Hello,
I am working on natural convection and radiation heat transfer problem.
Since my domain contains solid objects with finite thickness surrounded by fluid, I have to solve conduction in the solid and convection in fluid. At the interface between the solid-fluid, 'coupled' boundary condition is used.
For radiation, I am using S2S model. From Fluent theory guide, I understood that radiation is modeled as a source term in Energy equation.
I have the following queries in this context:
1. Whether the source term to account radiation is applied in the energy equation for the fluid region only? Or is it applied in the solid region also? Or a single energy equation is solved for solid and fluid domains?
2. At the solid-fluid interface, how the 'coupled wall' boundary condition is treated? Is it the heat flux balance between conduction, convection and radiation?
At the interface, is it correct to write:
(i) [k(delT/del n)]solid=[k(delT/del n)]fluid+q_radiation
and
(ii) Tsolid=Tfluid
Thanks in advance!
vidyadhar
Please have a eye on this.
http://jullio.pe.kr/fluent6.1/help/html/ug/node497.htm
Dear Vidyadhar Karlapalem
As we know, the energy exchange between two surfaces depends in part on their size, separation distance, and orientation. These parameters are accounted for by a geometric function called a “view factor”.
The surface-to-surface (S2S) radiation model can be used to account for the radiation exchange in an enclosure of gray-diffuse surfaces.
The S2S model assumes that all surfaces are gray and diffuse. Thus, according to the gray-body model, if a certain amount of radiation is incident on a surface, then a fraction is reflected, a fraction is absorbed, and a fraction is transmitted. The main assumption of the S2S model is that any absorption, emission, or scattering of radiation by the medium can be ignored. Therefore, only “surface-to-surface” radiation is considered for analysis.
It should be noted that for most applications, the surfaces in question are opaque to thermal radiation (in the infrared spectrum), so the surfaces can be considered opaque. For gray, diffuse, and opaque surfaces it is valid to assume that the emissivity is equal to the absorptivity and that reflectivity is equal to 1 minus the emissivity.
When the S2S model is used, you also have the option to define a “partial enclosure”. This option allows you to disable the view factor calculation for walls with negligible emission/absorption or walls that have uniform temperature. The main advantage of this option is to speed up the view factor calculation and the radiosity calculation.
Hope you find the description helpful sir.
Good luck.
Dear vidyadhar sir, as you select S2S Model, you can applied it to surface only( means solid domain). Generally radiation is a surface phenomenon and it occurs at the surface only, so we need not to apply it for fluid body. At the time of S2S applied, as the BEZAATPOUR Said we need to calculate view factors, it can be done by selecting the Options-Write data/read data and save the file in appropriate folder, and give the heat flux and emission data.
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