熔盐是太阳能热电系统中常用的传热和储热介质,为了提高熔盐的热导率,以改性天然石墨为导热填料,与硝酸熔盐(NaNO₃-7%-NaNO₂-40%-KNO₃-53%)制备了熔盐复合材料,采用扫描电镜、差式扫描量热仪(DSC)、激光导热系数测量仪和红外热像仪等手段对复合材料进行表征。未改性的天然石墨与熔盐界面相容性差,在液态熔盐中易分层。改性处理改善了天然石墨与熔盐的界面相容性,改性石墨在液态熔盐中分散性好,经过多次固-液相变后依然可以稳定分散。DSC循环测试表明改性天然石墨/熔盐复合材料有很好的稳定性,熔化热、熔点和比热容都有所降低。改性天然石墨添加量为25%,可将熔盐导热系数由0.76W/(m·K)提高至11.26W/(m·K)。结果表明改性天然石墨可以有效提高熔盐的热导率,进而提高传热和储热效率。但是添加改性石墨会降低比热容,因此在应用时需要对导热系数和比热容进行合理的优化选择。

Molten salt is an ideal medium for heat transfer and storage in solar thermal power generation industry.In order to increase thermal conductivity of molten salt,modified natural graphite was used as a thermal conductive filler to prepare molten salt (NaNO₃-7%-NaNO₂-40%-KNO₃-53%) composite.The modified natural graphite-molten salt composite was characterized by SEM,DSC,laser thermal conducting instrument and thermal infrared imager.Surface modification improved the interfacial compatibility of natural graphite and molten salt.Modified natural graphite dispersed better in molten salt than natural graphite.The composite had good thermal stability,but the melting enthalpy,melting point and specific heat capacity were lower than original salt.Adding 25g modified natural graphite to 100g molten salt,the thermal conductivity was increased from 0.76W/(m·K) to 11.3W/(m·K).The results indicated that modified natural graphite can effectively improve the thermal conductivity of molten salt.This method can improve heat transfer and heat storage efficiency in solar thermal power generation industry.The specific heat capacity of molten salt composite was reduced caused by the additive,so it was necessary to choose the optimized dosage in practical applications.