3d swirl flow reactor technology

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

1

Chemreactor-XX, Luxembourg, Luxembourg, 05/12/2012

0.8

1

1.2

0 0.25 0.5 0.75 1

T

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r/D [-]

0.8

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Non uniform radialtemperature

Non uniform radialtemperature

Coke layerCoke layer

Coke formation during steam cracking

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2

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

3


* 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

4


Experimental set-up

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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:

= =

!" =

6


Tube surface roughness

7


#$$ %, , '(

* 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


Effect of tube bend

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CFD Model

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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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Relative error = 3.2%Relative error = 3.2%

Velocity magnitude axial position

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SFT-MSFT-M

Re = 2 104Re = 2 104

Velocity field: effect of Re

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Re [103]

0 m 1m 2m 3m 4m

115

22

SFT-MSFT-M

Velocity field: effect geometry

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0 m 1m 2m 3m 4m

SFT-HSFT-H

SFT-MSFT-M

Re = 2 104Re = 2 104

Wall shear stress

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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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1 turn

4 turns 10 turns

SFT-MSFT-M


D

Temperature experiments

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Relative error = 12.6%Relative error = 12.6%General overpredictionGeneral overprediction

Temperature field

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Re [103]

0 m 0.5m 1m 1.5m 2m

111

22

K

SFT-MSFT-M

Cross sectional uniformity

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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

0.04

2.1 2.6 3.1 3.6

C

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[

-

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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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SFT-MSFT-M

1 helix 2helix 4helix



Azimuthal coordinate [rad] Azimuthal coordinate [rad]

Azimuthal coordinate [rad] Azimuthal coordinate [rad]

H

e

a

t

f

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x

[

k

W

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m

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Outline

Experimental set-up

Model validation


Effect of tube bend

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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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D

SFT-MSFT-M

0.0 16.7 m/s

4.00m 4.50m 5.00m 5.50m 6.00m

A

z

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Axial position [m] Axial position [m]

Outline

Experimental set-up

Model validation


Effect of tube bend

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Velocity vectors in bend

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[] 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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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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Heat transfer processing

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Heat transfer processing

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Wall shear stress in Swirl Decay

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SFT-MSFT-M

Azimuthal coordinate [rad]Axial coordinate [m]

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3d swirl flow reactor technology

Documents

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