20.500.12556/RUL-102475 Strukturirane bakrene površine za izboljšan prenos toplote pri mehurčkastem vrenju Structured copper surfaces for enhanced nucleate boiling heat transfer V delu obravnavamo vpliv mehanskega in laserskega strukturiranja bakrenih vzorcev na izboljšanje prenosa toplote pri mehurčkastem vrenju vode v bazenu. Vzorce smo mehansko obdelali z brušenjem ali peskanjem oz. lasersko strukturirali z namenom izdelave mikrojamic ali oksidne plasti; na eni površini smo po vzoru literature izdelali mikrokanale. Površine smo okarakterizirali z uporabo meritev topografije, izdelavo SEM posnetkov, EDS analizo kemijske sestave in meritvami kota omočenja. Na merilni progi lastne konstrukcije smo izvedli eksperimente z nasičenim vrenjem redestilirane vode v bazenu, pri čemer smo zabeležili vrelne krivulje posameznih površin pred prvim nastopom kritične gostote toplotnega toka in po njem ter izračunali koeficiente toplotne prestopnosti. Dosegli smo kritične gostote toplotnega toka do 1220 kW m-2 na mehansko obdelanih površinah, do 1580 kW m-2 na lasersko strukturiranih površinah in 1897 kW m-2 na površini z mikrokanali, kar predstavlja 46 %, 89 % oz. 127 % izboljšanje napram referenčni površini; izboljšanje koeficienta toplotne prestopnosti v primerjavi z referenčno površino znaša do 159 % (mehanska obdelava), 174 % (lasersko strukturiranje) oz. 296 % (mikrokanali). Ugotovili smo, da lasersko strukturiranje zagotavlja stabilne površine, ki se med zaporednimi meritvami minimalno spreminjajo. Prav tako smo opazili pojav spremembe površinske kemije kot posledice nastopa kritične gostote toplotnega toka, kar je imelo velik vpliv na prenos toplote z vrenjem. In the present work, the influence of mechanical and laser structuring of copper samples on enhanced nucleate pool boiling heat transfer is investigated. Samples were either mechanically treated using sanding or sandblasting or laser structured to produce microcavities or a surface oxide layer; microchannels were machined onto one sample. Characteristics of surfaces were determined through the use of topography measurement, SEM imaging, EDS surface chemical composition analysis and contact angle measurement. A pool boiling experimental setup of our own design was used to determine boiling heat transfer characteristics of structured surfaces during saturated boiling of twice-distilled water. Boiling curves were recorded before and after the first onset of critical heat flux and heat transfer coefficients were calculated. The following critical heat flux was reached: up to 1220 kW m-2 on mechanically treated surfaces, up to 1580 kW m-2 on laser treated surfaces and 1897 kW m-2 on the surface with microchannels; this represents 46 %, 89% and 127 % improvement in regards to the reference surface, respectively. Heat transfer coefficient improvement ranged from 159 % (mechanical treatment) and 174 % (laser treatment) to 296 % (microchannels). It was determined that laser structuring produces stable surfaces with minimal deviation between consecutive measurements. Additionally, a change of surface chemistry was recorded after the first onset of the critical heat flux, which had a large influence on boiling heat transfer. mehurčkasto vrenje vrenje v bazenu izboljšan prenos toplote kritična gostota toplotnega toka strukturiranje površin laserski inženiring površin vrelna krivulja nucleate boiling pool boiling enhanced heat transfer critical heat flux structured surfaces laser surface engineering boiling curve true false false [M. Može] Slovenski jezik Angleški jezik Magistrsko delo 2018-08-31 07:46:04 2018-08-31 07:46:06 2022-08-15 03:41:59 0000-00-00 00:00:00 2018 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 536.24:621.9.048.7(043.2) 207358 16286747 1989.pdf 1989.pdf 1 0FB16A5919105BC27227B7083CDBBF53 6551a87d1e0b0c6c5a73360cd5df9b25acc3e192bf367376eb4bb072e0ccb75c 876750f2-a1b5-11eb-a523-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=112779 Fakulteta za strojništvo 0 0 0