heat flux balance problem

zhouziyi7123 · February 15, 2011, 03:27

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, 05:36

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, 06:30

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, 07:10

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, 03:57

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

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！！！

February 15, 2011, 03:27	heat flux balance problem	#1
zhouziyi7123 New Member Zhou Xu Join Date: Feb 2011 Posts: 3 Rep Power: 15	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!

February 15, 2011, 06:30	thanks	#3
zhouziyi7123 New Member Zhou Xu Join Date: Feb 2011 Posts: 3 Rep Power: 15	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.

May 21, 2014, 03:37	cfx radiation_model wall heat flux imbalance	#6
cscfx New Member Join Date: Oct 2013 Posts: 16 Rep Power: 12	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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February 15, 2011, 05:36		#2
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 16	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.

February 15, 2011, 07:10		#4
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 16	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.

February 17, 2011, 03:57		#5
zhouziyi7123 New Member Zhou Xu Join Date: Feb 2011 Posts: 3 Rep Power: 15	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?