Mathematical modeling and simulation are widely applied to investigate the fluid dynamics properties in fuel cells. Flow field design determines how effective the fuel is distributed along the diffusion layers and the catalyst. The computational fluid dynamics modeling approach allows an effective investigation of different flow field designs through examining concentration profiles in the porous regions, velocity profiles, and pressure drop in the flow channels of fuel cells. In this work, mathematical models considering both complete oxidation of ethanol and partial oxidation with by-products in Pt-based catalysts were implemented in a three-dimensional geometry using the ANSYS CFX software. Laminar flow in the flow channels, steady-state operation, isothermal, and non-isothermal conditions was assumed. Commonly used flow field designs were investigated: serpentine, double serpentine, parallel, interdigitated, and spot. The interdigitated flow field design presented the best results in the isothermal simulations, whereas in the non-isothermal simulations the double serpentine presented the best results.