分形翅片相变传热特性及优化

The low efficiency of the latent heat storage system attributed to low thermal conductivity of phase change material. A novel fractal fin to strengthen the solidification property of latent heat storage units was proposed. The enthalpy-porosity technique was utilized to build a transient two-dimensional model of shell and tube latent heat storage system. The results demonstrated that the length ratio and branch angle played an important role in solidification performance. The fractal structure improved the solidification speed and led to uniform temperature. The fractal fin displayed a remarkable heat transfer enhancement compared with a conventional fin. The structure optimization of fractal fin was conducted for solidification enhancement by artificial neural network and genetic algorithm. The optimized fin structure was obtained by genetic algorithm: the optimal fin length ratio was 1.425 and the two branch angles were 50° and 30° respectively， the solidification time of the latent heat storage unit with fractal fin after optimization was 76.9% shorter than the system with conventional fin. The sensitive analysis was applied to explore the effect of the parameters of fractal fin on solidification time. The results indicated that the solidification time of the system was more affected by the length ratio，followed by the first-order branch angle. More attention should be paid to the effect of the changes of these two parameters.