w3heattransferthermalstressia.docx

w3heattransferthermalstressia.docx

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w3heattransferthermalstressia

Note:

ThisworkshopprovidesinstructionsintermsoftheABAQUSGUIinterface.IfyouwishtousetheABAQUSKeywordsinterfaceinstead,pleaseseethe“Keywords”versionoftheseinstructions.

PleasecompleteeithertheKeywordsorInteractiveversionofthisworkshop.

Goals

Whenyoucompletethisworkshop,youwillbeableto:

∙Understandtheinputandoutputforasteady-stateandatransientheattransferanalysis.

∙Useanamplitudespecificationforloading.

∙Understandtheprocedurereadingtemperaturesintoastressanalysisfromanoutputdatabase（.odb）file.

∙Understandhowusersubroutinesareused（optional）.

Problemdescription

Thephysicalproblemisasquaretubewithacircularhole.Thetubeissurroundedbyafluid,andtheholeisfilledwithanotherfluid.Thetwo-dimensionalfiniteelementmodelwillcontainonlyaone-eighthsectorofthetube.ThetubegeometryisshowninFigureW3–1.Thethermalpropertiesofthetubearegivenbelow:

∙Thermalpropertiesofthetube:

Specificheat=485.7N·m/kg·°C

Density=7833.0kg/m3

Conductivity=11.19W/m·°C

FigureW3–1Squaretubewithcircularhole.

Preliminaries

1.Entertheworkingdirectoryforthisworkshop:

../heat_transfer/interactive/workshop3

2.Runthescriptws_ht_thermalStress.pyusingthefollowingcommand:

abaquscaestartup=ws_ht_thermalStress.py

TheabovecommandcreatesanABAQUS/CAEdatabasenamedthermalStress.caeinthecurrentdirectory.Themodelcontainsallthedatanecessarytorunasteady-stateheattransferanalysisofthetube.Youwillbeginthisworkshopbyrunningthissteady-stateheattransferanalysis.Later,youwillmodifythemodeltoperformadditionalthermalandstructuralanalysesofthetube.

Steady-stateheattransferanalysis

AppliedTemperatures

Wewillstartwithasteady-stateheattransferanalysisinwhichthefluidtemperaturesareapplieddirectlytothenodesoftheinnerandouterwallsofthetube.Thisapproachimpliesthatthefluidstouchingthewallsareinfiniteheatsinks.

3.Submitthejobnamedsteady_bctorunthemodelsteadyHeatTransfer.

4.Afterthejobcompletes,opensteady_bc.odbintheVisualizationmodule.Theundeformedmodelshapeisplottedbydefault.

5.UsetheResultsTreetodeterminethelocationsofthedifferentnodeandelementsets.

a.IntheResultsTree,expandtheElementSetsandNodeSetscontainersunderneaththeoutputdatabasenamedsteady_bc.odb.

b.Selectdifferentsets;thecorrespondingsetswillbehighlightedintheviewport.

c.Onceyouarefamiliarwiththelocationsofthedifferentsets,collapsethecontainers.

Onlyone-eighthofthecross-sectionneedstobemodeledbecauseofsymmetry.

QuestionW3–1:

Whatshouldtheboundaryconditionsbeatthosesymmetrylines?

Whataretheappliedboundaryconditionsinthemodel?

Thinkaboutthedifferencebetweenenforcingsymmetryforathermalboundaryascomparedtothatforadisplacementboundary.

6.Createacontourplotofthetemperature（variableNT11）.Theprocedureisprovidedbelow.Checkthecontourlinesatthesymmetrylines.Thecontourlinesshouldbenormaltotheedgeifthesymmetryconditionsarecorrectlyenforced.

d.Fromthemainmenubar,selectResultFieldOutput.

e.IntheFieldOutputdialogbox,selectNT11（nodaltemperature）astheprimaryvariable.ClickOK.

f.IntheSelectPlotStatedialogbox,chooseContourandclickOK.

Filmcoefficients（forsurfaceconvection）

Theinterfacebetweenthetubeandthefluidscanbemodeledmorerealisticallybydefiningfilmcoefficientsandsinktemperatures.

1.CopythemodelsteadyHeatTransfertoamodelnamedsteadyHeatTransfer-film.

a.IntheModelTree,clickmousebutton3onsteadyHeatTransferandselectCopyModelinthemenuthatappears.

b.EntersteadyHeatTransfer-filmasthenameofthenewmodel.

2.Inthenewmodel,removethetwoexistingboundaryconditionswhichsetthetemperatureoftheinnerandouterwalls.（Clickmousebutton3onthemintheModelTreeandchooseeitherDeleteorSuppress.）

3.Defineasurfacefilmconditionnamedholeonthesurfaceholewithafilmcoefficientof1500W/m2·°Candasinktemperatureof400°C.

Note:

DetailsofthesurfacefilmconditiondefinitionprocedurearegiveninWorkshop2.

4.Defineasurfacefilmconditionnamedouteronthesurfaceouterwithafilmcoefficientof30 W/m2·°Candasinktemperatureof500°C.

5.Createajobnamedsteady_filmforthemodelsteadyHeatTransfer-film.

6.Submitthejobforanalysis.Checkthejobmonitorforanymodelingerrorsandmakeanynecessarycorrections.

7.Afterthejobcompletes,opensteady_film.odbintheVisualizationmodule.

8.Createacontourplotoftemperature.Tocomparetheseresultstotheresultsintheappliedtemperaturemodel,youcandisplaybothcontourplotsatthesametimeasfollows:

a.Fromthemainmenubar,selectViewportCreate.

Thenewviewportappears.

b.Fromthemainmenubar,selectViewportTileVerticallytoarrangetheviewportssothatbothareclearlyvisible.

c.Inoneviewportopentheoutputdatabasefortheappliedtemperaturemodel,andintheotherviewportopentheoutputdatabaseforthesurfaceconvectionmodel.Createcontourplotsofthetemperature,andcomparethem.

QuestionW3–2:

Howdoestheplotforthemodelusingfilmconditionscomparetotheplotfortheappliedtemperaturemodel?

（Thinkabouthowthefilmconditionattributescouldbechangedsothattheresultswouldbethesameasfortheappliedtemperaturemodel.Thisprocessisanoptionalexerciseifyouhavetimeattheendoftheworkshop.）Howdotheresultsreflecttherelativemagnitudesofthefilmcoefficients?

9.Returntotheoriginalsingleviewport.

g.Toremoveoneoftheviewports,clickthedeletebuttoninthetoprightcorneroftheviewport.

h.Tomaximizetheremainingviewport,clickthemaximizebuttontotheleftofthedeletebutton.

Transientheattransferanalysis

Wewillnowmodelthecaseinwhichtheinnerandouterfluidsstartatthesametemperatureandthetemperatureoftheinnerfluidisrampeddownto400°Cover10secondsandisthenheldconstantatthattemperature（seeFigureW3–2below）.Thischangecanbespecifiedbyusinganamplitudecurve.

FigureW3–2Sinktemperaturevariationforsurfaceconvection.

CopythemodelsteadyHeatTransfer-filmtoamodelnamedtransientHeatTransfer.

Makethefollowingchangestotheheattransferstep（ModelTree:

Steps:

double-clickStep-1）:

i.Modifythestepdescriptionto"Transientheattransfer."

j.SetthestepresponsetypetoTransient.ABAQUS/CAEwillautomaticallychangethedefaultloadvariationto"Instantaneous."

k.Changethesteptimeperiodto10000.

l.Setthemaximumnumberofincrementsto200.

m.Specifyaninitialincrementsizeof2.5.

n.Endthestepwhenthetemperaturechangerateislessthan0.001.

o.Setthemaximumallowabletemperaturechangeperincrementto10.

Thus,thisstepspecifiesatransientanalysisthatendswhensteadystateisreached（definedbythetemperaturechangerate）.ABAQUSwilluseautomatictimeincrementationtokeepthemaximumtemperaturechangeatanynodeinanincrementunder10°C.

Createatabularamplitudecurvenamedtemp1withthedataprovidedinTableW3–1,sothattheamplitudemagnitudebeginsat500,rampsdownto400bytime10,andthenremainsconstant.

p.IntheModelTree,double-clickAmplitudes.

q.Nametheamplitudetemp1andacceptTabularastheamplitudetype.

r.EntertheamplitudedataprovidedinTableW3–1.

TableW3–1Amplitudedata.

Time

Amplitude

0.0

500.

10.0

400.

1000.0

400.

Editthefilmconditionhole,sothattemp1isthesinktemperatureamplitude（ModelTree:

Interactions:

double-clickhole）.Changethemagnitudeofthesinktemperatureto1.0（thisvaluewillbescaledbytheamplitudecurve）.

Createatemperaturefieldintheinitialsteptoassignaninitialtemperatureof500tothesetplate.

7.CreateajobnamedtransientHeatforthemodeltransientHeatTransfer.Theresultsfromthisanalysiswillbeusedtodrivethesubsequentstressanalysis;doubleprecisionoutputisdesirableinthiscase.Thus,setthenodaloutputprecisiontoFull.

8.Submitthejobforanalysisandmonitoritsprogress.

QuestionW3–3:

Whatdoyounoticeabouttheincrementsize?

Arethesizesofthelastincrementsreasonable?

9.OpentransientHeat.odbintheVisualizationmoduleandplottemperaturecontours.Comparethetemperaturesatvarioustimestothetemperaturesinthesteady-stateanalysis.

10.CreateX-Yplotsofthetemperaturevariationovertimeforafewdifferentnodes.Tryplottingtemperaturesforafewpointsalongthediagonalonthesameplot.

TherearetwowaystoobtaintheX-Ydataneededtocreatethesetemperatureplots.Onemethodistorequestthedataashistoryoutput,andreruntheanalysis.HistorydatamaybeusedtocreateX-Yplotsdirectly（ResultHistoryOutputintheVisualizationmodule）.ThesecondmethodistoextracttheX-Ydatafromthefieldoutput.Thedetailsofthistechniquefollow:

s.IntheResultsTree,double-clickXYData.

t.IntheCreateXYDatadialogbox,selectODBfieldoutputasthedatasource.

u.IntheVariablestabbedpageoftheXYDatafromODBFieldOutputdialogbox,chooseUniqueNodalasthevariableposition.ToggleonNT11:

Nodaltemperature.

v.ClicktheElements/Nodestabandselectthenodesetforwhichyouwouldliketoextractnodaltemperatures.

w.ClickPlot.

Thermal-stressanalysis

Thesamegeometrycanbeusedforastressanalysis.Wewilldefineaprobleminwhichtheinitialloadingisauniformpressurizationappliedtotheinnerwallofthetube.

11.CopythemodeltransientHeatTransfertoamodelnamedstress.

12.Addthe