Eksperimentalno preučevanje in modeliranje dinamike mehurčkov v konvektivnem vrenju
Oznaka in naziv projekta
NC-25003 Eksperimentalno preučevanje in modeliranje dinamike mehurčkov v konvektivnem vrenju
NC-25003 Experimental investigation and modelling of bubble dynamics in convective boiling
Logotipi ARIS in drugih sofinancerjev
Projektna skupina
Vodja projekta: dr. Tekavčič Matej
Sodelujoče raziskovalne organizacije: Povezava na SICRIS
- IJS R4 (Odsek za reaktorsko tehniko)
- CEA, Francija, dr. Raksmy Nop
Sestava projektne skupine: Povezava na SICRIS
dr. Matej Tekavčič, dr. Boštjan Končar, dr. Blaž Mikuž, Gregor Kozmus, Aljoša Gajšek (MR), Izak Kreuh (MR)
Vsebinski opis projekta / Project contents
SLO:
Izzivi trajnostne proizvodnje energije zahtevajo razvoj stroškovno konkurenčnih sistemov za pretvorbo energije z visoko učinkovitimi rešitvami za prenos toplote. Konvektivno vrenje je eden najučinkovitejših mehanizmov prenosa toplote, vendar le do meje kritičnega toplotnega toka (CHF). Prekoračitev omejitve CHF povzroči hitro poslabšanje prenosa toplote, torej hlajenja, kar vodi v nenadzorovano zvišanje temperature. Pri tem nastanejo mehanske poškodbe toplotno obremenjenih komponent. Razumevanje in obvladovanje CHF je torej ključno za načrtovanje varnih in učinkovitih sistemov.
Predlagani projekt se osredotoča na eksperimentalne in teoretične raziskave konvektivnega vrenja. Obstoječi eksperimenti običajno ne omogočajo direktnega opazovanja vrenja zaradi neprozorne testne sekcije. Večina eksperimentov je električno ogrevanih z nadzorovanim toplotnim tokom, kar omejuje delovanje in meritve preblizu CHF. V okviru predlaganega projekta bo v termohidravličnem laboratoriju THELMA na Institutu “Jožef Stefan” postavljen eksperiment s prozorno testno sekcijo in temperaturno nadzorovanim gretjem hladila z vodo. To nam bo omogočalo natančen nadzor režima konvektivnega vrenja pri visokih toplotnih tokovih. Testna sekcija bo omogočala hkratno direktno opazovanje vrenja in meritve temperature stene, ključni parameter pri modeliranju. Hkrati bomo z obdelavo posnetkov lahko merili porazdelitev velikosti mehurčkov, še en pomemben parameter, ki ga lahko uporabimo za preverjanje populacijskih modelov mehurčkov (PBM). V okviru teoretičnih raziskav se bomo ukvarjali predvsem z napovedmi porazdelitev deleža pare in velikosti mehurčkov v konvektivnem vrenju z metodami računalniške dinamike tekočin (CFD) in dvofluidnega modela. Osredotočili se bomo na modeliranje medfaznih sil med mehurčki in kapljevino, na primer dvižne sile, ter na modeliranje mehanizmov razpadov in združevanj mehurčkov v populacijskih modelih.
Osnovni podatki sofinanciranja so dostopni na spletni strani SICRIS.
ANG:
Challenges in sustainable energy production call for the development of cost-effective conversion systems incorporating highly efficient heat transfer solutions. Convective boiling can be one of the most efficient heat transfer mechanisms, but only up to the critical heat flux (CHF) limit. If exceeded, CHF leads to a rapid reduction of heat transfer, deterioration of cooling, uncontrolled rise of temperature and finally structural damage of components under heat loads. Understanding and controlling the phenomena is therefore crucial for the design of safe and competitive systems.
Proposed project focuses on experimental and theoretical research of convective boiling. Visual observation of boiling is typically not possible in existing experiments due to non-transparent test sections. Most experiments are also electrically heated and heat-flux controlled, which usually prevents operation too close to CHF limits. Transparent test section of the new improved temperature-controlled (water heated) annular flow boiling experiment in THELMA thermohydraulic laboratory at Jožef Stefan Institute will specifically allow for simultaneous visual observation of boiling alongside wall temperature measurements, the latter being a key parameter in modelling. The distribution of bubble sizes, another important parameter, will be obtained with image processing and used to evaluate population balance models (PBM). Theoretical studies will focus on the prediction of vapour and bubble size distribution in boiling flow with computational fluid dynamics (CFD) using the two-fluid modelling approach. Modelling efforts will focus on the modelling of bubble interfacial forces, such as lift force, and break-up and coalescence kernels of PBM. Model development and validation will be based on aforementioned boiling experiment together with existing data available in the literature.
Faze projekta in opis njihove realizacije
The project consists of two work packages (WP):
- WP1 - experimental investigations, with 12 person months (PM) of work (leader JSI)
- WP2 - modelling, with 6 PM of work (leader CEA)
The experimental part, led by JSI, with visual measurements of bubble size distribution, will aid in understanding of bubble coalescence and breakup processes, alongside effects of bubble interfacial forces. Visual data with simultaneous measurements of wall temperature will also develop our knowledge of near-wall bubble dynamics and mechanisms of boiling.
The theoretical modelling part, led by CEA, will focus on improving predictions of vapour fraction and bubble size distribution in convective boiling using the two-fluid modelling approach. In unison with experimental part, theoretical efforts will primarily aim to improve coalescence and breakup kernels of population balance models and modelling of interfacial forces, such as the lift force.
Project timetable and task descriptions are as follows:
- WP1 - experimental investigations (leader JSI):
- WP1 – Task 1 (year 1): horizontal configuration - measurement campaign and data post-processing [completed]
- WP1 - Task 2 (year 1-2): vertical configuration - measurement campaign and data post-processing [completed]
- WP1 - Task 3 (year 2): experimental data analysis to support model development [in-progress]
- WP2 - modelling (leader CEA):
- WP2 - Task 1 (year 1): initial simulations of THELMA experiment (horizontal and vertical) with existing convective boiling models [completed]
- WP2 - Task 2 (year 1-2): simulation results analysis and evaluation of the existing models [in-progress]
- WP2 - Task 3 (year 2): model improvement and validation with experimental data [in-progress]
Project milestones are:
- M1: completion of Task 1 in both WPs after 1st year, [completed]
- M2: completion of Task 2 and 3 in both WPs after 2nd year.