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How to control diverging value of temperature |
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October 14, 2021, 09:52 |
How to control diverging value of temperature
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#1 | |
Member
L S
Join Date: Apr 2016
Posts: 63
Rep Power: 10 |
I am trying to simulate subcooled flow boiling with the help of phaseChangeHeatFoam.
The geometry is made 2D representing a pipe flow situation. The case set up is attached with below. I have been observing during subcooled flow boiling, wherever there is no liquid in contact with the heated wall and only vapor is in contact, the wall temperature keeps rising infinitely like this (see maximum T = 7598.001 K): Quote:
How do I control the wall temperature? Is there any way to limit the temperature like some option in fvschemes or fvsolutions? Is there any way to provide minimum and maximum values limit in source code? |
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October 14, 2021, 11:19 |
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#2 |
Senior Member
Join Date: Apr 2020
Location: UK
Posts: 740
Rep Power: 14 |
From a quick look at your case, I can see that you are applying a constant gradient (i.e. constant heat flux) boundary condition on T at the wall. This applies whether there is liquid or gas next to the wall.
Now think about the physics - is this constant heat flux realistic? The answer is no, and that is why you are ending up with excessive wall temperatures, as the code is trying to achieve your BC. The heat transfer is much less efficient when there is vapour next to the wall, and this should therefore drop your heat flux ... So, can I suggest you have a rethink about your T boundary condition. Good luck, and come back and tell us how/when you have cracked it! |
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October 14, 2021, 11:28 |
Any idea on how to write heat flux?
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#3 |
Member
L S
Join Date: Apr 2016
Posts: 63
Rep Power: 10 |
I have been struggling a lot on how to apply the heat flux boundary condition with Scharge or Lee models as most tutorials are using constant wall temperature boundary condition.
Do you have any idea on how to effectively apply heat flux boundary condition using groovyBC? I tried using dT/dX = q''/keff; Where keff = alpha*k_L+(1-alpha)*k_V; k_L = Thermal conductivity of liquid and k_V = thermal conductivity of vapour. But, this was worsening the calculation. |
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Tags |
boiling, heat transfer, openfoam, phase change heat foam |
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