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, 0.41 in. water. The drop in trunk 1-2 is Q%50 X 0-41 or 0.107 in. of water. To handle the 850 cfm, the diameter here must be 11 in. The drop in trunk 5-1 is ^%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)/25Q of 0.41 or 0.123 in. Therefore, the drop in line 2-C and 2-B must be 0.41 — 0.123 or 0.287 in.
Line 2-0 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 7%-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
QQ + 1207 '¸1/2 0-287 or 0-218 in. Therefore the drop in line 5-3 must be
0.287-0.218 or 0.059 in. Line 5-3 resistively is 75 + 70 diameter in length. The same trial-and-error procedure will show that a 9j^-in. pipe is necessary.
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, 0.41 in. water. The drop in trunk 1-2 is Q%50 X 0-41 or 0.107 in. of water. To handle the 850 cfm, the diameter here must be 11 in. The drop in trunk 5-1 is ^%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)/25Q of 0.41 or 0.123 in. Therefore, the drop in line 2-C and 2-B must be 0.41 — 0.123 or 0.287 in.Line 2-0 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 7%-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 beQQ + 1207 '¸1/2 0-287 or 0-218 in. Therefore the drop in line 5-3 must be0.287-0.218 or 0.059 in. Line 5-3 resistively is 75 + 70 diameter in length. The same trial-and-error procedure will show that a 9j^-in. pipe is necessary.
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