Density-induced asymmetric pair of Dean vortices and its effects on mass transfer in a curved microchannel with two-layer laminar stream

Xuan, Jin; Leung, Michael K.H.; Leung, Dennis Y.C.; Ni, Meng

doi:10.1016/j.cej.2011.01.011

Cited by 22 publications

(9 citation statements)

References 23 publications

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“…(2) Re = vD h , by the variation of the Reynolds number for a channel with given radius of curvature. Xuan et al (2011) already studied the mass transport of a two-layer laminar flow in curved microchannels using different Re and channel aspect ratios by computational fluid dynamic simulations. They found that at properly selected parameters the mass transport at the liquid-liquid interface can be reduced, so that curved microchannels can be used also for co-laminar microfluidic devices, such as microfluidic fuel cells (Xuan et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Xuan et al (2011) already studied the mass transport of a two-layer laminar flow in curved microchannels using different Re and channel aspect ratios by computational fluid dynamic simulations. They found that at properly selected parameters the mass transport at the liquid-liquid interface can be reduced, so that curved microchannels can be used also for co-laminar microfluidic devices, such as microfluidic fuel cells (Xuan et al 2011). However a detailed study of curved microfluidic fuel cells as a novel, low cost and more efficient fuel cell, including the fluid dynamics and the electrochemical kinetics is still missing.…”

Section: Introductionmentioning

confidence: 99%

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Passive control of the concentration boundary layer in microfluidic fuel cells using Dean vortices

Rösing

Schildhauer

König

et al. 2019

Microfluid Nanofluid

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Microfluidic fuel cells are limited by the formation of concentration boundary layers at the electrodes, resulting in low power density and low fuel utilization. This work demonstrates a novel method to enhance the diffusion-limited mass transport by decreasing the size of the concentration boundary layer using Dean vortices. These vortices are induced by a curved microchannel and enhance the mass transport of fresh reactant towards the electrodes. Numerical simulations were performed to show the influence of the Dean vortices on the performance of a microfluidic fuel cell. Furthermore, a curved microfluidic device with segmented electrodes was fabricated, which allows to experimentally investigate the effect of the enhanced diffusion-limited mass transport on the current density of a model redox couple and thus to prove the concept and the numerical results. It is shown that the Dean vortices, evolving in the curved channel, cause a convective transport of fresh solution towards the electrodes yielding a high current density and resulting in an improvement of 30% using a curved microfluidic fuel cell instead of a straight one. On condition that diffusive and convective mass transport are well-balanced, this approach promises not only a higher power density, but also a much higher fuel utilization.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Passive control of the concentration boundary layer in microfluidic fuel cells using Dean vortices

Rösing

Schildhauer

König

et al. 2019

Microfluid Nanofluid

View full text Add to dashboard Cite

show abstract

“…A similar work was done by Xuan et al. 7 to investigate the phenomenon of a two layered laminar flow in a curved microchannel. Their numerical results revealed that due to the density difference between the two fluids, asymmetric pair of Dean vortices are formed.…”

Section: Introductionmentioning

confidence: 82%

The effects of longitudinal fins on thermal performance of a curved microchannel: A numerical study

Soltanipour

Pourmahmoud

Mirzaee

2014

Proceedings of the Institution of Mechanical Engineers, Part C:

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In this paper, flow structure, heat transfer, and entropy generation in an internally finned curved microchannel are studied. Three dimensional numerical simulations are performed using a finite volume approach. The effect of fin height, mass flow rate, and curvature radius on heat transfer enhancement and pressure losses are explored. The field synergy principle is employed to explain the heat transfer enhancement mechanism. The second law analysis is also performed to indicate the influence of fins on the entropy generation in the curved microchannel. It is found that regardless of mass flow rate, the fin height of a* = 0.35 provides the maximum heat transfer enhancement. Numerical results reveal that the ratio of heat transfer coefficient (and pressure drop) of finned microchannel to unfinned microchannel depends on the curvature radius and mass flow rate. The field synergy principle and the second law analysis confirm that for the fin height of a* = 0.35, the microchannel has the optimal thermal performance.

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“…In addition to the two parameters mentioned above, microchannel geometry, wall property, interfacial tension between two fluids and interstream mass diffusion were also discovered to influence the interfacial reorientation. Beyond simple interfacial tilting, laminar flow of density-stratified fluids together with Dean vortices have been shown to generate different types of curved interfaces (Xuan et al 2011). The Dean force in side-by-side two fluids system engenders a distorted but symmetric interface (Yamaguchi et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Gravity-induced swirl of nanoparticles in microfluidics

2013

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Parallel flows of two fluids in microfluidic devices are used for miniaturized chemistry, physics, biology and bioengineering studies, and the streams are often considered to remain parallel. However, as the two fluids do not always have the same density, interface reorientation induced by density stratification is unavoidable. In this paper, flow characteristics of an aqueous polystyrene nanofluid and a sucrose-densified aqueous solution flowing parallel in microchannels are examined. Nanoparticles 100 nm in diameter are used in the study. The motion of the nanoparticles is simulated using the Lagrangian description and directly observed by a confocal microscope. Matched results are obtained from computational and empirical analysis. Although solution density homogenizes rapidly resulting from a fast diffusion of sucrose in water, the nanofluid is observed to rotate for an extended period. Angular displacement of the nanofluid depends on the ratio of gravitational force to viscous force, Re/Fr2, where Re is the Reynolds number and Fr is the Froude number. In the developing region at the steady state, the angular displacement is related to y/Dh, the ratio between distance from the inlet and the hydraulic diameter of the microfluidic channel. The development of nanofluid flow feature also depends on h/w, the ratio of microfluidic channel’s height to width. The quantitative description of the angular displacement of nanofluid will aid rational designs of microfluidic devices utilizing multistream, multiphase flows.

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Density-induced asymmetric pair of Dean vortices and its effects on mass transfer in a curved microchannel with two-layer laminar stream

Cited by 22 publications

References 23 publications

Passive control of the concentration boundary layer in microfluidic fuel cells using Dean vortices

Passive control of the concentration boundary layer in microfluidic fuel cells using Dean vortices

The effects of longitudinal fins on thermal performance of a curved microchannel: A numerical study

Gravity-induced swirl of nanoparticles in microfluidics

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