JP2009204243A - Refrigerating device - Google Patents

Abstract

In a refrigeration apparatus that performs a multistage compression refrigeration cycle using a refrigerant that operates in a supercritical region, the operating efficiency is improved.
An air conditioner 1 uses carbon dioxide as a refrigerant, a two-stage compression type compression mechanism 2, a radiator, an expansion mechanism 5, an evaporator, and a first second-stage injection pipe 19. And an economizer heat exchanger 20 and a pre-cooling heat exchanger. The economizer heat exchanger 20 performs heat exchange between the refrigerant sent from the radiator to the expansion mechanism 5 and the refrigerant flowing through the first second-stage injection pipe 19. The precooling heat exchanger is a heat exchanger that cools the refrigerant sent from the radiator to the economizer heat exchanger 20. The first second-stage injection pipe 19 has a second-stage injection valve 19a that depressurizes the refrigerant, and is provided so as to branch the refrigerant sent from the precooling heat exchanger to the expansion mechanism 5.
[Selection] Figure 1

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus that performs a multistage compression refrigeration cycle using a refrigerant that operates in a supercritical region.

2. Description of the Related Art Conventionally, as one of refrigeration apparatuses that perform a multistage compression refrigeration cycle using a refrigerant that operates in a supercritical region, two-stage compression refrigeration using carbon dioxide as a refrigerant as disclosed in Patent Document 1 is performed. There are air conditioners that cycle. This air conditioner mainly includes a compressor having two compression elements connected in series, an outdoor heat exchanger, an indoor heat exchanger, and an outdoor heat exchanger and an indoor heat exchanger. It has a gas-liquid separator that separates the flowing refrigerant from gas and liquid, and a rear-stage injection pipe that returns the refrigerant from the gas-liquid separator to the rear-stage compression element.
JP 2007-232263 A

  In the above air conditioner, a part of the refrigerant flowing between the outdoor heat exchanger and the indoor heat exchanger after being discharged from the compression element on the rear stage side of the compressor is passed through the rear side injection pipe to the gas-liquid separator. The intermediate pressure injection is performed by joining the intermediate pressure refrigerant discharged from the compression element on the front stage side of the compressor and sucked into the compression element on the rear stage side by returning to the compression element on the rear stage side from While reducing the temperature of the refrigerant discharged from the compressor, the power consumption of the compressor is reduced to improve the operation efficiency.

  However, in such a configuration, the pressure of the refrigerant discharged from the compressor increases, and the gas-liquid separator pressure, which is the pressure of the refrigerant in the gas-liquid separator, rises to a pressure higher than the critical pressure. If it is difficult to separate the refrigerant in the separator into gas refrigerant and liquid refrigerant, intermediate pressure injection from the gas-liquid separator back to the compression element on the rear stage cannot be performed, and the operating efficiency cannot be improved. Cases may arise.

  In order to solve this problem, as disclosed in Patent Document 1, it is conceivable that the pressure of the refrigerant discharged from the compressor does not increase so that the gas-liquid separator pressure becomes lower than the critical pressure. However, considering the magnitude relationship between the temperature of water and air that serves as a cooling source for outdoor heat exchangers and indoor heat exchangers that function as refrigerant radiators, and the critical temperature (about 31 ° C) of carbon dioxide used as refrigerants Then, depending on the installation environment of the air conditioner, etc., the pressure of the refrigerant discharged from the compressor may be inevitably increased, so that the gas-liquid separator pressure rises to a pressure higher than the critical pressure. It cannot be completely prevented, and there may be a case where intermediate pressure injection using a gas-liquid separator cannot be performed. For this reason, it is desired that the operating efficiency can be improved even under operating conditions in which the gas-liquid separator pressure increases to a pressure higher than the critical pressure.

  An object of the present invention is to improve operating efficiency in a refrigeration apparatus that performs a multistage compression refrigeration cycle using a refrigerant that operates in a supercritical region.

  A refrigeration apparatus according to a first aspect of the present invention is a refrigeration apparatus that uses a refrigerant that operates in a supercritical region, and depressurizes a compression mechanism, a radiator, an evaporator, and a refrigerant sent from the radiator to the evaporator. An expansion mechanism, a rear-stage injection pipe, an economizer heat exchanger, and a precooling heat exchanger are provided. The compression mechanism has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the compression element on the front stage side among the plurality of compression elements by the compression element on the rear stage side. Here, the “compression mechanism” refers to a compressor in which a plurality of compression elements are integrally incorporated, a compressor in which a single compression element is incorporated, and / or a compressor in which a plurality of compression elements are incorporated. This means a configuration that includes a unit connected. In addition, “sequentially compresses the refrigerant discharged from the compression element on the front stage among the plurality of compression elements with the compression element on the rear stage” is referred to as “compression element on the front stage” and “compression element on the rear stage” It is not only meant to include two compression elements connected in series, but a plurality of compression elements are connected in series, and the relationship between the compression elements is the above-mentioned “previous-side compression element” ”And“ compression element on the rear stage side ”. The rear-stage injection pipe has a rear-stage injection valve that decompresses the refrigerant, and is a refrigerant pipe that branches the refrigerant sent from the radiator to the expansion mechanism and returns it to the rear-stage compression element. The economizer heat exchanger performs heat exchange between the refrigerant sent from the radiator to the expansion mechanism and the refrigerant flowing through the rear-stage injection pipe. The precooling heat exchanger cools the refrigerant sent from the radiator to the economizer heat exchanger. And the back | latter stage side injection pipe is provided so that the refrigerant | coolant sent to an expansion mechanism from a pre-cooling heat exchanger may be branched.

  In a refrigeration system that performs a multistage compression refrigeration cycle using a refrigerant that operates in the supercritical region, when using intermediate pressure injection, the gas-liquid separator pressure, which is the refrigerant pressure in the gas-liquid separator, is the critical pressure. In consideration of the possibility that it becomes difficult to separate the refrigerant in the gas-liquid separator into a gas refrigerant and a liquid refrigerant, instead of the intermediate pressure injection by the gas-liquid separator, It is conceivable to adopt intermediate pressure injection using an economizer heat exchanger.

  Here, in the intermediate pressure injection by this economizer heat exchanger, when the refrigerant sent from the radiator to the expansion mechanism is branched and returned to the compression element on the rear stage by using the rear stage injection pipe, the latter stage injection valve is used. The operation involves reducing the high-pressure refrigerant in the refrigeration cycle flowing through the rear-stage side injection pipe to near the intermediate pressure in the refrigeration cycle, which is the pressure of the refrigerant sucked into the rear-stage compression element. Since the decompression operation by the latter-stage injection valve is an isenthalpy expansion (an expansion in which the pressure decreases while the enthalpy of the refrigerant remains constant), the isentropic expansion (the refrigerant Unlike the expansion in which the pressure decreases while the entropy remains constant, a heat loss (hereinafter referred to as “expansion loss due to the post-stage injection valve”) occurs due to an increase in the entropy of the refrigerant before and after the decompression operation. It will be. And the expansion loss due to the rear-stage side injection valve leads to an increase in power consumption in the compression mechanism, thereby reducing the coefficient of performance and operating efficiency of the refrigeration cycle, so the expansion loss due to the rear-stage side injection valve is reduced. It is desirable to reduce as much as possible. However, the refrigerant branched to the rear-stage side injection pipe is only cooled by the radiator, and the degree of cooling is not sufficient, so there is a problem that the expansion loss due to the rear-stage side injection valve is large. In addition, when using a refrigerant that operates in a supercritical region such as carbon dioxide, compared to using a refrigerant that operates in a pressure region sufficiently lower than the critical pressure, such as R22 or R410A, Since the entropy change with respect to the temperature change of the refrigerant is large, the expansion loss due to the post-stage injection valve is large, and the effect on the coefficient of performance and operating efficiency of the refrigeration cycle is large, so the expansion due to the post-stage injection valve Reducing loss is very important in terms of improving the coefficient of performance and operating efficiency of the refrigeration cycle.

  Therefore, in this refrigeration apparatus, when performing intermediate pressure injection by an economizer heat exchanger, there is a problem that the temperature of the refrigerant branched into the rear-stage injection pipe is high, and refrigerant that operates in a supercritical region such as carbon dioxide In consideration of the characteristic of large entropy change with respect to the temperature change of the refrigerant when using a heat exchanger, a pre-cooling heat exchanger that cools the refrigerant sent from the radiator to the economizer heat exchanger is provided, and the downstream side injection pipe is pre-cooled. The refrigerant sent from the exchanger to the expansion mechanism is provided to be branched. For this reason, since the refrigerant sent from the radiator to the expansion mechanism is cooled by the pre-cooling heat exchanger and then branched to the rear-stage injection pipe, the temperature of the refrigerant decompressed by the rear-stage injection valve decreases. Compared with the case where no pre-cooling heat exchanger is provided, the temperature of the refrigerant depressurized by the rear-stage injection valve is lowered, and as a result, the expansion loss due to the rear-stage injection valve is significantly reduced. Even when a refrigerant that operates in a pressure range sufficiently lower than the critical pressure such as R22 or R410A is used, a precooling heat exchanger that cools the refrigerant sent from the radiator to the economizer heat exchanger is provided. If the post-stage side injection pipe is provided so as to branch the refrigerant sent from the pre-cooling heat exchanger to the expansion mechanism, the expansion loss due to the post-stage side injection valve is reduced as compared with the case where no pre-cooling heat exchanger is provided. However, since the entropy change with respect to the temperature change of the refrigerant is very small compared to the case of using a refrigerant operating in the supercritical region such as carbon dioxide, the degree of expansion loss due to the injection valve on the rear stage is reduced. Is very small, and the demerit of cost increase by adding a pre-cooling heat exchanger is considered to be greater.

  As described above, in this refrigeration apparatus, even if the intermediate pressure of the refrigeration cycle rises to near the critical pressure by performing the intermediate pressure injection by the economizer heat exchanger, it is discharged from the compression element on the rear stage side. This reduces the temperature of the refrigerant, reduces the power consumption of the compression mechanism, improves the operating efficiency, and has a problem that the temperature of the refrigerant branched to the rear-side injection pipe is high, and carbon dioxide, etc. Considering the characteristic of large entropy change with respect to temperature change of refrigerant when using refrigerant that operates in such a supercritical region, a precooling heat exchanger that cools the refrigerant sent from the radiator to the economizer heat exchanger is provided In addition, a rear injection pipe is provided so as to branch the refrigerant sent from the precooling heat exchanger to the expansion mechanism. In Rukoto, reduce swelling loss due stage injection valve, the coefficient of performance and operating efficiency of the refrigeration cycle can be further improved.

  The refrigeration apparatus according to the second invention is the refrigeration apparatus according to the first invention, wherein the precooling heat exchanger exchanges heat between the refrigerant sent from the radiator to the economizer heat exchanger and the refrigerant flowing on the suction side of the compression mechanism. It is a heat exchanger that performs.

  In this refrigeration apparatus, a refrigeration cycle is used as a precooling heat exchanger because a heat exchanger that performs heat exchange between the refrigerant sent from the radiator to the economizer heat exchanger and the refrigerant flowing on the suction side of the compression mechanism is used. In this case, a low-pressure refrigerant having the lowest temperature is used as a cooling source, so that an external cooling source is not required and a sufficient precooling effect can be obtained.

  The refrigeration apparatus according to a third aspect of the invention is the refrigeration apparatus according to the first or second aspect of the invention, wherein the economizer heat exchanger opposes the refrigerant sent from the radiator to the expansion mechanism and the refrigerant flowing through the rear side injection pipe. It is a heat exchanger which has a flow path which flows like this.

  In this refrigeration apparatus, since the temperature difference between the refrigerant sent from the radiator to the expansion mechanism in the economizer heat exchanger and the refrigerant flowing through the rear-stage injection pipe can be reduced, high heat exchange efficiency can be obtained.

  A refrigeration apparatus according to a fourth invention is the refrigeration apparatus according to any one of the first to third inventions, wherein the refrigerant operating in the supercritical region is carbon dioxide.

  As described above, according to the present invention, the following effects can be obtained.

  In the first or fourth invention, even when the intermediate pressure of the refrigeration cycle rises to near the critical pressure, the temperature of the refrigerant discharged from the compression element on the rear stage side is reduced and the consumption of the compression mechanism is reduced. When it is possible to reduce the power and improve the operation efficiency, and the problem is that the temperature of the refrigerant branched into the post-stage injection pipe is high, and the refrigerant that operates in the supercritical region such as carbon dioxide is used. In view of the characteristic that the entropy change with respect to the temperature change of the refrigerant is large, the expansion loss due to the post-stage injection valve can be reduced, and the coefficient of performance and the operation efficiency of the refrigeration cycle can be further improved.

  In the second invention, since the low-pressure refrigerant having the lowest temperature in the refrigeration cycle is used as a cooling source, an external cooling source is not required, and a sufficient precooling effect can be obtained.

  In 3rd invention, since the temperature difference of the refrigerant | coolant sent to the expansion mechanism from the radiator in an economizer heat exchanger and the refrigerant | coolant which flows through a back | latter stage side injection pipe can be made small, high heat exchange efficiency can be obtained.

  Hereinafter, an embodiment of a refrigeration apparatus according to the present invention will be described based on the drawings.

(1) Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner 1 as an embodiment of a refrigeration apparatus according to the present invention. The air conditioner 1 includes a refrigerant circuit 10 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 10 of the air conditioner 1 mainly includes a compression mechanism 2, a heat source side heat exchanger 4, an expansion mechanism 5, a first rear stage side injection pipe 19, an economizer heat exchanger 20, and a use side heat exchanger. 6 and a liquid gas heat exchanger 90.

  In this embodiment, the compression mechanism 2 includes a compressor 21 that compresses the refrigerant in two stages with two compression elements. The compressor 21 has a sealed structure in which a compressor drive motor 21b, a drive shaft 21c, and compression elements 2c and 2d are accommodated in a casing 21a. The compressor drive motor 21b is connected to the drive shaft 21c. The drive shaft 21c is connected to the two compression elements 2c and 2d. That is, in the compressor 21, two compression elements 2c and 2d are connected to a single drive shaft 21c, and the two compression elements 2c and 2d are both rotationally driven by the compressor drive motor 21b. It has a stage compression structure. The compression elements 2c and 2d are positive displacement compression elements such as a rotary type and a scroll type in the present embodiment. The compressor 21 sucks the refrigerant from the suction pipe 2a, compresses the sucked refrigerant by the compression element 2c, discharges the refrigerant to the intermediate refrigerant pipe 8, and discharges the refrigerant discharged to the intermediate refrigerant pipe 8 to the compression element 2d. And the refrigerant is further compressed and then discharged to the discharge pipe 2b. Here, the intermediate refrigerant pipe 8 sucks the intermediate-pressure refrigerant in the refrigeration cycle discharged from the compression element 2c connected to the front stage side of the compression element 2c into the compression element 2d connected to the rear stage side of the compression element 2c. It is a refrigerant pipe for making it. The discharge pipe 2b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 2 to the heat source side heat exchanger 4 as a radiator, and the discharge pipe 2b includes an oil separation mechanism 41 and a check mechanism 42. And are provided. The oil separation mechanism 41 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the compression mechanism 2 from the refrigerant and returns it to the suction side of the compression mechanism 2, and is mainly accompanied by the refrigerant discharged from the compression mechanism 2. An oil separator 41 a that separates the refrigeration oil from the refrigerant, and an oil return pipe 41 b that is connected to the oil separator 41 a and returns the refrigeration oil separated from the refrigerant to the suction pipe 2 a of the compression mechanism 2. The oil return pipe 41b is provided with a pressure reducing mechanism 41c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipe 41b. In the present embodiment, a capillary tube is used as the decompression mechanism 41c. The check mechanism 42 allows the refrigerant to flow from the discharge side of the compression mechanism 2 to the heat source side heat exchanger 4 as a radiator, and discharges the compression mechanism 2 from the heat source side heat exchanger 4 as a radiator. This is a mechanism for blocking the flow of refrigerant to the side, and a check valve is used in this embodiment.

  Thus, in this embodiment, the compression mechanism 2 has the two compression elements 2c and 2d, and the refrigerant discharged from the compression element on the front stage of these compression elements 2c and 2d is returned to the rear stage side. The compression elements are sequentially compressed by the compression elements.

  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 compression mechanism 2, and the other end is connected to the expansion mechanism 5 via the liquid gas heat exchanger 90 and the economizer heat exchanger 20. 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, and an electric expansion valve is used in this embodiment. . One end of the expansion mechanism 5 is connected to the heat source side heat exchanger 4 via the economizer heat exchanger 20 and the liquid gas heat exchanger 90, and the other end is connected to the use side heat exchanger 6. Further, in the present embodiment, the expansion mechanism 5 reaches the low pressure in the refrigeration cycle before sending the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator to the use side heat exchanger 6 as an evaporator. Reduce pressure.

  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 compression mechanism 2. Although not shown here, the use side heat exchanger 6 is supplied with water and air as a heat source for exchanging heat with the refrigerant flowing through the use side heat exchanger 6.

  The first second-stage injection pipe 19 is a refrigerant pipe that branches the refrigerant sent from the heat source-side heat exchanger 4 serving as a radiator to the expansion mechanism 5 and returns the refrigerant to the second-stage compression element 2d. More specifically, the 1st back | latter stage side injection pipe 19 is provided so that the refrigerant | coolant sent to the expansion mechanism 5 from the liquid gas heat exchanger 90 as a precooling heat exchanger may be branched. In the present embodiment, the first second-stage injection pipe 19 branches the refrigerant from a position on the upstream side of the expansion mechanism 5 (that is, between the liquid gas heat exchanger 90 as the precooling heat exchanger and the expansion mechanism 5). And is provided so as to return to the intermediate refrigerant pipe 8. The first second-stage injection pipe 19 is provided with a first second-stage injection valve 19a capable of opening degree control. In the present embodiment, the first second-stage injection valve 19a is an electric expansion valve.

  The economizer heat exchanger 20 includes a refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 and a refrigerant flowing through the first second-stage injection pipe 19 (more specifically, the first second-stage injection valve 19a. The heat exchanger performs heat exchange with the refrigerant after being reduced to near the intermediate pressure. In the present embodiment, the economizer heat exchanger 20 includes a refrigerant flowing through a position upstream of the expansion mechanism 5 (that is, between the position where the first second-stage injection pipe 19 is branched and the expansion mechanism 5) and the first second-stage. It is provided so as to exchange heat with the refrigerant flowing through the side injection pipe 19, and has a flow path that flows so that both refrigerants face each other. Moreover, in this embodiment, the economizer heat exchanger 20 is provided downstream from the position where the first second-stage injection pipe 19 is branched. For this reason, the refrigerant cooled in the heat source side heat exchanger 4 as the radiator passes through the liquid gas heat exchanger 90 as the precooling heat exchanger, and then is branched to the first second-stage injection pipe 19. In the economizer heat exchanger 20, heat is exchanged with the refrigerant flowing through the first second-stage injection pipe 19.

  The liquid gas heat exchanger 90 is a heat exchanger that functions as a precooling heat exchanger that cools the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the economizer heat exchanger 20. More specifically, the liquid gas heat exchanger 90 includes a refrigerant sent from the heat source side heat exchanger 4 as a radiator to the economizer heat exchanger 20 and a suction side of the compression mechanism 2 (here, use as an evaporator). It is a heat exchanger that performs heat exchange with the refrigerant flowing through the suction pipe 2a) between the side heat exchanger 4 and the compression mechanism 2. In the present embodiment, the liquid gas heat exchanger 90 has a position upstream of the economizer heat exchanger 20 (that is, a position where the heat source side heat exchanger 4 as a radiator and the first second-stage injection pipe 19 are branched). The refrigerant flows between the refrigerant flowing between the refrigerant and the refrigerant flowing on the suction side of the compression mechanism 2, and has a flow path through which both refrigerants face each other.

  Furthermore, the air conditioning apparatus 1 is provided with various sensors. Specifically, the intermediate refrigerant pipe 8 or the compression mechanism 2 is provided with an intermediate pressure sensor 54 that detects the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8. An economizer outlet temperature sensor 55 that detects the temperature of the refrigerant at the outlet of the economizer heat exchanger 20 on the first rear-stage injection pipe 19 side is provided at the outlet of the economizer heat exchanger 20 on the first rear-stage injection pipe 19 side. ing. The air conditioner 1 includes a control unit that controls the operation of each part of the air conditioner 1 such as the compression mechanism 2, the expansion mechanism 5, and the first second-stage injection valve 19 a, although not shown here. Yes.

(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. 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 ′, E, H, H ′, and N in FIGS. 2 and 3), and “low pressure”. Means low pressure in the refrigeration cycle (that is, pressure at points A, F, F ′, and Q in FIGS. 2 and 3), and “intermediate pressure” means intermediate pressure in the refrigeration cycle (that is, FIG. 2 and FIG. 2). (Pressures at points B1, G, J, J ′, and K in FIG. 3).

  During the cooling operation, the opening degree of the expansion mechanism 5 is adjusted. The opening degree of the first second-stage injection valve 19a is also adjusted. More specifically, in the present embodiment, the first second-stage injection valve 19a has an opening degree so that the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side becomes a target value. So-called superheat control is performed. In the present embodiment, the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first post-stage injection pipe 19 side is obtained by converting the intermediate pressure detected by the intermediate pressure sensor 54 into a saturation temperature, and the economizer outlet temperature sensor 55. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the above. Although not adopted in the present embodiment, a temperature sensor is provided at the inlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side, and the refrigerant temperature detected by this temperature sensor is used as the economizer outlet temperature sensor 55. The degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side may be obtained by subtracting from the refrigerant temperature detected by the above. Further, the adjustment of the opening degree of the first second-stage injection valve 19a is not limited to the superheat degree control, and for example, the opening degree is adjusted by a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 10 or the like. Also good.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 10, low-pressure refrigerant (see point A in FIGS. 1 to 3) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is compressed by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 1 to 3). The intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c joins with the refrigerant (see point K in FIGS. 1 to 3) returned from the first latter-stage injection pipe 19 to the latter-stage compression mechanism 2d. (Refer to point G in FIGS. 1 to 3). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the first second-stage injection pipe 19 is sucked into the compression element 2d connected to the second-stage side of the compression element 2c and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 1 to 3). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the 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 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 that functions as a refrigerant radiator, and is cooled by exchanging heat with water or air as a cooling source ( (See point E in FIGS. 1-3). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 serving as a radiator is sent to a liquid gas heat exchanger 90 serving as a precooling heat exchanger, and the suction side (here, the suction pipe) of the compression mechanism 2. It is cooled by exchanging heat with the refrigerant flowing through 2a) (see point N in FIGS. 1 to 3). A part of the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger is branched to the first second-stage injection pipe 19. And the refrigerant | coolant which flows through the 1st back | latter stage side injection pipe 19 is sent to the economizer heat exchanger 20 after reducing pressure to the intermediate pressure vicinity in the 1st back | latter stage side injection valve 19a (refer the point J of FIGS. 1-3). In addition, the refrigerant after branching to the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIGS. 1 to 1). (See point H in 3). On the other hand, the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as a precooling heat exchanger (points in FIGS. 1 to 3). K), as described above, the refrigerant is joined to the intermediate pressure refrigerant discharged from the preceding compression element 2c. The high-pressure refrigerant cooled in the economizer heat exchanger 20 is depressurized 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). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point Q in FIGS. 1 to 3). The low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is transferred from the heat source side heat exchanger 4 as the radiator to the economizer heat in the liquid gas heat exchanger 90 as the precooling heat exchanger. After being heated by exchanging heat with the refrigerant sent to the exchanger 20, it is sucked into the compression mechanism 2 (see point A in FIGS. 1 to 3). In this way, the cooling operation is performed.

  Thus, in the air conditioner 1 of the present embodiment, an economizer heat exchanger is considered in consideration of performing a two-stage compression refrigeration cycle using a refrigerant (here, carbon dioxide) that operates in a supercritical region. The intermediate pressure injection by 20 is adopted. For this reason, unlike the case of employing intermediate pressure injection by a gas-liquid separator, the gas-liquid separator pressure, which is the pressure of the refrigerant in the gas-liquid separator, rises to a pressure higher than the critical pressure, and the gas-liquid separator The intermediate pressure of the refrigeration cycle (here, the pressure in the intermediate refrigerant pipe 8) rises to near the critical pressure because there is no need to consider the possibility that it will be difficult to separate the refrigerant into gas refrigerant and liquid refrigerant. Even in such a case, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced without performing heat radiation to the outside (see points B1 and G in FIG. 3). Thereby, the temperature of the refrigerant discharged from the compression mechanism 2 is kept low (see points D and D ′ in FIG. 3), and compared with the case where the first second-stage injection pipe 19 is not provided, the point B1 in FIG. , D ′, D, and G, the heat dissipation loss corresponding to the area surrounded can be reduced, so that the power consumption of the compression mechanism 2 can be reduced and the operation efficiency can be improved.

  In addition, in the air conditioner 1 of the present embodiment, the entropy change with respect to the temperature change of the refrigerant when the refrigerant operating in the supercritical region such as carbon dioxide is used for the intermediate pressure injection by the economizer heat exchanger 20. In consideration of the characteristic that the refrigerant is large, a liquid gas heat exchanger 90 is provided as a precooling heat exchanger for cooling the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the economizer heat exchanger 20, and the first By providing the rear stage side injection pipe 19 so as to branch the refrigerant sent from the liquid gas heat exchanger 90 as the precooling heat exchanger to the expansion mechanism 5, the expansion loss (first stage) by the first rear stage side injection valve 19a is performed. 1 Thermal loss resulting from an increase in the entropy of the refrigerant before and after the pressure reducing operation by the second-stage injection valve 19a , And the less, thereby making it possible to "first-stage expansion loss due injection valve 19a") reduce, further enhancing the coefficient of performance and operating efficiency of the refrigeration cycle.

  This will be described in detail with reference to FIGS. Here, FIG. 4 is a pressure-entropy diagram illustrating a refrigeration cycle using R410A. In FIG. 4, the points Z and Z ′ illustrated in FIG. 3 are illustrated in a state of being overlapped with the points J and J ′, and thus are not illustrated here.

  First, in the intermediate pressure injection by the economizer heat exchanger 20, the refrigerant sent from the heat source side heat exchanger 4 serving as a radiator to the expansion mechanism 5 is branched using the first second stage side injection pipe 19 to compress the second stage side. When returning to the element 2d, the high-pressure refrigerant in the refrigeration cycle flowing through the first second-stage injection pipe 19 by the first second-stage injection valve 19a is in the refrigeration cycle that is the pressure of the refrigerant drawn into the second-stage compression element 2d. This involves an operation for reducing the pressure to near the intermediate pressure (that is, a change from the point N to the point J in FIGS. 2 and 3). The decompression operation by the first second-stage injection valve 19a is equal enthalpy expansion (expansion in which the pressure decreases while the enthalpy of the refrigerant remains constant, that is, a change from point N to point J in FIGS. 2 and 3). Therefore, unlike isentropic expansion (expansion in which the pressure decreases while the entropy of the refrigerant remains constant, that is, a change from point N to point Z in FIG. 3), which is an ideal decompression operation in the refrigeration cycle, 1 The expansion loss due to the second-stage injection valve 19a occurs. And the expansion loss by the 1st back | latter stage side injection valve 19a leads to the increase in the power consumption in the compression mechanism 2, and, thereby, the coefficient of performance and operating efficiency of a refrigerating cycle will fall, 1st back | latter stage side It is desirable to reduce the expansion loss due to the injection valve 19a as much as possible.

  Here, it is as follows when the expansion | swelling loss by the 1st back | latter stage side injection valve 19a in four cases including the expansion | swelling loss by the 1st back | latter stage side injection valve 19a in this embodiment is calculated | required. It should be noted that in obtaining the expansion loss due to the first second-stage injection valve 19a below, the evaporator is used both when carbon dioxide is used as the refrigerant (see FIG. 3) and when R410A is used (see FIG. 4). Operation in which the evaporating temperature in the use side heat exchanger 6 is 0 ° C. (see point F in FIGS. 3 and 4) and the refrigerant temperature on the suction side of the compression mechanism 2 is 10 ° C. (see point A in FIGS. 3 and 4). Under the conditions, the temperature of the high-pressure refrigerant at the outlet of the heat source side heat exchanger 4 as a radiator is 40 ° C. (see point E in FIGS. 3 and 4), and cooling is performed by the liquid gas heat exchanger 90 as a precooling heat exchanger. The temperature range is 5 ° C. (change from point E to point N in FIGS. 3 and 4), and the cooling temperature range by the economizer heat exchanger 20 is 5 ° C. (from point E to point H ′ in FIGS. 3 and 4). Change or change from point N to point H) It shall be assumed.

  Under such a premise, the expansion loss due to the first second-stage injection valve 19a in the present embodiment is point N (showing the high-pressure refrigerant branched to the first second-stage injection pipe 19), as shown in FIG. And point J (showing an intermediate-pressure refrigerant after the high-pressure refrigerant branched into the first second-stage injection pipe 19 is isoenthalpy-expanded by the first second-stage injection valve 19a) and point Z (first The pressure of the high-pressure refrigerant branched to the rear-stage injection pipe 19 is equivalent to the area of a substantially right-angled triangular portion surrounded by connecting with The value is 0.35 kJ / kg ° C.

  In the present embodiment, when the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided (that is, when only the economizer heat exchanger 20 and the first second-stage injection pipe 19 are provided), FIG. As shown in 2 and 3, the refrigerant circuit as a whole is a precooling heat exchanger that changes in the order of point A → point B1 → point D → point E → point H ′ → point F ′ → point Q → point A. The refrigeration cycle without cooling by the liquid gas heat exchanger 90 is performed, and the expansion loss due to the first second-stage injection valve 19a in this case is represented by point E (first rear-stage) as shown in FIG. The high pressure refrigerant branched to the side injection pipe 19) and point J ′ (the high pressure refrigerant branched to the first rear stage injection pipe 19 by the first second stage injection valve 19a is The intermediate pressure refrigerant after assuming that the high pressure refrigerant branched to the first second-stage injection pipe 19 is isentropically expanded is shown. ) And the area of a substantially right-angled triangular portion surrounded by tie, the value is 0.45 kJ / kg ° C.

  Further, when R410A is used as the refrigerant, the first second-stage injection valve 19a in the case where the liquid gas heat exchanger 90 as the precooling heat exchanger is provided on the upstream side of the economizer heat exchanger 20 as in the present embodiment. As shown in FIG. 4, the expansion loss due to is caused by the point N (showing the high-pressure refrigerant branched to the first second-stage injection pipe 19) and the point J (first second-stage injection valve 19a). An intermediate-pressure refrigerant after the high-pressure refrigerant branched into the side injection pipe 19 is expanded by isentropic expansion and a point Z (the high-pressure refrigerant branched into the first second-stage injection pipe 19 is isentropically expanded. Is equivalent to the area of a substantially right-angled triangular portion surrounded by linking the refrigerant with a value of 0.03. The kJ / kg ℃.

  Further, when R410A is used as the refrigerant, the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided (that is, only the economizer heat exchanger 20 and the first second-stage injection pipe 19 are provided). As shown in FIG. 4, the entire refrigerant circuit is precooling heat exchange that changes in the order of point A → point B1 → point D → point E → point H ′ → point F ′ → point Q → point A. A refrigeration cycle without cooling by the liquid gas heat exchanger 90 as a vessel is performed, and the expansion loss due to the first second-stage injection valve 19a in this case is point E (first 1 shows a high-pressure refrigerant branched to the first rear-stage injection pipe 19, and a point J ′ (a high pressure branched to the first second-stage injection pipe 19 by the first second-stage injection valve 19a). Intermediate pressure when the refrigerant of the first pressure is expanded by equal enthalpy expansion) and point Z ′ (the high pressure refrigerant branched to the first second-stage injection pipe 19 is assumed to be isentropic expanded) Corresponds to the area of a substantially right-angled triangular portion surrounded by linking the pressure and the value is 0.058 kJ / kg ° C.

  Then, from the value of the expansion loss by the first second-stage injection valve 19a, when carbon dioxide is used as the refrigerant, the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided (that is, the economizer) Compared to the case where only the heat exchanger 20 and the first second-stage injection pipe 19 are provided), the case where the liquid gas heat exchanger 90 as the precooling heat exchanger is provided upstream of the economizer heat exchanger 20 The expansion loss due to the first second-stage injection valve 19a is small, and the difference is 0.10 kJ / kg ° C. Even when R410A is used as the refrigerant, the liquid gas heat exchanger 90 as the precooling heat exchanger 90 (That is, when only the economizer heat exchanger 20 and the first second-stage injection pipe 19 are provided) In addition, in the case where the liquid gas heat exchanger 90 as the precooling heat exchanger is provided upstream of the economizer heat exchanger 20, the expansion loss due to the first second-stage injection valve 19a is smaller, but the difference is 0. It turns out that it is 0.025kJ / kg degreeC. When carbon dioxide is used as the refrigerant, the expansion loss value by the first second-stage injection valve 19a is about 10 times larger than when R410A is used as the refrigerant, and carbon dioxide is used as the refrigerant. When used, and when either R410A is used, when the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided (that is, only the economizer heat exchanger 20 and the first second-stage injection pipe 19) Expansion loss due to the first second-stage injection valve 19a is reduced when the liquid gas heat exchanger 90 as the precooling heat exchanger is provided upstream of the economizer heat exchanger 20 than when the economizer heat exchanger 20 is provided. The degree of reduction of the expansion loss by the first second-stage injection valve 19a is higher than that when R410A is used. Better when using carbon dioxide as a refrigerant it is seen that about four times larger.

  And this means that the first rear stage in the case where the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided (that is, only the economizer heat exchanger 20 and the first rear injection pipe 19 are provided). The refrigerant branched to the injection pipe 19 is only cooled by the heat source side heat exchanger 4 as a radiator, and is caused by an insufficient degree of cooling. The economizer heat exchanger 20 Whether or not the liquid gas heat exchanger 90 as a precooling heat exchanger is provided on the upstream side affects the expansion loss due to the first second-stage injection valve 19a, and refrigerant operating in a supercritical region such as carbon dioxide When using a refrigerant (see FIG. 3), when using a refrigerant that operates in a pressure range sufficiently lower than the critical pressure, such as R410A (see FIG. 4). This is due to the fact that the entropy change with respect to the temperature change of the refrigerant is large, and a refrigerant that operates in a pressure range sufficiently lower than the critical pressure such as R22 or R410A is used as the refrigerant. In the case of use, whether or not the liquid gas heat exchanger 90 as the precooling heat exchanger is provided on the upstream side of the economizer heat exchanger 20 has little effect on the expansion loss due to the first second-stage injection valve 19a. In the case where a refrigerant operating in a supercritical region such as carbon dioxide is used, whether or not a liquid gas heat exchanger 90 as a precooling heat exchanger is provided on the upstream side of the economizer heat exchanger 20 is the first latter stage. The side injection valve 19a has a large effect on expansion loss, meaning that it has a large effect on the coefficient of performance and operating efficiency of the refrigeration cycle.That is, in the air conditioner 1 that performs a two-stage compression refrigeration cycle using a refrigerant that operates in a supercritical region such as carbon dioxide, when performing intermediate pressure injection by the economizer heat exchanger 20, It can be seen that reducing the expansion loss due to the injection valve 19a is very important from the viewpoint of improving the coefficient of performance and operating efficiency of the refrigeration cycle.

  Therefore, in the air conditioner 1 of the present embodiment, when the intermediate pressure injection by the economizer heat exchanger 20 is performed, there is a problem that the temperature of the refrigerant branched into the first second-stage injection pipe 19 is high, and carbon dioxide or the like Considering the characteristic (see FIG. 3) that the entropy change with respect to the temperature change of the refrigerant when using a refrigerant that operates in such a supercritical region is used, as described above, the heat source side heat exchanger 4 as a radiator. A liquid gas heat exchanger 90 is provided as a precooling heat exchanger that cools the refrigerant sent to the economizer heat exchanger 20, and the first second-stage injection pipe 19 is provided from the liquid gas heat exchanger 90 as a precooling heat exchanger. The refrigerant sent to the expansion mechanism 5 is provided to be branched. For this reason, the refrigerant sent from the heat source side heat exchanger 4 as the radiator to the expansion mechanism 5 is cooled by the liquid gas heat exchanger 90 as the precooling heat exchanger, and then branched to the first second-stage injection pipe 19. Since the temperature of the refrigerant depressurized by the first second-stage injection valve 19a is lowered, the first second-stage injection valve 19a is compared with the case where the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided. As a result, the temperature of the refrigerant reduced in pressure decreases, and as a result, the expansion loss due to the first second-stage injection valve 19a is greatly reduced. Even when a refrigerant that operates in a pressure range sufficiently lower than the critical pressure, such as R22 or R410A (see FIG. 4), is used from the heat source side heat exchanger 4 as a radiator to the economizer heat exchanger 20. A liquid gas heat exchanger 90 is provided as a precooling heat exchanger for cooling the refrigerant sent to the refrigerant, and the first second-stage injection pipe 19 is sent from the liquid gas heat exchanger 90 as a precooling heat exchanger to the expansion mechanism 5. If the refrigerant is provided so as to be branched, the expansion loss due to the first second-stage injection valve 19a is reduced as compared with the case where the liquid gas heat exchanger 90 as the precooling heat exchanger is not provided, Thus, compared to the case of using a refrigerant operating in the supercritical region such as carbon dioxide (see FIG. 3), is the entropy change with respect to the temperature change of the refrigerant very small? , Is very small extent that the expansion loss caused by the first second-stage injection valve 19a is reduced, is considered to be the larger demerit cost due to the addition of the liquid-gas heat exchanger 90 as a pre-cooling heat exchanger.

  Further, the precooling heat exchanger provided on the upstream side of the economizer heat exchanger 20 is not limited to the liquid gas heat exchanger 90 in the present embodiment, but as in the present embodiment, When the liquid gas heat exchanger 90 that performs heat exchange between the refrigerant sent from the heat source side heat exchanger 4 to the economizer heat exchanger 20 and the refrigerant flowing on the suction side of the compression mechanism 2 is used, the temperature is the highest in the refrigeration cycle. Since a low-pressure refrigerant (see points F and Q in FIGS. 2 and 3) is used as a cooling source, an external cooling source is not required and a sufficient precooling effect can be obtained. it can. Moreover, in the present embodiment, the liquid gas heat exchanger 90 flows such that the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 and the refrigerant flowing on the suction side of the compression mechanism 2 face each other. Since a heat exchanger having a flow path is employed, a refrigerant sent from the heat source side heat exchanger 4 as a radiator in the liquid gas heat exchanger 90 to the expansion mechanism 5 and a refrigerant flowing on the suction side of the compression mechanism 2 Temperature difference can be reduced, high heat exchange efficiency can be obtained, and the precooling effect can be further enhanced.

  Moreover, in the air conditioning apparatus 1 of this embodiment, as the economizer heat exchanger 20, from the heat source side heat exchanger 4 (more specifically, the liquid gas heat exchanger 90 as a precooling heat exchanger) as a radiator. Since a heat exchanger having a flow path in which the refrigerant sent to the expansion mechanism 5 and the refrigerant flowing through the first second-stage injection pipe 19 face each other is employed, a heat source as a radiator in the economizer heat exchanger 20 A temperature difference between the refrigerant sent from the side heat exchanger 4 (more specifically, the liquid gas heat exchanger 90 as a precooling heat exchanger) to the expansion mechanism 5 and the refrigerant flowing through the first second-stage injection pipe 19 is reduced. And high heat exchange efficiency can be obtained.

(3) Modification 1
In the above-described embodiment, the first second-stage injection pipe 19 is positioned upstream of the economizer heat exchanger 20 (that is, between the liquid gas heat exchanger 90 as the precooling heat exchanger and the economizer heat exchanger 20). However, as shown in FIG. 5, the first second-stage injection pipe 19 is branched from a position downstream of the economizer heat exchanger 20 (that is, between the economizer heat exchanger 20 and the expansion mechanism 5). The refrigerant circuit 110 may be used.

  Next, the operation | movement at the time of air_conditionaing | cooling operation in the structure of this modification is demonstrated using FIGS. Here, FIG. 6 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation, and FIG. 7 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. The operation control in the following cooling operation is performed by the control unit (not shown) in the above-described embodiment.

  During the cooling operation, the opening degree of the expansion mechanism 5 is adjusted. Moreover, the opening degree adjustment of the 1st back | latter stage side injection valve 19a is made like the above-mentioned embodiment.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 110, the low-pressure refrigerant (see point A in FIGS. 5 to 7) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is compressed by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 5 to 7). The intermediate-pressure refrigerant discharged from the front-stage compression element 2c merges with the refrigerant (see point K in FIGS. 5 to 7) returned from the first rear-stage injection pipe 19 to the rear-stage compression mechanism 2d. (Refer to point G in FIGS. 5 to 7). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the first second-stage injection pipe 19 is sucked into the compression element 2d connected to the second-stage side of the compression element 2c and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe. 2b (see point D in FIGS. 5 to 7). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 6) by the two-stage compression operation by the compression elements 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 that functions as a refrigerant radiator, and is cooled by exchanging heat with water or air as a cooling source ( (See point E in FIGS. 5-7). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 serving as a radiator is sent to a liquid gas heat exchanger 90 serving as a precooling heat exchanger, and the suction side (here, the suction pipe) of the compression mechanism 2. It is cooled by exchanging heat with the refrigerant flowing through 2a) (see point N in FIGS. 1 to 3). A part of the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger is branched to the first second-stage injection pipe 19. And the refrigerant | coolant which flows through the 1st back | latter stage side injection pipe 19 is pressure-reduced to the intermediate pressure vicinity in the 1st back | latter stage side injection valve 19a, Then, it is sent to the economizer heat exchanger 20 (refer the point J of FIGS. 5-7). ) As described above, heat is exchanged with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see point K in FIGS. 5 to 7), and as described above, The intermediate pressure refrigerant discharged from the preceding-stage compression element 2c joins. The high-pressure refrigerant cooled in the economizer heat exchanger 20 is depressurized 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. 5-7). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point A in FIGS. 5-7). The low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is transferred from the heat source side heat exchanger 4 as the radiator to the economizer heat in the liquid gas heat exchanger 90 as the precooling heat exchanger. After being heated by exchanging heat with the refrigerant sent to the exchanger 20, it is sucked into the compression mechanism 2 (see point A in FIGS. 1 to 3). In this way, the cooling operation is performed.

  Thus, also in the present modification, during the cooling operation, the point that the refrigeration cycle that changes in the order of point A → point B1 → point D → point E → point H → point F → point Q → point A is performed. Although it is the same as the cooling operation in the above-described embodiment (see FIGS. 2, 3, 6, and 7), the branch position of the first second-stage injection pipe 19 is the economizer heat exchanger in the above-described embodiment. In this modification, the upstream side of the economizer heat exchanger 20 is different from the upstream side of the 20. And in this modification, the expansion loss by the 1st back | latter stage side injection valve 19a can further be reduced from the above-mentioned embodiment by the difference with this above-mentioned embodiment.

  This will be described in detail with reference to FIGS. Here, FIG. 8 is a pressure-entropy diagram illustrating a refrigeration cycle using R410A. In FIG. 8, the points Z and Z ′ illustrated in FIG. 7 are illustrated in a state of being overlapped with the points J and J ′, and thus are not illustrated here.

  Here, when the expansion loss due to the first second-stage injection valve 19a in the four cases including the expansion loss due to the first second-stage injection valve 19a in the present modification is obtained, the following is obtained. It should be noted that, in obtaining the expansion loss due to the first second-stage injection valve 19a below, the above-described implementation is performed both when carbon dioxide is used as the refrigerant (see FIG. 7) and when R410A is used (see FIG. 8). Similarly to the embodiment, the evaporation temperature in the use side heat exchanger 6 as an evaporator is 0 ° C. (see point F in FIGS. 7 and 8), and the refrigerant temperature on the suction side of the compression mechanism 2 is 10 ° C. (see FIGS. 7 and 8). The temperature of the high-pressure refrigerant at the outlet of the heat source side heat exchanger 4 as a radiator is 40 ° C. (see point E in FIGS. 7 and 8), and the economizer heat exchanger 20 Assume that the temperature of the high-pressure refrigerant at the outlet is 35 ° C. (see point H in FIGS. 7 and 8).

  Under such a premise, the expansion loss due to the first second-stage injection valve 19a in the present modification is a point H (showing a high-pressure refrigerant branched to the first second-stage injection pipe 19) as shown in FIG. And point J (showing an intermediate-pressure refrigerant after the high-pressure refrigerant branched to the first second-stage injection pipe 19 is isoenthalpy-expanded by the first second-stage injection valve 19a) and point Z (first The high-pressure refrigerant branched to the rear-side injection pipe 19 is equivalent to the area of a substantially right-angled triangular portion surrounded by linking the high-pressure refrigerant and the medium-pressure refrigerant when it is assumed that the refrigerant has been subjected to isentropic expansion. The value is 0.17 kJ / kg ° C.

  Further, in this modification, the first second-stage injection pipe 19a is expanded by the first second-stage injection valve 19a when the first second-stage injection pipe 19 is branched from the upstream position of the economizer heat exchanger 20 (that is, in the case of the above-described embodiment). As shown in FIG. 7, the loss is represented by a point N (showing a high-pressure refrigerant branched to the first second-stage injection pipe 19) and a point J ′ (first second-stage injection valve 19a). The intermediate-pressure refrigerant after the high-pressure refrigerant branched into the injection pipe 19 is expanded by isentropic expansion and the point Z ′ (the high-pressure refrigerant branched into the first second-stage injection pipe 19 is isentropically expanded. Is equivalent to the area of a substantially right-angled triangular portion surrounded by connecting the refrigerant with a value of 0.35. The J / kg ℃.

  Further, when R410A is used as the refrigerant, the first rear-stage injection pipe 19 is positioned downstream of the economizer heat exchanger 20 (that is, between the economizer heat exchanger 20 and the expansion mechanism 5) as in the present modification. As shown in FIG. 8, the expansion loss due to the first second-stage injection valve 19a when branched from the point is indicated by point H (showing a high-pressure refrigerant branched to the first second-stage injection pipe 19) and point J (Shows an intermediate-pressure refrigerant after the high-pressure refrigerant branched to the first second-stage injection pipe 19 is iso-enthalpy-expanded by the first second-stage injection valve 19a) and a point Z (first second-stage injection pipe) 19 shows an intermediate-pressure refrigerant when it is assumed that the high-pressure refrigerant branched to 19 is isentropically expanded). Substantially corresponds to the area of the right-angled triangular portion to be, the value is 0.017kJ / kg ℃.

  Further, when R410A is used as the refrigerant, the first second-stage injection when the first second-stage injection pipe 19 is branched from the upstream position of the economizer heat exchanger 20 (that is, in the case of the above-described embodiment). As shown in FIG. 8, the expansion loss due to the valve 19a is caused by a point N (showing a high-pressure refrigerant branched to the first second-stage injection pipe 19) and a point J ′ (first first-stage injection valve 19a). The high-pressure refrigerant branched to the first second-stage injection pipe 19 is shown as an intermediate-pressure refrigerant after isoenthalpy expansion of the high-pressure refrigerant branched to the first second-stage injection pipe 19 and the high-pressure refrigerant branched to the first second-stage injection pipe 19 The surface of the part of the substantially right triangle that is surrounded by connecting the refrigerant Corresponds to, the value is 0.033kJ / kg ℃.

  Then, from the value of the expansion loss by the first second-stage injection valve 19a, when carbon dioxide is used as the refrigerant, the first second-stage injection pipe 19 is branched at a position upstream of the economizer heat exchanger 20. Compared to the case where the first second-stage injection pipe 19 is branched at a position downstream of the economizer heat exchanger 20, the expansion loss due to the first second-stage injection valve 19a is smaller, and the difference is 0. .18 kJ / kg ° C., and even when R410A is used as the refrigerant, the first second-stage injection pipe 19 is branched from the position upstream of the economizer heat exchanger 20 in comparison with the case where the first second-stage injection pipe 19 is branched. When the side injection pipe 19 is branched at a position downstream of the economizer heat exchanger 20, the first rear Although expansion loss by side injection valve 19a is small, the difference is found to be 0.016kJ / kg ℃. When carbon dioxide is used as the refrigerant, the expansion loss value by the first second-stage injection valve 19a itself is about 10 times larger than when R410A is used as the refrigerant, and carbon dioxide is used as the refrigerant. When used, and when R410A is used, when the first second-stage injection pipe 19 is branched at a position downstream of the economizer heat exchanger 20 at a position downstream of the economizer heat exchanger 20 In this case, the expansion loss due to the first second-stage injection valve 19a is reduced, but the degree of reduction of the expansion loss due to the first second-stage injection valve 19a is that carbon dioxide is used as the refrigerant compared to the case where R410A is used. It can be seen that the case is about 10 times larger.

  And when this uses the refrigerant | coolant which operate | moves in a supercritical area like a carbon dioxide (refer FIG. 7), the refrigerant | coolant which operate | moves in a pressure area sufficiently lower than a critical pressure like R410A is used. Compared to the case (see FIG. 8), this is due to the fact that the entropy change with respect to the temperature change of the refrigerant is large, which is sufficiently lower than the critical pressure such as R22 or R410A as the refrigerant. Whether to branch the first second-stage injection pipe 19 at a position upstream of the economizer heat exchanger 20 or a position downstream of the economizer heat exchanger 20 when using a refrigerant that operates in the pressure region Has a small effect on the expansion loss due to the first second-stage injection valve 19a, but a refrigerant operating in a supercritical region such as carbon dioxide is used as the refrigerant. Whether the first rear-stage injection pipe 19 is branched at a position upstream of the economizer heat exchanger 20 or whether it is branched at a position downstream of the economizer heat exchanger 20 is expanded by the first rear-stage injection valve 19a. The effect on loss is large, which means that the effect on the coefficient of performance and operating efficiency of the refrigeration cycle is large. That is, in the air conditioner 1 that performs a two-stage compression refrigeration cycle using a refrigerant that operates in a supercritical region such as carbon dioxide, when performing intermediate pressure injection by the economizer heat exchanger 20, It can be seen that reducing the expansion loss due to the injection valve 19a is very important from the viewpoint of improving the coefficient of performance and operating efficiency of the refrigeration cycle.

  Therefore, in the air conditioner 1 of the present modified example, when intermediate pressure injection is performed by the economizer heat exchanger 20, the entropy change with respect to the temperature change of the refrigerant when a refrigerant operating in a supercritical region such as carbon dioxide is used. As described above, the refrigerant sent from the heat source side heat exchanger 4 serving as a radiator to the expansion mechanism 5 is an economizer heat exchanger. The refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 after the heat exchange in 20 is provided so as to branch. For this reason, the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 is cooled by heat exchange in the economizer heat exchanger 20 and then branched to the first second-stage injection pipe 19. Therefore, before the refrigerant sent to the expansion mechanism 5 from the heat source side heat exchanger 4 serving as a radiator through the first rear-stage side injection tube 19 is subjected to heat exchange in the economizer heat exchanger 20, the heat source side heat serving as a radiator is obtained. Compared with the case where the refrigerant sent from the exchanger 4 to the expansion mechanism 5 is branched, the amount of heat exchanged in the economizer heat exchanger 20 is increased and the size of the economizer heat exchanger 20 is slightly increased. The temperature of the refrigerant depressurized by the rear-stage injection valve 19a decreases, and as a result, the expansion by the first rear-stage injection valve 19a occurs. Loss will be greatly reduced. Even when a refrigerant that operates in a pressure range sufficiently lower than the critical pressure such as R22 or R410A is used (see FIG. 8), heat exchange on the heat source side using the first rear-stage injection pipe 19 as a radiator. If the refrigerant sent from the heat exchanger 4 to the expansion mechanism 5 is heat-exchanged in the economizer heat exchanger 20, the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 is branched. The heat source side heat exchanger 4 as a radiator before the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 through the first rear-stage injection tube 19 is heat-exchanged in the economizer heat exchanger 20. As described above, although the expansion loss due to the first second-stage injection valve 19a is reduced compared to the case where the refrigerant sent from the first to the expansion mechanism 5 is branched. Compared to the case of using a refrigerant operating in a supercritical region such as carbon dioxide (see FIG. 7), since the entropy change with respect to the temperature change of the refrigerant is very small, the expansion loss due to the first second-stage injection valve 19a. It is considered that the demerit that the amount of heat exchanged in the economizer heat exchanger 20 is increased and the size of the economizer heat exchanger 20 is increased is large.

(4) Modification 2
In the above-described embodiment and its modification, in the air conditioner 1 that performs the two-stage compression refrigeration cycle that uses the refrigerant that operates in the supercritical region and is configured to be capable of cooling operation, the heat source as a radiator The refrigerant sent from the side heat exchanger 4 to the expansion mechanism 5 is branched and returned to the compression element 2d on the rear stage side, and from the heat source side heat exchanger 4 as a radiator to the expansion mechanism 5 An economizer heat exchanger 20 that performs heat exchange between the refrigerant to be sent and the refrigerant flowing through the first second-stage injection pipe 19 is provided, and a liquid gas heat exchanger 90 as a precooling heat exchanger is provided upstream of the economizer heat exchanger 20. However, in addition to this configuration, the cooling operation and the heating operation may be switched.

  For example, as shown in FIG. 9, in the refrigerant circuit 10 (see FIG. 1) of the above-described embodiment in which the two-stage compression type compression mechanism 2 is adopted, the cooling operation and the heating operation can be switched. The switching mechanism 3 is provided, and instead of the expansion mechanism 5, the first expansion mechanism 5 a and the second expansion mechanism 5 b are provided, and the refrigerant circuit 210 is provided with the bridge circuit 17 and the receiver 18. it can.

  The switching mechanism 3 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 210. During the cooling operation, the heat source side heat exchanger 4 is used as a radiator for the refrigerant discharged from the compression mechanism 2 and used. In order for the side heat exchanger 6 to function as an evaporator of the refrigerant cooled in the heat source side heat exchanger 4, the discharge side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 are connected and the compressor 21 The suction side and the use side heat exchanger 6 are connected (refer to the solid line of the switching mechanism 3 in FIG. 9; hereinafter, the state of the switching mechanism 3 is referred to as “cooling operation state”). In order for the exchanger 6 to function as a radiator for the refrigerant discharged from the compression mechanism 2 and for the heat source side heat exchanger 4 to function as an evaporator for the refrigerant cooled in the utilization side heat exchanger 6, Connect discharge side and use side heat exchanger 6 In addition, it is possible to connect the suction side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 (see the broken line of the switching mechanism 3 in FIG. 9; hereinafter, the state of the switching mechanism 3 is referred to as “heating operation”. State ”). In this modification, the switching mechanism 3 is a four-way switching valve connected to the suction side of the compression mechanism 2, the discharge side of the compression mechanism 2, the heat source side heat exchanger 4, and the use side heat exchanger 6. The switching mechanism 3 is not limited to a four-way switching valve, and is configured to have a function of switching the refrigerant flow direction as described above, for example, by combining a plurality of electromagnetic valves. There may be.

  As described above, the switching mechanism 3 circulates the refrigerant in the order of the compression mechanism 2, the heat source side heat exchanger 4, the liquid gas heat exchanger 90, the economizer heat exchanger 20, the expansion mechanisms 5 a and 5 b, and the use side heat exchanger 6. Cooling operation state to be performed, and heating operation for circulating the refrigerant in the order of the compression mechanism 2, the use side heat exchanger 6, the liquid gas heat exchanger 90, the economizer heat exchanger 20, the expansion mechanisms 5 a and 5 b, and the heat source side heat exchanger 4. It is configured to be able to switch between states.

  The bridge circuit 17 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 6, and is connected to a receiver inlet pipe 18 a connected to the inlet of the receiver 18 and an outlet of the receiver 18. It is connected to the receiver outlet pipe 18b. The bridge circuit 17 has four check valves 17a, 17b, 17c, and 17d in this modification. The inlet check valve 17a is a check valve that only allows the refrigerant to flow from the heat source side heat exchanger 4 to the receiver inlet pipe 18a. The inlet check valve 17b is a check valve that allows only the refrigerant to flow from the use side heat exchanger 6 to the receiver inlet pipe 18a. That is, the inlet check valves 17a and 17b 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 18a. The outlet check valve 17 c is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18 b to the use side heat exchanger 6. The outlet check valve 17d is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18b to the heat source side heat exchanger 4. That is, the outlet check valves 17c and 17d have a function of circulating the refrigerant from the receiver outlet pipe 18b 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 18a, and an electric expansion valve is used in this modification. Further, in the present modification, the first expansion mechanism 5a, during the cooling operation, causes the high-pressure refrigerant cooled in the heat source side heat exchanger 4 to pass through the liquid gas heat exchanger 90, the economizer heat exchanger 20, and the receiver 18. Before being sent to the use-side heat exchanger 6, the pressure is reduced to near the saturation pressure of the refrigerant. During heating operation, the high-pressure refrigerant cooled in the use-side heat exchanger 6 is converted into the liquid gas heat exchanger 90, the economizer heat exchanger 20 and Before being sent to the heat source side heat exchanger 4 via the receiver 18, the pressure is reduced to near the saturation pressure of the refrigerant.

  The receiver 18 is depressurized by the first expansion mechanism 5a so as to be able to store surplus refrigerant generated according to the operating state such as the refrigerant circulation amount in the refrigerant circuit 210 is different between the cooling operation and the heating operation. The inlet is connected to the receiver inlet pipe 18a, and the outlet thereof is connected to the receiver outlet pipe 18b. The receiver 18 has a suction return pipe 18f that can extract the refrigerant from the receiver 18 and return it to the suction pipe 2a of the compression mechanism 2 (that is, the suction side of the compression element 2c on the front stage side of the compression mechanism 2). It is connected. The suction return pipe 18f is provided with a suction return on-off valve 18g. The suction return on-off valve 18g 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 18b, and an electric expansion valve is used in this modification. Further, in the present modification, the second expansion mechanism 5b becomes a low pressure in the refrigeration cycle before the refrigerant decompressed by the first expansion mechanism 5a is sent to the use side heat exchanger 6 via the receiver 18 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 18.

  Thus, when the switching mechanism 3 is in the cooling operation state by the bridge circuit 17, the receiver 18, the receiver inlet pipe 18 a and the receiver outlet pipe 18 b, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is , The inlet check valve 17a of the bridge circuit 17, the liquid gas heat exchanger 90, the economizer heat exchanger 20, the first expansion mechanism 5a of the receiver inlet pipe 18a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the bridge. It can be sent to the use side heat exchanger 6 through the outlet check valve 17 c of the circuit 17. When the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 is converted into the inlet check valve 17b of the bridge circuit 17, the liquid gas heat exchanger 90, the economizer heat. It is sent to the heat source side heat exchanger 6 through the exchanger 20, the first expansion mechanism 5a of the receiver inlet pipe 18a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17d of the bridge circuit 17. It can be done.

  And in this modification, the economizer heat exchanger 20 is the 1st expansion mechanism 5a from the heat-source side heat exchanger 4 which functions as a radiator at the time of cooling operation, or the utilization side heat exchanger 6 which functions as a radiator at the time of heating operation. Is provided so as to perform heat exchange between the refrigerant sent to the refrigerant and the refrigerant flowing through the first second-stage injection pipe 19, and the liquid gas heat exchanger 90 functions as a radiator during cooling operation. Or it is provided so that the refrigerant | coolant sent to the economizer heat exchanger 20 from the utilization side heat exchanger 6 which functions as a heat radiator at the time of heating operation may be cooled, and the 1st back | latter stage side injection pipe 19 is the liquid gas heat exchanger 90. Is provided so as to branch the refrigerant sent to the economizer heat exchanger 20. That is, also in this modification, when performing intermediate pressure injection by the economizer heat exchanger 20, there is a large entropy change with respect to the temperature change of the refrigerant when using a refrigerant operating in a supercritical region such as carbon dioxide. In consideration of the above, a liquid gas heat exchanger 90 is provided as a precooling heat exchanger that cools the refrigerant sent from the heat source side heat exchanger 4 or the use side heat exchanger 6 as a radiator to the economizer heat exchanger 20. In addition, the first post-stage injection pipe 19 is provided so as to branch the refrigerant sent from the liquid gas heat exchanger 90 as the precooling heat exchanger to the first expansion mechanism 5a.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIG.9 and FIG.2. Here, the refrigeration cycle during the cooling operation in the present modification will be described with reference to FIG. 2, and the refrigeration cycle during the heating operation will be described by substituting points E and F in FIG. It shall be. The operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment.

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in a cooling operation state indicated by a solid 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 first second-stage injection valve 19a is adjusted in the same manner as in the above-described embodiment.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 210, the low-pressure refrigerant (see point A in FIGS. 9 and 2) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is increased by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 9 and 2). The intermediate-pressure refrigerant discharged from the front-stage compression element 2c merges with the refrigerant (see point K in FIGS. 9 and 2) returned from the first rear-stage injection pipe 19 to the rear-stage compression mechanism 2d. (Refer to point G in FIGS. 9 and 2). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the first second-stage injection pipe 19 is sucked into the compression element 2d connected to the second-stage side of the compression element 2c and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe. 2b (see point D in FIGS. 9 and 2). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the 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 2c and 2d. Has been. Then, the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It replaces and it cools (refer the point E of FIG. 9, FIG. 2). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17, and is a liquid gas heat exchanger as a precooling heat exchanger. Then, the refrigerant is cooled by exchanging heat with the refrigerant flowing through the suction side (here, the suction pipe 2a) of the compression mechanism 2 (see point N in FIGS. 9 and 2). A part of the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger is branched to the first second-stage injection pipe 19. And the refrigerant | coolant which flows through the 1st back | latter stage side injection pipe 19 is pressure-reduced to intermediate pressure vicinity in the 1st back | latter stage side injection valve 19a, Then, it sends to the economizer heat exchanger 20 (refer the point J of FIG. 9, FIG. 2). . Further, the refrigerant after being branched to the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 9, (See point H in FIG. 2). On the other hand, the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as a precooling heat exchanger (points in FIGS. 9 and 2). K), as described above, the refrigerant is joined to the intermediate pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is depressurized to near the saturation pressure by the first expansion mechanism 5 a and temporarily stored in the receiver 18. Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is used. And is sent to the use side heat exchanger 6 functioning as a refrigerant evaporator (see point F in FIGS. 9 and 2). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point Q in FIGS. 9 and 2). The low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is transferred from the heat source side heat exchanger 4 as the radiator to the economizer heat in the liquid gas heat exchanger 90 as the precooling heat exchanger. After being heated by exchanging heat with the refrigerant sent to the exchanger 20, it is sucked into the compression mechanism 2 (see point A in FIGS. 9 and 2). In this way, the cooling operation is performed.

  And although detailed explanation is omitted, also in the configuration of this modification, with respect to the intermediate pressure injection by the economizer heat exchanger 20, the expansion loss due to the first second-stage injection valve 19a is reduced as in the above-described embodiment, The effect of further improving the coefficient of performance and operating efficiency of the refrigeration cycle can be obtained.

<Heating operation>
During the heating operation, the switching mechanism 3 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. Furthermore, the opening degree of the first second-stage injection valve 19a is adjusted by superheat degree control similar to that during cooling operation.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 210, the low-pressure refrigerant (see point A in FIGS. 9 and 2) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is increased by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 9 and 2). The intermediate-pressure refrigerant discharged from the front-stage compression element 2c merges with the refrigerant (see point K in FIGS. 9 and 2) returned from the first rear-stage injection pipe 19 to the rear-stage compression mechanism 2d. (Refer to point G in FIGS. 9 and 2). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the first second-stage injection pipe 19 is sucked into the compression element 2d connected to the second-stage side of the compression element 2c and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe. 2b (see point D in FIGS. 9 and 2). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the 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 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 is sent to the use-side heat exchanger 6 that functions as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. Cooling is performed after replacement (refer to point E in FIG. 9 and FIG. 2 as point F). Then, the high-pressure refrigerant cooled in the use side heat exchanger 6 as a radiator flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and is a liquid gas heat exchanger as a precooling heat exchanger. Then, the refrigerant is cooled by exchanging heat with the refrigerant flowing through the suction side (here, the suction pipe 2a) of the compression mechanism 2 (see point N in FIGS. 9 and 2). A part of the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger is branched to the first second-stage injection pipe 19. And the refrigerant | coolant which flows through the 1st back | latter stage side injection pipe 19 is pressure-reduced to intermediate pressure vicinity in the 1st back | latter stage side injection valve 19a, Then, it sends to the economizer heat exchanger 20 (refer the point J of FIG. 9, FIG. 2). . Further, the refrigerant after being branched to the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 9, (See point H in FIG. 2). On the other hand, the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as a precooling heat exchanger (points in FIGS. 9 and 2). K), as described above, the refrigerant is joined to the intermediate pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is depressurized to near the saturation pressure by the first expansion mechanism 5 a and temporarily stored in the receiver 18. Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b 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 17d of the bridge circuit 17 Then, it is sent to the heat source side heat exchanger 4 that functions as a refrigerant evaporator (refer to point F in FIGS. 9 and 2 as point E). 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 Q in FIGS. 9 and 2). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 as the evaporator is transferred from the use side heat exchanger 6 as the radiator to the economizer heat in the liquid gas heat exchanger 90 as the precooling heat exchanger. After being heated by exchanging heat with the refrigerant sent to the exchanger 20, it is sucked into the compression mechanism 2 (see point A in FIGS. 9 and 2). In this way, the heating operation is performed.

  And in the configuration of this modification, since the same operation as the cooling operation is performed in the heating operation, the intermediate pressure injection by the economizer heat exchanger 20 is the same as in the cooling operation in the heating operation. The expansion loss due to the first second-stage injection valve 19a can be reduced, and the effect of further improving the coefficient of performance and operating efficiency of the refrigeration cycle can be obtained.

  Further, in the refrigerant circuit 210 described above, the first second-stage injection pipe 19 is branched from the upstream position of the economizer heat exchanger 20, but the first second-stage injection pipe is similar to the first modification. You may make it acquire the effect which further improves the coefficient of performance and operating efficiency of a refrigerating cycle by branching 19 from the position of the downstream of the economizer heat exchanger 20. FIG.

(5) Modification 3
In the refrigerant circuit 210 (see FIG. 9) in the second modification described above, as described above, in both the cooling operation in which the switching mechanism 3 is in the cooling operation state and the heating operation in which the switching mechanism 3 is in the heating operation state, By performing the intermediate pressure injection by the economizer heat exchanger 20, the temperature of the refrigerant discharged from the compression element 2d on the rear stage side is lowered, and the power consumption of the compression mechanism 2 is reduced to improve the operation efficiency. Yes. And, since the intermediate pressure injection by the economizer heat exchanger 20 can be used even under the condition that the intermediate pressure in the refrigeration cycle has increased to near the critical pressure, the refrigerant circuits 10, 110, As in 210 (see FIGS. 1, 5, and 9), the configuration having one usage-side heat exchanger 6 is considered advantageous when a refrigerant that operates in the supercritical region is used.

  However, for the purpose of performing cooling and heating according to the air conditioning load of a plurality of air-conditioned spaces, the configuration includes a plurality of usage-side heat exchangers 6 connected in parallel to each other, and each usage-side heat exchanger In order to obtain the refrigeration load required in each use side heat exchanger 6 by controlling the flow rate of the refrigerant flowing through the receiver 6, the receiver 18 as a gas-liquid separator and the use side heat exchanger 6 can be obtained. The use side expansion mechanism 5c may be provided so as to correspond to each use side heat exchanger 6.

  For example, as shown in FIG. 10, in the refrigerant circuit 210 (see FIG. 9) having the bridge circuit 17 in the above-described modification 2, a plurality (here, two) of use side heats connected in parallel to each other. While providing the exchanger 6, it is used so that it may respond | correspond to each utilization side heat exchanger 6 between the receiver 18 (more specifically, the bridge circuit 17) as a gas-liquid separator, and the utilization side heat exchanger 6. A refrigerant circuit in which a side expansion mechanism 5c is provided, the second expansion mechanism 5b provided in the receiver outlet pipe 18b is deleted, and a third expansion mechanism 5d is provided in place of the outlet check valve 17d of the bridge circuit 17 310. In this modification, the use side expansion mechanism 5c and the third expansion mechanism 5d are electric expansion valves.

  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 3 is in the cooling operation state. In the condition where 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 20 is the same as in the second modification. Injection is advantageous.

  However, as in the heating operation in which the switching mechanism 3 is in the heating operation state, each use-side expansion mechanism 5c is used as a radiator so that the refrigeration load required in each use-side heat exchanger 6 as a radiator can be obtained. The flow rate of the refrigerant flowing through each usage-side heat exchanger 6 is controlled, and the flow rate of the refrigerant passing through each usage-side heat exchanger 6 as a radiator is the same as that of each usage-side heat exchanger 6 as a radiator. Under conditions generally determined by the refrigerant decompression operation by the opening degree control of the use side expansion mechanism 5c provided on the downstream side and the upstream side of the economizer heat exchanger 20, the opening degree control of each use side expansion mechanism 5c is performed. The degree of decompression of the refrigerant varies depending not only on the flow rate of the refrigerant flowing through each use side heat exchanger 6 as a radiator but also on the state of flow distribution among the use side heat exchangers 6 as a plurality of radiators. Multiple use-side swelling Since the degree of decompression may vary greatly between the mechanisms 5c, or the degree of decompression in the use-side expansion mechanism 5c may be relatively large, the refrigerant pressure at the inlet of the economizer heat exchanger 20 becomes low. In such a case, the amount of heat exchanged in the economizer heat exchanger 20 (i.e., the flow rate of the refrigerant flowing through the first second-stage injection pipe 19) may be reduced, making it difficult to use. In particular, in such an air conditioner 1, a heat source unit mainly including the compression mechanism 2, the heat source side heat exchanger 4 and the receiver 18 and a utilization unit mainly including the utilization side heat exchanger 6 are connected by a communication pipe. When configured as a separate type air conditioner, depending on the arrangement of the utilization unit and the heat source unit, this connection pipe can be very long, and therefore the influence of the pressure loss is also added, and the economizer heat exchanger 20 The refrigerant pressure at the inlet of the refrigerant will further decrease. If the refrigerant pressure at the inlet of the economizer heat exchanger 20 is likely to drop, 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 by a gas-liquid separator that can be used is advantageous even under a condition in which the pressure difference from the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8 is small.

  Therefore, in the present modification, as shown in FIG. 10, in order to allow the receiver 18 to function as a gas-liquid separator and perform intermediate pressure injection, the receiver 18 is provided with a second second-stage injection pipe 18c. Thus, during the cooling operation, intermediate pressure injection by the economizer heat exchanger 20 is performed, and during the heating operation, intermediate pressure injection by the receiver 18 as a gas-liquid separator can be performed.

  The second second-stage injection pipe 18c is a refrigerant pipe that can perform intermediate pressure injection by extracting the refrigerant from the receiver 18 and returning it to the second-stage compression element 2d of the compression mechanism 2. In this modification, The upper part is provided so as to connect the intermediate refrigerant pipe 8 (that is, the suction side of the compression element 2d on the rear stage side of the compression mechanism 2). The second second-stage injection pipe 18c is provided with a second second-stage injection on-off valve 18d and a second second-stage injection check mechanism 18e. The second second-stage injection on / off valve 18d is a valve that can be opened and closed, and is a solenoid valve in this modification. The second second-stage injection check mechanism 18e allows the refrigerant flow from the receiver 18 to the second-stage compression element 2d and blocks the refrigerant flow from the second-stage compression element 2d to the receiver 18. In this embodiment, a check valve is used. The second rear injection pipe 18c and the suction return pipe 18f are integrated with each other on the receiver 18 side. Further, the second rear-stage injection pipe 18c and the first rear-stage injection pipe 19 are integrally formed on the intermediate refrigerant pipe 8 side.

  The receiver inlet pipe 18a is provided with an expansion mechanism bypass valve 5e so as to bypass the first expansion mechanism 5a. In this modification, the expansion mechanism bypass valve 5e is an electromagnetic valve.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIG. 10, FIG. 2 and FIG. Here, FIG. 11 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation. In addition, the refrigeration cycle during the cooling operation in this modification will be described with reference to FIG. Note that 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, points D, D ′, E, H, H ′, N in FIG. 2 and points D, D ′, F, H in FIG. 11). , Pressure at N), and “low pressure” means low pressure in the refrigeration cycle (ie, pressure at points A, F, F ′, Q in FIG. 2 and points A, E, Q in FIG. 10). , “Intermediate pressure” means the intermediate pressure in the refrigeration cycle (that is, the pressure at points B1, G, J, J ′, K in FIG. 2 and points B1, G, I, L, M in FIG. 11). ing.

<Cooling operation>
During the cooling operation, the switching mechanism 3 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. Further, the third expansion mechanism 5d and the expansion mechanism bypass valve 5e are fully closed. When the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the first second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. The intermediate pressure injection by the economizer heat exchanger 20 for returning the refrigerant to the compression element 2d on the rear stage side is performed. More specifically, the second second-stage injection on / off valve 18d is closed, and the first second-stage injection valve 19a is adjusted in opening degree as in the above-described embodiment.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 310, the low-pressure refrigerant (see point A in FIGS. 10 and 2) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is increased by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 10 and 2). The intermediate-pressure refrigerant discharged from the front-stage compression element 2c joins with the refrigerant (see point K in FIGS. 10 and 2) returned from the first rear-stage injection pipe 19 to the rear-stage compression mechanism 2d. (Refer to point G in FIGS. 10 and 2). Next, the intermediate-pressure refrigerant joined with the refrigerant returning from the first second-stage injection pipe 19 (that is, subjected to intermediate-pressure injection by the economizer heat exchanger 20) is compressed by being connected to the second-stage side of the compression element 2c. It is sucked into the element 2d, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 10 and 2). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the 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 2c and 2d. Has been. Then, the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It is exchanged and cooled (see point E in FIGS. 10 and 2). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17, and is a liquid gas heat exchanger as a precooling heat exchanger. Then, the refrigerant is cooled by exchanging heat with the refrigerant flowing through the suction side (here, the suction pipe 2a) of the compression mechanism 2 (see point N in FIGS. 10 and 2). A part of the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger is branched to the first second-stage injection pipe 19. And the refrigerant | coolant which flows through the 1st back | latter stage side injection pipe 19 is pressure-reduced to intermediate pressure vicinity in the 1st back | latter stage side injection valve 19a, Then, it sends to the economizer heat exchanger 20 (refer FIG. 10, point J of FIG. 2). . Further, the refrigerant after being branched to the first second-stage injection pipe 19 flows into the economizer heat exchanger 20 and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 10, (See point H in FIG. 2). On the other hand, the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as a precooling heat exchanger (points in FIGS. 10 and 2). K), as described above, the refrigerant is joined to the intermediate pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIG. 10). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b, and is sent to the usage-side expansion mechanism 5c through the receiver outlet pipe 18b and the outlet check valve 17c of the bridge circuit 17 to be used. The refrigerant is decompressed by 5c 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. 10 and 2). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point Q in FIGS. 10 and 2). And the low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is transferred from the heat source side heat exchanger 4 as the radiator in the liquid gas heat exchanger 90 as the precooling heat exchanger. After being heated by exchanging heat with the refrigerant sent to the economizer heat exchanger 20, the refrigerant is sucked into the compression mechanism 2 (see point A in FIGS. 10 and 2). In this way, the cooling operation is performed.

  Thus, in the air-conditioning apparatus 1 of this modification, in the cooling operation in which the switching mechanism 3 is in the cooling operation state, the first downstream side heat exchanger 4 as the heat radiator and the first heat source side expansion mechanism. Since the pressure of the refrigerant on the upstream side of the expansion mechanism 5a is kept high and 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, the intermediate pressure by the economizer heat exchanger 20 By performing the operation using the injection, the flow rate of the refrigerant returned to the compression element 2d on the rear stage side is ensured as much as possible to maximize the operation efficiency by the intermediate pressure injection, and the economizer heat exchanger As for the intermediate pressure injection by 20, as in the above-described embodiment, the expansion by the first second-stage injection valve 19a is performed. Reduce the loss, it is possible to obtain the effect of further improving the coefficient of performance and operating efficiency of the refrigeration cycle.

<Heating operation>
During the heating operation, the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG. The opening degree of the third expansion mechanism 5d and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Further, the expansion mechanism bypass valve 5e is fully opened so that pressure reduction by the first expansion mechanism 5a is not performed. When the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the second rear-stage injection pipe 18c. Intermediate pressure injection is performed by the receiver 18 that returns to the compression element 2d on the rear stage side. More specifically, the second second-stage injection on / off valve 18d is opened, and the first second-stage injection valve 19a is fully closed.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 310, low-pressure refrigerant (see point A in FIGS. 10 and 11) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is compressed by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 10 and 11). The intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c is returned from the receiver 18 to the latter-stage compression mechanism 2d through the second latter-stage injection pipe 18c (see point M in FIGS. 10 and 11). It cools by joining (refer the point G of FIG. 10, FIG. 11). Next, the intermediate-pressure refrigerant that has joined the refrigerant returning from the second latter-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is connected to the latter-stage side of the compression element 2c. The compressed element 2d is sucked and further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 10 and 11). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is subjected to the 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 2c and 2d, as in the cooling operation. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the compression mechanism 2 is sent to the use-side heat exchanger 6 that functions as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It replaces and it cools (refer the point F of FIG. 10, FIG. 11). Then, the high-pressure refrigerant cooled in the use-side heat exchanger 6 as a radiator is reduced to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and enters the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17. And is sent to a liquid gas heat exchanger 90 as a precooling heat exchanger, and is cooled by exchanging heat with the refrigerant flowing through the suction side (here, the suction pipe 2a) of the compression mechanism 2 (FIG. 10, (See point N in FIG. 11). The high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger passes through the expansion mechanism bypass valve 5e and is temporarily stored in the receiver 18, and gas-liquid separation is performed (FIG. 10, (See points I, L, and M in FIG. 11). The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the second second-stage injection pipe 18c, and has the intermediate pressure discharged from the first-stage compression element 2c as described above. It will join the refrigerant. Then, the liquid refrigerant stored in the receiver 18 is sent to the bridge circuit 17 through the receiver outlet pipe 18b, and is reduced in pressure by the third expansion mechanism 5d to become a low-pressure gas-liquid two-phase refrigerant. To the heat source side heat exchanger 4 functioning as (see point E in FIGS. 10 and 11). 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. 10 and 11). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 as the evaporator is transferred from the use side heat exchanger 6 as the radiator to the economizer heat in the liquid gas heat exchanger 90 as the precooling heat exchanger. After heat is exchanged with the refrigerant sent to the exchanger 20 and heated, the refrigerant is sucked into the compression mechanism 2 (see point A in FIGS. 10 and 11). In this way, the heating operation is performed.

  Thus, in the air conditioning apparatus 1 of the present modification, in the heating operation in which the switching mechanism 3 is in the heating operation state, the refrigerant pressure on the downstream side of the use side expansion mechanism 5c may be low, and the gas-liquid separation Since the pressure difference between the compressor pressure and the intermediate pressure in the refrigeration cycle is small, the refrigerant returned to the compression element 2d on the rear stage side by performing the operation using the intermediate pressure injection by the receiver 18 as a gas-liquid separator. As a result, the operation efficiency can be improved to the maximum by intermediate pressure injection.

  Further, in the refrigerant circuit 310 described above, the first second-stage injection pipe 19 is branched from the position upstream of the economizer heat exchanger 20, but, as in the first modification, the first second-stage injection pipe. By branching 19 from a position downstream of the economizer heat exchanger 20, an effect of further improving the coefficient of performance of the refrigeration cycle and the operation efficiency during the cooling operation may be obtained.

(6) Modification 4
In the refrigerant circuit 310 (see FIG. 10) in the third modification described above, the intermediate pressure injection by the economizer heat exchanger 20 and the intermediate pressure injection by the receiver 18 as a gas-liquid separator are performed, whereby the compression element 2d on the rear stage side is performed. The temperature of the refrigerant discharged from the compressor is reduced, the power consumption of the compression mechanism 2 is reduced, the operation efficiency is improved, and the intermediate pressure injection by the economizer heat exchanger 20 is a precooling heat exchanger. By providing the liquid gas heat exchanger 90 on the upstream side of the economizer heat exchanger 20, it is possible to reduce the expansion loss due to the first second-stage injection valve 19a and to further improve the coefficient of performance and the operating efficiency of the refrigeration cycle. In addition to this configuration, the compression element 2 on the front stage side can be used. An intermediate refrigerant tube 8 for sucking the refrigerant discharged from the rear-stage compression element 2d into an intermediate refrigerant tube 8 that functions as a refrigerant cooler discharged from the front-stage compression element 2c and sucked into the rear-stage compression element 2d. A cooler 7 may be further provided.

  For example, as shown in FIG. 12, in the refrigerant circuit 310 (see FIG. 10) having the bridge circuit 17 in the above-described modification 3, the refrigerant circuit 410 provided with the intermediate cooler 7 and the intermediate cooler bypass pipe 9 is provided. can do.

  The intermediate cooler 7 is a heat exchanger that is provided in the intermediate refrigerant pipe 8 and functions as a refrigerant cooler that is discharged from the preceding compression element 2c and sucked into the compression element 2d. The intercooler 7 is a heat exchanger that uses water or air as a heat source (that is, a cooling source). Thus, the intermediate cooler 7 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 410.

  An intermediate cooler bypass pipe 9 is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate cooler 7. The intermediate cooler bypass pipe 9 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate cooler 7. The intermediate cooler bypass pipe 9 is provided with an intermediate cooler bypass opening / closing valve 11. The intermediate cooler bypass on-off valve 11 is an electromagnetic valve in this modification. In the present modification, the intermediate cooler bypass opening / closing valve 11 is basically closed when the switching mechanism 3 is in the cooling operation state, and controlled to be opened when the switching mechanism 3 is in the heating operation state. The In other words, the intercooler bypass opening / closing valve 11 is controlled to be closed when the cooling operation is performed and to be opened when the heating operation is performed.

  Further, the intermediate refrigerant pipe 8 has a position on the intermediate cooler 7 side from the connection with the intermediate cooler bypass pipe 9 (that is, an intermediate from the connection with the intermediate cooler bypass pipe 9 on the inlet side of the intermediate cooler 7). A cooler on / off valve 12 is provided on a portion of the cooler 7 up to the connection portion on the outlet side. The cooler on / off valve 12 is a mechanism that limits the flow rate of the refrigerant flowing through the intermediate cooler 7. The cooler on / off valve 12 is an electromagnetic valve in this modification. The cooler on / off valve 12 is basically controlled to be opened when the switching mechanism 3 is in a cooling operation state and closed when the switching mechanism 3 is in a heating operation state. That is, the cooler on / off valve 12 is controlled to be opened when the cooling operation is performed and closed when the heating operation is performed. The cooler on / off valve 12 is provided at a position on the inlet side of the intermediate cooler 7 in this modification.

  The intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the front-stage compression element 2c to the suction side of the rear-stage compression element 2d, and from the discharge side of the rear-stage compression element 2d to the front stage. A check mechanism 15 for blocking the flow of the refrigerant to the compression element 2c on the side is provided. The check mechanism 15 is a check valve in this modification. In the present modification, the check mechanism 15 is provided in a portion from the outlet side of the intermediate cooler 7 of the intermediate refrigerant pipe 8 to the connection portion with the intermediate cooler bypass pipe 9.

  The intermediate cooler 7 and the intermediate cooler bypass pipe 9 are both upstream of the first second-stage injection pipe 19 and the second second-stage injection pipe 18c (that is, the first-stage compression element 2c and the first second-stage injection pipe). Between the pipe 19 and the second rear-stage injection pipe 18c).

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIG. 12, FIG. 13, FIG. Here, FIG. 13 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation in the present modification. In addition, the refrigeration cycle during the heating operation in this modification will be described with reference to FIG. Note that 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, H, N in FIG. 13 and points D, D ′, F, H, N in FIG. 11). “Low pressure” means low pressure in the refrigeration cycle (that is, pressures at points A, F, Q in FIG. 13 and points A, E, Q in FIG. 11), and “intermediate pressure” means refrigeration. This means the intermediate pressure in the cycle (that is, the pressure at points B1, C1, G, J, and K in FIG. 13 and points B1, G, I, L, and M in FIG. 11).

<Cooling operation>
During the cooling operation, the switching mechanism 3 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. Further, the third expansion mechanism 5d and the expansion mechanism bypass valve 5e are fully closed. When the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the first second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. The intermediate pressure injection by the economizer heat exchanger 20 for returning the refrigerant to the compression element 2d on the rear stage side is performed. More specifically, the second second-stage injection on / off valve 18d is closed, and the opening degree of the second second-stage injection valve 19a is adjusted in the same manner as in the above-described embodiment. Further, the cooler on / off valve 12 is opened, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is closed, so that the intermediate cooler 7 functions as a cooler.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 410, the low-pressure refrigerant (see point A in FIGS. 12 and 13) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is increased by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 12 and 13). The intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c is cooled by exchanging heat with water or air as a cooling source in the intermediate cooler 7 (see point C1 in FIGS. 12 and 13). ). The refrigerant cooled in the intermediate cooler 7 is further cooled by joining with the refrigerant (see point K in FIGS. 12 and 13) returned from the first second-stage injection pipe 19 to the second-stage compression mechanism 2d. (See point G in FIGS. 12 and 13). Next, the intermediate-pressure refrigerant joined with the refrigerant returning from the first second-stage injection pipe 19 (that is, subjected to intermediate-pressure injection by the economizer heat exchanger 20) is compressed by being connected to the second-stage side of the compression element 2c. It is sucked into the element 2d, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 12 and 13). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 13) by the two-stage compression operation by the compression elements 2c and 2d. Has been. Then, the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It is exchanged and cooled (see point E in FIGS. 12 and 13). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17, and is a liquid gas heat exchanger as a precooling heat exchanger. 90, and is cooled by exchanging heat with the refrigerant flowing through the suction side (here, the suction pipe 2a) of the compression mechanism 2 (see point N in FIGS. 12 and 13). A part of the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger is branched to the first second-stage injection pipe 19. And the refrigerant | coolant which flows through the 1st back | latter stage side injection pipe 19 is pressure-reduced to intermediate pressure vicinity in the 1st back | latter stage side injection valve 19a, Then, it sends to the economizer heat exchanger 20 (refer the point J of FIG. 12, FIG. 13). . Further, the refrigerant after being branched into the first second-stage injection pipe 19 flows into the economizer heat exchanger 20 and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 12, (See point H in FIG. 13). On the other hand, the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as a precooling heat exchanger (points in FIGS. 12 and 13). K), as described above, the refrigerant is joined to the intermediate pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to the vicinity of the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIG. 12). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b, and is sent to the usage-side expansion mechanism 5c through the receiver outlet pipe 18b and the outlet check valve 17c of the bridge circuit 17 to be used. The refrigerant is decompressed by 5c to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the use-side heat exchanger 6 that functions as an evaporator of the refrigerant (see point F in FIGS. 12 and 13). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point Q in FIGS. 12 and 13). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 as the evaporator is transferred from the use side heat exchanger 6 as the radiator to the economizer heat in the liquid gas heat exchanger 90 as the precooling heat exchanger. Heat is exchanged with the refrigerant sent to the exchanger 20 and then sucked into the compression mechanism 2 (see point A in FIGS. 12 and 13). In this way, the heating operation is performed.

  In the configuration of the present modification, in addition to the intermediate injection using the economizer heat exchanger 20 and the first second-stage injection pipe 19, the cooling of the refrigerant sucked into the second-stage compression element 2d by the intermediate cooler 7 is performed. Thus, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced (see points C1 and G in FIG. 13), and in addition to the effect in the above-described modification 3, the refrigerant is discharged from the compression mechanism 2. The temperature of the refrigerant to be applied can be further reduced (see point D in FIG. 13). Thereby, the power consumption of the compression mechanism 2 can be further reduced and the operation efficiency can be further improved.

<Heating operation>
During the heating operation, the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG. The opening degree of the third expansion mechanism 5d and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Further, the expansion mechanism bypass valve 5e is fully opened so that pressure reduction by the first expansion mechanism 5a is not performed. When the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the second rear-stage injection pipe 18c. Intermediate pressure injection is performed by the receiver 18 that returns to the compression element 2d on the rear stage side. More specifically, the second second-stage injection on / off valve 18d is opened, and the first second-stage injection valve 19a is fully closed. Further, the cooler on / off valve 12 is closed, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is opened, so that the intermediate cooler 7 does not function as a cooler.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 410, the low-pressure refrigerant (see point A in FIGS. 12 and 11) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is increased by the compression element 2c. And compressed to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 12 and 11). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c passes through the intermediate cooler bypass pipe 9 without passing through the intermediate cooler 7 (that is, without being cooled). Cooled by passing through (see point C1 in FIG. 12) and joining with the refrigerant (see point M in FIGS. 12 and 11) returned from the receiver 18 to the second-stage compression mechanism 2d through the second latter-stage injection pipe 18c. (Refer to point G in FIGS. 12 and 11). Next, the intermediate-pressure refrigerant that has joined the refrigerant returning from the second latter-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is connected to the latter-stage side of the compression element 2c. The compressed element 2d is sucked and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 12 and 11). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is subjected to the 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 2c and 2d, as in the cooling operation. ) Compressed to a pressure exceeding Then, the high-pressure refrigerant discharged from the compression mechanism 2 is sent via the switching mechanism 3 to the use side heat exchanger 6 that functions as a refrigerant radiator, and air, water, and heat as a cooling source. It is exchanged and cooled (see point F in FIGS. 12 and 11). Then, the high-pressure refrigerant cooled in the use-side heat exchanger 6 as a radiator is reduced to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and enters the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17. The refrigerant flows in and is sent to a liquid gas heat exchanger 90 as a precooling heat exchanger, and is cooled by exchanging heat with the refrigerant flowing through the suction side (here, the suction pipe 2a) of the compression mechanism 2 (FIG. 12, (See point N in FIG. 11). The high-pressure refrigerant cooled in the liquid gas heat exchanger 90 as the precooling heat exchanger passes through the expansion mechanism bypass valve 5e and is temporarily stored in the receiver 18, and gas-liquid separation is performed (FIG. 10, (See points I, L, and M in FIG. 11). The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the second second-stage injection pipe 18c, and has the intermediate pressure discharged from the first-stage compression element 2c as described above. It will join the refrigerant. Then, the liquid refrigerant stored in the receiver 18 is sent to the bridge circuit 17 through the receiver outlet pipe 18b, and is reduced in pressure by the third expansion mechanism 5d to become a low-pressure gas-liquid two-phase refrigerant. To the heat source side heat exchanger 4 that functions as (see point E in FIGS. 12 and 11). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and evaporated by exchanging heat with air or water as a heating source (FIGS. 12 and 11). (See point Q).

  In the configuration of this modification, similarly to the above-described modification 3, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side is set by the intermediate injection using the receiver 18 and the first rear stage injection pipe 19. Since it can be kept low, the temperature of the refrigerant discharged from the compression mechanism 2 can be kept low. However, unlike the cooling operation, the intermediate cooler 7 is not allowed to function as a cooler, and compared to the case where the intermediate cooler 7 is functioned as a cooler in the same manner as the cooling operation, the external cooler 7 is externally operated. The heat loss to the heat sink is suppressed, and the decrease in the heating capacity in the use side heat exchanger 6 as a heat radiator is suppressed.

  Further, in the refrigerant circuit 410 described above, the first second-stage injection pipe 19 is branched from the upstream position of the economizer heat exchanger 20. However, as in the first modification, the first second-stage injection pipe is used. By branching 19 from a position downstream of the economizer heat exchanger 20, an effect of further improving the coefficient of performance of the refrigeration cycle and the operation efficiency during the cooling operation may be obtained.

(7) Modification 5
In the above-described embodiment and its modification, the refrigerant discharged from the front-stage compression element of the two compression elements 2c and 2d by the single uniaxial two-stage compression structure 21 is used as the rear-stage compression element. The two-stage compression type compression mechanism 2 that compresses sequentially in the above-described manner is configured. However, a multistage compression mechanism may be employed rather than a two-stage compression type such as a three-stage compression type, A multistage compression mechanism may be configured by connecting in series a plurality of compressors incorporating a compression element and / or a plurality of compressors incorporating a plurality of compression elements. In addition, when it is necessary to increase the capacity of the compression mechanism, such as when many use-side heat exchangers 6 are connected, parallel multistage compression in which two or more multistage compression type compression mechanisms are connected in parallel. A compression mechanism of the type may be adopted.

  For example, as shown in FIG. 14, in the refrigerant circuit 410 (see FIG. 12) having the bridge circuit 17 in the above-described modification 4, instead of the two-stage compression mechanism 2, a two-stage compression mechanism The refrigerant circuit 510 may employ the compression mechanism 102 in which 103 and 104 are connected in parallel.

  In the present modification, the first compression mechanism 103 includes a compressor 29 that compresses the refrigerant in two stages with two compression elements 103c and 103d. The first suction mechanism 103 is branched from the suction mother pipe 102a of the compression mechanism 102. The branch pipe 103a and the first discharge branch pipe 103b that joins the discharge mother pipe 102b of the compression mechanism 102 are connected. In the present modification, the second compression mechanism 104 includes the compressor 30 that compresses the refrigerant in two stages with the two compression elements 104c and 104d, and the second suction mechanism branched from the suction mother pipe 102a of the compression mechanism 102. The branch pipe 104 a and the second discharge branch pipe 104 b that joins the discharge mother pipe 102 b of the compression mechanism 102 are connected. Since the compressors 29 and 30 have the same configuration as that of the compressor 21 in the above-described embodiment and its modifications, the reference numerals indicating the parts other than the compression elements 103c, 103d, 104c, and 104d are the 29th and 30th, respectively. The description will be omitted here, with a replacement for the base. The compressor 29 sucks the refrigerant from the first suction branch pipe 103a, and after discharging the sucked refrigerant by the compression element 103c, discharges the refrigerant to the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8. The refrigerant discharged to the first inlet-side intermediate branch pipe 81 is sucked into the compression element 103d through the intermediate mother pipe 82 and the first outlet-side intermediate branch pipe 83 constituting the intermediate refrigerant pipe 8, and the refrigerant is further compressed. It is configured to discharge to one discharge branch pipe 103b. The compressor 30 sucks the refrigerant from the first suction branch pipe 104a, compresses the sucked refrigerant by the compression element 104c, and then discharges the refrigerant to the second inlet side intermediate branch pipe 84 constituting the intermediate refrigerant pipe 8. The refrigerant discharged to the two inlet side intermediate branch pipes 84 is sucked into the compression element 104d through the intermediate mother pipe 82 and the second outlet side intermediate branch pipe 85 constituting the intermediate refrigerant pipe 8, and further compressed, so that the second discharge is performed. It is comprised so that it may discharge to the branch pipe 104b. In the present modification, the intermediate refrigerant pipe 8 is configured so that the refrigerant discharged from the compression elements 103c and 104c connected to the upstream side of the compression elements 103d and 104d is compressed by the compression element 103d connected to the downstream side of the compression elements 103c and 104c. , 104 d is a refrigerant pipe for inhalation, and mainly a first inlet side intermediate branch pipe 81 connected to the discharge side of the compression element 103 c on the front stage side of the first compression mechanism 103, and a front stage of the second compression mechanism 104. A second inlet side intermediate branch pipe 84 connected to the discharge side of the compression element 104c on the side, an intermediate mother pipe 82 where both the inlet side intermediate branch pipes 81 and 84 merge, and a first branch branched from the intermediate mother pipe 82. A first outlet-side intermediate branch pipe 83 connected to the suction side of the compression element 103d on the rear stage side of the compression mechanism 103, and a suction part of the compression element 104d on the rear stage side of the second compression mechanism 104 branched from the intermediate mother pipe 82 And a second outlet-side intermediate branch tube 85 connected to the. The discharge mother pipe 102b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 102 to the switching mechanism 3. The first discharge branch pipe 103b connected to the discharge mother pipe 102b has a first oil separation. A mechanism 141 and a first check mechanism 142 are provided, and a second oil separation mechanism 143 and a second check mechanism 144 are provided in the second discharge branch pipe 104b connected to the discharge mother pipe 102b. ing. The first oil separation mechanism 141 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the first compression mechanism 103 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the first compression mechanism 103. The first oil separator 141a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and the first oil separator that is connected to the first oil separator 141a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102 And an oil return pipe 141b. The second oil separation mechanism 143 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the second compression mechanism 104 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the second compression mechanism 104. The second oil separator 143a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and the second oil separator that is connected to the second oil separator 143a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102 And an oil return pipe 143b. In this modification, the first oil return pipe 141b is connected to the second suction branch pipe 104a, and the second oil return pipe 143c is connected to the first suction branch pipe 103a. For this reason, the refrigerant discharged from the first compression mechanism 103 is caused by a deviation between the amount of refrigeration oil accumulated in the first compression mechanism 103 and the amount of refrigeration oil accumulated in the second compression mechanism 104. Even if there is a bias between the amount of refrigerating machine oil accompanying and the amount of refrigerating machine oil accompanying the refrigerant discharged from the second compression mechanism 104, the amount of refrigerating machine oil in the compression mechanisms 103 and 104 is The amount of refrigerating machine oil will return more to the smaller side, so that the bias between the amount of refrigerating machine oil accumulated in the first compression mechanism 103 and the amount of refrigerating machine oil accumulated in the second compression mechanism 104 is eliminated. It has become. Further, in the present modification, the first suction branch pipe 103a has a portion between the junction with the second oil return pipe 143b and the junction with the suction mother pipe 102a at the junction with the suction mother pipe 102a. The second suction branch pipe 104a is configured such that the portion between the junction with the first oil return pipe 141b and the junction with the suction mother pipe 102a is the suction mother pipe. It is comprised so that it may become a downward slope toward the confluence | merging part with 102a. For this reason, even if one of the compression mechanisms 103 and 104 is stopped, the refrigerating machine oil returned from the oil return pipe corresponding to the operating compression mechanism to the suction branch pipe corresponding to the stopped compression mechanism is It will return to the suction | inhalation mother pipe 102a, and it becomes difficult to produce the oil shortage of the compression mechanism during driving | operation. The oil return pipes 141b and 143b are provided with pressure reducing mechanisms 141c and 143c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipes 141b and 143b. The check mechanisms 142 and 144 allow the refrigerant flow from the discharge side of the compression mechanisms 103 and 104 to the switching mechanism 3, and block the refrigerant flow from the switching mechanism 3 to the discharge side of the compression mechanisms 103 and 104. It is a mechanism to do.

  As described above, in this modification, the compression mechanism 102 includes the two compression elements 103c and 103d, and the refrigerant discharged from the compression element on the front stage among the compression elements 103c and 103d is used as the compression element on the rear stage side. And the first compression mechanism 103 configured to sequentially compress the first and second compression elements 104c and 104d, and the refrigerant discharged from the compression element on the front stage of the compression elements 104c and 104d The second compression mechanism 104 configured to sequentially compress with the compression element is connected in parallel.

  In the present modification, the intermediate cooler 7 is provided in the intermediate mother pipe 82 that constitutes the intermediate refrigerant pipe 8, and the refrigerant discharged from the compression element 103c on the front stage side of the first compression mechanism 103 and the second compression mechanism This is a heat exchanger that cools the refrigerant combined with the refrigerant discharged from the compression element 104c on the upstream side of 104. That is, the intermediate cooler 7 functions as a cooler common to the two compression mechanisms 103 and 104. Therefore, the circuit configuration around the compression mechanism 102 when the intermediate cooler 7 is provided for the parallel multi-stage compression type compression mechanism 102 in which the multi-stage compression type compression mechanisms 103 and 104 are connected in parallel in a plurality of systems is simplified. It has been.

  Further, the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the compression element 103c on the front stage side of the first compression mechanism 103 to the intermediate mother pipe 82 side, In addition, a non-return mechanism 81 a for blocking the flow of the refrigerant from the intermediate mother pipe 82 side to the discharge side of the preceding compression element 103 c is provided, and the second inlet-side intermediate branch constituting the intermediate refrigerant pipe 8 is provided. The pipe 84 allows the refrigerant to flow from the discharge side of the compression element 104c on the front stage side of the second compression mechanism 103 to the intermediate mother pipe 82 side, and the compression element 104c on the front stage side from the intermediate mother pipe 82 side. A check mechanism 84a is provided for blocking the flow of the refrigerant to the discharge side. In this modification, check valves are used as the check mechanisms 81a and 84a. For this reason, even if one of the compression mechanisms 103 and 104 is stopped, the refrigerant discharged from the compression element on the front stage side of the operating compression mechanism passes through the intermediate refrigerant pipe 8 to the front stage of the stopped compression mechanism. Therefore, the refrigerant discharged from the compression element on the upstream side of the operating compression mechanism passes through the compression element on the upstream side of the compression mechanism that is stopped. Thus, the refrigerant oil of the stopped compression mechanism does not flow out to the suction side, so that the shortage of the refrigerating machine oil when starting the stopped compression mechanism is less likely to occur. In addition, when the priority of operation is provided between the compression mechanisms 103 and 104 (for example, when the first compression mechanism 103 is a compression mechanism that operates preferentially), it corresponds to the above-described stopped compression mechanism. Since this is limited to the second compression mechanism 104, only the check mechanism 84a corresponding to the second compression mechanism 104 may be provided in this case.

  Further, as described above, when the first compression mechanism 103 is a compression mechanism that operates preferentially, since the intermediate refrigerant pipe 8 is provided in common to the compression mechanisms 103 and 104, the first operating mechanism is in operation. The refrigerant discharged from the upstream compression element 103c corresponding to the compression mechanism 103 is sucked into the downstream compression element 104d of the stopped second compression mechanism 104 through the second outlet side intermediate branch pipe 85 of the intermediate refrigerant pipe 8. Accordingly, the refrigerant discharged from the compression element 103c on the front stage side of the operating first compression mechanism 103 passes through the compression element 104d on the rear stage side of the second compression mechanism 104 that is stopped. There is a possibility that the refrigerating machine oil of the stopped second compression mechanism 104 flows out to the discharge side and there is a shortage of refrigerating machine oil when starting the stopped second compression mechanism 104. Therefore, in the present modification, an opening / closing valve 85a is provided in the second outlet-side intermediate branch pipe 85, and when the second compression mechanism 104 is stopped, the opening / closing valve 85a causes the second outlet-side intermediate branch pipe 85 to The refrigerant flow is cut off. Thereby, the refrigerant discharged from the compression element 103c on the front stage side of the first compression mechanism 103 in operation passes through the second outlet side intermediate branch pipe 85 of the intermediate refrigerant pipe 8, and the rear stage side of the stopped second compression mechanism 104. Therefore, the refrigerant discharged from the compression element 103c on the front stage side of the first compression mechanism 103 during operation becomes the compression element on the rear stage side of the second compression mechanism 104 that is stopped. The refrigeration oil of the second compression mechanism 104 that is stopped through the discharge side of the compression mechanism 102 through 104d does not flow out, so that the refrigeration oil when starting the second compression mechanism 104 that is stopped is prevented. The shortage of is even less likely to occur. In this modification, an electromagnetic valve is used as the on-off valve 85a.

  In the case where the first compression mechanism 103 is a compression mechanism that operates preferentially, the second compression mechanism 104 is started after the first compression mechanism 103 is started. 8 is provided in common to the compression mechanisms 103 and 104, the pressure on the discharge side of the compression element 103c on the front stage side of the second compression mechanism 104 and the pressure on the suction side of the compression element 103d on the rear stage side are Starting from a state where the pressure on the suction side of the compression element 103c and the pressure on the discharge side of the compression element 103d on the rear stage side become higher, it is difficult to start the second compression mechanism 104 stably. Therefore, in this modification, an activation bypass pipe 86 is provided to connect the discharge side of the compression element 104c on the front stage side of the second compression mechanism 104 and the suction side of the compression element 104d on the rear stage side. When the on-off valve 86a is provided and the second compression mechanism 104 is stopped, the on-off valve 86a blocks the refrigerant flow in the startup bypass pipe 86, and the on-off valve 85a provides the second outlet-side intermediate branch pipe. The refrigerant flow in 85 is interrupted, and when the second compression mechanism 104 is activated, the on-off valve 86a allows the refrigerant to flow into the activation bypass pipe 86, whereby the second compression mechanism 104 The starting bypass pipe 8 does not join the refrigerant discharged from the first-stage compression element 104c with the refrigerant discharged from the first-stage compression element 104c of the first compression mechanism 103. When the operating state of the compression mechanism 102 is stabilized (for example, when the suction pressure, the discharge pressure, and the intermediate pressure of the compression mechanism 102 are stabilized), the on-off valve 85a The refrigerant can flow into the second outlet-side intermediate branch pipe 85, and the flow of the refrigerant in the startup bypass pipe 86 is blocked by the on-off valve 86a so that the normal cooling operation can be performed. It has become. In this modification, one end of the activation bypass pipe 86 is connected between the on-off valve 85a of the second outlet side intermediate branch pipe 85 and the suction side of the compression element 104d on the rear stage side of the second compression mechanism 104. The other end is connected between the discharge side of the compression element 104 c on the front stage side of the second compression mechanism 104 and the check mechanism 84 a of the second inlet side intermediate branch pipe 84 to start the second compression mechanism 104. At this time, the first compression mechanism 103 can be hardly affected by the intermediate pressure portion. In this modification, an electromagnetic valve is used as the on-off valve 86a.

  In addition, operations such as cooling operation and heating operation of the air conditioner 1 of the present modification are changed due to the fact that the circuit configuration around the compression mechanism 102 is slightly complicated by the compression mechanism 102 provided in place of the compression mechanism 2. Except for this point, the operation is basically the same as the operation in the above-described modified example 4 (FIGS. 11, 12, 13 and related descriptions), and thus the description thereof is omitted here.

  Also in the configuration of the present modification, it is possible to obtain the same effects as those of the above-described modification 4.

  Further, in the refrigerant circuit 510 described above, the first second-stage injection pipe 19 is branched from the upstream position of the economizer heat exchanger 20. However, as in the first modification, the first second-stage injection pipe is used. By branching 19 from the position downstream of the economizer heat exchanger 20, an effect of further improving the coefficient of performance and the operation efficiency of the refrigeration cycle during the cooling operation may be obtained.

(8) Other Embodiments Although the embodiments of the present invention and the modifications thereof have been described with reference to the drawings, the specific configuration is not limited to these embodiments and the 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 use-side heat exchanger 6, and heat exchange is performed in the use-side heat exchanger 6. The present invention may be applied to a so-called chiller type air conditioner provided with a secondary heat exchanger for exchanging heat between the water or brine and indoor 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.

  In addition, the expansion mechanism 5, the first expansion mechanism 5a, the second expansion mechanism 5b, the use side expansion mechanism 5c, and the third expansion mechanism 5d in the above-described embodiment and its modifications are not limited to the electric expansion valve. A positive displacement or centrifugal expander may be applied.

  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.

  By using the present invention, it is possible to improve the operation efficiency in a refrigeration apparatus that performs a multistage compression refrigeration cycle using a refrigerant that operates in a supercritical region.

It is a schematic block diagram of the air conditioning apparatus as one Embodiment of the freezing apparatus concerning 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. FIG. 4 is a pressure-entropy diagram illustrating a refrigeration cycle using R410A. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1. 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 1 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 1 was illustrated. FIG. 4 is a pressure-entropy diagram illustrating a refrigeration cycle using R410A. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2. It is a schematic block diagram of the air conditioning apparatus concerning the modification 3. 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 a schematic block diagram of the air conditioning apparatus concerning the modification 4. 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 4 was illustrated. It is a schematic block diagram of the air conditioning apparatus concerning the modification 5.

Explanation of symbols

1 Air conditioning equipment (refrigeration equipment)
2,102 Compression mechanism 4 Heat source side heat exchanger (radiator, evaporator)
5 Expansion mechanism 5a First expansion mechanism 6 User side heat exchanger (evaporator, radiator)
19 1st latter stage side injection pipe 19a 1st latter stage side injection valve 20 Economizer heat exchanger 90 Liquid gas heat exchanger (pre-cooling heat exchanger)

Claims (4)

A refrigeration system using a refrigerant operating in a supercritical region,
A compression mechanism (2, 102) having a plurality of compression elements and configured to sequentially compress the refrigerant discharged from the front-stage compression elements of the plurality of compression elements by the rear-stage compression elements. When,
A radiator (4, 6),
An evaporator (6, 4);
An expansion mechanism (5, 5a) for reducing the pressure of the refrigerant sent from the radiator to the evaporator;
A rear injection valve (19a) for decompressing the refrigerant, a rear injection pipe (19) for branching the refrigerant sent from the radiator to the expansion mechanism and returning it to the compression element on the rear stage;
An economizer heat exchanger (20) for exchanging heat between the refrigerant sent from the radiator to the expansion mechanism and the refrigerant flowing through the rear-stage injection pipe;
A precooling heat exchanger (90) for cooling the refrigerant sent from the radiator to the economizer heat exchanger,
The latter-stage injection pipe is provided so as to branch the refrigerant sent from the precooling heat exchanger to the expansion mechanism,
Refrigeration equipment (1).   The pre-cooling heat exchanger (90) exchanges heat between the refrigerant sent from the radiator (4, 6) to the economizer heat exchanger (20) and the refrigerant flowing on the suction side of the compression mechanism (2, 102). The refrigeration apparatus (1) according to claim 1, wherein the refrigeration apparatus (1) is a heat exchanger.   The economizer heat exchanger (20) flows so that the refrigerant sent from the radiators (4, 6) to the expansion mechanism (5, 5a) and the refrigerant flowing through the rear-stage injection pipe (19) face each other. The refrigeration apparatus (1) according to claim 1 or 2, wherein the refrigeration apparatus (1) is a heat exchanger having a flow path.   The refrigerating apparatus (1) according to any one of claims 1 to 3, wherein the refrigerant operating in the supercritical region is carbon dioxide.

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