Modeling of a novel cathode flow field design with optimized sub-channels to improve drainage for proton exchange membrane fuel cells

Water management is the primary factor affecting the output performance of proton exchange membrane fuel cells. Aiming to effectively deal with the flooding problem during the cell operation in a cathode flow field, this paper proposes a novel sub-channel design based on a wave-like flow field. The effects of sub-channel wall properties and channel geometry on the water removal capacity of the sub-channel are numerically evaluated by using the volume of fluid (VOF) method. Verification experiments are carried out to observe the water dynamics from droplets accumulation to detachment. The results reveal that the sub-channel achieves drainage performance by enhancing the gas pressure difference to overcome the wall adhesion. A wall contact angle of not less than 110 degrees and an included angle to the main channel of not more than 60 degrees are the prerequisites for the effective water removal of the sub-channel. The optimal design of the sub-channel is obtained to achieve better drainage performance. In addition, it is found that the effects of the sub-channel on water droplets will be weakened when the main channel period is densified to 1.5 mm or less, which is usually adopted to improve the mass transfer capacity under the ribs.