MgO/Molten salt interfacial thermal transport and its consequences on thermophysical property enhancement: A molecular dynamics study

Abstract

The solid-liquid interface between molten salt and solid oxides is ubiquitous in the molten salt nanocomposite with enhanced heat storage and transfer properties for concentrating solar power (CSP) systems. Understanding the microscopic mechanisms of interfacial thermal transport on this solid-liquid interface have great significance for evaluating the effective thermal properties of nanocomposites. This study combines equilibrium and non-equilibrium molecular dynamics simulations to explore the thermal transport and its connection with interfacial microstructure at the solid MgO-molten Hitec salt interface. Simulation results indicate that the enhancement of thermal transport can be ascribed primarily to the highly ordered adsorption structure of molten salt ions formed at the MgO surface, and the effect medium model incorporated with the simulated interfacial thermal resistance can reproduce the thermal conductivity of nanocomposite accurately. Further investigation indicates that the stronger adsorption at the MgO (110) surface leads to smaller interfacial thermal resistance than the MgO (100) surface, while the heat transfer parallel to the slab does not show much difference in both surfaces. These findings have illustrated the enrichment of molten salt ions at the solid surface does have a strong enhancement effect on their heat transfer properties and it is also necessary to incorporate the contribution from this interfacial thermal transport enhancement when predicting the thermophysical properties of molten salt nanocomposite materials.