On the viscosity of molten salts and molten salt mixtures and its temperature dependence

Molten salts and molten salt mixtures (will be referred as molten salts for convenience) are important heat storage media and heat transfer fluids for concentrated solar power plants and molten salt reactors. Besides the heat capacity, the thermal conductivity, and the thermal and chemical stability, the viscosity is also widely studied by experimental measurements and theoretical predictions because of the importance in engineering applications. In this work, the experimental viscosities of molten salts are compiled from literatures, and a novel empirical equation is proposed for the prediction of the temperature dependence of viscosity of molten salts. This novel empirical equation extends the Arrhenius equation with three empirical parameters and performs better than the Arrhenius equation for the applications to fluorides, chlorides, nitrates, and carbonates. Finally, its physical basis is discussed and the empirical parameters are recommended for molten salts with experimental viscosity being reported in literatures.