Experimental and numerical investigation of the melting behavior of a phase change material in a horizontal latent heat accumulator with longitudinal and annular fins

Thermal energy storage technology using phase change materials (PCMs) is applied as a novel approach to the conversion and management of intermittent and unstable energy. However, the performance of thermal storage is significantly affected by the poor heat conduction of PCMs. In this study, in order to improve the thermal performance of the latent heat thermal energy storage (LHTES), the melting process of the PCM with annular and longitudinal fins was investigated numerically and experimentally. In order to carry out a proper investigation, the tests were performed under the same temperature conditions. In addition, the volumes of the annular and longitudinal fins and the total theoretical energy stored in the PCM are almost the same. From the results, it can be seen that the heat exchanger (HX) with longitudinal fin performs better compared to the longitudinal fin in the PCM melting process. Compared to the HX with annular fins, the PCM melted almost 17 % earlier in the HX with longitudinal fins in the experimental mode. In the simulation mode with longitudinal fins, it also performed almost 13 % better than with the annular fins. The contours of the liquid fraction from the numerical simulation showed that in horizontal LHTES with longitudinal and annular fins, the entire volume of PCM inside the HX shell was completely melted after 180 and 215 min, respectively. Considering the results, it can be stated that an energy storage system utilizing a shell-and-tube heat exchanger with longitudinal fins can serve as a solution for unstable systems, such as solar energy systems.