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4

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!

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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 Pengâ€“Robinson EOS, while and  are the ideal gas enthalpy and entropy at the reference state.

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#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 ,