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1、IVaporDisengagementDynamicsHaroldG.FisherChairman,DIERSTechnicalCommittee1.OVERVIEWItisnecessarytoconsiderliquidcarryoverintothereliefdevicetodesignasafeemergencyreliefsystemforarunawayreactioninaprocessvessel[I].Generally,thepresenceoftwo-phasevapor-liquidfloww
2、illrequirealargeremergencyreliefarearelativetoallvaporventing.1-1.VaporDisengagementDynamicsThevaporandliquidmotioninsideareactororstoragevesselduringemer-gencyreliefventingisanextremelycomplexhydrodynamicproblem.Thequestionofvaporversustwo-phasevapor-liquidreli
3、efdependsprimarilyontheprevailingdisengagementregime,thatis,bubblyand/orfoamy-likebehaviororchurn-turbulentbehavior.Theformerregimeisindicativeofrelativelylittlevapordisengagement.Incontrast,significantvapordisen-gagementispossiblewiththechurn-turbulentregime;th
4、atis,thevapor-liquidphaseratioenteringthereliefdevicecandiffersubstantiallyfromtheaveragequalityinthevessel.Whilereliablefirst-orderestimatesofsignificantvapordisengagementarenowpossibleforsimple,single-componentsystems,thedescriptionofthesephenomenaisnotprecise
5、forchemicallyreactingsystems.Theformanddegreeofbubblyandorfoamybehaviorarehighlydependentontheparticularsystempropertiesandminutequantitiesofimpurities.Rathersmallamountsofimpurities,suchasdetergentinwaterordissolvedpolymerinethylbenzene,promotefoamingbehavior.F
6、oamingbehaviorseverelylimitstheextentofvapordisengagement.Anextensivetreatmentofvapordisen-gagementdynamicsispresentedinAppendicesI-AtoI-C.1-2.DesignConsiderationsBasedonexperiencegainedintheDIERSprogram,designapplicationsusingapartialvapor-liquiddisengagementan
7、alysisappeartobespecializedand,becauseofthepotentialforintroducinganunsafebias,shouldbeusedwithextremecaution.Ingeneral,itisdifficulttoprecludeviscousorfoamingcharacteristics,whicheffectivelypreventsignificantvapordisengagementunderemergencyconditions.Unlessvapo
8、rdisengagementcharacterizationdataareavailableforagivensystemunderprototypicrunawayreliefcon-ditions,ahomogeneousvapor-liquidmixtureenteringthereliefdeviceshouldbecon
