Enhanced Water Removal from PEM Fuel Cells Using Acoustic Pressure Waves

Liquid water management remains a primary challenge in developing next generation low temperature proton exchange membrane fuel cells. This work demonstrates the use of acoustic pressure waves superimposed on reactant channel air flow as an effective means to enhance liquid water removal from gas diffusion layer surfaces. Experiments were conducted for a range of acoustic vibration frequencies; 20 to 120 Hz with 20 Hz intervals. Water transport was visualized using a CCD camera mounted over a transparent ex-situ PEM fuel cell test channel. Cumulative water areas were measured along the flow channel along with two-phase flow pressure drop for water fluxes of 400, 600, and 800 μℓ/h and a superficial air velocity of 1.82 m/s. Results show that superimposing acoustic pressure waves on the air flow can reduce liquid water build up and, therefore, reduce two-phase flow pressure drops. Cumulative water area was reduced almost 85% with an acoustic vibration frequency of 80 Hz compared to the 0 Hz case. Additionally, at 80 Hz the lowest two-phase flow pressure drop was recorded. Finally, a comparison of energy usage is made between different acoustic vibration application methods.