Effects of Microstructure on Water Removal in the U-Shaped Region of PEMFC Serpentine Flow Channel

The proton-exchange membrane fuel cell (PEMFC) bipolar plate serpentine flow channel U-shaped region is prone to the accumulation effect, which poses serious difficulties for fuel cell water management. As a result, a deep understanding of water transport in the U-shaped region is essential to improve the fuel cell performance. Under this direction, in this work, the impact of the different microstructure parameters and initial conditions on water transport in the U-shaped region was compared with and without microstructure using the volume of the fluid method. On top of that, the velocity field distribution in the X-direction and the pressure drop distribution in the flow channel were also analyzed. From the acquired results, it was demonstrated that due to the secondary flow caused by the bending property of the microstructure, the droplet movement time in the U-shaped region was significantly shortened after the microstructure was added in the U-shaped region. The initial conditions strongly affected the droplet motion, and a larger contact angle enhanced the wall hydrophobicity to facilitate the droplet discharge. An increase in the droplet diameter led also to a rise in the windward area and shear force, which shortened droplet discharge time. Interestingly, if the waveform microstructure has too-large crests, gullies will be created that will impede the droplet motion and increase the amplitude of the droplet oscillation, resulting in excessive pressure drop in the flow channel. A too-large period led to increased droplet momentum loss, whereas a short period reduced the wall contact angle, which is not conducive to drainage. The microstructure spacing significantly affected the droplet motion, and the reduced spacing increased the airflow diffusion effect to accelerate the flow rate. The main focus of this work was led on the application of the microstructure in a U-shaped region of the serpentine flow channel, which is of great specific significance for droplet removal inside the flow channel.