Study on Water Transport Mechanisms of the PEMFC Based on a Visualization Platform and Water Balance Model

It is widely acknowledged that the water balance issue is extremely important for improving the performance and durability of the proton exchange membrane fuel cell. In the presented paper, the visualization platform of the single fuel cell and the water balance model were built to investigate the water transport mechanisms. A transparent 25 cm2 single fuel cell with serpentine flow channels was adopted. Based on the experimental data, firstly, the change rate of water content in the fuel cell was calculated quantitatively and the reliability of the water balance model was rigorously validated. Then, the water state in the fuel cell as the qualitative finding was observed online to assist the research of water transport mechanisms. Finally, the effects of inlet gas temperature, inlet gas humidity, and hydrogen/air stoichiometry on the EIS, the voltage, and the water content in the fuel cell were studied quantitatively, respectively. The corresponding relationship between the performance and the water content in the fuel cell was obtained.

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Numerical Analysis of Water Transport in PEM Fuel Cell Membranes Using a Phenomenological Model

2nd International Conference on Fuel Cell Science, Engineering and Technology ◽

10.1115/fuelcell2004-2444 ◽

2004 ◽

Author(s):

P. C. Sui ◽

N. Djilali

Keyword(s):

Fuel Cell ◽

Water Content ◽

Water Transport ◽

Phenomenological Model ◽

Proton Exchange Membrane ◽

Proton Exchange ◽

Operating Conditions ◽

Design Parameters ◽

Exchange Membrane ◽

And Diffusion

A numerical investigation on the water transport across the membrane of a proton exchange membrane fuel cell is carried out to gain insight into water management issues, which are crucial to the efficient operation of such fuel cells. The transport equation of water content based on a phenomenological model, which includes an electro-osmotic drag term and a diffusion term, is solved using the finite volume method for a 1-D configuration with the assumption of a uniform temperature distribution. Transport properties including the drag coefficient and diffusion coefficient of water in the membrane and the ionic conductivity of the membrane are expressed as functions of water content and temperature. The effects on the water flux across the membrane and on overall membrane protonic conductivity due to variations of these properties are studied. The numerical results show that water transport in the membrane is mainly determined by the relative strength of electro-osmotic drag and diffusion, which are affected by operating conditions such as current density and relative humidity at the membrane surface, and design parameters such as membrane thickness and membrane material. Computed water fluxes for different humidity boundary conditions indicate that for a thick membrane, e.g. Nafion 117, electro-osmotic drag dominates transport over a wide range of operating conditions, whereas for a thin membrane, e.g. Nafion 112, diffusion of water becomes equally important under certain conditions. Implications of the one-dimensional investigation on comprehensive CFD based modelling of proton exchange membrane fuel cell are also discussed.

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