Heat transfer analysis of a PCM in shell-and-tube thermal energy storage unit with different V-shaped fin structures

This study provides an alternative solution to enhance melting performance of phase change material by designing a novel V-shaped fin. Nineteen cases with different V-shaped fins is designed, the effects of angle, length, number and arrangement of fins on heat transfer performance of heat storage unit were studied. The response surface method was used to optimize the structure. Assessments on the melting fraction, temperature field, velocity distribution, and uniformity for melting are made. Results demonstrate that due to the effect of natural convection, the upper part melting speed is accelerated, resulting in a significant difference in the heat storage efficiency between the upper and lower half regions. The melting time of the lower half of the heat storage unit without fins accounting for 62.5 % of the whole melting time. Based on the above analysis, more and longer fins should be considered to be arranged at the bottom of the heat storage unit to improve the heat storage performance of the system. As noticed, the structure parameters change of fins has a significant effect on reducing the melting time of the whole phase change material. It can be found that there are optimal values for the structure parameters. The optimal fin structure parameters (fin angle alpha = 55 , fin length L-1 = 9 mm, fin number N = 5, branch angle beta = 55, and branch length L-3 = 3) obtained. The heat storage efficiency of the optimal fin structure was 2.57 times that without fins, and the heat storage time was shortened by 61.05 %. To be conclusive, adding fins to a heat exchanger is more beneficial than no fins, saving more energy storage time.