AmovingsubgridmodelforsimulationofrefloodheattransferOriginalResearchArticle

Inthequenchfrontandfrothregionthethermal-hydraulicparametersexperienceasharpaxialvariation.Theheattransferregimechangesfromsingle-phaseliquid,tonucleateboiling,totransitionboilingandfinallytofilmboilinginasmallaxialdistance. Oneofthemajorlimitationsofallthecurrentbest-estimatecodesisthatarelativelycoarsemeshisusedtosolvethecomplexfluidflowandheattransferprobleminproximityofthequenchfrontduringreflood.Theuseofafineaxialmeshfortheentirecorebecomesprohibitivebecauseofthelargecomputationalcostsinvolved.Moreover,asthemeshsizedecreases,thestandardnumericalmethodsbasedonasemi-implicitscheme,tendtobecomeunstable. Asubgridmodelwasdevelopedtoresolvethecomplexthermal-hydraulicproblematthequenchfrontandfrothregion.ThismodelisaFineHydraulicMovingGrid(FHMG)thatoverliesacoarseEulerianmeshintheproximityofthequenchfrontandfrothregion.Thefinemeshmovesinthecoreandfollowsthequenchfrontasitadvancesinthecorewhiletherodscoolandquench.TheFHMGsoftwarepackagewasdevelopedandimplementedintotheCOBRA-TFcomputercode.ThispaperpresentsthemodelanddiscussespreliminaryresultsobtainedwiththeCOBRA-TF/FHMGcomputercode.