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Gas-Gas interface in a closed environment (Immiscible species)

Posted 10.05.2021, 22:28 GMT-4 2 Replies

Ettore Gastaldi
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Hi everybody,

I'm trying to figure out how to model the interface between two immiscible gases in a closed environment. The application of interest is a variable conductance heat pipe (VCHP) where the sodium vapor is placed inside a vertical cylindrical tube together with an inert gas (helium), which having a lower density than sodium tends to be in the upper part of the tube. As the applied heat load decrease/increase, the sodium-helium interface moves higher or lower within the tube due to pressure. I tried to model that behavior with the Moving Geometry interface but i get error any time I run the simulation. Is it correct to use Moving Geometry for this case? I searched for similar simulations with the interface between two gases but I never found anything, at most some examples about interfaces behaviour between a liquid (e.g. water) and a gas (e.g. air) solved with Level Set/ Phase Change or Moving Mesh interfaces.

Thank you in advance

2 Replies Last Post 11.05.2021, 21:08 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 4 years ago 11.05.2021, 04:03 GMT-4

Ettore,

Hm, I am not the CFD guy, but is something like immiscible gases really existing? Would two species build an interface? Never heard of something like that. But I am happy to learn. Do you have any references for this?

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Ettore, Hm, I am not the CFD guy, but is something like immiscible gases really existing? Would two species build an interface? Never heard of something like that. But I am happy to learn. Do you have any references for this? Cheers Edgar
Ettore Gastaldi
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Posted: 4 years ago 11.05.2021, 21:08 GMT-4

Hi Edgar, thanks for your reply. You are right the term 'immiscible' is misused in this case. I just wanted to make the reader understand the concept that the two gases tend to stratify at different levels of height inside the tube, so I have to use two different domains for helium and for sodium as it cannot be considered a mixture. My goal is to model their behavior when subjected to thermal loads. If the temperature rises, the pressure will increase accordingly and the sodium vapor will 'squeeze' the helium at the top of the tube over time. I want to model this behavior. If anyone was able to solve the problem I would be grateful to them. Bye

Hi Edgar, thanks for your reply. You are right the term 'immiscible' is misused in this case. I just wanted to make the reader understand the concept that the two gases tend to stratify at different levels of height inside the tube, so I have to use two different domains for helium and for sodium as it cannot be considered a mixture. My goal is to model their behavior when subjected to thermal loads. If the temperature rises, the pressure will increase accordingly and the sodium vapor will 'squeeze' the helium at the top of the tube over time. I want to model this behavior. If anyone was able to solve the problem I would be grateful to them. Bye

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