U.S. patent application number 13/932174 was filed with the patent office on 2013-11-14 for internal heat exchanger.
This patent application is currently assigned to ContiTech Kuehner GmbH & Cie. KG. The applicant listed for this patent is ContiTech Kuehner GmbH & Cie. KG. Invention is credited to Nikhil Baxi, Eugene Dianetti.
Application Number | 20130299143 13/932174 |
Document ID | / |
Family ID | 49547731 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130299143 |
Kind Code |
A1 |
Baxi; Nikhil ; et
al. |
November 14, 2013 |
INTERNAL HEAT EXCHANGER
Abstract
The present invention provides a heat exchanger having an inner
tube forming an inner flow path and having an inlet and an outlet;
an outer tube radially surrounding at least a portion of the inner
tube and spaced radially outwardly therefrom to form an annular
space; and a thermally conductive spiral element wound around the
inner cube and disposed in the space, wherein the spiral element
forms, in conjunction with the inner tube and the outer tube, a
helical flow path through the space, the helical flow path in fluid
communication with an inlet and an outlet of the outer tube, and
wherein the outer tube is thermally isolated from the spiral
element. The invention further provides for collars connecting the
outer tube to the inner tube.
Inventors: |
Baxi; Nikhil; (Cordova,
TN) ; Dianetti; Eugene; (Collierville, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ContiTech Kuehner GmbH & Cie. KG |
Oppenweiler |
|
DE |
|
|
Assignee: |
ContiTech Kuehner GmbH & Cie.
KG
Oppenweiler
DE
|
Family ID: |
49547731 |
Appl. No.: |
13/932174 |
Filed: |
July 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/US2011/067775 |
Dec 29, 2011 |
|
|
|
13932174 |
|
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Current U.S.
Class: |
165/154 |
Current CPC
Class: |
F25B 2327/001 20130101;
F28D 7/106 20130101; F28F 2270/00 20130101; F25B 40/00 20130101;
F28D 7/026 20130101; F28F 1/12 20130101; F28F 13/00 20130101; F25B
27/00 20130101; F28D 2021/008 20130101 |
Class at
Publication: |
165/154 |
International
Class: |
F28F 1/12 20060101
F28F001/12 |
Claims
1. A heat exchanger comprising: an inner tube forming an inner flow
path and having an inlet and an outlet; an outer tube radially
surrounding at least portion of the inner tube and spaced radially
outwardly therefrom to form an annular space; and a thermally
conductive spiral element wound around the inner tube and disposed
in the space, wherein the spiral element forms, in conjunction with
the inner tube and the outer tube, a helical flow path through the
space, the helical flow path in fluid communication with an inlet
and an outlet of the outer tube, and wherein the outer tube is
thermally isolated from the spiral element.
2. The heat exchanger of claim 1, wherein the outer tube is
thermally isolated from the spiral element by being spaced radially
outwardly from the spiral element, forming an annular gap defining
a bypass flow path.
3. The heat exchanger of claim 2, wherein the bypass flow path
accommodates less than about 5% of total flow through the bypass
and helical flow paths.
4. The heat exchanger of claim 2, wherein the bypass flow path
accommodates less than about 1% of total flow through the bypass
and helical flow paths.
5. A heat exchanger comprising: an inner tube forming an inner flow
path and having an inlet and an outlet; an outer tube radially
surrounding at least portion of the inner tube and spaced radially
outwardly therefrom to form an annular space; and a thermally
conductive spiral element wound around the inner tube and disposed
in the space, wherein the spiral element surrounds the inner tube
and forms, in conjunction with the inner tube and the outer tube, a
helical flow path through the annular space, the helical flow path
in fluid communication with an inlet and an outlet of the outer
tube, and wherein the spiral element continuously contacts the
inner tube along a major length of the spiral element, and the
spiral element is either integrally attached to the inner tube, as
by welding or brazing, or resiliently biased against the inner tube
such that the spiral element is tightly held against the inner
tube.
6. The heat exchanger of claim 5, wherein the inner tube has an
outer diameter surface that is smooth.
7. The heat exchanger of claim 5, wherein the outer diameter
surface is of uniform diameter along the length thereof surrounded
by the spiral element.
8. The heat exchanger of claim 5, wherein the outer tube is
thermally isolated from the spiral element by an insulation
layer.
9. The heat exchanger of claim 8, wherein the insulating layer
extends along substantially the entire inside surface of the outer
tube, extends along only the spiral element, or is intermittently
disposed along the length of the inside surface of the outer tube
so as to act as a spacer.
10. The heat exchanger of claim 9, wherein the spiral element is
not attached to at least one of the inner tube or outer tube.
11. The heat exchanger of claim 5, wherein the turns of the spiral
element are axially spaced apart.
12. The heat exchanger of claim 5, wherein the spiral element is
welded to the inner tube.
13. The heat exchanger of claim 8, wherein the spiral element is in
contact with the inner tube for substantially all of the length of
the spiral element.
14. The heat exchanger of claim 5, wherein axial ends of the outer
tube are welded to the inner tube.
15. The heat exchanger of claim 5, wherein the outer tube is
connected to the inner tube by collars at respective axial ends of
the outer tube.
16. The heat exchanger of claim 5, further comprising a first
collar configured to secure the outer tube to the inner tube at a
first axial end of the outer tube, the first collar including a
first radial hole and the helical flow path is in fluid
communication with the first radial hole.
17. The heat exchanger of claim 16, further comprising a second
collar configured to secure the outer tube to the inner tube at a
second axial end of the outer tube, the second collar including a
second radial hole, wherein the helical flow path is in fluid
communication with the second radial hole.
18. The heat exchanger of claim 17, wherein the first collar
includes a central bore having a diameter substantially equal to an
outer diameter of the inner tube, a first counter bore with a
diameter intermediate of the diameter of the central bore and a
diameter of a second counter bore, the diameter of the second
counter bore being substantially equal to outside diameter of the
outer tube, and wherein the central bore receives the inner tube
and the second counter bore receives the outer tube therein.
19. The heat exchanger of claim 18, wherein the first radial hole
is disposed in the first counter bore.
20. A heat exchanger comprising: an inner tube forming an inner
flow path and having an inlet and an outlet; an outer tube spaced
radially outwardly of the inner tube and radially surrounding at
least portion of the inner tube at an overlap region forming a gap
therein; a thermally conductive spiral element wound around the
inner tube and disposed in the gap of the overlap region; and a
first collar configured to secure the outer tube to the inner tube
at a first axial end of the cuter tube, the first collar including
a first radial hole; wherein the spiral element forms, in
conjunction with the inner tube and the outer tube, a helical flow
path through the gap of the overlap region, and the helical flow
path is in fluid communication with the first radial hole.
21. The heat exchanger of claim 20, further comprising a second
collar configured to secure the outer tube to the inner tube at a
second axial end of the outer tube, the second collar including a
second radial hole, wherein the helical flow path is in fluid
communication with the second radial hole.
22. The heat exchanger of either of claim 21, wherein the first
collar includes a central bore having a diameter substantially
equal to an outer diameter of the inner tube, a first counter bore
with a diameter intermediate of the diameter of the central bore
and a diameter of a second counter bore, the diameter of the second
counter bore being substantially equal to outside diameter of the
outer tube, and wherein the central bore receives the inner tube
and the second counter bore receives the outer tube therein.
23. The heat exchanger of claim 22, wherein the first radial hole
is disposed in the first counter bore.
24. The heat exchanger of claim 23, wherein the outer tube is
thermally isolated from the spiral element.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of
international patent application PCT/US2011/067775, filed Dec. 29,
2011, designating the United States and claiming priority from U.S.
Provisional Application No. 61/427,822 filed Dec. 29, 2010, and the
entire content of both applications is hereby incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an internal heat exchanger,
and more particularly to a double pipe internal heat exchanger for
an automotive application Wherein the pipes are separated by a
spring or spiral element providing a helical outer fluid
passageway.
BACKGROUND OF THE INVENTION
[0003] Heat exchangers are often used in, for example, air
conditioners that may used in motor vehicles, for example, in the
form of CO.sub.2 air conditioners. An internal heat exchanger
serves to transfer heat from the refrigerant on the high-pressure
side to the refrigerant on the low-pressure side, whereby the
so-called coefficient of performance, that is, the ratio of
refrigeration capacity and input power of the air conditioner, is
significantly increased.
[0004] Efficiency and performance gains may be achieved by the use
of a coaxial heat exchanger where the liquid refrigerant flows
around the outside of the suction tube. Heat is transferred from
the liquid to the suction line which increases sub-cooling in the
liquid line. However, known internal heat exchangers may not always
maximize the heat transfer in a short compact length of suction
line.
SUMMARY OF THE INVENTION
[0005] The present invention provides a heat exchanger having an
inner tube forming an inner flow path and having an inlet and an
outlet; an outer tube radially surrounding at least a portion of
the inner tube and spaced radially outwardly therefrom to form an
annular space; and a thermally conductive spiral element wound
around the inner tube and disposed in the space, wherein the spiral
element forms, in conjunction with the inner tube and the outer
tube, a helical flow path through the space, the helical flow path
in fluid communication with an inlet and an outlet of the outer
tube, and wherein the outer tube is thermally isolated from the
spiral element.
[0006] The outer tube may be thermally isolated from the spiral
element by being spaced radially outwardly from the spiral element,
forming a bypass flow path.
[0007] The bypass flow path may accommodate less than about 5% of
total flow through the bypass and helical flow paths.
[0008] The bypass flow path may accommodate less than about 1% of
total flow through the bypass and helical flow paths.
[0009] The outer tube may be thermally isolated from the spiral
element by an insulation layer interposed between the spiral
element and the outer tube.
[0010] The spiral element may be welded to the inner tube.
[0011] The spiral element may be held tightly against the outer
diameter of the inner tube such as by the inherent resiliency of
the spiral element which may be in the form of a spring. More
particularly, the spiral element may have when not assembled to the
inner tube (unsprung state) an inner diameter less than the outer
diameter of the inner tube such that the spiral element can be
resiliently expanded to slip over the inner tube and then released
with the resiliency of the spiral element causing the spiral
element to contract around the inner tube and be held to the inner
tube under a radially inward biasing force.
[0012] The spiral element may foe in contact with the inner tube
for substantially all of the length of the spiral element.
[0013] Axial ends of the outer tube may be welded to the inner
tube.
[0014] The outer tube may be connected to the inner tube by collars
at respective axial ends of the outer tube.
[0015] The spiral element may be free to move axially relative to
at least one of the inner and outer tubes, and particularly the
outer tube, so that the heat exchanger can be bent along its axial
length without damaging the heat exchanger.
[0016] The foregoing general features of the invention may apply
individually or collectively to a heat exchanger according to
another aspect of the invention, which heat exchanger includes an
inner tube forming an inner flow path and having an inlet and an
outlet; an outer tube radially surrounding at least portion of the
inner tube and spaced radially outwardly therefrom to form an
annular space; and a thermally conductive spiral element wound
around the inner tube and disposed in the space, wherein the spiral
element surrounds the inner tube and forms, in conjunction with the
inner tube and the outer tube, a helical flow path through the
annular space, the helical flow path in fluid communication with an
inlet and an outlet of the outer tube, and wherein the spiral
element continuously contacts the inner tube along a major length
of the spiral element, and the spiral element is either integrally
attached to the inner tube, as by welding or brazing, or
resiliently biased against the inner tube such that the spiral
element is tightly held against the inner tube.
[0017] The inner tube has an outer diameter .surface that is
smooth.
[0018] The outer diameter surface is of uniform diameter along the
length thereof surrounded by the spiral element.
[0019] The foregoing general features of the invention may apply
individually or collectively to a heat exchanger according to
another aspect of the invention, which heat exchanger includes an
inner tube forming an inner flow path and having an inlet and an
outlet; an outer tube spaced radially outwardly of the inner tube
and radially surrounding at least portion of the inner tube at an
overlap region forming an annular space therein; a thermally
conductive spiral element wound around the inner tube and disposed
in the space of the overlap region; and a first collar configured
to secure the outer tube to the inner tube at a first axial end of
the outer tube, the first collar including a first radial hole;
wherein the spiral element forms, in conjunction with the inner
tube and the outer tube, a helical flow path through the space of
the overlap region, and the helical flow path is in fluid
communication with the first radial hole.
[0020] The heat exchanger may further include a second
collar-configured to secure the outer tube to the inner tube at a
second axial end of the outer tube, the second collar including a
second radial hole, wherein the helical flow path is in fluid
communication with the second radial hole.
[0021] The first collar may include a central bore having a
diameter substantially equal to an outer diameter of the inner
tube, a first counter bore with a diameter intermediate of the
diameter of the central bore and a diameter of a second counter
bore, the diameter of the second counter bore being substantially
equal to outside diameter of the outer tube, and wherein the
central bore receives the inner tube and the second counter bore
receives the outer tube therein.
[0022] The first radial hole may be disposed in the first counter
bore.
[0023] The outer tube may be thermally isolated from the spiral
element.
[0024] The foregoing and other features of the invention are
hereinafter described in greater detail with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention will now be described with reference to the
drawings wherein:
[0026] FIG. 1 is a schematic view of an automotive air conditioning
system;
[0027] FIG. 2 is a perspective view of a heat exchanger in
accordance with the present invention including the outer tube and
collars shown in phantom outline;
[0028] FIG. 3 is a partial cross-sectional view of the heat
exchanger;
[0029] FIG. 3A is an enlarged portion of FIG. 3, but showing an
adaption of the heat exchanger wherein an inner spiral element is
spaced from and thus relatively thermally isolated with respect to
the cuter tube;
[0030] FIG. 4 is a side view of the heat exchanger;
[0031] FIG. 5 is a perspective view of another heat exchanger in
accordance with the present invention including the outer tube
shown in phantom outline;
[0032] FIG. 6 is a partial cross-sectional view of the heat
exchanger of FIG. 5; and,
[0033] FIG. 7 is a side view of the heat exchanger of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0034] A heat exchanger in accordance with the present invention
may be used In a number of applications, but, for ease of
explanation and comprehension, will be described herein in
reference to an air conditioning system for use in an automobile.
Further, the use of the terms pipe and tube and the like (tubular
members) are used interchangeably and do not necessarily denote a
limiting definition unless the context demands otherwise. Also, the
term "spiral" is intended to encompass "helical" and is used
interchangeably therewith.
[0035] FIG. 1 is a schematic view of an example air conditioning
system 100 that may be used in accordance with aspects of the
present invention. A vehicle may have an engine room 1 holding an
engine 10 therein and a passenger compartment 2 separated from the
engine room 1 by a dash panel 3. The air conditioning system 100
may have a refrigerant cycle device 100A including an expansion
valve 131 and an evaporator 141, and an interior unit 100B.
Components of the refrigerant cycle device 100A (usually excluding
the expansion valve 131 and the evaporator 141) may be disposed in
a predetermined mounting space of the engine room 1. The interior
unit 100B may be arranged in an instrument panel placed in the
passenger compartment 2.
[0036] The interior unit 100B may include a blower 102, the
evaporator 141, a heater 103, and an air conditioner case 101
housing the components of the interior unit 100B. The blower 102
may take in outside air or inside air selectively and send air to
the evaporator 141 and the heater 103. The evaporator 141 is a
cooling heat exchanger that evaporates a refrigerant used for a
refrigeration cycle to make the evaporating refrigerant absorb
latent heat of vaporisation from air so as to cool the air. The
heater 103 may use hot water (for example, engine-cooling water)
for cooling the engine 10 as heat source to heat air to be blown
into the passenger compartment 2.
[0037] An air mixing door 104 may be disposed near the heater 103
in the air conditioner case 101. The air mixing door 104 may be
operated to adjust the mixing ratio between cool air cooled by the
evaporator 141 and hot air heated by the heater 103 so that air
having a desired temperature is sent into the passenger compartment
2.
[0038] The refrigerant cycle device 100A may include a compressor
110, a condenser 120, the expansion valve 131 and the evaporator
141. Tubes 150 may connect those components of the refrigerant
cycle device 100A to form a closed circuit. At least one
double-wall tube 160 of the present invention may be placed in the
tubes 150. The condenser 120 (for example a refrigerant radiator,
gas cooler, or the like) may serve as a high-pressure heat
exchanger for cooling high-pressure high-temperature refrigerant.
The evaporator 141 may serve as a low-pressure heat exchanger and
may be disposed to cool air passing therethrough. The expansion
valve 131 is a pressure reducer, such as a throttle or an
ejector.
[0039] In the illustrated example, the compressor 110 is driven by
the engine 10 to compress a low-pressure refrigerant to provide a
high-temperature high-pressure refrigerant in the refrigerant cycle
device 100A. A pulley 111 is attached to the drive shaft of the
compressor 110. A drive belt 12 is extended between the pulley 111
and a crankshaft pulley 11 to drive the compressor 110 by the
engine 10. The pulley 111 is linked to the drive shaft of the
compressor 110 by an electromagnetic clutch (not shown). The
electromagnetic clutch connects the pulley 111 to or disconnects
the pulley 111 from the drive shaft of the compressor 110. The
condenser 120 is connected to a discharge side of the compressor
110. The condenser 120 is a heat, exchanger that cools the
refrigerant by outside air to condense the refrigerant vapor into
liquid refrigerant.
[0040] The expansion valve 131 reduces the pressure of the
refrigerant discharged from the condenser 120 and makes the
refrigerant expand. The expansion valve 131 may be a
pressure-reducing valve capable of reducing the pressure of the
liquid refrigerant in an isentropic state. The expansion valve 131
included in the interior unit 100B usually is placed near the
evaporator 141. The expansion valve 131 may be a
temperature-controlled expansion valve having a variable orifice
and may be capable of controlling the flow of the refrigerant
discharged from the evaporator 141 and flowing into the compressor
110 so that the refrigerant is heated at a predetermined degree of
superheat. As described above, the evaporator 141 is a cooling heat
exchanger for cooling air to be blown into the passenger
compartment. The discharge side of the evaporator 141 is connected
to the suction side of the compressor 110.
[0041] The double-wall tube 160 may be formed by combining a part
of a high-pressure tube 151 and a part of a low-pressure tube 152
in the tubes 150. The high-pressure tube 151 extends between the
condenser 120 and the expansion valve 131 to carry the
high-pressure refrigerant before being decompressed. The
low-pressure tube 152 extends between the evaporator 141 and the
compressor 110 to carry a low-temperature low-pressure refrigerant
after being decompressed and cooled.
[0042] For example, when the above-described air conditioning
system is implemented, the following process may occur: when a
passenger in a passenger compartment desires to operate the air
conditioning system 100 for a cooling operation, an electromagnetic
clutch may be engaged to drive the: compressor 110 by the engine
10. Then, the compressor 110 sucks in the refrigerant discharged
from the evaporator 141, compresses the refrigerant and discharges
the high-temperature high-pressure refrigerant into the condenser
120. The condenser 120 cools the high-temperature high-pressure
refrigerant into a liquid refrigerant state with a substantially
totally liquid phase. The liquid refrigerant from the condenser 120
flows into the expansion valve 131 through the liquid tube 164
connected to the double-wall tube 160, and through the annular
space formed between the inner tube 162 and the outer tube 161 of
the double-wall tube 160. The expansion valve 131 reduces the
pressure of the liquid refrigerant and allows the liquid
refrigerant to expand. The evaporator 141 evaporates the liquid
refrigerant into a substantially saturated gas refrigerant. The
refrigerant evaporated by the evaporator 141 absorbs heat from air
flowing through the evaporator 141 to cool the air to be blown into
the passenger compartment. The saturated gas refrigerant evaporated
by the evaporator 141, that is, the lower-temperature low-pressure
refrigerant, flows through the suction tube, the inner tube 162 and
the suction tube into the compressor 110.
[0043] Heat is transferred from the higher-temperature
higher-pressure refrigerant (up to about 600 Psi, for example)
flowing through the double-wall tube 160 to the lower-temperature
lower-pressure refrigerant flowing through double-wall tube 160.
Consequently, in the double-wall tube 160, the higher-temperature
higher-pressure refrigerant is cooled and the lower-temperature
lower-pressure refrigerant is heated. The liquid refrigerant
discharged from the condenser 120 typically is sub-cooled and the
temperature thereof drops while the liquid refrigerant is flowing
through the double-wall tube 160. The saturated gaseous refrigerant
discharged from the evaporator 141 typically is superheated into a
gaseous refrigerant having a degree of superheat.
[0044] Turning now to FIGS. 2 and 3, the double-wall tube heat
exchanger 160 is shown in accordance with the invention. In FIG. 2,
the outer tube 161 is shown in ghost-lines so that interior
components of the heat exchanger can be seen as well.
[0045] A helically wound spring or other spiral element 170 may be
wound around the inner tube 162 and defines, along with the inner
surface of the outer tube 161 and the outer surface of the inner
tube 162, a helical passageway for flow of fluid (for example,
liquid refrigerant). The spiral element 170 may be tightly wound or
otherwise in direct or indirect thermal contact with the inner tube
162 in order to improve thermal conductivity therebetween. For
example, the outer surface of the inner tube 162 may be smooth in
order to maximize the contact area with the spiral element 170
wrapped around it. Optionally, the spiral element 170 may be welded
to the inner tube 162 in order to improve the thermal conductivity
therebetween. The inner, outer and spiral element each may be of
uniform diameter at least over the axially coextensive portions
thereof.
[0046] As noted, the spiral element may be held tightly against the
outer diameter of the inner tube, such as for example by the
inherent resiliency of the spiral element which may foe in the
form, of a spring. More particularly, the spiral element may have
when not assembled to the inner tube (unsprung state) an inner
diameter less than the cuter diameter of the inner tube such that
the inner tube such that spiral element can be resiliently expanded
to slip over the inner tube and then released with the resiliency
of the spiral element causing the spiral element to contract around
the inner tube and be held to the inner tube under a radially
inward biasing force.
[0047] The spiral element 170 may be made from a material having a
high thermal conductivity, for example metallic material such as,
for example, aluminum. Inner and outer tubes 162 and 161 may also
be made of thermally conductive materials, for example metallic
materials such as, for example, aluminum.
[0048] The outer tube 161 has an inlet 180 and an outlet 181. The
inlet 180 may be connected to, for example, the condenser 120 of
the air-conditioning system 100. The liquid is therefore forced to
sweep the outer surface of the inner tube 162 and the spiral
element 170 along a helical path. This flow path may have a reduced
cross-sectional area as compared with a double-wall heat exchanger
without a spiral element of corresponding size. This reduced
cross-sectional area flow path increases the velocity of fluid flow
and, therefore, increases the effectiveness of the convection
cooling. Further, the helical flow path increases the length of the
flow path, as compared with a double-wall heat exchanger without
the spiral element, while using the same amount of physical space.
The increased length of the flow path may also increase the
efficiency of the heat transfer occurring in the heat exchanger
160. The spiral element 170 may be thermally isolated from the
inner surface of the outer tube 161 as illustrated in FIG. 3A. This
thermal isolation may be accomplished by, for example, an annular
gap 175 between the outer tube 161 and the spiral element 170. This
gap may thus form a bypass flow path.
[0049] Preferably, the bypass flow path may account for less than
about 5% of the total flow between the inner and outer tubes (162,
161). More preferably, the bypass flow path may account for less
than about 1% of the total flow between the inner and outer tubes
(162, 161). This thermal isolation may exhibit surprising
performance by, for example, preventing conduction from the outer
tube 161 to the spiral element 170 and the inner tube 162.
[0050] Alternatively, the thermal isolation may, for example, be
accomplished by one or more layers of insulating material 185. The
insulating material 185 may extend along substantially the entire
inside surface of the outer tube 161, may extend along only the
spiral element, or may be intermittently disposed along the length
of the inside surface of the outer tube so as to act as a
spacer.
[0051] The outer tube 161 may be attached indirectly to the inner
tube 162 by, for example, one or more end collars 190, as shown in
FIGS. 2 to 4. An end collar 190 may be, for example, a cylindrical
piece including a central bore 191 sized to fit around the outer
surface of the inner tube 162. The end collar 190 may further
include a first counter bore (or counter sink) 192 sized to be
larger than the inner tube 162 but smaller than the outer surface
of the outer tube 161.
[0052] Finally, the collar 190 may include a second counter bore
193 sized to fit the outer surface of the outer tube 161. The
collar 190 may have a radial hole or passage (195, 196) for acting
as an inlet and/or outlet to the collar and the helical flow path.
The radial hole may be located at the first counter bore 192.
[0053] Alternatively, the outer tube 161 may be directly attached
to the inner tube by, for example swaging and/or welding as is
shown in FIGS. 5 to 7. The outer tube 161 may include a first and
second radial hole (197, 198) for acting as an inlet and/or outlet
to the helical flow path.
[0054] Although the flow through the outer helical path has been
shown and described as being in the same direction as flow through
the inner pipe, the flow may also be reversed, resulting in a
counter-current flow of the gas and liquid phase refrigerant. Such
a counter-current flow may be desirable in some cases and may
result in different heat transfer efficiency. Tubes made of a
material other than aluminum, such as steel or copper, may be used
instead of the tubes 161 and 162 made of aluminum.
[0055] As will be appreciated, the spiral element may be free to
move axially relative to at least one of the inner and outer tubes,
and particularly the outer tube, so that the heat exchanger can be
bent along its axial length without damaging the heat
exchanger.
[0056] Although the double-wall tube 160 of the invention has been
described as used to the refrigerant cycle device 100A of the
automotive air conditioning system 100, the present invention is
not limited thereto in its practical application. The double-wall
tube 160 may be suitably used for domestic air conditioners. When
the double-wall tube 160 is used for the domestic air conditioner,
the temperature of the atmosphere around the outer tube 161 is
lower than that of air in the engine room 1. Therefore, the
lower-pressure refrigerant can be set to pass through the space
between the inner tube 162 and outer tube 161 and the
higher-pressure refrigerant can be set to pass through the inside
passage of the inner tube 162 when the heat transferring condition
between the higher-pressure refrigerant and the lower-pressure
refrigerant permits.
[0057] The refrigerant that flows through the double-wall tube 160
is not limited to the refrigerant employed in the refrigerant cycle
device 100A, a refrigerant having physical properties different
from those of the refrigerant employed in the refrigerant cycle
device 100A may be used. For example, refrigerant flowing in
different directions, refrigerants respectively having different
temperatures or refrigerants respectively having different
pressures may be used in combination. Furthermore, different fluids
other than the refrigerant of the refrigerant- cycle device 100A
can be used in the double-wall tube 160.
[0058] Although the invention has been shown and described with
respect to a certain embodiment or embodiments, it is obvious that
equivalent alterations and modifications will occur to others
skilled in the art upon the reading and understanding of this
specification and the annexed drawings. In particular regard to the
various functions performed by the above described elements
(components, assemblies, devices, compositions, et cetera), the
terms (including a reference to a "means") used to describe such
elements are intended to correspond, unless otherwise indicated, to
any element which performs the specified function of the described
element (that is, that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary embodiment or
embodiments of the invention. In addition, while a particular
feature of the invention may have been described above with respect
to only one or more of several illustrated embodiments, such
feature may be combined with one or more other features of the
other embodiments, as may foe desired and advantageous for any
given or particular application.
[0059] It is understood that the foregoing description is that of
the preferred embodiments of the invention and that various changes
and modifications may be made thereto without departing from the
spirit and scope of the invention as defined in the appended
claims.
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