A Discussion on Utilization of Heat Pipe and Vapor Chamber Technology as a Primary Device for Heat Extraction from Photon
Absorber
Kamlesh J.Suthar, AlexanderLurie,&PatricDenHartog
Advanced PhotonSourceEngineering SupportDivisionArgonneNational Laboratory,USA
MEDSI2016,9/11- 9/16,Barcelona,Spain
Outline
§ ProblemDescription
§ ResultofWaterCooledDesign
§ HeatPipe– Whatisaheatpipe?
– Theoretical Limitations ofHeatTransport
§ FEA– Recommended methods
– Conductivity FromThermalResistance
§ FEA(cont.)– 3Layers&RuleofThumb
Conductivity
– SmallTemperatureDrop
– FEAResults
§ Alternatives
§ Conclusions
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Problem Description
§ CurrentDesignofB:CA1– 2.9KW
– Limited space
§ Problems– Max.Temperature
– Temperature GradientandThermal Stresses
FEAThermalSteadyStateAnalysis[1]
B:CA1AbsorberinAssembly [1]
B:CA1Drawing[1]
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FEA Result of Baseline Design
§ ThermalAnalysisofB:CA1– WorstCaseScenario
– RiskImposingThermalGradient
– HighMaximumTemperature
WaterCooledThermalSteadyStateFEA
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The Heat pipe
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What is the Heat pipe?
Ref:http://www.thermoguide.co.il/Heat_pipes.html
§ Heatpipe
§ ImagefromVendor
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Heat Pipe Background
HeatPipeFlowDiagram[2]
Copper-WaterSinteredPowderHeatPipe(CutOpen)
§ TwoPhaseHeatTransportDevice– PhaseChangePhenomenonw/Anti-ParallelFlow
– LargeVarietyofWickTypes
– FlexibleGeometry
– LowVibrationExpectations
– Equivalent ThermalConductivitythatis10to1000timeshigherthanmetalinsameshape hc =5000- 200,000W/m
2/Kk =2000- 100,000W/m/K
§ Flowwithintheheatpipe
§ FigurefromVendor
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Advantage and Limitations
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Typical Characteristics of heat pipes
• Veryhigheffective thermal conductivity (~100kW/m/K)compared toCu(0.4kW/m/K)
• Vibrationfreeoperationcanbepossible• Cantransportheattoalargedistance• Theyoffer thepossibility ofmorecompactdesign andefficientmeansto
removeheat• LongOperatingLife (20+years)withoutanymaintenance.• Finalheatremoval canbedoneviaconduction,orradiationheattransfer
Advantages:
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Heat pipe limits–operating envelope
§ TransportLimitations– Viscous/vaporpressure
– Sonic
– Entrainment
– Boiling
– Capillary Pressure
Reference:http://www.thermopedia.com/content/835/ExampleHeatPipeLimitationGraphfromIndustryVender[3]
§ Heatpipelimits–operatingenvelope
§ FigurefromVendor
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Vapor Pressure or Viscous Limit
§ Usuallyoccursatstart-up
§ Theminimumpressureatthecondenserendofthepipecanbeverysmallduetocoldorhotstartupanddifferenceintemperature.
§ Thevaporpressuredropbetweentheextremeendoftheevaporatorandtheextremeendofthecondenser,representsarestrictioninoperation.
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Sonic Limit
§ Atatemperatureabovethevaporpressurelimitintheheatpipe,thevaporvelocitycanbecomparablewithsonicvelocity
§ Atthispoint,thevaporflowwithintheheatpipebecomes"choked".
§ Toavoidchokedflowconditions(i.e.,soniclimit)istoworkbelowthislimitofthemaximumrateofheattransfer.
Reference:http://www.thermopedia.com/content/835/
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Entrainment Limit
§ Thevaporvelocityincreaseswithtemperatureandmayproduceveryhighshearforceonthereturningliquidflowfromthecondensertotheevaporator,whichcauseentrainmentoftheliquidtowardsevaporatorbytheflowofvapor.
§ Therestrainingforceonliquidcounterby surfacetension,thatisamajorparameterindeterminingtheentrainmentlimit.Entrainmentwillcauseastarvationoffluid.Restrictionoffluidflowfromthecondenserandeventual"dryout"conditionattheevaporator.
Reference:http://www.thermopedia.com/content/835/
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Circulation Limit
§ Thedrivingpressure forliquidcirculationwithintheheatpipeisgivenbythecapillaryforceestablishedwithinthewickstructure,givenbyfollowingequation.
whereΔplisthefrictionalpressuredropinliquidandΔpv isthefactionalpressuredropinthevapor.
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Boiling Limit
§ Excessiveheatinputcancreatethiscondition.Thetemperaturedropacrossthewickstructureintheevaporatorregionincreases withincreaseinincomingheatflux.
§ Apointisreachedwhentemperaturedifferenceexceedsthedegreeofsuperheatthatcannotsustaininrelationtonucleateboilingconditions.ThisconditionoftheonsetofBoilingwithinthewickstructurecaninterfereswithliquidcirculation.Thiscanleadtothe"dryout”condition,whileinthecaseofconstantheatflux,thiscancause"BurnOut"oftheevaporatorcontainment.
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Theoretical limits of Heat Pipe
§ MATLAB– 1000+linesw/GUI
– Outputs• LimitationsPlot
• FigureofMeritPlot
• MaximumHeatTransport
• ThermalResistance
• Equivalent ThermalConductivity
• Othercharacteristic values
– OptimizationonDesignParameters
HeatTransferLimitationsonFeasibleHeatPipeDesign
HeatPipeLimitationPlot
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Finite Element Analysis
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FEA cases
1. Pipeismodelledasahyperconductiverodbyequivalentthermalconductivity
2. Multiplelayersoftheheatpipearemodelled
3. Variationsonthehyper-conductiverodandmultiplelayermodelsimulationsareperformedwhichtreattemperatureasaconstant2-5℃ differenceandaltertheconductivitiestoachievethis.
4. Treattheheatpipe’stemperaturedifferenceasafewdegreesconstant.Setthecontactthermalconductancetochangethethermalconductivityoftheheatpipetoachievedesiredtemperaturechange.
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FEA Comparison
§ Generally,itwasfoundthat,regardlessofthemethodused,aheatpipereducesthetemperaturegradientontheabsorbersurface
§ Theworst-casesscenariosshowedonlyamarginalimprovement
§ whileothersindicatedalargerbenefitisachievable,butallcasessuggestedthattheheatpipeisareasonableoptioninthisapplication.
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FEA Results
§ MaximumTemperatureoftenlower,butwhenhigheritstilliswithinareasonablerangeandonlyintheoverestimatemethods
§ Temperaturegradientimprovedeveninworstofmodels
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Is it reliable?
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RELIABILITY ISSUES
Start-upConditions
§ Duringstartupthetemperaturegradientmayvaryconsiderably.
§ Conditionssuchas– nonuniformdistributionsofthefluid,whichlackcondensablegasesresultinginasuddendropoffintemperature.
§ Failureisalegitimateconcernundersuchconditions.
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Structural Stability
§ Itisimportanttonotethatheatpipesmayberequiredtowithstandvibrations,shock,andseveretemperatures.
§ CopperandGlidCop™,maybeusedtoconstructaheatpipewithverythinwallsowingtothestrengthsofthosematerials.
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Reliability Issues continued….
§ Possibilities include:capillarypumping failure,boiling,dry-out fromafrozen fluidsrestrictingtheself-replenishing nature,andentrainmentoftheliquidflow.
§ Inaddition, lowthermalresistanceatthecondenser canoverwhelmthesystemandenhance theprobability thatsuchfailureswilloccur.
§ Therearewaystoavoid someofthesefailuremodes,forexampleutilizing anentrainment limitwhichexceeds soniclimit.
§ However, solutions tosuchproblems, andthedegree towhichtheymaybeavoidedarestronglydependent onthespecificapplication.
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Manufacturing Concerns
§ Thedevelopment ofashell,theinsertionofawick,andfillingthepipewithfluidasitissealedoffatoneoftheends.
§ Afterwards, someexperimentation isneedonanygivenheatpipetoensure itperforms asintended.
§ Atthesametime,toachieve thedesignneeded, theevaporative sectionneedstobebuiltinto theabsorber itselfforalltheheatpipes.
§ Theprecise ofmanufacturingmethodscanalsogenerateheatpipewithdifferentpressure ineachproductanditdoesofferconcerns thatarisefrommanufacturing process.
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Contact Variance
§ Anothermajorconcernisthethermalinteractionbetweentheheatpipeandtheabsorber.
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Material Compatibility for Operation
§ Somefluidandsolidcombinationswillresultinchemicalreactionsthatdevelopgaspocketswhichhamperorceaseoperationoftheheatpipe.
§ WaterisknowntobegenerallycompatiblewithcopperhowevercompatibilitybetweenwaterandGlidCopTM-anothercommonabsorbermaterial,islessestablished.
§ TheAcetoneorsomerefrigerantswouldbesomepotentialalternativesbybeingcompatiblewithboth.
§ However,thesewouldoffernotabledowngradesinperformancecapabilities.
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Solution?
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Other Two-Phase Heat Exchanger Solutions
§ FlatHeatPipe(“VaporChamber”)– GeometricChallenge
– SpreadsEffectively
§ PumpedTwoPhaseCooling– TypicallyIsothermal
– HighHeatFluxCapacity
– RequiresLowerFlowrate
VaporChamber[5]
PumpedTwoPhaseCoolingDiagram [6]
§ VaporChamberimage
§ VaporTwophasecoolingsystemimage
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Conclusion
§ Heatpipesofferanattractivesolutionforefficientandcompacttransportofheatinphotonabsorberapplications.
§ Simulations showthatheatpipesoffertangibleimprovementsoverconventionalwatercooling.
§ However,anumberofpotentiallimitationsshouldbeweighedagainsttheperformanceimprovements.
§ Theseincludepotentiallymorecomplexandcostlyfabrication,limitedoperationalpredictability,andreliability.
§ Continuedinvestigationiswarranted,particularlyastherequirementsfornextgenerationacceleratorscontinuetobecomemorechallenging.
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Acknowledgements
§ JeremyNudell,BenjaminStillwell,andBranBrajuskovic
§ AdvancedPhotonSourceEngineeringSupportDivision
§ DOEandDOEandArgonneNationalLaboratory’sSummerUndergraduateInternshipProgram
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Questions?
_________________________________________References1. JeremyNudell,“MBAVacuumSystem– ConceptualDesignofAbsorbers”,ArgonneNationalLaboratory,2015.
2. "Isobar®HeatPipe."IsobarHeatPipe.N.p.,n.d.Web.28July2015.
3. "HeatPipeCalculator|CopperWaterHeatPipes."ACTAdvancedCoolingTechnologies.N.p.,n.d.Web.28July2015.
4. Lu,Zesheng,andBinghuiMa."EquivalentThermalConductivityofHeatPipes."FrontiersofMechanicalEngineeringinChina (n.d.):n.pag.Springer.01Dec.2008.Web.29July2015.
5. "VaporChambersandTheirUseinThermalManagement(part2of2)- AdvancedThermalSolutions."AdvancedThermalSolutions.N.p.,10Dec.2010.Web.28July2015.
6. "PumpedTwo-PhaseCooling,HighHeatFluxApplications."ACTAdvancedCoolingTechnologies.N.p.,n.d. Web.28July2015.
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Government license:
§ Thesubmittedmanuscript/presentationhasbeencreatedbyUChicago Argonne,LLC,OperatorofArgonneNationalLaboratory(“Argonne”).Argonne,aU.S. DepartmentofEnergyOfficeofSciencelaboratory,isoperatedunderContractNo.DE-AC02-06CH11357.TheU.S. Governmentretainsforitself,andothersactingonitsbehalf,apaid-upnonexclusive,irrevocableworldwidelicenseinsaidarticletoreproduce,preparederivativeworks,distributecopiestothepublic,andperformpubliclyanddisplaypublicly,byoronbehalfoftheGovernment. TheDepartmentofEnergywillprovidepublicaccesstotheseresultsoffederallysponsoredresearchinaccordancewiththeDOEPublicAccessPlan.
