In this article, we derive a general form of local volume-averaging theory
and apply it to a model of zinc-air conversion batteries. Volume-averaging
techniques are frequently used for the macroscopic description of micro-porous
electrodes. We extend the existing method by including reactions between
different phases and time-dependent volume fractions of the solid phases as
these are continuously dissolved and reconstructed during operation of
conversion batteries. We find that the constraint of incompressibility for
multi-component fluids causes numerical instabilities in simulations of
zinc-air battery cells. Therefore, we develop a stable sequential semi-implicit
algorithm which converges against the fully implicit solution. Our method
reduces the coupling of the variables by splitting the system of equations and
introducing an additional iteration step.Comment: 13 pages, 10 figure