Thermal conductivities of gaseous mixtures containing polar gases. More than one polar constituent

Abstract

Thermal conductivities of binary and ternary mixtures containing more than one polar gas have been measured at 50 and 100°C. The systems investigated are: SO₂+(CH₃)₂O; SO₂+ CH₃Cl; (CH₃)₂O + CH₃Cl; SO₂+(CH₃)₂O + CH₃Cl. The apparatus is of the two-wire type in which measurements are made relative to known standards. For all three binary systems, experimental values of the thermal conductivity show positive departures from the molar average (mean departure for 54 mixtures +1.2 %) in contrast to the previous findings for viscosities, which vary almost linearly with composition. For ternary mixtures, the experimental thermal conductivities show greater departures from the molar average (mean departure for 14 mixtures +4.0 %).

The results are discussed in terms of the experimental Wassiljewa coefficients A_ij, and comparisons are made with the predictions of approximations based on rigorous theory (Hirschfelder-Eucken) and with those of the Lindsay and Bromley approximation. The predictions of the Hirschfelder-Eucken theory for binary mixtures underestimate the experimental observations by 2.7 % on average; for ternary mixtures, the average underestimate is 6.4 %. The possible causes of this failure of the Hirschfelder-Eucken theory are discussed, and some new suggestions are put forward based on different assignments of the translational and internal contributions to the thermal conductivities of the pure gases. With some of the proposed modifications, the calculated predictions come close to the experimental uncertainty of the measured values.