Tutorial: SOFC Model
Introduction
The purpose of this tutorial is to demonstrate the use of the Solid Oxide Fuel Cell (SOFC)
model in FLUENT 6.3. The SOFC model is provided as an add-on module with the standard
FLUENT licensed software. The SOFC module comprises a UDF library (containing a set
of user-defined functions) and a pre-compiled scheme library (containing the graphical and
text user interface). The SOFC module has to be loaded and activated before calculations
can be performed.
This tutorial demonstrates how to do the following:
• Load the SOFC module in FLUENT.
• Set the parameters for the SOFC model.
• Define new solid materials for the anode, the cathode, and the electrolyte.
• Set up appropriate boundary conditions and multigrid control parameters.
• Perform postprocessing to examine the distribution of current, voltage, temperature,
and species throughout the fuel cell.
Prerequisites
This tutorial assumes that you are familiar with the FLUENT interface, and that you have
a have a good understanding of the basic setup and solution procedures. Some steps will
not be shown explicitly.
In this tutorial, you will use the SOFC model. If you have not used this model before, refer
to the Fuel Cell Modules Manual.
The SOFC add-on module is installed with the standard installation of FLUENT in a folder
called addons/sofc1.2 in your installation area.
The SOFC module is provided as an addon module with the standard FLUENT licensed
software. A special license is required to use the SOFC module.
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SOFC Model
Problem Description
The tubular SOFC under consideration is shown in Figure 1. The anode inlet is fed
with 2.48949e−07 kg/s of humidified hydrogen at 973 K. The cathode inlet is fed with
1.3705e−05 kg/s of air at 973 K. The cathode and anode comprise two concentric cylinders, each 130 mm long. The inner and outer diameters of the cathode are 4 and 6 mm
respectively. The inner and outer diameters of the anode are 6 and 7 mm respectively.
The active electrolyte material, which has a thickness of 40 microns, is pressed between the
anode and cathode layers.
In this simulation, the outer walls of the anode and cathode current collectors are kept
insulated. The fuel and oxidizer travel through the porous anode and cathode materials
toward the electrolyte region. Fuel is oxidized electrochemically at the interface of the
electrolyte region and the anode. Oxygen in the incoming air is reduced electrochemically
at the interface of the electrolyte region and the cathode. As a result of the overall reaction,
water is formed at the anode side. The SOFC model is used to examine the current, voltage,
species, and temperature distribution throughout the fuel cell.
Figure 1: Schematic of the Problem
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SOFC Model
Preparation
1. Copy the file, tubular sample.msh to your working folder.
2. Start the 3DDP (3ddp) version of FLUENT.
Setup and Solution
Step 1: Grid
1. Read the mesh file (tubular sample.msh).
2. Scale the grid.
Grid −→Scale...
(a) Select mm in the Grid Was Created In drop-down list in the Unit Conversion group
box.
(b) Click Scale.
(c) Close the Scale Grid panel.
3. Merge the zones fluid and flow-channel1-an.
Grid −→Merge...
(a) Select fluid from the Multiple Types selection list.
(b) Select fluid and flow-channel1-an from the Zones of Type list.
(c) Click Merge.
4. Merge the zones, inlet-an and inlet-an:033.
(a) Select mass-flow-inlet from the Multiple Types selection list.
(b) Select inlet-an and inlet-an:033 from the Zones of Type selection list .
(c) Click Merge and close the Merge Zones panel.
5. Rename the electrolyte zone to wall-electrolyte-cathode.
Define −→Boundary Conditions...
(a) Select electrolyte from the Zone selection list and click the Set... button to open
the Wall panel.
i. Enter wall-electrolyte-cathode for Zone Name.
ii. Click OK to close the Wall panel.
6. Rename the electrolyte-shadow zone to wall-electrolyte-anode-shadow.
7. Check and display the grid (Figure 2).
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SOFC Model
Y
X
Z
Grid
FLUENT 6.3 (3d, dp, pbns, lam)
Figure 2: Grid Display
Step 2: Models
1. Retain the default solver settings.
2. Enable the Energy Equation.
Define −→ Models −→Energy...
3. Enable a Laminar flow simulation.
Define −→ Models −→Viscous...
Ensure that the Viscous Heating option is disabled.
4. Define the species model.
Define −→ Models −→ Species −→Transport & Reaction...
(a) Select Species Transport from the Model list.
(b) Disable Inlet Diffusion and enable Diffusion Energy Source, Full Multicomponent
Diffusion, and Thermal Diffusion from the Options list.
(c) Click OK to close the Species Model panel.
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SOFC Model
5. Load the SOFC module using TUI commands.
You may have to press the <Enter> key to get the > prompt.
> define/models/addon-module
FLUENT Addon Modules:
0. none
1. MHD Model
2. Fiber Model
3. PEM Fuel Cell Model
4. SOFC Fuel Cell Model
5. Population Balance Model
Enter Module Number: [0] 4
FLUENT reports the following in the console window:
Step 3: SOFC model
1. Set the parameters for the SOFC model.
Define −→ Models −→ SOFC −→SOFC Model Control Panel...
(a) Enter 0.3 for Current Underrelaxation Factor.
(b) Set the Electrochemical and Electrical Parameters as follows:
Parameters
Total System Current
Electrolyte Thickness
Electrolyte Resistivity
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Values
8 Amp
4e-05 m
0.1
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SOFC Model
(c) Click OK to close the Define SOFC Model Parameters panel.
2. Set the activation parameters for the SOFC model.
Define −→ Models −→ SOFC −→Activation Panel...
(a) Set the parameters as shown in the table:
Parameters
Anode Exchange Current Density
Anode H2 Mole Fraction Reference
Anode H2O Mole Fraction Reference
Cathode Exchange Current Density
O2 Mole Fraction Reference
Values
1e+20
1
1
512
1
(b) Click OK to close the Define Activation Parameters panel.
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3. Specify the anode interface components for the SOFC model.
Define −→ Models −→ SOFC −→Anode Interface Setup...
(a) Select wall-electrolyte-anode-shadow from the Zone(s) selection list.
(b) Enable Anode Interface.
(c) Click OK to close the Anode Interface Setup panel.
4. Specify the cathode interface components for the SOFC model.
Define −→ Models −→ SOFC −→Cathode Interface Setup...
(a) Select wall-electrolyte-cathode from the Zone(s) selection list.
(b) Enable Cathode Interface.
(c) Click OK to close the Cathode Interface Setup panel.
5. Set the parameters for the electric field model.
Define −→ Models −→ SOFC −→Electric Field Input Panel...
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(a) Select anode from the Conductive Regions - 1 selection list and enter 333330 for
Conductivity.
(b) Select cathode from the Conductive Regions - 2 selection list and enter 7937 for
Conductivity.
(c) Select cathode-cc and anode-cc from the Conductive Regions - 3 selection list and
enter 1.5e+07 for Conductivity.
(d) Select wall-cathode-cc from the Contact Surfaces - 1 selection list and enter 1e-08
for Contact Resistance.
(e) Select wall-cathode-cc from the Contact Surfaces - 2 selection list and enter 1e-07
for Contact Resistance.
(f) Select wall-voltage-tap from the Voltage Tap Surface selection list.
(g) Select wall-current-tap from the Current Tap Surface selection list.
(h) Retain the default values for the other parameters.
(i) Click OK to close the Define Electric Field Model Parameters.
6. Specify the tortuosity parameters for the SOFC model.
Define −→ Models −→ SOFC −→Tortuosity Setup...
(a) Select anode from the Zone(s) selection list and enable Enable Tortuosity.
(b) Enter 3 for Index: Thread 5 and click Apply.
(c) Select cathode from the Zone(s) selection list and enable Enable Tortuosity.
(d) Enter 3 for Index: Thread 5 and click Apply.
(e) Click OK to close the Tortuosity Interface Setup panel.
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Step 4: Materials
1. Set the Adjust function to adjust function.
Define −→ User-Defined −→Function Hooks...
2. Set the Number of User-Defined Scalars to 1.
Define −→ User-Defined −→Scalars...
Ensure that the Flux Function is set to none.
3. Set the Number of User-Defined Memory Locations to 13.
Define −→ User-Defined −→Memory...
4. Create new solid materials.
Define −→Materials...
(a) Create anode-material.
i. Select solid from the Material Type drop-down list.
ii. Enter anode-material for Name and delete the entry forguiChemical Formula.
iii. Enter 3030, 595.1, and 6.23 for Density, Cp, and Thermal Conductivity respectively.
iv. Click Change/Create.
(b) Create cathode-material.
i. Enter cathode-material for Name and delete the entry for Chemical Formula.
ii. Enter 4375 and 1.15 for Density and Thermal Conductivity respectively.
iii. Select piecewise-linear from the Cp drop-down list to open the Piecewise-Linear
Profile panel.
A. Set Points to 2.
B. For Point 1, enter 1073.15 and 570 for Temperature and Value respectively.
C. For Point 2, enter 1273.15 and 565 Temperature and Value respectively.
D. Click OK to close the Piecewise-Linear Profile panel.
(c) Create current-collector-material.
i. Under Name, enter current-collector-material and delete the entry under Chemical Formula.
ii. Specify the Density, Cp, and Thermal Conductivity to 8900, 446, and 72
respectively.
iii. Click Change/Create.
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SOFC Model
(d) Create electrolyte-material.
i. Enter electrolyte-material for Name and delete the entry for Chemical
Formula.
ii. Enter 5371, 585.2, and 2.2 for Density, Cp, and Thermal Conductivity respectively.
iii. Click Change/Create.
5. Edit the mixture-template mixture material.
(a) Copy hydrogen from the FLUENT material database.
i. Click the Fluent Database... button to open the Fluent Database Materials
panel.
ii. Select fluid from the Material Type drop-down list.
iii. Select hydrogen (h2) from the Fluent Fluid Materials drop-down list.
iv. Click Copy and close the Fluent Database Materials panel.
(b) Click the Edit... button to the right of the Mixture Species drop-down list and
arrange the materials in the Selected Species list as follows:
i. h2o
ii. o2
iii. h2
iv. n2
(c) Select ideal-gas-mixing-law from the Thermal Conductivity and Viscosity drop-down
lists.
(d) Select user-defined for Mass Diffusivity and select diffusivity::sofc1.2 as the userdefined function.
(e) Retain the default values for the other parameters.
(f) Click Change/Create and close the Materials panel.
Step 5: Operating Conditions
Retain the default operating conditions.
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Step 6: Boundary Conditions
Define −→Boundary Conditions...
1. Set the boundary conditions for the anode zone.
(a) Enable Source Terms.
(b) Click the Source Terms tab and select udf source::sofc1.2 for Mass, h2o, h2, and
Energy.
(c) Enable Porous Zone and click the Porous Zone tab to set the following parameters:
i. Enter 1e+13 for Viscous Resistance for Direction-1, Direction-2, and Direction3.
ii. Enter 0.3 for Porosity in the Fluid Porosity group box and select anodematerial from the Solid Material Name drop-down list.
iii. Retain the default values for the other parameters.
(d) Click OK to close the Fluid panel.
2. Set the boundary conditions for the cathode zone.
(a) Enable Source Terms.
(b) Click the Source Terms tab and select udf source::sofc1.2 for Mass, o2, and Energy
respectively.
(c) Enable Porous Zone and click the Porous Zone tab to set the following parameters:
i. Enter 1e+13 for Direction-1, Direction-2, and Direction-3 in the Viscous Resistance group box.
ii. Enter 0.3 for Porosity and select cathode-material from the Solid Material
Name drop-down list.
iii. Retain the default values for the other parameters.
(d) Click OK to close the Fluid panel.
3. Set the boundary conditions for the anode-cc zone.
(a) Select current-collector-material in the Material Name drop-down list.
(b) Enable Source Terms and select udf source in the Energy drop-down list.
(c) Retain the default values for the other parameters.
4. Set the boundary conditions for the cathode-cc zone.
(a) Select current-collector-material from the Material Name drop-down list.
(b) Enable Source Terms and select udf source::sofc1.2 for Energy.
(c) Retain the default values for the other parameters.
(d) Click OK to close the Solid panel.
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SOFC Model
5. Set the boundary conditions for the inlet-an zone.
(a) Enter 2.48949e-07 kg/s for Mass Flow-Rate.
(b) Select Normal to Boundary from the Direction Specification Method drop-down
list.
(c) Click the Thermal tab and enter 973 K for Total Temperature.
(d) Click the Species tab and enter 0.5248 and 0.4752 for h2o and h2 respectively
in the Species Mass Fractions group box.
(e) Retain the default values for the other parameters.
(f) Click OK to close the Mass-Flow Inlet panel.
6. Set the boundary conditions for the inlet-ca zone.
(a) Enter 1.3705e-05 kg/s for Mass Flow-Rate.
(b) Click the Thermal tab and enter 973 K for Total Temperature.
(c) Select Normal to Boundary from the Direction Specification Method drop-down
list.
(d) Click the Species tab and enter 0.2329 for o2 in the Species Mass Fractions group
box.
(e) Retain the default values for the other parameters.
(f) Click OK to close the Mass-Flow Inlet panel.
7. Close the Boundary Conditions panel.
Step 7: Solution
1. Enter 5000000 pascal for Maximum Absolute Pressure.
Solve −→ Controls −→Limits...
2. Enable the plotting of residuals.
Solve −→ Monitors −→Residual...
(a) Enable Plot from the Options group box.
(b) Define the absolute criteria for all the equations as follows:
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Residual
continuity
x-velocity
y-velocity
z-velocity
energy
h2o
o2
h2
uds-0
Convergence
Criterion
1e-06
1e-06
1e-06
1e-06
1e-07
1e-06
1e-06
1e-06
1e-08
(c) Click OK to close the Residual Monitors panel.
3. Initialize the flow field.
Solve −→ Initialize −→Initialize...
(a) Retain the default values for all the parameters and click Init.
(b) Close the Solution Initialization panel.
4. Change the SOFC Model parameters.
Define −→ Models −→ SOFC −→SOFC Model Control Panel...
• Enable SOFC Model
• Enable Species Sources
• Enable Electrolyte Conductivity Submodel
The Enable Electrolyte Conductivity Submodel option allows the electrolyte conductivity to change as a function of temperature.
• Enable Surface Energy Source
The Enable Surface Energy Source option includes the heat addition due to electrochemistry and all the reversible processes.
• Disable CO Electrochemistry
• Click OK to close the Define SOFC Model Parameters.
5. Run the simulation till all the residuals are decreasing.
6. Enable Volumetric Energy Source.
Define −→ Models −→ SOFC −→SOFC Model Control Panel...
The Enable Volumetric Energy Source option includes the ohmic heating throughout the
electrically conducting zones.
7. Continue the simulation until convergence is achieved.
8. Save the case and data files (tubular sample.cas.gz and tubular sample.dat.gz).
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SOFC Model
Figure 3: Scaled Residuals
Step 8: Postprocessing
1. Create the custom field function, voltage-volts.
Define −→Custom Field Functions...
(a) Select User Defined Scalars... and User Scalar 0 from the Field Functions drop-down
lists and click Select.
(b) Enter voltage-volts for New Function Name and click Define.
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(c) Close the Custom Field Function Calculator panel.
2. Display filled contours of current-density-amp/m2.
(a) Enable Draw Grid from the Options group box to open the Grid Display panel.
i. Select Feature from the Edge Type group box.
ii. Select wall-anode-cc:031, wall-anode-cc:032, wall-anode-side, wall-cathode-cc:029,
wall-cathode-side, wall-current-tap, wall-electrolyte-cathode, and wall-electrolyteinert from the Surfaces selection list.
iii. Close the Grid Display panel.
(b) Disable Auto Range from the Options group box.
(c) Enter 1500 and 10200 for Min and Max respectively.
(d) Select wall-electrolyte-cathode from the Surfaces selection list and click Display
(Figure 4).
1.02e+04
9.77e+03
9.33e+03
8.90e+03
8.46e+03
8.03e+03
7.59e+03
7.16e+03
6.72e+03
6.29e+03
5.85e+03
5.42e+03
4.98e+03
4.55e+03
4.11e+03
3.68e+03
3.24e+03
2.81e+03
2.37e+03
1.94e+03
1.50e+03
Y
ZX
Contours of current-density-amp/m2
FLUENT 6.3 (3d, dp, pbns, spe, lam)
Figure 4: Contours of current-density-amp/mˆ 2
3. Display filled contours of nernst-voltage-volts.
(a) Disable Auto Range from the Options group box.
(b) Enter 0.775 and 0.981 for Min and Max respectively.
(c) Select wall-electrolyte-cathode from the Surfaces selection list and click Display
(Figure 5).
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SOFC Model
9.81e-01
9.71e-01
9.60e-01
9.50e-01
9.40e-01
9.29e-01
9.19e-01
9.09e-01
8.99e-01
8.88e-01
8.78e-01
8.68e-01
8.57e-01
8.47e-01
8.37e-01
8.26e-01
8.16e-01
8.06e-01
7.96e-01
7.85e-01
7.75e-01
Y
ZX
Contours of nernst-voltage-volts
FLUENT 6.3 (3d, dp, pbns, spe, lam)
Figure 5: Contours of nernst-voltage-volts
4. Display filled contours of activation-overpotential-volts.
(a) Disable Auto Range from the Options group box.
(b) Enter 0.117 and 0.205 for Min and Max respectively.
(c) Select wall-electrolyte-cathode from the Surfaces selection list and click Display
(Figure 6).
5. Display filled contours of voltage-volts.
(a) Disable Auto Range.
(b) Enter 0.647 and 0.693 for Min and Max respectively.
(c) Select wall-electrolyte-cathode from the Surfaces selection list and click Display
(Figure 7).
6. Display filled contours of Static Temperature.
(a) Disable Auto Range from the Options group box.
(b) Enter 1150 and 1360 for Min and Max respectively.
(c) Select wall-electrolyte-cathode from the Surfaces selection list and click Display
(Figure 8).
7. Display filled contours of Mass fraction of h2.
(a) Disable Auto Range from the Options group box.
(b) Enter 0.035 and 0.35 for Min and Max respectively.
(c) Select wall-electrolyte-anode-shadow from the Surfaces selection list and click Display (Figure 9).
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2.05e-01
2.01e-01
1.96e-01
1.92e-01
1.87e-01
1.83e-01
1.79e-01
1.74e-01
1.70e-01
1.65e-01
1.61e-01
1.57e-01
1.52e-01
1.48e-01
1.43e-01
1.39e-01
1.35e-01
1.30e-01
1.26e-01
1.21e-01
1.17e-01
Y
ZX
Contours of activation-overpotential-volts
FLUENT 6.3 (3d, dp, pbns, spe, lam)
Figure 6: Contours of activation-overpotential-volts
6.93e-01
6.91e-01
6.88e-01
6.86e-01
6.84e-01
6.82e-01
6.79e-01
6.77e-01
6.75e-01
6.72e-01
6.70e-01
6.68e-01
6.65e-01
6.63e-01
6.61e-01
6.59e-01
6.56e-01
6.54e-01
6.52e-01
6.49e-01
6.47e-01
Y
ZX
Contours of voltage-volts
FLUENT 6.3 (3d, dp, pbns, spe, lam)
Figure 7: Contours of voltage-volts
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1.36e+03
1.35e+03
1.34e+03
1.33e+03
1.32e+03
1.31e+03
1.30e+03
1.29e+03
1.28e+03
1.27e+03
1.26e+03
1.24e+03
1.23e+03
1.22e+03
1.21e+03
1.20e+03
1.19e+03
1.18e+03
1.17e+03
1.16e+03
1.15e+03
Y
ZX
Contours of Static Temperature (k)
FLUENT 6.3 (3d, dp, pbns, spe, lam)
Figure 8: Contours of Static Temperature
3.50e-01
3.34e-01
3.18e-01
3.03e-01
2.87e-01
2.71e-01
2.55e-01
2.40e-01
2.24e-01
2.08e-01
1.92e-01
1.77e-01
1.61e-01
1.45e-01
1.30e-01
1.14e-01
9.80e-02
8.22e-02
6.65e-02
5.07e-02
3.50e-02
Y
ZX
Contours of Mass fraction of h2
FLUENT 6.3 (3d, dp, pbns, spe, lam)
Figure 9: Contours of Mass Fraction of h2
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Summary
In this tutorial, you learned how to set up and model a solid oxide fuel cell. Hydrogen is
the only gaseous fuel participating in the electrochemistry. The model provides detailed
information on the distribution of current and voltage on all the electrically conducting
regions, along with species and temperature distribution throughout the fuel cell.
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