Transient phase change heat transfer in a metal foam-phase change material heatsink subject to a pulse heat flux

摘要

In the present study, the effect of using a layer of metal foam in a composite metal foam - phase change heatsink is addressed. The bottom of the heatsink is subjected to a pulse heat flux, while the top of the heatsink is exposed to an external cooling convective flow. The melting/solidification of the Phase Change Materials (PCMs) is modeled using the enthalpy porosity approach. The partial differential equations governing the natural con-vective flow and the heat transfer in the clear flow region and porous layers of the heatsink are introduced and transformed into a non-dimensional form using non-dimensional variables. The Finite Element Method (FEM) with an automatic time-step and grid adaptation is employed to solve the governing equations. The model and the numerical code are validated by comparison to several results obtained in recent works available in the literature. The effect of the surrounding heat transfer by convection and the fusion temperature of the PCM on the heatsink performance and on the phase change behavior is investigated. The results show that melting heat transfer occurs during the activation of the pulse heat flux while the solidification commences with a small delay after the pulse heat flux turns off. The heatsink presents a major benefit when the external cooling power is weak. Moreover, a heatsink with a lower fusion temperature shows a better cooling efficiency. The presence of a metal foam layer notably improves the cooling efficiency of the heatsink. However, the location of the porous layer shows a minimal effect on the heatsink efficiency.