Fractal Flow Fields: A New Design of Gas Flow Channels in Polymer Electrolyte Fuel Cells

Design of gas flow channels is a crucial factor that determines the overall performance of polymer electrolyte fuel cells PEFCs). Conventional design is the serpentine flow field where the anode or the cathode gas flows through a zigzag patterned groove machined on the surface of carbon plate [1]. The problem of this design is that under the rib the gas distribution is low and also water flooding tends to occur at high current density. Recently, T. V. Nguyen et al. developed a new design of flow field where a pair of comb like groves, inlet and outlet channels, are carved on serarator carbon meterilas [2]. This design has an advantage of realizing a forced gas flow from one channel to the other, effective removal of generated water and so on. In this work we report a new flow field that can eliminate the flow channel groove in the separator, make it into a mere thin sheet and thus improve drastically the volume and weight power density of the PEFC system. This design is called fractal flow field, because it is based on the repetitive patterns of same geometric form, subdivided into smaller ones, as shown in Fig. 1.