Enhanced nucleate boiling of Novec 649 on thin metal foils via laser-induced periodic surface structures

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

The low boiling temperature of dielectric fluids makes them suitable for satisfying the cooling requirements of advanced high-energy-density devices commonly found in microelectronics. However, the high wettability/wickability of such coolants significantly affects the boiling dynamics, opening new research questions on the crucial role played by micro- and nanostructures on the boiling surface. While different studies point out the importance of microscale grooves, pillars and cavities to promote nucleation and enhance boiling heat transfer coefficient (HTC) for water, the scientific data to support such observations for dielectric fluids is sparse. In this regard, the present work provides an experimental investigation of the nucleate boiling enhancement of Novec 649 on thin metallic stainless-steel foils with tailored, laser-induced periodic surface structures (LIPSS). Femtosecond laser surface texturing was utilized to produce LIPSS with a periodicity of approx. 720 nm, while selected samples additionally included microscale grooves with a depth of 19.6 µm and a width of 25 µm, overlapped with the LIPSS features (labelled as GLIPSS). During boiling performance evaluation, high-speed IR thermography was used to measure the transient temperature fields of the boiling surface. LIPSS samples exhibited a reduction in wall superheat at the onset of boiling from 28 K to about 16 K, resulting in an HTC enhancement of about +65 %. Analysis of IR data was performed through multiscale proper orthogonal decomposition (mPOD) and revealed that the HTC enhancement in the presence of LIPSS is related to a faster heat transfer dynamics (dominant frequency: +54 %) occurring at a smaller spatial scale (dominant mean active site diameter: −12.5 %) and larger spatial density (dominant mean active site density: +39 %). Furthermore, the results for GLIPSS samples revealed a weak impact of micro features to the boiling performance of Novec 649, implying that sub-microscale surface topography is crucial to promote boiling in applications using dielectrics.

• Language: English
• Keywords: nucleate boiling, heat transfer enhancement, dielectric fluids, thin metallic foils, laser microstructuring, surface structures, laser induced periodic surface structures
• 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: 13 str.
• Numbering: Vol. 236, pt. D, art. 121803
• PID: 20.500.12556/RUL-152102-c8de9726-203e-a07a-cc6d-c2a5207169b3
• UDC: 536.24:544:66.02
• ISSN on article: 1359-4311
• DOI: 10.1016/j.applthermaleng.2023.121803
• COBISS.SI-ID: 170665731
• Publication date in RUL: 03.11.2023

Record is a part of a journal

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

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: mehurčkasto vrenje, izboljšan prenos toplote, dielektrični fluidi, tanke kovinske folije, lasersko mikrostrukturiranje, površinske strukture