How define absorptivity in CFX?

P.Azari · April 24, 2016, 03:27

Hello to everybody
I want to modeling a flat plate solar collector with Ansys CFX.
I have a problem to define absorptivity of absorber plate
the absorptivity of absorber plate is 0.96 and emissivity is 0.07

thanks

P.Azari · May 2, 2016, 00:42

Please answer me.

ghorrocks · May 2, 2016, 01:18

Have a look at material properties and the radiation model settings, especially for wall boundary conditions. This is all discussed in the documentation.

Opaque · May 2, 2016, 09:13

Unfortunately, ANSYS CFX does not support your model directly.

ANSYS CFX radiation wall boundary condition assumes the wall is "gray", or it has a full spectral variation.

Your model has already been reduced from spectral to a non-spectral/nor gray form. Please note your model does not satisfy Kirchoff's law since absorptivity != emissivity any longer.

If you have the spectral information, you should run a spectral model in ANSYS CFX.

Hope the above helps,

P.Azari · May 7, 2016, 00:50

Thank you dear Opaque and dear ghorrocks

April 24, 2016, 03:27	How define absorptivity in CFX?	#1
P.Azari New Member Peyman Join Date: Apr 2016 Posts: 3 Rep Power: 10	Hello to everybody I want to modeling a flat plate solar collector with Ansys CFX. I have a problem to define absorptivity of absorber plate the absorptivity of absorber plate is 0.96 and emissivity is 0.07 thanks

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May 2, 2016, 00:42		#2
P.Azari New Member Peyman Join Date: Apr 2016 Posts: 3 Rep Power: 10	Please answer me.

May 2, 2016, 01:18		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Have a look at material properties and the radiation model settings, especially for wall boundary conditions. This is all discussed in the documentation.

May 2, 2016, 09:13		#4
Opaque Senior Member Join Date: Jun 2009 Posts: 1,804 Rep Power: 32	Unfortunately, ANSYS CFX does not support your model directly. ANSYS CFX radiation wall boundary condition assumes the wall is "gray", or it has a full spectral variation. Your model has already been reduced from spectral to a non-spectral/nor gray form. Please note your model does not satisfy Kirchoff's law since absorptivity != emissivity any longer. If you have the spectral information, you should run a spectral model in ANSYS CFX. Hope the above helps,

May 7, 2016, 00:50		#5
P.Azari New Member Peyman Join Date: Apr 2016 Posts: 3 Rep Power: 10	Thank you dear Opaque and dear ghorrocks