Modeling Thermal Conductivity of Concentrated and Mixed-Solvent Electrolyte Systems

A comprehensive model has been developed for calculating the thermal conductivity of aqueous, nonaqueous, and mixed-solvent electrolyte systems ranging from dilute solutions to fused salts or pure solutes. The model consists of a correlation for calculating the thermal conductivity of solvent mixtures and a method for predicting the effect of electrolyte components. The thermal conductivity of multicomponent solvent mixtures can be represented using surface area parameters and thermal conductivities of pure solvents in conjunction with a single binary parameter per solvent pair. The effect of electrolytes is modeled by accounting for a contribution of individual ions, which is quantified by the Riedel coefficients, and a contribution of specific interactions between ions or neutral species. Formulations have been developed for the contributions of individual ions and species-species interactions to represent the effect of multiple solvents. In addition to solvent composition, the species-species interaction term is also a function of ionic strength. The model accurately reproduces experimental thermal conductivity data over a wide range of electrolyte concentrations in aqueous and nonaqueous systems. In particular, the model has been shown to be accurate for aqueous acids and bases (e.g., H2SO4, HNO3, H3PO4, NaOH, and KOH) up to the limit of a pure acid or base, various nitrates ranging from dilute solutions to fused salts, and other salts in water and various organic solvents. The model has been coupled with thermodynamic equilibrium calculations to reproduce the effects of complexation or other ionic reactions on thermal conductivity.