Diffusion and thermal conductivity of the mixture of paraffin and polystyrene for thermal energy storage: A molecular dynamics study

The development of thermal energy storage material is of vital importance to relieve the severe challenges of energy crisis. Phase change material and microencapsulated phase change material for energy storage is an important branch of thermal energy storage technology. In this paper, the simplified amorphous cell model was constructed with n-octacosanoic (C28H58), n-docosane (C22H46) and polystyrene (PS), which was used to investigate the heat and mass transfer of this system by performing molecular dynamics (MD) and non-equilibrium molecular dynamics methods (NEMD). The simulation results showed that the self-diffusion of this system will enhance with increasing temperature. Furthermore, higher temperature contributes to the extension of catenulate molecules, especially for polystyrene, which actually enhances the mass transfer of system. In addition, the thermal conductivity of the system increases with continuously increasing temperature, but the values are lower than that of pure paraffin. Therefore, the high thermal conductivity additives are required to be added into the mixture in order to improve the ability of heat transfer of the material.