This formula can also be used for calculating the frictional losses for flues, in which case, C = the perimeter of the flue in feet, H = the length of the flue in feet, the other values being the same as for stacks.
The available draft is equal to the difference between the theoretical draft from formula ([25]) and the loss from formula ([26]), hence:
d1
=
available draft
=
KH
-
f W² C H
––––––––––––––––
A³
(27)
[Table 53] gives the available draft in inches that a stack 100 feet high will produce when serving different horse powers of boilers with the methods of calculation for other heights.
[TABLE 53] AVAILABLE DRAFT CALCULATED FOR 100-FOOT STACK OF DIFFERENT DIAMETERS ASSUMING STACK TEMPERATURE OF 500 DEGREES FAHRENHEIT AND 100 POUNDS OF GAS PER HORSE POWER FOR OTHER HEIGHTS OF STACK MULTIPLY DRAFT BY HEIGHT ÷ 100
Horse Power
Diameter of Stack in Inches
36
42
48
54
60
66
72
78
84
90
96
102
108
114
120
132
144
100
.64
200
.55
.62
300
.41
.55
.61
400
.21
.46
.56
.61
500
.34
.50
.57
.61
600
.19
.42
.53
.59
700
.34
.48
.56
.60
.63
800
.23
.43
.52
.58
.61
.63
900
.36
.49
.56
.60
.62
.64
1000
.29
.45
.53
.58
.61
.63
.64
1100
.40
.50
.56
.60
.62
.63
.64
1200
.35
.47
.54
.58
.61
.63
.64
.65
1300
.29
.44
.52
.57
.60
.62
.63
.64
.65
1400
.40
.49
.55
.59
.61
.63
.64
.65
.65
1500
.36
.47
.53
.58
.60
.62
.63
.64
.65
.65
1600
.31
.43
.52
.56
.59
.62
.63
.64
.65
.65
1700
.41
.50
.55
.58
.61
.62
.64
.64
.65
1800
.37
.47
.54
.57
.60
.62
.63
.64
.65
1900
.34
.45
.52
.56
.59
.61
.63
.64
.64
2000
.43
.50
.55
.59
.61
.62
.63
.64
2100
.40
.49
.54
.58
.60
.62
.63
.64
2200
.38
.47
.53
.57
.59
.61
.62
.64
2300
.35
.45
.52
.56
.59
.61
.62
.63
2400
.32
.43
.50
.55
.58
.60
.62
.63
2500
.41
.49
.54
.57
.60
.61
.63
Horse Power
Diameter of Stack in Inches
36
42
48
54
60
66
72
78
84
90
96
102
108
114
120
132
144
2600
.47
.53
.56
.59
.61
.62
.64
.65
2700
.45
.52
.55
.58
.60
.62
.64
.65
2800
.44
.59
.55
.58
.60
.61
.64
.65
2900
.42
.49
.54
.57
.59
.61
.63
.65
3000
.40
.48
.53
.56
.59
.61
.63
.64
3100
.38
.47
.52
.56
.58
.60
.63
.64
3200
.45
.51
.55
.58
.60
.63
.64
3300
.44
.50
.54
.57
.59
.62
.64
3400
.42
.49
.53
.56
.59
.62
.64
3500
.40
.48
.52
.56
.58
.62
.64
3600
.47
.52
.55
.58
.61
.63
3700
.45
.51
.55
.57
.61
.63
3800
.44
.50
.54
.57
.61
.63
3900
.43
.49
.53
.56
.60
.63
4000
.42
.48
.52
.56
.60
.62
4100
.40
.47
.52
.55
.60
.62
4200
.39
.46
.51
.55
.59
.62
4300
.45
.50
.54
.59
.62
4400
.44
.49
.53
.59
.62
4500
.43
.49
.53
.58
.61
4600
.42
.48
.52
.58
.61
4700
.41
.47
.51
.57
.61
4800
.40
.46
.51
.57
.60
4900
.45
.50
.57
.60
5000
.44
.49
.56
.60
FOR OTHER STACK TEMPERATURES ADD OR DEDUCT BEFORE MULTIPLYING BY HEIGHT ÷ 100 AS FOLLOWS[52]
For 750 Degrees F. Add .17 inch.
For 650 Degrees F. Add .11 inch.
For 550 Degrees F. Add .04 inch.
For 400 Degrees F. Deduct .09 inch.
For 700 Degrees F. Add .14 inch.
For 600 Degrees F. Add .08 inch.
For 450 Degrees F. Deduct .04 inch.
For 350 Degrees F. Deduct .14 inch.
[Pg 242]
Fig. 33. Diameter of Stacks and Horse Power they will Serve
