关键词: 熔盐, Al₂O₃, 微观结构, 热物性, 分子动力学

Abstract:

Chloride salts have become the most promising high-temperature thermal energy storage materials due to their low cost and high heat storage density. However, they also have the disadvantages of low specific heat capacity and weak thermal conductivity. Therefore, it is urgent to carry out the thermal property enhancement work of chloride salts. In this paper, LiCl-NaCl-KCl ternary eutectic salt was selected as the thermal energy storage material, and Al₂O₃ nanoparticle was used as the dopant. The microscopic model of molten salt nanofluid was constructed by molecular dynamics simulation method. The effects of temperature and nanoparticles on the microscopic structure and thermal property of molten salt were studied, and the "structure-effect relationship" of molten salt nanofluid was analyzed. The results show that within the temperature range of 673-1073K, the density, viscosity and thermal conductivity of molten salt and its nanofluid decrease with the increase of temperature. However, the addition of nanoparticles increases the density, viscosity and thermal conductivity of molten salt. The increase of temperature causes the position of the first peak of the radial distribution function of the system to gradually decrease, and the intensity of the peak gradually weakens, the particle number density around the central ion decreases, the coordination number decreases, the association between particles weakens, and the self-diffusion coefficient increases, the diffusion ability of molten salt enhances. However, nanoparticles enhance the association between cations and anions in the system, reduce the distance between ions, increase the coordination number, and decrease the self-diffusion coefficient, weakening the diffusion ability of the system.

Key words: Molten salt, Al₂O₃, Microstructure, Thermophysical property, Molecular dynamics