Significant heat transfer enhancement in microchannels with herringbone-inspired microstructures

Marschewski, Julian; Brechbühler, Raphael; Jung, Stefan; Ruch, Patrick; Michel, Bruno; Poulikakos, Dimos

doi:10.1016/j.ijheatmasstransfer.2015.12.039

Cited by 67 publications

(26 citation statements)

References 45 publications

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“…Equipping rectangular channels with vortex generators (VGs) has been demonstrated to be a promising method to passively augment the heat transfer performance [10][11][12][13][14]. Vortex generators with various shapes such as wing [15], winglet [16], rib [17,18], pin fin [19] and surface protrusions [20][21][22][23] have been utilised for heat transfer enhancement applications. The pressure difference between two sides of VGs leads to flow separation from the side edges, which generates longitudinal, transverse and horseshoe vortices [24].…”

Section: Introductionmentioning

confidence: 99%

Laminar convective heat transfer of shear-thinning liquids in rectangular channels with longitudinal vortex generators

Ebrahimi

Naranjani

Milani

et al. 2017

Chemical Engineering Science

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Heat and fluid flow in a rectangular channel heat sink equipped with longitudinal vortex generators have been numerically investigated in the range of Reynolds numbers between 25 and 200. Aqueous solutions of carboxymethyl cellulose (CMC) with different concentrations (200-2000 ppm), which are shear-thinning non-Newtonian liquids, have been utilised as working fluid. Three-dimensional simulations have been performed on a plain channel and a channel with five pairs of vortex generators. The channels have a hydraulic diameter of 8 mm and are heated by constant wall temperature. The vortex generators have been mounted at different angles of attack and locations inside the channel. The shear-thinning liquid flow in rectangular channels with longitudinal vortex generators are described and the mechanisms of heat transfer enhancement are discussed. The results demonstrate a heat transfer enhancement of 39-188% using CMC aqueous solutions in rectangular channels with LVGs with respect to a Newtonian liquid flow (i.e. water). Additionally, it is shown that equipping rectangular Page 2 of 40 channels with LVGs results in an enhancement of 24-135% in heat transfer performance visà-vis plain channel. However, this heat transfer enhancement is associated with larger pressure losses. For the range of parameters studied in this paper, increasing the CMC concentration, the angle of attack of vortex generators and their lateral distances leads to an increase in heat transfer performance. Additionally, heat transfer performance of rectangular channels with longitudinal vortex generators enhances with increasing the Reynolds number in the laminar flow regime.

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Section: Introductionmentioning

confidence: 99%

Laminar convective heat transfer of shear-thinning liquids in rectangular channels with longitudinal vortex generators

Ebrahimi

Naranjani

Milani

et al. 2017

Chemical Engineering Science

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“…This scaling is much steeper than in a purely laminar flow, in which the limiting current follows the theoretically predicted 1/3 regime. In addition, we showed that the benefits of flow promoters in terms of improved heat transfer outperform the penalty of higher pressure losses [30]. Due to the analogy between heat and mass transfer we expect this finding to hold true for the enhancement of performance of microfluidic redox flow cells in the presence of flow promoters.…”

Section: Introductionmentioning

confidence: 53%

“…We experimentally quantify the performance benefits of such a redox flow cell microsystem with integrated flow promoters. [29,30].…”

Section: Introductionmentioning

confidence: 99%

On the mass transfer performance enhancement of membraneless redox flow cells with mixing promoters

Marschewski

Ruch

Ebejer

et al. 2017

International Journal of Heat and Mass Transfer

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Membraneless flow cells for electrochemical energy conversion exploit the laminarity of microscale flows to avoid undesirable mixing of reactants. To increase the performance of microfluidic redox flow cells we employ herringbone-inspired flow promoters, thereby increasing convection of each individual species to the electrodes, while minimizing reactant mixing. Polarization curves from electrochemical discharge measurements with a dilute anthraquinone / iron redox system reveal that the presence of flow promoters substantially boosts device performance. Mass transfer enhancement for devices with flow promoters is demonstrated through both higher limiting currents and increased power density; the former is more than double compared to a plain reference microchannel for Reynolds numbers of Re > 155. The chaotic mixing effect induced by the flow promoters becomes also apparent in the scaling regimes, the limiting currents are proportional to Re 0.58 instead of Re 1/3 (as for purely laminar flow). Further, we quantify the area specific resistance (ASR) of the electrolyte in our membraneless devices finding a reduction of more than one order of magnitude compared to the ASR of conventional membranes employed in redox flow cells. Overcoming mass transfer limitations, this work highlights the necessity of passive mixers in significantly raising the performance of microfluidic flow cells.

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“…As it is reported in numerous publications, flow chemistry has proven useful as a way of controlling chemical reactions in general and specifically for reactions which are otherwise difficult to control [1][2][3][4][5][6]. Safety concerns, such as heat transfer, are lower in microchannels, because of the small volumes employed [7][8][9][10]. In addition, microreactors and especially segmented flows offer the ability to precisely manipulate the reactant concentrations and the residence time of a chemical reaction travelling through a channel.…”

Section: Introductionmentioning

confidence: 99%

Opening of New Synthetic Routes Using Segmented Microflow in Multistep Syntheses

et al. 2017

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The application of microfluidics in organic chemistry is a valuable tool to access new synthesis pathways and to break limitations set by traditional batch chemistry. In the past, the majority of research focused on solving problems associated with individual reactions. It is necessary to advance the field by incorporating flow chemistry in longer multistep syntheses to open more direct paths towards complicated compounds. Several strategies were developed to meet the demands of a four‐step synthesis, which includes biphasic nitrations, gaseous substrates, and very fast reactions on multifunctional molecules. A unique micro flow setup was applied in each reaction to meet its specific requirements.

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Significant heat transfer enhancement in microchannels with herringbone-inspired microstructures

Cited by 67 publications

References 45 publications

Laminar convective heat transfer of shear-thinning liquids in rectangular channels with longitudinal vortex generators

Laminar convective heat transfer of shear-thinning liquids in rectangular channels with longitudinal vortex generators

On the mass transfer performance enhancement of membraneless redox flow cells with mixing promoters

Opening of New Synthetic Routes Using Segmented Microflow in Multistep Syntheses

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