Microstructure and thermal properties of NaCl–ZnCl2 molten salt by molecular dynamics simulation and experiment

Abstract

Zn−based chloride molten salts have been candidate heat transfer and storage media in solar thermal power attributed to excellent thermal properties and high thermal stability, while associated thermal properties at high temperature are still insufficient in research. In this work, microstructure and thermal properties of NaCl–ZnCl 2 molten salt have been investigated by molecular dynamics simulation based on Born−Mayer−Huggins potential and experimental measurement. Encouragingly, the trends of all properties from simulation are consistent with experimental data, and the errors are 6.97% in density and 7.42% in specific heat, respectively. As temperature increases, the distance between ion clusters centers on cations increases and the internal of ion clusters shrinks, thus density and viscosity decrease with the whole structure of NaCl–ZnCl 2 becoming looser, and thermal conductivity decreases because smaller Zn–Cl distance in [ZnCl n ] structure causes shorter phonon mean free path and larger thermal resistance. As content of ZnCl 2 decreases, density, specific heat capacity and viscosity decrease with the whole structure becoming looser, but thermal conductivity increases due to larger Zn–Cl distance. Besides, the correlation equations for properties−temperature−composition of NaCl–ZnCl 2 (0–100 mol. % ZnCl 2 , 578 K–1073 K) have been further identified for its utilization in advanced thermal storage systems. • NaCl–ZnCl 2 has been studied by molecular dynamics simulation and experiment. • Ion clusters center on cations and stable network structure [ZnCl n ] (n = 5–6) forms. • Density and viscosity decrease as temperature rising or content of ZnCl 2 dropping. • Thermal conductivity drops for shorter Zn–Cl distance and phonon mean free path. • Correlations for properties-temperature-composition of NaCl–ZnCl 2 are identified.