Experimental measurements of critical heat flux in expanding microchannel arrays

Mark J. Miner, Patrick Phelan, Brent A. Odom, Carlos A. Ortiz

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The effect of an expanding microchannel cross-section on flow boiling critical heat flux (CHF) is experimentally investigated across four rates of expansion. A pumped-loop apparatus is developed to boil R-134a in an array of microchannels cut into copper; a test section is designed to facilitate interchange of the microchannel specimens, allowing consistency across experiments. An optimum expansion angle allowing maximum heat flux is observed, the location of which increases with the mass flow rate. The boiling number does not indicate any optimum in the range observed, showing a nearly monotonic increase with expansion angle. The familiar increase in critical heat flux with mass flux is observed, though expansion shifts the CHF-mass flux curves in a favorable direction. The existence of an optimum expansion angle confirms an earlier qualitative hypothesis by the authors and suggests that microchannel heat sinks offer opportunities for methodical improvement of flow boiling stability and performance.

Original languageEnglish (US)
Article number101501
JournalJournal of Heat Transfer
Issue number10
StatePublished - 2013


  • Heat and mass transfer
  • Heat transfer enhancement
  • Micro/nanoscale heat transfer
  • Two-phase flow and heat transfer

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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