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-   -   Natural convection in a closed domain help! (http://www.cfd-online.com/Forums/fluent/86397-natural-convection-closed-domain-help.html)

 Yr0gErG March 21, 2011 22:23

Natural convection in a closed domain help!

Hi guys, I am currently trying to simulate natural convection in a closed car cabin being subjected to irradiation.
However, due to the lack of time I have no time to explore the use of the radiation models.
What thermal wall boundary conditions would be best suited for the task?
I am assuming that the heat comes in only from the front and rear windscreens and the rest of the walls are adiabatic.

 Yr0gErG March 23, 2011 04:37

help?

Hi if it helps more, I am trying to get a temperature distribution that makes physical sense in a car cabin model. Model is meshed using tri and quad cell types. Data shows that the front and rear windscreens reach a temperature close to 330-340K on a very hot day, irradiation = 550 W/m^2.
I am currently relying solely on the flow and energy equations to get my results out.
The big problem is that I am unsure where to plug my values into the boundary conditions for the front and rear windscreens, which i have defined as walls.
If i put 550W/m^2 into the heat flux under the Thermal tab, temperature of the cabin space reaches well over 5000K.
And with the other tabs such as temperature and convection i get strange images (like a green space with red spots)

 jsm March 23, 2011 05:32

Hi,

If you know heat flux value in the windscreen then you can directly apply in wall boundary. But solve in the transient solver.

If temperature rise is around 340k, I think you need not to enable the radiation. But I am not sure how much radiation heat will go in to the cabin.

 Yr0gErG March 23, 2011 06:27

Quote:
 Originally Posted by jsm (Post 300679) Hi, If you know heat flux value in the windscreen then you can directly apply in wall boundary. But solve in the transient solver.
By wall boundary do you mean the Heat generation rate + wall thickness parts?
Also, what do you mean by transient solver? Density solver or unsteady state solver? Is the a certain procedure for that? Thanks for replying by the way!

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