Pulsed neutron imaging for differentiation of ice and liquid water towards fuel cell vehicle applications

• Published in: Physical chemistry chemical physics : PCCP Vol. 23; no. 2; pp. 162 - 171
• Main Authors: Higuchi, Yuki, Setoyama, Daigo, Isegawa, Kazuhisa, Tsuchikawa, Yusuke, Matsumoto, Yoshihiro, Parker, Joseph Don, Shinohara, Takenao, Nagai, Yasutaka
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 21.01.2021
• Subjects: Capillary tubes; Electric vehicles; Electrolytic cells; Field of view; Flow simulation; Freeze-thaw; Freezing; Fuel cells; Ice formation; Imaging; Melting; Neutron beams; Neutrons; Proton exchange membrane fuel cells; Spallation; Spatial resolution; Water; Water distribution; Water engineering
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp03887c

This study is the first report on liquid water and ice imaging conducted at a pulsed spallation neutron source facility. Neutron imaging can be utilised to visualise the water distribution inside polymer electrolyte fuel cells (PEFCs). Particularly, energy-resolved neutron imaging is a methodology capable of distinguishing between liquid water and ice, and is effective for investigating ice formation in PEFCs operating in a subfreezing environment. The distinction principle is based on the fact that the cross sections of liquid water and ice differ from each other at low neutron energies. In order to quantitatively observe transient freezing and thawing phenomena in a multiphase mixture (gas/liquid/solid) within real PEFCs with high spatial resolution, a pulsed neutron beam with both high intensity and wide energy range is most appropriate. In the validation study of the present work, we used water sealed in narrow capillary tubes to simulate the flow channels of a PEFC, and a pulsed neutron beam was applied to distinguish ice, liquid water and super-cooled water, and to clarify freezing and thawing phenomena of the water within the capillary tubes. Moreover, we have enabled the observation of liquid water/ice distributions in a large field of view (300 mm × 300 mm) by manufacturing a sub-zero environment chamber that can be cooled down to −30 °C, as a step towards in situ visualisation of full-size fuel cells. Water/ice identification images throughout the thawing process of ice in a metal capillary by using a pulsed neutron source.