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Constant Heat Flux / Temperatures too high

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Old   February 16, 2006, 14:14
Default Constant Heat Flux / Temperatures too high
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Didio
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Hi all,

I am trying to model the tempertare field in a ventilated space using Fluent and am having difficulty with one of the boundary conditions. I have a heated plate in the middle of my room. If a I specify a constant temperature bc I get a solution that works, but isn't what I'm concerned with. If I specify a constant flux (say 1000W for a 1kW heater) I all of a sudden egt temperaturesin my domain of 5000K, which is obviously ridiculous. Even when I reduce the heat flux to less than 40 W (less than a light bulb) I still get ridiculous answers.

Has anyone else encountered this and if so what can I do?

Diogo
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Old   February 16, 2006, 14:49
Default Re: Constant Heat Flux / Temperatures too high
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vivek
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What are the boundary conditions you apply to the wall of the room. If u say all the walls are adiabatic, then the heat added by the hot plate just stays inside the room and the temperature keeps on increasing until infinity. Try to define a zone where you can apply a mass flow boundary or a constant pressure boundary.This will take care of the heat being carried away by advection.
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Old   February 16, 2006, 21:57
Default Re: Constant Heat Flux / Temperatures too high
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Didio
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No that's not the problem - I have a flow in at low level and out at a high level, which as you said i sprecisely supposed to carry the heat away, but it doesn't do that and temperature doesn't climb to infinity, but some unrealistically high level.

Thanks for the suggestion though
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Old   February 17, 2006, 13:07
Default Re: Constant Heat Flux / Temperatures too high
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Evan Rosenbaum
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Have you compared the heat flux you are trying to apply with the FLUENT-computed heat flux when you apply the constant temperature condition? This might help steer you toward the source of the problem.
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