Novel high thermal stability LiF-Na2CO3-K2CO3 eutectic ternary system for thermal energy storage applications

A novel eutectic composition in the LiF-Na2CO3-K2CO3 ternary system was predicted using thermodynamic modeling based on Gibbs energy of fusion and designed for thermal energy storage or metal heat treatment. The Differential Calorimetry Scanning (DSC) technique was used to experimentally measure the melting point of the eutectic composition in the ternary system which was determined to be 694.40 K. Heat capacity of the eutectic composition of the ternary system was also measured using DSC from solid to liquid state and the results were plotted as function of temperature. The upper temperature limit for thermal stability of the eutectic mixture was determined in different atmospheres using the Thermogravimetric Analyzer (TGA). The high upper temperature limit for thermal stability ensures the large working temperature range of the LiF-Na2CO3-K2CO3 ternary system. Thermal conductivity of the ternary system was also studied by using a simplified inverse method. The relatively high thermal conductivity indicates its high efficiency of energy storage. Based on the measured thermodynamic properties, physical properties and its high energy storage density, this ternary system can be used as heat transfer fluid for thermal energy storage application.