Abstract:

This study is aimed to deal with the non-crystallization caused by condensate depression of Na₂S₂O₃·5H₂O, to improve the cycle stability of composite phase change materials, and to inhibit phase separation. In solving these problems, CaSO₄ and 1-naphthol (C₁₀H₈O) are used as nucleating agents, and PAAS and CMC as thickeners. Composite phase change materials are analysed by the cooling curve and DSC. The experiments show that adding CaSO₄ with mass fraction of 1% and 5% and C₁₀H₈O of 0.5% and 3% can help enormously in the nucleation of Na₂S₂O₃·5H₂O. When the thickeners are added, the naphthol system would not crystallize after cooling. For the CaSO₄ system, the effect of the PAAS thickener is better than that of CMC. The phase transition temperature of Na₂S₂O₃·5H₂O+1%CaSO₄+2%PAAS composite is 47.7℃, and the latent heat of phase change is 200.4J/g. The phase transition temperature of Na₂S₂O₃·5H₂O+5% CaSO₄+2% PAAS composite is 48.2℃, and the latent heat of phase change is 213.4J/g. After high-low temperature cycle test, the phase transition temperature of 1% CaSO₄ composite is 47.6℃, and the latent heat of phase change is 192.4J/g, which is decreased by 3.99% compared with the pre-circulation phase change. The phase transition temperature of the composite material of 5% CaSO₄ is 47.8℃ and the latent heat of phase change is 211.2J/g, which is 1.03% lower than that before the cycle. The 5% CaSO₄ system is better than the 1% CaSO₄ system. The latent heat value and phase transition temperature change little before and after cycling, showing good cycling stability.

Key words: sodium thiosulfate pentahydrate, calcium sulfate, naphthol, CMC, PAAS, cycling stability, condensate depression, phase separation

摘要：

为了解决Na₂S₂O₃·5H₂O存在的过冷度过大导致不结晶的问题，提高复合相变材料的循环稳定性并抑制相分离现象，以CaSO₄和1-萘酚（C₁₀H₈O）为成核剂；聚丙烯酸钠（PAAS）和羧甲基纤维素钠（CMC）为增稠剂进行改良，通过步冷曲线和差示扫描量热法（DSC）对复合相变材料进行了研究。实验结果表明：加入质量分数为1%和5%的CaSO₄、0.5%和3%的C₁₀H₈O对Na₂S₂O₃·5H₂O有较好的成核作用。萘酚体系在加入增稠剂后降温冷却时不出现结晶现象。对于CaSO₄体系，增稠剂PAAS效果优于CMC，Na₂S₂O₃·5H₂O+1%CaSO₄+2%PAAS复合材料相变温度47.7℃，相变潜热为200.4J/g；Na₂S₂O₃·5H₂O+5%CaSO₄+2%PAAS复合材料相变温度48.2℃，相变潜热为213.4J/g；经过100次高低温循环后，1%CaSO₄的复合材料相变温度47.6℃，相变潜热为192.4J/g，相较循环前相变潜热降低了3.99%。5%CaSO₄的复合材料相变温度47.8℃，相变潜热211.2J/g，相比循环前下降1.03%。5% CaSO₄体系较优于1% CaSO₄体系，循环前后潜热值、相变温度变化不大，循环稳定性良好。

关键词: 五水硫代硫酸钠, 硫酸钙, 1-萘酚, 羧甲基纤维素钠, 聚丙烯酸钠, 循环稳定性, 过冷度, 相分离