Improved flow field design for air-cooled proton exchange membrane fuel cells

As a portable power source, air-cooled proton exchange membrane fuel cells (PEMFCs) have the advantages of high energy density, low weight, and zero-emission. However, direct supply of ambient air by fan may cause high local temperature and membrane electrode dehydration, resulting in unstable performance and durability issues. In this study, the air flow field design of air-cooled PEMFCs is compared and optimized aiming to improve the mass and heat transfer characteristics. For this purpose, a three-dimensional, multi-disciplinary, non-isothermal numerical model is developed and validated through experimental tests of an in-house developed 800 W air-cooled PEMFC stack. It is revealed that the PEMFC performance, especially under high current load conditions, can be improved by increasing the channel depth. The obtained results indicate that the higher rib-channel width ratio is favorable to air-cooled PEMFC performance, but it may lead to considerable non-uniform distributions of temperature and current density. Moreover, the effectiveness of utilizing the zigzag flow channel for air-cooled PEMFCs is assessed. It is found that the best cell performance can be obtained when the tilt angle of zigzagged flow field equals to 2.5°.