Flow within a water droplet subjected to an air stream in a hydrophobic microchannel

Abstract

Two-phase air–water flow in an experimental model of a polymer electrolyte membrane fuel cell (PEMFC) gas distribution channel is investigated using quantitative flow imaging of the liquid phase. A rectangular gas channel model was fabricated from polydimethylsiloxane (PDMS), glass and carbon paper. A micro-digital-particle-image-velocimetry (micro-DPIV) technique was used to provide qualitative and quantitative visualizations of flow inside a water droplet adhering to the bottom wall of a gas channel and exposed to an air flow within the channel. Velocity measurements in a central cross-sectional plane inside a droplet placed in the channel are reported for a range of air flow rates. The relationships between air velocity in the channel, secondary rotational flow inside a droplet, droplet deformation and contact angle hysteresis are examined. The resulting flow fields provide insight into the interactions between the air and water flows that occur at the gas–liquid interface.