Nitrogen Cooling

[NDA277]

Without using process simulation software, I'd like to estimate:

(1) the temperature decrease of a nitrogen vapor stream going from +70 Deg. F and 5,000 psig through a PSV to 0 psig.

(2) the temperature decrease of a nitrogen liquid stream going from +20 Deg. F and 5,000 psig through a PSV to 0 psig.

Any suggestions?

Thanks...

 

[sshep]

NDA227,
To get a grip on this, use a PV or PH, diagram. This is constant enthalpy. As a calculation using a diagram or tables, it doesn't get any simpler. The final temp in #2 is the boiling point of N2.
Good luck,
Sshep

 

[PaoloPemi]

in addition to the comments of Sshep,
you can find a solution, by trial and error with Nitrogen tables,
std. procedures calculate vena contracta condition and model at constant entropy, then constant enthalpy to find outlet conditions.
This requires some work and for case 2) you must consider also VLE,
as alternative (which I suggest) you can model directly the valve as isentropic nozzle,
usually I do this in Excel with PRODE PROPERTIES with has a specific macro to model a PSV with different methods.

 

[dcasto]

go to NIST webbook

 

[poli60]

more or less...

 

[poli60]

ooops... starting points now corrected. apologize :-(

 

[sshep]

Thanks Poli60,

Now that we see the diagram and critical point, it shows the distinction of "liquid" and "vapor" to be completely meaningless in the original query.

best wishes,
sshep