Neutron imaging of water distribution in full size automotive fuel cells
The high penetration of neutrons through large thicknesses of metals (e.g. > 10 cm of aluminum) allows imaging the water distribution in single fuel cells of full size design, even between the thick compression bodies requested to ensure enough flatness over a large area. For the single cell to have thermal boundary conditions similar to those of a cell integrated in a stack, the compression bodies are heated and a specific temperature gradient is applied to mimic the temperature gradient in the cell itself.
The beam diameter and detector size at the NEUTRA beam line of PSI allows imaging objects up to a size of 350 mm (horizontal) x 380 mm (vertical) in a single shot. Typical exposure times of 5 to 10 seconds allow observing the temporal evolution of water in the flow channels. With accumulated exposure time of 2-3 minutes, a low noise image is obtained, allowing identifying the presence of water in the GDLs in regions free of channel water.
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