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-   -   Coupled vs Seg - Natural vs. Forced Convection (https://www.cfd-online.com/Forums/siemens/56187-coupled-vs-seg-natural-vs-forced-convection.html)

 Alex July 16, 2007 08:24

Coupled vs Seg - Natural vs. Forced Convection

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.

 PETE July 17, 2007 04:53

Re: Coupled vs Seg - Natural vs. Forced Convection

which star version do you use? Do you really have a large difference for coupled and segregated in case of natural conv.?

 Alex July 17, 2007 05:19

Re: Coupled vs Seg - Natural vs. Forced Convection

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?

 chin October 5, 2007 00:18

Re: Coupled vs Seg - Natural vs. Forced Convection

what is the difference between natural and forced convenction? plz post me reply to my mail

 Alex October 5, 2007 06:37

Re: Coupled vs Seg - Natural vs. Forced Convection

Natural = Bouyancy driven due to changes in air density with temperature. Forced = Fan driven.

 sivaraj.c December 12, 2007 05:58

Re: Coupled vs Seg - Natural vs. Forced Convection

what is the difference between natural and forced convenction?

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