JT equation for gas condensing scenario

[Phani Y]

Can someone please share any information on the JT equation for gas condensing to liquid scenario? I mean I want to calculate the theoretical temperature of the condensed gas at the outlet of the turbo expander, given the inlet temperature, pressure and composition.

In case the information I provided is insufficient, please quote an example and answer.

 

[PaoloPemi]

in order to calculate outlet temperature (given, for example, outlet pressure) you can solve mass & energy balance,
the formulation depends from thermodynamic model (ideal, EOS, multi-parameter as GERG etc.),
normally one would use a process simulator (Aspen, Promax etc.) or a thermodynamic library (I have Prode Properties),
do you wish to code yourself the whole procedure ?
Not simple, a thermodynamic library (or a simulator) could help with fluid properties etc. etc.

 

[rotw]

I mean I want to calculate the theoretical temperature of the condensed gas at the outlet of the turbo expander, given the inlet temperature, pressure and composition.

Does not make sense. Expansion process thru turbo expander is NOT a JT expansion. Expansion thru valve IS.

See dicussion here:

https://www.eng-tips.com/viewthread.cfm?qid=354044

 

[PaoloPemi]

while I agree with rotw about modeling expansion valves solving a isentropic operation,
I prefer to model turbo expanders as polytropic processes, see the note "POLYTROPIC VERSUS ISENTROPIC" in attached tutorial,
that allows more flexibility but you need to solve a complex operation (polytropic process with phase equilibria) hence my suggestion to prefer a well tested software solution...

 

[rotw]

Paolo,

while I agree with rotw about modeling expansion valves solving a isentropic operation

I suppose you mean 'modeling expansion valves' is isenthalpic (J-T)?

BTW Interesting article attached. Thanks.

 

[georgeverghese]

There are equations and graphs in Perry Chem Engg Handbook 6th edition (in the Process Machinery chapter) that will help with calculating the exit temp from a turbo expander, but this procedure is only for single phase gas product at the exit. For a partially condensed exit stream, a simulation program with a suitable equation of state that covers the 2 phase region will be required.