Enhanced thermal performance of binary eutectic chloride salt by integrating nanoparticles: A molecular dynamics study

Abstract

Chloride salts are considered the most promising high-temperature thermal energy storage media for next-generation concentrating solar power (CSP) plants. To enhance the thermal performance of NaCl-KCl eutectic salt phase change material (PCM), composite phase change materials (CPCMs) were developed by separately integrating Al₂O₃, CuO, and SiO₂ with PCM. The microstructure evolution and thermophysical properties of the materials were investigated by means of molecular dynamics (MD) simulations, the simulation results were in good agreement with the available experimental data, and the mechanism of thermal performance enhancement was elucidated from a microscopic perspective. The figure of merit (FOM) was introduced as an evaluation criterion for the thermal characteristics of the materials. CuO nanoparticles exhibited the most significant effect on the thermal conductivity of PCM, with a maximum increase of 28.1 %. Al₂O₃ nanoparticles appeared the best performance in improving the specific heat capacity of PCM, with an increase of 9.2 %. Although the integration of nanoparticles increased material viscosity, Al₂O₃ nanoparticles induced only a 14.2 % rise in viscosity of the base salt at high temperature. Based on microscopic energy analysis, the thermal performance enhancement was attributed to the increase in average potential energy of the atoms in the system, which would strengthen the interatomic interactions. The FOM confirmed that Al₂O₃ nanoparticles held the greatest potential for application in the optimization of the overall performance of CSP power plants. This study is expected to provide valuable guidance for the design and application of molten salt-based high-temperature thermal energy storage materials.