Charging performance optimization of a latent heat storage unit with fractal tree-like fins

摘要

The significant deficiency of the latent heat storage (LHS) technology is the poor heat charging and discharging efficiency. Here invokes a fractal tree-like fin to strengthen the melting property of LHS units inspired by bionics in nature. A transient melting model of the shell-and-tube LHS unit with tree-like fins is built and solved numerically. The structure optimization of fractal tree-like fins is conducted for charging enhancement by response surface method (RSM). The results report that the length ratio and thickness index play considerable roles in the competition between natural convection suppression and heat conduction improvement during melting processes. Compared with the plate fin, the distribution of tree-like fins in a multi-level fashion provides point-toarea networks for high heat flows, which benefits to the melting rate acceleration and uniform temperature field owing to that the thermal conduction improvement is more remarkable than convection suppression. More significantly, the total melting duration of the LHS unit with optimal tree-like fins reduces by 26.7%, and the averaged heat storage rate increases by 45.4% relative to the plate fins case. Therefore, a fractal tree-like fin with alpha = 1.07 and Delta = 0.65 is recommended in practical applications for maximizing energy charging performance of LHS units.