In this paper, a thorough model for the porous diffusion layer of a polymer electrolyte fuel cell (PEFC) is presented that accounts for multicomponent species diffusion, transport and formation of liquid water, heat transfer, and electronic current transfer. The governing equations are written in nondimensional form to generalize the results. The set of partial differential equations is solved based on the finite volume method. The effect of downscaling of channel width, current collector rib width, and diffusion layer thickness on the performance of polymer electrolyte membrane (PEM) fuel cells is systematically investigated, and optimum geometric length ratios (i.e., optimum diffusion layer thicknesses, optimum channel, and rib widths) are identified at decreasing length scales. A performance number is introduced to quantify losses attributed to mass transfer, the presence of liquid water, charge transfer, and heat transfer. Based on this model it is found that microchannels (e.g., as part of a tree network channel system in a double-staircase PEM fuel cell) together with diffusion layers that are thinner than conventional layers can provide substantially improved current densities compared to conventional channels with diameters on the order of 1 mm, since the transport processes occur at reduced length scales. Possible performance improvements of 29, 53, and 96 % are reported.

1.
Senn
,
S. M.
, and
Poulikakos
,
D.
, 2004, “
Tree Network Channels as Fluid Distributors Constructing Double-Staircase Polymer Electrolyte Fuel Cells
,”
J. Appl. Phys.
0021-8979,
96
(
1
), pp.
842
852
.
2.
Vargas
,
J. V. C.
,
Ordonez
,
J. C.
, and
Bejan
,
A.
, 2004, “
Constructal Flow Structure for a PEM Fuel Cell
,”
Int. J. Heat Mass Transfer
0017-9310,
47
(
19–20
), pp.
4177
4193
.
3.
Senn
,
S. M.
, and
Poulikakos
,
D.
, 2005, “
Multistage Polymer Electrolyte Fuel Cells Based on Nonuniform Cell Potential Distribution Functions
,”
Electrochem. Commun.
,
7
(
7
), pp.
773
780
.
4.
Bejan
,
A.
, 2000,
Shape and Structure, From Engineering to Nature
,
Cambridge University Press
, Cambridge.
5.
Bejan
,
A.
, 1996, “
Entropy Generation Minimization: The New Thermodynamics of Finite-Size Devices and Finite-Time Processes
,”
J. Appl. Phys.
0021-8979,
79
(
3
), pp.
1191
1218
.
6.
Senn
,
S. M.
, and
Poulikakos
,
D.
, “
Pyramidal Direct Methanol Fuel Cells
,” International Journal of Heat and Mass Transfer, [under review].
7.
Kulikovsky
,
A. A.
, 2000, “
Two-Dimensional Numerical Modeling of a Direct Methanol Fuel Cell
,”
J. Appl. Electrochem.
0021-891X,
30
(
9
), pp.
1005
1014
.
8.
Kulikovsky
,
A. A.
,
Divisek
,
J.
, and
Kornyshev
,
A. A.
, 1999, “
Modeling the Cathode Compartment of Polymer Electrolyte Fuel Cells: Dead and Active Reaction Zones
,”
J. Electrochem. Soc.
0013-4651,
146
(
11
), pp.
3981
3991
.
9.
Kulikovsky
,
A. A.
,
Divisek
,
J.
, and
Kornyshev
,
A. A.
, 2000, “
Two-Dimensional Simulation of Direct Methanol Fuel Cell—A New (Embedded) Type of Current Collector
,”
J. Electrochem. Soc.
0013-4651,
147
(
3
), pp.
953
959
.
10.
Kulikovsky
,
A. A.
, 2003, “
Quasi-3D Modeling of Water Transport in Polymer Electrolyte Fuel Cells
,”
J. Electrochem. Soc.
0013-4651,
150
(
11
), pp.
A1432
A1439
.
11.
Yi
,
J. S.
, and Van
Nguyen
,
T.
, 1999, “
Multicomponent Transport in Porous Electrodes of Proton Exchange Membrane Fuel Cells Using the Interdigitated Gas Distributors
,”
J. Electrochem. Soc.
0013-4651,
146
(
1
), pp.
38
45
.
12.
Natarajan
,
D.
, and
Van Nguyen
,
T.
, 2001, “
A Two-Dimensional, Two-Phase, Multicomponent, Transient Model for the Cathode of a Proton Exchange Membrane Fuel Cell Using Conventional Gas Distributors
,”
J. Electrochem. Soc.
0013-4651,
148
(
12
), pp.
A1324
A1335
.
13.
He
,
W. S.
,
Yi
,
J. S.
, and
Van Nguyen
,
T.
, 2000, “
Two-Phase Flow Model of the Cathode of PEM Fuel Cells Using Interdigitated Flow Fields
,”
AIChE J.
0001-1541,
46
(
10
), pp.
2053
2064
.
14.
Natarajan
,
D.
, and
Van Nguyen
,
T.
, 2003, “
Three-Dimensional Effects of Liquid Water Flooding in the Cathode of a PEM Fuel Cell
,”
J. Power Sources
0378-7753,
115
(
1
), pp.
66
80
.
15.
Wang
,
Z. H.
,
Wang
,
C. Y.
, and
Chen
,
K. S.
, 2001, “
Two-Phase Flow and Transport in the Air Cathode of Proton Exchange Membrane Fuel Cells
,”
J. Power Sources
0378-7753,
94
(
1
), pp.
40
50
.
16.
You
,
L. X.
, and
Liu
,
H. T.
, 2002, “
A Two-Phase Flow and Transport Model for the Cathode of PEM Fuel Cells
,”
Int. J. Heat Mass Transfer
0017-9310,
45
(
11
), pp.
2277
2287
.
17.
Berning
,
T.
, and
Djilali
,
N.
, 2003, “
A 3D, Multiphase, Multicomponent Model of the Cathode and Anode of a PEM Fuel Cell
,”
J. Electrochem. Soc.
0013-4651,
150
(
12
), pp.
A1589
A1598
.
18.
Nam
,
J. H.
, and
Kaviany
,
M.
, 2003, “
Effective Diffusivity and Water-Saturation Distribution in Single- and Two-Layer PEMFC Diffusion Medium
,”
Int. J. Heat Mass Transfer
0017-9310,
46
(
24
), pp.
4595
4611
.
19.
Weber
,
A. Z.
,
Darling
,
R. M.
, and
Newman
,
J.
, 2004, “
Modeling Two-Phase Behavior in PEFCs
,”
J. Electrochem. Soc.
0013-4651,
151
(
10
), pp.
A1715
A1727
.
20.
Bird
,
R. B.
,
Stewart
,
W. E.
, and
Lightfoot
,
E. N.
, 1960,
Transport Phenomena
,
Wiley
, New York.
21.
Meyers
,
J. P.
, and
Newman
,
J.
, 2002, “
Simulation of the Direct Methanol Fuel Cell—II. Modeling and Data Analysis of Transport and Kinetic Phenomena
,”
J. Electrochem. Soc.
0013-4651,
149
(
6
), pp.
A718
A728
.
22.
Kaviany
,
M.
, 1991,
Principles of Heat Transfer in Porous Media
,
Springer
, New York.
23.
Pasaogullari
,
U.
, and
Wang
,
C. Y.
, 2004, “
Two-Phase Transport and the Role of Micro-Porous Layer in Polymer Electrolyte Fuel Cells
,”
Electrochim. Acta
0013-4686,
49
(
25
), pp.
4359
4369
.
24.
Udell
,
K. S.
, 1985, “
Heat Transfer in Porous Media Considering Phase-Change and Capillarity—The Heat Pipe Effect
,”
Int. J. Heat Mass Transfer
0017-9310,
28
(
2
), pp.
485
495
.
25.
Leverett
,
M. C.
, 1941, “
Capillary Behavior in Porous Solids
,”
Trans. AIME
0096-4778,
142
, pp.
152
169
.
26.
Scheidegger
,
A. E.
, 1960,
The Physics of Flow Through Porous Media
,
University of Toronto Press
, Toronto.
27.
Springer
,
T. E.
,
Zawodzinski
,
T. A.
, and
Gottesfeld
,
S.
, 1991, “
Polymer Electrolyte Fuel-Cell Model
,”
J. Electroanal. Chem. Interfacial Electrochem.
0022-0728,
138
(
8
), pp.
2334
2342
.
28.
Dagan
,
G.
, 1989,
Flow and Transport in Porous Formations
,
Springer
, Berlin.
29.
Kulikovsky
,
A. A.
, 2002, “
The Voltage-Current Curve of a Polymer Electrolyte Fuel Cell: “Exact” and Fitting Equations
,”
Electrochem. Commun.
,
4
(
11
), pp.
845
852
.
30.
Senn
,
S. M.
, and
Poulikakos
,
D.
, 2004, “
Polymer Electrolyte Fuel Cells With Porous Materials as Fluid Distributors and Comparisons With Traditional Channeled Systems
,”
ASME J. Heat Transfer
0022-1481,
126
(
3
), pp.
410
418
.
31.
Bevers
,
D.
,
Wohr
,
M.
,
Yasuda
,
K.
, and
Oguro
,
K.
, 1997, “
Simulation of a Polymer Electrolyte Fuel Cell Electrode
,”
J. Appl. Electrochem.
0021-891X,
27
(
11
), pp.
1254
1264
.
32.
Lampinen
,
M. J.
, and
Fomino
,
M.
, 1993, “
Analysis of Free-Energy and En-tropy Changes for Half-Cell Reactions
,”
J. Electrochem. Soc.
0013-4651,
140
(
12
), pp.
3537
3546
.
33.
Senn
,
S. M.
, and
Poulikakos
,
D.
, 2004, “
Laminar Mixing, Heat Transfer and Pressure Drop in Tree-Like Microchannel Nets and Their Application for Thermal Management in Polymer Electrolyte Fuel Cells
,”
J. Power Sources
0378-7753,
130
(
1–2
), pp.
178
191
.
34.
Patankar
,
S. V.
, 1980,
Numerical Heat Transfer and Fluid Flow
,
Hemisphere
, New York.
35.
Mantzaras
,
J.
,
Freunberger
,
S. A.
,
Büchi
,
F. N.
,
Roos
,
M.
,
Brandstätter
,
W.
,
Prestat
,
M.
,
Gauckler
,
L. J.
,
Andreaus
,
B.
,
Hajbolouri
,
F.
,
Senn
,
S. M.
,
Poulikakos
,
D.
,
Chaniotis
,
A. K.
,
Larrain
,
D.
,
Autissier
,
N.
, and
Maréchal
,
F.
, 2004, “
Fuel Cell Modeling and Simulations
,”
Chimia
0009-4293,
58
(
12
), pp.
857
868
.
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