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

Abstract

In this article three different techniques for visualizing gas-liquid mass transfer are reviewed according to their applications in air-water systems. The three techniques are: Planar Laser Induced Fluorescence (PLIF with the use of fluorescent resorufin), PLIF with Inhibition (PLIF-I with the use of a ruthenium complex), and a colorimetric technique (using a redox reaction with the pink-colored dye resorufin).For comparison purpose, the three techniques were conducted in the same experimental set-up to characterize the local oxygen mass transfer from a single air bubble (with equivalent diameter ~1 mm) rising in water. This paper rigorously compares these three techniques and aims to point out their advantages and limitations. The comparison was divided into two parts: the visualization and the quantification of the mass transfer. The discussion focused on the image quality, the required equipment, and the accuracy of the quantification results including the mass flux, the diffusion coefficient and the mass transfer coefficient. A guideline was provided for choosing the technique that most accurately visualizes and characterizes the local mass transfer in gas-liquid systems.

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] .…”

“…Typical online methods include laser-induced fluorescence technique (LIF) and colorimetric technique, they both offer appealing advantages over those offline methods, such as high visual resolution, absence of end-effect and quick response time [11] . LIF technique involves the addition of a fluorescent dye, of which the fluorescence intensity under laser excitation decreases or increases with the concentration of certain compound (e.g., concentration of the dye itself or other ions like H + ).…”

“…Note that k L theoretically equals to 1/(1/ k L,W +1/ mk L,O ) for liquid-liquid system, where k L,W and k L,O are respectively the mass transfer coefficients from water and organic phases, but k L ≈ k L,W in current case, as explained above. For gas-liquid systems, k L = k L,W (mass transfer resistance in gas phase is usually negligible), and was reported to be in the magnitude of 10 −4 m/s [ 11 , 21 , 23 , 24 ] in gas-liquid microreactors using this resazurin system. Thus, here we assume that the overall mass transfer coefficient k L in our liquid-liquid system is in the same magnitude, leading to Ha = 17.7.…”

Child droplets from micro-explosion of emulsion and immiscible two-component droplets

“…There is also a limited number of research findings (e.g., [5,10,15,16]) on the integral characteristics of child droplets, because the processes under study are fast-paced and their recording requires complex and expensive recording systems [1,8,9,14,[19][20][21][22][23][24][25][26][27][28], as well as dedicated data processing algorithms. For instance, the key methods for recording the characteristics of child droplets are as follows: Particle Tracking Velocimetry (PTV) [19,20] for the velocities and trajectories of child droplets; Schlieren Photography (SP) [21,22] for their number and size; Laser Induced Phosphorescence (LIP) [23][24][25], Planar Laser Induced Fluorescence (PLIF) [9,26,27], and 2-Color Laser Induced Fluorescence (2-Color LIF) [1,8,14,28] for their temperature. The methodologies for determining the velocities [19,20] and sizes [21,22] of child droplets are robust, while temperatures are recorded in rather sophisticated ways.…”

Using Pop-Culture to Engage Students in the Classroom

“…and famous shows used for this purpose include The Price is Right 63 , The Big Bang Theory 64 , CSI , The Simpsons 66 , Bones 67 , ER and House 68 . Trending games are also an interesting pathway to involve students in general chemistry courses [90][91][92][93][94][95][96][97] . Educators have included pop-culture elements to solve educational escape games, e.g.…”