Structure optimization of tree-shaped fins for improving the thermodynamic performance in latent heat storage

Tree-shaped fins have widely been approved to enhance heat transfer performance in the field of latent heat storage. However, the structure of tree-shaped fins should be optimized to amplify its performance advantages, which are rarely addressed in previous studies. An unsteady numerical model is established to study the thermal performance advantages of tree-shaped fins. A method by coupling a genetic algorithm and a CFD simulation is utilized to optimize the structure of the tree-shaped fins based on the melting and solidification processes of a Phase Change Material (PCM). The results indicate that structural optimization is important and necessary for the application of tree-shaped fins especially in latent heat storage systems. Compared with the radial fins, the optimized tree-shaped fins reduce the phase transition time by 38.83%in the melting process and by 32.71% in the solidification process. Also, the optimized tree-shaped fins increase the average heat transfer rate and average heat transfer coefficient by 65.70% and 65.54% in the melting process while 51.51% and 51.00% respectively in the solidification process. The optimization results also shows that the optimized tree-shaped fins based on different heat transfer processes all show the characteristics of gradually increasing branch length and decreasing branch angle, that is, L₀<L₁<L₂, β₁>β₂. Interestingly, the optimized structure of the tree-shaped fins based on PCM melting differs from that of the PCM solidification process because of the difference in heat transfer mechanisms. This study provides a method for the structural optimization of tree-shaped fins and increases the application prospect of tree-shaped fins in the field of latent heat storage.