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Calculation Of Thermodynamic Properties For Isentropic Compressor


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#1 Matt93

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Posted 08 September 2017 - 12:25 AM

Hi,

 

I'm trying to calculate the thermodynamic properties of a pure ethylene stream as it goes through a compressor. I know the inlet conditions of S,H,T,P and i know the outlet pressure of the stream and the adiabatic efficiency of the compressor is 75%.

 

However, i'm not not sure how i can use the peng robinson EOS to find out the temperature of the exiting stream for 100% adiabatic efficiency. I know i can equate the entropy change function to zero. But the function contains Z. What is the way that this problem is normally solved? 

 

Thank you!

4.gif,
where 5.gif is in kJ/mol and 6.gif is in kJ/[mol K]; the superscript 7.gif represents an ideal gas, the subscript 8.gif refers to the reference state, and 9.gif and 10.gif are the enthalpy and entropy departure functions for a real gas calculated from the Peng–Robinson EOS, while 11.gifand 12.gif are the ideal gas enthalpy and entropy at the reference state.
 
14.gif,
23.gif,
 
 


#2 Pilesar

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Posted 08 September 2017 - 04:08 PM

Perhaps find a generalized compressibility chart to estimate the compressibility factor as a function of reduced temperature and reduced pressure.



#3 MrShorty

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Posted 08 September 2017 - 04:40 PM

If the central part of the question is how to find Z, then one should be able to solve the PR EOS for z=PV/RT fairly readily. The Wikipedia page gives the cubic polynomial form for the PR EOS in Z, which one should readily be able to solve for Z. https://en.wikipedia...uation_of_state

 

Is that what you are needing, or is there more to the question?



#4 sylvo

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Posted 09 September 2017 - 12:27 PM

I suggest you use a compressibility chart to get your compressibility factor or better still you can get your Z using PV/RT, if you know your critical temperature and pressure

#5 breizh

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Posted 12 September 2017 - 06:32 AM

hi ,

This may help you too.

 

Breizh

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