Hi,

Many fundamentals books about refrigeration systems say about screw compressors that the pressure ratio is = Vi^k...so far so good....but they say that k is the isentropic exponent.

The above statement is wrong. Even for piston compressor I don't think correct...and for screw compressors is totally wrong because the oil will cool a good part of the compressed gas...so my opinion is that the politropic exponent will be between an isothermal process and the isentropic.

Because the gas is been cooling during the compressing process the final pressure at the discharge port will be lower than if it will been cooled. So the pressure ratio for the same Vi ratio is less than the obtained for the isentropic compressing process.


Awaiting your comments