IV high viscosity flashing two-phase flow.pdf

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1、IVHighViscosityFlashingTwo-PhaseFlowAlbertR.MullerChairman,DIERSHighViscosityVentFlowProjectsCommitteeHarryS.ForrestChairman,DIERSPhaseHILarge-ScaleIntegralTestCommitteeHaroldG.FisherChairman,DIERSTechnicalCommitteeI.INTRODUCTION1-1.GeneralDiscussionofHighViscosityFlowinReliefSystems

2、ChapterII,"PressureReliefSystemFlow,"coversmostaspectsofflashingtwo-phaseflowinwhichbothliquidandvaporand/orgasarepresentatthesametimeinareliefsystem.Mostofthesimplifiedmodelsdevelopedforthedesignofemergencyreliefsystemsarespecificforturbulentflowwherethefrictionlossisasmallfractiono

3、fthetotalpressuredrop.Simplifiedmodelsbasedonlaminarflowhavealsobeendeveloped(seeAppendixIV-A).Experimentswithviscousfluids(e.g.,rubbercementat20%solidsandpolystyrene-ethylbenzenesolutionsat60%polymer)illustratedtheeffectofhighviscosityinincreasingthefrictionlossinareliefline.Inturbu

4、lentflashingflowsystems,arelieflineof1000pipediametersinlengthisrequiredtoreducetheflowto50%ofthatinafrictionlessnozzleofthesamediameter.However,inlaminarflashingflowwithaliquidphaseviscosityofover100centipoise,thefrictionallossofasmalldiameterrelieflinewitha200LIDreducedtheflowtoabo

5、utonetenththatofafrictionlessnozzle.ForagivenviscosityandrelieflineLID,thefrictionlossincreasesasthepipediameterdecreases.Ifthepipediameterissmallenough,theflowratemaybeseveralordersofmagnitudelessthanthatforfrictionlessnozzleflow.Afewexperimentsindicatedthattheeffectofliquidviscosit

6、yonfrictionlosscouldbeminimizedforpipingconfigurationswithanareaflowreductionlessthan7pipediametersfromthevesselfollowedbyalargerdiametertailpipe.Thisresultappearstobeduetoachangefromaliquidtoavaporcontinuousflowregime.However,theparametersthatcontroltherelieflineflowregimearenotfull

7、yunderstoodandtherecommendedmethodtodesignreliefsystemsforviscousflowisdirectscalingusingthemethodsdescribedinthissection.1-2.WhyHighViscositySystemsRequireSpecialConsiderationMostoftheexperimentalworkearlyintheDIERSprojectwaswithlow-viscositysystems(i.e.,systemsthathadviscositiesles

8、sthan50centi