GPSA 12TH ED FIG 13-27 ATTACHED

[tomato5]

hello i have a question regarding this figure

take fluid with k = 1.30 and a compression ratio of 9 go x direction and meet curve which is about 72% isentropic efficiency following the curved path and 72% polytropic efficiency

if we take the straight vertical lines we would read about 64% isentropic and about 76% polytropic efficiency

but isentropic efficiency is always greater than polytropic efficiency?

Comments>

a request please respond if you have a definite explanation, if it is only a conjecture please ignore

thank you

 

[gruntguru]

The curved lines on the right are lines of constant polytropic efficiency. Lines of constant isentropic efficiency are vertical ie the RH dot on your red line sits at 72% polytropic and 64% isentropic efficiency.

Isentropic efficiency is always less than polytropic for compressors. For expanders its the other way around.

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