Role of easy-to-activate nucleation sites in pool boiling

Yi Liu, Ming-Chang Lu*, Dongyan Xu

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations

Abstract

Nucleate boiling from heated surfaces is an efficient heat transfer approach by taking advantage of the large latent heat of vaporization of liquids. Despite decades of research, the mechanism triggering the critical heat flux is still unclear because of the difficulty posted by the random flow nature at high heat fluxes. In this work, we show that the effectiveness of nucleation sites, usually characterized at low heat fluxes, significantly affects the heat transfer coefficient and the critical heat flux in pool boiling. Boiling experiments were conducted on a total of four types of microstructured surfaces with controlled effectiveness of nucleation sites and surface wettability. It is shown that surfaces with easy-to-activate nucleation sites have much higher heat transfer coefficients than those surfaces with ineffective nucleation sites. More importantly, our study reveals that excellent critical heat flux (up to 219.4 W/cm2) is attainable only when the surface has good wetting property but is free of easy-to-activate nucleation sites. With the presence of easy-to-activate nucleation sites, only limited critical heat fluxes can be achieved irrespective of the surface wettability, suggesting a suppression effect of nucleation sites on the critical heat flux. A wetting-deterioration mechanism is proposed to explain the suppression effect of easy-to-activate nucleation sites on the critical heat flux. Easy-to-activate nucleation sites continuously generate bubbles that block the liquid to cool down the hot surface and thus lead to early dry-out.

Original languageEnglish
Pages (from-to)653-660
Number of pages8
JournalInternational Heat Transfer Conference
Volume2018-August
DOIs
StatePublished - 1 Jan 2018
Event16th International Heat Transfer Conference, IHTC 2018 - Beijing, China
Duration: 10 Aug 201815 Aug 2018

Keywords

  • Critical heat flux
  • Easy-to-activate nucleation sites
  • Heat transfer coefficient
  • Microstructured surfaces
  • Pool boiling

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