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Important dimensionless numbers. Resistance coefficient = Euler number Relates cyclone pressure drop to some characteristic velocity: Gives ratio to pressure forces to inertial forces Constant for given cyclone geometry, important for scaleup What characteristic velocity should we use?
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Important dimensionless numbers • Resistance coefficient = Euler number • Relates cyclone pressure drop to some characteristic velocity: • 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)
Stokes 50 number (Stk50) • Physical significance: Ratio of centrifugal force (less buoyancy) to the drag force acting on a particle of diameter x50 • - 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 • 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
