Transcript Document

Important dimensionless numbers
• Resistance coefficient = Euler number
– Relates cyclone pressure drop to some characteristic velocity:
Eu 
p
(  f v 2 / 2)
• Gives ratio to pressure forces to inertial forces
• Constant for given cyclone geometry, important for scaleup
• What characteristic velocity should we use?
– One based on gas flow rate q/cross sectional area (D = cyclone
diameter)
4q
v
 D2
Stokes 50 number (Stk50)
• Physical significance: Ratio of centrifugal force (less buoyancy) to the
drag force acting on a particle of diameter x50
Stk50 
2
x50
 pv
18  D
•  - gas viscosity, density is particle density, D is cyclone body diam.,
char.velocity is same as previous.
• x50 = Cut size… at this diameter, 50 percent of particles will be
collected
Cool rule of thumb:
• For well-designed cyclones, there is a direct
correlation between Eu and Stk50
12
Eu 
Stk50
• This is pretty neat because you could find
x50 by knowing specifics about cyclone
For hw problem 1, Rhodes 7.2
• Info about size distribution given in dFc/dx
and dF/dx format
Size range (microns)
Feed size
distribution, dF/dx
Coarse product size
distribution, dFc/dx
6.6-9.4
9.4-13.3 13.3-18.7 18.7-27.0
27-37
37-53
0.05
0.2
0.35
0.25
0.1
0.05
0.016
0.139
0.366
0.3
0.12
0.06