Nanofluids behavior in thermal systems.

1. Prepared By: Sartaj Singh
Department of Mechanical Engineering
Designation: M.E. Scholar
TOPIC:
Effects of nanofluids in the enhancement of
thermo physical properties: A Review

2. CONTENTS
 Introduction to nanofluids
 Effect of thermal conductivity
 Effect of various thermo physical properties
 Literature survey
 Conclusions
 References

3. Introduction of Nano-fluid
 Since the last decade nanofluids have been widely used in heat transfer applications.
 Nanofluids are the mixture of nanoparticles in a base fluid was first experimented in
1993 by Choi et. al. [1]
 Considering heat transfer it highly depends upon the thermal conductivity of the
nanofluids. The thermal conductivity of nanoparticles depends upon many factors
such as particle shape, particle size, Fraction volume, viscosity, etc.
 Maxwell [2] who first presented a theoretical model for calculating the thermal
conductivity of the suspension particles called nanoparticles.
 Further his procedure was followed by experimental studies such as in Hamilton –
Crosser [3] and Wasp [4].

4.  These models work very well in predicting the thermal conductivity. But these
suspensions had some drawbacks [5].
(1) The particles prepared using above models settle very rapidly forming a layer
on the surface thus reducing the heat transfer capacity of the fluid
(2) If the fluid circulation rate is increased, sedimentation is reduced, but the
erosion of heat transfer devices increased rapidly.
(3) Due to the large particle size, clogging occurs in the flow channels if the
channels are narrow
(4) The pressure drop in the fluid increases
 Stability is also an important property in nanoparticles.

5. Effect of particle size and volume fraction on the thermal conductivity of
nanofluids
 Nanofluids offers the processing of nanoparticles of various sizes in the range of 5-
100 nm.
 An enhanced thermal conductivity is measured in Al7OCu30/EG nanofluids by
varying the size of Al7OCu30 nanoparticles in the range from 9 nm to 83 nm. [6]
 In water and Ethylene Glycol based nanofluids consisting of Al2Cu and Ag2Al
nanoparticles, by taking low particle size the thermal conductivity increased.
 So it has been found that the effective thermal conductivity of a nanofluid increases
with decreasing nanoparticle size
 Various experiments conducted by experimenters showed the same result

6. Fig. 1 Graph between particle Diameter and particles fraction
As the particle size reduces the thermal conductivity of the nanofluid gets increased
[7].

7. A study investigated by Lee et al [8] shows the ratio of thermal conductivity
of nanofluid to that of volume fraction of nanoparticles.

8. Effect of thermo- physical properties
 Temperature of nanofluids is also responsible for effective thermal conductivity
 Al2O3 and CuO nanoparticles were investigated [9,10]. In this study the oxide nanofluids in
the temperature range between 21 to 50◦C are experimented. The results showed an almost
threefold increase in conductivity enhancement (i.e., 10% became 30%).
 Results shown in Figures 3 and 4, respectively.
Figure 3 Figure 4

9.  At room temperature, metals in solid form have larger thermal conductivities than
fluids.
 For example, the thermal conductivity of copper at room temperature is 700 times
greater than that of water and 3000 times greater than that of engine oil [11]
 The thermal conductivity of metallic liquids is much greater than that of nonmetallic
liquids. Therefore, the thermal conductivities of fluids that contain suspended solid
metallic particles is expected to be enhanced when compared with conventional
fluids

10. Material Thermal Conductivity
(W/m-K)
Metallic solids
Silver
Copper
Aluminum
429
401
237
Nonmetallic solids
Silicon 148
Metallic liquids
Sodium at 644 K 72.3
Nonmetallic liquids
Water
Engine Oil
0.613
0.145
Table 2. Thermal Conductivity (W/m-K) of various materials at 300K
Some of the examples are shown in the following figure.

11.  Haddad et al [12] studied the effect of Brownian motion using Cuo/water
nanofluids for volume fractions of 8%. Their result showed that there was greater
heat transfer when Brownian motion effects are considered. If not considering
these effects deterioration in heat transfer was observed. And as discussed above
there is adverse effect on heat transfer if nanoparticle concentration is increased. It
is also shown that there is no effect on the isotherms and stream lines shapes with
the presence of Brownian motion. Isotherm and stream lines of their result are
shown in fig 5.
Figure 5.

12.  In another study by Michael P. Beck and Yanhui Yuan [13] they investigated the
effect of particle size by using alumina nanofluids with two type of base fluid
(water and ethylene glycol). They prepare seven nanofluids of diameter 8-282 nm.
Their result showed that the thermal conductivity decreases as the particle size
decrease below 50 nm.

13. Literature Review
Title of Paper Author Work done Conclusion
1. Heat Transfer in
Nanofluids [14]
S.K. Das,
S.U.S. Choi
H.E Patel
Investigated the effect of
heat transfer in nanofluid
by investigating thermal
conductivity of the
nanofluid
Enhanced Thermal
conductivity of various
nanofluid but the thermal
conductivity varies when
particle size is decreased or
increased
2. Thermal
conductivity of
nanofluids [15]
A.K. Singh Measuring of thermal
conductivity with
Transient hot wire
method
In case of Cu-water
nanofluid the thermal
conductivity enhancement
is 17 per cent for 4 per cent
nanoparticle volume
fraction.
CuO ethylene glycol
nanofluid is 4 per cent

14. Title of Paper Author Work done Conclusion
3. Effect of
particle size on
the heat transfer
in nanofluids [16]
K.B. Anoop, T.
Sundararajan,
Sarit K. Das
The primary objective was to
evaluate the effect of particle
size on convective heat
transfer with alumina–water
nanofluids.
Two particle sizes were used,
one with average particle size
off 45 nm and the other with
150 nm.
It was observed that both
nanofluids showed higher heat
transfer characteristics than the
base fluid and the nanofluid
with 45 nm particles showed
higher heat transfer coefficient
than that with 150 nm particles
4. Enhancing
thermal
conductivity of
fluids with
nanoparticles [17]
S. U. S. Choi &
J. A. Eastman
In this paper an innovative
new class of heat transfer
fluids engineered by
suspending metallic
nanoparticles in conventional
heat transfer fluids.
The resulting "nanofluids"
exhibit high thermal
conductivities compared
to those of currently used heat
transfer fluids, and they
represented the best hope for
enhancement of heat transfer.

15. Title of Paper Author Work done Conclusion
5. Dispersion
behavior and
thermal
conductivity
characteristics
of Al2O3–H2O
nanofluids [18]
D. Zhu, X. Li,
Nan Wang, X.
Wang, J.Gao,
Hua Li a
In their study, Al2O3–H2O
nanofluids were synthesized,
their dispersion behaviors and
thermal conductivity in water
were investigated
under different pH values
The effect of pH on the stability
of the alumina suspension was
critical. At pH 8.0, a good
dispersion of alumina particles
was obtained
6. Effect of
Brownian
motion in heat
transfer
enhancement [19]
Zoubida
Haddad, Eiyad
Abu-Nada,
Hakan F.
Oztop, Amina
Mataoui
In their study they studied
natural convection heat
transfer and flow of fluid of
CuO + Water nanofluids.
An enhancement in heat transfer
is observed at any volume
fraction of nanoparticles if
considering the role of Brownian
motion
However, the enhancement is
more pronounced at low volume
fraction of nanoparticles

16. CONCLUSION
 The present review gives a comprehensive overview of the various researches
carried out in the field of nanofluids. This review summarizes thermo-physical
properties of nanofluids are which greatly and immensely help to enhance the heat
transfer rate in cooling and heat transfer applications. All the properties like thermal
conductivity, particle size, particle shape, Brownian motion etc are being carried
out in this paper which plays a major role in enhanced heat transfer. As the particle
size decreases enhancement in heat transfer increases which result in better heat
transfer due to less clogging and sedimentation. As the temperature increases
thermal conductivity of the nanofluid also increases. Many researches are still
going on in this field for better futuristic scope of nanofluids in industries for heat
transfer applications and will define the future of nanofluids with better results.

17. Refrences
[1] S. Choi. Enhancing thermal conductivity of fluid with nanoparticle in: D.A. Siginer, H.P. Wang (Eds.) Developments and
application of Non-Newtonian flows. Vol. 231/MD 66, ASMEFED, 1995, pp. 99-105
[2] Maxwell J.C A treatise on electrical and magnetism, 2nd ed. Vol. 1, Clarendon Press, Oxford, UK, 1881
[3] Hamilton, R. L., and Crosser, O. K., Thermal Conductivity of Heterogeneous Two Component Systems, Industrial and
Engineering Chemistry Fundamentals, vol. 1, no. 3, pp. 187–191, 1962.
[4] Wasp, E. J., Kenny, J. P., and Gandhi, R. L., Solid-Liquid Flow Slurry Pipeline Transportation, Series on Bulk Materials
Handling, Trans. Tech. Publications, 1:4, Clausthal, Germany, 1977
[5] Sarit Kumar Das, Stephen U. S. Choi, Hrishikesh E. Patel Heat Transfer in Nanofluids— A Review Heat Transfer
Engineering, 27(10):3–19, 2006
[6] M. Chopkar, P.K. Das, I. Manna, Synthesis and characterization of nanofluid for advanced heat transfer applications, Scr.
Mater. 55 (2006) 549-552
[7] K.B. Anoop, T. Sundararajan, Sarit K. Das Effect of particle size on the convective heat transfer in nanofluid in the developing
region. International Journal of Heat and Mass Transfer 52 (2009) 2189–2195
[8] Lee, S., Choi, S. U. S., Li, S., and Eastman, J. A., Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles,
Transactions of ASME, Journal of Heat Transfer, vol. 121, pp. 280–289, 1999.
[9] Das, S. K., Putra, N., Thiesen, P., and Roetzel, W., Temperature Dependence of Thermal Conductivity Enhancement for
Nanofluids, Transactions of ASME, Journal of Heat Transfer, vol. 125, pp. 567–574, 2003.
[10] Lee, S., Choi, S. U. S., Li, S., and Eastman, J. A., Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles,
Transactions of ASME, Journal of Heat Transfer, vol. 121, pp. 280–289, 1999
[11] Stephen U. S. Choi1 And J. A. Eastman2 Enhancing Thermal Conductivity Of Fluids With Nanoparticles* ANL/MSD/CP-
84938 CONf-951135- AF29 Revised Jan 11, 1995
[12] Zoubida Haddad et al., ‘’Natural convection in nanofluids: Are the thermophoresis and Brownian motion effects significant
in nanofluid heat transfer enhancement?’’, International Journal of Thermal Sciences 57 (2012) 152e162
[13] Michael P. Beck and Yanhui Yuan, “The effect of particle size on the thermal conductivity of alumina nanofluids’’, J Nanopart
Res (2009) 11:1129–1136 DOI 10.1007/s11051-008-9500-2

18. [14] S.K. Das et al (2006) Heat Transfer in Nanofluids— A Review
[15] A. K. Singh, Thermal conductivity of nanofluid Vol. 58, No. 5, September 2008, pp. 600-607
[16] K.B. Anoop, T. Sundararajan, Sarit K. Das, Effect of particle size on the convective heat transfer in nanofluid in the
developing region (2009) 2189–2195
[17] Stephen U. S. Choi 1and Jeffrey A. Eastman 2, ENHANCING THERMAL CONDUCTIVITY OF FLUIDS WITH
NANOPARTICLES ANL/MSD/CP-84938 CONF-95135-29 JAN 1995
[18] D. Zhu, X. Li, Nan Wang, X. Wang, J.Gao, Hua Li a, Dispersion behavior and thermal conductivity characteristics of Al2O3–
H2O nanofluids, Current Applied Physics 9 (2009) 131–139
[19] Zoubida Haddad a,b, Eiyad Abu-Nada c, Hakan F. Oztop a,*, Amina Mataoui, Are the thermophoresis and Brownian motion
effects significant in nanofluid heat transfer enhancement? International Journal of Thermal Sciences 57 (2012) 152e162

19. THANK YOU