Title Page
ABSTRACT (KOREAN)
ABSTRACT
Contents
NOMENCLATURE 21
CHAPTER 1. INTRODUCTION 38
1.1. Introduction 38
1.2. Literature review on PEM Fuel Cell systems 41
1.3. Literature review on Hydrogen Storage systems 49
1.4. The objective of the dissertation 53
CHAPTER 2. NUMERICAL MODEL 58
2.1. Multi-scale PEM Fuel cell model 58
2.1.1. Micro-scale CL model 62
2.1.2. 3-D macro-scale two-phase PEMFC model 71
2.1.3. Boundary conditions and numerical implementations 77
2.2. Metal hydride hydrogen storage model 82
2.2.1. Model assumptions 82
2.2.2. Conservation equations and source terms 83
2.2.3. Thermal properties combined with copper foams 86
2.2.4. Pressure–composition isotherm 87
2.2.5. Initial and boundary conditions 90
2.3. Multi-objective optimization Model 93
2.3.1. Motivation 93
2.3.2. Multi-objective optimization of PEM Fuel Cell 93
2.3.3. Multi-objective of Metal hydride 114
CHAPTER 3. Results and Discussion of Multi-scale PEM Fuel Cell simulation 119
3.1. Introduction 119
3.2. Results and Discussion 120
3.3. Conclusions 133
CHAPTER 4. Results and Discussion of Metal hydride 135
4.1. Introduction 135
4.2. Results and Discussion 135
4.2.1. Copper foam-based DU bed geometries 135
4.2.2. Comparison of reference and scale-up DU beds 138
4.3. Conclusions 149
CHAPTER 5. Results and Discussion of PEM Fuel Cell optimization 150
5.1. Introduction 150
5.2. Results and Discussion 151
5.2.1. Fitting of the second order polynomial equation 151
5.2.2. CCD analysis 155
5.2.3. ANOVA 162
5.2.4. Diagnostics of model adequacy 167
5.2.5. Impacts of independent factors on responses 171
5.2.6. Confirmative tests 175
5.2.7. Optimum Design 182
5.3. Conclusions 190
CHAPTER 6. Results and Discussion of Metal hydride optimization 192
6.1. Introduction 192
6.2. Results and Discussion 193
6.2.1. Fitting of the second-order polynomial equation 193
6.2.2. The second-order model and ANOVA 197
6.2.3. Adequacy of the model 199
6.2.4. Impacts of independent factors on responses 205
6.3. Conclusion 208
CHAPTER 7. Summary and Future Work 209
7.1. Summary of research 209
7.2. Future Work 212
REFERENCES 215
CURRICULUM VITAE 236
Table 1. Governing equations of a 3D two-phase PEM fuel cell model. 72
Table 2. Source/sink terms of a 3D two-phase PEM fuel cell model. 73
Table 3. Kinetic, physiochemical and transport properties. 75
Table 4. Cell dimensions and operating conditions. 78
Table 5. Thermal properties. 79
Table 6. Boundary conditions. 80
Table 7. Thermal-physical properties and operating conditions. 88
Table 8. PEM fuel cell model: Governing equations. 97
Table 9. PEM fuel cell model: Source/sink terms. 98
Table 10. Kinetic, transport, and physiochemical properties of the fuel cell. 100
Table 11. Expressions used in the two-phase mixture model. 102
Table 12. Transport properties in the electrolyte. 104
Table 13. Boundary conditions. 107
Table 14. RSM experimental parameters and their ranges. 110
Table 15. Experimental range and levels of the independent variables. 115
Table 16. Simulation cases for different designs of CL and the degradation levels. 121
Table 17. Training conditions using the four design variables (GDL thickness [X₁], channel depth [X₂], channel width [X₃], and land width [X₄]), and the responses (cell voltage [Y₁] and pressure drop [Y₂]) according to CCD. Training data set and... 153
Table 18. Comparison of the results of different statistical models for the cell voltage. 157
Table 19. Comparison of the results of different statistical models for the pressure drop. 158
Table 20. Lack of Fit result of the cell voltage. 159
Table 21. Lack of Fit result of the pressure drop. 160
Table 22. Statistical parameters related to the best initial model. 161
Table 23. Estimated regression coefficients and the corresponding ANOVA results of the data of the estimated quadratic model for cell voltage. 163
Table 24. Estimated regression coefficients and the corresponding ANOVA results of the data of the estimated quadratic model for the pressure drop. 165
Table 25. Comparison of the results obtained using CFD and RSM based on the four design parameters (GDL thickness [X₁], channel depth [X₂], channel width [X₃], and land width [X₄]), and responses (cell voltage [Y₁] and pressure drop [Y₂]).... 178
Table 26. Comparison of pressure drops obtained through CFD and analytically calculation for Opt. point and Ref. point at three different... 189
Table 27. CCD experiments and experimental results. 194
Table 28. Comparison of different statistical models for the performance of bed. 195
Table 29. Lack of Fit result for performance of bed 196
Table 30. Statistical parameters related to the best initial model. 196
Table 31. Analysis of variance regression model for metal hydride bed performance. 198
Fig. 1. Schematic of a PEM fuel cell fed by a hydrogen storage bed. 40
Fig. 2. Micro-scale oxygen penetration via ionomer and liquid layerson a spherical agglomerati on in a cathode CL is seen schematically. 60
Fig. 3. Micro-and macro-scale computational domains of a PEMFC with the coupling variables exchanged during multiscale simulations. 61
Fig. 4. Catalyst structures of Pt/TiO₂/C and Pt/C with different degrees of catalyst... 68
Fig. 5. (a) Copper foam-based DU bed (1xdesign) that can contain 1.86 kg of DU for 70-g maximum tritium capacity and (b) schematic diagram of... 92
Fig. 6. Profile of a meshed proton exchange membrane (PEM) fuel cell under inhomogeneous compression. 95
Fig. 7. (a) Polarization behaviors under four different CL design and degradation conditions, and individual voltage losses at the... 126
Fig. 8. Comparison of oxygen transport resistances for four differentsimulation cases as a function of current density (RT vs current density).[이미지참조] 127
Fig. 9. Contours of oxygen concentration distributions on Pt surface at I=1.0 A/cm². 130
Fig. 10. Contours of current density distributions in themembrane at I=1.0 A/cm². 131
Fig. 11. Comparison of the additional voltage drops across the TiO₂ particles at the current densities of (a) 0.25 A/cm², (b) 0.5 A/cm²,... 132
Fig. 12. Schematic diagram of scale-up DU bed design (5xdesign) with different aspect ratios (L/D): (a) L/D=1.5L1x/1.825D1x, (b)...[이미지참조] 137
Fig. 13. Comparison of DU hydride temperature evolution curves for the reference DU bed for 1.86 kg of DU loading (1xdesign) and three... 139
Fig. 14. Three-dimensional contours of DU hydride temperature evolutions for the reference DU bed for 1.86 kg of DU loading... 141
Fig. 15. Comparison of H/U atomic ratio evolution curves for the reference DU bed for 1.86 kg of DU loading (1xdesign) and three... 145
Fig. 16. Three-dimensional contours of H/U atomic ratio evolutions for the reference DU bed for 1.86 kg of DU loading (1xdesign) and three... 148
Fig. 17. Plot of (a, b) predicted versus simulated values, (c, d) residual versus run order, and (e, f) residual versus predicted values for the cell... 168
Fig. 18. Pareto chart for the estimated effect of the parameters on the (a) cell voltage and (b) pressure drop. X₁, X₂, X₃, X₄, Y₁, and Y₂ denote... 170
Fig. 19. Surface and contour plots showing the interactive effect of the parameters (X₁, X₂, X₃, X₄) on Y₁. 172
Fig. 20. Surface and contour plots showing the interactive effect of the parameters (X₁, X₂, X₃, X₄) on Y₂. 174
Fig. 21. Comparison of the result obtained using response surface methodology (RSM) and a CFD software for the (a) cell voltage and... 176
Fig. 22. Scattering of 30 sample runs (blue spheres) and 43 test runs (black spheres) to determine the accumulation area (Gray zone) with... 177
Fig. 23. Comparison of the optimum and reference designs at I=2.0 A/cm²: (a) Polarization behaviors, (b) Overpotential breakdown, (c)... 186
Fig. 24. Normal probability plot of residuals of different model items. 200
Fig. 25. Predicted value versus actual value of different model items. 202
Fig. 26. Residuals versus run number. 203
Fig. 27. Plot of residual versus predicted response for Y₁. 204
Fig. 28. (a) Surface and contour plots showing the interactive effect of parameters X₁, X₃, on the Y₁. (b) the interactive effect of parameters X₁,... 207