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分别在密封和未密封条件下对六水合氯化镁(MgCl2·6H2O)进行600次加速热循环实验,研究其作为太阳能中温蓄热材料的可行性。采用差示扫描量热仪、X射线衍射仪和多路温度测试仪测试不同次数热循环后样品的相变温度、相变潜热、晶体结构和过冷度。结果表明,未密封状态下,200次热循环后,MgCl2·6H2O的相变潜热降低54.2%,并有新相MgCl2·4H2O产生;密封状态下,600次热循环后,MgCl2·6H2O的相变温度和峰值温度的变化分别在±1%和±4%内,相变潜热的变化在-15.2%~+1.5%内(300次热循环后变化异常);同时,MgCl2·6H2O凝固时几乎没有过冷现象,过冷度在0~2.2℃之间。密封状态下,MgCl2·6H2O在太阳能中温蓄热应用中是一种很有发展前景的材料。
600 cycles of accelerated thermal cycling of magnesium chloride hexahydrate (MgCl 2 · 6H 2 O) were conducted respectively under sealed and unsealed conditions, and its feasibility as a medium temperature thermal storage material for solar energy was studied. The phase transition temperature, phase transition latent heat, crystal structure and degree of undercooling were measured by differential scanning calorimeter, X-ray diffraction and multi-channel temperature tester. The results show that after 200 thermal cycles, the latent heat of transformation of MgCl2 · 6H2O decreases 54.2%, and the new phase MgCl2 · 4H2O is produced. After 600 thermal cycles, the phase transition of MgCl2 · 6H2O The changes of temperature and peak temperature were within ± 1% and ± 4%, respectively, and the changes of latent heat of transformation were within -15.2% ~ + 1.5% (abnormal changes after 300 thermal cycles). At the same time, MgCl2 · 6H2O almost did not Too cold phenomenon, undercooling between 0 ~ 2.2 ℃. In the sealed state, MgCl2 · 6H2O is a very promising material in the application of solar thermal storage.