A study of surfactant effects on the liquid-phase motion around a zigzagging-ascent bubble using a recursive cross-correlation PIV

Chemical Engineering Journal

2010

a b s t r a c tQuantitatively characterizing long-period fluctuations, which reflect the large-scale structure of a bubbly flow in a bubble column reactor, is essential to improving the reactor efficiency. We propose a newly developed method to extract the long-period fluctuations based on point-wise void fraction measurements. The validity of the new method is demonstrated via characterization of long-period fluctuations in a bubble column approximately 400 mm in diameter and 2000 mm in height. First, the characteristics of liquid-phase motion induced by a single bubble-swarm are described based on the results obtained via LDA measurements. The large-scale liquid-phase motion is characterized by an individual bubble cluster (i.e. a region with the same void fraction). We explain the premise of our new method based on these results. Second, we show that the bubbly flows in the bubble column can be divided into three regions (i.e. a time-spatially fluctuated region, a transition region, and a pseudo-homogenous region) based on differences in the distribution patterns of bubble diameters and velocities as well as those between time-series point-wise void fractions obtained from four-point simultaneous measurements. The spatial fluctuations fade out with height from the column bottom. Finally, analyzing the time-series point-wise void fractions measured via four-tip optical-fiber probe (F-TOP), we demonstrate that the long-period fluctuations can be extracted via waveform analysis. The characteristic spectrum pattern also fades out with height. The extracted long-period fluctuations are in good agreement with those obtained from the visualization results for the flows.

Section: Buoyancy-driven Flow Induced By a Single Bubble-swarmsupporting

confidence: 88%

“…On the scale of a single bubble, local pseudo-turbulence is induced by the buoyancy current [7]. On an intermediate scale of a single bubble-swarm, the vortical structure, which is characterized by eddies of its surrounding liquid, appears with a size on the order of the bubble-swarm diameter.…”

Section: Introductionmentioning

confidence: 99%

Quantitative characterizations of long-period fluctuations in a large-diameter bubble column based on point-wise void fraction measurements

Higuchi

Chemical Engineering Journal

2010

“…We have investigated the environmental acceptability of the GLAD system based on a series of computational findings that were derived in consideration of the results from our previous studies, which include the performance of CO 2 dissolution in a laboratory-scale small apparatus (4), (13) ; confirmatory experiments on the environmental performance (5) ; confirmation of the pump-up performance in a large-scale apparatus (12) ; determination of the surrounding liquid motion of a bubble (9), (15) ; consideration of the relation between the bubble motion and the surface contamination (16), (17) ; examination of turbulent bubbly flows in large-diameter vessels (14), (18) .…”

Section: Discussion Of the Environmental Acceptability Of The Glad Symentioning

confidence: 99%

Deep Ocean CO2 Sequestration via GLAD (Gas-Lift Advanced Dissolution) System

Kajishima

Tsuchiya

2011

JEE

To mitigate global warming, a system that can dissolve huge amount of gaseous CO 2 expelled from a fossil fuel-fired power plant into the ocean, which must be at the same time eco-friendly to the ocean environment, is indispensable. We propose a system of sequestrating such CO 2 in the deep ocean water based on gas-lift effects, the so-called GLAD (Gas-Lift Advanced Dissolution) system. The primary system is an inverse-J (originally) pipeline set in the ocean at a depth of 200−3000 m. In the system, pumping powered by buoyancy of the dissolving CO 2 bubbles is used to transport CO 2-rich seawater to great depths. In the present paper, we outline the GLAD system and summarize its related fundamental studies for the purpose of designing a highly efficient and extremely reliable system.

“…A hypodermic needle (c) (outer diameter: 0.65 mm; inner diameter: 0.4 mm) was positioned at the bottom of the vessel. Single bubbles with high reproducibility 7, 8 of size, orientation, and ascent trajectory were launched from the needle at an arbitrary interval through a bubble launch device (BLD) (e). The BLD, composed of two pressure controllers, an audio speaker, an amplifier, and a function generator, permitted to completely control bubble formation and launch 7, 8.…”

Section: Methodsmentioning

confidence: 99%

“…Conventional methods or algorithms 11, 12 for calculating the volume and surface area of a spherical bubble were inadequate for the present study due to the zigzag motion 7 and surface oscillation (mode 2.2) 5, 6 of the examined bubble. Hence, a new method was developed 8 for calculating the volume and surface area of such bubbles from projection images captured as described in Sects.…”

Section: Image Processing For Calculating Bubble Volume and Surfacementioning

confidence: 98%

Influence of Bubble‐Surface Contamination on Instantaneous Mass Transfer

Huang

2015

Chem Eng & Technol

The relationship between instantaneous mass transfer, bubble motions, and bubble-induced surrounding liquid motions is discussed on the basis of precise measurements in time and space. The influence of bubble-surface contamination on the above is considered quantitatively through comparison with those in a purified system. The bubble's surface motion, centroid motion, volume, and surface area were acquired precisely from moment to moment using two high-speed cameras and an own innovative image processing method. The dissolution process of CO 2 was visualized via the laser-induced fluorescence/8-hydroxypyrene-1,3,6-trisulfonic acid (LIF/HPTS) method. Combining these experimental results carefully, the effects of the surfactant on the mass transfer, bubble motions, and vortex mechanism are discussed.