U.S. patent application number 14/759953 was filed with the patent office on 2015-12-10 for thermal transfer system.
The applicant listed for this patent is WOODS HOLE OCEANOGRAPHIC INSTITUTION. Invention is credited to Glenn McDonald.
Application Number | 20150354902 14/759953 |
Document ID | / |
Family ID | 50033806 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150354902 |
Kind Code |
A1 |
McDonald; Glenn |
December 10, 2015 |
THERMAL TRANSFER SYSTEM
Abstract
A thermal transfer system for a pressure vessel adapted for use
in an underwater environment includes a housing having a bore
adapted to receive a heat pipe. Embodiments of the housing include
a mounting flange for mounting the housing to the pressure vessel,
a radially extending profile to enhance thermal transfer between
the housing and the underwater environment, and an aperture in
fluidic communication with the bore. A method of providing thermal
transfer between an interior of the pressure vessel and the
underwater environment includes inserting the heat pipe into the
bore, sealing a distal end of the bore, and mounting the housing to
the pressure vessel.
Inventors: |
McDonald; Glenn; (Marston
Mills, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WOODS HOLE OCEANOGRAPHIC INSTITUTION |
Woods Hole |
MA |
US |
|
|
Family ID: |
50033806 |
Appl. No.: |
14/759953 |
Filed: |
January 10, 2014 |
PCT Filed: |
January 10, 2014 |
PCT NO: |
PCT/US2014/011053 |
371 Date: |
July 9, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61750892 |
Jan 10, 2013 |
|
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|
Current U.S.
Class: |
165/45 ;
165/104.26 |
Current CPC
Class: |
F28D 15/0275 20130101;
H05K 7/20336 20130101; H05K 7/20936 20130101; F28F 1/12
20130101 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Claims
1. A thermal transfer system for a pressure vessel adapted for use
in an underwater environment, the thermal transfer system
comprising: an elongate housing forming a bore adapted to receive
therein a heat pipe, the housing comprising: a mounting flange
disposed at a proximal end of the housing for mounting the housing
to and aligning the bore with an aperture formed in the pressure
vessel; a radially extending profile disposed at least partially
along an intermediate portion of the housing, the profile adapted
to enhance thermal transfer between the housing and the underwater
environment; and an aperture formed in a distal end of the housing
in fluidic communication with the bore.
2. The thermal transfer system of claim 1, wherein the pressure
vessel forms at least a portion of at least one of an underwater
vehicle and a moored component.
3. The thermal transfer system of claim 1, wherein the housing bore
is sized to receive the heat pipe in at least one of a close
sliding fit, a braze fit, and a shrink fit.
4. The thermal transfer system of claim 1, wherein the heat pipe
comprises a sealed housing including a working fluid disposed
therein.
5. The thermal transfer system of claim 1, wherein the mounting
flange forms a series of apertures defining a bolt hole pattern for
receiving fasteners therethrough for affixing the flange to the
pressure vessel.
6. The thermal transfer system of claim 5, wherein the mounting
flange further forms a circumferential groove on a radial face
thereof adapted to receive a gland seal for sealing the flange to
an exterior surface of the pressure vessel.
7. The thermal transfer system of claim 6 further comprising a
gland seal disposed in the groove.
8. The thermal transfer system of claim 1, wherein the proximal end
of the housing comprises an extension adapted to be received in the
pressure vessel aperture.
9. The thermal transfer system of claim 8, wherein the extension
forms a circumferential groove on an outer surface thereof adapted
to receive a gland seal for sealing the extension in the pressure
vessel aperture.
10. The thermal transfer system of claim 9 further comprising a
gland seal disposed in the groove.
11. The thermal transfer system of claim 1, wherein the proximal
end of the housing comprises a threaded portion.
12. The thermal transfer system of claim 1, wherein the radially
extending profile comprises a plurality of fins.
13. The thermal transfer system of claim 12, wherein the plurality
of fins are disposed from the mounting flange to the distal end of
the housing.
14. The thermal transfer system of claim 1, wherein the bore
comprises the distal end aperture.
15. The thermal transfer system of claim 1 further comprising a
faceplate removably affixed to the distal end of the housing to
seal the distal end aperture.
16. The thermal transfer system of claim 15, wherein the faceplate
forms a series of apertures defining a bolt hole pattern for
receiving fasteners therethrough for affixing the cap to the distal
end of the housing.
17. The thermal transfer system of claim 16, wherein at least one
of the faceplate and the distal end of the housing forms a
circumferential groove on a respective radial face thereof adapted
to receive a gland seal for sealing the cap to the distal end of
the housing.
18. The thermal transfer system of claim 17 further comprising a
gland seal disposed in the groove.
19. The thermal transfer system of claim 1 further comprising the
heat pipe.
20. The thermal transfer system of claim 19 further comprising a
component in thermal communication with the heat pipe.
21. The thermal transfer system of claim 1 further comprising the
pressure vessel.
22. A method of providing thermal transfer between an interior of a
pressure vessel adapted for use in an underwater environment and
the underwater environment, the method comprising the steps of:
inserting a heat pipe into a bore formed in an elongate housing,
the bore extending from a proximal end to a distal end of the
housing; thereafter, sealing the distal end of the bore; and
mounting the proximal end of the housing to the pressure vessel so
that an exposed portion of the heat pipe extends into the interior
of the pressure vessel.
23. The method according to claim 22, wherein the pressure vessel
forms at least a portion of at least one of an underwater vehicle
and a moored component.
24. The method according to claim 22, wherein the housing bore is
sized to receive the heat pipe in at least one of a close sliding
fit, a braze fit, and a shrink fit.
25. The method according to claim 24 further comprising the step of
inserting a thermal compound into the bore to enhance thermal
transfer between the heat pipe and the housing when there exists
the close sliding fit.
26. The method according to claim 22, wherein the heat pipe
comprises a sealed housing including a working fluid disposed
therein.
27. The method according to claim 22, wherein the mounting step
comprises bolting the housing to the pressure vessel.
28. The method according to claim 27, further comprising the step
of sealing the housing to the pressure vessel.
29. The method according to claim 22, wherein the distal end of the
housing comprises a thermal transfer system.
30. The method according to claim 29, wherein the thermal transfer
system comprises a plurality of fins.
31. The method according to claim 22, wherein the sealing step
comprises attaching a faceplate to the distal end of the
housing.
32. The method according to claim 31, wherein the attaching step
comprises bolting the faceplate to the distal end of the
housing.
33. The method according to claim 31, further comprising the step
of sealing the faceplate to the distal end of the housing.
34. The method according to claim 22 further comprising the step of
mounting a component in thermal communication with the exposed
portion of the heat pipe.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of, and
incorporates herein by reference in its entirety, U.S. Provisional
Patent Application No. 61/750,892, which was filed on Jan. 10,
2013.
TECHNICAL FIELD
[0002] In various embodiments, the invention relates to heat
transfer systems and, more particularly, to devices and methods for
cooling pressure vessels in underwater environments.
BACKGROUND
[0003] Oceanographic systems for use in underwater environments
often include electronic components, housed within pressure
vessels, that generate heat and may cause the temperature inside
the pressure vessels to become excessive. Cooling devices may be
needed for removing heat from the pressure vessels, to extend
longevity and efficiency of the electronic components and/or
prevent undesired drifts in instrumentation.
[0004] The need for cooling of electronic components in
oceanographic systems is particularly significant for large,
all-electric, remotely operated vehicles (ROVs) and cabled
sea-floor observatories, which may utilize high power and telemetry
electronics. Although power-conversion devices have become smaller
and more efficient, the overall heat load per unit volume within
pressure vessels has increased dramatically. From a heat transfer
standpoint, the challenge is to remove a sufficient amount of heat
from the pressure vessels despite the limited heat transfer surface
area available within the pressure vessels.
[0005] Existing devices and methods for transferring heat from
pressure vessels in underwater environments include dry contact
methods, forced water cooling, and oil immersion techniques.
Unfortunately, each of these existing approaches has its drawbacks.
For example, in many instances, the surface area available for heat
transfer within the vessel may be inadequate for dry contact and
oil immersion methods. Further, forced water cooling methods
require moving parts (e.g., a pump) and are ineffective when the
moving parts fail and/or when an energy source for the moving parts
is not available.
[0006] There is a need for improved heat transfer systems for
pressure vessels in underwater environments. In particular, needs
exist for cooling systems that occupy minimal space within the
pressure vessels, operate passively (e.g., no mechanical moving
parts), and achieve sufficient heat transfer rates to meet current
and future demands.
SUMMARY OF THE INVENTION
[0007] In general, embodiments of the present invention feature
devices and methods for removing heat from pressure vessels in
underwater environments. The devices and methods achieve high rates
of heat transfer from the pressure vessels while occupying minimal
space within the pressure vessels. The devices and methods also
operate passively, without the use of mechanical moving parts,
making the devices less susceptible to failure than previous
devices, with little or no need for maintenance. Passive operation
of the devices also eliminates the need for a separate energy
source (e.g., a battery) for operating the device. The devices and
methods may instead be driven entirely by a temperature difference
between the inside of the pressure vessel and the underwater
environment outside of the pressure vessel.
[0008] In one aspect, embodiments of the invention relate to a
thermal transfer system for a pressure vessel adapted for use in an
underwater environment. The thermal transfer system includes a
housing (e.g., an elongate housing) forming a bore adapted to
receive a heat pipe (e.g., in a close sliding fit, a braze fit,
and/or a shrink fit). The housing includes: a mounting flange or
connection member disposed at a proximal end of the housing for
mounting the housing to and aligning the bore with an aperture
formed in the pressure vessel; a radially extending profile
disposed at least partially along an intermediate portion of the
housing, the profile adapted to enhance thermal transfer between
the housing and the underwater environment; and an aperture formed
in a distal end of the housing in fluidic communication with the
bore.
[0009] In certain embodiments, the pressure vessel forms at least a
portion of an underwater vehicle and/or a moored component. The
heat pipe may include, for example, a sealed housing including a
working fluid disposed therein. In one embodiment, the mounting
flange or connection member forms a series of apertures defining a
bolt hole pattern for receiving fasteners therethrough for affixing
the flange to the pressure vessel. The mounting flange may also
form a circumferential groove on a radial face thereof adapted to
receive a gland seal for sealing the flange to an exterior surface
of the pressure vessel. A gland seal may be disposed in the
groove.
[0010] In some embodiments, the proximal end of the housing
includes an extension adapted to be received in the pressure vessel
aperture. The extension may form a circumferential groove on an
outer surface thereof adapted to receive a gland seal for sealing
the extension in the pressure vessel aperture. A gland seal may be
disposed in the groove. The proximal end of the housing (e.g., the
connection member) may include a threaded portion (e.g., for
securing the housing in a threaded opening). In one embodiment, the
radially extending profile includes a plurality of fins, which may
be disposed from the mounting flange or connection member to the
distal end of the housing. In various embodiments, the bore
includes the distal end aperture. The thermal transfer system may
also include a faceplate removably affixed to the distal end of the
housing to seal the distal end aperture. In one embodiment, the
faceplate forms a series of apertures defining a bolt hole pattern
for receiving fasteners therethrough for affixing the cap or
faceplate to the distal end of the housing.
[0011] In certain embodiments, the faceplate and/or the distal end
of the housing form a circumferential groove on a respective radial
face thereof adapted to receive a gland seal for sealing the cap or
faceplate to the distal end of the housing. A gland seal may be
disposed in the groove. In various embodiments, the thermal
transfer system also includes the heat pipe, which may include at
least one bend. The thermal transfer system may also include a
component (e.g., a heated component and/or a heat generating
component) in thermal communication with the heat pipe. In some
embodiments, the thermal transfer system includes a heat transfer
device in thermal communication with the heat pipe and including at
least one fin. A fan may be in fluidic communication with the heat
transfer device (e.g., by blowing air on the at least one fin). In
one embodiment, the thermal transfer system includes the pressure
vessel.
[0012] In another aspect, embodiments of the invention relate to a
method of providing thermal transfer between an interior of a
pressure vessel adapted for use in an underwater environment and
the underwater environment. The method includes the steps of:
inserting a heat pipe into a bore formed in a housing (e.g., an
elongate housing), the bore extending from a proximal end to a
distal end of the housing; thereafter, sealing the distal end of
the bore; and mounting the proximal end of the housing to the
pressure vessel so that an exposed portion of the heat pipe extends
into the interior of the pressure vessel.
[0013] In certain embodiments, the pressure vessel forms at least a
portion of an underwater vehicle and a moored component. The
housing bore is preferably sized to receive the heat pipe in a
close sliding fit, a braze fit, and/or a shrink fit. The method may
also include the step of inserting a thermal compound into the bore
to enhance thermal transfer between the heat pipe and the housing
when there exists the close sliding fit. The heat pipe may include
or consist essentially of a sealed housing including a working
fluid disposed therein. In one embodiment, the mounting step
includes bolting the housing to the pressure vessel.
[0014] In various embodiments, the method also includes the step of
sealing the housing to the pressure vessel. The distal end of the
housing may include a thermal transfer system or radially extending
profile, which may include a plurality of fins. The sealing step
may include attaching a faceplate to the distal end of the housing.
For example, attaching the faceplate may include bolting the
faceplate to the distal end of the housing. The faceplate may also
be sealed to the distal end of the housing. In one embodiment, the
method also includes the step of mounting a component (e.g., a
heated component and/or a heat generating component) in thermal
communication with the exposed portion of the heat pipe.
[0015] The method may also include the step of mounting a heat
transfer device to the exposed portion of the heat pipe, wherein
the heat transfer device includes at least one fin. In one
implementation, the method includes blowing an internal pressure
vessel fluid (e.g., air) on the heat transfer device to achieve
convective heat transfer between the internal pressure vessel fluid
and the heat transfer device. At least one bend may be introduced
to the heat pipe.
[0016] These and other objects, along with advantages and features
of embodiments of the present invention herein disclosed, will
become more apparent through reference to the following
description, the figures, and the claims. Furthermore, it is to be
understood that the features of the various embodiments described
herein are not mutually exclusive and can exist in various
combinations and permutations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In the drawings, like reference characters generally refer
to the same parts throughout the different views. Also, the
drawings are not necessarily to scale, emphasis instead generally
being placed upon illustrating the principles of the invention. In
the following description, various embodiments of the present
invention are described with reference to the following drawings,
in which:
[0018] FIG. 1 is a schematic, cross-sectional view of a pressure
vessel and a cooling device, in accordance with an illustrative
embodiment of the invention;
[0019] FIG. 2 is a schematic, exploded view of a cooling device and
heat generating components, in accordance with an illustrative
embodiment of the invention;
[0020] FIG. 3 is a schematic, cross-sectional view of a cooling
device having a heat pipe, in accordance with an illustrative
embodiment of the invention;
[0021] FIG. 4 is a schematic, cross-sectional view of a cooling
device having two heat pipes, in accordance with an illustrative
embodiment of the invention;
[0022] FIG. 5 is a schematic, perspective view of four cooling
devices mounted to an endcap for a pressure vessel, in accordance
with an illustrative embodiment of the invention;
[0023] FIG. 6 is a schematic, side view of a cooling device having
an internal flow path for a cooling fluid, in accordance with an
illustrative embodiment of the invention;
[0024] FIG. 7 is a schematic, side view of a cooling device with a
bent heat pipe installed within a pressure vessel, in accordance
with an illustrative embodiment of the invention;
[0025] FIG. 8 is a schematic, perspective view of the cooling
device and the pressure vessel of FIG. 7, in accordance with an
illustrative embodiment of the invention; and
[0026] FIG. 9 is a schematic, perspective view of a heat transfer
device thermally coupled to a cooling device, in accordance with an
illustrative embodiment of the invention.
DESCRIPTION
[0027] Referring to FIG. 1, in various embodiments, a thermal
transfer system or cooling device 10 is provided for removing heat
from an interior portion of a pressure vessel 12. In general, the
pressure vessel 12 includes or contains heat generating components
14 (e.g., power converters or processors) that generate heat within
the pressure vessel 12, and the cooling device 10 transfers this
heat to a fluid (e.g., water) outside of the pressure vessel 12. By
removing heat from the pressure vessel 12, the cooling device 10
may prevent the temperature within the vessel 12 from becoming
excessive, which may cause the heat generating components 14 to
fail or otherwise perform improperly.
[0028] In the depicted embodiment, the pressure vessel 12 is
substantially cylindrical and includes a central tube portion 16
and two endcaps 18 mounted to axial ends of the tube portion 16.
Alternatively, the pressure vessel 12 may be or include any other
shape, such as spherical. The pressure vessel 12 may be made of any
material(s) having the desired thermal and mechanical properties.
For deep sea applications, the pressure vessel 12 is preferably
made of one or more materials that are capable of withstanding
extremely high pressures and are corrosion resistant. A preferred
material for the pressure vessel 12 is titanium (e.g., grade 5),
due to its high strength to weight ratio. In one example, the
endcaps 18 are made of grade 5 titanium, with each endcap 18 having
a diameter of about 10 inches and a thickness of about 2
inches.
[0029] Still referring to the embodiment in FIG. 1, the cooling
device 10 includes a housing 20 and a heat pipe 22. The housing 20
is attached to one of the endcaps 18 of the pressure vessel 12 and
resides substantially outside of the pressure vessel 12, within the
surrounding fluid. The heat pipe 22 includes a warm end 24 and a
cool end 26 and passes through an opening 28 in the pressure vessel
12. The warm end 24 of the heat pipe 22 is in thermal communication
with the one or more heat generating components 14 within the
pressure vessel 12. The cool end 26 of the heat pipe 22 is disposed
in a bore or cavity 30 within the housing 20. During operation of
the cooling device 10, the heat pipe 22 transfers heat from the
heat generating components 14 to the housing 20, which then
transfers the heat to the surrounding fluid. Like the pressure
vessel 12, the housing 20 is preferably made from titanium (e.g.,
grade 5), although any other material (e.g., aluminum, copper,
and/or stainless steel) that provides the desired structural and
thermal properties may be utilized.
[0030] The housing 20 may be secured to the endcap 18 using any
suitable attachment method or connection member. For example, as
depicted, the housing 20 may include a threaded end 31 that engages
with threads in the opening 28 of the endcap 18. Alternatively or
additionally, the housing 20 may include a flange portion 32 that
is secured to the endcap 18 using, for example, one or more screws
or other fasteners. In general, the housing 20 and/or the pressure
vessel 12 include one or more seals 33 (e.g., gland seals, pressure
resistant seals, or the like disposed in grooves) to provide a
sealed connection and prevent materials (e.g., water) from entering
or exiting the pressure vessel 12.
[0031] The heat pipe 22 is typically a sealed, thermally conductive
pipe or tube (e.g., a copper tube) that contains a working fluid or
phase-change material. In its liquid form, the phase change
material evaporates when it comes into contact with the warm end 24
of the tube. The vapor then travels to the cool end 26 of the tube
where the phase change material condenses back to a liquid,
releasing latent energy. The liquid returns to the warm end 24 of
the tube (e.g., with the aid of capillary action along the tube
wall) where the liquid evaporates again and the cycle is repeated.
Advantageously, the heat pipe 22 contains no moving mechanical
parts and generally requires little or no maintenance. Compared to
conventional heat sinks, the heat pipe 22 is generally smaller and
lighter (i.e., less thermal inertial) and has a faster response
time. The small size of the heat pipe 22 occupies minimal space
within the pressure vessel 12, and allows the packaging geometry
within the pressure vessel 12 to accommodate other design
requirements. A suitable heat pipe for the cooling devices
described herein is a THERMAL PIN.TM., manufactured by NOREN
products, Inc., of Menlo Park, Calif., or a heat pipe manufactured
by Thermacore, Inc., of Lancaster, Pa. A cylindrically shaped heat
pipe with water or water and alcohol as the phase change material
may work well in many applications.
[0032] In general, the heat pipe 22 may have any size and/or shape.
For example, a diameter or cross-dimension of the heat pipe 22 may
be from about 0.1 inches to about 1 inch, or preferably about 0.25
inches, about 0.375 inches, or about 0.5 inches. An axial length of
the heat pipe 22 may be, for example, from about 4 inches to about
40 inches, or preferably about 20 inches. Actual diameters and/or
axial lengths may vary from application to application.
[0033] Although the cooling device 10 generally includes a heat
pipe 22 that is a separate component from the housing 20, in
alternative embodiments, the housing 20 and the heat pipe 22 may be
the same component. For example, the housing 20 may include an
integrated heat pipe that is fabricated directly into the housing
20.
[0034] In general, to achieve optimal heat transfer between the
heat generating components 14 and the cooling device 10, it is
preferable to position the hottest components 14 closest to the
housing 20. Such positioning minimizes the distance heat must
travel through the heat pipe 22 before being transferred to the
housing 20 and the surrounding environment. Heat transfer between
the components 14 and the heat pipe 22 is also improved by keeping
any intermediate layers (e.g., metal layers) as thin and thermally
conductive as possible (e.g., by using thin layers of copper or
aluminum), and by avoiding any air gaps between the components 14
and the heat pipe 22. Flat surfaces are generally preferable to
improve contact between the heat pipe 22 and the components 14, and
to avoid air gaps. Any air gaps may be filled with suitable heat
conductive pastes and/or other heat conductive materials, such as
settable polymers and/or glues.
[0035] FIG. 2 is an exploded view of the housing 20, the heat pipe
22, and the heat generating components 14, in accordance with
certain embodiments of the invention. As depicted, the heat
generating components 14 are attached to a mounting plate 34 having
a bore 36 for receiving the warm end 24 of the heat pipe 22. The
heat generating components 14 may be attached to the mounting plate
34 using any acceptable attachment device, such as screws and/or
adhesive. In the depicted embodiment, the mounting plate 34
includes two separate plates that together form the bore 36 for
receiving the heat pipe 22. A thermally conductive grease, paste
(e.g., a silver-based thermal compound), or self-setting heat
conducting putty paste or glue, may be included within the bore 36,
to improve heat transfer between the bore 36 and the heat pipe
22.
[0036] Referring to FIG. 3, in certain embodiments, a distal end of
the housing 20 includes a face plate 40 which may be removed to
facilitate insertion of the cool end 26 of the heat pipe 22 into
the cavity 30 (e.g., to allow gases to escape). The face plate 40
may be attached to the remainder of the housing 20 using, for
example, screws or other fasteners. One or more seals 42 (e.g.,
gland seals disposed within grooves) may be included to provide a
sealed connection. In various embodiments, the cavity 30 is sized
and toleranced to achieve a small gap (e.g., about 0.001 inches)
and a close sliding fit between the heat pipe 22 and the cavity 30,
around the outer surface of the heat pipe 22. A thermally
conductive grease or paste (e.g., a silver-based thermal compound)
may be disposed within the gap to eliminate air pockets and improve
heat transfer between the cavity 30 and the heat pipe 22. Due to
the small gap and the grease filling the gap, a vacuum lock may be
achieved within the cavity 30 that maintains the heat pipe 22 in a
fixed position within the cavity 30. In alternative applications,
the heat pipe 22 may be secured to the housing 20 with a braze fit
and/or a shrink fit.
[0037] In certain instances, when the heat pipe 22 is pressed into
the housing 20, a vapor lock prevents the heat pipe 22 from fully
seating in the housing 20, due to an inability of gas to escape
from the cavity 30. By removing the face plate 40 during insertion
of the heat pipe 22, however, any gases trapped behind the heat
pipe 22 can freely escape from the housing 20, which allows the
heat pipe 22 to be fully seated within the housing 20. After the
heat pipe 22 is properly seated, the face plate 40 may be
reinstalled to seal or plug the cavity 30.
[0038] In some implementations, the face plate 40 is replaced with
a plug or other suitable device for sealing the cavity. For
example, a threaded plug may be inserted into a threaded end of the
cavity 30 to seal the cavity 30. The face plate 40 or other sealing
device is preferably removable to facilitate replacement,
insertion, or removal of the heat pipe 22, as needed.
[0039] In general, the outer surface of the housing 20 is designed
to promote heat transfer with and/or resist the hydrostatic
pressure of the surrounding fluid. For example, in the depicted
embodiment, the housing 20 includes one or more fins 44 that extend
radially from the housing 20, to increase an outer surface area of
the housing 20. The fins 44 may have any shape and orientation, but
generally are shaped in a way to optimize heat transfer and prevent
housing collapse due to hydrostatic pressure. For example, the fins
44 may be aligned with a circumferential direction (as shown)
and/or an axial direction of the housing 20. Other surface
features, such as textures, roughness, or protrusions may likewise
be utilized to improve the heat transfer from the housing 20. In
certain embodiments, the fins 44 extend in a radial direction from
the housing 20 by a distance from about 0.1 inches to about 4
inches, from about 0.5 inches to about 2 inches, or about 1 inch.
Alternatively, the housing 20 may not include the fins 44.
[0040] In certain embodiments, the fins 44 on the housing 20 are
shaped and/or configured to promote convective heat transfer with
the surrounding fluid. For example, when the housing 20 is attached
to or forms part of a moving underwater vehicle, the fins 44 may be
arranged in a corkscrew pattern or include channels that direct or
funnel the fluid over the fins 44. Such fin arrangements may be
used to increase fluid velocities over the fins 44, thereby
increasing heat transfer coefficients and heat transfer rates
between the fins 44 and the surrounding fluid.
[0041] In various embodiments, the cooling devices described herein
include more than one heat pipe per cooling device. For example,
referring to FIG. 4, a housing 50 may include two cavities 30 for
receiving two heat pipes 22. With more than one heat pipe 22, the
housing 50 is generally capable of removing more heat from within
the pressure vessel. In general, any number of heat pipes 22 may be
included within a single cooling device. As depicted, the housing
50 may include a flange portion 52 with openings 54 for receiving
one or more fasteners (e.g., screws) to secure the housing 50 to
the pressure vessel.
[0042] Likewise, in some embodiments, the endcap may include more
than one opening for receiving more than one cooling device. For
example, referring to FIG. 5, an endcap 60 includes four openings
for receiving four cooling devices 10. Each cooling device 10
includes the housing 20 and the heat pipe 22 inserted within the
housing 20. Inside the pressure vessel, heat generating components
14 are attached to mounting plates 64, which include bores for
receiving the heat pipes 22. As depicted, the mounting plates 64
may be attached to endplates 66 that may help stabilize or position
the mounting plates 64. One or both endplates 66 may be secured to
the endcap 60 using, for example, spacers 68 and/or screws. In
general, using multiple cooling devices 10 per endcap increases the
available rate of heat transfer from the pressure vessel. While the
cooling devices described herein are generally intended for use in
underwater environments, in some instances, a cooling device is
used to cool a pressure vessel that is above water (e.g., on the
deck of a ship). Referring to FIG. 6, to provide heat removal in
above-water applications, a housing 70 may include an internal
passage or flow path 72 through which a cooling liquid (e.g.,
water) is pumped. A fitting may be attached at each end of the flow
path 72 to connect the flow path 72 to tubing and/or a pump. As the
cooling liquid is pumped through the housing 70, the cooling device
transfers heat from the heat generating components to the cooling
liquid. The flowrate of the cooling liquid through the housing 70
can be adjusted depending on the temperature of the cooling water,
the material used for the housing and the amount of heat to be
removed.
[0043] Alternatively, heat removal in above-water applications may
be provided by contacting an outer surface of a housing with the
cooling liquid. For example, a sleeve, tube, or hose may be fitted
over a finned surface of the housing, and the cooling liquid may be
pumped through the sleeve, tube, or hose. The finned surface may
include a corkscrew or other fin pattern that directs the cooling
liquid over and around the housing to achieve improved convective
heat transfer between the housing and the cooling liquid. After
passing through the sleeve, tube, or hose, the cooling liquid may
drain away from the unit and/or return to the cooling liquid
supply, which may be a tank or other body of water (e.g., an ocean,
lake, or river).
[0044] Referring to FIGS. 7 and 8, in certain embodiments, a heat
pipe 76 includes one or more bends 78 that allow the heat pipe 76
to occupy a desired position within a pressure vessel 80. For
example, the pressure vessel 80 may include electrical components
82 or other objects disposed within a center of the pressure
vessel, such that a warm end 84 of the heat pipe 76 cannot occupy
the center of the pressure vessel 80. In such instances, the heat
pipe 76 may not extend in a straight line from the housing 20 but
may, instead, be bent to avoid the center of the pressure vessel
80. In the depicted embodiment, two heat pipes 76 are bent to avoid
the center of the pressure vessel 80 and position the warm ends 84
of the heat pipes 76 closer to an interior wall 86 of the pressure
vessel 80. The bent shape also allows the warm end 84 of the heat
pipe 76 to be elevated above the housing 20, which may improve heat
transfer efficiency within the heat pipe 76. For example, by
elevating the warm end 84 of the heat pipe 76, condensate within
the heat pipe 76 may be able to collect more easily, due to
gravity, at a lower, cool end of the heat pipe 76, such that the
condensate is more easily wicked back up to the warm end 84.
[0045] Referring to FIG. 9, in some implementations, a warm end 90
of a heat pipe 92 is attached to or otherwise in thermal
communication with a heat transfer device 94. The heat transfer
device 94 may include a bore 96 for receiving the heat pipe 92,
e.g., in a close sliding fit, a braze fit, or a shrink fit. The
heat transfer device 94 may also include one or more fins 98 for
increasing heat transfer rates to a fluid (e.g., air) within the
pressure vessel. A fan 100 may be used to blow the fluid within the
pressure vessel across the heat transfer device 94, to achieve
forced convection between the heat transfer device 94 and the
fluid. Advantageously, the heat transfer device 94 allows the
temperature of the fluid within the pressure vessel to be
controlled, which may also help control the temperature of remote
components within the pressure vessel (e.g., components that are
not directly attached or thermally coupled to the heat pipe 92). In
the depicted embodiment, heating generating components 102 (e.g.,
dc-dc converters) are attached to the heat transfer device 94. Heat
from the heat generating components 102 may be transferred by
conduction through the heat transfer device 94 and into the heat
pipe 92, which transfers the heat to a housing 104.
[0046] In certain embodiments, the objects or components to be
cooled need not be housed or contained within a pressure vessel.
For example, the objects or components to be cooled may be
thermally isolated from the surrounding environment but be exposed
to the same pressure as the surrounding environment.
[0047] In underwater applications, the pressure vessel 12 may be a
component of an underwater vehicle, such as an ROV or an Autonomous
Underwater Vehicle (AUV). For example, an ROV 80 may include one or
more pressure vessels 12, and each pressure vessel 12 may include
any number (e.g., 1, 2, or 4) of cooling devices. In alternative
applications, the pressure vessel 12 may be moored, for example, as
a component in a sea-floor observatory.
[0048] Various techniques may be used to manufacture the cooling
devices described herein. A brief list of acceptable machining and
fabrication techniques includes: wire electrodynamic machining
(wire EDM), ram EDM, abrasive water jet machining, electroplating
and electroforming, modern bonding methods, spin welding, friction
stir welding, vacuum furnace brazing, and hydrogen furnace brazing.
Water-jet and EDM methods lend themselves to working refractory
metals and other hard-to-machine metals such as titanium and
copper. EDM is appropriate when tight tolerances are required. Wire
EDM is most often used with plate stock and ram EDM is most often
employed when blind holes are needed in refractory metal. Water jet
also is excellent for hard-to-machine plate stock, but should be
utilized when designs are not predicated on higher tolerances and
exactness of fit that conventional lathe and mill operation are
capable of performing. In instances where limited cross-sectional
areas are available in conductive interfaces, it may be important
to maximize the effective contact area. While being mindful of
intermediate assembly requirements, modern bonding methods should
be considered to ensure effective contact.
[0049] Advantageously, the cooling devices and methods described
herein may be used to transfer heat from any objects or components
that generate or otherwise store heat. The objects or components
may be, for example, electronics, solid state electronics, power
converters, processors, data storage devices, motors, friction
points, winches, batteries, power sources, fluids (e.g., hot water
or air), and lights.
EXPERIMENTS
[0050] For the cooling devices described herein, a heat transfer
rate q may be expressed as q=hA(T.sub.in-T.sub.out), where h is a
heat transfer coefficient, A is a heat transfer area (e.g., an
outer surface area of the housing), T.sub.in is a temperature
inside the vessel, and T.sub.out is a temperature outside the
vessel. When the cooling device includes a single heat pipe, the
heat transfer rate q may be, for example, from about 5 W to about
500 W, or from about 25 W to about 100 W. For example, with a
single half-inch heat pipe (i.e., a heat pipe with a diameter of
0.5 inches), the heat transfer rate q achieved by the cooling
device may be from about 50 W to about 70 W. When the cooling
device includes more than one heat pipe, the heat transfer rate q
may increase accordingly, though not necessarily in a linear
fashion. For example, in one experiment, the heat transfer rate was
measured to be about 100 W for a cooling device that included two
half-inch heat pipes. In one instance, four cooling devices, each
having two half-inch heat pipes, were measured to achieve a heat
transfer rate of about 400 W.
[0051] In general, the heat transfer rate q for the cooling devices
is proportional to a difference between the temperature inside the
vessel and the temperature outside the vessel T.sub.out. For
example, when the outside temperature T.sub.out is reduced, the
heat transfer rate from the vessel may be correspondingly
increased. In one experiment, the temperatures inside and outside
the vessel (i.e., T.sub.in, and T.sub.out, respectively) were
measured during steady state operation of a cooling device having
two heat pipes. The test indicated that the cooling device was
capable of maintaining a temperature difference of 30.degree. C.
between these two locations.
[0052] In general, the heat transfer rate q achieved by the cooling
devices described herein increases as the difference between
T.sub.in, and T.sub.out increases. The cooling devices may remove
heat from the pressure vessel when T.sub.in is greater than
T.sub.out.
[0053] In various embodiments, the heat transfer coefficient h for
a cooling device with a single heat pipe may be, for example, from
about 100 W/m.sup.2-K to about 300 W/m.sup.2-K. In one instance,
the heat transfer coefficient h was estimated to be about 180
W/m.sup.2-K, through experimentation and numerical analysis.
Exemplary system parameters for the cooling devices and methods
described herein are presented in Table 1.
TABLE-US-00001 TABLE 1 Exemplary system parameters. Parameter Min.
Typical Max. Number of heat pipes per housing 1 1 4 Number of
cooling devices per endcap 1 2 4 Heat transfer for cooling devices
(W) 5 50 500 Heat pipe length (inches) 4 20 40 Heat pipe diameter
(inches) 0.1 0.5 1 Radial height of fins on housing (inches) 0 1
4
[0054] Each numerical value presented herein, for example, in a
table, a chart, or a graph, is contemplated to represent a minimum
value or a maximum value in a range for a corresponding parameter.
Accordingly, when added to the claims, the numerical value provides
express support for claiming the range, which may lie above or
below the numerical value, in accordance with the teachings herein.
Absent inclusion in the claims, each numerical value presented
herein is not to be considered limiting in any regard.
[0055] The terms and expressions employed herein are used as terms
and expressions of description and not of limitation, and there is
no intention, in the use of such terms and expressions, of
excluding any equivalents of the features shown and described or
portions thereof. In addition, having described certain embodiments
of the invention, it will be apparent to those of ordinary skill in
the art that other embodiments incorporating the concepts disclosed
herein may be used without departing from the spirit and scope of
the invention. The features and functions of the various
embodiments may be arranged in various combinations and
permutations, and all are considered to be within the scope of the
disclosed invention. Accordingly, the described embodiments are to
be considered in all respects as only illustrative and not
restrictive. Furthermore, the configurations, materials, and
dimensions described herein are intended as illustrative and in no
way limiting. Similarly, although physical explanations have been
provided for explanatory purposes, there is no intent to be bound
by any particular theory or mechanism, or to limit the claims in
accordance therewith.
* * * * *