brief overview: mission- and aircraft-level thermal

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Virginia Tech

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-1

ARPA-EKick-offMeeting:EnergyStorageandPowerGenerationSystemIntegrationPanel

BriefOverview:Mission-andAircraft-levelThermalManagementSystems

Dr.MichaelvonSpakovskyRobertE.Hord,Jr.ProfessorinMechanicalEngineering

MechanicalEngineeringDepartment(0170)CenterforEnergySystemsResearch

VirginiaTechBlacksburg,VA24060

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Virginia Tech AircraftThermalManagementSubsystem(TMS):

Source/Sink(EnergyStorage)Issues

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-2

q  Numerousheatsources:―  Cabin/cockpit―  Air-cooledavionics―  Liquid-cooledavionics―  Engine―  EPS+(generators,motors,

pumps,compressors,e-actuators,powernetwork,controllers,etc.)

q  Limitedheatsinks(energystorage):―  Ramair―  Engine―  Environment

q  MEA/AEA,DEW,andISRaddingtoandincreasingthesizeandintensitiesofheatsources

q  Survivability,compositematerials,etc.areeliminatingheatsinksorshrinkingtheircapacities ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014

ColdPAOLoop

HotPAOLoop

EnvironmentalControl

Sub-system

VaporCompressionSub-SystemFuelLoop

Sub-System

RamAir

RamAir

Cabin/Cockpit

AvionicsEPS+

AvionicsEPS+

Propulsion Sub-system

heatsourceheatsink

TMSBoundary

Environment

activecooling

intermediateheatsink

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Virginia Tech TMSTrendsandTechnicalIssues

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-3

q  Integratedaircraft-andmission-levelTMSdesigniscriticaldueto§  increasedheatloads§  decreasedthermalenergystorageand

rejectioncapabilities

q  Nonlinearheatloadandsinktrendsdrivenby§  MEAsandAEAs§  increasedfuelefficienciesleadingtoless

on-boardfuel§  increasedengineefficienciesleadingto

higherT’sandhigherheatloads§  high-Pfuelpumpswithhigherheatloads§  needforgreatermaneuverability(e.g.,

fueldraulicactuatorsforthrustvectoring)§  compositematerials(e.g.,forless

weight,survivability,etc.)§  DirectedEnergyWeapons(DEWs)and

highpowerISRsensors

Criticalityoftheincreasedheatloadfortypicalstate-of-the-artmilitaryaircraft(ClearedforPublicRelease,AFRLRZ09-0609)

§  safety(i.e.,fuelassinknotavailableforcommercialaircraftandbecomingmorelimitedformilitaryaircraft)

q  TMSbecomingmainelectricpowerconsum-erandelectricalpowersubsystem(EPS)requiringgreaterTMScapabilities

ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014

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Virginia Tech AircraftThermalManagementSystem(TMS):

NeedforMission-/Aircraft-levelIntegratedDesign

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-4

AFS-A PS ECS VC/PAOS FLS ES CHS OLS FCS

Weight (lbm) 14980.8 5418.3 1297.1 1608.1 491.5 929.5 325.3 37.8 429.3

% empty weight 58.7% 21.2% 5.1% 6.3% 1.9% 3.6% 1.3% 0.1% 1.7%

OptimizedAAFTMSrepresentsonly13%to11.5%ofthetotalemptyweightoftheaircraftyetplaysacriticalroleinensuringthermallimitsarenotbreached

Mission-andaircraft-leveloptimizedsupersonicair-to-air

fighter(AAF)results:1st

ILGOiteration

Source:adaptedfromK.Smith,2009,M.S.Thesis,VirginiaTech.

Wetasopposedtodryweight

values

AFS-A PS ECS VC/PAOS FLS ES CHS OLS FCS

Weight (lbm) 9628.4 3678.8 749.5 909.9 280.4 899.5 325.3 37.8 404.4

% empty weight 56.9% 21.7% 4.4% 5.4% 1.7% 5.3% 1.9% 0.2% 2.4%

Mission-andaircraft-leveloptimizedsupersonicAAFresults:

Globaloptimum

OptimizingtheTMSindependentlyofotheraircraftsub-systemsandthemissionwillsignificantlyaltertheTMSresultsandmaycausethermallimitsto

bebreached

Remainingwithinthermallimitsmakesthedifferencebetweenachievingamissionornot

ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014

AAFandTMSreduction:53.4%

and43%

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Virginia Tech Aircraft-andMission-levelMDO:

OptimalUseofFLSasHeatSink

Fueltanktemperatureversustimeovertheentiremissionfortheoptimalvehicle

toff–takeoffscc1–1stsubsoniccruise/climbcap–combatairpatrolcacc–combataccelerationscc2–2ndsubsoniccruise/climbloit–loiter

298

300

302

304

306

308

310

312

314

0 300 600 900 1200 1500 1800 2100 2400 2700 3000

Time (Sec)

Tem

pera

ture

(K)

With AFS degrees of freedom Without AFS degrees of freedom

scc1

cap

cacc

scc2

loit

toff

Source:adaptedfromD.Rancruel,2002,M.S.Thesis,VirginiaTech.

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-5

ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014

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Virginia Tech TMSSynergieswiththe

ElectricalPowerSubsystem(EPS)

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-6

q  EPS-TMSdesignoptimizationwouldtakeadvantageofbenefitsresultingfromthermal-electricalenergymanagementto§  reducepeakpowerdemands§  reduceoverallinstalledenergyconversion,

storage,andtransportcapacities

q  EPS-TMSdesignoptimizationwouldquantifythebenefitsofsynergiestoimproveTMS(VCSandACM)performancevia,e.g.,§  electronicstocontrolthepressuresatwhich

compressorscutinandout§  electronicexpansionvalvesfortemperature

control§  separatehighandlowpressureelectronic

switchestopreventcompressors,etc.fromoperatingoutsideofsafelimits

§  electroniccontrolstoadjustcompressoroperationfordifferingcoolingloadsandreducedenergyconsumption

©2007TheBoeingCompany

q  EPS-TMSdesignoptimizationwouldquantifythebenefitsofsynergiesfortheEPS§  forlocalizedtemperaturecontrolof

powerelectronics(e.g.,thermoelectricgeneratorsandcoolers,heatpipes,…)

§  foraircraftmonitoringandpredictivemaintenance(e.g.,engineandaircraftskinoverheating,deicing,etc.)

§  forelectricallydrivenECSs(e.g.,usingfuelcells,…)

ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014

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Virginia Tech EPSLocalCoolingTechniques

db-7ARPA-EKick-offMeeting:REEACHProgram-27January2021

ManylocalcoolingchoicesfortheEPS,allofwhichmustultimatelyinterfacewiththeTMS,particularlyduetosurvivabilityrequirementsandtheuseofcompositematerials:

q  Heatspreadingq  Aircooling

§  piezofans§  syntheticjetcooling(topright)§  nano-lightning(bottomleft)

q  LiquidCooling§  heatpipes§  coldplates(topleft)§  microchannels§  electrohydrodynamic(bottom

right)§  electrowetting

q  Liquidmetalcooling

q  Spraycoolingq  Liquidjetimpingementq  Thermo-chemical

accumulators

q  Immersioncoolingq  Solidstatecooling

§  thermoelectric§  superlattice§  heterostructure§  thermionic§  thermotunneling Source:adaptedfromDr.WernerJ.A.Dahm,ASU,Thermal

Sciences&MaterialsWorkshop,Kettering,OH,16-17August2011.

ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014

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Virginia Tech HeatPipesforHighExternalThermalLoads

8

q  ExamplesofheatpipesforthermallymanagingtheheatloadsatleadingedgesincludeD-Shapedheatpipes,I-coreheatpipes,andheatspreaders.

q  D-shapedandI-coreheatpipesarebuiltdirectlyintothematerialthatformstheleadingedge(seebelow).Thedisadvantageisthatitcanleadtodeformationoftheheatpipesduringthemanufacturingprocesswhentheleading-edgematerialisbentintoitsfinalshape.

q  Twotypesofheatspreadersareshownbelow,aperiodicverticalI-truss-system(left)andaperiodictriangular-truss-system(right)

q  Bothprovidestructuralsupporttotheleadingedge,increasingthebendingstiffnessandcompressivestrength,whilethetriangular-trusssystemallowsforflowinmultipledirections,facilitatingtheflowofvapor. Source:S.D.Kasen,ThermalManagement

atHypersonicLeadingEdges,Ph.D.dissertation,UniversityofVirginia(2013)

ARPA-EKick-offMeeting:REEACHProgram-27January2021

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Virginia Tech PhaseChangeMaterialsforHighInternal

ThermalLoadsq  PCMenergystoragecanaddresscriticalthermalloadsonhighperformanceaircraftsinceit

providesameansforcoolingincreasedthermalloadsduetothe§  Increaseduseofcompositesontheaircraftskin;§  Increasedpowerrequirementsfornewsystems(e.g.,MEA/AEA,DEWs,ISRsensors,etc.);§  Reducedornoorrestrictedfuelonboard.

q  PCMsarecontainedintankswithinteriormatricesmadeofhighconductingmaterials(e.g.,carbonfoam)tohelpdistributeheattothePCM.

Source:Reed,W.C.,vonSpakovsky,M.R.,andRaj,P.,ComparisonofHeatExchangerandThermalEnergyStorageDesignsforAircraftThermalManagementSystems,AIAASciTec(2016).

Pentadecane Hexadecane Octadecane

EffectiveThermalConductivity W/m/K 220.16 165.12 165.12

EffectiveDensity kg/m^3 1054.4 1057.1 1098.3

PhysicalparametersofPCMmaterials.

Pentadecane Hexadecane Octadecane

MeltTemperature °C 10 18 27ThermalConductivity W/m/K 0.2 0.15 0.15

Density kg/m^3 768 770 800LatentHeatofFusion kJ/kg 205 237 244

PhysicalparametersofPCM-carbonfoamcomposite.

ARPA-EKick-offMeeting:REEACHProgram-27January2021

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Virginia Tech SomeConclusions

ARPA-EKick-offMeeting:REEACHProgram-27January2021db-10

q  Numberofheatsourceshasalwaysbeenlarge,whilethenumberofheatsinkshasalwaysbeenlimited

q MEA/AEA,DEW,ISR,increasedengineefficiencies,high-Pfuelpumps,theneedforgreatermaneuverability,etc.areaddingtoandincreasinginahighlynon-linearfashionthesizeandintensitiesofheatsources

q  Survivability,compositematerials,increasedfuelefficiencies,safety,etc.areeliminatingheatsinksorshrinkingtheircapacities

q  Reachingthermallimitsarerealthreatstothecompletionofmissionsandtothedesignandconstructionofcomplexmissions

q  TMSisbecomingthemainelectricpowerconsumerandtheEPSisrequiringgreaterTMScapabilities

q  Using“dryweight”toassessTMSviabilitymustbereplacedwithanassessmentof“wetweight”inordertoaddresstheseriousissueofthermallimits.

q  Assessmentmustbedoneasearlyinthedesignprocessaspossible,i.e.,duringtheconceptualdesignphase

q  Theneedforamission-andaircraft-levelMDA/MDOconceptualdesignframeworkisacute.

ClearedforPublicRelease:88ABW-2014-4186/RQ-14-664,3SEPT2014