Experimental and theoretical studies of critical heat flux of flow boiling in microchannels with microbubble-excited high-frequency two-phase oscillations

Li, Wenming; Yang, Fanghao; Alam, Tamanna; Khan, Jamil A.; Li, Chen

doi:10.1016/j.ijheatmasstransfer.2015.04.061

Cited by 23 publications

(12 citation statements)

References 53 publications

(101 reference statements)

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“…Using the results in the two-nozzle configuration 29,30 as a baseline, Figure 2 summarizes the major enhancements obtained in this study. Figure 2(a) shows that a peak CHF of 1016 W/cm 2 is obtained at a moderate mass velocity of 680 kg/m 2 s, meaning a $63% enhancement compared to the baseline at a mass velocity of 750 kg/m 2 s. 22 Considering the pumping power budget, the CHF enhancement is more pronounced, approximately 95% higher for a given pressure drop, as illustrated in Figure 2(b). Figure 2(c) shows that a sustained HTC of 131 kW/m 2 K at a mass velocity of 680 kg/m 2 s is achieved, 30% higher than that at a mass flux of 1350 kg/m 2 s on the baseline near CHF conditions.…”

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confidence: 91%

“…[18][19][20][21] Inlet restrictors were considered as one of the most effective ways to improve CHF, 8 however, at a cost of pressure drop. The state of the art CHF enhancement techniques have been reviewed by Li et al 22 A CHF higher than 30 kW/cm 2 has been achieved in microtube flow boiling at a mass velocity of 38 111 kg/m 2 s with an exit vapor quality less than 0.1. 23 Most recently, a tapered microchannel configuration has been developed and demonstrated a CHF of 1070 W/cm 2 at an inlet mass velocity of 2624 kg/m 2 s with a low pressure drop of 30 kPa owing to the increased liquid inertia force and vapor removal capability.…”

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confidence: 99%

“…The measurement uncertainties of mass flux, pressure, voltage, current, temperature, and microfabrication resolution are 61%, 61.5%, 60.5%, 60.5%, 61 C, and 3 lm, respectively. 22 Uncertainty propagations are calculated using methods developed by Kline and McClintock. 31 Uncertainties of the present CHF, average HTC, and pressure drop have been estimated to be less than 610 W/cm 2 , 60.3 kW/m 2 k, and 5 kPa, respectively.…”

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confidence: 99%

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Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities

Alam

et al. 2017

Applied Physics Letters

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In a microchannel system, a higher mass velocity can lead to enhanced flow boiling performances, but at a cost of two-phase pressure drop. It is highly desirable to achieve a high heat transfer rate and critical heat flux (CHF) exceeding 1 kW/cm2 without elevating the pressure drop, particularly, at a reduced mass velocity. In this study, we developed a microchannel configuration that enables more efficient utilization of the coolant through integrating multiple microscale nozzles connected to auxiliary channels as well as microscale reentry cavities on sidewalls of main microchannels. We achieved a CHF of 1016 W/cm2 with a 50% less mass velocity, i.e., 680 kg/m2s, compared to the two-nozzle configuration developed in our previous studies. Two primary enhancement mechanisms are: (a) the enhanced global liquid supply by four evenly distributed micronozzles, particularly near the outlet region and (b) the effective management of local dryout by the capillary flow-induced sustainable thin liquid film resulting from an array of microscale cavities. A significantly improved heat transfer coefficient of 131 kW/m2 K at a mass velocity of 680 kg/m2s is attributed to the enhanced nucleate boiling, the established capillary/thin film evaporation, and the induced advection from the present microchannel configuration. All these significant enhancements have been achieved with a ∼55% lower two-phase pressure drop.

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Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities

Alam

et al. 2017

Applied Physics Letters

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“…Research on the impact of periodic dynamic instabilities in systems with phase transitions on two-phase condensing flow in minichannels has already been carried out and described for currently withdrawn refrigerants [12,[14][15][16][17][18][19][20][21][22][23].…”

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confidence: 99%

Regression Model of Dynamic Pulse Instabilities during Condensation of Zeotropic and Azeotropic Refrigerant Mixtures R404A, R448A and R507A in Minichannels

2022

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This paper presents experimental research and mathematical modeling data concerning the impact of unit dynamic instabilities on the phase-transition condensation processes of the zeotropic mixtures R404A and R448A and azeotropic R507A refrigerants in pipe minichannels. The R507 refrigerant is currently used as a temporary substitute for R404A, whereas R448A is a sustainable prospective substitute for R404A. The study presents experimental testing data for the condensation processes of these refrigerants in pipe minichannels and a proposal for the use of dimensional analysis, including the P-Buckingham theorem, to determine the regression relationship explaining the propagation of unit dynamic instabilities. Based on the experimental studies performed, regression computational models were developed and showed satisfactory agreement in the range of 20% to 25%. They give the possibility to identify, in a utilitarian, way the speed of propagation of temperature and pressure instabilities during the liquefaction of refrigerants. The study was carried out on pipe minichannels with an internal diameter of di = 3.3, 2.3, 1.92, 1.44 and 1.40 mm.

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“…The vital bottleneck in deciphering their relative importance coincides with the lack of high spatiotemporal diagnostic systems capable of independent temperature, heat flux, and flow-field measurements 20,21 . For example, during the bubble ebullition cycle, synchronized temperature and flow-field measurements are needed at spatial-and temporal-resolutions of <5 μm and <200 μs, respectively 17 -i.e., length-and time-scales that can resolve the difference between both (1) microlayer and interline evaporation during bubble growth and (2) micro-convection and transient conduction after bubble release.…”

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Transient and local two-phase heat transport at macro-scales to nano-scales

Mehrvand

Putnam

2018

Commun Phys

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Two-phase cooling has become a promising method for improving the sustainability and efficiency of high energy-density and power-density devices. Fundamentally, however, two-phase thermal transport is not well understood for local, transient processes, especially at critical to near-critical heat fluxes at the macro, micro, and nano-scales. Here we report spatiotemporal characterization of the single-bubble ebullition cycle in a hot-spot heating configuration with heat fluxes approaching 3 kW cm −2 . In particular, we experimentally reconstruct the spatiotemporal heat transfer coefficient in terms of its proportionality at both the macro-scale (l >> 1 μm) and the micro-to-nanoscale (l < 1 μm). We show that the maximum rates of heat transfer occur during the microlayer evaporation stage of the ebullition cycle, corresponding to critical maxima in the heat transfer coefficient of~160 ± 40 kW m −2 K −1 and~5300 ± 300 kW m −2 K −1 at the macro-scale and micro-to-nanoscale, respectively.

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Experimental and theoretical studies of critical heat flux of flow boiling in microchannels with microbubble-excited high-frequency two-phase oscillations

Cited by 23 publications

References 53 publications

Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities

Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities

Regression Model of Dynamic Pulse Instabilities during Condensation of Zeotropic and Azeotropic Refrigerant Mixtures R404A, R448A and R507A in Minichannels

Transient and local two-phase heat transport at macro-scales to nano-scales

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