Forced Convection CFD + Heat analysis

[maxedvardsson6198]

Hello!

I´m doing an uncoupled CFD+Heat analysis of a processor and heat sink surrounded by air with prescribed inlet velocity. Processor is generating heat. Pretty straightforward.

I am trying to find the minimum amount of (tetrahedal) elements needed between the fins of the heat sink for the temperature to converge at specific points of the heat sink. The problem is that the finer mesh i do at these points, the higher the temperature becomes.

I´ve used 3 layered Boundary Layer and started out with 2 elements (->100 deg C) and refined to 12 elements (-> 170 deg C). Granted, the velocity at a few points between the fins hasnt completely converged either, but the difference in velocity between the model with 2 elements across and model with 12 elements across is about 10-15%, which isnt near the 70% difference in heat.

(FYI, refining everything else except the confided space between the fins didnt render in any significant temperature change)

My questions are:

Are there any "general rules" for these analyses, concerning amount of elements across in a confided space?

Also, could there be any specific analysis parameters i should give extra attention to, besides mesh-refinement?

Any other idea/thought/input of any kind is very welcome!

/Max