The effect of micro-encapsulation on thermal characteristics of metallic phase change materials

Micro-encapsulated phase change material with metallic core can work under high temperature for energy storage purpose, making it an appealing candidate for renewable energy technologies, such as thermal energy storage for concentrating solar power plants. The objective of this work is to study the impact of encapsulation on the thermal performance of the micro-encapsulated phase change materials under various operating conditions. To evaluate the thermal performance of the micro-encapsulated phase change material particles, the governing equation of transient heat conduction with phase change in spheres with composite walls is solved numerically. The impact of encapsulation shell on the convective heat transfer rate, total energy absorption, latent heat ratio, energy density, and duration of phase change is presented and analyzed under different operating conditions. Three different core materials including tin, aluminum and copper with distinct Stephan numbers are investigated. In addition to the encapsulation shell effect, this model can be used to study micro-encapsulated phase change materials with different material compositions, core to shell ratios, and it can be used to analyze the impact of air gaps in between materials. Understanding the thermal performance at particle level is essential, and the results of this study could potentially be used as input for thermal energy storage system level analysis, such as the charging and discharging processes.

具有金属芯的微胶囊相变材料可在高温下用于储能，这使其成为可再生能源技术（例如聚光太阳能发电厂的热能储存）的理想选择。本研究的目的是研究在各种运行条件下封装对微胶囊相变材料热性能的影响。为了评估微胶囊相变材料颗粒的热性能，对具有复合壁的球体中伴有相变的瞬态热传导控制方程进行了数值求解。阐述并分析了在不同运行条件下封装壳对对流换热速率、总能量吸收、潜热比、能量密度以及相变持续时间的影响。研究了三种具有不同斯蒂芬数的不同芯材，包括锡、铝和铜。除了封装壳的影响外，该模型还可用于研究具有不同材料成分、芯壳比的微胶囊相变材料，并且可用于分析材料之间气隙的影响。了解颗粒层面的热性能至关重要，本研究的结果可能会用作热能储存系统层面分析（例如充放电过程）的输入。