Particle Deposition Mechanisms: Mass Diffusion

Tube Deposition

Consider a constant velocity gas flow in a tube of length L and radius R. The residence time is t = L/u where u is the gas velocity. Assuming that the wall deposition process is similar to that of a uniform concentration near a wall, and using (20) it follows that

(21)

or

(22)

A detailed duct flow analysis shows

(23)

Diffusion Velocity

The diffusion velocity is defined as

(24)

Similarly, a diffusion force may be defined as

(25)