Page 316 - High Temperature Solid Oxide Fuel Cells Fundamentals, Design and Applications

292 High Temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications

hl and h2 thickness of layer 1 and 2, respectively
AH enthalpy of formation
I, i current density
io the exchange current density
iH2 limiting current density due to H2 transport
io2 limiting current density due to O2 transport
concentration limiting current
iC
kl rate constant for shift reaction
kH2 rate constant for H2 oxidation
kco rate constant for CO oxidation
Kshift equilibrium constant for the shift reaction
1 the length of the fI ow path
la, 1, thickness of anode and cathode, respectively
m1, m2, reaction order parameter
m3, m4
m Weibull parameter
n unit vector normal to the boundary
PH2 H2 partial pressure in the anode fuel channel
PH20 H20 partial pressure in the anode fuel channel
Po29 P02.c oxygen partial pressure in the cathode air channel
P02.a oxygen partial pressure in the anode fuel channel
P flow pressure
Pcell cell power density
Pstack stack power density
Pex electric power
P stands for ‘product’
Q nonviscous volumetric heat generation term
Qgen heat generation
&ohm ohmic heat
Qirr. heat generation due to irreversibIe process
Qrev.a reversible heat generation at the anode
Qrev,c reversible heat generation at the cathode
Qrev.tota1 total reversible heat generation
Qvis viscous heat generation term
R gas constant
Ri ohmic resistance
Re Reynolds number
r stands for ‘reactant’
Si entropy of species i (i = 02, 02-, el)
T temperature
Ts and Tf solid and fluid temperatures
AT change in temperature
t time
Ui diffusion velocity of species i
Uf fuel utilisation
V voltage