第二类边界条件下硬脂酸固液相变蓄能研究

Research on the Stearic Energy Storage System with Solid-Liquid Phase Change under the Second Boundary Condition

通过引入有效导热系数来考虑自然对流对固液相变传热的影响,将相变蓄能模型简化为仅用能量方程描述,采用显热容法及正态分布液相率模型进行了求解.与硬脂酸固液相变实验的比较表明:自然对流对相变传热的影响不可忽略;修正后的有效导热系数经验公式能更准确地描述等热流边界条件下的固液相变过程;在等壁温边界条件下,相变速率随时间的推移而减小;在等热流边界条件下,相变速率随时间的推移而增大.

An effective thermal conductivity was introduced to consider the effect of natural convection on heat transfer of solid-liquid phase change, and then the mathematic model on the energy storage system with solid-liquid phase change was simplified so that it was described by the energy equation only. The present model was solved with the apparent heat capacity method and the normal distribution model of liquid fraction. The comparison between the stearic energy storage experiment results and the calculations data shows that the effect of natural convection on heat transfer with phase change can not be neglected. The corrected empirical formula of effective thermal conductivity can describe the solid-liquid phase change with constant heat flux more exactly. The moving velocity of solid-liquid interface decreases with time in constant temperature boundary and increases with time in constant heat flux boundary.