Gas hold-up and liquid film thickness in Taylor flow in rectangular microchannels

Warnier, M.J.F.; Rebrov, Evgeny V.; Croon, M.H.J.M. de; Hessel, Volker; Schouten, J.C.

doi:10.1016/j.cej.2007.07.008

Cited by 56 publications

(33 citation statements)

References 12 publications

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“…43 The liquid slug length of Taylor flow in microchannels is determined by the system parameters such as the superficial gas and liquid velocities, the fluid properties and the surface properties of the microchannel. 44,45 In general, increasing the gas velocity at a constant liquid velocity leads to shorter liquid slugs, and our experimental results demonstrated this principle, as shown in Figure 8a. Moreover, some researchers [46][47][48] had proposed empirical correlations for predicting the length of liquid slug of Taylor flow in microchannels due to its importance.…”

Section: Effect Of Superficial Gas Velocity On Hydrodynamics and Liqusupporting

confidence: 59%

Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

Chen

Yuan

2011

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com).The miscible liquid-liquid two phases based on Taylor flow in microchannels was investigated by high-speed imaging techniques and Villermaux/Dushman reaction. The mixing based on Taylor flow was much better compared with that without introducing gas in microchannels, even the ideal micromixing performance could be obtained under optimized superficial gas and liquid velocities. In the mixing process based on Taylor flow, the superficial gas and liquid velocities affected the lengths and the velocities of Taylor bubble and liquid slug, and finally the micromixing performance. The formation process of Taylor flow in the inlets, the initial uniform distribution of reactants and the internal circulations in the liquid slug, and the thin liquid films all improved the mixing performance. Furthermore, a modified Peclet number that represented the relative importance of diffusion and convection in the mixing process was proposed for explaining and anticipating micromixing efficiency.

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Section: Effect Of Superficial Gas Velocity On Hydrodynamics and Liqusupporting

confidence: 59%

Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

Chen

Yuan

2011

AIChE Journal

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“…The pressure drop over a single gas bubble is described by the classical theory of Bretherton (1961), of which, the applicability is extended up to a capillary number Ca gl of 0.01 and Reynolds numbers Re gl in the order of 10 2 using the scaling analysis of Aussillous and Quéré (2000). The pressure drop per unit channel length is obtained by combining the contributions of both sources using a mass balance based Taylor flow model previously developed by the authors (Warnier et al 2007). The model shows that (1) the additional pressure drop caused by the presence of the gas bubbles depends on the bubble frequency and the bubble velocity, and (2) its contribution to the overall pressure drop relative to that of the frictional pressure drop in the liquid phase decreases with increasing gas bubble velocity.…”

Section: Discussionmentioning

confidence: 99%

“…Kreutzer et al (2005b) Aussillous and Quéré (2000) is used to obtain an expression for the pressure drop over a single gas bubble accounting for non-negligible liquid film thickness. A mass balance-based model for gasliquid Taylor flow previously developed by the authors (Warnier et al 2007) is used to describe the fraction of channel length occupied by liquid having a non-zero velocity causing the liquid frictional pressure drop. The mass balance based model is then also used to obtain the pressure drop per unit channel length from the liquid frictional pressure drop and the pressure drop over a single gas bubble.…”

Section: The Pressure Drop Over a Single Gas Bubblementioning

confidence: 99%

Pressure drop of gas–liquid Taylor flow in round micro-capillaries for low to intermediate Reynolds numbers

Warnier

Croon

Rebrov

et al. 2009

Microfluid Nanofluid

128

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In this paper, a model is presented that describes the pressure drop of gas-liquid Taylor flow in round capillaries with a channel diameter typically less than 1 mm. The analysis of Bretherton (J Fluid Mech 10:166-188, 1961) for the pressure drop over a single gas bubble for vanishing liquid film thickness is extended to include a non-negligible liquid film thickness using the analysis of Aussillous and Quéré (Phys Fluids 12 (10):2367-2371, 2000). This result is combined with the Hagen-Poiseuille equation for liquid flow using a mass balance-based Taylor flow model previously developed by the authors (Warnier et al. in Chem Eng J 135S:S153-S158, 2007). The model presented in this paper includes the effect of the liquid slug length on the pressure drop similar to the model of Kreutzer et al. (AIChE J 51(9):2428-2440, 2005). Additionally, the gas bubble velocity is taken into account, thereby increasing the accuracy of the pressure drop predictions compared to those of the model of Kreutzer et al. Experimental data were obtained for nitrogen-water Taylor flow in a round glass channel with an inner diameter of 250 lm. The capillary number Ca gl varied between 2.3 9 10 -3 and 8.8 9 10 -3 and the Reynolds number Re gl varied between 41 and 159. The presented model describes the experimental results with an accuracy of ±4% of the measured values.

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“…The first axial part (3.3 cm) of the micro channel is empty and the second part (3.3 cm) contains a hexagonal array of 3-lm pillars having a height of 50 lm. Different pitches (x pillar and y pillar ) are used Microfluid Nanofluid (2010) 9:131-144 133 (width:height) is well-described for slug/Taylor and bubbly flow by the Armand correlation (Armand 1946;Warnier et al 2008):…”

Section: Two-phase Gas Hold-upmentioning

confidence: 99%

Gas–liquid dynamics at low Reynolds numbers in pillared rectangular micro channels

Loos

Schaaf

Tiggelaar

et al. 2009

Microfluid Nanofluid

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Most heterogeneously catalyzed gas-liquid reactions in micro channels are chemically/kinetically limited because of the high gas-liquid and liquid-solid mass transfer rates that can be achieved. This motivates the design of systems with a larger surface area, which can be expected to offer higher reaction rates per unit volume of reactor. This increase in surface area can be realized by using structured micro channels. In this work, rectangular micro channels containing round pillars of 3 lm in diameter and 50 lm in height are studied. The flow regimes, gas hold-up, and pressure drop are determined for pillar pitches of 7, 12, 17, and 27 lm. Flow maps are presented and compared with flow maps of rectangular and round micro channels without pillars. The Armand correlation predicts the gas hold-up in the pillared micro channel within 3% error. Three models are derived which give the single-phase and the two-phase pressure drop as a function of the gas and liquid superficial velocities and the pillar pitches. For a pillar pitch of 27 lm, the Darcy-Brinkman equation predicts the single-phase pressure drop within 2% error. For pillar pitches of 7, 12, and 17 lm, the Blake-Kozeny equation predicts the single-phase pressure drop within 20%. The two-phase pressure drop model predicts the experimental data within 30% error for channels containing pillars with a pitch of 17 lm, whereas the Lockhart-Martinelli correlation is proven to be nonapplicable for the system used in this work. The open structure and the higher production rate per unit of reactor volume make the pillared micro channel an efficient system for performing heterogeneously catalyzed gas-liquid reactions.

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Gas hold-up and liquid film thickness in Taylor flow in rectangular microchannels

Cited by 56 publications

References 12 publications

Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

Pressure drop of gas–liquid Taylor flow in round micro-capillaries for low to intermediate Reynolds numbers

Gas–liquid dynamics at low Reynolds numbers in pillared rectangular micro channels

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