September 19, 2001
Willet Science Center 109
Flow in Microchannels”
Abstract: Core-film flow is two-phase flow in an enclosed channel comprised of a liquid film coating the channel sides that surrounds a gaseous core flow. Such a flow exists in the passages of a proton-exchange membrane (PEM) fuel cell. Stability of the core flow and thickness of the film is critical to the supply of O2 in the electrochemical reaction. A study is proposed to investigate the hydrodynamic characteristics of core-film flow in microchannels, theoretically and experimentally. The theoretical effort consists of a linear stability analysis, first of two-phase flow in a circular channel (core-annular flow) and second, if warranted, of two-phase flow in square microchannels. The square-channel analysis is more complicated due to the necessary consideration of a two-dimensional basic-state flow, and could prove to be a considerable contribution to the study of shear-flow instabilities. The results will provide velocities, growth-rates and wavelengths of the interface disturbances associated with pinch-off of the core flow which should help determine when liquid hold-up is possible and ways to prevent it. The experimental efforts will be performed at the Glenn Research Center (NASA) which will attempt to establish and observe steady- and transient-flow structures and measure disturbance properties allowing comparisons to the theoretical results. The presentation will focus of the theoretical efforts but will encourage discussion of possible experimental approaches.
join us for light refreshments at 4:15.