A scaling analysis inquiring into two-phase flow reversal
conference paper
Physical processes limit the maximum achievable heat flux when miniaturising heat transfer equipment. In case of boiling heat transfer literature reports large pressure fluctuations, flow instabilities, and possible vapour backflow. The occurrence of the flow instabilities during boiling in small channels (defined by the Confinement Number, Co > 0.5) are explained by the formation of slug bubbles blocking the entire channel. These particular bubbles are likely to emerge during nucleate flow boiling in small diameter channels. Slug bubble blockage during flow boiling is investigated experimentally by creating a single hotspot in a small-diameter channel (Co∼5). For different liquid flow rates the detachment length of such a blocking slug bubble is determined. A scaling analysis offers to insight into the physical phenomena causing the flow instabilities. The position of the bubble caps as a function of time is identified as an important parameter. Copyright © 2008 by ASME.
Topics
BackflowBoiling heat transferDetachment lengthFlow boilingFlow instabilitiesFunction of timeHeat transfer equipmentHot spotLiquid flow ratesPhysical phenomenaPhysical processPressure fluctuationScaling analysisSmall channelsSmall diameter channelsHeat exchangersHeat transferMicrochannelsMultiphase flowHeating equipment
TNO Identifier
360859
ISBN
0791848345
9780791848340
9780791848340
Source title
6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, 23 June 2008 through 25 June 2008, Darmstadt
Pages
601-608
Files
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