Computational fluid dynamics modeling of flow in fuel cell channels
Date
1997
Authors
Bowers, Martin William
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Abstract
Proton Exchange Membrane (PEM) Fuel Cells present an opportunity for highly efficient and low emission power generation for transportation purposes. The PEM fuel cell features the more environmentally compatible fuel source of hydrogen as well as a comparatively low operating temperature of around 80° Celcius. With these fundamental advantages, the PEM fuel cell is poised to become a major factor in worldwide transportation applications. A fundamental understanding of many of the transport process that occur in a fuel cell has yet to be developed.
This thesis presents a computational fluid dynamics (CFO) study of flow in fuel cell channels undertaken to provide understanding of the basic hydrodynamic processes behind the operation of fuel cells. The model was also desirable for the purpose of providing design information for new fuel cells. The model is based on the numerical solution, using a commercial CFO code: CFX-4.1, of the full Navier Stokes equations coupled with chemical concentration transport equations.
The model is validated for simplified conditions for which data is available in the literature. The final model developed in this thesis features a three dimensional duct with an attached porous section and accounts for the slip velocity at the interface, which is found to be an important factor in the determination of the flow field.
The most important factor determining the flow solution is the permeability of the porous section. The pressure drop across the porous section causes a uniform suction velocity distribution through the porous section. This suction velocity creates a distribution layer within the duct above the porous section that initiates the uniform velocity within the porous section. The maximum mass transport ability of the duct was modeled utilizing a diffusive boundary condition at the catalyst layer interface. The results indicate that the convective transport abilities of the duct do not limit the supply of reactant and hence do not limit the operation of the fuel cell.