20.500.12556/RUL-162464 Hierarchical surfaces with open microchannels and laser-induced microcavities for enhancement of pool boiling critical heat flux 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. pool boiling heat transfer enhancement microchannel surfaces critical heat flux surface engineering laser texturing vrenje v bazenu izboljšani prenos toplote mikrokanalne površine kritična gostota toplotnega toka inženiring površin lasersko strukturiranje true false true Angleški jezik Slovenski jezik Članek v reviji 2024-09-24 08:22:46 2024-09-24 08:22:47 2024-09-28 03:30:21 0000-00-00 00:00:00 2024 0 0 12 str. Vol. 235, art. 126192 Dec. 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 536.2:66.046.7 1879-2189 10.1016/j.ijheatmasstransfer.2024.126192 208632579 Zelec,_Hadzic,_Moze,_Golobic_-_Hierarchical_surfaces_with_open_microchannels_and_laser-induced_microcavities_for_enhancement_of_pool_boiling_critical_heat_flux.pdf Zelec,_Hadzic,_Moze,_Golobic_-_Hierarchical_surfaces_with_open_microchannels_and_laser-induced_microcavities_for_enhancement_of_pool_boiling_critical_heat_flux.pdf 1 D388F63103E865124F6FBC3445CA615F 762faac61741afb8f88759cd7feb97028390bad3fce55ee68c034c8d83c2abf1 ac6125d0-7a3d-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=191797 https://www.sciencedirect.com/science/article/pii/S0017931024010226 1 4c45a227-7a3d-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=191796 Fakulteta za strojništvo 0 0 0