Aerosol Transport – Inertia

:: Section 9

Inertial Impaction

II. Impaction Efficiency

Impaction, as can be seen, is the mechanism for the collection in the system, and it is more effective for larger particles. Stokes number (Stk) can be used to classify the potential whether the particle will be collected. It contains both flow velocity and particle diameter. In addition, we use "nozzle diameter" to represent the obstacle. Stk therefore can be expressed as:

where ρ_p is particle density, d_p is particle diameter, U is flow velocity, η is air viscosity, D_j is nozzle diameter.

The impaction efficiency (E_I) is a function of the Stokes number, and it increases as Stk increases.

How to increase the collection efficiency of aerosols by impaction?