Mass diffusion characteristics on performance of polymer electrolyte membrane fuel cells with serpentine channels of different width.

• PEMFCs with 0.3, 0.5, and 1.0 mm-thick flow channels/ribs are tested. • The effect by increasing operating pressure in different channels is investigated. • Diffusion of reactants by varying channels and pressure are investigated. • Non-dimensional flow characteristics are investigated based on Sh, Re and Sc. Variation in performance of polymer electrolyte membrane fuel cells (PEMFCs) is analyzed, focusing on operating pressure and change in the width of the flow channels. At 0 bar, the maximum power densities are 431, 569, and 799 mW/cm2 with the width of 1.0, 0.5, and 0.3 mm, and at 3.0 bar, the maximum power densities are enhanced to 650, 829, and 914 mW/cm2, respectively. A pair of bipolar plates having the largest width exhibit the highest effect of the pressurized operation, and thus the most considerable change rate in maximum power density (50.8%). To investigate the diffusion phenomenon in the flow channels, a correlation is derived by introducing non-dimensional parameters. The dimensionless number associated with vertical diffusion, Sherwood number, decreases with lessening the width of flow channels and increasing the operating pressure, and diffusion characteristics of PEMFCs are generalized through Sherwood number correlation consisting of Reynolds and Schmidt number. Polymer electrolyte membrane fuel cell; Electrochemical impedance spectroscopy; Flow channel; Diffusion; Sherwood number [Display omitted] [ABSTRACT FROM AUTHOR]