多角度肋片强化相变材料换热仿真分析

Simulation Analysis of Heat Transfer Enhancement of Phase Change Materials with Multi-angle Fins

目的 针对太阳能热利用领域中相变材料的封装结构提出圆柱体相变蓄热棒,并设计多角度肋片以加快相变材料融化速率。方法 采用CFD仿真技术,分析不同形状肋片对蓄热棒中相变材料融化特性的影响,计算各模型相变材料的融化时间、温度响应速率和平均传热系数。结果 在800 W/m2的热流边界条件下,无肋片蓄热棒的相变材料完全融化需要2813s,设计的12组肋片中Tra–45模型性能最优,相变材料的融化时间比无肋片对照组的缩短了5.4%;Tra–45模型中相变材料温度分布集中,且最高温度上升了6℃,Tra–45模型的温度响应速率较对照组的提升了5%;Tra–45模型的平均换热系数达到9.97W/(m2·K),较对照组的提升了2.8%。结论 蓄热棒内增加梯形45°肋片后,相变材料融化速率加快,蓄热棒内温度分布均匀。同时,相变材料的温度响应速率提高,平均换热系数显著增加,可满足频繁充放热的需求。

The work aims to propose a cylindrical phase change heat storage rod(PCM-rod) according to the encapsulation structures of phase change materials in solar thermal utilization and design multi-angle fins to accelerate the melting rate of phase change materials. The effects of different shapes of fins on the melting characteristics of the phase change material in the heat storage rod was analyzed by CFD simulation technology, and the melting time, temperature response rate and average heat transfer coefficient of each model phase change material were calculated. The calculation results under the heat flow boundary condition of 800 W/m~2 showed that it took 2 813 s to completely melt the phase change material in the PCM-rod without fins, and the Tra-45 model had the best performance among the 12 groups of fins designed. The melting time of the phase change material was shortened by 5.4% compared with the control without rib.The temperature distribution of the phase change material in the Tra-45 model was concentrated, and the maximum temperature increased by 6 ℃. The temperature response rate of the Tra-45 model was increased by 5% compared with the control group, and the average heat transfer coefficient reached 9.97 W/(m~2·K), which was 2.8% higher than that of the control group. After the trapezoidal 45° fins are added to the heat storage rod, the melting rate of the phase change material is accelerated, and the temperature distribution in the heat storage rod is uniform. At the same time, the temperature response rate of the phase change material is improved, and the average heat transfer coefficient is significantly increased,which can meet the needs of frequent heat charging/release of the phase change material.