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

Horse Power For Ventilation 100043

150 H.P. DE LAVAL TURBINE BL0WER.

TABLE IX.

Diameter of Shell in Inches.

Number of Tubes.

Diameter of Tubes in Inches.

Length of Tubes in Feet.

Horse Power.

Size of Grate in

Inches.

Size of

Uptake 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 +

----------------

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.