U.S. patent application number 11/749782 was filed with the patent office on 2007-11-22 for heat exchanger assembly.
Invention is credited to Andreas Fiedler.
Application Number | 20070266714 11/749782 |
Document ID | / |
Family ID | 38710726 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070266714 |
Kind Code |
A1 |
Fiedler; Andreas |
November 22, 2007 |
HEAT EXCHANGER ASSEMBLY
Abstract
A heat exchanger assembly for transferring heat across a wall of
a housing is disclosed. The assembly comprises an outer heat
exchanger having an outer ring disposed outside the housing and
having an interior surface in contact with an exterior surface of
the wall; an inner support disposed inside the housing and having
an exterior surface; and a plurality of inner heat fins connecting
the exterior surface of the inner support to an interior surface of
the wall of the housing.
Inventors: |
Fiedler; Andreas; (Santa
Barbara, CA) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Family ID: |
38710726 |
Appl. No.: |
11/749782 |
Filed: |
May 17, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60802174 |
May 19, 2006 |
|
|
|
Current U.S.
Class: |
62/6 ;
29/890.03 |
Current CPC
Class: |
F25B 9/14 20130101; F28F
1/12 20130101; F02G 2255/20 20130101; F28F 2275/12 20130101; F02G
2256/02 20130101; F28F 2275/025 20130101; F28F 1/105 20130101; F02G
1/053 20130101; Y10T 29/4935 20150115 |
Class at
Publication: |
62/6 ;
29/890.03 |
International
Class: |
F25B 9/00 20060101
F25B009/00; B21D 53/02 20060101 B21D053/02 |
Claims
1. A heat exchanger assembly for transferring heat across a wall of
a housing, the assembly comprising: an outer heat exchanger
comprising an outer ring disposed outside the housing and having an
interior surface in contact with an exterior surface of the wall;
an inner support disposed inside the housing and having an exterior
surface; and a plurality of inner heat fins connecting the exterior
surface of the inner support to an interior surface of the wall of
the housing, at least a portion of the outer ring and at least a
portion of the inner heat fins sandwiching at least a portion of
the housing wall.
2. The heat exchanger assembly as set forth in claim 1, wherein the
inner heat fins are integral with the inner support.
3. The heat exchanger assembly as set forth in claim 2, wherein the
outer ring is shrink-fitted on the housing and the inner support
and inner heat fins are shrink-fitted in the housing.
4. The heat exchanger assembly as set forth in claim 3, wherein the
outer ring, inner support and inner heat fins are made of a
material having a higher thermal expansion coefficient than the
wall.
5. The heat exchanger assembly of claim 4, wherein the outer ring,
inner support and inner heat fins are made of aluminum.
6. The heat exchanger assembly as set forth in claim 1, wherein the
outer heat exchanger further comprises a plurality of outer heat
fins outwardly projecting from the outer ring.
7. The heat exchanger assembly as set forth in claim 6, wherein the
outer heat fins are welded, soldered or bonded by a
thermo-conductive adhesive to the outer ring.
8. The heat exchanger assembly as set forth in claim 1, wherein the
inner support further comprises an interior surface.
9. The heat exchanger assembly as set forth in claim 8, wherein the
interior surface of the inner support is adapted to form a gas
bearing or a seal portion, or both, with a sliding member movably
disposed through interior surface of the inner support.
10. The heat exchanger assembly as set forth in claim 8, further
comprising a solid annular ring portion connected to the inner
support or the inner fins and having an outer surface configured to
be in contact with the interior surface of the wall of the housing
when the annular ring portion is installed in the housing.
11. The heat exchanger assembly as set forth in claim 10, wherein
the annular ring portion is integral with the inner support or the
inner heat fins, or both.
12. The heat exchanger assembly as set forth in claim 11, further
comprising a sealant on the outer surface of the annular ring
portion.
13. A component of a Stirling cycle machine, comprising: a housing
comprising a wall defining an interior volume and adapted to seal
within the interior volume a working gas, the interior volume
comprising a compression region where the working gas is subject to
intermittent compression and expansion; an outer heat exchanger
comprising an outer ring disposed outside the housing and having an
interior surface in contact with an exterior surface of the wall; a
plurality of outer heat fins connected to the outer ring; an inner
support disposed inside the housing and having an exterior surface;
and a plurality of inner heat fins connecting the exterior surface
of the inner support to an interior surface of the wall of the
housing, at least a portion of the outer ring and at least a
portion of the inner heat fins sandwiching at least a portion of
the housing wall.
14. The component as set forth in claim 13, wherein the inner heat
fins are integral with the inner support.
15. The component as set forth in claim 14, wherein the outer ring
is shrink-fitted on the housing and the inner support and inner
heat fins are shrink-fitted in the housing.
16. The component as set forth in claim 15, wherein the outer ring,
inner support or inner heat fins are made of a material having a
higher thermal expansion coefficient than the wall.
17. The component as set forth in claim 15, further comprising a
sealant between the outer ring and the housing.
18. The component of claim 16, wherein the outer ring, inner
support or inner heat fins are made of aluminum, and wherein the
housing wall is made of stainless steel at least in portions in
contact with the outer ring and plurality of inner heat fins.
19. The component as set forth in claim 13, wherein the inner
support comprises an interior surface.
20. The component as set forth in claim 19, wherein the interior
surface of the inner support is adapted to form a gas bearing or a
seal portion, or both, with a sliding member movably disposed
through interior surface of the inner support.
21. A heat exchanger assembly for transferring heat across a wall
of a housing, the assembly comprising: an outer ring disposed
outside the housing and having an interior surface in contact with
an exterior surface of the wall; a plurality of outer heat fins
outwardly projecting from the outer ring; and a plurality of inner
heat fins extending inwardly from the interior surface of the wall,
at least a portion of the outer ring and at least a portion of the
inner heat fins sandwiching at least a portion of the housing
wall.
22. The heat exchanger assembly as set forth in claim 21, wherein
the inner heat fins are brazed, soldered or bonded with a
thermo-conductive adhesive to the interior surface of the wall.
23. The heat exchanger assembly as set forth in claim 21, wherein
the inner heat fins are shrink-fitted to the housing.
24. The heat exchanger assembly as set forth in claim 21, wherein
the outer heat fins are shrink-fitted to the outer ring.
25. The heat exchanger assembly as set forth in claim 21, further
comprising a solid annular ring portion connected to the inner fins
and having an outer surface configured to be in contact with the
interior surface of the wall of the housing when the annular ring
portion is installed in the housing.
26. The heat exchanger assembly as set forth in claim 25, wherein
the annular ring portion is integral with the inner heat fins.
27. A method for making a heat exchanger assembly for transferring
heat across a wall of a housing, the method comprising: positioning
an outer heat exchanger comprising an outer ring outside the
housing such that an interior surface of the outer ring is in
contact with an exterior surface of the wall; positioning a
plurality of outer heat fins on the outer ring; positioning an
inner support inside the housing; and connecting an interior
surface of the wall and an exterior surface of the inner support
using a plurality of inner heat fins such that at least a portion
of the inner heat fins and at least a portion of the outer ring
sandwich at least a portion of the housing wall.
28. The method as set forth in claim 27, further comprising
constructing the inner support and the plurality of inner heat fins
from the same piece of material.
29. The method as set forth in claim 28, wherein constructing
comprises forming an integral body comprising the inner support and
inner heat fins by removing material from the piece.
30. The method as set forth in claim 29, wherein removing comprises
machining.
31. The method as set forth in claim 27, further comprising forming
an aperture through the inner support.
32. The method as set forth in claim 27, wherein positioning the
outer ring comprises shrink-fitting the outer ring on the housing;
and connecting the interior surface of the wall and the exterior
surface of the inner support using the inner heat fins comprises
shrink-fitting the inner heat fins and the inner support inside and
against the housing wall.
33. The method as set forth in claim 32, wherein shrink-fitting the
outer ring on the housing comprises subjecting the outer ring to a
higher temperature than the housing, and subjecting the inner heat
fins and inner support to a lower temperature than the housing.
34. The method of claim 32, further comprising shrink-fitting a
plurality of outer heat fins to the outer ring.
35. The method of claim 32, further comprising applying a sealant
between the outer ring and the housing wall.
36. The heat exchanger assembly of claim 1, wherein the outer heat
exchanger further comprises a heat-transfer structure in thermal
contact with the outer ring and adapted to transfer heat from or to
the outer ring.
37. The heat exchanger assembly of claim 36, wherein the
heat-transfer structure comprises a tubing or channel adapted to
carry a heat-transfer fluid.
38. The heat exchanger assembly of claim 1, wherein the outer ring
comprises a mounting structure adapted to affix a heat-transfer
structure to the outer ring.
39. A heat exchanger assembly for transferring heat across a wall
of a housing, the assembly comprising: an inner support disposed
inside the housing and having an exterior surface; and a plurality
of inner heat fins connecting the exterior surface of the inner
support to an interior surface of the wall of the housing.
40. The heat exchanger assembly of claim 39, further comprising an
outer heat transfer structure in thermal contact with an exterior
surface of the housing wall, at least a portion of the outer
heat-transfer structure and at least a portion of the inner heat
fins sandwiching at least a portion of the housing wall.
41. The heat exchanger assembly of claim 40, wherein the
heat-transfer structure comprises a tubing or channel adapted to
carry a heat-transfer fluid.
42. The heat exchanger assembly of claim 39, further comprises a
mounting structure adapted to affix a heat-transfer structure to
the housing wall.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of the U.S. Provisional
Application Ser. No. 60/802,174, filed on May 19, 2006. The
aforementioned U.S. Provisional Application Ser. No. 60/802,174 is
incorporated herein by reference.
BACKGROUND
[0002] The application relates to heat exchangers. More
particularly, the invention relates to a heat exchanger assembly
for transferring heat between the interior and exterior of a
housing through a portion of the housing wall.
[0003] Heat exchangers are typically used to conduct heat between
two media without intermixing between the media. In a typical
environment where a heat exchanger may be used, a first medium is
isolated from a second medium by a wall. A heat exchanger is
attached to at least one side of the wall and has a structure, such
as heat fins, that provides a sufficiently large surface area for
establishing the desired heat exchange rate with the surrounding
medium.
[0004] As an example, in a Stirling cycle machine, such as a
Stirling cryocooler or a Stirling engine, a sealed housing contains
a working gas, a portion of which is periodically compressed and
expanded. The heat generated by the compression and other sources
is to be transferred to the outside of the housing and dissipated.
The effectiveness of the heat exchangers has a significant impact
on the efficiency of a Stirling cycle machine relative to the
Carnot efficiency. A variety of designs for heat exchangers exist
for Stirling cycle machines. For example, in certain cryocoolers
for refrigerating superconductor filter circuits used in base
stations for wireless telephone networks, the heat exchanger
assembly for dissipating heat from the working gas includes an
external heat exchanger. The external heat exchanger includes heat
fins circumferentially distributed around a columnar segment of the
cryocooler housing and radially projecting from the segment. The
heat fins are made from one or more pleated sheets of thermal
conductors such as sheet copper and affixed to the housing by
welding, brazing or the use of an adhesive. An internal heat
exchanger is typically also used to transfer heat from the working
gas to the housing.
[0005] A cryocooler housing for such applications is typically
constructed with stainless steel, which is a poor thermal conductor
compared to copper and aluminum. The housing wall is therefore
typically thin (wall thickness typically less than 1 mm) in order
to minimize the radial temperature gradient inside the wall thus
allowing a maximum thermal conduction and an optimum heat removal
in the area of the heat exchanger. However, a reduced thickness of
the housing wall results in a relatively high thermal resistance or
poor thermal conductivity in circumferential directions. High
resistance to circumferential heat conduction is undesirable
because heat needs to be adequately conducted in circumferential
directions to the bases of the heat radiating structures for a heat
exchanger to function properly.
[0006] U.S. Pat. No. 6,446,336 ("the '336 patent") discloses a heat
exchanger for transferring heat across a housing wall. The heat
exchanger has an outer ring seated against the exterior surface of
a portion of the housing and supporting radially outwardly
projecting external heat fins. The heat exchanger further has an
inner ring seated against the interior surface of the portion of
the housing wall and supporting radially inwardly projecting
internal heat fins. The disclosed heat exchanger has certain
advantages over prior art in heat transfer and structural
characteristics. However, in certain applications, it is desirable
to have rigid internal heat fins such as machined heat fins. It is
very difficult to make such heat fins in an inwardly projecting
configuration, as disclosed in the '336 patent. Further, in some
applications, it is desirable to have an internal passageway,
defined by the tips of the internal heat fins, to be highly
concentric with the housing and/or other components, such as the
compressor bore, of the Stirling cycle machine to. For example,
such precise alignment is often needed to achieve desired close
tolerances between stationary and moving components, such as
between an internal heat exchanger and a displacer in a Stirling
cycle machine and between the compressor bore and the compression
piston, which is coaxial with the displacer. With the configuration
disclosed in the '336 patent, it is difficult to achieve the
desired precision in alignment.
[0007] For these and other reasons, there is a need for an improved
heat exchanger assembly.
SUMMARY
[0008] This application discloses an improved heat exchanger
assembly. In one embodiment of the invention, an outer ring made of
a thermal conductor, such as copper, or aluminum, is positioned
between external heat fins and an exterior surface of the housing
wall, thereby providing improved heat distribution from the housing
wall to the external heat fins. An inner support made of a thermal
conductor, such as copper, or aluminum, is positioned inside the
housing wall and supports inner heat fins, which abut an interior
surface of the housing wall. At least a portion of the outer ring
and at least a portion of the inner heat fins sandwich at least a
portion of the housing wall. The inner support provides the
structural backing that enables the inner heat fins to be in direct
contact with the housing wall by a variety of methods, including
shrink-fitting. The inner heat fins can be press-fitted,
shrink-fitted, or otherwise bonded, to the housing wall, and the
outer ring can be press-fitted, shrink-fitted, or otherwise bonded,
to the housing wall.
[0009] In another embodiment of the invention, a component of a
Stirling cycle machine comprises a housing comprising a wall
defining an interior gas volume and adapted to seal within the
interior gas volume a working gas, the interior working gas volume
comprising a compression region where the working gas is subject to
intermittent compression and expansion; an outer ring disposed
outside the housing and having an interior surface in contact with
an exterior surface of the wall; a plurality of outer heat fins
projecting from the outer ring; an inner support disposed inside
the housing and having an exterior surface; and a plurality of
inner heat fins connecting the exterior surface of the inner
support to an interior surface of the wall of the housing. At least
a portion of the outer ring and at least a portion of the inner
heat fins sandwich at least a portion of the housing wall.
[0010] In another embodiment of the invention, a heat exchanger
assembly comprises an outer ring disposed outside the housing and
having an interior surface in contact with an exterior surface of
the wall; a plurality of outer heat fins outwardly projecting from
the outer ring; and a plurality of inner heat fins projecting
inwardly from the interior surface of the wall. At least a portion
of the outer ring and at least a portion of the inner heat fins
sandwich at least a portion of the housing wall. The inner heat
fins can be attached to the interior surface of the housing wall by
methods including brazing and soldering.
[0011] In another embodiment of the invention, a method for making
a heat exchanger assembly for transferring heat across a wall of a
housing comprises positioning an outer ring outside the housing
such that an interior surface of the outer ring is in contact with
an exterior surface of the wall; positioning a plurality of outer
heat fins on the outer ring; positioning an inner support inside
the housing; and connecting an interior surface of the wall and an
exterior surface of the inner support using a plurality of inner
heat fins such that at least a portion of the inner fins and at
least a portion of the outer ring sandwich at least a portion of
the housing wall. The inner heat fins can be shrink-fitted to the
housing wall, and the outer ring can be shrink-fitted on the
housing wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Other objects and advantages of the invention will become
apparent upon reading the following detailed description and upon
reference to the drawings in which:
[0013] FIG. 1 schematically shows a Stirling cryocooler in an
embodiment of the invention;
[0014] FIG. 2 shows a cross-sectional view of the heat exchanger
assembly of the Stirling cryocooler shown in FIG. 1;
[0015] FIG. 3 shows a portion of an outer heat fins in another
embodiment of the invention;
[0016] FIG. 4 shows a portion of an outer heat fins in an
alternative embodiment of the invention;
[0017] FIG. 5 is a perspective view of an internal heat exchanger
in an alternative embodiment of the invention;
[0018] FIG. 6 is a cross-sectional view of the internal heat
exchanger shown in FIG. 5;
[0019] FIG. 7(a) is a schematic cross-sectional view of a portion
of the Stirling cryocooler in an embodiment of the invention,
showing the outer ring and inner heat fins sandwiching a portion of
the house wall; and
[0020] FIG. 7(b) is a schematic cross-sectional view of a portion
of the Stirling cryocooler in an embodiment of the invention,
showing a portion of the outer ring and a portion of the inner heat
fins sandwiching a portion of the house wall
[0021] FIG. 8 shows a schematic cross-sectional view of a further
alternative embodiment of the invention.
[0022] FIG. 9 shows a schematic cross-sectional view of another
alternative embodiment of the invention.
[0023] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof have been shown
by way of example in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific embodiments is not intended to limit the
invention to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0024] Various embodiments will be described in detail with
reference to the drawings, wherein like reference numerals
represent like parts and assemblies throughout the several views.
Reference to various embodiments does not limit the scope of the
claims attached hereto. Additionally, any examples set forth in
this specification are not intended to be limiting and merely set
forth some of the many possible embodiments for the appended
claims. In particular, while the embodiments illustrated herein are
described in the context of Stirling cycle machines such as
Stirling cryocoolers, other embodiments not limited to Stirling
cycle machines are possible.
[0025] Referring to FIG. 1, in an embodiment of the invention, a
heat exchanger assembly is employed in a Stirling cycle machine,
which is configured as a cryocooler 100 includes sealed columnar
housing 120, with sections of various diameters disposed along a
longitudinal axis 150. The gas space inside the housing 120 is
generally divided into a working space 124 and a bounce space 126
by seals. The housing 120 includes at one end a cold finger 110,
which houses a displacer assembly 114. The cold finger 110 also
includes a cold heat exchanger, or heat acceptor unit, 112, which
serves to transfer heat from the exterior of the housing 120 to a
working gas confined in the working space 124. The cryocooler
housing 120 also encloses in its interior volume a linear motor 170
and a piston 180 driven by the motor for compressing and expanding
a portion of the working gas in a compression region 160. The
cryocooler 100 further includes a vacuum flange 130, which is also
used for positioning the heat acceptor unit 112 in a vacuum
chamber. In addition, a warm heat exchanger assembly 200 is
positioned to be in thermal contact with the compression region 160
for dissipating heat from the working gas to the exterior of the
housing 120.
[0026] The general structures and operation of Stirling cycle
machines, including those of Stirling cryocoolers, are well known
in the art. For example, a Stirling cryocooler with a housing
section having different diameters drawn from a single piece of
stainless steel is disclosed in the U.S. patent application Ser.
No. 10/729,719, filed Dec. 5, 2003, and issued on Nov. 21, 2006, as
U.S. Pat. No. 7,137,259. The aforementioned U.S. Pat. No. 7,137,259
is incorporated herein by reference.
[0027] Referring to FIG. 2, the warm heat exchanger assembly 200 in
this illustrative embodiment includes outer heat fins 220 outside
the housing wall 122 of the housing 120, an outer ring 210, which
is seated against an exterior surface of the housing wall 122 and
supports the outer heat fins 220. The assembly further includes
inner heat fins 230 inside the housing wall 122 of the housing 120.
The assembly 200 further includes an inner support member 240,
which is disposed inside, and in contact with, the inner heat fins
230. At least a portion of the outer ring 210 and at least a
portion of the inner heat fins 230 sandwich at least a portion of
the housing wall. That is, at least a portion of the outer ring 210
and at least a portion of the inner heat fins 230 occupy the same
axial position range (I, in the examples shown in FIGS. 7(a) and
7(b)) along the longitudinal axis 150.
[0028] In the illustrative embodiment of the invention, the inner
support member 240 is integral with the inner heat fins 230. That
is, both the inner support member 240 and the inner heat fins 230
are fabricated out of a single starting piece. For example, the
fins can be formed on the inner support member 240 by removing
material from the starting piece by machining, water cutting, laser
cutting, chemical etching and other suitable techniques. The
integral structure of the inner heat fins 230 and the inner support
member 240 can also be formed by mold casting, powder metallurgy
and any other suitable techniques for making metal parts.
Alternatively, inner heat fins can be fabricated separately from
the inner support member 240 and attached to the inner support
member 240 by any suitable technique, including welding, brazing
and soldering.
[0029] The inner heat fins 230 can be affixed to the housing wall
122 by a variety of suitable methods, including press-fitting,
shrink fitting and bonding with a conductive adhesive. In this
illustrative embodiment, the inner heat fins 230 are affixed to the
housing wall 122 by shrink-fitting. The requisite rigidity to
withstand the shrink-fitting process is supplied by the combined
structure of the inner heat fins 230 and the inner support member
240. The inner support member 240 and inner heat fins 230 in this
case are made of aluminum, which has a higher thermal expansion
coefficient than the housing wall 122, which is made of a stainless
steel. Other suitable material combinations can also be used. For
example, copper, its alloys or other materials that have higher
thermal conductivities can be used. In cases, such as for copper,
where the thermal expansion coefficient of the inner fins is
similar to that of the housing wall such that shrink-fitting may be
unsuitable, other methods such as press-fitting and bonding can be
used to affix the inner heat fins 230 to the housing wall 122. In
attaching the inner heat fins 230 to the housing wall 122 by
shrink-fitting, the assembly of the heat fins 230 and inner support
240 are placed in a medium, for example liquid nitrogen, having a
lower temperature than the housing wall 122 before positioned
inside the housing wall 122. Upon being warmed up, the assembly of
the heat fins 230 and inner support 240 become shrink-fitted to the
housing wall 122. Alternatively, the housing wall 122 can be heated
before being slid over the inner heat fins 230 and then allowed to
cool. Shrink fitting allows the inner heat fins 230 to be attached
to the housing wall 122 without the need for other joining
techniques such as welding, brazing and soldering, which tend to
introduce non-uniform deformation into the components being
joined.
[0030] For certain applications, such as in a Stirling cycle
machine having a displacer, an interior surface 250 can be formed
in the inner support 240, as shown in FIG. 2, to accommodate a
sliding member (erg., the displacer) moving through the aperture
defined by the interior surface 250. Moreover, the interior surface
250 in an illustrative embodiment is ground or honed to be
concentric with the housing 120 and/or other components, such as
the compressor bore, of the Stirling cycle machine and sufficiently
smooth to act as a seal and/or a bearing surface for the sliding
member. For example, in an embodiment for a Stirling cryocooler,
the interior surface 250 is sized to accommodate a displacer and
has the requisite tolerance and smoothness to form a displacer seal
and for realizing a displacer gas bearing, which has gas ports for
discharging pressurized gas in between the displacer surface and
the interior surface 250 of the inner support 240.
[0031] Referring again to FIG. 2, the outer ring 210 is disposed
between, and in contact with, the housing wall 122 and the outer
heat fins 220. In this illustrative embodiment of the invention,
the outer ring 210 is a cylindrical annular ring circumferentially
surrounding the housing wall 122. The outer ring 210 in this
illustrative embodiment is made of a material having a higher
thermal conductivity, than the thermal conductivity of material for
the housing wall 122. For example, the housing wall is typically
made of a stainless steel. In such a case, copper, aluminum or
their respective alloys or other materials that have higher thermal
conductivities can be used for the outer ring.
[0032] As noted above, low heat flow resistance in circumferential
directions is important for the proper functioning of a heat
exchanger, and the prior art addresses this issue by using both an
external and internal rings. In this respect, the illustrative
embodiments of the invention employ a single outer ring 210 to
achieve the same functionality as two rings used in the prior art,
thereby reducing the components needed and simplifying the
manufacturing process.
[0033] The outer ring 210 can be affixed to the housing wall 122 by
a variety of methods. For example, an adhesive with good thermal
conduction properties, such as a thermo-conductive adhesive, which
has metal particles embedded in the resin, can be used to bond the
outer ring 210 to the housing wall 122. The outer ring 210 can also
be press-fitted, shrink-fitted, or otherwise connected, to the
housing wall 122 in a similar way as discussed above for
shrink-fitting the inner heat fins inside the housing. For example,
an aluminum outer ring 210 can be heated prior to being slipped
over a portion of a stainless steel housing 120 and then cooled to
shrink-fit on the housing 120. In another embodiment of the
invention, a sealant is applied between the outer ring 210 and the
housing wall 122 prior to shrink-fitting to seal any gap between
the outer ring 210 and the housing wall 122. This is useful in
applications where the outer ring is connected to, or used as part
of, a flange for a gas-tight chamber (e.g., a vacuum flange in a
Stirling cryocooler). A variety of sealants well known in the art
can be used to suit particular applications.
[0034] In addition to conducting heat away from housing wall 122,
the outer ring 210 also serves to enhance the structural integrity
of the housing wall 122, which is typically very thin, as mentioned
above. In Stirling cooler applications, the interior of housing 120
is typically pressurized. It is therefore particularly desirable
and typically more effective to reinforce the housing wall 122 from
outside in Stirling cooler applications.
[0035] The outer heat fins 220 can be affixed to the outer ring 210
by a variety of methods, including welding, brazing and bonding
with an adhesive. Instead of affixing the outer heat fins 220 to
the outer ring 210, the outer heat fins 220 can be made from the
same starting piece of material as the outer ring 210 in similar
ways as described above for the inner heat fins 230.
[0036] As alternatives to the structures described above, the heat
fins 220, 230 can be constructed from one or more pleated sheets of
thin metal, such as copper. They can be shaped in a variety of ways
as need to suit the particular design. For example, with further
reference to FIG. 3, the outer heat fins 220 comprise fins 322
constructed from one or more pleated sheets of thin copper, but can
be constructed from other thermal conductors and in other forms
suitable for the specific application. For example, as show in FIG.
4, the heat fins 422 of the outer heat fins 420 can be constructed
from individual sheets of copper.
[0037] In a further illustrative embodiment of the invention, as
shown in FIGS. 5 and 6, an internal heat exchanger 500 includes
inner heat fins 530 and inner support member 540 similar to the
internal heat exchangers in the illustrative embodiments discussed
above. In addition, an annular ring portion 590 is connected to the
inner heat fins 530 and inner support member 540. The annular ring
portion 590 in this embodiment is radially coextensive with the
heat fins 530 on the outside and defines a chamber 592 on the
inside and in fluid communication with the channels 532 between the
inner heat fins 530. The annular ring portion 590 and the housing
wall 122 form a seal between the working space and bounce space
when the internal heat exchanger 500 is installed in the housing
120, with the longitudinal axis 550 of the heat exchanger 500
aligned with the longitudinal axis 150 of the housing 120.
[0038] In this example, the heat exchanger 500, the annular ring
portion 590, the inner heat fins 530 and the inner support member
540 are an integral piece, made by cutting channels 532 (i.e.,
spaces between the inner heat fins 530) in a cylindrical stock
partially through the length of the stock. Non-integral
configuration of the annular ring portion 590, the inner heat fins
530 and the inner support member 540 can also be used.
[0039] As in certain other embodiments described above, the
internal heat exchanger 500 can be affixed to the housing 120 by
press-fitting, shrink-fitting, or other bonding methods, with both
the inner fins 530 and the annular ring portion 590 in contact with
the housing wall 122. In the example where the annular ring portion
590, the inner heat fins 530 and the inner support member 540 are
an integral piece, the entire heat exchanger 500 can be affixed to
the housing 120 as a whole. In cases where non-integral
configurations of the annular ring portion 590, the inner heat fins
530 and the inner support member 540 are used, the annular ring
portion 590 and the inner heat fins 530 can be affixed to the
housing 120 by press-fitting, shrink-fitting, or other bonding
methods. The inner support member 540 can further be press-fitted,
shrink-fitted or otherwise bonded to the interior of the inner heat
fins 530. Further, as with the outer ring 210, a sealant can be
applied between the annular ring portion 590 and the housing wall
122 to eliminate any gap between them to further ensure a gas-tight
seal.
[0040] In another embodiment of the invention, the inner support
member 540 is omitted, with the inner heat fins 530 entirely
supported by the annular ring portion 590.
[0041] A further alternative embodiment of the invention is
schematically shown in FIG. 8. In this embodiment, the heat
exchanger assembly 800 includes is similar to that (200) shown in
FIG. 2 but without the external heat fins. The exchanger assembly
800 in this illustrative embodiment includes an outer ring 810,
which is seated against an exterior surface of the housing wall
122. The assembly 800 further includes inner heat fins 830 inside
the housing wall 122. The assembly 800 further includes an inner
support member 840, which is disposed inside, and in contact with,
the inner heat fins 830.
[0042] Optionally, the embodiment shown in FIG. 8 can further
include additional heat transfer structures, or provisions for
attaching additional heat-transfer structures, for transferring
heat to or from the outer ring 810. Symbolically indicated at label
850 in FIG. 8, these structures and provisions can include tubings
mounted on the surface of the outer ring 810, or channels formed
within the outer ring 810, for carrying heat transfer fluids, such
as water. The structures and provisions can also include heat sinks
such as a volume of material with a large thermal mass. Further
examples include recesses, protuberances or other structures on the
outer ring 810 for affixing heat-transfer structures.
[0043] In another illustrative embodiment of the invention,
schematically shown in FIG. 9, a heat exchanger assembly 900
includes inner heat fins 930 inside the housing wall 122, and an
inner support member 940, which is disposed inside, and in contact
with, the inner heat fins 930. Unlike certain other illustrative
embodiments, the heat exchanger assembly 900 in this case is
without an ring-shaped outer heat exchanger portion. Instead, the
heat exchanger assembly 900 includes other outer heat transfer
structures, or provisions for attaching outer heat-transfer
structures, for transferring heat to or from the housing wall 122.
Symbolically indicated at label 950 in FIG. 9, these structures and
provisions can include tubings mounted on the outer surface of the
housing wall 122. The structures and provisions can also include
heat sinks such as a volume of material with a large thermal mass.
The volume material can further include channels 952 for carrying a
heat transfer fluid, such as water, other fluids or gasses. Further
examples include recesses, protuberances or other structures on the
housing wall 122 for affixing heat-transfer structures.
[0044] Thus, the illustrative embodiments of the invention offer
several advantages over prior art devices and methods. Among the
advantages are the ease of manufacturing of inner heat fins that
project outwardly from the inner support, the compatibility with
shrink-fitting process for contacting the inner heat fins with the
housing, and the compatibility with precision alignment of an
interior surface of the inner support for forming gas bearing or
seal, or both, with a sliding member movably disposed through the
interior surface.
[0045] All patents and publication referred to above are
incorporated herein by reference. The particular embodiments
disclosed above are illustrative only, as the invention may be
modified and practiced in different but equivalent manners apparent
to those skilled in the art having the benefit of the teachings
herein. Furthermore, no limitations are intended to the details of
construction or design herein shown, other than as described in the
claims below. It is therefore evident that the particular
embodiments disclosed above may be altered or modified and all such
variations are considered within the scope and spirit of the
invention. Accordingly, the protection sought herein is as set
forth in the claims below.
* * * * *