Melting of multiple PCMs with different arrangements inside a heat exchanger for energy storage

Abstract

Latent heat storage using Phase Change Materials (PCMs) is an important promising solution for addressing the renewable energy fluctuation problem. The low thermal conductivity of PCMs that substantially contributes to very slow storage and recovery of energy is a major obstacle. This study investigated the performance of multiple PCMs for different arrangements in a horizontally positioned heat exchanger during melting of the PCMs. The results identified the effects of conduction and natural convection heat transfer for different PCM arrangements in the heat exchanger. Numerical simulations were conducted for the defined geometries. The model developed for the study was validated against a published related study. Results in the form of liquid fraction contour and Nusselt number ratio plots are presented and discussed. It was found that the application of multiple arrangement of the PCMs has different effects on the heat transfer mechanisms. Natural convection has a significant positive effect on the heat transfer characteristics of these systems in all the arrangements studied. The parallel arrangement enhances conduction, leading to 40% reduced melting time, when only conduction heat transfer is considered, but it suppresses natural convection, while the series arrangement enhances natural convection heat transfer significantly. Compared to all the arrangements studied, the series arrangement was found to be superior for energy storage. With it, 15.5% reduction in complete melting time was achieved compared to the single PCM arrangement. Natural convection enhancement in this arrangement led to 50% complete melting time reduction, compared to the case of only conduction heat transfer. It was also found that the application of multiple PCMs increases the storage capacity by about 25%.