Radiation modeling
Hello, I have a very basic question on the radiation modeling in fluent.
Suppose I have a solid body, and the surface is defined as convection and radiation BCs. The ambient temperature is fixed. Only heat conduction and radiation are modeled in this case. How can define the radiation BC in fluent? It seems that all models need to include fluid or semitransparent solid region. Thanks, Eric 
You can find your best answer in fluent tutorial . Chapter 5
Modeling radiation and natural convection You could find in: http://my.fit.edu/itresources/manual.../tg/node67.htm 
Hi Eric,
If the surface is on the outside of the domain (a onesided wall) you do not need to model radiation in the solver. You only need to consider the conduction. the radiation models in the solver is for use when the heat is radiated inside the solution domain. hope this helps. 
HP Kritzinger,
Yes, the surface is on the outside of the domain. The surfice is exposed to ambient with temperature much lower than the surface temperature. I believe the radiation is equivalent to nature convection based on my calculation. I want to include the radiation in the modeling. But I cannot find any way to do that in Fluent. Like what you said, the models in the solver are for use when the heat radiation is happened inside the domain, instead of the domain surface and ambient. thanks anyway for your help! If the surface is on the outside of the domain (a onesided wall) you do not need to model radiation in the solver. You only need to consider the conduction. the radiation models in the solver is for use when the heat is radiated inside the solution domain. hope this helps.[/QUOTE] 
Mehr,
Thanks a lot. I was aware of the tutorial (Chapter 5). But it seems that all models are only used inside the domain, instead of the surfice (and ambient). THanks, Qihong Quote:

If I understand correctly, all you need is to change the wall to a mixed type in the GUI panel. On the wall boundary conditions window, under the Thermal tab, Select "Mixed" under Thermal Conditions. This gives you the option to specify both radiation and convection on a exterior surface.
regards 
Mystic_cfd,
Thanks a lot! I tried it before but it seems that the radiation flux will be zero when I do the postprocessing. Should I turn on any radiation model in the solver? Thanks, Eric Quote:

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