Using the “Red Bottle” Experiment for the Visualization and the Fast Characterization of Gas–Liquid Mass Transfer

Abstract

This paper presents a demonstration of the visualization and the characterization of gas−liquid mass transfer in a small bubbly column. The aim is to show how simple experiments can be used to directly quantify mass transfer without the need of sophisticated probes or complex titrations. The method here proposed is based on the "red bottle" reaction, i.e., the reversible oxidation by oxygen of dihydroresorufin to red resorufin. This reaction produces a distinctive red color, and in the specific condition identified, the time required to turn from colorless to red solution can be directly correlated with the inverse of the volumetric mass transfer coefficient k L a (s −1). Therefore, this reaction can be used to estimate the mass flux of oxygen transferred from the gas phase (bubbles) to the liquid phase and to study how this flux is affected by geometrical and operating parameters of bubbly flows. The lab work described is thus very convenient for education purposes. This is the first visual demonstration allowing mass transfer to be quantified with good precision, opening up a wide range of applications.

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

“…To calculate the overall volumetric mass transfer coefficient, k L -Áa, simply and directly, it was assumed in a first step that C Ã O 2 L , and k L Áa were kept constant during the whole mass transfer process and using the average gas-liquid hydrodynamics, e.g., hU B i. From the stoichiometry of dihydroresorufin and O 2 , two moles of DH react with one mole of O 2 , and the relationships between C O 2 L ðXÞ and the resazurin concentration are (Dietrich et al, 2019):…”

“…(7). Various authors (Dietrich et al, 2019;Yang et al, 2017a) have found that the enhancement factor E is equal to 1 when the order of magnitude of k L was about 10 À4 m s À1 , typically in millireactors. Therefore, E was considered equal to 1 here.…”

“…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).…”

Hydrodynamics of Gas–Liquid Slug Flows in a Long In-Plane Spiral Shaped Milli-Reactor

“…The liquid phase consisted of solutions containing D-glucose anhydrous (Fischer-Scientific, CAS 50-99-7), sodium hydroxide (VWR, CAS1310-73-2) and resazurin (Sigma Aldrich, CAS 62758-13-8, molar mass 229.19 g mol -1 , purity 84%). This choice of liquid phase was motivated by the fact that this study was a preliminary work for implementing the colourimetric dye-based method proposed by Dietrich et al [39,40] to quantify the local gas-liquid mass transfer. The D- Table 2.…”

Characterization of Bubble Shapes in Non‐Newtonian Fluids by Parametric Equations

“…It is generally agreed that non-Newtonian fluids have complex rheological properties (e.g., shear thinning, viscoelasticity, etc.) leading to a variety of bubble shapes, such as teardrop or elongated bubbles [13][14][15][16][17][18].…”