Melting performance analysis of phase change materials in different finned thermal energy storage

This study proposes helical-fin as an innovative structure for latent heat thermal energy storage systems. A three-dimension numerical model considering natural convection was established to research the melting process of PCM in finned LHTES units. To evaluate the new fin structure, the melting process of PCM in conventional finned LHTES systems was firstly simulated and compared with the innovative LHTES unit at the same heat transfer surface area. The results indicate that the fin structure has a remarkable effect on the charging process. Embedding the double-helical fin into phase change materials area can achieve the best thermal performance in a vertical LHTES. Meanwhile, quadruple-helical finned LHTES can achieve the best thermal performance in a horizontal thermal energy storage unit. Compared with the conventional finned LHTES units, the complete melting time is reduced by 31.0% in vertical LHTES. Moreover, the effects of HTF inlet direction and velocity on the thermal performance were investigated. The results reveal that the LHTES unit exhibits a uniform temperature field and better thermal performance when the direction of HTF inlet is opposite to the direction of gravitational acceleration. Increasing the inlet velocity of the HTF greatly affects the charging process of the finned LHTES unit.