Abstract In this work, thermal properties of five phase change materials (PCMs) with medium phase change temperature including mannitol, sebacic acid (SA), SA/expanded graphite (EG) composite, LiNO3-KCl eutectic salt and LiNO3-KCl/EG composite, were characterized using temperature history (T-history) method with improved accuracy. The studies on mannitol showed that although the T-history method could yield a supercooling degree which was lower than that from differential scanning calorimetry (DSC) determination, the severe supercooling and great latent heat loss during mannitol's solidification were still the problems which hindered the use of this material. As for the rest materials, slight or no supercooling phenomena were observed and the obtained phase change temperatures were well matched to literature data. The latent heat measurements of these four materials proved a proportional relationship between the PCM/EG composite's latent heat and PCM's mass fraction. However, the latent heat values determined by T-history were higher than the DSC results. Therefore, repeated studies were still required to further evaluate the latent heat storage densities of these materials. The results in this work could play key roles in design, simulation and modification of latent thermal energy storage (LTES) systems based on these medium-temperature PCMs for solar heat applications.

中文翻译：

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使用温度历史法表征太阳能热储能中温相变材料

摘要 本文研究了甘露醇、癸二酸 (SA)、SA/膨胀石墨 (EG) 复合材料、LiNO3-KCl 共晶盐和 LiNO3-KCl/EG 复合材料等五种中等相变温度的相变材料 (PCMs) 的热性能。 , 使用温度历史 (T-history) 方法进行表征，提高了精度。对甘露醇的研究表明，虽然T-history法可以得到低于差示扫描量热法(DSC)测定的过冷度，但甘露醇凝固过程中过冷严重和潜热损失大仍然是阻碍其使用的问题。这种材料。至于其余材料，观察到轻微或没有过冷现象，并且获得的相变温度与文献数据很好地匹配。这四种材料的潜热测量证明了 PCM/EG 复合材料的潜热和 PCM 的质量分数之间的比例关系。然而，T-history 确定的潜热值高于 DSC 结果。因此，仍需要反复研究以进一步评估这些材料的潜热储存密度。这项工作的结果可以在基于这些用于太阳能热应用的中温 PCM 的潜热能储存 (LTES) 系统的设计、模拟和修改中发挥关键作用。仍需要反复研究以进一步评估这些材料的潜热储存密度。这项工作的结果可以在基于这些用于太阳能热应用的中温 PCM 的潜热能储存 (LTES) 系统的设计、模拟和修改中发挥关键作用。仍需要反复研究以进一步评估这些材料的潜热储存密度。这项工作的结果可以在基于这些用于太阳能热应用的中温 PCM 的潜热能储存 (LTES) 系统的设计、模拟和修改中发挥关键作用。