Specific heat ratio in gas compression 2

[Meshry]

In gas compressor; what is the specific heat ration? How could it affect the compressor performance?
in compressor's data sheet; I can see Cp/Cv varying with the temperature. is this the only parameter which could affect it?

thanks

 

[apetri]

for a description of J. M. Schultz method see "The Polytropic Analysis of Centrifugal Compressors" published on 1962, those values are calculated at some predetermined conditions (see the paper or ASME PTC 10 for the details...) you can start calculating the Schultz polytropic head correction factor and then proceed...
With the large diffusion of computers new, more complex but more accurate methods have been proposed and nowadays one can model compressors, expanders etc. (for both gas and gas + liquid) in Microsoft Excel quickly and accurately...
comparing results from Schultz method and the 4 points Integration of Z function available in Prode Properties differences (head) can be about 0.001 or above (depending from fluids and pressure ratios), note that integration method is very accurate due to adopted procedure while Schultz and GPSA adopt some sort of averaged values to reduce the errors...