Title Page
ABSTRACT (KOREAN)
ABSTRACT
Contents
NOMENCLATURE 21
CHAPTER 1. Introduction 26
1.1. Background 26
1.2. Fundamentals of hydrogen based electrochemical systems 28
1.2.1. Fundamentals of alkaline water electrolysis 28
1.2.2. Fundamentals of electrochemical hydrogen compressor 29
1.3. Literature review of hydrogen based electrochemical systems 30
1.3.1. Literature review of alkaline water electrolysis 30
1.3.2. Literature review of electrochemical hydrogen compressor 36
1.4. Objective and organization of the dissertation 40
CHAPTER 2. Model description 45
2.1. Numerical model of alkaline water electrolysis 45
2.1.1. Model assumptions 45
2.1.2. Conservation equations and source/sink terms 46
2.2. Numerical model of electrochemical hydrogen compressor 57
2.2.1. Model assumption 57
2.2.2. Conservation equations and source/sink terms 58
2.2.3. Solid mechanics model for EHC cell 66
2.3. Implementation procedures for simulation using User-Defined Functions in ANSYS Fluent 67
CHAPTER 3. Multidimensional modeling of zero-gap alkaline water electrolysis cells 78
3.1. Motivation 78
3.2. Model description 79
3.2.1. Boundary conditions 79
3.2.2. Numerical implementation procedures 81
3.3. Results and discussion 81
3.4. Conclusions 87
CHAPTER 4. Modeling of gas evolution processes in porous electrodes of zero-gap alkaline water electrolysis cells 102
4.1. Motivation 102
4.2. Model description 103
4.2.1. Nucleation theory and bubble formation model 103
4.2.2. Boundary conditions 105
4.2.3. Numerical implementation procedures 106
4.3. Results and discussion 107
4.4. Conclusions 114
CHAPTER 5. Coupled mechanical and electrochemical modeling and simulations for electrochemical hydrogen compressor cells 129
5.1. Motivation 129
5.2. Experimental 130
5.3. Model description 131
5.3.1. Boundary conditions 131
5.3.2. Numerical implementation procedures 133
5.4. Results and discussion 134
5.5. Conclusions 142
CHAPTER 6. Impact of critical design factors on the performance and mechanical characteristics of electrochemical hydrogen compressor cells 160
6.1. Motivation 160
6.2. Experimental 161
6.3. Model description 162
6.3.1. Boundary condition 162
6.3.2. Numerical implementation procedures 163
6.4. Results and discussion 164
6.5. Conclusions 174
CHAPTER 7. Conclusions and future works 196
7.1. Conclusions 196
7.2. Future work 198
Bibliography 200
Curriculum vitae 212
Table 2.1. Physio-chemical, kinetic and transport properties (Chapter 3). 68
Table 2.2. Physiochemical, kinetic, and transport properties (Chapter 4). 70
Table 2.3. Physiochemical, kinetic, and transport properties (Chapter 5). 73
Table 2.4. Physiochemical, kinetic, and transport properties (Chapter 6). 75
Table 2.5. Catalyst layer specifications. 77
Table 3.1. Cell dimensions and operating conditions 89
Table 4.1. Cell dimensions and operating conditions. 116
Table 5.1. Cell dimensions, and operation conditions 145
Table 6.1. Cell components dimensions, and operation conditions. 177
Table 6.2. Summary of geometric details of parametric cases and calculated results. 178
Figure 1.1. Schematic of an AWE cell with key components and transport processes. 43
Figure 1.2. Schematic diagram of an EHC cell with major components and key transport processes. 44
Figure 3.1. Computational geometry and mesh configuration of a zero-gap AWE cell with a porous separator. 90
Figure 3.2. Comparison of simulated and measured polarization curves at the constant electrolyte velocity of 32.64 cm³/min. The experimental... 91
Figure 3.3. (a) Solid electrode and electrolyte phase potential and (b) overpotential distributions along the cell thickness. (c) Individual... 93
Figure 3.4. Concentration distributions of (a) water and (b) OH- over the plane cutting across the middle of the AWE domain at the high,... 95
Figure 3.5. Concentration distributions of (a) hydrogen from the HER in the negative electrode and (b) oxygen from the OER in the positive... 97
Figure 3.6. Influence of the OH- diffusion term in the charge conservation equation (Eq. (42)) on the OH- concentration contours. Comparison with... 98
Figure 3.7. Influence of the OH- diffusion term in the charge conservation equation (Eq. (42)) on the electrolyte potential distribution along the cell... 100
Figure 4.1. Computational domain and mesh configuration of a zero-gap AWE cell. 117
Figure 4.2. (a) Comparison of simulated and experimentally measured I-V curves at an operating temperature T of 80 ℃ and (b) effect of... 119
Figure 4.3. Comparison of I-V curves for electrolyte flow rates of 0.1 and 0.01 m/s for (a) the small-scale cell with l = 5.4 cm and (b)... 121
Figure 4.4. Individual voltage losses of the large-scale cell with l = 27 cm for constant flow rates of (a) uin = 0.1 m/s and (b) uin = 0.01 m/s....[이미지참조] 123
Figure 4.5. Contours of OH⁻ molar concentration over the plane cutting across the center of the large-scale cell with l = 27cm at operating... 124
Figure 4.6. Contours of H₂ molar concentration over the plane cutting across the center of the large-scale cell with l = 27cm at operating... 125
Figure 4.7. Contours of H₂ volume fraction over the plane cutting across the center of the large-scale cell with l = 27cm at operating current... 126
Figure 4.8. Contours of O₂ molar concentration over the plane cutting across the center of the large-scale cell with l = 27cm at operating... 127
Figure 4.9. Contours of O₂ volume fraction over the plane cutting across the center of the large-scale cell with l = 27 cm at operating current... 128
Figure 5.1. (a) Experimental EHC cell hardware and components and (b) experimental setup for measurements of polarization and impedance curves. 146
Figure 5.2. (a) Schematic diagram of the computational domain and (b) mesh configuration with boundary conditions. 147
Figure 5.3. Comparison of simulated and experimentally measured I-V curves at (a) different cathode outlet pressures of 1bar and 10bar and... 148
Figure 5.4. Contours of the absolute pressure profiles along the anode and cathode gas channels at (a) 0.1 A/cm² and (b) 0.5 A/cm² for the... 150
Figure 5.5. Contours of gas velocity profiles along the anode and cathode gas channels at (a) 0.1 A/cm² and (b) 0.5 A/cm² for the hydrogen... 151
Figure 5.6. (a) contours of the water content (λ) distributions over the middle plane of anode and cathode catalyst layers, (b) net water molar flux... 153
Figure 5.7. (a) contours of ionic current density distribution in the membrane, (b) breakdown of individual overpotentials, and (c) comparison... 155
Figure 5.8. Contours of deformation and von-Mises stress distribution: (a) Pd = 1 bar and (b) Pd = 10 bar.[이미지참조] 157
Figure 5.9. (a) contours of the water content distributions in the membrane, (b) breakdown of the individual overpotentials, and (c) comparison of the... 159
Figure 6.1. (a) Experimental setup for measurements of polarization and impedance curves and experimental EHC cell hardware and components,... 180
Figure 6.2. (a) Deformation contours and (b) von-Mises stress distributions for EHC cells with varying membrane thicknesses. The operating... 181
Figure 6.3. (a) Polarization and WDR curves of simulated and measured data for EHC cells with varying membrane thicknesses, (b) net water molar... 183
Figure 6.4. (a) Deformation contours, (b) von-Mises stress distributions, (c) polarization and WDR curves of simulated data for EHC cells, and (d) net... 187
Figure 6.5. (a) Deformation contours, (b) von-Mises stress distributions, (c) polarization and WDR curves of simulated data for EHC cells, (d) net water... 190
Figure 6.6. Decomposition of EHC cell voltage into its respective overpotentials under different cell design parameters. The operating... 192
Figure 6.7. Von-Mises stress distributions for EHC cells using (a) carbon paper and (b) titanium as GDL materials. The operating conditions include... 193
Figure 6.8. Comparison of (a) polarization and WDR curves for EHC cells utilizing either a carbon paper or titanium foam utilizing as GDL materials,... 195