Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.18 No.4 (December 2017) 15 - 23 

ISSN: 1997-4884 

 
 
 
 
 

Study and Analysis of Concentric Shell and Double Tube Heat 

Exchanger Using Tio2 Nanofluid 
 

Bassma Abbas Abdulmajeed and Noor Sabih Majeed   
College of Engineering- University of Baghdad 

 

Abstract 

   In this paper, nanofluid of TiO2/water of concentrations of 0.002% and 0.004% 

volume was used. This nanofluid was flowing through heat exchanger of shell and 

concentric double tubes with counter current flow to the hot oil. The thermal 

conductivity of nanofluid is enhanced with increasing concentrations of the TiO2, this 

increment was by 19% and 16.5% for 0.004% and 0.002% volume respectively 

relative to the base fluid (water). Also the heat transfer coefficient of the nanofluid is 

increased as Reynold's number and nanofluid concentrations increased too. The heat 

transfer coefficient is increased by 66% and 49% for 0.004% and 0.002% volume 

respectively relative to the base fluid. This study showed that the friction factor of 

nanofluid was decreased as Reynold's number increased. 

 

Key words: nanofluid, TiO2/water, shell and double tube heat exchanger, enhanced 

thermal conductivity, enhanced heat transfer coefficient. 

 

Introduction

   Nowadays, the world is experiencing 

many confronts in with heat transfer 

problems in different engineering 

processes. To increase heat transfer, 

many investigators found that 

nanofluid is one of the suitable coolant 

which increase the efficiency of 

various engineering instruments. The 

nanofluids are the perfect fluids for 

rapid heating and cooling. [1, 2]  

   Choi and Eastman in 1990 are the 

first who started to study nanofluids. 

Later many researchers continued their 

studies comprising different 

nanoparticles such as Al2O3, TiO2 and 

CuO. [3, 4]  

   Pak and Cho, 1998 studied the effect 

of Al2O3/water and TiO2/water 

nanofluids of concentration 3%volume 

flowing into horizontal tube, they 

found that the Nusselt number was 

increased with increasing volume 

concentration of nanofluid and 

Reynold's number was increased too 

[5]. Ding et al, 2007 investigated the 

TiO2/EG nanofluid in forced 

convection.  

   The heat transfer coefficient was 

enhanced relative to base fluid, 

because of the thermal conduction 

enhancing [6]. Duangthongsuk and 

Wongwises, 2009 studied the effect of 

TiO2/water nanofluid in a heat 

exchanger of concentration of 0.2%.   

   The higher temperature affected the 

nanofluid working in heat exchanger.     

    

 

University of Baghdad 
College of Engineering 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 



Study and Analysis of Concentric Shell and Double Tube Heat Exchanger Using Tio2 Nanofluid 

  

  

16                                  IJCPE Vol.18 No.4 (Dec. 2017)                -Available online at: www.iasj.net 
 

   They found that the heat transfer 

coefficient was increased when the 

temperature of the nanofluid was low 

[7]. Yannar et al, 2011 studied 

different types of nanofluids 

(Al2O3/water, TiO2/water and CuO 

/water) of different concentration 1%, 

1% and 3% respectively, of spiral pipe 

heat exchanger. The heat transfer 

coefficient increased by 28% of 0.8% 

concentration [8]. Kavitha et al, 2012 

studied the effect of TiO2/water 

nanofluid used in the transient hot wire 

device. The thermal conductivity of 

nanofluid was increased by using 

spherical shape nanoparticles. The 

thermal conductivity depended on 

some factors such as: size, shape and 

stability of nanofluids [9].  

   Arani and Amani, 2012 studied the 

effect of TiO2/water nanofluid of 

concentration range from 0.002 to 0.02 

by volume and the particle size of 

30nm in a double pipe heat exchanger 

of counter current arrangement.  They 

found that the Nusselt number 

increased as Reynold's number 

increased [10]. Abdul Hamid et al, 

2015  studied the effect of TiO2/water- 

EG (Ethylene glycol) in volume ratio 

60: 40 nanofluid of three 

concentrations of 0.5%, 1% and 1.5% 

on the pressure drop in a horizontal 

tube, they found that the pressure drop 

was increased with the increasing 

volume concentration and decrease 

with increasing the temperature of 

nanofluid [11]. They studied the effect 

of TiO2/water of particle size 50nm of 

three concentrations 0.5%, 1% and 

1.5% on heat transfer coefficient. The 

maximum enhancement was by 

22.75% and 28.92% at temperature of 

50C and 70C at concentration of 

1.5% concentration [12].  

 

 

 

 

   In this study, investigating the TiO2/ 

water nanofluid of two volume 

concentrations of 0.002, 0.004% of 50 

nm particle size in shell and double 

concentric tubes heat exchanger in 

turbulent flow region was 

accomplished. 
 

Experimental Setup 

   The shell and double concentric 

tubes heat exchanger constructed by 

[13] was used in this work. 

   Three streams of fluids were 

designed to work in the shell and 

double concentric tube heat exchanger, 

two flows as hot fluids and one cold 

nanofluids in the opposite direction.     

   The heat exchanger had a (1.3m) 

length and with effective tube length of 

(1.08m).  The shell inner diameter is 

(203mm), and the shell outer diameter 

is (220mm). Baffles of thickness 

(6mm) were spaced by distance of 

(100mm). The inner tubes were made 

of carbon steel, with (20mm) inside 

diameter and (25mm) outside diameter.    

   They were divided as triangular (30) 

tube pattern. The clearance between 

two adjacent tubes is (6.25mm), and 

the tubes pitch is (31.25mm). A second 

group of 16 carbon steel tubes of 

(6mm) inside diameter and (10mm) 

outside diameter, as concentric inner 

tubes, were used to offer two passes 

tube side. 
 

Preparation of Nanofluid 

   Nanofluids were prepared by two 

step method of preparation.  The 

nanopowders are dispersed in the water 

(base fluid) at specific concentrations 

(0.002 and 0.004) % by volume.  The 

nanopowders were weighed by using 

electronic balance in the hood of 

laboratory to avoid the pollution with 

nanoparticles.  

   A 250 litter of nanofluids were 

prepared each time using a speed 

homogenizer (Ultra – Turax Janke 

&Kunkel KG) to keep the 

nanoparticles in motion.  



Bassma Abbas Abdulmajeed and Noor Sabih Majeed  

 

-Available online at: www.iasj.net                      IJCPE Vol.18 No.4 (Dec. 2017)                        17 
 

   This motion stabilizes the suspension 

and prevents the agglomeration and 

sedimentation.  The shear mixing 

device is of 10000 rpm. The mixing 

continued for 2 hours. The shear 

agitation continued for 48 hours. The 

densities of nanofluid and oil were 

measured by pcknometer of 10 ml, 

while the viscosities were measured by 

viscometer ASTM D445 Viscometer 

Bath.  

   The thermal conductivities for 

nanofluid and oil was measured by 

KD2 Pro thermal property analyzer 

(decagon Device, Pullman, WA, 

USA). The temperature at which the 

thermal conductivity of nanofluid was 

measured was 25C, while for oil 

ranged as (85, 75, 65, 55 C). 
 

Procedure 

   The cold feed or nanofluid tank is of 

capacity of 300 litter and was 

supported by a mixer on the top to 

prevent coagulations and 

sedimentation of nanoparticles. The 

mixer has three paddles of width 

(20cm) and (3mm) thickness, with a 

speed of (100 rpm). 

   A centrifugal pump (Type, SP24T) 

was used to pump the nanofluids. The 

nanofluid enters the heat exchanger at 

the annulus side between the shell and 

inner tubes, and exits from the 

exchanger to the collector tank.  

   The nanofluid returns back to the 

main tank, where it was left for a 

certain period of time for cooling it to 

the desired temperature and it's was 

measured using a portable 

thermocouple (type k). The hot feed 

(oil) was entered in a tank with square 

front face provided by two heaters to 

reheat the oil at the desired 

temperature with a thermostat 

connected to the controlling board to 

control the temperature.  

   The oil has been pumped by 

centrifugal pump with provided by 

gate valve on the pipes before enter to 

the flow meter. The feed is divided 

into two parts supported by pressure 

gauge at the inlet and outlet of the 

exchanger.  

   A second tank was used to collect the 

oil, which gets out from the heat 

exchanger. The two oil streams were 

provided with two thermocouples type 

(K) to record the temperature for both 

shell and inner tubes of heat 

exchanger.  

   On the cold feed side, the nanofluid 

is pumped and the oil centrifugal pump 

is started at the same time at the 

desired flow rates of both fluids. When 

the flow of both fluids were in a steady 

state, the cold side nanofluid flow was 

at rate of (45) l/min and a temperature 

of 20 C, while the hot oil was pumped 

at varied flow rates (30, 40, 50) l/min, 

and at in temperatures between 85 C 

to 55 C.     

   The pressures are recorded at the 

inlet and outlet of the heat exchanger 

for both pipe and shell sides, annulus 

tube and inner tubes. The procedure is 

repeated for flow rate of cold nanofluid 

in the annulus side as (15, 25, 35) 

l/min with fixed temperature of 20 C.   

   This step was repeated after 

changing the setting of thermostat by 

10 C step for temperature of hot oil 

from 55 to 85C. Fig.(1) shows the 

whole equipment's process. 

 

 

Fig. 1, Rig of Experimental Process 



Study and Analysis of Concentric Shell and Double Tube Heat Exchanger Using Tio2 Nanofluid 

  

  

18                                  IJCPE Vol.18 No.4 (Dec. 2017)                -Available online at: www.iasj.net 
 

   The mass flow rate in the annulus of 

the concentric tube is a function of the 

density of the fluid, the velocity of the 

fluid, flow cross sectional area and the 

number of tubes, as in [13]. 
 

P

tC

N

NAu
m 2

22

2




                  … (1) 

 
where the inner flow cross sectional 

area of the annulus passages is: 

 

 2
1

2

22
4

dDA
C




                    … (2) 

 
and (Np) is the number of tubes per 

pass in the heat exchanger, u2 the 

velocity of fluid in annulus, Reynolds 

number is calculated as follows: 

 

2

22
2

Re



h

du


                         … (3) 

 
The hydraulic diameter of the annulus 

is: 

 

12
dDd

h


                              … (4) 

 

to calculate the Prandtl Number: 

 

2

22
2

Pr
k

Cp


                            … (5) 

 
By using Colburn equation, the Nusselt 

number, [14]: 

 

33.08.0
PrRe023.0

k

hd
h

            … (6) 

The pressure loss inside tubes of 

circular cross section or annulus 

passage in a shell and double 

concentric tube heat exchangers is the 

sum of the friction loss within the 

tubes and the turn losses between the 

passes of the exchanger. 
 

2
44

2

22
22

u
N

d

LN
fP

p

h

p 












        … (7) 

 
 

and the friction factor in annulus 

passages: 

 
25.0

2
Re316.0


f

 
                        … (8) 

For 2300 <Re <105 
 

   Overall heat transfer coefficient U12 

between (the fluid in the shell side and 

fluid in the annulus passage), [15]. 
 

22

12

11

2

12
1

ln
2

1

hD

D

k

D

hD

D
U

w





   … (9) 

 
   The second overall heat transfer 

coefficient U23 between (the fluid in 

the annulus passage and the fluid in the 

inner tube side), [15]. 
 

32

12

21

2

23
1

ln
2

1

hd

d

k

d

hd

d
U

w





… (10) 

 

Results and Discussion 

Thermal Conductivity of Nanofluid 

   The thermal conductivity of 

nanofluid increased due to the thermal 

properties of nanoparticles which has 

higher thermal conductivity than water 

[16]. For 0.002% volume of TiO2, the 

thermal conductivity was increased by 

16.5% from the base fluid at 

temperature of 25C and that is due to 

the stable nanofluids preparation as in 

[17].  

    

 

 



Bassma Abbas Abdulmajeed and Noor Sabih Majeed  

 

-Available online at: www.iasj.net                      IJCPE Vol.18 No.4 (Dec. 2017)                        19 
 

    By doubling the concentration of the 

titanium oxide, the thermal 

conductivity was increased by 

increasing the concentration of 

nanoparticles by 19% from the base 

fluid (water). This is in agreement with 

[18]. Table (1) shows the values of 

thermal conductivities of base fluid 

and nanofluid with titanium oxide 

nanoparticles. 
 

Table 1, thermal conductivity of 

TiO2/water 

Fluids 
TiO2 

Concentration% 

Thermal 

conductivity 

K (W/m.k) 

Base fluid 

(water) 
0 0.612 

TiO2/water 
0.002 0.713 

0.004 0.724 

 

The Effect of Nanofluid on Heat 

Transfer Coefficient 

   The heat transfer coefficient of 

nanofluid increased as Reynold's 

number increased, and this is due to 

enhancing of thermal conductivity of 

TiO2 nanofluid.  

   Also the Brownian motion of the 

nanoparticles in the base fluid 

promoted which led to the good 

distribution of these particles in the 

base fluid.  

   Figs. (2) and (3) showed that the heat 

transfer coefficient of two 

concentrations 0.002 % and 0.004% 

volume of TiO2 increased as Reynold's 

number of nanofluids increased. 
 

 

Fig. 2, Heat Transfer Coefficient of 

Nanofluid of TiO2 of concentration 

0.002 % against Reynold's number at 

different nanofluid flow rates of (15, 

25, 35, 45) l/min with different 

temperatures of oil. 
 

   The maximum value of heat transfer 

coefficient was at temperature of 85 C 

for oil. This is because of the large 

difference between the inlet 

temperatures of the two streams 

entering the heat exchanger. This 

agreed with Ehsan, 2016 [19]. The heat 

transfer coefficient of nanofluid 

increased as volume concentration of 

TiO2 was increased.  This agreed with 

Reza A., 2014 [20] of diffident flow 

rates of nanofluids (15, 25, 35, 45) 

l/min and different temperatures and 

flow rates of oil. 
 

 

Fig. 3, Heat Transfer Coefficient of 

Nanofluid of TiO2 of concentration 

0.004 % against Reynold's number at 

different nanofluid flow rates of (15, 

25, 35, 45) l/min with different 

temperatures of oil 
 



Study and Analysis of Concentric Shell and Double Tube Heat Exchanger Using Tio2 Nanofluid 

  

  

20                                  IJCPE Vol.18 No.4 (Dec. 2017)                -Available online at: www.iasj.net 
 

   Fig. (4) showed a comparison 

between three types of fluids, 0.002 % 

TiO2, 0.004% TiO2 and base fluid 

water. The figure shows that TiO2 

nanofluid of concentration 0.004% 

volume has high values of heat transfer 

coefficient with respect other fluids. 

This enhancement represented by 66% 

and 49% increase for 0.002 % TiO2 

and 0.004% TiO2 respectively than the 

base fluid. 

 

 

Fig.4, Heat Transfer Coefficient of 

different fluids Reynold's number at 

different nanofluid flow rates of (15, 

25, 35, 45) l/min with temperatures of 

85C of oil 

 

The Effect of Nanofluid on Friction 

Factor 

   The friction factor decreased as 

Reynold's number increased as shown 

in Figs. (5) and (6). This is due to the 

increasing in the flow velocity of 

nanofluids [21]. The friction factor was 

increased with increasing in 

concentration of nanoparticles. This is 

due to viscosity of nanofluids which 

increased with increasing of the 

nanofluids concentration that causes 

slow motion nanofluids namly 

increasing friction factor [22]. Figs. (5) 

and (6) shows that the friction factor 

was increased when the temperature of 

oil was decreased, at maximum flow 

rate of TiO2 nanofluid of 45 l/min. 
 
 

 

 
 

 

Fig. 5, Friction factor against the 

Reynold's Number at 0.002% volume 

of TiO2 nanofluid of flow rate 45 

(l/min) and different oil temperatures 

at constant  flow rate of 50 (l/min) 

 

 

Fig.6, friction factor against the 

Reynold's Number at 0.004% volume 

of TiO2 nanofluid of flow rate 45 

(l/min) and different oil temperatures 

at constant  flow rate of 50 (l/min) 
 

   In Fig. (7) the comparison between 

fluids showed that the base fluid water 

has higher friction factor followed by 

0.002% of TiO2 nanofluid and that was 

because of the lower Reynold's number 

of fluid compared to 0.004% TiO2 

nanofluid. 
 

 

 

 
 

 

 
 

 

 
 

 
 



Bassma Abbas Abdulmajeed and Noor Sabih Majeed  

 

-Available online at: www.iasj.net                      IJCPE Vol.18 No.4 (Dec. 2017)                        21 
 

 

Fig. 7, friction factor against flow rate 

of nanofluids at constant oil flow rate 

50 (l/min) and temperature of 85C of 

different fluids and concentration. 

 

Conclusion 

1- The thermal conductivity of 
nanofluids increased with increasing 

in volume concentrations of TiO2 

nanoparticles at temperature of 

20C. The enhancement in thermal 

conductivities of 0.004% and 

0.002% volume concentration for 

TiO2/water nanofluids by 19% and 

16.5% respectively over base fluid. 

2- The heat transfer coefficient was 
increased as Reynold's number and 

volume concentration increased too. 

This enhancement of heat transfer 

coefficient for 0.004% and 0.002% 

of TiO2/water nanofluids by 66% 

and 49% respectively from the base 

fluid. 

3- Friction factor of nanofluids 
decreased as Reynold

'
s number was 

increased. The friction factor of 

nanofluids are lower than the base 

fluid because the flow of the base 

fluid is in the laminar flow region, 

so that the high volume of friction 

factor was appeared. 
 

 

 
 

 

 
 

 
 

 

 
 

Nomenclature 
 

Symbol 

 

Description 

 

Units 

Ac 

Cross 

sectional area 

of the tube in 

conventional 

heat 

exchanger 

m
2 

Cp Specific heat J/kg.K 

D 

Diameter of 

the tube (first 

bundle) in 

new heat 

exchanger 

m 

d 

Diameter of 

the inner tube 

(second 

bundle) in 

new heat 

exchanger 

m 

dh 

Hydraulic 

diameter of 

the annulus in 

the new heat 

exchanger 

m 

f 
Friction 

factor 
- 

h 
Heat transfer 

coefficient 
W/ m

2
.K 

k 
Thermal 

conductivity 
W/m.˚C 

L 

length of the 

heat 

exchanger 

m 

m 
Mass flow 

rate  
Kg/min 

Nu 
Nusselt 

number k

hd
Nu   

Np 
number of 

tubes per pass 
- 

Nt 
 total number 

of the tubes 
- 

Pr 
Prandtle 

number 
k

Cp
Pr  

Re 
Reynolds 

number 

ud
Re   

T Temperature ˚C
 

U 

Overall heat 

transfer 

coefficient  

W/m
2
˚C 

u Fluid velocity m/s 

 



Study and Analysis of Concentric Shell and Double Tube Heat Exchanger Using Tio2 Nanofluid 

  

  

22                                  IJCPE Vol.18 No.4 (Dec. 2017)                -Available online at: www.iasj.net 
 

Greek Symbols 

 

Units 

 

Description 

 

Symbol 

ΔT Temperature 

difference 

˚C 

ρ Density kg/m
3 

μ Dynamic 

viscosity 

kg/m.s 

ΔP Pressure drop Pa 
 

Subscript 

Symbols Description 

1 Oil (shell side) 

2 TiO2/water (annulus 

side) 

3 Oil (inner tube side) 

12 shell and annulus 

23 annulus and inner tube 

 Base fluid 

n Nanofluid 

t Tube side 

p Nanoparticle  
 

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-Available online at: www.iasj.net                      IJCPE Vol.18 No.4 (Dec. 2017)                        23 
 

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