Self-Diffusion Coefficients of Carbon Dioxide at 1180°—1680°K

Abstract

Self‐diffusivities of carbon dioxide at 1180°—1680°K have been determined by a new version of the continuous flow method. Results can be correlated with previous low‐temperature data (mean error 1.5%) in terms of a single set of parameters of the Lennard‐Jones (6–12) potential (σ=2.70 Å, ε/k=871°K) valid for the entire temperature range (195°—1680°K). Literature values of viscosity (200°—1500°K) may also be correlated by a single set of parameters (σ=3.94 Å, ε/k=200°K). It is suggested that one can include both viscosity and self‐diffusivity data in the same correlation if the nonsphericity of the CO₂ molecule, which may have the strongest effect at high temperatures, is accounted for. This can be done approximately by use of the nonsphericity factors calculated by Curtiss and co‐workers for rigid, spherocylindrical molecules, if one assumes a temperature dependence for the factor such that it becomes about unity at room temperature.