Analiza procesa nukleacije in rasti parnega mehurčka ob prisotnosti visokofrekvenčnih tlačnih fluktuacij

Cilenšek, Urban (author), Golobič, Iztok (mentor), Zupančič, Matevž (comentor)

Mehurčkasto vrenje je eden od najpomembnejših načinov prenosa toplote, vendar sta njegov nadzor in optimizacija še vedno izjemno zahtevna. Magistrska naloga obravnava vpliv visokofrekvenčnih tlačnih nihanj, proizvedenih z ultrazvočnim generatorjem megle, na nastanek in rast posameznega mehurčka. Eksperimentalna analiza je bila izvedena na tanki kovinski foliji z bifilno površino v režimu mehurčkastega vrenja destilirane vode v bazenu z uporabo hitrotekoče kamere, infrardeče termografije in ultrazvočnega generatorja megle, ki je deloval pri frekvenci 1,7 MHz. Meritve so zajemale čas čakanja, temperaturo nukleacije, odvedeno lokalno gostoto toplotnega toka in premere mehurčkov pri gostotah toplotnih tokov od 40 do 90 kW$m^-2$. Rezultati kažejo sistematično podaljšanje časa čakanja za 58,8-84,4 %, povišanje nukleacijskih temperatur za 1,5-6,84 K in povečanje premerov mehurčkov za 20,55-56,82 %. Gostota odvedenega toplotnega toka se je povečala za 1,49-20,81 %.

• Language: Slovenian
• Keywords: mehurčkasto vrenje, vrenje v bazenu, lasersko strukturirane površine, visokofrekvenčna tlačna nihanja, hitrotekoča infrardeča termografija
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Year: 2025
• Number of pages: XX, 68 str.
• PID: 20.500.12556/RUL-171365
• UDC: 536.2:66.046.7:534-8(043.2)
• COBISS.SI-ID: 246658563
• Publication date in RUL: 23.08.2025

Secondary language

• Language: English
• Title: Analysis of nucleation and growth process of vapor bubble in the presence of high-frequency pressure fluctuations

Abstract

Nucleate boiling is one of the most important heat transfer mechanisms, yet its control and optimization remain extremely challenging. This master's thesis investigates the influence of high-frequency pressure fluctuation produced by an ultrasonic mist generator on the formation and growth of individual bubbles. The experimental analysis was conducted on a thin metal foil with a biphilic surface under nucleate pool boiling conditions with distilled water, using a high-speed camera, infrared thermography, and an ultrasonic mist generator operating at 1.7 MHz frequency. Measurements included waiting time, nucleation temperature, heat flux removal, and bubble diameters at heat fluxes ranging from 40 to 90 kW$m^-2$. Results show systematic prolongation of waiting time by 58.8-84.4 %, increase in nucleation temperatures by 1.5-6.84 K, and enlargement of bubble diameters by 20.55-56.82 %. Heat flux removal increased by 1.49-20.81 %.

• Keywords: nucleate boiling, pool boiling, laser-textured surfaces, high-frequency pressure fluctuation, high-speed infrared thermography