Hi again, just wondering about this:
"Air is compressed in a reversible polytrophic process (pv^n=constant) from an initial state of 15 bar and
100 ° to a final pressure of 50 bar. The polytropic exponent is n=1.3. Calculate the change in
entropy per mass of air."
Would we use perfect gas relationships - specific - pv=RT at state 1. Looking at entropy in tables though, they show a change in entropy. Not sure about this one.