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Laboratory for Chemical Technology, Ghent Universityhttp://www.lct.UGent.be
3D swirl flow reactor technology for pyrolysis processes:
computational fluid dynamics study
Carl M. Schietekat, Marco M. Van Goethem, Kevin M. Van Geem, Guy B. Marin
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
0.8
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Non uniform radialtemperature
Non uniform radialtemperature
Coke layerCoke layer
Coke formation during steam cracking
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
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3D reactor technology
Better heat transfer =
less cokes / more flow
Better heat transfer =
less cokes / more flow
Higher pressure drop=
Lower olefins selectivity?
Higher pressure drop=
Lower olefins selectivity?
More uniform radialtemperature
More uniform radialtemperature
Swirl Flow Tube design
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
* Veryan Medical Limited: BioMimics 3DTM
Arteries are helically twisted
better crossmixing
Less accumulation of fattydepositis on artery wall
for tubular chemical reactors: heat transfer, uniform cross-section
for stent design:
patented in 2011 for use in cracking furnaces
helical centerline
Outline
Experimental set-up
Model validation
Swirl decay after SFT
Effect of tube bend
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Experimental set-up
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
compressor
flow metermanometer
thermocouple
static mixer
thermocouple
test tube steam jacket
- 3 test tubes:
- 14 pressure experiments (adiabatic)- 14 temperature experiments (last 2m heated with steam jacket)
SFT-MSFT-M
SFT-HSFT-H
STRAIGHTSTRAIGHT
A [m] P [m]
x x
0.0061 286.2
0.0083 217.8
Experimental data processing
Darcy-Weisbach equation:
=
2
Heat transfer to fluid:
= =
!" =
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Tube surface roughness
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
#$$ %, , '(
* N.H. Chen, Ind. Eng. Chem. Fundam., 18 (1979) 296-297297.
min,- .,/01 ,#$$ % , , '(
,/012
34
% = 13.49:
; , '( =#$$ 13.4 10>?, , '(
#$$ 0, , '(
Outline
Experimental set-up
Model validation
Swirl decay after SFT
Effect of tube bend
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
CFD Model
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Turbulence: Reynolds Stress Model Enhanced wall treatment (Wolfstein)
Material properties: ideal gas cp, , k temperature polynomials
Computational Fluid Dynamics FLUENT 13.0 Gambit 2.4.6
Extrusion cross section
Twall = 373.15K
Pout = 101325 Pamass flow inlet
Boundary conditions:
>23 106 cells
Pressure drop experiments
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Relative error = 3.2%Relative error = 3.2%
Velocity magnitude axial position
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
SFT-MSFT-M
Re = 2 104Re = 2 104
Velocity field: effect of Re
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Re [103]
0 m 1m 2m 3m 4m
115
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SFT-MSFT-M
Velocity field: effect geometry
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
0 m 1m 2m 3m 4m
SFT-HSFT-H
SFT-MSFT-M
Re = 2 104Re = 2 104
Wall shear stress
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Pa
Pa
SFT-HSFT-H
SFT-MSFT-M@ = 9 ABAC
2 turns
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Azimuthal coordinate [rad]
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Wall shear stress along axial direction
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
1 turn
4 turns 10 turns
SFT-MSFT-M
Azimuthal coordinate [rad]
D
Temperature experiments
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Relative error = 12.6%Relative error = 12.6%General overpredictionGeneral overprediction
Temperature field
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Re [103]
0 m 0.5m 1m 1.5m 2m
111
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K
SFT-MSFT-M
Cross sectional uniformity
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
SFT-MSFT-M
SFT-HSFT-H
STRAIGHTSTRAIGHT Re = 6 104Re = 6 104
EF = , HIJ 34 ,
HI
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
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2.1 2.6 3.1 3.6
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Axial position in straight tube [m]STRAIGHT SFT-M SFT-H
more uniform cross sectional temperature profilemore uniform cross sectional temperature profile
Heat flux
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
SFT-MSFT-M
1 helix 2helix 4helix
Azimuthal coordinate [rad]
Azimuthal coordinate [rad]
Azimuthal coordinate [rad] Azimuthal coordinate [rad]
Azimuthal coordinate [rad] Azimuthal coordinate [rad]
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Outline
Experimental set-up
Model validation
Swirl decay after SFT
Effect of tube bend
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Swirl number
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ratio tangentialto axial momentum
K = LMNOPQRSLMOTQR
ratio tangentialto axial momentum
K = LMNOPQRSLMOTQR
2m4m2m
SFT-MSFT-M
SFT-HSFT-H
Swirl decay
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
D
SFT-MSFT-M
0.0 16.7 m/s
4.00m 4.50m 5.00m 5.50m 6.00m
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Axial position [m] Axial position [m]
Outline
Experimental set-up
Model validation
Swirl decay after SFT
Effect of tube bend
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Velocity vectors in bend
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
[] 0 90 180
Re = 2 104Re = 2 104
SFT-MSFT-M
STRAIGHTSTRAIGHT
Z
Conclusions
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Experimental: SFT enhances heat transfer with limited increase of the pressure drop
CFD: good agreement for Fanning friction factor.
Nu number slight overprediction
Swirl flow is fully developed after 7-10 pitches. A helical low velocityand high temperature zone is created near the tube wall
Temperature uniformity in a cross section is improved
Swirl exponential decays at 0.3-0.6 m-1 depending on Re
Swirl flow is lost after a straight bend for Re < 20 103
SFT: promising technology for application in steam crackers
Acknowledgments
FWO-Vlaanderen
The Long Term Structural Methusalem Funding
STEVIN Supercomputer Infrastructure
LCT @ UGent: Amit Mahulkar, David Van Cauwenberge, Georges Verenghen, Nick Vandewiele, Thomas Dijkmans
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Glossary
SFT: Swirl Flow Tube, a tube has a helicalcenterline. The helix amplitude is smaller than orequal to the tube radius.
Swirl flow: a whirling or eddying flow of fluid. Swirl number: ratio of tangential over axial
momentum transfer Wall shear stress: component of stress coplanar
with the wall. It is the product of the viscosity andthe derivative of axial speed to radial coordinate.
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Heat transfer processing
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Heat transfer processing
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
Wall shear stress in Swirl Decay
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Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012
SFT-MSFT-M
Azimuthal coordinate [rad]Axial coordinate [m]
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