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Coupled vs Seg - Natural vs. Forced Convection

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Old   July 16, 2007, 08:24
Default Coupled vs Seg - Natural vs. Forced Convection
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Alex
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I am running a simulation to determine the effect of forced convection flow over a hot component.

Initially I am running a sim to match experimental results for the case temperature against CFD CHT results, using coupled solver. Then I intend to apply a forced velocity of air over the part to determine the reduction in case temperature due to this forced convection.

Two questions:

1- Why is there such a large difference in the case temperature for coupled vs. segregated solvers in natural convection (buoyancy-driven flow)?

2- Which solver should I use to compare forced vs. natural convection? For individual models I would use coupled for natural and segregated for forced and assume incompressible flow but I want to keep all parameters the same apart from the air velocity.

Would you recommend sticking to coupled for both and applying the ideal gas law for forced convection?

Thanks.
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Old   July 17, 2007, 04:53
Default Re: Coupled vs Seg - Natural vs. Forced Convection
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PETE
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which star version do you use? Do you really have a large difference for coupled and segregated in case of natural conv.?

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Old   July 17, 2007, 05:19
Default Re: Coupled vs Seg - Natural vs. Forced Convection
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Alex
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STAR-CCM+ 2.08. I adjusted the setup and have managed to get the coupled solver to agree closely with test results for the buoyancy driven flow. Initially the coupled solver was suggesting a few degrees temp increase when segregated was suggesting over 30deg.

Is the coupled solver likely to give good results for forced convection flow?
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Old   October 5, 2007, 00:18
Default Re: Coupled vs Seg - Natural vs. Forced Convection
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chin
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what is the difference between natural and forced convenction? plz post me reply to my mail
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Old   October 5, 2007, 06:37
Default Re: Coupled vs Seg - Natural vs. Forced Convection
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Alex
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Natural = Bouyancy driven due to changes in air density with temperature. Forced = Fan driven.
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Old   December 12, 2007, 05:58
Default Re: Coupled vs Seg - Natural vs. Forced Convection
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sivaraj.c
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what is the difference between natural and forced convenction?
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