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1、InternationalJournalofHeatandFluidFlow27(2006)135–143www.elsevier.com/locate/ijhffCharacterizationoffluiddynamicbehaviourandchannelwalleffectsinmicrotubea,*baG.P.Celata,M.Cumo,S.McPhail,G.ZummoaENEA,InstituteofThermalFluidDynamics,ViaAnguillarese301,00060SantaMariadiGaleria,Rome,ItalybU
2、niversityofRome‘LaSapienza’,CorsoVittorioEmanueleII,244Rome,ItalyReceived11December2004;receivedinrevisedform28March2005;accepted28March2005Availableonline16June2005AbstractSometimescontradictoryresultsavailableforfluidflowinmicropipesshowthatmuchisyettobeverifiedinmicrofluiddynamics.Int
3、hisstudytheinfluenceofchannelwallroughnessandofchannelwallhydrophobicityonadiabaticflowincircularmicrochannelsisinvestigated,varyingindiameterfrom70lmto326lm.Thehydrodynamicbehaviourofwaterinsmoothtubesdownto30lminnerdiameter(ID)isalsoascertained.Withinthecurrentexperimentalaccuracyiti
4、sfoundthattheclassicalHagen–Poiseuillelawforfrictionfactorvs.ReynoldsnumberisrespectedforalldiametersmeasuredandRe>300.Withdegassedwater,noeffectofslipflowduetohydrophobicchannelwallswasnotedevenat70lmID,whichmightsuggestthattheliquidslipflowphenomenonisassociatedwithlocaldesorptionofdi
5、ssolvedgasesonthehydrophobicsurface,asreportedelsewhereintheliterature.Forrough-enedglasschannels,anincreaseinDarcyfrictionfactorabove64/Rewasobservedonlyatthesmallestdiametermeasured,126lm.Althoughtheroughnesslevelsofthesechannelswereupto10timescoarserthantheuntreated,smoothglasstub
6、es,probablythehigherfactorwascausedbyactualdeformationofchannelcircularity,ratherthanincreasedfrictionattherougherwall,assimilarbehaviourwasobservedinaTeflontube,alsoofimperfectcircularityofcross-section.Forallexperiments,noanticipatedtransitiontoturbulentflowwasobserved,whichmeansthat
7、thetransitionalReynoldsnum-berwasalwaysfoundbetweenRe2000andRe3000.Finally,anintroductiontotheimportanceofviscousdissipationinmicrochannelsisadded,withquantitativeindicationsofitsinfluenceonhydrodynamicproperties.Itisputforwardasbeinganalternativetopressuremeasurementsinthecharacter
8、izationofthe
