Page 170 - Air Pollution Control Engineering

03_chap_wang.qxd 05/05/2004 12:49 pm Page 149
Cyclones 149

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Q Gas volumetric flow rate [m /s, or L/min in Eqs. (64) and (73)]
3
Q Emission stream flow rate at actual condition (ft /min)
a
Re Reynolds number based on the cyclone annular dimension
ann
RPM Respirable fraction
S Internal height of the cyclone exit duct (vortex finder) (m)
T Temperature (K)
TPM Thoracic fraction
U Ambient wind speed (m/s)
U Duct velocity (ft/min)
duct
v Gas velocity at the cyclone entry (m/s)
i
v Gas velocity at the cyclone exit (m/s)
o
v Saltation velocity (ft/s)
s
v Gas tangential velocity (m/s)
t
v Gas maximum tangential velocity (m/s)
tmax
v Particle terminal velocity (m/s)
ts
v m Terminal velocity of the particle collected with 50 % efficiency in the
ts
Barth model (m/s)
3
V Volume below the exit duct, excluding the central axis (m )
H
V Annular volume between S and the end of the vortex length (Z ),
nl c
3
excluding the central axis (m )
3
V Annular volume between S and the medium height of the entry duct (m )
s
x Standardized normal variable
x Particle mass fraction of diameter D in the entry
i i
x Particle mass fraction of diameter D in the exit
oi i
W Fan power (W)
c
Z c Height of the cyclone central axis (m)
α Constant in Eq. (7)
β Exponent related to the cut diameter in the Iozia and Leith model
Γ Constant in Eq. (61) (µm)
∆H Dimensionless parameter
∆P Pressure drop (Pa)
η Cyclone efficiency for a particle of aerodynamic diameter D ae
η i Collection efficiency of a particle of diameter D i
η 0 Overall particle collection efficiency
θ Gas average residence time (s)
θ Normalized collection efficiency
λ Friction coefficient
λ Gas mean free path (m)
µ Gas viscosity (kg/ms)
ρ Gas density (kg/m )
3
ρ p Particle density (kg/m )
3
ρ unit Unit density (kg/m )
3
σ Geometric standard deviation
τ i Relaxation time (s)
ψ Cutoff size parameter
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