添加硝酸镁对硝酸钠储热热物性的影响

Influence of magnesium nitrate on the thermophysical property of sodium nitrate

蓄热是提高可再生能源储热容量、实现低谷电高效利用的关键技术,而熔盐是一种高效传热储热材料。通过将不同比例Mg(NO3)2添加到NaNO3中,配制了9种不同质量比的二元混合硝酸盐;采用差示扫描量热法和热重分析法分别对混合硝酸盐的初始熔化温度、初晶点及分解温度进行了实验研究,探索不同比例混合熔盐的共晶特性;同时对共晶熔盐不同温度下的比热变化规律进行了研究。结果表明:等质量比的混合熔盐能够达到较好的共晶,其初始熔化温度为355.4℃,熔化结束温度为364.3℃;初始结晶温度为368.5℃;分解温度为33.1℃。进一步测试了该配比二元混合硝酸盐在熔化前和熔化后的比热,发现其余可共熔二元混合硝酸盐的熔点温度基本维持在340℃,初晶点温度基本维持在240～250℃,分解温度基本维持在430～440℃。

Heat storage is one of the key technologies to improve the storage capacity of renewable energy and to realize the efficient utilization of off-peak power.Molten salt is an efficient heat transfer and storage material.By adding Mg(NO3)2 to NaNO3 at various mass ratios,nine binary nitrate specimens were prepared.The initial melting temperature,primary crystal point and decomposition temperature of mixed nitrates were experimentally studied with differential scanning calorimetry and thermogravimetric analysis.The eutectic properties of mixed salts with different mass ratios were investigated.The variation of specific heat of eutectic molten salts with temperature was experimentally studied.The results showed that within the nine mixed molten salts at different mass ratios,No.05,i.e.Mg(NO3)2 and NaNO3 with the identical mass proportion,can reach the state of eutectic crystal,with the initial melting temperature at 355.4℃,the melting temperature at 364.3℃,the initial crystallization temperature at 368.5℃,and the decomposition temperature at 33.1℃.The remaining binary nitrate specimens which could reach eutectic showed the similar melting temperature at around 340℃,the initial crystal point temperature at 230~250℃,and the decomposition temperature range was in the range of 430~440℃.