Numerical Analysis of the Vertical Motion of a Single Micron-Sized Particle in a Thermal Gradient Diffusion Chamber with Electrostatic Levitation

A model to describe the vertical motion of a single micron-sized insoluble particle electrically suspended in an upward thermal gradient diffusion chamber is developed. Motion of the particle is determined by five forces: gravitational, electrostatic, aerodynamic drag, thermophoretic, and diffusiophoretic. Condensation/evaporation effects are taken into account. The model predicts the behavior of an aerosol particle with specified characteristics in a diffusion chamber. The use of an aqueous salt solution as the lower pool establishes two regions in the chamber: an undersaturated region with respect to water vapor in the lower portion of the chamber and a supersaturated region in the upper portion. This unique saturation profile combined with certain operating conditions of the chamber leads to an oscillatory motion of the particle.