Numerical study using lattice Boltzmann method on melting and solidification of NEPCM placed inside a rectangular cavity with a new double-fin arrangement

Adding fins to improve the efficiency of LHTES (Latent heat thermal energy storage) systems is a commonly followed measure. Significant research has been conducted on the role of unequal fin-lengths in the heat-storage process. However, the literature does not contain a detailed treatment of the enhancement effect of unequal fins on heat release. In this study, the geometric symmetry of the melting system is inverted to reduce the blocking effect of unequal fins on solidification. Three groups of LHTES systems, with different length ratios and without fins, were compared. A composite PCM composed of paraffin and copper oxide was used to simulate the phase change process of the LHTES system under natural convection by using the LBM model based on enthalpy at constant wall temperatures of 343 and 323 K. This study found that compared to the design without fins, the melting times were reduced by 16.7 %, 22.55 %, and 33.06 % when the length ratios of the three groups of fins were 1, 0.6, and 0.3333, respectively, and the solidification times were reduced by 57.54 %, 50.99 %, and 47.33 %, respectively. When only a single melting process is considered, unequal fin-lengths with large differences in length are selected. When considering the comprehensive process of heat storage and release, fins with equal lengths are a better choice.