A combined passive water vapor exchanger and exhaust gas diffusion barrier for fuel cell applications

Fuel cells operating on hydrocarbon fuels require water vapor injection into the fuel stream for fuel reforming and the prevention of carbon fouling. Compared to active water recovery systems, a passive approach would eliminate the need for a separate water source, pumps, and actuators, and thus reduce parasitic thermal losses. The passive approach developed in this paper employs a capillary pump that recovers the water vapor from the exhaust, while providing a diffusion barrier that prevents exhaust gases from entering the fuel stream. Benchtop proof tests have proven the feasibility of the passive fuel humidifier concept, and have provided a calibration factor for a computational design tool that can be used for industrial applications.