Boiling flow characteristics in microchannels with very hydrophobic surface to super-hydrophilic surface

Ting Y. Liu, P. L. Li, C. W. Liu, C. Gau

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

Boiling flow process plays a very important role to affect the heat transfer in a microchannel. Different boiling flow modes have been found in the past which leads to different oscillations in temperatures and pressures. However, a very important issue, i.e. the surface wettability effects on the boiling flow modes, has never been discussed. The current experiments fabricated three different microchannels with identical sizes at 105 × 1000 × 30000 μm but at different wettability. The microchannels were made by plasma etching a trench on a silicon wafer. The surface made by the plasma etch process is hydrophilic and has a contact angle of 36° when measured by dipping a water droplet on the surface. The surface can be made hydrophobic by coating a thin layer of low surface energy material and has a contact angle of 103° after the coating. In addition, a vapor-liquid-solid growth process was adopted to grow nanowire arrays on the wafer so that the surface becomes super-hydrophilic with a contact angle close to 0°. Different boiling flow patterns on a surface with different wettability were found, which leads to large difference in temperature oscillations. Periodic oscillation in temperatures was not found in both the hydrophobic and the super-hydrophilic surface. During the experiments, the heat flux imposed on the wall varies from 230 to 354.9 kW/m2 and the flow of mass flux into the channel from 50 to 583 kg/m2s. Detailed flow regimes in terms of heat flux versus mass flux are also obtained.

Original languageEnglish
Pages (from-to)126-134
Number of pages9
JournalInternational Journal of Heat and Mass Transfer
Volume54
Issue number1-3
DOIs
Publication statusPublished - 2011 Jan 15

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes

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