Pool boiling performance of water and self-rewetting fluids on hybrid functionalized aluminum surfaces

Može, Matic (author), Vajc, Viktor (author), Zupančič, Matevž (author), Šulc, Radek (author), Golobič, Iztok (author)

The boiling performance of functionalized hybrid aluminum surfaces was experimentally investigated for water and self-rewetting mixtures of water and 1-butanol. Firstly, microstructured surfaces were produced via chemical etching in hydrochloric acid and the effect of the etching time on the surface morphology was evaluated. An etching time of 5 min was found to result in pitting corrosion and produced weakly hydrophilic microstructured surfaces with many microcavities. Observed cavity-mouth diameters between 3.6 and 32 µm are optimal for efficient nucleation and provided a superior boiling performance. Longer etching times of 10 and 15 min resulted in uniform corrosion and produced superhydrophilic surfaces with a micropeak structure, which lacked microcavities for efficient nucleation. In the second stage, hybrid surfaces combining lower surface energy and a modified surface microstructure were created by hydrophobization of etched aluminum surfaces using a silane agent. Hydrophobized surfaces were found to improve boiling heat transfer and their boiling curves exhibited a significantly lower superheat. Significant heat transfer enhancement was observed for hybrid microcavity surfaces with a low surface energy. These surfaces provided an early transition into nucleate boiling and promoted bubble nucleation. For a hydrophobized microcavity surface, heat transfer coefficients of up to 305 kW m$^{−2}$ K$^{−1}$ were recorded and an enhancement of 488% relative to the untreated reference surface was observed. The boiling of self-rewetting fluids on functionalized surfaces was also investigated, but a synergistic effect of developed surfaces and a selfrewetting working fluid was not observed. An improved critical heat flux was only obtained for the untreated surface, while a lower critical heat flux and lower heat transfer coefficients were measured on functionalized surfaces, whose properties were already tailored to promote nucleate boiling.

• Language: English
• Keywords: pool boiling, nucleate boiling, surface modification, functionalized surfaces, heat transfer enhancement, self-rewetting fluids
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: 27 str.
• Numbering: Vol. 9, iss. 6, art. 1058
• PID: 20.500.12556/RUL-127676
• UDC: 536.242:66.046.7
• ISSN on article: 2227-9717
• DOI: 10.3390/pr9061058
• COBISS.SI-ID: 67560707
• Publication date in RUL: 18.06.2021

Record is a part of a journal

• Title: Processes
• Shortened title: Processes
• Publisher: MDPI AG
• ISSN: 2227-9717
• COBISS.SI-ID: 523353113

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.
• Licensing start date: 17.06.2021

Secondary language

• Language: Slovenian
• Keywords: vrenje v bazenu, mehurčkasto vrenje, površinska modifikacija, funkcionalizirane površine, izboljšan prenos toplote, samoomočljivi fluidi