# Heat transfer between two closed cavities with natural convection

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October 28, 2014, 05:39
Heat transfer between two closed cavities with natural convection
#1
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Cezary
Join Date: Jul 2014
Posts: 5
Rep Power: 9
Hi,

I am modelling a 2D axisymmetric heat transfer between two closed cavities. One is filled with air, another with helium. Heat source is placed at the axis. BC is a constant temperature at the wall of the outer domain - air. Heat is being transferred through the natural convection (no pressure BC, no inlet or outlet). I am using Fluent software. My question is: Is it possible to determine different operating conditions for those domains, as Fluent requires operating density and pressure for natural convection calculations. Helium and air are under different pressure and of course have different densities. Had anyone solve such case?

I am working also on 3D version of this problem, however calculations are quite time consuming, so I use 2D for preliminary settings.

In the picture green is helium, blue is air.

I would appreciate any possible help with this case.

Does using 0 for operating density solve the problem? Is it obligatory for solver to use operating density for natural convection?

Regards,
Czarulla
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Last edited by Czarulla; November 4, 2014 at 09:40. Reason: new idea

 November 19, 2014, 07:18 #2 New Member   Cezary Join Date: Jul 2014 Posts: 5 Rep Power: 9 For other users, I have solved the problem. There is no possibility of setting two different operating pressure and densities. However, my fault was using incompressible ideal gas model. Now I use ideal gas model and set operating density to 0, operating pressure equal pressure in one domain. When both domains have different pressure, you need to patch appropriate pressure in both domains. Remember that ideal gas model is using pressure in cell + operating pressure for calculating density. What is more, Full Bouyancy option have to be picked. With that option you can simulate your transient with natural convection.

 August 5, 2020, 12:36 #3 Member   Himanshu Join Date: Jan 2017 Posts: 33 Rep Power: 7 Hello sir, Why is the reason of setting operating density to 0 for ideal gas?