The influence of elliptic aspect ratio and inclination angle on the melting characteristic of phase change material in concentric cylindrical enclosure

Thermal energy storage using phase change material plays a major role to solve the mismatch between energy demand and supply. In this study, the effect of the inner elliptic tube aspect ratio of a double-pipe latent heat thermal storage unit and its inclination angle is numerically and experimentally investigated. The 3D numerical model is developed using ANSYS FLUENT 17.2 and the finite volume method with the enthalpy-porosity technique under the same mass of PCM and the area of heat transfer while altering the aspect ratio. The predictions of the numerical model were compared favorably with the corresponding experimental results. Temperature distribution, velocity vectors, melt fraction, and total melting times are numerically investigated. Results show that the inclination angle at which minimum melting time takes place depends on the aspect ratio of the inner elliptic tube. The minimum total melting time for aspect ratios of 0.4, 0.6, 0.8, and 1 occurs at inclination angles of 30 degrees, 45 degrees, 75 degrees, and 90 degrees respectively. Furthermore; the optimized condition was with an aspect ratio of 0.4 and an inclination angle of 30 degrees.