Two-Phase Flow Pressure Drop Hysteresis under Typical Operating Conditions for a Proton Exchange Membrane Fuel Cell

Abstract

Two-phase flow pressure drop hysteresis was studied under conditions typical of an operating PEM fuel cell. Two-phase flow hysteresis occurs when the gas and liquid flow rates are increased and decreased along the same path but exhibit different pressure drops. Variables studied include temperature (30-90 o C), air stoichiometry (1-4), and gas diffusion layer. The results were analyzed relative to a baseline of fully humidified air at 75 o C and a stoichiometry of 2 with a SGL Carbon 25 BC GDL. The percentage change between ascending and descending pressure drop is used to quantify the relative magnitude of the hysteresis. It was found that a sufficient air stoichiometry (≥4) can reduce the hysteresis, the GDL properties affect the water breakthrough mechanism and shift the onset of the hysteresis zone, and higher temperatures reduce the relative magnitude of the hysteresis effect. These results correlate well with photographs of the cathode channel two-phase flow.

Water Transport Through Porous Media and in Flow Channels of Proton Exchange Membrane Fuel Cell

“…Anderson (191) Two-phase flow pressure drop hysteresis for different temperatures, air stoichiometries, and GDL ex situ The pressure drop hysteresis becomes less significant at higher temperatures.…”

“…They have studied the effects of different parameters on the two-phase flow pressure drop hysteresis by conducting both in-situ and exsitu experiments. The parameters they studied include channel outlet configuration (vertical or straight-through) (15), the initial water balance condition in the gas channel (11,15), channel inclination angle (16), flow stoichiometry (11,17,191), GDL characteristics (11,191), temperature (17,191) and inclusion of microporous layer (17).…”

“…The effect of the temperature on the pressure drop hysteresis is studied by Anderson et al (17,191), with the results shown in Figure 16. It can be observed from the They assumed that the pressure drop over a small interval follows the LM method.…”