We already know that one B. T. U. will raise the temperature of 1 cubic foot of air 55 degrees, or it will raise 100 cubic feet 1/100 of 55 or 55/100 of 1 degree, therefore to raise 100 cubic feet 1 degree it will take 1/ 55/100 or 100/55 B. T. U., and to raise 100 cubic feet through 100 degrees it would take 100/55 X 100 B. T. U. In other words, the B. T. U. required to raise any given volume of air through any number of degrees in temperature is equal to

Volume of air in cubic ft. X Degrees raised / 55

150 H.P. DE LAVAL TURBINE BL0WER.

 Diameter of Shell in Inches. Number of Tubes. Diameter of Tubes in Inches. Length of Tubes in Feet. Horse Power. Size of Grate inInches. Size ofUptake in Inches. Size of smokepipe in sq. in. 30 28 2 1/2 6 8.5 24x36 10x14 140 7 9.9 24x36 10x14 140 8 11.2 24x36 10x14 140 9 12.6 24x42 10x14 140 10 14.0 24x42 10x14 140 36 34 2 1/2 8 13.6 30x36 10x16 160 9 15.3 30x42 10x18 180 10 16.9 30x42 10x18 180 11 18.6 30x48 10x20 200 12 20.9 30x48 10x20 200 42 34 3 9 18.5 36x42 10x20 200 10 20.5 36x42 10x20 200 11 22.5 36x48 10x25 250 12 24.5 36x48 10x25 250 13 26.5 36x48 10x28 280 14 28.5 36x54 10x28 280 48 44 3 10 30.4 42x48 10x28 280 11 33.2 42x48 10x28 280 12 35.7 42x54 10x32 320 13 38.3 42x54 10x32 320 14 40.8 42x60 10x36 360 15 43.4 42x60 10x36 360 16 45.9 42x60 10x36 360 54 54 3 11 34.6 48x54 10x38 380 12 37.7 48x54 10x38 380 13 40.8 48x54 10x38 380 14 43.9 48x54 10x38 380 15 47.0 48x60 10x40 400 16 50.1 48x60 10x40 400 46 3 1/2 17 53.0 48x60 10x40 400 60 72 3 12 48.4 54x60 12x40 460 13 52.4 54x60 12x40 460 14 56.4 54x60 12x40 460 15 60.4 54x66 12x42 500 16 64.4 54x66 12x42 500 64 3 1/2 17 71.4 54x72 12x48 550 18 75.6 54x72 12x48 550 66 90 3 14 70.1 60x66 12x48 500 15 75.0 60x72 12x52 620 16 80.0 60x72 12x52 620 78 3 1/2 17 86.0 60x78 12x56 670 18 91.1 60x78 12x56 670 19 96.2 60x78 12x56 670 62 4 20 93.1 60x78 12x56 670 72 114 3 14 87.4 66x72 12x56 670 15 93.6 66x72 12x56 670 16 99.7 66x78 12x62 740 98 3 1/2 17 106.4 66x78 12x62 740 18 112.6 66x84 12x66 790 19 118.8 66x84 12x66 790 72 4 20 107.3 66x84 12x66 790

Example - How many B. T. U. are required to raise 100,000 cubic feet of air 70 degrees ?

100,000 X 70 = 127,272 +

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To compute the H. P. required for the ventilation of a building we multiply the total air supply in cubic feet per hour by the number of degrees through which it is to be raised, and divide the result by 55. This gives the B. T. U. per hour, which divided by 33,000 will give the H. P. required. In using this rule always take the air supply in cubic feet per hour.

Example. - A high school has 10 class rooms, each occupied by 50 pupils. Air is to be delivered to the rooms at a temperature of 70 degrees. What will be the total H. P. required to heat and ventilate the building when it is 10 degrees below zero if the heat loss through walls and windows is 1,320,000 B. T. U. per hour?

Cubic feet of air = 3000 X 10 X 50 = 1,500,000

To heat this quantity we need

1,500,000 X 80 = 2,181,800 B. T. U. 55

Total B. T. U. = 1,500,000 + 2,181,800 = 3,501,800

Boiler H. P. = 3,501,800/ 33,000 = 106. Ans.