One of the common applications in electronic packaging is a heat sink inside an air cooled natural convection enclosure with inlet and outlet vents. This problem of predicting heat sink performance is not fully addressed in the literature. In the present study an unmerical investigation of free convection heat transfer is initated inside an electronic module with a flat plate heat sink to determine the effects of enclosure effect on the thermal performance of the flat plate heat sink. The cooling performance of the flat plate heat sink in free convection is numerically investigated from a practical point of view by Flotherm CFD software. The numerical study was conducted in the range of Rayleigh number between 10~2 and 10~5 and Prandtl number of 0.71. Finally, an empirical model for the Nusselt number as a function of the Rayleigh number is developed based on the numerical results. The empirical correlation for the Nusselt number includes the effect of the heat sink geometry (number of fins, fin height, fin pitch, and heat sink length). The present model and numerical results are compared to existing empirical models existing in the literature.
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