Preparation and thermal properties of eutectic phase change materials (EPCMs) with nanographite addition for cold thermal energy storage

The main research objective of this paper is to develop a low-temperature Eutectic Phase Change Material (EPCM) for use in the Cold Storage Thermal Storage (CETS), with the aim of improving energy efficiency during the cold storage process and addressing energy crises and environmental concerns. In this study, capric acid, n-octanoic acid, and n-tetradecane are prepared as low-temperature EPCMs by melt blending, with the addition of nanographite to enhance their thermal conductivity. The thermal performance parameters, chemical stability, and thermal stability of the EPCMs under phase change cycles are tested and evaluated by using macroscopic experimental methods, DSC, FTIR, and infrared thermal imaging. The research results indicate that the G-2 low-temperature EPCM, prepared by mixing capric acid, n-octanoic acid, n-tetradecane, and nanographite with a mass ratio of 0.231:0.469:0.3:0.06, has optimal thermal properties, specifically including a melting point of 0.32 °C, a melting latent heat of 163.3 J/g, a thermal conductivity of 0.83 W/m·K, and an undercooling of 0.47 °C. These properties make it suitable for cold storage operations. Nanographite can effectively improve the thermal conductivity of EPCM, and a 6 % addition proportion can lead to a 417.45 % increase in thermal conductivity and a 64.39 % decrease in undercooling. However, once the content of nanographite exceeds 6 %, the stability of the EPCM will undergo a significant decline. Furthermore, the results of DSC, FTIR, and infrared thermal imaging confirm that capric acid, n-octanoic acid, n-tetradecane, and nanographite can be effectively co-melted with each other, the heat transfer framework function of nanographite improves the efficiency of latent heat utilization in EPCM, and the G-2 sample maintains acceptable chemical and thermal stability even after undergoing 200 phase change cycles.