Determination of the Binary Diffusion Coefficients and Interaction Viscosities of the Systems Carbon Dioxide–Nitrogen and Ethane–Methane in the Dilute Gas Phase from Accurate Experimental Viscosity Data Using the Kinetic Theory of Gases

Abstract

AbstractThe results of viscosity measurements at moderate densities on the two gaseous mixtures carbon dioxide–nitrogen and ethane–methane including the pure gases between 253.15 K and 473.15 K, originally performed by Humberget al.at Ruhr University Bochum, Germany, using a rotating-cylinder viscometer between 0.1 MPa and 2.0 MPa, were employed to determine the interaction viscosity,$$\eta _{12}^{(0)}$$η12(0), and the product of molar density and diffusion coefficient,$$(\rho D_{12})^{(0)}$$(ρD12)(0), each in the limit of zero density. The isothermal viscosity data were evaluated by those authors with density series restricted to the second order at most to derive the zero-density viscosities and initial density viscosity coefficients,$$\eta _\textrm{mix}^{(0)}$$ηmix(0)and$$\eta _\textrm{mix}^{(1)}$$ηmix(1), for the mixtures, as well as,$$\eta _i^{(0)}$$ηi(0)and$$\eta _i^{(1)}$$ηi(1)($$i=1,2$$i=1,2), respectively, for the pure gases. Humberget al.have already compared their$$\eta _\textrm{mix}^{(0)}$$ηmix(0)and$$\eta _i^{(0)}$$ηi(0)data for carbon dioxide–nitrogen and ethane–methane with corresponding viscosity values theoretically computed for the nonspherical potentials of the intermolecular interaction. Now we employed$$\eta _\textrm{mix}^{(0)}$$ηmix(0)and$$\eta _\textrm{mix}^{(1)}$$ηmix(1)as well as$$\eta _i^{(0)}$$ηi(0)and$$\eta _i^{(1)}$$ηi(1)in two procedures to derive$$\eta _{12}^{(0)}$$η12(0)values. For this, we needed$$A_{12}^*$$A12∗values (ratio between effective cross-sections of viscosity and diffusion). But the second procedure applying the initial density viscosity coefficients$$\eta _\textrm{mix}^{(1)}$$ηmix(1)and$$\eta _i^{(1)}$$ηi(1)failed to yield reasonable$$\eta _{12}^{(0)}$$η12(0)values. The first procedure should provide the best results when it is possible to use$$A_{12}^*$$A12∗values computed for the nonspherical potential. The effect is comparatively small if$$\eta _{12}^{(0)}$$η12(0)is determined. But if$$(\rho D_{12})^{(0)}$$(ρD12)(0)is calculated from$$\eta _{12}^{(0)}$$η12(0)using$$A_{12}^*$$A12∗values for the nonspherical potential, the impact is several percent. Moreover, the experimentally based$$\eta _{12}^{(0)}$$η12(0)and$$(\rho D_{12})^{(0)}$$(ρD12)(0)data agree with theoretically calculated values for the nonspherical potentials.