, for cooling the air in summer for theaters ; but this is a STEAM HEATING AND VENTILATION. 145 luxury which has not as yet been employed to a large extent. It must always be remembered that any apparatus of the kind de- scribed will add to the resistance through which the fan has to force its air, and will therefore lessen its capacity, or must be made up by increased speed and power. Figure 88. The Eliminator of the Air-Washing Apparatus. Measuring air currents. Before closing a chapter on the ap- paratus of ventilating systems it seems necessary to say a few words about the instrument most always used for testing pur- poses. It is not the author's intention to treat of the many Figure 89. The Anemometer. methods to be employed in testing ve* iting apparatus for dif- ferent objects, but the anemometer, w>. >-h is used to measure air velocities, is so generally employed, and so necessary in inspect- ing plants, that a brief description seems advisable. There are many forms, but they all consist of a set of vanes attached to a 146 STEAM HEATING AND VENTILATION. revolving shaft like a small windmill or disk fan and a registering device as shown in Figure 89. They are rarely accurate, and should not be used ^ without being calibrated. This is usually ac- complished by attaching the instrument to the end of a stick about 8 or 10 feet long, and revolving in a circle at different uni- form speeds in still air and plotting a diagram showing the rela- tion between the actual velocities and the reading of the instru- ment. This will give data for correcting the indications of the instrument obtained during a test, INDEX. Adams, Henry Boilers Form of direct-indirect radiator Cast-iron, setting t-5 Capacities of 32 Air Types of 31 Action of, in radiators.... 18, 20, 56 Brick, Heat losses through.... 62, 64 Amount of, required for individ- Bronzing, Radiator 46 uals under different conditions 99 Butler, W. F. Circulation Handbook on ventilation 7 Around radiators 43 In rooms 96, 110 Carbonic-acid gas Cooling of 144 Amount given oil by individuals S9 Flow of Relation of, to purity of air 97 In ducts , 113 Carpenter, Prof. R. C. In heated ventilating flue 130 Centrifugal fan capacities 127 Through indirect radiators 50 Coefficients of heat transmission Leakage into buildings 60 of building substances 62 Pressures of, in ventilating sys- Power to drive centrifugal fans.. 128 terns 115 Radiator tests 39 Purification of 143 Rule for direct radiation 67 Purity, standards of 97 Rule for steam pipe sizes 76 Specific heat and weight of.... 61 Tests of effect of paint on radi- Velocities of ator 4G In ducts 116 Condensation Measurement of 145 Coefficient of radiator 43 Through inlets and outlets 112 Indirect radiators Volumes required for different Tests of 51. buildings and different periods Curves of, in 54 of occupancy 100 Relative, in radiators at differ- Air inlets ent steam pressures 45 Diffusers for, Cooley, Prof. M. E. Theaters 108 Tests of wrought-iron pipe coils 45 Upward svstem of ventilation 106 Cooling, Air 144 Indirect radiators 91 Proper arrangement of J09 Dampers Velocities through 112 Mixing 143 Air outlets Use of, in air ducts 117 Proper location of 109 Denton & Jacobus, Profs. Velocities through 112 Radiator tests 43 Air valves, see Valves. Tests of extension-surface radi- Anchors, riser 85 ators 45 Anemometer 145 Desaguliers. Dr. System of ventilation 8 Baldwin, William J. Diffusers Heat-transmitting power of For theaters 108 building substances 62 For U. S. Senate chamber 306 Rule for direct radiation 63 Drainage of pipes 78 Rule for pipe sizes 72 Ducts Tests of indirect radiators El Arrangement of Tests of radiator condensation For indirect radiator installa- at different pressures 45 tions 92 Billings, Dr. John S. Schemes for 117 T,eakaere of air into buildings... CO Branch 116 Blessed, W. S. Brick underground 122 .tieat given off by heating coils 132 Flow of air in .113 INDEX. Layout of, in the basement of a Hcod, Charles large building 119 Coefficient of heat transmission Materials tor 121 through glass 62 Underground 94 Huyett, M. C. Expansion Centrifugal fan capacities 125 Method of providing for, in pipes 79 Kn nSi n J intS - 81 Jacobus & Denton, Profs. JH.XpOSUre Rurlintnr t^etc At Influence of, in determining ra- TeStsof extension-surface -radl diatlon 63, b5 iators 45 Blackman Kinealy, Prof. J. H. Capacity of 129 Capacities of disk fans 129 Centrifugal Sizes of flues for indirect radia- Capacity of 125 tors ?1 Capacities, of, compared by dif- ferent formulas 140 Mills, J. H. Description of 124 Rule for direct radiation 66 Power to drive 127 Rule for pipe sizes 73 Combined unit of heater and.... 133 System of piping 16 Disk Tests of indirect radiators 51 Capacities of 129 Mills' system of piping 16 Description of 125 Monroe, William S. Tests of, with heating coils 136 Radiator tests 40 Filters for air purification 143 Rule for direct radiation 8 Flues Rule for pipe sizes 73 For indirect radiator installa- Tests of fans and heating coils.. 136 tions DO Muffler tank in an office building Heated, velocity in the 130 power plant 89 Several outlets from same 121 Friction Paints, Effect of, on radiation 46 In steam pipes 77 Parkes. Individual exhalation of See under Ducts, etc. carbonic-acid gas 99 Paul vacuum system of steam Glass, Window heating 28 Heat losses through 62, 64 Pettenkofer, Individual exhalation Governors, Pump of carbonic-acid gas 99 On closed and open heaters.. 23, 26 Plenum chambers in duct sys- Gray, Dr., Tests of indirect radia- terns 117 tors 51 Pressures Air, in ventilating systems 115 Hangers Heating at high 19 Indirect radiator supports 91 Pumps Pipe, expansion 87 Automatic for return water 27 Heat Vacuum 29 Amount given off by direct rad- Pipes iators 43 Drainage of 17 Amount given off by indirect Expansion of 7& radiators 50, 51, 70 Protection of 86 Loss in buildings 60 Supports for 6 Required for ventilation 61 Pipe covering Heaters, Feed-water Values of different kinds of... 90 Location of, in an office building Pipe sizes plant 89 Baldwin's rule 72 Open and closed or pressure Carpenter & Sickles' rule for 76 types 22, 23 For high-pressure systems r .5 Value of 22 For vacuum systems 75 Heating, Steam Mills' rule for ' 73 Earliest instance 7 Monroe's rule for 73 Exhaust Radiator connections 76 Arrangement of 21, 23 Pipe systems Considerations of 19 One-pipe Gravity IS Arrangement of mains for 78 High pressure 19 Overhead or Mills' .'.. 36 Vacuum .-.. 28 Simple type 13 Heating coils Sizes of radiator connections Arrangement in air ducts 140 to 76 Capacity of 132 With separate return main.... 15 For use with fans 131 Overhead system Influence of depth of 135 Description of large 83 Tests of, with fans 136 Two-pipe Velocity of air through 132, 134 Arrangement of mains for 78 Hogan, John J, Overh'ead 17 Coefficient of heat transmission Simple type 34 through glass... ^ 62 Sizes of radiator connections. . 76 INDEX. Piping Arrangement of main in an of- fice building power plant 8? Connections to feed-water heat- ers 23 For indirect radiator installa- tions Heating coil connections 131, 141 Radiant heat, amount of, from va- rious types of radiators 38 Radiation Boiler capacity for required amount of 32 Calculation of 85 Direct Adaptation of 10 Baldwin's rule for C3 Carpenter's rule for 67 Mills' rule for 66 Monroe's rule for 68 Willett's rule for 66 Wolff's rule for 69 Direct-indirect Adaptation of 11 Rule for 71 Indirect Adaptation of 10 Rule for 70 Raaiant heat from 38 Radiators Action of 36 Air circulation in hot-water and steam types E6 Circulation of 18, 55 Classification according to sur- face 34 Connections One and two-pipe 58 Riser 79 Sizes of 76 Direct, circulation in , 57 Direct-indirect Action of.. 54 Settings, type of 94 Types of 35 Extension-surface, tests of 45 Flue Compared with open 45 Types of 33 Gold's pin 58 Hot-water Compared with steam 45 Types of 34, 37 Indirect Circulation in 58 Heating residences by 92 Theory of 48 Types of 36 Location of 46 Measuring 34 Narrow and wide compared with high and low.....' 44, 45 One, two and three-column types 32 Painting of 46 Protection of connections to 86 Tests of 38 Water in 79 Wrought-imn 33 Reed, J. R. Tests of indirect rad- iators 51 Registers Velocity of air through 116 Return mains. Location of 78 Richards. C. B. Tests of indirect radiators 51 Risers Anchors for 85 Concealment in columns 81 Connections of, to mains 78 Location of 83 Sickles, E. C. Rule for steam pipe sizes 76 Sleeves, Floor 86 Snow, Walter B. Influence of velocity of air in heaters and of the depth of heaters 134 Steam Flow of, in pipes 72, 76 Proportion of heat energy avail- able for heating 19 Supports Indirect radiator 91 Tables Air velocities at different duct pressures; Chap, ix 115 Amount of air per person in buildings of various kinds; Ta- ble 2, Chap, vii 101 Capacity of heating coils; Chap. x 132 Capacity of steam pipes; Table v, Chap, vi 77 Carbonic-acid gas exhalation; Chap, vii 99 Cast-iron boiler capacities; Chap. iii... 32 Centrifugal fan-wheel capacity coefficients; Table ii, Chap. x. 126 Condensation in radiators at dif- ferent pressures; Chap, iii 45 Effect of by-pass on air deliv- ery and power; Table vii, Chap. x 137 Fan and heating-coil tests; Ta- bles v and vi, Chap, x 136, 137 Flue sizes for indirect radia- tors; Chap, vi 91 Heat-transmitting power of building substances; Chap, v 62 Pipe sizes according to Baldwin and Mills; Table i, Chap. vi. 73 Pipe sizes, according to Monroe; Table ii, Chap, vi 74 Pipe sizes, Webster vacuum sys- tem; Table iii, Chap, vi 76 Quantity of air moved by ex- haust fans; Table iii, Chap, x 129 Quantity of air supplied by blowers, and power required to drive; Table i, Chap, x 127 Radiator connections; Table iv, Chap, vi 76 Tests of indirect radiators; Chap, iv 51 Velocity of air in heated flues; Table iv, Chap, x 130 Volume of air necessary to maintain given degree of pur- ity for different periods; Ta- ble i, Chap, vii 100 Temperatures Air in heating- coils 132 Tests Standards, in radiator tests 43 (See under apparatus concerned.) Thermostats Use with mixing dampers 143 INDEX. .56, Thomas, R. H. Air washing ap- paratus 144 Traps, automatic, for return wa- ter 27 Tredgold, Thomas. Treatise on heating and ventilation 7 Unwin, Prof. W. C. Flow of air in round pipes 114 Valves Air Automatic Location of radiator. Radiators Back pressure Forms of Location of For a vacuum system in a Chi- cago office building Location of, in heating systems. Reducing pressure Form of Location of Ventilation Air circulation in rooms Amount of heat required for. 61, By gravity Early examples of artificial Need of proper Plenum and exhaust systems Upward versus downward 110 Wall coils, Wrought-iron Efficiency of pipe, -15 Warner, W. Tests of indirect rad- iators 51 Water In radiators 79 Spray for air purification 143 Water line of heating systems.. 27 Webster, Warren, & Co. Pipe sizes for vacuum system.. 75 System of steam heating 28 Willett, James R. Capacities of cast-iron boilers... 31 Rule for direct radiation 66 Wind Influence of, on air leakage into buildings 60 Wolff, Alfred R. Air velocity through indirect radiators 50 Capacities of disk fans 129 Centrifugal fan capacities 125 Coefficients of heat transmission of building substances 62, 63 Form of direct-indirect radiator setting 95 Rule for direct radiation 69 Velocity of air through heated ventilating flues 130 Wood Heat losses throuerh ....62, 64 Woodbridge, Prof. S. H. Upward versus downward ven- tilation 105 Wren, Sir Christopher. Attempt at ventilation 8 Ventilation and Heating, By JOHN S. BILLINGS, A. M., M. D., LL.D., Edinb. and Harvard. D. C. L. Oxon. Member of the National Academy of Sciences. Surgeon, U. S. Army, etc. FROM THE PREFACE. IN preparing this volume my object has been to produce a book which will not only be useful to students of architecture and engineering, and be convenient for reference by those engaged in the practice of these professions, but which can also be understood by non-professional men who may be interested in the important subjects of which it treats ; and hence technical expressions have been avoided as much as possible, and only the sim- plest formulae have been employed. It includes all that is practically important of my book on the Principles of Ventilation and Heating, the last edition of which appeared in 1889 ; but it is substantially a new work, with numerous illustrations of recent practice. For many of these I am indebted to THE ENGINEERING RECORD, in which the descriptions first appeared. JOHN S. BILLINGS. TABLE OF CONTENTS. CHAPTER I. Introduction. Utility of Ventilation. CHAPTER II. History and Literature of Ventilation. CHAPTER III. The Atmosphere : Its Chemical and Physical Properties. CHAPTER IV. Carbonic Acid. CHAPTER V. Conditions Which Make Ventilation Desirable or Necessary. Physiology of Respiration. Gaseous and Particulate Impurities of Air. Sewer Air. Soil Air. Dangerous Gases and Dusts in Particular. Occupations or Processes of Manufacture. Drying Rooms. CHAPTER VI. On Moisture in Air, and Its Relations to Ventilation. CHAPTER VII. Quantity of Air Required for Ventilation. CHAPTER VIII. On the Forces Concerned in Ventilation. CHAPTER IX. Examination and Testing of Ventilation. CHAPTER X. Methods of Heating. Stoves. Furnaces. Fireplaces. Steam and Hot Water. Thermostats. CHAPTER XI. Sources of Air Supply. Filtration of Air. Fresh Air Flues and Inlets. By-passes. " CHAPTER XII. Foul-Air or Upcast Shafts. Cowls. Svphons. CHAPTER XIII. Ventilation of Mines. CHAPTER XIV. Ventilation of Hospitals and Barracks. Barrack Hospitals. Hos- S'.tals for Contagious Diseases. Blegdam ospitals. U. S. Army Hospitals. Cam- bridge Hospital. Hazleton Hospital. Barnes Hospital. New York Hospital. Johns Hopkins Hospital. Hamburg Hos- pital. Insane Asylums. Barracks. CHAPTER XV. Ventilation of Halls of Audience and Assembly Rooms. The Houses of Parliament. The U. S. Capi- tol. The New Sorbonne. The New York Music Hall. The Lenox Lyceum. CHAPTER XVI. Ventilation of Theaters. Manchester Theaters. Grand Opera House in Vienna. Opera House at Frank- fort-on-the-Main. Metropolitan Opera House, New York. Madison Square Theater. Academy of Music, Baltimore. Pu'eblo Opera House. Empire Theater, Philadelphia, CHAPTER XVII. Ventilation of Churches. Dr. Hall's Church, New York. Hebrew Temple, Keneseth-Israel, Philadelphia. CHAPTER XVIII. Ventilation of Schools. Bridgeport School. Jackson School, Min- neapolis. Garfield School. Chicago. Bryn Mawr School, near Philadelphia. College of Physicians and Surgeons, New York. CHAPTER XIX. Ventilation of Dwelling Houses. CHAPTER XX. Ventilation of Tunnels, Railway Cars, Ships. Shops, Stables. Sewers. Cooling of Air. Conclusion. Over 500 Pages. 2JO Illustrations. Sent Postpaid on Receipt of $4.00. THE ENGINEERING RECORD, 21 PARK ROW, NEW YORK. THE WAINWRIGHT SAFETY VALVE SOFT fil/BSf, EVEN FLOW FEED WATER HEATER is IN USE IN THE LARGEST POWER STATIONS IN THE COUNTRY, ALSO THE WAINWRIGHT EXPANSION JOINTS. Send for Catalogue. The Taunton Locomotive Manufacturing Company, Taunton, Mass. American Steam and Hot- Water Heating Practice* From THE ENGINEERING RECORD. A Selected Reprint of Descriptive Articles, Questions and Answers* With Five Hundred and Eighty-Five Illustrations* PREFACE* THE ENGINEERING RECORD (prior to 1887 THE SANITARY EN- GINEER) has for sixteen years made its department of Steam and Hot- Water Heating and Ventilation a prominent feature. Besides the weekly illustrated descriptions of notable and interesting current work, a great variety of questions in this field have been answered. In 1888 Steam- Heating Problems was published. This was a selection of questions, answers, and descriptions that had been published during the preceding nine years, and dealt mainly with steam heating. The present book is intended to supplement this former publication, and includes a selection of the descriptions of hot-water, steam-heating and ventilating installa- tions in the different classes of buildings in the United States, prepared by the staff of THE ENGINEERING RECORD, besides a collection of ques- tions and answers on problems arising in this department of building engineering, covering the period since 1888, in which the heating of dwellings by hot water has become popular in the United States. The favor with which Steam-Heating Problems has been received encourages the hope that American Steam and Hot- Water Heating Practice may likewise prove useful to those who design, construct and have charge of ventilating and heating apparatus. Size, 8x JJ inches* Three Hundred and Seventeen Pages* Price, $4.00; postpaid* THE ENGINEERING RECORD, 21 PARK ROW, NEW YORK. Pipe Threading. . . = Cutting Machines Combining in design all tHat is latest and best, and fully guaranteed as to construction FIG. I. Apex Nipple and Pipe Mill Machine IS SHOWN BY FIG. I. The gearing is entirely protected from dust ; six different speeds pos- sible with but a three-step cone. Pump is out of way of operator ; vise open or closed while machine is in motion. Nipple grips may be closed on threaded ends of pipe without in- jury to thread, thus avoiding the necessity of screwing nipple into grips after they are closed ; this feature possessed by no other machine. With this machine we furnish an au- tomatic threading gauge. Both left and right-hand threads may be made. A description in more detail will be found in our catalogue. Combined Hand and Power Pipe Threading and Cutting Machine IS SHOWN BY FIG. II. We make this machine in several sizes. It is so arranged that either hand or power may be used at will, and it may be readily taken from its base and us3i as a portable hand machine. It occupies less floor space and guaranteed to do better work than any other combined machine on the market. Equipment substantially the same as that of our portable machine, the description of which follows. FIG. II. Our Portable Machine IS SHOWN BY FIG. III. Made in a number of sizes. In quality of work and rapidity of action, both in threading and cutting, this machine is far superior to any other. The possible range of its work is greater, and quicker changes from size to size 'are a feature. We furnish with this machine our Standard Adjustable Quick Opening and Closing Die Head and our improved Cutting-off Knife. The chasers are set by graduation to any size desired, are released from threading while in motion, open to permit the cutting of the pipe, and closed instantly and positively ; readily replaced by other sizes. The vise is self-centering and actuated by rack and pinion. Gears completely housed from dust and to no part of the machine are chips accessible, to its detriment. We issue a complete catalogue fully describing and illustrating the various types of our machines and will be glad to send it on request. THE HERRELL flFQ. CO., Toledo, Ohio. European Office: The Fairbanks Co., 16 Great Eastern St., London, E. C. FIG. Water- Works for Small Cities and Towns, By JOHN GOODELL. PUBLISHERS' ANNOUNCEMENT. THIS book is a, description of the methods of construction of the various portions of a water-works plant, outside of a few features, like pumps, which are now left, in a large measure, to the manufacturers of standard specialties. Even in respect to these specialties enough general information is given to enable anyone with ordinary intelligence to understand the technical descriptions in manufacturers' catalogues and the statements of their agents. The theory of the flow of water, the strength of materials entering into a water-works plant, of the wind pressure on stand-pipes and similar matters are mentioned as briefly as possible because they are thoroughly taught in technical schools and explained in numerous text books. On the other hand, there is no book giving a general account of the methods of building and maintaining works, dams, pipe lines, reservoirs, stand pipes and other fea- tures in sufficient detail to enable an engineering student to understand properly the ap- plication of the theories he learns in school. There is another class to whom it is believed the book will ba particularly valuable, and that is superintendents of works and engineers who may have occasion to require tho compilation of the best information of any feature of such a plant. Even if a superinten- dent is thoroughly acquainted with the subject on which he must prepare a report, it often happens that from lack of experience in writing he may have difficulty in preparing it. In such a case, 'it is confidently believed, this book will prove of assistance, particularly as it has been written very largely with the idea of proving serviceable to men without technical education called upon to act as members of a water commission. In view of the fact that the information presented has been acquired by correspondence with water-works officials in many parts of the country and a review of all the published information of value on the subject, it is believed that even engineers and water-works managers cf experience in their specialty will find the book of interest in a number of par- ticulars. TABLE OF CONTENTS. CHAPTER I. SURFACE WATER The Yield of Catchment Areas Gauging Stream Flow The Meaning of Water Analyses. CHAPTER IT. EARTH DAMS Clay -Gravel Masonry Core Walls Water in Earthwork Cross-section cf the Embankment Starting the Core Wall. CHAPTER ITI. MINOR DETAILS OF RESERVOIRS Outlet Pipes Gate-Houses Waste- Weirs. CHAPTER IV. TIMBER DAMS Brush Dams Crib Dams Framed Dams. CHAPTER V. MASONRY DAMS Foundations Materials Eart h Backing Design Specifications Rock-Fill Dams. CHAPTER VT. SPECIAL FEATURES OF RIVER AND POND SUPPLIES Head-Works Effect of Storage on Water Odors in Water. CHAPTER VII. GROUND-WATER SUP- PLIES Methods of Collecting Ground Water Quantity of Ground Water. CHAPTER VIII. THE UTILIZATION OF SPRINGS Springs in Plains Hillside Springs. CRAPTER IX. OPEN WELLS. CHAPTER X. DRIVEN WELLS Sinking Wells Air in Wells Well Specifications. CHAPTER XI. DEEP AND ARTESIAN WELLS Sinking Wells Specifications Yield of Wells Quality of Ground Water. CHAPTER XII. PUMPS Steam Consumption Power Pumps Details of the Water End Special Power Pumps. CHAPTER XIII. THE AIR LIFT. CHAPTER XIV. PUMPING STATIONS. CHAPTER XV. INTAKES AND INTAKE PIPES. CHAPTER XVI. CLARIFICATION AND PURIFICATION OF WATER Turbidity Slow Sand Filters Mechani- cal Filters. CHAPTER XVII. THE PIPE SYSTEM Flow of Water in Pipes Data Concern- ing Pipe and Accessories -Submerged Pipe Clay Pipes and Open Channels. CHAPTER XVIII. SERVICE RESER- VOIRS AND STAND PIPES Concrete-Lined Reservoirs Asphalt- Lined Reservoirs Stand Pipes and Water Towers Substitutes for Stand Pipes. CHAPTER XIX. THE QUANTITY OF WATER TO BE PROVIDED Relative Capacities of Small Works for Domestic Supply and Fire Protection The Influence of Small Street Mains- Fire Streams. CHAPTER XX. THE WATER WORKS DEPARTMENT Financial Considerations Checking Water Keeping up the Works. Bound in Cloth, 8vo. 28J Pages. Price, $2.00, Postpaid. THE 2J PARK ROW, ENGINEERING RECORD, NEW YORK. -MASON Reducing Valves ARE THE WORLD'S STANDARD VALVES For automatically reducing and absolutely maintaining an even steam or air pressure. THey are adapted for every need and guaranteed to -worK perfectly in every instance. For Vacuum Systems of Heating we maKe a special valve. WRITE FOR FULL INFORMATION AND SPLENDID REFERENCES. THE MASON REGULATOR CO., BOS T*. A ASS "' / T~ A HE best designed system of heating and ventila- tion may be rendered almost worthless by the use of inferior apparatus inferior either in design, material or workmanship. Our design represents the most advanced practice. Mechanical Draft Fans. The circula- tion in this coil is posi- tive, either under vac- uum or 100 .Ifce. steam pressure. We cheerfully furnish plans and drawings to those interested. Massachusetts Fan Company, Room 50, Stock Exchange Building, = BOSTON, MASS. American Plumbing Practice. From THE ENGINEERING RECORD. A. Selected Reprint of Articles Describing Notable Plumbing Installations in the United States, and Questions and Answers on Problems Arising in Plumbing and House Drainage. With Five Hundred and Thirty-Six Illustrations. PREFACE. THE. ENGINEERING RECORD, prior to 1887 THE SANITARY EN- GINEER, has for 17 years given much attention to domestic water supply, house drainage, ventilation, and plumbing. Beside the frequent illustrated descriptions of notable and interesting current work, a great variety of questions in this field have been answered. In 1885 "Plumbing and House Drainage Problems" was published. The present volume, " American Plumbing Practice," is a compilation of illustrated descriptions of plumbing installations in modern buildings of every character, together with Notes and Queries touching interesting- points developed in practice, from articles which have appeared in THE ENGINEERING RECORD since the publication of "Plumbing and House Drainage Problems/' Within this period the towering office building has been developed, involving special problems of drainage and plumbing. The equipment of hotels, hospitals, amusement halls, swimming baths, and other public buildings has been upon the most thorough and elaborate scale, and in the description of the plumbing of residences examples may be found of nearly every class of dwelling. Its division of Notes and Queries is intended to supplement "Plumbing Problems/ 7 bringing these queries well up to date. The greater part of the book consists of descrip- tive matter nowhere else available in this permanent form. Sent Postpaid on Receipt of $3.00. THE ENGINEERING RECORD, 21 PARK ROW, NEW YORK. GURNEY HEATERS Are of uniform excellence. In all of them the heating surfaces are so arranged as to produce a maximum of heat from a minimum amount of coal. All are made from the best grades of iron, have the most efficient types of grates, and embody all the latest improvements. The "Doric "and "400 Series," Steam and Hot Water Heaters are made for a moderate line of work, particularly house heating purposes, and the "BRIGHT IDEA" Series for the larger systems. Their capacities are fully guaranteed. SEND FOR LATEST TRADE CATALOGUE. GURNEY HEATER flFQ. CO., 74 Franklin St., Boston. Ill Fifth Ave., New York. Western Selling Agents: JAMES B. CLOW & SONS, 222-224 Lake St., Chicago, III. ASBESTOS AND MAGNESIA PRODUCTS NON-HEAT-CONDUCTING COVERINGS FOR HEATING AND POWER PLANTS Send for pamphlet "SAVE FUEL. ' ' Asbesto, Sponge Felted, Magnesia, Asbestos Fire Felt. Asbestocel (Air-Cell). Sectional Pipe and Boiler Coverings. Keystone Hair Insulation Structural Insulator, Sound Deadener, Cold Preserver. "Nonburn" Asbestos Building Paper. Asbesto-Metallic Steam Packings. H. W. JOHNS-MANVILLE CO., 100 WILLIAM STREET, NEW YORK. MILWAUKEE. CHICAGO. CLEVELAND ST. LOUIS. PITTTSBURGH. BOSTON. PHILADELPHIA. NEW ORLEANS. Some Details of Water-Works Construction, By W. R. BILLINGS. Formerly Superintendent of Water-Works at Taunton, Mass. With Illustrations from Sketches by the Author* AUTHOR'S INTRODUCTORY NOTE. Some questions addressed to the editor of THE ENGINEERING RECORD by persons in the employ of new water-works indicated that a short series of practical articles on the Details of Constructing a Water- Works Plant would be of value; and, at the suggestion of the editor, the preparation of these papers was undertaken for the columns of that journal. The task has been an easy and agreeable one, and now, in a more convenient form than is afforded by the columns of the paper, these notes of actual experience are offered to the water-works fraternity, with the belief that they may be of assistance to beginners and of some interest to all. TABLE OF CONTENTS. CHAPTER I. MAIN PIPES Materials Cast-Iron Cement-Lined Wrought Iron Salt-Glazed Clay Thick- ness of Sheet Metal Methods of Lining List of Tools Tool-Box Derrick Calking Tools Furnace Transportation Handling Pipe Cost of Carting Dis- tributing Pipe. CHAPTER II. FIELD WORK Engineering or None Pipe Plans Spe- cial Pipe Laying out a Line Width and Depth of Trench Time-Keeping Book Disposition of Dirt Tunneling Sheet Piling. CHAPTER III. TRENCHING AND PIPE- LAYING Caving Tunneling Bell-Holes Stony Trenches Feathers and Wedges Blasting Rocks and Water Laying Cast-Iron Pipe Derrick Gang Hand- ling the Derrick Skids Obstructions Pipe Derrick g th Left in Pipes Laying Pipe in Quicksand Cutting Pipe. CHAPTER IV. P I P E-L A Y I N G AND JOINT-MAKING Laying Cement-Lined Pipe "Mud" Bell and Spigot Yarn Lead Jointers Roll Calking Strength of Joints Quantity of Lead. CHAPTER V. HYDRANTS, GATES, AND SPECIALS. CHAPTER VI. SERVICE PIPES Definition Materials Lead vs. Wrought Iron Tapping Mains for Services Dif- ferent Joints Compression Union Cup. CHAPTER VII. SERVICE-PIPES AND METERS Wiped Joints and Cup-Joints The Law- rence Air-Pump Wire-Drawn Solder Weight of Lear Service-Pipe Tapping Wrought- Iron Mains Service- Boxes Meters. Large 8vo. Cloth, $2.00, Postpaid* THE ENGINEERING RECORD, 21 PARK ROW, NEW YORK. 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 remaining ignorant of something he would most gladly know of. The "Webster System" of Steam Circulation for Heating Purposes lays claim to an efficiency and economy which, if vindicated, constitute 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. \Varren AVebster (SL Co., Camden, N. J. NEW YORK, 322 Broadway. PHILADf LPHIA, 1105 Stephen Girard Bldg. BOSTON, 743 Fremont Bldg. CHICAGO, 1509 Monadnock Bldg. ST. LOUIS, 621 Century Bidg. STEAM PIPE AND BOILER COVERINGS ASBESTOS GOODS TRADE SUPPLIED CONTRACTS EXECUTED ROBERT A. KEASBEY Telephone is i s coniandt 83 Warren Street, Ne'w York The "EM-ESS" SELF-CLOSING FAUCETS having been honestly made by us for twenty years, were naturally reliable, never "stuck open," and de- servedly popular. Hence the numerous imitations that have appeared. The word "Doherty" is now pub- lic property, and is used simply to designate a type of self-closing Faucet which is made by so many people that the name no longer affords a guarantee of dura- bility. Plainly specify The "Em-Ess" Self-C los- ing Cocks, which are made by us, exclusively, and look for our stamp. The MEYER=SNIFFEN CO., Ltd., CLOSING 5 East 19th Street, New York. PHILADELPHIA. WESTFIELD, MASS. THE H. B. SMITH CO. 133-135 CENTRE STREET, N. Y. Manufacturers of The Mercer Boiler. STEAM & WATER HEATING APPARATUS For all Kinds of Buildings. Send for Catalogue. '' BOILERS. Mills, Mercer, Gold, Cottage, Menlo. RADIATORS] Imperial, Princess, Union, Royal Union, (Direct), j Sovereign, Coronet, Diadem, etc. RADIATORS j Gold's School Pins, R & L Nipple Pins, (Indirect), j Drum Pins, etc. Reliable News Regarding New Construction. THE ENGINEERING RECORD work for which bids are to be asked, likewise reports of bids submitted all care- fully edited in order to eliminate items of no value to a contractor, manufacturer or dealer in building and engineering supplies. It was established in 1877, and spends a good deal of money to secure and print only useful items. Hence the reputation for reliability which it has attained. Its Contracting news and Advertisements inviting bids for projected work from the Government, State and Municipal authorities, cover work in all sections of the United States and Canada. They relate to Water- Works, Sewers, Sewage Disposal, Bridges, Public Build- ings, Business Buildings, Schools, Railroad Depots, New Manufactories, Dwellings (exceeding $10,000 in value), Railroads, Electric Railways, Power, Gas and Electric Light Plants, Paving, Roadmaking, Street Cleaning, Garbage Disposal, U. S. Government Work and Miscellaneous Work including contract prices as recorded in bids submitted. Each issue contains important news items not previously published elsewhere. It is issued so as to reach subscribers within a radius of 400 miles of New York, on Saturday; within fifteen hundred miles, on Monday, and the Pacific Coast, on Thursday, of each week. Hot- Water Heating and Fitting, A Treatise on the Practice of Warming: by Hot Water, with Modern Methods Described and Explained. By WILLIAM J. BALDWIN, M. E. The book contains much of the matter on this subject which has appeared in the columns of THE ENGINEERING RECORD, together with a large amount of additional original data; the whole containing a large amount of practical and useful information of great value to the Engineer, Architect, Mechanic, and Householder. Handsomely bound in cloth and fully illustrated, 392 pp. Among the questions treated are the following: The cause cf the circulation of the water within heating apparatus. Motion explained by the use of diagrams. liow to find the velocity of .the flow of water in pipes of an apparatus. Simple lormulse explaining the laws which govern the flow of water in an apparatus. Diagrams showing the coefficients of the curve of the expansion of the water. Diagram showing the velocity of water in feet per second when the height from which it flows is known. The use of the diagrams in estimating the flow of the water through the apparatus. Table of the quantity of water in U. S. gal- lons that will pass through pipes of a given diameter. Table giving the friction loss in inches of the water head for each ten feet of length of different sizes of clean iron pipes discharging given quantities of water per minute. The loss of head by friction and resistance of elbows. Saving by long radius elbows. Saving by smooth elbows. Resistance caused to the flow of water by elbows and return bends. Resistance caused by valves, etc., and how it may be made less. How to find the flow of water through main pipes of an apparatus. To find the quantity of water in U. S. gal- lons that will pass when the total head is known. To find the fM^meter of a pipe for a given discharge of water. To find the discharge of pipes for given diameters. How to compute radiating surfaces. Experiments of Tredgold and Hood in warm- ing surface. modern investigators on Experiments of radiators. How to find the amount of water that should pass through a radiator to do certain duty. How to determine the size of inlet and out- let to hot-water radiators. How to estimate the quantity of water that should pass through a radiator for a loss of 10 degrees. Diagram giving the diameter of flow and re- turn pipes when the radiating surface and the length of the pipes are known. Experiments illustrating use of diagram in the. piping of buildings. The different systems of mains used in hot- water heating. Treatment of single circuits. Branch circuits. Compound circuits. How to proportion the apparatus for in- direct heating. Heat given off per square foot of surface. Loss of heat through walls and windows of a room. Heat lost by ventilation how to consider it. How to find heating surface of a room warmed by indirect radiation. Comparative experiments with hot-water coils. Diagram of sizes of main pipes for indirect radiation. Examples of buildings warmed by hot water. Boilers used in hot- water apparatus. Direct and indirect radiators used in hot- water apparatus. Expansion tanks and how they should be used. Special fittings for hot-water apparatus. How to conduct experiments in testing the efficiency of hot-water radiators. How to control fires by the temperature of water. Large 8vo. 392 Pages, Fully Illustrated. Sent Postpaid on Receipt of $2.50. THE 21 PARK ROW, ENGINEERING RECORD, NEW YORK. RETURN TO: CIRCULATION DEPARTMENT 198 Main Stacks LOAN PERIOD 1 Home Use 2 3 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS. Renewals and Recharges may be made 4 days prior to the due date. Books may be renewed by calling 642-3405. DUE AS STAMPED BELOW. UG I L'32 FORM NO. DD6 UNIVERSITY OF CALIFORNIA, BERKELEY 50M 6-00 Berkeley, California 94720-6000