Optimization of tree-shaped fin structures towards enhanced absorption performance of metal hydride hydrogen storage device: A numerical study

Abstract Tree-shaped fins were introduced to improve the heat transfer of metal hydride reactor. A two-dimensional steady-state model was first applied to obtain the optimal geometric structures of tree-shaped fins using genetic algorithm with the constraint of fixed fin mass. Then, the hydrogen absorption performance of MH reactors with embedded radial fins and tree-shaped fins were numerically studied and compared using a multi-physical model. It was indicated that the hydrogen absorption time for 90% saturation for the reactor with optimized tree-shaped fins nearly decreases by 20.7% as compared with that for radial fins. The heat transfer and absorption performance of MH reactor were much sensitive to the length ratio of tree-shaped fins, which can be improved with increasing the length ratio. Besides, the performance of optimized tree-shaped fins reactor with variable angle ratio was only slightly better than that for fixing angle ratio at 1, indicating that the angle ratio of tree-shaped fins can be kept at 1 for simplifying the design. Moreover, the absorption performance of the reactor can be enhanced with increasing the maximum branch level of tree-shaped fins. Furthermore, it was shown that the optimized geometric structures of tree-shaped fins under different MHs thermal conductivities are nearly identical.