Melting/solidification of phase change material in a multi-tube heat exchanger in the presence of metal foam: effect of the geometrical configuration of tubes

Abstract

One of the likely methods for enhancing heat transfer in a latent thermal energy storage system is the conception of a thermal unit. In this study, the orientation of oval tubes (horizontal, vertical, and oblique) in phase change material (PCM, C19-C20)-based shell-tube heat exchanger was analyzed with respect to the metal foam (MF) type (graphite, copper, and nickel) in comparison to the case of pure PCM. For this purpose, a two-dimensional mathematical model was developed to investigate the thermal efficiency of the PCM-metal foam based composite energy storage unit. It was concluded that the orientation of the oval tubes (oblique, horizontal, and vertical) has a negligible impact on the performance of the thermal unit during the melting/solidification processes. Based on the liquid/solid fraction, total enthalpy and the average temperature in the annular space, the performance of a heat exchanger during fusion/solidification periods is in the order: copper-MF > graphite-MF > nickel-MF > pure PCM. Whatever the adopted MF or the geometry of tubes, the melting process is expedited compared to the solidification mechanism.