Research Papers

Heat Transfer in Microchannels—2012 Status and Research Needs

[+] Author and Article Information
Satish G. Kandlikar

Gleason Professor of Mechanical Engineering,
Rochester Institute of Technology,
Rochester, NY 14618
e-mail: sgkeme@rit.edu

Stéphane Colin

Université de Toulouse,
INSA, ICA (Institut Clément Ader),
31077 Toulouse, France
e-mail: stephane.colin@insa-toulouse.fr

Yoav Peles

Mechanical, Aerospace, and Nuclear Engineering,
Rensselaer Polytechnic Institute,
Troy, NY 12180
e-mail: pelesy@rpi.edu

Srinivas Garimella

George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332
e-mail: sgarimella@gatech.edu

R. Fabian Pease

Electrical Engineering Department,
Stanford University,
Stanford, CA 94305
e-mail: pease@stanford.edu

Juergen J. Brandner

Karlsruher Institut fuer Technologie (KIT),
Campus North,
D-76344 Eggenstein-Leopoldshafen,
Karlsruhe, Germany
e-mail: juergen.brandner@kit.edu

David B. Tuckerman

Tuckerman & Associates, Inc.,
Lafayette, CA 94559
e-mail: d.tuckerman@comcast.net

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received July 31, 2012; final manuscript received March 13, 2013; published online July 26, 2013. Assoc. Editor: Zhuomin Zhang.

J. Heat Transfer 135(9), 091001 (Jul 26, 2013) (18 pages) Paper No: HT-12-1415; doi: 10.1115/1.4024354 History: Received July 31, 2012; Revised March 13, 2013

Heat transfer and fluid flow in microchannels have been topics of intense research in the past decade. A critical review of the current state of research is presented with a focus on the future research needs. After providing a brief introduction, the paper addresses six topics related to transport phenomena in microchannels: single-phase gas flow, enhancement in single-phase liquid flow and flow boiling, flow boiling instability, condensation, electronics cooling, and microscale heat exchangers. After reviewing the current status, future research directions are suggested. Concerning gas phase convective heat transfer in microchannels, the antagonist role played by the slip velocity and the temperature jump that appear at the wall are now clearly understood and quantified. It has also been demonstrated that the shear work due to the slipping fluid increases the effect of viscous heating on heat transfer. On the other hand, very few experiments support the theoretical models and a significant effort should be made in this direction, especially for measurement of temperature fields within the gas in microchannels, implementing promising recent techniques such as molecular tagging thermometry (MTT). The single-phase liquid flow in microchannels has been established to behave similar to the macroscale flows. The current need is in the area of further enhancing the performance. Progress on implementation of flow boiling in microchannels is facing challenges due to its lower heat transfer coefficients and critical heat flux (CHF) limits. An immediate need for breakthrough research related to these two areas is identified. Discussion about passive and active methods to suppress flow boiling instabilities is presented. Future research focus on instability research is suggested on developing active closed loop feedback control methods, extending current models to better predict and enable superior control of flow instabilities. Innovative high-speed visualization and measurement techniques have led to microchannel condensation now being studied as a unique process with its own governing influences. Further work is required to develop widely applicable flow regime maps that can address many fluid types and geometries. With this, condensation heat transfer models can progress from primarily annular flow based models with some adjustments using dimensionless parameters to those that can directly account for transport in intermittent and other flows, and the varying influences of tube shape, surface tension and fluid property differences over much larger ranges than currently possible. Electronics cooling continues to be the main driver for improving thermal transport processes in microchannels, while efforts are warranted to develop high performance heat exchangers with microscale passages. Specific areas related to enhancement, novel configurations, nanostructures and practical implementation are expected to be the research focus in the coming years.

Copyright © 2013 by ASME
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Fig. 1

Nusselt number for a fully developed flow in a microtube (a) or in a parallel-plate microchannel and (b) with uniform wall heat flux as a function of Knudsen and modified Brinkman numbers, σP = 1, ζT = 1.67

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Fig. 2

Example of enhancement technique proposed by Steinke and Kandlikar [32]

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Fig. 3

Oblique fin geometry for enhancing single-phase liquid flow. Adapted from Ref. [37].

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Fig. 4

SEM image of one of the offset strip-fin geometries employed by Colgan et al. [39] and Steinke and Kandlikar [40]. Fin length = 250 μm, fin and channel widths = 50 μm, channel depth = 200 μm.

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Fig. 5

Temperature nonuniformity along the coolant flow length for an open gap, a conventional microchannel, and a variable density fin structure. Adapted from Ref. [41].

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Fig. 6

SEM image of the roughness profile on the sidewall of the channel, adapted from Ref. [45]

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Fig. 7

Heat transfer performance of three structured roughness profiles with water, adapted from Ref. [45]

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Fig. 8

The vapor venting microchannel to suppress flow boiling instabilities 0proposed by David et al. [82]

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Fig. 9

A SEM image of the microchannel and the reentrant cavities used by Kuo and Peles to suppress flow boiling instabilities [73]

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Fig. 10

Description of two-phase flow regimes and patterns [90]

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Fig. 11

Comparison of vapor–liquid distribution on a (a) frame and (b) local basis for Tsat = 30  °C, G = 200 kg m−2 s−1 [92]

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Fig. 12

Intermittent flow unit cell [101]

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Fig. 13

Surface microscale cooler for high power electronics cooling obtained with laminar flow. Left: Assembled copper device; Center: Copper device without lid; Right: SEM of internal structure. Reproduced with permission from KIT.

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Fig. 14

Stainless steel microscale heat exchangers for process engineering. From top left clockwise: Crossflow heat exchanger cores of different sizes; a crossflow core coupled to fittings; a heat exchanger for process engineering; a countercurrent/cocurrent design. Reproduced with permission from KIT.




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