导热-对流混合作用下相变材料动态传热机理研究

With the high energy storage density and stable temperature during phase transition, solid-liquid phase change material is widely used for energy conservation in buildings. The heat transfer during phase transition was controlled by heat conduction and convection in most conditions; while it was revealed only by heat conduction in most research, which led some error for predicting heat transfer mechanism during phase transition. To solve this problem, a scalable cavity is designed for the observation of the formation and transformation of natural convection as well as the heat transfer during energy storage process. Then with the data from experiments, the energy conservation, momentum conservation and mass conservation equations are solved by mesoscopic method. The dynamic heat transfer mechanism of phase change material in the presence of heat conduction and convection during solid-liquid phase transition is analyzed theoretically. Based on the model, the heat transfer of phase change material within different cavities under complicated engineer conditions is simulated to get the variation of heat transfer during solid-liquid phase transition. This research can be used for performance prediction, optimal design and the application of thermal energy storage technology.

固-液相变材料具有储能密度大、等温传热等优点，广泛应用于建筑节能系统，其相变过程一般包含导热和对流共同作用，而已有成果多以单一导热机理解析蓄放热过程，难以准确反映固-液相变过程的动态传热规律。为此，本项目拟设计可伸缩方腔，首先试验研究其内相变材料蓄热过程自然对流行为的形成和演化规律及其对蓄热过程的影响；然后采用介观模拟方法求解能量方程、动量方程和连续性方程，结合试验成果，研究相变材料蓄热过程的导热-对流动态传热机理；最后基于蓄热过程的动态传热模型，模拟复杂工况下不同结构内对流的形成和发展特性及其对传热过程的影响，获得动态蓄热过程主要传热机制（导热/对流）的变化规律，以期为相变蓄热系统性能预测、优化设计及相变蓄热技术有效应用提供科学的理论依据和有力的技术支撑。

固-液相变材料因其相变过程可储存和释放大量热量而广泛应用于建筑节能系统中，其相变传热过程受导热和对流传热机制共同影响。为准确反应对流作用对相变传热过程的影响，本项目从单因素影响下相变材料熔化传热、多因素耦合影响下相变材料熔化传热和相变传热过程性能评价等三方面开展了相变传热过程的试验和理论研究。对于单因素影响下相变材料熔化传热过程，试验观察了不同边界温度、风速和方腔结构内石蜡材料熔化过程中相界面位置、温度随传热过程的变化，揭示了不同影响因素对传热热流、液相率等参数的影响规律；对于多因素耦合影响下相变材料熔化传热过程，开展了不同影响因素的敏感性分析，获得了各因素对熔化传热过程中温度、热流等参数的影响权重，并开展了多因素作用下的交叉实验，提出了最优的传热性能边界条件和方腔结构，在不增加成本的情况下提高了石蜡的传热效率；对于相变传热过程性能评价，确定了石蜡蓄热过程中的导热-对流动态传热相互作用机制，提出了石蜡蓄热过程的传热机制变化评价指标，为相变蓄热系统性能预测、优化设计及相变蓄热技术有效应用提供了科学的理论依据和有力的技术支撑。