Hydrodynamics and gas-liquid mass transfer around a confined sliding bubble

Abstract

An experimental investigation of gas-liquid mass transfer in the wake of a confined air bubble sliding under an inclined wall in a 2D Hele-Shaw cell is reported. A colorimetric technique based on an oxygen-sensitive dye was used to visualize the oxygen transfer. Bubble velocities, shape eccentricities, interfacial areas and, for the first time, the instantaneous spatio-temporal distribution of oxygen concentration fields in the bubble wake, have been investigated for upper wall inclination angles of 10° ≤ α ≤ 60° and Archimedes numbers of 783 ≤ Ar ≤ 3221. Image processing has allowed, through a specific approach, a quantification of mass transfer. The calculation of the mass flux allowed the deduction of the liquid-side mass transfer coefficient kL. Experiments reveals that, at low angles of inclination, bubble velocities decelerates, shape eccentricities increased, and the instantaneous spatial and temporal distribution of oxygen concentration fields illustrated two distinct regions underneath the sliding bubble: a single vortex loop enclosing the near wake where oxygen is transferred, and a far wake containing oxygen in the form of a single long strip. When inclination angles and bubble sizes were increasing, velocities were increasing, the vortex elongated gradually until it disappears at high angles where total mass fluxes increased. This increase of bubble velocities has increased liquid-side mass transfer coefficient kL allowing a scaling law between the Sherwood number and the modified Archimedes number Ar.sin(α) to be proposed.

Gas-liquid mass transfer around Taylor bubbles flowing in a long, in-plane, spiral-shaped milli-reactor

“…In keeping with this context, the present work reports investigations on the gas-liquid mass transfer process around Taylor bubbles flowing in the same long, in-plane, spiral-shaped milli-reactor as the one used in . The resazurin-based colorimetric method described by Dietrich and Hebrard (2018); Dietrich et al ( , 2019, Kherbeche et al (2019Kherbeche et al ( , 2013 and Liu et al (2020) is implemented to measure the equivalent oxygen concentration fields inside the liquid slugs throughout the 3 m long tube. Two different configurations, in which the tube curvature changes continuously, are considered in order to cover a larger range of cur-vature ratios (i.e., Dean numbers).…”

A colorimetric technique to characterize mass transfer during liquid-liquid slug flow in circular capillaries

“…Note : Calibration curve must be monotonic in order to make quantitative calculation, but it may not be linear, depending on the superposition of mass transfer information within and outside of the focus planes [11] and dye concentration [27] .…”

Comparison of three different techniques for gas-liquid mass transfer visualization

“…As for the non-invasive and instantaneous advantages, Yang et al [46] further investigated the mass transfer contribution of the bubble formation stage to the overall process. The liquid side mass transfer coefficients at the moment immediately after the pinch-off stage were obtained and founded bigger than in the flowing stage, which demonstrated that the contribution of the bubble formation stage to overall mass transfer was reasonably large [47,48]. Furthermore, Yang et al [49] studied the mass transfer intensification in a square meandering channel.…”