Study on the Physical Stability of Solar Salt Under Constant Temperature and Thermal Shock Conditions

In this work, the evolution of behavior and stability of the thermodynamic properties of solar salt (60% NaNO3 and 40% KNO3) under long-term constant temperature and thermal shock conditions were studied. Two thousand hours of constant temperature experiments were conducted at 565 °C, along with 500 thermal shock cycle experiments. The changes in key thermodynamic parameters, such as melting point, decomposition temperature, specific heat capacity, thermal conductivity, and viscosity of the samples before and after treatment were compared and analyzed. The results show that the melting point and decomposition temperature of the solar salt change little after the thermal stability experiment, with maximum change rates of 7.9% and 6.2%, respectively. The specific heat capacity decreased slightly, but the thermal shock samples in the middle temperature region showed a certain enhancement; the thermal conductivity was basically stable, and the viscosity increased slightly. In summary, the solar salt has good thermal stability and shows good application prospects in thermal energy storage in the field of medium and low temperatures.