20.500.12556/RUL-134748 Numerical modeling of non-condensable gases transport in two-phase flow Numerično modeliranje transporta nekondenzibilnih plinov v dvofaznem toku The presence of non-condensable gases at the gas-liquid interface significantly decreases the heat and mass transfer, and disturbs the fluid flow. Thus, modeling the transport of non-condensable gases in two-phase flow is of great importance in nuclear reactor safety. Non-condensable gases transport in two-phase flow is considered as a multi-component flow, where the non-condensable gases are assumed to be homogeneously mixed with steam in the gas phase. Modeling of non-condensable gases transport has been already done by Computational Fluid Dynamics, system thermal-hydraulics codes, and numerical simulations. This work is dedicated to the Apros thermal-hydraulics system code. Some stability and convergence issues can show up when modeling non-condensable gases in the the current version of the code Apros 6; for example, when the gas phase consists of a high mass fraction of non-condensable gas with a very low mass fraction of steam. In the present work, a new procedure is proposed to integrate the non-condensable gases transport equation solution in the two-fluid six equations solution algorithm to develop a new thermal-hydraulic solver. A new pressure equation is derived based on considering the non-condensable gas transport equation solution from the beginning of the numerical algorithm formulation. This is expected to improve the stability and convergence by ma- king the non-condensable gas transport equation solution more tightly coupled with the pressure equation. The oscillating U-tube numerical benchmark test case was simulated to verify and validate the new implementation of the new pressure equation. The results of the oscillating U-tube show good agreement with the analytical solution when using a dense nodalization. The second test performed was the simulation of experiments on con- densation in the presence of non-condensable gases in the separate test facility CONAN. Experiments were simulated with a constant heat transfer coefficient and a heat transfer coefficient, obtained from the Uchida correlation. The simulation results were quantita- tively reasonable. Moreover, the results showed qualitatively the same behavior as the experimental data. In addition, a hypothetical case with a varying velocity behavior was also simulated (with a constant heat transfer coefficient). Prisotnost nekondenzibilnih plinov na vmesni površini plin-kapljevina znatno zmanjšuje prenos toplote in snovi ter vpliva na tok tekočine. Zato je modeliranje transporta nekondenzibilnih plinov v dvofaznem toku zelo pomembno pri varnosti jedrskih reaktorjev. Transport nekondenzibilnih plinov v dvofaznem toku se obravnava kot večkomponentni tok, kjer se predpostavlja, da so nekondenzibilni plini homogeno pomešani z vodno paro v plinasti fazi. Modeliranje transporta nekondenzibilnih plinov je bilo že opravljeno v računski dinamiki tekočin, sistemskih termo-hidravličnih programih in drugih numeričnih simulacijah. To delo je namenjeno obravnavi termo-hidravličnega sistemskega programa Apros. Pri modeliranju nekondenzibilnih plinov v sedanji verziji programa Apros 6 se lahko pojavijo nekateri problemi stabilnosti in konvergence; kot primer, ko je plinasta faza sestavljena iz velikega masnega deleža nekondenzibilneg plina in nizkega masnega deleža vodne pare. V tem delu je predlagan novi postopek za vključitev enačb transporta nekondenzibilnih plinov v reševanje šest-enačbnega dvo-fluidnega modela dvofaznega toka s ciljem razvoja novega termo-hidravličnega algoritma za reševanje. Nova tlačna enačba je izpeljana na podlagi obravnave nekondenzibilnega plina od samega začetka formulacije numeričnega algoritma. Pričakujemo, da bo to izboljšalo stabilnost in konvergenco s tem, ko bodo enačbe transporta nekondenzibilnih plinov bolj tesno sklopljene s tlačno enačbo. Za preverjanje in validacijo novega algoritma reševanja je bil simuliran testni primer nihajoče U-cevi. Rezultati se pri uporabi goste nodalizacije dobro ujemajo z analitično rešitvijo. Drugi preizkus je bil simulacija eksperimentov kondenzacije v prisotnosti nekondenzibilnih plinov, ki so bili izvedeni v separatni eksperimentalni napravi CONAN. Pri simulacijah sta bila uporabljena dva različna pristopa: konstanten koeficient prenosa toplote in koeficient prenosa toplote, dobljen s korelacijo Uchida. Dobljeni rezultati simulacij so bili kvantitativno smiselni. Rezultati so pokazali tudi kvalitativno enako vedenje kot eksperimentalni rezultati. Poleg tega je bil simuliran še hipotetični primer s spreminjajočim obnašanjem hitrosti, s predpisanim konstantnim koeficientom prenosa toplote. Apros non-condensable gases two-phase flow thermal hydraulics system codes. Apros nekondenzibilni plini dvofazni tok termo-hidravlični sistemski programi. true false false Angleški jezik Slovenski jezik Magistrsko delo/naloga 2022-01-29 08:15:02 2022-01-29 08:15:12 2022-09-14 04:09:41 0000-00-00 00:00:00 2021 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 123011 90436355 4228.pdf 4228.pdf 1 3A2B42636F31F060ACE754737B74D45B 2a43f169850044ec70f6ed27de1d988e33c6207cbf6551355a0177ebca06d562 fdbc98fe-80d2-11ec-abdb-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=153370 Fakulteta za matematiko in fiziko 0 0 0