Abstract:

The sodium sulphate decahydrate has limited use in solar greenhouses due to problems such as supercooling, phase separation, high temperature of the phase transition and liquid phase leakage. In this paper, Na₂HPO₄·12H₂O was added to improve supercooling, potassium chloride to reduce the phase transition temperature, and resin as a matrix to resolve phase separation and liquid phase leakage. The mass fraction of Na₂SO₄·10H₂O+80%Na₂HPO₄·12H₂O+6%KCl+6% resin was tested for temperature rise and fall, DSC and cycle stability. Because of adding 80% Na₂HPO₄·12H₂O, the degree of supercooling and the latent heat of phase change were 1.35℃ and 268.7J/g, respectively. With adding 6% KCl, the temperature of phase change can reach 23.89℃ and latent heat was 183.25J/g. Finally, adding 6% resin can suppress phase separation and liquid phase leakage of phase change materials. Its crystallization temperature, the temperature of phase change, subcooling degree and phase transition latent heat were 11.56℃, 22.61℃, 1.41℃ and 143.6J/g, respectively. The composite molding phase change material was no liquid phase leakage with heating to 50℃. The latent heat of the cycle after 100 was 127.8J/g, which was 11.2% lower than one cycle. The obtained composite molded phase change material had advantages such as a large latent heat value, the appropriate temperature of phase transition and good thermal stability, and can be applied to the field of solar greenhouses.

Key words: phase change, composites, supercooling, phase transition temperature, latent heat of phase change, stability

摘要：

十水硫酸钠因过冷度、相分离、相变温度过高和液相泄漏等问题，限制了其在日光温室中的应用，所以需要对其进行改性研究。本文通过添加十二水磷酸氢二钠改善过冷度、氯化钾降低相变温度以及树脂作基体解决相分离和液相泄漏，制备出了Na₂SO₄·10H₂O+80% Na₂HPO₄·12H₂O+6% KCl+6%树脂（质量分数，余同）的复合定形相变材料，并进行了升降温、差示扫描量热仪（DSC）和循环稳定性的测试。结果表明：添加80%十二水磷酸氢二钠，其过冷度和相变潜热分别为1.35℃和268.7J/g；再添加6% KCl可以使相变温度达到温室所需温度23.89℃，且潜热为183.25J/g；最后加入6%树脂可以抑制相变材料的相分离和液相泄漏等问题，其凝固温度为11.56℃，熔化温度为22.61℃，过冷度为1.41℃，相变潜热为143.6J/g。复合定形相变材料在加热到50℃时，没有液相泄漏产生；经过100次循环，其潜热降为127.8J/g，比循环1次衰减了11.2%。得到的复合定形相变材料具有潜热值较大、相变温度合适、热稳定性较好等优点，适合应用于日光温室领域。

关键词: 相变, 复合材料, 过冷度, 相变温度, 相变潜热, 稳定性