High heat flux flow boiling in silicon multi-microchannels – Part III: Saturated critical heat flux of R236fa and two-phase pressure drops

The critical heat flux (CHF) limit is an important consideration in the design of most flow boiling systems. Before the use of microchannels under saturated flow boiling conditions becomes widely accepted in cooling of high-heat-flux devices, such as electronics and laser diodes, it is essential to have a clear understanding of the CHF mechanism. This must be coupled with an extensive database covering a wide range of fluids, channel configurations, and operating conditions. The experiments required to obtain this information pose unique challenges. Among other issues, flow distribution among parallel channels, conjugate effects, and instrumentation need to be considered. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result of either an upstream compressible volume instability or an excursive instability rather than the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher if the flow is stabilized by an orifice at the entrance of each channel. The nature of CHF in microchannels is thus different than anticipated, but recent advances in microelectronic fabrication may make it possible to realize the higher power levels.

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High heat flux flow boiling in silicon multi-microchannels – Part I: Heat transfer characteristics of refrigerant R236fa

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2008.03.006 ◽

2008 ◽

Vol 51 (21-22) ◽

pp. 5400-5414 ◽

Cited By ~ 87

Author(s):

Bruno Agostini ◽

John Richard Thome ◽

Matteo Fabbri ◽

Bruno Michel ◽

Daniele Calmi ◽

...

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Flow Boiling ◽

High Heat ◽

High Heat Flux ◽

Heat Transfer Characteristics ◽

Flux Flow ◽

Transfer Characteristics

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High Heat Flux Subcooled Flow Boiling of Methanol in Microtubes

Volume 3: Advanced Fabrication and Manufacturing; Emerging Technology Frontiers; Energy, Health and Water- Applications of Nano-, Micro- and Mini-Scale Devices; MEMS and NEMS; Technology Update Talks; Thermal Management Using Micro Channels, Jets, Sprays ◽

10.1115/ipack2015-48734 ◽

2015 ◽

Cited By ~ 2

Author(s):

Farzad Houshmand ◽

Hyoungsoon Lee ◽

Mehdi Asheghi ◽

Kenneth E. Goodson

Keyword(s):

Heat Flux ◽

Pressure Drop ◽

Flow Boiling ◽

High Heat ◽

Heat Fluxes ◽

Two Phase ◽

Subcooled Flow Boiling ◽

Subcooled Flow ◽

Inner Diameter ◽

Phase Pressure

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm2 is investigated. Methanol was propelled into microtubes (ID = 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (1/ID), while for a given inner diameter, it decreases with increasing heated length.

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Flow Boiling in Microgaps for Thermal Management of High Heat Flux Microsystems

Journal of Electronic Packaging ◽

10.1115/1.4034317 ◽

2016 ◽

Vol 138 (4) ◽

Cited By ~ 9

Author(s):

Xuefei Han ◽

Andrei Fedorov ◽

Yogendra Joshi

Keyword(s):

Heat Flux ◽

High Speed ◽

Flow Boiling ◽

Experimental Studies ◽

High Heat ◽

Bubble Nucleation ◽

Inlet Temperature ◽

High Heat Flux ◽

Two Phase ◽

Outlet Pressure

In the first part of this paper, a review of fundamental experimental studies on flow boiling in plain and surface enhanced microgaps is presented. In the second part, complimentary to the literature review, new results of subcooled flow boiling of water through a micropin-fin array heat sink with outlet pressure below atmospheric are presented. A 200 μm high microgap device design was tested, with a longitudinal pin pitch of 225 μm, a transverse pitch of 135 μm, and a diameter of 90 μm, respectively. Tested mass fluxes ranged from 1351 to 1784 kg/m2s, and effective heat flux ranged from 198 to 444 W/cm2 based on the footprint surface area. The inlet temperature varied from 6 to 12 °C, and outlet pressure ranged from 24 to 36 kPa. The two-phase heat transfer coefficient showed a decreasing trend with increasing heat flux. High-speed visualizations of flow patterns revealed a triangular wake after bubble nucleation. Flow oscillations were seen and discussed.

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On the Operational Parameters Effects on Two-Phase Pressure Drop Characteristics of Reentrant Copper Microchannels

Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems ◽

10.1115/mnhmt2016-6514 ◽

2016 ◽

Author(s):

Daxiang Deng ◽

Qingsong Huang ◽

Yanlin Xie ◽

Wei Zhou ◽

Xiang Huang ◽

...

Keyword(s):

Heat Flux ◽

Pressure Drop ◽

Mass Flux ◽

Heat Sink ◽

Flow Boiling ◽

Heat Fluxes ◽

High Heat Flux ◽

Two Phase ◽

Cooling Systems ◽

Phase Pressure

Two-phase boiling in advanced microchannel heat sinks offers an efficient and attractive solution for heat dissipation of high-heat-flux devices. In this study, a type of reentrant copper microchannels was developed for heat sink cooling systems. It consisted of 14 parallel Ω-shaped reentrant copper microchannels with a hydraulic diameter of 781μm. Two-phase pressure drop characteristics were comprehensively accessed via flow boiling tests. Both deionized water and ethanol tests were conducted at inlet subcooling of 10°C and 40°C, mass fluxes of 125–300kg/m2·s, and a wide range of heat fluxes and vapor qualities. The effects of heat flux, mass flux, inlet subcoolings and coolants on the two-phase pressure drop were systematically explored. The results show that the two-phase pressure drop of reentrant copper microchannels generally increased with increasing heat fluxes and vapor qualities. The role of mass flux and inlet temperatures was dependent on the test coolant. The water tests presented smaller pressure drop than the ethanol ones. These results provide critical experimental information for the development of microchannel heat sink cooling systems, and are of considerable practical relevance.

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