Environmental Engineering Reference
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Air flow
Diffusion
Inertial impaction
Air flow
Sedimentation
(A)
Air flow
Electric charge
effects
+
Air flow
Interception
Air flow
Air flow
(B)
Cloud settling
FIGURE 3.5
Particle deposition mechanisms in a bifurcating airway (A). Inertial impaction, sedimentation,
and diffusion (B). Interception, electrostatic charge, and cloud motion. (Adapted from Martonen, T.B. et al.,
Respir. Care
, 45, 712, 2000. With permission.)
where
β =
τ θ
V
a b
(3.23)
d
a
(Note that deposition eficiency is dependent upon τ, as deined in Section 3.2.2.) These equations
can be used to simulate particle deposition in the peripheral airways of the tracheobronchial tree.
An equation applicable to fully developed (parabolic) velocity proile, appropriate for more distal
airways, has been presented by Landahl.
100
However, airstream velocities are typically quite small
in such areas, so the impaction deposition eficiency
per se
is negligible.
3.7.1.1.2 Turbulent Conditions
Deposition eficiency for inertial impaction for turbulent low conditions is
24,101
−
4τ θ
π
V
d
⎡
⎢
⎤
⎥
a b
P I
( )
= −
1 exp
(3.24)
Turbulent lows, such as those requiring the use of Equation 3.24, may occur in the upper tracheo-
bronchial airways of the human lung.
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