Characteristics of liquid water transport and corner effect in microfluidic channels of PEM fuel cell

The water generated in the catalyst layer flows through the GDL (gas diffusion layer) and passes through the microfluidic channels of fuel cells. In this study, characteristics of water motion in the microfluidic channels are investigated corresponding to various Reynolds numbers and compression ratios of GDL. Gas can bypass the rib to the adjacent channel and flows through the GDL underneath the slug. To remove the slug, the bypass distance (%) and gas flow rate should be larger than 13%. The cross-section shape of the slug in 1-wall hydrophobic GDL and 3-walls hydrophilic acrylic channel is an analogous upside-down trapezoid. Since the required GDL compression ratio should be over 13% to eliminate liquid water instead of simply increasing the volumetric gas flow, the residual droplets are received at the vertical corner in the channel, compared to the arc corner. The regimes of liquid water flow in the 1-wall hydrophobic GDL and 3-walls hydrophilic acrylic channel are summarized as slug motion, compressed drop motion, elongate droplet motion, drop oscillation, and cap drop motion. These results provide improved physical models predicting the state of water hold-up and flooding in PEM fuel cells.