Molecular dynamics study on the adsorption and thermal properties of paraffin in graphene

Abstract

Graphene is a promising filler to solve the low thermal conductivity and the leakage of phase change materials (PCM). Understanding the adsorbing process of PCM in porous graphene nanosheets and thermal property of composites is essential for practical application. The simulations reveal that the maximum adsorption range is 15 Å. The final structures of composites look like a spherical structure. The maximum adsorbing percentage of paraffin is 81.72% with the density of graphene at 0.3 g/cm3, which has a storage efficiency of 75.88%. With the increasing density, the total diffusion coefficients of composites slightly decrease in the range of 4∼5 × 10−10 m2/s. A dense phase around graphene affects the phase change behavior of paraffin. By analyzing the interaction energy and the phonon vibration coupling, the thermal conductivity of composites is found to increase with the increasing density of graphene. Due to the coactions of small calculated size and interfacial thermal resistance between graphene and paraffin, the current values of thermal conductivity are lower than the expected ones. In this paper, the optimum density of graphene is 0.5 g/cm3, at which latent heat and thermal conductivity of composites are 84.17 J/g and 0.51 W/m·K, respectively.