Rapid expansion of Helium: wrong behavior in regards to Joule-Thomson effect

antb · July 12, 2013, 10:51

Hello,

I am simulating the rapid expansion of a variety of gas in a near vacuum cavity, so the Joule-Thomson effect (http://en.wikipedia.org/wiki/Joule%E...Thomson_effect) comes in play.

As far as I understand, this effect is only possible with non-ideal (real) gases, so I am pleased to see that I am able to see it with my current solver (rhoCentralFoam) and thermophysical properties.

The only problem is that this effect doesn't exist for a particular gas (Helium) and temperature (300 K), as can be seen from this graph: http://upload.wikimedia.org/wikipedi...n_curves_2.svg (note the different sign). But openFoam seems to not take this into account and still give me a cooling expansion.

What is wrong with the model, and how can I account for that?

ziemowitzima · June 25, 2014, 11:06

Hi,
I am dealing actually with similar problem.
But in my case I think that OF does not care properly for the "rapid gas expansion".
I have flow where cold He is inletting to the warm surrounding 300K. I think it does not behave correctly because it does not expand as rapid as "it should".
I am using reactingFOAM and ideal gas equation.

Any suggestions ?

Thanks
MM

July 12, 2013, 10:51	Rapid expansion of Helium: wrong behavior in regards to Joule-Thomson effect	#1
antb New Member Join Date: Jul 2013 Posts: 2 Rep Power: 0	Hello, I am simulating the rapid expansion of a variety of gas in a near vacuum cavity, so the Joule-Thomson effect (http://en.wikipedia.org/wiki/Joule%E...Thomson_effect) comes in play. As far as I understand, this effect is only possible with non-ideal (real) gases, so I am pleased to see that I am able to see it with my current solver (rhoCentralFoam) and thermophysical properties. The only problem is that this effect doesn't exist for a particular gas (Helium) and temperature (300 K), as can be seen from this graph: http://upload.wikimedia.org/wikipedi...n_curves_2.svg (note the different sign). But openFoam seems to not take this into account and still give me a cooling expansion. What is wrong with the model, and how can I account for that?

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June 25, 2014, 11:06		#2
ziemowitzima Senior Member Mieszko Młody Join Date: Mar 2009 Location: POLAND, USA Posts: 145 Rep Power: 17	Hi, I am dealing actually with similar problem. But in my case I think that OF does not care properly for the "rapid gas expansion". I have flow where cold He is inletting to the warm surrounding 300K. I think it does not behave correctly because it does not expand as rapid as "it should". I am using reactingFOAM and ideal gas equation. Any suggestions ? Thanks MM