JP2010112579A - Refrigerating device - Google Patents

Abstract

In a refrigeration apparatus in which multistage compression is performed in parallel by a plurality of compressors, the reliability of the refrigeration apparatus is improved by surely starting the subsequent compressor.
SOLUTION: Two uniaxial two-stage compressors 3c and 3d connected in parallel discharge refrigerant from the discharge ports of the compression elements 3dm and 3cn on the front stage to the intermediate pressure path 7, and from the intermediate pressure path 7 The refrigerant is sucked into the suction ports of the compression elements 3cn and 3dn on the rear stage side. When one of the compressors 3c, 3d has already been started, an oil separation mechanism is used as a pressure equalization path for equalizing the discharge port and the suction port of the downstream compression element 3cn, 3dn. 21 and 22 are provided. The oil separation mechanisms 21 and 22 connect the discharge passage 3b and the intermediate pressure passage 7 through oil separators 21a and 22a, pressure reduction mechanisms 21b and 21b, and oil return pipes 21c and 22c.
[Selection] Figure 1

Description

  The present invention relates to a refrigeration apparatus that performs a multistage compression refrigeration cycle, and more particularly to a refrigeration apparatus that performs multistage compression in parallel with a plurality of compressors.

Conventionally, as one of refrigeration apparatuses that perform a multistage compression refrigeration cycle, there is an air conditioner that performs a two-stage compression refrigeration cycle as disclosed in Patent Document 1. This air conditioner mainly includes a compressor having two compression elements connected in series, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger.
JP 2007-232263 A

  In the air conditioning apparatus described above, the refrigerant discharged from the compression element on the front stage side of the compressor is sucked into the compression element on the rear stage side of the compressor and further compressed, so that the refrigerant is discharged from the compression element on the rear stage side of the compressor. For example, in an outdoor heat exchanger that functions as a refrigerant radiator, the temperature difference between air or water as a heat source and the refrigerant becomes large, and heat is radiated in the outdoor heat exchanger. Since the loss increases, there is a problem that high operating efficiency is difficult to obtain.

  To solve this problem, an intermediate cooler that functions as a refrigerant cooler that is discharged from the compression element on the front stage and sucked into the compression element on the rear stage is used. By providing it in the intermediate refrigerant pipe to be sucked into the compression element, the temperature of the refrigerant sucked into the latter-stage compression element is lowered, and as a result, the temperature of the refrigerant discharged from the latter-stage compression element is lowered. It is conceivable to reduce the heat dissipation loss in the outdoor heat exchanger. When such an intercooler is used, particularly when it is necessary to increase the capacity of the compression mechanism, a plurality of multistage compressors may be connected in parallel, and the intermediate refrigerant pipe may be shared.

  However, when multiple multistage compressors are connected in parallel and the intermediate refrigerant pipe is shared, if the number of compressors to be operated can be changed according to the demand for compression capacity, the start of the later compressor Occasionally, there is a problem that it is difficult to start the subsequent compressor due to the pressure difference between the suction port and the discharge port of the compression element in the compression element on the rear stage side.

  An object of the present invention is to improve the reliability of a compression mechanism by surely starting a subsequent compressor in a refrigeration apparatus that performs multistage compression in parallel with a plurality of compressors.

  The refrigeration apparatus according to the first invention includes a compression mechanism, an expansion mechanism, a heat source side heat exchanger, a use side heat exchanger, an intermediate pressure path, and a first pressure equalization path. The compression mechanism includes a suction path, a discharge path, a first compression section, and a second compression section. The first compression unit includes a first low pressure compression element and a first high pressure compression element, and the first low pressure compression element and the first high pressure compression element are driven by the same drive source. The second compression unit includes a second low-pressure compression element and a second high-pressure compression element, and the second low-pressure compression element and the second high-pressure compression element are driven by the same drive source. The refrigerant sucked from the suction path is increased in pressure by the first low pressure compression element and the second low pressure compression element. And a 1st high pressure compression element and a 2nd high pressure compression element raise the pressure of a refrigerant | coolant further than a 1st low pressure compression element and a 2nd low pressure compression element, and it discharges from a discharge path. At that time, the second compression unit can be activated after the first compression unit. Here, the “first compression unit” and the “second compression unit” are a compressor in which a plurality of compression elements are integrated, a compressor in which a single compression element is integrated, and / or a plurality of compression elements. Means a configuration including a plurality of connected compressors.

  The expansion mechanism decompresses the refrigerant sent from the discharge path of the compression mechanism and returns it to the suction path. A heat source side heat exchanger is provided between one of the expansion mechanism and the suction path of the compression mechanism and between the expansion mechanism and the discharge path of the compression mechanism, and the use side heat exchanger is provided on the other. As for the heat source side heat exchanger and the use side heat exchanger, those provided between the expansion mechanism and the discharge path of the compression mechanism function as a refrigerant cooler, and between the expansion mechanism and the suction path of the compression mechanism. The provided one functions as a refrigerant heater.

  The intermediate pressure path returns the refrigerant discharged from the discharge port of the first low pressure compression element and the discharge port of the second low pressure compression element to the suction port of the first high pressure compression element and the suction port of the second high pressure compression element. The first pressure equalizing path is provided between the intermediate pressure path and the discharge port of the second high-pressure compression element. The first pressure equalization path can equalize the intermediate pressure path and the discharge port of the second high-pressure compression element when the second compression unit is stopped.

  According to the present invention, the first pressure equalization path can equalize the intermediate pressure path and the discharge port of the second high pressure compression element when the second compression unit is stopped. As a result, the first compression unit is operated prior to the second compression unit. Therefore, even when a pressure difference is generated between the discharge path and the intermediate pressure path of the compression mechanism, The pressure difference between the discharge port of the second high-pressure compression element and the intermediate pressure path is almost eliminated. As a result, when the second compression unit is driven after the first compression unit is driven, the pressure between the suction port and the discharge port of the second high pressure compression element driven by the same drive source as the second low pressure compression element It is possible to prevent the difference from being generated by the first pressure equalizing path, and to suppress the force generated by the pressure difference that hinders the driving of the subsequent second compression section.

  A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, further comprising a second pressure equalization path provided between the intermediate pressure path and the suction port of the first low-pressure compression element. The second pressure equalization path can equalize the intermediate pressure path and the suction port of the first low-pressure compression element when the second compression unit is stopped.

  According to the present invention, the second pressure equalizing path can equalize the intermediate pressure path and the suction port of the second low-pressure compression element when the second compression unit is stopped. As a result, the first compression unit is operated prior to the second compression unit. Therefore, even when a pressure difference is generated between the suction path and the intermediate pressure path of the compression mechanism, The pressure difference between the suction port of the second low-pressure compression element and the intermediate pressure path is almost eliminated. As a result, when the second compression unit is driven after the first compression unit is driven, a pressure difference is generated between the suction port and the discharge port of the second low-pressure compression element of the second compression unit. This can be prevented by the pressure path, and the force that hinders the driving of the subsequent second compression section can be further reduced.

  A refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus of the first or second aspect, wherein the first pressure equalizing path is composed of an oil separator, a pressure reducing mechanism, and an oil return pipe. The oil separator is inserted in the discharge passage and connected to the discharge port of the second high-pressure compression element. The oil return pipe is connected to the oil separator and the intermediate pressure path. The decompression mechanism decompresses the fluid flowing through the oil return pipe.

  According to the present invention, the oil separator, the pressure reducing mechanism, and the oil return pipe can perform pressure equalization between the intermediate pressure path and the second high pressure compression element when the second compression unit is stopped, and the second high pressure compression element Oil discharged from the discharge port can be returned to the intermediate pressure path.

  A refrigeration apparatus according to a fourth invention is the refrigeration apparatus according to any one of the first to third inventions, and is a third pressure equalizing path provided between the intermediate pressure path and the discharge port of the first high-pressure compression element. Is further provided. The third pressure equalization path can equalize the intermediate pressure path and the discharge port of the first high pressure compression element when the first compression unit is stopped. The first compression unit can be activated after the second compression unit.

  According to the present invention, the third pressure equalizing path can equalize the intermediate pressure path and the discharge port of the first high pressure compression element when the first compression unit is stopped. As a result, the second compression unit is operated prior to the first compression unit. Therefore, even when a pressure difference is generated between the discharge path and the intermediate pressure path of the compression mechanism, The pressure difference between the discharge port of the first high-pressure compression element and the intermediate pressure path is almost eliminated. As a result, when the first compression unit is driven after the second compression unit is driven, a pressure difference is generated between the suction port and the discharge port of the first high-pressure compression element of the first compression unit. A force that hinders driving of the later-described first compression section can be removed by the pressure path.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects of the present invention, further comprising an intermediate cooler interposed in the intermediate pressure path and an injection path. The intermediate cooler cools the refrigerant returned to the suction port of the first high-pressure compression element and the suction port of the second high-pressure compression element. The injection path branches the refrigerant before being decompressed by the expansion mechanism and injects it into the intermediate pressure path between the intermediate cooler and the suction port of the first high-pressure compression element.

  According to the present invention, the refrigerant returned to the suction ports of the first high pressure compression element and the second high pressure compression element can be cooled by the intermediate cooler, and the refrigerant before being decompressed by the expansion mechanism is injected from the injection path. By doing so, heat can be transferred and the refrigerant can be cooled without throwing away heat.

  In the refrigeration apparatus according to the first aspect of the invention, when the second compression unit is activated after the first compression unit in a state where the first compression unit is activated, the subsequent second compression unit is stably and reliably activated. This can improve the reliability of the refrigeration apparatus.

  In the refrigeration apparatus according to the second aspect of the present invention, when the second compression unit is activated behind the first compression unit, the force that hinders the activation of the second compression unit can be further reduced, so that the compression mechanism can be switched smoothly. be able to.

In the refrigeration apparatus of the third aspect of the invention, the first pressure equalization path also serves as a mechanism for separating the oil, so that the structure of the refrigeration apparatus can be prevented from becoming complicated in order to improve the reliability of the refrigeration apparatus.

  In the refrigeration apparatus according to the fourth aspect of the invention, whether the first compression unit is the first and the second compression unit is the second generation, or the second compression unit is the first and the first compression unit is the second generation, the later one is used. Since it can start stably and reliably, since it becomes possible to replace the first and second compressors with the first and second compressors, the operation of the refrigeration apparatus can be performed flexibly.

  In the refrigeration apparatus according to the fifth aspect of the present invention, in the compression mechanism in which the first compression unit and the second compression unit can be operated in parallel, the refrigerant temperature discharged from the compression mechanism can be lowered by one intermediate cooler and one injection path. Therefore, it is possible to improve the operation efficiency of the refrigeration apparatus while suppressing the cost for adding the cooling function.

(1) Basic Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner according to an embodiment of the present invention. The air conditioner 1 includes a refrigerant circuit 2 configured to be capable of cooling operation, and performs a two-stage compression refrigeration cycle using a refrigerant (here, carbon dioxide) that operates in a supercritical region. Device.

  The refrigerant circuit 2 of the air conditioner 1 mainly includes a compression mechanism 3, a heat source side heat exchanger 4, an expansion mechanism 5, a use side heat exchanger 6, and an intermediate cooler 7d. The intermediate cooler 7 d is provided in the intermediate pressure path 7.

  In this embodiment, the compression mechanism 3 includes a suction passage 3a, a discharge passage 3b, and two compressors 3c and 3d that compress the refrigerant in two stages using two compression elements. The two compressors 3c and 3d are connected in parallel, and one compressor drive motor 3cb and 3db, one drive shaft 3cc and 3dc, and 2 in each casing 3ca and 3da, respectively. It has a sealed structure in which two compression elements 3 cm, 3 cn, 3 dm, 3 dn are accommodated. The compressor drive motors 3cb and 3db are coupled to the drive shafts 3cc and 3dc, respectively. The drive shafts 3cc and 3dc are connected to the two compression elements 3cm and 3cn and the two compression elements 3dm and 3dn, respectively. That is, in the compressor 3c, two compression elements 3cm and 3cn are connected to a single drive shaft 3cc, and the two compression elements 3cm and 3cn are both rotationally driven by the compressor drive motor 3cb. It has a stage compression structure. Similarly, in the compressor 3d, two compression elements 3dm and 3dn are coupled to a single drive shaft 3dc, and the two compression elements 3dm and 3dn are both rotationally driven by a compressor drive motor 3db. It has a compression structure. The compression elements 3 cm, 3 cn, 3 dm, and 3 dn are positive displacement compression elements such as a rotary type and a scroll type in the present embodiment.

  The compressor 3c connects a suction port of a compression element 3cm to the other end of the suction branch pipe 3ab branched from the suction mother pipe 3aa of the suction path 3a, and discharges a branch pipe 3bb that joins the discharge mother pipe 3ba of the discharge path 3b. Is connected to the discharge port of the compression element 3cn. In addition, the compressor 3 c is connected to one end of a discharge-side intermediate branch pipe 7 a that joins the discharge-side intermediate mother pipe 7 c of the intermediate pressure path 7, and a discharge port of a compression element 3 cm on the front stage side is connected to the suction side of the intermediate pressure path 7. The suction port of the downstream compression element 3cn is connected to the other end of the suction side intermediate branch pipe 7f branched from the intermediate mother pipe 7e. Similarly, the compressor 3d connects the suction port of the compression element 3dm to the other end of the suction branch pipe 3ac branched from the suction mother pipe 3aa of the suction path 3a, and discharges the refrigerant into the discharge mother pipe 3ba of the discharge path 3b. A discharge port of the compression element 3dn is connected to one end of the branch pipe 3bc. In addition, a discharge port of the compression element 3dm on the upstream side is connected to one end of the discharge side intermediate branch pipe 7b that joins the discharge side intermediate mother pipe 7c of the intermediate pressure path 7, and from the suction side intermediate mother pipe 7e of the intermediate pressure path 7 A suction port of the compression element 3cn on the rear stage side is connected to the other end of the branched suction side intermediate branch pipe 7f.

  The compression mechanism 3 uses the configuration of the compressors 3c and 3d to suck the refrigerant sucked from the one suction passage 3a by dividing the refrigerant into the two compression elements 3cm and 3dm on the front side, and to compress the refrigerant on the front side. The refrigerant compressed at 3 cm and 3 dm is further compressed by two downstream compression elements 3cn and 3dn, and then the refrigerant compressed by the two compression elements 3cn and 3dn is combined and discharged from one discharge passage 3b. In the process of sucking from the suction passage 3a and discharging from the discharge passage 3b, the compression mechanism 3 compresses the refrigerant sucked from the suction passage 3a by the two compression elements 3cm and 3dm, and then discharges the two compression elements 3cm and 3dm. From the compression elements 3 cm and 3 dm and the refrigerant combined in the intermediate pressure path 7 is divided and sucked from the suction ports of the compression elements 3 cn and 3 dn.

  Thus, in this embodiment, the compression mechanism 3 has four compression elements 3cm, 3cn, 3dm, 3dn, the compression elements 3cm, 3dm are connected in parallel to each other, and the compression elements 3cn, 3dn are They are connected to each other in parallel. Of these compression elements 3 cm, 3 cn, 3 dm, 3 dn, the refrigerant compressed to the intermediate pressure by the preceding compression elements 3 cm, 3 dm is sequentially compressed to a higher pressure by the subsequent compression elements 3 cn, 3 dn. It is configured.

  The intermediate pressure path 7 connected to the compression mechanism 3 has, at one end thereof, the other end of the discharge-side intermediate branch pipe 7a, which is connected at one end to the discharge port of the compression element 3cm, is connected to the oil separation mechanism 25 and the check mechanism. 27 is connected to one end side of the discharge-side intermediate mother pipe 7c. Further, the intermediate pressure path 7 is discharged at one end side through the oil separation mechanism 26 and the check mechanism 28 at the other end of the discharge-side intermediate branch pipe 7b connected to the discharge port of the compression element 3dm. It is connected to one end side of the side intermediate mother pipe 7c. On the other hand, the other end side of the intermediate pressure path 7 is connected to one end of the suction side intermediate branch pipe 7f whose other end is connected to the suction port of the compression element 3cn to the other end side of the suction side intermediate mother pipe 7e. At the same time, one end of the suction side intermediate branch pipe 7g connected to the suction port of the compression element 3dn is connected to the other end side of the suction side intermediate mother pipe 7e. The refrigerant having the same pressure flows between the suction side intermediate branches 7f and 7g.

  The intermediate pressure path 7 is provided with an intermediate cooler 7d. One end of the intermediate cooler 7d is connected to the other end of the discharge side intermediate mother pipe 7c, and the other end of the intermediate cooler 7d is connected to the suction side intermediate mother pipe. It is connected to one end of the tube 7e. The intermediate cooler 7d is a heat exchanger that functions as a refrigerant cooler that is discharged from the discharge ports of the compression elements 3cm and 3dm on the upstream side and sucked into the suction ports of the compression elements 3cn and 3dn. Although not shown here, the intermediate cooler 7d is supplied with water and air as a cooling source for exchanging heat with the refrigerant flowing through the intermediate cooler 7d. Thus, the intermediate cooler 7d can be called a cooler using an external heat source in the sense that it does not use the refrigerant circulating in the refrigerant circuit 2.

  The oil separation mechanisms 25, 26 are mechanisms for separating the refrigerating machine oil discharged mixed with the refrigerant discharged from the compression elements 3 cm, 3 dm from the refrigerant and returning it to the suction path 3 a of the compression mechanism 3. The oil separation mechanisms 25, 26 mainly return oil separators 25 a, 26 a that separate the refrigerant oil discharged from the refrigerant from the refrigerant, and return the refrigerant oil separated from the refrigerant to the suction path 3 a of the compression mechanism 3. Oil return pipes 25c and 26c and pressure reducing mechanisms 25b and 26b for reducing the pressure of the refrigerating machine oil flowing through the oil return pipes 25c and 26c are provided. The oil separator 21a, the pressure reducing mechanism 21b, and the oil return pipe 21c are connected in this order from the discharge side intermediate branch pipe 7a to the suction branch pipe 3ac. The oil separator 22a, the pressure reducing mechanism 22b, and the oil return pipe 22c are connected in this order from the discharge side intermediate branch pipe 7b to the suction branch pipe 3ab. Thereby, the discharge side intermediate branch pipes 7a and 7b and the suction branch pipes 3ab and 3bc are connected in a so-called stagnation state by the oil separation mechanisms 25 and 26. As the decompression mechanisms 25b and 26b, capillary tubes are used in this embodiment.

  In the present embodiment, the discharge side intermediate branch pipes 7a, 7b and the suction branch pipes 3ab, 3bc are connected to each other by the oil separation mechanisms 25, 26, so that the refrigeration accumulated in the compression element 3cm. The amount of refrigerating machine oil in the refrigerant discharged from the compression element 3 cm and the refrigerant discharged from the compression element 3dn due to the bias generated between the amount of machine oil and the amount of refrigerating machine oil accumulated in the compression element 3dm Even if there is a bias between the amount of refrigerating machine oil and the amount of refrigerating machine oil, the amount of refrigerating machine oil will return more to the smaller of the amount of refrigerating machine oil among the compression elements 3 cm and 3 dm. The bias in the amount of accumulated refrigeration oil is eliminated.

  The check mechanisms 27 and 28 are connected between the discharge ports of the oil separators 25a and 26a and the discharge-side intermediate mother pipe 7c, and supply refrigerant from the discharge ports of the compression elements 3cm and 3dm to the discharge-side intermediate mother pipe 7c. This is a mechanism for allowing the flow and blocking the flow of the refrigerant from the discharge-side intermediate mother pipe 7c to the discharge ports of the compression elements 3 cm and 3 dm. In this embodiment, a check valve is used.

  For this reason, even if either one of the compressors 3c and 3d is stopped, the refrigerant discharged from the compression element on the front stage side of the operating compressor passes through the intermediate pressure path 7 and the front stage of the stopped compressor. Therefore, the refrigerant discharged from the compression element on the front stage side of the compressor in operation passes through the compression element on the front stage side of the stopped compressor, so that the compression mechanism 3 does not reach the discharge side of the compression element on the side. Therefore, the refrigerant oil of the stopped compressor does not flow out to the suction side of the compressor, so that the shortage of the refrigerator oil when starting the stopped compressor is less likely to occur. In addition, when the priority of operation is provided between the compressors 3c and 3d (for example, when the compressor 3c is a compressor that operates preferentially), it corresponds to the above-described stopped compressor. Since there is only the compressor 3d, in this case, only the check mechanism 28 corresponding to the compressor 3d may be provided.

  On the other hand, oil separation mechanisms 21 and 22 and check mechanisms 23 and 24 are provided in the discharge passage 3 b for sending the refrigerant discharged from the compression mechanism 3 to the heat source side heat exchanger 4. The discharge branch pipe 3bb has one end connected to the discharge port of the compression element 3cn of the compressor 3c, and the other end connected to one end side of the discharge mother pipe 3ba via the oil separation mechanism 21 and the check mechanism 23. The discharge branch pipe 3bc has one end connected to the discharge port of the compression element 3dn of the compressor 3d, and the other end connected to one end side of the discharge mother pipe 3ba via the oil separation mechanism 22 and the check mechanism 24. Yes. The other end of the discharge mother pipe 3ba is connected to the heat source side heat exchanger 4. As a result, the refrigerant discharged from the compressor 3c and the refrigerant discharged from the compressor 3d separately pass through the oil separation mechanisms 21, 22 and the check mechanisms 23, 24, respectively, and merge at the discharge mother pipe 3ba, It enters into the heat source side heat exchanger 4 as a radiator.

  The oil separation mechanisms 21 and 22 are mechanisms for separating the refrigeration oil discharged mixed with the refrigerant discharged from the compressors 3c and 3d from the refrigerant and returning them to the compression elements 3cn and 3dn. The oil separation mechanisms 21 and 22 mainly include oil separators 21a and 22a that separate the refrigerant oil discharged from the refrigerant from the refrigerant, and the refrigerant oil separated from the refrigerant to the suction ports of the compression elements 3cn and 3dn. Oil return pipes 21c and 22c returning to the connected intermediate path 7 and pressure reducing mechanisms 21b and 22b for reducing the pressure of the refrigerating machine oil flowing through the oil return pipes 21c and 22c are provided. An oil separator 21a is inserted in the discharge passage 3, and the oil separator 21a, the pressure reducing mechanism 21b, and the oil return pipe 21c are connected in this order from the discharge branch pipe 3bb to the suction side intermediate branch pipe 7g. An oil separator 22a is inserted in the discharge passage 3, and the oil separator 22a, the pressure reducing mechanism 22b, and the oil return pipe 22c are connected in this order from the discharge branch pipe 3bc to the suction side intermediate branch pipe 7f. . Thereby, the discharge branch pipes 3bb and 3bc and the suction side intermediate branch pipes 7f and 7g are connected to each other in a so-called stagnation state by the oil separation mechanisms 21 and 22. As the decompression mechanisms 21b and 22b, capillary tubes are used in the present embodiment. The check mechanisms 23 and 24 are connected between the discharge ports of the oil separators 21a and 22a and the discharge mother pipe 3ba, and allow the refrigerant to flow from the discharge path 3b of the compression mechanism 3 to the heat source side heat exchanger 4. And it is a mechanism for interrupting | blocking the flow of the refrigerant | coolant from the heat source side heat exchanger 4 to the discharge path 3b of the compression mechanism 3, and the non-return valve is used in this embodiment.

  In the present embodiment, since the discharge side intermediate branch pipes 7a and 7b and the suction branch pipes 3ab and 3bc are connected to each other by the oil separation mechanisms 25 and 26, the refrigeration accumulated in the compression element 3cn. The amount of refrigerating machine oil in the refrigerant discharged from the compression element 3cn and the refrigerant discharged from the compression element 3dn due to the bias generated between the amount of machine oil and the amount of refrigerating machine oil accumulated in the compression element 3dn Even if there is a bias between the amount of the refrigerating machine oil and the amount of the refrigerating machine oil, the amount of refrigerating machine oil returns to the smaller of the amount of refrigerating machine oil among the compression elements 3cn and 3dn. The bias in the amount of accumulated refrigeration oil is eliminated.

  The heat source side heat exchanger 4 is a heat exchanger that functions as a refrigerant radiator. One end of the heat source side heat exchanger 4 is connected to the discharge path 3 b of the compression mechanism 3, and the other end is connected to one end of the expansion mechanism 5. Although not shown here, the heat source side heat exchanger 4 is supplied with water and air as a cooling source for exchanging heat with the refrigerant flowing through the heat source side heat exchanger 4.

  The expansion mechanism 5 is a mechanism that depressurizes the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the use side heat exchanger 6 as an evaporator. In the present embodiment, the expansion mechanism 5 is cooled in the heat source side heat exchanger 4. The sent high-pressure refrigerant is depressurized to near the low pressure in the refrigeration cycle before being sent to the use-side heat exchanger 6. In the present embodiment, an electric expansion valve is used for the expansion mechanism 5. One end of the expansion mechanism 5 is connected to the heat source side heat exchanger 4, and the other end is connected to the use side heat exchanger 6.

  The use side heat exchanger 6 is a heat exchanger that functions as a refrigerant evaporator. One end of the use side heat exchanger 6 is connected to the expansion mechanism 5, and the other end is connected to the suction path 3 a of the compression mechanism 3. Although not shown here, the use side heat exchanger 6 is supplied with water or air as a heat source for exchanging heat with the refrigerant flowing in the use side heat exchanger 6.

  Furthermore, although not shown here, the air conditioner 1 has a control unit that controls the operation of each part of the air conditioner 1 such as the compression mechanism 3 and the expansion mechanism 5.

(2) Operation | movement of an air conditioning apparatus Next, operation | movement of the air conditioning apparatus 1 of this embodiment is demonstrated using FIGS. 1-3. 2 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation, and FIG. 3 is a temperature-entropy diagram illustrating the refrigeration cycle during the cooling operation. In addition, the operation control in the following cooling operation is performed by the above-described control unit (not shown). In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, and E in FIGS. 2 and 3), and “low pressure” means low pressure in the refrigeration cycle. (Ie, pressure at points A and F in FIGS. 2 and 3), and “intermediate pressure” means intermediate pressure in the refrigeration cycle (ie, pressure at points B and C in FIGS. 2 and 3). is doing.

<Cooling operation>
During the cooling operation, the opening degree of the expansion mechanism 5 is adjusted. In the state of the refrigerant circuit 2, low-pressure refrigerant (see point A in FIGS. 1 to 3) is sucked into the compression mechanism 3 from the suction passage 3a and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure path 7 (see point B in FIGS. 1 to 3). The intermediate pressure refrigerant discharged from the compression mechanism 3 flows into the oil separators 25a and 26a constituting the oil separation mechanisms 25 and 26, and the refrigerating machine oil in the refrigerant is separated. The refrigerating machine oil separated from the intermediate pressure refrigerant in the oil separators 25a and 26a flows into the oil return pipes 25c and 26c constituting the oil separation mechanisms 25 and 26, and is provided in the oil return pipes 25c and 26c. After the pressure is reduced by the pressure reducing mechanisms 25b and 26b, the pressure is returned to the suction branch pipes 3ac and 3ab of the suction passage 3a and is again sucked into the compression mechanism 3.

  The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is cooled by exchanging heat with water or air as a cooling source in the intermediate cooler 7 d (points in FIGS. 1 to 3). C). The refrigerant cooled in the intermediate cooler 7d is then sucked into the compression elements 3cn and 3dn connected to the downstream side of the compression elements 3cm and 3dm, further compressed, and discharged from the compression mechanism 3 to the discharge passage 3b. (See point D in FIGS. 1 to 3). Here, the high-pressure refrigerant discharged from the compression mechanism 3 has a critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 2) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn. Compressed to over pressure. Then, the high-pressure refrigerant discharged from the compression mechanism 3 flows into the oil separators 21a and 22a constituting the oil separation mechanisms 21 and 22, and the refrigerating machine oil in the refrigerant is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separators 21a and 22a flows into the oil return pipes 21c and 22c constituting the oil separation mechanisms 21 and 22, and is decompressed in the oil return pipes 21c and 22c. After the pressure is reduced by the mechanisms 21 b and 22 b, the pressure is returned to the suction-side intermediate branch pipes 7 g and 7 f of the intermediate pressure path 7 and again sucked into the compression mechanism 3.

  Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 21 and 22 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanisms 23 and 24. The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 1 to 3). reference). The high-pressure refrigerant cooled in the heat source-side heat exchanger 4 is decompressed by the expansion mechanism 5 to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the use-side heat exchanger 6 that functions as a refrigerant evaporator. (See point F in FIGS. 1 to 3). The low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated and evaporated in the use-side heat exchanger 6 by exchanging heat with water or air as a heating source. (Refer to point A in FIGS. 1 to 3). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 3. In this way, the cooling operation is performed.

  Thus, in the air conditioning apparatus 1, the intermediate cooler 7d is provided by providing the intermediate cooler 7d in the intermediate pressure path 7 for sucking the refrigerant discharged from the compression elements 3cm and 3dm into the compression elements 3cn and 3dn. When the intermediate cooler 7d is not provided because it functions as a cooler (in this case, in the order of point A → point B → point D ′ → point E → point F in FIGS. 2 and 3) The refrigerant temperature sucked into the compression elements 3cn and 3dn on the downstream side of the compression elements 3cm and 3dm is reduced (see points B and C in FIG. 3), and the compression elements 3cn, The temperature of the refrigerant discharged from 3dn also decreases (see points D and D ′ in FIG. 3). For this reason, in this air conditioner 1, in the heat source side heat exchanger 4 that functions as a radiator of the high-pressure refrigerant, compared to the case where the intermediate cooler 7d is not provided, water or air as a cooling source and the refrigerant The temperature difference can be reduced and the heat dissipation loss can be reduced, so that the operation efficiency can be improved.

  The above description is a case where in the compression mechanism 3, the compressors 3c and 3d are simultaneously operated in parallel. For example, the refrigeration load may change and it may be necessary to drive both of the compressors 3c and 3d that have been operated by only one of the compressors 3c and 3d of the compression mechanism 3. In such a case, for example, if the compressor 3c is operated in advance, if there is no oil separation mechanism 22, the pressure of the suction port of the compression element 3dn of the compressor 3d becomes an intermediate pressure. It becomes higher than the pressure at the discharge port of 3dn, and a large load is applied at the time of starting, so that starting becomes difficult. Due to the oil separation mechanism 22, when the compressor 3 d is operated behind the compressor 3 c, the discharge port and the suction port of the compression element 3 dn are equalized by the oil separation mechanism 22. As described above, the oil separation mechanism 22 functions as a pressure equalization path, so that the compressor 3c can be operated first and the compressor 3d can be started without difficulty. Further, since the oil separation mechanism 21 is provided, the compressor 3d can be operated first, and the compressor 3c can be operated later. Accordingly, it is possible to cope with the case where the capacity required for the compression mechanism 3 changes during operation of the compression mechanism 3 and the number of compressors 3c and 3d must be changed. Flexible operation becomes possible.

(3) Modification 1
In the above-described embodiment, the air conditioner capable of cooling operation using the two-stage compression refrigeration cycle has been described, but in addition to this configuration, by providing a switching mechanism that switches between cooling operation and heating operation, The cooling operation and the heating operation can be switched.

  FIG. 4 is a schematic configuration diagram of an air conditioner according to the first modification. As shown in FIG. 4, the air conditioner 1 </ b> A includes a switching mechanism 8 and a receiver 9 that can switch between a cooling operation and a heating operation in the configuration of the refrigerant circuit 2 (see FIG. 1) of the above-described embodiment. In addition, a bridge circuit 10 is added, and the refrigerant circuit 2 </ b> A is provided in which a first expansion mechanism 5 a and a second expansion mechanism 5 b are provided instead of the expansion mechanism 5.

  The switching mechanism 8 is a mechanism for switching the direction of refrigerant flow in the refrigerant circuit 2A. During the cooling operation, the heat source side heat exchanger 4 functions as a radiator for the refrigerant discharged from the compression mechanism 3, and the use side heat exchanger 6 functions as an evaporator for the refrigerant cooled in the heat source side heat exchanger 4. Therefore, the discharge path 3b of the compression mechanism 3 and one end of the heat source side heat exchanger 4 are connected, and the suction path 3a of the compressor 3 and the other end of the use side heat exchanger 6 are connected (switching in FIG. 4). Refer to the solid line of the mechanism 8, and the state of the switching mechanism 8 is hereinafter referred to as “cooling operation state”). On the other hand, during heating operation, the use side heat exchanger 6 is used as a radiator for the refrigerant discharged from the compression mechanism 3, and the heat source side heat exchanger 4 is used as an evaporator for the refrigerant cooled in the use side heat exchanger 6. In order to make it function, the discharge path 3b of the compression mechanism 3 and the other end of the use side heat exchanger 6 are connected, and the suction path 3a of the compression mechanism 3 and one end of the heat source side heat exchanger 4 are connected (FIG. 4). ), The state of the switching mechanism 8 is hereinafter referred to as “heating operation state”).

  In the present modification, the switching mechanism 8 is a four-way switching valve connected to the suction path 3 a of the compression mechanism 3, the discharge path 3 b of the compression mechanism 3, the heat source side heat exchanger 4, and the use side heat exchanger 6. The switching mechanism 8 is not limited to the four-way switching valve, and is configured to have a function of switching the refrigerant flow direction similar to that described above, for example, by combining a plurality of electromagnetic valves. There may be.

  Thus, the switching mechanism 8 is a cooling operation state in which the refrigerant is circulated in the order of the compression mechanism 3, the heat source side heat exchanger 4, the first expansion mechanism 5a, the receiver 9, the second expansion mechanism 5b, and the use side heat exchanger 6. And the heating operation state in which the refrigerant is circulated in the order of the compression mechanism 3, the use side heat exchanger 6, the first expansion mechanism 5a, the receiver 9, the second expansion mechanism 5b, and the heat source side heat exchanger 4. It is configured.

  The bridge circuit 10 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 6, and receives a receiver inlet pipe 9 a connected to the inlet of the receiver 9 and a receiver connected to the outlet of the receiver 9. It is connected to the outlet pipe 9b. The bridge circuit 10 includes four check valves 10a, 10b, 10c, and 10d in the present modification. The inlet check valve 10a is a check valve that allows only the refrigerant to flow from the heat source side heat exchanger 4 to the receiver inlet pipe 9a. The inlet check valve 10b is a check valve that only allows the refrigerant to flow from the use side heat exchanger 6 to the receiver inlet pipe 9a. That is, the inlet check valves 10a and 10b have a function of circulating the refrigerant from one of the heat source side heat exchanger 4 and the use side heat exchanger 6 to the receiver inlet pipe 9a. The outlet check valve 10 c is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 9 b to the use-side heat exchanger 6. The outlet check valve 10 d is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 9 b to the heat source side heat exchanger 4. That is, the outlet check valves 10c and 10d have a function of circulating the refrigerant from the receiver outlet pipe 9b to the other of the heat source side heat exchanger 4 and the use side heat exchanger 6.

  The first expansion mechanism 5a is a mechanism that depressurizes the refrigerant provided in the receiver inlet pipe 9a, and an electric expansion valve is used in this modification. In the present modification, the first expansion mechanism 5a converts the high-pressure refrigerant cooled in the heat source side heat exchanger 4 into the refrigerant before being sent to the use side heat exchanger 6 via the receiver 9 during the cooling operation. The pressure is reduced to near the saturation pressure, and during the heating operation, the high-pressure refrigerant cooled in the use-side heat exchanger 6 is reduced to near the saturation pressure of the refrigerant before being sent to the heat source side heat exchanger 4 via the receiver 9.

  The receiver 9 is depressurized by the first expansion mechanism 5a so as to be able to accumulate surplus refrigerant generated according to the operation state such as the refrigerant circulation amount in the refrigerant circuit 2A being different between the cooling operation and the heating operation. It is the container provided in order to accumulate the refrigerant | coolant after a short time. Therefore, the inlet of the receiver 9 is connected to the receiver inlet pipe 9a, and the outlet thereof is connected to the receiver outlet pipe 9b. The receiver 9 also has a suction return pipe that can extract the refrigerant from the receiver 9 and return it to the suction path 3a of the compression mechanism 3 (that is, the suction ports of the compression elements 3cm and 3dm on the front stage side of the compression mechanism 3). 30 is connected. The suction return pipe 30 is provided with a suction return on / off valve 30a. The suction return on / off valve 30a is an electromagnetic valve in this modification.

  The second expansion mechanism 5b is a mechanism that depressurizes the refrigerant provided in the receiver outlet pipe 9b, and an electric expansion valve is used in this modification. In the present modification, the second expansion mechanism 5b is configured to reduce the refrigerant decompressed by the first expansion mechanism 5a to a low pressure in the refrigeration cycle before sending it to the use-side heat exchanger 6 via the receiver 9 during the cooling operation. In the heating operation, the refrigerant decompressed by the first expansion mechanism 5a is further decompressed until it reaches a low pressure in the refrigeration cycle, before being sent to the heat source side heat exchanger 4 via the receiver 9.

  Thus, in this modification, when the switching mechanism 8 is in the cooling operation state by the bridge circuit 10, the receiver 9, the receiver inlet pipe 9a, and the receiver outlet pipe 9b, the heat source side heat exchanger 4 is cooled. The high-pressure refrigerant is supplied to the inlet check valve 10a of the bridge circuit 10, the first expansion mechanism 5a of the receiver inlet pipe 9a, the receiver 9, the second expansion mechanism 5b of the receiver outlet pipe 9b, and the outlet check valve 10c of the bridge circuit 10. It can be sent to the use side heat exchanger 6 through. In addition, when the switching mechanism 8 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 is converted into the first expansion mechanism of the inlet check valve 10b of the bridge circuit 10 and the receiver inlet pipe 9a. 5a, the receiver 9, the second expansion mechanism 5b of the receiver outlet pipe 9b, and the outlet check valve 10d of the bridge circuit 10 can be sent to the heat source side heat exchanger 4.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIGS. Here, FIG. 5 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation, and FIG. 6 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Here, the refrigeration cycle during the cooling operation will be described with reference to FIGS. In addition, operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment. In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, and E in FIGS. 2 and 3 and points D, D ′, and F in FIGS. 5 and 6). "Low pressure" means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 2 and 3 and pressure at points A and E in FIGS. 5 and 6), “Intermediate pressure” means an intermediate pressure in the refrigeration cycle (that is, pressure at points B, C, and C ′ in FIGS. 2, 3, 5, and 6).

<Cooling operation>
During the cooling operation, the switching mechanism 8 is in the cooling operation state indicated by the solid line in FIG. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted.

  In the state of the refrigerant circuit 2A, the low-pressure refrigerant (see point A in FIGS. 2 to 4) sucked into the compression mechanism 3 from the suction passage 3a is cooled in the heat source side heat exchanger 4 (see FIG. 2). The description of the process up to 2) is omitted because it is the same as the refrigerant circuit 2 of the embodiment.

  The high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 9a through the inlet check valve 10a of the bridge circuit 10 and is reduced to the vicinity of the saturation pressure by the first expansion mechanism 5a. It is temporarily stored (see point I in FIG. 4). Then, the refrigerant stored in the receiver 9 is sent to the receiver outlet pipe 9b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 10c of the bridge circuit 10 And is sent to the use-side heat exchanger 6 that functions as a refrigerant evaporator (see point F in FIGS. 2 to 4). And the refrigerant | coolant of the low-pressure gas-liquid two-phase state sent to the utilization side heat exchanger 6 will be heated by performing heat exchange with the water and air as a heating source, and will evaporate (FIG. 2 figure). (See point A in 4). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 3 via the switching mechanism 8. In this way, the cooling operation is performed.

  As described above, in the air conditioner 1A, as in the above-described embodiment, the heat source side heat exchanger 4 that functions as a radiator for the high-pressure refrigerant has a cooling source as compared with the case where the intermediate cooler 7d is not provided. As a result, it becomes possible to reduce the temperature difference between water or air and the refrigerant, and to improve the operation efficiency.

  Further, during the cooling operation, in the compression mechanism 3, one of the compressors 3 c and 3 d can be started first and the other can be operated later, similarly to the embodiment, and the flexible operation of the compression mechanism 3 can be performed. It becomes possible.

<Heating operation>
During the heating operation, the switching mechanism 8 is in a heating operation state indicated by a broken line in FIG. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted.

  In the state of the refrigerant circuit 2A, the low-pressure refrigerant (see point A in FIGS. 4 to 6) is sucked into the compression mechanism 3 from the suction passage 3a and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure path 7 (see point B in FIGS. 4 to 6). The intermediate pressure refrigerant discharged from the compression mechanism 3 flows into the oil separators 25a and 26a constituting the oil separation mechanisms 25 and 26, and the refrigerating machine oil in the refrigerant is separated. The refrigerating machine oil separated from the intermediate pressure refrigerant in the oil separators 25a and 26a flows into the oil return pipes 25c and 26c constituting the oil separation mechanisms 25 and 26, and is provided in the oil return pipes 25c and 26c. After the pressure is reduced by the pressure reducing mechanisms 25b and 26b, the pressure is returned to the suction branch pipes 3ac and 3ab of the suction passage 3a and is again sucked into the compression mechanism 3. The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is cooled by exchanging heat with water or air as a cooling source in the intermediate cooler 7 d (points in FIGS. 4 to 6). C). The refrigerant cooled in the intermediate cooler 7d is then sucked into the compression elements 3cn and 3dn connected to the downstream side of the compression elements 3cm and 3dm, further compressed, and discharged from the compression mechanism 3 to the discharge passage 3b. (Refer to point D in FIGS. 4 to 6).

  Here, the high-pressure refrigerant discharged from the compression mechanism 3 is subjected to the critical pressure (that is, the critical point CP shown in FIG. 5) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn as in the cooling operation. Is compressed to a pressure exceeding the critical pressure Pcp). Then, the high-pressure refrigerant discharged from the compression mechanism 3 flows into the oil separators 21a and 22a constituting the oil separation mechanisms 21 and 22, and the refrigerating machine oil in the refrigerant is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separators 21a and 22a flows into the oil return pipes 21c and 22c constituting the oil separation mechanisms 21 and 22, and is decompressed in the oil return pipes 21c and 22c. After the pressure is reduced by the mechanisms 21 b and 22 b, the pressure is returned to the suction ports of the compression elements 3 d and 3 c and is sucked into the compression mechanism 3 again.

  Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 21 and 22 is sent to the use side heat exchanger 6 that functions as a refrigerant radiator through the check mechanisms 23 and 24 and the switching mechanism 8. Then, it is cooled by exchanging heat with water or air as a cooling source (see point F in FIGS. 4 to 6). The high-pressure refrigerant cooled in the use-side heat exchanger 6 flows into the receiver inlet pipe 9a through the inlet check valve 10b of the bridge circuit 10, and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIG. 4). Then, the refrigerant accumulated in the receiver 9 is sent to the receiver outlet pipe 9b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 10d of the bridge circuit 10 is obtained. And is sent to the heat source side heat exchanger 4 functioning as a refrigerant evaporator (see point E in FIGS. 4 to 6). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by exchanging heat with water or air as a heating source to evaporate (FIGS. 4 to 5). (See point A in 6). The low-pressure refrigerant heated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 3 via the switching mechanism 8. In this way, the heating operation is performed.

  In the air conditioner 1A, during the heating operation, in the compression mechanism 3, one of the compressors 3c and 3d can be started first, and the other can be operated later, as in the cooling operation. Flexible operation is possible.

(4) Modification 2
In the air conditioner 1A of the first modification, the intermediate-pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the front stage passes through the intermediate cooler 7d during the heating operation, as in the cooling operation. Unlike the cooling operation, the operation may be configured to pass through the bypass without passing through the intercooler 7d (that is, not cooled).

  FIG. 7 is a schematic configuration diagram of an air-conditioning apparatus according to Modification 2. As shown in FIG. 7, the refrigerant circuit 2B of the air conditioner 1B of the present modification has the configuration of the refrigerant circuit 2A (see FIG. 4) of the modification 1 in addition to the intermediate cooler bypass pipe 7i and the intermediate cooler on / off valve 7h. And an intermediate cooler bypass opening / closing valve 7j. During the cooling operation, in order to allow the refrigerant to pass through the intermediate cooler 7d, the intermediate cooler opening / closing valve 7h is opened and the intermediate cooler bypass opening / closing valve 7j is closed. On the other hand, during the heating operation, the intermediate cooler opening / closing valve 7h is closed and the intermediate cooler bypass opening / closing valve 7j is opened so that the refrigerant passes through the intermediate cooler bypass pipe 7i.

  Unlike the cooling operation, the heating operation passes through the intermediate cooler bypass pipe 7i without passing through the intermediate cooler 7d (that is, not cooled) (point C in FIGS. 7 to 9). The compression elements 3cm, 3dm are sucked into the compression elements 3cn, 3dn and further compressed and discharged from the compression mechanism 3 to the discharge passage 3b (see FIGS. 4 to 9). (See point D).

  In this way, in the heating operation in which the switching mechanism 8 is in the heating operation state, the intermediate cooler 7d is not functioned as a cooler by the intermediate cooler bypass pipe, and therefore only the intermediate cooler 7d is provided or When the intercooler 7d is caused to function as a cooler as in the above cooling operation (in this case, in FIGS. 5 and 6, point A → point B → point C ′ → point D ′ → point F → point (Refer to points D and D ′ in FIG. 6), the temperature of the refrigerant discharged from the compression mechanism 3 is suppressed. For this reason, in this air conditioning apparatus 1, compared to the case where only the intermediate cooler 7d is provided or the case where the intermediate cooler 7d functions as a cooler as in the above-described cooling operation, heat dissipation to the outside is suppressed, It becomes possible to suppress a decrease in the temperature of the refrigerant supplied to the use-side heat exchanger 6 functioning as a refrigerant radiator, and the enthalpy difference between points D and F in FIG. It is possible to prevent a decrease in operating efficiency by suppressing a decrease in heating capacity corresponding to a difference from the enthalpy difference.

(5) Modification 3
In the above-described modification 2, the air conditioner that performs the cooling operation and the heating operation using the two-stage compression refrigeration cycle and does not function the intermediate cooler during the heating operation has been described. 7), an intermediate pressure injection can be performed by providing an injection pipe and an economizer heat exchanger.

  FIG. 10 is a schematic configuration diagram of an air-conditioning apparatus according to Modification 3. As shown in FIG. 10, the air conditioner 1 </ b> C includes a refrigerant circuit 2 </ b> C in which an injection pipe 11 and an economizer heat exchanger 12 are provided in the configuration of the refrigerant circuit 2 </ b> B (see FIG. 7) of the above-described modification 2. Composed.

  The injection pipe 11 has a function of branching the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 and returning it to the compression elements 3cn and 3dn on the rear stage side of the compression mechanism 3. The injection pipe 11 is provided so as to branch the refrigerant flowing through the receiver inlet pipe 9a and return it to the suction side of the subsequent compression elements 3cn and 3dn. More specifically, the injection pipe 11 is connected to the position upstream of the first expansion mechanism 5a of the receiver inlet pipe 9a (that is, when the switching mechanism 8 is in the cooling operation state, the heat source side heat exchanger 4 and The refrigerant is branched from the first expansion mechanism 5a) and returned to the downstream position of the intermediate cooler 7d in the intermediate pressure path 7. The injection pipe 11 is provided with an injection opening / closing valve 11a capable of opening degree control. The injection on-off valve 11a is an electric expansion valve in this modification.

  The economizer heat exchanger 12 is reduced to a refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 and a refrigerant flowing through the injection pipe 11 (more specifically, to the vicinity of the intermediate pressure in the injection on-off valve 11a). It is a heat exchanger that performs heat exchange with the refrigerant after being performed. In this modification, the economizer heat exchanger 12 is positioned upstream of the first expansion mechanism 5a of the receiver inlet pipe 9a (that is, when the switching mechanism 8 is in the cooling operation state, the heat source side heat exchanger 4 And a refrigerant flowing between the first expansion mechanism 5a and the refrigerant flowing through the injection pipe 11, and has a flow path through which both refrigerants face each other. . In this modification, the economizer heat exchanger 12 is provided on the downstream side of the position where the injection pipe 11 is branched from the receiver inlet pipe 9a. For this reason, the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 is branched into the injection pipe 11 before heat exchange is performed in the economizer heat exchanger 12 in the receiver inlet pipe 9a. Thereafter, the economizer heat exchanger 12 exchanges heat with the refrigerant flowing through the injection pipe 11.

  As described above, in this modification, when the switching mechanism 8 is in the cooling operation state, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is converted into the inlet check valve 10a of the bridge circuit 10 and the economizer heat. It is sent to the use side heat exchanger 6 through the exchanger 12, the first expansion mechanism 5a of the receiver inlet pipe 9a, the receiver 9, the second expansion mechanism 5b of the receiver outlet pipe 9b, and the outlet check valve 10c of the bridge circuit 10. It can be done. In addition, when the switching mechanism 8 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 is supplied to the inlet check valve 10b, the economizer heat exchanger 12, the receiver inlet pipe of the bridge circuit 10. The heat can be sent to the heat source side heat exchanger 4 through the first expansion mechanism 5a of 9a, the receiver 9, the second expansion mechanism 5b of the receiver outlet pipe 9b, and the outlet check valve 10d of the bridge circuit 10.

  Furthermore, in this modification, the intermediate pressure path 7 or the compression mechanism 3 is provided with an intermediate pressure sensor 13 that detects the pressure of the refrigerant flowing through the intermediate pressure path 7. An economizer outlet temperature sensor 14 for detecting the temperature of the refrigerant at the outlet of the economizer heat exchanger 12 on the injection pipe 11 side is provided at the outlet of the economizer heat exchanger 12 on the injection pipe 11 side.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIGS. Here, FIG. 11 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation, FIG. 12 is a temperature-entropy diagram illustrating the refrigeration cycle during the cooling operation, and FIG. FIG. 14 is a pressure-enthalpy diagram illustrating a refrigeration cycle during heating operation, and FIG. 14 is a temperature-entropy diagram illustrating a refrigeration cycle during heating operation. In addition, operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment. In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, E, and H in FIGS. 11 and 12, and points D, D ′, and FIGS. 13 and 14). "Pressure at F and H)" and "low pressure" means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 11 and 14 and pressure at points A and E in FIGS. 13 and 14). The “intermediate pressure” means the intermediate pressure in the refrigeration cycle (that is, the pressure at points B, C, G, J, and K in FIGS. 11 to 14).

<Cooling operation>
During the cooling operation, the switching mechanism 8 is in the cooling operation state indicated by the solid line in FIG. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. The opening degree of the injection on-off valve 11a is also adjusted. More specifically, in this modification, the injection on / off valve 11a is adjusted in opening degree so that the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 12 on the injection pipe 11 side becomes a target value. Control is to be made. In this modification, the degree of superheat of the refrigerant at the outlet on the injection pipe 11 side of the economizer heat exchanger 12 is detected by the economizer outlet temperature sensor 14 by converting the intermediate pressure detected by the intermediate pressure sensor 13 into a saturation temperature. It is obtained by subtracting the saturation temperature value of this refrigerant from the refrigerant temperature. In order to make the intermediate cooler 7d function, the intermediate cooler on / off valve 7h is opened and the intermediate cooler bypass on / off valve 7j is closed.

  In the state of the refrigerant circuit 2C, low-pressure refrigerant (see point A in FIGS. 10 to 12) is sucked into the compression mechanism 3 from the suction passage 3a and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure path 7 (see point B in FIGS. 10 to 12). The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is cooled by exchanging heat with water or air as a cooling source in the intermediate cooler 7 d (points in FIGS. 10 to 12). C). The refrigerant cooled in the intermediate cooler 7d is further cooled by joining with the refrigerant (see point K in FIGS. 10 to 12) returned from the injection pipe 11 to the compression mechanism 3d on the rear stage side (see FIG. 10 to FIG. 10). (See point G in FIG. 12).

  Next, the intermediate pressure refrigerant that merged with the refrigerant returning from the injection pipe 11 (that is, subjected to intermediate pressure injection by the economizer heat exchanger 12) is compressed to the compression element 3cn connected to the downstream side of the compression elements 3cm and 3dm. , 3dn and further compressed, and discharged to the discharge passage 3b of the compression mechanism 3 (see point D in FIGS. 10 to 12). Here, the high-pressure refrigerant discharged from the compression mechanism 3 is subjected to a critical pressure (that is, the criticality shown in FIG. 11) by a two-stage compression operation by the compression elements 3 cm and 3 dm on the low pressure side and the compression elements 3 cn and 3 dn on the high pressure side. The pressure is compressed to a pressure exceeding the critical pressure Pcp) at the point CP.

  The high-pressure refrigerant discharged from the compression mechanism 3 flows into the oil separators 21a and 22a constituting the oil separation mechanisms 21 and 22, and the refrigerating machine oil in the refrigerant is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separators 21a and 22a flows into the oil return pipes 21c and 22c constituting the oil separation mechanisms 21 and 22, and is decompressed in the oil return pipes 21c and 22c. After the pressure is reduced by the mechanisms 21 b and 22 b, the pressure is returned to the suction ports of the compression elements 3 cn and 3 dn and again sucked into the compression mechanism 3.

  Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 21 and 22 is sent to the heat source side heat exchanger 4 that functions as a refrigerant radiator through the check mechanisms 23 and 24 and the switching mechanism 8. It is done. The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 10 to 12). reference). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 9 a through the inlet check valve 10 a of the bridge circuit 10, and a part thereof is branched to the injection pipe 11. And the refrigerant | coolant which flows through the injection pipe | tube 11 is sent to the economizer heat exchanger 12 after depressurizing to the intermediate pressure vicinity in the injection on-off valve 11a (refer the point J of FIGS. 10-12).

  Moreover, the refrigerant | coolant after branching to the injection pipe | tube 11 flows into the economizer heat exchanger 12, and heat-exchanges with the refrigerant | coolant which flows through the injection pipe | tube 11, and is cooled (refer the point H of FIGS. 10-12). On the other hand, the refrigerant flowing through the injection pipe 11 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see point K in FIGS. 10 to 12), and Thus, the intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is joined. The high-pressure refrigerant cooled in the economizer heat exchanger 12 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 9 (see point I in FIG. 10). Then, the refrigerant stored in the receiver 9 is sent to the receiver outlet pipe 9b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 10c of the bridge circuit 10 And is sent to the use-side heat exchanger 6 that functions as a refrigerant evaporator (see point F in FIGS. 10 to 12). The low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated and exchanged with water or air as a heating source to evaporate (FIGS. 10 to 10). 12 point A). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 3 via the switching mechanism 8. In this way, the cooling operation is performed.

  In the configuration of this modified example, as in the above-described modified example 2, in the cooling operation in which the switching mechanism 8 is in the cooling operation state, the intermediate cooler 7d is in a state of functioning as a cooler. The heat radiation loss in the heat source side heat exchanger 4 can be reduced as compared with the case where the vessel 7d is not provided.

  Moreover, in the configuration of the present modification, the injection pipe 11 and the economizer heat exchanger 12 are provided to branch the refrigerant sent from the heat source side heat exchanger 4 to the expansion mechanisms 5a and 5b, and to the downstream compression elements 3cn and 3dn. Therefore, the temperature of the refrigerant sucked into the compression elements 3cn and 3dn on the rear stage side can be further reduced without performing heat radiation to the outside like the intermediate cooler 7d (point of FIG. 12). C and G). Thereby, the temperature of the refrigerant discharged from the compression mechanism 3 can be further suppressed (see points D and D ′ in FIG. 12), and the operating efficiency can be further improved as compared with the case where the injection pipe 11 is not provided. it can.

  Further, during the cooling operation, in the compression mechanism 3, one of the compressors 3 c and 3 d can be started first and the other can be operated later, similarly to the embodiment, and the flexible operation of the compression mechanism 3 can be performed. It is possible.

<Heating operation>
During the heating operation, the switching mechanism 8 is in a heating operation state indicated by a broken line in FIG. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Further, the opening degree of the injection on-off valve 11a is adjusted in the same manner as in the above-described cooling operation. Then, the intermediate cooler on / off valve 7h of the intermediate pressure passage 7 is closed and the intermediate cooler bypass on / off valve 7j of the intermediate cooler bypass pipe 7i is opened, so that the intermediate cooler 7d does not function as a cooler. The

  In the state of the refrigerant circuit 2C, low-pressure refrigerant (see point A in FIGS. 10, 13, and 14) is sucked into the compression mechanism 3 from the suction passage 3a, and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure passage 7 (see point B in FIGS. 10, 13, and 14). The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the front stage side does not pass through the intermediate cooler 7 d (that is, is not cooled), unlike the cooling operation, and is not cooled. 7i (see point C in FIGS. 10, 13, and 14) and merged with the refrigerant (see point K in FIGS. 10, 13, and 14) returned from the injection pipe 11 to the downstream compression mechanism 3d. (See point G in FIGS. 10, 13, and 14). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the injection pipe 11 is sucked into the compression elements 3cn and 3dn connected to the downstream side of the compression elements 3cm and 3dm, and further compressed, and is discharged from the compression mechanism 3 to the discharge path. 3b (see point D in FIGS. 10, 13, and 14). Here, the high-pressure refrigerant discharged from the compression mechanism 3 is subjected to the critical pressure (that is, the critical point CP shown in FIG. 13) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn as in the cooling operation. Is compressed to a pressure exceeding the critical pressure Pcp). Then, the high-pressure refrigerant discharged from the compression mechanism 3 flows into the oil separators 21a and 22a constituting the oil separation mechanisms 21 and 22, and the refrigerating machine oil in the refrigerant is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separators 21a and 22a flows into the oil return pipes 21c and 22c constituting the oil separation mechanisms 21 and 22, and is decompressed in the oil return pipes 21c and 22c. After the pressure is reduced by the mechanisms 21 b and 22 b, the pressure is returned to the suction ports of the compression elements 3 cn and 3 dn and again sucked into the compression mechanism 3. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanisms 21 and 22 is sent to the use side heat exchanger 6 that functions as a refrigerant radiator through the check mechanisms 23 and 24 and the switching mechanism 8. Then, it is cooled by exchanging heat with water or air as a cooling source (see point F in FIGS. 10, 13, and 14). Then, the high-pressure refrigerant cooled in the use side heat exchanger 6 flows into the receiver inlet pipe 9 a through the inlet check valve 10 b of the bridge circuit 10, and a part thereof is branched to the injection pipe 11. And the refrigerant | coolant which flows through the injection pipe | tube 11 is sent to the economizer heat exchanger 12 after depressurizing to the intermediate pressure vicinity in the injection on-off valve 11a (refer the point J of FIG.10, FIG.13, FIG.14). Further, the refrigerant branched into the injection pipe 11 flows into the economizer heat exchanger 12 and is cooled by exchanging heat with the refrigerant flowing through the injection pipe 11 (point H in FIGS. 10, 13, and 14). reference). On the other hand, the refrigerant flowing through the injection pipe 11 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 serving as a radiator (see point K in FIGS. 10, 13, and 14). As described above, the intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is joined. The high-pressure refrigerant cooled in the economizer heat exchanger 12 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 9 (see point I in FIG. 10). Then, the refrigerant accumulated in the receiver 9 is sent to the receiver outlet pipe 9b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 10d of the bridge circuit 10 is obtained. And is sent to the heat source side heat exchanger 4 functioning as a refrigerant evaporator (see point E in FIGS. 10, 13, and 14). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by heat exchange with water or air as a heating source to evaporate (FIG. 10, FIG. 10). 13, see point A in FIG. The low-pressure refrigerant heated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 3 via the switching mechanism 8. In this way, the heating operation is performed.

  In the configuration of this modified example, as in the above-described modified example 2, in the heating operation in which the switching mechanism 8 is in the heating operation state, the intermediate cooling is performed in the same manner as when the intermediate cooler 7d is provided or in the above-described cooling operation. Compared to the case where the vessel 7d is made to function as a cooler, heat radiation to the outside can be suppressed, a reduction in heating capacity can be suppressed, and a reduction in operating efficiency can be prevented.

  In addition, in the configuration of the present modification, the injection pipe 11 and the economizer heat exchanger 12 are provided to branch the refrigerant sent from the heat source side heat exchanger 4 to the expansion mechanisms 5a and 5b in the same way as in the cooling operation. Therefore, the temperature of the refrigerant sucked into the compression elements 3cn and 3dn on the rear stage side is further suppressed without performing heat radiation to the outside like the intermediate cooler 7d. (See points B and G in FIG. 14). Thereby, the temperature of the refrigerant discharged from the compression mechanism 3 is further suppressed (see points D and D ′ in FIG. 14), and the operating efficiency can be further improved as compared with the case where the injection pipe 11 is not provided. it can.

  Further, as an advantage common to the cooling operation and the heating operation, in the configuration of this modification, as the economizer heat exchanger 12, the refrigerant sent from the heat source side heat exchanger 4 or the use side heat exchanger 6 to the expansion mechanisms 5a and 5b. Since the heat exchanger having a flow path that flows so that the refrigerant flowing through the injection pipe 11 and the refrigerant flow through the injection pipe 11 is employed, the expansion mechanism is connected from the heat source side heat exchanger 4 or the use side heat exchanger 6 in the economizer heat exchanger 12. The temperature difference between the refrigerant sent to 5a and 5b and the refrigerant flowing through the injection pipe 11 can be reduced, and high heat exchange efficiency can be obtained.

  And, since the intermediate pressure injection by the economizer heat exchanger 12 can be used even under the condition that the intermediate pressure in the refrigeration cycle is increased to near the critical pressure, the refrigerant circuits 2, 2A, 2B (see FIG. 1, FIG. 7, FIG. 10), it is considered that the configuration having one user-side heat exchanger 6 is particularly advantageous when a refrigerant operating in the supercritical region is used. .

  Also in the present modified example, similarly to the above-described modified example 1, during the heating operation in which the switching mechanism 8 is in the heating operation state, the refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side through the intermediate cooler bypass pipe 7 i. Is sucked into the compression elements 3cn and 3dn on the rear stage side, so that a heat loss from the intermediate cooler 7d to the outside when the switching mechanism 8 is in a heating operation state can be prevented. During the heating operation in which the mechanism 8 is in the heating operation state, it is possible to suppress a decrease in the heating capacity in the use side heat exchanger 6 as a refrigerant radiator.

  In the air conditioner 1C, during the heating operation, in the compression mechanism 3, one of the compressors 3c and 3d can be started first and the other can be operated later, as in the cooling operation. 3 flexible operation is possible.

(6) Modification 4
Although not adopted in the third modification, a temperature sensor is provided at the inlet of the economizer heat exchanger 12 on the injection pipe 11 side, and the refrigerant temperature detected by the temperature sensor is detected by the economizer outlet temperature sensor 14. You may make it obtain the superheat degree of the refrigerant | coolant in the exit by the side of the injection pipe 11 of the economizer heat exchanger 12 by subtracting from refrigerant | coolant temperature. Further, the adjustment of the opening degree of the injection on-off valve 11a is not limited to superheat degree control, and for example, it may be configured to open a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 2C.

(7) Modification 5
In the above-described modification 3, the air conditioner that performs intermediate pressure injection during the cooling operation and the heating operation using the two-stage compression refrigeration cycle has been described. In addition to the configuration of the modification 3 (see FIG. 10), Thus, by providing a plurality of use side heat exchangers connected in parallel to each other, it is possible to perform cooling and heating according to the air conditioning load of the plurality of air conditioned spaces.

  FIG. 15 is a schematic configuration diagram of an air-conditioning apparatus according to Modification 5. As shown in FIG. 15, the air conditioner 1 </ b> D performs intermediate pressure injection by causing the receiver 9 to function as a gas-liquid separator in addition to the configuration of the refrigerant circuit 2 </ b> C (see FIG. 10) of Modification 3 described above. In order to make it possible, the injection pipe 15 is connected to the receiver 9 to perform intermediate pressure injection by the economizer heat exchanger 12 during cooling operation, and by the receiver 9 as a gas-liquid separator during heating operation. A refrigerant circuit 1D that enables intermediate pressure injection is provided.

  The injection pipe 15 is a refrigerant pipe that can perform intermediate pressure injection by extracting the refrigerant from the receiver 9 and returning it to the compression elements 3cn and 3dn on the rear stage side of the compression mechanism 3. In this modification, the upper part of the receiver 9 The intermediate pressure path 7 (that is, the suction side of the compression elements 3cn and 3dn on the rear stage side of the compression mechanism 3) is provided so as to be connected. The injection pipe 15 is provided with an injection opening / closing valve 15a and an injection check mechanism 15b. The injection on / off valve 15a is a valve that can be opened and closed, and is an electromagnetic valve in this modification. The injection check mechanism 15b allows the refrigerant to flow from the receiver 9 to the downstream compression elements 3cn and 3dn, and blocks the refrigerant flow from the downstream compression elements 3cn and 3dn to the receiver 9. This is a mechanism, and a check valve is used in this modification. The injection pipe 15 and the suction return pipe 30 are integrated with each other on the receiver 9 side. Further, the injection pipe 15 and the injection pipe 11 are integrated with each other on the intermediate pressure path 7 side. In the present modification, the use side expansion mechanism 5c is an electric expansion valve. Moreover, in this modification, as mentioned above, since the injection pipe 11 and the economizer heat exchanger 12 are used during the cooling operation, and the injection pipe 15 is used during the heating operation, the economizer heat exchanger 12 is used. Since it is not necessary to make the flow direction of the refrigerant constant regardless of the cooling operation or the heating operation, the bridge circuit 10 is omitted and the configuration of the refrigerant circuit 1D is simplified.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIG. 11, FIG. 12, FIG. Here, FIG. 16 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation, and FIG. 17 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Here, the refrigeration cycle during the cooling operation in the present modification will be described with reference to FIGS. 11 and 12. In addition, the operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment. In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, E, and H in FIGS. 11 and 12, and points D, D ′, and FIGS. 16 and 17). "Low pressure" means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 11 and 12, and pressure at points A and E in FIGS. 16 and 17). , “Intermediate pressure” means an intermediate pressure in the refrigeration cycle (ie, points B, C, G, J, K in FIGS. 11 and 12, and points B, C, G, I, L, Pressure at M).

<Cooling operation>
During the cooling operation, the switching mechanism 8 is in the cooling operation state indicated by the solid line in FIG. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 8 is in the cooling operation state, the intermediate cooler on / off valve 7h of the intermediate pressure passage 7 is opened, and the intermediate cooler bypass on / off valve 7j of the intermediate cooler bypass pipe 7i is closed. The intermediate cooler 7d is in a state of functioning as a cooler. Further, when the switching mechanism 8 is in the cooling operation state, intermediate pressure injection by the receiver 9 as a gas-liquid separator is not performed, and the refrigerant heated in the economizer heat exchanger 12 is passed through the injection pipe 11 in the subsequent stage. Intermediate pressure injection is performed by the economizer heat exchanger 12 that returns to the compression elements 3cn and 3dn on the side. More specifically, the injection on / off valve 15a is closed, and the opening degree of the injection on / off valve 11a is adjusted in the same manner as in the third modification.

  In the state of the refrigerant circuit 1D, a low-pressure refrigerant (see point A in FIGS. 15, 11, and 12) is sucked into the compression mechanism 3 from the suction passage 3a, and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure path 7 (see point B in FIGS. 15, 11, and 12). The intermediate pressure refrigerant discharged from the preceding compression elements 3 cm and 3 dm is cooled by exchanging heat with water or air as a cooling source in the intermediate cooler 7 d (FIGS. 15, 11, and FIG. (See point C on 12). The refrigerant cooled in the intermediate cooler 7d is further cooled by joining with the refrigerant returned to the compression mechanism 3d on the rear stage side from the injection pipe 11 (see point K in FIGS. 15, 11, and 12) ( (See point G in FIGS. 15, 11, and 12). Next, the intermediate pressure refrigerant that merged with the refrigerant returning from the injection pipe 11 (that is, subjected to intermediate pressure injection by the economizer heat exchanger 12) is compressed to the compression element 3cn connected to the downstream side of the compression elements 3cm and 3dm. , 3dn and further compressed, and discharged from the compression mechanism 3 to the discharge passage 3b (see point D in FIGS. 15, 11, and 12). Here, the high-pressure refrigerant discharged from the compression mechanism 3 has a critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 11) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn. Compressed to over pressure. Then, the high-pressure refrigerant discharged from the compression mechanism 3 is sent via the switching mechanism 8 to the heat source side heat exchanger 4 that functions as a refrigerant radiator, and water, air, and heat as a cooling source. It replaces and it cools (refer the point E of Drawing 15, Drawing 11, and Drawing 12). A part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator is branched to the injection pipe 11. And the refrigerant | coolant which flows through the injection pipe | tube 11 is sent to the economizer heat exchanger 12 after depressurizing to near intermediate pressure in the injection on-off valve 11a (refer the point J of FIG.15, FIG.11, FIG.12). In addition, the refrigerant after being branched into the injection pipe 11 flows into the economizer heat exchanger 12 and is cooled by exchanging heat with the refrigerant flowing through the injection pipe 11 (point H in FIGS. 15, 11, and 12). reference). On the other hand, the refrigerant flowing through the injection pipe 11 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 serving as a radiator (see point K in FIGS. 15, 11, and 12). As described above, the intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is joined. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 12 is depressurized to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 9 (point I in FIGS. 15, 11, and 12). reference). Then, the refrigerant stored in the receiver 9 is sent to the use-side expansion mechanism 5c, and is decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, which functions as a refrigerant evaporator. It is sent to the side heat exchanger 6a (see point F in FIGS. 15, 11, and 12). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6a as the evaporator is heated and exchanged with water and air as the heating source to evaporate ( (See point A in FIGS. 15, 11, and 12). Then, the low-pressure refrigerant heated and evaporated in the use side heat exchanger 6a as the evaporator is again sucked into the compression mechanism 3 via the switching mechanism 8. In this way, the cooling operation is performed.

  Further, during the cooling operation, in the compression mechanism 3, one of the compressors 3 c and 3 d can be started first and the other can be operated later, similarly to the embodiment, and the flexible operation of the compression mechanism 3 can be performed. It is possible.

<Heating operation>
During the heating operation, the switching mechanism 8 is in a heating operation state indicated by a broken line in FIG. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 8 is in the heating operation state, the intermediate cooler on / off valve 7h of the intermediate pressure path 7 is closed, and the intermediate cooler bypass on / off valve 7j of the intermediate cooler bypass pipe 7i is opened, The intermediate cooler 7d does not function as a cooler. Further, when the switching mechanism 8 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 12 is not performed, and the refrigerant is compressed from the receiver 9 as the gas-liquid separator through the injection pipe 15 on the downstream side. Intermediate pressure injection is performed by the receiver 9 that returns to the elements 3cn and 3dn. More specifically, the injection on / off valve 15a is opened, and the injection on / off valve 11a is fully closed.

  In the state of the refrigerant circuit 1D, low-pressure refrigerant (see point A in FIGS. 15 to 17) is sucked into the compression mechanism 3 from the suction passage 3a and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure path 7 (see point B in FIGS. 15 to 17). The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the front stage side does not pass through the intermediate cooler 7 d (that is, is not cooled), unlike the cooling operation, and is not cooled. By passing through 7i (see point C in FIGS. 15 to 17) and joining the refrigerant (see point M in FIGS. 15 to 17) returned from the receiver 9 to the compression mechanism 3d on the rear stage through the injection pipe 15. It is cooled (see point G in FIGS. 15 to 17). Next, the intermediate-pressure refrigerant that merged with the refrigerant returning from the injection pipe 15 (that is, the intermediate-pressure injection by the receiver 9 as a gas-liquid separator) was connected to the downstream side of the compression elements 3 cm and 3 dm. The air is sucked into the compression elements 3cn and 3dn, further compressed, and discharged from the compression mechanism 3 to the discharge path 3b (see point D in FIGS. 15 to 17). Here, the high-pressure refrigerant discharged from the compression mechanism 3 is subjected to the critical pressure (that is, the critical point CP shown in FIG. 16) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn as in the cooling operation. Is compressed to a pressure exceeding the critical pressure Pcp). The high-pressure refrigerant discharged from the compression mechanism 3 is sent via the switching mechanism 8 to the use-side heat exchanger 6a that functions as a refrigerant radiator, so that water, air as a cooling source, and heat It replaces and it cools (refer the point F of FIGS. 15-17). The high-pressure refrigerant cooled in the use-side heat exchanger 6a as a radiator is decompressed to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and then temporarily stored in the receiver 9 and gas-liquid separation is performed. Performed (see points I, L, M in FIGS. 15-17). Then, the gas refrigerant separated from the gas and liquid in the receiver 9 is extracted from the upper part of the receiver 9 by the injection pipe 15 and, as described above, is converted into an intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the front side. Will join. The liquid refrigerant stored in the receiver 9 is decompressed by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant ( (See point E in FIGS. 15-17). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 serving as the evaporator is heated by performing heat exchange with water and air serving as the heating source, and evaporates ( (See point A in FIGS. 15 to 17). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 as the evaporator is again sucked into the compression mechanism 3 through the switching mechanism 8. In this way, the heating operation is performed.

  The configuration of the present modification is different from Modification 3 in that the intermediate pressure injection by the receiver 9 as a gas-liquid separator is performed instead of the intermediate pressure injection by the economizer heat exchanger 12 during the heating operation. Can obtain the same effects as those of the third modification.

  Although not shown in detail, in the refrigerant circuit 2C (see FIG. 10) having the bridge circuit 10 in the above-described modification 3, a plurality (here, two) connected to each other in parallel as in the modification 5. The use side heat exchanger is provided, and the receiver 9 (more specifically, the bridge circuit 10) as a gas-liquid separator and the use side heat exchanger are adapted to correspond to each use side heat exchanger. The use side expansion mechanism is provided, the second expansion mechanism 5b provided in the receiver outlet pipe 9b is deleted, and the refrigerant is reduced to the low pressure in the refrigeration cycle during the heating operation, instead of the outlet check valve 10d of the bridge circuit 10. It is conceivable to provide a third expansion mechanism for reducing the pressure.

  Even in such a configuration, the first expansion mechanism 5a as the heat source side expansion mechanism after being cooled in the heat source side heat exchanger 4 as the radiator, like the cooling operation in which the switching mechanism 8 is in the cooling operation state. In the condition that the pressure difference from the high pressure in the refrigeration cycle to the vicinity of the intermediate pressure in the refrigeration cycle can be used without performing any significant pressure reduction operation, the intermediate pressure by the economizer heat exchanger 12 is the same as in the third modification. Injection is advantageous.

  However, as in the heating operation in which the switching mechanism 8 is in the heating operation state, each use side expansion mechanism serves as a radiator so that the refrigeration load required in each use side heat exchanger can be obtained. The flow rate of the refrigerant flowing through the use side heat exchanger is controlled, and the flow rate of the refrigerant passing through each use side heat exchanger as a radiator is downstream of each use side heat exchanger and the economizer heat exchanger 12. In the conditions generally determined by the decompression operation of the refrigerant by the opening control of the use side expansion mechanism provided upstream, the degree of the decompression of the refrigerant by the opening control of each use side expansion mechanism is as a radiator. The degree of decompression between the plurality of usage-side expansion mechanisms will vary depending not only on the flow rate of the refrigerant flowing through each usage-side heat exchanger, but also on the flow distribution between the usage-side heat exchangers as a plurality of radiators. Is a very different state May occur or the degree of decompression in the use-side expansion mechanism may be relatively large, which may reduce the refrigerant pressure at the inlet of the economizer heat exchanger 12. In such a case, the economizer heat There is a possibility that the exchange heat amount (that is, the flow rate of the refrigerant flowing through the injection pipe 11) in the exchanger 12 becomes small and difficult to use. In particular, such an air conditioner has a separate type in which a heat source unit mainly including a compression mechanism 3, a heat source side heat exchanger 4 and a receiver 9 and a utilization unit mainly including a utilization side heat exchanger are connected by a communication pipe. When the air conditioner is configured, the connecting pipe may be very long depending on the arrangement of the utilization unit and the heat source unit. Therefore, the influence of the pressure loss is also added, and the inlet of the economizer heat exchanger 12 is added. In this case, the pressure of the refrigerant is further reduced. If the refrigerant pressure at the inlet of the economizer heat exchanger 12 is likely to decrease, the gas-liquid separator pressure and the intermediate pressure in the refrigeration cycle (if the gas-liquid separator pressure is lower than the critical pressure) Here, intermediate pressure injection with a gas-liquid separator that can be used is advantageous even under a condition in which the pressure difference with the pressure of the refrigerant flowing through the intermediate pressure passage 7 is small.

  In the air conditioner 1D, during the heating operation, in the compression mechanism 3, one of the compressors 3c and 3d can be started first and the other can be operated later, as in the cooling operation. 3 flexible operation is possible.

(8) Modification 6
In the above-described modified example 5, the intermediate pressure injection is performed during the cooling operation and the heating operation using the two-stage compression refrigeration cycle, so that the cooling and heating according to the air conditioning load of the plurality of air-conditioned spaces are possible. Although the air conditioner has been described, in addition to the configuration of the modified example 5 (see FIG. 15), it is possible to provide a function of supercooling the refrigerant sent from the receiver to each user-side expansion mechanism.

  In the configuration as in the modified example 5, during the cooling operation, the refrigerant (see point I in FIG. 15) that is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 9 is used for each use. Although distributed to the side expansion mechanism 5c, if the refrigerant sent from the receiver 9 to each usage-side expansion mechanism 5c is in a gas-liquid two-phase state, there is a risk of causing drift when distributing to each usage-side expansion mechanism 5c. This is because it is desirable to make the refrigerant sent from the receiver 9 to each use-side expansion mechanism 5c as supercooled as possible.

  FIG. 18 is a schematic configuration diagram of an air-conditioning apparatus according to Modification 6. As shown in FIG. 18, the air conditioner 1E includes a supercooling heat exchanger 16 and a suction return pipe between the receiver 9 and the use-side expansion mechanism 5c in addition to the configuration of the refrigerant circuit 1D in the above-described modification 5. The refrigerant circuit 2 </ b> E provided with 17 is provided.

  The supercooling heat exchanger 16 is a heat exchanger that cools the refrigerant sent from the receiver 9 to the use-side expansion mechanism 5c. More specifically, the supercooling heat exchanger 16 branches a part of the refrigerant sent from the receiver 9 to the utilization side expansion mechanism 5c during the cooling operation, and sucks the compression mechanism 3 (that is, as an evaporator). The heat exchanger exchanges heat with the refrigerant flowing through the suction return pipe 17 returning to the suction path 3a) between the use side heat exchanger 6a and the compression mechanism 3, and the flow path flows so that both refrigerants face each other. Have. Here, the suction return pipe 17 is a refrigerant pipe that branches the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5c and returns it to the suction side (that is, the suction path 3a) of the compression mechanism 3. . The suction return pipe 17 is provided with a suction return valve 17a whose opening degree can be controlled. In the supercooling heat exchanger 16, a refrigerant sent from the receiver 9 to the use side expansion mechanism 5c and a suction return valve 17a are provided. Heat exchange with the refrigerant flowing through the suction return pipe 17 after the pressure is reduced to near low pressure is performed. The suction return valve 17a is an electric expansion valve in this modification. A supercooling heat exchanger outlet temperature sensor 18 for detecting the temperature of the refrigerant at the outlet of the supercooling heat exchanger 16 on the suction return pipe 17 side is provided at the outlet of the supercooling heat exchanger 16 on the suction return pipe 17 side. Yes. The suction passage 3 a or the compression mechanism 3 is provided with a suction pressure sensor 19 that detects the pressure of the refrigerant flowing on the suction side of the compression mechanism 3.

  Next, operation | movement of the air conditioning apparatus 1E of this modification is demonstrated using FIGS. 16-20. Here, FIG. 19 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation, and FIG. 20 is a temperature-entropy diagram illustrating the refrigeration cycle during the cooling operation. The refrigeration cycle during the heating operation in this modification will be described with reference to FIGS. In addition, the operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment. In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, E, I, and R in FIGS. 19 and 20 and points D, D ′, and F in FIGS. 16 and 17). "Low pressure" means low pressure in the refrigeration cycle (that is, pressure at points A, F, F, S ', U in FIGS. 19 and 20 and points A and E in FIGS. 16 and 17). "Intermediate pressure" means an intermediate pressure in the refrigeration cycle (ie, points B, C, G, J, K in FIGS. 19 and 20, and points B, C, in FIGS. 16 and 17). Pressure in G, I, L, and M).

<Cooling operation>
During the cooling operation, the switching mechanism 8 is in a cooling operation state indicated by a solid line in FIG. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. And since the switching mechanism 8 will be in a cooling operation state, the intermediate cooler on-off valve 7h of the intermediate pressure path 7 is opened. By closing the intermediate cooler bypass opening / closing valve 7j of the intermediate cooler bypass pipe 7i, the intermediate cooler 7d functions as a cooler.

  Further, when the switching mechanism 8 is in the cooling operation state, intermediate pressure injection by the receiver 9 as a gas-liquid separator is not performed, and the refrigerant heated in the economizer heat exchanger 12 is passed through the injection pipe 11 in the subsequent stage. Intermediate pressure injection is performed by the economizer heat exchanger 12 that returns to the compression elements 3cn and 3dn on the side. More specifically, the injection on / off valve 15a is closed, and the opening degree of the injection on / off valve 11a is adjusted in the same manner as in the third modification. Further, when the switching mechanism 8 is in the cooling operation state, the degree of opening of the suction return valve 17a is adjusted because the subcooling heat exchanger 16 is used. More specifically, in this modification, the suction return valve 17a is adjusted in opening so that the degree of superheat of the refrigerant at the outlet of the supercooling heat exchanger 16 on the suction return pipe 17 side becomes a target value. Superheat control is performed. In this modification, the degree of superheat of the refrigerant at the outlet on the suction return pipe 17 side of the supercooling heat exchanger 16 is calculated by converting the low pressure detected by the suction pressure sensor 19 into a saturation temperature, and the supercooling heat exchange outlet temperature sensor 18. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the above.

  In the state of the refrigerant circuit 2E, the low-pressure refrigerant (see point A in FIGS. 18 to 20) is sucked into the compression mechanism 3 from the suction passage 3a and first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, it is discharged into the intermediate pressure path 7 (see point B in FIGS. 18 to 20). The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the preceding stage side is cooled by exchanging heat with water or air as a cooling source in the intermediate cooler 7 d (points in FIGS. 18 to 20). C). The refrigerant cooled in the intermediate cooler 7d is further cooled by joining with the refrigerant (see point K in FIGS. 18 to 20) returned from the injection pipe 11 to the compression mechanism 3d on the rear stage side (see FIGS. 18 to 20). (See point G in FIG. 20). Next, the intermediate pressure refrigerant that merged with the refrigerant returning from the injection pipe 11 (that is, subjected to intermediate pressure injection by the economizer heat exchanger 12) is compressed to the compression element 3cn connected to the downstream side of the compression elements 3cm and 3dm. , 3dn and further compressed, and discharged from the compression mechanism 3 to the discharge passage 3b (see point D in FIGS. 18 to 20). Here, the high-pressure refrigerant discharged from the compression mechanism 3 has a critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 19) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn. Compressed to over pressure. Then, the high-pressure refrigerant discharged from the compression mechanism 3 is sent via the switching mechanism 8 to the heat source side heat exchanger 4 that functions as a refrigerant radiator, and water, air, and heat as a cooling source. It is exchanged and cooled (see point E in FIGS. 18 to 20). A part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator is branched to the injection pipe 11. And the refrigerant | coolant which flows through the injection pipe | tube 11 is sent to the economizer heat exchanger 12 after depressurizing to the intermediate pressure vicinity in the injection on-off valve 11a (refer the point J of FIGS. 18-20). Moreover, the refrigerant | coolant after branching to the injection pipe | tube 11 flows into the economizer heat exchanger 12, and heat-exchanges with the refrigerant | coolant which flows through the injection pipe | tube 11, and is cooled (refer FIG. 18-20 point H). On the other hand, the refrigerant flowing through the injection pipe 11 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat-source-side heat exchanger 4 serving as a radiator (see point K in FIGS. 18 to 20). Thus, the intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the upstream side is joined. The high-pressure refrigerant cooled in the economizer heat exchanger 12 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 9 (see point I in FIGS. 18 to 20). A part of the refrigerant stored in the receiver 9 is branched to the suction return pipe 17. And the refrigerant | coolant which flows through the suction return pipe | tube 17 is sent to the supercooling heat exchanger 16 after depressurizing to the low pressure vicinity in the suction return valve 17a (refer point S of FIGS. 18-20). Further, the refrigerant branched into the suction return pipe 17 flows into the supercooling heat exchanger 16 and is further cooled by exchanging heat with the refrigerant flowing through the suction return pipe 17 (points in FIGS. 18 to 20). R). On the other hand, the refrigerant flowing through the suction return pipe 17 is heated by exchanging heat with the high-pressure refrigerant cooled in the economizer heat exchanger 12 (see the point U in FIGS. 18 to 20), and the suction side of the compression mechanism 3 (Here, the refrigerant flows through the suction passage 3a). The refrigerant cooled in the supercooling heat exchanger 16 is sent to the use-side expansion mechanism 5c and decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, and functions as a refrigerant evaporator. To the use side heat exchanger 6a (see point F in FIGS. 18 to 20). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6a as the evaporator is heated and exchanged with water and air as the heating source to evaporate ( (See point A in FIGS. 18-20). Then, the low-pressure refrigerant heated and evaporated in the use side heat exchanger 6a as the evaporator is again sucked into the compression mechanism 3 via the switching mechanism 8. In this way, the cooling operation is performed.

  Further, during the cooling operation, in the compression mechanism 3, one of the compressors 3 c and 3 d can be started first and the other can be operated later, similarly to the embodiment, and the flexible operation of the compression mechanism 3 can be performed. It is possible.

<Heating operation>
During the heating operation, the switching mechanism 8 is in a heating operation state indicated by a broken line in FIG. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 8 is in the heating operation state, the intermediate cooler on / off valve 7h of the intermediate pressure path 7 is closed, and the intermediate cooler bypass on / off valve 7j of the intermediate cooler bypass pipe 7i is opened, The intermediate cooler 7d does not function as a cooler. Further, when the switching mechanism 8 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 12 is not performed, and the refrigerant is compressed from the receiver 9 as the gas-liquid separator through the injection pipe 15 on the downstream side. Intermediate pressure injection is performed by the receiver 9 that returns to the elements 3cn and 3dn. More specifically, the injection on / off valve 15a is opened, and the injection on / off valve 11a is fully closed. Further, when the switching mechanism 8 is in the heating operation state, the supercooling heat exchanger 16 is not used, so that the suction return valve 17a is also fully closed.

  In the state of the refrigerant circuit 2E, low-pressure refrigerant (see point A in FIGS. 18, 16, and 17) is sucked into the compression mechanism 3 from the suction passage 3a, and is first compressed to an intermediate pressure by the compression elements 3cm and 3dm. Then, the liquid is discharged into the intermediate pressure passage 7 (see point B in FIGS. 18, 16, and 17). The intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the front stage side does not pass through the intermediate cooler 7 d (that is, is not cooled), unlike the cooling operation, and is not cooled. The refrigerant that passes through 7i (see point C in FIGS. 18, 16, and 17) and is returned from the receiver 9 to the compression mechanism 3d on the rear stage through the injection pipe 15 (see point M in FIGS. 18, 16, and 17). ) To join (see point G in FIGS. 18, 16, and 17). Next, the intermediate-pressure refrigerant that merged with the refrigerant returning from the injection pipe 15 (that is, the intermediate-pressure injection by the receiver 9 as a gas-liquid separator) was connected to the downstream side of the compression elements 3 cm and 3 dm. The air is sucked into the compression elements 3cn and 3dn, further compressed, and discharged from the compression mechanism 3 to the discharge passage 3b (see point D in FIGS. 18, 16, and 17). Here, the high-pressure refrigerant discharged from the compression mechanism 3 is subjected to the critical pressure (ie, the critical point CP shown in FIG. 16) by the two-stage compression operation by the compression elements 3 cm, 3 cn, 3 dm, and 3 dn as in the cooling operation. Is compressed to a pressure exceeding the critical pressure Pcp). The high-pressure refrigerant discharged from the compression mechanism 3 is sent via the switching mechanism 8 to the use-side heat exchanger 6a that functions as a refrigerant radiator, so that water, air as a cooling source, and heat It replaces and it cools (refer point F of Drawing 18, Drawing 16, and Drawing 17). The high-pressure refrigerant cooled in the use-side heat exchanger 6a as a radiator is decompressed to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and then temporarily stored in the receiver 9 and gas-liquid separation is performed. (See points I, L, and M in FIGS. 18, 16, and 17). Then, the gas refrigerant separated from the gas and liquid in the receiver 9 is extracted from the upper part of the receiver 9 by the injection pipe 15 and, as described above, is converted into an intermediate pressure refrigerant discharged from the compression elements 3 cm and 3 dm on the front side. Will join. The liquid refrigerant stored in the receiver 9 is decompressed by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant ( (See point E in FIGS. 18, 16, and 17). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 serving as the evaporator is heated by performing heat exchange with water and air serving as the heating source, and evaporates ( (See point A in FIGS. 18, 16, and 17). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 as the evaporator is again sucked into the compression mechanism 3 through the switching mechanism 8. In this way, the heating operation is performed.

  And in the structure of this modification, while the same effect as the said modification 5 is acquired, the refrigerant | coolant sent to the utilization side expansion mechanism 5c from the receiver 9 at the time of air_conditionaing | cooling operation (refer the point I of FIGS. 18-20) ) Can be cooled to a supercooled state by the supercooling heat exchanger 16 (see FIGS. 19 and 20, points I and R), so that there is less possibility of causing drift when distributing to each use side expansion mechanism 5 c. Can do.

  In the air conditioner 1E, during the heating operation, in the compression mechanism 3, one of the compressors 3c and 3d can be started first and the other can be operated later, as in the cooling operation. 3 flexible operation is possible.

(9) Modification 7
Although not adopted in the modification 6, a temperature sensor is provided at the inlet of the supercooling heat exchanger 16 on the suction return pipe 17 side, and the refrigerant temperature detected by the temperature sensor is used as the supercooling heat exchanger temperature sensor. The degree of superheat of the refrigerant at the outlet on the suction return pipe 17 side of the supercooling heat exchanger 16 may be obtained by subtracting it from the refrigerant temperature detected by 18. Further, the adjustment of the opening degree of the suction return valve 17a is not limited to the superheat control, and may be such that, for example, a predetermined opening degree is opened according to the refrigerant circulation amount in the refrigerant circuit 2E.

(10) Modification 8
In the above-described embodiment and its modification, the refrigerant discharged from the preceding compression element of the two compression elements 3 cm, 3 cn, 3 dm, 3 dn by a single uniaxial two-stage compression structure 3 c, 3 d. The compression mechanism 3 of the two-stage compression type is configured to sequentially compress the first and second compression elements, but a multi-stage compression mechanism may be adopted rather than the two-stage compression type such as the three-stage compression type. Alternatively, a multistage compression mechanism may be configured by connecting in series a plurality of compressors incorporating a single compression element and / or a plurality of compressors incorporating a plurality of compression elements. Further, when it is necessary to increase the capacity of the compression mechanism, such as when a large number of use side heat exchangers are connected, a parallel multistage compression type in which two or more multistage compression type compression mechanisms are connected in parallel. The compression mechanism may be adopted.

(11) Other Embodiments Embodiments of the present invention and modifications thereof have been described above with reference to the drawings. However, specific configurations are not limited to these embodiments and modifications thereof, and Changes can be made without departing from the scope of the invention.

  For example, in the above-described embodiment and its modification, water or brine is used as a heating source or a cooling source for performing heat exchange with the refrigerant flowing in the usage-side heat exchanger 6, and in the usage-side heat exchangers 6 and 6a. The present invention may be applied to a so-called chiller type air conditioner provided with a secondary heat exchanger for exchanging heat between water or brine subjected to heat exchange and room air.

  Moreover, even if it is another type of refrigeration apparatus of the above-described chiller type air conditioner, the present invention can be used as long as it performs a multistage compression refrigeration cycle using a refrigerant operating in the supercritical region as a refrigerant. Applicable.

  Further, the refrigerant operating in the supercritical region is not limited to carbon dioxide, and ethylene, ethane, nitrogen oxide, or the like may be used.

<Features>
(A)
According to the above-described embodiment and the modification, when the compressor 3c corresponds to the first compression unit, the oil separation mechanism 22 (first pressure equalization path) causes the compressor 3d (second compression unit) to be stopped. The intermediate pressure path 7 and the discharge port of the compression element 3dn (second high-pressure compression element) can be equalized. That is, the compressor 3c is operated prior to the compressor 3d, and therefore, even if a pressure difference is generated between the discharge passage 3b of the compression mechanism 3 and the intermediate pressure passage 7, the compressor 3d (first The pressure difference between the discharge port of the compression element 3dn (second high pressure compression element) and the intermediate pressure path 7 of the (2 compression section) is almost eliminated. Thereby, when driving the compressor 3d (second compression unit) after driving the compressor 3c (first compression unit), the same compressor drive motor 3db (drive) as the compression element 3dm (second low-pressure compression element) The oil separation mechanism 22 (first pressure equalizing path) prevents a pressure difference between the suction port and the discharge port of the compression element 3dn (second high-pressure compression element) driven by the power source), and the subsequent compressor The force generated by the pressure difference that hinders the driving of 3d (second compression unit) can be suppressed. As a result, when the compressor 3d (second compression unit) is started later than the compressor 3c in a state where the compressor 3c (first compression unit) is activated, the subsequent compressor 3d is stabilized. It can start up reliably and can improve the reliability of the refrigeration apparatus.

  On the other hand, when the compressor 3d is the first compression unit and the compressor 3c is the second compression unit, the oil separation mechanism 21 corresponds to the first pressure equalizing path, and the compression element 3cn serves as the second high-pressure compression element. Equivalent to. Thus, even if the compressor 3c and the compressor 3d are replaced, the same effect can be obtained. In addition, when the first and last start of the compressors 3c and 3d are determined, the first pressure equalizing path can be effective only in one side.

(B)
According to the above-described embodiment and modification, when the compressor 3c corresponds to the first compression unit, the oil separation mechanism 26 (second pressure equalization path) causes the compressor 3d (second compression unit) to stop. The intermediate pressure path 7 and the suction port of the compression element 3dm (second low pressure compression element) can be equalized. That is, the compressor 3c (first compression unit) is operated prior to the compressor 3d (second compression unit), so that a pressure difference is generated between the suction passage 3a and the intermediate pressure passage 7 of the compression mechanism 3. Even in this case, the pressure difference between the suction port of the compression element 3dm (second low pressure compression element) of the compressor 3d (second compression unit) and the intermediate pressure path 7 is almost eliminated. Thereby, when driving the compressor 3d after driving the compressor 3c, the pressure difference between the suction port and the discharge port of the compression element 3dm (second low-pressure compression element) of the compressor 3d (second compression unit). Can be prevented by the oil separation mechanism 26 (second pressure equalization path), and the force that hinders the driving of the subsequent compressor 3d (second compression section) can be further reduced. As a result, when starting the compressor 3d behind the compressor 3c, the force that hinders the start of the compressor 3d can be kept small, so that the ability of the compression mechanism 3 can be switched smoothly.

  On the other hand, when the compressor 3d is the first compression section and the compressor 3c is the second compression section, the oil separation mechanism 25 corresponds to the second pressure equalization path, and the compression element 3cm becomes the second low-pressure compression element. Equivalent to. Thus, even if the compressor 3c and the compressor 3d are replaced, the same effect can be obtained. In addition, when the first and last start of the compressors 3c and 3d are determined, the second pressure equalizing path is effective even with only one.

(C)
According to the embodiment and the modification described above, the first pressure equalizing path is constituted by the oil separation mechanisms 21 and 22, and the intermediate pressure path 7 and the compression element 3cn are constituted by the oil separators 21a and 22a and the oil return pipes 21c and 22c. , 3dn (second high pressure compression element) can be equalized when the compressors 3c, 3d (second compression section) are stopped, and discharged from the discharge ports of the compression elements 3cn, 3dn (second high pressure compression element). The oil to be returned can be returned to the intermediate pressure path 7. As a result, since the first pressure equalizing path also serves as a mechanism for separating oil, it is possible to prevent the structure of the refrigeration apparatus from becoming complicated in order to improve the reliability of the refrigeration apparatus.

(D)
According to the embodiment and the modification described above, when the first pressure equalization path is the oil separation mechanism 22, the oil separation mechanism 21 corresponds to the third pressure equalization path, and the first pressure equalization path is the oil separation mechanism 21. In some cases, the oil separation mechanism 22 corresponds to a third pressure equalizing path. The oil separation mechanism 21 (third pressure equalization path) equalizes the intermediate pressure path 7 and the discharge port of the compression element 3cn (first high pressure compression element) when the compressor 3c (first compression section) is stopped. it can. That is, the compressor 3d (second compression unit) is operated prior to the compressor 3c (first compression unit), so that a pressure difference is generated between the discharge passage 3b of the compression mechanism 3 and the intermediate pressure passage 7. Even if it is, the pressure difference between the discharge port of the compression element 3cn (first high pressure compression element) of the compressor 3c and the intermediate pressure path is almost eliminated. Thereby, when driving the compressor 3c (first compression unit) after driving the compressor 3d (second compression unit), there is a pressure difference between the suction port and the discharge port of the compression element 3cn of the compressor 3c. Occurrence can be prevented by the oil separation mechanism 21, and the force that hinders the driving of the subsequent compressor 3c can be removed. As a result, even when the compressor 3c is the first and the compressor 3d is the second-generation, and when the compressor 3d is the first and the compressor 3c is the second-generation, the latter can be started stably and reliably. Since it is possible to replace the compressor 3c and the compressor 3d in the first and last order, the operation of the refrigeration apparatus can be performed flexibly.

(E)
According to the third to eighth modifications described above, the refrigerant returned to the suction port of the compression elements 3cn and 3dn (the first high pressure compression element and the second high pressure compression element) can be cooled by the intermediate cooler 7d. By injecting the refrigerant before being decompressed by the expansion mechanism 5a from the injection pipe 11 (injection path), the heat can be transferred and the refrigerant can be cooled without throwing away heat. As a result, in the compression mechanism 3 in which the compressor 3c and the compressor 3d can be operated in parallel, the refrigerant temperature discharged from the compression mechanism 3 is lowered by one intermediate cooler 7d and one injection pipe 11 (injection path). Therefore, the operating efficiency of the refrigeration apparatus can be improved while suppressing the cost for adding the cooling function.

It is a schematic block diagram of the air conditioning apparatus which concerns on one Embodiment of this invention. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation was illustrated. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is a schematic block diagram of the air conditioning apparatus which concerns on the modification 1. It is a pressure-enthalpy diagram in which the refrigerating cycle at the time of heating operation in the air harmony device concerning modification 1 was illustrated. It is a temperature-entropy diagram in which the refrigerating cycle at the time of heating operation in the air harmony device concerning modification 1 was illustrated. It is a schematic block diagram of the air conditioning apparatus which concerns on the modification 2. It is a pressure-enthalpy diagram in which the refrigeration cycle at the time of heating operation in the air harmony device concerning the modification of modification 2 was illustrated. It is a temperature-entropy diagram in which the refrigerating cycle at the time of heating operation in the air harmony device concerning the modification of modification 2 was illustrated. It is a schematic block diagram of the air conditioning apparatus by the modification 3. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation in the air conditioning apparatus concerning the modification 3 was illustrated. It is the temperature-entropy diagram in which the refrigerating cycle at the time of the cooling operation in the air conditioning apparatus concerning the modification 3 was illustrated. It is a pressure-enthalpy diagram in which the refrigerating cycle at the time of heating operation in the air harmony device concerning modification 3 was illustrated. It is the temperature-entropy diagram by which the refrigerating cycle at the time of the heating operation in the air conditioning apparatus concerning the modification 3 was illustrated. It is a schematic block diagram of the air conditioning apparatus concerning the modification 5. It is a pressure-enthalpy diagram in which the refrigerating cycle at the time of heating operation in the air harmony device concerning modification 5 was illustrated. It is the temperature-entropy diagram in which the refrigerating cycle at the time of the heating operation in the air conditioning apparatus concerning the modification 5 was illustrated. It is a schematic block diagram of the air conditioning apparatus concerning the modification 6. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation in the air conditioning apparatus concerning the modification 6 was illustrated. It is the temperature-entropy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation in the air conditioning apparatus concerning the modification 6 was illustrated.

Explanation of symbols

1, 1A, 1B. 1C, 1D, 1E Air conditioning equipment (refrigeration equipment)
3 Compression mechanism 3c, 3d Compressor (first compression unit, second compression unit)
3 cm, 3 cn, 3 dm, 3 dn Compression element 8 Switching mechanism 4 Heat source side heat exchanger 6 User side heat exchanger 7 Intermediate pressure path 7d Intermediate cooler 11 Injection pipe (injection path)
21, 22 Oil separation mechanism (first pressure equalization path, third pressure equalization path)
25, 26 Oil separation mechanism (second pressure equalization path)

Claims (5)

The suction path (3a), the discharge path (3b), the first low-pressure compression element (3 cm, 3 dm) for increasing the pressure of the refrigerant sucked from the suction path, and the same drive source (3cb, A first compression section (3c, 3d) having a first high-pressure compression element (3cn, 3dn) driven by 3db) to increase the pressure of the refrigerant further than the first low-pressure compression element and discharged from the discharge passage; The second low-pressure compression element (3 dm, 3 cm) that can be activated after the first compression unit and increases the pressure of the refrigerant sucked from the suction passage, and the same drive source (3 db, 3 cb) as the second low-pressure compression element A compression mechanism including a second compression section (3d, 3c) having a second high-pressure compression element (3dn, 3cn) that is driven to increase the pressure of the refrigerant further than the second low-pressure compression element and discharge the refrigerant from the discharge passage. (3) and
An expansion mechanism (5) that decompresses the refrigerant sent from the discharge path of the compression mechanism and returns the refrigerant to the suction path of the compression mechanism;
A heat source side heat exchanger (4) provided between the expansion mechanism and the discharge path or the suction path of the compression mechanism and functioning as a refrigerant cooler or a heater;
A use-side heat exchanger (6) provided between the expansion mechanism and the suction path or the discharge path of the compression mechanism and functioning as a refrigerant heater or cooler;
An intermediate pressure path for returning the refrigerant discharged from the discharge port of the first low pressure compression element and the discharge port of the second low pressure compression element to the suction port of the first high pressure compression element and the suction port of the second high pressure compression element ( 7) and
The intermediate pressure path is provided between the intermediate pressure path and the discharge port of the second high pressure compression element, and when the second compression unit is stopped, the intermediate pressure path and the discharge port of the second high pressure compression element are equalized. And a first pressure equalizing path (22, 21).   The intermediate pressure path is provided between the intermediate pressure path and the suction port of the second low-pressure compression element, and when the second compression section is stopped, the intermediate pressure path and the suction port of the second low-pressure compression element are equalized. The refrigeration apparatus according to claim 1, further comprising a second pressure equalization path (26, 25) that can be made.   The first pressure equalizing path is connected to the oil separator (26a, 25a) inserted in the discharge path and connected to the discharge port of the second high-pressure compression element, and to the oil separator and the intermediate pressure path. The refrigeration apparatus according to claim 1 or 2, comprising a connected oil return pipe (26c, 25c) and a pressure reducing mechanism (26b, 26a) for reducing the pressure of fluid flowing through the oil return pipe. The intermediate pressure path is provided between the intermediate pressure path and the discharge port of the first high pressure compression element, and when the first compression section is stopped, the intermediate pressure path and the discharge port of the first high pressure compression element are equalized. A third pressure equalizing path (21, 22) that can be
The refrigeration apparatus according to any one of claims 1 to 3, wherein the first compression unit can be started after the second compression unit. An intermediate cooler (7d) that is inserted in the intermediate pressure path and cools the refrigerant returned to the suction port of the first high-pressure compression element and the suction port of the second high-pressure compression element;
The apparatus further comprises an injection path (11) for branching the refrigerant before being decompressed by the expansion mechanism and injecting the refrigerant into the intermediate pressure path between the intermediate cooler and the suction port of the first high-pressure compression element. Item 5. The refrigeration apparatus according to any one of Items 1 to 4.

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