LONGITUDINAL FINNED HEAT SINKS WITH UNHEATED AND HEATED SHROUDS IN BUOYANCY INDUCED CONVECTION

摘要

This paper reports the effects of the presence of unheated and heated shrouds on the thermal performance of longitudinal finned heat sinks. Experimental studies and numerical modeling were conducted to determine the impact of the shroud clearance and shroud heating. The first part of the study deals with the effects of an unheated shroud on finned heat sinks of different fin height (H), fin pitch (p) and length (L), where 12.7 mm < H < 50.8mm, 6.8mm < p < 35mm, 82.6mm < L < 152.4mm. The experimental and numerical results reveal an optimum clearance for maximum heat transfer. For example, an improvement of 5% in the heat transfer performance was noted for H = 50.8mm, p = 17.6mm and L = 152.4mm, until the clearance ratio, c/H was reduced from 3 to 0.25. For clearance ratios, c/H < 0.25, the heat transfer performance decreased by as much as 10%. For different shroud heating levels, φ, defined as the ratio of excess shroud temperature to the excess heat sink temperature over ambient, it is seen that heating of the shroud does not impact the thermal performance of the heat sink as long as the clearance ratio c/H > 0.25. Below c/H = 0.25 the heat transfer performance degrades with increase in φ.