Thermophoretic properties of nonspherical particles and large molecules

✍ Scribed by Pedro Garcia-Ybarra; Daniel E. Rosner

• Publisher: American Institute of Chemical Engineers
• Year: 1989
• Tongue: English
• Weight: 764 KB
• Volume: 35
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690350115

✦ Synopsis

The Kn, >> 1 gas-kinetic approach of Waldmann (1959, 1961) is extended to predict the thermophoretic properties of nonspherical aerosol particles, and massive nonspherical gas molecules. Calculations are presented for sphero-cylindrical particles (molecules) of arbitrary aspect ratio, L / R, predicting that in a local temperature gradient grad T they will thermophoretically drift: i) more rapidly when their major axis is aligned with -grad T; ii) at a velocity different from that of a sphere of radius R equal to the cylinder radius: iii) at an angle with respect to -grad T when their major axis is not parallel to, nor perpendicular to, -grad T; and iv) without a net torque tending to orient the particle with respect to -grad T. Important corollaries are that nonspherical particles in a temperature gradient should also experience new thermophoretically-induced coagulation mechanisms. We predict that the orientation-averaged thermal diffusion factor aT should increase approximately linearly with particle (molecule) length.