Patrik M

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Work package 3 Thermal management
17. November 2005
Patrik Müller Andres Bolleter
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Content

• - Resume thermal concept
• - Theoretical thermal resistance
• - Thermal measurement
• - Redesign vacuum insulation
• - Status WP3
• - Next steps
• - Miscellaneous to other WP

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Resume thermal concept
Vacuum insulation / insulation
Air
Insulation
Exhaust
Stack
Air
Vacuum insulation / insulation
Fuel
Exhaust
Separation of in- and outlet (heat exchanger)
Shape cylindrical or cubical
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Resume thermal concept
Three insulation-possibilities

• Vacuum chamber
• Vacuum chamber filled with porous insulation
  (WDS)
• Insulation material (WDS, Aerogel)

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Steel foil
Vacuum-Insulation
Outer Vacuum-Housing
Inner Vacuum-Housing
Air / Gas
Exhaust
Stack
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Thermally self-sustained ?SOFC
Comments on the paper A thermally self-sustained
micro solid oxide fuel-cell stack with high power
density

• Idea is to use the exothermic oxidation reaction
  to locally sustain the 500-600C which is needed
  for the electrochemical reaction
• Fuel utilization of experiments at 1
• Therefore 99 is released as heat
• OneBat-project efficiency 40
• Insulation needed

Z. Shao, S. M. Haile, J. Ahn, P. D. Ronney, Z.
Zhan, S. A. Barnett, A thermally self-sustained
micro solid-oxide fuel-cell stack with high power
density, 2005, Nature Publishing Group
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Theoretical thermal resistance
Simulation
Measurements
T2
Insulation
Stack
T1
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Thermal measurement
Aim determination of thermal resistant
Microtherm Super G Thermal conductivity 0.028
W/mK _at_ 400C
Dummy stack Pmax 12 W Ø 8 x 4 mm
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Measurements Silica Aerogel
t2
t3
t1
t4
t1 500C t2 48C t3 147C t4
23C Dimensions 14 x 30 x 45 mm (?
8 C)
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Measurements vacuum insulation
t2
t3
t1
t4
t1 500C t2 148C t3 102C t4
23C Pressure 210-3 mbar Dimensions Ø 22 x 2
mm (? 8 C)
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Measurements vacuum insulation
t2
t4
t1
t3
? Ptotal 1.6 W to keep the stack temperature
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Redesign vacuum insulation

• Reduced buckling
• Matching thermal expansion
• Pre-stressing
• Compact design
• Dimension adaptation on simulation results
• Slimmer frame
• ? Not tested yet reliability

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Silica Aerogel reliability
1 hours _at_ 1100C
1 hours _at_ 1000C
1 hours _at_ 900C
1 hours _at_ 800C
1 hours _at_ 700C
24 hours _at_ 600C
untreated
SEM picture by magic Brandon, MNW ETHZ
? By now no information about long-term and
insulation stability
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Status WP3
WP 3.1 Thermal System Design Milestones Month
3 - thermal insulation concept (T inside
550C, T outside 50C) (ZHW) Month 12 -
system integration concept incl. thermal
management concept heat exchanger design
compatible with GPU designs and micro-fabrication
(ZHW) Deliverables Month 3 - design from ZHW
? NTB for fabrication
?
?
WP 3.2 Fabrication Concept of Thermal System
Milestones Month 6 - test structures for
validation of critical points of the concept (?T
500C) (NTB) Month 9 - test results of first
designs Month 12 - thermal system design
demonstrator with simulated heat sources (dummy
stack, reformer, post-combustor) (NTB)
?
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Next steps

• Comparing first measurements with simulations
• If discrepancies to large why ?
• Redesign of concept
• Reliability vacuum insulation
• Setup of second measurements without
  gas-channels
• Closer to concept
• Comparing second measurements with simulations
• Third set of measurements with simulations

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WP 1 structuring Pt-Electrode
Process combination of lift-off and shadow mask

• Parameter
• Development time
• Resist thickness
• Exposing dose
• Adhesion

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WP 2 gas processing unit
Test device Foturan cannel 1 x 1 x 5 / 10 / 15
mm

• Input needed for fabrication (month 6)
• Final reformer design
• 3 designs of post-combustor
• ? Drawings with all dimensions (CAD-File, dxf
  etc..)

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Thermo-mechanical simulations

• What could be gained out of simulation
• Sensitivity of parameters can be evaluated
• Source of stresses can be localized easier then
  by measurement
• Design-criteria

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Thermo-mechanical simulations

• What inputs would these simulations require?
• Geometry
• Expansion coefficients
• E-module, Poisson Ratio

• Where could thermo-mechanical simulations be used
• As an additional tool for system design
• To support cell-measurements, gaining insights

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Questions ?
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Thermo-mechanical simulations
Resulting from elevated temperatures the major
structural problem foreseen with planar SOFCs is
their thermal stresses The stresses
occurring in both cells are lying beyond the
limit principal stress peak arises at the
beginning of the process (startup process).
Largest stress occurs in a ceramic cell fuelled
with prereformed methane and it is located in the
electrolyte layer at interface with the anode
A. Selimovic, M. Kemm, T. Torisson, M. Assadi,
Steady state and transient thermal stress
analysis in planar solid oxide fuel cells,
Journal of Power Sources, 2005