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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

INVESTIGATING THE RELATIONSHIP BETWEEN SURFACE WICKABILITY AND CRITICAL HEAT FLUX DURING POOL BOILING

Youngsup Song
Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

Yangying Zhu
Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA

Daniel J. Preston
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

H. Jeremy Cho
Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

Zhengmao Lu
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

Evelyn N. Wang
Device Research Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02149, USA

DOI: 10.1615/IHTC16.bae.023315
pages 1183-1189


KEY WORDS: Boiling and evaporation, Heat transfer enhancement, wickability, critical heat flux (CHF)

Abstract

Enhancement and estimation of critical heat flux (CHF) is one of the most important research areas of pool boiling heat transfer. It is well-known that microstructured surfaces can extend the limit of CHF up to ~250% higher than that of a flat surface. The mechanism for this enhancement has generally been accepted as the wickability of structured surfaces originating from liquid propagation within the surface structures driven by capillary pressure. We investigated the applicability of this theory based on the accumulated data of previous studies and experimental data. We first calculated capillary pressure and permeability of structured surfaces to characterize liquid propagation rate analytically. We then performed pool boiling experiments on silicon micropillar surfaces to measure CHF values. We found that there is no obvious relationship between the measured CHF and calculated wickability. Our results suggest that although liquid wicking has been found to be important, the wickability defined by previous works alone is not sufficient to describe CHF. In addition to the wickability, we propose that there may be other important parameters that also change along with the surface structures. This work will help elucidate careful prediction of CHF in high flux applications including heat exchangers, nuclear reactors, and integrated circuits.

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