Transient response of proton exchange membrane fuel cell with serpentine flow field

The transient response of a proton exchange membrane fuel cell (PEMFC) with a serpentine flow field design is investigated using a three-dimensional numerical model. The simulations consider three different flow field designs, with 7, 11 and 15 bends, respectively. For the flow field with 11 bends, three different channel width ratios are considered, namely 25%, 50% and 75%. The simulation results show that for all of the flow field designs, an overshoot in the local current density occurs when the voltage is reduced instantaneously from 0.7 V to 0.5 V due to the high and uniform oxygen mass fraction. Conversely, a significant undershoot occurs when the voltage is increased instantaneously from 0.5 V to 0.7 V owing to the low and non-uniform oxygen mass fraction. The overshoot and undershoot phenomena are particularly evident in the PEMFC with a 15-bend flow field. For the flow field with 11 bends, the channel width ratio has little effect on the current density at an operating voltage of 0.7 V. However, at an operating voltage of 0.5 V, the current density and oxygen concentration both increase with an increasing channel width ratio. As a result, a more significant overshoot phenomenon is observed in the flow field with a width ratio of 75%.