Centrifugal Compressor Performance
Centrifugal Compressor Performance
(OP)
thread798-84662: Centrifugal Compressors-Polytropic VS Adiabatic I would like to calculate shaft power (kW or HP) for a centrifugal compressor used in refrigeration. I can (I think) calculate gas horsepower but the result is almost half of the actual input power.





RE: Centrifugal Compressor Performance
SHP = m * (H(p) / [n(p) * 3300])* 1.02
m = gas mass flow rate; n(p) = polytropic efficiency; H(p) = polytropic head; 1.02 = 2% gear losses
Polytropic head (ft):
H(p) = (1545/MW)*Z(avg)*T(1)*(n/(n-1))*[(P(2)/P(1))^(n-1/n)-1]
MW = gas molecular weight; Z = compressibility; T(1) = inlet temperature, R; n = compression coefficient; P(1) = suction pressure, psia; P(2) = discharge pressure, psia
RE: Centrifugal Compressor Performance
It looks like SHP = GHP *1.02, where GHP is gas horsepower.
GHP= m * (778.16 / 33000)* {h(2)-h(1)]
If so that means I am on the right track. Now, next step is to find a way to estimate (calculate) the mass flow for the two side loads from the economizer.