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- 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
164
THERMAL PERFORMANCE AND FLOW ANALYSIS OF NANOFLUIDS IN
A SHELL AND TUBE HEAT EXCHANGER
S. Bhanuteja1
, D.Azad2
1
(P.G Student, Department of Mechanical Engineering, AITAM, Tekkali)
2
(Associate professor, Department of Mechanical Engineering, AITAM, Tekkali)
ABSTRACT
This paper reports the thermal performance of a Counter-flow Shell and Tube Heat exchanger
using nano fluids as the working fluids. Finite volume Method was used to solve the three-
dimensional steady, turbulent developing flow and conjugate heat transfer in a Shell and tube heat
exchanger. The nano fluids used were Ag, Al2O3, CuO, SiO2, and TiO2 and the performance was
compared with water. The thermal performance and flow of the Shell and tube heat exchanger was
analyzed using different nanofluids. Temperature profile, heat transfer coefficient, pressure profile,
was obtained from the simulations. The results are evaluated in terms of effectiveness, heat transfer
rate, and Overall heat transfer coefficient.
Keywords: Heat exchanger, Heat transfer enhancement, Nanoparticle, Nanofluids, pressure drop.
I. INTRODUCTION
The two factors that limit the heat transfer coefficient are reductions in channel dimensions
were accompanied by higher pressure drop; and the amount of heat transfer was limited by the heat
transfer fluids used. Traditional transfer fluids used in heat exchangers are mainly water, ethylene-
glycol and oil. The heat transfer performance of the traditional fluids is low; this causes heat transfer
enhancement efficiency to be lower. In order to enhance the thermal conductivity of the traditional
fluid and heat transfer characteristics, the solid particles are suspended into the base fluid used in the
heat exchangers. Adding particles into the base fluid enhances the thermal conductivity, because the
thermal conductivity of the solid metal particles is higher than the base fluid. H.A. Mohammeda et
al. [1] tested the new heat transfer fluids engineered by dispersing nano particles having smaller
diameter than 100 nm into the base fluid are called as nano fluid. Using nano fluids in heat exchange
systems enhances thermal conductivity. Heat transfer coefficient increases by the increase of the
thermal conductivity. Farajollahi et al. [2] performed an experimental analysis to study heat transfer
of nanofluids in a shell and tube heat exchanger. The nanofluids used were Al2O3/water and
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 4, Issue 5, September - October (2013), pp. 164-172
© IAEME: www.iaeme.com/ijmet.asp
Journal Impact Factor (2013): 5.7731 (Calculated by GISI)
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IJMET
© I A E M E
- 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
165
TiO2/water under turbulent flow conditions to investigate the effects of Peclet number, volume
concentration of suspended particles, and particle type on the heat transfer characteristics. The results
indicate that addition of nanoparticles to the base fluid enhances the heat transfer performance and
results in larger heat transfer coefficient than that of the base fluid at the same Peclet number. Mapa
and Mazhar [3]. tested the effect of nanofluids in mini heat exchanger. Their experiments tested the
heat transfer performance in the heat exchanger using water/water as working fluids, and using water
and nanofluid with concentration of 0.01% and 0.02% volume. They concluded that nanofluids
enhance the heat transfer rate, and stated that the presence of nanoparticles reduced the thermal
boundary layer thickness. Several other researchers have reported similar trend in the increase of
heat transfer in conventional fluids by the addition of nanoparticles. For example, Masuda et al. [4]
and Xuan and Li [5] stated that with low nanoparticle concentrations (1–5% volume), the thermal
conductivity of the suspensions can increase by more than 20%. Since Choi et al. [6] reported that
the addition of a small amount (less than 1% volume) of nanoparticles to traditional heat transfer
liquid approximately doubled the thermal conductivity of the fluid, the frenzy into nanofluids
research for heat transfer applications is started.
II. OBJECTIVES OF THE PRESENT WORK
The present work begins with the thermal performance analysis of a shell and tube heat
exchanger. For this we have chosen an existing 2 ton capacity of counter flow shell and tube heat
exchanger and is modeled. By the flow field analysis, the performance of shell and tube heat
exchanger is done with nano fluids and was compared with water. In this R22 is used as a primary
refrigerant (hot fluid) and water based nanofluids used were Ag, Al2O3, CuO, SiO2, and TiO2 (cold
fluids). Analysis through computer predictions costs less than laboratory or field experiments and
provides higher level of confidence.
In the light of above discussion, the present work has been taken up aiming at achieving the
following objectives.
• To perform thermal analysis on a shell and tube heat exchanger using ANSYS 12, after modeling
the heat exchanger.
• To observe the effect on temperature rise and pressure drop along the length of tube and shell.
• To study the heat transfer enhancement capabilities of coolant.
1. Geometric modeling
The geometric modeling of shell and tube heat exchanger was made. The heat exchanger
specifications are listed in Table1. The 3D meshed geometry of circular type shell and tube heat
exchanger is shown in fig1.
Fig 1: Meshing of Geometry
- 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
166
Table 1. Specifications of a Heat exchanger
1 Shell outer diameter 100mm
2 Shell thickness 10mm
3 Length of the shell 150mm
4 Shell material Stainless steel
5 Tube outer diameter 20mm
6 Tube thickness 1mm
7 Tube material Copper
8 Type of tube layout Circular layout
9 Type of tube arrangement Inline arrangement
10 No of tubes inside the shell 6
2. Properties of the working fluid
The model which has been developed is taken for further analysis. Here R22 is used as a
refrigerant (Hot fluid) and the nano fluids (cold fluids) used were Ag, Al2O3, CuO, SiO2, and TiO2.
Required Properties are shown in Table 2.
The thermo physical properties of required nanofluids at different volumetric concentrations are
calculated using the following equations.
Density: ߩ ൌ ሺ1 െ Øሻߩ ߩ
Heat capacity: ሺߩܿሻ ൌ ሺ1 െ ሻ൫ߩܿ൯
ሺ൫ߩܿ൯
Thermal conductivity: ݇ ൌ
ାଶ್ାଶሺି್ሻØ
ାଶ್ିሺି್ሻØ
Viscosity: ߤ ൌ ߤሺ1 2.5ሻ
Where Ø is particle volume fraction, the subscript “nf” refers to nanofluid, “bf” refers to base fluid,
and “p” refers to particle.
Table 2. Thermo physical properties of Nano fluids at volume fraction of 2%
3. Data collection and analysis
The shell side fluid temperature is taken as 54.40C and for tube is 23.30C. Inlet mass flow
rate is 0.1584 kg/ sec. For the same inlet conditions the performance of the Shell and tube heat
exchanger was analyzed using different nanofluids and was compared with water.
Nano fluids Density
(kg/m3)
Heat
capacity
( J/kg K)
Viscosity
(N s/m3)
Thermal
conductivity
( W/m K)
H2O 998.2 4182 0.001003 0.613
Ag–H2O 1188.236 3484.436 0.00105315 0.650366928
Al2O3–H2O 1057.636 3925.475 0.00105315 0.648823843
CuO– H2O 1108.236 3754.264 0.00105315 0.647218493
SiO2– H2O 1022.236 4032.254 0.00105315 0.621942641
TiO2– H2O 1063.236 3902.529 0.00105315 0.643637682
- 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
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4. Calculations
• The general relation for heat transfer is as follows:
Q = m Cp (To−Ti) --------------- (1)
• The heat removed from the hot fluid, Qh, and the heat absorbed by the cooling liquid, Qc, are
calculated by the following equations.
ܳ ൌ ܳܿ ൌ ݉ܿܿܥሺ∆ܶܿሻ ---------------- (2)
ܳ ൌ ݄ܳ ൌ ݄݄݉ܥሺ∆݄ܶሻ ---------------- (3)
• The total heat transfer coefficient is defined as:
ܷ ൌ
ொ
.ெ்
----------------- (4)
ܦܶܯܮ ൌ
்ି்ି்ି்
ூ
ష
ష
----------------- (5)
• Effectiveness (ε)
Under ideal condition, using the value of actual heat transfer rate (q) from the energy
conservation equation, the effectiveness valid for all flow arrangement of the two fluids is given
by
εଵ ൌ
்,ି்,
்,ି்,
----------------- (6)
εଶ ൌ
்,ି்,
்,ି்,
----------------- (7)
II. RESULTS AND DISCUSSION
The analysis has been carried out with R22 is used as a primary refrigerant (hot fluid) and
water based nanofluids used were Ag, Al2O3, CuO, SiO2, and TiO2 as cold fluids. During each
analysis for the same inlet conditions the temperatures of both hot and cold streams were recorded.
From that data the heat transfer rates, overall heat transfer coefficient, effectiveness and pressure
drop can be calculated.
1. Thermal field analysis of the Shell and Tube Heat exchanger
This section discusses the effects on the temperature profile of the Shell and Tube Heat
exchanger, heat transfer coefficient, and heat transfer rate for various nanofluids. The effect of
various nanofluids on the dimensionless temperature profile of the Shell and Tube Heat exchanger is
shown in below fig. The nanoparticle concentration used in this case is 2%. It can be observed that
the overall bulk temperature of the nanofluids (cold fluid) is higher than of water. This is an
indication of higher amount of heat received by the nanofluids compared to water, thus raising the
overall bulk temperature of the fluids. The temperature contour obtained from analysis is shown
below in fig2. From analysis the outlet temperatures of various nano fluids are recorded, and are
listed in Table 3. The temperature rise along tube length for tested fluids is plotted in fig 3. Fig3.
indicates that among the nanofluids tested, Ag obtained the highest overall bulk temperature,
followed by CuO, TiO2, Al2O3, SiO2, and finally water.
- 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
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Fig2. Temperature contour of a circular tube heat exchanger
Table 3. Outlet Temperatures of various nano fluids along tube length of a shell and tube heat
exchanger
Fig3. Temperatures of nanofluids along tube length
The heat transfer rate along tube length is calculated using equation (1), for various nano fluids, and
is listed in Table 4.
Fig 4. Heat rate comparison among nanofluids
tube
length
in mm
Water Ag-H2O
Al2O3-
H2O
CuO-
H2O
SiO2-
H2O
TiO2-
H2o
temp in
k
temp in
k
temp in
k
temp in
k
temp in
k
temp in
k
0 296.4 296.4 296.4 296.4 296.4 296.4
50 301 302.7 301.3 301.7 301.3 301.3
100 303 304.7 303.8 304.3 303.7 303.7
150 304.6 306.3 305 305.6 306.5 305
- 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
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Table 4. Heat rate(J/sec) of various nano fluids along tube length of a shell and tube heat exchanger
Finally by increasing the thermal conductivity of cold fluid heat transfer rate is increased. Fig
4. Shows water has high heat transfer rate because of its high specific heat as 5431.92 J/sec. Among
the nanofluids tested heat transfer rate increases to 6450.96 J/sec by SiO2 followed by, CuO, water,
Al2O3, TiO2, and Ag.
The Overall heat transfer coefficient along length of the shell is calculated using equation (4).
Calculated values are shown in Table 5.
Fig 5. Overall heat transfer coefficient of nanofluids
Table 5. Overall heat transfer coefficient (W/mm2K) of various nano fluids along length of the shell
The overall heat transfer coefficient is influenced by the thickness and thermal conductivity
of the mediums through which heat is transferred. The larger the coefficient, the easier heat is
transferred. Fig 5. Depicts that SiO2 nanofluid has the highest value followed by, CuO, Al2O3,
TiO2, Ag, and finally water.
2. Flow field analysis of a shell and tube heat exchanger
This section analyses the effects of various nano fluids on the pressure drop profile. Changes
in pressure drop along tube length are shown in Table 6.
tube
length
in mm Water Ag-H2O
Al2O3-
H2O
CuO-
H2O
SiO2-
H2O
TiO2-
H2o
0 0 0 0 0 0 0
50 3047.17 2925.25 3046.8 3746.45 3129.67 3028.98
100 4372.03 4360.28 4601.28 4935.81 4662.57 4512.57
150 5431.91 5077.79 5347.43 5887.29 6450.96 5316.18
tube length
(mm) Water
Ag-
H2O
Al2O3-
H2O
CuO-
H2O
SiO2-
H2O
TiO2-
H2O
0 0 0 0 0 0 0
50 0.00233 0.00232 0.00236 0.00306 0.00242 0.00235
100 0.00354 0.00382 0.00389 0.00435 0.00392 0.00381
150 0.00464 0.00469 0.00473 0.00553 0.00602 0.00471
- 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
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Fig 6. Pressure drop profile of Heat exchanger using different nanofluids
Table 6. Pressure values of nano fluids along tube length
Pressure drop( Pa) comparison
Length (mm) 0 50 100 150
H2O 101370.172 101356.625 101334.047 101325.016
Al2O3 101369.578 101356.211 101338.383 101325.016
Ag 101364.68 101352.781 101338.3 101325.008
CuO 101367.539 101354.781 101337.773 101325.016
SiO2 101369.539 101356.823 101337.734 101325.007
TiO2 101369.359 101356.055 101338.313 101325.008
Fig 6. Indicates that among the nanofluids tested, SiO2 nanofluid has the highest pressure
drop, followed by Al2O3, TiO2, water, CuO and finally Ag.
The performance of the Shell and tube heat exchanger is presented in terms of effectiveness.
Effectiveness of cold fluid is calculated using equation (7), and the values are listed in Table 7.
Fig 7. Effectiveness of various nano fluids
- 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME
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Table 7. Effectiveness of cold fluid along tube length
Fig 7. Results that Ag nanofluid has the highest effectiveness value followed by CuO, SiO2,
TiO2, Al2O3, and finally water.
III. CONCLUSIONS
The analysis was completed by increasing the thermal conductivity of cold fluid. Here an
approach has been taken to make comparative study of heat transfer between the R22 refrigerant and
various nanofluids. Based on the results obtained from the analysis the following conclusions have
been drawn out.
a) Among the nanofluids tested, Ag obtained the highest overall bulk temperature, followed by
CuO, TiO2, Al2O3, SiO2, and finally water.
b) By increasing the thermal conductivity of cold fluid heat transfer rate is increased. Water has
high heat transfer rate because of its high specific heat as 5431.92 J/sec. Among the nanofluids
tested heat transfer rate increases to 6450.96 J/sec by SiO2 followed by, CuO, water, Al2O3, TiO2,
Ag.
c) The overall heat transfer coefficient is influenced by the thickness and thermal conductivity of
the mediums through which heat is transferred. The larger the coefficient, the easier heat is
transferred. SiO2 nanofluid has the highest value followed by, CuO, Al2O3, TiO2, Ag, and finally
water.
d) Among the fluids tested, SiO2 nanofluid has the highest pressure drop, followed by Al2O3, TiO2,
water, CuO and finally Ag. Water did not obtain the lowest pressure drop in this case due to
higher average velocity it had compared with CuO and Ag along the channel length.
e) Results indicated that Ag nanofluid has the highest value followed by, CuO, SiO2, TiO2, Al2O3,
and finally water.
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