Synthesis and Characterization of Nanofluids …
21
They found a 69.62% enhancement in heat transfer coefficient for 0.5 vol.% PANI
nanofluid.
Applications of nanofluid as car radiator coolant have also been found by many
researchers. Naraki et al. (2013) experimentally examined the heat transfer coefficient of CuO/water nanofluids in a car radiator coolant under laminar flow conditions.
It has been reported that there is 8% increase in the heat transfer coefficient of the
CuO nanofluids compared to water. However, it has been further pointed out that
even though there is an increase in the thermal performance of the car radiator with
application of the nanofluid, the factors like sedimentation and stability should also
be considered before their application. Studies on thermo-physical properties comprising thermal conductivity, density, viscosity and specific heat of Al 2 O 3 -based
nanofluids as car radiator coolants have been conducted by Elias et al. (2014). Similarly, Al 2 O 3 -based nanofluids using ethylene glycol as a basefluid have been studied
for car radiator application by Goudarzi and Jamali (2017). For this purpose, the
authors used a radiator with wire coil inserts and reported that the thermal performance of the radiator can be enhanced up to 14% by the use of Al 2 O 3 /ethylene glycol
nanofluids. Ali et al. (2015) investigated the application of ZnO nanofluids as car
radiator coolants and found an enhancement in heat transfer of 46% for a nanofluid
of concentration 0.2 vol.%.
Nanofluids for cooling applications in electronic systems have also been studied widely. Selvakumar and Suresh (2012) studied the application of CuO/water
nanofluid in a thin-channelled copper heat sink. A highest value of convective heat
transfer coefficient of 29.63% was reported for the water block by using 0.2 vol.%
CuO nanofluid compared to deionized water. Similar study has been presented by
Sohel et al. (2014) using Al 2 O 3 /water nanofluids in an electronic heat sink that helped
them achieve 18% improvement in the heat transfer coefficient compared to distilled
water. They compared their study with the one previously made by Selvakumar and
Suresh (2012) and found that the Al 2 O 3 /water nanofluid reduces the heat sink base
temperature more than that reduced using the CuO/water nanofluid, even though the
heat input is thrice the heat input for study using CuO/water nanofluid. Khaleduzzaman et al. (2015) studied the compatibility of Al 2 O 3 /water nanofluid to be used
in a heat sink by investigating its stability. They studied Al 2 O 3 /water nanofluids in
the volume concentration range of 0.1–0.25 vol.% and found that they are satisfactorily stable and that there is no sedimentation and clogging occurring using these
nanofluids. Khatak et al. (2015) studied the effect of ZnO nanofluid in spray cooling
of electronic devices. They observed that a 0.05 vol.% ZnO nanofluid was successful
in decreasing the specimen surface temperature by 15% at a heat input and nanofluid
flowrate of 180 W and 20 ml/min, respectively.
Nanofluids have also found applications in effective extraction of the solar energy.
Efficiency of a solar collector has been studied by applying Al 2 O 3 /water nanofluid
as an absorbing medium by Yousefi et al. (2012). For the study, they used a flat plate
solar collector and passed the nanofluid to study the effect of nanofluid flowrate,
concentration of nanoparticles in the nanofluid and use of surfactant. 28.3% increase
in the thermal efficiency of the solar collector has been reported when 0.2 wt%
Al 2 O 3 /water nanofluid was passed through the collector. Gupta et al. (2015) also
21
They found a 69.62% enhancement in heat transfer coefficient for 0.5 vol.% PANI
nanofluid.
Applications of nanofluid as car radiator coolant have also been found by many
researchers. Naraki et al. (2013) experimentally examined the heat transfer coefficient of CuO/water nanofluids in a car radiator coolant under laminar flow conditions.
It has been reported that there is 8% increase in the heat transfer coefficient of the
CuO nanofluids compared to water. However, it has been further pointed out that
even though there is an increase in the thermal performance of the car radiator with
application of the nanofluid, the factors like sedimentation and stability should also
be considered before their application. Studies on thermo-physical properties comprising thermal conductivity, density, viscosity and specific heat of Al 2 O 3 -based
nanofluids as car radiator coolants have been conducted by Elias et al. (2014). Similarly, Al 2 O 3 -based nanofluids using ethylene glycol as a basefluid have been studied
for car radiator application by Goudarzi and Jamali (2017). For this purpose, the
authors used a radiator with wire coil inserts and reported that the thermal performance of the radiator can be enhanced up to 14% by the use of Al 2 O 3 /ethylene glycol
nanofluids. Ali et al. (2015) investigated the application of ZnO nanofluids as car
radiator coolants and found an enhancement in heat transfer of 46% for a nanofluid
of concentration 0.2 vol.%.
Nanofluids for cooling applications in electronic systems have also been studied widely. Selvakumar and Suresh (2012) studied the application of CuO/water
nanofluid in a thin-channelled copper heat sink. A highest value of convective heat
transfer coefficient of 29.63% was reported for the water block by using 0.2 vol.%
CuO nanofluid compared to deionized water. Similar study has been presented by
Sohel et al. (2014) using Al 2 O 3 /water nanofluids in an electronic heat sink that helped
them achieve 18% improvement in the heat transfer coefficient compared to distilled
water. They compared their study with the one previously made by Selvakumar and
Suresh (2012) and found that the Al 2 O 3 /water nanofluid reduces the heat sink base
temperature more than that reduced using the CuO/water nanofluid, even though the
heat input is thrice the heat input for study using CuO/water nanofluid. Khaleduzzaman et al. (2015) studied the compatibility of Al 2 O 3 /water nanofluid to be used
in a heat sink by investigating its stability. They studied Al 2 O 3 /water nanofluids in
the volume concentration range of 0.1–0.25 vol.% and found that they are satisfactorily stable and that there is no sedimentation and clogging occurring using these
nanofluids. Khatak et al. (2015) studied the effect of ZnO nanofluid in spray cooling
of electronic devices. They observed that a 0.05 vol.% ZnO nanofluid was successful
in decreasing the specimen surface temperature by 15% at a heat input and nanofluid
flowrate of 180 W and 20 ml/min, respectively.
Nanofluids have also found applications in effective extraction of the solar energy.
Efficiency of a solar collector has been studied by applying Al 2 O 3 /water nanofluid
as an absorbing medium by Yousefi et al. (2012). For the study, they used a flat plate
solar collector and passed the nanofluid to study the effect of nanofluid flowrate,
concentration of nanoparticles in the nanofluid and use of surfactant. 28.3% increase
in the thermal efficiency of the solar collector has been reported when 0.2 wt%
Al 2 O 3 /water nanofluid was passed through the collector. Gupta et al. (2015) also