2. Adjust the size of the trunk and laterals so that the pressure drop between each hood and the datum R is the same as in the longest line, 0.4i in. water. The drop in trunk 1-2 is 6%50 X0.41 or 0.107 in. of water.
To handle the 850 cfm., the diameter here must be 11 in.
The drop in trunk R-1 is 1%50 X 0.41 or 0.0164 in., and, to handle 1250 cfm., the diameter must be 13 in.
The pressure drop in line R-2 is(10 65)/250 of 0.41 or 0.123 in.
There- fore, the drop in line 2-C and 2-B must be 0.11 0.123 or 0.287 in Line 2-C is 60 ft. long and contains two elbows and a hood.
The total elbow and hood resistance is 120 pipe diameters.
Trial-and-error procedure will show that a 74-in. pipe of equivalent length of 135 ft. will give a pressure drop of nearly 0.287 in.
when delivering 300 cu ft. per min. The pressure drop in section 2-3 which includes the elbow at 2 would be 45 507.512 or in.
Therefore drop in line B-3 must be of 0.287 0.218 the 60 1207.512 0.287-0.218 or 0.059 in. Line B-3 resistively is 75 70 diameter in length The same trial-and-error procedure will show that a 9-in.
pipe is necessary IUS)