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-   -   heat extraction (http://www.cfd-online.com/Forums/phoenics/51511-heat-extraction.html)

M. Pijnenborg November 14, 2002 08:28

heat extraction
 
Hi folks,

I would like to implement a negative heat flux into my model. So far I have done several test with a blockage domain fluid and a plate. For both cases negative and positive heat fluxes are tested, none of the cases showed any effects. I am using the Extended Simple Chemical Reacting System (7-gas model), this might influences the heat fluxes.

Anybody any suggestions???

Thanks,

Marc

herve November 15, 2002 09:00

Re: heat extraction
 
hi,

First of all, try to isolate more closely the potential problem. The 7-gas issue is likely to be irrelevant

Therefore, I would recommend your to test your "negative heat flux" on a case with a constant-property-fluid material (air at 20C for instance), on a geometry that you should keep as simple as possible (2D typically).

If the problem persues, then you'll be in a position of identyfing more precisely what goes wrong.

Yours,

H.

leonmills November 17, 2002 21:51

Re: heat extraction
 
Marc,

I use Pv3.4 with bloackages in the domain with a positive heat flux alot.

A few things that I use when toble shooting.

Check if the heat flux is set as per unit volume or by 'abosulte value' - tag in the vr editor setting (I think these are the words).

Try setting the heat flux to some mucher larger - 10 to 100 time what you are looking at. It may juct be that at the heat flux levels you are talking about are too small to have a significant impact on the model.

Hope this helps.

Leon


Mark Russell November 18, 2002 07:06

Re: heat extraction
 
Completely concur with the above posts.

To gain confidence with Phoenics, and indeed any CFD, test the configuration in stages. Set up a simplified case that allows you to see if you have implemented the conditions correctly. In addition to the '2d' and 'large value' suggestions you could also try to solve a diffusion only problem - that way you should be able to see the heat being drawn into the heat sink from the rest of the material. It might be, as implied, that the value of heat sink is so small that convection effects are dominating and that you simply cant see it.

Hoping that this helps and that 'grandmother and eggs' doesn't spring to mind.

Mark Russell


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