U.S. patent application number 13/672514 was filed with the patent office on 2013-07-04 for modular heat shield and heat spreader.
This patent application is currently assigned to Teledyne Scientific & Imaging, LLC. The applicant listed for this patent is Teledyne Scientific & Imaging, LLC. Invention is credited to Qingjun Cai, Bing-Chung Chen, Ya-Chi Chen, Kyle D. Gould, TADEJ SEMENIC.
Application Number | 20130168057 13/672514 |
Document ID | / |
Family ID | 48693910 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130168057 |
Kind Code |
A1 |
SEMENIC; TADEJ ; et
al. |
July 4, 2013 |
MODULAR HEAT SHIELD AND HEAT SPREADER
Abstract
A modular heat shield and heat spreader ("MHS") includes top and
bottom panels, and a plurality of thermally conductive pillars
located between the panels and which support the top panel. A
continuous pool of liquid between the panels surrounds some portion
of the pillars. Heat to which the top panel is exposed is conducted
through the top panel and at least some of the pillars. The heat
changes the phase of some of the liquid to a vapor, which spreads
the heat to an area larger than that of the heat source and thereby
dissipates the heat away from the source at a lower heat flux than
that associated with the flux from the source. The MHS preferably
includes wicking material on some of the pillars and on the
underside of the top panel, such that the wicking material is
saturated with the liquid and heated by the conducted heat.
Inventors: |
SEMENIC; TADEJ; (Camarillo,
CA) ; Chen; Bing-Chung; (Newbury Park, CA) ;
Cai; Qingjun; (Newbury Park, CA) ; Chen; Ya-Chi;
(Simi Valley, CA) ; Gould; Kyle D.; (Los Angeles,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Teledyne Scientific & Imaging, LLC; |
Thousand Oaks |
CA |
US |
|
|
Assignee: |
Teledyne Scientific & Imaging,
LLC
Thousand Oaks
CA
|
Family ID: |
48693910 |
Appl. No.: |
13/672514 |
Filed: |
November 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61581930 |
Dec 30, 2011 |
|
|
|
Current U.S.
Class: |
165/104.26 ;
165/104.21 |
Current CPC
Class: |
H01L 2924/0002 20130101;
F28D 15/046 20130101; H01L 2924/00 20130101; H01L 2924/0002
20130101; F28F 2265/12 20130101; F28D 15/0233 20130101; F28F
2265/10 20130101; B64G 1/50 20130101; F28D 15/02 20130101; H01L
23/427 20130101; H01S 5/02469 20130101 |
Class at
Publication: |
165/104.26 ;
165/104.21 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with Government support under Office
of Naval Research contract N00014-10-C-252 awarded by the United
States Department of Defense. The Government has certain rights in
this invention.
Claims
1. A modular heat shield and heat spreader (MHS), comprising: a top
panel; a bottom panel; a plurality of thermally conductive pillars
located between said top and bottom panels such that said pillars
support said top panel; and a continuous pool of liquid between
said top and bottom panels such that at least a portion of at least
some of said pillars is surrounded by said liquid; such that heat
from a heat source to which said top panel is exposed is conducted
through said top panel and at least some of said pillars and said
heat changes the phase of at least some of said liquid to a vapor,
said vapor spreading said heat to an area larger than the area of
the heat source and thereby dissipating said heat away from said
heat source at a lower heat flux than that associated with said
heat flux from said heat source.
2. The MHS of claim 1, further comprising wicking material on at
least some of said pillars and on the underside of at least a
portion of said top panel, such that at least some of said wicking
material is saturated with said liquid and heat from said heat
source is conducted through at least some of said liquid saturated
wicking material.
3. The MHS of claim 2, wherein additional wicking material is
formed into columns adjacent to at least some of said pillars which
connect said top and bottom panels such that the liquid can flow
from said continuous pool of liquid to the top panel through said
wicking material columns.
4. The MHS of claim 2, further comprising a wicking material on the
topside of at least a portion of said bottom panel, such that at
least some of said liquid is transported against gravity via said
wicking material when the heat shield and heat spreader is
tilted.
5. The MHS of claim 1, arranged such that said liquid pool includes
only as much liquid as needed to fill the voids between said
wicking material.
6. The MHS of claim 1, wherein said top and bottom panels and said
pillars form a single module, said MHS comprised of a plurality of
said modules joined together at their edges such said modules share
a common continuous pool of liquid and said vapor can dissipate
heat away from the modules nearest said heat source towards other
ones of said modules.
7. The MHS of claim 6, wherein the top and bottom panels of each of
said modules is arranged such that each module is hermetically
sealed.
8. The MHS of claim 6, wherein the modules making up said MHS have
different sizes and shapes.
9. The MHS of claim 1, further comprising a surface to be shielded,
said MHS deployed atop said surface to be shielded.
10. The MHS of claim 9, wherein said surface to be shielded is a
landing spot on an amphibious ship or an aircraft carrier, such
that said MHS shields the flight deck from airplane exhaust
plumes.
11. The MHS of claim 9, wherein said MHS is used to shield said
surface from concentrated directed energy devices such as high
power lasers.
12. The MHS of claim 1, wherein the top panel of said MHS is used
as a mounting surface for one or more electronic components.
13. The MHS of claim 1, wherein said MHS includes heat sink fins on
said bottom panel for improved heat dissipation to the
environment.
14. The MHS of claim 1, further comprising a conformable layer on
the bottom side of said bottom panel.
15. The MHS of claim 1, further comprising a pressure relief valve
arranged to exhaust air or air and vapor from said MHS when the air
and vapor pressure between said top and bottom panels exceeds a
predetermined threshold.
16. The MHS of claim 1, further comprising a ramp coupled to at
least one MHS module.
17. The MHS of claim 1, further comprising compressible pads
located between said bottom plate and the bottoms of said
pillars.
18. The MHS of claim 1, wherein said top and bottom panel form a
cylindrical shell which is deployed vertically such that it forms a
cylindrical enclosure which surrounds said heat source with said
top panel nearest said heat source, said pool of liquid located at
the bottom of said enclosure, further comprising a wicking material
on at least some of said pillars and on the inside of at least a
portion of said top panel such that liquid from said liquid pool is
transported up the sides of said enclosure via said wicking
material.
19. A modular heat shield and heat spreader (MHS), comprising: a
plurality of modules, each of which comprises: a top panel; a
bottom panel; a plurality of thermally conductive pillars located
between said top and bottom panels such that said pillars support
said top panel; and wicking material on at least some of said
pillars and on the underside of at least a portion of said top
panel; said modules joined together at their edges to form a MHS
capable of being deployed atop a surface to be shielded; and a
common continuous pool of liquid between the top and bottom panels
of said modules such that at least a portion of at least some of
said pillars is surrounded by said liquid and at least some of said
wicking material is saturated with said liquid; such that heat from
a heat source to which one or more of said top panels is exposed is
conducted through the top panel and said liquid saturated wicking
material, said liquid present in the voids of said wicking material
changing to a vapor state when sufficiently heated such that said
vapor dissipates said heat away from the modules nearest said heat
source towards other ones of said modules where said vapor
condenses and said condensate returns to said common continuous
pool of liquid.
20. The MHS of claim 19, wherein said modules are joined together
so as to form a watertight seal along each module-to-module
junction.
21. A modular heat shield and heat spreader (MHS), comprising: a
plurality of modules, each of which comprises: a top panel; a
bottom panel; a plurality of pillars located between said top and
bottom panels such that said pillars support said top panel, said
top and bottom panels joined together to form a hermetically sealed
enclosure; and wicking material attached to said top and bottom
panels and also formed into wick columns located between the
pillars so that the wick columns connect the top panel wicking
material and the bottom panel wicking material; at least one of
said modules including one or more areas to which heat generating
electronic devices are to be attached and including heat sink fins
which are attached to the opposite side of the module, each of said
modules charged with an amount of working fluid that is equal to or
larger than the volume of all the voids in the wicking material; a
plurality of said modules of the same or different size placed next
to each other to form a MHS; such that heat from said heat
generating electronic devices attached to one side of the MHS is
conducted through the top panel and the wicking material and said
liquid present in said voids such that said heat changes the phase
of said working fluid to a vapor state, said vapor spreading the
heat to the entire module, said heat sink fins dissipating the heat
to the environment and thereby changing said vapor to a liquid
which is wicked back to the top panel wicking material via said
wick columns.
22. The heat shield of claim 21, wherein at least some of the
pillars located between the top and the bottom panels are bonded to
both the top and the bottom panels to enable the MHS to operate at
elevated pressures and prevent mechanical deformation of MHS
panels.
23. The heat shield of claim 21, wherein said modules and wicking
material comprise aluminum or magnesium and said working fluid
includes a corrosion inhibitor that promotes passivation of the
wicking material during operation and prevents generation of
non-condensable gas within the module.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of provisional patent
application No. 61/581,930 to T. Semenic et al., filed on Dec. 30,
2011.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates generally to heat shields, and more
particularly to heat shields and heat spreaders capable of
protecting surfaces from high temperature heat sources or lowering
the temperature of heat generating components attached to a heat
spreader by effectively spreading the heat over a large area.
[0005] 2. Description of the Related Art
[0006] In many applications, high temperature and large area heat
sources impinge on structural surfaces and cause thermal damage. As
a result, frequent structural repairs may be required that are not
only costly, but may also cause down time. An example is thermal
damage to a flight deck caused by high temperature exhaust plumes
from an aircraft. Temperatures on the top surface of a flight deck
can in some cases approach or exceed annealing temperatures, and
thus cause permanent thermal deformation. This problem may result
in limiting the frequency with which aircraft operations can be
practiced on the flight deck, to allow sufficient cooling time. The
flight deck is also likely to require more frequent repairs than
the rest of the ship, and any non-skid coating applied to the
flight deck is likely to delaminate after being repeatedly heated
with high temperature exhaust plumes.
[0007] In other applications, components that generate significant
amounts of waste heat, such as the semiconductor dies of power
electronics, are attached to heat sinks that spread and transfer
the heat to a heat transfer medium. However, in many cases, such
heat sinks are unable to sufficiently cool the electronics
components, compromising the performance, lifetime, and reliability
of those components.
[0008] One approach to handling large area heat sources of this
kind is a heat spreader made from large plates with embedded heat
pipes; an example is shown in FIG. 1. The heat spreader 10 includes
a number of parallel heat pipes 12 embedded in an aluminum plate
14, a number of which can be placed adjacent to each other to
increase the effective thermal conductivity of the heat spreader.
Heat from a heat source 16 is conveyed away (18) from the source
via the heat pipes on which the heat impinges.
[0009] However, heat pipes of this sort have a number of drawbacks.
For example, heat can only propagate in one direction, making the
heat spreader inefficient. Thermal resistance between adjacent
plates is high, which can result in large temperature differences
across the gaps 20 between the plates and inefficient heat
transfer. In addition, only a small number of the heat pipes 22 in
adjacent plates are heated, resulting in high heat fluxes into heat
pipe evaporators, which can cause the evaporators to dry out. Also,
plates with embedded heat pipes are not scalable, and are not
suitable for large area heat shields and heat spreaders.
SUMMARY OF THE INVENTION
[0010] A modular heat shield and heat spreader is presented which
addresses the challenges noted above.
[0011] The present modular heat shield and heat spreader ("MHS")
includes a top panel, a bottom panel, and a plurality of thermally
conductive pillars located between the top and bottom panels such
that the pillars support the top panel. There is preferably a
continuous pool of liquid between the top and bottom panels, such
that at least a portion of at least some of the pillars is
surrounded by the liquid. When so arranged, heat from a heat source
to which the top panel is exposed is conducted through the top
panel and at least some of the pillars. The heat changes the phase
of at least some of the liquid to a vapor, and the vapor spreads
the heat to an area larger than that of the heat source and thereby
dissipates the heat away from the source at a lower heat flux than
that associated with the heat flux from the source.
[0012] The MHS preferably includes wicking material on at least
some of the pillars and on the underside of at least a portion of
the top panel, such that at least some of the wicking material is
saturated with the liquid and heated by the conducted heat. Wicking
material may also be formed into columns adjacent to at least some
of the pillars such that liquid can flow from the continuous pool
to the top panel through the wicking material columns.
[0013] The MHS is preferably made from modules, each of which is
made with support pillars between a top and bottom panel. To form a
large area heat spreader, multiple modules are joined together at
the module edges and may share a common continuous pool of liquid,
and vapor can transfer and dissipate heat away from the modules
nearest the heat source towards other ones of the modules. The top
and bottom panels of each module are preferably arranged such that
each module is hermetically sealed. The modules making up the MHS
can have different sizes and shapes.
[0014] These and other features, aspects, and advantages of the
present invention will become better understood with reference to
the following description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a plan view of a known heat spreader with embedded
heat pipes.
[0016] FIGS. 2a and 2b are plan and sectional views, respectively,
of a MHS in accordance with the present invention.
[0017] FIG. 3 is a sectional view of one possible embodiment of a
MHS module in accordance with the present invention.
[0018] FIG. 4 is a sectional view of another possible embodiment of
a MHS module in accordance with the present invention.
[0019] FIG. 5 is a sectional view of another possible embodiment of
a MHS module in accordance with the present invention.
[0020] FIG. 6 is a perspective view of one possible embodiment of a
large area MHS made from multiple MHS modules.
[0021] FIG. 7 is a cutaway view of an integral pressure relief
valve as might be used with a MHS module in accordance with the
present invention.
[0022] FIG. 8 is a sectional view of another possible embodiment of
a MHS module in accordance with the present invention.
[0023] FIGS. 9a, 9b and 9c are perspective, sectional and plan
views, respectively, of a cylindrical MHS in accordance with the
present invention.
[0024] FIGS. 10a and 10b are perspective and close-up views of a
ramp assembly as might be used with a MHS module in accordance with
the present invention.
[0025] FIGS. 11a, 11b, and 11c are sectional views of different
types of joints that might be used between MHS modules in
accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The basic principles of the present modular heat shield and
heat spreader (MHS) are illustrated in the plan and sectional views
shown in FIGS. 2a and 2b, respectively. The MHS 30 is typically
made up of a number of individual MHS modules 32, which may be
different shapes and sizes that are assembled over a surface 34
which needs to be shielded from one or more high temperature, large
area heat sources. Each module includes a top panel 36 and a bottom
panel 38; the top and bottom panels are joined together at joints
40 to form a watertight enclosure which is preferably hermetically
sealed.
[0027] A plurality of thermally conductive pillars 42 are located
between the top and bottom panels such that they support top panel
36. A wicking material 44 is preferably (though not necessarily) on
at least some of the pillars and on the underside of at least a
portion of top panel 36; additional wicking material 45 may be
formed into columns adjacent to at least some of the pillars. A
continuous pool of liquid 46 is located between the top and bottom
panels such that at least a portion of at least some of pillars 42
is surrounded by the liquid and such that at least some of the
wicking material (if present) is saturated with the liquid.
[0028] In operation, heat from a heat source 50 to which top panel
36 is exposed is conducted 52 through the top panel, the liquid
saturated wicking material 44 and 45 (if present), and at least
some of thermally conductive pillars 42. The heat changes the phase
of at least some of the liquid 46 in the pool and in the voids of
the wicking material to a vapor 54, which spreads the heat to an
area larger than the area of the heat source and thereby dissipates
heat away from the heat source at a lower heat flux than that
associated with the heat flux from the heat source. The vapor
condenses outside the heat impingement zone and rejects the heat to
the ambient air, while the condensate drips into the liquid pool
46.
[0029] The MHS may include through-holes 56 to accommodate surface
protrusions or to attach the MHS to the surface being shielded. The
wicking material 44 and 45, which may be as simple as a porous
coating, serves to enhance boiling and evaporation of liquid 46,
and provides capillary liquid transport between the pool and the
underside of top panel 36.
[0030] The MHS components are preferably mechanically strong and
corrosion resistant. A surface 34 protected by the present MHS 30
will be cooler than it would be otherwise, and thus may prevent
thermal deformations that would otherwise occur. Some of the key
benefits of the MHS are: (1) a modular design which is scalable to
any size and can accommodate surface protrusions, (2) low weight as
a result of a large vapor space inside the MHS, (3) high lateral
thermal conductivity as a result of using vapor 54 to transfer and
spread the heat, (4) resistance to mechanical impacts as a result
of using mechanically strong panels and structural supporting
elements, and (5) durability and long life as a result of using
corrosion resistant and compatible materials to construct the
MHS.
[0031] The most basic MHS design, illustrated in FIG. 3, includes
no wicking material--heat is conducted to liquid pool 46 via the
supporting elements 42 (ribs or pillars) only. In operation, heat
conducts through top panel 36 and pillars 42 and boils the working
fluid 46. Heat 50 is absorbed by the latent heat of vaporization
and is removed with vapor 54.
[0032] As shown in FIG. 4, the pillars 42 could also include a
porous coating or wicking material 60. This provides for more
effective boiling that results in a lower top panel surface
temperature. Porous coating 60 provides artificial nucleation sites
that result in smaller vapor bubbles and higher bubble departure
frequency than would uncoated (smooth) supporting elements. The
porous coating 60 also serves to increase the heat transfer surface
area.
[0033] There may also be a porous coating or wicking material on
the underside of some or all of the top panel 36, as was shown in
FIG. 2b. In this design, capillary forces transport the liquid
through pores of the wicking material from the continuous liquid
pool 46 in the area beneath the heat impingement zone. Heat from
heat source 50 conducts through top panel 36 and the liquid
saturated wicking material 44 and evaporates the working fluid from
the top surface of the wick. This design is expected to result in a
lower top panel surface temperature than the designs shown in FIGS.
3 and 4.
[0034] Any of the MHS designs could include compressible pads 70 on
the bottoms of pillars 42, as shown in FIG. 5. Pads 70 compress
during mechanical impacts and absorb some of the mechanical
loading. The pads could be made of a low thermal conductivity
material such as silicone rubber, so as to minimize heat conduction
into the surface 34 being shielded. An MHS might also include a
conformable foam 72 affixed to the underside of bottom panels 38
that serves to conform the bottom of the MHS to minor protrusions
74 from shielded surface 34. Foam 72 can also function to minimize
heat conduction from the MHS into shielded surface 34, to absorb
mechanical impacts by compression of the foam, to act as an
electrical insulator between the MHS and shielded surface 34, and
to provide a seal between the MHS and the shielded surface.
[0035] As noted above, the MHS is typically formed from multiple
modules, with the top and bottom panels of each module arranged
such that each module is hermetically sealed. This is further
illustrated in FIG. 6, in which individual modules 80 are assembled
into a large area MHS 82; the modules may be affixed to an optional
mounting frame 84. The large area MHS may be used to shield a
surface from a single heat source such as an aircraft exhaust
plume, or act as a heat spreader and an effective heat transfer
device that can remove waste heat from a single or multiple heat
sources 86 such as electronic devices. Each module may include heat
sink fins 88 affixed to the bottom panel for improved heat
dissipation to the environment. Each module is preferably charged
with an amount of working fluid that is equal to or larger than the
volume of all the voids in the wicking material.
[0036] At elevated pressures, a top and/or bottom panel may start
to deform or bulge if the two panels are only joined at the
periphery. This can be avoided if at least some of the pillars are
bonded in some fashion to the top and bottom panels by, for
example, providing additional fixing points for some of the
pillars. One method might be to make some of the pillars with a
larger diameter so that a through-hole can be formed down the
center of the pillars, and then using bolts to bolt the top panels
to the bottom panels. An o-ring or a gasket could be used to seal
around the pillars with through-holes. In an alternative design,
some or all of the pillars could be brazed at the tips to hold both
panels together.
[0037] The present MHS can be used in numerous applications. As
noted above, the surface to be shielded may be a landing spot on an
amphibious ship or an aircraft carrier, such that the MHS shields
the flight deck from airplane exhaust plumes. One or more MHS
modules might also be used to dissipate heat from one or more
electronic components or devices. Another possible application is
to use an MHS as described herein to shield a surface from
concentrated directed energy devices such as high power lasers.
Many other possible applications are envisioned.
[0038] A MHS module might optionally include an integral pressure
relief valve (IPRV) to exhaust air from the reservoir containing
the pool of liquid when triggered by excessive internal vapor
pressure or by the increase in air pressure due to heating. A
cutaway view of one possible IPRV embodiment is shown in FIG. 7.
The IPRV 100 consists of a valve body 102, the central portion of
which includes a piston 104, a spring 106, an O-ring 108 and an
exhaust port 110, a liquid barrier 112 and a porous barrier 114.
The spring constant is selected based on the required cracking and
reseal pressure. When the internal pressure within the MHS is
sufficiently high, the IPRV opens and air 116 and vapor 118 start
to flow toward piston 104. Both air and vapor have to pass through
porous barrier 114. While flowing through the porous barrier, some
of the vapor will condense. The porous barrier thickness and pore
size are preferably optimized such that most of the vapor condenses
within the porous barrier and returns to pool 120, with mostly just
air 116 passing through the porous barrier. The latent heat of
condensation is conducted through the porous barrier into the
liquid pool 120 or top panel 36. Air then flows around liquid
barrier 112, through the holes in piston 104 and out of the MHS via
exhaust port 110. As soon as the pressure inside the MHS module
drops to the reseal pressure, spring 106 pushes piston 104 against
the IPRV body and seals the MHS. O-ring 108 is used as a seal
between piston 104 and the IPRV body.
[0039] IPRV 100 could be set to any pressure, depending on the
application. An IPRV that is set to a lower pressure will open soon
after heating begins and the air in the liquid reservoir expands.
On the other hand, an IPRV that is set to a higher pressure will
remain closed during normal operation. The IPRV should be set to
open only when the MHS internal pressure exceeds normal operating
pressure, so as to minimize the loss of liquid from pool 120. It is
expected that an MHS module with an IPRV that has a high pressure
set point will remain closed most of the time, and will thus lose
less working fluid during operation. Providing a relief valve in
this way is desirable, as it is expected that an MHS with less air
will cool faster and may result in a lower top surface
temperature.
[0040] A wicking material might also be affixed to the topside of
at least a portion of the bottom panel, thereby enabling liquid to
be transported against gravity when the MHS is tilted. This is
illustrated in FIG. 8. Connected open cell foam or wick 130 can be
included on the bottom panels 38 to transfer the working fluid 46
from one side of the reservoir to the other side against gravity,
using the bottom panel wick's capillary pumping.
[0041] Applications that use a MHS to protect surfaces from high
temperature heat sources will in general require a flat MHS design.
However; some applications require a cylindrical heat shield that
can be placed around--and thereby intercept radiation from--the
heat source(s). One possible embodiment of such a cylindrical MHS
is shown in the perspective, sectional and plan views depicted in
FIGS. 9a, 9b and 9c, respectively. Here, a top panel 140 and a
bottom panel 142 form a cylindrical enclosure 144, with support
pillars 146 located between the top and bottom panels. The
cylindrical enclosure is deployed vertically, such that an
enclosure is formed which surrounds a heat source 148--with top
panel 140 located nearest the source, the pool of liquid 150
located between the top and bottom panels at the bottom of the
enclosure, and a wicking material 152 on at least some of the
pillars and on the inside of at least a portion of the top panel
such that liquid from the liquid pool is transported up the sides
of the enclosure against gravity via the wicking material. As the
heat source is surrounded, the heat source can be pointing in any
direction.
[0042] For applications where the heat source is at or below the
top level of the liquid within the cylindrical MHS assembly, the
wicking material is not required. The cylindrical MHS could be
built from any number of cylinders that are placed on top of each
other. Seals 154 are used to seal the gaps between the cylinders.
Flexible wick structures such as foams or screens are preferably
placed close to the seals to provide bridges for the working fluid
between adjacent modules. The gap between the top and bottom panels
is used to transport vapor and to return condensed liquid back to
the liquid pool. The heat is absorbed by evaporation or boiling,
and the resulting vapor spreads the heat to the entire cylindrical
MHS assembly. The vapor condenses outside the heat zone and rejects
the heat to the environment. The outside of bottom panels 142 could
also include fins for more effective heat dissipation to the
environment. A cylindrical MHS with high temperature working fluids
such as liquid metals could enable shielding of very high
temperature heat sources (e.g. plasmas) that would not be possible
with conventional solid heat shields.
[0043] The present MHS may also include a ramp coupled to at least
one module to provide better access to the MHS top surface; this is
illustrated in FIG. 10a, with a close-up view of the ramp/surface
interface shown in FIG. 10b. The ramp 160 could be made of
individual panels and attached to some or all or some of the
peripheral MHS modules. The ramp panels could be welded 162 to the
shielded surface 34 to prevent any fluids from wicking underneath
the MHS and causing corrosion of the shielded surface. As noted
above, there may be a conformable foam 72 affixed to the underside
of the MHS bottom panel, which may also extend to the underside of
ramp 160, that serves to conform the bottom of the ramp to minor
protrusions 74 from shielded surface 34. An electrical insulator
layer 164 might also be installed between the outer edge of the
ramp and a layer 166 made from the same material as the shielded
surface.
[0044] One of the key advantages of the present MHS is that it can
be assembled where it is required, from any number of modules. The
joints between the panels could be rigid (e.g., welded, brazed,
soldered, or glued seals), flexible (e.g., gasket or o-ring seals),
or a combination of both. A MHS with seals of the first type is
shown in FIG. 11a. Two modules 170, 172 are shown. In this example,
the joints 174 between the top panel 36 and bottom panel 38 of each
module are formed by a method such as welding, brazing or
soldering.
[0045] Flexible seals are illustrated in FIG. 11b. Again, two
modules 180, 182 are shown. Here, the top panels 184, 186 and the
bottom panels 188, 190 should have overlapping lips 192, 194 on
their edges, with gaskets 196 fitting in-between the lips.
[0046] For the two modules 200, 202 shown in FIG. 11c, the top
panels 204, 206 are joined using a gasket 208, while bottom panels
210, 212 are joined with a rigid joint 214. An advantage of using a
rigid joint for the bottom panels and a flexible joint for the top
panels is that the rigid joint on the bottom will result in better
sealing of the reservoir, while the flexible joint on the top makes
it easy to change top panels if they are damaged. Bottom panels are
less likely to get damaged.
[0047] As noted above, the present MHS has numerous applications.
Examples include shielding from high energy sources (e.g. hot
exhaust plumes, directed energy weapons or high temperature
plasmas) and spreading and transferring heat from electronics
devices (e.g. cooling semiconductor dies, cooling laser diodes, or
cooling concentrated photovoltaic cells).
[0048] The MHS modules and wicking material are preferably made
from lightweight materials such as aluminum or magnesium. The
working fluid preferably includes a corrosion inhibitor that
promotes passivation of the wicking material during operation and
prevents generation of non-condensable gas within the
enclosure.
[0049] The embodiments of the invention described herein are
exemplary and numerous modifications, variations and rearrangements
can be readily envisioned to achieve substantially equivalent
results, all of which are intended to be embraced within the spirit
and scope of the invention as defined in the appended claims.
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