Simultaneous measurement of bubble size, velocity and void fraction in two-phase bubbly flows with time-resolved X-ray imaging

Abstract

Key parameters of two-phase flows, such as void fraction and microscale bubble size, shape and velocity, were simultaneously measured using time-resolved X-ray imaging. X-ray phase-contrast imaging was employed to obtain those parameters on microbubbles. The void fraction was estimated from X-ray absorption. The radii of the measured microbubbles were mostly smaller than 20 µm, and the maximum velocity was 39.442 mm s(-1), much higher than that in previous studies. The spatial variations of the void fraction were consecutively obtained with a small time interval. This technique would be useful in the experimental analysis of bubbly flows in which microbubbles move at high speed.

Water transport in polymer electrolyte membrane fuel cell: Degradation effect of gas diffusion layer

“…Owing to the coherence of the synchrotron source, both absorption-and phasecontrast imaging mechanisms can be adopted in synchrotron X-ray imaging to observe two-phase flows. [31][32][33] In previous studies, only the absorption contrast and the Beer-Lambert law were adopted to investigate the amount of water clogged in aging GDLs. Based on the absorption contrast, averaged water saturation and its relationship with the PEMFC performance were quantitatively visualized in GDL layers or flow channels of PEMFCs.…”

“…Water transport in fuel cells is associated with two‐phase flows 7 and wetting. Owing to the coherence of the synchrotron source, both absorption‐ and phase‐contrast imaging mechanisms can be adopted in synchrotron X‐ray imaging to observe two‐phase flows 31‐33 . In previous studies, only the absorption contrast and the Beer‐Lambert law were adopted to investigate the amount of water clogged in aging GDLs.…”