An experimental and numerical investigation of constrained melting heat transfer of a phase change material in a circumferentially finned spherical capsule for thermal energy storage

Constrained melting heat transfer of a phase change material (PCM) in a circumferentially finned spherical capsule was studied with application to latent heat thermal energy storage (TES). Attention was paid primarily to revealing the influence of fin height on melting heat transfer and TES performance of the PCM system. Visualized experiments were performed to observe the liquid-solid interface evolutions during melting, and to validate the numerical simulations that were conducted based on the enthalpy method. By means of measuring the instantaneous volume expansion upon melting, an indirect experimental method was proposed and implemented to acquire quantitatively the variations of melt fraction and heat transfer rate. Good consistency was observed between the experimental and numerical results. A combination of the two was able to offer an in-depth understanding on the fin effects by providing detailed knowledge on the interface evolutions and natural convective flow and heat transfer as well. It was shown that the TES performance is enhanced with increasing the fin height, and that the melting duration time is shortened up to nearly 30% at the highest fin height studied. The enhancement was attributed to the combined positive effects due to the presence of the fin, which are enhanced heat conduction by the extended heat transfer area and local natural convection induced in the vicinity of the fin. (C) 2016 Elsevier Ltd. All rights reserved.