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03_chap_wang.qxd 05/05/2004 12:48 pm Page 116
116 José Renato Coury et al.

 (1.18kg m 3 )(20m s ) (6.4 ) 
2
∆P =  
 2 

()a ∆P = 1510 kg = 1510 Pa
ms 2

()b ∆P = 1204 kg = 1204 Pa
ms 2

()c ∆P = 1133 kg = 1133 Pa
ms 2
Table 3 shows that the experimental value found by Dirgo and Leith was 1407 Pa.
Therefore, the result given by Eq. (32) is the closest and provides some safety margin.
In this case, the calculated fan power [Eq. (43)] with 0.55 efficiency is
)(
3
(0.1812 m s 1510 N m 2 )
W =
c
0.55
Nm
W = 497 = 497 W
c
s
Example 2
Use the grade efficiency results given by the Iozia and Leith model to calculate the overall
efficiency for the entry velocities of 10, 15, and 20 m/s. Assume that the size distribution
3
of the particles is that listed in Table 4 and that the powder concentration is 0.02 kg/m .
Determine the concentration and size distribution at the equipment exit as well as the pres-
sure drop for the velocity of 20 m/s. The physical properties of the particles and the gas
are the same as in the previous example.

Table 4
Particle Size Distribution Utilized in Example 2
Size range (µm) x (in mass basis)
i
0–1 0.01
1–2 0.02
2–4 0.04
4–6 0.06
6–8 0.08
8–10 0.10
10–20 0.13
20–30 0.15
30–40 0.12
40–50 0.10
50–60 0.07
60–70 0.05
70–80 0.04
80–90 0.02
90–100 0.01