2/09/2014 | pag. 1 Novel Multiscale approach to Transport phenomena in Electrochemical Processes Integrating the research of different partners SBO 04

11/04/23 | pag. 1

Novel Multiscale approach to Transport phenomena in Electrochemical Processes

Integrating the research of different partners

SBO 04 0094 29 May 2008

Heidi Van Parys, Thomas Nierhaus, Pedro Maciel, Steven Van Damme

Mutech

Vakgroep elektrotechniek

MutechTitel van de presentatie11/04/23 | pag. 2

Outline

Introduction of the team

Test reactors

Software approach

Flow solvers Single phase flow

Two phase flow

Extending the team

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Introduction of the team

Heidi Van Parys– IRDE Experiments

Thomas Nierhaus– Morpheus and PLaS

Pedro Maciel– COOLFluiD

Steven Van Damme– MITReM library

Titel van de presentatie11/04/23 | pag. 3

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Test reactors

Parallel flow reactor (PFR)

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Test reactors

Inverted rotating disc electrode (IRDE)

Water jacket

water jacket

RDE electrode

O-ring

Platinum grid

Reference electrode

30mm

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Software approach Software approach

Flow solverMorpheus or COOLFluiD

Electrochemical solverMITReM library

Bubble solverPLaS

Post processing

Flow field

Gas molar production rate

Bubble size distributionBubble velocityBubble position

Momentum exchange

Gas volume fraction

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Software approach

Governing equations– Fluid flow

• Continuous representation• Incompressible Navier-Stokes• Closure relation for momentum transfer (bubbles)


Software approach

Φ

cρcτ

cρ

p

cρ

uutu

u

111

0

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Software approach

Governing equations– Electrochemistry

• Bruggeman model

• Bubble production model


Software approach

0

0

ii i i i i

i ii

z Fv c D c D c U

RTz c

1

1

i i

i i

c c

D D

g gg t S

g

jRTV dSdt

p n F

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Software approach

Governing equations– Bubble equation motion (Euler-Lagrange)

• Mass-point approximation• Sphericity assumption• Drag, lift, virtual mass & buoyancy forces• Momentum-back coupling on the flow


Software approach

guvuLC

Dt

uDvubt

v

t

x

2))()((23)(2

v

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Flow solvers

Morpheus– Navier-Stokes solver with plug-in extensions

– Two-phase flow (PLaS interface)– Electrochemistry (MITReM interface)

– Widely portable (Linux, Windows, Mac...)– Parallel computations (MPI)– Limited dependence on external packages

– Parallel linear solvers (SAMGp, Trilinos, SuperLU)– Meshing tool (Metis)– Tecplot– MPI distribution (LAM, MPICH, OpenMPI)

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Morpheus– Fast and robust time integration scheme

– Crank-Nicholson with convective velocity extrapolation– Large time steps with a single linear solve

– Unstructured tetrahedral (3D) grids – Space discretization by Finite Elements

– Galerkin FEM with stabilization terms

– At least 2nd order accuracy in time and space

Flow solvers


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Flow solvers

COOLFluiD– Multi-physics solver– Fluid flow

• RDS spacial discretization• Incompressible Navier-Stokes (Single-phase, Steady-state)• RANS turbulence modeling (k-e / k-w)

– Link to electrochemistry code• MITReM library (Electrolyte & electrostatic models)• Convection + diffusion + migration + reactions

– Link to particle tracking code• PLaS library

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Single phase flow

MITReM Model– Electrochemistry

Component D (10−9 m2/s) c (mol/m3)

H+ 9.311 5.8

Na+ 0.773 200

SO42− 0.618 102.9

H 2 0

Electrode reaction kox kred αox αred

H H+ + e− 0 4e-6 m/s 0 0.5

2H2O O2 + 4H+ + 4e− 1e-12 mol/m2s 0 0.058 0

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Single phase flow

PFR with MITReM– κ = 1.74 S/m– Polarization curves

050

100150200250300350400450500

1.0 1.5 2.0 2.5

J (A

/m2 )

V-U (V)

experiment

simulation

-250

-200

-150

-100

-50

0

-1.5 -1.0 -0.5 0.0 0.5 1.0

J (A

/m2 )

V-U (V)

experiment

simulation

H2 reaction O2 reaction

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Single phase flow

PFR with MITReM– Current response

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

-3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

I cath

ode

(A)

Vcathode - Vanode (V)

@ 0.001 m/s

@ 0.010 m/s

@ 0.100 m/s

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Single phase flow

PFR with MITReM– Current density profile at 2V

0.0

0.5

1.0

1.5

2.0

2.5

0.38 0.40 0.42 0.44 0.46 0.48

Log

J (A

/m2 )

x (m)

@ 0.001 m/s

@ 0.010 m/s

@ 0.100 m/s

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Single phase flow

PFR with MITReM– cH profile at 2V

0.001 m/s 0.010 m/s 0.100 m/s

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Single phase flow

PFR with MITReM– If the total current and even the current density

distribution is the same, the dissolved gas concentration can be very different depending on the hydrodynamics.

– J same bubble production.

– cH very different bubble production.

See Flora for experimental observations

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Single phase flow

PFR flow field– COOLFluiD

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Single phase flow

PFR flow field– COOLFluiD– Laminar (Re~100)

• Vinlet ~ 1e-2 m/s

– Computational grid• ~100.000 nodes• Electrochemistry layer

(1e-6m)

flow


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Single phase flow


IRDE flow field– Morpheus simulations– Flow fields for different rpm

– 250rpm– 500rpm– 1000rpm

– Computational grid– 41.500 nodes– 145.500 tetrahedral elements– Electrochemistry layer (1e-6m)– Fluid boundary layer (2e-4m)

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Single phase flow

IRDE flow field– Rotation-induced vetical downflow velocity

250rpm 500rpm

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Single phase flow

IRDE flow field– Rotation-induced vertical downflow velocity

250rpm 500rpm

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Two phase flow

PFR with bubbles– SFELES/PLaS simulations– Flow speeds in the PFR 0.004 m/s – 10 m/s– Reynolds number range 20 – 50.000– Laminar & turbulent flow regimes

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Two phase flow

PFR with bubbles– Fully turbulent model channel (Re=2600)– Advection & buoyancy play macroscopic role– TBL interaction plays mesoscopic role

Bubbles align with vortices in TBL (Centripetal force)

Bubbles move faster in high-speed streaks (Drag)

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Two phase flow


PFR with bubbles and MITReM– Fully coupled simulations– Laminar flow conditions

– Steady-state flow (COOLFluiD)– Unsteady flow (Morpheus)

– Real geometry (0.864m * 0.1m * 0.01m)

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Two phase flow


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Two phase flow

– ∆V=0.2V• Cathode at bottom• Anode on top

(downstream)

– Laminar (Re=100)• Vinlet ~ 1e-2 m/s

– Computational grid• ~100.000 nodes• Electrochemistry layer

(1e-6m)

– Parallel

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PFR with MITReM and dissolved H


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Two phase flow


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Two phase flow

PFR with MITReM and dissolved H

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Two phase flow


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Two phase flow

PFR with MITReM and H bubbles

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Movie!Current density

– ∆V=2.0V– ~Laminar? Vin 1m/s...


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Two phase flow


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Two phase flow

PFR with MITReM and H bubbles

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Movie!Dissolved H

– ∆V=2.0V– ~Laminar? Vin 1m/s...


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Two phase flow


IRDE with bubbles– Experimental data for 250rpm

Test case: H2-bubbles

0.1M Na2SO4 / pH = 2.5

2H+ + 2 e- H2

Potential: -2V/ NHE

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Two phase flow


IRDE with bubbles– Quantitative evaluation of two-phase flow

0 50 100 150 200 250 300 350 4000

10

20

30

40

50

60

70

80

90

100

Num

ber

of b

ubbl

es (

-)

Diameter (m)

ExperimentMean: 144.52 μm

Std: 75.55 μm

Bubble size distribution for 0rpm

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Simulation inputMean: 122.94 μm

Std: 57.15 μm


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Two phase flow



0 100 200 300 400 5000

20

40

60

80

100

Num

ber

of b

ubbl

es (

-)

Diameter (m)


ExperimentMean: 152.52 μm

Std: 80.01 μm

SimulationMean: 131.94 μm

Std: 45.55 μm

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Two phase flow



50 100 150 200 250 3000

20

40

60

80

100

120

140

160

180

200

Num

ber

of b

ubbl

es (

-)

Diameter (m)


ExperimentMean: 63.77 μmStd: 29.16 μm

SimulationMean: 70.62 μmStd: 22.14 μm

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Two phase flow


IRDE with bubbles– Morpheus/PLaS simulations– Diameter spectrum from experiments at 0rpm

250rpm 500rpm 1000rpm

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Extending the team

Additional future collaborations– Flora Tomasoni

• Measurements in the PFR• Post-processing of electrochemical solver output

(J, c, ...) to bubble solver input (d, v, ...)

– Pawel Skuza• Micro-scale simulations of bubble evolution from

electrodes• Correlations for macro-scale (MITReM)

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Documents

2/09/2014 | pag. 1 Novel Multiscale approach to Transport phenomena in Electrochemical Processes Integrating the research of different partners SBO 04