外文翻译轴流管壳式换热器壳侧流体进 出口分布挡板的理论研究.docx

外文翻译轴流管壳式换热器壳侧流体进 出口分布挡板的理论研究.docx

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外文翻译轴流管壳式换热器壳侧流体进出口分布挡板的理论研究

外文翻译---轴流管壳式换热器壳侧流体进出口分布挡板的理论研究

外文翻译

THEORETICALINVESTIGATIONOFFLUIDDISTRIBUTORIN

THEINLET/OUTLETREGIONOFSHELL-SIDEOFSHELL-AND-TUBEHEATEXCHANGERWITHLONGITUDINALFLOW

ZENGWen-Liang1，2,HUXian-ping1,DENGXian-h1

（1.TheKeyLab.ofEnhancedHeatTransfer&EnergyConservationoftheMinistryofEducation,SouthChinaUniversityofTechnology,Guangzhou510640,China;2.TheChemistryandMaterialsDepartment,HengyangNormalUniversity,Hengyang　421001,China）

Abstract:

Presentsthetheoreticalinvestigationoffluiddistributorintheregionofinlet/outletofshell-sideofshell-and-tubeheatexchangerwithlongitudinalflowinthispaper.Itisadvancedthestructuraloptimalmathematicalmodelamongthevariousstructuralparametersofshell-sideofheatexchanger.Themodelprovidesreferenceanddirectionnotonlyforexperimentalandnumericalinvestigationofthisproblem,butalsofortheotherprocesswithfluiddistribution.

Keywords:

shell-and-tubeheatexchanger;longitudinalflow;fluiddistribution;structuraloptimization;theoreticalmodel

CLCNumber:

TQ051.5　　　　DocumentCode:

A

0　Introduction

Becauseofsuchadvantagesaslowerpressuredropofshell-side,largerlogarithmicmeantemperaturedifference（LMTD）,eliminatingvibrationofheat-transfertubes,andbetteroverallheattransferperformance,shell-and-tubeheatexchangerswithaxialflowhavebecomemorepopularinvariousareasofindustrialprocesscomparingwithshell-and-tubeheatexchangerswithsegmentbaffles.Withthescaleofindustrialproductiondevicesbecomelagerandlarger,heatexchangerasatypeofuniversalequipmentinindustrialprocessalsoneedtosatisfytherequirementofindustrialprocess,andtheheattransfercapabilityofheatexchangerbecamelargerandlarger.Becausethelengthoftubeofshell-and-tubeheatexchangerisdecidedbyprocessingtechnologycondition,itisnecessarytoenlargethediameterofshell-sideinordertoenlargetheheattransfercapability.Withtheincreasingofdiameterofheatexchangeranddecreasingoftheratiooflengthanddiameter（L/D）,shell-sidefluidflowmaldistributionbecamemorebadlyandpressuredropofshell-sideincreasedmorequickly,itisnotonlyreducetheoverallheattransferperformanceofheatexchangerbutalsoinducevibrationofheat-transfertubes.TheseareprovedbyZHOUSen-quan[1],ChiouJ.P[2],UlrichMohrandHorstGelbe[3].Inordertomakefluidflowhomo-distribution,constructingafluidflowdistributorandsettingitintheregionofinletoroutletofequipmenthavebeencarriedoutbyS.S.Mousavi,K.Hooman[4]andL.Maharaj,J.Pocock,B.K.Loveday[5].Butthereisnoanyreportoffluidflowdistributorabouttheshell-sideofshell-and-tubeheatexchangerwithaxialflow,especiallythelarge-scaleandsuper-largescaleheatexchanger.Settingfluiddistributoralsohasadvantageanddisadvantageatthesametime.Ononehandshell-sidefluidflowmaldistributioncanbeimprovedquickly,ontheotherhandpressuredropofshell-sidebeincreasedquicklyatsametime.Soitisveryimportanttodevelopthetheoretical,numerical,andexperimentalinvestigationoffluidflowdistributorofshell-and-tubeheatexchanger.Thepurposeofthisresearchprogramistooptimizestructuralparameterofheatexchanger,toimproveshell-sidefluidflowmaldistribution,toreduceshell-side-pressuredrop,andtoenhanceoverallheattransferperformance,bytheoretical,numerical,andexperimentalinvestigationmethodsrespectively.Inthispaper,itwillintroduceoptimalmathematicalmodelamongthevariousstructuralparametersofheatexchangerbytheoreticalmethods.

1　PhysicalModel

Theoverallshell-sidestructuraldrawingandthepositionoffluidflowdistributorofshell-and-tubeheatexchangerwithaxialflowareshownasFig.1（a）.Fig.1（b）isthesketchmapofshell-sideflowdistributorstructure.Infact,itiseasilytounderstandthefluiddistributorstructureasthatisaspecifiedpunchedratioboardpunchedmanymini-ostiolesonitfromtheFig.1（b）.Thepurposeoftheoreticalinvestigationistofoundamathematicalmodelwhichbringsouttheoptimalpunchedratioofdistributorasafunctionofparameterofheatexchanger.Themainaspectsaffectingthefluidflowdistributionofshellsideareshownasfollows:

（1）punchedratioofdistributor;

（2）rowsofcrossingtubes;（3）arrangementstyleoftubes;（4）tubepitch;（5）tubeouterdiameter.

　Fig.1　Schematicdrawingofshellsideconfigurationofshellandtube

heatexchangerswithaxialflow

Inordertoexpresstheresearchedphysicalmodelmoreconcisely,itisbetreatedasarectangleheat

exchangerwithaxialflowwhenwetakeintoaccountthepartialunitanditsinletandoutletonly.The

heatexchangerismadeupof36tubesspecificationofφ25mm×2.5mm×1000mm.Theexteriordimensionofheatexchangerisacubewiththedimensionof360mm×120mm×1000mm.TheelevationofheatexchangerisshowninFig.2（a）.ArrangementstylesandparameteroftubesisshowninFig.2（b）.

2　MathematicalModel

Inordertofoundthemathematicalmodelintheoreticalmethod,atheoreticalanalysismodelmustbebuiltfirstlyasFig.3.Thefollowingassumptionsandilluminationarenecessaryformodelingfluidflowingthroughtheinletregionanddistributor.

（1）Manymini-ostiolesbepunchedinthefluiddistributedbaffle,anddiameterofmini-ostiolesisinfinitesimal.

（2）Punchedratioofdistributedbaffleisacontinuousfunctionwithxcoordinate.

（3）FluidflowinthexdirectionasshowninFig.3.

（4）Fluidflowvelocitythroughdistributedbaffleisuniform.

Basedaboveassumptionsandnextanalysis,itiseasytodeducethevelocitydistributionofxdirectionandpressuredropofxdirection,zdirection,andx-zdirectionrespectively.

2.1　Velocitydistributionofxcoordinate

MassbalanceEquationoftheinfinitesimalisshowninFig.4,andthedifferentialEquationofx

Fig.4　SchematicDrawingofanalyzedarea

directionvelocityisobtainedasEqua.

（1）:

（1）

　　WhereAxandAzdenotetheareaofxcoordinateandzcoordinate,respectively.

And

;

（2）

Theboundaryconditionis:

x=Xwithu（x）=0,sotheintegralofEqua.

（2）canbeexpressedasfollows:

（3）

（4）

2.2　Pressuredropofxcoordinate

TheenergybalanceEquationoftheinfinitesimalareaisshowninFig.4.ItsdifferentialEquationof

xdirectionpressuredropcanbeobtainedasfollow:

（5）

　　WhereDHishydraulicdiameterofshell-side.

Theboundaryconditionisx=0withΔp（x）=0,sotheintegraloftheEqua.（5）canbeexpressedas:

（6）

（7）

2.3　Pressuredropofx2zdirection

Accordingtodistributionandlocalflowpressuredropoffluidflowfromxdirectionturntozdirection,wecanobtainitslocalpressuredropEquationasfollow:

（8）

2.4　Pressuredropofzcoordinate

AccordingtothegenericEquationoflocalpressuredropoffluid,wecanobtainitslocalpressure

dropEquationoffluidflowthroughmini2ostiolesofdistributorbaffleinzdirectionasfollow:

（9）

　WhereA（x）denotepunchedratioasafunctionofindependentvariablex.

2.5　Homo-distributionEquation

Itiswellknownthattheconditionofhomo-distributionoffluidflowthroughdistributorbafflecanbededucedbymechanicalenergybalanceEquationfrominlettocrosssectionofoutlet.Thebasichomo-distributionEquationisshownasfollow:

（10）

2.6　Analysisandsolution

CombiningEqua.（7）,（8）,（9）withEqua.（10）,itwillobtainthefollowingEquation:

（11）

　Whenx=X,thenitcanbededucedthepressuredropofboundarycondition:

and

　Puttingthepressuredropunderx=XintoEqua.（10）,thenitcanbededucedthefollowingEquation:

（12）

　AssociatingwithEqua.（11）andEqua.（12）,andsimplifyingexpression,thenitcanbededucedthefollowingEquation:

（13）

　Undertheidealmodel,optimalpunchedratiocanbeexpressedasfollow:

（14）

3　MathematicalModelofIn-line-squareAlignedTubeBundle

Forthein-line-squarealignedtubebundleofshell-sideofshell-and-tubeheatexchanger,wedefine

astubepitch,dasouterdiameter,andLasinstallationdistance.Sotuberowsofshell-sideunderin-line-squarealignedcanbeexpressesas

:

andputtingthemintoEqua.（4）,thenthevelocityofxdirectioncanbeexpressedas:

（15）

　AccordingtotheEqua.（7）,（8）,and（9）,thepressuredropofxdirection,x-zdirection,andzdirectionatin-line-squarealignedconditionofshell-sidecanalsobewrittenasEqua.（16）,（17）and（18）,respectively:

（16）

Where

denoteslocalpressuredropcoefficientofcrossingatubeatthein-line-squarealigned.

（17）

（18）

　PuttingEqua.（16）,（17）and（18）intoEqua.（10）,itcanbededucedasfollow.

（19）

Whenx=X,itcanbededucedthepressuredropofboundaryconditionasfollow:

and

　AndputtingthemintoEqua.（10）,thenitcanbededucedthefollowingEquation:

（20）

AssociatingwithEqua.（19）andEqua.（20）,andsimplifyingexpression,thenitcanbededucedfollowingEquation:

（21）

　Underthein-line-squarealignedtubebundleofshell-sideofshell-and-tubeheatexchanger,optimalpunchedratiooffluiddistributorintheinletoroutletregioncanbeexpressedasfollow:

（22）

　InEqua.（15）toEqua.（21）,AzandAxcanbeexpressedasfollows:

（23）

（24）

　Itdefine

anddenotetheratioofoutdiameteroftubetotubepitch,puttingitandEqua.（23）and（24）intoEqua.（22）,itwillbededucedfollowEquation

（25）

FromEqua.（2