Thermal property measurement and heat storage analysis of LiNO3/KCl – expanded graphite composite phase change material

A LiNO3/KCl-expanded graphite (EG) composite phase change material (PCM) was prepared for solar thermal energy storage application at high temperature (∼200 °C). In such composite material, eutectic system LiNO3/KCl is characterized by high phase change latent heat and EG serves as the heat transfer promoter. Investigations by means of differential scanning calorimetry (DSC), hot disk analyzer and heat storage performance tests in a latent thermal energy storage (LTES) unit were devoted to the thermal property measurement and heat storage performance analysis of the LiNO3/KCl–EG composite. Experimental results revealed that the melting temperature of the composite material was close to that of the eutectic LiNO3/KCl, and the phase change latent heat ranging from 142.41 to 178.10 J/g was dependent on its mass fraction of EG. The thermal conductivities of the composites were 1.85–7.56 times higher compared with the eutectic LiNO3/KCl, and the conductivity value varied with the EG mass content and the apparent density of the composite. In addition, the heat transfer in the composite material during the heat storage process was enhanced through the thermal conductivity improvement, while the heat storage duration was affected by the phase change latent heat and the apparent density of the composite material.