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CFX does not solve heat transfer at fluid-solid interfaces

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Old   April 5, 2015, 16:04
Default CFX does not solve heat transfer at fluid-solid interfaces
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Hi everyone,


I’m simulating natural convection of air between two parallel solid plates. The plates are tilted of 45° with the horizontal. The dimensions of the plates are about 1 m per 1.5 m and the air gap is about 1.5 cm. All domains are specified as thermal energy model and I set the interfaces between the solids and the fluid as “conservative interface heat flux”. The variables all converge in the final solution, then I have the following problem: The fluid dynamics seems to be good but the heat transfer is unreal. The wall convective heat transfer is much smaller than the expected value, near to zero, as the wall convective heat transfer also is near to zero. The heat transfer that I obtained is almost totally equal to the Wall Radiative Heat Flux. The strange fact is that, trying to make a diagnostic, I deleted the solid domains of the two flat plates and simulated only the air between them, keeping all configurations except the interfaces that I substituted for boundary conditions of fixed temperature, equal to the average temperature that I firstly obtained in each interface with the parallel plates. When I make this test the heat transfer calculations seemed to be very near to the expected, with Wall Convective Heat Transfer about 100 times higher than the value obtained when I simulated all the geometries.
Does anyone have an idea of what may be happening and what would be the solution to this problem? The size of the mesh in both sides of the interfaces are the same order of magnitude.


Thanks in advance!
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Old   April 6, 2015, 20:28
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Glenn Horrocks
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Have you checked your imbalances? Your simulation may not have converged adequately. This is a common problem with CHT simulations.
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Old   April 7, 2015, 01:08
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Sounds to me like you didn't check the box "heat transfer" in the interface specification on the tree.
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cht coupling, fluid-solid coupling, heat transfer coefficeint, natural convectin

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