PEM fuel cells thermal and water management fundamentals /
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 eff...
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Format: | Electronic eBook |
Language: | English |
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[New York, N.Y.] (222 East 46th Street, New York, NY 10017) :
Momentum Press,
2013.
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Online Access: | An electronic book accessible through the World Wide Web; click to view |
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Table of Contents:
- Preface
- List of figures
- List of tables
- Nomenclature
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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.