Numerical study of PCM melting performance in a rectangular container with various longitudinal fin structures

This paper uses the enthalpy -porosity technique to conduct a three-dimensional numerical investigation on the effect of adding longitudinal fins in energy storage units to enhance the melting process, with a specific focus on natural convection. By reducing the extension length of the upper part of the fins and increasing the extension length at the bottom, the work aims to enhance heat transfer while reducing obstruction to convection. The effects of rectangular, trapezoidal, and triangular longitudinal fins with thicknesses of 0.2, 0.25, and 0.3 mm on the melting characteristics were compared while maintaining a constant filling volume of RT42 phase change material (PCM) within the rectangular container. The results indicate that the enhanced heat transfer capacity of fins with different structures increases as the fin length increases. Triangular fins exhibit the most significant heat transfer enhancement effect, with the least hindrance to convection. When the fin thickness is 0.2 mm, the triangular fin decreases the melting completion time by 15.7 %, increases the heat storage rate by 18.7 % compared to the rectangular fin, and exhibits optimal natural convection intensity and temperature distribution in the energy storage unit. Additionally, the maximum flow velocity and average Nusselt number can be increased by 21.2 % and 18.5 %, respectively. It was also found that triangular fins are more suitable for hightemperature working conditions.