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Kritična gostota toplotnega toka na lasersko strukturirani površini pri mehurčkastem vrenju FC-72
Križan, Peter (Author), Gregorčič, Peter (Mentor) More about this mentor... This link opens in a new window, Golobič, Iztok (Co-mentor)

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Abstract
V magistrski nalogi smo preučevali vpliv ključnih parametrov površin na proces mehurčkastega vrenja in razvoj kritične gostote toplotnega toka v bazenu dielektričnega fluida FC-72. Z bliskovnim nanosekundnim laserjem smo teksturirali površine trakcev iz nerjavnega jekla z namenom izdelave hrapavih površin z različnimi topografskimi značilnostmi. Te smo ovrednotili s pomočjo vrstičnega elektronskega mikroskopa (SEM), optičnega interferometra ter naprave za merjenje hitrosti omočenja površin. Lasersko teksturiranim trakcem smo na eksperimentalni progi za nasičeno mehurčkasto vrenje FC-72 določali vrednosti kritične gostote toplotnega toka (CHF). Ugotovili smo, da so se vsem površinam izboljšale vrednosti CHF v primerjavi z neobdelano površino, najboljšim do 75%. S parametri hrapavosti smo popisali topografije površin, te pa primerjali z rezultati CHF. Spoznali smo, da zgolj parametri hrapavosti površin niso primerni za napovedovanje CHF. Nanj vpliva kombinacija teh parametrov skupaj s kompleksno topografijo površine in njeno omočljivostjo. Slednja je dober parameter za napovedovanje CHF pri isti topografiji, kar smo pokazali s staranjem vzorcev. Potrdili smo Hsujevo in Kandlikarjevo teorijo o vplivu aktivnih nukleacijskih mest na izboljšanje prenosa toplote z izdelavo ter popisom mikro jamic in zasutih mikro kanalov.

Language:Slovenian
Keywords:vrenje v bazenu kritična gostota toplotnega toka lasersko teksturiranje omočljivost kapilarni vlek topografija hrapavost mikro jamice
Work type:Master's thesis (m2)
Tipology:2.09 - Master's Thesis
Organization:FS - Faculty of Mechanical Engineering
Year:2018
Publisher:[P. Križan]
UDC:536.2:519.6(043.2)
COBISS.SI-ID:16288539 Link is opened in a new window
Views:169
Downloads:251
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Secondary language

Language:English
Title:Critical heat flux of laser structured surfaces in pool boiling of FC-72
Abstract:
The present work investigates influence of surface parametres on nucleate pool boiling of FC-72 and their impact on critical heat flux development. The stainless steel surface of ribbon heaters was textured using a pulsed nanosecond laser to increase it's roughness and create various surface structures. Analysis of surface topografy was performed using scaning electron microscopy (SEM), optical interferometry and surface wickability measurements. Pool boiling experiments of saturated FC-72 were performed to determine critical heat flux (CHF) values of laser textured surfaces. We achieved enhacement of CHF values up to 75% for all ribbon heaters samples in comparison with non-textured one. Surface roughness parameters were used to analyse surface topography. Furthermore, impact of these parameters on CHF enhancement was investigated. We concluded that combination of several surface roughness parameters in combination with complex surface topography and surface wickability impact on CHF values. Aging of samples proved surface wickability as a sufficient parameter for CHF development of the particular surface. Hsu And Kandlikar's theory of active nucleation sites was confirmed using SEM to determine microcavities.

Keywords:pool boiling critical heat flux direct laser texturing wettability wickability topography roughness micro cavities

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