Interfacial mass transport in steady three-dimensional flows in microchannels

Kirtland, Joseph D.; Siegel, Corey R; Stroock, Abraham D.

doi:10.1088/1367-2630/11/7/075028

Cited by 13 publications

(11 citation statements)

References 45 publications

(81 reference statements)

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“…3) The measured rates match quantitatively with the predictions of our modified Graetz theory 34,35 with no adjustable parameters: the prefactors of the best fits lines in Figure 20(c) match the predictions within 20%; the exponents (-1/3) are those predicted.…”

Section: Esupporting

confidence: 70%

“…Enhancement of rates with three-dimensional laminar flows Our analysis predicts 34,35 that the introduction of three-dimensional (3-D) flows within laminar systems can provide significantly higher rates of interfacial transfer. To test our predictions quantitatively, we have worked in microfluidic potential cells (Figure 20(a)) with structured electrodes (Figure 20(b)).…”

Section: Ementioning

confidence: 94%

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Transport Phenomena and Interfacial Kinetics in Planar Microfluidic Membraneless Fuel Cells

Abruña

2013

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Abstract:Our work is focused on membraneless laminar flow fuel cells, an unconventional fuel cell technology, intended to create a system that not only avoids most typical fuel cell drawbacks, but also achieves the highest power density yet recorded for a non-H 2 fuel cell. We have employed rigorous electrochemistry to characterize the high-energydensity fuel BH 4 -, providing important mechanistic insight for anode catalyst choice and avoiding deleterious side reactions. Numerous fuel cell oxidants, used in place of O 2 , are compared in a detailed, uniform manner, and a powerful new oxidant, cerium ammonium nitrate (CAN), is described. The high-voltage BH 4 -/CAN fuel/oxidant combination is employed in a membraneless, room temperature, laminar-flow fuel cell, with herringbone micromixers which provide chaotic-convective flow which, in turn, enhances both the power output and efficiency of the device. We have also been involved in the design of a scaled-up version of the membraneless laminar flow fuel cell intended to provide a 10W output. Research FindingsA.Electroanalytical investigation of borohydride (BH 4 -): Oxidation mechanism, best catalysts, and performance optimization.Our search for a highly soluble fuel for microfluidic fuel cell applications quickly focused on BH 4 -, most commonly used as its sodium salt, NaBH 4 . This compound has considerable solubility in aqueous solutions (>14 M), a high electron recovery per molecule (8e -, Reaction 1), a very low potential for oxidation in base (-1.44 V vs. Ag/AgCl), and extremely fast kinetics at room temperature:Thus, it has approximately the same low onset potential for oxidation as H 2 , allowing for high voltage systems. However, because of its very high solubility, about 14,000 times that of H 2 , it can have a theoretical maximum current density that is multiple orders of Reaction E°' (V vs. Ag/AgCl, 1M NaOH)

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Section: Esupporting

confidence: 70%

Section: Ementioning

confidence: 94%

Transport Phenomena and Interfacial Kinetics in Planar Microfluidic Membraneless Fuel Cells

Abruña

2013

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“…mass or heat) at solid-liquid boundaries in laminar channel flows is a fundamental transport phenomenon found in numerous applications. Mass transfer applications include: chemical (Zhang et al 1996;Gervais & Jensen 2006;Kirtland et al 2009) and biological (Vijayendran et al 2003;Squires et al 2008;Hansen et al 2012) microfluidic reactors and sensors, membrane extraction techniques (Jönsson & Mathiasson 2000;Marczak et al 2006), micro-mixers (Kamholz et al 1999;Ismagilov et al 2000;Kamholz & Yager 2001Stone et al 2004;Jiménez 2005;Capretto et al 2011), membraneless electrochemical fuel cells (Ferrigno et al 2002;Cohen et al 2005;Braff et al 2013), cross-flow membrane filtration (Porter 1972;Bowen & Jenner 1995;Visvanathan et al 2000;Herterich et al 2015), crystal dissolution (Bisschop & Kurlov 2013), aquifer remediation (Borden & Kao 1992;Kahler & Kabala 2016), and cleaning (Wilson 2005;Fryer & Asteriadou 2009;Lelieveld et al 2014;Pentsak et al 2019) and decontamination (Fitch et al 2003;Settles 2006) in channels. Heat transfer applications include: film cooling (Acharya & Kanani 2017), heat exchangers (Kakaç & Liu 2002;Ayub 2003), and cooling and heating in micro-channels (Sobhan & Garimella 2001;Avelino & Kakaç 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Also, scalar transfer at the boundary is often a critical rate-limiting step compared to other processes, particularly for mass transfer owing to low mass diffusivities compared to advection or reaction rates as commonly found in applications (e.g. Gervais & Jensen 2006;Squires et al 2008;Kirtland et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional advective–diffusive boundary layers in open channels with parallel and inclined walls

Etzold

Landel

Dalziel

2020

International Journal of Heat and Mass Transfer

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We study the steady laminar advective transport of a diffusive passive scalar released at the base of narrow three-dimensional longitudinal open channels with non-absorbing side walls and rectangular or truncatedwedge-shaped cross-sections. The scalar field in the advective-diffusive boundary layer at the base of the channels is fundamentally three-dimensional in the general case, owing to a three-dimensional velocity field and differing boundary conditions at the side walls. We utilise three-dimensional numerical simulations and asymptotic analysis to understand how this inherent three-dimensionality influences the advective-diffusive transport as described by the normalised average flux, the Sherwood Sh or Nusselt numbers for mass or heat transfer, respectively. We show that Sh is well approximated by an appropriately formulated two-dimensional calculation, even when the boundary layer structure is itself far from two-dimensional. This important result can significantly simplify the modelling of many laminar advection-diffusion scalar transfer problems: the cleaning or decontamination of confined channels, or transport processes in chemical or biological microfluidic devices. The different transport regimes found depend on the channel geometry and a characteristic Péclet number Pe based on the ratio of the cross-channel diffusion time and the longitudinal advection time. We develop asymptotic expressions for Sh in the various limiting regimes, which mainly depend on the confinement of the boundary layer in the lateral and base-normal directions. In the case of truncated wedge channels, further regimes are identified owing to curvature effects, which we capture through a curvaturerescaled Péclet number. In all cases, we offer a comparison between our three-dimensional simulations, the asymptotic results and our two-dimensional simplifications, and can thus quantify the error in the flux from the simplified calculations.

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“…Kirtland et al has presented a detailed theoretical prediction of the mass transfer rates across moving interfaces and across internal interfaces between convectively disconnected sets in the flows. He extended the modified Graetz behavior to low Reynold's number laminar flows (Kirtland et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Bilayer staggered herringbone micro-mixers with symmetric and asymmetric geometries

Choudhary

Bhakat

Singh

et al. 2010

Microfluid Nanofluid

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Micro-mixing is an important research area for various applications in sensing and diagnostics. In this paper, we present a performance comparison of several different passive micromixer designs based on the idea of staggered herringbone mixers (SHM). The working principle in such designs includes the formation of centers of flow rotation thus leading to multiple laminations with decreasing sizes of the lamellae as the flow passes over staggered structures. We have realized different layout designs of staggered herringbones inside micro-channels and compared their mixing performance. An overall reduction in mixing time and length has been observed as the degree of asymmetry within these structures is increased. The layouts of these staggered structures are based on herringbone bilayers wherein these layers are positioned on the top and bottom walls of a micro-channel. Fluorescence microscopy and computational fluid dynamics (CFD) based modeling have been used to observe the extent of mixing and understand the reasons behind the enhanced mixing effects. We have further varied the degree of asymmetry of the herringbone bilayers and investigated mixing as a function of the asymmetry. We have developed a novel microfabrication strategy to realize these micro-devices using an inexpensive non-photolithographic technique which we call micro-replication by double inversion (MRDI). The paper basically attempts to develop an overall understanding of the mixing process by letting two fluids flow pass over a variety of asymmetric structures.Keywords Micromixer Á Micromixing Á Staggered herringbones Á Microfabrication Á Micro-replication by double inversion (MRDI) Á Bilayer Á Asymmetry

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Interfacial mass transport in steady three-dimensional flows in microchannels

Cited by 13 publications

References 45 publications

Transport Phenomena and Interfacial Kinetics in Planar Microfluidic Membraneless Fuel Cells

Transport Phenomena and Interfacial Kinetics in Planar Microfluidic Membraneless Fuel Cells

Three-dimensional advective–diffusive boundary layers in open channels with parallel and inclined walls

Bilayer staggered herringbone micro-mixers with symmetric and asymmetric geometries

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