Design optimization and thermophysical characteristics of NaF-KCl reciprocal salts by theoretical predictions and experimental measurements for the high latent heat storage

Fluoride/chloride reciprocal salts are promising high temperature latent heat storage materials. However, few studies have focused on the phase behaviors and thermophysical properties of the fluoride/chloride mixtures. The novel NaF-KCl reciprocal salt was designed and optimized by thermodynamic calculation and experimental measurement. The eutectic point of the NaF-KCl reciprocal salt was placed at 27.3 mol% NaF and 922.1 K, consistent with experimental values. The thermophysical properties of fusion enthalpy, specific heat capacity, density and electric conductance were empirically predicted and experimentally determined. The latent heat reached 454.8 J/g, which was higher than that of established molten salts. The solid and liquid-state specific heat capacity were 0.9293 and 1.1397 J center dot g(-1)center dot K-1, respectively. The density of NaF-KCl salts increased from 1.650 to 1.700 g center dot cm(-3) with temperature risen from 920 K to 1030 K. The average value of electric conductance was 2.42 S center dot cm(-1). The thermophysical properties were empirically predicted, and well agreed with the experimental measurements except for the fusion enthalpy. The Cost of per kJ energy of NaK-KCl was evaluated, and 7 % - 68 % lower than that of established molten salts. Results showed that NaF-KCl reciprocal salts could be a promising candidate material for high temperature heat storage due to their superior heat storage capacity and competitive cost. This work can provide key data for multicomponent fluoride/chloride reciprocal salt design, and expand the selection of high temperature latent heat storage materials.

Automated summary

This study designed and optimized a novel NaF-KCl reciprocal salt through thermodynamic calculation and experimental measurement. The results showed that the eutectic point of NaF-KCl reciprocal salt was at 27.3 mol% NaF and 922.1 K, consistent with experimental values. The thermophysical properties of the salt, including fusion enthalpy, specific heat capacity, density, and electric conductance, were empirically predicted and experimentally determined. The NaF-KCl reciprocal salt exhibited a higher latent heat, lower energy cost, and good agreement between empirical predictions and experimental measurements.