Abstract
Rib/channel dimensions significantly affect mass transfer, product water discharge, and electron transport. Aiming for high-power density stacks, bipolar plate thickness has been continually reduced, and microflow fields with the width and height smaller than 1 mm currently lack thorough experimental study. In this article, three stainless-steel plates were designed and fabricated, featuring rib/channel widths of 0.2:0.8 mm (SS-0.2/0.8), 0.3:0.7 mm (SS-0.3/0.7), and 0.5:0.5 mm (SS-0.5/0.5). SS-0.5/0.5 gained a 59.05% peak power density enhancement over a graphite plate G1.0/1.0 with rib/channel widths of 1.0:1.0 mm. Furthermore, sensitivities of microflow fields to cathode inlet humidity (RHc), anode/cathode inlet pressures (P (a)/P (c)), and cell operating temperature (T (cell)) were investigated. The optimal performance was observed at a low RHc. When RHc increased to 60%, SS-0.5/0.5 was more likely to accumulate water under the rib when operating at a high current density, rapidly increasing the mass transport resistance. Microflow fields had a negligible sensitivity to P (a)/P (c) since decrease in channel width below 1 mm is sufficient for the favorable mass transfer. Increasing T (cell) showed a dominant impact on decreasing concentration loss via facilitating diffusion of reactant gases through the electrode surfaces and alleviating the liquid water accumulation due to an increase in the saturation vapor pressure of water.