Abstract:

The composite phase change materials with a porous medium metal skeleton can improve the low thermal conductivity of pure phase change materials and further improve the heat transfer rate of composite phase change materials, which has essential research significance. This research uses the finite element method to propose the construction of a two-stage backbone branch hierarchical structure metal skeleton and combines it with a paraffin square cavity. Form composite phase change heat transfer materials with better heat transfer performance and add finned tube structures on this basis to further optimize the heat transfer performance of composite phase change materials. The results show that the finned tube structure has a significant impact on the phase change heat transfer process, and the phenomenon of flow velocity protrusion near the transverse main stem can make the melting front more inclined, and the annular flow heat transfer in the cavity quickly moves towards the lower part of the square cavity. The optimized composite phase change material can shorten the solid-liquid phase transition time by 37.4% compared to the uniform skeleton composite phase change material. The trough of the instantaneous phase transition rate curve in the initial melting stage is increased by 1.88 times, and the temperature uniformity is improved, resulting in a 20.9% reduction in the maximum temperature difference at 800s after melting. This research modified the skeleton structure under a constant porosity and improved the heat storage rate of composite phase change materials through a more reasonable volume distribution of the metal skeleton.

Key words: phase change, composites, hierarchical structures, flow, heat transfer, numerical simulation

摘要：

添加金属骨架的多孔介质复合相变材料可以改善纯相变材料的低导热性能，进一步提高复合相变材料的传热速率，具有重要研究意义。本研究采用数值模拟，提出构建主干-分支两级分级结构金属骨架并与石蜡方腔相结合，形成传热效果更好的复合相变传热材料，并在此基础上添加翅片管结构来进一步优化复合相变材料的传热性能。结果表明，翅片管结构对相变传热过程影响显著，在横向主干附近产生的流速突进现象可使熔化前沿更加倾斜，腔内环状流动传热快速向方腔下部移动。优化后的复合相变材料相较于均匀骨架复合相变材料固液相变时间可缩短37.4%，熔化初期瞬时液化速率曲线的波谷提高了1.88倍并且使熔化后期800s时的最大温差减小了20.9%，提高了温度均匀性。本研究在定孔隙率情况下对骨架结构进行了改变，通过更合理的金属骨架体积分布提高了复合相变材料的储热速率。

关键词: 相变, 复合材料, 分级结构, 流动, 传热, 数值模拟