Optical Thermal Lens Technique To Measure Thermo-Optical Properties of
Nano-Engine Oil Lubricant
Faris Mohammed Ali
Department of Communication, Engineering Technical college\Najaf, Al-Fourat Al-Awssat Technical University, Kufa, Najaf, Iraq
E-mail\ [email protected] , [email protected]
HP:009647704149998
Abstract:
Nano engine oil (Nanofluids), a mixture of nanoparticles or nanotube and fluids,
have exceptional potential to enhancement their thermal properties. The single wall
carbon nanotube (SWNT) was suspended in engine oil lubricant: Fuchs TITAN
universal HD SAE 10w/30 and Fuchs TITAN GT1 pro-flex SAE 5w/30 with 0.5%
volume fraction, and Titanium dioxide (TiO2) 18 nm was suspended in engine oil
lubricant: Fuchs TITAN universal HD SAE 10w/30 and Fuchs TITAN GT1 pro-flex
SAE 5w/30 with 0.2% volume fraction. Sonication processing with high-powered
pulses was used to ensure the dispersion of nanotube and nanoparticles in good
uniformity in the engine oil lubricant. The optical thermal lens technique was used to
measure thermo-optical properties of nano-engine oil lubricant. The results show that
the thermo-optical properties of the samples have higher than the base fluid (engine
oil). In addition to, the particles materials have significant influence on thermo-optical
properties, where it is increased with the single walled carbon nanotubes more than
titanium dioxide nanoparticles.
Introduction:
superlative performance cooling is one of the most essential needs of many industrial
technologies[1]. However, a primary limitation in developing energy efficient heat
transfer fluids which have low thermal conductivity required for superlative
performance cooling. wherefore, modern nanotechnology can produce nonmetallic or
metallic particles of nano size dimensions, these nanomaterials have unique thermal,
optical, mechanical, electrical and magnetic properties. Therefore, nanofluids can be
produced by suspending nanomaterials with average sizes below 100 nm in base
fluids [2]. The use of nanofluids in heat exchangers, especially in micro-cooling
systems, may result in energy and cost savings and should facilitate the trend of
device miniaturization [3]. The experimental work has been focused on measurements
of thermal conductivity as a function of type of nanoparticles, size, concentration,
and temperature. The most popular techniques for measuring thermal properties of
nanofluids are the transient hot-wire method [4; 5; 6; 7; 8] 3-ω method [9; 10] and
temperature oscillation method [11; 12]. The effective thermal diffusivities and
thermal conductivities of nanofluids were typically measured using a transient hot
wire (THW) method, which is regard one of the most accurate ways to determine the
thermal properties of nanofluids [13]. The enhancement of thermal conductivity of
CuO-water, Al2O3-water and Cu-Oil nanofluids have been reported by Eastman and
Choi [14] by using the transient hot wire THW method. Ehsan-o-llah Ettefaghi et al.
have used Multi-walled carbon nanotube (MWCNTs) dispersed in engine oil SAE 20
W 50 as base fluid which is prepared by planetary ball mill. They have reported the
thermal conductivity increased by 22.7% at 0.5 wt% concentration and the amount of
flash point and pour point increased by 13% and 3.3%, respectively [15].
The hot wire-laser beam displacement technique have been proposed by Faris
Mohammed A. and W. Mahmood Mat Yunus to measure thermal diffusivity and
thermal conductivity of the aluminum and aluminum oxide nanoparticles dispersed
inside distilled water, ethylene glycol (EG), and ethanol base fluids. They found that
that the thermal conductivity and thermal diffusivity increased linearly with
increasing volume fraction concentration of nanoparticles in the respective base
fluids. In addition, the thermal conductivity and thermal diffusivity increased faster in
the Al2O3 nanofluids than in all the three base fluids [16].
Mohammad hassan Vasheghani et al. studied the effect of Al2O3 phases on the
enhancement of thermal conductivity and viscosity of nanofluids in engine oil by
using hot wire method, their results showed that by adding 4wt% of α-Al2O3 and ɤ-
Al2O3 nanoparticles to the base fluid engine oil thermal conductivity have increased
by 31% and 37%, respectively. In addition, they were observed that the differences in
thermal conductivity comes from higher specific surface area of ɤ-Al2O3 compared to
the α-Al2O3 which is the result of porosity difference [17]. Karthik R. et al. [18] have
investigated the enhancement thermal conductivity of copper (II) oxide-DI water
nanofluids using a tailor- made measurement device that uses the 3ω technique, they
concluded that The enhancement in thermal conductivity over the base fluid for the
tested conditions is observed to be 13 to 25%. A comparison between the measured
data and the predicted ones using established correlations reveals that the deviation in
prediction is within ±10%.
Recently a few optical techniques for measuring thermal conductivity or thermal
diffusivity of nanofluids. Putnam et al.[19] have used an optical beam deflection
technique for measurements of the thermal diffusivity of fluid mixtures and
suspensions of nanoparticles with a precision of better than 1% . Venerus et al.
proposed an optical technique called forced Rayleigh scattering to measure thermal
diffusivity of Au nanoparticle suspension in water and an Al2O3 nanoparticle
suspension in a petroleum oil [20]. Shaikh et al. used a modern laser flash technique
(LFA 447) to measure the effective thermal conductivity of exfoliated graphite, heat
treated nanofibers, and CNTs in polyalphaolefin oil as the base fluid [21].
To the best of our knowledge there are few systematic studies of thermal conductivity
and thermal diffusivity reported in the literature regarding the use of single walled
carbon nanotubes (SWCNT) and Titanium dioxide TiO2 suspensions in engine oil
lubricant (SAE 10W30) and (SAE 5W30), particularly at smaller volume.
In the present work a new model of optical thermal lens technique was developed for
measuring new thermo-optical properties of nanofluids.
Materials and Methods:
1- Theory
The optical thermal techniques have used electromagnetic radiation to induce non
radiative de-excitation of excited states which have led to change in temperature of
sample. This a rise in temperature can be measured by different techniques, these
techniques have used laser beam as the excitation. Optical thermal lens techniques
deserve attention because it is a high sensitivity optical technique. Furthermore, it is
noninvasive, nondestructive, considerably faster and simpler than photothermal
techniques which reported previously [19-21] and it does not require any particular
sample treatment.in addition, it reduces the heat transfer due to radiation and
convection when compared to steady state techniques, since it consists of a transient
method. Indeed, it has been used to obtain optical and thermal properties at room
temperature of nanofluids and nanomaterials.
The optical thermal lens effect is caused by the deposition of heat via non-radiative
decay processes after the laser beam has been absorbed by the sample which has
Gaussian intensity profile (TEM00).
The first step in the development of the optical thermal lens model is to consider the
heat source profile Q(r) is proportional to the Gaussian intensity profile, which can
be expressed as:
I e (r )=(2 Pe
πwe2 )exp ¿) (1)
Where, Pe (mW) is the excitation laser power, we (µm) is the excitation beam waist at
the sample position.
By the heat conduction equation which is depend on the employed boundary
condition that have been developed the infinitive aberrant model for the optical mode
mismatched thermal lens configuration. Using the conditions
∆ T (r ,0 )=0 , (r<∞ )∧∆ T ( ∞, t )=0 , ( t>0 ) , the temporal evolution of the temperature
profile ∆ T (r ,t )in the sample is given by [22]
∆ T (r ,t )=2P e A e
πCρw e2∗∫
0
t
¿¿ (2)
In which Ae the optical absorption coefficient at the excitation beam wavelength (cm-
1 ), C the specific heat (J K-1 g-1 ), ρ is the density (g cm-3) and tc the characteristic
optical thermal lens time constant (s) which is defined by:
t c=w e
2
4 D; D= K
ρC (3)
Where D is thermal diffusivity (m2 s-1) and K is thermal conductivity (W/ m. K).
The temperature evolution of the optical thermal lens depends on the parameter tc
given by Eq. (3), which is related to the thermal diffusivity D. Therefore, parameters
Ae and D which are related to the amplitude and tc of the optical thermal lens signal,
respectively, can be determined by optical thermal lens experiment.
However, this temperature rise, which carries a Gaussian profile, induces a slight
distortion in the probe beam wave front that can be associated with the optical path
length change of the sample with respect to the axis of the beam as:
Φ λp
2 π=l0( ds
dT )p
[∆ T (r , t )−∆ T (0 , t)] (4)
In which Φ is the phase shift induced when the probe beam passes through the optical
thermal lens,λ p is the probe beam wavelength, l0 is the sample thickness and ( dsdT )
p is
the temperature coefficient of the optical length at the probe beam wavelength.
Finally, using Fresnell diffraction theory, the probe beam intensity at the detector
plane can be written as an analytical expression for absolute determination of the
thermo-optical properties of the sample as [22];
I ( t )=I (0)¿¿ (5)
Where, m=(wp
we)
2
and V=Z1
Zc in which Zc≪Z2 .
Here,
Here, w p (µm) is the probe beam radius at the nanofluid sample, Zc is the confocal
distance of the probe beam, Z1 is the distance from the probe beam waist to the
nanofluid sample, Z2 the distance between the nanofluid sample and the detector, I(t)
is the temporal dependence of the probe beam intensity at the detector, I(0) is the
initial value of I(t), and I(0) equal to I(t) when the transient time t or θ is 0, and θ is
approximately the thermally induced phase shift of the probe beam (at r = 0 and
r =√2 we ) after passing through the nanofluid sample, which is given by:
θ=−Pe Ae l0
K λp( ds
dT )p (6)
It is important to note that the parameter ( dsdT ) have described the whole optical path
length change induced by the excitation beam, that means for nanofluid samples
(liquid) we have ( dsdT )=( dn
dT ). While, for solid material it depends on several
mechanisms such as the stress optical coefficient, end-face curvature, and the sample
bulging during the illumination.
By using least square curve fitting of the optical thermal lens experimental data with
Eq.(5), tc and θ can be determined.
In this project, we have used Zc is (2.5 cm), Z1 is (5.5 cm), w p is (198 µm) and w eis (45
µm). Therefore, m is 19.36, V is 2.2.
2- Experiment
The schematic diagram of the optical mode mismatched thermal lens experimental
setup is shown in Figure 1, where these mode configuration has been shown the most
sensitive experimental setup for the optical mismatched thermal lens measurements.
This experimental arrangement used two laser beams with different spot sizes at the
nanofluids sample position as shown in Figure 2. The measurement was performed
by a CW He-Ne (2 mW) laser operated at wavelength of 632.8 nm was used as a
probe laser beam and a 165 LG Argon-Ion laser (10 mW ) operated at wavelength of
514 nm was used as an excitation source . The lasers were mounted on a stage
completed with alignment facilities.
The optical mode mismatched thermal lens measurements were performed using time
resolved method. The time-resolved method permits the measurement of the
development of the thermal lens in a short period of time, and the advantage of this
procedure is that it allows to measure the sample thermal diffusivity.
The excitation laser beam was modulated by Shutter System SR470 then the
excitation beam was focused by a lens (Plano-Convex PCX1304) of focal length of
50 mm to focus the excitation beam onto a nanofluids sample which is resides in a
Cole-Parmer quartz cell with dimension of (20.5 x 10.5) mm. The quartz cell was
fixed on a three-dimension position mechanism stage .The probe beam (He-Ne ) laser
was focused by a lens (Plano-Convex PCX1304) of 60 mm focal length away from
the quartz cell and it is aligned at a small angle (about 2°) with respect to the
excitation beam. A pinhole positioned in front of the position sensitive detector
(PSD, S1880) (PSD2) to select the probe beam central part only.
the excitation beam is used to induce the thermal lens in the central part of the probe
beam and a consequent change in its intensity in the position sensitive detector, PSD1.
The output voltage of the position sensitive detectors (PSDs) were coupled to a digital
storage oscilloscope (Lecroy 9310A) to record the time evolution of TL signal. The
LABVIEW software was used to capture the TL data from oscilloscope.
Computer
Oscilloscope
Pinhole
He-Ne probe Beam Laser)Sample (Quartz
Cell
Mirror 3
Mirror 1 Ar+ Excitation Laser
Mirror 2
Lens 1Shutter
Lens 2
PSD 1
PSD 2
Fig. 1 Schematic diagram of the optical mode mismatched thermal lens experimental
setup
Fig. 2 Geometric diagram excitation and probe beams position
3- Prepare of Nanofluid Samples
Nanofluids sample are prepared by using one step technique method, similar to the
one reported by Choi [23]. With single step method (one step) technique the
nanoparticles are directly dispersed in the base fluids in a single process. The single
wall carbon nanotube (SWNT), 0.7-1.3 nm diameter (704113 ALDRICH, Sigma
Aldrich Co. LLC, Malaysia), Titanium dioxide (TiO2), 18 nm (798525 ALDRICH,
Sigma Aldrich Co. LLC, Malaysia) were suspended in engine oil lubricant as base
fluid: Fuchs TITAN universal HD SAE 10w/30 and Fuchs TITAN GT1 pro-flex SAE
5w/30. The single wall carbon nanotube of volume fraction 0.5%, Titanium dioxide
(TiO2) of volume fraction 0.2% nanoparticles are dispersed in engine oil lubricant
were mixed and kept in an ultrasonic bath (SW12H) for more than 3 hours to ensure
properly dispersion. Furthermore, the nanofluids is subjected to intensified ultra-
sonication by immersing a probe type sonication (Scientz-IID, 950W) for 6 hours to
Wp Lens 2Lens 1
)Sample (Quartz Cell
w0
Z1
achieve maximum possible de-agglomeration of particles. sodium deoxycholate
(DOC) was used as a surfactant for the mixture SWNT with engine oil lubricant as
reported by Wenseleers et al. [24], while, hexadecyltrimethylammonium bromide
(CTAB) was used as a surfactant for the mixture Titanium dioxide (TiO2) with engine
oil lubricant. A Transmission Electronic Microscopy TEM (Hitachi 7100 TEM) was
used to measure the particle size, the particle distribution, and the morphology of
SWNT and nanoparticles in the base fluids (engine oil lubricant).as shown in Figure
1-4.
Fig.1 TEM image single wall carbon nanotube (SWNT) dispersed in Fuchs TITAN
universal HD SAE 10w/30 at volume fraction 0.5 %
100 nm
Fig.2 TEM image single wall carbon nanotube (SWNT) dispersed in Fuchs TITAN
GT1 pro-flex SAE 5w/30 at volume fraction 0.5 %
Fig.3 TEM image Titanium dioxide (TiO2) dispersed in Fuchs TITAN universal HD
SAE 10w/30 at volume fraction 0.2 %
Fig.4 TEM image Titanium dioxide (TiO2) dispersed in Fuchs TITAN GT1 pro-flex
SAE 5w/30 at volume fraction 0.2 %
Result and Discussion
The optical thermal lens effect of nanofluids was based on their laser induced heating
and time resolved monitoring on the thermal effects. So, to verify and evaluate the
25 nm
50 nm
reliability of the experimental measurement of optical thermal lens, firstly we measure
the thermo-optical properties of engine oil lubricant unused, then compare this result
with the literature result of engine oil lubricant and showed a good agreement with
references [25; 26; 27] . The results have shown in Table 1.
Table 1 Results of engine oil lubricant unused
engine oilThermal
Diffusivity x10-8
(m2/s)
Reference value of Thermal
Diffusivity x10-8
(m2/s)
Thermal Conductivity
(W/m.K)
Reference value of `(W/m.K)
Fuchs TITAN SAE 10w/30
8.54 8.5325
8.5326
8.5527
0.144 0.14425
0.14527
Fuchs TITAN SAE 5w/30
8.57 8.5525
8.57270.145 0.14426
0.14627
The measurement of the thermo-optical properties of single walled carbon nanotube
SWNT (0.7-1.3 nm diameter) and Titanium dioxide TiO2 (18 nm) suspension in
engine oil lubricant which are Fuchs TITAN SAE 10w/30 and Fuchs TITAN SAE
5w/30 nanofluid samples were conducted. The single walled carbon nanotube SWNT
were prepared at volume fraction 0.5% and Titanium dioxide were prepared at
volume fraction 0.2% suspension in different engine oil as base fluids; Fuchs TITAN
SAE 10w/30 and Fuchs TITAN SAE 5w/30.
Figures 1 to 4 show TEM for the SWNT and TiO2 nanoparticle distribution of the
sample in engine oil as base fluids (Fuchs TITAN SAE 10w/30 and Fuchs TITAN
SAE 5w/30) after 9 hours in the sonication process (ultrasonic bath and probe type
sonication). The images 1 and 2 show that the SWNT were aggregated to form
nanotubes clusters and evenly distributed in the engine oil base fluids. These TEM
images reveal that the single walled carbon nanotube are highly cluster-dispersed.
while, the images 3 and 4 show that the TiO2 nanoparticles were aggregated to form
nanoparticle clusters and evenly distributed in the engine oil. These TEM images
show that the nanoparticles are highly cluster-dispersed with an average size of about
25-50 nm and are spherical in shape.
The thermally induced phase shift of the probe beam θ and the characteristic optical
thermal lens time constant tc were obtained by fitting equation 5 to the normalized
optical thermal lens time evolution data and finally the thermo physical properties
(thermal diffusivity and thermal conductivity) can be calculated from equation 3.
Where, the specific heat Cp have been determined by ordinary calorimetry and the
density ρ have been determined by Archimedes' method. the experimental have been
conducted at room temperature. Figures 5 and 6 show the typical time evolution of
optical thermal lens signals for the SWNT nano-lubricant engine oil (Fuchs TITAN
SAE 10w/30) and TiO2 nano-lubricant engine oil (Fuchs TITAN SAE 5w/30) samples
respectively, where the solid line represent the best fit of equation 5 to the
experimental data and the symbols (o) denote to the experimental data.
The thermo-optical properties of nano-lubricant engine oil samples have listed in
Table 2.
Table 2 Results of thermo-optical properties of nano-lubricant engine oil
Nanofluid samples θ tc (s)Thermal
Diffusivity x10-8
(m2/s)
Thermal Conductivity (W/m.K)
SWNT+SAE 10w/30 0.09861±0.0002 0.00342±0.00001
14.64±0.114 0.465 ±0.002
SWNT+ SAE 5w/30 0.09135±0.0001 0.00332±0.00003
15.23±0.158 0.489±0.003
TiO2+ SAE 10w/30 0.08736±0.0001 0.00441±0.00002
11.47±0.245 0.291±0.001
TiO2+ SAE 5w/30 0.08487±0.0003 0.00427±0.00004
11.83±0.188 0.315±0.003
The results of thermal diffusivity of SWNT (0.7-1.3 nm diameter) Nanotubes
dispersion in Fuchs TITAN SAE 10w/30 and Fuchs TITAN SAE 5w/30 at volume
fraction 0.5% were 14.64 x 10-8 ± 0.114, 15.23 x 10-8 ± 0.158 (m2/s) respectively.
while Thermal conductivity were 0.465 ±0.002, 0.489±0.003 (W/m.K) respectively.
In addition, The results of thermal diffusivity of TiO2 (18 nm) nanoparticles
dispersion in Fuchs TITAN SAE 10w/30 and Fuchs TITAN SAE 5w/30 at volume
fraction 0.2% were 11.47 x 10-8 ± 0.245, 11.83 x 10-8 ± 0.188 (m2/s) respectively.
While, thermal conductivity were 0.291±0.001, 0.315±0.003 (W/m.K) respectively.
So, the enhancements in thermal diffusivity and thermal conductivity have an obvious
increase by adding nanotubes and nanoparticles. This observation can provide an
insight into the mechanism of thermal exchanger transport in nanofluids. We
particularly mention the volume fraction of nanoparticles or nanotubes dependence of
thermal diffusivity and thermal conductivity, because thermal diffusivity and
conductivity would show more enhancements if the nanoparticles or nanotubes
formed suspensions in base fluids (engine oil). Single Walled Carbon Nanotubes
(SWNT) nanofluid exhibits 71.42% enhancement in thermal diffusivity with 0.5%
volume fraction of nanotubes in Fuchs TITAN universal HD SAE 10w/30, while
Single Walled Carbon Nanotubes (SWNT) nanofluid presents 77.71% enhancement
with 0.5% volume fraction nanotubes in Fuchs TITAN GT1 pro-flex SAE 5w/30.
Moreover, the enhancement in thermal conductivity were 222.91% and 237.24% for
SWNT suspension in Fuchs TITAN universal HD SAE 10w/30 and SWNT
suspension in Fuchs TITAN GT1 pro-flex SAE 5w/30 respectively.
The enhancement of thermo physical properties (diffusivity and conductivity) of TiO2
nanofluids suspension in Fuchs TITAN universal HD SAE 10w/30 and Fuchs TITAN
GT1 pro-flex SAE 5w/30 at volume fraction 0.2% were 34.3%, 38.03%, 102.08%,
and 117.24%, respectively. We observed also that SWNT suspension in Fuchs TITAN
GT1 pro-flex SAE 5w/30 have higher thermal diffusivity and thermal conductivity
values compared to the TiO2 nanoparticles in Fuchs TITAN GT1 pro-flex SAE 5w/30.
The comparison between thermal diffusivity and conductivity of SWNT and TiO2
nanofluids in different base fluid at same volume fraction, the Fuchs TITAN GT1 pro-
flex SAE 5w/30 base fluid has the highest thermal diffusivity and thermal
conductivity. According to the results which are presented above, the nano (nanotube
and nanoparticle) suspension in engine oil demonstrates some unique and novel
thermal properties when compared to the traditional heat transfer of engine oil. There
are several mechanisms that will enhance the thermal properties of nano-engine oil:
Brownian motion of nano, interfacial liquid layer (liquid layer at liquid particle
interface), nano- structuring / aggregation, and effects of nano clustering [28; 29].
First, Brownian motion, by which nano move through the fluid and possibly collide,
thereby enabling direct solid-solid transport of heat from one to another, can be
expected to increase thermophysical properties of nanofluid. Brownian motion of
nano could contribute to the thermophysical enhancement through two ways, direct
contribution due to motion of nano that transports heat, and indirect contribution due
to micro-convection or nano-convection of fluid surrounding individual nano. The
direct contribution of Brownian motion has been taken by comparing the time scale of
particle motion with that of heat diffusion in the fluid. Equivalently we can compare
the time required for particle to move by the distance equal to its size with time
required for heat to move in the liquid by the same distance. The indirect contribution
has also been shown to play a minute role through the same reasoning for the direct
contribution and also through molecular modeling[28; 29; 30; 31].Second reason,
which is important for the enhancement thermal diffusivity and thermal conductivity
of the nanofluid, interfacial liquid layer or some time called (liquid layer at liquid
particle interface) would lead to an Increase in the estimate value of thermal
diffusivity and thermal conductivity of nanofluid and an increase thermal diffusivity
and thermal conductivity with increase particle size. Considering that the molecular
structure of liquid at the solid interface is more ordered, possibilities of larger thermal
conductivity of this ordered liquid layer and 'tunneling' of heat carrying phonons from
one particle to another were put forward. For strong solid–liquid interactions, typical
of those in nanofluids with metallic nanoparticles, a percolating network of
amorphous-like fluid structures can emerge which can facilitate additional thermal
conduction paths [31]. However, an interface effect that could enhance thermal
conductivity is the layering of the fluid at the solid interface, by which the atomic
structure of the liquid layer is significantly more ordered than that of bulk liquid.
Given that crystalline solids (which are obviously ordered) display much better
thermal transport than liquids, such liquid layering at the interface would be expected
to lead to a higher thermal conductivity. To evaluate an upper limit for the effect of
the interfacial layer, we suppose that the thermal conductivity of this interfacial fluid is
exactly the same as that of the solid nanoparticle. The resultant larger effective volume
of the nanoparticle-layered-fluid structure could enhance the thermal conductivity of
nanofluid. Third reason of enhancement thermophysical properties of nanofluids is the
nano structuring / aggregation have dominated mechanism for the thermophysical
properties enhancement of nanofluids, due to interconnected nano in the fluid
enhances the thermophysical properties. The nano-agglomeration is a similar process
for nano to settle in the fluid due to the larger mass that results in a particle gradient in
the fluid. The “particle free” zone has a higher thermal resistance compared to the
particle rich zone. The suppression of agglomeration of the nanoparticles is also very
important for designing effective heat transport nanofluids. It is understood that the
heat transfer can be much faster along the backbone of the agglomeration. Finally,
Clustering of the nano becomes more effective in fluids with a higher volume
fraction. This clustering has a major effect on thermophysical properties
measurements of the nanofluid. By creating paths of lower thermal conductivity
resistance, clustering of particles into percolating would have a major effect on the
thermophysical properties. The effective volume of the cluster, i.e., the volume from
which other clusters are excluded, can be much larger than the physical volume of the
particles. Since within such clusters heat can move very rapidly, the volume fraction
of the highly conductive phase is larger than the volume of the solid, which
significantly increases thermophysical properties.
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.40.445
0.45
0.455
0.46
0.465
0.47
0.475
0.48
0.485
0.49 Theoretical Optical Thermal LensExperimental Data
O p ti c al
T h er m al
L e n s Si g n al
(a r b.
u m it s)
Time(s)
Fig. 5 time evolution of optical thermal lens signals for the SWNT nano-lubricant engine oil Fuchs TITAN SAE 10w/30
-0.2 0 0.2 0.4 0.6 0.8 1 1.20.47
0.475
0.48
0.485
0.49
0.495
0.5
0.505
0.51Theoretical Optical Thermal lens
Experimental dataO
ptica
l Ther
mal
Len
s Si
gnal
(a
rb.
umits
)
Time(s
Fig. 6 time evolution of optical thermal lens signals for the TiO2 nano-lubricant engine oil Fuchs
TITAN SAE 5w/30
Conclusions:
This study have been discussed the use of optical thermal lens technique for the
investigation of the thermo-optical properties of nano-engine oil lubricant. optical
thermal lens technique provides a fast and precise technique to determine absolute
values of thermo-optical properties of nano-engine oil lubricant. Thus, the optical
thermal lens technique is a new technique to study thermo-optical properties of nano-
engine oil lubricant. Optical thermal lens technique is advantageous as it is non-
contacting and can be used in thick samples as well as in thin films. However it
requires laser beams with good transverse mode (close to TEM00). The thermo-optical
properties for Single walled carbon nanotube SWNT (0.7-1.3 nm diameter) and
titanium dioxide TiO2 (18 nm) suspension in engine oil lubricant (Fuchs TITAN
universal HD SAE 10w/30 and Fuchs TITAN GT1 pro-flex SAE 5w/30 ) were
determined. However, to the best of our knowledge these nano engine oil lubricant
samples which were used in this study were new samples, therefore, the values of the
thermo-optical properties of these nano engine oil samples are new.
The results show that the thermo-optical properties of all samples of nanofluid have
higher than the base fluid (engine oil). In addition to, the particles materials have
significant influence on thermo-optical properties, where it is increased with the
single walled carbon nanotubes more than titanium dioxide nanoparticles as shown in
results. The covering of nanoparticles type plays an important role in their thermal
properties.
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