| Popis: |
Theoretical expressions for the motion of spherical aerosol particles in gas mixtures having both temperature and composition gradients are obtained that cover the free-molecule to the continuum regime. The theoretical model treats the aerosol particles as one component of the multicomponent mixture, and yields explicitly the complete pressure and composition dependence of thermodiffusiophoresis. Effects of molecular internal degrees of freedom are included, but not effects connected with the thermal conductivity of the aerosol particles. Thermophoresis and diffusiophoresis are found to interact in three ways with each other in thermodiffusiophoresis. Thermophoresis itself is enhanced in a mixture, diffusiophoresis itself is enhanced in the presence of a temperature gradient, and there is also a direct coupling term involving the translational thermal diffusion factor of the gas mixture. It is shown how to extend the model to include finite boundary spacings, and the case of thermophoresis for a single gas in transition with respect to both particle diameter and boundary spacing is worked out in detail. There is reasonable agreement of the present results with previous theoretical and experimental work where they overlap. |
