ExperimentalstudyontheeffectofanglesandpositionsofmixingvanesonCHFina2×2rodbundlewithworkingfluidR-134aOriginalResearchArticle

Inthispaper,theCHFexperimentontheeffectofanglesandpositionofmixingvaneswasperformedina2×2rodbundle.Thetestsectionhadrectangulargeometryinwhichfourrod,eachwithadiameterof9.5mm,wereinserted.Therod-to-rodgapwas3.15mm,andtherod-to-wallgapwas1.575mm.Itwasverticallyinstalledinthetestloopandwasuniformlyheatedbyelectricity.Theheatinglengthwas1.125m.TheworkingfluidwasR-134a.Themassfluxrangedfrom1000to1800kg/m2.Thetestpressurerangedfrom14.67to25.67bar.CHFdatainthe2×2rodbundlewithoutamixingvanewerecomparedtotheBowringcorrelationandaCHFlook-uptableatequivalenthydraulicdiameter.Forthiscomparison,Kattoʹsfluid-to-fluidmodelisapplied.Theresultshadagoodagreementwitherrorratesof16and20%.IntheCHFexperimentwiththemixingvaneswithvariousangles,theanglesofthemixingvaneswere20–40°.TheCHFenhancementratio(CER)waslargestat30°.CHFwasenhancedupto19%.ACHFexperimentonthepositionofthemixingvanewasalsoperformed.Intheexperimentonthepositionofmixingvane,CERwasreducedwithincreasingdistancebetweengridandCHFlocationbecauseswirlflowdecayed.WealsoperformedtheCHFexperimentonmixingvanedevelopedbyKAIST.