Enhanced heat conduction in molten salt containing nanoparticles: Insights from molecular dynamics

Abstract

The addition of nanoparticles is a promising strategy to manipulate the thermal transport property of molten salt, which is an important thermal energy storage material for concentrating solar power. The molecular dynamics simulations have been conducted to investigate the mechanisms of enhanced heat transfer in binary molten salt based nanocomposite with nonmetallic nanoparticle SiO2. The results show that the thermal conductivity of molten salt is increased by introducing nanoparticles, which is up to 54.5% increase under 10%wt. loading of SiO2 nanoparticle. Moreover, the thermal conductivity increases as the nanoparticle loading rises. To elucidate the underlying mechanisms for the enhancement of thermal conductivity, the mean square displacement and size effect of nanoparticle, the structure and density of the ordered layer were analyzed. It is found that the possible mechanisms, including the Brownian motion of nanoparticle, the micro-convection of base fluid, and the ordered layer at the solid-liquid interface, for enhanced heat transfer proposed in previous literatures cannot explain the change in thermal conductivity of molten salt. The increment in thermal conductivity can be attributed to the improved probability and frequency of ion collision, as evidenced by the change of potential energy. The present findings verify the applicability for the molten salt-nanoparticle composite, moreover, highlight the correlation between the potential energy and the enhancement of thermal conductivity, which may provide guidance on the chosen of materials and design of the molten salt-nanoparticle composite.