A heat sink integrating fins within high thermal conductivity phase change material to cool high heat-flux heat sources

Abstract

Removing heat from heat generating sources at a high heat flux is a serious challenge in many industries, e.g., high power electronics. Towards this end, this numerical study demonstrates the performance of a new heat sink design that integrates high conductivity fins within high thermal conductivity phase change materials (PCM) i.e., Gallium (Ga) metal. The bases of the fins are attached to the bottom heat sink base that receives heat directly from the hot source that requires cooling whereas the upper parts of the fin are exposed to the ambient. Two heat flux levels from the heat source are considered i.e., 3 and 10 W/cm2. A major novelty aspect of this work is rooted in the way fins are installed in the heatsink such that they facilitate creating temperature imbalance between different regions of the molten PCM hence inducing effective natural circulations that lead to clear enhancement in heat removal from the hot sink base. As such, our proposed fins are not merely a way to enhance thermal conductivity of used PCM. In addition to this, they have by far more reaching implications by forming a second heat escape path from the hot base to the outer surroundings, in addition to direct heat transfer from the hot sink base into molten PCM and subsequently to the solid PCM above it. The upper fins parts exposed to the cool ambient surroundings play a crucial role in respect to the above by sucking heat from bottom hotter fin parts. The aforementioned buoyancy-driven circulating motions augmented by induced temperature imbalance caused by the fins smooth out temperature gradients and alleviate peak temperatures at the sink base. The levels of temperatures attained in the presence of the fins were found to be much lower than cases with no fins. The effectiveness of buoyancy was quantified by performing simulations with and without buoyancy effects. The role played by the fins becomes so decisive in limiting peak temperatures especially under the higher heat flux levels.