Enhancement of Reaction Rates by Segmented Fluid Flow in Capillary Scale Reactors

Ahmed, Batoul; Barrow, David A.; Wirth, Thomas

doi:10.1002/adsc.200505480

Cited by 139 publications

(93 citation statements)

References 40 publications

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“…In the case of multiphase systems, the Reynolds numbers are low, but the flow can be nonlinear due to interactions at the interface between the immiscible fluids (Thorsen et al, 2001). In the case of two-phase flow in microchannels, the interfacial tension (∼ /d) and the viscous forces (∼ · u/d) control the flow patterns because they depend on the channel diameter (Ahmed et al, 2006;Akbar et al, 2003;Kreutzer et al, 2005). The effects of gravity (∼ · g · H) and inertia (∼ · u 2 ) become negligible at the micrometer scale (Atencia and Beebe, 2005).…”

Section: Analysis Of the Flow Patterns Based On Capillary And Reynoldmentioning

confidence: 99%

“…The main problem in the control of flow pattern is due to the flow dependence on the experimental parameters like: the linear velocity (Burns and Ramshaw, 2001), the ratio of the phases, the fluid properties (Burns et al, 1998;Burns and Ramshaw, 1999), the channel geometries and the construction material (Ahmed et al, 2006) of the microreactor. Therefore, all these parameters must be considered simultaneously.…”

Section: Introductionmentioning

confidence: 99%

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Liquid–liquid two-phase flow patterns and mass transfer characteristics in rectangular glass microreactors

Dessimoz

Cavin

Renken

et al. 2008

Chemical Engineering Science

377

255

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The flow of two immiscible fluids was investigated in rectangular glass microchannels with equivalent diameters of 269 and 400 m. Deionised water, dyed toluene and hexane were selected as probe fluids. Flow patterns were obtained for Y-and T-junction of two micro-channels and monitored by a photo-camera. Volumetric velocities of water and organic phase varied between 1 and 6 ml/h. The formation mechanism of slug and parallel flow was studied and the mass transfer performances of two flow patterns were compared. The shape of the interface between the immiscible liquids was controlled by a competition between the viscous forces and the local interfacial tension. The flow patterns could be correlated with the mean Capillary and Reynolds numbers. The mass transfer coefficients for parallel and slug flow were determined using instantaneous neutralisation (acid-base) reaction. The two flow patterns showed the same global volumetric mass transfer coefficients in the range of 0. 2-0. 5 s −1 , being affected mainly by the base concentration in water for parallel flow and by the linear velocity in the case of the slug flow.

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Section: Analysis Of the Flow Patterns Based On Capillary And Reynoldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Liquid–liquid two-phase flow patterns and mass transfer characteristics in rectangular glass microreactors

Dessimoz

Cavin

Renken

et al. 2008

Chemical Engineering Science

377

255

View full text Add to dashboard Cite

show abstract

“…This approach meets the need for accurate, localized temperature data to characterize salient features of droplet evaporation, as called for in past studies. 33,36 In addition, such data are critical to applications in which the droplet temperatures control physical processes other than evaporation, such as voltage-induced modulation of droplet temperatures for biosensing, 37 control of reaction rates in droplet microfluidics, 38,39 and temperature modulation to denature DNA for polymerase chain reactions. 40,41 The methodology is also broadly applicable for characterizing the temperature of curved interfaces.…”

Section: -2mentioning

confidence: 99%

Spatiotemporal infrared measurement of interface temperatures during water droplet evaporation on a nonwetting substrate

Chandramohan

Weibel

Garimella

2017

Applied Physics Letters

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High-fidelity experimental characterization of sessile droplet evaporation is required to understand the interdependent physical mechanisms that drive the evaporation. In particular, cooling of the interface due to release of the latent heat of evaporation, which is not accounted for in simplified vapor-diffusion-based models of droplet evaporation, may significantly suppress the evaporation rate on nonwetting substrates, which support tall droplet shapes. This suppression is counteracted by convective mass transfer from the droplet to the air. While prior numerical modeling studies have identified the importance of these mechanisms, there is no direct experimental evidence of their influence on the interfacial temperature distribution. Infrared thermography is used here to simultaneously measure the droplet volume, contact angle, and spatially resolved interface temperatures for water droplets on a nonwetting substrate. The technique is calibrated and validated to quantify the temperature measurement accuracy; a correction is employed to account for reflections from the surroundings when imaging the evaporating droplets. Spatiotemporally resolved interface temperature data, obtained via infrared thermography measurements, allow for an improved prediction of the evaporation rate and can be utilized to monitor temperature-controlled processes in droplets for various lab-on-a-chip applications.

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“…Ahmed et al 121 used segmented microflow to accelerate the hydrolysis of the acetate (1). Acetonitrile as a solvent together with aqueous sodium hydroxide created a homogeneous system, which was combined with an inert immiscible solvent (hexane) to divide the reaction solution into segments and to achieve intense mixing in the microchannel.…”

Section: Hydrolysis Of P-nitrophenolmentioning

confidence: 99%

“…Ahmed et al 121 investigated the hydrolysis of p-nitrophenyl acetate (1), dissolved in toluene, with aqueous sodium hydroxide as a biphasic reaction as given in the following:…”

Section: Hydrolysis Of P-nitrophenolmentioning

confidence: 99%

Microstructured Reactors for Multiphase Reactions: State of the Art

Kashid

Kiwi‐Minsker

2009

Ind. Eng. Chem. Res.

203

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The manufacture of chemicals in microstructured reactors (MSR) has become recently a new branch of chemical reaction engineering focusing on process intensification and safety. MSR have an equivalent hydraulic diameter up to a few hundreds of micrometers and, therefore, provide high mass-and heat-transfer efficiency increasing the reactor performance drastically, compared to the conventional one. This article provides a comprehensive overview of the state of the art of the MSR applied for multiphase reactions. The reactions are classified based on the number of phases involved: fluid-fluid, fluid-solid, and three phase reactions. In the first part of the review, limitations of conventional reactors are discussed in brief. Furthermore, different types of MSR and their advantages with respect to their conventional counterparts are described. Particular attention is given to the identification of the parameters that control the flow pattern formed in microcapillaries regarding the mass-transfer efficiency. Case studies of various multiphase reactions carried out in MSR are discussed in detail.

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Enhancement of Reaction Rates by Segmented Fluid Flow in Capillary Scale Reactors

Cited by 139 publications

References 40 publications

Liquid–liquid two-phase flow patterns and mass transfer characteristics in rectangular glass microreactors

Liquid–liquid two-phase flow patterns and mass transfer characteristics in rectangular glass microreactors

Spatiotemporal infrared measurement of interface temperatures during water droplet evaporation on a nonwetting substrate

Microstructured Reactors for Multiphase Reactions: State of the Art

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