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.

中文翻译：

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具有创新分形树形翅片的相变换热器 (PCHE) 热性能的数值研究

为了缓解能源短缺和环境问题，提高热能存储系统的能量充放电效率具有重要意义。在此背景下，本文提出了一种具有分形树形翅片的创新相变换热器 (PCHE)。对具有分形树形翅片的 PCHE 中的凝固行为进行了数值研究。分析和讨论了 PCHE 中的动态温度响应和凝固前沿演化。此外，引入总凝固时间和能量充电效率两个评价标准，定量研究翅片材料对凝固传热特性的影响。结果表明，分形树形鳍片导致相变材料（PCM）的温度分布均匀。由于其高导热性，翅片的温度响应比PCM更快。此外，分形树形翅片打破了传统PCHE中凝固前沿逐渐向前的限制，显着提高了能量释放性能。分形树形翅片的材料是影响PCHE凝固性能的重要因素。纯铜翅片的PCHE的能量放电性能最好，而白铜翅片的能量放电性能最差。然而，从实际应用的角度来看，铝是最好的潜在替代品，因为它具有相对较高的导热率、较轻的重量和较低的成本。