Chemical Engineering June 2018 - 57

Cover Story
NOMENCLATURE
A Arrhenius coefficient
B(λ) Spectral absorbance, -
cp Specific heat, J/kgK
cw Drag coefficient, -
cx Concentration of component x, mol/m3
d Tube diameter, m
D Impeller diameter, m
EA Activation energy, J/mol
E(λ) Spectral extinction coefficient, m-1
f
Frequency, s-1
fB Blade-passing frequency, s-1
H Tank height, m
I0
I
k
Incident radiant power, W/m2
Radiant power, W/m2
Reaction rate constant, s-1 (for 1st
order)
Κ(λ) Absorption coefficient, m-1
n
Impeller speed, s-1
p Pressure, N/m2
P Impeller power, W
q˙
r
Impeller pumping rate, m3/s
Conversion rate, mol/m3s
R Universal gas constant, J/molK
S(λ) Scattering coefficient, m-1
t
time, s
T Temperature, K
TD Tank diameter, m
v
V Volume, m3
x
xi
z
Length scale, m
Reaction order for reactant i
Number of contacts of a fluid element
with the irradiated zone, -
zB Number of impeller blades, -
α Heat-transfer coefficient, W/m2K
ε
η Dynamic viscosity, Pas
θ
Blend time, s
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w
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JUNE 2018
several agitators. The redundant switches
(level switch low low/level switch high high;
LSLL/LSHH) provide additional safety for
this fundamental function.
Concluding remarks
Photochemical processes break customary
rules of reactor engineering and design and
Call the
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Molar absorption coefficient, m2/mol
Sr
Strouhal number
Pr
Re
Prandtl number
Reynolds number
Flow velocity, m/s
Nu
Nusselt number
κ Molar absorption coefficient (Naperian), m2/mol
λ Wavelength, m
λ Thermal conductivity (in Nu and Pr), W/mK
ρ Density, kg/m3
Dimensionless numbers
NP
Power number
Q
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Chemical Engineering June 2018

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