22. Januar 2013
- Jörg Roth
Paul Scherrer Institut, Villingen, Schweiz
The distribution of liquid water in the gas diffusion layer (Toray 060, 10 % PTFE ) of polymer electrolyte fuel cells under operation is investigated for different gas flow rates in the adjacent flow channels by X-ray tomography.The reproducibility for different realizations of the fuel cell and the characteristic length scale of the water accumulation is investigated. It was found that the local water distribution pattern on the small scale is mainly driven by the substrate structure, while on a larger scale, the boundary condition at the GDL/flow field interface determines the distribution pattern. The GDL area of the sub domain, capable of representing the water distribution characteristic of the whole domain within an error of 10 % is found to be around 1.4 mm² - 1.6 mm² in the region of flow channels and 0.6 mm² in the region of the ribs. A dependency of the representative area on the saturation was observed. The fiber structure has been found to be representative for an area larger than 0.5 mm², also with 10% error.
Pfaffenwaldring 61, Raum U1.003 (MML), Universität Stuttgart