Mench M.M. Fuel Cell Engines
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Index 511
disadvantages of, 410
durability of, 408–409
electrode/electrolyte system in, 407
electrolyte loss over time in, 407–408
operation of, 402–403
PEFC vs., 403–404
Physical spray deposition (catalyst layer
manufacturing technique), 289–290
Pinhole formation, 358–359
Pipeline, hydrogen delivery by, 444–445
PIV (particle image velocimetry), 476
Planar design (SOFC), 385, 386
Platinum:
as cost factor, 403–404
dissolution and migration of, 360
Polarization curve, 121–186, 300–301
application study, 185–186
and concentration polarization, 168–175
diagnostic tools for measuring losses, see
Diagnostic tools
electrical shorts, losses due to, 175–176
model summary, 181–183
predicting change in, 182–183
region I losses, 126–157
and activation polarization, 126–132
and Butler–Volmer (BV) kinetic model,
132–154
and electrical double layer, 126–127
and Langmuir/Tekmin model of kinetics,
154–157
region II losses, 157–167
calculation examples, 159–161, 163–164,
166–167
and cell assembly, 164–166
and contact resistance, 161–163
and electronic/ionic resistance, 158–161
region III losses, 168–175
region IV losses, 175–181
regions of, 121–123
species crossover, losses due to, 176–181
and zero-dimensional steady-state model,
125–126
Police Barracks (Central Park, New York City),
402
Polymer electrolyte fuel cells (PEFCs), 6–7, 11,
13, 15–17, 19, 23, 285–371. See also
Hydrogen PEFCs
alternatives to, 380–381
capillary flow in, 259–260
cell ohmic loss limiting current calculation
for, 163–164
conductivity of, 41, 159
degradation of, 356–362
chemical modes, 359–362
physical modes, 356–359
diffusion in, 227–228
diffusion media in, 323–324
direct alcohol PEFCs, 339–356
electron transport in, 210
equivalent ohmic loss thermal network for,
166
estimated temperature gradient inside,
272–273
flow field configurations and stack design for,
325–339
asymmetric channel properties, 330–331
considerations in, 325–326
direction of flow, 331–332
manifold, 336–339
mesh designs, 330
patterns, 328–329
for portable and automotive applications,
334–336
and reactant bypass, 332–334
trade-offs in, 326–327
gas-phase flow in, 219–222
and heat dissipation from stacks, 274–275
heat generation from, 263
heat transfer in, 264–265, 272–273
interfacial flow between phases and film
resistance in, 228–229, 231–233
interfacial/morphological effects in, 324–325
microporous layer in, 321–323
mud cracking in, 324
multidimensional effects in, 362–368
current distribution, 364–368, 469–470
temperature distribution, 363, 364, 473
water and species distribution, 363, 364,
470–472
multiphase flow in, 247, 250, 259–260
PAFC vs., 403–404
resistance calculation for, 166–167
solid polymer electrolyte in, 195. See also
Solid polymer electrolytes
sweep rate of, 459
water balance in, 298–321
and flooding, 299–301
importance of, 298–301
local balance, 310–321
overall balance, 302–310
Polymer electrolyte membrane (PEM) fuel
cells, 9
512 Index
Polytetrafluoroethylene (PTFE), 195, 196,
247–248, 255–256
Porosity, 218, 245
Porous media, gas-phase flow in, 218–223
Porous media, multiphase flow in, 243–263
basic governing parameters for, 245–250
contact angle, 246, 247
permeability, 248–250
porosity, 245
saturation, 246
surface tension, 246–248
wettability, 245
capillary transport, 251–263
and capillary pressure, 251–254
Leverett approach, 254–257
microporous layer, effect of, 257–258
modified Leverett approach, 255–256
PEFC, local saturation in diffusion media
of, 259–260
and imbibition/drainage, 261–262
PEFC porous media, 243–245, 259–260
and phase change, 262–263
Portable fuel cells, 19
Potassium carbonate, 17
Potassium hydroxide, 411
Power, 42–43
Prandtl number, 271, 273
Pressure (P), 63–64
open-circuit voltage dependence on
temperature and, 101–102
single-phase flow and drop in, 233–239
from consumption of reactant, 238–239
from frictional losses, 234–238
thermodynamic effect of increase in, 111
Proton hopping, 198
P
sat
(saturation water vapor pressure), 92
Psychrometrics, 91–96
defined, 91
and evaporation/condensation, 95–96
maximum water uptake in flow, calculation
of, 94–95
PTFE, see Polytetrafluoroethylene
PureMotion
TM
fuel cell, 11
Radiation, heat transfer by, 273–274
Raney metals, 417
Rate of reaction, 34
RDE (rotating disk electrode), 463
Reactant, consumption of, for single-phase flow
in channels, 238–239
Reactant bypass, 332–334
Reactant starvation, 357
Reactant utilization efficiency, measures of,
48–50
Reduction, electrochemical, 31
Regenerative fuel cells, 22
Relative humidity, 92
Relative permeability, 249–250
Resistance, 40–41, 158
contact, 161–163
estimating total fuel-cell, 159–161
Resistivity (ρ), 41, 158–159
Reversible fuel cell systems, 34, 35
Reversible process, maximum electrical work
for, 96–97
Reversible voltage, see Maximum expected
voltage (E
◦
)
Rolls Royce Fuel Cell Systems (RRFCS), 381
Rotating disk electrode (RDE), 463
Rotational motion (of molecules), 70
Roughness factor (a), 141–143
RRFCS (Rolls Royce Fuel Cell Systems), 381
Salem, H. S., 219
Saturation, as multiphase flow parameter, 246
Saturation water vapor pressure (P
sat
), 92
Schmidt number, 273
Schrempp, J
¨
urgen, 453
Schroeder’s paradox, 201
SECA, see Solid State Energy Conversion
Alliance
Second law of thermodynamics, 211, 213
Segmented-cell-in-series design (SOFC),
389–390
Sensible enthalpy, 75
Sensors, electrochemical, 30
Separator plate corrosion, 397
Service history, fuel-cell, and activation
polarization losses, 129
SHE, see Standard hydrogen electrode
Siemens, Werner von, 41
Siemen (S) (unit), 40–41
Siemens (Siemens-Westinghouse), 13, 274, 381,
385, 387
σ , see Conductivity
Silicon phosphate, 407
Single-walled nanotubes (SWNTs), 437
Slug flow regime, 240–244, 299, 300, 302–304
Slurry tape casting (catalyst layer
manufacturing technique), 290
Socioeconomic impact, of fuel cells, 24–25
Sodium borohydride, 433
Index 513
Sodium hydroxide, 411
Solid oxide fuel cells (SOFCs), 8–10, 13–16,
23, 381–392
advantages of, 391
conductivity of, 41, 159
design issues with, 382–385
development of, 381
disadvantages of, 391–392
durability of, 390–391
heat generation from, 263
in-plane design, 388
ion transport in, 202–205
manufacturing of, 382
monolithic design, 389
ohmic losses in, as function of electrolyte
thickness, 203–205
operating temperature of, 381–382
planar design, 385, 386
segmented-cell-in-series design, 389–390
stress tubular design, 385–388
Solid-phase specific heat, 74
Solid polymer electrolyte (SPE) fuel cells, 9
Solid polymer electrolytes:
in H
2
PEFCs, 288
ion transport in, 195–202
and Nafion ionic conductivity, 201–202
and water uptake, 198–201
Solid State Energy Conversion Alliance
(SECA), 14, 381
South Korea, 1, 392
Soviet Union, 16, 23
Space flight, 16, 23, 412–413
Space Shuttle, 16, 412
Species crossover, losses due to, 176–181
Species distribution, measurement of,
470–472
Specific heat, 71–74
constant-pressure, 71
constant-volume, 71
gas-phase, 71–73
liquid- and solid-phase, 74
SPE (solid polymer electrolyte) fuel cells, 9
Stacks, see Fuel cell stack(s)
Standard hydrogen electrode (SHE), 38–40
Standard temperature and pressure (STP), 74
Startup power systems, 296
Steam reformation (for hydrogen production),
440–441
Stefan–Boltzmann constant, 273
Stefan–Maxwell diffusion model, 216
Stoichiometric ratio, 49
Stoichiometry:
defined, 49
flow, 174–175
and utilization, 49–50
Stokes–Einstein equation, 226
STP (standard temperature and pressure), 74
Stress tubular design (SOFC), 385–388
Sulfonated PTFE, 196
SuperGrid, 445
Surface diffusion, 233
Surface tension, as multiphase flow parameter,
246–248
Sweep rate, 459
SWNTs (single-walled nanotubes), 437
Symmetry factor (β), 134–137
T, see Temperature
Tafel plots, 463–465
Tafel reaction, 33
Technology, fuel-cell, 1
Temkin model of kinetics, 155–156
Temperature (T ), 63
distribution of, in PEFC, 363, 473
and heat flux driven flow, 314
and liquid viscosity, 194
maximum efficiency and change in, 100–101
open-circuit voltage dependence on pressure
and, 101–102
Texas Instruments, 392
Thermal voltage (E
◦◦
), 97–99, 106
Thermodynamics, defined, 62
Thermodynamic control volume, 6
Thermodynamic equilibrium, 62
Thermodynamics of fuel cell systems, 62–116
change of enthalpy:
nonreacting species/mixtures, 78–82
reacting species/mixtures, 83–91
efficiency, thermodynamic, 96–106
enthalpy, 70–71, 77–78
enthalpy of formation, 74–75
example, 67–69
expected open-current voltage, calculation of,
111–114
internal energy, 69–70
latent heat, 75–77
and Nernst voltage, 106–114
nonideal behavior, 64–67
oxygen enhancement, effect of, 110–111
pressure, 63–64
pressure increase, effect of, 111
psychrometrics, 91–96
514 Index
Thermodynamics of fuel cell systems
(Continued)
sensible enthalpy, 75
specific heat, 71–74
temperature, 63
Thermodynamic systems, 5–6
3M, 196
t
i
, see Transference number
TMM, see Trimethoxymethane
Tortuosity, 218
Toshiba, 19, 392
Toyota, 121
TPB, see Triple-phase boundary
Transference number (t
i
), 175–176
Transportation applications, 21–22
Transport in fuel cell systems, 191–279
channels, single-phase flow in, 233–239
and consumption of reactant, 238–239
and frictional losses, 234–238
and pressure drop, 233–234
channels and porous media, multiphase flow
in, 239–263
basic governing parameters, 245–250
capillary transport, 251–263
gas channels, 239–244
PEFC porous media, 243–245
electron transport, 209–210
and heat generation, 263–264
heat transport, single-phase, 264–275
and conduction, 264–267
and convection, 267–272
and radiation, 273–274
ion transport, 191–209
in ceramic electrolytes, 202–205
and conductivity, 195
and current flow, 191
in liquid electrolytes, 205–209
mechanisms of, 191–193
Nernst–Planck equation governing,
193–194
in solid polymer electrolytes, 195–202
mass transport, gas-phase, 210–233
and diffusion in general, 210–218
interfacial flow between phases,
228–232
Knudsen diffusion, 223–226
liquids, diffusion through, 226–227
polymer electrolyte, diffusion through,
227–228
porous media, 218–223
surface diffusion, 233
Trimethoxymethane (TMM), 341–342, 355
Trioxane, 341–342, 355
Triple-phase boundary (TPB), 53–54
Truck, hydrogen delivery by, 444
U, see Internal energy
Union Carbide, 413
United Kingdom, fuel-cell-related patents in,
1, 2
United States:
fuel-cell-related patents in, 1, 2
hydrogen production in, 449
molten carbonate fuel cell development in,
392
phosphoric acid fuel cell development in, 398
space program in, 16, 23
U.S. Army, 14–15, 392
U.S. Department of Energy (DOE), 14, 286,
287, 381, 427, 437
United Technologies Corporation (UTC), 8, 15,
19, 23, 329
United Technologies Corporation Fuel Cells
(UTC Fuel Cells), 398
University of California–Davis, 399
UTC, see United Technologies Corporation
UTC Power Corporation, 11, 15, 22
V (volt), 37
Van der Veer, Jeroen, 1
Van der Waals, Johannes Diderik, 65
Van der Waals equation of state, 65
Vaporization, latent heat of, 76–77
Vehicles, fuel-cell, 121
Vibrational motion, 69
Virial equations of state, 65
Viscosity, and temperature, 194
Visualization tools, fuel cell, 474–477
Volmer reaction, 33
Volt (V), 37
Volta, Alessandro, 37
Voltage, 37–39
maximum expected, 97
reversible, 97
thermal, 97–99
Voltage reversal, 357
W. L. Gore and Associates, 196
Wantanabe, M., 178
Waste heat, 4
Water balance (in PEFCs), 298–325
and flooding, 299–301
importance of, 298–301
Index 515
local balance, 310–321
calculation example, 316, 317
and catalyst layer mass balance,
315–316
and electro-osmotic drag, 312–314
and gas-phase transport, 321
and heat flux driven flow, 314
and hydraulic permeability, 312
liquid accumulation, location of,
317–321
Nafion, diffusion and water uptake in,
311–312
and net transport coefficient, 314–315
and water flux in membranes, 310
and maintenance of high-performance
electrode, 321–325
overall balance, 302–310
calculation example, 305–306
drying condition, adjustment for, 307
flooding condition, adjustment for, 307,
308
and memory effect, 308–309
time scale for liquid water accumulation,
309–310
with transient operation, 306–307
visualization techniques for determining,
476–478
Water–gas shift (WGS) reaction, 439
Water management:
in direct methanol fuel cells (DMFCs),
345–348
in phosphoric acid fuel cells (PAFCs), 406
Water uptake (λ), in Nafion, 198–201, 312
Water uptake in a flow, calculation of
maximum, 94–95
Water vapor pressure (P), 92
Watt-hour, 37
Westinghouse, 385. See also Siemens
(Siemens-Westinghouse)
Wettability, 245
Wetting fluid, 245
WGS (water–gas shift) reaction, 439
Wiedemann–Franz law, 267
Work, 4
flow, 70
maximum electrical, for reversible process,
96–97
X-ray microtomography, 476
Yale University, 14
Yttria-stabilized zirconia (YSZ), 202–203, 381,
382
Zawodzinski, T. A., 313
Zero-dimensional steady-state model, 125–126