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Evaluation of enhanced nucleate boiling performance through wall- temperature distributions on PDMS-silica coated and non-coated laser textured stainless steel surfaces
Zupančič, Matevž (Author), Može, Matic (Author), Gregorčič, Peter (Author), Sitar, Anže (Author), Golobič, Iztok (Author)

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Abstract
Nucleate boiling was examined on Joule heated stainless steel foils, functionalized by PDMS-silica coating and/or nanosecond-laser texturing. The nucleating bubbles and transient temperature fields were visual- ized through high-speed IR and video recordings. The differences in boiling performance were evaluated through wall-temperature distributions. Results confirmed that smooth surfaces require high activation temperatures and produce larger bubbles, while wall-temperature distributions display higher standard deviations, higher local superheats, and bimodal shapes. Similarly, relatively high activation temperatures were observed on the superhydrophilic surface, where the enhanced liquid replenishment on the active nucleation sites reduces the bubble departure diameters and prevents formation of local hotspots. Consequently, the analyzed temperature distributions have negative skewness and decreased standard deviation. The highest heat transfer coefficient was achieved on a laser textured surface with nonuniform wettability and multi-scale microcavities. Here, nucleation site density was as high as 200 cm-2 at 300 kW/m2 , while wall-temperature distributions demonstrated by far the lowest standard deviation. The temperature distributions also proved that annealed PDMS-silica coating significantly increased the thermal resistance of the entire heater. On the contrary, laser textured surfaces provided an even better boiling performance compared to coated surfaces and did not increase heater's thermal resistance. This additionally endorses the coating-free, direct laser texturing method as a cutting-edge technology in the development of surfaces capable of significantly enhanced boiling heat transfer.

Language:English
Keywords:enhanced boiling heat transfer, high-speed IR thermography, wall-temperature distributions, PDMS-silica coating, nanosecond laser texturing
Work type:Article (dk_c)
Tipology:1.01 - Original Scientific Article
Organization:FS - Faculty of Mechanical Engineering
Year:2017
Number of pages:str. 419-428
Numbering:Vol. 111
UDC:536.24(045)
ISSN on article:0017-9310
DOI:10.1016/j.ijheatmasstransfer.2017.03.128 Link is opened in a new window
COBISS.SI-ID:15473691 Link is opened in a new window
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Downloads:414
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Record is a part of a journal

Title:International journal of heat and mass transfer
Shortened title:Int. j. heat mass transfer
Publisher:Pergamon Press
ISSN:0017-9310
COBISS.SI-ID:3064335 This link opens in a new window

Document is financed by a project

Funder:ARRS - Agencija za raziskovalno dejavnost Republike Slovenije (ARRS)
Project no.:P2-0392, P2-0223
Name:Optodinamika, Prenos toplote in snovi

Secondary language

Language:Slovenian
Keywords:izboljšan prenos toplote pri vrenju, hitrotekoča IR termografija, temperaturna porazdelitev na grelni površini, PDMS-silika premaz, strukturiranje z nanosekundnimi laserskimi bliski

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