how to define two boundary conditions on a surface

abhinavrajan · July 17, 2019, 12:33

how to define heat flux at a surface and heat losses form same surface at the same time in Fluent?

LuckyTran · July 17, 2019, 15:51

What do you mean by heat loss? And why is that not the same as a heat flux? How can you have 2 boundary conditions? You have a boundary condition, and that's it. Please explain...

abhinavrajan · July 17, 2019, 16:14

If I am giving heat input to a curved surface of receiver of solar dish collector, there will be convection and radiation heat transfer from the same surface at same time to ambient.

In this condition, I can not define the mix thermal conditions at surface at which heat flux thermal condition already applied.

how to figure out the heat going to ambient due to convection and radiation from surface which has a heat flux input?

LuckyTran · July 19, 2019, 10:15

You can probably use the mixed thermal condition in fluent and model your solar load as a volumetric heat source.

Give it the htc and free stream temperature for convection. If applicable, give it the emissitivity and radiation temperature for the radiation losses.

Then use the heat generation rate and give your wall a thickness such that you get the desired solar load.

July 17, 2019, 12:33	how to define two boundary conditions on a surface	#1
abhinavrajan New Member Tamil Nadu Join Date: Jun 2019 Location: Chennai Posts: 3 Rep Power: 7	how to define heat flux at a surface and heat losses form same surface at the same time in Fluent?

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July 17, 2019, 15:51		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,762 Rep Power: 66	What do you mean by heat loss? And why is that not the same as a heat flux? How can you have 2 boundary conditions? You have a boundary condition, and that's it. Please explain...

July 17, 2019, 16:14		#3
abhinavrajan New Member Tamil Nadu Join Date: Jun 2019 Location: Chennai Posts: 3 Rep Power: 7	If I am giving heat input to a curved surface of receiver of solar dish collector, there will be convection and radiation heat transfer from the same surface at same time to ambient. In this condition, I can not define the mix thermal conditions at surface at which heat flux thermal condition already applied. how to figure out the heat going to ambient due to convection and radiation from surface which has a heat flux input?

July 19, 2019, 10:15		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,762 Rep Power: 66	You can probably use the mixed thermal condition in fluent and model your solar load as a volumetric heat source. Give it the htc and free stream temperature for convection. If applicable, give it the emissitivity and radiation temperature for the radiation losses. Then use the heat generation rate and give your wall a thickness such that you get the desired solar load.