room of some 1,200 cu. ft. capacity. The windows and doors were closed. All samples were taken while standing perfectly free, about the middle of the room. Each series runs through about half an hour's time. For that shown on the left the temperature was 34°F. and the reinspiration amounts to 2.3%. For that shown at the right the temperature was 70°F. and the reinspiration amounts to 2%. The former was taken late at night, the latter late the next morning. The changing CO2 in the general air of the room may be accounted for by the presence of the experimenter; and the difference in the CO2 of this air for the two confined space. The results of an experiment carried out in a small bedroom of about 1,000 cu. ft., and also at the low temperature of 43°F., are illustrated in Fig. 6. The room has one window and two doors. A strong FIG. 5.—(EXP. 23). SHOWING THE INSPIRED AIR IN A ROOM WITH A TEMPERATURE series by pure air entering from without THE EFFECT OF VENTILATION CURRENTS It is reasonable to suppose that the greater the volume of air supplied to a room the less evident will be the phenomenon of reinspiration, because of the greater motion imparted to the air of the In wind was blowing without. The series. FIG. o Standing.- Air still. Standing. Air moving at rate of 200 ft. per minute. THAT 7. (EXPER. 12). SHOWING above experiment. When one sits or stands directly between the inlet and the outlet, and the air-supply is large, the proportion of the breath which is reinspired may drop to nearly nothing. By the employment of properly directed artificial currents it is quite easy to prevent reinspiration entirely. This may be readily accomplished by means of an electric fan, provided the face is free to receive the breeze. If there is obstruction to the free flow of the current of air, the results may be quite different, as will be demonstrated later. Fig. 7 shows very well what happens in a fan current moving at the rate of 200 ft. per minute when there is no obstruction (curve B), and also what happens in the same place when the fan is shut off (curve 4). Such an experiment also serves well as a control of the technic, which was identical for the two series. The room in which it was made contains 2,500 cu. ft. and had a temperature of 68°F. The same result may be obtained by walking about the room, thus creating one's own current of some 200 to 300 ft. per minute, and leaving behind at each step the expired breath. The walking may be confined to a very small circle without any change in the results. It is equally effective to stand with the head above a radiator, which, when well heated, will cause an upward convection current of some 200 ft. per minute. In connection with the avoidance of reinspiration by induced air currents, the interesting observation has been made that when the back is turned to the breeze a little of the expired air is often reinhaled in spite of the current. This is interpreted to mean that the eddies formed in front of the face prevent an immediate removal of the expired air. Two experiments made while standing in a narrow hallway with a very regular flow of air, and which illustrate this, are shown in Fig. 8. In that shown at the left the current was just perceptible, presumably about 150 ft. per minute; in that at the right the current was 300 ft. per minute. The samples in each series were taken alternately, one while facing toward, then one while facing away from, the air current. (To be continued) Forced Circulation Hot Water System With Boilers (Concluded from December, 1913 Issue). PIPE SIZES. Because of the widely varying conditions encountered in each installation, the proportioning of pipe sizes was determined largely by the judgment and experience of the designing engineer. Orinarily, the velocity in trunk mains is made from 5 to 10 ft per second, but in this particular installation the velocity in no case is more than 6 ft., because of the low friction head desired and the contemplated addition to the group of buildings. Table 1 gives the loss of friction in feet per 100 ft. of flow and return main. These values were computed from the formula: Loss in friction in feet per 100 ft. of flow and return mains equals 0.32 V 1.86 6x10D 1.25 where V is the velocity in feet per second and D is the diameter of the pipe in inches. Table 2, which gives the average values for the drop in pounds per 100 ft. of flow and return mains, was only used as a help towards assuming velocities which would give a definite loss in friction per 100 ft. of mains. It will be seen that a different friction loss must be considered in the different mains because of their difference in length, loca The main from the power house to the first branch, 475 ft., will supply 17,700 sq. ft. of radiation. A velocity was then determined which would give approximately 21⁄2 as the loss in friction in feet per 100 ft. of flow and return main. By the use of the tables given an allowable velocity of 5 ft. per second was decided upon, which will require a 7-in. main as the main to supply 17,700 sq. ft. of radiation. This size will be of sufficient capacity to deliver power; and the laundry and other medium pressure apparatus require approximately 30 boiler horse power. Adding to this amount 5 H. P. for pumps and 20% for reserve capacity, this brings the horsepower to 288. To supply this amount three 150 H. P. boilers were installed and so connected that either of the three can be used to supply steam or hot water or cut out of the system entirely. Space has been left and provision made for another boiler which is to be installed with the power plant. Each of the three units are horizontal return tubular brickset boilers for a working pressure of 150 lbs. and to be used for either hot water heating or for supplying high pressure steam. BALANCED DRAFT SYSTEM. The boiler plant is furnished with a balanced draft system, consisting of three 16-in. Typhoon steam turbine blowers set in the back walls of the settings and connected by brick ducts to deliver through the bridge walls, where adjustable cast-iron shutters with handles through the boiler fronts are set. A regulating steam valve, operated by the damper regulator in the smoke breeching, controls the system. HOT WATER HEATER. The hot water heater, which at present is only to utilize the exhaust steam from the pumps, is of such a size that it will also be able to take sufficient steam from the engines to heat the circulating water from 190° to 202° F. The latter figure will be the temperature of the outgoing water, except in extreme cold weather when the boilers will be used to supply the additional heat. The normal load on the power plant will be 65 K. W., which will be sufficient to furnish exhaust steam to the heater 600 gal. per min.x60x8 1-3 lbs. where 55 is the pounds of exhaust steam per kilowatt and 971 is the heat in one pound of steam at 1 lb. gauge pressure. The surface of the heater tubes necessary to warm this amount of water was determined by dividing the total amount of heat required per hour for the circulating water by the amount of heat that 1 sq. ft. of heater tube surface will dissipate per hour. 1 sq. ft. of clean tube surface will give up 427 B. T. U. per degree difference in outside and in SECOND STORY OF POWER HOUSE, METROPOLITAN SANATORIUM, SHOWING AN UNUSUAL GROUPING OF RADIATORS IN CENTER OF BUILDING. for heating the 600 gal. per minute from 190° to 202° F. It was not deemed advisable to install a heater with a capacity great enough to take care of the heating in extreme weather because there will be comparatively little of this kind of weather and because it is not likely that the generators will be carrying more than 65 K. W., at which load the steam from the engines is not sufficient to raise the water through more than 12° F. It will be seen that the exhaust steam from the engine, when generating 65 K. W. per hour will be sufficient to raise the temperature of the water 12° by dividing the B. T. U. in the exhaust |