Assessment on the melting performance of a phase change material based shell and tube thermal energy storage device containing leaf-shaped longitudinal fins

Abstract

This work concerns the development of a leaf-shaped longitudinal fin for the melting performance enhancement in a shell and tube thermal energy storage device. A two-dimensional code with the consideration of natural convection is established to simulate the phase transition process in phase change material (PCM), and the reliability is validated through comparing of the numerical results with published experimental data. The dynamic temperature evolution and response of the leaf-shaped fin with enhanced performance is first analysed. The effects of the fin length, fin angle and fin material on the melting performance are then studied and discussed. Finally, the fin shape effect on PCM melting process is assessed by considering two different configurations of rectangular and triangular sub-branches under the same working conditions. The results show that the leaf-shaped fin with ever-increasing length of sub-branches offers extra thermal surface to contact the PCMs that located at the far side of the heating source, and hence achieves uniform heat transfer rate and accelerates the melting process in the device. For a fixed fin volume in the device, the fin length exhibits significant influence on the melting rate with the complete melting duration being shortened by 14.2 % when the value varies from 22 mm to 25 mm. Moreover, the performance enhancement induced by the leaf-shaped fin can be further strengthened by optimizing the fin sub-branch angle and shape. It is revealed that the fin with a branch angle of 75° achieves an acceleration of whole melting process by 12 % compared to the fin with branch angle of 90°. The total melting time in the fin with triangular shape of sub-branches can be reduced by 30.1 % in comparison with the fin with rectangular configuration of sub-branches.