Gerald W. Recktenwald
Presented at the 1995 ASME International Mechanical Engineering Congress and Exhibition, 12-17 November 1995, San Francisco, CA.
Appears in Cooling and Thermal Design of Electronic Systems American Society of Mechanical Engineers, HTD-Vol. 313, EEP-Vol. 15, C. Amon (ed.), pp. 129-136.
Convective heat transfer from electronic devices mounted on a printed circuit board is simulated with an efficient Computational Fluid Dynamics (CFD) model. The computer time necessary to calculate a solution to the flow field is greatly reduced by solving the depth-averaged (DA) flow equations for the fluid flowing above the devices. The DA flow field is then coupled to the full, three-dimensional energy equation in the fluid and in the solid materials comprising the circuit board and the electronic devices. Because the temperature is determined by solving the conjugate problem, no heat transfer coefficient needs to be specified on the outer surface of the devices. This paper provides an overview of the theory behind the depth-averaged and three-dimensional energy equation models. Incorporation of the essentially two-dimensional depth-averaged flow fields in the three-dimensional energy equation is described. The combination of the DA flow field and the three-dimensional energy equation does not yield the same level of detail as a conventional three-dimensional CFD code. The advantage of this approach, however, is that it makes significantly lower demands on the computational hardware and it obtains useful solutions in much less time than conventional CFD codes.
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