Transport properties of high temperature air components: A review

The methods for the calculation of the transport properties of high temperature gases are reviewed from the points of view of both kinetic theory and transport cross sections. Particular emphasis is given to the poor convergence of the Chapman-Enskog method for calculating the thermal conductivity of free electrons and of the possible sources of errors when applying well known simplified formulae for calculating the translational thermal conductivity of heavy components and the viscosity of partially ionized gases. The transport cross sections (collision integrals) of high temperature air components are then discussed by comparing old and new calculations particularly emphasizing atom-atom, atom-molecule and atom-ion interactions. Special consideration is dedicated to the knowledge of transport cross sections of electronically excited states. The role of inelastic processes in affecting the transport cross sections is also briefly discussed. Finally the possibility to extend the results to non equilibrium situations is analysed.