In the recent years, Proton Exchange Membrane Fuel Cell (PEMFC) has attracted much attention as a source of green energy and alternative to internal combustion engines. The PEMFC produces electrical power with heat and water as only byproducts. Water is needed to providing proper hydration of membrane and its ionic conductivity in PEMFCs, but excess water accumulation known as flooding phenomenon decreases reaction sites on gas diffusion and increases mass transport loss and consequently it leads to performance loss of PEMFC. Proper water management depends on characterization and study two-phase flow phenomenon of PEMFC as flooding. In the present work, the two-phase flow in the cathode channel of transparent PEMFC with single serpentine flow field is studied by direct optical visualization and utilization of Digital Image Processing for different inlet flow parameters and operational conditions. Liquid water accumulation in the cathode channel is quantified and the water coverage ratio is calculated as a scale of water content of the cathode channel in the unsteady and time-averaged states. Increasing the temperature and stoichiometry decrease the accumulation of liquid water in the cathode channel while increasing the reactants relative humidity leads to accumulation of more liquid water. Observations show in higher cathode stoichiometries, the effect of anode stoichiometry on the water coverage ratio decreases. The effect of anode stoichiometry on the water coverage ratio is more than the cathode stoichiometry.

In higher anode stoichiometries, the effect of cathode stoichiometry on the water coverage ratio decreases so that the change in cathode stoichiometry has no significant effect on the values of water coverage ratio.

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