Revised Model for the Thermal Conductivity of Multicomponent Electrolyte Solutions and Seawater

Abstract

A previously developed model for calculating the thermal conductivity of electrolyte solutions has been revised. The model represents the effect of electrolytes by introducing two terms in addition to the thermal conductivity of the solvent, i.e., a contribution of individual species expressed using modified Riedel coefficients and an ionic strength-dependent term that accounts for interactions between species. The revision improves and simplifies the ionic strength dependence of the species interaction term. The model has been parameterized based on extensive data for binary, ternary, and quaternary aqueous solutions containing the $\hbox {Na}^{+}, \hbox {K}^{+}, \hbox {Mg}^{2+}, \hbox {Ca}^{2+}, \hbox {Cl}^{-}, \hbox {SO}_{4}^{2-}, \hbox {HCO}_{3}^{-}$, and $\hbox {Br}^{-}$ ions at temperatures ranging from 273 K to 573 K and pressures up to at least 1000 bar. Good agreement between the calculations and experimental data has been obtained with an overall average deviation of 0.44 %. Further, the model has been used to predict the thermal conductivity of seawater and to evaluate the consistency and accuracy of experimental seawater data in view of those for its key components. While older seawater data suffer from significant discrepancies and are not in satisfactory agreement with the model, the predictions are in an excellent agreement with the recent data of Sharqawy. Finally, a much simplified yet accurate model has been formulated specifically for seawater by recasting the complete model in terms of salinity (rather than concentrations of individual components), temperature, and pressure.