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-   -   heat flux balance problem (http://www.cfd-online.com/Forums/fluent/85005-heat-flux-balance-problem.html)

zhouziyi7123 February 15, 2011 04:27

heat flux balance problem
 
Hello,

I want to simulate the heat transfer through a window placed between indoor and outdoor environmental conditions. After several failures, I reduce my model to just a rectangular that represents the window glass.

I define constant temperature walls for the two glass surfaces, and the top and bottom walls are adiabatic. But the heat transfer through the two surfaces are still not in balance, e.g., -116 W for the hot surface and 150 W for the cold surface.

I searched through the forum. Actually people had posted similar questions before, but no one had ever replied. Please help!

alastormoody11 February 15, 2011 06:36

chk this link: http://www.philonnet.gr/downloads/an...s_tutorial.pdf

It shows procedure to solve ur problem.

Also if all you are solving is conduction in the glass by giving BCs across the two surface I hardly see the need to use FLUENT for the simulation.

zhouziyi7123 February 15, 2011 07:30

thanks
 
Eventually I want to simulate double glazing with frame and spacer, so there will be convection and radiation in the glazing and frame cavities.

I've read the link document. I don't see how it solves my problem. It doesn't mention the inconsistency of the heat flux through the two surfaces.

alastormoody11 February 15, 2011 08:10

Note the convergence criterion:
convergence criterion of 1.0e-10

U never mentioned what was your criterion for convergence.

Also try with finer grids.

Also note the following remark:
Difficulty in obtaining convergence or poor accuracy may result if input values are used outside the upper and lower limits suggested in the problem overview.

zhouziyi7123 February 17, 2011 04:57

After 14500 interations, the energy residual remains stable around 1e-7, and the continuity residual is 1e-5. The heat balance is almost achieved.

What do you think of the residuals? Should I run more interations? or change the pressure or momentum to second order?

cscfx May 21, 2014 03:37

cfx radiation_model wall heat flux imbalance
 
when i use three plate (between the plate, there is air.) to calculate radiation between the plate,the left plate is high temperature plate,the right plate is low temperature ,i find that wall heat flux is imbalance in different surface,that is, the wall heat flux in the left plate ,the media plate and the right plate don't agree to each other
and the radiation model is DT(Surface to Surface).
anyone can give me a help? thx!!!


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