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International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 12, December 2018, pp. 580–591, Article ID: IJCIET_09_12_064

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=12

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

USING THE NANOFLUID TO IMPROVE THE

HEAT TRANSFER IN THE DOUBLE PIPE HEAT

EXCHANGER

Israa Abdullah Hussien

Asst.Prof.Dr.MaatheAbdulwahed, Asst.Prof.Khalid M. Owaid,

Al–Mustansiriyah University, College of Engineering,Materials Engineering Dept.

ABSTRACT

Heat transfer is the science that seeks to predict the energy transfer that may take

place between material bodies as a result of a temperature difference. In the present

work Experimental investigation of heat transfer enhancement in double pipe heat

exchanger with and without addition of nanofluid have been carried out. Experimental

work included to design of double pipe heat exchanger with calculated dimensions

.Four type of working fluids are used (distilled water and distilled water with different

volume concentration (0.3,1.2and 2.1). Zinc Oxide ZnO nanoparticle powder with 20

nm diameter is dispersed in distilled water with different volume concentrations 0.3,

1.2 and 2.1 % by volume is used as nanofluid. The nanofluids were prepared by using

ultrasonic cleaner with 10 hours of continuous sonication at 1200 W (sonication

power). The sedimentation in nanofluids was observed after about six hours. The

working fluid of 2.1%ZnO was chosen as an optimum according to the results that

obtained from experimental work. The experimental results indicate that heat transfer

coefficient is increased by increasing particles volume concentration as well as

Reynolds, heat flow and Nusslet Number

Keywords: Heat transfer coefficient, nanofluid, Nusselt number.

Cite this Article: Israa Abdullah Hussien, Using the Nanofluid to Improve the Heat

Transfer in the Double Pipe Heat Exchanger, International Journal of Civil Engineering

and Technology, 9(12), 2018, pp. 580–591

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=12

1. INTRODUCTION

Enhancement of Heat transfer achived by employing various techniques mythologies such as

increasing either heat transfer surface or increasing heat transfer coefficient between the fluid

and surface that allow high heat transfer rate in small volume. In general, the enhancement

techniques can be divided into two types: active and passive techniques as follow:



The active techniques require external forces, e.g. electric field, acoustic, and surface

vibration.

The passive techniques require special surface geometries such as roughness surface,

treated surface and extended surface or fluid additives. Both techniques have been used for

improving heat transfer in heat exchangers. Due to their compact structure and high heat

transfer coefficient, double pipe has been introduced as one of the passive heat transfer

enhancement techniques and are widely used in various industrial applications. Recently

another technique to enhance heat transfer rate by adding nano-sized particles of highly

thermally conductive materials have been used such as, metal, metal oxides into base fluid to

improve thermal conductivity of fluid. The dispersion or suspension this particle in the base

fluid is called nanofluid.

2. LITERATURE REVIEW

Murshed and others (2005)studied experimentally the increasing of thermal conductivity buy

using nanofluids which are prepared by dispersing TiO2 nanoparticles in rod-shapes

of ∅10nm×40nm (diameter by length) and in spherical shapes of ∅15 nm in deionized water.

The experimental results show that the thermal conductivity increases with an increase of

particle volume fraction. For TiO2 particles of ∅10nm×40nm and ∅15 nm dimensions with

maximum 5% volume fraction, the enhancement is observed to be nearly 33%.

Suresha and others (2009) studied the experimental investigations and theoretical

determination of effective thermal conductivity and viscosity of Al2O3/H2Onanofluid are

reported in this paper. Al2O3/water nanofluid with a nominal diameter of 43nm at different vol-ume

concentrations (0.33–5%) at room temperature were used for the investigation. Both the

thermal conductivity and viscosity of nanofluids increase with the nanoparticle volume

concentration.

Rajan and others (2012) studied thermal conductivity enhancements CuO–water

nanofluids which were prepared from non-spherical CuO nanoparticles by dispersing them in

water through the aid of ultra sonication along with the use of Tiron as dispersant. Thermal

conductivity enhancements of 13% and 44% have been obtained with 0.016vol% CuO–water

nanofluids at 28°C and 55°C respectively.

Reza Aghayari and others (2016) showed that the heat transfer of a fluid containing

nanoparticles of aluminum oxide with the water volume fraction (0.1–0.3) percent has been

reported. Heat transfer of the fluid containing nano water aluminum oxide with a diameter of

about 20 nm in a horizontal double pipe counter flow heat exchanger under turbulent flow

conditions was studied. The results showed that the heat transfer of nanofluid in comparison

with the heat transfer of fluid is slightly higher than 12 percent.

Seyfollah Saedodin(2017) studied experimentally the thermal conductivity of

CuO/EGâ “water nanofluid in different temperatures and solid volume fractions . The

nanofluid has been prapared in different solid concentrations ranging from 0.1% to 2% and

temperatures within 20 to 50 °C. Based on the experimental data, new correlations for

predicting the thermal conductivity of CuO/EGâ “water at different temperatures have been

proposed. The results indicate that with the increase of the solid concentration, the thermal

conductivity of the nanofluid increases. Also, the thermal conductivity of the nanofluid

increases while the temperature increases.

Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger


Figure. 1: Comparison of thermal conductivity of different conventional heat transfer fluids and

solids

3. PREPARATION OF NANOFLUID

The first key step in applying nanophase particles to change the heat transfer performance of

conventional fluids is preparation of nanofluid. In order to get stable, durable suspension, with

low agglomeration of particles, the nanoparticles and the distilled water are mixed directly

using electric mixer (1950 RPM) for 20 minutes. Nanofluid samples are prepared for different

concentrations by dispersing pre – weighed quantities of dry (Zinc Oxide (ZnO) (30 nm))

nanoparticle in (3 litters) the volume of distilled water used in the test rig. The process results

in uniform dispersions for the duration of the experiments. The properties (density,thermal

conductivity and specific heat) for the nanoparticle usedare listed in table 1.

3.1. Properties of Nanofluids

The thermo physical properties of the prepared ZnO/water nanofluid are determined at the

fluids’ bulk mean temperature, Tb by using the correlations widely used in the literature. The

density of the nanofluid is determined using Pak and Cho’s equation (Pak and Cho1998).

Ρ�� 1 φ�ρ � � φρ� (1)

Where � is volume fraction of nano particle. Indices of p, bf and nf refers to nanoparticles,

base fluid, and nanofluid, respectively. The specific heat of the nanofluid is calculated using

Xuan and Roetzel’s equation (Xuan and Roetzel 2000).

Cp � �1 φ�Cp � � φCp� (2)

Hamilton and Crosser (Hamilton and Crosser1962) developed one of the basic models for

the prediction of thermal conductivity of nanofluids as follows:

Knf= (��

�� (3)

Where n is the empirical shape factor. Thermal conductivity of nanofluids also can be

calculated by using Wasp (1977) model that is defined as the following:



Knf= (��

�� (4)

Finally, (Timofeeva et al, 2007) introduce the effective medium theory to compute thermal

conductivity of Nano fluid, which defined as below:

1+3 �]�� (5)

The viscosity model used in this work is developed by Brinkman (1952)

( )waternf µ

ϕµ

−=

5.21

1

(6)

Bachelor (1977) developed a regression equation (7) for viscosity of nanofluids with

spherical shape nanoparticles as follows:

!�" = #1 + 2.5� + 6.2��]!� (7)

Einstein has developed a viscosity correlation (Drew and passman- 1999) in terms of

nanoparticle volume concentration in the base fluid, when the nanoparticle volume

concentration is lower than 5%, and is given by

!�" = #1 + 2.5� +]!� (8)

Wong and Xu (1999) proposed a model to predict the dynamic viscosity of nanofluid that

expressed as following:

!�" = #1 + 3.7� + 123��]!� (9)

Heat transfer coefficient is calculated from:

U� = �+,+-

∗ /0-

�+, 1234, 4-5 6

789: � /0,

(10)

Where:

Ao=;<=> , Ai=;<B>

Heat transfer rateThe (W) is calculated from

Qh =mD Cp (T� − TF) (11)

Where Q is the rate of heat transfer (W), G D is the nanofluid mass flowrate (kg/s) and Cp is

the specific heat capacity of the nanofluid (J/Kg.K). The heat transfer rate can also be

determined from the Newton’s Law of Cooling:

QC=GD Cp (HI −Ti) (12)

Table 1: Physical properties of ZnO nanoparticle and water

Specific

Heat

(J/kg K)

Thermal

conductivity

(W/mK)

Density

(Kg/m3)

Mean

Diameter

(nm)

Nanoparticle

/fluid S. No

860 50 6500 30 ZnO 1

4178 0.628 998 - Water 2



3. EXPERIMENTAL PROCEDURE

The setup used in this experiment as shown in Fig.2. This experimental setup consists of two

tanks (tank ’A‘and 'B‘) with a capacity of 500 ltrs were used to store the water.1200 W

immiscible heater is fitted in the tank ‘A‘to heat the water. Two centrifugalpumps were used

to circulate the water into the test section. One pump is used tocirculate the cold water in the

outer tube and the other pump is used to circulate thehot water in the inner tube. The outer pipe

of the test section is made of PVC, 50.8 mm outside diameter and 42.9 mm inner diameter. The

inner tube is made from smooth copper tubing with 12.7 mm outer diameter and 10.2 mm inner

diameter and the heat exchange length of 82 cm. To reduce the heat loss from the system the

test section is perfectly insulated by using rock wool. The K- type thermocouples are used to

measure the temperature at the inlet and outlet side tubes.

Figure.2: schematic diagram of the experimental test rig.

4. RESULT AND DISCUSSION

Figures (3, 4,5and6) show the effect of ZnO nanoparticles concentration on the convective heat

transfer coefficient comparing with different working fluids at the same working conditions

.These figures clearly show that the convective heat transfer coefficient of the ZnO/water

nanofluid is higher than other fluids. The highest heat transfer coefficient is obtained by using

2.1 Vol% of ZnO/water nanofluid.



Figure. 3: Comparison of heat transfer coefficient of different working fluids at inlet temperature

=35oc

Figure. 4: Comparison of heat transfer coefficient of different working fluids at inlet temperature

=45oc

Figure 5: Comparison of heat transfer coefficient of different working fluids at inlet temperature

=55oc



Figure 6: Comparison of heat transfer coefficient of different working fluids at inlet temperature

=65oc

Figures (7,8,9and10) show the effect of ZnO nanoparticles concentration on the Nusselt

number of comparing with different working fluids at the same working conditions .These

figures clearly show that the Nusselt number of the ZnO/water nanofluid is higher than other

fluids .The highest Nusselt number is obtained by using 2.1 Vol% of ZnO/water nanofluid.

Figure 7: Comparison of Nusslet number of different working fluids at inlet temperature =35oc




Figure. 9: Comparison of Nusslet number of different working fluids at inlet temperature =55oc


Figures (11, 12,13and14) show the effect of ZnO nanoparticles concentration on the heat

transfer rate comparing with different working fluids at the same working conditions. These

figures clearly show that the heat transfer raste of the ZnO/water nanofluid is higher than other

fluids .The highest heat transfer rate is obtained by using 2.1 Vol% of ZnO/water nanofluid.

Figure 11: Comparison of Heat transfer rate of different working fluids at inlet temperature =35oc






5. CONCLUSION

The following conclusions were derived from thiswork:

• Addition of small amount of ZnO nanoparticles into distilled water as the bas fluid

would increase the rate of heat transfer, Nusslet number and convection heattransfer

coefficient by at least 20.6%, 17.4 %and 22.8 % respectively.



• Volume concentration has a sufficient effect on heat transfer .As the volume loading

increases, the thermal conductivity increases, which consequently increases the heat

transfer.

• The heat transfer rate and the convection heat transfer coefficient is significantly

affected by the change in nanoparticle volume concentration by an average of

29.3% and 64.1% for each increase in volume loading, respectively.

• Comparing the three volume concentrations, it can be observed that 2.1% volume

loading produces greater increase in rate of heat transfer, Nusslet number and

convection heat transfer coefficient.

Table (1) enhancement in Nusselt number

Vol % JD kg/s Enhancement %

0 0.02162 0

0.3 0.02162 7.3

1.2 0.02162 9.7

2.1 0.02162 11.2

0 0.02495 0

0.3 0.02495 8.7

1.2 0.02495 12.3

2.1 0.02495 14.1

0 0.02820 0

0.3 0.02820 10.2

1.2 0.02820 14.6

2.1 0.02820 17.4

Table (2) enhancement in heat transfer coefficient


0 0.02162 0

0.3 0.02162 5.4

1.2 0.02162 9.8

2.1 0.02162 12.5

0 0.02495 0

0.3 0.02495 9.8

1.2 0.02495 15.4

2.1 0.02495 19.5

0 0.02820 0

0.3 0.02820 12

1.2 0.02820 18.1

2.1 0.02820 22.8



Table (3) enhancement in heat transfer rate


0 0.02162 0

0.3 0.02162 5.8

1.2 0.02162 11.6

2.1 0.02162 13.9

0 0.02495 0

0.3 0.02495 6.3

1.2 0.02495 15.2

2.1 0.02495 17.7

0 0.02820 0

0.3 0.02820 7.8

1.2 0.02820 16.5

2.1 0.02820 20.6

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