Particle Deposition Mechanisms: Mass Diffusion

Diffusion in a Tube Flow

Consider a laminar flow in a tube with . At distances very close to the wall, that is for small y,

(43)

Figure 4. Schematics of convective diffusion in a pipe.

The convective diffusion equation then becomes

(44)

The appropriate boundary conditions are

y=0 ,

(45)

Introducing similarity variable

(46)

Equation (44) may be restated as

(47)

The solution to (47), which satisfies (45), is given by

(48)

The diffusion to the wall is given as

(49)

(50)

The diffusion layer thickness is determined by

(51)

where

(52)

The total diffusion for a length L is given by

(53)