Molecular dynamics simulation of thermal properties of modified graphene / n-octadecane composite phase change material

Abstract

Phase change materials have been widely used in building energy-saving and off-peak energy storage systems, but most phase change materials limit their application because of their low thermal conductivity. Improving their heat transfer performance and revealing the heat transfer mechanism from a microscopic perspective are the keys to practical applications. The PCM system composed of n-octadecane and modified graphene was established by molecular dynamics simulation and the influence of macro thermal properties was analyzed from a microscopic perspective including end-to-end distance and torsional angle distribution, radial distribution function, and self-diffusion coefficient. The results show that the thermal conductivity of PCMS increases with increased modified graphene content. When the mass fraction is 26.88%, the thermal conductivity increases by 44.5%, which is consistent with the trend of experimental values. The addition of modified graphene resulted in a more concentrated distribution of n-octadecane molecules, indicating that the arrangement of n-octadecane molecules was affected, increasing the thermal conductivity of n-octadecane. The deviation of phase transition temperature from the experimental value is less than 1%.