A Numerical Investigation Into the Interaction Between Current Flow and Fuel Consumption in a Segmented-in-Series Tubular SOFC

A typical segmented-in-series tubular solid oxide fuel cell (SOFC) consists of flattened ceramic support tubes with rows of electrochemical cells fabricated on their outer surfaces connected in series. It is desirable to design this type of SOFC to operate with a uniform electrolyte current density distribution to make the most efficient use of the available space and possibly to help minimize the onset of cell component degradation. Predicting the electrolyte current density distribution requires an understanding of the many physical and electrochemical processes occurring, and these are simulated using the newly developed SOHAB multiphysics computer code. Of particular interest is the interaction between the current flow within the cells and the consumption of fuel from an adjacent internal gas supply channel. Initial simulations showed that in the absence of fuel consumption, ionic current tends to concentrate near the leading edge of each electrolyte. Further simulations that included fuel consumption showed that the choice of fuel flow direction can have a strong effect on the current flow distribution. The electrolyte current density distribution is biased toward the upstream fuel flow direction because ionic current preferentially flows in regions rich in fuel. Thus the correct choice of fuel flow direction can lead to more uniform electrolyte current density distributions, and hence it is an important design consideration for tubular segmented-in-series SOFCs. Overall, it was found that the choice of fuel flow direction has a negligible effect on the output voltage of the fuel cells.