Abstract:

Chloride salts are promising high-temperature thermal energy storage materials due to their low cost and high heat storage density. However, their low specific heat capacity and poor thermal conductivity limit their performance, necessitating enhancement strategies. In this study, LiCl-NaCl-KCl ternary eutectic salt was selected as the storage medium, and Al₂O₃ nanoparticles were introduced as dopants. A microscopic model of the molten salt nanofluid was constructed using molecular dynamics simulation to investigate the effects of temperature and nanoparticles on the microstructure and thermophysical properties. The structure-property relationship of the nanofluid was analyzed. Results show that, within the temperature range of 673—1073 K, the density, viscosity, and thermal conductivity of both the base salt and nanofluid decrease with increasing temperature. The addition of nanoparticles, however, increases these properties. As temperature rises, the first peak position of the radial distribution function shifts to shorter distances and its intensity weakens, indicating reduced particle number density around central ions, lower coordination numbers, weakened interparticle association, and increased self-diffusion coefficients, thereby enhancing the diffusion ability of the molten salt. Conversely, nanoparticles strengthen the association between cations and anions, shorten ion-ion distances, increase coordination numbers, and reduce self-diffusion coefficients, ultimately weakening the system's diffusion ability.

Key words: molten salt, Al₂O₃, microstructure, thermophysical property, molecular dynamics