Thermal conductivity of aqueous ZnCl2 solutions at high temperatures and high pressures

The thermal conductivity of H2O + ZnCl2 solutions was measured over the temperature range 293-473 K using a parallel-plate apparatus. Data cover the pressure range from 0.1 to 100 MPa. Measurements were made on six isobars, namely, 0.1, 20, 40, 60, 80, and 100 MPa. The concentrations studied were 2.5, 5, 10, 15, 20, and 25 wt % ZnCl2. The accuracy of the measurements was estimated to be +/-1.6%. The effect of temperature, pressure, and concentration on the thermal conductivity behavior was studied. The thermal conductivity shows a linear dependence on pressure and concentration at all isotherms for each concentration. Along each isobar a given concentration shows the thermal-conductivity maximum at temperatures between 405 and 417 K. The measured values of thermal conductivity are compared with the experimental and correlation results of other investigators. Our experimental results for the H2O + ZnCl2 system confirm the results obtained by DiGuilio et al. (DiGuilio, R. M.; et al. ASHRAE Traits. 1990, 96, 702; DiGuilio, R. M.; Teja, A. S. Ind. Eng. Chem. Res. 1992, 31, 1081) and Bleazard et al. (Bleazard, J. G.; et al. AIChE Symp. Ser. 1994, 298, 23; Bleazard, J. G.; Teja, A/ S. J. Chem. Eng. Data 1995, 40, 732). The constant-composition curves are not parallel to those for pure water at high pressures and high concentrations. A new correlation which yields the correct temperature, pressure, and concentration behavior of thermal conductivity is proposed. The pressure and temperature coefficients of the thermal conductivity have been studied.