Crossover Residual Entropy Scaling of the Viscosity and Thermal Conductivity of Carbon Dioxide

The crossover method is applied to the residual entropy scaling of viscosity and thermal conductivity to overcome the failure of the original model in the description of critical enhancement. Carbon dioxide is selected as a demonstration. One can derive the thermodynamic properties and fluid characteristic parameters required by the residual entropy scaling and critical enhancement term from the crossover multiparameter equation of state or crossover volume-translated Soave-Redlich-Kwong equation of state. The critical enhancement effects on viscosity and thermal conductivity are calculated using crossover functions based on the mode-coupling theory. It is found that the reduced value of the background part extracted from the near-critical viscosity and thermal conductivity data follows a univariate function of residual entropy, which is unified for the gaseous, liquid, and supercritical regions. The crossover models better represent the viscosity and thermal conductivity near the critical point with no deterioration in accuracy in the crossover region. The model incorporating the multiparameter equation of state takes advantage of the faithful representation of experimental data while the model of the volume-translated Soave-Redlich-Kwong equation of state is more feasible to be extended to other fluids and mixtures.