Preparation and characterization of sodium thiosulfate pentahydrate/expanded graphite phase change energy storage composites

Abstract In order to solve the problems of high supercooling, poor thermal conductivity and phase separation after repeated use of Na 2 S 2 O 3 ·5H 2 O with additives. In this paper, Na 2 S 2 O 3 ·5H 2 O is used as the matrix phase change material, and 1% sodium carboxymethyl cellulose, 3% SrCl 2 ·6H 2 O, and 10% expanded graphite (EG) are added to prepare the modified Na 2 S 2 O 3 ·5H 2 O composite phase change energy storage material. Based on the existing research, the effects of reducing supercooling, improving thermal conductivity, and improving stability are further optimized. The phase change temperature, supercooling degree, heat release time, phase change latent heat, and thermal conductivity of the material are tested by temperature data acquisition instrument, differential scanning calorimeter, hot disk thermal constant analyzer, and other instruments. The effect of EG on the thermal conductivity of the Na 2 S 2 O 3 ·5H 2 O composite phase change energy storage material was explored from the microstructure through a digital scanning electron microscope; Fourier transform infrared spectroscopy verified the composition of the composite phase change materials. After 200 cycles of melting and solidification, the improved composite phase change material has a phase change temperature of 43.49°C, a supercooling degree of 2.19°C, a phase change latent heat of 198.7 J/g, and a thermal conductivity of 3.42 W/m·K. Composite phase change material shows good thermal stability and provides strong support for phase change energy storage technology.