Termohidrauličke oscilacije dvofaznog toka

master's thesis

• Title (english): Two-phases flow thermohydraulic oscillation
• Author: Josip Krtolačić
• Mentor: Dražen Lončar (mentor)
• Committee member: Neven Duić (predsjednik povjerenstva)
• Committee member: Hrvoje Juretić (član povjerenstva)
• Committee member: Tomislav Pukšec (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2023-05-10, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Process Energy Engineering

Abstract

Oscilacije dvofaznog toka mogu izazvati pogonske probleme ili pucanje dijelova postrojenja, pa je predviđanje oscilacija neophodno za njihovo sprječavanje. Dan je pregled režima strujanja smjese kapljevina-para i opis termohidrauličkih oscilacija dvofaznog toka. Opisane su najviše istražene nestabilnosti dvofaznog toka koje se ujedno i najčešće pojavljuju. Klasifikacija je provedena slijedom opisa u dostupnoj literaturi. Režimi strujanja bit će bitni kod računanja pada tlaka i koeficijenta prijelaza topline u poglavlju - Numerička simulacija, u kojem je izvedena diskretizacija jednadžbi koje opisuju sustav metodom konačnih volumena i objašnjavaju se načini rješavanja problema numeričke matematike implementirani pri razvoju rješavača. Na kraju su izloženi rezultati četiriju simulacija, tri prikazuju različite tranzijentne pojave, dok četvrta pokazuje pojavu numeričkih nestabilnosti i divergencije.

Abstract (english)

Oscillations of two-phase flow can cause operational problems or even the rupture of plant and system components, so predicting oscillations is necessary for their prevention. A review of the flow regimes of the liquid-vapor mixture and a description of the thermohydraulic oscillations of two-phase flow are given. The most extensively studied and most frequently occurring instabilities of two-phase flow are described, and a classification is conducted based on the available literature. Flow regimes will be important in calculating pressure drop and heat transfer coefficient in the chapter - "Numerical Simulation", where the discretization of equations describing the system is performed using the finite volume method and ways of solving numerical mathematics problems implemented in the solver development are explained. Finally, the results of four simulations are presented, three of which show different transient phenomena, while the fourth shows the occurrence of numerical instabilities and divergence.

• Keywords: nestabilnosti dvofaznog toka; oscilacije; isparivač; metoda konačnih volumena; numerička simulacija
• Keywords (english): two-phase flow instabilities; oscillations; evaporator; finite volume method; numerical simulation
• Language: croatian
• URN:NBN: urn:nbn:hr:235:716788
• Study programme: Title: Mechanical Engineering; specializations in: Design, Process and Energy Engineering, Production Engineering, Engineering Modelling and Computer Simulation, Marine Engineering, Industrial Engineering and Management, Materials Engineering, Mechatronics and Robotics, Autonomous Systems; Course: Process and Energy Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-05-12 17:26:49