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-   -   Thin wall vs Solid wall in Heat Transfer problem? (http://www.cfd-online.com/Forums/fluent/107576-thin-wall-vs-solid-wall-heat-transfer-problem.html)

 Kristofer. October 1, 2012 16:27

Thin wall vs Solid wall in Heat Transfer problem?

Hi!

Iīm doing a master thesis where Iīm simulating the following simple case (it will be more complicated later on, when I get this case to work properly):

-A small (50x50x50mm) hollow box
-5 mm above that a sun-protecting thin plate
-surrounding (and inside the box) fluid is air (v=0.5 m/s)
-and I've applied the solar ray tracing.

The most important output is the temperature on and inside the box, which right now as I simulate doesnīt change at all, the plate is absorbing all the heat.

Iīve done many tutorials on heat transfer (natural convection, different radiation models etc.) but I still have some questions:

-Should I do the geometry on the plate (and the box) as a thin wall or should I mesh like the real geometry? Big differences on computational efforts?

-Why isnīt the temperature on the box changing at all? The heat from the plate should have some impact on the box, even if it is opaque?

-The energy-residual goes down the first 100-200 iterations but itīs constant after that (10e-05 to 10e-06 depending on different things), and as long as I continue calculation the plate gets hotter and hotter, any advice on finding equilibrium with the solar ray tracing? Maybe I should do calculations overnight?

If you could help me with any of these questions, I owe you a beer! :)

Kris

 Brazil_Lazzarini October 5, 2012 05:37

are u using solar ray tracing or DO-irradiation? I think it depends. If you have thin wall you should activate the shell conduction. This is what i found out when i tried to simulate automobile-sun-heating but then i gave up because it seemed impossible. would also appreciate som help with the solar load model!

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