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Chloride molten salts have become a potential heat storage material for the design of a new generation of concentrating solar power (CSP) (>700 °C) due to its abundant reserves and low cost. The difficulty of measuring the high-temperature thermal properties of chlorides can be effectively solved by using molecular dynamics simulation. However, it is challenging to get the thermophysical properties of multi-component molten salts containing CaCl2 due to the lack of Born–Mayer–Huggins (BMH) potential parameters of CaCl2. Through comparative analysis of the structure and thermal properties of CaCl2, including density and thermal conductivity, a set of Born–Mayer–Huggins (BMH) potential parameters of CaCl2 named SP2 is determined in this study. The density, specific heat capacity, and thermal conductivity of nine eutectic molten salts are simulated, including NaCl-CaCl2, KCl-CaCl2, NaCl-CaCl2-MgCl2, and NaCl-CaCl2-KCl, and the simulation results are found to be in good agreement with the experimental results. It is also found that the SP2 parameters are able to predict the thermal properties and structure of molten multicomponent chlorides including calcium. [ABSTRACT FROM AUTHOR]

Molten chloride salt is recognized as a promising heat transfer and storage medium in concentrating solar power in recent years, but there is a serious lack for thermal property data of molten chloride salts. In this work, local structures and thermal properties for molten chloride salt—including NaCl, MgCl2, and ZnCl2—were precisely simulated by Born–Mayer–Huggins (BMH) potential in a rigid ion model (RIM) and a polarizable ion model (PIM). Compared with experimental data, distances between cations, densities, and heat capacities of molten chloride slats calculated from PIM agree remarkably better than those from RIM. The polarization effect brings an extra contribution to screen large repulsive Coulombic interaction of cation–cation, and then it makes shorter distance between cations, larger density and lower heat capacity. For NaCl, MgCl2, and ZnCl2, PIM simulation deviations of distances between cations are respectively 3.8%, 3.7%, and 0.3%. The deviations of density and heat capacity for NaCl between PIM simulation and experiments are only 0.6% and 2.2%, and those for MgCl2 and ZnCl2 are 0.7–10.7%. As the temperature rises, the distance between cations increases and the structure turns into loose state, so the density and thermal conductivity decrease, while the ionic self-diffusion coefficient increases, which also agree well with the experimental results. [ABSTRACT FROM AUTHOR]

NaCl–CaCl 2 molten salt is considered as a promising high-temperature heat transfer and storage fluid for advanced nuclear power plants and concentrating solar power plants in the field of renewable energy utilization. However, the comprehensive physical properties and their microscopic mechanisms for the molten NaCl–CaCl 2 are failed to be measured accurately due to the extremely measuring condition. In this work, the ab-initio molecular dynamics simulation is used to investigate its microstructures and thermophysical properties for entire operating temperatures. It reveals that ion clusters are formed in terms of three for face-sharing, two for edge-sharing, and one for corner-sharing Cl− ions between the coordination shells of two neighboring cations. The coordination numbers of Na+-Cl- and Ca2+-Cl- ion pairs decrease from 5.88 to 6.46 at 783 K to 5.33 and 6.02 at 1173 K respectively. Meanwhile, the reliable and meaningful values of densities, ion self-diffusion coefficients, viscosities, and thermal conductivities were evaluated from 783 to 1173 K. It suggests that the distances and interactions between ions pairs determine thermodynamic properties directly. The ab-initio molecular dynamics simulation is proved to be an effective way to obtain the essential data for the designs of heat transfer and thermal energy storage systems in practical applications. • Ab-initio molecular dynamics simulations are applied for NaCl–CaCl 2. • Approach-to-equilibrium molecular dynamics method is used for thermal conductivity. • The correlation between microstructures and thermophysical properties are studied. • The distances and interactions between ion pairs determine its properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Molten chloride salt is recognized as a promising heat transfer and storage medium in concentrating solar power (CSP) in recent years, but there is a serious lack for thermal property data of molten chloride salts under high-temperature condition. In this work, temperature and component dependence of local structure and physical properties for binary KCl–MgCl 2 mixture were computed by molecular dynamics simulations (MD) method based on Born–Mayer–Huggins (BMH) potential. As the temperature rises, the distances between ions change and the structures turn into loose state, thus the density, thermal conductivity and the shear viscosity decrease, which also agree well with the experimental results. The calculation errors of thermal properties are mainly within 8%. The results show that density and thermal conductivity have negative linear correlation with temperature. Specific heat capacity is invariant with temperature at a constant pressure. When K+ increases in the salt, thermal conductivity is significantly improved, and shear viscosity and specific heat capacity decrease. The formulas of temperature-thermal properties-component correlations are obtained, which provide the fundamental property database for the precise design of high-temperature thermal storage system. ● Structures and thermal properties of KCl–MgCl 2 were calculated by MD simulations. ● Properties of KCl–MgCl 2 were influenced by component and temperature. ● With increasing K+, coordination structures became looser and densities decreased. ● The correlations of properties and component/temperature were obtained. [ABSTRACT FROM AUTHOR]