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Title: Bubble confinement in flow boiling of FC-72 in a ''rectangular'' microchannel of high aspect ratio

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. Boiling is induced in a single microchannel geometry (hydraulic diameter 727 {mu}m), using a refrigerant FC-72, to investigate the effect of channel confinement on bubble growth. A transparent, metallic, conductive deposit has been developed on the exterior of the rectangular microchannel, allowing simultaneous uniform heating and visualisation to be achieved. The data presented in this paper is for a particular case with a uniform heat flux applied to the microchannel and inlet liquid mass flowrate held constant. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop across the microchannel over time. Bubble nucleation and growth, as well as periodic slug flow, are observed in the microchannel test section. The periodic pressure fluctuations evidenced across the microchannel are caused by the bubble dynamics and instances of vapour blockage during confined bubble growth in the channel. The variation of the aspect ratio and the interface velocities of the growing vapour slug over time, aremore » all observed and analysed. We follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble during flow boiling of FC-72 in a microchannel, from analysis of our results, images and video sequences with the corresponding pressure data obtained. (author)« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [1]
  1. School of Engineering, University of Edinburgh, The King's Buildings, Mayfield Road, Edinburgh, EH9 3JL (United Kingdom)
  2. (UI, UII) - CNRS Laboratoire IUSTI, UMR 6595, 5 Rue Enrico Fermi, Marseille 13453 (France)
  3. Aix-Marseille Universite (UI, UII) - CNRS Laboratoire IUSTI, UMR 6595, 5 Rue Enrico Fermi, Marseille 13453 (France)
Publication Date:
OSTI Identifier:
21350399
Resource Type:
Journal Article
Resource Relation:
Journal Name: Experimental Thermal and Fluid Science; Journal Volume: 34; Journal Issue: 8; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; VAPORS; BOILING; ASPECT RATIO; PERIODICITY; BUBBLES; TWO-PHASE FLOW; FLUCTUATIONS; CONFINEMENT; REFRIGERANTS; BUBBLE GROWTH; IMAGES; LIQUIDS; NUCLEATION; VELOCITY; PRESSURE DROP; TIME DEPENDENCE; HEATING; INSTABILITY; INTERFACES; MASS; FLOW VISUALIZATION; FLUORINATED ALIPHATIC HYDROCARBONS; DUCTS Confined bubbles; Flow boiling; Microchannels