IMI Interdisciplinary Mathematics InstituteCollege of Arts and Sciences

Recent Work in Micro/Nano-scale Two-phase Heat Transfer

  • Oct. 2, 2012
  • 2:30 p.m.
  • LeConte 312


Two-phase heat transfer is the most efficient heat transfer mechanism and widely employed in energy conversion, thermal management and fluid control. Interface plays imperative roles in governing local liquid supply and distribution, bubble dynamics, droplet dynamics, and hence, the overall heat transfer and hydrodynamic processes. Three topics are covered in this talk. 1) Self-exited and modulated two-phase oscillations. A new microchannel architecture consisting of a main channel connected to two auxiliary channels has been successfully developed and fabricated. It was shown to significantly enhance flow boiling heat transfer in microchannels. The new actuation mechanism powered by high frequency microscale vapor bubble growth and collapse processes can create and sustain strong mixing in microchannels. 2) A unified two-phase flow pattern and associated flow boiling phenomena. Ultra-efficient flow boiling phenomena in microchannels in the unified two-phase flow pattern, i.e., single annular nanobubble flow, which was formed through sophisticatedly controlling the bubble growth, separations and interactions and transforming the surface tension force, was experimentally demonstrated and systematically characterized. 3) Boiling on hydrophobic-hydrophilic composite interfaces, which were synthesized from functionalized multiwall carbon nanotubes (FMWCNTs) by introducing hydrophilic functional groups on the surfaces of pristine MWCNTs. The apparent contact angle of the nano-engineered interface can be smoothly tuned from 13.7˚ to 139.8˚ by varying the concentration of the hydrophilic functional groups. FMWCNTs with partially hydrophobic and partially hydrophilic properties create functional interfaces, which can significantly enhance micro/nanoscale transport phenomena for applications such as the nucleation process, fluid friction management and manipulation of droplet motions.

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