Visualization of pool boiling on enhanced surfaces

Liang Han Chien, Ralph L. Webb

Research output: Contribution to journalJournal Article peer-review

88 Scopus citations

Abstract

This work reports experiments to visualize nucleate boiling on an enhanced tubular surface having sub-surface tunnels and surface pores. The finned copper tube had 1575 fins/m (40 fins/in) and 0.8 mm fin height. The fins are covered by a thin foil sheet having 0.23 mm pores at 1.5 mm pore pitch along each interfin region. Data are provided for two foil cover sheets, one copper and the other a transparent plastic. The uniqueness of this work is that the visualization method allowed direct observation of the boiling process in the subsurface tunnels. Use of a high speed camera with 30×magnification allowed detailed observation of the evaporation process in the tunnels and of the vapor bubbles emerging from the pores. The experiments were conducted for saturated and subcooled boiling in the horizontal and vertical orientations. For the vertical tube, the saturated boiling experiments showed that all of the tunnels were vapor filled except for liquid menisci in the corners. This was also true for the horizontal tube at high heat flux. For the horizontal tube at low heat flux, portions of the tunnel length was liquid filled. A large portion (70-90%) of the region was vapor filled except for liquid menisci in the corners, and the remaining part of the region had oscillating menisci. These experiments provide conclusive proof that the heat transfer mechanism in the subsurface tunnels is evaporation on the menisci in the corners.

Original languageEnglish
Pages (from-to)332-341
Number of pages10
JournalExperimental Thermal and Fluid Science
Volume16
Issue number4
DOIs
StatePublished - 04 1998
Externally publishedYes

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