Thin wall vs Solid wall in Heat Transfer problem?

Kristofer. · October 1, 2012, 17:27

Hi!

I´m doing a master thesis where I´m 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 doesn´t change at all, the plate is absorbing all the heat.

I´ve 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 isn´t 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 it´s 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, 06:37

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!

October 1, 2012, 17:27	Thin wall vs Solid wall in Heat Transfer problem?	#1
Kristofer. New Member Kristofer Rasmusson Join Date: Sep 2012 Posts: 5 Rep Power: 14	Hi! I´m doing a master thesis where I´m 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 doesn´t change at all, the plate is absorbing all the heat. I´ve 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 isn´t 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 it´s 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

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October 5, 2012, 06:37		#2
Brazil_Lazzarini New Member Kristiano Gomez Join Date: Oct 2012 Posts: 1 Rep Power: 0	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!