Experimental measurements on thermophoresis in the transition region

Measurements of thermophoretic velocities of carnauba wax, polystyrene latex, silver particles and sodium chloride have been performed by injecting the aerosol as a thin sheet into a laminar flow of clean gas, with a temperature gradient established across it. These measurements have enabled us to compare the experimental data with the known theories. The aerosol radius range was 0.11–0.83 μm. The measured reduced thermophoretic velocity was found to depend only on the Knudsen number, in the range 0.09–0.7, and not on the gas/particle conductivity ratio.