Thermophysical properties and heat transfer performance of Al2O3/R-134a nanorefrigerants.
International Journal of Heat and Mass Transfer 57 (2013) 100–108
Contents lists available at SciVerse ScienceDirect
International Journal of Heat and Mass Transfer
journal homepage: www.elsevier.com/locate/ijhmt
Thermophysical properties and heat transfer performance of Al2O3/R-134a
nanorefrigerants
I.M. Mahbubul a,⇑, S.A. Fadhilah a,b, R. Saidur a,c, K.Y. Leong d, M.A. Amalina a
a
Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
Department of Thermal-Fluids, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia
c
UM Power Energy Dedicated Advanced Centre (UMPEDAC), Level 4, Wisma R&D, University of Malaya, 59990 Kuala Lumpur, Malaysia
d
Department of Mechanical Engineering, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Malaysia
b
a r t i c l e
i n f o
Article history:
Received 26 January 2012
Received in revised form 18 September 2012
Accepted 2 October 2012
Available online 31 October 2012
Keywords:
Thermal conductivity
Viscosity
Pressure drop
Pumping power
Heat transfer coefficient
a b s t r a c t
The past decade has seen the rapid development of nanofluids science in many aspects. In recent years,
refrigerant-based nanofluids have been introduced as nanorefrigerants due to their significant effects over
heat transfer performance. This study investigates the thermophysical properties, pressure drop and heat
transfer performance of Al2O3 nanoparticles suspended in 1, 1, 1, 2-tetrafluoroethane (R-134a). Suitable
models from existing studies have been used to determine the thermal conductivity and viscosity of
the nanorefrigerants for the nanoparticle concentrations of 1 to 5 vol.%. The pressure drop, pumping power
and heat transfer coefficients of nanorefrigerant in a horizontal smooth tube have also been investigated
with the same particle concentration at constant velocity of 5 m/s and uniform mass flux of 100 kg/m2 s. In
this study, the thermal conductivity of Al2O3/R-134a nanorefrigerant increased with the augmentation of
particle concentration and temperature however, decreased with particle size intensification. In addition,
the results of viscosity, pressure drop, and heat transfer coefficients of the nanorefrigerant show a significant increment with the increase of volume fractions. Therefore, optimal particle volume fraction is
important to be considered in producing nanorefrigerants that can enhance the performance of refrigeration systems.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Nanofluids attracted many attentions of researchers around the
world as a significant alternative to increase the heat transfer performance. Nanofluids, firstly, demonstrated by Choi [1] at Argonne
National Laboratory that were defined as suspensions of nanoparticles into base fluids with the typical length scale of particles is
1–100 nm. Recently (since 2005), nanorefrigerants have introduced as one kind of nanofluids that can enhance the performance
of a refrigeration system [2]. By using nanoparticles in refrigeration
system, three main advantages can be obtained [3]; (1) nanoparticle as an additive can increase the solubility between the lubricant
and the refrigerant. (2) Thermal conductivity and heat transfer
characteristics of the refrigerant can be increased. (3) Nanoparticles dispersion into lubricant may decrease the friction coefficient
and wear rate. However, there are contradictory results as well
available in literature. Henderson et al. [4] showed that direct
dispersion of SiO2 with R-134a decreases the boiling heat transfer
coefficient with the augmentation of nanoparticle concentrations.
Moreover, they found that the heat transfer coefficient of
⇑ Corresponding author. Tel.: +60 3 7967 7611; fax: +60 3 7967 5317.
E-mail address: mahbub_ipe@yahoo.com (I.M. Mahbubul).
0017-9310/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.10.007
R-134a/POE/CuO increased accordingly with the nanoparticle
volume concentrations.
Thermophysical properties are the fundamental properties that
need to be investigated to gain the maximum output from nanorefrigerants. The thermal conductivity of a nanorefrigerant is proportional to the heat transfer coefficient. The heat transfer coefficient
of higher thermal conductivity nanorefrigerant is larger than the
fluids with lower thermal conductivity at same Nusselt number
[5]. The nanorefrigerant thermal conductivity can be enhanced
by increasing the volume fraction of nanoparticles suspended into
refrigerant or by using nanoparticles with high thermal conductivities [6–8]. Thermal conductivity can be varied due to the effects of
particle volume fraction, nanoparticle types, refrigerants, particle
sizes, and particle shapes. The interfacial layers developed in nanofluids has been proven as the contributor to the enhancement of
thermal conductivity [9–11]. Besides the interfacial layer, nanoparticle aggregation in nanofluids forms’s nanoparticles clustering
around that enhances the thermal conductivity [6]. Brownian motion due to nanoparticles suspension also has an indirect role in
producing particle clustering [12]. Jiang et al. [6] investigated the
thermal conductivity of nanorefrigerant experimentally by suspending different types of nanoparticles into R-113 refrigerant,
and a model was developed by using resistance network method.
Contents lists available at SciVerse ScienceDirect
International Journal of Heat and Mass Transfer
journal homepage: www.elsevier.com/locate/ijhmt
Thermophysical properties and heat transfer performance of Al2O3/R-134a
nanorefrigerants
I.M. Mahbubul a,⇑, S.A. Fadhilah a,b, R. Saidur a,c, K.Y. Leong d, M.A. Amalina a
a
Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
Department of Thermal-Fluids, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia
c
UM Power Energy Dedicated Advanced Centre (UMPEDAC), Level 4, Wisma R&D, University of Malaya, 59990 Kuala Lumpur, Malaysia
d
Department of Mechanical Engineering, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Malaysia
b
a r t i c l e
i n f o
Article history:
Received 26 January 2012
Received in revised form 18 September 2012
Accepted 2 October 2012
Available online 31 October 2012
Keywords:
Thermal conductivity
Viscosity
Pressure drop
Pumping power
Heat transfer coefficient
a b s t r a c t
The past decade has seen the rapid development of nanofluids science in many aspects. In recent years,
refrigerant-based nanofluids have been introduced as nanorefrigerants due to their significant effects over
heat transfer performance. This study investigates the thermophysical properties, pressure drop and heat
transfer performance of Al2O3 nanoparticles suspended in 1, 1, 1, 2-tetrafluoroethane (R-134a). Suitable
models from existing studies have been used to determine the thermal conductivity and viscosity of
the nanorefrigerants for the nanoparticle concentrations of 1 to 5 vol.%. The pressure drop, pumping power
and heat transfer coefficients of nanorefrigerant in a horizontal smooth tube have also been investigated
with the same particle concentration at constant velocity of 5 m/s and uniform mass flux of 100 kg/m2 s. In
this study, the thermal conductivity of Al2O3/R-134a nanorefrigerant increased with the augmentation of
particle concentration and temperature however, decreased with particle size intensification. In addition,
the results of viscosity, pressure drop, and heat transfer coefficients of the nanorefrigerant show a significant increment with the increase of volume fractions. Therefore, optimal particle volume fraction is
important to be considered in producing nanorefrigerants that can enhance the performance of refrigeration systems.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Nanofluids attracted many attentions of researchers around the
world as a significant alternative to increase the heat transfer performance. Nanofluids, firstly, demonstrated by Choi [1] at Argonne
National Laboratory that were defined as suspensions of nanoparticles into base fluids with the typical length scale of particles is
1–100 nm. Recently (since 2005), nanorefrigerants have introduced as one kind of nanofluids that can enhance the performance
of a refrigeration system [2]. By using nanoparticles in refrigeration
system, three main advantages can be obtained [3]; (1) nanoparticle as an additive can increase the solubility between the lubricant
and the refrigerant. (2) Thermal conductivity and heat transfer
characteristics of the refrigerant can be increased. (3) Nanoparticles dispersion into lubricant may decrease the friction coefficient
and wear rate. However, there are contradictory results as well
available in literature. Henderson et al. [4] showed that direct
dispersion of SiO2 with R-134a decreases the boiling heat transfer
coefficient with the augmentation of nanoparticle concentrations.
Moreover, they found that the heat transfer coefficient of
⇑ Corresponding author. Tel.: +60 3 7967 7611; fax: +60 3 7967 5317.
E-mail address: mahbub_ipe@yahoo.com (I.M. Mahbubul).
0017-9310/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.10.007
R-134a/POE/CuO increased accordingly with the nanoparticle
volume concentrations.
Thermophysical properties are the fundamental properties that
need to be investigated to gain the maximum output from nanorefrigerants. The thermal conductivity of a nanorefrigerant is proportional to the heat transfer coefficient. The heat transfer coefficient
of higher thermal conductivity nanorefrigerant is larger than the
fluids with lower thermal conductivity at same Nusselt number
[5]. The nanorefrigerant thermal conductivity can be enhanced
by increasing the volume fraction of nanoparticles suspended into
refrigerant or by using nanoparticles with high thermal conductivities [6–8]. Thermal conductivity can be varied due to the effects of
particle volume fraction, nanoparticle types, refrigerants, particle
sizes, and particle shapes. The interfacial layers developed in nanofluids has been proven as the contributor to the enhancement of
thermal conductivity [9–11]. Besides the interfacial layer, nanoparticle aggregation in nanofluids forms’s nanoparticles clustering
around that enhances the thermal conductivity [6]. Brownian motion due to nanoparticles suspension also has an indirect role in
producing particle clustering [12]. Jiang et al. [6] investigated the
thermal conductivity of nanorefrigerant experimentally by suspending different types of nanoparticles into R-113 refrigerant,
and a model was developed by using resistance network method.