U.S. patent application number 14/119919 was filed with the patent office on 2014-11-27 for thermal transfer device with reduced vertical profile.
This patent application is currently assigned to Aavid Thermalloy, LLC. The applicant listed for this patent is John R. Cennamo, Randolph H. Cook, Sukhvinder S. Kang, Bradley R. Whitney. Invention is credited to John R. Cennamo, Randolph H. Cook, Sukhvinder S. Kang, Bradley R. Whitney.
Application Number | 20140345829 14/119919 |
Document ID | / |
Family ID | 47259642 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140345829 |
Kind Code |
A1 |
Kang; Sukhvinder S. ; et
al. |
November 27, 2014 |
Thermal Transfer Device with Reduced Vertical Profile
Abstract
A thermal transfer device having a reduced vertical profile. The
device includes a condenser with substantially vertical internal
cooling fins. An inlet conducts a thermal transfer fluid in a vapor
state to the tops of the cooling fins where the vapor condenses and
flows down the fins to the bottom of the condenser. The bottom of
the condenser is angled towards an outlet for conducting the liquid
thermal transfer fluid to a reservoir for holding the fluid. The
inlet and the outlet are both positioned at a height above the
level of the thermal transfer fluid in liquid state in the
reservoir. The device may also include fins on the exterior of the
condenser for providing cooling surfaces which do not contact the
thermal transfer fluid in either the liquid or vapor states.
Inventors: |
Kang; Sukhvinder S.;
(Concord, NH) ; Cennamo; John R.; (Gilford,
NH) ; Whitney; Bradley R.; (Epsom, NH) ; Cook;
Randolph H.; (Gilford, NH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kang; Sukhvinder S.
Cennamo; John R.
Whitney; Bradley R.
Cook; Randolph H. |
Concord
Gilford
Epsom
Gilford |
NH
NH
NH
NH |
US
US
US
US |
|
|
Assignee: |
Aavid Thermalloy, LLC
Laconia
NH
|
Family ID: |
47259642 |
Appl. No.: |
14/119919 |
Filed: |
May 27, 2011 |
PCT Filed: |
May 27, 2011 |
PCT NO: |
PCT/US11/38299 |
371 Date: |
February 10, 2014 |
Current U.S.
Class: |
165/104.21 |
Current CPC
Class: |
H01L 23/427 20130101;
H05K 7/20318 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101; F25B 39/04 20130101; H05K 7/20336
20130101 |
Class at
Publication: |
165/104.21 |
International
Class: |
F25B 39/04 20060101
F25B039/04 |
Claims
1. A condenser for use in a thermal transfer device and adapted to
be coupled to a reservoir for holding a thermal transfer fluid in
at least one of a liquid state and a vapor state, the condenser
comprising: an inlet for receiving the thermal transfer fluid in a
vapor state from the reservoir; an outlet for returning the thermal
transfer fluid to the reservoir in a liquid state; and first and
second header spaces; said inlet being positioned at a height
relative to the reservoir which is greater than a height of said
outlet and being configured to introduce the thermal transfer fluid
in said vapor state to said first header space; said outlet being
configured to conduct the thermal transfer fluid in said liquid
state from said second header space; each of said inlet and said
outlet being positioned at a height above a level of the thermal
transfer fluid in its liquid state in the reservoir; an array of
substantially vertical fins disposed within the condenser; wherein
said fins define passages therebetween, said passages opening into
said first and second header spaces and permitting the flow of the
thermal transfer fluid therethrough.
2. The condenser of claim 1, wherein said first and second header
spaces are separated from each other.
3. The condenser in claim 1 wherein said first and second header
spaces comprise one header space
4. The condenser of claim 1, wherein said inlet and said outlet
form a single conduit.
5. The condenser of claim 1, wherein said inlet and said outlet are
on the same side of said condenser.
6. The condenser of claim 1, wherein said condenser has a bottom
surface positioned so that it slopes in a direction of said outlet
to facilitate the flow of the thermal transfer fluid to said outlet
when the thermal transfer fluid is in its liquid state.
7. The condenser of claim 1, wherein each of said fins has a
plurality of flutes on at least one side thereof.
8. The condenser of claim 7, wherein said flutes are on opposing
sides of said fins.
9. The condenser of claim 8, wherein said flutes are disposed in
matched pairs on said opposing sides of said fins.
10. The condenser of claim 8, wherein said flutes are disposed on
said opposing sides of said fins in a staggered relationship.
11. The condenser of claim 1, wherein the depth of said condenser
is greater than the height, thereby permitting the thermal transfer
device to have a reduced vertical profile.
12. The condenser of claim 1, further comprising a second plurality
of fins on the exterior of said condenser, said second plurality of
fins not being in contact with the thermal transfer fluid in either
its liquid or vapor state.
13. The condenser of claim 1, further comprising a liquid cold
plate in at least one of above or below the condenser chamber in
thermal communication with said chamber.
14. A thermal transfer device for use in an environment with a
small vertical clearance, the device comprising: a reservoir for
holding a thermal transfer fluid in a liquid state; a condenser
having an inlet for receiving the thermal transfer fluid in a vapor
state from said reservoir; an outlet for returning the thermal
transfer fluid to said reservoir in the liquid state; and first and
second header spaces; said inlet being positioned above said outlet
and being configured to introduce the thermal transfer fluid in its
vapor state to said first header space; said outlet being
configured to conduct the thermal transfer fluid in its liquid
state from said second header space; each of said inlet and said
outlet being positioned at a height above a level of the thermal
transfer fluid in its liquid state in said reservoir; and an array
of substantially vertical fins disposed within said condenser;
wherein said fins define passages therebetween, said passages
opening into said first and second header spaces and permitting the
flow of the thermal transfer fluid therethrough; whereby the
thermal transfer fluid in its vapor state may enter the condenser
through said inlet into said first header space, whereupon it flows
through the tops of said passages to contact said fins, where the
vapor condenses, whereupon it flows back through the bottom of said
passages to said second header space and then to said outlet for
return to the reservoir.
15. The thermal transfer device of claim 14, further comprising a
first conduit for conducting the thermal transfer fluid from said
reservoir to said inlet.
16. The thermal transfer device of claim 15, wherein said first
conduit is adapted to conduct the thermal transfer fluid in its
vapor state from said reservoir to said inlet.
17. The thermal transfer device of claim 15, further comprising a
second conduit for conducting the condensed thermal transfer fluid
in its liquid state from said outlet to said reservoir.
18. The thermal transfer of claim 14, wherein said condenser has a
bottom surface positioned so that it slopes in the direction of
said outlet to facilitate the flow of the thermal transfer fluid to
said outlet when the thermal transfer fluid is in its liquid
state.
19. The thermal transfer device of claim 14, wherein each of said
fins has a plurality of flutes on at least one side thereof.
20. The thermal transfer device of claim 14, further comprising a
second plurality of fins on the exterior of said condenser, said
second plurality of fins not being in contact with the thermal
transfer fluid in either its liquid or vapor state.
21. The thermal transfer device of claim 14, wherein the depth of
said condenser is greater than the height thereof, thereby
permitting the thermal transfer device to have a reduced vertical
profile.
22. The thermal transfer device of claim 14, further comprising:
means for attaching an external thermal transfer apparatus to the
thermal transfer device to provide thermal contact with said
condenser, and to provide additional thermal transfer capacity to
the thermal transfer device.
23. The thermal transfer device of claim 22, further comprising a
thermal transfer medium applied to the exterior of said condenser
to provide thermal conduction between the thermal transfer
apparatus and said condenser.
24. The thermal transfer device of claim 23, wherein said thermal
transfer medium is selected from one of a thermally conductive pad,
a thermally conductive gel and a thermally conductive grease.
25. The thermal transfer device of claim 22, wherein said means for
attaching includes a spring which urges the external thermal
transfer apparatus into contact with said condenser.
26. The thermal transfer device of claim 22, further comprising a
barrier component.
27. The thermal transfer device of claim 26, wherein said barrier
component is one wall of an enclosure.
28. The thermal transfer device of claim 27, wherein said enclosure
substantially surrounds said thermal transfer device.
29. The thermal transfer device of claim 27, wherein said enclosure
substantially surrounds said reservoir of said thermal transfer
device.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention is directed to a thermal transfer device,
such as a closed loop fluid cooling system having at least one
evaporator, at least one condenser and one or more fluid conduits
connecting the evaporator and condenser for use in indirectly
cooling objects with a cooling fluid and, more particularly, to a
thermal transfer device having a reduced vertical profile for
conducting a cooling fluid into indirect thermal contact with an
object to be cooled in a compact environment.
[0003] 2. Description of the Related Art
[0004] Passive closed loop two-phase fluid cooling systems are
well-known thermal transfer devices used for cooling objects that
generate excessive heat, such as, without limitation, computer
chips. The term passive is meant to denote a system which uses no
mechanized pump to circulate the cooling fluid. The motivation for
the fluid to circulate in a passive system comes from buoyancy
changes and phase changes in the fluid as heat is added. The
evaporator is generally placed in thermal contact with the object
to be cooled, and a cooling fluid in liquid form is passed over a
surface which separates the liquid from the actual object to be
cooled. In this fashion, heat may be transferred between the fluid
and the object, without the fluid ever coming into direct contact
with the object. The addition of heat to the fluid causes at least
a portion of the fluid to vaporize. The vapor is then conveyed to
the condenser. Heat is released as the vapor re-condenses to a
liquid state. The condensed liquid is returned to the evaporator
and the vaporization-condensation cycle repeats. FIG. 1a depicts
such a prior art condenser 100, and FIG. 1b shows a detail thereof.
Prior art condensers commonly use tubes 102 of circular cross
section, or flattened tubes which approximate an oval or
rectangular cross section, to provide the condensation surfaces.
These tubes are typically disposed with their longitudinal axis
vertical. A multitude of air cooling fins 104 with apertures
dimensioned to fit the perimeters of these tubes are arranged
horizontally. Note that in the prior art condenser 100 of FIG. 1
the air cooling fins 104 are interspersed with the condenser tubes
and as such the air cooling fins and condenser tubes occupy the
same vertical region above the liquid header tank 106 and below the
vapor header tank 108. A vapor conduit 110 conducts heated vapor to
vapor header tank 108 and a condensate return line 112 returns
liquid condensate 114 to a reservoir 116.
[0005] This prior art configuration thus requires that all of the
air cooling fins 104 are located above the collection point for the
condensed fluid (condensate 114), specifically, above the liquid
header tank 106. This is the single biggest limitation of the prior
art condenser. This limitation of the prior art condenser can best
be illustrated by comparing FIG. 1 to FIG. 2 which depicts the
instant invention. In FIG. 2 it can be seen that air cooling fins
118 are located above and below the region of the condenser
chamber. Although
[0006] FIG. 2 depicts air cooling fins 118 both above and below the
region of the condenser chamber 120 it should be understood that
the air cooling fins 118 could be placed either above or below the
condenser chamber 120. The air cooling fins 118 are not
interspersed with the condenser fins (within condenser 120, and not
shown in FIG. 2). This means that the condenser fins need not be
spaced as far apart from each other horizontally as in the prior
art's design as they need not pass cooling air between them. This
in turn means that although the condenser fins of the instant
invention are shorter along their vertical axis than the prior art
design, their closer horizontal spacing allows for more fins to be
used and therefore for a total condensate surface area
substantially equal to the prior art design. The instant invention
can likewise be configured to provide a total air cooling fin area
substantially equal to the prior art design. The key benefit of the
invention is that the collection point for the condensed fluid
(liquid condensate 114) is located substantially higher than that
of the prior art design. This key benefit of the invention, the
ability to locate the condensate surface area and the collection
point for the condensed liquid high in the space available and well
above the level of the evaporator component, is most apparent in
the embodiment of FIG. 4. Referring again to FIG. 1, the difference
between the height of liquid in the reservoir (RH) and the height
of fluid in the condenser (CH) is the gravitational height (GH),
sometimes referred to as gravitational head. As can be seen in the
Figures, GH-2 of FIG. 2 is substantially larger that GH-1 of FIG.
1. The ability of each design to return condensate from the
condenser to the reservoir is directly tied to their respective
gravitational heights, GH-1 and GH-2. Where, for a given available
height (AH), both the prior art design and the invention can be
configured to have substantially equal air cooling fin area and
internal condenser surface area, the invention can operate at a
higher heat load by virtue of its higher GH. This is because the
mass transport rate of condensate return is directly related to the
maximum amount of heat transfer achievable.
[0007] To further illustrate the advantage of the invention over
the prior art design refer again to FIG. 3. FIG. 3 depicts a prior
art type design configured to provide the same gravitational height
as with the invention (GH-2). As can be seen in FIG. 3, this
configuration provides for substantially less vertical space for
the air cooling fins and condenser tubes as there is a region 122
below the condenser that cannot be used. The reduction in air
cooling fin area and condenser tube area renders this configuration
inferior to the invention.
[0008] For the reasons recited above, the invention can transfer a
higher heat load compared to condensers of the prior art design in
applications demanding a relatively low available height (AH),
i.e., "low profile" designs.
[0009] There are examples of prior art type condensers that have
been re-oriented to achieve a low profile but these typically
accomplish a low profile at the expense of another significant
design consideration.
[0010] For example, U.S. Pat. No. 7,422,052 discloses a low profile
cooling system with a substantially horizontally disposed condenser
component. The condenser is generally similar to prior art
vertical, or standing, condensers, except that it is angled closer
to the horizontal while still at a shallow incline. This provides
the benefit of a reduced vertical profile, at the expense of a
substantially increased horizontal profile.
[0011] U.S. Pat. No. 7,231,961 also discloses a low profile cooling
system. This reference specifies a condenser as "a long chamber
having a narrow interior channel". This chamber is oriented with
its "long" dimension oriented substantially parallel to the
horizontal plane where the horizontal plane is taken to mean the
plane on which the device to be cooled is mounted, e.g., the plane
of a circuit board bearing the chip/processor to be cooled. One
side of this chamber (a substantially vertical exterior surface) is
populated with air cooling fins. Based on the dimensional ranges
recited, which define the length, width and height of this chamber,
one could describe the chamber as simply a singular condenser tube,
much like many of the condenser tubes described earlier with
reference to prior art condensers. In this case, the singular
condenser tube is disposed with its longitudinal axis horizontal
instead of vertical. As such, the design achieves a low vertical
profile simply by placing the condenser tube in a horizontal
configuration. This is done clearly at the expense of gravitational
height. This limitation is expressly recited in column 5, lines
12-19;
[0012] "Typically, the condensers of thermosyphons are placed over
or higher than the evaporators to utilize gravity to force the
liquid from the condenser to the evaporator. This placement is not
possible in spaces where the available height is severely limited.
Although part of the condenser may be higher than the evaporator,
or vice versa, the condenser and evaporator are approximately
horizontal to each other in the present invention."
[0013] It should also be pointed out that this prior art design
requires a significant portion of the internal volume of the
condenser to be occupied by standing liquid.
[0014] This represents a well know limitation on the performance of
a condenser in that no condensation can occur on condenser surfaces
embedded in standing liquid, a situation often referred to as
"flooding of the condenser".
[0015] Accordingly, although condensers are generally well known
and widely used, there is a continuing need to make condensers more
efficient, and, therefore, more competitive, cost-effective and
useful. It is especially useful to provide a condenser that can be
used for cooling an object in a very compact environment while
providing adequate internal condenser surface area coupled with
adequate gravitational height for transport of the condensate.
SUMMARY OF THE INVENTION
[0016] It is therefore an object of the invention to provide a
thermal transfer device which provides efficient and effective
cooling of objects which may tend to overheat, such as computer
chips.
[0017] It is a further object of the invention to provide an
improved thermal transfer device having a reduced vertical profile
for use in applications where there is limited vertical clearance
or headroom.
[0018] In accordance with these and other objects of the invention
there is provided a thermal transfer device which includes a
chamber having substantially vertical condenser fins for condensing
a heated thermal transfer fluid from vapor to liquid. The chamber
has an inlet for receiving the vapor and an outlet for conducting
the condensed fluid in its liquid state back to a reservoir. The
inlet and the outlet are both positioned at a level higher than the
level of the liquid thermal transfer fluid in the reservoir. The
vertical condenser fins which provide the condensing surfaces are
positioned substantially in the vertical space between the inlet
and the outlet. The benefit of this arrangement is that it leaves a
larger portion of the available vertical height for gravitational
return of the condensate to the evaporator. This arrangement
likewise allows for a significant change in the height of the
liquid in the liquid return line without the negative consequence
of driving liquid into the condenser component (which, if it
occurs, renders some portion of the condenser inoperative). This
structure permits the device to achieve good condensation
performance and have an overall reduced vertical profile.
Additionally, this structure permits the device to have an overall
reduced vertical profile in which the depth of the chamber is
greater than the height of the interior of the chamber.
[0019] In preferred embodiments of the invention, the condenser
fins within the chamber may include flutes on their surfaces to
increase the effective cooling surface within the chamber. The
flutes may be disposed in matched opposed pairs on opposed sides of
the fins, or may be staggered in alternation on opposing sides as a
matter of design choice. As typically applied to the cooling of
electrical apparatus or electronic apparatus one or more of the
external surfaces of the chamber will be fitted with a multitude of
air cooling fins in thermal communication with the chamber. The
surfaces employed are most typically the top or bottom surface.
Although a multitude of fins (sometimes referred to as an array of
fins) are most commonly employed, a singular fin can be used as
well. Air is passed over the air cooling fin or fins either by
natural convection means or by forced convection means. Designing,
fabricating and employing air cooling fins for use in natural or
forced convection cooling is well known in the art of cooling
system design. As an alternative to the use of one or more air
cooling fins, a liquid cold plate can be placed on either the top
surface or bottom surface of the chamber, or both. Used in this
manner, a cold plate will be fixed to the chamber in so as to be in
thermal communication with the chamber. A cooling fluid is
circulated through the cold plate. The cooling provided by the
cooling fluid causes the vapor inside the chamber to condense. The
term "Liquid Cold Plate" is interchangeable with "Liquid Cooled
Heat Sink" and both terms are well known in the art. An example of
a liquid cooled heat sink is disclosed in U.S. Pat. No. 5,829,516
and is herein incorporated by reference.
[0020] Other objects and features of the present invention will
become apparent from the following detailed description considered
in conjunction with the accompanying drawings. It is to be
understood, however, that the drawings are designed solely for
purposes of illustration and not as a definition of the limits of
the invention, for which reference should be made to the appended
claims. It should be further understood that the drawings are not
necessarily drawn to scale and that, unless otherwise indicated,
they are merely intended to conceptually illustrate the structures
and procedures described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] For a further description of the invention, reference is
made to the exemplary embodiments shown in the drawings, in which
like numerals refer to like parts.
[0022] FIGS. 1a and 1b are a schematic illustration of a prior art
thermal transfer device;
[0023] FIGS. 2a and 2b are a schematic illustration of the
inventive thermal transfer device;
[0024] FIGS. 3a and 3b are a schematic illustration of a prior art
thermal transfer device configured with the condenser elevated
above the surface on which the evaporator sits;
[0025] FIGS. 4a and 4b are a schematic illustration of the
preferred embodiment of the inventive thermal transfer device
configured for operation in low vertical profile applications;
[0026] FIG. 5 is a schematic illustration of a chamber used in a
first embodiment of the inventive thermal transfer device;
[0027] FIG. 6a is a schematic illustration of a secondary
embodiment of the chamber used in the inventive thermal transfer
device;
[0028] FIG. 6b is a schematic illustration of a tertiary embodiment
of the chamber used in the inventive thermal transfer device;
[0029] FIG. 7 is a perspective view of the thermal transfer device
of FIG. 4 showing a multitude of air cooled fins attached to the
bottom of the condenser chamber, with arrows depicting cooling air
traversing the air cooled fins;
[0030] FIG. 8 is a perspective view of the condenser component of
the thermal transfer device of FIG. 4 with a cut-away in the top of
the chamber to allow viewing of internal structure;
[0031] FIGS. 9a and 9b are cross-sections of differing embodiments
of fins and flutes used in the inventive thermal transfer
device;
[0032] FIG. 10 is a schematic cross-section of a single tube
embodiment of the inventive thermal transfer device;
[0033] FIG. 11 is a perspective view of a further embodiment of the
inventive thermal transfer device with a liquid cooled heat sink,
also known as a liquid cold plate, placed in thermal communication
with lower external surface of condenser chamber, with arrows
depicting cooling fluid entering and leaving the liquid cold
plate;
[0034] FIGS. 12a, 12b and 12c are schematic illustrations of the
preferred embodiment of the invention mounted on a circuit board
and further comprising a bulkhead to separate the region of the
circuit board from the region of the condenser component;
[0035] FIG. 13a is a schematic illustration of the condenser
component of the inventive thermal transfer device where the
condenser chamber is shown in cross-section and the condenser
chamber is located in vertical region B, entirely above vertical
region A where one array of air cooling fins is located; and
[0036] FIG. 13b is a schematic illustration of the condenser
component of the inventive thermal transfer device where the
condenser chamber is shown in cross-section and the condenser
chamber is located in vertical region B, substantially above
vertical region A where one array of air cooling fins is
located.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0037] In accordance with a preferred embodiment of the invention
there is shown, generally at 10 in FIG. 4, a thermal transfer
device, or "closed loop fluid cooling system" in accordance with
the invention. Thermal transfer device 10 includes a reservoir 12
acting as an evaporator, for holding a thermal transfer fluid 14, a
first conduit 16 for conducting thermal transfer fluid 14 out of
reservoir 12 when the thermal transfer fluid is in a vapor state,
and a second conduit 18 for conducting thermal transfer fluid 14
back to reservoir 12 once thermal transfer fluid 14 has condensed
from its vapor state to a liquid state. The maximum height to which
the liquid portion of the thermal transfer fluid can rise before
flooding the condensing surfaces is denominated as h in FIG. 4.
[0038] In the preferred embodiment, thermal transfer fluid 14 is
water or deionized water. Where a design places specific
requirements on the cooling fluid, e.g., freeze tolerance,
corrosion resistance or that the cooling fluid be electrically
non-conductive, organic cooling fluids such as alcohols,
refrigerants such as R134A or engineered fluids such as 3M
Fluorinert or Novec Liquids may be used.
[0039] Thermal transfer device 10 also includes a chamber 20,
acting as a condenser, having an inlet 22 (FIG. 7) coupled to first
conduit 16 and an outlet 24 coupled to second conduit 18. In the
preferred embodiment, chamber 20 is hermetic and made of metal,
such as aluminum or copper.
[0040] FIGS. 5 and 8 show one of a plurality of substantially
vertical condenser fins 26 positioned within chamber 20 to provide
cooling surfaces for thermal transfer fluid 14 to condense from its
vapor state when it is introduced to chamber 20 to its liquid state
for return to reservoir 12. Fins 26 are spaced from one another to
form passages therebetween through which thermal transfer fluid 14
may flow, and contact more of the surfaces of cooling fins 26. To
facilitate the distribution of vapor along all passages, a first
open header space 32 (FIGS. 5 and 6a) is provided at the top of
chamber 20. First open header space 32 spans substantially the
entire width of chamber 20, which permits the unimpeded flow of
thermal transfer fluid 14 in a vapor state over the entire width of
chamber 20, and then along the passages to the entire depth of
chamber 20. (Depth, width and height orientations are shown in FIG.
8.) Allowing the smooth distribution of the vapor to the entire
depth and width of 20 exposes the maximum cooling surface area of
cooling fins 26 in a most efficient manner.
[0041] To facilitate the return flow of thermal transfer fluid 14
to reservoir 12, a second open header space 34 is provided. Second
open header space extends substantially the entire width of chamber
20 and opens into outlet 24. Although in the proffered embodiment
of the invention two open header spaces are provided, a singular
contiguous header space (illustrated as 33 in FIG. 6b) can be used
as a matter of design choice as the higher density of the
condensate (compared to the vapor) will lead to the condensate
naturally collecting in the lower portion of the singular header
space leaving the upper portion available for the vapor.
[0042] Inlet 22 may either be positioned in the top of chamber 20,
as shown in FIGS. 5 and 6b, or in the side of chamber 20 as shown
in FIG. 6a. In either configuration, the vapor of thermal transfer
fluid 14 will enter first header space 32, and condense on fins 26
as described. The choice of construction is a mere matter of design
choice and will depend upon the requirements of the application,
and the selection of the appropriate position for inlet 22 is well
within the skill of one of ordinary skill in the art.
[0043] The structural arrangement of the present invention allows
for all of the condensing surfaces to be located gravitationally
above the liquid level in both the reservoir and the liquid return
conduit. This structure provides the further benefit that the
condensing surfaces, together with the chamber housing them, occupy
a relatively small portion of the vertical height available for the
entire thermal transfer device.
[0044] FIG. 7 shows an embodiment of the invention in which air
cooled fins 30' are attached to the bottom external surface of the
condenser chamber. Alternatively, a liquid-cooled cold plate 30 as
shown in FIG. 11, or any other known method of providing cooling to
condenser, can be used in place of the air cooled fins.
[0045] A further possibility for improving the performance of
thermal transfer device 10 is to provide fins 26 with flutes 40, as
shown in FIGS. 9a and 9b. Flutes 40 may be either positioned as
matched pairs on opposing sides of fins 26 (FIG. 9a) or in a
staggered arrangement as shown in FIG. 9b, as a matter of design
choice.
[0046] It is also possible to realize the benefits provided by the
invention by use of a single port 36 as both an input and an
output, as shown in FIG. 10, as a matter of design choice. In
single port 36, vapor 42 may flow upwards while liquid 44 may flow
down.
[0047] In another embodiment of the invention shown in FIG. 12, a
thermal transfer device 40, together with the microprocessor being
cooled is mounted on a circuit board. The circuit board, which
includes an electrical connector 42 disposed near one of its
peripheral edges, can be inserted into another structure such as a
slot within a computer chassis. Thermal transfer device 40 bears a
liquid cold plate 44 which provides the cooling means for condenser
20 as well as an electrical connector 46 dimensioned to mate with
electrical connecter 42 on the circuit board. Arranged as such,
when the circuit board is inserted in the chassis, electrical
connectors 42, 46 mate with each other and condenser 20 mates with
liquid cold plate 44. The mating between condenser 20 and liquid
cold plate 44 must provide good thermal communication between the
two components in order to transfer heat efficiently, for this
reason an interface material 48 to promote thermal transfer such as
a thermal grease or gel, or a thermal interface pad is placed
between the mating surfaces. In typical practice, solid/non-grease
interface materials such as graphite-based pads are permanently
fixed to the surface of one component by means of an adhesive. The
surface without adhesive contacts the other component. This allows
the two components to be assembled or "mated" and disassembled
repeatedly without damage to the interface material. The cooling
fluid circulating through the liquid cold plate 44 can be provided
by a number of means well known in the art of cooling of servers,
mainframe computers and telecom equipment. Two specific examples
are as follows; [1] a dedicated stand-alone chiller can provide the
cooling fluid, typically de-ionized water at a pre-determined
temperature and at a pre-determined volumetric flow rate. The
temperature of the liquid entering the cold plate is set according
to the desired maximum operating temperature of the microprocessor
being cooled. The volumetric flow rate of the cooling fluid is set
according to the total amount of wattage that needs to be
transferred and by the maximum desired temperature rise of the
cooling fluid within the liquid cold plate. The determining of set
points for both of these parameters, cooling fluid temperature
entering the cold plate, and volumetric flow rate of the cooling
fluid, can be accomplished with well known and long standing
engineering methods and would not require an undue amount of
experimentation. Alternatively, [2] the building facility housing
the equipment being cooled, for example, a data center housing and
supporting many servers, could provide cooling water at a
sufficient volumetric flow rate at a pre-determined temperature and
pressure. This is sometimes referred to as "utility water".
Designing the liquid cold plate based on these values to achieve
the thermal transfer required can, as in the previous example, be
accomplished with well known and long standing engineering
methods.
[0048] The advantage of this embodiment is that a fluid cooled
electronic component such a chip or micro processor together with
the circuit board on which it is mounted can be removed for repair
or replacement without disturbing the plumbing providing cooling
fluid to, or removing cooling fluid from, the liquid cold plate
component. This in turn lowers the risk of using water to
indirectly cool an electronic component in that in normal
operation, including service and maintenance, there is less risk of
cooling water escaping and damaging the electronic components. This
benefit can be further enhanced by providing a physical barrier,
for example a bulkhead or wall 50 separating the circuit board
region from the liquid cold plate region. Taken to extreme, the
physical barrier could be in the form of an enclosure (such as
suggested by dotted line 52) housing the circuit board where the
condenser component and electrical connector protrude through one
wall of enclosure. As shown in FIG. 12c, the structure could even
completely enclose condenser 20, leaving interface material 48 on
the exterior of enclosure 52'.
[0049] In FIG. 12 the liquid cold plate mates with the inclined
bottom surface of condenser 20. Liquid cold plate 44 is provided
with a correspondingly angled upper surface. The circuit board is
moved horizontally to engage both electrical connector 46 and
liquid cold plate 44. A spring 54 urges the upper surface of the
liquid cold plate towards the lower surface of the condenser
component to provide good thermal communication at the interface.
As with air cooled fins, a liquid cold plate can be used on the
lower surface of the condenser, the upper surface, or both.
[0050] Although in FIG. 12 the liquid cold plate has an inclined
surface, this simply represents a design choice. A cold plate whose
upper and lower surfaces are parallel (as is most commonly the
case) can be used by inclining the entire cold plate as needed to
mate with the inclined surface of the condenser component.
[0051] In any embodiment or configuration, the inventive thermal
transfer device has a reduced vertical profile when compared to
known prior art devices, and provides improved and efficient
thermal transfer, particularly for applications providing a limited
vertical space by virtue of the invention's configuration.
[0052] Thus, while there have shown and described and pointed out
fundamental novel features of the invention as applied to a
preferred embodiment thereof, it will be understood that various
omissions and substitutions and changes in the form and details of
the devices illustrated, and in their operation, may be made by
those skilled in the art without departing from the spirit of the
invention. For example, it is expressly intended that all
combinations of those elements which perform substantially the same
function in substantially the same way to achieve the same results
are within the scope of the invention. Moreover, it should be
recognized that structures and/or elements shown and/or described
in connection with any disclosed form or embodiment of the
invention may be incorporated in any other disclosed or described
or suggested form or embodiment as a general matter of design
choice. It is the intention, therefore, to be limited only as
indicated by the scope of the claims appended hereto.
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