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6.4 Cyclone 169

! 1=2
4:5lW
d 50 ¼ ð6:62Þ
pN e u g q
p
With the computed cut size above, the fractional efficiency of the cyclone is
described as a function of particle size, d p , and cut size, d 50 :

1

g d p ¼ ð6:63Þ
2
1 þ d 50 d p
Example 6.3: Cyclone efficiency
A conventional cyclone has a body diameter of 20 cm and other geometries are
3
listed in the table as follows. It operates at an inlet volumetric flow rate of 360 m /h.
Assume standard condition, plot its fractional efficiency curve versus particle
aerodynamic diameter.
Ratio
Height of inlet, H/D 0.5
Width of inlet, W/D 0.25
Length of body, L B /D 1.75
Cone length, L C /D 2

Solution
First, we calculate the dimension of the cyclone as follows:

Dimension
Body diameter, D (m) 0.2
Height of inlet, H 0.1
Width of inlet, W 0.05
Diameter of gas exit, D e 0.1
Length of body, L B 0.35
Cone length, L C 0.4
The number of turns from Eq. (6.58)is
0:35 þ 0:5 0:4
L B þ 0:5L C
N e ¼ ¼ ¼ 5:5
H 0:1
The inlet area of this cyclone is

2
A ¼ HW ¼ 0:005 m