Thermal Conductivity and Viscosity of Aqueous K2SO4 Solutions at Temperatures from 298 to 575 K and at Pressures up to 30 MPa

The thermal conductivity of three (0.239, 0.499, and 0.782 mol·kg−1) and the viscosity of four (0.0658, 0.2055, 0.3050, and 0.4070 mol·kg−1) binary aqueous K2SO4 solutions have been measured with coaxial-cylinder (steady-state) and capillary-flow techniques, respectively. Measurements were made at pressures up to 30 MPa, and the range of temperature was 298–575 K. The total uncertainties of the thermal conductivity, viscosity, pressure, temperature, and composition measurements were estimated to be less than 2%, 1.6%, 0.05%, 30 mK, and 0.02%, respectively. The measured values of the thermal conductivity and viscosity of K2SO4 (aq) were compared with data and correlations reported in the literature. The reliability and accuracy of the experimental method was confirmed with measurements on pure water with well known (IAPWS standards) thermal conductivity and viscosity values (deviations, AAD, within 0.31 % and 0.52 %, respectively). The values of the viscosity A-, B-, and D-coefficients of the extended Jones–Dole equation for the relative viscosity (η/η0) of aqueous K2SO4 solutions as a function of temperature were studied. The maximum of the B-coefficient near 340 K has been found. The derived values of the viscosity A- and B-coefficients were compared with results predicted by the Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data. The behavior of the concentration dependence of the relative viscosity of aqueous K2SO4 solutions is discussed in terms of the modern theory of transport phenomena in electrolyte solutions.