Centrifugal Compressor Performance 1

[whenry]

thread798-84662 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.

 

[bchoate]

Compressor shaft horse power:

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

 

[whenry]

Thanks,

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.