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1、ChmidEngineeringScience,Vol.48,No.12.pp.2251-2265.1993.0009-2509/93S6.00+0.00F’rintalinGreatBritain.Q1993FergamonPressLtdMIXINGOFHOMOGENEOUSSOLIDSINBUBBLINGFLUIDIZEDBEDS:THEORETICALMODELLINGANDEXPERIMENTALINVESTIGATIONUSINGDIGITALIMAGEANALYSISKOKS.LIM,VENKATA
2、S.GURURAJANandPRADEEPK.AGARWAL+DepartmentofChemicalEngineering,UniversityofAdelaide,GPO‘Box498,Adelaide,Australia,SO01(Firstreceived22October1991;acceptedforpublicationinrevisedform9September1992)Ahstrnct-Anautomatednon-intrusiveimageanalysismethodhasbeendeve
3、lopedforfollowingthecourseofsolidsmixingintwo-dimensionalbubblingfluid&dbeds.Inthisinvestigation,experimentaldatahavebeenobtainedontheaxialmixingofuniformsolids.Oscillationsintheconcentrationresponse,resultingfromthegrosscirculationofthesolids,havebeenobserve
4、dexperimentally.Theseoscillationsbecomeincreasinglymoreprominentasthebedparticlesizeincreases.Thesemeasurementshavebeenusedtoevaluatethethree-phasecounter-currentback-mixingmodel(Gwynetal.).Thebubbleparametersrequiredforthemodelwereobtainedfromindependentexpe
5、rimentsconductedasapartofthisinvestigation;theexchangecoefficient,however,wasfoundbyparameterestimationusingthesolidsmixingdata.Withthischoiceofoarameters.thecounter-currentflowmodelhasbeenfoundtoaredicttheexberimentaltrendsreasonablywell.The’estimatedvaluesf
6、ortheexchangecoefficientdondtcomparefaiourablywiththepredictionsofthemodelsavailableintheliterature(YoshidaandKunii,andChibaandKobayashi).Thesemodelspredictthatthewakeexchangecoefficientshouldincreasewithincreaseintheminimumfluid-izationofthebedparticles.Ourr
7、esults,ontheotherhand,showthatthewakeexchangecoe&ientincreaseswithU&J,,,,forU,/U,-=z3andthevalues,inthisregion,areindependentoftheparticlesize.Inlinewiththeseresults,theexperimentalmeasurementsofChibaandKobayashi,forinjectedbubblesinatwo-dimensionalfluid&dbed
8、ofparticlessmallerthanthoseusedinthisinvestigation,arefoundtobeinexcellentagreementwiththelowerboundofourestimations.INTRODUCTIONcients;astrongadvantageofthisapproachistheeaseItiswell-rec
