Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 272

80

simulation result (10L/min)
Cheng et al-Subject A (1996)
Cheng et al-Subject B (1996)
Cheng et al-Subject C (1996)
Cheng et al-Subject D (1996)

60

40

20

0

0 20 40 60 80 100 120 140 160

Particle Diameter (nm)

Fig. 8.31 Deposition efficiency of 1-150 nm particles in a human nasal cavity at a steady inhalation
rate of 10 L/min

manda1nmparticle are both approximately
80 %; however their different deposition mechanisms will inherently lead to different
deposition patterns as shown in Fig. 8.32 . The deposition pattern fora1nmparticle
shows an even distribution, not only throughout the entire nasal cavity, but also
within each region. This even distribution is a result of the Brownian motion, which
disperses the particles in random directions. In contrast, the deposition pattern for the
22

The deposition efficiency for a 22 μ

m particle shows localised regions of deposition, which are caused by changes
in direction of the flow field. As discussed earlier, the change of flow direction
for inertial particles is the primary characteristic that defines particle deposition by
inertial impaction. Thus the flow field is extremely important for the deposition of
micron particles that experience inertial impaction.
Figure 8.33 shows the effects of airflow rates on the deposition efficiency of
submicron and micron particles. Micron particles smaller than 10

μ

m exhibit low
deposition efficiencies (<15 %);, however, the deposition efficiency increases rapidly
when the diameter is larger than 10

μ

m. The deposition efficiency increases with
an increase in the particle size as well as with an increase in the flow rate. Both the
particle size and flow rate contribute to the inertial parameter. For submicron particles,
the deposition efficiency increases with a decrease in the particle size. However for
the flow rate, the three deposition curves in Fig. 8.33 a converge when the particle
size approaches 15 nm. The deposition efficiency decreases as the particles increase

μ