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Int. J. Nanosci. Nanotechnol., Vol. 10, No. 3, Sept. 2014, pp.
153-162
Calculation of Heat Transfer Coefficient of MWCNT-TiO2
Nanofluid in Plate Heat Exchanger
M. A. Safi1, A. Ghozatloo1,2*, A. A. Hamidi3, M.
Shariaty-Niassar1
1- Transport Phenomena and Nanotechnology Laboratory, Department
of Chemical Engineering,
College of Eng., University of Tehran, Tehran, I. R. Iran
2- Faculty member of Research Institute of Petroleum Industry
(RIPI), West blvd. Azadi Sport
Compl ex,Tehr an, I.R.Iran 3- Department of Chemical
Engineering, College of Eng., University of Tehran, Tehran, I. R.
Iran
Abstract:
(*) Corresponding author: [email protected]
(Received: 30 Dec. 2013 and accepted: 18 July 2014)
The objective of the present study is the synthesis of MWCNT-TiO
hybrid nanostructures by solvothermal
synthesis method with TiCl as precursor. The heat transfer
enhancement due to the use of MWCNT-TiO
nanofluid was investigated. As-prepared hybrid materials were
characterized by X-ray diffraction (XRD)
and scanning electron microscopy (SEM). The results showed that
MWCNTs were uniformly decorated with
anatase nanocrystals. The heat transfer performance of the plate
heat exchanger (PHE) was investigated using
MWCNT-TiO nanofluid at various volume flow rates, a wide range
of concentrations and inlet temperatures.
The performance is discussed in terms of heat transfer
coefficient ratio. The results showed that the heat
transfer coefficient of the nanofluid was more than that of the
base fluid (Distilled Water). The heat transfer
coefficient was enhanced with increasing the nanofluid
concentration from 0.02 to 0.08 wt.% and volume flow
rate from 2 to 3.5 LPM. Conversely, the heat transfer
coefficient decreased with increasing the nanofluid inlet
temperature from 36 to 60oC.
Keywords: Nanofluids, Plate heat exchanger, Heat transfer,
Hybrid
1. INTRODUCTION
The plate heat exchangers (PHEs) are compact
and efficient, widely used in many engineering
applications because of their high thermal
efficiency, compactness, usefulness in varying
loads, flexibility and ease of sanitation. To take
care of the growing demand for energy density,
heat transfer capacity needs to be increased and
this can be attained by the use of a fluid with better
transport properties. Innovative heat transfer fluids
suspended by nanometer-sized solid particles are
called ‘nanofluids’ which was coined by Choi
in 1995 [1]. These fluids include metal oxides,
chemically stable metals and several allotropes of
carbon with thermal conductivities typically an
order-of-magnitude higher than those of the base
fluids and with sizes significantly smaller than 100
nm[2].
The heat transfer enhancement when using
nanofluids may be affected by several mechanisms
such as Brownian motion, sedimentation, dispersion
of the suspended particles, thermophoresis,
diffusiophoresis, layering at the solid/liquid
interface and ballistic phonon transport. It should
be noted that the increase in thermal conductivity
might be offset by the increase in viscosity and
decreased the effective specific heat of nanofluid.
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However, various experiments showed significantheat transfer
enhancement with little penalty
ofpressuredropinheatexchangerapplications[3-6].Carbon nanotubes
(CNTs) have drawn extensiveattention owing to their promising
applicationsin various fields. One of the most
importantapplications is employing CNTs as scaffolds
ofvariousoxideslikeTiO2[7]toconstructfunctionalcarbon-based hybrids
or composites. Manymethods including self-assembly, sol–gel
coating[8], hydrothermal, solvothermal, and liquid/vaporphase
deposition have recently been developed toprepare this kind of
hybrids. Most of these methods
aregenerallyemployedinaqueousreactivesystems[7]wherepristinehydrophobicCNTsrequiretobepre-oxidized
in strong acids into their
hydrophilicformscontaining–OHand–COOH.However,theoxidization
usually causes uncontrollable damageto the structure of CNTs [8],
undesired surfacedefects and shortening of CNTs, which
exertsadverseeffectsontheconductivityandmechanicalpropertiesofpristineCNTs.Therefore,itbecomesimportant
to develop new strategies for preparinguniform hybrids with
pristine CNTs as startingsupports[9].Theobjectiveof
thepresentstudyis thesynthesisof MWCNT-TiO2 hybrid by solvothermal
method andinvestigatingtheheattransferenhancementdueto the use
ofMWCNT-TiO2 nanofluid in a PHE.Experiments were conducted in a
wide range ofconcentrations (0.02, 0.04, 0.06 and 0.08
wt.%),temperatures(36,44,52and60oC)andvolumeflowrates(2,2.5,3and3.5LPM).
2.EXPERIMENTALPROCEDURES
2.1.Materials
ThemultiwallcarbonnanotubewaspurchasedfromResearch Institute of
Petroleum Industry (RIPI).Sulfuricacid(H2SO4),Nitricacid(HNO3),
titanium
chloride(TiCl4)andEthanolwerepurchasedfromMerckKGaA(Darmstadt,Germany).
2.2. Functionalization of Multiwall CarbonNanotube
Theraw-MWCNTsweresonicatedfor3hat60oC
in an ultrasonic bathwith a (v/v, 3:1)mixture
ofconcentratedH2SO4
andHNO3tointroduceoxygencontainingfunctionalgroupson
theraw-MWCNTsurface.TheloadofMWCNTswas1gfor80mLof the blended acid
solution. Then the mixturewas diluted by distilledwater, and it was
filteredand washed repeatedly till the washing
showednoacidity.ThecleanMWCNTsweredried in theoven at
60oCfor12hours[10].Thereactionschemefor the
treatmentofCNTsusingAcid treatment isshowninFigure1.
Figure 1: Scheme reaction for Acid treatment of CNTs
2.3.SynthesisofMWCNT-TiO2 hybrid
The MWCNT-TiO2 hybrid nanostructures wereprepared from titanium
chloride by solvothermalmethod. Briefly, 0.5 mL TiCl4 (4.55 mmol)
wasslowly dropped into 40 mL ethanol and stirredmagnetically to
provide a completely transparentyellow solution. Desired amounts of
MWCNTwere dissolved, placed in the ultrasonic bath
for45minanddispersed in thesolution.Then
itwastransferredtoaTeflon-lined,stainlessautoclaveandstored at
120oC for 24 h, until it turned into gray or dark precipitate.The
precipitatewas separated
bycentrifugationandwashedcarefullywithanhydrousethanol(3×20mL)toremoveorganicspecies.Thecollectedmaterialswerelefttodryinanovenat60oC
for12handthencalcinedatdifferenttemperatures(100–400oC) for 2 h to
obtain theMWCNT-TiO2
hybridnanostructures[11].Thesamplescontained50wt.%MWCNTinthispaper.
2.4.PreparationsofNanofluids
In order to prepare the samples (MWCNT-TiO2
nanofluids),atwo-stepprocesswasused.MWCNT-TiO2 with a wide range of
concentrations
(0.02,0.04,0.06and0.08%wt)wasmixedupwithabasefluid,i.e.distilledwater,andplacedintheultrasonic
Safi,et al.
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155
device(BANDELINSONOPULSHD3200,140W,20kHz,Figure2)for45min[12].
Figure 2: Ultrasonic device in laboratory
2.5. Experimental setup and procedure
Anexperimentalsetupwasdevelopedtoinvestigatethe heat transfer
coefficient of the nanofluid asshown in Figure 3 and 4.A commercial
PHEmanufacturedbyGEAGermanyhaswas for thispurpose.The geometric
details of the plates andthe heat exchanger are provided in Table 1
andFigure5.
Figure 3: Photograph of the experimental setup
Theexperimental setupmainly included twoflowloops, for the hot
and cold fluids (nanofluid and
water flow loops) as illustrated in Figure 4.
Thedeviceconsistedofastainlesssteeltank,aheater,apump,aplateheatexchanger,twogatevalves,5on/offvalves,2rotameters,5resistancethermocouples,PLCandacomputer.Thestoragetankwasmadeofstainlesssteel304topreventcorrosionandthetanksizewas15×12×12cm.Toavoidheatloss,thetankwasmade
of two layers of glasswoolwith
somespacebetweenthem.Forheatingthenanofluida2kWheaterwasbuilt
inthestoragetank.Nanoparticlesdonotprecipitatebecauseofthemixingduetothefluidflowinsidetheexchanger.Four
RTD PT-100 probes measure the inlet andoutlet temperatures of each
stream. To controltheflow rate of the nanofluid and coldwater
tworotameterswereused.FlowrateoftheNnanofluidvariedfrom2to3.5LPMwhereasflowrateofthecoldstreamwas1LPMinalltests.Theminimumrequirednanofluidforthesetupis1100ml.A
typical test normally lasted approximately
60min.Thistimeintervalwasrequiredforthesystemto achieve
steady-state conditions. In order toestablish whether the system
reached the steady-state conditions, the temperatureswere
constantlymonitored.
Table 1: Geometrical parameters of tested plate heat
exchanger
282Verticaldistance,H(cm)
239Vertical distance between centers of ports,H1
(cm)127Horizontaldistance,W(cm)
84Horizontal distance between centers of ports,W1 (mm)19.5Port
length, S (mm)
-196~204OperationTemperature,(0C)33maximum operation pressure,
(bar)6Number of plates
2.05Meanchannelspacing,bc (mm)0.6Platethickness(mm)0.16Total
area of heat transfer (m2)
2.6. Data analysis
Experimental data was used to calculate the heattransfer
coefficient of the nanofluids. Reynoldsnumber of coldwater can be
calculated based on
International Journal of Nanoscience and Nanotechnology
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156
channelmassvelocityandhydraulicdiameterofthechannelasfollows[13]:
Re w hww
G Dµ
= (1)
Where Dh=2bc is the hydraulic diameter.
Thechannelmassvelocityisobtainedfromthefollowingrelationship:
/ . .ww ch cG m n b W•
= (2)
Where 3chn = for cold and 2 for hot stream,respectively.The heat
has been removed by nanofluids andabsorbedbythecoldwater, cQ
,iscalculatedbyEq.(3)usingthemeasuredtemperatureandmass-flowrate.
Figure 4: Schematic diagram of the experimental setup
Safi,et al.
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157
,cc c p cQ m c T•
= ∆ (3)
The fluid properties are evaluated at
bulktemperatureswhicharecalculatedas:
,c c, c,o( ) / 2b iT T T= + (4)
TheNusseltof
thecoldfluidcanbecalculatedbythefollowingequation[14]:
0.66 0.330.455Re Prc c cNu = (5)
Thesevaluesareobtainedfromthestandardizationonthewateroftheexchangerbytheconstructor.ThePrandtlnumberisdefinedasfollows:
( )Pr c p cc
c
Ck
µ=
(6)
Theheattransfercoefficientofwater(coldstream)canbecalculatedbythefollowingequation:
.c hc
c
Nu Dhk
=
(7)
The overall heat transfer coefficient is
calculatedusingEq.(8)basedontheexperimentaldata:
. .c
LMTD
QUA F T
=∆
(8)
WhereAisthetotalheattransferareaofthePHEandFisthetemperaturecorrectionfactor,whichcanbetakenequalto1inthecaseofthecountercurrentflow.
( ) ( )( )
( )
nf, w, nf, w,
nf, w,
nf, w,
ln
i o o iLMTD
i o
o i
T T T TT
T TT T
− − −∆ =
− −
(9)
The heat transfer coefficient of nanofluids
areevaluatedusingoverallheattransfercoefficientandwater heat
transfer coefficient. Given the thermalconductivityof theplate,k,
and its
thickness,∆x,theheattransfercoefficientofnanofluidsisobtainedfromthefollowingrelationship:
nf
w
hx
U h k
= ∆
− −
11 1 (10)
3. RESULTS
3.1. FTIR spectroscopyThe functionalization & chemical
structure ofMWCNTwereidentifiedbyFTIR(ThermoScientific,Nicolet
6700). Typically 100 scans over the range4000–500 cm-1were taken
from each samplewitha resolution of 2 cm-1 and summed to provide
the spectra.TheresultsareshowninFigure6.The broad band of FTIR
spectra between 3000and 3700 cm-1 corresponds to the presence of
theoxygenatedgroups[15].Thepresenceofcarboxylfunctional groups and
OH groups could alsobe detected at around 1768 cm-1 and 3454 cm-1,
respectively[16].Thepeaksat1647cm-1and1225cm-1canbeattributedtoC=CbandingvibrationsofaromaticstructuresandC-Obanding,
respectively[17].
Figure 5: Basic geometric parameters of plate heat exchanger
International Journal of Nanoscience and Nanotechnology
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158
Figure 6: FTIR of raw-MWCNT and func-MWCNT
3.2.SEMimaging
The morphology of the TiO2 on MWCNT wasexamined by SEM image.
Scanning ElectronMicroscope (SEM)was carried out usingKYKY-EM3200
at 40 kV. The SEM images of thefunctionalizedMWCNTandMWCNT-TiO2
hybrid
areshowninFigure7.Ascanbeseen,theMWCNTscoatedwithwell-dispersedTiO2particlesareclearlyshown,indicatingthattheMWCNTsandTiO2
had anintimatecontact.
3.3 XRD analysis
X-raydiffraction(XRD)patternswereanalyzedbyanX-ray
diffractometer (BrukerAXS.,
Germany)usingCuKαradiationsourceat40kV.TheXRDpatterns of the
functionalized MWCNT and
MWCNT-TiO2hybridareshowninFigure8TheXRDpatternsrevealthatonlyanatasephaseofTiO2canbeidentified.ThepristineMWCNTshavetwo
typical diffraction peaks (002 and 101).
ForMWCNT-TiO2hybridthemaindiffractionpeaksofanataseTiO2(101,004,200,105,211,and204)areclearlyshown[9].
Figure 8: XRD patterns of the func-MWCNT and MWCNT-TiO2
hybrid
BasedonScherrer equation thecrystalline sizeofthe anatase phases
is 2.3 nm.
3.4.Heattransfercoefficientofnanofluid
To evaluate the reliability and accuracy of
themeasurements,experimentalsystemwastestedwithdistilledwaterbeforemeasuringtheheattransferofnanofluids.TheresultsareshowninFigure9.
Figure 7: SEM image of a) func-MWCNT, b) MWCNT-TiO2 hybrid
Safi,et al.
a) b)
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159
Figure 9: Variation of heat transfer coefficient of distilled
water nanofluid tested at different volume flow rates with various
temperatures: a) 360C, b)
44oC, c) 52oC, d) 60oC Figure 10 shows the variations of heat
transfercoefficient of MWCNT-TiO2 nanofluid withdifferent weight
concentrations (0.02, 0.04, 0.06and 0.08wt.%) in awide range of
volume flow
rates (2,2.5,3and3.5LPM)andat
theflowrateofcoldwaterequalto1LPM.AsshowninFigure10, the heat
transfer coefficient increases
withincreasingweightfractionofnanoparticles.Addingnanoparticles
increases particle collisions andinteractions.Nanoparticle
penetration and
relativemotionsnearthewallplatesmayalsoincreasetheheat
transfer.Figure11showsthevariationsoftheheattransfercoefficient
ratio of MWCNT-TiO2 nanofluid
atdifferentvolumeflowrates(2,2.5,3and3.5LPM),differentconcentrations(0.02,0.04,0.06and0.08wt.%)andataflowrateofcoldwaterequal
to1LPM.Ataconstantinlettemperatureandaparticleweight concentration
of nanoparticles, a
higherflowrateofnanofluidscausesagreaterheattransfercoefficient
ratio. As the flow rate of nanofluidsincreases, the influence of
nanoparticle collisionon the wall surface increases which leads
totemperaturerise.Theoutcomeofthisinvestigations
nanofluincreasetemperaratios o Fig. 12differenand 3.5ratio ofthe
inleincreasi1- Rapinanopar2- Deplconduct
Fig. 10.
uids causes es, the inuature rise. Tf nanouids
22 shows thnt temperatu5 LPM) andf the heat tret temperatuing
the nanoid alignmenrticles. letion of partivity layer
. Variation of h
a greater huence of nanThe outcoms increases he variationures
(36, 44d at a ow rransfer coefure. The douid inlet t
nt of nanopa
rticles in theat the wall.
a)
c) heat transfer coe
with va
heat transfenoparticle c
me of this invsignicantlyns of heat 4, 52 and 60rate of
coldfcients (na
decrease in temperature
articles in lo
e near-wall
efficient of MWarious temperat
10
er coefciecollision on vestigationsy. transfer co
0 0C) in a wd water equanouid to the heat tr
e can be dueower viscos
uid phase
WCNT-TiO2/watures: a) 36 0C,
ent ratio. Athe wall su
s showed th
oefcient ofwide range oual to 1 LPMthe base u
ransfer coefe attributed sity uids, le
e, leading to
ater nanofluid teb) 44 0C, c) 52
As the ow urface increahat the heat
f MWCNTof volume fM. Accordiuid) increasfcient of to two
factoeading to le
o an intrinsi
b)
d) ested at differen
0C, d) 60 0C
rate of naases which transfer co
T-TiO2 nanoflow rates (2ing to Fig. ses with decthe nanouors
[18]: ess contact b
cally lower
nt weight conce
anouids leads to efcient
ouid at 2, 2.5, 3 122, the creasing uid with
between
thermal
entrations Figure 10: Variation of heat transfer coefficient of
MWCNT-TiO2 /water nano-
fluid tested at different weight concentrations with various
temperatures: a) 36oC, b) 44oC, c) 52oC, d) 60oC
International Journal of Nanoscience and Nanotechnology
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160
nanofluincreasetemperaratios o Fig. 12differenand 3.5ratio ofthe
inleincreasi1- Rapinanopar2- Deplconduct
Fig. 10.
uids causes es, the inuature rise. Tf nanouids
22 shows thnt temperatu5 LPM) andf the heat tret temperatuing
the nanoid alignmenrticles. letion of partivity layer
. Variation of h
a greater huence of nanThe outcoms increases he variationures
(36, 44d at a ow rransfer coefure. The douid inlet t
nt of nanopa
rticles in theat the wall.
a)
c) heat transfer coe
with va
heat transfenoparticle c
me of this invsignicantlyns of heat 4, 52 and 60rate of
coldfcients (na
decrease in temperature
articles in lo
e near-wall
efficient of MWarious temperat
10
er coefciecollision on vestigationsy. transfer co
0 0C) in a wd water equanouid to the heat tr
e can be dueower viscos
uid phase
WCNT-TiO2/watures: a) 36 0C,
ent ratio. Athe wall su
s showed th
oefcient ofwide range oual to 1 LPMthe base u
ransfer coefe attributed sity uids, le
e, leading to
ater nanofluid teb) 44 0C, c) 52
As the ow urface increahat the heat
f MWCNTof volume fM. Accordiuid) increasfcient of to two
factoeading to le
o an intrinsi
b)
d) ested at differen
0C, d) 60 0C
rate of naases which transfer co
T-TiO2 nanoflow rates (2ing to Fig. ses with decthe nanouors
[18]: ess contact b
cally lower
nt weight conce
anouids leads to efcient
ouid at 2, 2.5, 3 122, the creasing uid with
between
thermal
entrations
Fig. 11.
Fig. 12.
4. ConcIn this methodThe heawas caconcentas follo
1)
Variation of hevario
Variation of he
clusion paper, anat
d and characat transfer
alculated. Ttrations, owws: The heat trnanouid.
a)
c) eat transfer coefous weight con
a)
c) eat transfer coef
volume
tase TiO2 ncterized by Xcoefficient
The experimw rates and
ransfer coefAt the tem
fficient of MWcentrations: a) 0
fficient of MWe flow rates: a)
nanoparticleXRD, SEMof a MWC
ments wered inlet temp
fcient decmperatures
11
CNT-TiO2/wat0.02 wt. %, b) 0
WCNT-TiO2/wat2 LPM b) 2.5 L
s were anchM and FT-IRCNT-TiO2 ne done in eratures of
creased withof 44 and
ter nanofluid te0.04 wt. %, c) 0
ter nanofluid teLPM, c) 3 LPM
hored on CR techniquesnanouid o
a wide rthe nanoflu
h increasing60 0C, th
b)
d)ested at differen0.06 wt. %, d) 0
b)
d) ested at differen
M, d) 3.5 LPM
CNTs surfacs. owing in a ange of n
uid. The ma
g the inlet e heat tran
nt volume flow r0.08 wt. %
nt inlet temperat
ce via solvo
counter oanoparticle
ajor conclus
temperaturnsfer coef
rates with
tures with
othermal
ow PHE weight
sions are
e of the cient of
Fig. 11.
Fig. 12.
4. ConcIn this methodThe heawas caconcentas follo
1)
Variation of hevario
Variation of he
clusion paper, anat
d and characat transfer
alculated. Ttrations, owws: The heat trnanouid.
a)
c) eat transfer coefous weight con
a)
c) eat transfer coef
volume
tase TiO2 ncterized by Xcoefficient
The experimw rates and
ransfer coefAt the tem
fficient of MWcentrations: a) 0
fficient of MWe flow rates: a)
nanoparticleXRD, SEMof a MWC
ments wered inlet temp
fcient decmperatures
11
CNT-TiO2/wat0.02 wt. %, b) 0
WCNT-TiO2/wat2 LPM b) 2.5 L
s were anchM and FT-IRCNT-TiO2 ne done in eratures of
creased withof 44 and
ter nanofluid te0.04 wt. %, c) 0
ter nanofluid teLPM, c) 3 LPM
hored on CR techniquesnanouid o
a wide rthe nanoflu
h increasing60 0C, th
b)
d)ested at differen0.06 wt. %, d) 0
b)
d) ested at differen
M, d) 3.5 LPM
CNTs surfacs. owing in a ange of n
uid. The ma
g the inlet e heat tran
nt volume flow r0.08 wt. %
nt inlet temperat
ce via solvo
counter oanoparticle
ajor conclus
temperaturnsfer coef
rates with
tures with
othermal
ow PHE weight
sions are
e of the cient of
Figure 11: Variation of heat transfer coefficient of
MWCNT-TiO2/water nano-fluid tested at different volume flow rates
with various weight concentrations: a)
0.02 wt.%, b) 0.04 wt.%, c) 0.06 wt.%, d) 0.08 wt.%
Figure 12: Variation of heat transfer coefficient of
MWCNT-TiO2/water nano-fluid tested at different inlet temperatures
with volume flow rates: a) 2 LPM b)
2.5 LPM, c) 3 LPM, d) 3.5 LPM
Safi,et al.
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161
showed that the heat transfer coefficient ratios
ofnanofluidsincreasessignificantly.Figure 12 shows the variations
of heat
transfercoefficientofMWCNT-TiO2nanofluidatdifferenttemperatures(36,44,52and60oC)inawiderangeof
volume flow rates (2, 2.5, 3 and 3.5 LPM)and at a flow rate of
coldwater equal to
1LPM.AccordingtoFigure12,theratiooftheheattransfercoefficients
(nanofluid to the basefluid)
increaseswithdecreasingtheinlettemperature.Thedecreaseintheheattransfercoefficientofthenanofluidwithincreasing
the nanofluid inlet temperature can
bedueattributedtotwofactors[18]:1. Rapid alignment of nanoparticles
in lower
viscosityfluids,leadingtolesscontactbetweennanoparticles.
2. Depletion of particles in the near-wall
fluidphase,leadingtoanintrinsicallylowerthermalconductivitylayeratthewall.
4.CONCLUSION
In this paper, anatase TiO2 nanoparticles wereanchored on CNTs
surface via
solvothermalmethodandcharacterizedbyXRD,SEMandFT-IRtechniques.The
heat transfer coefficient of a MWCNT-TiO2 nanofluid flowing in a
counter flow PHE wascalculated.The experimentswere done in
awiderange of nanoparticle weight concentrations, flowrates and
inlet temperatures of the
nanofluid.Themajorconclusionsareasfollows:The heat transfer
coefficient decreased
withincreasingtheinlettemperatureofthenanofluid.Atthe temperatures
of 44 and 60oC, the heat transfer coefficient of MWCNT-TiO2
nanofluid
enhanced16.1%and13.7%at0.06wt.%and2LPMcomparedwiththatofdistilledwater.The
heat transfer coefficient enhanced with theaddition of
nanoparticles to the base fluid.At
theconcentrationsof0.04and0.08wt.%ofMWCNT-TiO2 nanoparticles, the
heat transfer
coefficientincreased18.6%and20.2%comparedwiththatofdistilledwaterat36oCand3.5LPM.Theheattransfercoefficientincreasedsignificantlywith
increasing the volumetric flow rate of the
nanofluid.At the volume flow rates of 2.5 and
3LPMofMWCNT-TiO2nanofluid,theheattransfercoefficientenhanced11.1%and13%at0.02wt.%and52oCcomparedwiththatofdistilledwater.
ACKNOWLEDGEMENT
TheauthorswishtothanktheTransportPhenomenaandNanotechnologyLaboratory
(TPNT) for theirgreatsupporttothisproject.
ABBREVIATIONS
MWCNT: multiwallcarbonnanotubeXRD: X-raydiffractionSEM:
scanningelectronmicroscopyPHE: plateheatexchangerLPM:
litterperminute
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