Effects of Brownian Diffusion on Deposition

So far, the analysis Has not taken into account the effects of the Brownian motion which allows diffusive leakage through the dust free space to the heated surface. This effect has also been studied in some detail in connection with wafer contamination (Friedlanderet al., 1988 Ye et al. 1991). The equation for simultaneous convection, diffusion, thermophoresis and sedimentation for the nne dimensional stagnation fiow configuration is 

Finally, we wish to note that themtophoresis is the controlling mechanism of particle transport in the fabrication of optical fibers by the modified chemical vapor deposition process. In this application, submicron silica particles and associated trace amounts of dopant aerosol oxides are deposited on the inside of a quartz tube. Experiment and theory are discussed by Simpkins et al. (1979). 

1 The stream function and radial velocity distribution function for a low-Reynold.s-number flow around a sphere are given by the following expressions due to Stokes  

2 Estimate the collection efficiency of a filter mat (cr = 0.0057) composed of glass fibers 4 

3 It is proposed to build a diffusion battery composed of a bundle of capillary tubes to determine the average particle size of an aero.sol. For a tube diameter of 1 mm and a length of 20 cm, deiemiine the velocity at which particles of Jp = 0,05 /tm are 9Q% removed. Check to be sure the How is laminar. Die temperature is 20 C. and the gas is air. 

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