Thermophoresis of Aerosol Spheroids
Abstract:An analytical study is presented for the thermophoretic motion of a freely suspended aerosol spheroid in a uniform prescribed temperature gradient that is oriented arbitrarily with respect to its axis of revolution. The Knudsen number is assumed to be small so that the fluid flow is described by a continuum model with a thermal slip at the particle surface. In the limit of small Peclet and Reynolds numbers, the appropriate energy and momentum equations are solved in the quasisteady situation using the bifocal-coordinate transformations. Explicit expressions for the thermophoretic velocity and force are obtained for various cases of prolate and oblate spheroidal particles. The average thermophoretic velocity and force for an ensemble of identical, noninteracting spheroids with random orientation distribution are also determined. The results indicate that the shape and relative thermal conductivity of a spheroidal particle and its orientation with the thermal gradient can have significant effects on its thermophoretic behavior.
Document Type: Research Article
Affiliations: Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China
Publication date: July 1, 2004