US20080202157A1

US20080202157A1 - Internal heat exchanger for automotive air conditioner

Info

Publication number: US20080202157A1
Application number: US12/036,851
Authority: US
Inventors: Hisatoshi Hirota
Original assignee: TGK Co Ltd
Current assignee: TGK Co Ltd
Priority date: 2007-02-23
Filing date: 2008-02-25
Publication date: 2008-08-28
Also published as: CN101251321A; EP1961598A1; JP2008207630A; KR20080078584A

Abstract

An internal heat exchanger for an automotive air conditioner which is capable of securing length of the internal heat exchanger necessary for heat exchange by a double pipe even when an evaporator and an expansion valve are disposed where the distance to a partition wall is short. Between an expansion valve and evaporator, and a partition wall, a first double pipe is disposed which is formed by surrounding an inner pipe connected to an inlet port of the expansion valve with an outer pipe connected to an outlet port of the evaporator, and a second double pipe is disposed within an engine room which is formed by surrounding an inner pipe with an outer pipe, in a manner extended from the first double pipe. The first double pipe and the second double pipe are connected by a pipe connecting member such that the connecting portions of the pipes are prevented from disconnection.

Description

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority of Japanese Application No. 2007-044500 filed on Feb. 23, 2007 and entitled “Internal Heat Exchanger for Automotive Air Conditioner”.

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to an internal heat exchanger for an automotive air conditioner, and more particularly to an internal heat exchanger for an automotive air conditioner, for performing heat exchange between high-temperature refrigerant having flowed out from a condenser and low-temperature refrigerant returning to a compressor, within a refrigeration cycle of an automotive air conditioner.
2. Description of the Related Art
For automotive air conditioners, it has been proposed in view of environmental problems that refrigerant used in refrigeration cycles thereof should be switched from a substitute flon (HFC-134a) to natural refrigerant (carbon dioxide). Although the system of a refrigeration cycle using carbon dioxide as refrigerant has the same basic structure, in general, to enhance the efficiency of the system, an internal heat exchanger is used in the refrigeration cycle using carbon dioxide (see e.g. Japanese Unexamined Patent Application Publication No. 2001-108308).
The internal heat exchanger is configured such that heat exchange is performed between refrigerant flowing through a passage from a gas cooler that cools high-temperature, high-pressure refrigerant compressed by a compressor to an expansion valve and refrigerant flowing through a passage from an accumulator to the compressor. This causes refrigerant having flowed out from the gas cooler to be further cooled by the internal heat exchanger whereby the enthalpy of refrigerant lowered at the inlet ports of the expansion valve and an evaporator. Further, refrigerant drawn from the accumulator is further superheated by the internal heat exchanger whereby the enthalpy of the refrigerant is increased at the inlet of the compressor, so that it is possible to enhance the efficiency of the system, that is, the performance coefficient and cooling power of the refrigeration cycle.
In contrast, also for a refrigeration cycle using HFC-134a or gases having characteristics equivalent or similar to HFC-134a, as refrigerant, a system employing the internal heat exchanger is contemplated, and it is expected that the efficiency of the system is improved.
The internal heat exchanger as described above has a high-pressure passage and a low-pressure passage formed therein, for passing high-temperature, high-pressure refrigerant, and for passing low-temperature, low-pressure refrigerant, respectively, and is configured such that heat can be exchanged between refrigerants flowing through these passages. The high-pressure passage has a pipe connected to an inlet side thereof for receiving condensed liquid refrigerant sent from a receiver, and a pipe connected to an outlet side thereof for delivering the liquid refrigerant to the expansion valve. The low-pressure passage has a pipe connected to an inlet side thereof, for receiving refrigerant having flowed from the evaporator, and a pipe connected to an outlet side thereof for delivering the refrigerant to the inlet of the compressor.
In contrast, the present applicant has proposed to cause pipes of the refrigeration cycle to function as an internal heat exchanger instead of disposing an independent device of the internal heat exchanger in the refrigeration cycle (Japanese Patent Application No. 2006-338152). According to this proposal, a double pipe, which is formed by concentrically arranging a high-pressure pipe for passing high-temperature, high-pressure refrigerant, and a low-pressure pipe for passing low-temperature, low-pressure refrigerant, is disposed such that heat exchange is performed between refrigerant flowing through an inner pipe, and refrigerant flowing through a space between the inner pipe and an outer pipe, via the inner pipe. At one end of the double pipe, the high-pressure pipe is connected to an inlet of the expansion valve which has the evaporator disposed adjacent thereto, and the low-pressure pipe is connected to an outlet of the evaporator. Further, to the other end of the double pipe is attached a pipe joint for branching the passages of the double pipe. The pipe joint is disposed such that an end face thereof which has two independent openings for the branches is exposed to the engine room at a partition wall which separates the engine room and a vehicle compartment, whereby the high-pressure pipe from the receiver and the low-pressure pipe to the compressor both disposed in the engine room are separately attached to the end face of the pipe joint. This is because as to the procedure of assembly in the engine room, a pipe of a high-pressure system can be disposed in advance, but a pipe of a low-pressure system is required to be attached to the compressor after the engine is finally mounted in the engine room, since the compressor is mounted on the engine, and hence it is necessary to connect the pipe of the low-pressure system and the pipe of the high-pressure system in the engine room separately from connection of the evaporator and the expansion valve in the vehicle compartment. More specifically, in the above-described proposal, the evaporator and the expansion valve within the vehicle compartment are connected to the partition wall by the double pipe so as to cause the double pipe as piping in the vehicle compartment to serve as the internal heat exchanger.
As described above, the construction for causing the double pipe as piping laid between the evaporator and the expansion valve, and the partition wall to serve as the internal heat exchanger does not necessarily function effectively since the disposed locations of the evaporator and the expansion valve in the vehicle compartment are different depending on the vehicle. For example, when the evaporator and the expansion valve are arranged in the vicinity of the partition wall, the double pipe laid between the evaporator and the expansion valve, and the partition wall inevitably becomes short. This causes a problem in that the double pipe cannot secure a sufficient length necessary for performing heat exchange.

SUMMARY OF THE INVENTION

The present invention has been made in view of these points, and an object thereof is to provide an internal heat exchanger for an automotive air conditioner which is capable of securing a sufficient length of the internal heat exchanger necessary for heat exchange even when a double pipe disposed between a partition wall, and an evaporator and an expansion valve is short.
To attain the above object, there is provided an internal heat exchanger for an automotive air conditioner, for performing heat exchange between high-temperature, high-pressure refrigerant condensed within a refrigeration cycle, and low-temperature, low-pressure refrigerant evaporated within the refrigeration cycle, comprising a first double pipe that is disposed between an inlet port of an expansion valve and an outlet port of an evaporator, arranged in a compartment of a vehicle, and a partition wall for separating an engine room of the vehicle and the compartment of the vehicle, such that a first outer pipe is disposed in a manner surrounding a first inner pipe, a second double pipe that is disposed within the engine room, such that a second outer pipe is disposed in a manner surrounding a second inner pipe, the second inner pipe and the second outer pipe being connected to the first inner pipe and the first outer pipe at the partition wall, and a pipe-connecting member that connects the first double pipe and the second double pipe such that connecting portions thereof are prevented from being disconnected from each other.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of mounting of an internal heat exchanger according to a first embodiment of the present invention and an expansion valve.

FIGS. 2A and 2B are views of an internal heat exchanger according to a second embodiment of the present invention, in which FIG. 2A is a cross-sectional view of part of a first double pipe, and FIG. 2B is a cross-sectional view of part of a second double pipe.

FIG. 3 is a cross-sectional view of an internal heat exchanger according to a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described in detail with reference to drawings showing a preferred embodiment thereof.
FIG. 1 is a view showing an example of mounting of an internal heat exchanger according to a first embodiment of the present invention and an expansion valve.
In a refrigeration cycle of an automotive air conditioner, a compressor, a condenser, and a receiver, none of which are shown, are arranged in an engine room of a vehicle, and an expansion valve 2 and an evaporator 3 are arranged in a vehicle compartment separated from the engine room by a partition wall 1. In the illustrated example, the expansion valve 2 is accommodated in a casing 4 which is mounted on an end face of the evaporator 3 in a manner covering an inlet port and an outlet port of the evaporator 3. Within the casing 4, a refrigerant outlet of the expansion valve 2 is connected to the inlet port of the evaporator 3. The expansion valve 2 and the evaporator 3 within the vehicle compartment are connected to the receiver and the compressor within the engine room via the internal heat exchanger 10.
The internal heat exchanger 10 is separated into a first double pipe 11 on the vehicle compartment side and a second double pipe 12 on the engine room side with the partition wall 1 as a boundary. The first double pipe 11 comprises an inner pipe 11 a and an outer pipe 11 b disposed concentrically with the inner pipe 11 a in a manner surrounding the same. Similarly, the second double pipe 12 comprises an inner pipe 12 a and an outer pipe 12 b disposed concentrically with the inner pipe 12 a in a manner sounding the same.
The inner pipe 11 a of the first double pipe 11 extends into the casing 4 through an opening formed in a side surface of the casing 4, and is directly connected to the inlet port of the expansion valve 2 accommodated in the casing 4 such that the inner pipe 11 a supplies high-temperature, high-pressure refrigerant to the expansion valve 2. The outer pipe 11 b is connected to the opening formed in the side surface of the casing 4 such that low-temperature, low-pressure refrigerant derived from the evaporator 3 is guided into a space between the outer pipe 11 b and the inner pipe 11 via the casing 4.
The first double pipe 11 is flexibly formed, and hence to reinforce an end thereof opposite to an end thereof attached to the casing 4, a hollow cylindrical reinforcing member 14 is joined to the outer pipe 11 b, and a shock-absorbing support material 13 is mounted on an outer periphery of the reinforcing member 14. The shock-absorbing support material 13 is pressed against the partition wall 1 by the elasticity of the first double pipe 11, and in this state, supports the reinforcing member 14 disposed to extend through a through hole 1 a of the partition wall 1.
On the other hand, the second double pipe 12 has the inner pipe 12 a thereof connected to the inner pipe 11 a of the first double pipe 11, and the outer pipe 12 b thereof connected to the reinforcing member 14. A pipe-connecting member 15 is fitted on respective connecting portions of the reinforcing member 14 and the outer pipe 12 b, and constrains respective ribs formed on the reinforcing member 14 and the outer pipe 12 b to each other to thereby hold the reinforcing member 14 and the outer pipe 12 b connected in a state prevented from being disconnected from each other. Further, in the illustrated example, a joint member 16 bent into an L-shape is joined to an end of the outer pipe 12 b opposite to the connecting portion thereof. After an engine is placed in the engine room, an intake pipe of the compressor mounted on the engine is connected to the joint member 16. Further, in the illustrated example, the inner pipe 12 a of the second double pipe 12 is extended out through the joint member 16, and a portion of the joint member 16 from which the inner pipe 12 a extends out is hermetically joined to the inner pipe 12 a by brazing. A part of the inner pipe 12 a extended out of the joint member 16 serves as a pipe for introducing high-temperature, high-pressure refrigerant.
Next, a description will be given of the operation of the refrigeration cycle including the internal heat exchanger configured as above. It should be noted that arrows appearing in FIG. 1 indicate respective directions of refrigerant flow.
First, although not shown in FIG. 1, within the engine room, the compressor is driven by the engine to compress refrigerant, and the compressed high-temperature, high-pressure refrigerant is condensed by the condenser. The condensed refrigerant is separated into gas and liquid by the receiver, and the liquid refrigerant obtained by the gas/liquid separation is introduced into the internal heat exchanger 10. The liquid refrigerant introduced into the internal heat exchanger 10 flows through the inner pipe 12 a of the second double pipe 12 and the inner pipe 11 a of the first double pipe 11, and is sent to the expansion valve 2. The expansion valve 2 throttles and expands the liquid refrigerant into low-temperature, low-pressure refrigerant, and supplies the low-temperature, low-pressure refrigerant into the evaporator 3. In the evaporator 3, the supplied refrigerant exchanges heat with air in the vehicle compartment whereby it is evaporated, which cools the air in the vehicle compartment. The refrigerant evaporated by the evaporator 3 is introduced into the internal heat exchanger 10 through the casing 4. The refrigerant introduced into the internal heat exchanger 10 is caused to flow through a passage between the inner pipe 11 a and the outer pipe 11 b of the first double pipe 11 and a passage between the inner pipe 12 a and outer pipe 12 b of the second double pipe 12, and then flows through the joint member 16 to the intake pipe, to be drawn into the compressor.
The expansion valve 2 controls the flow rate of refrigerant sent into the evaporator 3 based on the temperature and pressure of refrigerant having flowed out from the evaporator 3, whereby refrigerant passing through the evaporator 3 is completely evaporated, and further the refrigerant having flowed out from the evaporator 3 is controlled such that it has a predetermined degree of superheat.
Further, the internal heat exchanger 10 performs heat exchange between the high-temperature, high-pressure refrigerant flowing through the inner pipe 12 a of the second double pipe 12 and the inner pipe 11 a of the first double pipe 11, and the low-temperature, low-pressure refrigerant flowing through the passage between the inner pipe 11 a and outer pipe 11 b of the first double pipe 11 and the passage between the inner pipe 12 a and outer pipe 12 b of the second double pipe 12. This causes refrigerant entering the expansion valve 2 to be further cooled by the internal heat exchanger 10 whereby the enthalpy of refrigerant at the inlet port of the expansion valve 2 and further that of refrigerant at the inlet port of the evaporator 3 are reduced, and at the same time causes refrigerant drawn into the compressor to be further superheated by the internal heat exchanger 10 whereby the enthalpy of refrigerant at an inlet port of the compressor is increased. This makes it possible to enhance the performance coefficient of the refrigeration cycle, which is represented by the ratio with the enthalpy difference between the inlet port of the evaporator 3 and the inlet port of the compressor and the enthalpy difference between the inlet port and an outlet port of the compressor, thereby making it possible to improve the cooling power of the refrigeration cycle and the efficiency of the system.
As described above, the internal heat exchanger 10 is configured to be connectably separated at an intermediate portion, so that also in a vehicle in which the distance from the expansion valve 2 and the evaporator 3 to the through hole 1 a of the partition wall 1 is short, the internal heat exchanger 10 can be extended into the engine room by the second double pipe 12, whereby it is possible to ensure a length sufficient for heat exchange, which cannot be ensured only by the first double pipe 11.
Further, the internal heat exchanger 10 is configured such that high-pressure refrigerant is caused to flow through the inner pipe 11 a of the first double pipe 11 and the inner pipe 12 a of the second double pipe 12, and hence even if refrigerant leaks via connecting portions of the inner pipes, it leaks into the low-pressure side passages, which eliminates the fear that refrigerant leaks into the atmosphere.
FIGS. 2A and 2B are views of an internal heat exchanger according to a second embodiment of the invention. FIG. 2A is a cross-sectional view of part of a first double pipe, and FIG. 2B is a cross-sectional view of part of a second double pipe. It should be noted that in FIGS. 2A and 2B, component elements identical to those shown in FIG. 1 are designated by identical reference numerals, and detailed description thereof is omitted.
As is distinct from the internal heat exchanger according to the first embodiment in which low-pressure refrigerant returning from the evaporator 3 to the compressor is caused to flow though the passages between the respective inner pipes and the outer pipes associated therewith, in the internal heat exchanger according to the second embodiment, high-pressure refrigerant is caused to flow though the passages.
The constructions of the expansion valve 2 and the casing 4 to which is connected the first double pipe 11 are the same as those shown in FIG. 1, and the inlet port of the expansion valve 2 is positioned substantially in the center of the opening formed in the side surface of the casing 4, and therefore in the present internal heat exchanger, the construction of the first double pipe 11 to which are connected the expansion valve 2 and the casing 4 is changed. More specifically, as shown in FIG. 2A, in the first double pipe 11, a connecting member 17 for changing the direction of refrigerant flow is joined to an end (upper end as viewed in FIG. 2A) of the first double pipe 11 to which are connected the expansion valve 2 and the casing 4. The connecting member 17 has a hollow cylindrical portion 17 a formed substantially in the center thereof such that the hollow cylindrical portion 17 a extends toward the casing 4. The central opening of the hollow cylindrical portion 17 a is formed such that it extends approximately to the center of the connecting member 17 in the direction of the depth thereof toward the first double pipe 11, and further extends therefrom through a side of the hollow cylindrical portion 17 a. Thus, the hollow cylindrical portion 17 a forms a high-pressure passage of the internal heat exchanger, and is connected to the inlet port of the expansion valve 2. Further, the connecting member 17 has a low-pressure passage 17 b in which part of the periphery of the hollow cylindrical portion 17 a extends therethrough to an end face (lower end face, as viewed in FIG. 2A) thereof opposite from an end thereof connected to the inlet port of the expansion valve 2 such that the part is generally U-shaped in cross-section. The lower end face of the connecting member 17 is formed to have a hollow cylindrical shape, and is joined to the inner pipe 11 a of the first double pipe 11. Furthermore, the connecting member 17 is joined to the outer pipe 11 b of the first double pipe 11 at a position upstream of the position where the high-pressure passage is open. This makes it possible to interchange the refrigerant flows between the inside and outside the inner pipe 11 a of the first double pipe 11 with each other.
On the other hand, the second double pipe 12 has the inner pipe 12 a expanded on a side thereof opposite to the side where it is connected the first double pipe 11, whereby the inner pipe 12 a and the outer pipe 12 b are joined to each other at their contact portions to close the passage formed between the inner pipe 12 a and the outer pipe 12 b. The outer pipe 12 b is joined to a high-pressure pipe 5 for introducing high-temperature, high-pressure refrigerant, in the vicinity of where outer pipe 12 b and the inner pipe 12 are joined. Further, the expanded portion of the inner pipe 12 a forms a joint for connecting the second double pipe 12 to the intake pipe of the compressor.
The first double pipe 11 and the second double pipe 12 are connected at the partition wall 1 by a generally employed method for connecting between double pipes.
The internal heat exchanger according to the second embodiment is configured such that high-temperature, high-pressure refrigerant is caused to flow through the passage between the inner pipe 11 a and outer pipe 11 b of the first double pipe 11, and the passage between the inner pipe 12 a and outer pipe 12 b of the second double pipe 12, so that the outer pipe 11 b of the first double pipe 11 and the outer pipe 12 b of the second double pipe 12 always have a high temperature. This prevents dew condensation on the internal heat exchanger, thereby making it unnecessary to cover the outer periphery of the internal heat exchanger with a heat insulator.
FIG. 3 is a cross-sectional view of an internal heat exchanger according to a third embodiment of the present invention. It should be noted that in FIG. 3, component elements identical to those shown in FIG. 1 and FIGS. 2A and 2B are designated by identical reference numerals, and detailed description thereof is omitted.
The internal heat exchanger according to the third embodiment interchanges the directions of refrigerant flows in the vehicle compartment and the engine room with each other. The first double pipe 11 in the vehicle compartment is configured such that high-temperature, high-pressure refrigerant is caused to flow through the passage between the inner pipe 11 a and outer pipe 11 b, and low-temperature, low-pressure refrigerant is caused to flow through the inner pipe 11 a. The second double pipe 12 in the engine room is configured such that high-temperature, high-pressure refrigerant is caused to flow through the inner pipe 12 a, and low-temperature, low-pressure pressure refrigerant is caused to flow through the passage between the inner pipe 12 a and outer pipe 12 b.
To this end, the first double pipe 11 has opposite ends thereof provided with connecting members 17 and 18 for changing the direction of a refrigerant flow. The connecting member 17 connected to the expansion valve 2 and the casing 4 is the same as the connecting member 17 provided in the internal heat exchanger according to the second embodiment, and a high-pressure pipe 19 connected to the opening of the inlet port of the expansion valve 2 is joined to the hollow cylindrical portion 17 a extending axially outward from approximately the center of the connecting member 17. The connecting member 18 is connected to the second double pipe 12 in the engine room, and a high-pressure pipe 20, to which is connected the inner pipe 12 a of the second double pipe 12, is joined to a hollow cylindrical portion 18 a extending axially outward from approximately the center of the connecting member 18. The outer pipe 12 b of the second double pipe 12 is inserted into an outer hollow cylindrical portion 18 b of the connecting member 18. The outer hollow cylindrical portion 18 b is formed into a shape in which the cylindrical portion 18 b and the outer pipe 12 b are connected to each other by the pipe-connecting member 15.
The second double pipe 12 is the same as the second double pipe 12 disposed in the internal heat exchanger 10 according to the first embodiment. To an end of the outer pipe 12 b is joined the L-shaped joint member 16, and the inner pipe 12 a is extended out through the joint member 16. To an end of the inner pipe 12 a is joined the high-pressure pipe 5 disposed between the internal heat exchanger 10 and the receiver.
Although in the first to third preferred embodiments described above, the descriptions have been given of the example of the construction in which low-pressure or high-pressure refrigerant is caused to flow through the outer pipe 11 b of the first double pipe 11 and the outer pipe 12 b of the second double pipe 12, and the example of the construction in which high-pressure refrigerant is caused to flow through the outer pipe 11 b of the first double pipe 11 and low-pressure refrigerant is caused to flow through the outer pipe 12 b of the second double pipe 12, the internal heat exchanger 10 may be configured such that low-pressure refrigerant is caused to flow through the outer pipe 11 b of the first double pipe 11 and high-pressure refrigerant is caused to flow through the outer pipe 12 b of the second double pipe 12.
The internal heat exchanger of the automotive air conditioner according to the present invention is capable of separately arranging the first double pipe and the second double pipe in the vehicle compartment and the engine room, and hence it is possible to allocate the length of the internal heat exchanger necessary for heat exchange, also to the engine room side in a vehicle in which the evaporator and the expansion valve are arranged in the vicinity of the partition wall. Further, part of the internal heat exchanger is disposed in a manner extended into the engine room, whereby an end of the internal heat exchanger on a side connected to the intake pipe of the compressor is positioned forward of the partition wall, which is difficult to access during work. This makes it easy to connect between the compressor secured on the engine and the intake pipe of the compressor, after the engine has been mounted in the engine room.
The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.

Claims

1. An internal heat exchanger for an automotive air conditioner, for performing heat exchange between high-temperature, high-pressure refrigerant condensed within a refrigeration cycle, and low-temperature, low-pressure refrigerant evaporated within the refrigeration cycle, comprising:

a first double pipe that is disposed between an inlet port of an expansion valve and an outlet port of an evaporator, arranged in a compartment of a vehicle, and a partition wall for separating an engine room of the vehicle and the compartment of the vehicle, such that a first outer pipe is disposed in a manner surrounding a first inner pipe;

a second double pipe that is disposed within the engine room, such that a second outer pipe is disposed in a manner surrounding a second inner pipe, said second inner pipe and said second outer pipe being connected to said first inner pipe and said first outer pipe at the partition wall; and

a pipe-connecting member that connects said first double pipe and said second double pipe such that connecting portions thereof are prevented from being disconnected from each other.

2. The internal heat exchanger as claimed in claim 1, wherein said second double pipe has said second outer pipe joined to a joint member for connection to an intake pipe of a compressor, said second inner pipe being extended out through said joint member.

3. The internal heat exchanger as claimed in claim 2, wherein said second inner pipe is integrally formed with a pipe for introducing high-temperature, high-pressure refrigerant.

4. The internal heat exchanger as claimed in claim 1, wherein said first double pipe includes a connecting member being joined to said first inner pipe and said first outer pipe at an end of said connecting member opposite to a side where said first double pipe is connected to said second double pipe, whereby said connecting member has a hollow cylindrical body of a high-pressure passage formed to extend axially in an approximately central position of said first inner pipe such that a central opening of said hollow cylindrical body communicates with a space formed between said first inner pipe and said first outer pipe, and a low-pressure passage formed therethrough to an end face on a side where part of a periphery of said hollow cylindrical body is joined to said first inner pipe, and

wherein said second double pipe closes a passage formed between said second inner pipe and said second outer pipe on a side opposite from a side where said first double pipe is connected to said second double pipe, and has a pipe joined thereto for introducing high-temperature, high-pressure refrigerant into the passage, said second inner pipe extended outward of a joint position of said second outer pipe and said pipe, to form a joint for being connected to an intake pipe of a compressor.

5. An internal heat exchanger as claimed in claim 1, wherein said first double pipe has connecting members at respective opposite ends thereof, each connecting member having a hollow cylindrical body of a high-pressure passage formed to extend axially in an approximately central position of said first inner pipe such that a central opening of said hollow cylindrical body communicates with a space formed between said first inner pipe and said first outer pipe, and a low-pressure passage formed therethrough to an end face on a side where part of a periphery of said hollow cylindrical body is joined to said first inner pipe