Experimental study on the characteristics of air–water two-phase flow in vertical helical rectangular channel

Liu, Xianfei; Yang, Guang

doi:10.1016/j.ijmultiphaseflow.2015.03.012

Cited by 39 publications

(21 citation statements)

References 21 publications

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“…Liu等人 [14,15] (ⅱ) 模拟研究. 除了张丽等人 [12] 对矩形截面螺旋通道流动特性进行数值模拟, 并得到和实验测量值相近的结果外, Mohammed等人 [16] 模拟了不同螺距对其压降的影响, 发现改变螺距对压降并无明显改变; 而随着螺旋半径的减小和螺旋管内径的增加, 压降增大.…”

Section: 层流状态下的流动特性unclassified

A review on fluid flow and heat transfer in helical channel

Lin¹,

Liu²,

Feng³

et al. 2017

Chin. Sci. Bull.

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Section: 层流状态下的流动特性unclassified

A review on fluid flow and heat transfer in helical channel

Lin¹,

Liu²,

Feng³

et al. 2017

Chin. Sci. Bull.

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“…In addition, often vertical, but not horizontal, helical reactors have been examined, e.g. (Che et al 2020;Colombo et al 2015;Li et al 2017;Liu et al 2015;Mandal and Das 2003;Mansour et al 2020b;Mei et al 2020;Murai et al 2006;Zhu et al 2017Zhu et al , 2019, since accumulation of bubbles in the upper part of the coils is avoided like that. Also micro-channels with Taylor bubble experiments, e.g.…”

Section: Introductionmentioning

confidence: 99%

Experimental characterization of mixing and flow field in the liquid plugs of gas–liquid flow in a helically coiled reactor

2021

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Flow mixing of two miscible liquids with the addition of gas bubbles is a process often found in industrial chemical apparatus for the production of primary matter. The ongoing optimization of such processes also involves the transformation of batch to continuous mode operation. In that case, the use of helically coiled tubes is an interesting alternative, since those reactors have narrow residence time distributions, very good radial mixing properties and excellent mass transfer can be realized between gases and liquids. For these reasons, in this study the mixing of two miscible liquids with addition of air bubbles in gas–liquid flows has been characterized in a horizontal helically coiled reactor in the laminar flow regime at $${\text{Re}}_{{{\text{total}}}} = 300 \ldots 1088$$ Re total = 300 … 1088 . Eight different superficial liquid velocities and five superficial gas velocities were investigated. In order to characterize mixing in the liquid plugs between two bubbles, laser-induced fluorescence of resorufin was used and particle image velocimetry has been employed to characterize the flow field. Pseudo-3D-visualizations of the resorufin concentration and the Q-criterion, representing the mixing efficiency and vorticity, respectively, were established for individual liquid plugs from the time-resolved measurement results. A time-resolved mixing coefficient, as well as a mean mixing coefficient obtained from multiple liquid plugs, is calculated from the fluorescence images for all examined flow conditions. The experimental results clearly show an increase in the mixing coefficient compared to single-phase conditions, caused by the bubbles. However, distinct mixing pattern, depending on the flow structure, can be recognized on different locations inside the liquid plug. Compared to a stationary case without air bubbles, mixing is worse behind the bubbles and increases inside the plug, reaching a maximum mixing coefficient in front of the next bubble. Overall the mixing coefficient is always increased by the presence of the bubbles. Pseudo-3D-visualizations of the Q-criterion and the vorticity show the presence of secondary vortices right in front of the bubbles, shifted to the outer tube walls, and in addition to the steady Dean vortices. In small plugs, these secondary vortices appear in the whole plug and increase the mixing coefficient drastically. Graphical Abstract

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“…Similarly, two-phase flows in helical tubes are very important for the performance of different processes in chemical industries, refrigeration systems, and steam generators. ,− The presence of a second (gaseous) phase along with the mainstream of water as well as the centrifugal force make the flow much more complicated compared to the single-phase flow. ,, When an air–water mixture flows in a helical pipe, the higher-density fluid (water) is moved to the outer side of the channel due to the centrifugal force, while the gas is moved toward the inner side of the pipe. ,, The phase distributions in helical pipes were also found to be obviously asymmetric due to the unbalanced forces . The flow complexity depends on the flow rates and the gas volume fraction, which determine the two-phase flow regime.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Gas–Liquid Two-Phase Flow Regimes for Upward Flow in a Helical Pipe

Mansour

Landage

Khot

et al. 2019

Ind. Eng. Chem. Res.

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This study presents numerical investigations of air–water two-phase flows for upward flow in a vertical helical pipe. The numerical simulations were done in accordance with the experimental work of Zhu et al. 2017, which aimed at identifying the different flow regimes and the transition maps of the flow [Chem. Eng. J. 2017, 308, 606–618]. Accordingly, the same geometrical parameters and flow conditions were retained in the simulations. The main objectives are (1) to assess the ability of the volume of fluid (VOF) model to accurately predict the two-phase flow regimes and (2) to provide further details about the two-phase interaction processes. This includes the distribution of the two phases, the velocity profiles, and the secondary flow structures under two-phase flow conditions. Mesh and time step independence tests were first performed to minimize discretization errors. The numerical results were then validated against experimental velocity profiles from the literature, showing very good agreement. Flow conditions corresponding to all the possible two-phase flow regimes were considered in the simulations, discussing the accuracy of the numerical modeling and some characteristics of each distinct flow regime. In most cases, the numerical flow regimes are very comparable to the experiments. However, very fine bubbles could not be resolved with the employed mesh resolution (7.64 million cells); they would require an even finer, computationally too expensive mesh. Finally, the internal flow details have been compared between single- and two-phase flows, revealing very complex streamlines and velocity profiles under two-phase flow conditions compared to the Dean vortices observed for single-phase flows.

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Experimental study on the characteristics of air–water two-phase flow in vertical helical rectangular channel

Cited by 39 publications

References 21 publications

A review on fluid flow and heat transfer in helical channel

A review on fluid flow and heat transfer in helical channel

Experimental characterization of mixing and flow field in the liquid plugs of gas–liquid flow in a helically coiled reactor

Numerical Study of Gas–Liquid Two-Phase Flow Regimes for Upward Flow in a Helical Pipe

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