Molecular dynamics simulation of thermophysical properties of NaCl-SiO2 based molten salt composite phase change materials

It is urgently needed to improve the thermal properties of molten salt based phase change materials used for effective storage and utilization of solar energy. In this paper, the physical model of NaCl-SiO2 composite phase change materials (CPCM) was established. An effective method based on molecular dynamics (MD) simulation was proposed and validated to predict the thermal properties of CPCM. The structural deformation during phase transition process of CPCM system was observed and the radial distribution function (RDF) was calculated to analyze the local structure. The results indicate that the thermal conductivity of NaCl is enhanced remarkably with a maximum increase of 44.2% by adding 2.4% volume fraction of SiO2 nanoparticles and the mechanism of the thermal conductivity enhancement was discussed at the atomic level. The shear viscosity increases with the increase of the volume fraction of nanoparticles, with a maximum average increase of 23.6%. The relationship between self-diffusion coefficient and temperature is approximate to predict melting point. The force field and simulation methods adopted in this paper are desired to be useful for the prediction of thermal properties and further investigation into molten salts based thermal energy storage systems.