Modeling and evaluation of an integrated microfluidic fuel processor for miniature power sources

An integration scheme for a 20 w proton exchange membrane (PEM) fuel processor involving the steam reforming of methanol fuel was studied. The integration system incorporates four major components, i.e., vaporizer, reformer, preferential oxidation reactor and combustor, several internal heat exchangers, and some internal thermal barriers. A complete two-dimensional CFD simulation of the integrated system involving flow, heat and mass transfer as well as chemical reactions was performed. In this PEM fuel cell processing, the steam reforming was the slowest step, so the design of the steam reformer is the key for controlling the total size of the fuel processor. A high performance catalyst for the steam reformer was demanded. The thermal barriers between the processing units were critical for maintaining the temperature difference between the integrated components. Simulation results showed that these thermal barriers occupy a significant amount of the total space. A material with low thermal conductivity would help to reduce the total processor volume. Although in the process simulation, an isothermal condition for each reaction unit was assumed, the temperature in each processing unit was not constant after the thermal integration. The state and flow direction of the input streams, the size of the processing components, heat exchangers and thermal barriers were all determined from the CFD simulation. This is an abstract of paper presented at the AIChE Spring National Meeting (Orlando, FL 4/24-26/2006).