Numerical study on the discharging performance of a latent heat thermal energy storage system with fractal tree-shaped convergent fins

In this paper, an innovative fractal tree-shaped convergent fin (FTSCF) is embedded into a latent heat thermal energy storage system (LHTESS) to numerically investigate the parametric influences of FTSCF including FTSCF number N, maximum branching level m, length ratio α, branch convergence β, level convergence γ, rotation angle δ of the branch at the outermost level and branching angle θu on the discharging performance of the LHTESS under the fixed total fin volume. The results imply that increasing N, m, and α significantly reduces the complete solidification time τ of the phase change material (PCM). Further, the τ of the PCM demonstrates a pattern of initial decrease followed by an increase under the influences of β, γ, and δ, indicating the presence of an optimal FTSCF structure maximizing the discharging efficiency of LHTESS. Compared to the fins without branch convergence, the minimum τ of PCM within the LHTESS reduces by 4.33 %, 5.03 %, and 12.42 % by the branch convergence β when γ = 0.5, 0.707, and 1. In addition, the minimum τ of PCM monotonically decreases when θ1 = θ2 increases from 50° to 90°. The present work provides a technique to improve the discharging performance of the LHTESS by using fin convergence.