52
7.4 Predicting Pressure Drop
To predict a pressure drop at flows outside the capacity of the flow bench do the following.
1.
Record the actual test pressure and the actual flow 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 flow 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 flowed 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 flow 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 flow rate of 500 CFM.
7.0 Flowbench Theory
