(690a) Microct X-Ray Imaging of Water Movement In a PEM Fuel Cell

Proper water management has long been identified in the literature as a key component for optimal fuel cell performance. Current literature suggests that the lack of in-situ water data is slowing the progress of water management technology. In the previous literature, water motion has been examined with magnetic resonance imaging (MRI) and neutron imaging(NI), but in this report an entirely new technique was used: microCT. Micro CT uses a high resolution X-ray imaging system to look through the graphite flow channels to provide accurate pictures of water inside of an operating PEM fuel cell. Acquisitions times vary from 2 second to 30 seconds.

The results so far, show qualitative agreement with previous measurements done by MRI and NI, but the resolution is much higher with micro-CT, so many more details can be observed. Water was observed emerging as water droplets on the surface of the diffusion layer. The droplet grew in size, and eventually detached into the flow channels. Drops in the flow channels were found to distort from the expected circular shape before they start to move. Some deviation in the shape of water droplets is observed, when compared to predictions from the modeling literature. This is believed to be due to the role of the channel side walls, as well as possible non-uniformities in the flow channel surface.