Thermal properties of Na2CO3–NaCl–KCl ternary eutectic salt for high-temperature thermal energy storage: Experimental and deep potential molecular dynamics combined

With the global energy structure transitioning toward decarbonization, molten salts serve as critical media for efficient thermal energy storage and transfer in large-scale utilization of renewable energy. However, the experimental measurements of the thermal properties of high-temperature molten salts suffer severe obstacles due to their strong corrosiveness and toxicity, necessitating high-precision multiscale predictive models. This study focuses on the Na2CO3-NaCl-KCl ternary eutectic molten salt system, integrating experimental measurement with deep potential molecular dynamics simulation to systematically investigate its high-temperature thermal properties. The experimental results show that the melting point, enthalpy of fusion, and specific heat capacity of ternary eutectic salt is 852.65 K, 392.00 J/g, and 1.268 J/(g K), respectively, indicating the outstanding heat storage capacity. Initial datasets generated from first-principle molecular dynamics are optimized using the DP-GEN enhanced sampling strategy, and the simulation results reveal that the density decreased from 1.776 g/cm3 (873 K) to 1.690 g/cm3 (1073 K), with a maximum deviation of 2.68% compared to experimental data. The specific heat capacity is 1.276 J/(g K), exhibiting a negligible error of 0.63% against experimental values. Viscosity declined from 3.117 mPa s (873 K) to 1.755 mPa s (1073 K), consistent with the Stokes-Einstein relationship, while thermal conductivity slightly decreased with rising temperature. This study validates the high accuracy and reliability of the DP model in predicting thermal properties of molten salt and provides theoretical insights for material design and operational optimization of high-temperature molten salt thermal energy storage systems.