Reply To: Air Heat Transfer Coefficient – SteadyStateThermal Simulation – ANSYS Mechanical

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I found the chapter about natural convection on that book, and seems that estimation of htc thorugh the formulas of natural convection for an horizontal cylinder works, but only if I model the resistors as simple cylinders... If I use the original and detailed CAD model, the htc estimated in this way is much different from the htc that I must use in order to match the FEA and real temperatures. I think this happens because of the complex geometry, since we have many fins on the real resistor

Now I have 2 other questions: the first is, is it a good idea to define an htc for each surface of the geometry of the real resistor? since there are horizontal, vertical and inclined surfaces, maybe I can find a value for each of them through the formulas... It is a bit boring, but maybe could work, what do you think?

The other question is: I started doing those simple examples (just resistors that heat up and are cooled by natural convection) in order to understand better how to model the air behaviour with the convection boundary condition, inside ANSYS Mechanical. If I have to work on a more sophisticated model, for example a PCB with many components mounted on it, closed by a plastic case, should I have to evaluate again the htc of the air for each component and for each surface (both internal surfaces and external surfaces?)