PEM fuel cells : thermal and water management fundamentals

Title:

Personal Author:

Wang, Yun

Publication Information:

New York : Momentum Press, 2013

Physical Description:

xxx, 386 p. :bill. ; 27 cm.

ISBN:

9781606502457

Subject Term:

Proton exchange membrane fuel cells

Added Author:

Chen, Ken S.

Cho, Sung Chan

Available:*

Library	Item Barcode	Call Number	Material Type	Item Category 1	Status
Searching... PSZ JB	30000010321721	TK2933.P76 W36 2013 f	Open Access Book	Book	Searching... Unknown

Polymer Electrolyte Membrane (PEM) fuel cells convert chemical energy in hydrogen into electrical energy with water as the only by-product. Thus, PEM fuel cells hold great promise to reduce both pollutant emissions and dependency on fossil fuels, especially for transportation-passenger cars, utility vehicles, and buses-and small-scale stationary and portable power generators. But one of the greatest challenges to realizing the high efficiency and zero emissions potential of PEM fuel cells technology is heat and water management. This book provides an introduction to the essential concepts for effective thermal and water management in PEM fuel cells and an assessment on the current status of fundamental research in this field. The book offers you: - An overview of current energy and environmental challenges and their imperatives for the development of renewable energy resources, including discussion of the role of PEM fuel cells in addressing these issues; - Reviews of basic principles pertaining to PEM fuel cells, including thermodynamics, electrochemical reaction kinetics, flow, heat and mass transfer; and - Descriptions and discussions of water transport and management within a PEM fuel cell, including vapor- and liquid-phase water removal from the electrodes, the effects of two-phase flow, and solid water or ice dynamics and removal, particularly the specialized case of starting a PEM fuel cell at sub-freezing temperatures (cold start) and the various processes related to ice formation.

Author Notes

Yun Wang obtained his BS from Peking (Beijing) University in China in 1998, and his PhD in Mechanical Engineering from Pennsylvania State University (PSU) in 2006. At PSU, he worked with Prof. Chao-Yang Wang on PEM fuel cells at the Electrochemical Engine Center. He joined the Mechanical and Aerospace Engineering faculty at the University of California, Irvine in 2006. He is currently the director of the Renewable Energy Resources Lab and Associate Professor at the UC Irvine.
Ken S. Chen earned his PhD from the University of Minnesota in Chemical Engineering. He joined Sandia National Labs in 1993, where he is currently a principal member of the technical staff. Dr. Chen has led several collaborative research efforts involving academic, industry, and national labs, which have focused on critical phenomena controlling PEM fuel cell performance, Dr. Chen is an author or co-author or more than 110 archival publications of which about half are on PEM fuel cells and related topics.
Sung Chan Cho is a PhD candidate at the University of California, Irvine. He received an M.S. degree in Mechanical and Aerospace Engineering at Korean Aerospace University and was a Lead Analysis Engineer at GM Korea.

Preface	p. xi
List of Figures	p. xiii
List of Tables	p. xxiii
Nomenclature	p. xxv
1 Introduction	p. 1
1.1 Energy Challenges	p. 1
1.2 Fuel Cells and their Roles in Addressing the Energy Challenges	p. 3
1.3 PEM Fuel Cells	p. 5
1.3.1 PEM Fuel Cell Operation	p. 5
1.3.2 Current Status of PEM Fuel Cells	p. 7
1.3.3 Thermal and Water Management	p. 8
2 Basics of PEM Fuel Cells	p. 11
2.1 Thermodynamics	p. 11
2.1.1 Internal Energy and the First Law of Thermodynamics	p. 11
2.1.2 Enthalpy Change	p. 13
2.1.3 Entropy Change and the Second Law of Thermodynamics	p. 14
2.1.4 Gibbs Free Energy and Thermodynamic Voltage	p. 17
2.1.5 Chemical Potential and Nernst Equation	p. 19
2.1.6 Relative Humidity and Phase Change	p. 20
2.2 Electrochemical Reaction Kinetics	p. 23
2.2.1 Electrochemical Kinetics	p. 24
2.2.2 Electrochemical Mechanisms in PEM Fuel Cells	p. 26
2.2.3 Linear Approximation and Tafel Equation	p. 29
2.3 Voltage Loss Mechanisms and a Simplified Model	p. 30
2.3.1 Open Circuit Voltage (OCV)	p. 30
2.3.2 Activation Loss	p. 30
2.3.3 Ohmic Loss	p. 31
2.3.4 Transport Voltage Loss	p. 32
2.3.5 Current-Voltage (I-V) Curve and Operation Efficiency	p. 32
2.3.6 Role of Water and Thermal Management	p. 33
2.4 Chapter Summary	p. 34
3 Fundamentals of Heat and Mass Transfer	p. 37
3.1 Introduction	p. 37
3.2 Conservation Equations	p. 38
3.2.1 General Forms	p. 38
3.2.2 Mass and Momentum Conservation	p. 40
3.2.3 Energy Equation	p. 41
3.2.4 Species Transport Equation	p. 42
3.3 Constitutive Equations	p. 43
3.3.1 A Lattice Model	p. 43
3.3.2 Fourier's Law and Fick's Law	p. 46
3.4 Scaling and Dimensionless Groups	p. 46
3.4.1 Scaling and Dimensionless Equations	p. 46
3.4.2 Dimensionless Groups	p. 51
3.5 Chapter Summary	p. 51
4 Water and its Transport in the Polymer Electrolyte Membrane	p. 53
4.1 Introduction to the Polymer Electrolyte Membrane	p. 53
4.2 Ion Transport and Ionic Conductivity	p. 55
4.2.1 Proton Transport	p. 55
4.2.2 Ionic Conductivity Correlations	p. 55
4.2.3 Ionic Conductivity Measurement	p. 63
4.3 Water Transport in Polymer Electrolyte Membranes	p. 67
4.3.1 Transport Mechanisms	p. 68
4.3.2 Water Holding Capacity	p. 71
4.4 Water Quantification Using Neutron Radiography	p. 73
4.5 Ion Transport in Cathode Catalyst Layers	p. 75
4.5.1 Variation in Water Content in Catalyst Layers	p. 75
4.5.2 Proton Transport in Cathode Catalyst Layers	p. 77
4.5.3 Multiple-Layered Cathode Catalyst Layers	p. 80
4.6 Chapter Summary	p. 82
5 Vapor-Phase Water Removal and Management	p. 87
5.1 Mass Transport Overview	p. 87
5.2 Diffusion	p. 88
5.2.1 Diffusivity	p. 88
5.2.2 Molecular Versus Knudsen Diffusion	p. 90
5.2.3 Diffusion in GDLs	p. 91
5.3 Species Convection	p. 94
5.3.1 Flow Modeling with Constant-Flow Assumption	p. 94
5.3.2 Flow Formulation Without the Constant-Flow Assumption	p. 94
5.3.3 Convection in GDLs	p. 101
5.4 Pore-Scale Transport	p. 102
5.4.1 Stochastic Material Reconstruction	p. 103
5.4.2 Pore-Scale Transport Modeling	p. 105
5.4.3 Pore-Level Phenomena	p. 108
5.5 Transient Phenomena	p. 114
5.5.1 Transient Terms and Time Constants	p. 114
5.5.2 Transient Undergoing Constant Voltage or Step Change in Voltage	p. 115
5.5.3 Transient Undergoing Constant Current or Step Change in Current	p. 119
5.6 Water Management Between a PEM Fuel Cell and Fuel Processor	p. 122
5.6.1 Water Balance Model	p. 123
5.6.2 Effect of the Steam-to-Carbon Ratio	p. 126
5.7 Chapter Summary	p. 128
6 Liquid Water Dynamics and Removal	p. 131
6.1 Multiphase Flow Overview	p. 131
6.1.1 Modeling Multi-Phase Flows	p. 132
6.2 Multiphase Flow in GDLS/CLS	p. 133
6.2.1 Experimental Visualization	p. 134
6.2.1.1 X-ray Imaging	p. 135
6.2.1.2 Neutron Radiography	p. 135
6.2.2 Multiphase Mixture (M 2 ) Formulation	p. 136
6.2.2.1 Flow Equations	p. 137
6.2.2.2 Species Transport	p. 138
6.2.2.3 Model Prediction	p. 141
6.2.3 Carbon Paper (CP) Versus Carbon Cloth (CC)	p. 144
6.2.4 Spatially Varying Properties	p. 148
6.2.4.1 Through-Plane Variation in The GDL Property	p. 148
6.2.4.2 In-Plane Property Variation and the Effect of Land Compression	p. 153
6.2.4.3 Microporous Layers (MPLs)	p. 154
6.3 Multiphase Flow in Gas Flow Channels (GFCS)	p. 159
6.3.1 Experimental Visualization	p. 160
6.3.2 Two-Phase Flow Patterns	p. 160
6.3.3 Modeling Two-Phase Flow	p. 164
6.3.3.1 The Mixture Model	p. 167
6.3.3.2 Two-Fluid Modeling	p. 178
6.4 Water Droplet Dynamics at the GDL/GFC Interface	p. 187
6.4.1 Force Balance on a Spherical-Shape Droplet	p. 188
6.4.2 Droplet Deformation	p. 193
6.4.3 Droplet Detachment	p. 196
6.4.3.1 Control Volume Method	p. 196
6.4.3.2 Derivation Using the Drag Coefficient (C D )	p. 202
6.5 Chapter Summary	p. 205
7 ICE Dynamics and Removal	p. 209
7.1 Subfreezing Operation-Overview	p. 209
7.2 Ice Formation	p. 211
7.2.1 Water Transport and Conservation	p. 211
7.2.2 Three Cold-Start Stages	p. 214
7.2.2.1 First Stage: Membrane Hydration	p. 214
7.2.2.2 Second Stage: Ice Formation	p. 215
7.2.2.3 Third Stage: Ice Melting	p. 216
7.3 Voltage Loss Due to Ice Formation	p. 220
7.3.1 Spatial Variation of the Oxygen Reduction Reaction (ORR)	p. 220
7.3.2 The ORR Rate Under Subfreezing Temperature	p. 222
7.3.3 Oxygen Profile in the Catalyst Layer	p. 223
7.3.4 Voltage Loss Due to Ice Formation	p. 227
7.3.5 A Model of Cold-Start Cell Voltage	p. 228
7.4 State of Subfreezing Water	p. 231
7.5 Chapter Summary	p. 233
8 Thermal Transport and Management	p. 237
8.1 Heat Transfer Overview	p. 237
8.1.1 Heat Transfer and Its Importance	p. 237
8.1.2 Heat Transfer Modes	p. 240
8.1.2.1 Heat Conduction	p. 240
8.1.2.2 Convective Heat Transfer	p. 241
8.1.2.3 Heat Radiation	p. 243
8.1.3 Heat Transfer in Porous Media	p. 245
8.2 Heating Mechanisms	p. 246
8.2.1 The Entropic Heat	p. 247
8.2.2 Irreversibility of the Electrochemical Reactions	p. 248
8.2.3 The Joules Heat	p. 248
8.3 Steady-Slate Heat Transfer	p. 269
8.3.1 One-Dimensional (1D) Heat Transfer Analysis	p. 250
8.3.2 Two-Dimensional (2D) Heat Transfer Analysis	p. 251
8.3.3 Numerical Analysis	p. 252
8.3.3.1 Macroscopic Model Prediction	p. 252
8.3.3.2 Pore-Level Heat Transfer	p. 255
8.4 Transient Phenomena	p. 257
8.4.1 General Transient Operation	p. 257
8.4.2 Transient Subfreezing Operation	p. 260
8.4.2.1 Temperature Evolution and Voltage Loss	p. 260
8.4.2.2 Activation Voltage Loss	p. 262
8.4.2.3 Ohmic Voltage Loss	p. 263
8.5 Experimental Measurement of Thermal Conductivity	p. 265
8.6 Cooling Methods	p. 268
8.6.1 Heat Spreaders Cooling	p. 269
8.6.2 Cooling by Air or Liquid Flow	p. 272
8.6.3 Phase-Change-Based Cooling	p. 273
8.7 Example: A Thermal System of Automotive Fuel Cells	p. 275
8.7.1 A Lumped-System Model of a PEM Fuel Cell	p. 276
8.7.2 Bypass Valve	p. 277
8.7.3 Radiator	p. 278
8.7.4 Transport Delay	p. 279
8.7.5 Fluid Mixer	p. 280
8.7.6 Cathode Intercooler	p. 280
8.7.7 Anode Heat Exchanger	p. 281
8.8 Chapter Summary	p. 282
9 Coupled Thermal-Water Management! Phase Change	p. 285
9.1 Introduction to Phase Change	p. 285
9.2 Vapor-Liquid Phase Change: Evaporation and Condensation	p. 287
9.2.1 Vapor-Phase Water Diffusion and Heat Pipe Effect	p. 288
9.2.2 GDL De-Wetting	p. 290
9.2.3 GDL De-Wetting and Voltage Loss	p. 295
9.2.4 A General Definition of the Damkohler Number, Da	p. 300
9.2.4.1 Local Healing and Vapor-Phase Removal	p. 301
9.2.4.2 A Specific Damkohier Number	p. 303
9.2.4.3 Liquid-Free Passages	p. 305
9.2.4.4 2D Numerical Simulation	p. 306
9.3 Freezing/Thawing	p. 312
9.3.1 Temperature Spatial and Temporal Variation	p. 312
9.3.2 Non-Isothermal Cold Start	p. 313
9.3.3 Freezing/Thawing and Degradation	p. 314
9.4 System-Level Analysis of Coupled Thermal and Water Management	p. 319
9.4.1 Flow Rates of Species and Two-Phase Flows	p. 320
9.4.2 Energy Balance	p. 323
9.5 Chapter Summary	p. 325
Appendix II.A Thermodynamic Properties of Air, Hydrogen Gas, and Water Vapor	p. 329
Appendix II.B Calculation of the Enthalpy, Entropy, and Gibbs Free Energy For a Substance and the Overall PEM Fuel Cell Reaction	p. 333
Appendix III.A Mass, Momentum, and Energy Conservation Equations in the Cartesian, Cylindrical and Spherical Coordinates	p. 337
Appendix III.B Mathematical Basics and Relations	p. 343
Appendix III.C Henry's Constant for Selected Gases in Water at Moderate Pressure	p. 347
Appendix IV.A Membrane Materials	p. 349
Appendix IV.B Ion Transport in Electrolytes	p. 353
Appendix V.A Transport Properties of Typical Gases at Atmospheric Pressure	p. 359
Appendix VI.A Governing Equations of Multiphase Flow and Heat Transfer in Porous Media	p. 363
Appendix VI.B Multiphase Mixture Model in Porous Media	p. 367
Appendix VIII.A Thermal Properties of Selected Materials	p. 373
Index	p. 381

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