JP2008151374A - Vapor compression type refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vapor compression type refrigerating cycle comprising an accumulator capable of preventing flowing of a liquid-phase refrigerant into a vapor outflow tube in low load, and reducing cycle variability in low load. <P>SOLUTION: In this vapor compression type refrigerating cycle comprising a compressor, a radiator, an internal heat exchanger, a pressure reducing machine, an evaporator, and the accumulator for separating the refrigerant flowing out from the evaporator and allowing the separated gas-phase refrigerant to flow out to a suction side of the compressor, a part disposed inside of the accumulator, of the vapor outflow pipe 22 of the accumulator 6 is at least partially constituted as a multitubular structure, and a plurality of pores 32 are formed on inner and outer tubular walls of the multitubular structural part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vapor compression refrigeration cycle, and more particularly to a vapor compression refrigeration cycle having an improved accumulator and suitable as a refrigeration cycle using a carbon dioxide refrigerant.

  From the viewpoint of environmental considerations, carbon dioxide refrigerant has been proposed as an alternative refrigerant in vehicle air conditioners (for example, Patent Document 1). Carbon dioxide refrigerant is non-toxic and non-flammable, but has a low critical temperature (about 31 ° C) and a transcritical cycle (supercritical refrigeration cycle) in which the high pressure side pressure of the refrigeration cycle becomes supercritical (about 7.4 MPa). Become. In general, since the coefficient of performance of refrigeration (COP: Coefficent of Performance) is worse than that using chlorofluorocarbon, it is required to improve it.

  As one of the methods, there is a method of exchanging heat between the high-pressure side refrigerant on the radiator outlet side and the low-pressure side refrigerant on the evaporator outlet side using an internal heat exchanger. As a result, the enthalpy on the evaporator inlet side is reduced by reducing the high-pressure side refrigerant temperature, and the enthalpy difference in the evaporator is increased, thereby improving the refrigeration coefficient of performance (COP).

Furthermore, a configuration is also known in which an accumulator is installed in front of the internal heat exchanger on the low pressure side so as to cope with fluctuations in required refrigerant amount due to changes in the external environment. The accumulator is a liquid storage tank that takes in and out the refrigerant in the cycle, and separates the gas and liquid by disposing the vapor outlet pipe above the liquid surface of the liquid phase refrigerant (interface between the gas phase refrigerant and the liquid phase refrigerant). Thus, the gas phase refrigerant is caused to flow out from the vapor outflow pipe toward the compressor side.
Japanese Patent Publication No. 7-18602

  However, when the load is low, the amount of refrigerant necessary in the vapor compression refrigeration cycle decreases, so the amount of liquid-phase refrigerant stored in the accumulator increases. Therefore, the liquid level of the stored liquid phase refrigerant rises, and the gas-liquid two phase refrigerant flowing in from the accumulator inlet pipe collides with the liquid phase refrigerant stored in the accumulator, so that the liquid level of the liquid phase refrigerant is changed. There is a problem that the liquid phase refrigerant flows into a steam outflow pipe installed in the accumulator due to a large fluctuation. If the gas-phase refrigerant containing a large amount of liquid-phase refrigerant is supplied to the compressor during the subsequent cycles, the performance of the refrigeration cycle will fluctuate greatly, and a significant improvement in the refrigeration coefficient of performance (COP) cannot be expected. .

  Accordingly, an object of the present invention is to focus on the problems as described above, and suppress an inflow of liquid-phase refrigerant into the steam outlet pipe even at low load, thereby reducing cycle fluctuations at low load. Is to provide a vapor compression refrigeration cycle.

  In order to solve the above problems, a vapor compression refrigeration cycle according to the present invention includes a compressor that sucks and compresses a refrigerant, a radiator that radiates the compressed refrigerant, and heat exchange between the radiated refrigerant and the low-pressure side refrigerant. Further, the internal heat exchanger for cooling, the decompressor for decompressing the cooled refrigerant, the evaporator for evaporating the decompressed refrigerant, and the refrigerant flowing out from the evaporator are separated into a gas phase refrigerant and a liquid phase refrigerant and separated. In the vapor compression refrigeration cycle provided with an accumulator that causes the gas-phase refrigerant to flow out to the suction side of the compressor, at least a part of a portion provided in the accumulator of the vapor outflow pipe of the accumulator is configured in a multiple tube structure, and the multiple A plurality of pores are provided on the inner and outer tube walls of the tube structure portion, respectively.

  By configuring the vapor outflow pipe of the accumulator as described above, the refrigerant flowing into the accumulator from the refrigerant inflow pipe is separated into gas and liquid as in the prior art, and then the separated gas-phase refrigerant has a multi-tube structure. Passes through the pores provided in the outer tube wall, then passes through the pores provided in the inner tube wall and enters the steam outflow pipe, from there a predetermined destination in the cycle, that is, internal heat exchange To the compressor through the low pressure side of the vessel. Even if some liquid phase refrigerant is included, the passage through the pores at least twice causes a speed increase and a collision with the tube wall due to the flow path cross-sectional area being reduced, and the liquid phase refrigerant It is shaken off from the gas phase refrigerant and properly separated. Therefore, even when the liquid phase refrigerant is stored up to the upper part in the accumulator at a low load or the like and the liquid level of the liquid phase refrigerant stored by the gas-liquid mixed refrigerant flowing in from the refrigerant inflow pipe vigorously fluctuates. The gas-phase refrigerant in which the liquid-phase refrigerant is appropriately separated is effectively discharged and the cycle fluctuation is effectively reduced.

  In the structure of the accumulator, the multi-tube structure of the multi-tube structure portion can be either a double tube structure or a structure having more than a triple tube. However, if too many multi-tube structures are used, the number of times of passage through the pores may be excessive and the pressure loss may become too large.

  The pores are preferably provided above the liquid level of the stored liquid stored in the accumulator. If it is disposed below the liquid level, the liquid phase refrigerant simply communicates with the inside and outside of the wall through the pores, and the above-described gas-liquid separation performance cannot be obtained.

  Further, the steam outflow pipe may be structured so as to be integrated with the multiple pipe structure portion. If comprised in this way, it can handle as one steam outflow pipe member including a multiple pipe structure part, a number of parts can be reduced, and management and an assembly are facilitated.

  The accumulator may have a structure having a collision plate disposed opposite to the refrigerant inflow pipe. The collision plate is preferably provided with a plurality of small holes. If such a collision plate is provided, the gas-liquid separation performance up to the pores can be improved, and the gas-liquid separation performance of the accumulator as a whole is improved.

  It is preferable to adopt the following forms for the pores. That is, it is preferable that the cross-sectional area of the pores provided on the outer tube wall of the multiple pipe structure portion is larger than the cross-sectional area of the pores provided on the inner tube wall. Further, the position of the accumulator in the height direction of the pores provided on the outer tube wall of the multiple tube structure part is set to a position different from the position of the accumulator in the height direction of the pores provided on the inner tube wall. Preferably it is. If comprised in this way, even if the liquid phase refrigerant | coolant which was not able to be isolate | separated well in the pore part provided in an outer tube wall is contained, it can isolate | separate in the pore part provided in an inner tube wall. This makes it possible to perform target gas-liquid separation more reliably.

  Moreover, it is preferable that a steam outflow pipe has an oil return hole in the lower part. In this way, an appropriate amount of oil stored in the lowermost part of the accumulator can be sucked up along with the outflow of the gas-phase refrigerant, and the oil is appropriately used as a lubricating oil for the compressor. It becomes possible to supply.

  The cross-sectional area of the oil return hole is preferably smaller than both the cross-sectional area of the pores provided in the multiple pipe structure portion and the cross-sectional area of the refrigerant inflow pipe. The amount of oil that is returned may be very small, and if the excess oil is returned, the performance of the refrigeration cycle is impaired.

  Moreover, it is also possible to provide a partition in the accumulator so that the refrigerant flowing in from the refrigerant inflow pipe may wrap around and reach the pores of the multiple pipe structure portion. By providing such a partition wall, the refrigerant flowing from the refrigerant inflow pipe does not directly reach the pores, so that it is possible to appropriately perform gas-liquid separation before reaching the pores. .

  Such a structure according to the present invention is suitable particularly when a carbon dioxide refrigerant is used, which is used in a high pressure region and has a high degree of demand for installation of an internal heat exchanger or an accumulator. Further, the present invention is suitable for a vehicle air conditioner that requires a reduction in the size of the entire refrigeration cycle and improvement in mountability.

  As described above, according to the vapor compression refrigeration cycle according to the present invention, at least a part of the accumulator of the vapor outflow pipe is configured as a multi-tube structure having pores, so that the gas phase from which the liquid-phase refrigerant flows out. Inflow into the refrigerant can be appropriately suppressed, and in particular, liquid phase refrigerant can be prevented from flowing into the steam outlet pipe at low loads, and cycle fluctuations at low loads can be reduced. Thus, the cycle refrigeration coefficient of performance can be improved. As a result, it is possible to realize a vapor compression refrigeration cycle having excellent performance, particularly when a carbon dioxide refrigerant is used.

Hereinafter, the present invention will be described in detail together with preferred embodiments.
First, FIG. 1 shows a circuit configuration example of an air conditioner schematically showing a vapor compression refrigeration cycle according to the present invention. In the configuration of FIG. 1, reference numeral 1 denotes a compressor that compresses the refrigerant, and 2 denotes a radiator (gas cooler) that radiates the refrigerant compressed by the compressor 1 using an external heat exchange medium (for example, air). The vapor compression refrigeration cycle includes an internal heat exchanger 3 that further cools the refrigerant radiated by the radiator 2 (high-pressure side refrigerant), a decompressor 4 that decompresses the cooled refrigerant, and a decompressed refrigerant. An evaporator 5 that evaporates the refrigerant, and an accumulator 6 that separates the refrigerant that has flowed out of the evaporator 5 into a gas-phase refrigerant and a liquid-phase refrigerant, and causes only the gas-phase refrigerant to flow out to the low-pressure side circuit of the internal heat exchanger 3. I have. The low-pressure side refrigerant heat-exchanged by the accumulator 6 is again sucked into the compressor 1 and compressed. These devices are sequentially connected to form a refrigeration circuit 11 (refrigeration cycle). In addition, the arrow in FIG. 1 has shown the flow of the refrigerant | coolant.

  The internal heat exchanger 3 can reduce the high-pressure side refrigerant pressure in a transcritical cycle in which the high-pressure side refrigerant pressure during the cycle operation such as carbon dioxide is in a supercritical state. This is because the temperature of the high-pressure side refrigerant can be reduced by exchanging heat between the high-pressure side refrigerant and the low-pressure side refrigerant. Furthermore, since the refrigerant temperature on the high-pressure side can be reduced, the enthalpy on the inlet side of the evaporator 5 can be reduced, and by increasing the enthalpy difference in the evaporator 5, an improvement in the refrigeration coefficient of performance (COP) can be expected. However, the internal heat exchanger 3 has an advantage that the high-pressure side refrigerant temperature can be reduced, but increases the suction-side refrigerant temperature of the compressor 1. Since the compressor 1 theoretically changes isentropically, there is a demerit that when the suction side refrigerant temperature of the compressor 1 rises, the power of the compressor 1 becomes larger than when the suction side refrigerant temperature of the compressor 1 is low. Have both.

  In addition, when a refrigerant having a high pressure on the high-pressure side such as carbon dioxide is used, it is difficult to provide a liquid storage tank on the high-pressure side due to problems such as ensuring pressure resistance. Therefore, it is common to install the accumulator 6 on the low pressure side.

  FIG. 2 is a structural diagram of an accumulator used for a conventional refrigeration cycle, shown for comparison. The accumulator 6 is configured so as to cope with fluctuations in the required refrigerant amount due to changes in the external environment. The accumulator 6 is a liquid storage tank for taking in and out the refrigerant in the cycle, and by disposing the vapor outflow pipe above the liquid refrigerant liquid surface (interface), the gas-liquid is separated from the vapor outflow pipe through the vapor outflow pipe. This is a device to be drained. Further, the lubricating oil flowing into the accumulator 6 is returned to the compressor 1. Actually, even if an oil separator or the like is used, it is difficult to separate the refrigerant and the lubricating oil 100%, and the lubricating oil circulates in the refrigeration cycle together with the refrigerant.

  A refrigerant inflow pipe 21 connected to the outlet refrigerant pipe of the evaporator 5 is provided on the upper surface of the accumulator 6, from which refrigerant and lubricating oil (oil) flow into the accumulator 6. Due to the difference in specific gravity, the inflowing refrigerant and lubricating oil accumulate the lubricating oil having a large specific gravity in the bottom oil layer 27, and then the liquid phase refrigerant having the next large specific gravity is formed as the liquid refrigerant layer 26 on the oil layer 27. . The gas phase refrigerant having the smallest specific gravity is formed as the gas refrigerant layer 25 above the liquid refrigerant layer 26, and the gas phase refrigerant in the gas refrigerant layer 25 flows out from the vapor outlet pipe 22. At that time, a small amount of lubricating oil is sucked up from the oil return hole 24, and the lubricating oil accumulated in the accumulator 6 is returned to the compressor 1 through the internal heat exchanger 3. A refrigerant inflow pipe 21 and a steam outflow pipe 22 are accommodated in the pressure resistant container 23.

In contrast to such a conventional configuration, in the present invention, the accumulator is configured as follows, for example.
(Example 1)
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 3 shows the internal structure of the accumulator according to the first embodiment of the present invention. Basically, as described with reference to FIG. 2, the refrigerant inflow pipe 21 connected to the outlet refrigerant pipe of the evaporator 5 is provided on the upper surface of the accumulator 6, from which refrigerant and lubricating oil flow into the accumulator 6. . Due to the difference in specific gravity, the inflowing refrigerant and lubricating oil accumulate the lubricating oil having a large specific gravity in the bottom oil layer 27, and then the liquid phase refrigerant having the next large specific gravity is formed as the liquid refrigerant layer 26 on the oil layer 27. . The gas phase refrigerant having the smallest specific gravity is formed as the gas refrigerant layer 25 above the liquid refrigerant layer 26, and the gas phase refrigerant in the gas refrigerant layer 25 flows out from the vapor outlet pipe 22. At that time, a small amount of lubricating oil is sucked up from the oil return hole 24, and the lubricating oil accumulated in the accumulator 6 is returned to the compressor 1 through the internal heat exchanger 3. The refrigerant inflow pipe 21 and the vapor outflow pipe 22 are accommodated in a pressure vessel 23.

  In the first embodiment, a part of the steam outflow pipe 22 is configured in a double pipe structure, and the chamber outside the double pipe structure is configured as a gas-liquid refrigerant separation chamber 31. Furthermore, pores 32 are provided in the inner and outer tube walls (pipe surfaces) of the vapor outflow tube 22 and the gas-liquid refrigerant separation chamber 31 having a double tube structure. The positions of these pores 32 are installed at positions sufficiently higher than the liquid refrigerant layer 26. With such a structure, the liquid refrigerant layer 26 is liquid leveled by the refrigerant that has flowed in from the refrigerant inflow pipe 21 in a state where the liquid refrigerant layer 26 is stored up to the upper part in the accumulator 6 at a low load or the like. Even if the (interface) fluctuates, the liquid-phase refrigerant is less likely to flow directly into the vapor outlet pipe 22, and cycle fluctuations can be reduced.

  In addition, since the dryness of the refrigerant flowing into the accumulator 6 is small as a refrigerant state at the time of low load, a refrigerant containing a relatively large amount of liquid phase refrigerant flows out. By providing the gas-liquid refrigerant separation chamber 31 having the structure and the pores 32 on the pipe surface, the liquid phase refrigerant having a large specific gravity collides with the wall surface and is separated into the gas-liquid refrigerant. By providing the pores 32 in the steam outlet pipe 22 as the inner pipe wall, it becomes possible to more efficiently separate the gas and liquid, and the stability of the cycle can be improved by the good gas-liquid separation.

  Here, the cross-sectional area of the pores 32 provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure is larger than the cross-sectional area of the pores 32 provided on the surface of the vapor outflow pipe 22. preferable. The cross-sectional area of the pores 32 provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure is preferably set to a size equal to or smaller than the cross-sectional area of the refrigerant inflow pipe 21. Furthermore, the cross-sectional area of the pores 32 provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure, the cross-sectional area of the pores 32 provided on the surface of the vapor outflow pipe 22, and the cross-sectional area of the refrigerant inflow pipe 21. It is preferable to design so that the cross-sectional area of the oil return hole 24 is smaller than either. This increases the collision rate by increasing the refrigerant flow rate due to the pressure loss when the refrigerant passes through the pores 32 provided on the surfaces of the gas-liquid refrigerant separation chamber 31 and the vapor outflow pipe 22 having a double pipe structure. The configuration aims to improve the gas-liquid separation performance.

  Further, the lubricating oil is sucked up from the oil return hole 24 due to the pressure difference between the pressure in the steam outflow pipe 22 and the pressure in the accumulator 6 container. Since the oil return hole 24 has a small sectional area, impurities in the refrigeration cycle may be clogged. Therefore, although not shown, it is preferable to attach a filter to the oil return hole 24 portion.

  Moreover, it is preferable that the positions of the fine holes 32 provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure and the fine holes 32 provided on the surface of the vapor outflow pipe 22 do not coincide with each other in the horizontal direction. By adopting such a structure, the liquid phase refrigerant that could not be separated by the pores 32 provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure was provided on the surface of the vapor outlet pipe 22. Since it can be separated at 32, the separation efficiency is improved.

  Incidentally, if the upper surface (upper wall) of the accumulator 6 is used as the upper lid as the configuration of the gas-liquid separation chamber 31 having a double-pipe structure, only the lower lid is required, leading to a reduction in the number of parts.

  In the present invention, the gas-liquid separation chamber 31 having a double-pipe structure and the refrigerant inflow pipe 21 can be integrated by brazing or welding. As a result, the pipe and the accumulator 6 body are assembled by integration. Strength can be increased, and improvement of product reliability can be expected. Furthermore, the number of parts can be reduced, and parts management and assembly can be facilitated.

(Example 2)
FIG. 4 shows the internal structure of the accumulator in Embodiment 2 of the present invention. The structure shown in FIG. 4 is different from the structure shown in FIG. 3 in that the lower lid is a collision plate 41 having a small hole 42 as a configuration of the gas-liquid separation chamber 31 having a double tube structure. By adopting such a structure, the interface of the liquid refrigerant layer 26 fluctuates due to the refrigerant that flows in vigorously from the refrigerant inflow pipe 21 in a state where the liquid refrigerant layer 26 is stored up to the upper part in the accumulator 6 at a low load or the like. Can be reduced. When the load is low, a refrigerant having a particularly low dryness flows in. Therefore, a liquid phase refrigerant having a relatively large specific gravity flows in, and the stored refrigerant interface easily changes due to the momentum from the refrigerant inflow pipe 21 of the accumulator 6. By causing the refrigerant to collide with the collision plate 41 and causing the gravity drop from the small hole 42, the turbulent fluctuation of the refrigerant interface can be reduced. Further, by providing the partition wall 43, it is possible to prevent the refrigerant flowing in from the refrigerant inflow pipe 21 from directly flowing into the pores 32 provided on the surface of the gas-liquid separation chamber 31 having a double pipe structure. The excellent gas-liquid separation performance by the pores 32 provided on the outer wall and the inner wall of the structure can be maintained at a desirable performance.

  Furthermore, since the refrigerant inflow pipe 21 and the vapor outflow pipe 22 are both on the upper surface of the accumulator 6 here, for example, when carbon dioxide is used as the refrigerant of the vehicle air conditioner, it is possible to expect downsizing of the apparatus and improvement in mountability. .

  As described above, according to the accumulator 6 configured as described above, the gas / liquid refrigerant separation chamber 31 having the double pipe structure is provided in a part of the steam outflow pipe 22, and the vapor outflow pipe 22 and the double pipe structure are further provided. The pores 32 are provided on the pipe surface of the gas-liquid refrigerant separation chamber 31, and these positions are installed at positions sufficiently higher than the liquid refrigerant layer 26, so that the liquid refrigerant layer 26 is accumulator when the load is low. 6, even if the interface of the liquid refrigerant layer 26 fluctuates and fluctuates due to the refrigerant that has flowed in vigorously from the refrigerant inflow pipe 21 in the state where it has been stored up to the upper part in the inside, the direct flow into the vapor outflow pipe 22 is lessened, and the cycle fluctuation is reduced. Can be reduced.

  Further, as the refrigerant state at the time of low load, since the dryness of the refrigerant flowing into the accumulator 6 is small, the refrigerant containing a relatively large amount of liquid phase refrigerant tends to flow out, but the vapor outflow pipe 22 and the double pipe structure By providing the pores 32 on the pipe surfaces of the gas-liquid refrigerant separation chamber 31, the liquid-phase refrigerant having a large specific gravity collides with the wall surface, enabling efficient gas-liquid refrigerant separation, and cycle stability. Can be improved. In addition, by adopting a structure in which the positions of the pores provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure and the pores provided on the surface of the steam outflow pipe 22 do not coincide with each other in the horizontal direction, Since the liquid phase refrigerant that could not be separated by the pores provided on the surface of the gas-liquid separation chamber 31 having a double-pipe structure can be separated by the pores provided on the surface of the vapor outflow pipe 22, higher separation efficiency can be achieved. Obtainable.

  In addition, when the load is low, refrigerant with a particularly low dryness flows in and liquid phase refrigerant with a relatively large specific gravity flows in, and the stored refrigerant interface tends to fluctuate due to the momentum from the accumulator inflow piping, but the inflowing refrigerant collides with it. It is possible to reduce the fluctuation of the refrigerant interface by causing the plate 41 to collide and the gravity drop from the small hole 42.

  Further, if the upper surface of the accumulator 6 is used as the upper lid as the configuration of the gas-liquid separation chamber 31 having a double tube structure, only the lower lid is required. If the refrigerant inlet pipe 21 and the refrigerant inflow pipe 21 are integrated by brazing or welding, the assembly strength between the pipe and the accumulator 6 body is increased, and improvement in product reliability can be expected.

  Furthermore, since both the refrigerant inflow pipe 21 and the vapor outflow pipe 22 are on the upper surface of the accumulator 6, when carbon dioxide is used as the refrigerant of the vehicle air conditioner, it is possible to expect downsizing of the apparatus and improvement in mountability.

  The vapor compression refrigeration cycle according to the present invention can be applied to any vapor compression refrigeration cycle provided with an accumulator between an evaporator and an internal heat exchanger, and in particular, a refrigeration cycle using a carbon dioxide refrigerant, especially for vehicles. It is suitable as a vapor compression refrigeration cycle used in an air conditioner.

It is an equipment distribution diagram showing typically a form example of a vapor compression refrigeration cycle concerning the present invention. It is the longitudinal cross-sectional view (FIG.2 (B)) of the conventional accumulator shown for the comparison, and the cross-sectional view (FIG.2 (A)) which follows the AA line of FIG.2 (B). It is the longitudinal cross-sectional view (FIG. 3 (B)) of the accumulator in Example 1 of this invention, and the cross-sectional view (FIG. 3 (A)) which follows the AA line of FIG. 3 (B). It is the longitudinal cross-sectional view (FIG.4 (B)) of the accumulator in Example 2 of this invention, and the cross-sectional view (FIG.4 (A)) which follows the AA line of FIG.4 (B).

Explanation of symbols

1 Compressor 2 Radiator (gas cooler)
3 Internal heat exchanger 4 Pressure reducer 5 Evaporator 6 Accumulator 11 Refrigeration circuit (refrigeration cycle)
21 Refrigerant inflow pipe 22 Steam outflow pipe 23 Pressure vessel 24 Oil return hole 25 Gas refrigerant layer 26 Liquid refrigerant layer 27 Oil layer 31 Gas liquid refrigerant separation chamber 32 Fine hole 41 Collision plate 42 Small hole 43 Partition

Claims (13)

  A compressor that sucks and compresses the refrigerant; a radiator that dissipates the compressed refrigerant; an internal heat exchanger that further cools the dissipated refrigerant by heat exchange with the low-pressure side refrigerant; and a decompressor that decompresses the cooled refrigerant. A vapor compression type equipped with an evaporator for evaporating the decompressed refrigerant, and an accumulator for separating the separated refrigerant into a gas-phase refrigerant and a liquid-phase refrigerant and outflowing the separated gas-phase refrigerant to the suction side of the compressor In the refrigeration cycle, at least a part of a portion provided in the accumulator of the steam outlet pipe of the accumulator is configured in a multi-tube structure, and a plurality of pores are provided on the inner and outer tube walls of the multi-tube structure portion, respectively. A vapor compression refrigeration cycle characterized by that.   The vapor compression refrigeration cycle according to claim 1, wherein the multi-tube structure portion is configured in a double tube structure.   The vapor compression refrigeration cycle according to claim 1 or 2, wherein the pores are provided above the liquid level of the stored liquid stored in the accumulator.   The vapor compression refrigeration cycle according to any one of claims 1 to 3, wherein the vapor outflow pipe is assembled integrally with the multiple pipe structure portion.   The vapor compression refrigeration cycle according to any one of claims 1 to 4, wherein the accumulator has a collision plate disposed inside the accumulator so as to face the refrigerant inflow pipe.   The vapor compression refrigeration cycle according to claim 5, wherein the collision plate is provided with a plurality of small holes.   The vapor compression type according to any one of claims 1 to 6, wherein a cross-sectional area of pores provided in an outer pipe wall of the multiple pipe structure portion is larger than a cross-sectional area of pores provided in an inner pipe wall. Refrigeration cycle.   The position in the accumulator height direction of the pores provided on the outer tube wall of the multiple tube structure part is set to a position different from the position in the accumulator height direction of the pores provided in the inner tube wall. The vapor compression refrigeration cycle according to any one of claims 1 to 7.   The vapor compression refrigeration cycle according to any one of claims 1 to 8, wherein the vapor outflow pipe has an oil return hole in a lower portion thereof.   10. The vapor compression refrigeration cycle according to claim 9, wherein a cross-sectional area of the oil return hole is smaller than any of a cross-sectional area of a pore provided in the multiple pipe structure portion and a cross-sectional area of a refrigerant inflow pipe.   The vapor according to any one of claims 1 to 10, wherein a partition wall is provided in the accumulator so that the refrigerant flowing from the refrigerant inflow pipe wraps around and reaches the pores of the multiple pipe structure portion. Compression refrigeration cycle.   The vapor compression refrigeration cycle according to any one of claims 1 to 11, wherein the refrigerant used is made of carbon dioxide.   The vapor compression refrigeration cycle according to any one of claims 1 to 12, comprising a refrigeration cycle used for a vehicle air conditioner.

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