Single bubble dynamics on superheated superhydrophobic surfaces

Yinxiao Li, Ke Zhang, Ming-Chang Lu, Chuanhua Duan*

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

This work explores single bubble dynamics on superheated superhydrophobic surfaces and the corresponding heat transfer mechanism of water pool boiling. The superhydrophobic surfaces are prepared by coating a thin layer of polytetrafluoroethylene on top of silicon substrates with electroless etched silicon nanowires. It is observed that a vapor film covers the whole superhydrophobic surface when it is immersed in water. Once the surface is superheated, single bubble forms and departs from the vapor film. We find that the bubble growth rate shows little dependence on surface superheat and applied heat flux at large superheats due to the presence of the vapor layer, which seriously limits the heat transfer from the superheated superhydrophobic surface. The bubble departure diameter is mainly determined by the static force equilibrium, but local disturbance and surface superheat also play important roles. There is a plateau of bubble departure frequency at large superheats, which is a result of the constant departure velocity limit. Accompanying the continuous bubble formation and departure, a smooth boiling curve is observed. The corresponding heat transfer coefficient (HTC) first increases and then slowly decreases as the superheat increases, showing a peak at a superheat of ∼50 K. Such HTC change is explained by the heat flux partitioning model, suggesting latent heat transport due to water vaporization and bulk liquid water convection after bubble departure contribute together to the heat removal on superhydrophobic surfaces. Insights gained from pool boiling on superhydrophobic surfaces might provide design guidelines for new surfaces excellent in heat removal or hydrodynamic drag reduction.

Original languageEnglish
Pages (from-to)521-531
Number of pages11
JournalInternational Journal of Heat and Mass Transfer
Volume99
DOIs
StatePublished - 1 Aug 2016

Keywords

  • Bubble departure diameter/frequency
  • Bubble dynamics
  • Bubble growth
  • Pool boiling
  • Superhydrophobic surfaces

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