
383Fuel Cell Components and Design
In approach 1, the average conductivity is estimated based on the average
water content in the membrane as
σλσλ(,)()T
T
303
1268
1
303
1
K
exp
,
where the average water content in the membrane is given as
=
∫
1
0
a
a
e
d
e
.
The membrane ohmic resistance is then computed from
η
σλ
ohm
e
ASR==
a
.
In approach 2, the membrane ionic resistance is given by integrating over
the membrane thickness as
R
z
t
m
d
a
=
∫
σλ
0
(9.15c)
and ohmic loss from
η
ohm
= iR
m
.
9.3.1.10 Water Diffusivity in Naon
Diffusion coefcient of water in Naon-117 is measured experimentally by
Zawodzinski et al. (1991) (Springer et al., 1991) and the ...