JP2018059655A - Refrigeration cycle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for sufficiently securing a flow rate of a refrigerant from a condenser to an evaporator.SOLUTION: A refrigeration cycle device (100) includes: an evaporator (6); a compressor (3); a condenser (4); a steam route (7) including a first portion (7a) for connecting an outlet of the evaporator (6) and an inlet of the compressor (3) and a second portion (7b) for connecting an outlet of the compressor (3) and an inlet of the condenser (4); a return route (5) for connecting an outlet of the condenser (4) and an inlet of the evaporator (6); a valve (8) disposed in a return route (5); and a heat exchanger (9) disposed between the outlet of the condenser (4) and an inlet of the valve (8) in the return route (5) and configured to exchange heat between a refrigerant in the evaporator (6) and a refrigerant to be supplied to the valve (8).SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a refrigeration cycle apparatus.

  In refrigeration cycle apparatuses such as air conditioners and chiller apparatuses, chlorofluorocarbon refrigerants or alternative chlorofluorocarbon refrigerants are widely used. However, these refrigerants have problems such as destruction of the ozone layer and global warming. Then, the air conditioning apparatus which used water as a refrigerant | coolant with a very small load with respect to a global environment is proposed.

  As shown in FIG. 4, the conventional refrigeration cycle apparatus 300 includes an evaporator 301, a first compressor 302, a second compressor 303, a condenser 304, a vapor path 305, a liquid path 306, and an expansion mechanism 307. . In the refrigeration cycle apparatus 300, water is used as a refrigerant.

International Publication No. 2012/147366

  A refrigeration cycle apparatus using water as a refrigerant operates at a pressure in a low vacuum region. In such a refrigeration cycle apparatus, the volume of the gas phase refrigerant is much larger than the volume of the liquid phase refrigerant. This makes it difficult to control the flow rate of the refrigerant in the path for moving the refrigerant from the condenser to the evaporator.

  An object of the present disclosure is to provide a technique for sufficiently securing the flow rate of the refrigerant from the condenser to the evaporator.

That is, this disclosure
An evaporator,
A compression mechanism including at least one compressor;
A condenser,
A vapor path including a first portion connecting the outlet of the evaporator and the inlet of the compression mechanism, and a second portion connecting the outlet of the compression mechanism and the inlet of the condenser;
A return path connecting the outlet of the condenser and the inlet of the evaporator;
A valve disposed in the return path;
A heat exchanger arranged in the return path between the outlet of the condenser and the inlet of the valve and configured to exchange heat between the refrigerant inside the evaporator and the refrigerant to be supplied to the valve When,
A refrigeration cycle apparatus is provided.

  According to the technology of the present disclosure, it is possible to sufficiently ensure the flow rate of the refrigerant from the condenser to the evaporator. That is, it is possible to provide a refrigeration cycle apparatus capable of steady operation for a long time.

FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present disclosure. FIG. 2 is a configuration diagram of a refrigeration cycle apparatus according to a modification. FIG. 3 is a configuration diagram of the refrigeration cycle apparatus according to the second embodiment of the present disclosure. FIG. 4 is a configuration diagram of the refrigeration cycle apparatus described in Patent Document 1.

(Knowledge that became the basis of this disclosure)
When a refrigerant having a very large volume in the gas phase compared to the volume in the liquid phase is used in the refrigeration cycle apparatus, the following problems are likely to occur. That is, when the steam is trapped in the pipe on the downstream side of the expansion valve, the flow pressure loss in the pipe is greatly increased. Further, the flow path is blocked by the flash vapor inside the expansion valve. Due to these factors, the flow rate of the refrigerant to be returned from the condenser to the evaporator is greatly reduced, or the refrigerant does not flow from the condenser toward the evaporator. As a result, the refrigerant is depleted in the evaporator, making it difficult to continue the operation of the refrigeration cycle apparatus.

The refrigeration cycle apparatus according to the first aspect of the present disclosure includes:
An evaporator,
A compression mechanism including at least one compressor;
A condenser,
A vapor path including a first portion connecting the outlet of the evaporator and the inlet of the compression mechanism, and a second portion connecting the outlet of the compression mechanism and the inlet of the condenser;
A return path connecting the outlet of the condenser and the inlet of the evaporator;
A valve disposed in the return path;
A heat exchanger arranged in the return path between the outlet of the condenser and the inlet of the valve and configured to exchange heat between the refrigerant inside the evaporator and the refrigerant to be supplied to the valve When,
It is equipped with.

  According to the first aspect of the present disclosure, the liquid-phase refrigerant of the condenser is cooled by the heat exchanger on the path from the condenser to the valve, and becomes a supercooled state. Therefore, the flash evaporation amount of the refrigerant that has passed through the valve is reduced, and the void ratio is also reduced. The refrigerant passes through the valve while maintaining the liquid phase state. Therefore, it becomes possible to ensure a sufficient flow rate of the refrigerant passing through the valve. In addition, the refrigerant to be supplied from the condenser to the valve can be efficiently cooled by the liquid-phase refrigerant stored in the evaporator and / or the gas-phase refrigerant generated in the evaporator. There is no need to supply a cooling fluid such as air or cooling water from the outside. It is easy to calculate the heat balance of the refrigeration cycle.

  In the second aspect of the present disclosure, for example, the heat exchanger of the refrigeration cycle apparatus according to the first aspect is disposed inside the evaporator. According to the second aspect, it is not necessary to supply a cooling fluid such as air or cooling water from the outside, and it is not necessary to take out the refrigerant from the evaporator. Therefore, complication of the structure of the refrigeration cycle apparatus can be avoided.

  In the third aspect of the present disclosure, for example, the evaporator of the refrigeration cycle apparatus according to the second aspect is a pressure vessel configured so that a gas-liquid interface parallel to a horizontal plane is formed therein, and the heat exchange The vessel is arranged in the lower part inside the evaporator. According to the third aspect, liquid phase refrigerant can be reliably brought into contact with the heat exchanger, so that efficient heat exchange can be expected. As a result, it is possible to employ a heat exchanger with a small size.

  In the fourth aspect of the present disclosure, for example, the compression mechanism of the refrigeration cycle apparatus according to any one of the first to third aspects includes a first compressor, a second compressor, and the first compressor. An intermediate path connecting the discharge port and the suction port of the second compressor, the intermediate path includes an intermediate cooler, and the return path includes an outlet of the condenser, the intermediate cooler, And an upstream part connecting the intermediate cooler and the inlet of the evaporator, and the valve and the heat exchanger are arranged in the downstream part . According to such a configuration, the temperature of the gas-phase refrigerant compressed by the first compressor can be efficiently cooled by the liquid-phase refrigerant to be transferred from the condenser to the evaporator.

  In the fifth aspect of the present disclosure, for example, the valve and the heat exchanger arranged in the downstream portion of the return path of the refrigeration cycle apparatus according to the fourth aspect are respectively a first valve and a first heat exchanger. When defined, the refrigeration cycle apparatus includes the second valve disposed in the upstream portion of the return path, and the upstream side of the return path between the outlet of the condenser and the inlet of the second valve. And a second heat exchanger disposed in the portion. According to the fifth aspect, the liquid-phase refrigerant of the condenser is cooled by the second heat exchanger on the path from the condenser to the second valve, and is in a supercooled state. Therefore, the flash evaporation amount of the refrigerant that has passed through the second valve is reduced, and the void ratio is also reduced. The refrigerant passes through the second valve while maintaining the liquid phase state. Therefore, it becomes possible to ensure a sufficient flow rate of the refrigerant passing through the second valve.

  In the sixth aspect of the present disclosure, for example, the second heat exchanger of the refrigeration cycle apparatus according to the fifth aspect is disposed inside the intermediate cooler. According to the sixth aspect, there is no need to supply a cooling fluid such as air or cooling water from the outside, and there is no need to take out the refrigerant from the intermediate cooler. Therefore, complication of the structure of the refrigeration cycle apparatus can be avoided.

  In the seventh aspect of the present disclosure, for example, the refrigeration cycle apparatus according to the first to sixth aspects is filled with a refrigerant having a negative saturated vapor pressure at normal temperature. Each configuration described above exhibits a particularly high effect in a refrigeration cycle apparatus using such a refrigerant.

  In the eighth aspect of the present disclosure, for example, the refrigerant of the refrigeration cycle apparatus according to the seventh aspect includes water as a main component. A refrigerant containing water is useful as a low GWP refrigerant.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

(Embodiment 1)
As shown in FIG. 1, the refrigeration cycle apparatus 100 includes an evaporator 6, a compressor 3, a condenser 4, a vapor path 7, and a return path 5. A valve 8 and a heat exchanger 9 are arranged in the return path 5. The refrigerant to be supplied to the valve 8 (first valve) is cooled in the heat exchanger 9 by at least one fluid selected from the group consisting of a gas phase refrigerant (refrigerant vapor) and a liquid phase refrigerant (refrigerant liquid). The

  The refrigeration cycle apparatus 100 includes a refrigerant mainly containing a substance having a saturated vapor pressure at normal temperature (Japanese Industrial Standard: 20 ° C. ± 15 ° C./JIS Z8703) and a negative pressure (absolute pressure lower than atmospheric pressure). Filled. Examples of such a refrigerant include a refrigerant containing water as a main component and an HFO refrigerant typified by R1233zd. These refrigerants are known as low GWP refrigerants. For reasons such as freezing prevention, it is also possible to use a refrigerant containing water as a main component and mixed with 10 to 40% in terms of mass% of ethylene glycol, naive brine, inorganic salts, and the like. The “main component” means a component that is contained most in mass ratio.

  The refrigeration cycle apparatus 100 includes a heat absorption circuit 30 and a heat dissipation circuit 40. The heat absorption circuit 30 is a heat load connected to the evaporator 6. The heat dissipation circuit 40 is a heat load connected to the condenser 4. Heat is given to the refrigerant stored in the evaporator 6 from the outside through the heat absorption circuit 30. Heat is released from the refrigerant stored in the condenser 4 to the outside through the heat dissipation circuit 40.

  The heat absorption circuit 30 is a circuit for cooling a fluid such as air or water using the liquid-phase refrigerant stored in the evaporator 6. The heat absorption circuit 30 includes a heat exchanger 32, a pump 34, a flow path 30a, and a flow path 30b. The flow path 30 a has one end connected to the evaporator 6 and the other end connected to the inlet of the heat exchanger 32. The flow path 30 b has one end connected to the outlet of the heat exchanger 32 and the other end connected to the evaporator 6. The pump 34 is disposed in the flow path 30a. Examples of the heat exchanger 32 include a fin tube heat exchanger and a plate heat exchanger. When the refrigeration cycle apparatus 100 is an air conditioner, the heat exchanger 32 can be a part of an indoor unit. The indoor air can be cooled by circulating a liquid phase refrigerant through the heat absorption circuit 30. The heat exchanger 32 may be a liquid-liquid heat exchanger that exchanges heat between a liquid such as water, ethylene glycol, and propylene glycol and a liquid-phase refrigerant. The heat exchanger 32 gives heat of the fluid to be cooled which is a gas or a liquid to the refrigerant.

  The heat dissipation circuit 40 is a circuit used to take heat from the refrigerant stored in the condenser 4. The heat dissipation circuit 40 includes a heat exchanger 42, a pump 46, a flow path 40a, and a flow path 40b. The flow path 40 a has one end connected to the condenser 4 and the other end connected to the inlet of the heat exchanger 42. The flow path 40 b has one end connected to the outlet of the heat exchanger 42 and the other end connected to the condenser 4. The pump 46 is disposed in the flow path 40a. The condenser 4 has, for example, a structure of a shell tube heat exchanger. The flow paths 40 a and 40 b are each connected to a heat exchange tube 44 disposed inside the shell of the condenser 4. The heat exchanger 42 is, for example, a fin tube heat exchanger. When the refrigeration cycle apparatus 100 is an air conditioner, the heat exchanger 42 can be part of an outdoor unit. The heat dissipation circuit 40 is filled with a liquid phase heat medium such as water, ethylene glycol, or propylene glycol.

  The evaporator 6 and the heat absorption circuit 30 may have a structure of a shell tube heat exchanger like the condenser 4 and the heat dissipation circuit 40. That is, the evaporator 6 may be an indirect heat exchanger in which the liquid phase refrigerant and other heat medium indirectly exchange heat. Similarly to the evaporator 6 and the heat absorption circuit 30, the condenser 4 and the heat dissipation circuit 40 may be configured to directly circulate liquid phase refrigerant to the heat exchanger 42. That is, the condenser 4 may be a direct heat exchanger in which heat exchange is directly performed between the gas-phase refrigerant and the liquid-phase refrigerant.

  The evaporator 6 is comprised by the container which has heat insulation and pressure resistance, for example. The evaporator 6 stores the liquid-phase refrigerant and evaporates the refrigerant inside. A gas-liquid interface parallel to the horizontal plane can be formed inside the evaporator 6. The refrigerant heated in the endothermic circuit 30 boils and evaporates in the evaporator 6. That is, a part of the refrigerant liquid stored in the evaporator 6 is heated by the heat absorption circuit 30 and used to heat the liquid refrigerant in the saturated state. The temperature of the liquid-phase refrigerant stored in the evaporator 6 and the temperature of the gas-phase refrigerant generated in the evaporator 6 are 5 ° C., for example.

  The compressor 3 sucks and compresses the gas-phase refrigerant generated in the evaporator 6. The compressor 3 may be a positive displacement compressor or a speed compressor. The positive displacement compressor is a compressor that sucks and discharges a refrigerant according to a change in volume and raises the pressure of the refrigerant. Examples of the positive displacement compressor include a rotary compressor, a screw compressor, and a scroll compressor. The speed type compressor is a compressor that increases the pressure of the refrigerant by giving momentum to the refrigerant and decelerating the speed of the refrigerant. Examples of the speed type compressor (turbo compressor) include a centrifugal compressor and an axial flow compressor. The compressor 3 may include a mechanism for changing the rotation speed, such as a motor driven by an inverter. The temperature of the refrigerant at the discharge port of the compressor 3 is 120 ° C., for example.

  The steam path 7 has a first portion 7a and a second portion 7b. The first portion 7 a connects the outlet (steam outlet) of the evaporator 6 and the suction port of the compressor 3. The second portion 7 b connects the discharge port of the compressor 3 and the inlet (steam inlet) of the condenser 4. The gas-phase refrigerant generated in the evaporator 6 is guided to the compressor 3 through the first portion 7 a of the vapor path 7. The refrigerant compressed by the compressor 3 is guided to the condenser 4 through the second portion 7 b of the vapor path 7. The steam path 7 can be configured by a plurality of pipes.

  The condenser 4 is comprised by the container which has heat insulation and pressure resistance, for example. The condenser 4 condenses the refrigerant and stores a liquid-phase refrigerant generated by condensing the refrigerant. A gas-liquid interface parallel to the horizontal plane can be formed inside the condenser 4. In the present embodiment, the refrigerant of the overheated refrigerant indirectly condenses by condensing with the heat medium cooled by releasing heat to the external environment. That is, the gas-phase refrigerant is cooled and condensed by the heat medium of the heat dissipation circuit 40. The temperature of the liquid-phase refrigerant stored in the condenser 4 is 35 ° C., for example.

  The return path 5 is a path for returning the refrigerant from the condenser 4 to the evaporator 6. The return path 5 connects the outlet of the condenser 4 and the inlet of the evaporator 6. A valve 8 and a heat exchanger 9 are arranged in the return path 5. Specifically, the return path 5 includes a first portion 5a and a second portion 5b. The first portion 5 a connects the outlet (liquid outlet) of the condenser 4 and the inlet of the valve 8. The second portion 5 b connects the outlet of the valve 8 and the inlet (liquid inlet) of the evaporator 6. The heat exchanger 9 is arranged in the return path 5 between the outlet of the condenser 4 and the inlet of the valve 8. The return path 5 can be constituted by a plurality of pipes.

  The valve 8 is a valve for controlling the flow rate of the refrigerant in the return path 5. The valve 8 is typically a flow control valve (electric expansion valve), and may be a valve having a constant flow path cross-sectional area such as a capillary tube.

  The heat exchanger 9 (first heat exchanger) is a heat exchanger for cooling the refrigerant to be supplied from the condenser 4 to the valve 8. Specifically, the heat exchanger 9 is configured to exchange heat between the refrigerant inside the evaporator 6 and the refrigerant to be supplied to the valve 8. The liquid phase refrigerant stored in the condenser 4 has a saturation temperature corresponding to the condensation pressure. The liquid-phase refrigerant in the condenser 4 is cooled by the heat exchanger 9 on the path from the condenser 4 to the valve 8 and is in a supercooled state. Therefore, the flash evaporation amount of the refrigerant that has passed through the valve 8 is reduced, and the void ratio (gas-liquid volume ratio) is also reduced. The refrigerant passes through the valve 8 while maintaining the liquid phase state. Therefore, it is possible to ensure a sufficient flow rate of the refrigerant passing through the valve 8. Under a wide range of operating conditions such as rated conditions, partial load conditions, and overload conditions, the refrigeration cycle apparatus 100 can be stably operated over a long period of time. When the heat exchanger 9 is in contact with the gas-phase refrigerant inside the evaporator 6, the temperature of the refrigerant at the inlet of the valve 8 is, for example, in the range of 7 to 15 ° C. When the heat exchanger 9 is in contact with the liquid-phase refrigerant inside the evaporator 6, the refrigerant at the inlet of the valve 8 exhibits a lower temperature (for example, 5 ° C.).

  In the present embodiment, the heat exchanger 9 is disposed inside the evaporator 6. Therefore, the refrigerant to be supplied from the condenser 4 to the valve 8 is cooled by removing heat from the liquid-phase refrigerant stored in the evaporator 6 and / or the gas-phase refrigerant generated in the evaporator 6. The It is not necessary to supply a cooling fluid such as air or cooling water from the outside, and it is not necessary to take out the refrigerant from the evaporator 6 to the outside. Therefore, according to this embodiment, complication of the structure of the refrigeration cycle apparatus 100 can be avoided. It is also easy to calculate the heat balance of the refrigeration cycle.

  Specifically, the heat exchanger 9 is arranged in the lower part inside the evaporator 6. The lower part of the evaporator 6 means a part below the middle position of the evaporator 6 in the vertical direction (height direction). The entire heat exchanger 9 may be located below the evaporator 6. According to such a configuration, the liquid phase refrigerant can be reliably brought into contact with the heat exchanger 9, so that efficient heat exchange can be expected. As a result, it is possible to employ a heat exchanger 9 having a small size.

  The structure of the heat exchanger 9 is not particularly limited. The heat exchanger 9 may have a known heat exchanger structure such as a fin tube heat exchanger or a shell tube heat exchanger. When the heat exchanger 9 has a structure of a shell tube heat exchanger, the container constituting the evaporator 6 is also used as the shell of the heat exchanger 9. The heat exchanger 9 includes a meandering or wound heat transfer tube disposed inside the evaporator 6.

  In the present embodiment, the outlet end of the return path 5 (specifically, the outlet end of the second portion 5 b) is located in the space portion of the evaporator 6. When the outlet end of the return path 5 is located at such a position, it is possible to avoid applying pressure due to the liquid-phase refrigerant stored in the evaporator 6 to the outlet side of the valve 8. As a result, more accurate flow rate control can be achieved.

(Modification)
In the refrigeration cycle apparatus 102 shown in FIG. 2, the heat exchanger 9 is disposed outside the evaporator 6. According to this configuration, the refrigerant to be supplied to the valve 8 is the heat exchanger 9 by at least one cooling fluid selected from the group consisting of a gas phase refrigerant, a liquid phase refrigerant, and another heat medium. Can be cooled. The other heat medium may be air or water. Other configurations of the refrigeration cycle apparatus 102 are as described with reference to FIG.

  Also in this modification, the structure of the heat exchanger 9 is not particularly limited. For example, when the refrigerant flowing through the return path 5 is cooled with a cooling gas such as air or a gas-phase refrigerant, the heat exchanger 9 is a gas-liquid such as a finned tube heat exchanger or a shell and tube heat exchanger. It may have a heat exchanger structure. When cooling the coolant flowing through the return path 5 with cooling liquid such as cooling water or liquid phase coolant, the heat exchanger 9 is a plate heat exchanger, brazing heat exchanger, double pipe heat exchanger, or the like. It may have a liquid-liquid heat exchanger structure.

(Embodiment 2)
The refrigeration cycle apparatus 104 according to the present embodiment is different from the refrigeration cycle apparatus 100 described in the first embodiment in that it includes a plurality of compressors 3 and 13. In the present embodiment, the compressor 3 in the first embodiment is referred to as a first compressor 3. The valve 8 and the heat exchanger 9 are referred to as a first valve 8 and a first heat exchanger 9, respectively. The description regarding the first embodiment is also incorporated in this embodiment.

  The refrigeration cycle apparatus 104 further includes a second compressor 13 and an intermediate path 12 in addition to the configuration of the refrigeration cycle apparatus 100 of the first embodiment. The intermediate path 12 has one end connected to the discharge port of the first compressor 3 and the other end connected to the suction port of the second compressor 13. The first compressor 3, the intermediate path 12, and the second compressor 13 constitute a compression mechanism 20. The evaporator 6 and the first compressor 3 are connected by the first portion 7 a of the steam path 7. The second compressor 13 and the condenser 4 are connected by the second portion 7 b of the steam path 7. In other words, the outlet of the evaporator 6 and the inlet of the compression mechanism 20 are connected by the first portion 7 a of the steam path 7. The outlet of the compression mechanism 20 and the inlet of the condenser 4 are connected by the second portion 7 b of the steam path 7.

  The intermediate path 12 includes a first portion 12a, an intermediate cooler 22, and a second portion 12b. The intermediate path 12 is a path for guiding the refrigerant from the first compressor 3 to the second compressor 13. The first portion 12 a of the intermediate path 12 has one end connected to the discharge port of the first compressor 3 and the other end connected to the intermediate cooler 22. The first portion 12 a is a path for guiding the refrigerant compressed by the first compressor 3 to the intermediate cooler 22. The second portion 12 b of the intermediate path 12 has one end connected to the intermediate cooler 22 and the other end connected to the suction port of the second compressor 13. The second portion 12 b is a path for guiding the refrigerant cooled by the intermediate cooler 22 to the second compressor 13. The intermediate cooler 22 is disposed between the first compressor 3 and the second compressor 13. The gas-phase refrigerant is compressed by the first compressor 3, cooled by the intermediate cooler 22, and further compressed by the second compressor 13.

  As with the first compressor 3, the second compressor 13 may be a positive displacement compressor or a speed compressor. The model of the first compressor 3 may be the same as or different from the model of the second compressor 13. The second compressor 13 may include a mechanism for changing the rotational speed, such as a motor driven by an inverter. The temperature of the refrigerant at the discharge port of the first compressor 3 and the temperature of the refrigerant at the discharge port of the second compressor 13 are 120 ° C., for example.

  The intermediate cooler 22 is a tank having an intermediate pressure chamber and capable of storing a liquid-phase refrigerant. The intercooler 22 is typically configured by a container having heat insulation and pressure resistance. The temperature of the liquid refrigerant stored in the intercooler 22 is, for example, 20 ° C.

  In the present embodiment, the return path 5 includes an upstream portion 15 and a downstream portion 25. The upstream portion 15 connects the outlet of the condenser 4 and the intermediate cooler 22. The downstream portion 25 connects the intermediate cooler 22 and the inlet of the evaporator 6. The upstream portion 15 of the return path 5 is a path for guiding the liquid-phase refrigerant stored in the condenser 4 to the intermediate cooler 22. The downstream portion 25 of the return path 5 is a path for guiding the liquid-phase refrigerant stored in the intermediate cooler 22 to the evaporator 6. The first valve 8 and the first heat exchanger 9 are disposed in the downstream portion 25. According to such a configuration, the temperature of the gas-phase refrigerant compressed by the first compressor 3 can be efficiently cooled with the liquid-phase refrigerant to be transferred from the condenser 4 to the evaporator 6.

  The refrigeration cycle apparatus 104 further includes a second valve 18 and a second heat exchanger 19. The second valve 18 is disposed in the upstream portion 15 of the return path 5. The second heat exchanger 19 is disposed in the upstream portion 15 of the return path 5 between the outlet of the condenser 4 and the inlet of the second valve 18. The first valve 8 is disposed in the downstream portion 25 of the return path 5. The first heat exchanger 9 is disposed in the downstream portion 25 of the return path 5 between the outlet of the intermediate cooler 22 and the inlet of the first valve 8.

  The upstream portion 15 of the return path 5 includes a first portion 15a and a second portion 15b. The first portion 15 a connects the outlet (liquid outlet) of the condenser 4 and the inlet of the second valve 18. The second portion 15 b connects the outlet of the second valve 18 and the inlet (liquid inlet) of the intercooler 22. The downstream portion 25 of the return path 5 also includes a first portion 25a and a second portion 25b. The first portion 25 a connects the outlet (liquid outlet) of the intercooler 22 and the inlet of the first valve 8. The second portion 25 b connects the outlet of the first valve 8 and the inlet (liquid inlet) of the evaporator 6. The return path 5 can be constituted by a plurality of pipes.

  The second valve 18 is a valve for controlling the flow rate of the refrigerant in the upstream portion 15 of the return path 5. The second valve 18 is typically a flow control valve (electric expansion valve), and may be a valve having a constant flow path cross-sectional area such as a capillary tube.

  The second heat exchanger 19 is a heat exchanger for cooling the refrigerant to be supplied from the condenser 4 to the second valve 18. Specifically, the second heat exchanger 19 is configured to exchange heat between the refrigerant in the intermediate cooler 22 and the refrigerant to be supplied to the second valve 18. The liquid-phase refrigerant stored in the intercooler 22 has a saturation temperature corresponding to the condensation pressure. The liquid-phase refrigerant in the condenser 4 is cooled by the second heat exchanger 19 on the path from the condenser 4 to the second valve 18 and is in a supercooled state. Accordingly, the flash evaporation amount of the refrigerant that has passed through the second valve 18 is reduced, and the void ratio (gas-liquid volume ratio) is also reduced. The refrigerant passes through the second valve 18 while maintaining a liquid phase state. Therefore, it is possible to ensure a sufficient flow rate of the refrigerant passing through the second valve 18. Under a wide range of operating conditions such as rated conditions, partial load conditions, and overload conditions, the refrigeration cycle apparatus 104 can be steadily operated for a long time. The temperature of the refrigerant at the inlet of the second valve 18 is, for example, 20 ° C.

  In the present embodiment, the second heat exchanger 19 is disposed inside the intermediate cooler 22. Therefore, the refrigerant to be supplied from the condenser 4 to the second valve 19 takes heat to the liquid-phase refrigerant stored in the intermediate cooler 22 and / or the gas-phase refrigerant in the intermediate cooler 22. And cooled. It is not necessary to supply a cooling fluid such as air or cooling water from the outside, and it is not necessary to take out the refrigerant from the intermediate cooler 22 to the outside. Therefore, according to this embodiment, the structure of the refrigeration cycle apparatus 104 can be prevented from becoming complicated. It is also easy to calculate the heat balance of the refrigeration cycle.

  Specifically, the second heat exchanger 19 is disposed in the lower part inside the intermediate cooler 22. The lower part of the intermediate cooler 22 means a part below the intermediate position of the intermediate cooler 22 in the vertical direction (height direction). The entire second heat exchanger 19 is located below the intermediate cooler 22. According to such a configuration, since the liquid refrigerant can be brought into contact with the second heat exchanger 19 with certainty, efficient heat exchange can be expected. As a result, the second heat exchanger 19 having a small size can be employed.

  As with the first heat exchanger 9, the structure of the second heat exchanger 19 is not particularly limited. The 2nd heat exchanger 19 may have the structure of well-known heat exchangers, such as a fin tube heat exchanger and a shell tube heat exchanger. When the second heat exchanger 19 has a shell tube heat exchanger structure, the container constituting the intermediate cooler 22 is also used as the shell of the second heat exchanger 19. The second heat exchanger 19 includes a meandering or wound heat transfer tube disposed inside the intercooler 22.

  In the present embodiment, the outlet end of the upstream portion 15 of the return path 5 (specifically, the outlet end of the second portion 15 b) is located in the space portion of the intermediate cooler 22. When the outlet end of the upstream portion 15 is located at such a position, it is possible to avoid applying pressure due to the liquid-phase refrigerant stored in the intermediate cooler 22 to the outlet side of the second valve 18. As a result, more accurate flow rate control can be achieved.

  According to the present embodiment, in addition to the effects obtained in the first embodiment, the following effects can be obtained. The liquid phase refrigerant stored in the condenser 4 has a saturation temperature corresponding to the condensation pressure. The liquid phase refrigerant is guided from the condenser 4 to the intercooler 22. The liquid phase refrigerant exchanges heat with the liquid phase refrigerant stored in the intermediate cooler 22 in the second heat exchanger 19 and is cooled to a saturation temperature corresponding to the vapor pressure inside the intermediate cooler 22. As a result, flash evaporation of the refrigerant passing through the second valve 18 is suppressed. The refrigerant passes through the second valve 18 while maintaining a liquid phase state. Therefore, a predetermined flow rate of refrigerant can flow through the second valve 18. Even in a refrigeration cycle that has been made highly efficient by two-stage compression and two-stage expansion, long-time operation is possible under all operating conditions including rated load conditions and partial load conditions.

  The refrigeration cycle apparatus disclosed in the present specification is useful for an air conditioner, a chiller, a heat storage device, and the like, and is particularly useful for a domestic air conditioner and a commercial air conditioner.

3 Compressor 4 Condenser 5 Return path 5a First part 5b of return path Second part 6 of return path Evaporator 7 Steam path 7a First part 7b of steam path Second part 8 of steam path First valve 9 First Heat exchanger 12 Intermediate path 13 Second compressor 15 Upstream portion 18 Second valve 19 Second heat exchanger 20 Compression mechanism 22 Intermediate cooler 25 Downstream portions 100, 102, 104 Refrigeration cycle apparatus

Claims (8)

An evaporator,
A compression mechanism including at least one compressor;
A condenser,
A vapor path including a first portion connecting the outlet of the evaporator and the inlet of the compression mechanism, and a second portion connecting the outlet of the compression mechanism and the inlet of the condenser;
A return path connecting the outlet of the condenser and the inlet of the evaporator;
A valve disposed in the return path;
A heat exchanger arranged in the return path between the outlet of the condenser and the inlet of the valve and configured to exchange heat between the refrigerant inside the evaporator and the refrigerant to be supplied to the valve When,
A refrigeration cycle apparatus comprising:   The refrigeration cycle apparatus according to claim 1, wherein the heat exchanger is disposed inside the evaporator. The evaporator is a pressure vessel configured so that a gas-liquid interface parallel to a horizontal plane is formed inside,
The refrigeration cycle apparatus according to claim 2, wherein the heat exchanger is disposed at a lower portion inside the evaporator. The compression mechanism includes a first compressor, a second compressor, and an intermediate path connecting a discharge port of the first compressor and a suction port of the second compressor,
The intermediate path includes an intermediate cooler;
The return path includes an upstream portion connecting the outlet of the condenser and the intermediate cooler, and a downstream portion connecting the intermediate cooler and the inlet of the evaporator;
The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the valve and the heat exchanger are arranged in the downstream portion. When the valve and the heat exchanger arranged in the downstream portion of the return path are defined as a first valve and a first heat exchanger, respectively,
The refrigeration cycle apparatus includes:
A second valve disposed in the upstream portion of the return path;
A second heat exchanger disposed in the upstream portion of the return path between the outlet of the condenser and the inlet of the second valve;
The refrigeration cycle apparatus according to claim 4, further comprising:   The said 2nd heat exchanger is a refrigerating-cycle apparatus of Claim 5 arrange | positioned inside the said intercooler.   The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein the refrigeration cycle apparatus is filled with a refrigerant having a negative saturated vapor pressure at room temperature. The refrigeration cycle apparatus according to claim 7, wherein the refrigerant includes water as a main component.