New Model for Thermal Conductivity and Viscosity of Molten Salts

Liquid salts (which are generally called molten salts at high temperatures and ionic liquids at low temperatures) play a critical role in the production and processing of many materials and are receiving renewed interest as high temperature heat transfer fluids in Concentrated Solar Power (CSP) plants. Unfortunately, reliable thermophysical properties of molten salts, such as thermal conductivity and viscosity, are either rarely available or subject to large experimental uncertainties. In this work, a new model based on the rough hard-sphere theory is proposed for thermal conductivity and viscosity of molten salts. This model incorporates a smooth hard-sphere contribution using the properties of argon, as well as characteristic parameters based on the melting point of the molten salt. Thermal conductivity and viscosity of monovalent and multivalent molten salts have been correlated using this approach and some of the discrepancies in published data have been resolved. For salts with a common anion, a single adjustable parameter in the model exhibits regular behavior with the molecular weight of the salt. Thermal conductivity and viscosity of several molten-salt mixtures have also been predicted.