Heats of transport of ideal gases and gas mixtures

Abstract

Kinetic theory expressions for thermal transpiration interpreted within the framework of non-equilibrium thermodynamics provide a detailed description of the heat of transport in terms of gas properties. For a pure monatomic gas, the heat of transport decreases from a constant value in the Knudsen limit to zero in the continuum region, the variation being an inverse quadratic function of pressure. For this case, the heat of transport depends markedly on temperature. Inelastic collisions involving rotational degrees of freedom, as occur in polyatomic gases, result in small but measurable deviations from monatomic gas behaviour. With binary gas mixtures, interactions between the different species cause appreciable deviations from simple mixing rules.