Photophoresis of an Aerosol Sphere in a Spherical Cavity

Huan J. Keh

• Department of Chemical Engineering, National Taiwan University, Taipei 106-17, Taiwan, ROC

Revised: May 31, 2001
Accepted: May 31, 2001

Keh, H.J (2001). Photophoresis of an Aerosol Sphere in a Spherical Cavity. Aerosol Air Qual. Res. 1: 21-30. https://doi.org/10.4209/aaqr.2001.06.0003

ABSTRACT

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.

Keywords: Photophoresis; Aerosol sphere; Boundary effect