Thermal Conductivity of Aqueous ZnCl₂ Solutions at High Temperatures and High Pressures

Abstract

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 Trans. 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.

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

“…The absolute uncertainty of the calculated values of the thermal conductivity of H 2 O + K 2 SO 4 is 0.00238 W·m −1 ·K −1 . Abdulagatov and Magomedov [29][30][31][32][33][34][35][36][37][38][39] developed a correlation equation to describe the thermal conductivity of aqueous salt solutions at high temperatures and high pressures, λ sol (T , P , x) = λ 0 (P , T ) 1 − A(x + 2 × 10 −4 x 3 ) − 2 × 10 −8 P T x, (4) λ 0 (P , T ) = 7 × 10 −9 T 3 − 1.511×10 −5 T 2 + 8.802 × 10 −3 T − 0.8624 + 1.6×10 −6 P T,…”

“…For pure water this maximum occurs at temperatures between 409 and 421 K at pressures between 20 and 60 MPa. The pressure and composition dependences of the thermal conductivity maximum for aqueous salt solutions were studied by Abdulagatov and Magomedov [31,34,35,37]. The thermal conductivity maximum of the H 2 O + K 2 SO 4 solutions is shifted to high temperatures as the pressure is increased, while the maximum of the λ − T curves decreases with concentration of K 2 SO 4 .…”

“…Along each isopleth-isotherm, the thermal conductivity increases almost linearly (the slope (∂λ/∂P ) TX is almost constant) as the pressure increases up to 30 MPa and is not parallel to those of pure water, especially at high K 2 SO 4 concentrations and high temperatures (see Fig. 4, see also [31,[51][52][53]). The slopes of the water isotherms (λ − P ) are slightly higher than the slopes of solution isotherms, especially at high pressures and high K 2 SO 4 concentrations.…”

“…The main objective of the paper is to provide new accurate experimental thermal conductivity and viscosity data for binary H 2 O + K 2 SO 4 solutions at high temperatures (up to 575 K) and high pressures (up to 30 MPa) for compositions up to 0.782 mol·kg −1 using coaxial-cylinder (steady-state) and capillary-flow techniques, respectively, which have been previously used for accurate measurements on other systems at high temperatures and high pressures [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. The present results expand considerably the temperature, pressure, and concentration ranges for which thermal conductivity and viscosity data for aqueous K 2 SO 4 solutions are available.…”

“…This work is a part of a continuing program on the transport properties (thermal conductivity and viscosity) of electrolytes in aqueous solutions at high temperatures and high pressures. In previous studies [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] we measured the thermal conductivity and viscosity of 30 aqueous salt solutions at high temperatures (up to 573.15 K) and high pressures (up to 100 MPa) using coaxial-cylinder, parallel-plate, and capillary-flow techniques.…”