The paper contains new, representative equations for the viscosity and thermal conductivity of carbon dioxide. The equations are based in part upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the low-density thermal conductivity at high temperatures, all available data are shown to be inconsistent with theoretical expectation and have therefore been abandoned in favor of a theoretical prediction. Similarly, the liquid-phase thermal conductivity has been predicted owing to the small extent and poor quality of the experimental information. In the same phase the inconsistencies between the various literature reports of viscosity measurements cannot be resolved and new measurements are necessary. In the critical region the experimentally observed enhancements of both trans: port properties are well represented by theoretically based equations containing just one adjustable parameter. The complete correlations cover the temperature range 200 K~T < 1500 K for viscosity and 200 K~T~l000 K for thermal conductivity, ~nd pressures up to 100 MPa. The uncertainties associated with the correlation vary according to the thermodynamic state from ± 0.3% for the viscosity of the dilute gas near room temperature to ± 5% for the thermal conductivity in the liquid phase. Tables of the viscosity and thermal conductivity generated by the representative equations are provided to assist with the confirmation of computer implementations of the calculation procedure.

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We present a solution of the mode-coupling equations for the dynamics of critical fluctuations which incorporates the crossover from the singular behavior of the transport properties of fluids asymptotically close to the critical point to the regular behavior of these properties far away from the critical point. Good agreement is obtained with experimental thermal diffusivity, thermal conductivity, and viscosity data for carbon dioxide at all temperatures and pressures where critical effects in these transport properties are observed.

We extend the application of the mode-coupling theory for the dynamics of critical fluctuations in fluids into the non-asymptotic critical region. An approximate solution of the mode-coupling equations yields a set of representative equations for the thermal conductivity and the viscosity of one-component fluids which incorporates the crossover from asymptotic singular behavior near the critical point to the regular behavior of these transport properties far away from the critical point. The equations for the critical enhancements of the thermal conductivity and the viscosity depend on the background transport properties of the fluid, the equilibrium thermodynamic properties of the fluid, and one fluid-dependent wave-number cutoff qD, which is indicative of the crossover length scale. We compare our crossover model with experimental data for the thermal diffusivity, the thermal conductivity, and the viscosity of carbon dioxide and ethane.

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