Abstract A novel method of microcosmic-visualizing was employed in investigating the supercooling stability of a phase change material (PCM). The supercooling behavior of the PCM under circumstances of different surface free energy was studied both dynamically and statically, and a theory analysis of how the surface free energy of the substrate affects the stable supercooling of PCM was carried out. The results showed that, the PCM droplets phase changed after a 20-cm free fall on substrate with larger surface free energy, while remained supercooled on substrate with lower surface free energy. The PCM in PTFE container initiated crystallization at −8.99 °C, withstood over 400% on hours at liquid state compared with the sample in glass container, while a large supercooling degree of over 57 °C was achieved. It indicated that containers made of materials with lower surface free energy could be considerably beneficial in stabilizing supercooling of PCMs, which could give a guide to the practical application on long-term energy storage of PCMs. What is more, the surface free energy theory also works on the air-liquid interface. The oil-covered PCM sample withstood a temperature of 5 °C for 10 months without crystalized in a refrigerator, showing great potential on supercooling stabilization.

中文翻译：

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用微观可视化方法分析五水硫代硫酸钠稳定过冷的表面自由能

摘要 采用一种新的微观可视化方法研究相变材料（PCM）的过冷稳定性。动态和静态研究了不同表面自由能条件下PCM的过冷行为，并对基体表面自由能对PCM稳定过冷的影响进行了理论分析。结果表明，PCM液滴在具有较大表面自由能的基材上自由下落20 cm后相变，而在具有较低表面自由能的基材上保持过冷状态。聚四氟乙烯容器中的 PCM 在 -8.99 °C 开始结晶，与玻璃容器中的样品相比，在液态下承受了超过 400% 的小时数，同时实现了超过 57 °C 的大过冷度。这表明由具有较低表面自由能的材料制成的容器在稳定相变材料的过冷方面有很大的好处，这可以为相变材料长期储能的实际应用提供指导。此外，表面自由能理论也适用于气液界面。油覆盖的 PCM 样品在 5°C 的温度下可承受 10 个月而没有在冰箱中结晶，显示出在过冷稳定方面的巨大潜力。