# How to combine convection and heat flux BC?

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 December 21, 2023, 10:06 How to combine convection and heat flux BC? #1 New Member   nicolas Claverie Join Date: Sep 2022 Posts: 3 Rep Power: 3 Hello, I want to simulate a solid sphere in open air receiving a constant heat flux. Basically the BC of my sphere should be a combination of air_to_sphere { type externalWallHeatFluxTemperature; mode power; Q uniform 5; // 5 W received on the boundary kappaMethod solidThermo; value uniform 300; } for the constant heat flux, and air_to_sphere { type compressible::turbulentTemperatureRadCoupledMixed; Tnbr T; kappaMethod solidThermo; value uniform 314; } For the convection. Is there a way to do that? One option would be to add a constant radiation flux on the sphere but I never used radiation in a model so I am not very confortable to do that. PS: install information if relevant: Windows 11 pro 22H2 WSL 2.0.9.0 Ubuntu 22.04.3 LTS Openfoam 2306

 December 21, 2023, 13:00 #2 Senior Member   Join Date: Apr 2020 Location: UK Posts: 665 Rep Power: 14 You want to specify both the heat flux and the HTC, without any radiation present? Surely this is over-specifying the boundary condition? And what do you mean by "convection" ... it can't be the usual meaning, i.e. convection to the fluid inside the domain, since you are already specifying the heat flux (which will in turn define the boundary surface temperature) ... and the only way the code could achieve this would be to set both the boundary temperature and the cell temperature, which is not allowed. If you mean "conduction" through the wall, rather than "convection", i.e. set an external surface temperature and a heat transfer coeff thru the wall, then this is over-constrained & impossible to implement. So I am a bit puzzled my friend as to what you are trying to achieve. It doesn't sound physical. Ofc, I may have misunderstood ...

 Tags boundaries condition, convection, heat transfer, openfoam