Numerical analysis on heat transfer and melting characteristics of a solid-liquid phase change process in a rectangular cavity inserted with bifurcated fractal fins

Abstract

To improve the thermal transmission performance of latent heat thermal energy storage systems, bifurcated fractal fins inspired by leaf venation structures in nature are inserted into a typical vertical rectangular cavity. Melting thermal behaviors of lauric acid in the models with bifurcated fractal fins having different fin location ratios εd, fin length ratios εl, and fin numbers N are numerically studied. Increasing εd, εl, and N yields the enhancement of liquid fractions, and a maximum melting time reduction of 63.6% is achieved by the case with εl = 0.75 and N = 3. Raising εd is conducive to melting convection flows during the natural convection regime. Whereas, the effect of εl is primarily driven through thermal conduction area enhancement. In addition, the results imply that as εl increases, the impact of increasing N leads to a shift in flow intensity from enhancement to suppression. As against the flat fin, the bifurcated fractal fin has a superior thermal transmission efficiency thanks to the larger heat transfer surface area, and the benefit is more pronounced as the branching level changes from k = 2 to k = 3.