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7.4 Predicting Pressure Drop
To predict a pressure drop at ows outside the capacity of the ow bench do the following.
1. Record the actual test pressure and the actual ow rate.
2. Now you can predict what the test pressure (pressure drop) would be if you actually had the power to
test at higher rates of ow as follows:
Given:
Pa Actual measured pressure drop
Pt Theoretical pressure drop
Fa Actual Flow rate
Ft Theoretical Flow Rate
Pt = [(Ft/Fa)^2] x Pa
Example: You tested an intercooler and found that it owed 320 cfm at 46” H
2
O. Given the measured
data, you would like to know an estimate of what the pressure drop might be if you could ow at
500 CFM
Fa = 320 CFM
Pa = 46”H2O
Ft = 500 CFM
Then:
Pt =[( 500/320)^2] x 46
Pt = 112.3“ H
2
O
Your part is estimated to drop about 112.3” H2O at a ow rate of 500 CFM.
7.0 Flowbench Theory
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