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Journal ArticleDOI

Review of two-phase flow instabilities in macro- and micro-channel systems

01 Aug 2020-International Journal of Heat and Mass Transfer (Pergamon)-Vol. 157, pp 119738
TL;DR: A systematic overview of all key two-phase instabilities focusing on the fundamental mechanisms leading to their occurrence is provided, with emphasis on how these mechanisms may change depending on whether flow may be classified as macro- or micro-channel.
About: This article is published in International Journal of Heat and Mass Transfer.The article was published on 2020-08-01. It has received 74 citations till now.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a single-connected pore space model was established by reconstructing the real micron CT scanned images of carbonate rocks, and the VOF (volume of fluid) method using FSF (filtered surface force) formulation was adopted on OpenFOAM platform to simulate the oil-water two-phase flow process at the pore scale.

40 citations

Journal ArticleDOI
TL;DR: In this article, the effects of four 90-degree horizontal elbows with different curvature radii (17, 34, 51, and 68 cm) and an identical rectangular cross-section (20 * 34mm) on a gas-liquid slug flow pattern have been studied experimentally and numerically.
Abstract: In the present research, the effects of four 90-degree horizontal elbows with different curvature radii (17, 34, 51, and 68 cm) and an identical rectangular cross-section (20 * 34 mm) on a gas–liquid slug flow pattern have been studied experimentally and numerically. Gas and liquid superficial velocities in numerical and experimental parts were set in 2.5 m/s and 0.44 m/s, respectively. In the computational fluid dynamics section, the distribution of volume fraction, velocity, pressure, turbulence intensity, and swirling intensity parameters were investigated using the VoF model and the SST k-ω method. Experimental studies were conducted utilizing pressure data and signal processing tools to study the dominant frequency of slug flow alongside bandwidth distribution as well as the Shannon entropy. The results exhibited that although the dominant frequency of slug flow did not change after passing the 90-degree elbow, the frequency signal's bandwidth increased. In this regard, the application of Shannon entropy quantity revealed that the frequency distribution signal experienced a greater increase in bandwidth as the elbows’ curvature radius increases. The turbulent intensity of the elbows’ outlet reveals that by increasing the curvature radius, the flow field behaves smoother. Also, swirling intensity distribution shows that decreasing the elbow radius leads to increment in the swirling intensity.

32 citations

Journal ArticleDOI
TL;DR: In this article, a three-dimensional numerical study on two-phase flow boiling in rectangular microchannel with wavy vertical wall configuration is considered that can be utilized for heat dissipation in high flux electronics devices.

28 citations

Journal ArticleDOI
01 Mar 2022
TL;DR: In this paper , the effects of four 90-degree horizontal elbows with different curvature radii (17, 34, 51, and 68 cm) and an identical rectangular cross-section (20 * 34 mm) on a gas-liquid slug flow pattern have been studied experimentally and numerically.
Abstract: In the present research, the effects of four 90-degree horizontal elbows with different curvature radii (17, 34, 51, and 68 cm) and an identical rectangular cross-section (20 * 34 mm) on a gas–liquid slug flow pattern have been studied experimentally and numerically. Gas and liquid superficial velocities in numerical and experimental parts were set in 2.5 m/s and 0.44 m/s, respectively. In the computational fluid dynamics section, the distribution of volume fraction, velocity, pressure, turbulence intensity, and swirling intensity parameters were investigated using the VoF model and the SST k-ω method. Experimental studies were conducted utilizing pressure data and signal processing tools to study the dominant frequency of slug flow alongside bandwidth distribution as well as the Shannon entropy. The results exhibited that although the dominant frequency of slug flow did not change after passing the 90-degree elbow, the frequency signal's bandwidth increased. In this regard, the application of Shannon entropy quantity revealed that the frequency distribution signal experienced a greater increase in bandwidth as the elbows’ curvature radius increases. The turbulent intensity of the elbows’ outlet reveals that by increasing the curvature radius, the flow field behaves smoother. Also, swirling intensity distribution shows that decreasing the elbow radius leads to increment in the swirling intensity.

24 citations

References
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Journal ArticleDOI
Issam Mudawar1
TL;DR: This paper explores the recent research developments in high-heat-flux thermal management and demonstrates that, while different cooling options can be tailored to the specific needs of individual applications, system considerations always play a paramount role in determining the most suitable cooling scheme.
Abstract: This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, microchannel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of individual applications, system considerations always play a paramount role in determining the most suitable cooling scheme. It is also shown that extensive fundamental electronic cooling knowledge has been amassed over the past two decades. Yet there is now a growing need for hardware innovations rather than perturbations to those fundamental studies. An example of these innovations is the cooling of military avionics, where research findings from the electronic cooling literature have made possible the development of a new generation of cooling hardware which promise order of magnitude increases in heat dissipation compared to today's cutting edge avionics cooling schemes.

824 citations

Journal ArticleDOI
TL;DR: In this paper, a systematic experimental investigation of two-phase flow patterns in microchannels was the objective of this study, using air and water, experiments were conducted in circular micro channels with 1.1 and 1.45mm inner diameters, and in semi-triangular (triangular with one corner smoothed) cross-sections with hydraulic diameters 1.09 and 149mm.

822 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe aspects of the work relating to boiling in single, small-diameter tubes as part of a study of compact two-phase heat exchangers.

739 citations


"Review of two-phase flow instabilit..." refers background in this paper

  • ...Study Transition Criteria Notes Kew & Cornwell, 1997 [62] Co > 0.5 for microscale Co 0.5 for macroscale Early transition criteria, state if hydraulic diameter is less than half the capillary length, flow is confined (micro-channel), more than half, flow is not confined (mini/macro-channel)....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the authors identify the causes and mechanisms of thermal-hydrodynamic instabilities in boiling flow in a water-cooled reactor, an evaporator, or an electronic cooling system.

708 citations

Journal ArticleDOI
TL;DR: In this article, an experimental study of heat transfer and flow regimes during condensation of refrigerants in horizontal tubes was conducted, where measurements were made in smooth, round tubes with diameters ranging from 3.14 mm to 7.04 mm.
Abstract: An experimental study of heat transfer and flow regimes during condensation of refrigerants in horizontal tubes was conducted. Measurements were made in smooth, round tubes with diameters ranging from 3.14 mm to 7.04 mm. The refrigerants tested were R-12, R-22, R-134a, and near-azeotropic blends of R-32/R-125 in 50 percent/50 percent and 60 percent/40 percent compositions. The study focused primarily on measurement and prediction of condensing heat transfer coefficients and the relationship between heat transfer coefficients and two-phase flow regimes. Flow regimes were observed visually at the inlet and outlet of the test condenser as the heat transfer data were collected. Stratified, wavy, wavy annular, annular, annular mist, and slug flows were observed. True mist flow without a stable wall film was not observed during condensation tests. The experimental results were compared with existing flow regime maps and some corrections are suggested. The heat transfer behavior was controlled by the prevailing flow regime. For the purpose of analyzing condensing heat transfer behavior, the various flow regimes were divided into two broad categories of gravity-dominated and shear-dominated flows. In the gravity dominated flow regime, the dominant heat transfer mode was laminar film condensation in the top of the tube. This regime was characterized by heat transfer coefficients that depended on the wall-to-refrigerant temperature difference but were nearly independent of mass flux. In the shear-dominated flow regime, forced-convective condensation was the dominant heat transfer mechanism. This regime was characterized by heat transfer coefficients that were independent of temperature difference but very dependent on mass flux and quality. Heat transfer correlations that were developed for each of these flow regimes successfully predicted data from the present study and from several other sources.

673 citations