液相自然对流传热可显著提升相变材料的融化储热效率。为了明确相变材料融化储热中的自然对流增强效应，通过开展侧边恒定热源下的相变石蜡融化储热试验，获取相变石蜡融化前缘的倾斜特征，证实了液相自然对流对融化储热的影响。建立流-固-热三场耦合下的相变材料融化储热计算模型，对比试验测试与理论计算结果，验证计算模型的正确性。分析自然对流传热影响的尺寸效应和方向性，并进一步研究加热温度和初始温度等因素对储热效率的影响。结果表明，在侧边恒定温度热源下，方腔内液相自然对流运动将导致倾斜状的融化前缘，并提升了13.1倍的融化储热效率。液相自然对流影响存在尺寸效应，在方腔边长小于2mm后其增强效应基本可忽略不计。同时，液相自然对流运动受热源方向影响显著，热源方向角由90°向270°旋转时，液相自然对流效应将被逐渐激活，流动状态将由单一大环流向若干无规则小环流转变，最终在底部热源下达到最大储热效率，并转变为波浪形的融化前缘形态。加热温度由60℃增至100℃时，自然对流增强系数提升了20%。初始温度由25℃降至5℃时，自然对流增强系数降低了10.2%。

Natural convection heat transfer of liquid phase can significantly improve the melting heat storage efficiency of PCM (phase change materials). In order to clarify the enhancement effect of natural convection during the melting heat storage of PCM, the melting heat storage experiment of phase change paraffin under constant heat source on side was carried out. The inclined melting front of phase change paraffin were obtained which can be used to prove the effect of liquid natural convection on melting heat storage. Based on the fluid-solid-thermal coupling theory, the calculation model of melting heat storage in PCM was established. The correctness of the calculation model was verified by comparing the test results with the theoretical calculation results. The size effect and directivity of natural convection heat transfer were analyzed, and then the influence of heating temperature and initial temperature on heat storage efficiency were studied. The results show that, at a constant temperature heat source on the side, the natural convection movement of liquid phase in the square cavity will lead to a inclined melting front, and improve the melting heat storage efficiency by 13.1 times. There is a size effect of natural convection in liquid phase, the enhancement effect can be basically negligible when the side length of the square cavity is less than 2mm. Meanwhile, the natural convection movement of liquid phase is significantly affected by the direction of heat source. When the heat source direction angle rotates from 90° to 270°, the liquid phase natural convection effect will be gradually activated, the flow state of liquid phase will change from a single large circulation to several small irregular circulation. Finally, the maximum heat storage efficiency is achieved under the bottom heat source, and change into a wavy melting front. When the heating temperature increases from 60℃ to 100℃, the natural convection enhancement coefficient is increased by 20%. When the initial temperature drops from 25℃ to 5℃, the natural convection enhancement coefficient decreased by 10.2%.

国家自然科学基金项目（51908197）；河南省科技攻关项目（242102240026）