不同盐水比对三水醋酸钠混合体系稳定过冷影响的研究

Influence of different ratio of salt and water on the stable super-cooling of sodium acetate solution

相变材料的过冷在蓄热方面一直被认为是一大缺点,但是使材料处于长期、稳定的过冷状态,可以使季节性储热成为可能。为了保持稳定高效的内能,保持储热材料过冷的稳定是一个重要的前提。采用三水醋酸钠作为储热介质,加入不同比例的去离子水形成盐水质量比不同的混合体系,研究其在不同冷却速度和冷却温度条件下溶液过冷的稳定情况及多次循环后的过冷度。结果表明,冷却速度越快、冷却温度越低,溶液的过冷稳定性越差;溶液中含水比例越高,其过冷的稳定性越好但相变温度越低。经过100次循环后,在-20℃的冷却环境中,混合体系过冷度降低约10℃,在0℃以上依旧保持稳定过冷。差示扫描量热分析表明,盐水质量比为3∶3的三水醋酸钠混合体系的平均相变潜热值最高,为291.6kJ/kg。与商用热袋相比,盐水质量比为3∶3的三水醋酸钠混合体系具有更高潜热值和相变温度并有更好的过冷稳定性,具有较大应用潜力。

Utilizing stable super-cooling of phase change material makes it possible to store thermal energy partly loss free.This principle makes seasonal heat storage possible.To keep high and stable energy content,the supercooling stability of thermal storage fluid is an important prerequisite.In the experiment,the heat storage fluid was sodium acetate trihydrate with different proportions of deionized water.The super-cooling stability of each sample was researched at the different cooling rate and the different cooling temperatures.The results showed that at the lower cooling temperature and higher cooling rate,the super-cooling stability of sample became worse.Also,the higher the water content in the sample,the better the super-cooling stability,but the lower the melting temperature.After 100 cycles,the super-cooling degree was reduced about 10℃in a cooling environment at-20℃.According to DSC tests,the latent heat value of sodium acetate trihydrate system with the salt to water ratio of 3∶3 was the highest.Compared with commercially available reusable heat packs,the sample with the salt to water ratio of 3∶3 had higher latent heat value(291.6 kJ/kg),the melting temperature and better super-cooling stability,which had great potential in thermal storage.