Experimental investigation and comparison of subcooled flow boiling of TiO2 nanofluid in a vertical and horizontal tube

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Original Article

Experimental investigation andcomparison of subcooled flow boilingof TiO2 nanofluid in a vertical andhorizontal tube

E Abedini1,2, A Behzadmehr1, H Rajabnia1, SMH Sarvari3 and

SH Mansouri3

Abstract

In this study, variations of local heat transfer coefficient are obtained in subcooled flow boiling conditions for water/TiO2

nanofluid in a vertical and horizontal tube. The results for the base fluid are compared with the predictions of the well

known Shah correlation and Gnielinski formula for laminar and turbulent flows for single-phase forced convection and

also with Chen correlation for subcooled flow boiling. A good agreement between the results is realized. At the

subcooled regime, heat transfer coefficient of nanofluid is less than that of the base fluid and it decreases by increasing

nanoparticle concentration for both of the channels; however, addition of the nanopraticles into the fluid causes that thevapor volume fraction increases.

Keywords

Experimental, nanofluid, subcooled, flow boiling

Date received: 2 2 2; accepted: 2 October 2012

Introduction

Nanofluid has been extensively investigated. Eastman

et al.1 measured the thermal conductivity of nanofluid

and a 60% improvement of the thermal conductivity

was achieved as compared to the base fluids for

5 vol.% of nanoparticles. Li and Peterson2 investi-

gated the effects of variations in the temperature

and volume fraction on the effective thermal conduct-

ivity of CuO and Al2O3/water suspensions. Results

showed that nanoparticle material, diameter, volume

fraction, and bulk temperature have significant effects

on the thermal conductivity of the nanofluids. Xuan

and Li3 investigated convective heat transfer charac-

teristics for Cu/water nanofluid into a straight tube

with a constant heat flux at the wall. Their results

showed that the nanofluids give considerable enhance-

ment of heat transfer rate compared to the pure water.

In addition, to investigate the nanofluid behavior

in the single phase application, many experimental

and theoretical works were dedicated to multiphase

regime. The dispersion of small amount of nanopar-

ticles into a fluid has significant effect on the boiling

process.4,5 Some studies reported heat transfer coeffi-

cient enhancement in pool boiling.6–10 Some investi-

gations showed degradation of nucleate boiling heat

transfer coefficient in nanofluids.4,11,12 Li et al.13

observed that the pool boiling heat transfer for

CuO/water nanofluid is deteriorated. They claimed

the reason of deterioration is decrease of the active

nucleation sites by nanoparticle deposition. Liu

et al.14 studied pool boiling of carbon nanotubes in

water. They found enhancement of heat transfer rate.

Kwark et al.15 investigated pool boiling of Al2O3,

CuO, and diamond nanoparticles in water. They

observed boiling heat transfer coefficient is

unchanged. Suriyawong and Wongwises16 studied

pool boiling of TiO2 nanoparticles in water on Cu

and Al plates with two surface roughnesses (0.2 and

4 mm). In their work, boiling heat transfer coefficient

degraded for all nanoparticle concentrations and the

surface roughnesses.

1Mechanical Engineering Department, University of Sistan and

Baluchestan, Zahedan, Iran2Mechanical Engineering Department, Hormozgan University, Bandar

Abbas, Iran3Department of Mechanical Engineering, Shahid Bahonar University,

Kerman, Iran

Corresponding author:

E Abedini, Mechanical Engineering Department, University of Sistan and

Baluchestan, Zahedan, Iran.

Email: [email protected]

Proc IMechE Part C:

J Mechanical Engineering Science

0(0) 1–12

! IMechE 2012

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Situ et al.17 simulated effect of bubble departure

frequency on the subcooled convective boiling. Their

numerical results indicated that the higher departure

frequency causes the lower wall temperature. In add-

ition, they found that the void fraction tends to

decrease by increasing departure frequency. Peng

et al.18 measured convective boiling heat transfer coef-

ficient of CuO nanoparticles in R-113 inside copper

tube. Boiling heat transfer coefficient enhanced up to

30%. In subcooled flow boiling of nanofluids, Kim

et al.19 observed that the heat transfer performance

decreases in nanofluids at low mass flow rate and it

can increase at high mass flow rate, under high heat

flux. A summary of investigations16,18–33 on boiling of

the nanofluids is listed in Table 1.

In this table, some of works show enhancement of

heat transfer,18,25,27,28 some of them show deterior-

ation of heat transfer,16,22,31 and other works show

little change of heat transfer.20,24,29

Witharana21 in 2003 conducted an experiment to

study the effect of pool boiling of nanofluids. In his

experimental work, Au/water nanofluid showed heat

transfer coefficient enhancement, but SiO2/water and

SiO2/EG showed deterioration of heat transfer

coefficient.

Zhou23 in 2004 mentioned all nanofluids contain-

ing metallic nanoparticles enhance heat transfer while

the nanofluids containing non-metallic or metallic

oxide nanoparticles reduce convection heat transfer

compared to the conventional heat transfer fluids.

This result has agreement with the Witharana’s21

work.

Another interesting result was demonstrated by

Prakash et al.26 They showed that the heat transfer

increases with the rough heater surface and it

decreases significantly with the smooth surface.

It seems that in addition to the flow condition,

nanoparticle type, heater surface, and the direction

of the heater in pool boiling, can be important.30

Henderson et al.32 showed that the heat transfer

coefficient decreases with direct dispersion of SiO2

nanoparticles in R-134a in comparison with the pure

R-134a. They found this degradation is due to diffi-

culties in obtaining a stable dispersion. They obtained

excellent dispersion for a mixture of R-134a and

polyolester oil with CuO nanoparticles, and found

that for this mixture, the heat transfer coefficient

increases more than 100% over baseline R-134a/

polyolester results.

Thus, after this literature review, it can be resulted

that many researchers worked on pool boiling of

nanofluid but there are few works on the subcooled

flow boiling and also there is no comparison between

the different directions of the flow channel.

In this study, the heat transfer coefficients of TiO2/

water nanofluid and pure water are measured at the

subcooled flow boiling regime inside the vertical and

horizontal tubes at the atmospheric pressure.

Variations of the heat transfer coefficient are

investigated by increasing nanoparticle concentration

and by changing tube orientation.

Experimental apparatus

The experimental system which is made for this study

to measure the heat transfer coefficient, is shown sche-

matically in Figure 1. The experiments are performed

at atmospheric pressure. Equipments that are used in

this setup are as following: a water storage tank at the

ambient pressure, a centrifugal pump, turbine flow

meter with an uncertainty less than 2%, a preheating

section, a test section, and a condenser. The test sec-

tion is resistively heated using DC power supply with

10V rated output voltage and 500A rated output cur-

rent connected to the tube ends by copper electrodes.

The electric power supplied to the test section is mea-

sured with a calibrated wattmeter with an uncertainty

less than 0.5%. The test section is a circular tube. The

material of the test tube is stainless steel 316 and the

effective length of the test tube is 1m with an inner

diameter of 10mm and the thickness 1.0mm. Five

groups of K-type thermocouples are equally attached

on the outer surface of the tube along the length of the

channel. Each group includes three thermocouples.

The temperatures of thermocouples are recorded by

a data acquisition system. The thermocouples were

carefully calibrated before installation.

Due to electricity flow in the tube wall, a mica sheet

(electricity insulation) with 0.1mm thickness is

inserted between the tube wall and the thermocouple

head. For steady-state condition, it is needed to pro-

vide constant temperature at the inlet of the tube. For

this reason, the bulk temperature sensor at the inlet of

the tube is related to a temperature control system

connected to the preheater section. Also, preheater

is used to remove non-condensable gas by circulating

the fluid for an hour in the beginning of the process.

The working fluid is circulated by a centrifugal

pump and is heated by the heating power in the test

section and preheater section and it is cooled by the

condenser. The test section was thermally isolated

with fiber glass. The system reaches steady-state con-

dition after 40min.

The end effect of the tube can impress the tempera-

ture of the thermocouples. Thus, to decrease this

effect, the end group of the thermocouples is located

1 cm before the outlet of the tube. The bulk tempera-

tures of the inlet and outlet of the test section are

measured by two PT100 sensors that are inserted

into the two calming chambers before and after the

test section with a precision of 0.1 �C. The maximum

uncertainty of the wall temperatures and bulk tem-

peratures are 0.5 �C and 0.8 �C, respectively. Heat

loss is between 2% and 3% of the heat flux.

Heat flux in the test section is calculated as

q00 ¼VI

�DiLð1Þ

2 Proc IMechE Part C: J Mechanical Engineering Science 0(0)


Table

1.Asummaryofinvestigationsonboilingofthenanofluids.

Author

Flow

conditions

Nanofluid

Results

Youet

al.20

Poolboilingoncartridge

Al 2O

3/water

Nucleate

boilingchangeslittle

Witharana2

1Poolboilingoncylindricalvessel

Au,SiO

2/water,EG

Au/water

nanofluid

showed

heattransfer

coeffi-

cientenhancement,butSiO

2/water,SiO

2/EG

showed

itsdeterioration

Das

etal.22

Poolboilingontubularheater

Al 2O

3/water

Inclusionofnanoparticles

degraded

theboiling

perform

ance

byincreasingthewallsuperheat

Zhou23

Poolboilingoncopper

tubewith

acousticcavitation

Cu/acetone

Theresultsindicated

that

thecopper

nanoparti-

cles

andacousticcavitationhas

significant

influence

onheattransport

Vassallo

etal.24

PoolboilingonNiCrwire

SiO

2/water

Littlechange

ofheattransfer

Dinget

al.25

Poolboilingonstainless

steelplate

Al 2O

2/water

andTiO

2/water

Heattransfer

enhancesforboth

nanofluids

Prakashet

al.26

Poolboilingonverticaltubularheater

Al 2O

3/water

Heattransfer

increaseswithrough

heatersurface

anditdecreases

significantlywithsm

ooth

surface

Shiet

al.27

Poolboilingoncopper

block

Al 2O

3,Fe/water

Heattransfer

enhancementupto

60%

Truong2

8Poolboilingonstainless

steelwire

Al 2O

3,SiO

2/water

Heattransfer

enhancementupto

68%

Chopkaret

al.29

Poolboilingoncopper

block

ZrO

2/water

Littlechange

ofheattransfer

Prakashet

al.30

Poolboilingontubularheaters

atvari-

ousorientations

Al 2O

3/water

Horizontalheatershowed

enhancementand

inclined

heatershowed

deteriorationofheat

transfer

Pengetal.18

Flow

boilinginsidecopper

tube

CuO/R-113

Heattransfer

coefficientenhancesupto

30%

TrisaksriandWongw

ises

31

Poolboilingoncopper

surface

TiO

2/R-141b

Heattransfer

deteriorates

Kim

etal.19

Flow

boilinginsideverticalstainless

steel

tube

Al 2O

3,ZnO,anddiamondnanoparti-

cles

inwater

Heattransfer

coefficientdecreases

andit

increasesalittlewithhighheatflux.

Hendersonetal.32

Flow

boilingonhorizontalcopper

tube

SiO

2/R-134aandCuO/

R134aþpolyolester

oil

Heattransfer

coefficientofSiO

2/R-134ananofluid

decreases

incomparisonwithpure

fluid

andit

increases100%

forCuO/R134aþpolyolester

oiloverthebaselineR-134a/polyolester

SuriyawongandWongw

ises

16

PoolboilingonCuandAlplates

TiO

2/water

Heattransfer

deteriorates

Abedini et al. 3


where V and I are the measured voltage and current

and Di and L the inner diameter and the length of the

tube, respectively.

The convective heat transfer coefficient is obtained

by

heff ¼q00

Tw ÿ Tf

ð2Þ

Tf is calculated by considering a linear profile for bulk

temperature by obtaining inlet and outlet bulk tem-

peratures. Vapor volume fraction is low in subcooled

flow boiling. In this study, the low heat flux is applied

to provide a very low volume fraction of vapor.

On the other hand, in this study, the linear rela-

tionship between the temperatures in the inlet and the

outlet of the tube was investigated by a numerical

simulation and the numerical results confirmed that

on specified conditions in the present experiments,

there is nearly a linear relationship between the bulk

temperatures along the channel length. Therefore, it

would be reasonable to assume a linear profile for the

bulk temperature of the tube. The maximum uncer-

tainty in the calculated heat transfer coefficient is

6.5%.

Nanofluid preparation

In this study, TiO2 nanoparticles and water are used

to provide nanofluid. Size and purity of the nanopar-

ticles are 20 nm and 99%, respectively. The TiO2

nanofluid is subjected to 1 h with 100W power of son-

ication in an ultrasonic homogenizer. The nanofluids

are prepared without surfactants. The apparent dens-

ity is considered for making nanofluid with the con-

centration of 0.1%, 0.5%, and 2.5% volume fraction.

The preparation of nanofluid must insure proper dis-

persion of nanoparticles in the liquid. In this study,

nanofluids are found stable and the stability is lasted

over a week for 0.1 vol.% and more than 6 h for

2.5 vol.%.

Validation

Single phase forced convection and subcooled flow

boiling are two flow regimes that are tested to validate

this study. Shah33 correlation and Gnielinski34 correl-

ation are used for validating the Nusselt number in

single phase regime and Chen35 correlation is applied

for predicting the temperature in subcooled flow boil-

ing of the base fluid. Shah33 correlation is

Nulocal ¼

1:953RePrD

Z

� �1=3

ðRePrD=ZÞ33:3

4:364þ0:0722RePrD

ZðRePrD=ZÞ533:3

8

>

>

<

>

>

:

ð3Þ

Gnielinski correlation is used for turbulent flow and it

is as following36

Nulocal ¼f=8 Reÿ 1000ð ÞPr

1þ 12:7ffiffiffiffiffiffiffi

f=8p

Pr2=3 ÿ 1ð Þ1þ

D

Z

� �2=3" #

f ¼1

1:82 logReÿ 1:64ð Þ2

ð4Þ

Chen correlation is as below

hFC ¼kl

Di

� �

0:023GDi

�l

� �0:8�lcp,l

kl

� �0:4

ð5Þ

Figure 1. Schematic representation of the flow system.



hNB ¼ 0:00122k0:79f c0:45p,f �0:49f

�0:5�0:29f h0:24fg �0:24g

" #

Tw ÿ Tsatð Þ0:24

� Pÿ Psatð Þ0:75S ð6Þ

S ¼1

1þ 2:53� 10ÿ6 GDi=�f

ÿ �1:17ð7Þ

As shown in Figure 2, the difference between the

experimental data and the Shah correlation is low.

However, the discrepancy between the results happens

at the last cross section which is believed to be the end

effect.

The experimental data for the turbulent flow

regime are predicted by the Gnielinski correlation.

Uncertainty is about 8% that is the least in compari-

son to other well-known existing correlations

(Figure 3). (Modified Gnielinski model for the

Nusselt number takes into account the heat flux by

means of the factor (Pr/Prw)0.11. Since the wall tem-

perature changes with the heat flux, Prandtl number

at the wall temperature Prw changes as well. However,

due to the small exponent of 0.11, the correction

factor is not very much.)

The experimental data for the subcooled flow boil-

ing regime was predicted by the Chen correlation

(Table 2). This correlation is used to find Tw but it

cannot provide variations of the wall temperature

along the channel length. For this reason, in this

study, the average temperature along the channel

length is compared with the prediction of this

correlation.

Table 2 shows a good agreement between the mea-

sured wall temperatures and the predicted data

obtained by the Chen correlation.

Figure 2. Comparison of the experimental result with Shah correlation in vertical tube.

Figure 3. Comparison of the experimental result with Gnielinski correlation in horizontal tube.

Abedini et al. 5


Results and discussion

Subcooled flow boiling experiments using TiO2 nano-

fluids (0.01%, 0.1%, 0.5%, and 2.5% concentrations)

with different concentrations are conducted in atmos-

phere pressure through a vertical and horizontal tube.

Pure water and nanofluid flow rates are tested at three

different values of the mass flux (G¼ 137, 210, and

303 kg/(m2s)) for evaluating the variation of heat

transfer coefficient.

In the boiling region, in contrast to the single phase

region, there is no boundary layer. Thus, the oper-

ation of the nanoparticles near the surface can be

completely different in subcooled boiling regime com-

pared with the single phase. There is a thin film layer

near the surface that causes to create vapor

bubble.36,37 During the nucleate boiling process,

nanoparticles are deposited on the surface.

Nanoparticles settle out from the nanofluids and

form a porous layer on the surface. Microlayer evap-

oration with subsequent settlement of the nanoparti-

cles initially contained in it could be the reason for the

formation of the porous layer.5

Such sedimentation changes the number of micro-

cavities and the contact angle of the surface. In fact,

nanoparticles impress the nucleate sites, size, and the

departure frequency of the vapor bubbles. Moreover,

it changes thermal properties of the fluid.

Figures 4 to 9 show the result for the pure water

and nanofluid in G¼ 137 kg/(m2s). Use of the nano-

fluid in subcooled flow regime has a negative effect on

the heat transfer coefficient in vertical and horizontal

tubes (Figures 4 and 6). Variations of the wall tem-

perature also are shown for vertical and horizontal

tubes in Figures 5 and 7, respectively. These figures

show that the nucleate boiling begins near the first

measurement cross section of the channel. By increas-

ing heat flux in constant mass flux, nucleate boiling

happens at throughout the channel (Figures 8 and 9).

Moving along the channel, due to the increase of

nanoparticle effect on the nucleate sites and then on

the bubbles, variation of the heat transfer coefficient is

very low at the start section and it is considerable at

the end section of the channel (Figures 4, 6, 8 and 9).

In these figures, it is clear that the nanofluid decreases

the heat transfer coefficient and it degrades more by

Table 2. Comparison of the experimental results with the predictions by Chen correlation.

Tin (�C) Tout (

�C) Heat flux (kW/m2) Mass flux (kg/(m2s)) Twallÿsubcooled (K) Tprediction (K)

55.6 89.5 51.5 137 378 377

56.5 97.6 63 137 381.9 378.7

52.2 78.9 62.5 210 378.3 380

58.4 91.5 76.5 210 381.3 381.6

61.8 88 88 303 381 382.3

63.1 93.3 102 303 384.7 383.3

Figure 4. Effect of increasing concentration of nanoparticles on heat transfer coefficient with subcooled boiling near the first

measurement cross section in vertical tube.



increasing nanoparticle concentration in vertical and

horizontal tubes.

In this study, concentration of 2.5% with apparent

density is equal to 0.29% with true density and con-

centration of 0.5% with apparent density is equal to

0.058% with true density. Thus, as a whole, concen-

tration is low. Therefore, sedimentation cannot be

high and difference between sedimentation in horizon-

tal tube and the vertical tube is low.

On the other hand, more sedimentation can create

more nucleate sites and then create more vapor bub-

bles. It is well known that the vapor buoyancy is more

effective in horizontal tube than that in vertical tube.

In fact, it seems that the more vapor buoyancy

compensate the more sedimentation in horizontal

tube. Moreover, sedimentation is not uniform and

the same for both of the orientations and it can

change during the process.

In higher mass flux (G¼ 210 kg/(m2s), G¼ 303 kg/

(m2s): Figures 10 to 13), Reynolds number of the inlet

flow increases and the laminar flow becomes the tur-

bulent flow.

In higher mass flux (G¼ 210 kg/(m2s), G¼ 303 kg/

(m2s)), there is the same situation (Figures 10 to 13).

Nanoparticles cause the heat transfer coefficient

deteriorates. As seen in previous figures, increasing

the mass flux (the mass flux of G¼ 137 kg/(m2s) com-

pared to the mass flux of G¼ 210 kg/(m2s) and


measurement cross section in horizontal tube.

Figure 5. Effect of increasing concentration of nanoparticles on the wall temperature with subcooled boiling near the first meas-

urement cross section in vertical tube.

Abedini et al. 7


Figure 7. Effect of increasing concentration of nanoparticles on the wall temperature with subcooled boiling near the first meas-

urement cross section in horizontal tube.

Figure 8. Effect of increasing concentration of nanoparticles on heat transfer coefficient with subcooled boiling throughout the

vertical tube.


horizontal tube.




vertical channel.


measurement cross section in horizontal tube.


measurement cross section of the vertical tube.

Abedini et al. 9


G¼ 303 kg/(m2s), the negative effect of the nanofluid

on the heat transfer coefficient decreases that has

agreement with the results of Kim et al.19

Another interesting result is the increase of vapor

volume fraction in nanofluid compared to the pure

water. As observed from Table 3, for G¼ 137 kg/

(m2s), G¼ 210 kg/(m2s), and G¼ 303 kg/(m2s), tem-

perature difference between the outlet and the inlet

of the vertical tube decreases by increasing nanopar-

ticle concentration. There is the same behavior in

horizontal tube. Applied heat flux is partitioned

between the phases of liquid and vapor. Decreasing

the bulk temperature at the end of the channel means

the vapor volume fraction increases. Thus, in spite of

increasing vapor volume fraction, heat transfer coef-

ficient decreases in nanofluid. During nanofluid boil-

ing, the heater surface is coated with a porous layer of

nanoparticles and it significantly increases surface

wettability.5 In fact, the bubble departure size

increases with the increase of surface wettability.

TiO2 deposition causes to decrease of contact angle

and then the bubble grows and spreads over the

wall.38,39 This causes the bubble emission frequency

decreases and then the heat transfer coefficient

deteriorates.

As mentioned before, Situ et al.17 simulated the

effect of bubble departure frequency on subcooled

convective boiling. They found that the lower depart-

ure frequency is caused the higher wall temperature

and the higher void fraction.

Another reason for the heat transfer deterior-

ation could be the change in the thermal properties

near the wall surface. As mentioned before, the nucle-

ate boiling causes the nanoparticles deposit on

the surface. This increases the nanoparticle concentra-

tion near the wall. At last, viscosity increases in

this region and it impresses the heat transfer

performance.

Conclusions

In this study, subcooled flow boiling of the

TiO2/water nanofluid is investigated. Investigation

of the heat transfer coefficient of nanofluid shows it

deteriorates in subcooled flow boiling regime and

decreases more by increasing nanoparticle concentra-

tion in vertical and horizontal tubes. On the other

hand, the negative effect of the nanoparticles on the

heat transfer coefficient decreases in higher mass flux.

In subcooled flow boiling, the bulk temperature

decreases at the end of the channel in nanofluid com-

pared to the pure water that means the vapor volume

fraction increases in the nanofluid.


measurement cross section of the horizontal tube.

Table 3. Temperature difference between outlet and inlet of the vertical tube.

ToutÿTin

q00 ¼ 51 kW/m2,

G¼ 137 kg/(sm2)

q00 ¼ 63 kW/m2,

G¼ 137 kg/(sm2)

q00 ¼ 76.5 kW/m2,

G¼ 210 kg/(sm2)

q00 ¼ 102 kW/m2,

G¼ 303 kg/(sm2)

Pure water 33.4 39.8 33.4 30.1

Nanofluid 0.5% 32.8 39.3 31.6 29.1

Nanofluid 2.5% 29.9 37.1 31.1 29



Funding

This research received no specific grant from any

funding agency in the public, commercial, or not-for-profit

sectors.

References

1. Eastman JA, Choi US, Li S, et al. Enhanced thermal

conductivity through the development of nanofluids.

In: Proceedings of the symposium on nanophase and

nanocomposite materials II, Boston, MA, USA, 2–6

December, 1997, vol. 457, pp.3–11. Materials

Research Society: Warrendale, PA.

2. Li CH and Peterson GP. Experimental investigation of

temperature and volume fraction variations on the

effective thermal conductivity of nanoparticle suspen-

sions (nanofluids). J Appl Phys 2006; 99: 084314–1–8.

3. Xuan Y and Li Q. Investigation on convective heat

transfer and flow features of nanofluids. J Heat

Transfer 2003; 125: 151–155.

4. Bang C and Chang SH. Boiling heat transfer perform-

ance and phenomena of Al2O3–water nano-fluids from

a plain surface in a pool. Int J Heat Mass Transfer 2005;

48: 2407–2419.

5. Kim SJ, Bang IC, Buongiorno J, et al. Surface wettabil-

ity change during pool boiling of nanofluids and its

effect on critical heat flux. Int J Heat Mass Transfer

2007; 50: 4105–4116.

6. Tu JP, Dinh N and Theofanous T. An experimental

study of nanofluid boiling heat transfer. In:

Proceedings of 6th international symposium on heat

transfer, Beijing, China, 15–19 June 2004.

7. Tu JP, Dinh N and Theofanous TG. Burnout in high

heat flux boiling: the hydrodynamic and physic-chemi-

cal factors. In: 42nd AIAA aerospaces sciences meeting

and exhibit, 5–6 January 2004, Reno, NV, USA.

8. Park KJ and Jung D. Enhancement of nucleate boiling

heat transfer using carbon nanotubes. Int J Heat Mass

Transfer 2007; 50: 4499–4502.

9. Wen D and Ding Y. Experimental investigation into the

pool boiling heat transfer of aqueous based -alumina

nanofluids. J Nanopart Res 2005; 7(2): 265–274.

10. Lv LC and Liu ZH. Boiling characteristics in small ver-

tical tubes with closed bottom for nanofluids and nano-

particles-suspensions. Heat Mass Transfer 2008; 45:

1–9.

11. Das SK, Putra N and Roetzel W. Pool boiling charac-

teristics of nanofluids. Int J Heat Mass Transfer 2003;

46: 851–862.

12. Kim SJ. Pool boiling heat transfer characteristics of

nanofluids. MSc Thesis, Massachusetts institute of tech-

nology, USA, 2007.

13. Li CH, Wang BX and Peng XF. Experimental investi-

gations on boiling of nano-particle suspensions. In:

Proceedings of the 5th international conference on boiling

heat transfer conference, Montego Bay, Jamaica, 4–8

May 2003.

14. Liu ZH, Yang XF and Xiong JG. Boiling characteris-

tics of carbon nanotube suspensions under sub-atmo-

spheric pressures. Int J Therm Sci 2010; 49(7):

1156–1164.

15. Kwark SM, Kumar R, Moreno G, et al. Pool boiling

characteristics of low concentration nanofluids. Int J

Heat Mass Transfer 2010; 53: 972–981.

16. Suriyawong A and Wongwises S. Nucleate pool boiling

heat transfer characteristics of TiO2-water nanofluids at

very low concentrations. Exp Therm Fluid Sci 2010;

34(8): 992–999.

17. Situ R, Tu JY, Yeoh GH, et al. Assessment of effect of

bubble departure frequency in forced convection sub-

cooled boiling. In: 16th Australasian fluid mechanics

conference, Crown Plaza, Gold Coast, Australia, 2–7

December 2007.

18. Peng H, Ding G, Jiang W, et al. Heat transfer charac-

teristics of refrigerant-based nanofluid flow boiling

inside a horizontal smooth tube. Int J Refrig 2009;

32(6): 1259–1270.

19. Kim SJ, McKrell T, Buongiorno J, et al. Subcooled

flow boiling heat transfer of dilute alumina, zinc

oxide, and diamond nanofluids at atmospheric pres-

sure. Nucl Eng Des 2010; 240: 1186–1194.

20. You SM, Kim JH and Kim KH. Effect of nanoparticles

on critical heat flux of water in pool boiling heat trans-

fer. Appl Phys Lett 2003; 83: 3374–3376.

21. Witharana S. Boiling of refrigerants on enhanced sur-

faces and boiling of nanofluids. PhD Thesis, The Royal

Institute of Technology, Sweden, 2003.

22. Das SK, Putra N and Roetzel W. Pool boiling charac-

teristics of nano-fluids. Int J Heat Mass Transfer 2003;

46: 851–862.

23. Zhou DW. Heat transfer enhancement of copper nano-

fluid with acoustic cavitation. Int J Heat Mass Transfer

2004; 47(14–16): 3109–3117.

24. Vassallo P, Kumar R and Amico SD. Pool boiling heat

transfer experiments in silica–water nano-fluids. Int J

Heat Mass Transfer 2004; 47: 407–411.

25. Ding Y, Chen H, Wang L, et al. Heat transfer intensi-

fication using nanofluids. KONA 2007; 25(25): 23–38.

26. Prakash NG, Anoop KB and Das SK. Mechanism of

enhancement/deterioration of boiling heat transfer

using stable nanoparticles suspensions over vertical

tubes. J Appl Phys 2007; 102: 074317-1–7.

27. Shi MH, Shuai MQ, Chen ZQ, et al. Study on pool

boiling heat transfer of nano-particle suspensions on

plate surface. J Enhanced Heat Transfer 2007; 14(3):

223–231.

28. Truong BH. Determination of pool boiling critical heat

flux enhancement in nanofluids. Undergraduate Thesis,

MIT, USA, May 2007.

29. Chopkar M, Das AK, Manna I, et al. Pool boiling heat

transfer characteristics of ZrO2–water nanofluids from

a flat surface in a pool. Heat Mass Transfer 2007; 44:

999–1004.

30. Prakash NG, Anoop KB, Sateesh G, et al. Effect of

surface orientation on pool boiling heat transfer of

nanoparticle suspensions. Int J Multiphase Flow 2008;

34: 145–160.

31. Trisaksri V and Wongwises S. Nucleate pool boiling

heat transfer of TiO2-R141b nanofluids. Int J Heat

Mass Transfer 2009; 52(5–6): 1582–1588.

32. Henderson K, Park YG, Liu L, et al. Flow-boiling heat

transfer of R-134a-based nanofluids in a horizontal

tube. Int J Heat Mass Transfer 2010; 53: 944–951.

33. Shah RK. Thermal entry length solutions for the circu-

lar tube and parallel plates. In: Proceedings of the 3rd

national heat and mass transfer conference, Indian

Institute of Technology, Bombay, I (Paper HMT-11-

75), 11–13 December, 1975.

Abedini et al. 11

1


34. Gnielinski V. New equations for heat and mass transfer

in turbulent pipe and channel flow. Int Chem Eng 1976;

16: 359–368.

35. Chen JC. Correlation for boiling heat transfer to satu-

rated fluids in convective flow. Ind Eng Chem Process

Des Dev 1966; 5(3): 322–329.

36. Torikai K, Hori M, Akiyama M, et al. Boiling heat

transfer and burnout mechanism in boiling-water

cooled reactor. In: Third United Nations international

conference on the peaceful uses of atomic energy,

Geneva, Switzerland, 31 August–9 September 1964,

paper no. 28, p.580.

37. Snyder NW and Robin TT. Mass-transfer model in

subcooled nucleate boiling. J Heat Transfer 1969; 91:

404–412.

38. Phan HT, Caney N, Marty P, et al. Surface wettability

control by nanocoating: the effects on pool boiling heat

transfer and nucleation mechanism. Int J Heat Mass

Transfer 2009; 52: 5459–5471.

39. Ahn HS and Kim MH. The effect of micro/nanoscale

structures on CHF enhancement. Nucl Eng Technol

2011; 43: 205–216.

Appendix

Notation

A current (A)

c specific heat (J/kgK)

D diameter (m)

G mass flux (kg/m2s)

h specific enthalpy (J/kg)

k thermal conductivity (W/mK)

L tube heater length (m)

Nu Nusselt number

P pressure (Pa)

Pr Prandtl

q00 heat flux (W/m2)

Re Reynolds number

S nucleate boiling suppression parameter

T temperature (K)

v specific volume (m3/kg)

V voltage (V)

Z distance (m)

� dynamic viscosity (Ns/m2)

� density (kg/m3)

� surface tension (N/m)

Subscripts

a apparent

b bulk liquid

eff effective

f liquid phase at saturation condition

fg liquid-to-vapor transition at saturated

condition

FC forced convection

g vapor phase at saturated condition

i inner

l liquid phase

NB nucleate boiling

o outer

p constant pressure

sat saturation

w wall


Experimental investigation and comparison of subcooled flow boiling of TiO2 nanofluid in a vertical and horizontal tube

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