A theoretical framework for reliable predictions of thermal conductivity of multicomponent molten salt mixtures: KCl-NaCl-MgCl2 as a case study

Abstract

The next generations of Concentrated Solar Thermal Power (CSTP) systems use anhydrous salts as the heat transfer fluid and thermal storage medium. Unfortunately, a severe lack of experimental data is observed for the thermal transport properties of molten salt mixtures, generating constraints in exploring new potential materials for CSTP systems. The present paper presents a reliable theoretical framework for the prediction of both the thermal conductivity and thermal diffusivity of multicomponent molten salts. As a case study, the thermal conductivity of the NaCl-KCl-MgCl 2 system is predicted as a function of temperature and composition. This system is considered as a one of the most promising thermal storage medium of the next generation of CSTP systems. The temperature dependent thermal conductivity of pure MgCl 2 is formulated based on atomistic simulations via classical and Ab initio equilibrium molecular dynamics. Thereafter, to assess the predictive capability of the proposed methodology, the thermal conductivity and thermal diffusivity of KCl-MgCl 2 and NaCl-KCl-MgCl 2 molten mixtures are predicted as a function of both temperature and composition and compared to the available experimental data and the present first principles simulations. A good agreement is achieved with both experimental and first principle data, indicating the robustness of the proposed methodology. • A Theoretical framework to predict the thermal conductivity of PCM from 298 K up to above the melting established. • The temperature dependent thermal conductivity of molten MgCl 2 is re-assessed based on AIMD. • The thermal conductivity of NaCl-KCl-MgCl 2 is predicted via Kinetic Theory and Equilibrium Molecular Dynamics. • The predicted capability of the proposed approach is demonstrated through comparison with most recent experimental data.