Mechanisms for thermal conduction in molten salt-based nanofluid

The addition of nanoparticles to molten salt can enhance its utility as a thermal energy storage material for concentrating solar power plants. The heat transfer property of solar salt loaded with Al2O3 nanoparticle is investigated by molecular dynamics simulations. The results show that the introduction of Al2O3 nanoparticles improves the thermal conductivity of solar salt, but its enhancement effect is not as significant as SiO2 nanoparticles. The increased thermal conductivity cannot be explained by the previously proposed hypothesis, such as the Brownian motion of nanoparticles, microconvection of base liquid, ordered layer of base liquid and coulombic potential energy. New insights into heat conduction performance of molten salt based nanofluid are given from the perspectives of material components and heat flux fluctuation modes. It is found that the nanofluid thermal conductivity is mainly contributed by the atom motions and interactions between atoms in Al2O3 nanoparticle, rather than in base fluid. The heat flux is concentrated in nanoparticle, which promotes the heat transfer. Furthermore, the collision involving the work done by the interatomic forces or the virial interaction dominates the heat conduction in nanofluid with lower mass fraction (< 6%), while the potential energy and collision both contribute to the nanofluid with higher mass fraction (> 6%). These new findings make a step forward in understanding the heat conduction mechanisms of molten salt based nanofluid. (c) 2022 Elsevier Ltd. All rights reserved.