
472 Fuel Cells
11.3.2 Anode Electrode
Water transport by diffusion mass transport
d
HO,a
2
2
2
0
x
= .
(11.39a)
Integration of this equation and substituting boundary conditions lead to
the expression for water mass ux based on Fick’s law of diffusion as
JD
xx
L
HO,a aHO,H
eff
HO,a HO,ae
a
222
=
−
ρ
(11.39b)
where
HO,a
= water concentration at the anode surface
HO,ae
= water concentration at the anode–electrolyte interface
This equation (Equation 11.39b) for water mass ux through the anode can
also be expressed in a form analogous to an electrical circuit as
J
xx
R
HO,a a
HO,a O,ae
HO,a
2
2
=
−
ρ ,
(11.40a)
where
R
L
D
HO,a
a
HO,H
eff
2
= .
(11.40b)
Consider