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Inconsistent heat flux

Posted Jan 2, 2019, 2:47 p.m. EST Heat Transfer, Results & Visualization Version 5.3a 2 Replies

Rocco Coppejans
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Hi,

I am new to COMSOL and am having trouble with inconsistent heat flux results.

I made a simple model consisting of three blocks. Blocks 2 and 3 are completely enclosed inside block 1. Blocks 2 and 3 are copper while block 1 is stainless steel. I specified that block 2 is a heat source with a heat rate (p_0 = 10W) of 10W. Block 3 is at a constant temperature of 200K.

I measure the heat flux through block 3 by selecting all six of its surfaces and doing a surface integral over nxht.dfluxx + nyht.dfluxy + nz*ht.dfluxz.

When I run the simulation I would expect that the heat from block 2 heats up all of the material in block 1, increasing the temperature difference between block 1 and 3 until 10W flows into block 3. In other words, I expect that the heat added to the system by block 2 will be removed from the system by block 3.

However, when I run the simulation I find that only ~3.6W leaves the system via block 3.

Best Wishes Rocco

2 Replies Last Post Jan 10, 2019, 10:53 a.m. EST
Jeff Hiller COMSOL Employee

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Posted: 6 years ago Jan 3, 2019, 1:32 p.m. EST

Hello Rocco,

This Knowledge Base entry may help.

Jeff

PS: Note that if the temperature is fixed at 200K in domain 3, you should remove domain 3 from your geometry.

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Jeff Hiller
Hello Rocco, This [Knowledge Base entry](https://www.comsol.com/support/knowledgebase/973/) may help. Jeff PS: Note that if the temperature is fixed at 200K in domain 3, you should remove domain 3 from your geometry.
Rocco Coppejans
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Posted: 6 years ago Jan 10, 2019, 10:53 a.m. EST

Hi Jeff

Thank you very much for the help.

My mistake was that the fixed temperature boundary condition was completely contained inside my geometry.

Rocco

Hi Jeff Thank you very much for the help. My mistake was that the fixed temperature boundary condition was completely contained inside my geometry. Rocco

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