Development of an image measurement technique for size distribution in dense bubbly flows

Lau, YM Yuk Man; Deen, NG Niels; Kuipers, J.A.M.

doi:10.1016/j.ces.2013.02.043

Cited by 166 publications

(109 citation statements)

References 33 publications

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“…Only projected bubble images could be obtained. This problem is well known and, despite some proposals (Bian et al, 2013;Sahagian and Proussevitch, 1998), a solution is far from being reached and the use of 2D projected images is a common way of processing bubble images (Karn et al, 2015;Lage and Espósito, 1999;Lau et al, 2013aLau et al, , 2013bWongsuchoto et al, 2003). However, the bubble shape data obtained by this approach are considered reliable: the bubble shape information allowed the extrapolation of correlations for the aspect ratio (Besagni, 2016; and flow regime transition criteria .…”

Section: Image Analysis: Uncertaintiesmentioning

confidence: 99%

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

111

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A B S T R A C TSome authors, in the last decades, have observed the dual effect of viscosity on gas holdup and flow regime transition in small-diameter and small-scale bubble columns. This work concerns the experimental investigation of the dual effect of viscosity on gas holdup and flow regime transition as well as bubble size distributions in a large-diameter and large-scale bubble column. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, and can be operated with gas superficial velocities in the range of 0.004-0.20 m/s. Air was used as the dispersed phase, and various water-monoethylene glycol solutions were employed as the liquid phase. The water-monoethylene glycol solutions that were tested correspond to a viscosity between 0.9 mPa s and 7.97 mPa s, a density between 997.086 kg/m 3 and 1094.801 kg/m 3 , a surface tension between 0.0715 N/m and 0.0502 N/m, and log 10 (Mo) between −10.77 and −6.55 (where Mo is the Morton number). Gas holdup measurements were used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. An image analysis method was used to investigate the bubble size distributions and shapes for different gas superficial velocities, for different solutions of watermonoethylene glycol. In addition, based on the experimental data from the image analysis, a correlation between the bubble equivalent diameter and the bubble aspect ratio was proposed. The dual effect of viscosity, previously verified in smaller bubble columns, was confirmed not only with respect to the gas holdup and flow regime transition, but also for the bubble size distributions. Low viscosities stabilize the homogeneous flow regime and increase the gas holdup, and are characterized by a larger number of small bubbles. Conversely, higher viscosities destabilize the homogeneous flow regime and decrease the gas holdup, and the bubble size distribution moves toward large bubbles. The experimental results suggest that the stabilization/destabilization of the homogeneous regime is related to the changes in the bubble size distributions and a simple approach, based on the lift force, was proposed to explain this relationship. Finally, the experimental results were compared to the dual effect of organic compounds and inorganic compounds: future studies should propose a comprehensive theory to explain all the dual effects observed.

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Section: Image Analysis: Uncertaintiesmentioning

confidence: 99%

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

111

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“…Nonintrusive measurement techniques are preferred over intrusive methods because the flow conditions are not disturbed, and image analysis is attracting growing attention. Image analysis has been mostly applied to rectangular/small-scale (Lau et al, 2013a(Lau et al, , 2013bZaruba et al, 2005) or medium scale (Schäfer et al, 2002) bubble columns, but there is a lack of studies concerning BSDs in largediameter bubble columns. Furthermore, studies analyzing the bubble size distributions near the sparger are uncommon (Hur et al, 2013), and the influence of the liquid velocity on the bubble shape and bubble size distribution is far from being understood (Besagni and Inzoli, 2016b).…”

Section: Introductionmentioning

confidence: 99%

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

Besagni

Inzoli

2016

Chemical Engineering Science

114

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“…The optical image analyses have been used recently for quantifying the bubble size distribution. [63][64][65][66] Luo et al 67 utilized the visualization technique to study the bubble characteristics and bubble formation behavior. A number of studies have been recently conducted using this approach with different algorithms for image analysis.…”

Section: Non-intrusive Techniquesmentioning

confidence: 99%

“…A number of studies have been recently conducted using this approach with different algorithms for image analysis. 8,65,66,[68][69][70][71][72][73][74] Although it is very convenient and time efficient for online monitoring and analysis of a large number of images, to implement this technique for real-time analysis of the bubbly flow images from different engineering applications pose multifarious challenges. Generally, due to the excessive coalescence and breakup of bubbles, most of the proposed techniques for bubble image processing produce significant errors when applied to flows with high gas and liquid velocities.…”

Section: Non-intrusive Techniquesmentioning

confidence: 99%

“…the Fischer-Tropsch process for hydrocarbon synthesis, hydrogenation of unsaturated oil, coal liquefaction, fermentation, waste water treatment etc. 4,5 Bubbly flows are also ubiquitously found in flotation cells 6 and spargers 7 and have recently been investigated extensively for aeration studies. [8][9][10][11][12] Concentration, size and velocity distributions of solid or liquid particles suspended in gas or liquid are important in many processes such as meteorological research, biology, environmental protection, chemistry, medicine and agricultural engineering.…”

Section: Introductionmentioning

confidence: 99%

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2017

IPCSE

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Abbreviations BSD, bubble size distribution; PET, positron emission tomography; PIV, particle image velocimetry, RPT; radioactive particle tracking; NMR, nuclear magnetic resonance imaging IntroductionMultiphase flow systems have been applied extensively in chemical, physical, petrochemical and biochemical processing industries.1-3 Among different multiphase flow systems, bubbly flow is a two phase flow where small bubbles are dispersed or suspended in a liquid continuum. Typical features of this flow are moving and deformable interfaces of bubbles in time and space domains and complex interactions between the interfaces, and also between the bubbles and the liquid flow. Bubbly flows occur frequently in natural systems and are also used for different applications in energy-producing and chemical and petroleum industries. Some of the common applications involve bubble columns which are used as reactors in a variety of chemical and biochemical processes, e.g. the Fischer-Tropsch process for hydrocarbon synthesis, hydrogenation of unsaturated oil, coal liquefaction, fermentation, waste water treatment etc. 4,5 Bubbly flows are also ubiquitously found in flotation cells 6 and spargers 7 and have recently been investigated extensively for aeration studies. [8][9][10][11][12] Concentration, size and velocity distributions of solid or liquid particles suspended in gas or liquid are important in many processes such as meteorological research, biology, environmental protection, chemistry, medicine and agricultural engineering. Further, commercial activities such as conversion of natural gas to fuels and chemicals have prompted further fundamental research in fluid and bubble dynamics, transport phenomena and the effects due to scale up of three-phase fluidization systems.The prediction of pressure drop and wall heat transfer is necessary in many of these processes and these are strongly dependent upon the concentration, morphology and spatial distribution of the bubbles. 13 Similarly, in many liquid-gas systems, gases are dispersed in liquids to obtain large interfacial area for chemical reactions, heat and mass transfer processes. The rate of these processes is determined by bubble surface area flux which is closely linked to the bubble size distribution. 14 DiscussionDifferent techniques have been employed to measure bubble size distributions. Broadly, it can be divided into two categoriesintrusive and non-intrusive techniques.15 Both these methods have been extensively reported in the literature and a brief description of different intrusive and non-intrusive techniques is provided below, Intrusive techniquesConsiderable intrusive techniques have been developed to study bubble behavior in gas-liquid and gas-liquid-solid fluidized systems. These intrusive techniques include impedance (conductivity or resistivity) probes, capillary suction probes, 16 optical fiber probes, ultrasound probes, endoscopic probes, wire-mesh sensors 17 and hot film anemometry.The impedance probe has been applied to measure the bubble volume f...

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Development of an image measurement technique for size distribution in dense bubbly flows

Cited by 166 publications

References 33 publications

The dual effect of viscosity on bubble column hydrodynamics

The dual effect of viscosity on bubble column hydrodynamics

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

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