Optimal Reynolds number for liquid-liquid mixing in helical pipes

Mansour, Michael; Khot, Prafull; Thévenin, Dominique; Nigam, K.D.P.; Zähringer, Katharina

doi:10.1016/j.ces.2018.09.046

Cited by 34 publications

(19 citation statements)

References 57 publications

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“…The liquid superficial velocity has little influence on the mixing result, whereas the main increase in mixing coefficient is related to the gas superficial velocity. The single-phase case has a well-known (Mansour et al 2019(Mansour et al , 2020c) maximum at Re total = 700 , which corresponds to a superficial liquid velocity of u s, l = 0.1756 m∕s , with a mixing coefficient of M c = 0.68 . The highest mixing coefficients of M c > 0.9 in the two-phase experiments were reached with maximum gas velocity ( u s, g = 0.0221 m∕s ) and liquid velocities of 0.075 m∕s < u s, l < 0.176 m∕s , corresponding to total Reynolds numbers of 388 < Re total < 788 (light blue region in Fig.…”

Section: Mixing Pattern and Mixing Coefficientmentioning

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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Section: Mixing Pattern and Mixing Coefficientmentioning

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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“…Mixing was examined numerically in the HCTR geometry, using the fluid properties of the TMS, and in geometry G1, applying the water fluid properties, with parameter variations of the pitch b and the curvature ratio . Similar to former investigations, the CFD code Star-CCM + was used [12,[19][20][21].…”

Section: Mixing Inside the Liquid Phasementioning

confidence: 99%

“…Responsible for this intensified mixing characteristics and also for the enhanced mass transfer, as will be shown in the next section, are the secondary flow pattern inside the helical tube. These Dean-vortices can be visualized from 3D-velocity measurements [17] and from the calculated velocity fields [21] as shown in Fig. 7.…”

Section: Mixing Inside the Liquid Phasementioning

confidence: 99%

Helically coiled segmented flow tubular reactor for the hydroformylation of long-chain olefins in a thermomorphic multiphase system

Jokiel

Kaiser

Kováts

et al. 2019

Chemical Engineering Journal

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“…Computational fluid dynamics (CFD) has emerged as an attractive tool to study the process intensification by means of Dean vortices reacting systems. The impact of Dean vortices in microsystems has been studied by CFD to evaluate the pressure drop [29,30], the heat transfer [31,32] and to predict the mixing intensification in coiled flow inverters [33,34,35,36] and helical micromixers [37,38]. However, fluid dynamics simulations in high aspect ratio coiled microreactors (length to diameter ratio) remain computationally challenging, due to the mesh refinement needed to capture the geometric curvatures of the reactor.…”

Section: Introductionmentioning

confidence: 99%

CFD modeling of pharmaceuticals and CECs removal by UV/H2O2 process in helical microcapillary photoreactors and evaluation of OH radical rate constants

Moreira

Puma

2021

Chemical Engineering Journal

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Optimal Reynolds number for liquid-liquid mixing in helical pipes

Cited by 34 publications

References 57 publications

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

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

Helically coiled segmented flow tubular reactor for the hydroformylation of long-chain olefins in a thermomorphic multiphase system

CFD modeling of pharmaceuticals and CECs removal by UV/H2O2 process in helical microcapillary photoreactors and evaluation of OH radical rate constants

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