UID:
almafu_9959239624402883
Format:
1 online resource (420 p.)
Edition:
1st ed.
ISBN:
1-299-45668-5
,
1-60650-247-6
Content:
Polymer electrolyte membrane (PEM) fuel cells, which convert the chemical energy stored in hydrogen fuel directly and efficiently to electrical energy with water as the only by-product, have the potential to reduce our energy usage, pollutant emissions, and dependency on fossil fuels. Tremendous efforts have been made so far, particularly during the last couple of decades or so, on advancing the PEM fuel cell technology and fundamental research. In addition to the large number of research and review paper publications, several classic books have been published and are available in the market, which are primarily for introductory level readers. There are, however, very few books that address the graduate-level or advanced aspects of PEM fuel cells and are based on the first principles or conservation laws, dimensionless analysis, time constant evaluation, and numerical simulation by solving partial differential equations. There are abundant knowledge regarding flow, heat transfer, and mass transport in general engineering, which has been successfully extended to the water and thermal management of PEM fuel cells. This book contributes to this aspect of PEM fuel cell technology; that is, it focuses on the fundamental understanding of phenomena or processes involved in PEM fuel cells.
Note:
Includes index.
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Preface -- List of figures -- List of tables -- Nomenclature --
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1. Introduction -- 1.1 Energy challenges -- 1.2 Fuel cells and their roles in addressing the energy challenges -- 1.3 PEM fuel cells -- 1.3.1 PEM fuel cell operation -- 1.3.2 Current status of PEM fuel cells -- 1.3.3 Thermal and water management --
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2. Basics of PEM fuel cells -- 2.1 Thermodynamics -- 2.1.1 Internal energy and the first law of thermodynamics -- 2.1.2 Enthalpy change -- 2.1.3 Entropy change and the second law of thermodynamics -- 2.1.4 Gibbs free energy and thermodynamic voltage -- 2.1.5 Chemical potential and Nernst equation -- 2.1.6 Relative humidity and phase change -- 2.2 Electrochemical reaction kinetics -- 2.2.1 Electrochemical kinetics -- 2.2.2 Electrochemical mechanisms in PEM fuel cells -- 2.2.3 Linear approximation and Tafel equation -- 2.3 Voltage loss mechanisms and a simplified model -- 2.3.1 Open circuit voltage (OCV) -- 2.3.2 Activation loss -- 2.3.3 Ohmic loss -- 2.3.4 Transport voltage loss -- 2.3.5 Current-voltage (I-V) curve and operation efficiency -- 2.3.6 Role of water and thermal management -- 2.4 Chapter summary --
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3. Fundamentals of heat and mass transfer -- 3.1 Introduction -- 3.2 Conservation equations -- 3.2.1 General forms -- 3.2.2 Mass and momentum conservation -- 3.2.3 Energy equation -- 3.2.4 Species transport equation -- 3.3 Constitutive equations -- 3.3.1 A lattice model -- 3.3.2 Fourier's law and Fick's law -- 3.4 Scaling and dimensionless groups -- 3.4.1 Scaling and dimensionless equations -- 3.4.2 Dimensionless groups -- 3.5 Chapter summary --
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4. Water and its transport in the polymer electrolyte membrane -- 4.1 Introduction to the polymer electrolyte membrane -- 4.2 Ion transport and ionic conductivity -- 4.2.1 Proton transport -- 4.2.2 Ionic conductivity correlations -- 4.2.3 Ionic conductivity measurement -- 4.3 Water transport in polymer electrolyte membranes -- 4.3.1 Transport mechanisms -- 4.3.2 Water holding capacity -- 4.4 Water quantification using neutron radiography -- 4.5 Ion transport in cathode catalyst layers -- 4.5.1 Variation in water content in catalyst layers -- 4.5.2 Proton transport in cathode catalyst layers -- 4.5.3 Multiple-layered cathode catalyst layers -- 4.6 Chapter summary --
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5. Vapor-phase water removal and management -- 5.1 Mass transport overview -- 5.2 Diffusion -- 5.2.1 Diffusivity -- 5.2.2 Molecular versus Knudsen diffusion -- 5.2.3 Diffusion in GDLs -- 5.3 Species convection -- 5.3.1 Flow modeling with constant-flow assumption -- 5.3.2 Flow formulation without the constant-flow assumption -- 5.3.3 Convection in GDLs -- 5.4 Pore-scale transport -- 5.4.1 Stochastic material reconstruction -- 5.4.2 Pore-scale transport modeling -- 5.4.3 Pore-level phenomena -- 5.5 Transient phenomena -- 5.5.1 Transient terms and time constants -- 5.5.2 Transient undergoing constant voltage or step change in voltage -- 5.5.3 Transient undergoing constant current or step change in current -- 5.6 Water management between a PEM fuel cell and fuel processor -- 5.6.1 Water balance model -- 5.6.2 Effect of the steam-to-carbon ratio -- 5.7 Chapter summary --
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6. Liquid water dynamics and removal -- 6.1 Multiphase flow overview -- 6.1.1 Modeling multi-phase flows -- 6.2 Multiphase flow in GDLS/CLS -- 6.2.1 Experimental visualization -- 6.2.1.1 X-ray imaging -- 6.2.1.2 Neutron radiography -- 6.2.2 Multiphase mixture (M2) formulation -- 6.2.2.1 Flow equations -- 6.2.2.2 Species transport -- 6.2.2.3 Model prediction -- 6.2.3 Carbon paper (CP) versus carbon cloth (CC) -- 6.2.4 Spatially varying properties -- 6.2.4.1 Through-plane variation in the GDL property -- 6.2.4.2 In-plane property variation and the effect of land compression -- 6.2.4.3 Microporous layers (MPLs) -- 6.3 Multiphase flow in gas flow channels (GFCS) -- 6.3.1 Experimental visualization -- 6.3.2 Two-phase flow patterns -- 6.3.3 Modeling two-phase flow -- 6.3.3.1 The mixture model -- 6.3.3.2 Two-fluid modeling -- 6.4 Water droplet dynamics at the GDL/GFC interface -- 6.4.1 Force balance on a spherical-shape droplet -- 6.4.2 Droplet deformation -- 6.4.3 Droplet detachment -- 6.4.3.1 Control volume method -- 6.4.3.2 Derivation using the drag coefficient (CD) -- 6.5 Chapter summary --
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7. Ice dynamics and removal -- 7.1 Subfreezing operation-overview -- 7.2 Ice formation -- 7.2.1 Water transport and conservation -- 7.2.2 Three cold-start stages -- 7.2.2.1 First stage: membrane hydration -- 7.2.2.2 Second stage: ice formation -- 7.2.2.3 Third stage: ice melting -- 7.3 Voltage loss due to ice formation -- 7.3.1 Spatial variation of the oxygen reduction reaction (ORR) -- 7.3.2 The ORR rate under subfreezing temperature -- 7.3.3 Oxygen profile in the catalyst layer -- 7.3.4 Voltage loss due to ice formation -- 7.3.5 A model of cold-start cell voltage -- 7.4 State of subfreezing water -- 7.5 Chapter summary --
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8. Thermal transport and management -- 8.1 Heat transfer overview -- 8.1.1 Heat transfer and its importance -- 8.1.2 Heat transfer modes -- 8.1.2.1 Heat conduction -- 8.1.2.2 Convective heat transfer -- 8.1.2.3 Heat radiation -- 8.1.3 Heat transfer in porous media -- 8.2 Heating mechanisms -- 8.2.1 The entropic heat -- 8.2.2 Irreversibility of the electrochemical reactions -- 8.2.3 The Joules heat -- 8.3 Steady-state heat transfer -- 8.3.1 One-dimensional (1D) heat transfer analysis -- 8.3.2 Two-dimensional (2D) heat transfer analysis -- 8.3.3 Numerical analysis -- 8.3.3.1 Macroscopic model prediction -- 8.3.3.2 Pore-level heat transfer -- 8.4 Transient phenomena -- 8.4.1 General transient operation -- 8.4.2 Transient subfreezing operation -- 8.4.2.1 Temperature evolution and voltage loss -- 8.4.2.2 Activation voltage loss -- 8.4.2.3 Ohmic voltage loss -- 8.5 Experimental measurement of thermal conductivity -- 8.6 Cooling methods -- 8.6.1 Heat spreaders cooling -- 8.6.2 Cooling by air or liquid flow -- 8.6.3 Phase-change-based cooling -- 8.7 Example: a thermal system of automotive fuel cells -- 8.7.1 A lumped-system model of a PEM fuel cell -- 8.7.2 Bypass valve -- 8.7.3 Radiator -- 8.7.4 Transport delay -- 8.7.5 Fluid mixer -- 8.7.6 Cathode intercooler -- 8.7.7 Anode heat exchanger -- 8.8 Chapter summary --
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9. Coupled thermal-water management: phase change -- 9.1 Introduction to phase change -- 9.2 Vapor-liquid phase change: evaporation and condensation -- 9.2.1 Vapor-phase water diffusion and heat pipe effect -- 9.2.2 GDL de-wetting -- 9.2.3 GDL de-wetting and voltage loss -- 9.2.4 A general definition of the Damkohler number, Da -- 9.2.4.1 Local heating and vapor-phase removal -- 9.2.4.2 A specific Damkohler number -- 9.2.4.3 Liquid-free passages -- 9.2.4.4 2D numerical simulation -- 9.3 Freezing/thawing -- 9.3.1 Temperature spatial and temporal variation -- 9.3.2 Non-isothermal cold start -- 9.3.3 Freezing/thawing and degradation -- 9.4 System-level analysis of coupled thermal and water management -- 9.4.1 Flow rates of species and two-phase flows -- 9.4.2 Energy balance -- 9.5 Chapter summary.
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Also available in print.
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English
Additional Edition:
ISBN 1-60650-245-X
Language:
English
Keywords:
Electronic books.
DOI:
10.5643/9781606502471
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