Significant Nusselt number increase in microchannels with a segmented flow of two immiscible liquids: An experimental study

Asthana, Ashish; Zinovik, Igor; Weinmueller, Christian; Poulikakos, Dimos

doi:10.1016/j.ijheatmasstransfer.2010.11.048

Cited by 75 publications

(48 citation statements)

References 24 publications

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“…It is seen that there is enhancement of the heat transfer coefficient in the two-phase systems compared to the single-phase organic liquid. This enhancement is seen to be up to seven times the single-phase heat transfer coefficient in the case of dodecane, similar to results observed in microchannels by Asthana et al (2011) and Janes et al (2010), particularly for segmented two-phase flow. With curved channels such as in spiral plate heat exchangers, changes in flow patterns from smoothly stratified flow to more mixed flow are expected at lower velocities, resulting in enhanced heat transfer even at low velocities.…”

Section: Two-phase Heat Transfer Coefficientssupporting

confidence: 88%

Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger

Sathiyan

Rangarajan

Ramachandran³

2013

Braz. J. Chem. Eng.

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-This work presents new predictive correlations for heat transfer to immiscible liquid-liquid mixtures in a spiral plate heat exchanger. Liquid-liquid heat transfer studies were carried out in spiral plate heat exchangers for the water-octane, water-kerosene, and water-dodecane systems. For each composition of the mixture, the mass flow rate of the cold fluid was varied, keeping that of the hot fluid and the fluid inlet temperatures constant. Two-phase cold flow rates were in the laminar range, while the hot fluid flow was turbulent. Calculations of the LMTD (log mean temperature difference) correction factor showed that the flow was countercurrent. Heat transfer coefficients of the two-phase liquids were found to be strongly dependent on the composition of the liquid mixture and exhibited abrupt transitions as a function of the compositions. Given the absence of predictive correlations in the literature that sufficiently capture this compositiondependence, new empirical correlations were developed using part of the experimental data, with the composition of the cold fluid as an explicit variable. Statistical analysis of the regression yielded satisfactory results. The correlations were tested against the rest of the experimental data and were found to predict heat transfer coefficients within ± 15%. These preliminary studies should be useful in designing compact exchangers for handling two-phase water-organics mixtures.

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Section: Two-phase Heat Transfer Coefficientssupporting

confidence: 88%

Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger

Sathiyan

Rangarajan

Ramachandran³

2013

Braz. J. Chem. Eng.

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“…Many experiments have been performed to measure the heat transfer enhancement in microchannels with droplets, slugs, or plugs [9]. Some experiments used cylindrical microtubes [10,11,12,13], while others used rectangular microchannels [14,15,16,17]. Their experimental results showed significant enhancement of heat transfer when comparing with single phase flow, and the Nusselt numbers are several times higher than the single phase counterpart.…”

Section: Introductionmentioning

confidence: 99%

“…Regarding the geometries of microchannels, most simulations were performed with cylindrical microcapillaries [18,20,22,21,23,19] or two dimensional (2D) microchannels [8], where the three dimensional (3D) effect on the flow and on the heat transfer process cannot be considered. However, in most microchannel heat exchangers, the microchannels usually have rectangular or other non-circular cross sections [14,15,16,17]. When droplets move in microchannels, liquid films often form beneath the droplets.…”

Section: Introductionmentioning

confidence: 99%

Three dimensional features of convective heat transfer in droplet-based microchannel heat sinks

Che

Wong

Nguyen

et al. 2015

International Journal of Heat and Mass Transfer

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Convective heat transfer in droplet-based microchannel heat sinks can be enhanced by the recirculating vortices due to the presence of interfaces. In rectangular microchannels, the three dimensional structures of the vortices and the 'gutters' (i.e., the space between the curved droplet interface and the corner of the microchannel) can significantly affect the heat transfer process. Numerical simulations of the heat transfer process are performed to study the three dimensional features in droplet-based microchannel heat sinks. The finite volume method and the level set method are employed to simulate the flow dynamics, the evolution of the interface, and the heat transfer. The results show that the 'gutters' can hinder the heat transfer process because of its parallel flow, whereas the recirculating flow in droplets and in slug regions between successive droplets can enhance the heat transfer by advecting hot fluid towards the center of the droplets/slugs and advecting fresh fluid towards the wall of the channel. The effects of the length of droplets, the aspect ratio of the channel cross sections, and the Peclet number are analyzed.

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“…These devices and systems generate large heat fluxes at component level, which is the result of two main trends: the escalation of power dissipation from components; and the reduction in available surface area from which to transfer heat. Today's microprocessors generate heat fluxes of order 100 W/cm 2 , while in high end microprocessors this value is closer to 300 W/cm 2 [1]. Consequently, a significant body of research exists focused solely on the development of high heat flux removal technologies.…”

Section: Introductionmentioning

confidence: 99%

Local Nusselt number enhancements in liquid–liquid Taylor flows

Eain

Egan

Punch

2015

International Journal of Heat and Mass Transfer

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a b s t r a c tThermal management has emerged as a critical requirement to ensure the performance and reliability of electronic devices and systems. System level heat fluxes are approaching the limits of conventional forced air cooling, and there is a need to develop alternative cooling techniques for devices such as processors, power amplifiers and laser arrays. This paper examines the potential heat transfer enhancements of a two phase liquid-liquid Taylor flow regime. The primary focus of the work was to examine the influence of slug length and carrier phase variations on the local Nusselt numbers. An experimental facility was designed and commissioned to subject the flow to a constant heat flux boundary condition, a boundary condition commonly encountered in thermal management applications. Local temperature measurements were acquired using a high resolution infrared thermography system. Experiments were carried out over slug length, Capillary and Prandtl numbers that spanned several orders of magnitude in a minichannel geometry. Reductions in carrier slug length and increases in dispersed slug length were found to augment the heat transfer rates, with the greatest enhancements observed in flows with carrier slug lengths approaching the channel diameter. The thickness of the liquid film separating the dispersed slugs from the heated capillary walls was found to play a significant role in the removal of heat, with increases in film thickness resulting in a reduction in the heat transfer rates. Based on the characteristics identified, a novel correlation is proposed to model the flow in the thermally developing and fully-developed regions.

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Significant Nusselt number increase in microchannels with a segmented flow of two immiscible liquids: An experimental study

Cited by 75 publications

References 24 publications

Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger

Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger

Three dimensional features of convective heat transfer in droplet-based microchannel heat sinks

Local Nusselt number enhancements in liquid–liquid Taylor flows

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