Page 317 - High Temperature Solid Oxide Fuel Cells Fundamentals, Design and Applications

Cell. Stack and System Modelling 293

cathode porosities
anode porosities
‘thermoneutral voltage’
fluid velocity
WeibuIl function, the probability of failure
viscous work
number of electrons participatingin the electrode reaction

anodic transfer coefficient
thermal expansion coefficient
resistivity
fuel cell electrical efficiency
overpotential or polarisation
anode polarisation
activation polarisation
cathode polarisation
concentration polarisation
cathode activation, cathode concentration, anode
activation, and anode concentration polarisations,
respectively
thermal conductivity
effective viscosity
Poisson’s ratio
density of the species i
electronic conductivity
effective ionic conductivity
ionic conductivity
thermal stress
material-specific characteristic stress of the WeibuII
function
anode and cathode tortuosities
non-Newtonian viscous losses
electrical potential
rate of production of species i
lcth direction momentum source term

11.1 Introduction
Mathematical models that predict performance can aid in understanding and
development of solid oxide fuel cells (SOFCs). A mathematical simulation of a
SQPC is helpful in examining issues such as temperatures, materials, geometries,
dimensions, fuels, and fuel reformation and in determining their associated
performance characteristics. When physical properties or reaction kinetics
are not known reliably, they can be estimated by fitting performance data on
small-size, laboratory-scale cells to a mathematical model. The performance of a