20.500.12556/RUL-139827 Vpliv ultrazvoka na prenos toplote pri vrenju Influence of ultrasound on heat transfer during boiling Vrenje je proces pri katerem pride do fazne spremembe iz kapljevinastega v plinasto agregatno stanje. Zaradi fazne spremembe se prenese velika količina toplote pri majhni temperaturni razliki med grelno površino in tekočino. Vrenje v bazenu je eden najučinkovitejših načinov prenosa toplote, vendar ga želimo zaradi vrste različnih aplikacij izboljšati. Eden od načinov izboljšanja prenosa toplote pri vrenju je s pomočjo ultrazvočnega valovanja. Pri vrenju se grelna površina prekrije s parno fazo in prenos toplote se zmanjša, saj para deluje kot izolator. Ultrazvočni valovi pospešijo odstopanje mehurčkov z grelne površine in na ta način preprečujejo združevanje mehurčkov in nastajanje parnega filma. S pomočjo hitre kamere smo vizualizirali proces vrenja brez prisotnost ultrazvoka in pri različnih amplitudah sonotrode. Proces vrenja je bil posnet pri različnih toplotnih fluksih in posledično v različnih režimih vrenja. Eksperiment je pokazal pozitiven vpliv ultrazvoka na odstranjevanje parnih mehurčkov z grelne površine. Vpliv ultrazvoka je največji pri nižjih toplotnih fluksih in se z naraščanjem toplotnega fluksa manjša. Boiling is a process in which phase change occurs from a liquid to a gaseous aggregate state. Due to phase changes, a large amount of heat is transferred at small temperature differences between the heating surface and the liquid. Pool boiling is one of the most efficient methods of heat transfer, but we want to improve it due to the range of different applications. One way to improve heat transfer in boiling is to use ultrasonic waves. During boiling, the heating surface is covered with the vapor phase and the transfer of heat is reduced, as the vapor acts as an insulator. The ultrasonic waves accelerate the departure of the bubbles from the heating surface and in this way prevent the bubbles to merge and form a vapor film. With the help of a high-speed camera, we visualized the boiling process without the presence of ultrasound and at different sonotrode amplitudes. The boiling process was recorded at different heat fluxes and consequently in different boiling regimes. The experiment showed the positive influence of ultrasound on the removal of vapor bubbles from the heating surface. The influence of ultrasound is greatest at lower heat fluxes and decreases as the heat flux increases. vrenje izboljšanje prenosa toplote ultrazvok hitra kamera boiling heat transfer enhancement ultrasound high-speed camera true false false Slovenski jezik Angleški jezik Diplomsko delo/naloga 2022-09-07 15:05:00 2022-09-07 15:05:04 2022-11-04 12:13:04 0000-00-00 00:00:00 2022 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 21816 128085763 Lazar_Tina_-_Vpliv_ultrazvoka_na_prenos_toplote_pri_vrenju.pdf Lazar_Tina_-_Vpliv_ultrazvoka_na_prenos_toplote_pri_vrenju.pdf 1 D8164CAE901D685B7AB72112ED636886 c2cbc653111705ab9d8268559a9f115b91722dc632cf7de3d88f902b70435371 a3579447-2ead-11ed-92af-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=160455 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0