Investigations on the thermal stability, long-term reliability of LiNO3/KCl - expanded graphite composite as industrial waste heat storage material and its corrosion properties with metals

The aim of this work was to investigate the properties of LiNO3/KCl-expanded graphite (EG) composite phase change material (PCM) concerning its long-term usage for industrial waste heat storage. Studies on the thermal stability and long-term reliability of this composite PCM as well as its compatibility with metals that commonly used in industries were conducted. By means of thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC), the initial thermal decomposition temperature of the composite PCM was found to be 315 °C, and less than 1% and around 4% changes in phase change temperature and phase change latent heat, respectively, were obtained after repeated melting/solidification cycles. Gravimetric analysis of different metal specimens after enduring 500 thermal cycles in contact with the composite PCM revealed that stainless steel 304L and carbon steel C20 could be considered as more suitable containment materials than brass H68 for long-term use. The results of this work not only confirmed the great potential of LiNO3/KCl-EG composite PCM to be used as industrial waste heat storage medium, but also could facilitate experimental and numerical researches on the LiNO3/KCl-EG composite PCM-assisted latent heat storage systems in future.