TheEnhancementofConvec/veHeatTransferinanAluminumOxideNanoaerosol

EmpiricalStudyMaulinTrivediDec9,2015

MechanicalandManufacturingEngineering

Applica/ons

§  Deep-cooledcombinedturbojetcycle—  ThrustoverwiderangeofMach

number—  Intakeairhasveryhigh

temperature—  Energyextractedisaddedback

tofuelstream§  Heattransferapplica/onsuse

fluidsorairasheatcarriers.—  Thermalconstraints—  Physicalconstraints—  Cost

2

Figure1:DASSGN1EngineConceptFrom:h(ps://en.wikipedia.org/wiki/Space_Engine_Systems

Applica/ons

§  Heattransferapplica/onsusefluidsorairasheatcarriers.— Thermalconstraints— Physicalconstraints— Cost

§  Reac/onEnginesLtd.— Highsurfacearea

§  SpaceEngineSystems— Enhancedthermalproper/es

Figure2:SABREPre-coolerFrom:h(p://www.reac;onengines.co.uk/heatex_work.html

3

Background

§  Solidpar/clesinsuspensionincreasesthermalconduc/vity(Maxwell,1881).— Massorvolumefrac/onofpar/cles— Surfaceareatovolumera/o

§  Nanopar/cles— Sizes1-100nm— Veryhighsurfaceareatovolumera/o

§  Nanofluids:Nanopar/clessuspendedinliquidphasecarriers(Choi,1995).

§  Nanoaerosols:Nanopar/clessuspendedingaseousphasecarriers.

4

Background:Nanofluids

§  40%heattransferenhancement(Herisetal.,2006).

§  39%increaseinheattransfer(Xuanetal.,2003).

§  Dependencyonmassfrac/onandReynoldsnumber

Figure3:NusseltnumbervsPecletnumberFrom:Heris,S.Z.,Etemad,S.G.,&Esfahany,M.N.(2006).Experimentalinves/ga/onofoxidenanofluidslaminarflowconvec/veheattransfer.Interna;onalCommunica;onsinHeatandMassTransfer,33(4),529-535. 5

Background:Nanoaerosol

Figure4:Nusseltnumbervsmassloading Figure5:Nusseltnumbervspar/clesizeAdaptedfrom:Murray,D.B.(1994).Localenhancementofheattransferinapar/culatecrossflow—IIExperimentaldataandpredictedtrends.Interna;onaljournalofmul;phaseflow,20(3),505-513.

6

Background:Mechanisms

§  Increasedthermalcapacity

§  Conduc/onbetweenimpac/ngpar/cles

§  Thermalenergytransportbyreboundingpar/cles

§  Flowstructureeffects

§  Othereffects(Williams,2015)

§  Limi/ngmechanisms

7

Mo/va/on

§  Nanopar/clesvs.Micro-par/cles§  Availabilityinaerospaceindustryasanalterna/vefuel

— Largeenergycontentperunitvolumeandmass— Lowerigni/ontemperaturesandhigherburningrate— Safeandefficientstorage

§  Nanofluidsareproveneffec/veinheattransferapplica/ons§  Volumetricheatcapacityofnanoaerosolismuchhighercompared

tonanofluids— ρCpra/oismuchhigherfornanoaerosolthanfornanofluids

8

Objec/ves

§  Firstexperimentalinves/ga/on§  Lowpar/cleconcentra/on

— Massfrac/onfornanofluids,O(10-1)— Massfrac/onfornanoaerosols,O(10-4)

§  Theore/calmodeltopredictenhancement§  Par/clesizevs.heattransferenhancement

9

ExperimentalSet-up:Cont.

10Figure6:ExperimentalSchema/c

ExperimentalSet-up:Cont.

11Figure6:ExperimentalSchema/c

Hot-Wire Flow

ExperimentalSet-up

12Figure7:ExperimentalSet-up

PressureRegulator

CompressedAir

PressureGauge

FlowMeter

Par/cleInjector

UpstreamThermistor

HotWire

DownstreamThermistor

Par/cleCollec/onTank

Air-onlyTests

§  Validateexperimentalapparatus§  PerformedoverflowReynoldsnumberrangeof1420-11,200§  Nusseltnumbercalculatedbyequa/ngconvec/veheat

transferratetothechangeinenthalpy§  Experimentalresults(withoutpar/cles)werecomparedto

Zukauskasempiricalrela/onof§  Establishbaseline

13

Air-onlyTests:Cont.

14

0

2

4

6

8

10

12

14

16

18

20

0 2000 4000 6000 8000 10000 12000

NusseltNum

ber

ReynoldsNumber[tubediameter],Re

ZukauskasRela/onExperimentalAirTests

Figure8:Valida/onofexperimentalset-up

AirTests:Cont.

15

0

2

4

6

8

10

12

14

16

18

20

0 2000 4000 6000 8000 10000 12000

NusseltNum

ber

ReynoldsNumber[wirediameter],Re

ZukauskasRela/onExperimentalAirTests

Figure8:Valida/onofexperimentalset-up

FlowCondi/onsForPar/cleTests

Nanopar/cle:Informa/on

§  Approximatelysphericalwith112nmavg.dia.

§  Agglomeratesofavg.870nm.

§  Dispersedthroughcustom-builtinjec/onsystem.

16

Figure9:SEMimageofAl2O3par/cles

Nanopar/cle:Injec/onSystem

§  Gravityassistedthroughorificeof0.75mm

§  Oscilla/onsprovidedtopreventclogging

§  510mmoftubingallowssemlingofbiggerpar/cles

17

Figure10:Par/cleInjec/onSystem

Par/cleHousing

Off-balanceMotor

Air-flowpipe

UpstreamThermistor

Par/cleTests

§  Experimentswithpar/cleswereperformedatflowReynoldsnumbers:6000,7500and8900.

§  Par/cleflowratemeasuredanereachtestusinghighlysensi/vemassbalance.

§  Par/clemassloadingrangedfrom0.01%-0.33%.§  NusseltnumberateachReynoldsnumbercalculatedusing

samemethodologyasairtests.— Effec/veproper/es

18

ExperimentalResults:Cont.

19

Figure11:EffectofmassloadingonNuatRe=6000

y=9.5795x0.5809R²=0.70653

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35%

%NuIncrease

%Par/cleMassLoading

Raw%NuIncrease Predicted%NuIncrease 95%LowerCI 95%UpperCI

ExperimentalResults:Cont.

20

Figure12:EffectofmassloadingonNuatRe=7500

y=5.3126x0.5338R²=0.61755

0%

5%

10%

15%

20%

25%

30%

35%

40%

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35%

%NuIncrease

%Par/cleMassLoading

Raw%NuIncrease Predicted%NuIncrease 95%LowerCI 95%UpperCI

ExperimentalResults:Cont.

21Figure13:EffectofmassloadingonNuatRe=8900

y=0.9927x0.2821R²=0.46192

0%

5%

10%

15%

20%

25%

30%

35%

40%

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35%

%NuIncrease

%Par/cleMassLoading

Raw%NuIncrease Predicted%NuIncrease 95%LowerCI 95%UpperCI

ErrorAnalysis

§  Systema/cerrorscalculatedbasedoninstrumenta/onandsensorlimita/ons.

§  Randomerrorscalculatedbasedont-distribu/onforα=0.05.

§  Randomerrorissignificantlyhigherthansystema/cerrors.

§  Student’st-testbetweenbaselinetestandpar/cletestatlowestpar/cleconcentra/onshowssignificantincreaseinNusseltnumber.

22

9

10

11

12

13

14

15

16

17

550 600 650 700 750 800 850 900 950

NusseltNum

ber

Cross-flowReynoldsNumber

AirTest Par/cleTest

Figure 14: Student's t-test for 95% confidencebetweenair-onlyandlowestpar/cleloadingtests

Model:Con/nuum

§  Con/nuumregime,Kn<0.01— Murray’smodelforincreasedthermalcapacity— (𝑁𝑢↓𝑁𝐴 /𝑁𝑢↓𝑎  )↓𝐼𝑇𝐶 = [1+ 𝜂↓𝑡 𝑆↓𝐿 𝑐↓𝑝 ↓𝑟𝑎𝑡𝑖𝑜 ]↑0.37 

§  𝜂↓𝑡 = 𝜏↓𝑟𝑒𝑠 /𝜏↓𝑟𝑒𝑙  ;𝜏↓𝑟𝑒𝑙 = 𝑑↓𝑝 𝜌↓𝑝 𝑐↓𝑝 ↓𝑝 /6ℎ↓𝑝  §  Othereffectsareconsiderednegligibleduetolowpar/cle

loading— Flowstructuremodifica/on— Par/clerebound— Radia/on

23

Model:Free-molecular

§  Free-molecularregime,Kn>10— ModifiedMurray’smodelusingthefree-molecularrelaxa/on/me,τrel

— ObtainedfromFilippovandRosner’senergybalance§  𝜌↓𝑝 𝐶↓𝑝↓𝑝  𝑉↓𝑝 𝑑𝑇↓𝑝 /𝑑𝑡 =𝛼𝜋𝑎↑2 𝑛↓𝑔 𝑐 𝑘↓𝑏 (1/2 (𝑇↓𝑝 − 𝑇↓𝑔 )(𝛾+1/𝛾−1 ))

§  𝜏↓𝑟𝑒𝑙 = 2𝜌↓𝑝 𝑐↓𝑝 𝑑↓𝑝 /9𝑛↓𝑔 𝑐 𝑘↓𝑏  ; 𝑛↓𝑔 = 𝑃𝑁↓𝑎𝑣 /𝑅𝑇 ; 𝑐 =√8𝑘↓𝑏 𝑇↓𝑔 /𝜋𝑚↓𝑔   

— Subs/tuteτrelintoMurray’smodeltoobtainNusseltnumberenhancement

24

Model:Transi/on

§  Transi/onregime,0.01<Kn<10— HarmonicmeansuggestedbySherman(1963)wasusedtointerpolate𝑞↓𝑡𝑟  .

— 𝜏↓𝑟𝑒𝑙,𝑡𝑟 = 𝜌↓𝑝 𝑐↓𝑝 𝑑↓𝑝 ↑2 /𝑞↓𝑡𝑟  /𝑞↓𝑐   12𝑘↓𝑓  ; 𝑞↓𝑡𝑟  /𝑞↓𝑐   = 1/1+ 19/6 𝐾𝑛 

— Thera/o 𝑞↓𝑡𝑟  /𝑞↓𝑐   canbeobtainedfromLiu(2006).— Knudsennumbereffectsareincorporatedintothe/mescale

25

Model:Comparison

26

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

1.90

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35%

NuRa

/o[N

u_su/N

u_a]

SolidMassFrac/on,%[m_solid/m_air*100]ExperimentalFit ExperimentalData Transi/onalModel

MurrayModel FreeMolecularModel 95%ConfidenceBand

Figure15:Comparisonofcon;nuummodel,free-molecularmodel,transi;onalmodelandexperimentaldataforRe=6000

27

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

1.90

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35%

NuRa

/o[N

u_su/N

u_a]

SolidMassFrac/on,%[m_solid/m_air*100]ExperimentalFit ExperimentalData Transi/onalModel

MurrayModel FreeMolecular 95%ConfindenceBand

Figure16:Comparisonofcon;nuummodel,free-molecularmodel,transi;onalmodelandexperimentaldataforRe=7500

Model:Comparison

28

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

1.90

0.00% 0.05% 0.10% 0.15% 0.20% 0.25% 0.30% 0.35%

NuRa

/o[N

u_su/N

u_a]

SolidMassFrac/on,%[m_solid/m_air*100]ExperimentalFit ExperimentalData Transi/onalModel

MurrayModel FreeMolecularModel 95%ExperimentalBand

Figure17:Comparisonofcon;nuummodel,free-molecularmodel,transi;onalmodelandexperimentaldataforRe=9000

Model:Comparison

Model:EffectofPar/cleSize

29

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

0 10 20 30 40 50 60 70 80 90 100

NusseltNum

berR

a/o

Par/cleDiameter,[nm]

SolidLoading0.25% SolidLoading0.5% SolidLoading0.75% SolidLoading1%

Figure18:Effectofpar/clesizeonNusseltnumberra/oatRe=9000usingtransi/onalmodel

Discussion:Experimental

§  Onlysmallpar/clemassloadingisrequiredtoprovidealargeincreasetoNusseltnumber.

§  Murray(1994)required~100%massloadingtoachievesimilarresults.

§  Higherenhancementamributedto:— Smallerpar/cles— LowerReynoldsnumber

30

From:Murray,D.B.(1994).Localenhancementofheattransferinapar/culatecrossflow—IIExperimentaldataandpredictedtrends.Interna;onaljournalofmul;phaseflow,20(3),505-513.

Discussion:Experimental

§  Onlysmallpar/clemassloadingisrequiredtoprovidealargeincreasetoNusseltnumber.

§  Murray(1994)required~100%massloadingtoachievesimilarresults.

§  Higherenhancementamributedto:— Smallerpar/cles— LowerReynoldsnumber

31

From:Murray,D.B.(1994).Localenhancementofheattransferinapar/culatecrossflow—IIExperimentaldataandpredictedtrends.Interna;onaljournalofmul;phaseflow,20(3),505-513.

Discussion:Model

§  EffectsofincreasedReynoldsnumberandturbulencemodifica/onareinsignificant.

§  Therelaxa/on/merepresents63%ofheattransfer,thusresul/nginhigherpredic/onofheattransferenhancement.

§  Experimentaldatabetweencon/nuumandfree-molecularpredic/on.

§  Transi/onalmodelagreeswithexperimentaldata.— For0.01<Kn<10

§  Manyothereffectsarenotincluded.

32

Conclusion

§  Heattransferenhancementusingnanoaerosolhasbeenexperimentallydemonstratedforthefirst/me.

§  Largeheattransferenhancement(~36%)wasobservedatrela/velylowpar/cleloading(~0.35%).

§  Experimentaldataisprovedtobesta/s/callysignificant.§  ObservedtrendsareconsistentwiththeoryproposedbyMurray.§  Murray’smodelismodifiedforfree-molecularandtransi/onregime.

—  Transi/onmodelagreeswithexperimentaldata.—  Transi/onmodelextendedtopredicteffectofpar/clesizeovermassloading

0.25%-1%.—  Othereffectsneedtobeincorporated.

33

Acknowledgements

§  AlbertaInnovatesTechnologyFutures§  NaturalSciencesandEngineeringResearchCouncil§  SpaceEngineSystems§  UniversityofCalgary§  Dr.CraigJohansen

34

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Publica;ons-Fed,231,99-106.3.  ZeinaliHeris,S.,Etemad,S.G.,&NasrEsfahany,M.(2006).Experimentalinves/ga/on

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7.  Bianco,V.,Manca,O.,Nardini,S.,andVafai,K.,HeatTransferEnhancementWithNanouids,April12015,CRCPress

35