Flow and heat transfer characteristics of microencapsulated phase change material slurry in horizontal tubes.

Thermal or cold storage in refrigeration and air-conditioning systems is a promising way to alleviate the peak-valley difference of the electricity load. The thermal or cold storage by phase change material slurry is one of the good measures to be implemented in refrigeration and air conditioning systems. In the present study, we numerically investigate the flow and heat transfer characteristics of micro-encapsulated phase change material slurry (MPCS) in straight tubes under constant wall heat flux. The solid-liquid two-phase nature of micro-encapsulated phase change material slurry is properly taken into consideration in the theoretical modeling. And the comparison of the numerical results to the experimental results is carried out to validate the theoretical modeling. It is found that the imhomogeneity presents in the case of horizontal tube due to the effect of the gravity. And the heat transfer characteristics of micro-encapsulated phase change material slurry can be classified into different regions, in which different heat transfer mechanisms are elucidated.

制冷与空调系统中的蓄热/蓄冷技术，是缓解电力负荷峰谷差的极具前景的解决方案。采用相变材料浆体的蓄热/蓄冷方式，是可应用于该类系统的优质实现途径之一。本研究针对恒壁面热流条件下直圆管内微胶囊相变材料浆体（micro-encapsulated phase change material slurry, MPCS）的流动与传热特性开展数值模拟研究。理论建模过程中充分考量了该浆体的固液两相流本质特性，并通过将数值模拟结果与实验结果对比完成了理论模型的验证。研究发现，受重力效应影响，水平管内的流动呈现出不均匀性；此外，微胶囊相变材料浆体的传热特性可划分为多个不同区域，各区域对应的传热机理均得到了阐明。