Electrochemistry

Electrochemistry is assumed assumed to occur on the anode interface with the electrolyte. It is calculated in appSrc file solveElectrochemistry.H. Global temperature is interpolated to the fuel mesh anode patch. Reactant oxidant species mole fractions are computed on the air mesh cathode patch and interpolated to the fuel mesh anode patch. Reactant and product fuel species are also calculated on the fuel mesh anode patch.

With all fields defined on the anode patch, the mole fractions, temperature, and specie properties are used to calculate the Nernst potential, E, via included appSrc file NernstEqn.H. Area specific resistance, R, is modelled by a function in included appSrc file ASRfunction.H. Current density i is then calculated as

$$i=\frac{E-V-\eta}{R}$$

where V and \(\eta\) are the present values of voltage and activation overpotential. The voltage is subsequently corrected using the present and prescribed mean current densities.

Electrochemical heating is calculated in included appSrc file electrochemicalHeating.H. Specie enthalpies are calculated and combined with enthalpy of formation and Joule heating in the electrolyte volume.

Species electrochemical mass fluxes are calculated and used to set Neumann boundary conditions on the cathode and anode patches for the calculation of air and fuel mass fractions, and Dirichlet conditions for the air and fuel velocities.