How natural convection affect cooling performance of PCM heat sink

Abstract

Phase change materials (PCMs) present great potential in extending the safe working time of electronic components that work intermittently or in an adiabatic cavity. Therefore, a clear understanding of the quantified contribution of natural convection and heat conduction in the cooling performance of PCM heat sink is essential to prolong the safe working time. In this paper, the quantified contribution of natural convection (η) was experimentally investigated by changing the heating position (bottom heat and top heating). Moreover, the effects of heat flux (q) and physical parameters were discussed on the average temperature during the overall fluctuation stage (Taf), the η, safe working time, etc. The results proved that the dominant factor for the overall melting process of paraffin gradually changed from heat conduction to natural convection when the temperature fluctuation stage appeared. Specifically, the cooling performance of the PCM heat sink at q=1.24∼3.11 W·cm−2 could be improved by natural convection for 50%∼58.7%, which depended on the Taf. Moreover, correlations consisted of the maximum allowable temperature, the liquidus temperature, and the heat flux were obtained to predict the η of paraffin in the range of q=1.24∼3.73 W·cm−2. It also presented an acceptable error (17%) in predicting the η of other organic PCMs. It should be noted that some synergistic enhancement technologies for heat conduction and natural convection should be developed in future works to prolong the safe working time of electronic components with high heat flux and low allowable temperature.