NUMERICAL STUDY ON THE THERMAL PERFORMANCE OF A PHASE CHANGE HEAT EXCHANGER (PCHE) WITH INNOVATIVE FRACTAL TREE-SHAPED FINS

Abstract

For alleviating energy shortage and environmental problems, it is of great importance to improve the energy charging and discharging efficiency of thermal energy storage systems. In this context, an innovative phase change heat exchanger (PCHE) with fractal tree-shaped fins is presented in this paper. A numerical investigation of the solidification behaviors in the PCHE with fractal tree-shaped fins is conducted. The dynamic temperature response and the solidification front evolution in the PCHE are analyzed and discussed. Furthermore, two evaluation criteria, including total solidification time and energy charging efficiency, are introduced to quantitatively study the effect of fin material on the solidification heat transfer characteristics. The results indicate that the fractal tree-shaped fin leads to a uniform temperature distribution of phase change material (PCM). The temperature response of fin is faster than that of PCM due to its high thermal conductivity. Moreover, the fractal tree-shaped fin breaks the restriction of gradually forward fashion of solidification front in the traditional PCHE and dramatically improves the energy discharging performance. The material of fractal tree-shaped fins is an essential factor affecting the solidification performance of the PCHE. The energy discharging performance of PCHE with pure copper fins is the best, whereas that with cupronickel fins is the worst. However, from the perspective of practical application, aluminum is the best potential alternative because of its relatively high thermal conductivity, lighter weight, and low cost.