Determination of Thermal Stress Effect on Slip Flow in Micro-particle Photopheresis in Gaseous Media

This chapter presents a study on photophoresis of a microparticle in gaseous media with focus on the effect of thermal stress slip, which is deemed as one of factors causing deviations of previous theoretical predictions from measurements. The present modified theory exhibits an effective agreement with the measurements and highlights the importance of the thermal stress slip in photophoresis of a particle, particularly one with a small radius when combined with an analysis of one order of magnitude. A schematic diagram of an isotropic homogenous particle suspended in a gas medium with a monochromatic, parallel, and linearly polarized light beam along the z direction has introduced in this chapter. The theoretical expressions combined with an order-of magnitude analysis demonstrate the significance of the thermal stress slip in micro-particle photophoresis and disclosed the reason for deviation of the previous theory at small particle size. Parametric analysis revealed that the influence of thermal stress becomes more pronounced with a reducing particle thermal conductivity and/or increasing Knudsen number.