[Alczem]

Hey everyone!


I am looking into setting up a CHT case with radiation using the fvDOM model. The geometry includes two fluid regions separated by a thin transparent wall (glass).


Is there any way I could allow the incident radiation G to get through the thin wall instead of being absorbed on one side of the wall and then emitted diffusively on the other side?


I tried to set the boudaryRadiationProperties to transparent for both regions but there is a clear difference in the G field at the thin wall. Maybe the transparent condition is used only for external walls? I would be grateful for any help


Thanks!

[dlahaye]

Not sure.

From https://www.openfoam.com/documentati...8H_source.html I deduce that wall emissivity and wall reflectivity are not set automatically to values that leave G unaffected.

[Alczem]

I agree, and the few tests I ran led me to think that even if the global heatflux is correct, the radiation is fully diffusive after it goes through the internal walls even if they are set to transparent, so no specular radiation. Hopefully it gets implemented in future releases or someone finds a workaround, I find transparent internal walls reoccuring in CHT cases.


Thanks for your answer

[dlahaye]

I would like to gain a better understanding of what you are wishing for.

Would you be able to elaborate?

Your case is loosely related to our work on conjugate heat transfer in furnaces. Thanks.

[Alczem]

Sure! Here is a very basic drawing of my case (arc lamp). I would like to account for the thickness of the glass bulb since it will be heating up too, but also let the heat radiate through it (assuming that the glass is almost perfectly transparent, the absorption coefficient is almost zero and the emitted radiation is mostly specular). The glass would be heated only through conduction with the fluid at the boundaries.



The tests I ran used the compressible::turbulentTemperatureRadCoupledMixed at the glass boundaries between the two fluid regions and transparent but G is not allowed to propagate freely if that makes sense (see second pictures).


Hopefully it is more understandable