Hierarchical surfaces with open microchannels and laser-induced microcavities for enhancement of pool boiling critical heat flux

Žalec, Domen (author), Hadžić, Armin (author), Može, Matic (author), Golobič, Iztok (author)

Technological advancements in various electronic devices, consumer or industrial power electronics, as well as higher demand for energy efficiency, have in recent years presented the need for advanced thermal management to enable the realization of their increased performance. Research in this field has taken up pace in the last decade, with various surface engineering techniques being proposed. This paper investigates enhancement of pool boiling performance with hierarchical microchannel copper surfaces, augmented with additional laser texturing and selective hydrophobization. The surfaces were fabricated with either straight or segmented microchannels of varying depths, while laser texturing was applied to either the base of the channels or the entire surface. Multiple families of surfaces with mini-, micro- and nanoscopic surface structures were created through different combination surface treatments, including milled microchannels, laser-induced surface structures and a hydrophobic coating. Pool boiling heat transfer performance tests were carried out with twice-distilled water in saturated state at atmospheric pressure. All engineered surfaces achieved an increase in the heat transfer coefficient (HTC) and the critical heat flux (CHF) values. The highest CHF value of 3142 kW m$^{−2}$ was recorded on a laser-textured surface with deep microchannels, with an improvement over the reference surface of 210 %, and a corresponding HTC of 132 kW m$^{−2}$ with enhancement of 214 %. On the other hand, the highest HTC value of 174 kW m$^{−2}$ was achieved on a hydrophobized laser textured surface shallow microchannels, with an improvement of 314 %, while its CHF value was 1963 kW m$^{−2}$ with an enhancement of 94 %. Laser-textured microchannel surfaces exhibited higher CHF values over their reference counterparts due to the fabricated microcavities on the microchannels, which facilitates improved liquid supply and nucleation. Fully superhydrophobic surfaces exhibit an HTC compared to surfaces characterized by mixed superhydrophobic and hydrophobic regions, which is ascribed to the larger surface area featuring a reduced energy barrier, thereby promoting a higher density of active nucleation sites. Additionally, the results of this study show that CHF increases with increasing channel depth, while HTC deteriorates with increasing channel depth. In general, non-hydrophobized surfaces with microchannels and laser-induced microcavities presented the highest improvements in CHF values, while still achieving notably enhanced HTC values, representing a very favorable combination for industrial applications.

• Language: English
• Keywords: pool boiling, heat transfer enhancement, microchannel surfaces, critical heat flux, surface engineering, laser texturing
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 12 str.
• Numbering: Vol. 235, art. 126192
• PID: 20.500.12556/RUL-162464
• UDC: 536.2:66.046.7
• ISSN on article: 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2024.126192
• COBISS.SI-ID: 208632579
• Publication date in RUL: 24.09.2024

Record is a part of a journal

• Title: International journal of heat and mass transfer
• Shortened title: Int. j. heat mass transfer
• Publisher: Elsevier
• ISSN: 1879-2189
• COBISS.SI-ID: 23007493

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.

Secondary language

• Language: Slovenian
• Keywords: vrenje v bazenu, izboljšani prenos toplote, mikrokanalne površine, kritična gostota toplotnega toka, inženiring površin, lasersko strukturiranje