U.S. patent application number 11/380668 was filed with the patent office on 2007-11-01 for a method for preparing carbon nanofluid.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Ching-Cheng Lin, Min-Sheng Liu.
Application Number | 20070253888 11/380668 |
Document ID | / |
Family ID | 38648518 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070253888 |
Kind Code |
A1 |
Liu; Min-Sheng ; et
al. |
November 1, 2007 |
A METHOD FOR PREPARING CARBON NANOFLUID
Abstract
The present invention provides a method for preparing a carbon
nanofluid. The method includes providing a base fluid, providing a
number of carbon nanotubes, combining the carbon nanotubes with the
base fluid, dispersing the carbon nanotubes substantially evenly in
the base fluid through a physical agitation operation, and cooling
a system performing the physical agitation operation during the
physical agitation operation. The present invention also provides a
carbon nanofluid capable of serving as a heat transfer fluid. The
carbon nanofluid includes about 99.8 to about 98% by volume of a
base fluid, and from about 0.2 to about 2.0% by volume of
functionalized carbon nanotubes substantially evenly-dispersed in
the base fluid.
Inventors: |
Liu; Min-Sheng; (Hsinchu
County, TW) ; Lin; Ching-Cheng; (Hsinchu City,
TW) |
Correspondence
Address: |
AKIN GUMP STRAUSS HAUER & FELD L.L.P.
ONE COMMERCE SQUARE
2005 MARKET STREET, SUITE 2200
PHILADELPHIA
PA
19103
US
|
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
Hsinchu
TW
|
Family ID: |
38648518 |
Appl. No.: |
11/380668 |
Filed: |
April 28, 2006 |
Current U.S.
Class: |
423/447.1 |
Current CPC
Class: |
B82Y 30/00 20130101;
C01B 2202/02 20130101; B82Y 40/00 20130101; C01B 2202/28 20130101;
C01B 2202/06 20130101; C01B 32/168 20170801; F28F 13/00 20130101;
C09K 5/10 20130101; C01B 32/174 20170801; F28D 1/06 20130101; C01B
2202/04 20130101 |
Class at
Publication: |
423/447.1 |
International
Class: |
D01F 9/12 20060101
D01F009/12 |
Claims
1. A method for preparing carbon nanofluid, the method comprising:
providing a base fluid; providing a number of carbon nanotubes;
combining the carbon nanotubes with the base fluid; and dispersing
carbon nanotubes substantially evenly in the base fluid through a
physical agitation operation; and cooling a system performing the
physical agitation operation during the physical agitation
operation.
2. The method according to claim 1, wherein the physical agitation
comprises ultrasonication.
3. The method according to claim 1, wherein the carbon nanotubes
comprise at least one of single-walled, double-walled and
multi-walled carbon nanotubes having a plurality of functional
groups introduced thereon.
4. The method according to claim 3, wherein each of the functional
groups comprises COOH.
5. The method according to claim 1, wherein the base fluid
comprises at least one of ethylene glycol, water and oil.
6. A method for preparing a fluid capable of serving as a heat
transfer agent, the method comprising: introducing a number of
functional groups onto carbon nanotubes for providing
functionalized carbon nanotubes; providing a base fluid; combining
the functionalized carbon nanotubes with the base fluid; and
dispersing the carbon nanotubes substantially evenly in the base
fluid through an ultrasonication operation; and cooling a system
performing the ultrasonication operation during the ultrasonication
operation.
7. The method according to claim 6, wherein introducing the
functional groups comprises treating with an acidic solution
comprising H.sub.2SO.sub.4 and HNO.sub.3 in a ratio of about
3:1
8. The method according to claim 7, further comprising purifying
the functionalized carbon nanotubes by high speed centrifugation
before combining the carbon nanotubes with the base fluid.
9. The method according to claim 8, wherein the carbon nanotubes
comprise at least one of single-walled, double-walled and
multi-walled carbon nanotubes.
10. The method according to claim 8, wherein each of the functional
groups comprises COOH.
11. The method according to claim 8, wherein the base fluid
comprises at least one of ethylene glycol, oil and water.
12. A carbon nanofluid capable of serving as a heat transfer fluid,
the carbon nanofluid comprising: (a) about 99.8 to about 98% by
volume of a base fluid; and (b) from about 0.2 to about 2.0% by
volume of functionalized carbon nanotubes substantially
evenly-dispersed in the base fluid, wherein the carbon nanofluid
has a thermal conductivity at least 1.3 times higher than a base
fluid having no carbon nanotubes.
13. The carbon nanofluid according to claim 12, wherein the
functionalized carbon nanotubes comprise at least one of
single-walled, double-walled and multi-walled carbon nanotubes with
a number of functional groups introduced thereon.
14. The carbon nanofluid according to claim 12, wherein the base
fluid comprises at least one of ethylene glycol, water and oil.
15. A carbon nanofluid made by the process of: introducing a number
of functional groups onto carbon nanotubes for providing
functionalized carbon nanotubes; providing a base fluid; combining
the functionalized carbon nanotubes with the base fluid; and
dispersing the carbon nanotubes substantially evenly in the base
fluid through an ultrasonication operation; and cooling a system
performing the ultrasonication operation during the ultrasonication
operation.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a carbon nanotechnology,
more particularly to a method for preparing carbon nanofluid with
enhanced thermal conductivity.
[0002] The thermal conductivity of heat transfer fluid plays an
important role in the development of energy-efficient heat transfer
equipment including electronics, heating, ventilating,
air-conditioning, refrigeration, and transportation. Development of
advanced heat transfer fluids is clearly essential to improve the
effective heat transfer behavior of conventional heat transfer
fluids. Low thermal conductivity is a primary limitation in the
development of energy-efficient heat transfer fluids required in
many industrial applications.
[0003] U.S. Pat. No 5,863,455 to Segal disclosed a colloidal fluid
having metallic particles in a carrier fluid to insulate and cool
an electromagnetic device which generates heat as a result of
utilizing high current densities and high alternative current (AC)
voltages inside the electromagnetic device. A new class of heat
transfer fluids has also been developed by suspending metal or
metal oxide particles in liquids as disclosed in U.S. Pat. No.
6,221,275 to Choi et al. The metal or metal oxide particles are
produced and dispersed in a vacuum while passing a thin film of the
fluid near the heated substrate.
[0004] Emerging carbon nanotechnology shows promise in many aspects
of engineering applications. Recently, carbon nanotubes have been
proposed with growing popularity as a stable nanomaterial with
enhanced thermal conductivity. However, carbon nanotubes are strong
and flexible, yet very cohesive. This makes it difficult to
evenly-disperse them into fluids for providing an efficient heat
transfer agent in the energy management.
BRIEF SUMMARY OF THE INVENTION
[0005] One example of the invention provides a method for preparing
a carbon nanofluid with enhanced thermal conductivity. The method
comprises providing a base fluid, providing a number of carbon
nanotubes, combining the carbon nanotubes with the base fluid, and
dispersing the carbon nanotubes substantially evenly in the base
fluid through a physical agitation operation, and cooling a system
performing the physical operation during the physical agitation
operation.
[0006] Another example of the invention provides a method for
preparing a fluid capable of serving as a heat transfer agent. The
method comprises introducing a number of functional groups onto
carbon nanotubes for providing functionalized carbon nanotubes,
providing a base fluid, combining the functionalized carbon
nanotubes with the base fluid, and dispersing the carbon nanotubes
substantially evenly in the base fluid through an ultrasonication
operation, cooling a system performing the ultrasonication
operation during the ultrasonication operation.
[0007] In a further another example, the present invention provides
a carbon nanofluid capable of serving as a heat transfer fluid. The
carbon nanofluid comprises about 99.8 to about 98% by volume of a
base fluid and from about 0.2 to about 2.0% by volume of
functionalized carbon nanotubes substantially evenly-dispersed in
the base fluid, wherein the carbon nanofluid has a thermal
conductivity at least 1.3 times higher than a base fluid having no
carbon nanotubes.
[0008] In yet one other example, the present invention provides a
carbon nanofluid made by the process of introducing a number of
functional groups onto carbon nanotubes for providing
functionalized carbon nanotubes, providing a base fluid, combining
the functionalized carbon nanotubes with the base fluid, and
dispersing the carbon nanotubes substantially evenly in the base
fluid through an ultrasonication operation, and cooling a system
performing the ultrasonication operation during the ultrasonication
operation.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] The foregoing summary, as well as the following detailed
description of the invention, will be better understood when read
in conjunction with the appended drawings. For the purpose of
illustrating the invention, there are shown in the drawings
embodiments which are presently preferred. It should be understood,
however, that the invention is not limited to the precise
arrangements and instrumentalities shown.
[0010] In the drawings:
[0011] FIG. 1 is a schematic diagram illustrating a laboratory
apparatus for generating functionalized carbon nanotubes according
to one embodiment of the invention;
[0012] FIG. 2 is a schematic diagram illustrating an ultrasonic
homogenizer arranged adjacent to a dual tube heat exchange system
according to another embodiment of the invention; and
[0013] FIG. 3 is a schematic diagram illustrating a dual tube heat
exchange system according to a further embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Reference will now be made in detail to the present
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. Wherever possible, the same reference
numbers will be used throughout the drawings to refer to the same
or like parts.
[0015] The present invention provides a method for preparing a
carbon nanofluid. The method comprises providing a base fluid,
providing a number of carbon nanotubes, combining the carbon
nanotubes with the base fluid, and dispersing the carbon nanotubes
substantially evenly in the base fluid through a physical agitation
operation, and cooling a system performing the physical agitation
during the physical agitation operation.
[0016] The carbon nanotubes described in the present invention
comprises at least one of single-walled, double-walled and
multi-walled carbon nanotubes having a plurality of functional
groups introduced thereon.
[0017] Therefore, the term "to functionalize" herein refers to
introduce a plurality of functional groups to surface of the carbon
nanomaterial by chemical modification such as acidic treatment for
enhancing thermal conductivity and solubility of the carbon
nanomaterial in the aqueous, inorganic or organic solutions.
[0018] In one embodiment of the invention, each of the functional
groups comprising COOH is introduced by treating the carbon
nanotubes with an acidic solution comprising at least one of
H.sub.2SO.sub.4, HNO.sub.3, HCl and CH.sub.3COOH. The
functionalized carbon nanotubes are combined with the base fluid
and then dispersed substantially evenly in the base fluid through a
physical agitation operation. During the physical agitation
operation, a cooling operation may be applied for cooling a system
performing the physical agitation operation during the physical
agitation operation.
[0019] In another embodiment of the invention, the carbon nanotubes
are surface-modified or functionalized by treating the carbon
nanotubes with the acidic solution comprising H.sub.2SO.sub.4 and
HNO.sub.3. As a result, the functional group comprising COOH is
introduced onto the surface of the carbon nanotubes. The
functionalized carbon nanotubes may be further purified by
subjecting to high speed centrifugation to separate the unbound
acidic mixture from the functionalized carbon nanotubes. Next, the
purified carbon nanotubes may be washed with the base fluid before
being combined with the base fluid and being dispersed in the base
fluid. The functionalized carbon nanotubes are combined with the
base fluid and then dispersed in the base fluid through a physical
agitation operation, such as magnetic force agitation or
ultrasonication operation. A cooling operation is performed for
cooling a system performing the physical agitation operation during
the physical agitation operation.
[0020] In a further embodiment of the invention, the carbon
nanotubes are surface-modified or functionalized by treating the
carbon nanotubes with an acidic solution including H.sub.2SO.sub.4
and HNO.sub.3 in a ratio of about 3:1. The functionalized carbon
nanotubes may be further purified by subjecting to high speed
centrifugation to separate the unbound acidic mixture from the
functionalized carbon nanotubes. Next, the purified carbon
nanotubes are washed with the base fluid before being combined with
and being dispersed within the base fluid. The purified carbon
nanotubes are then combined with the base fluid and dispersed in
the base fluid through an ultrasonication operation. During the
ultrasonication operation, a cooling operation may be applied to
cool a system performing the ultrasonication operation. In
accordance with one example, the ultrasonication operation may be
carried out using an ultrasonic homogenizer with a cooling system
arranged adjacent to the ultrasonic homogenizer for cooling the
ultrasonic homogenizer
[0021] Although the carbon nanotubes are functionalized by an
acidic solution as described in the above embodiments, it is noted
that the present invention is not limited to functionalizing the
carbon nanotubes using this particular technique. Other surface
modification techniques which cause addition or introduction of
functional groups on the carbon nanotubes may be adopted.
[0022] The invention also provides a method for preparing a fluid
capable of serving as a heat transfer agent. The method comprises
steps of introducing a number of functional groups onto carbon
nanotubes for providing functionalized carbon nanotubes, providing
a base fluid, combining the functionalized carbon nanotubes with
the base fluid, and dispersing the functionalized carbon nanotubes
substantially evenly in the base fluid through an ultrasonication
operation, and cooling a system performing the ultrasonication
operation during the ultrasonication operation.
[0023] Similarly, the carbon nanotubes, such as single-walled,
double-walled or multi-walled carbon nanotubes are functionalized
by treating the carbon nanotubes with an acid mixture including
H.sub.2SO.sub.4 and HNO.sub.3 in a ratio of about 3:1. The
functionalized carbon nanotubes may be further purified by high
speed centrifugation to separate the unbound acidic mixture from
the functionalized carbon nanotubes. Next, the purified carbon
nanotubes may be washed before being combined with and being
dispersed in the base fluid. The purified carbon nanotubes are then
combined with the base fluid and dispersed substantially evenly in
the base fluid through an ultrasonication operation. And during the
ultrasonication operation, a cooling operation is applied for
cooling a system performing the ultrasonication operation.
[0024] In one preferred embodiment, the functional groups are
introduced onto the carbon nanotubes by treating with an acid
mixture including H.sub.2SO.sub.4 and HNO.sub.3 in a ratio of about
3:1 in a laboratory apparatus as shown in FIG. 1. The laboratory
apparatus 1 comprises a beaker 10, a reflux system 11 coupled to
the beaker 10, and a heating table 12. The mixture in the beaker 10
is heated and stirred over the heating table 12. As the liquid is
heated over the boiling point to vaporize, the reflux system 11
condenses vaporized gas into liquid droplets and recycles them back
into the beaker 10. Next, the functionalized carbon nanotubes may
be purified by high speed centrifugation to separate the unbound
acidic mixture from the functionalized carbon nanotubes. The
purified carbon nanotubes may be washed with the base fluid before
being combined with and being dispersed in the base fluid.
[0025] The ultrasonication operation is performed using a
ultrasonic homogenizer 2 arranged adjacent to a dual tube heat
exchanger 3 which efficiently dissipates the heat generated by the
ultrasonic homogenizer 2 to cool the base fluid. Referring to FIG.
2, the ultrasonic homogenizer 2 comprises an ultrasonic probe 20
and a power supply 21 connected to the ultrasonic probe 20 for
supplying power required for the ultrasonication operation. The
ultrasonic probe 20 is arranged in such a way that a tip 20a of the
ultrasonic probe 20 is dipped in the base fluid to effect
dispersion. The dual tube heat exchanger 3 has an inner tube 30 in
which the base fluid is received and an outer tube 31 surrounding
the inner tube 30. The outer tube 31 is filled with a fluid to
dissipate or carry away the heat generated by the ultrasonic probe
20. The outer tube 31 has an inlet 311 arranged at a bottom end and
an outlet 312 arranged at a top end as shown in FIG. 2, such that
the fluid enters the outer tube 31 via the inlet 311 and exits via
the outlet 312 for cooling the ultrasonic homogenizer 2. So, the
ultrasonication operation is not interrupted as a result of
overheating the ultrasonic probe 20 with a substantially high power
supplied to the ultrasonic probe 20 over a period of time. This
ensures a constant output of high power during the ultrasonication
operation to achieve an optimal dispersion effect.
[0026] In accordance with another preferred embodiment of the
invention, the cooling system comprises the dual tube heat
exchanger 3 as illustrated in FIG. 2 and a cooling circulation
system 4. Referring to FIG. 3, the dual tube heat exchanger 3 is
connected to cooling circulation system 4 in such a way that the
fluid that flows out of the outer tube 31 is recycled via a pipe 40
back to the outer tube 31 for heat dissipation. And the pipe 40 may
be connected to a cooling bath 41 for further cooling of the fluid
in the pipe 40 before the fluid is re-directed back to the outer
tube 31 of the dual tube heat exchanger 3. Thus, with the cooling
system illustrated in FIG. 3, the fluid is efficiently recycled to
provide heat dissipation or cooling for the ultrasonic homogenizer
without wasting too much fluid in the cooling system. Therefore,
the overall cost for preparing the nanofluid is effectively
reduced.
[0027] It is noted that the cooling system in the present invention
is not limited to the specific devices or instrumentalities as
described in the above embodiments. For example, the cooling system
may be modified or improved in the knowledge of those skilled in
the heat exchange technique to achieve similar cooling effect on
the ultrasonic probe and the ultrasonic homogenizer.
[0028] In light of the preparation methods described above, the
present invention further provides a carbon nanofluid capable of
serving as a heat transfer fluid. The carbon nanofluid comprises
about 99.8 to about 98% by volume of a base fluid, and from about
0.2 to about 2.0% by volume of functionalized carbon nanotubes
substantially evenly-dispersed in the base fluid, wherein the
carbon nanofluid has a thermal conductivity at least 1.3 times
higher than a base fluid having no carbon nanotubes.
[0029] The present invention further provides a carbon nanofluid
made by the process of introducing a number of functional groups
onto carbon nanotubes for providing functionalized carbon
nanotubes, providing a base fluid, combining the functionalized
carbon nanotubes with the base fluid, and dispersing the carbon
nanotubes substantially evenly in the base fluid through an
ultrasonication operation, and cooling a system performing the
ultrasonication operation during the ultrasonication operation.
[0030] In accordance with the present invention, the base fluid
includes but is not limited to organic solvents, inorganic solvent
and aqueous solutions having carbon nanotubes substantially evenly
dispersed therein for serving as a heat transfer agent. And
depending on the actual application, the base fluid comprises at
least one of ethylene glycol, water and oil. While the present
invention also encompasses the carbon nanofluid mixed with
surfactants or dispersants and the preparation method thereof, it
is more preferable to prepare the fluid complex or carbon nanofluid
without adding the surfactants or dispersants which will
encapsulate or coat the carbon nanotubes to mask or reduce their
high thermal conductivity.
[0031] The invention will now be described in further detail with
reference to the following specific, non-limiting examples.
Preparation of Carbon Nanofluid
[0032] The carbon nanotubes of single-walled, double-walled or
multiple-walled were commercially available (Nanotech Port Co.,
Shenzhen, China) and purchased in the form of powder. The carbon
nanotubes were functionalized or surface modified by treating with
an acidic solution including H.sub.2SO.sub.4 and HNO.sub.3 in a
ratio of about 3:1 in the laboratory apparatus illustrated in FIG.
1. Next, the functionalized carbon nanotubes were purified by high
speed centrifugation to separate the unbound acidic solution from
the functionalized carbon nanotubes. The purified carbon nanotubes
were washed with the working fluid before dispersing the carbon
nanotubes in the base fluid by ultrasonication.
[0033] An ultrasonication process was performed using an ultrasonic
homogenizer in the presence of a cooling system, such as a dual
tube heat exchanger shown in FIG. 3, capable of dissipating heat
generated by the ultrasonication process. Therefore, as the carbon
nanotubes were dispersed by ultrasonication in the base fluid, the
heat generated by the ultrasonic probe could be dissipated
instantly as a result of the fluid flowing through the outer tube.
This ensured a stable operation of the ultrasonic homogenizer even
if a high power of about 300 to 600 W was supplied to the
ultrasonic probe over a period of time during the ultrasonication
operation. Accordingly, a constant output of substantially high
power was supplied during the ultrasonication operation to
substantially evenly disperse the carbon nanotubes in the base
fluid.
Thermal Conductivity Measurement
[0034] The thermal conductivity (k) of the carbon nanofluid was
measured with specially designed, computer-controlled equipment as
described (Lee et al., Journal of Heat Transfer, Vol. 121 pp. 280
(1999)). Thermal conductivities were measured as a function of
nanotube volume fractions at room temperature. For the measurement
of thermal conductivity, the carbon nanofluid was filled into the
vertical, cylindrical glass container of transient hot wire system.
The long glass container has an inner diameter of 19 mm and a
length of 240 mm. In the transient hot wire system, a platinum wire
having a diameter of about 76.2 .mu.m was immersed in the carbon
nanofluid. The platinum wire was simultaneously used as a heater
and as an electrical resistance thermometer for the carbon
nanofluid. The surface of platinum wire was coated with a thin
electrical insulation epoxy for preventing the platinum wire from
short circuitry. A temperature variation of the platinum wire was
obtained as a result of change in the electrical resistance with
time. The thermal conductivity was then estimated from Fourier's
Law. The thermal conductivity of the carbon nanofluid was inversely
proportional to the slope of the temperature versus time response
of the platinum wire. The transient hot wire system was calibrated
using deionized water and ethylene glycol at room temperature.
Uncertainty of the measurement was less than 2%.
EXAMPLE 1
Nanofluid A (Carbon Nanotubes/Ethylene Glycol)
[0035] The nanofluid A was prepared by dispersing multiple walled
carbon nanotubes in ethylene glycol. No surfactant was added to the
nanofluid A. And the carbon nanotubes were combined with and
dispersed in ethylene glycol through an ultrasonication operation
at 600 W for approximately one hour. During the ultrasonication
operation, a cooling operation was applied using a dual tube heat
exchanger as shown in FIG. 2 for cooling the nanofluid A during the
ultrasonication operation performed by an ultrasonic
homogenizer.
[0036] Next, the nanofluid A was subjected to thermal conductivity
measurement as described above. As listed in Table 1 below, the
thermal conductivity (represented by k value) was increased by
12.4% at a volume fraction of 0.01 (1 vol. %) for the carbon
nanotubes/ethylene glycol suspensions as compared with ethylene
glycol only. Therefore, small amount of carbon nanotubes dispersed
according to the present invention resulted in a significant
increase in the thermal conductivity of the base fluid.
TABLE-US-00001 TABLE 1 carbon nanotubes/ethylene glycol vol. % k
value increase (%) 0.2 1.6 0.4 3.6 0.5 7.6 1.0 12.4
EXAMPLE 2
Nanofluid B (Carbon Nanotubes/Water)
[0037] The nanofluid B was prepared by dispersing multiple walled
carbon nanotubes in the water. No surfactant was added to the
nanofluid B. And the carbon nanotubes were combined with and
dispersed in the water through an ultrasonication operation at 600
W for approximately one hour. During the ultrasonication operation,
a cooling operation was applied using a dual tube heat exchanger as
shown in FIG. 2 for cooling the nanofluid B during the
ultrasonication operation performed by an ultrasonic
homogenizer.
[0038] Next, the nanofluid B was subjected to thermal conductivity
measurement as described above. As listed in Table 2 below, the
thermal conductivity was increased by 17.8% at a volume fraction of
0.015 (1.5 vol. %) for the carbon nanotubes/water suspensions as
compared with water only. Therefore, small amount of carbon
nanotubes dispersed according to the present invention resulted in
a significant increase in the thermal conductivity of the working
fluid. TABLE-US-00002 TABLE 2 carbon nanotubes/water vol. % k value
increase (%) 0.25 2.6 1.0 9.5 1.5 17.8
EXAMPLE 3
Nanofluid C (Carbon Nanotubes/Synthetic Engine Oil)
[0039] The nanofluid C was prepared by dispersing multiple walled
carbon nanotubes in the synthetic engine oil. N-hydroxysuccinimide
(NHS) was added to the nanofluid C. And the carbon nanotubes were
combined with and dispersed in the synthetic engine oil through an
ultrasonication operation at 600 W for approximately one hour.
During the ultrasonication operation, a cooling operation was
applied using a dual tube heat exchanger as shown in FIG. 2 for
cooling the nanofluid C during the ultrasonication operation
performed by an ultrasonic homogenizer.
[0040] Next, the nanofluid C was subjected to thermal conductivity
measurement as described above. As listed in Table 3 below, the
thermal conductivity was increased by 30.3% at a volume fraction of
0.02 (2.0 vol. %) for the carbon nanotubes/synthetic engine oil
suspensions as compared with oil only. Therefore, small amount of
carbon nanotubes dispersed according to the present invention
resulted in a significant increase in the thermal conductivity of
the working fluid. TABLE-US-00003 TABLE 3 carbon
nanotubes/synthetic engine oil vol. % k value increase (%) 1.0 8.5
2.0 30.3
[0041] Although in the above embodiments, it is understood by one
skilled in the art that other base fluids having carbon
nanomaterial dispersed therein, whether functionalized or not, may
also be within the scope of the invention in view of the carbon
nanofluid and preparation method described in the present
invention. Other embodiments of the invention will be apparent to
those skilled in the art from consideration of the specification
and practice of the invention disclosed herein. It is intended that
the specification and examples be considered as exemplary only,
with a true scope and spirit of the invention being indicated by
the following claims.
[0042] It be appreciated by those skilled in the art that changes
could be made to the embodiments described above without departing
from the broad inventive concept thereof. It is understood,
therefore, that this invention is not limited to the particular
embodiments disclosed, but it is intended to cover modifications
within the spirit and scope of the present invention as defined by
the appended claims.
* * * * *