Numerical study on the melting performance of PCM by fractal fins in three-tube heat storage system

Abstract

In order to solve the problems of low heat storage efficiency and uneven melting in the PCM area of the traditional heat accumulator, this paper takes the three-tube phase change heat accumulator with eight longitudinal fins as the basic structure to ensure that the volume of the fins in the heat accumulator is unchanged. The longitudinal fins are fractal in the shape of ' Y ', and the influence of the length and branch angle of the Y-shaped fins on the heat storage performance of the three-tube phase change heat accumulator is simulated by FLUENT software. The results show that the addition of fractal fins to the triple-tube phase change heat accumulator increases the heat transfer area and facilitates the development of natural convection compared with the addition of ordinary longitudinal straight fins, which effectively shortens the time required for the complete melting of PCM. After comprehensive analysis, the root and branch of Y-shaped fins account for 25% and 75% of the total length respectively, and the branch angle is 60°, which is the best Y-shaped fin structure. The complete melting rate of PCM is obviously improved. Compared with the ordinary straight fin heat accumulator, the heat storage rate is increased by 16.1%, and the overall heat storage performance is improved. By optimizing the design, it is found that the eccentricity has a significant effect on the melting process of the PCM. When the eccentricity is 11.5%, the overall heat storage time is the least. Compared with the original structure without eccentricity, the heat storage speed is increased, and the heat storage time is saved by about 14%. It provides a basis for the structural optimization design of phase change heat system.