Steam:
Its Generation and Use

HEATING BY STEAM. In heating buildings by steam, the amount of boiler and heating pipe depends largely on the kind of building and its location. Wooden build- ings require more than stone, and stone more than brick. Iron fronts require still more, and glass in windows demands twenty times as much heat as the same surface in brick walls. Also if the heating be done by indirect radiation from 50 to 100 per cent, more will be required than when direct radiation is used. No rules can be given which will not require a liberal applica- tion of “the coefficient of common sense.” Radiating surface may be calculated by the rule: Add together the square feet of glass in the windows, the number of cubic feet of air tity of the air caused to pass through the coil in- creases. Thus one square foot radiating surface, with steam at 2120, has been found to heat 100 cubic feet of air per hour from zero to 150°, or 300 cubic feet from zero to ioo° in the same time. The best results are attained by using indirect radiation to supply the necessary ventilation, and direct radiation for the balance of the heat. The best place for a radiator in a room is beneath a window. Heated air cannot be made to enter a room unless means are provided for permitting an equal amount to escape. The best place for such exit openings is near the floor. Small pipes are more effective than large. When the diameter is doubled, 20 per cent, addi- tional surface should be allowed, and for three Northern Hospital for the Insane, Logansport Ind. with 400 H. P. of Babcock & Wilcox Boilers. Erected 1885. required to be changed per minute, and one- twentieth the surface of external wall and roof; multiply this sum by the difference between the required temperature of the room and that of the external air at its lowest point, and divide the product by the difference in temperature between the steam in the pipes and the required temperature of the room. The quotient is the required radiating surface in square feet. Each square foot of radiating surface may be depended upon in average practice to give out three heat units per hour for each degree of difference in temperature between the steam inside and the air outside, the range under different conditions being about 50 per cent, above or below that figure. In indirect heating, the efficiency of the radiating surface will increase, and the tern perature of the air will diminish, when the quqn- times the diameter, 30 per cent, additional is required. For indirect radiation that surface is most efficient which secures the most intimate contact of the current of air with the heated sur- face. Rooms on windward side of house require more radiating surface than those on sheltered side. Where the condensed water is returned to the boiler, or where low pressure of steam is used, the Diameter of Mains leading from the boiler to the radiating surface should be equal, in inches, to one-tenth the square root of the radiating sur- face, mains included, in square feet. Thus a i-inch pipe will supply 100 square feet of surface, itself included. Return pipes should be at least % inches in diameter, and never less than one- half the diameter of the main — longer returns requiring larger pipe. A thorough drainage of 67