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HIGH SPEED IMAGING AND TWO-PHASE FLOW PATTERNS DURING FLOW BOILING IN A SINGLE MICROCHANNEL

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Original languageEnglish
Title of host publicationPROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON NANOCHANNELS, MICROCHANNELS, AND MINICHANNELS, PTS A AND B
Place of PublicationNEW YORK
PublisherAmerican Society for Mechanical Engineers
Pages693-704
Number of pages12
ISBN (Print)978-0-7918-4834-0
Publication statusPublished - 2008
Event6th International Conference on Nanochannels, Microchannels, and Minichannels - Darmstadt, Germany
Duration: 23 Jun 200825 Jun 2008

Conference

Conference6th International Conference on Nanochannels, Microchannels, and Minichannels
CountryGermany
Period23/06/0825/06/08

Abstract

Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two phase flow at a fundamental level.

We induced boiling in a single microchannel geometry (hydraulic diameter 727 lam), using a refrigerant FC-72, to investigate several flow patterns. A transparent, metallic, conductive deposit has been developed on the exterior of rectangular microchannels, allowing simultaneous uniform heating and visualisation to be conducted.

The data presented in this paper is for a particular case with a uniform heat flux of 4.26 kW/m(2) applied to the microchannel and inlet liquid mass flowrate, held constant at 1.33x10(-5) kg/s. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop profiles across the microchannel over time.

Bubble nucleation, growth and coalescence, as well as periodic slug flow, are observed in the test section. Phenomena are noted, such as the aspect ratio and Reynolds number of a vapour bubble, which are in turn correlated to the associated pressure drops over time.

From analysis of our results, images and video sequences with the corresponding physical data obtained, it is possible to follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble over time.

    Research areas

  • SMALL-DIAMETER CHANNELS, HEAT-TRANSFER MODEL, EVAPORATION, MICROTUBES

ID: 18086309