Influence of preparation processes on thermophysical properties of molten salt

Molten salt has been widely studied as a heat storage material, but some properties of molten salt reported in different literature studies are not completely consistent. In order to make data comparison more convenient and improve the effectiveness of scientific research communication, reasons for the data discrepancy were studied. In this work, the relationship between the preparation of NaNO3–KNO3 binary molten salt and thermophysical properties was studied. Six preparation methods including static melting method, dissolution method, stirring evaporation method, boiling evaporation method, tap water dissolution method, and grinding method were adopted. The thermophysical properties studied include melting range, latent heat, and decomposition temperature. The experimental results show that all the above methods can be used to prepare NaNO3–KNO3 molten salt with good thermophysical properties except for the dissolution method, which would lead to uneven distribution of compositions. For the grinding method, it is found that the properties of molten salt are stable when the particle size is less than 96 µm. Samples prepared by these feasible methods have a melting point range of 220–240 °C. Their latent heat is more than 100 J/g and the decomposition temperature up to ∼580 °C. Thermal properties are affected to some extent by the preparing process, such as impurities in the solvent or the drying process.