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"wall to ambient" vs "wall" for radiation

Question asked by Khashayar Ebrahimi on Oct 4, 2019
Latest reply on Jan 13, 2020 by Joon Kim

Hello, I have a question regarding Solidworks flow simulation radiation simulation. I have an anodized plate-fin heatsink; the dimensions are 70*70*60 mm with ten fins (vertical) (the 60 mm is the heigh of the fins). I am doing natural convection analysis + radiation. I set up a simulation in Solidworks flow simulation and defined the anodized surfaces under user-defined. In the item properties, I identified the emissivity and solar absorptance factors. However, I am not sure how to pick the radiative surface types. There are two options: "Wall to ambient," and "wall." I am not sure which one is the appropriate one. For example, if I apply "wall to ambient", will it see the fins interactions on each other? or it assumes it is a gray body radiating energy to the ambient. If I pick "wall", it seems the model assumes part of radiated energy return back, and it increases heatsink temperature? Can someone provide insight into what is the best option between "wall to ambient," and "wall" options for natural convection/radiation from a heatsink?