U.S. patent application number 11/306527 was filed with the patent office on 2007-07-05 for heat pipes with self assembled compositions.
Invention is credited to Igor Victorovich Touzov.
Application Number | 20070151708 11/306527 |
Document ID | / |
Family ID | 38223166 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070151708 |
Kind Code |
A1 |
Touzov; Igor Victorovich |
July 5, 2007 |
Heat pipes with self assembled compositions
Abstract
Technology of the invention enables use of new engineering
materials in design of heat pipes with novel properties and
improved performance. In particular milled carbon fibers, carbon
nanotubes can be used for construction of high performance
wicks.
Inventors: |
Touzov; Igor Victorovich;
(Cary, NC) |
Correspondence
Address: |
IGOR V TOUZOV
212 CRESTONE DRIVE
CARY
NC
27513
US
|
Family ID: |
38223166 |
Appl. No.: |
11/306527 |
Filed: |
December 30, 2005 |
Current U.S.
Class: |
165/104.26 |
Current CPC
Class: |
F28D 15/046 20130101;
B82Y 30/00 20130101; F28F 21/02 20130101 |
Class at
Publication: |
165/104.26 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Claims
1. A heat pipe having a capillary structure commonly known as a
wick, and a liquid, wherein there is a chemical substance or
substances present on interface of the liquid and the material of
the wick, and said chemical substance or substances improve
capillary properties of said material with respect to said
liquid.
2. A device of claim 1, wherein said material is carbon in any of
its forms e.g. graphite, diamond, fullerene, fiber, amorphous.
3. A device of claim 1, wherein said material is natural or
synthetic polymer.
4. A device of claim 1, wherein said material is inorganic or
ceramic composite.
5. A device of claim 1, wherein said material is metal or
alloy.
6. A heat pipe wherein a wick structure composed primarily of
carbon fiber or carbon tube based material and a heat transfer
liquid of the pipe forms self-assembled layers or domains of
self-assembled structures on surface of graphite crystals or forms
self-assembled aggregates on edges and pits of crystal plates of
graphite.
7. A device of claim 6, wherein said liquid is one of commercially
available refrigerants which may include R-13, R-114 and
others.
8. A device of claim 6, wherein said wick composed of a felt like
material with primary content of milled graphite or carbon fibers
or tubes.
Description
CITED PUBLICATIONS
[0001] "Ordered Adlayers of a Non-Planar Molecule on a Surface:
Misfit Monolayers and Intercalated Bilayers as the Result of a
Dialkyl Amino Group", Gorman, C. B.; Miller, R. L., Touzov, I.,
Langmuir, 1998,14, 3052-3061
[0002] Tuzov I., Cramer K., Pfannemuller B., Magonov S. N., Whangbo
M. H., "Characterization of N-Alkyl-D Gluconamide Adsorbate
Structures by Atomic-Force Microscopy. 1. Microcrystals and layered
Structures", NEW JOURNAL OF CHEMISTRY 1996, Vol. 20, Iss 1, pp.
23-36.
[0003] Tuzov I., Cramer K., Pfannemuller B., Magonov S. N., Whangbo
M. H., "Characterization of N-Alkyl-D Gluconamide Adsorbate
Structures by Atomic-Force Microscopy. 2. Supramolecular
Structures", NEW JOURNAL OF CHEMISTRY 1996, Vol. 20, Iss 1, pp.
37-52.
[0004] Cramer K., Demharter S., Mulhaupt R., Frey H., Magonov S.
N., Tuzov I., Whangbo M. H., "Characterization of Supramolecular
Assemblies of N (N-Alkyl)-N'-D-Maltosylsemicarbazone Adsorbates by
Atomic-Force Microscopy", NEW JOURNAL OF CHEMISTRY 1996, Vol. 20,
Iss 1, pp. 2-11.
[0005] Tuzov I. V., Yaminsky I. V., "Scanning Force Microscopy
Visualization of Adsorption from Liquids", RUSSIAN CHEMICAL
BULLETIN 1 995, Vol. 44, Iss 11, pp. 2073-2078.
[0006] Tuzov I., Cramer K., Pfannemuller B., Kreutz W, Magonov S.
N., Molecular-Structure of Self-Organizes Layers of
N-Octyl-D-Gluconamide". ADVANCED MATERIALS, 1995, Vol. 7, Iss 7,
pp. 656-659.
[0007] Tuzov I. V., Klinov D. V., Demin V. V., "Catalytic Method
for modifying the Surface of Pyrolytic-Graphite", RUSSIAN CHEMICAL
BULLRTIN, 1994, Vol. 43, ISS 7, pp. 11 28-1131.
FIELD OF INVENTION
[0008] Objective of this invention is to provide solution that
improves overall efficiency of heat pipes and allows significant
size and weight reduction for thermal management solutions using
novel engineering materials.
PRIOR ART
[0009] Heat pipes are capable of producing significant heat flux
and have low weight characteristics. Their structure has two
essential elements a wick and a shell. Maximum transmitted heat is
commonly constrained by ability of the wick to transport working
liquid from condenser region to evaporating region.
[0010] Efficiency of the transport strongly bound to a surface
angle of the liquid on the wick material, effective average
capillary diameter, and effective average capillary length
throughout the wick structure. To reduce surface angle the material
of a wick should be compatible with selected liquid. Current use of
metal wicks is very common in conjunction with water.
[0011] Advances of new materials such as polymer, carbon, graphite,
and Al/SiC fibers have a potential that could improve some of
characteristics of heat pipes. Nevertheless they do not easily
merge into new designs of heat pipes. Prior art explored a
feasibility of use graphite fiber based structures to passively
transfer heat from heat sources (U.S. Pat. Nos. 6,286,591,
5,720,339, 5,269,369, 4,018,269). Unfortunately none of the
previous inventions provide sufficient heat conductivity in
moderate temperature range. Graphite and carbon wicks show high
efficiency when used in conjunction with liquid metals as a heat
transfer fluid (NASA). Unfortunately this requires very high
temperatures and introduces hazardous materials that restrict the
range of product applications.
[0012] Due to hydrophobic nature of graphite and carbon surfaces
the use of water as a working fluid is virtually impossible.
Objective of this invention is to demonstrate a use of nanoassembly
properties to allow employment of a broad variety of wick materials
in combinations with nontraditional working liquids. TABLE-US-00001
TABLE 1 Traditional liquids and materials for heat pipe selection.
Measured Heat Pipe Heat Pipe axial(8) Measured Temperature Working
Vessel heat flux surface(8) heat Range (.degree. C.) Fluid Material
(kW/cm2) flux (W/cm2) -200 to -80 Liquid Stainless 0.067 @ 1.01 @
-163.degree. C. Nitrogen Steel -163.degree. C. -70 to +60 Liquid
Nickel, 0.295 2.95 Ammonia Alumi- num, Stainless Steel -45 to +120
Methanol Copper, 0.45 @ 75.5 @ 100.degree. C. Nickel, 100.degree.
C. Stainless (x) Steel +5 to +230 Water Copper, 0.67 @ 146 @
170.degree. C. Nickel 200.degree. C. +190 to +550 Mercury*
Stainless 25.1 @ 181 @ 750.degree. C. +0.02% Steel 360.degree.
Magnes- C.* ium +0.001% +400 to +800 Potas- Nickel, 5.6 @ 181 @
750.degree. C. sium* Stainless 750.degree. C. Steel +500 to +900
Sodium* Nickel, 9.3 @ 224 @ 760.degree. C. Stainless 850.degree. C.
Steel +900 to +1,500 Lithium* Niobium 2.0 @ 207 @ 1250.degree. C.
+1% 1250.degree. C. Zirconium 1,500 + 2,000 Silver* Tantalum 4.1
413 +5% Tungsten
DETAILED DESCRIPTION
[0013] Preferred embodiment of the invention utilizes water as the
work liquid and uses graphite fibers for wick material. The liquid
composition contains minuscule amounts of surface active
nanostructural additive N-octyl-D-gluconamide. The additive as
shown on FIG. 1 forms stable liquid crystal monolayer on
hydrophobic surface of carbon or epitaxial crystalline monolayer of
surface of graphite. This nanostructure is self formed and creates
stable hydrophilic interface (SAM) between liquid water and the
wick.
[0014] For sustained operation of a heat pipe it is important that
nanoassembly does not migrates with the flow of the liquid and has
ability of self-regeneration. For lower temperature range
self-regenerative activity of N-octyl-D-gluconamide crystals
diminishes and this component can be substituted with
N-heptyl-D-gluconamide which is less efficient at high
temperatures.
[0015] Amount of the additive is chosen based on total surface area
of the wick. Some excess of the additive will not harm the pipe
operation as it will be adsorbed by evaporator surface. Due to
natural diffusion a miniscule amounts of the additive will remain
distributed through the volume of the liquid in form of
nano-particles and individual molecules. Array of nanostructures
formed by this compound is shown on FIG. 2. These structures absorb
free molecules from the solvent. Because of large size they are
limited in mobility and easily absorbed by the SAM layer.
Occasional damages in the crystalline nanostructure will utilize
these nanostructures to repair the damage.
[0016] Other chemicals and nanostructures such as detergent, and
liposomes can be used in place of the additive. Examples of such
substances are phospholipids, SDS, alcohols, organic acids, organic
salts etc. They are well known to chemists and biologists. Some of
them are well characterized as well as their self-assembled
behaviors. The methods of their synthesis and preparations are well
documented in scientific and industrial literature.
[0017] Graphite fibers are hydrophobic and will prevent capillary
phenomena for water. Use of proposed additives creates nanoscale
SAM (self assembled monolayer structure) covering entire surface
area of the fibers and permitting capillary transport for the
water. Benefits of using water are obvious. It has low chemical
activity, high specific heat of fusion and heat of evaporation.
[0018] Technology disclosed in this invention enables other wick
materials such as Kevlar, UHMWPE, glass, rubber, silicone, ceramic,
etc. to become usable in commercial heat pipes. Their advantages
and peculiarities are well known and do not alter the essence of
the invention. The liquid selection does not limit the subject of
the invention as there are well known guidelines for selection of
working fluid for heat management applications, and virtually any
liquid including metals can be employed within boundaries of the
technology of the invention. As an example a long chain thiols as
the additive component increase oleofilic properties of metal wick
thus increase its performance with organic solvents and inorganic
oils.
EXAMPLE
[0019] Sometime it is possible to select a liquid that is reveal
nanoassembly properties on interface with some solid materials. In
this case self assembled monolayer of molecules of the liquid or
their nanomers will be formed on solid interface. This behavior is
well known to occur for some compound on surface of HOPG. As
example 5-(N,N-Didecylamino)-2,4-pentadienal forms stable domains
visible through STM and SPM techniques. Interestingly enough broad
range of organic liquids reveal similar abilities. In particular
commercially available refrigerants: TABLE-US-00002 Freezing
Boiling point Point atmos- atmospheric pheric pres- Refri- Mole-
pressure 14.7 sure 14.7 gerant cular psia, 1 bar psia, 1 bar No.
Name Mass abs) (.degree. F.) abs (.degree. F.) R-11
Trichlorofluoromethane 137.38 75 -168 R-13 Chlorotrifluoromethane
104.47 -115 -294 R-13B1 Bromotrifluoromethane 148.93 -72 -270 R-14
Tetrafluoromethane 88.01 -198 -299 (Carbon tetrafluoride) R-22
Chlorodifluoromethane 86.48 -41 -256 R-40 Chloromethane 50.49 -12
-144 R-113 Trichlorotrifluoroethane 187.39 118 -31 R-114
1,2-dichloro-1,1,2,2- 170.94 39 -137 tetrafluoroethane R-115
Chloropentafluoroethane 154.48 -38 -159 R-123
Dichlorotrifluoroethane 152.93 82 -161 R-134a Tetrafluoroethane
102.03 -15 -142 R-142b 1-chloro-1,1-difluoro- 100.50 14 -204 ethane
R-290 Propane 44.10 -44 -306 RC-318 Octafluorocyclobutane 200.04 22
-43 R-500 Dichlorodifluorometh- 99.31 -28 -254 ane/Difluoroethane
R-502 Chlorodifluoromethane/ 111.63 -50 Chloropentafluoroethane
R-503 Chlorotrifluoromethane/ 87.50 -128 Trifluoromethane R-600
Butane 58.13 31 -217 R-600a Isobutane 58.13 11 -256 R-611 Methyl
formate 60.05 89 -146
These chemicals have dynamic viscosity at moderate temperatures
nearly an order or magnitude less then water. Use of carbon fibers
for wick material makes heat pipe construction 2-4 times lighter
than use of traditional metal wicks. In particular a felt like wick
can be constructed from low cost milled carbon fiber. In our
example R-114 refrigerant is used. At 60.degree. C. it has surface
tension of 0.007 N/m and viscosity of 0.000187 Pa*s, which allows
for construction of heat pipe with dimensions of traditional water
base pipe while having wick weight nearly three times less.
* * * * *