Boundary Effects for High Temperature Gases

Abstract

Phenomena closely related to the transport of mass, momentum and energy in gas mixtures are those which take place at the boundary of gas volumes. Firstly, because of the temperature gradient, there is a transport of dissociated and ionized particles to cooler regions giving rise to considerable increase in the heat transfer rate, and for ionized gases a loss in the number of the charged particles also. To keep the electric current flowing in the ionized gases, new charged particles have to be created. This starts with the generation of the charged particles like the electrons on the surface. This emission of electrons is one of the factors that determines whether or not a gas discharge is to be self-sustaining, and is, therefore, of considerable interest in the study of conduction of electricity through gases. In studying the various experiments on the electron emission taking place under ideal conditions, one must, however, take care in applying the results to gas discharges in which the emission phenomena are involved, for the electron emission is greatly influenced by the gas condition of the emitting surface. Usually, experiments on emission involve a careful preliminary outgassing of the surfaces in order to obtain results for gas-free surfaces.