Comparison of different approaches for thermal performance improvement of a phase change energy storage system

Performance improvement of a phase change material (PCM) thermal storage system is numerically investigated. A finite volume solver is employed to simulate the melting process of the PCM in different geometrical and boundary conditions. The numerical predictions are initially validated against available experimental data. Afterward, four different scenarios are investigated to improve the thermal characteristics of the phase change process. These scenarios include insertion of radial fins with different radial lengths, insertion of a porous layer on the PCM side of the heat transfer fluid (HTF) tube, doubling the HTF mass flow rate, and also increasing the HTF inlet temperature. The results indicate that all of these scenarios expedite the melting process, but at different rates. The insertion of the porous medium is shown to be more effective than using of radial fins. Moreover, according to the second-law analysis of the thermal storage system, using the porous layer provides a superior exergy efficiency compared to other enhancement scenarios. Overall, the addition of a metallic porous layer around the HTF tube is proven to be the most effective as well as the most efficient approach to improve the thermal characteristics of the energy storage system.