2 replies to this topic

[iplan]

I am required to evaluate the performance of a battery of reciprocating compressors working in parallel. Since the flow meter is a common one installed at the common discharge of all the compressors, individual flow can only be estimated by stopping individual compressors and computing the flow by the differences in total flow. To avoid this, I would like to know whether it is possible to estimate compressor efficiency ( polytropic or volumetric) without the flow component.

Many thanks in advance.

iplan

[kahlilj]

iplan,

Do you at least know the pressure ratio of the compressors? You could use the constant heat capacity method for isentropic efficiency of a gas turbine compressor from the following formula:

Eff= (C-1)/(T2/T1-1)

Where C= Pr^((Gamma-1)/Gamma)

Eff = isentropic efficiency
Pr = compressor pressure ratio
T2/T1 = compressor temperature ratio
Gamma = cp/cv for air (~1.4)

kahlil

I am required to evaluate the performance of a battery of reciprocating compressors working in parallel. Since the flow meter is a common one installed at the common discharge of all the compressors, individual flow can only be estimated by stopping individual compressors and computing the flow by the differences in total flow. To avoid this, I would like to know whether it is possible to estimate compressor efficiency ( polytropic or volumetric) without the flow component.

Many thanks in advance.

iplan

[iplan]

Hi,

Many thanks.The pressure ratios are known for each stage. I also estimated the polytropic efficiency through HYSYS. But I believe, the polytropic efficiency is mostly used for the centrifugal machines.

My understanding is that the volumetric efficiency in reciprocating compressors is hampered by passing suction valves, bad piston rings etc. If these components pass, they will also increase the suction temperature of the stage and in turn increasing discharge temperature also of the stage. Hence I request the forum experts to clarify whether it is correct if we correlate that a poor polytropic efficiency indicates a poor volumetric efficiency.

thanks again,
iplan