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Computational Fluid Dynamics in Chemical Reaction Engineering VJune 15th to 20th 2008, Whistler, British Columbia, Canada
Steffen Schütz, Gabriele Gorbach, Christian Winkler and Manfred Piesche
Institute of Mechanical Process Engineering IMVTUniversity of Stuttgart, Germany
A Simulation Model for the Separation of
Dispersed Liquid-Liquid Systems in Hydrocyclones
Based on the Coupling of CFD and Population Balances
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Goals
Calculation of flow field
Calculation of particle tracks
(e. g. Euler-Lagrange)
Interactions between phases
(e. g. Euler-Euler)
– Breakup / coalescence
(Population balances)
CFD software (e.g. FLUENTTM)
Modelling of liquid-liquid separation with particle-particle interaction
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Goals
User defined functions (UDF)
Breakup / coalescence (Population balances)
– Separation process
Calculation of flow field
Calculation of particle tracks
(e. g. Euler-Lagrange)
Interactions between phases
(e. g. Euler-Euler)
– Breakup / coalescence
(Population balances)
CFD software (e.g. FLUENTTM)
Modelling of liquid-liquid separation with particle-particle interaction
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Goals
User defined functions (UDF)
Breakup / coalescence (Population balances)
Separation process
Calculation of flow field
CFD software (e.g. FLUENTTM)
Modelling of liquid-liquid separation with droplet-droplet interaction in a hydrocyclone with direct impact of a non-homogeneous flow field
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Basics
Population theory
Solution strategy
Results
Summary and Outlook
Outline
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Basics – Separation Processes in Hydrocyclones
Continuous separators
Overflow
Underflow
Inlet
&oV
&uV
&inV
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Basics – Separation Processes in Hydrocyclones
Overflow
Underflow
Inlet
Continuous separators&oV
&uV
Calculation of particle tracks
using Euler-Lagrange model
“big” particle/droplet
“small” particle/droplet
Separation due to density difference
Phase with higher density:
Accumulation to larger radii
(here: dispersed water
droplets)
Phase with lower density:
Transport to smaller radii
(here: continuous diesel fuel)
&inV
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Qin(dp ) =
f · Qo(dp ) + g · Qu(dp )
g · Qu(dp )
f · Qo(dp )
Qin(dp )
1 10 100 10000,0
0,2
0,4
0,6
0,8
1,0
Qein
Ver
teilu
ngss
umm
e Q
(dp)
[-]
Tropfengröße dp [µm]
Cum
ulat
ive
size
dis
trib
utio
n Q
3(d p
) [1
]
Qin
Droplet size dp [µm]
Basics – Separation Processes Without Particle-Particle Interaction
e. g. stable droplets at
low concentrations
f = integral droplet mass fraction overflow
g = integral droplet mass fraction underflow
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Qin(dp ) ≠f · Qo(dp ) + g · Qu(dp )
g · Qu(dp )
f · Qo(dp )
Qin(dp )
1 10 100 10000,0
0,2
0,4
0,6
0,8
1,0
Qein
Ver
teilu
ngss
umm
e Q
(dp)
[-]
Tropfengröße dp [µm]
Cum
ulat
ive
size
dis
trib
utio
n Q
3(d p
) [1
]
Qin
Droplet size dp [µm]
Inte
ract
ion
e. g. interacting droplets
Basics – Separation Processes With Particle-Particle Interaction
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Qreal (dp ) =f · Qo(dp ) + g · Qu(dp )
g · Qu(dp )
f · Qo(dp )
Qin(dp )
1 10 100 10000,0
0,2
0,4
0,6
0,8
1,0
Qein
Ver
teilu
ngss
umm
e Q
(dp)
[-]
Tropfengröße dp [µm]
Cum
ulat
ive
size
dis
trib
utio
n Q
3(d p
) [1
]
Qin
Droplet size dp [µm]
Inte
ract
ion
e. g. interacting droplets
Basics – Separation Processes With Particle-Particle Interaction
Meyer: PhD Thesis (2001) University of Hannover
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
1 10 100 10000,0
0,2
0,4
0,6
0,8
1,0
Qein Qreal
Ver
teilu
ngss
umm
e Q
(dp)
[-]
Tropfengröße dp [µm]
g · Qu(dp )
f · Qo(dp )
Qin(dp )
Cum
ulat
ive
size
dis
trib
utio
n Q
3(d p
) [1
]
Droplet size dp [µm]
Inte
ract
ionBreakup
CoalescenceQreal (dp ) =f · Qo(dp ) + g · Qu(dp )
e. g. interacting droplets
Basics – Separation Processes With Particle-Particle Interaction
Qin
Meyer: PhD Thesis (2001) University of Hannover
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
Population Theory
Hulburt, H. M., Katz, S.Chemical Engineering Science 19 (1964), 555-574
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
( ) ( )
( ) ( ) ( ) ( )
ii i
i i i i
Fv F
t
B F B F D F D F+ − + −
∂ ρ+ ∇ ⋅ ρ
∂
= − + −
r
6447448 6447448
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
Population Theory
Birth Terms B(Fi)Droplet Coalescence
Death Terms D(Fi)Droplet Breakup
Hulburt, H. M., Katz, S.Chemical Engineering Science 19 (1964), 555-574
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
m
m*>m
Population Theory
Generation by breakup
( ) ( )
( ) ( ) ( ) ( )
ii i
i i i i
Fv F
t
B F B F D F D F+ − + −
∂ ρ+ ∇ ⋅ ρ
∂
= − + −
r
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
m
m*<m
m*>m
Generation by coalescence
Generation by breakup
Population Theory
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
( ) ( )
( ) ( ) ( ) ( )
ii i
i i i i
Fv F
t
B F B F D F D F+ − + −
∂ ρ+ ∇ ⋅ ρ
∂
= − + −
r
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
m
m*>m
Reduction by coalescence
Population Theory
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
( ) ( )
( ) ( ) ( ) ( )
ii i
i i i i
Fv F
t
B F B F D F D F+ − + −
∂ ρ+ ∇ ⋅ ρ
∂
= − + −
r
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
m
m*>m
m*<m
Reduction by breakup
Population Theory
Reduction by coalescence
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
( ) ( )
( ) ( ) ( ) ( )
ii i
i i i i
Fv F
t
B F B F D F D F+ − + −
∂ ρ+ ∇ ⋅ ρ
∂
= − + −
r
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
m
m*>m
m*<m
Reduction by breakup
Population Theory
Reduction by coalescence
Shift of droplet size distribution
with time and position is described
by population balances
Droplet mass as characteristic
particle property
Balancing of number density
distribution Fi [1/m³] of each
droplet size class i
( ) ( ) ( ) ( )ii i i i
Fv F B F D F
t± ±∂ ρ
+ ∇ ⋅ ρ = ± ±∂
r
Description by interaction kinetics
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Population Theory
( )( ) ( )( ) ( )( ) ( )( )
( ) ( ) ( ) ( )
( ) ( ) ( ) ( )
( ) ( ) ( ) ( )
( ) ( )
i i i i
m
coll i i0
m mmax
coll i i0
mmax
br im
br i
B F m, t B F m, t D F m, t D F m, t
1 m m*,m * g m m*,m * F m m*, t F m*, t dm *2
m,m * g m,m * F m, t F m*, t dm *
m * m,m * g m * F m*, t dm *
g m F m, t
+ − + −
−
− + − =
+ λ − − −
− λ
+ υ β
−
∫
∫
∫
Generation by coalescence
Reduction by coalescence
Generation by breakup
Reduction by breakup
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Kinetic approach of Coulaloglou/TavlaridesChemical Engineering Science 32 (1977), 1289-1297
Strongly empirical
Influence of turbulence on droplet breakup is not considered
Kinetic approach of Lehr (PhD Thesis (2001) University of Hannover, Germany)
Definition of critical velocity (only dependent of disperse phase)
Influence of turbulence on droplet breakup is considered
Population Theory
m
m*>m
m*<m
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Droplet Reduction by Separation
Relative transport of droplets with respect to mean flux driven by centrifugal
forces results in droplet separation at the cyclone walls and at the underflow
“Drift flux” described by transport laws for drag force
Droplet separation as further contribution to the death term ( )iD F−
cx
ti,d
m,ti
d
md
m
i,pd
Di,rel D
ad
c181
v α∇α
ν−
ρρ−ρ
µ
ρ=
rr
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Droplet Size Discretization
Non-equidistant droplet size discretization with discrete droplet size classes
Close size intervals with small droplets due to their high number concentration
Numerical correction to keep the droplet mass constant
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Solution Strategy
Flow field simulation with multiphase mixture model in FLUENTTM
Discretization of droplet size distribution into n droplet size classes
Each droplet size class corresponds to a quasi continuous phase i
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Flow field simulation with multiphase mixture model in FLUENTTM
Discretization of droplet size distribution into n droplet size classes
Each droplet size class corresponds to a quasi continuous phase i
Solution of phase averaged mass and momentum balance of
the mixture (n + 1 phases) with Reynolds-Stress-Model
Solution of transport equation for volume phase fraction αi of each phase i
Solution Strategy
( ) ( )m im i i i iv B ( ) D ( )
t± ±∂ ρ α
+ ∇ ⋅ ρ α = ± α ± α∂
r
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
( ) ( )m im i i i iv B ( ) D ( )
t± ±∂ ρ α
+ ∇ ⋅ ρ α = ± α ± α∂
r
Droplet volume
Solution Strategy
( ) ( ) ( ) ( )ii i i i
Fv F B F D F
t± ±∂ ρ
+ ∇ ⋅ ρ = ± ±∂
r
Flow field simulation with multiphase mixture model in FLUENTTM
Discretization of droplet size distribution into n droplet size classes
Each droplet size class corresponds to a quasi continuous phase i
Solution of phase averaged mass and momentum balance of
the mixture (n + 1 phases) with Reynolds-Stress-Model
Solution of transport equation for volume phase fraction αi of each phase i
corresponding i,p
ii V
Fα
=
Coupling condition
p,iV
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Solution Strategy
Calculation of droplet interaction kinetics
and droplet separation
with user defined subroutines
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Solution Strategy
Calculation of droplet interaction kinetics
and droplet separation
with user defined subroutines
Implementation into
birth and death terms
( ) ( )m im i i i iv B ( ) D ( )
t± ±∂ ρ α
+ ∇ ρ α = ± α ± α∂
r
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Calculation of droplet interaction kinetics
and droplet separation
with user defined subroutines
Implementation into
birth and death terms
Coupled solution
of the flow field with
population balances in FLUENTTM
Solution Strategy
( ) ( )m im i i i iv B ( ) D ( )
t± ±∂ ρ α
+ ∇ ρ α = ± α ± α∂
r
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Results – Cyclone Geometries
Conventional geometry Geometry with double cone (Smyth)Proc. 2nd Int. Conf. on Hydrocyclones (1984),
177-190, Bath, UK
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Results – Cyclone Geometries
Conventional geometry Geometry with double cone (Smyth)Proc. 2nd Int. Conf. on Hydrocyclones (1984),
177-190, Bath, UK
Cyclone separators with one or two inlets
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Separation of water droplets from diesel fuel
Density difference ∆ρ=170 kg/m³, interfacial tension σ=0.015 N/m
Droplet size distribution inlet:
Mean diameter d50e=300µm
Logarithmical discretization
into n=19 droplet size classes
Results – Phase Properties
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
A
A
m³/h1.0Vin =&
Results –Two Different Cyclone Geometries
m³/h1.0Vin =&
Reduced droplet breakup
Increased droplet coalescencedouble conegeometry
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
m³/h1.0Vin =&
Results –One and Two Cyclone Inlets
m³/h1.0Vin =&
Reduced droplet breakup
Increased droplet coalescence
A
A
A
A
secondinlet
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Results – Phase Distribution
µm805d 19, phase =p
m³/h1.0Vin =&
A
A
phase fraction
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
A
A
phase fraction i i d P,i i(B D ) V m+ −− ⋅ ρ ⋅ ⋅ ∆
m³/h1.0Vin =&
µm805d 19, phase =p
Results – Phase Distribution
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Summary and Outlook
Development of new method for coupled solution of population balances with
flow field
Modelling of droplet breakup and coalescence
Describing impact of droplet interactions on separation process
Good agreement between simulation and experiment
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Development of new method for coupled solution of population balances with
flow field
Modelling of droplet breakup and coalescence
Describing impact of droplet interactions on separation process
Good agreement between simulation and experiment
Further activities
Direct numerical simulation (DNS) of droplet-droplet interactions for definition
of kinetics (Empirical assumptions are no longer required for the solution of
population balances)
Summary and Outlook
Computational Fluid Dynamics in Chemical Reaction Engineering VJune 15th to 20th 2008, Whistler, British Columbia, Canada
Steffen Schütz, Gabriele Gorbach, Christian Winkler and Manfred Piesche
Institute of Mechanical Process Engineering IMVTUniversity of Stuttgart, Germany
A Simulation Model for the Separation of
Dispersed Liquid-Liquid Systems in Hydrocyclones
Based on the Coupling of CFD and Population Balances
A Simulation Model for the Separation of
Dispersed Liquid-Liquid Systems in Hydrocyclones
Based on the Coupling of CFD and Population Balances
Computational Fluid Dynamics in Chemical Reaction Engineering VJune 15th to 20th 2008, Whistler, British Columbia, Canada
Steffen Schütz, Gabriele Gorbach, Christian Winkler and Manfred Piesche
Institute of Mechanical Process Engineering IMVTUniversity of Stuttgart, Germany
Additional Slides
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Partially structured grid – cross-section at the inlet region
Discretization – 3D
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
ResultsVelocity and Pressure Distribution
azim
utha
l vel
ocity
axia
l vel
ocity
radi
al v
eloc
ity
pres
sure
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Daughter droplet distribution according to Chatzi
Daughter droplet distribution according to Lehr
Kinetic Approaches
( )( )
23 52 5 2 5c
32 3 3 5d 1 15 2 5c
9exp ln 2 d4
6ß m,m *d * 31 erf ln 2 d *
2
⎡ ⎤⎛ ⎞⎡ ⎤ρ⎛ ⎞⎢ ⎥⎜ ⎟− ε⎢ ⎥⎜ ⎟⎢ ⎥⎜ ⎟σ⎝ ⎠⎜ ⎟⎢ ⎥⎣ ⎦⎢ ⎥⎝ ⎠⎣ ⎦=⎛ ⎞⎡ ⎤⎡ ⎤π ρ ρ⎛ ⎞⎜ ⎟+ ε⎢ ⎥⎢ ⎥⎜ ⎟⎜ ⎟σ⎝ ⎠⎢ ⎥⎢ ⎥⎣ ⎦⎣ ⎦⎝ ⎠
( )( ) ( )
2
1 2 2
m *m6 2m,m * exp 18 .
m * 2 m *
⎡ ⎤⎛ ⎞−⎢ ⎥⎜ ⎟⎝ ⎠⎢ ⎥β = −
⎢ ⎥π⎢ ⎥⎣ ⎦
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Breakup frequency
Collision frequency
Coalescence efficiency
Kinetic Approaches –Coulaloglou and Tavlarides
( )( )
( )21 3
br 1 22 3 5 2 3d
1g d C exp C
d 1 d
⎡ ⎤σ + αε= −⎢ ⎥
+ α ρ ε⎢ ⎥⎣ ⎦
( ) ( )( ) ( )( )1 3 1 22 2 32 2 3
coll 3g d,d * C d d * d d *1ε
= + ++ α
( )( )
4c c
4 32d d *d,d * exp Cd d *1
⎡ ⎤η ρ ε ⋅⎛ ⎞λ = −⎢ ⎥⎜ ⎟+⎝ ⎠⎢ ⎥σ + α⎣ ⎦
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Breakup frequency
Coalescence function
Kinetic Approaches – Lehr
9 /57 /55 / 3 19 /15c
br 3 6 /5c
2 1g (d) 0.5 d expd
⎛ ⎞⎛ ⎞ρ σ⎛ ⎞ ⎜ ⎟= ⋅ ε −⎜ ⎟ ⎜ ⎟σ ρ⎜ ⎟⎝ ⎠ ε⎝ ⎠⎝ ⎠
( ) ( )coll
21 / 3
2 maxc crit 1 / 3
(d, d*) d,d * g d,d *
(d d*) min(v , v ) exp 14
Ω = λ ⋅
⎛ ⎞⎛ ⎞απ ⎜ ⎟⎜ ⎟= + − −⎜ ⎟⎜ ⎟α⎜ ⎟⎝ ⎠⎝ ⎠
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Characteristic and critical velocity
Kinetic Approaches – Lehr
( )2 / 31 / 3 2 / 3c
relative velocityturbulent fluctuation velocity
v max 2 d d * , v v *⎛ ⎞⎜ ⎟= ε + −⎜ ⎟⎜ ⎟⎝ ⎠
1424314444244443
Coalescence close to walls and in the overflow/underflow region
With high energy dissipation rate close to walls
characteristic velocity > critical velocity coalescence function only dependent on material data
critv 0.05m / s= parameter, dependent on material data
Institute of Mechanical Process Engineering, University of Stuttgart, GermanyECI Conference Computational Fluid Dynamics in Chemical Reaction Engineering V, Whistler, British Columbia, Canada
Coalescence correction term
Non-equidistant Droplet Size Discretization
Breakup correction term
coal k likl
i
m mK
m+
=
( )
br ii i
k i k kk 1
mK
m ,m m m=
=ν β ∆∑