Thermal management characteristics of a counter-intuitive finned heat sink incorporating detached fins impregnated with a high thermal conductivity-low melting point PCM

Abstract

Current conventional finned PCM heat sinks employ fins that are surrounded by PCM body while being attached to a hot base that receives heat from the source that requires cooling. The fins in this case enhance heat dissipation thus charging and discharging rates from the sink. In the present work, counter intuitively, we propose using a new fins concept wherein the bottom ends of the fins are lifted (i.e. detached) from the hot sink base, instead of being attached to the base. Thereby, the thermal management characteristics of a heat sink filled with solid gallium as a phase change material and integrating vertical plate fins within the gallium with different levels of fin detachment from the base of the sink that receives heat from the hot source are numerically investigated. The rationale behind considering the proposed lifted fins approach is twin-pronged: Firstly, lifting the fin while keeping its total height fixed, gives an additional room for greater PCM quantity to be stored in the sink thereby giving the sink larger capability to absorb latent heat from the hot source. Secondly, it would also imply that the extent of fin protruding out of the sink (given that total fin height is kept constant) would increase. Thus, fins outer surface area would also increase resulting in faster heat dissipation into the ambient. This study aims at shedding light on the benefits of fin lifting over the case of direct fin attachment to the base and the extent to which fin lifting could be beneficial for discharging heat from the sink during operation under high heat flux conditions. The impact of the extent of fin lifting on the buoyancy-driven internal motions within the molten gallium and thus the overall performance of the sink is investigated.