you can easily solve the polytropic compressor with Prode Properties, there is a specific unit in extended version (please contact Prode at 'www.prode.com'), that unit solves the model with the desired level of accuracy (it's a iterative procedure), however you can obtain equivalent (or very close) results by modeling the polytropic compressor as a series of isentropic units with predetermined polytropic efficiency, this is very simple with Prode Properties, for additional information see 'http://www.prode.com/docs/pppman.pdf' -decide the number of steps (I suggest 5 steps) and calculate the dp as (Pout-Pin) / nr. of steps -start from compressor inlet temperature and pressure -at these conditions calculate cp with the method =StrGCp and cv with the method =StrGCv , calculate k = cp/cv -calculate n (polytropic exponent) as n = polytropic efficiency * (k-1)/k -calculate P1=Pin+dp and T1 = Tin*(P1/pin)^(n-1)/n -at these conditions (P1,t1) calculate cp with the method =StrGCp and cv with the method =StrGCv , calculate k = cp/cv -proceed until to complete the steps -.... -once you have calculated the final (outlet) temperature you can calculate the enthalpy at inlet conditions (with Prode Properties) as H1 = StrH() and outlet conditions H2 = StrH() the difference being the enthalpy rise in the gas, you can then calculate the polytropic head from polytropic efficiency[/QUOTE]
Go to Profile
Mark as Read
