Effects of Expanded Graphite Compound of Different Sizes on Thermal Properties of NaNO₃-NaCl/Expanded Graphite

The rational use of energy is of great significance for the long-term stable development of the economy. However, energy such as solar energy and industrial waste heat are difficult to be utilized stably. The development of thermal storage technology can alleviate the instability of energy. In this paper, 96 wt% NaNO3-4 wt% NaCl (NN) was used as the thermal storage material and expanded graphite (EG) was used to adsorb NN binary phase change material (PCM). The effect of EG with different particle sizes on the thermal performance of NaNO3-NaCl/EG composite phase change material (CPCM) was studied. The results showed that the addition of EG reduced the supercooling degree of NN from 4.7 degrees C to 1.1 degrees C. The addition of EG powder increased the contact probability between fillers and provided more adsorption positions for PCM, increasing the latent heat of composites. The addition of 32 mesh EG-EG powder greatly increased the thermal conductivity of NN from 1.24 Wm(-1)K-1 to 5.43 Wm(-1)K-1. It is because the pores of large particle size EG are filled with EG powder, which is easy to form chain or network structure, forming more heat conduction pathways. The research provides some technical support for the application of phase change heat storage technology.