
250 Fuel Cells
Like in the convection heat transfer process, the convective mass transfer
of species i from the moving bulk uid to the solid surface is given by a con-
vection rate equation analogous to Newton’s law of cooling as
′′
∞
jh
ism s
, (6.81)
where h
m
is called the convection mass transfer coefcient or mass lm coef-
cient. The dening equation for the convection mass transfer coefcients is
obtained by comparing Equations 6.59 and 6.81 as
h
j
i
m
s
=
′′
−
(6.82a)
or
h
D
C
y
ij
i
y
m
s
=
−
∂
∂
−
=
∞
0
. (6.82b)
Like the convection heat transfer coefcient expressed as the Nusselt num-
ber, the convection mass transfer coefcient is also ex ...