Experimental investigation of single bubble dynamics on a novel high aspect ratio conical micro-cavity in saturated pool boiling: Impact of surface tension

Vodopivec, Matevž (author), Fontanarosa, Donato (author), Gebrekiros Berhe, Mulugeta (author), Bucci, Mattia (author), Može, Matic (author), Zupančič, Matevž (author), Castagne, Sylvie (author), Golobič, Iztok (author), Vetrano, Maria Rosaria (author)

The present work experimentally explores the role of the surface tension in the single DI water vapor bubble dynamics in the presence of a novel conical microcavity produced via femtosecond laser texturing. An organic surfactant was used to reduce the surface tension of DI water by dissolving it in small concentrations. The conical microcavity, manufactured with a high aspect ratio on a 100 µm-thick titanium foil, ensured stable nucleation even at low contact angles, aligning well with heterogeneous nucleation theory. Stable isolated bubble dynamics were established at a heat flux of 20 kW∕m$^2$. The study utilized IR visualization of transient surface temperature fields paired with high-speed visualization to capture synchronized images of bubble dynamics. Results show that nucleation inception occurs below 60 kW∕m$^2$ in the presence of the conical microcavity, while no nucleation was observed on a bare surface at the same heat flux. The bubble detachment diameter exhibits a non-monotonic dependency on surface tension, influenced by a dual growth mechanism. Reduced surface tension at first led to smaller detachment diameters and less buoyancy required for detachment, with no pinning observed. Further reduction triggered an increase in forces attaching the bubble to the surface, again increasing growth time and departure diameter. Results were also compared to predictions by empirical bubble departure models, including surface tension effects. The work contributes to improving the fundamental understanding of bubble evolution and associated effects of surface tension. It opens possibilities for the development of new or modified bubble nucleation, growth and departure models, including effects that are currently not being considered.

• Language: English
• Keywords: pool boiling, femtosecond laser texturing, bubble dynamics, surface tension, artificial nucleation site
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 13 str.
• Numbering: Vol. 279, pt. B, art. 127384
• PID: 20.500.12556/RUL-170990
• UDC: 532.612
• ISSN on article: 1359-4311
• DOI: 10.1016/j.applthermaleng.2025.127384
• COBISS.SI-ID: 243812099
• Publication date in RUL: 25.07.2025

Record is a part of a journal

• Title: Applied thermal engineering
• Shortened title: Appl. therm. eng.
• Publisher: Elsevier
• ISSN: 1359-4311
• COBISS.SI-ID: 1861910

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.