8542 KB243 KB0 KB2018Golobič, IztokPetkovšek, JureXXVI, 115 str., 30 cmCOBISSID:16208411URN:URN:NBN:SI:doc-CMAYQT6OslJ. Petkovšekvisokošolska delacritical heat fluxDisertacijedissertationsdoktorska delahot spotinfrardeče termografske meritveinfrared thermographykritična gostota toplotnega tokalokalno pregretjemehurčkasto vrenjenestacionarno temperaturno poljenucleate boilingtanki grelnikithin heaterstransient temperature fieldVrenjePrenos toplote in kritična gostota toplotnega toka pri mehurčkastem vrenju na tankih grelnikih| doktorsko delo|Experimental investigations of the nucleate pool boiling on thin heaters have been conducted by simultaneous observations of the boiling surface and by measurements of the transient temperature field on the heater. The local heat flux and the heat transfer coefficient distributions have been calculated at various boiling intensities. Fast and slow bubble growth mechanisms have been identified. Significant increase of the local heat flux has been calculated below the fast growing bubble at the nucleation phase. An important increase of local heat flux within the triple wall % liquid % vapor contact line of the slowly growing bubbles has been shown. The phenomenon of the chain coalescence has been presented together with its importance for cooling of the heated surface. During boiling at high heat flux, locally superheated spots on the heater surface expand and merge into large superheated areas. This can lead to the critical heat fluxEksperimentalne preiskave mehurčkastega vrenja na tankih grelnikih so bile izvedene s hkratnim opazovanjem vrelne površine ter merjenjem nestacionarnega temperaturnega polja na grelniku. Izračunane so bile porazdelitve lokalne gostote toplotnega toka in koeficienta toplotne prestopnosti pri različnih intenzivnostih vrelnega procesa. Identificirana sta bila mehanizma hitre ter počasne rasti mehurčka. Izračuni kažejo na močan lokalni porast gostote toplotnega toka ob nukleaciji hitro rastočega mehurčka. Pri počasi rastočih mehurčkih nastopa povečana lokalna gostota toplotnega toka v trojnem stiku grelnika, fluida ter parne faze v mehurčku. Prikazan je bil pojav verižne koalescence in njen pomen pri ohlajanju grelne površine. Lokalna pregretja grelne površine se pri visoko intenzivnem vrelnem procesu širijo in združujejo v obsežnejša pregreta področja. To lahko vodi v nastop kritične gostote toplotnega tokaTEXTvisokošolska delatheses and dissertationsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Ljubljani, Fakulteta za strojništvo