FINAL PROJECT: EVAPORATOR FAN...
Transcript of FINAL PROJECT: EVAPORATOR FAN...
![Page 1: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/1.jpg)
FINAL PROJECT: EVAPORATOR FAN DESIGN
ChristopherPhaneuf
BrianTovarME407:ComputationFluidDynamics
ProfessorScottBondi05May2008
![Page 2: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/2.jpg)
TABLEOFCONTENTS
1INTRODUCTION 1
1.1Objective 1
1.2HeatExchangerDesign 1
1.3FanTypes 22DESIGN 3 2.1Assumptions 3
2.2DesignConcept 3 2.3HeatExchangerRedesign 7 2.4DesignIntegration 153FANSIMULATION 16 3.1Preprocessing 17
3.1a)Full‐sizemodel 17
3.1b)Periodicmodel 18
3.1c)Shroud/manifold 23
3.2Solution 244RESULTS 25 4.1Postprocessing 25
4.1a)Fullfansimulation 25
4.1b)Periodicfansimualtion 29
4.1c)Shroud/manifoldsimulation 32
4.2FanPerformance 355DISCUSSION 36 5.1Generalresults 36 5.2CostEstimate 36 5.3Designbenefits 37APPENDIXI:DimensionedFanSchematics 38
APPENDIXII:HandCalculations 40
![Page 3: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/3.jpg)
1
1 INTRODUCTION
1.1 Objective
Norefrigerationcyclewouldbecompletewithoutanevaporator;noevaporatorwouldbecompletewithoutaheatexchangerandafan.Previousdesignandcomputationalfluiddynamicsanalysisaimedatthedevelopmentofanevaporatoryieldedanovelsingle‐passshell‐and‐tubeheatexchangerfeaturingannularfinsandperpendicularductingfortheinletandoutlet.Thisdevicecoolsairfrom100°Fto50°Fwhileminimizingthephysicalsizeandpressuredrop.Forallpastsimulations,flowthroughtheheatexchangerwassetatamid‐rangevelocityof250ft/min.Thesourceofthemovingairwasirrelevantuntilnow.
Todrivetheairthroughtheheatexchanger,acompact,energy‐efficientfanshallbedesignedtooperateatthreespeedscorrespondingtomeanflowvelocitiesof200,350,and500ft/min.Inaddition,thefanmustbecoupledtotheheatexchangerwithashroudoralternativeconnector.
1.2 HeatExchangerDesign
Thedesignofthefanandshroudbeganwherethefinaldesignofasimpleshell‐and‐tubeheatexchangerleftoff.Bydirectingairflowaroundaseriesofannularbaffles,moreturbulentmixingpromotesincreasedconvectivecoolingfromthelow‐temperaturerefrigerantpipe,whichisassumedtostayataconstanttemperaturealongitsentirelength.Plotsbelowdepicttheuniquegeometryandillustratetheeffectivecooling.
Figure1 Streamlinesfororiginalshell‐and‐tubeheatexchanger
![Page 4: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/4.jpg)
2
Figure2 Temperaturecontoursfororiginalshell‐and‐tubeheatexchanger
Theoriginalheatexchangerdesignperformedinaccordancewithrelativelylooserequirements.Thispromptedaneedtotesttheheatexchangerundernewlypresentedconditions,includingthevariableflowrateanddirectionofflow.
1.3 FanTypes
Mechanicalfanstylesandconfigurationsaremultifariousandsuitavarietyofneeds.Thetwobasicstypesareaxialandcentrifugalfans.Centrifugalfansareruggedmachinescommonlyusedforlarge,industrialapplications.Thedemandforacompactdesigneliminatesthisoptionandleavestheaxialfanstyleopentoadaptation.Elementsofthefansuchasmotortype,bladegeometry,andhousingpermitflexibilityofperformanceandallowspecificapplicationmatching.
![Page 5: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/5.jpg)
3
Figure3 Fantypes:centrifugal(left)1andaxial(right)2
2 DESIGN
2.1 Assumptions
Likemostengineeringproblems,acriticalsetofassumptionsisrequiredtorealizeandtesttheintegrationofafanforourevaporator.Detailsofpartswell,acousticeffects,bearingimplementation,inducedvibration,andotherphysicalnuancesencounteredintheoperationofafanareneglectedtosimplifythedesignandshiftemphasisonachievingbulkflowrequirements.AnothersimplificationisencounteredintheapproachtosolvingthegoverningfluidmechanicsequationsusingFLUENT.Thetwomainoptionswithinthesoftwareare1)steadystateanalysisusingmultiplereferenceframes,includingarotatingframeand2)unsteadyanalysisusingaslidingmesh.Duetoinexperiencewithunsteadysimulationsandalackofneedforthebehaviorcapturedbythistypeofsolution,asteadystateapproachwastaken.
2.2 DesignConcept
Duringtheearlierdesignoftheheatexchanger,severaldiscussionsaroseoverthemeansofairflowdelivery.Althoughthefinaldesignfeaturedperpendicularductsateachendofthedevice,themoreobviousandpotentiallymorecompactmethodofaxiallydirectedflowintotheheatexchangerwasconsidered.(Thiscorrespondedtotheoriginal2Daxisymmetricsimulationthatvalidatedthegeneralshell‐and‐tube/annularfinconcept.)Uponmorecriticalconsiderationofanaxialflowscheme,theideawasabandonedduetoquestionsoffeasibility.Itwasthoughtthatthepathoftherefrigerantpipeandthe
![Page 6: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/6.jpg)
4
fan/shroudsystemwouldconflict.Thepipewouldhavetobebenttoexitashroudandinturncreateabarrierforflowintotheheatexchanger.
Thetaskofdesigningafanfortheevaporatorbroughtustorevisittheideaofanaxiallyorientedflowsource.Callingonpastresearchexperienceinelectricmotortechnologies,muchofwhichiscenteredonfandesign,wedevisedanapproachofdirectlycouplingourheatexchangertoanaxialfanpoweredbyabrushless,permanentmagnetmotor.Theflexibilityofanouter,electricallycommutatedstatorandaninner,permanentmagnet‐equippedrotormakesthisconfigurationpossible.Onthesurface,theroughspecificationsprovidedforthefancomponentsresembleacommoncoolingfan.Thegeneralbladeshapeandsizecorrespondcloselywithmid‐sized,axialcoolingfans.Theprimarydifferenceslieintheslightlymorecomplexbladestyleandthedistributionofthepowercomponents.
Withmodelingandmeshinglimitationsinmind,thefanbladegeometrywaskeptsimple.Theprofileneededtobemoreinterestingandmorecapableofacceleratingfluidthanaflat,angledplatebutnotascomplexasthecarefullydesigned,low‐noisespecialtydesignsfoundinconsumerproducts.UsingSolidworks,asplineintheshapeofanairfoilwascreatedandoffsettogivethebladeathickness.Thetwoedgeswereclosedwithtangentarcsateachend.Thisouterprofilewascopiedontoanotherplane(whichwasoffsetbytheexpectedlengthoftheblade)andmodifiedtobesmallerandexhibitamoresevereangleofattackatthebase/hub.Thesetwoprofileswereloftedtogenerateasingle3‐dimentionalblade(Figure4)andexportedasaSTEPfiletobeimportedintopreprocessingsoftware.
Figure4 Fanbladegeometry
Themotivationbehindthemotordesigndepictedinthe2Dschematicbelowistheabilitytorunapipethroughthecenterwithoutaffectingtheoperationofthefan.Byplacingmagnetsofalternatingpolarityalongthecircumferenceofaretainingringontheoutsideofthefanbladesandbyguidingtherotationofthefanblades(rotor)withanouterbearing
![Page 7: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/7.jpg)
5
builtintothefanhousing(notshown),thecenterofthehubcanbehollowandallowthepassageoftherefrigerantpipe.Thismakesthepreviouslyabandonedideaofaxially‐drivenflowcompletelyconceivable.Theonlyothercomponentofthefanisthehousing/enclosure,whichisanordinaryplasticcasemodifiedtosupporttherotorwithabearingsupport.
Figure5 Fanmotorconcept:custominrunnerbrushlessPMmotor
Figure6 Fanassembly
![Page 8: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/8.jpg)
6
ABS(AcrylonitrileButadieneStyrene)plasticwasselectedforthebulkofthefanparts,excludingthesteelstatorlaminationsforthemotor,thecontrollingelectronicsandthemagnetsontherotor.Foruseinsimulations,keypropertiesweregathered:
Density=1080kg/m3(SG=1.08)
Specificheat=0.34Btu/lb°F
ThermalConductivity=0.1125Btu/hrft2°F
Maximumtemperature=180–200°F
UsingSolidworkstodeterminethevolumeoccupiedbyeachprimarycomponent,theapproximatemassofthefanwascalculatedfromthecorrespondingdensities.
(mfanblades=0.02612kg)+(mfancover=0.131kg)+(mstator=0.198kg)+(mmagnets=0.02kg)
=0.375kg
Weight=3.675N=approx.0.8lbs.
Technicalspecificationsforthisfanarepotentiallylimitless.Brushlessmotor‐basedfansareversatiledevices,controlledwithvariousfeedbackschemesandcapableofeitherlow‐speed,high‐torqueorhigh‐speed,lowtorqueapplications.Forthisparticularfan,thestatorisdesignedforrelativelyhighspeedsandappropriatelylowtorquegeneration.Thestatorteethwillfeaturethinmagneticwireandahighnumberofwindings.Theoptimalmeansofpoweringandcontrollingthefanfromline‐fed(wall)electricityisacomplexsystemsummarizedbythefollowingflowofcomponents:apowerrectifierandregulatorconvertingACtomanageableDC,avariablefrequencyinvertertosupplythree‐phasealternatingsquarewavecurrentpulsestothreesetsofstatorwindingsdistributedovertwelveteeth.SteadyspeedcontrolisaccomplishedwitheitherhalleffectsensorspositionedaroundtherotororamethodsensorlesscontrolthatestimatesrotationalvelocitybasedonmeasurementsofbackEMFthroughnon‐energizedwindingphasesduringeachcycle.[NOTE:Thesedetailsareseeminglyexcessiveforthepurposesofthisassignmentbutrepresentacarefullyselectedsetofcomponentsthatareeasilymanufacturedandmeettheoperatingdemandsoftheevaporator.]
Whilemostheatexchangersrequireashroudtoconverttheroundgeometryoftheeffectivefanareatothesquareorrectangularfaceofthetypicalcross‐flowheatexchanger,ourshell‐and‐tubegeometryobviatestheuseofashroud.Withminormodification,theroundcylinderisdirectlycoupledtothefan.Inlieuofashroudanalysis,theintroductionofa3‐inchsectionofpipemanifold(tobeexplainedinthefollowingsection)necessitatesastudyofthissegmentoftransitionbetweenthefanandthebafflesoftheheatexchanger.Additionally,thesimulationsofthefangeometrycapturetheflowin3‐inchlong,5‐inchdiameterstraightshrouddirectlyaftertherotatingflowaroundthefanblades.
![Page 9: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/9.jpg)
7
2.3 HeatExchangerRedesign
Tovalidatethedirectcouplingapproachofincorporatingthefanintotheevaporatordesign,theheatexchangermustbealteredandtestedforadequateperformancewiththeaxialinlet.Sinceafandiameterof5incheswasselectedfromthestartofthedesign,priortotheinitialstepsofredesigningtheheatexchanger,theoutershelldiameteroftheexchangerwasadjustedaccordingly.ThegeometryofolddesignwasreproduceddirectlyinGAMBITwiththefollowingchanges:theeliminationoftheperpendicularducting,theincreaseofshelldiameterto5inches,andtheuseoffacestosplitthevolumefortheannularfinsinordertousecoupledthermalboundaryconditions.Quadmesheswereappliedtoallfacesandthevolumemeshwasgeneratedtoyieldedacleanlyrevolvedsetof640,549elements.Thegeneralboundaryconditions(forthissimulationandallsubsequentvalidationruns)wereaninletspeedof250ft/min,refrigeranttemperatureof10°F,andcoupledfins.Thek‐epsilonrealizableturbulencemodelwasusedandsolutionscontrolswerekeptattheirdefaultsforthesakeofintermediatetests.Theresultswerenotpromising,confirmingtheexpectedissueswiththealternativeflowscheme.Theaxialflowdidnotinducethesamedegreeofmixingandthearea‐weightedoutlettemperaturewasjustunder80°F.Thisnecessitatedaseriesofsimulationscheckingtheeffectofminorgeometricmodificationstowardabettercoolingshell‐and‐tubeheatexchanger;however,despitemeasuressuchaslengtheningtheheatexchangerandapplyingtighterfinspacing,thecoolingcapabilitiesofthesingle‐passexchangerwithannularfinswasnoteffectivewithinreasonableconstraintsofcompactness(Tout=57°F/∆P=00.28).Thefollowingfiguredemonstratestheinadequateheattransferoftheoriginaldesignexperiencingaxialinflow.
Figure7 Post‐modification,single‐pass,15‐inch,9‐finheatexchanger
![Page 10: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/10.jpg)
8
Inanefforttoattainbetterperformancefromouraxially‐fedheatexchanger,thenextphaseoftheredesignborrowedfromthemorecommonstyleofshell‐and‐tubeheatexchangers,whichfeaturealargenumberpipeschanneledthroughtheinteriorandalternatingbafflesshapedliketruncatedcircles(Figure8).Byincorporatingamanifoldthatsplitsthesingle1‐inchpipeofrefrigerantinto7half‐inchpipes,morecoolingsurfaceareaisintroducedtothedesign.Additionally,bafflessimilartothosefoundwithinindustrialheatexchangersofthiskindwereincluded.
Thefirstattemptwiththistopologywasareturntotheoriginal12‐inchlengthandhad3baffles.Resultswerenotcompletelysuccessful(Tout=76.25°F/∆P=0.65inches‐water)butshowedroomforimprovement(Figure9).Alonger,15‐inchshellwith7bafflesat1.5‐inchspacingprovidedsufficientresultswithanoutlettemperatureof49.9°Fandapressuredropof2.2inchesofwater(Figures10‐15).Adrawbackofthisapproachistheinabilitytomatchthequalityofthemeshforthesingletube,axisymmetricdesign.The3DmeshwasmadewithTGridandconsistsof279,168elements.Also,whilethepressurelosswasgreaterthanthepreviousdesigns,themodelstillmettheprimaryrequirementofreducingtheairtemperature.Sincetheadditionofthemanifoldaffectstherefrigerantflow,asimulationofthedividingflowwasrunthoughameshof64,980elements(Figure16‐19).Thisconcludedtheheatexchangerredesignprocess.
Figure8 Commonshell‐and‐tubeheatexchanger3
![Page 11: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/11.jpg)
9
Figure9 7‐pipe,12‐inch,3‐baffleheatexchanger
Figure10 Residualshistoryforfinalheatexchangerredesign
![Page 12: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/12.jpg)
10
Figure11 Temperaturecontoursforfinalredesign
Figure12 Pressurecontoursforfinaldesign
![Page 13: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/13.jpg)
11
Figure13 Velocitycontoursforfinaldesign
Figure14 Pathlinescoloredbytemperature
![Page 14: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/14.jpg)
12
Figure15 Redesignedheatexchanger
![Page 15: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/15.jpg)
13
Figure16 Internalrefrigerantpipeflow‐‐manifoldmesh
Figure17 Pressurecontoursthroughmanifoldatmid‐plane
![Page 16: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/16.jpg)
14
Figure18 Velocitycontoursthroughmanifoldatmid‐plane
Figure19 Temperaturecontoursthroughmanifoldatmid‐plane
![Page 17: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/17.jpg)
15
2.4 DesignIntegration
Withthegeneralfanconceptdevelopedandmodeledandtheheatexchangeradaptedtothesizeofthefan,thetwopartswerecombined.Aflange,ormountingplate,wasaddedtotheendoftheheatexchangertoallowboltingtothefan.Figuresoftheassembled,in‐lineevaporatorweregeneratedwithSolidworks.
Figure20 Assembledevaporatorcomponents
Figure21 Evaporatorwithsectioncut
![Page 18: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/18.jpg)
16
Figure22 Explodedviewofevaporator
3 FanSimulation
Computationalfluiddynamicswasemployedtorefinethedetailsofourdesignandvalidatetheeffectivenessofthefan.Anaccuratesimulationcanprovideseveralmeasuresoffanperformancecriticaltotheoperationofanefficientandusableevaporator.Withthreedesiredsettingsforthefan,thesimulationprocesswasiterative.Addingtothenumberofrequirediterationwasthelackofexperienceandthereforenumerousissueswithmovingreferenceframes.
Sincethesymmetryoftheaxialfantypeslendsitselftoananalysisofonlyasectionofthefan,periodicboundarieswerefirstattempted.Althoughtheboundaryconditionsseemedtomakesense,resultspointedtomajorerrorsinthesetup.Followingmanypermutationsoflogicalboundaryconditions,thefailuretoyieldreasonableflowregimes,theperiodicconditionwasthesuspectedcause.Wetooktheapproachofmodelingtheentirefanstructure,whichintroducedmoreelementsbuteliminatedanypossibleproblemscausedbyanimproperperiodicconfiguration.Despitethesimplificationofthesimulation,resultsstillfailedtocapturetheintendedflowdirections.Lookingmorecloselyatthemixingplanetutorialthathadoriginallyguidedtheselectionofboundaryconditions,subtlesettingswerefoundtobedisparatewiththepastattemptsanduponadjustment,simulationseventuallyrevealedtheintendedflow.Byestimatingrotationalspeedsfromtheinitialresults,thecorrectvaluesforproducingthethreeoutletspeedsof200,350,and500ft/minwereeventuallydeterminedthroughtrialanderror.Toconfirmourabilitytouseperiodicconditions,wereturnedtomodelingonlyasinglebladeofthefan.Thefollowingsectionswillbrieflydepictthefull‐scalemeshandthentakeyouthroughthedetailedprocessesofcreatingthemeshandarrivingatasolutionfortheperiodicmodel.
![Page 19: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/19.jpg)
17
3.1 Preprocessing
3.1a)Full‐sizemodel
Figure23 Full‐sizemeshdisplayingallfacemeshes
Figure24 Close‐uponquad‐mappedfanbladewithboundarylayer
![Page 20: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/20.jpg)
18
3.1b)Periodicmodel
OncethegeneralfanconfigurationwasestablishedandthefanbladegeometrywasmodeledinSolidworks,preprocessingsoftwareknownasGAMBITwasusedtomodeltherelevantfluidvolume,createathree‐dimensionalmesh,andsetboundarytypestobefurtherdefinedinthesolver.
InGAMBIT,theimportofanytypeofnon‐nativefileleads,almostalways,toanexcessoflowergeometry.Forexample,somelinesorcurveshaveunnecessaryverticesalongtheedge.ThefirststepafterimportingtheSTEPfilegeneratedinSolidworksisaclean‐upoftheresultinggeometry,andforthiscasethatmeansacompletedismantlingoftheuppertopologiesandareconstructionoftheloftedfanbladefeature.Thishastobedonebeforetheairfoilvolumecanbesubtractedfromthepositiveairspace;otherwise,wewouldhavetoreconstructthatentiregeometryaltogetherandweprefertomakeourworkloadsimple.
Thefirstanomalyencounteredisthesingleloftededgesalongtheleadingandtrailingedgeoftheairfoilcross‐section.Afterboththevolumeandallthefaceshavebeenerasedfromtheimportedgeometry,thesetwoedgescanbedeleted.Whenonetakesacloserlookateachofthe(nowisolated)airfoils,youdiscovertheoverdefinedcurvesthatwereferredtoearlier.Theymustbereducedtoasinglecurveusingthesplit/mergeedgetoolbox.
Figure25 Exampleofsuperfluouslowergeometry
Thenwecanconnecttheairfoilstoeachotherthroughtheirfour(andonlyfour)existingvertices.Thiswillresultinthestraightloftthatwearelookingfor,butonlyafterthesixfaceshavebeencreatedandthevolumestitchedandsubtractedfromthecenterairspace.Itisnotimportanttosplitthisvolumewiththeairfoilvolumeandthenlaterdeleteit.Sinceweonlycareaboutthepositivespace,asimplesubtractionwillsuffice.Althoughsubtractionyieldsnoboundaryissues,theresultinggeometryrequiressomecleaningupsincetheSTEPfilegeometrysitsexactlytangenttothecylindricalvolume.Usingthesamemergeedgestoolfrombefore,thetwooutsideairfoiledges(specificallythosealongthe
![Page 21: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/21.jpg)
19
cylindersouterwall)needtobejoined.Thisjoiningdoesnotrequireadeconstructionoftheuppertopologicalentitieslikebefore;it'ssimplydoesn'thavethesameaim.
Figure26 Repairingsubtractedvolume
AperiodicboundaryconditionisusefulforthereductionoftheCPUtimerequired,andtoachieveaworkingmodelofthis,twocylindersweresubtractedfromoneanotherwhileapairofoppositelyrotatedbricksslicethegeometrydowntoaroundedwedgeshapedextrusion.Ifyoucanrecallfromthedesignsection,theradialdimensionsofthispart'scross‐sectionissuchthattheinnerdiameterisjustlargerthantheaxialpipecarryingrefrigerant;1.5inches,andtheouterdiameterissizedtofitexactlyalignedwiththeheatexchangerdiameter:aflatfiveinches.Thismeansthatthefanhassixbladesthatfitidenticallyontheinletfaceoftheheatexchangersothatnoarealconversionisrequired,reducingthenumberofpartsofthesystemandfurtherreducingcosts.
Figure27 Overallairspacewithvolumestobesubtractedfor60periodic
Whenweconsidertheflowofairthroughafansystem,weseethreesections.Thefirstistheairfromtheoutsidethattravelsthroughthefan,thesecondisthehighlyturbulentzonewherethebladessweepoutacylindricalvolume,andthelastistheairafterwards;theairintheheatexchanger.Forthisreasonwedivideourpositiveairspaceintothreesectionsofvaryingsize.Theseven‐inchheightoftheairspaceallowsacenteredvolumeofoneinchinheighttoencompassthefanbladesandresultsintwoequivalentthree‐inchsections;onebeforethefanandoneafterthefan.Aspecialboundaryconditionmustexisthereforfluidtoflowacrossitasifitwerenotaboundary.Toaccomplishthiswemustfirstsplitthe
![Page 22: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/22.jpg)
20
largervolumewithtworealfacesthatextendpastthelimitsofthevolume,justtobecertain.
Figure28 Splittingmainvolumearoundairfoil
Meshingbeginsfirstwithanunderstandingofperiodicboundaryconditions.Sinceeachperiodicboundarymustbelinkedformeshingbemeshingbegins,and,ifweconsiderourintentionstoconcentratethemeshingsizearoundtheairfoil,wearepresentedwithaproblem.Hereyoucansee,sincewehavetospecifyavertexforeachfaceanditmeshlinksthetwoadjacentedgestothecorrespondingoppositeface,whenwebegintoedgemeshonewitharatioalongtheaxialdirectionanduniformdensityedgemeshalongtheperpendiculartoflowedge,thereexistsaconflict;bothcan'texist.
Figure29 Edgemeshingalongperiodicboundarytypes
![Page 23: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/23.jpg)
21
Tosolvethisproblem,wetosplittheeightverticaledgesbyauvaluetocreateavertexinthecenterofeachsymmetricface.Nowwecanedgemeshthelongerofthetwoedgeswithanincreasingratio,andtheshorteredgewithaconstantspacingontheorderofthesmallest(thelastelement)fromthelongeredge,thirdlyandmostimportantofall,anindependentedgemeshisnowpossiblealongtheeightperpendicularedgesaswellasthefourairfoilloftedges.(Figure29).
Figure30 Methodofquad‐mappingtheinletandoutletvolumes
Forvolumemeshing,theordermatters.Asitis,thecentervolumewillnotmeshaHexMapscheme,simplybecausethehubsidefacewillresultinatoohighlyskewedmeshforittocomplete.Instead,acompromisemustbesetalongthesharedfacesoneithersideofthecentervolume;thevolumesbeforeandafterthefanwillhaveahexmapscheme,butthefanvolumeitselfwillbemeshedwithTGrid.Thisisunderstandable;itisdifficult(ifnotimpossible)topredicttheflowdirectionandtoconstructameshperpendiculartotheregionwiththemostexpectedturbulence.UsingaTGridschemeimpliesacertainamountoffreedom,andtorestrictthatfreedom,everyedgeofthevolumewasmeshedtoacertainqualitybeforethemeshingschemehadthefreedomtosetitsownconditions.Also,aboundarylayerwascreatedaroundtheairfoil.Theresultingmeshsizeis:372,160elements,938,893faces,226,643nodes.
![Page 24: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/24.jpg)
22
Figure31 Sectionofquad‐mappedfanbladeandsurrounding3Delements
Figure 32 Worst 25% of 3D elements according to equiskew
![Page 25: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/25.jpg)
23
A mesh analysis shows that the worst quarter of the tetrahedral shaped elements, based on their Equiskew feature, all reside in this center volume. This is completely acceptable since the flow direction in this region is difficult to predict. Most importantly, the airfoil itself has a quad-mapped face and the inlet and outlet interior faces of this volume are quad-mapped as well.
3.1 c) Shroud / manifold flow
Figure 33 Mesh for simulating flow around pipe manifold before entering exchanger
![Page 26: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/26.jpg)
24
3.2 Solution
ThemeshisreadintoFLUENTandcheckedforinconsistencies.Duringearlyattempts,gridcheckswouldoccasionallyfailduetoimproperlyconfiguredperiodicconditions.Oncehavinglearnedthecorrectmethodoflinkingfacemeshesandapplyingperiodicboundarytypes,thisnolongerpresentedanyproblems.ThemeshisscaledandunitsaresetforEnglishsysteminputs,includinglength,angularvelocity,pressure,temperature,andvelocity.Theenergyequationandk‐epsilonturbulencemodelareturnedon.BoundaryConditionsarelabeledinFigure34.Theproblemisinitializedanditerateduntilreachingconvergence.
Figure34 Modelboundaryconditions
![Page 27: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/27.jpg)
25
4 Results
4.1 Postprocessing
4.1a)Fullfansimulation
Figure35 Residualsforfull‐size,lowspeed
Figure36 Pathlinesthroughfull‐sizemodel
![Page 28: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/28.jpg)
26
Figure37 Pathlinesforlowspeedacrossmid‐plane(flowfromtoptobottom)
Figure38 Velocityvectorsforlowspeedthroughfanbladesection
![Page 29: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/29.jpg)
27
Figure39 Residualsforfull‐size,mediumspeed
Figure40 Pathlinesformediumspeedacrossmid‐plane,shroudandhub
![Page 30: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/30.jpg)
28
Figure41 Residualsforfull‐size,highspeed
Figure42 Pathlinesforhighspeedacrossmid‐plane,shroud,andhub
![Page 31: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/31.jpg)
29
4.1b)Periodicfansimulation
Figure43 Residualsforperiodic,lowspeed
Figure44 Pathlinesforlowspeedatmid‐plane
![Page 32: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/32.jpg)
30
Figure45 Residualsforperiodic,mediumspeed
Figure46 Pathlinesformediumspeedatmid‐plane
![Page 33: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/33.jpg)
31
Figure47 Residualsforperiodic,highspeed
Figure48 Pathlinesforhighspeedatmid‐plane
![Page 34: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/34.jpg)
32
Figure49 Pathlinesforhighspeedacrossfanblade,hub,andshroud
4.1c)Shroud/manifoldsimulation
Figure50 Residualsforshroudsimulationathighspeed
![Page 35: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/35.jpg)
33
Figure51 Pathlinesovermanifoldatmid‐plane
Figure52 Pressurecontoursatmid‐plane
![Page 36: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/36.jpg)
34
Figure53 Velocitycontoursatmid‐plane
Figure54 Temperaturecontoursatmid‐plane
![Page 37: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/37.jpg)
35
4.2 FanPerformance
Actualoutputvelocitiesofthefanwere:
Low‐speed(500rpm)=207ft/min
Medium‐speed(800rpm)=348ft/min
High‐speed(1000rpm)=444ft/min
Pressureincreases(head)throughthefanareminimalatabout0.015inchesofwater,notcompletelycompensatingforthepressuredropthroughtheheatexchanger.
Temperatureincreaseisnegligibleineachsimulation,reportinganincreaseontheorderof1·10‐3°F.
FLUENTprovedtobeextremelyusefulforreportingtheforcesandmomentsexperiencedbythefanblades,withoptionstowritethetotalforceduetobothpressureandviscousshearstresses,aswellasthemomentaroundeachaxiswithrespecttotheorigin(whichisconvenientlyatthecenterofthefanblades.Thefollowingvalueswerederivedfromtheperiodicmodel,allowingustodeterminetheforcesandtorquesonasinglebladeandsimplymultiplybysixfortheneteffect.Theforcesareusedforhandcalculationsofthestructuralstrengthofthefanbladesandthemomentsarehandingforcalculatedtherequiredpowerfromthemotor,sincebothtorqueandthesetrotationalspeedareknown.
SPEED Low Medium High
Fy(N) 0.001 0.0075 0.01217
Fz(N) 0.00115 0.00765 0.01234
Torque(Nm) 0.000069 0.0004675 0.000751
Angularspeed(rad/s) 52.36 99.5 125.664
Req.FanPower(W) 0.0216 0.279 0.566
![Page 38: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/38.jpg)
36
5 Discussion
5.1 GeneralResults
Throughcountlessiterationsofattemptedsimulations,attentiontothedetailsofsettingboundaryconditionsbecamethecriticalstepforyieldingreasonablenumbersforoutputflowandcorrespondingfanspeed.Forthesakeofthesizeandflowofthereport,thecoarserandfinermeshes,rangingfromabout200,000to1.8millionelementsfortheperiodicvolumes,runattheextremesofrotationalspeed,werenotshownbutservedasmeasuresofthelevelofdetailrequiredtocapturethefanflowconsistently.Thismeshsensitivitytestwassimilarlyperformedduringtheheatexchangerredesign,sincethemeshingprocesswasadverselyalteredbytheintroductionofmultiplepipesandasymmetricalbaffles.Thiswasatimesavingprocessthatensuredconsistentresultsovertherangeofspeeds.
5.2 CostEstimate
Thecostofthephysicalfanwaskeptlowforproductionconsiderations.BasedonrawmaterialspricingfromMcMaster‐Carr,thefanrequiresabout$15worthofplastic.Thepartsforprototypingthemotor,controller,andpowerconversioncouldbemanagedwithacombinationofoneofmanykitsfromaretailersuchasgobrushless.com(whichincludethematerialsforwindingacustomstatorandassemblingthepermanentmagnetrotor)andahome‐builtpowerandcontrolcircuit.Wehavepersonalexperienceinthisdepartment,havingbuiltathree‐phaseinverterforcontrollinganout‐runnerbrushlessmotorforahigh‐speed,rotaryvalveapplication.Althoughpricingwillbesubjecttoapersonalstockofbasicelectronicssuchaswiring,powertransistors(e.g.MOSFETS),diodes,atransformer,etc,thekitwillcostaround$30.Thistranslatestoasubtotalof$45fortheactualfan.
Laboristheotherfactorindeterminingthecostofdesigning,testing,andprototypingthefanconcept.Sincetheheatexchangerdesignimpressedtheprojectmanagers,ourhourlywageswereincreasedfrom$11/hrto$20/hr.Withapproximately70hoursputintothedesignandanalysisphases,andanestimated30hourstowardanexperimentalprototype,thelaborcostpeaksat$2,000.
Therefore,TOTALCOST=$2.045.00
![Page 39: FINAL PROJECT: EVAPORATOR FAN DESIGNchristopherphaneuf.com/cfd/me407_final_report[phaneuf-tovar].pdf · FINAL PROJECT: EVAPORATOR FAN DESIGN ... INTRODUCTION 1 1.1 ... Using Solidworks,](https://reader031.fdocuments.in/reader031/viewer/2022022501/5aa782ce7f8b9a294b8c30d4/html5/thumbnails/39.jpg)
37
5.3 DesignBenefits
Beforediscussingthebenefitsofourdesign,weshouldaddressthedrawbacks.Thecomplexityofthemotorchosentopowerthefansacrificestheruggednessofotheroptions,suchasasquirrel‐cageinductionmotor.Theneedtoincreasethesizeoftheheatexchangertoaccommodatetheaxialfanisunfortunatebutstillkeepsthedesignwithinareasonablesizeenvelope.Also,fanperformancedoesnotmeeteverycriteria,mostnotableitsinabilitytocompletelyovercomethepressurelossthroughtheheatexchanger.
Therearemanyadvantagestothefandesignpresentedhere.ThechoiceofmaterialssuchasABSplasticyieldsalight‐weight,low‐costfanwiththestrengthtowithstandtheforcesofoperationatmultiplespeeds,asverifiedbyhandcalculations.Theuseofabrushless,permanentmagnetsynchronousmotorisanotherkeyappealtothedesign,embracingthetrendsofincreasedsophisticationandincreasedaffordabilityofmotortechnologywithongoingadvancesinthepower‐electronicsandsensorindustries.Alongwiththerelativelycomplexelectroniccontrolschemecomesnumerousbenefitsincludinghighpowerdensity(mostlycreditedtotheuseofpowerfulpermanentmagnets),lowheatgeneration,lownoiseproduction,andhighoverallefficiency.Omissionofanofficialshroudpromotesconvectivecoolingintheheatexchangerbydirectlyintroducingtheturbulentswirlingexitingthefanintotheshelloftheheatexchanger.Theresultingfan,coupledwiththeredesignedheatexchanger,presentsacompact,in‐linepackagethatwouldbeattractiveformanyevaporatorapplications.Thisisadesignmadetoblowawayallcompetingproposals.
1http://longbiao.win.mofcom.gov.cn/en/plate01/product.asp?id=36105
2http://longbiao.win.mofcom.gov.cn/en/plate01/index.asp
3http://commons.wikimedia.org/wiki/Image:Straight‐tube_heat_exchanger_1‐pass.PNG