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

Abstract

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.

Keywords

nucleate boiling;heat transfer enhancement;dielectric fluids;thin metallic foils;laser microstructuring;surface structures;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UL FS - Faculty of Mechanical Engineering
UDC: 536.24:544:66.02
COBISS: 170665731 Link will open in a new window
ISSN: 1359-4311
Views: 246
Downloads: 27
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Metadata: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Other data

Secondary language: Slovenian
Secondary keywords: mehurčkasto vrenje;izboljšan prenos toplote;dielektrični fluidi;tanke kovinske folije;lasersko mikrostrukturiranje;površinske strukture;
Type (COBISS): Article
Pages: str. 1-13
Volume: ǂVol. ǂ236
Issue: ǂpt. ǂD
Chronology: Jan. 2024
DOI: 10.1016/j.applthermaleng.2023.121803
ID: 20720356