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页数:7页
时间:2019-07-06
《Heat transfer enhancement of nano-fluids》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、InternationalJournalofHeatandFluidFlow21(2000)58±64www.elsevier.com/locate/ijhHeattransferenhancementofnano¯uidsYiminXuan*,QiangLiSchoolofPowerEngineering,NanjingUniversityofScienceandTechnology,Nanjing210094,People'sRepublicofChinaReceived5February1999;accepted1September19
2、99AbstractThispaperpresentsaprocedureforpreparinganano¯uidwhichisasuspensionconsistingofnanophasepowdersandabaseliquid.Bymeansoftheprocedure,somesamplenano¯uidsareprepared.TheirTEMphotographsaregiventoillustratethestabilityandevennessofsuspension.Thetheoreticalstudyofthethe
3、rmalconductivityofnano¯uidsisintroduced.Thehot-wireapparatusisusedtomeasurethethermalconductivityofnano¯uidswithsuspendedcoppernanophasepowders.Somefactorssuchasthevolumefraction,dimensions,shapesandpropertiesofthenanoparticlesarediscussed.Atheoreticalmodelisproposedtodescr
4、ibeheattransferperformanceofthenano¯uid¯owinginatube,withaccountingfordispersionofsolidparticles.Ó2000ElsevierScienceInc.Allrightsreserved.Keywords:Nano¯uid;Enhancedheattransfer;Thehot-wireapparatus;DispersionNotationSubscriptseeectiveAqcross-sectionareaf¯uidathermaldiusivi
5、typparticlecpspeci®cheatxx-directionCconstantrr-directiondaveragediameterDthermaldispersioncoecientfFanningfrictionfactorhconvectiveheattransfercoecientkthermalconductivity1.IntroductionmnumberoftheparticlesperunitvolumenparticleempiricalshapefactorLowthermalconductivityof
6、process¯uidhindershighNulocalNusseltnumbercompactnessandeectivenessofheatexchangers,althoughaPePecletnumbervarietyoftechniquesisappliedtoenhanceheattransfer.Im-PrPrandtlnumberprovementofthethermalpropertiesofenergytransmissionqheat¯uxperunitlength¯uidsmaybecomeatrickofaugme
7、ntingheattransfer.AnrradialvariableinnovativewayofimprovingthethermalconductivitiesofRinnerradiusofthetube¯uidsistosuspendsmallsolidparticlesinthe¯uids.VariousReReynoldsnumbertypesofpowderssuchasmetallic,non-metallicandpolymericxaxialvariableparticlescanbeaddedinto¯uidstofo
8、rmslurries.Thethermalttimeconductivitiesof¯uidswithsuspendedparticlesareexpectedTt
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