Thermal characteristics of metal foams proportion on heat transfer enhancement in the melting and solidification process of phase change materials

Abstract

The melting/solidification of PCM “phase change material” (C19-C20) and cooling/heating of air (HTF “heat transfer fluid”) have been analyzed under the variation of temperature, by an increment of 2 K, on the external side of the heat exchanger (Tw ). Aluminum foam (20%, v/v) was used to improve the thermal conductivity of the adopted PCM (C19-C20). Eight cases were investigated during the melting (Tw : from 310 to 324 K) and solidification (Tw : from 284 to 298 K) periods of PCM (C19-C20). It has been shown that the melting/freezing processes of PCM were enhanced by increasing (from 310 to 324 K)/decreasing (from 298 to 284 K) the temperature on the external side of the heat exchanger. On the other side, the cooling/heating mechanisms of air were found to be less dependent on the temperature of the external side of the thermal unit. Additionally, it was observed that the decreasing/increasing of air (HTF) temperature were more rapid than the fusion/freezing processes of PCM. Based on the mass fraction profiles of the liquid PCM, it was retrieved that the fusion and solidification mechanisms proceeded in a quasi-homogeneous way as the melting or freezing of PCM were observed to take place gradually all around the center of the heat exchanger. Compared to the fusion process of PCM, its freezing regime was observed to be slower.