Viscosity and thermal conductivity equations for nitrogen, oxygen, argon, and air

New formulations for the viscosity and thermal conductivity for nitrogen, oxygen, argon, and air are given. Air is treated as a pseudo-pure fluid using an approach adopted from previous research on the equation of state for air. The equations are valid over all liquid and vapor states, and a simplified cross-over equation was used to model the behavior of the critical enhancement for thermal conductivity. The extrapolation behavior of the equations for nitrogen and argon well below their triple points was monitored so that both could be used as reference equations for extended corresponding states applications. The uncertainties of calculated values from the equations are generally within 2% for nitrogen and argon and within 5% for oxygen and air, except in the critical region where the uncertainties are higher. Comparisons with the available experimental data are given.