Volume 1, No. 1, June 2001, Pages 21-30 PDF(976 KB)
Photophoresis of an Aerosol Sphere in a Spherical Cavity
Huan J. Keh
Department of Chemical Engineering, National Taiwan University, Taipei 106-17, Taiwan, ROC
This study examines the quasisteady photophoretic motion of a spherical aerosol particle with arbitrary thermal conductivity and surface properties, located at the center of a spherical cavity and exposed to a radiative flux. Assuming a small Knudsen number, the fluid flow is described by a continuum model with a temperature jump, thermal creep, and frictional slip on the solid surfaces. In the limit of the small Peclet and Reynolds numbers, appropriate equations of conservation of energy and momentum are solved for the system and the photophoretic velocity of the particle is obtained in closed form. The normalized photophoretic mobility increases with the relative conductively of the particle. The boundary effect of the cavity wall on the photophoresis of an aerosol particle is generally quite significant in appropriate situations. In practical aerosol systems, the boundary effect on photophoresis is much weaker than on gravitational field driven motion.
Photophoresis; Aerosol sphere; Boundary effect.