管內(nèi)核心流區(qū)域?qū)α鱾鳠釓娀瘜嶒炑芯?pdf

1、華中科技大學(xué)碩士學(xué)位論文管內(nèi)核心流區(qū)域?qū)α鱾鳠釓娀瘜嶒炑芯啃彰嘿國P麟申請學(xué)位級別：碩士專業(yè)：工程熱物理指導(dǎo)教師：劉偉20070606華中科技大學(xué)碩士學(xué)位論文IIABSTRACTBasedontheanalysisofconvectiveheattransferenhancementtheyinsidetubesanewtheytoimprovetheoverallperfmanceofheatexchangershasbeenprop

2、osedinthearticlewhichinvestigatestheceflowareainsidethetubeinsteadoftheboundarylayerarea.Toachieveahighconvectiveheattransfercoefficientreducethedragfceakindoflargelengthtodiameterratiorodisusedintheceflowareainsidethetu

3、bes.Furthermeitcanreducethesizeoftheheatexchangerthusreducingthecostsassociatedwithbothmaterialmanufacturingoftheheatexchanger.Inthepresentstudytheexperimentsetuphasbeendetermined，waterisusedasthewkingfluid.Theexperiment

4、sarecarriedoutinsquarecirculartubesrespectively.IndertochecktheeffectoftheinternalrodsonboththeheattransferratepressureacrosstheheattransfertestsectionflowratesarevariedsuchthattheReynoldsnumbercouldvaryfrom1000to8500.Th

5、efirsttestisconductedwithaplaintubewithoutarod.Theresultsusingtheplaintubeserveasabasisfcomparisonfthecaseswithrods.Theresultsshowthattheaverageoverallheattransfercoefficientsinsquarecircularplaintubesareenhancedwithrods

6、byasmuchas220%190%ataconstantheatfluxrespectively.Althoughthepercentagesincreaseinpressurearelargerthanthepercentagesincreaseinheattransferratetheoverallperfmancesarebettercomparedwiththoseofplaintubes.Thatisbecauseacefl

7、owareawithmeunifmtemperatureprofilemeobviouslyvariedvelocityprofilehasbeenfmedgreatchangesinbothvelocitytemperatureprofileshavebeentakenplaceintheboundarylayerarea.ThisistheessentialcauseoftheincreaseinthevalueofPEC(Perf

8、manceEvaluationCriterion)thePEC1intheexperimentswhichmeansaconsiderableenhancementinheattransferfthegivenpumoingpower.Howeveritappearsmeclearlyinthelaminarflowthanintheturbulentflow.Atlastthestatisticalcrelationswithahig