U.S. patent application number 11/810764 was filed with the patent office on 2008-07-24 for vapor compression refrigeration circuit and automotive air-conditioning system using same.
This patent application is currently assigned to Sanden Corporation. Invention is credited to Yuuichi Matsumoto, Kenichi Suzuki, Masato Tsuboi.
Application Number | 20080173042 11/810764 |
Document ID | / |
Family ID | 38535648 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080173042 |
Kind Code |
A1 |
Matsumoto; Yuuichi ; et
al. |
July 24, 2008 |
Vapor compression refrigeration circuit and automotive
air-conditioning system using same
Abstract
A vapor compression refrigeration circuit comprises a
compressor, a heat radiator, a high-temperature section of an
internal heat exchanger, a pressure reducer, an evaporator, an
accumulator and a low-temperature section of the internal heat
exchanger disposed in this order in a circulation passage through
which a refrigerant circulates, when viewed along a direction of
flow of the refrigerant. The pressure reducer, the accumulator and
the internal heat exchanger are integrally formed.
Inventors: |
Matsumoto; Yuuichi;
(Isesaki-shi, JP) ; Tsuboi; Masato; (Isesaki-shi,
JP) ; Suzuki; Kenichi; (Takasaki-shi, JP) |
Correspondence
Address: |
COHEN, PONTANI, LIEBERMAN & PAVANE LLP
551 FIFTH AVENUE, SUITE 1210
NEW YORK
NY
10176
US
|
Assignee: |
Sanden Corporation
Isesaki-shi
JP
|
Family ID: |
38535648 |
Appl. No.: |
11/810764 |
Filed: |
June 7, 2007 |
Current U.S.
Class: |
62/498 ; 62/468;
62/509 |
Current CPC
Class: |
F25B 9/008 20130101;
F25B 2500/18 20130101; F28D 7/106 20130101; F25B 2341/0683
20130101; F25B 2400/051 20130101; F25B 2309/061 20130101; F25B
43/006 20130101; F28D 7/0025 20130101; F25B 40/00 20130101 |
Class at
Publication: |
62/498 ; 62/509;
62/468 |
International
Class: |
F25B 9/00 20060101
F25B009/00; F25B 43/02 20060101 F25B043/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2006 |
JP |
2006-164621 |
Claims
1. A vapor compression refrigeration circuit, comprising: a
compressor, a heat radiator, a high-temperature section of an
internal heat exchanger, a pressure reducer, an evaporator, an
accumulator and a low-temperature section of the internal heat
exchanger disposed in this order in a circulation passage through
which a refrigerant circulates, when viewed along a direction of
flow of the refrigerant, wherein the pressure reducer, the
accumulator and the internal heat exchanger are integrally
formed.
2. The vapor compression refrigeration circuit according to claim
1, wherein the pressure reducer is adjacent to the accumulator.
3. The vapor compression refrigeration circuit according to claim
2, further comprising a superheat reduction device for heat
exchange between a liquid-phase component of the refrigerant
accumulated in the accumulator and a vapor-phase component of the
refrigerant exiting the low-temperature section of the internal
heat exchanger.
4. The vapor compression refrigeration circuit according to claim
3, wherein the superheat reduction device includes a pipe disposed
in a part of the circulation passage between the low-temperature
section of the internal heat exchanger and the compressor, the pipe
passing across a bottom side part of the accumulator.
5. The vapor compression refrigeration circuit according to claim
4, wherein the superheat reduction device further includes surface
irregularities formed on at least one of inner and outer peripheral
surfaces of the pipe.
6. The vapor compression refrigeration circuit according to claim
5, wherein the pipe has an oil return hole for drawing in a
lubricating oil accumulated in the accumulator.
7. The vapor compression refrigeration circuit according to claim
6, wherein the pipe has an inlet end and an outlet end each
connected to an inner wall surface of the accumulator, where the
outlet end is at a higher position than the inlet end and a surface
of the liquid-phase component of the refrigerant accumulated in the
accumulator.
8. The vapor compression refrigeration circuit according to claim
7, wherein the refrigerant is CO.sub.2.
9. An automotive air-conditioning system, comprising: a vapor
compression refrigeration circuit provided in a vehicle, the vapor
compression refrigeration circuit comprising a compressor, a heat
radiator, a high-temperature section of an internal heat exchanger,
a pressure reducer, an evaporator, an accumulator and a
low-temperature section of the internal heat exchanger disposed in
this order in a circulation passage through which a refrigerant
circulates, when viewed along a direction of flow of the
refrigerant, wherein the pressure reducer, the accumulator and the
internal heat exchanger are integrally formed.
10. The automotive air-conditioning system according to claim 9,
wherein the pressure reducer is adjacent to the accumulator.
11. The automotive air-conditioning system according to claim 10,
further comprising a superheat reduction device for heat exchange
between a liquid-phase component of the refrigerant accumulated in
the accumulator and a vapor-phase component of the refrigerant
exiting the low-temperature section of the internal heat
exchanger.
12. The automotive air-conditioning system according to claim 11,
wherein the superheat reduction device includes a pipe disposed in
a part of the circulation passage between the low-temperature
section of the internal heat exchanger and the compressor, the pipe
passing across a bottom side part of the accumulator.
13. The automotive air-conditioning system according to claim 12,
wherein the superheat reduction device further includes surface
irregularities formed on at least one of inner and outer peripheral
surfaces of the pipe.
14. The automotive air-conditioning system according to claim 13,
wherein the pipe has an oil return hole for drawing in a
lubricating oil accumulated in the accumulator.
15. The automotive air-conditioning system according to claim 14,
wherein the pipe has an inlet end and an outlet end each connected
to an inner wall surface of the accumulator, where the outlet end
is at a higher position than the inlet end and a surface of the
liquid-phase component of the refrigerant accumulated in the
accumulator.
16. The automotive air-conditioning system according to claim 15,
wherein the refrigerant is CO.sub.2.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a vapor compression refrigeration
circuit and an automotive air-conditioning system using this
refrigeration circuit.
[0003] 2. Description of the Related Art
[0004] The refrigeration circuit is used, for example in an
automotive air-conditioning system, and has a circulation passage
for circulating a refrigerant therethrough. In the circulation
passage, generally, a compressor, a heat radiator (condenser or gas
cooler), a pressure reducer (expansion valve) and an evaporator are
inserted in this order when viewed along the direction of flow of
the refrigerant. In the circulation passage, also a vapor-liquid
separator for separating a vapor-phase component and a liquid-phase
component of the refrigerant is disposed downstream of the heat
radiator or downstream of the evaporator.
[0005] In recent years, out of consideration of environmental
problems, the development of a refrigeration circuit using a
refrigerant low in global warming potential (GWP) has been being
advanced. As an example of such refrigerant, atoxic and
noncombustible natural CO.sub.2 (carbon dioxide) is proposed. Since
the critical temperature of CO.sub.2 is low, specifically about
31.degree. C., the refrigeration circuit using CO.sub.2 as a
refrigerant is a transcritical cycle (supercritical cycle), and on
the high-pressure side of the refrigeration circuit, the
refrigerant comes into a supercritical state of about 7.4 MPa in
pressure, for example. In such refrigeration circuit, since
CO.sub.2 does not condense in the heat radiator, an accumulator as
a vapor-liquid separator is disposed downstream of the evaporator
in the circulation passage.
[0006] In addition, in some cases, in order to improve the
coefficient of performance (COP), the refrigeration circuit using
CO.sub.2 also includes an internal heat exchanger disposed in the
circulation passage, as disclosed in Unexamined Japanese Patent
Publication No. H11-193967, for example. Specifically, the internal
heat exchanger comprises a high-temperature section disposed
between the heat radiator and the pressure reducer in the
circulation passage and a low-temperature section disposed between
the accumulator and the compressor in the circulation passage. In
the internal heat exchanger, heat exchange takes place between a
high-pressure refrigerant flowing in the high-temperature section
and a low-pressure refrigerant flowing in the low-pressure section,
so that the refrigerant has a decreased enthalpy at the inlet of
the evaporator. Consequently, change in enthalpy of the refrigerant
produced in the evaporator increases, so that the COP of the
refrigeration circuit improves.
[0007] The conventional refrigeration circuit comprises, as major
devices, a compressor, a heat radiator, a pressure reducer, an
evaporator and an accumulator, and also comprises, as connecting
parts for connecting an inlet and an outlet of such major devices,
pipes disposed between such major devices and coupling members for
coupling the devices and the pipes.
[0008] Thus, the refrigeration circuit is composed of a large
number of major devices and connecting parts, so that assembling
the refrigeration circuit, and particularly, installing the
refrigeration circuit in a vehicle as a part of an automotive
air-conditioning system is cumbersome work, especially because the
engine room tends to be reduced in space.
[0009] Further, the refrigeration circuit using CO.sub.2 as a
refrigerant is higher in pressure on the high-pressure side,
compared with the conventional refrigeration circuit using an HFC
refrigerant. Thus, there is a concern about a leakage of the
refrigerant around the coupling member.
[0010] Further, the use of the internal heat exchanger in the
refrigeration circuit causes not only a decrease in ease of
installation in the vehicle and an increase in concern about the
refrigerant leakage, but also a rise in the refrigerant temperature
at the inlet and outlet of the compressor and therefore a decrease
in adiabatic efficiency (compression efficiency) of the
compressor.
SUMMARY OF THE INVENTION
[0011] The primary object of the present invention is to provide a
vapor compression refrigeration circuit which is composed of a
reduced number of major devices and connecting parts so that the
refrigerant leakage is prevented, and which is easy to assemble,
and an automotive air-conditioning system using this refrigeration
circuit.
[0012] In order to achieve this object, a vapor compression
refrigeration circuit according to this invention comprises a
compressor, a heat radiator, a high-temperature section of an
internal heat exchanger, a pressure reducer, an evaporator, an
accumulator and a low-temperature section of the internal heat
exchanger disposed in this order in a circulation passage through
which a refrigerant circulates, when viewed along a direction of
flow of the refrigerant, wherein the pressure reducer, the
accumulator and the internal heat exchanger are integrally
formed.
[0013] In the vapor compression refrigeration circuit according to
this invention, the pressure reducer, the accumulator and the
internal heat exchanger are integrally formed. In other words, the
pressure reducer, the accumulator and the internal heat exchanger
form one module. Thus, the major devices constituting the
refrigeration circuit are reduced in number, and also the
connecting parts are reduced in number, since the pipes and
coupling members used with the pipes for connecting the pressure
reducer, the accumulator and the internal heat exchanger are
reduced. Consequently, this vapor compression refrigeration circuit
is not only easy to assemble but also allows a reduction in
size.
[0014] Further, the reduction in the number of coupling members in
this vapor compression refrigeration circuit results in a reduction
in the risk of the refrigerant leakage around the coupling
members.
[0015] Desirably, the pressure reducer is adjacent to the
accumulator. This allows a further reduction in size.
[0016] In addition, since heat exchange takes place between the
pressure reducer and the accumulator, the heat transfer achieved in
the internal heat exchanger is less needed. This allows a reduction
in size of the internal heat exchanger and therefore allows a
further reduction in size of the refrigeration circuit.
[0017] Desirably, the vapor compression refrigeration circuit
further comprises a superheat reduction device for heat exchange
between a liquid-phase component of the refrigerant accumulated in
the accumulator and a vapor-phase component of the refrigerant
exiting the low-temperature section of the internal heat
exchanger.
[0018] In the desirable vapor compression refrigeration circuit,
the refrigerant has a decreased temperature at the inlet of the
compressor, which results in an increase in adiabatic efficiency
(compression efficiency) of the compressor. In addition, since the
degree of superheat of the refrigerant at the inlet of the
compressor is decreased, the compression of the refrigerant
requires less motive power. Consequently, this refrigeration
circuit has an improved COP.
[0019] Desirably, the superheat reduction device has a pipe
disposed in a part of the circulation passage between the
low-temperature section of the internal heat exchanger and the
compressor and the pipe passes across a bottom part of the
accumulator.
[0020] In the desirable refrigeration circuit, the superheat
reduction device has a simple structure which is constituted by the
pipe and ensures that heat exchange takes place between the
liquid-phase component of the refrigerant accumulated in the
accumulator and the vapor-phase component of the refrigerant
exiting the low-temperature section of the internal heat
exchanger.
[0021] Desirably, the superheat reduction device further has
surface irregularities formed on at least one of inner and outer
peripheral surfaces of the pipe. Due to the surface irregularities,
the pipe has an increased surface area, and therefore allows heat
exchange to take place efficiently, so that the COP of the
refrigeration circuit is further improved.
[0022] Desirably, the pipe has an oil return hole for drawing in a
lubricating oil accumulated in the accumulator. The oil return hole
ensures that the lubricating oil is returned to the compressor,
thereby ensuring the durability of the compressor.
[0023] Desirably, the pipe have an inlet end and an outlet end each
connected to an inner wall surface of the accumulator, where the
outlet end is at a higher position than the inlet end and a surface
of the liquid-phase component of the refrigerant accumulated in the
accumulator.
[0024] In the desirable refrigeration circuit, the pipe extends
also vertically within the accumulator, so that the liquid-phase
component of the refrigerant accumulated in the accumulator
contacts the pipe in a greater area. Thus, the pipe allows heat
exchange to take place efficiently, so that the COP of the
refrigeration circuit is further improved.
[0025] Further, the arrangement of the pipe with an outlet end at a
higher position than an inlet end prevents the refrigerant in
liquid form from exiting the accumulator, thereby preventing the
occurrence of liquid compression in the compressor.
[0026] Desirably, the refrigerant is CO.sub.2.
[0027] The desirable refrigeration circuit uses CO.sub.2 as a
refrigerant, and therefore is environmentally-friendly. In
addition, although this refrigeration circuit uses CO.sub.2 which
becomes high in pressure as a refrigerant, the refrigerant leakage
is prevented since the coupling members are reduced.
[0028] The present invention also provides an automotive
air-conditioning system provided with any one of the preceding
vapor compression refrigeration circuit.
[0029] Because of the use of the vapor compression refrigeration
circuit in any one of the preceding vapor compression refrigeration
circuit, the automotive air-conditioning system according to the
present invention can be easily installed in a vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus, are
not limitative of the present invention, and wherein:
[0031] FIG. 1 is a diagram showing the schematic structure of an
embodiment of a refrigeration circuit of an automotive
air-conditioning system according to the present invention,
[0032] FIG. 2 is a perspective view schematically showing a module
applied to the refrigeration circuit of FIG. 1,
[0033] FIG. 3A is a top view of the module of FIG. 2,
[0034] FIG. 3B is a front view of the module of FIG. 2,
[0035] FIG. 3C is a side view of the module of FIG. 2,
[0036] FIG. 3D is a back view of the module of FIG. 2,
[0037] FIG. 4 is a cross-sectional view along line IV-IV of FIG.
3A,
[0038] FIG. 5 is a diagram showing a heat exchange tube of the
module of FIG. 2 with an adaptor joined thereto,
[0039] FIG. 6 is a cross-sectional view along line VI-VI of FIG.
3A,
[0040] FIG. 7 is a cross-sectional view along line VII-VII of FIG.
3C,
[0041] FIG. 8 is a partial cross-sectional view showing, in detail,
a pipe used in the module of FIG. 2, in a straightened state,
[0042] FIG. 9 is a Mollier diagram for explaining the processes
taking place in the refrigeration circuit of FIG. 1, and
[0043] FIG. 10 is a perspective view showing a variant of the heat
exchange tube.
DETAILED DESCRIPTION
[0044] FIG. 1 shows an outline of an embodiment of a refrigeration
circuit of an automotive air-conditioning system. The refrigeration
circuit is a vapor compression type, and used to cool or dehumidify
air sent to a vehicle compartment 2.
[0045] The refrigeration circuit has a circulation passage 4, and a
CO.sub.2 refrigerant (R-744), which is a natural refrigerant, with
a small amount of lubricating oil contained as a refrigerating
machine oil, circulates through the circulation passage 4. The
circulation passage 4 extends from an engine room 6 to a front part
of a vehicle compartment 2, through a partition wall 8. The front
part of the vehicle compartment 2 is defined as a device space 12
by an instrument panel 10.
[0046] In the circulation passage 4, a compressor 14, a heat
radiator 16 and an evaporator 18 are disposed, and also an internal
heat exchanger module 20 is disposed. The module 20 has a structure
in which a pressure reducer (expansion valve), an accumulator
(vapor-liquid separator) and an internal heat exchanger are
integrally formed. Thus, practically, in the circulation passage
14, the compressor 14, the heat radiator (gas cooler) 16, a
high-temperature section (high-pressure section) of an internal
heat exchanger, a pressure reducer, the evaporator 18, an
accumulator, and a low-temperature section of the internal heat
exchanger are disposed in this order.
[0047] Next, the module 20 will be described.
[0048] As shown in FIGS. 2, 3A, 3B, 3C and 3D, the module 20
includes a block 22 in a shape of a rectangular parallelepiped, and
a box-shaped casing 24. The block 22 and the casing 24 are brazed
together in a side-by-side arrangement. The block 22 and the casing
24 form a unit in a shape of a rectangular parallelepiped. In other
words, the front face of the block 22 is flush with that of the
casing 24, while the rear face of the block 22 is flush with that
of the casing 24.
[0049] To the rear face of the unit formed by the joined block 22
and casing 24, two adapters 26, 26 are brazed. The two adapters 26,
26 are vertically spaced apart, and each adapter 26 has an oval
shape with a determined thickness. To the outer surface of each
adapter 26, each end of a U-shaped heat-exchange tube 28 is
connected by brazing.
[0050] In the front face of the unit, four ports 30, 32, 34 and 36
are open. Two ports 30, 32 are formed in the block 22, vertically
spaced apart, and the other two ports 34, 36 are formed in the
casing 24, vertically spaced apart. Although not shown, a pipe
extending from the outlet of the heat radiator 16 is connected to
the lower one 32 of the two ports 30, 32 formed in the block 22, by
means of a coupling member, while a pipe extending from the inlet
of the evaporator 18 is connected to the upper port 30 by means of
a coupling member.
[0051] Further, a pipe extending from the inlet of the compressor
14 is connected to the lower one 36 of the two ports 34, 36 formed
in the casing 24, by means of a coupling member, while a pipe
extending from the outlet of the evaporator 18 is connected to the
upper port 34 by means of a coupling member. It is to be noted that
the upper port 30 in the block 22 and the upper port 34 in the
casing 24 are located at the same height, and that the two pipes
extending from the evaporator 18 are connected to the respective
ports 30, 34, by means of one coupling member.
[0052] As shown in FIG. 4, in the block 22, a first internal flow
passage 38 is formed to extend straight from the lower port 32 to
the rear face. The first internal flow passage 38 has an end open
at the rear face of the block 22, and this open end of the first
internal flow passage 38 is covered with the lower adapter 26. In a
surface (inner surface) of the lower adapter 26 located on the
block 22 side, a groove (central groove) 40 is formed, and one end
of the central groove 40 communicates with the first internal flow
passage 38. The central groove 40 extends along the length of the
adapter 26, and the other end of the central groove 40 communicate
with a center hole 42 which passes through the center part of the
adapter 26 in the thickness direction thereof. The center hole 42
has an end open at a surface (outer surface) of the adapter 26
opposite to the block 22.
[0053] As shown in FIG. 5, the heat exchange tube 28 has a coaxial
double-tube structure and functions as an internal heat exchanger.
Specifically, the heat exchange tube 28 includes a small-diameter
tube 44, which is surrounded by a coaxial large-diameter tube 46.
In the heat exchange tube 28, a flow passage (high-temperature
section) 48 is defined inside the small-diameter tube 44, and this
inner flow passage 48 communicates with the center hole 42 of each
of the upper and lower adapters 26.
[0054] In the heat exchange tube 22, between the small-diameter
tube 44 and the large-diameter tube 46, a cylindrical flow passage
(low-temperature section) 52 approximately in the shape of a
cylinder is defined by means of column-shaped parts 50 integrally
connecting the small-diameter tube 44 and the large-diameter tube
46. Each adapter 26 has an upper hole 54 above the center hole 54
and a lower hole 56 below the center hole 42. Also the upper and
lower holes 54, 56 pass through the adapter 26 in the thickness
direction thereof. The respective ends of the upper and lower holes
54, 56 open at the outer surface of each of the upper and lower
adapters 26 are connected to the cylindrical flow passage 52 of the
heat exchange tube 28. Each adapter 26 has upper and lower grooves
58, 60 formed in the inner surface. When viewed along the length
direction of the adapter 26, the upper and lower grooves 58, 60
extend from the upper and lower holes 54, 56 in the direction
opposite to the central groove 40.
[0055] A second internal flow passage 62 formed in the block 22
communicates with an end of the central groove 40 formed in the
inner surface of the upper adapter 26. The second internal flow
passage 62 extends horizontally from the rear face of the block 22
toward the front face, halfway. The inner end of the second
internal flow passage 62 communicates with the lower end of a valve
hole 64 vertically extending in the block 22. The upper end of the
valve hole 64 communicates the inner end of a third internal flow
passage 66 which extends from the upper port 30 of the block 22
toward the rear face, halfway.
[0056] The upper end of the valve hole 64 is formed into a
spherical valve seat. A valve ball 68 is seated on the spherical
valve seat, from above. The block 22, the spherical valve seat of
the valve hole 64 and the valve ball 68 constitute a pressure
reducer. A helical compression spring 70 is loaded in contact with
the upper side of the valve ball 68. The helical compression spring
70 always exerts a downward force on the valve ball 68. Meanwhile,
a rod 72 which vertically extends in the block 22 is in contact
with the lower side of the valve ball 68. The lower end of the rod
72 is located in the first internal flow passage 38. The rod 72
expands and contracts depending on the temperature of its lower end
(thermal sensing part). Thus, the amount of lift of the valve ball
68 from the spherical valve seat, or in other words, the valve
opening degree of the pressure reducer is determined such that the
force exerted by the rod 72 balances the force exerted by the
helical compression spring 70.
[0057] As shown in FIGS. 6 and 7, the casing 24 is in the shape of
a box open to the block 22 side. The edge surrounding the opening
of the casing 24 is brazed to the corresponding side face of the
block 22.
[0058] In the rear wall of the casing 24, four connecting holes 72,
74, 76, 78 are formed, vertically spaced apart. The connecting
holes 72, 74, 76, 78 each pass through the thickness of the rear
wall of the casing 24, at the center of the width thereof. The
connecting holes 72, 74 form a pair corresponding to the upper
adapter 26, while the connecting holes 76, 78 form a pair
corresponding to the lower adapter 26. The ends of each pair of the
connecting holes 72, 74, 76, 78 which are open in the rear face of
the casing 24 communicate with the ends of the upper and lower
grooves 58, 60 formed in the inner surface of the corresponding
adapter 26, respectively. Thus, the connecting holes 72, 74, 76, 78
each communicate with the cylindrical flow passage 52 of the heat
exchange tube 28, through the adapter 26.
[0059] Inside the casing 24, a pipe (heat transfer pipe) 80 for
heat exchange, also called a low-fin tube, is arranged. As shown in
detail in FIG. 8, the pipe 80 has a helical ridge 82 formed
integrally on the outer peripheral surface of the pipe 80, as a
heat radiation fin. The outlet end of the pipe 80 is connected to
the inner surface of the front wall of the casing 24 by brazing,
and the lower port 36 is open within the region of the front wall
surrounded by this outlet end. The inlet end of the pipe 80 is
connected to the inner surface of the rear wall of the casing 24 by
brazing, and the lower pair of the connecting holes 76, 78 are open
within the region of the rear wall surrounded by this inlet
end.
[0060] Although the pipe 80 extends in a bottom side part of the
interior space 84 in a shape of a rectangular parallelepiped
defined by the casing 42, the inlet end of the pipe 80 is located
at a lower position than the outlet end. Thus, the pipe 80 extends
not only horizontally but also vertically. Although the
liquid-phase components of the refrigerant and the lubricating oil
accumulate in the bottom side part of the interior space 84, the
outlet end of the pipe 80 is located above the surface 86 of the
liquid-phase components accumulated.
[0061] The pipe 80 has an oil return hole 88 passing through the
peripheral wall thereof, at the bottom.
[0062] Referring to the Mollier diagram (p-h diagram) of FIG. 9,
the processes taking place in the above-described refrigeration
circuit will be described.
[0063] In this refrigeration circuit, the compressor 14 powered by
the engine suctions a refrigerant in a vapor phase of a low
temperature and pressure flowing from the port 36 of the module 20.
Point a in FIG. 9 represents the state of the refrigerant at the
inlet of the compressor 14.
[0064] The compressor 14 compresses the suctioned refrigerant into
a supercritical state of a high temperature and pressure, and
discharges it toward the heat radiator 16. In other words, the
compressor 14 performs suction, compression and discharge of the
refrigerant, so that the refrigerant is caused to circulate through
the circulation passage 4. Point b represents the state of the
refrigerant at the outlet of the compressor 14.
[0065] While passing though the heat radiator 16, the refrigerant
flowing from the compressor 14 is cooled by air coming from ahead
of the vehicle and from a fan, so that its temperature drops. Point
c represents the state of the refrigerant at the outlet of the heat
radiator 16.
[0066] The refrigerant that has exited the heat radiator 16 enters
the module 20 through the port 32. The refrigerant entering the
module 20 flows through the first internal flow passage 38 of the
block 22, the central groove 40 and the center hall 42 of the lower
adapter 26, successively, and then enters the inner flow passage 48
of the heat exchange tube 28. In the heat exchange tube 28, heat
exchange take place between the refrigerant flowing in the inner
flow passage 48 and the refrigerant flowing in the cylindrical flow
passage 52. Consequently, the refrigerant after exiting the inner
flow passage 48 has an enthalpy decreased by .DELTA.h2, compared
with before entering the inner flow passage 48. Point d represents
the state of the refrigerant after exiting the inner flow passage
48.
[0067] The refrigerant that has passed through the inner flow
passage 48 of the heat exchange tube 28 enters the second internal
flow passage 62 of the block 22, through the center hole 42 and the
central groove 40 of the upper adapter 26. Then, the refrigerant
flows through the valve hole 64 and the third internal flow passage
66, and once exits the module 30 through the port 30. Here, the
valve hole 64 is decreased in flow-passage cross-sectional area at
the upper end, due to the spherical valve seat and the valve ball
68 which constitute the pressure reducer. Thus, while passing
though the upper end of the valve hole 64, the refrigerant expands.
Due to this expansion, the pressure of the refrigerant drops to the
critical pressure or below. At the port 30, the refrigerant is in
the state of a vapor-liquid mixture, and point e represents this
state.
[0068] While passing though the evaporator 18, the liquid-phase
component of the refrigerant in the vapor-liquid mixture state
evaporates by taking heat from the surroundings, so that the air
flowing outside the evaporator 18 is cooled to become cold air. By
this cold air entering the vehicle compartment 2, the vehicle
compartment 2 is cooled or dehumidified. Point f represents the
state of the refrigerant at the outlet of the evaporator 18.
[0069] The refrigerant, of which the liquid-phase component has
almost completely evaporated in the evaporator 18, enters the
casing 24 of the module 20, through the port 34. The refrigerant
entering the casing 24 flows across the interior space 84 and
enters the connecting holes 72, 74, where the liquid-phase
component remaining in the refrigerant only in a very small amount
does not enter the connecting holes 72, 74 but collides against and
adheres to the inner surface of the casing 24. The liquid-phase
component of the refrigerant that has adhered then flows downward
along the inner surface and accumulates in the bottom side part of
the interior space 84. Thus, the casing 24 functions as an
accumulator.
[0070] The vapor-phase component of the refrigerant that has passed
through the interior space 84 enters the cylindrical flow passage
52 of the heat exchange tube 28, though the upper and lower grooves
58, 60 and the upper and lower holes 54, 56 of the upper adapter
26. As mentioned above, the refrigerant flowing in the cylindrical
flow passage 52 is heated by heat exchange with the refrigerant
flowing in the inner flow passage 52, so that its enthalpy is
increased by .DELTA.h1. Point g represents the state of the
refrigerant at the inlet of the pipe 80 after passing through the
cylindrical flow passage 52. According to the first law of
thermodynamic, .DELTA.h1.apprxeq..DELTA.h2.
[0071] The refrigerant that has passed through the cylindrical flow
passage 52 enters the pipe 80, through the upper and lower holes
54, 56 of the lower adapter 26, the upper and lower grooves 58, 60
and the connecting holes 76, 78. Heat exchange takes place also
between the refrigerant flowing though the pipe 80 and the
liquid-phase component of the refrigerant in contact with the outer
peripheral surface of the pipe 80, so that the enthalpy of the
refrigerant is decreased by .DELTA.h3. Point a represents the state
of the refrigerant at the port 36 after passing through the pipe
80.
[0072] The refrigerant that has passed through the pipe 80 exits
the module 20 through the port 36 and is again suctioned by the
compressor 14. It is to be noted that with the refrigerant flowing
through the pipe 80, the lubricating oil accumulated in the bottom
side part of the interior space 84 is drawn into the pipe 80
through the oil return hole 88. Thus, also the lubricating oil is
returned to the compressor 14 with the refrigerant.
[0073] In the described refrigeration circuit, the pressure
reducer, the accumulator and the internal heat exchanger are
integrated to the module 20 in an inseparable manner. Consequently,
the major devices constituting the refrigeration circuit are
reduced in number, and also the connecting parts are reduced in
number, since the pipes and coupling members used with the pipes
for connecting the pressure reducer, the accumulator and the
internal heat exchanger are reduced. Consequently, this
refrigeration circuit is not only easy to assemble but also allows
a reduction in size, so that the automotive air-conditioning system
using this refrigeration circuit is easy to install in the
vehicle.
[0074] Further, in this refrigeration circuit, the risk of the
refrigerant leakage around the coupling members is reduced, since
the coupling members are reduced.
[0075] Further, the module 20 used in this refrigeration circuit
has a lateral two-layer structure in which the block 22 including
the pressure reducer and the casing 24 forming the accumulator are
adjacent with their side faces against each other (in plane contact
with each other), which allows a further reduction in size.
[0076] Further, since the module 20 used in this refrigeration
circuit is designed such that heat exchange takes place between the
pressure reducer and the accumulator, the heat transfer achieved in
the internal heat exchanger is less need. This allows a reduction
in size of the heat exchange tube 28 as the internal heat
exchanger, and therefore allows a further reduction in size of the
refrigeration circuit. It is desirable to arrange such that, in the
heat exchange tube 28, the direction of the refrigerant flowing
through the inner flow passage 48 is opposite to the direction of
the refrigerant flowing through the cylindrical flow passage 52.
Such arrangement can provide a greater temperature difference
between the refrigerant in the inner flow passage 48 and the
refrigerant in the cylindrical flow passage 52, which results in an
increase in heat exchange efficiency.
[0077] Further, the module 20 used in this refrigeration circuit
includes the pipe 80 as a superheat reduction device. The pipe 80
allows heat exchange to take place between the liquid-phase
component of the refrigerant accumulated in the accumulator and the
vapor-phase component of the refrigerant exiting the
low-temperature section of the internal heat exchanger.
Consequently, the refrigerant has a decreased temperature at the
inlet of the compressor 14, which results in an increase in
adiabatic efficiency (compression efficiency) of the compressor 14
and a decrease in motive power required for compression of the
refrigerant. Specifically, in isentropic change in the compressor,
when the degree of superheat of the refrigerant is smaller, the
gradient .DELTA.P/.DELTA.h in the Mollier diagram is greater and
the motive power required for the compressor is smaller. Also for
this reason, this refrigeration circuit has an improved COP.
[0078] Although the superheat reduction device is not limited to a
particular structure, it is desirable to use the pipe 80, since the
simple structure constituted by the pipe 80 can ensure that heat
exchange takes place between the liquid-phase component of the
refrigerant accumulated in the accumulator and the vapor-phase
component of the refrigerant exiting the low-temperature section of
the internal heat exchanger.
[0079] Desirably, the superheat reduction device has surface
irregularities such as the ridge 82 on at least one of the inner
and outer peripheral surfaces of the pipe 80. With the greater
surface area, the pipe 80 enables efficient heat exchange, so that
the COP of the refrigeration circuit is further improved.
[0080] Desirably, the pipe 80 has the oil return hole 88. Such
arrangement ensures that the lubricating oil is returned to the
compressor 14, thereby ensuring the durability of the compressor
14.
[0081] Desirably, the pipe 80 has the outlet end at a higher
position than the inlet end. Such arrangement allows the pipe 80 to
extend also vertically within the accumulator, thereby allowing the
liquid-phase component of the refrigerant accumulated in the
accumulator to contact the pipe in a greater area. Thus, the pipe
80 allows heat exchange to take place efficiently, so that the COP
of the refrigeration circuit is further improved.
[0082] Further, the arrangement of the pipe 80 with the outlet end
at a higher position than the inlet end prevents the refrigerant in
liquid form from exiting the accumulator, thereby preventing the
occurrence of liquid compression in the compressor 14.
[0083] This refrigeration circuit uses CO.sub.2 as a refrigerant,
and therefore is environmentally-friendly. In addition, although
this refrigeration circuit uses CO.sub.2 which becomes high in
pressure as a refrigerant, the refrigerant leakage is prevented
since the coupling members are reduced.
[0084] The present invention is not limited to the above-described
embodiment but can be modified in various ways. For example, the
refrigerant is not limited to CO.sub.2.
[0085] In the described embodiment, although the material for each
of the components constituting the module 20 is not limited to a
particular one, it is desirable to use a metal high in thermal
conductivity, such as copper or aluminum, in order to improve the
efficiency of heat exchange between the pressure reducer and the
accumulator.
[0086] Although in the described embodiment, the heat exchange tube
28 having a double-tube structure is used, there can be used a heat
exchange tube 94 as shown in FIG. 9, which consists of three flat
tubes 92 with a plurality of minute holes 90 stacked in layers.
With the flat tubes stacked such that the high-pressure side and
the lower-pressure side alternate, the heat exchange tube 92
enables an improvement in heat exchange efficiency.
[0087] Although in the described embodiment, the pressure reducer
of the module 20 consists of a thermal expansion valve which varies
in valve opening degree depending on temperature, it can consist of
a variable orifice which varies in valve opening degree depending
on the flow rate of the refrigerant.
[0088] The invention thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *