Classification of bubbles in vertical gas–liquid flow: Part 1 – An analysis of experimental data

Qi, Fengsheng; Yeoh, Guan Heng; Cheung, Sherman C.P.; Tu, Jiyuan; Krepper, Eckhard; Lucas, Dirk

doi:10.1016/j.ijmultiphaseflow.2011.10.010

Cited by 20 publications

(5 citation statements)

References 30 publications

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“…The CoV is the most important variable for estimating the liquid distribution, widely used in various processes to classify the quality of the dispersed phase distribution. [ 55–60 ] The larger the CoV is, the worse the distribution uniformity is, and vice versa. The definition of CoV is expressed in Equation ().

CoV = \frac{\sqrt{\sum_{i}^{n} {(u_{L} - \overset{true¯}{u_{L}})}^{2} / n}}{\overset{u_{L}}{true}}

…”

Section: Resultsmentioning

confidence: 99%

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A new streamlined bubble‐cap distributor for high gas–liquid ratio and the liquid distribution mechanisms

Yong

et al. 2022

Can J Chem Eng

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The bubble‐cap distributor is the most commonly used and critical internal for trickle bed reactors but holds the inherited disadvantage of liquid central aggregation when operating at a high gas–liquid ratio. A new bubble‐cap distributor with a streamlined downcomer was developed in this paper to counter back the liquid aggregation and improve its comprehensive performance. The effect of the streamline parameters of the new distributor on liquid distribution was systematically explored by the coupled Euler–Euler‐population balance equation (PBE) model. Compared with the classical and polyline converging–diverging structures, the results showed that the streamlined downcomer was a key to generating radial velocity of two‐phase flow and reducing the liquid central aggregation for the bubble‐cap distributor. The mechanism of well‐distribution was explored for the new distributor. Lower converging and diverging angles enhance the distribution performance. A downcomer with a small converging angle and a 30° diverging angle was recommended for dispersing the central aggregated liquid column and acquiring the high distribution uniformity and spray covering circle. These data would be helpful to the optimal design and scale‐up of the bubble‐cap distributor in further industrial applications.

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CoV = \frac{\sqrt{\sum_{i}^{n} {(u_{L} - \overset{true¯}{u_{L}})}^{2} / n}}{\overset{u_{L}}{true}}

…”

Section: Resultsmentioning

confidence: 99%

“…to classify the quality of the dispersed phase distribution. [55][56][57][58][59][60] The larger the CoV is, the worse the distribution uniformity is, and vice versa. The definition of CoV is expressed in Equation (9).…”

Section: Characteristics Of Liquid Dispersionmentioning

confidence: 99%

A new streamlined bubble‐cap distributor for high gas–liquid ratio and the liquid distribution mechanisms

Yong

et al. 2022

Can J Chem Eng

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“…All model predictions are in good agreement with the measurements. As discussed by Qi et al, the wire mesh sensor measurements involve some uncertainty and error caused by the interaction of travelling bubbles near the wire. Comparing the wire mesh sensor data with other measurement techniques, the uncertainty was estimated as a maximum of around 2 %.…”

Section: Resultsmentioning

confidence: 99%

Comparative Analysis of Coalescence and Breakage Kernels in Vertical Gas‐Liquid Flow

et al. 2015

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The evolution of the bubble size distribution is an important consideration in vertical gas-liquid flow especially in determining the appropriate mass, momentum and heat transfer between two phases.In order to adequately capture the distribution and to account for its effect on the local hydrodynamics, which generally represents the dominant flow characteristic in such practical system, a numerical assessment has been performed to understand the six widely adopted different bubble coalescence and bubble breakage kernels. Three different breakage kernels have been selected where each kernel considers a different shape of the daughter size distribution of the bubbles such as the U-shape, bell-shape and M-shape. These are combined with different coalescence kernels. The bubble size distribution, void fraction, interfacial area concentration and gas velocity profiles are compared against the experimental data. Numerical results reveal that the effect on the two-phase flow structure is mainly due to the application of the different breakage kernels. Moreover, the predicted results also show that the bell-shape daughter size distribution favours equal breakage of bubbles; which could lead to the over-prediction of large bubbles. A more sophisticated model for handling bubble induced turbulence should nonetheless be applied in future investigations of vertical gas-liquid flow. This article is protected by copyright. All rights reserved

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“…On the other hand, when a gas-liquid flow is fully developed, the largest size of small bubbles can be observed and estimated. For example, when pipe diameter is within 50 mm −200 mm, the largest size is approximately less than 20 mm [21][22][23][24]. It is worth noting that the primary purpose of remeshing is to generate small bubbles missing in ERT tomograms.…”

Section: Data Re-meshingmentioning

confidence: 99%

Bubble mapping: three-dimensional visualisation of gas–liquid flow regimes using electrical tomography

Wang

Jia

Wang

2019

Meas. Sci. Technol.

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It is well known that electrical tomography is capable of 'seeing' through opaque pipe walls and flow media. However, due to the relatively low spatial resolution, electrical tomograms are ineffective on visualisation of small bubbles or sharp interfaces between large bubbles and the liquid. These limitations give rise to ambiguity in human and/or machine perception of flow dynamics from presenting bubble cluster and blurry boundaries of large bubbles in faint colour or grey. In this paper, a binary approach, called bubble mapping, is proposed to enhance the visibility of flow regime in gas-liquid pipeline flows. With the input gas concentration tomograms reconstructed by an electrical tomography, the method takes the major visual characteristics of typical flow regimes in common recognition as a prior knowledge and replaces the conventional colour mapping with a number of bubbles and their mergence with a thresholding value. With this approach, a stack of cross-sectional tomograms by electrical tomography is transformed and displayed as a collection of individual gas bubbles. The transformation is done with the help of a lookup table indexed by bubble size and an enhanced isosurface algorithm for vivid three-dimensional visualisation. This new approach has been applied to a gas-in-water flow rig and its performance is compared with photo images taken by a high-speed camera. Reasonable agreements have been obtained for common flow regimes including bubbly flow, stratified flow, plug flow, slug flow and annular flow in horizontal pipe and bubbly flow, slug flow and annular flow in vertical pipe. Results evidence the method can provide a photorealistic flow visualisation and therefore enhance the visibility of electrical tomograms for visual identification of flow regime, particularly for opaque media in industrial flows.

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Classification of bubbles in vertical gas–liquid flow: Part 1 – An analysis of experimental data

Cited by 20 publications

References 30 publications

A new streamlined bubble‐cap distributor for high gas–liquid ratio and the liquid distribution mechanisms

A new streamlined bubble‐cap distributor for high gas–liquid ratio and the liquid distribution mechanisms

Comparative Analysis of Coalescence and Breakage Kernels in Vertical Gas‐Liquid Flow

Bubble mapping: three-dimensional visualisation of gas–liquid flow regimes using electrical tomography

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