Flow and reaction in solid oxide fuel cells

A fuel cell is an electrochemical device that converts chemical energy into electrical energy. The essential difference between a fuel cell and a batt ery is that the fuel and oxidant are continually supplied to a fuel cell wh ereas a battery has a finite amount of fuel stored within it which eventual ly becomes exhausted, after which the battery has to be recharged or replac ed. We consider here a tubular cell which is run on methane. A mathematical model for the reaction and transport processes in the cell is presented. T his takes into account diffusion, advection and reaction as well as the ele ctrochemical flow of oxygen. When the device is running steadily, we perfor m an analysis, using the method of matched asymptotic expansions to find th e flow field, the mass fractions of each chemical species and the electrica l power output. These results are confirmed by a numerical technique and co mpared with experimental results.