4 replies to this topic

[Matt93]

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!

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where  is in kJ/mol and  is in kJ/[mol K]; the superscript  represents an ideal gas, the subscript  refers to the reference state, and  and  are the enthalpy and entropy departure functions for a real gas calculated from the Peng–Robinson EOS, while and  are the ideal gas enthalpy and entropy at the reference state.

 

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[Pilesar]

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

[MrShorty]

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?

[sylvo]

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

[breizh]

hi ,

This may help you too.

 

Breizh