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Old   June 27, 2003, 03:58
Default Radiation in subdomains
  #1
Micha
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Hi,

I have a geometry with a gaseous stream between two metall plates. The modell includes also conjugate heat transfer. Now, I would like to implement radiation, but only in a part of the area. How to do that?

I tried to define radiation boundaries to seperate the total radiation area, but I realized that I can do this only between two fluid cells. How to seperate the parts of the solids with and without radiation?

Thank you. Micha
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Old   June 27, 2003, 06:04
Default Re: Radiation in subdomains
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Alexey
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You have to patch the all wall boundary in the model, but you may try to impose for part of the boundaries that emessivity and reflectivity are about zero.
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Old   June 27, 2003, 06:41
Default Re: Radiation in subdomains
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Micha
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I tried several things so long, but what I don't manage to do is to seperate the solid area with and without radiation. In the userguide, one can read that you have to create a new cell type for the cells involved in radiation. So I seperated the two solid plates into cells with radiation switched on and one with radiation switched off. But how to define the interface between the two types? I tried wall bound but prostar doesn't accept it bringing up a warning message "user defined boundary (...) not applied". So I tried to define no boundaries between the the two types, but once again a error message occurs saying "cell (...) has radiation turned on but has a wall boundary defaulted to region 0". All the cells mentioned in the error message are cells at the interface. To define the boundary with radiation bound is also not possible, as this type has to be between two liquid cells. So I what to do?

Thanks in advance Micha
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Old   June 27, 2003, 07:02
Default Re: Radiation in subdomains
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Alexey
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You have to create on all boundaries between solid and fluid, boundaries of the conductive wall type and turn on radiation, then you have to patch all boundaries that bound area, where radiation may extend (inlet, outlet and so on), then for boundary where you needn`t radiation you have to set reflectivity and emissivity about zero (at first you have to make two different wall boundaries(with radiation and without))
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Old   June 27, 2003, 09:12
Default Re: Radiation in subdomains
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CJ Tune
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You can have solids of different material types (and thus radiation properties) side-by-side without needing to define any b/c between them. I don't think you can couple different materials so you'll need to make sure the faces match one-to-one (ie. vertices merged) at the interface of the two solids.
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Old   June 27, 2003, 09:47
Default Re: Radiation in subdomains
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Alexey
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radiation is a property of wall bc, rather than matirial...
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Old   June 29, 2003, 23:59
Default Re: Radiation in subdomains
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cjtune
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You can have transparent solids in your model.
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Old   July 18, 2003, 06:52
Default Re: Radiation in subdomains
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Micha
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Thank you very much for your answers. I got the solution now. The problem was, that I tried to switch on radiation in the solid materials. This is not correct. You have to define all boundaries concerning radiation on the FLUID cell faces between two solids which have a radiative heat flow between each other. And you have to switch on radiation for the FLUID CELLS not for the solids.

Micha
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