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-   -   Radiation CFX 5.5 (http://www.cfd-online.com/Forums/cfx/19522-radiation-cfx-5-5-a.html)

Mate March 18, 2003 08:17

Radiation CFX 5.5
 
Hello

I am working on oven for backing bread. I use P1 radiation method.

I would like to look only surface-to-surface radiation without air radiation. Is this posible with CFX5.5?

What should I take for absorbtion,scattering and reflection coefficient for air.

Could somebody tell me how CFX calculate radiative emission, incident radiation and radiation intensity? Equations pleace.

Thanks.

Jeff Moder March 18, 2003 13:56

Re: Radiation CFX 5.5
 
I am not a CFX user, but if you only want to do surface-to-surface radiation, i would recommend not using the P1 method if you want reasonable accuracy; you can probably get qualitative results for transparent media with P1, but heat flux errors could easily approach 30% or more. The P1 approximation is better suited to participating media with large absorption.

If CFX has a discrete ordinates or discrete transfer method, i would recommend using these, even if you only use a very small number of directions.

Sharks March 18, 2003 19:34

Re: Radiation CFX 5.5
 
I agree with Jeff's comments.

The P1 radiation model is not good for surface-to-surface radiation, but produces reasonably good results when the optical thickness >1 (we've used it with reasonable success for gas combustion problems).

For optically thin media, discrete transfer/ray trace based models are much better. These will be available in CFX-5.6 (available April ?)

Regards,

Sharks

Mate March 21, 2003 02:44

Re: Radiation CFX 5.5
 
Could someone give me useful value for absorbtion,scattering and reflection coefficient for air.


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