1. Numerical Simulation of Multi-scale Transport Processes and Reactions in PEM Fuel Cells Using Two-Phase Models Munir Ahmed Khan Division of Heat Transfer Dept. of Energy Sciences LTH

2. Heat Transfer / Energy Sciences / LTH Outline Introduction Brief History of Development Modeling Approach Numerical Modeling Results Conclusion

3. Heat Transfer / Energy Sciences / LTH PEMFC Schematic (Jacobson, 2004)

4. Heat Transfer / Energy Sciences / LTH History of PEMFC Development 1839 (Fuel Cell Principle) 1965 (NASA) 1968 (Nafion) 1969 (Biosatellite Missions) 1970 – 1989 (Abeyance) 1990 – Present (Ballard Power and Los Alamos Labs)

5. Heat Transfer / Energy Sciences / LTH Scientific Research Activities Scientific Research Experimental Approach Numerical Approach

6. Heat Transfer / Energy Sciences / LTH Numerical Approach

7. Heat Transfer / Energy Sciences / LTH Presented Modeling Interdigitated Flow Field Cathode Side Only 2-Phase –2 Phase Flow –2 Phase Temperature –2 Phase Current Agglomerate Catalyst Modeling

8. Heat Transfer / Energy Sciences / LTH Computational Domain (Larminie J, 2003) ComponentDimension (mm) Inlet0.4 Outlet0.4 Current Collector0.8 PTL thickness0.4 Catalyst layer thickness0.1

9. Heat Transfer / Energy Sciences / LTH Flow Fields (www.me.udel.edu)

10. Heat Transfer / Energy Sciences / LTH Bridging Numerical and Experimental Modeling Actual Machine Numerical Modeling Experimental Modeling

11. Heat Transfer / Energy Sciences / LTH Idealized Catalyst Layer Electrolyte Bulk Gas Pores Agglomerate Nafion Pt Particle Carbon Particle

12. Heat Transfer / Energy Sciences / LTH Transport Phenomena Multicomponent Diffusion Oxygen Dissolution Dissolved Oxygen Diffusion Electron Transport Proton Migration H2OH2O H+H+ H+H+ H2OH2O e-e- e-e- e-e- O2O2 O2O2 O2O2 O2O2 O2O2 O2O2

13. Heat Transfer / Energy Sciences / LTH Oxygen Reduction Reactions Reaction Steps Rate of Reaction

14. Heat Transfer / Energy Sciences / LTH Boundary Conditions 1.Inlet Gas Concentration Fluid Temperature Pressure Water Saturation 1 2.Catalyst/Membrane Interface Nominal Cathode Overpotential (NCO) 3.Current Collector Solid Phase Potential Solid Phase Temperature 2 3

15. Heat Transfer / Energy Sciences / LTH Velocity and Pressure Fields Velocity Distribution (m/s) Pressure Field (N/m 2 )

16. Heat Transfer / Energy Sciences / LTH Oxygen Mass Fraction

17. Heat Transfer / Energy Sciences / LTH Water Saturation

18. Heat Transfer / Energy Sciences / LTH Fluid Temperature (K)

19. Heat Transfer / Energy Sciences / LTH Solid Temperature (K)

20. Heat Transfer / Energy Sciences / LTH Membrane Phase Conductivity

21. Heat Transfer / Energy Sciences / LTH Cathode Overpotential (V)

22. Heat Transfer / Energy Sciences / LTH Model Verification & Comparison

23. Heat Transfer / Energy Sciences / LTH Conclusion Effect of Liquid Water –More prominent at higher current density Membrane Phase Conductivity –Highly dependant on water activity Losses –Higher losses are observed at higher current density Mass Limitation Effects –Adequately captured by agglomerate model Power –Maximum power is observed at 0.55 V

24. Heat Transfer / Energy Sciences / LTH THANKS TO ALL Jinliang Yuan Bengt Sundén HEC Pakistan Swedish Research Council & Special Thanks to