Temperature Dependent Convective BC for Conduction

General discussion about Elmer
Rich_B
Posts: 421
Joined: 24 Aug 2009, 20:18

Re: Temperature Dependent Convective BC for Conduction

Post by Rich_B »

Hello,

Thanks for explaining the plate in an oven scenario, that makes sense. Is the air in the oven being heated due to a heating element in the bottom of the oven? One possibility is something like a home cooking oven, with a bottom electric heating element in a closed cavity without a fan. Another possibility is an industrial batch heating oven, with heated air being circulated with a fan.

If it is a home cooking oven situation, is radiation from the bottom electric heating element a factor for you?

Just curious, it helps to know what physical arrangement is being investigated.

Rich.
Rich_B
Posts: 421
Joined: 24 Aug 2009, 20:18

Re: Temperature Dependent Convective BC for Conduction

Post by Rich_B »

Hello again,

Take a look at a similar forum post, it may be helpful for you:

viewtopic.php?t=7865

Rich.
Coffer_001
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Joined: 04 Apr 2012, 23:17
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

Thanks for sharing the code!
Coffer_001
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

My model is related to an industrial oven. There isn't a radiative component to it. Its all conduction with a convective BC.

Thank you for the reference to the Mcguirre post. That post moves around a bit but in the end it appears to be a computed convection problem involving an N-S solver. I'm just need to use a simple convective BC. No CFD is involved with this approach.

Thanks!
kevinarden
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Re: Temperature Dependent Convective BC for Conduction

Post by kevinarden »

One approach to consider is to include the gas around the plate in the model, still using heat equation only. The external boundary temperature can then be a variable of time and the heat conduction material property of the gas can be a variable of time.
Attached is a study
Results.pdf
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Coffer_001
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

That's an interesting work around. I need to think about that more.Seems like one would want to make the hypothetical gas very dense and with a very high specific heat. So far I evolve your idea into tricking it by adding another layer of a solid that has properties of hc and T infinity rather than going to a fluid. I'm having a LITTLE better luck with solids.

Here's a wild one for your consideration.Without delving into the internals of Elmer: What about calculating heat flux for each time step from hc (Tsolid-Tinfinity). The hc and Tinfinity would be given in tables in the sif or external files and Ts would be pulled from the model for a previous time step. That calculated heat flux would be a BC for the current time step. I wondered if that is what the Manual was suggesting?

I appreciate your help. Your efforts are greatly appreciated!
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