JP2013053757A - Refrigerant circuit system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerant circuit system in which the volume of a plurality of accumulators provided in series and the size of an oil return hole are appropriately set so as to achieve both the prevention of liquid backflow and the prevention of oil discharge from a compressor caused by deteriorated oil return.SOLUTION: In the refrigerant circuit system, a first accumulator 18 and a second accumulator 19 are provided in series inside the refrigerant suction pipe 20B of the compressor 9 along a refrigerant circulation direction. The first accumulator 18 and the second accumulator 19 are adapted to satisfy V1 > V2, where V1 is a volume of the first accumulator 18 and V2 is a volume of the second accumulator 19. The first accumulator 18 and the second accumulator 19 are also adapted to satisfy A1 < A2, where A1 is an opening area of a first oil return hole 37 provided in a refrigerant exit pipe 36 of the first accumulator 18 and A2 is an opening area of a second oil return hole 41 provided in a refrigerant exit pipe 40 of the second accumulator 19.

Description

  The present invention relates to a refrigerant circuit system that can be applied to a refrigerator, an air conditioner, a heat pump, and the like.

  In a refrigerant circuit system applicable to a refrigerator, an air conditioner, a heat pump, etc., in order to more effectively prevent liquid back to the compressor, a plurality of refrigerants along the refrigerant flow direction in the refrigerant suction pipe to the compressor Are provided in series (see, for example, Patent Documents 1 and 2).

  Thus, when a plurality of accumulators are arranged in series, the volume of the accumulator arranged on the upstream side in the refrigerant flow direction is made larger than the volume of the accumulator arranged on the downstream side, and the volume is reduced. In many cases, a small accumulator on the downstream side is attached to the outer periphery of the housing of the compressor and integrated with the compressor.

JP 2009-236397 A JP 2011-47545 A

  As described above, by arranging a plurality of accumulators in series, liquid back to the compressor can be more effectively prevented. However, if the size of the oil return hole provided in the refrigerant outlet piping of each accumulator is not set appropriately, liquid back to the compressor may not be prevented accurately, or oil return to the compressor may occur. However, there is a problem that the compressor may cause oil to rise due to deterioration.

  In particular, when an oil separator is provided in the refrigerant discharge pipe of the compressor and the oil separated by the oil separator is configured to return to the refrigerant suction pipe of the compressor via the oil return pipe, If the size of the oil return hole of the accumulator is not set appropriately, the amount of oil return from the oil separator to the compressor cannot be secured properly, the compressor will rise, and it may fail or be damaged due to poor lubrication. In order to generate a problem such as that, it was necessary to appropriately set the size of the oil return hole.

  The present invention has been made in view of such circumstances, and by appropriately setting the volumes and oil return holes of a plurality of accumulators provided in series, compression due to prevention of liquid back and deterioration of oil return It is an object of the present invention to provide a refrigerant circuit system capable of achieving both prevention of oil rising of a machine.

In order to solve the above problems, the refrigerant circuit system of the present invention employs the following means.
That is, the refrigerant circuit system according to the present invention is a refrigerant circuit system in which a first accumulator and a second accumulator are provided in series along a refrigerant flow direction in a refrigerant suction pipe of a compressor. And the second accumulator has V1> V2 when the volume of the first accumulator is V1 and the volume of the second accumulator is V2, and is provided in the refrigerant outlet pipe of the first accumulator. When the opening area of one oil return hole is A1, and the opening area of the second oil return hole provided in the refrigerant outlet pipe of the second accumulator is A2, A1 <A2.

  According to the present invention, when the volumes of the first accumulator and the second accumulator provided in series along the refrigerant flow direction in the refrigerant suction pipe of the compressor are V1 and V2, respectively, V1> V2 When the opening area of the first oil return hole provided in the refrigerant outlet pipe of the first accumulator is A1, and the opening area of the second oil return hole provided in the refrigerant outlet pipe of the second accumulator is A2. Since A1 <A2, even when a situation occurs in which a large amount of liquid refrigerant staying in the refrigerant circuit is liquid-backed to the compressor side at the time of system startup or transient operation, the volume The liquid refrigerant is reliably separated and held by the first accumulator in which V1 is large and the opening area A1 of the first oil return hole is small, and liquid back to the compressor can be prevented.Further, even if a liquid back from the first accumulator occurs, since the liquid refrigerant can be separated and held by the second accumulator, liquid back to the compressor can be steadily prevented. On the other hand, since the liquid back can be basically prevented by the first accumulator, even if the opening area A2 of the second oil return hole of the refrigerant outlet pipe of the second accumulator is set to be large, the risk of the occurrence of the liquid back is Almost no oil can be steadily returned to the compressor through the enlarged second oil return hole. Therefore, it is possible to improve the reliability with respect to the prevention of liquid back, and to reliably prevent the oil from going up due to a decrease in oil return.

  Furthermore, in the refrigerant circuit system of the present invention, in the above refrigerant circuit system, a ratio A2 / A1 between the opening area A1 of the first oil return hole and the opening area A2 of the second oil return hole is at least 1. It is characterized by being 1 or more.

  According to the present invention, since the ratio A2 / A1 between the opening area A1 of the first oil return hole and the opening area A2 of the second oil return hole is at least 1.1 or more, the first oil return hole The size of the second oil return hole is made larger than the first oil return hole by making the size of the hole of an appropriate size that can reliably prevent liquid back, and an area of 1.1 times or more Even if the oil is easily returned as a ratio, liquid back can be prevented steadily. Therefore, it is possible to achieve both prevention of liquid back and prevention of oil leakage from the compressor.

  Furthermore, in the refrigerant circuit system of the present invention, in the above refrigerant circuit system, when the oil charged in the compressor is an oil having compatibility with the refrigerant over the entire operating condition of the compressor, the ratio A2 / A1 is characterized by 1.1 ≦ A2 / A1 ≦ 2.

  According to the present invention, when the oil charged in the compressor is an oil having compatibility with the refrigerant in the entire operating condition of the compressor, A2 / A1 is set to 1.1 ≦ A2 / A1 ≦ 2. Therefore, it is possible not only to prevent both the liquid back and the oil from rising in the compressor, but also to discharge the liquid refrigerant accumulated in the first accumulator during the transient operation because the value of A2 / A1 is too large. While avoiding the risk of the amount being reduced and the first accumulator overflowing or gas-low operation, the liquid back can be reliably prevented and the oil return property can be ensured. Therefore, even when an oil such as a polyol ester-based oil (POE oil) having compatibility with the refrigerant is used as the lubricating oil for the compressor, the oil return property can be secured and the operation can be stably performed.

  Furthermore, in the refrigerant circuit system according to the present invention, in the above refrigerant circuit system, when the oil charged in the compressor is oil that is incompatible with the refrigerant in the whole or part of the operating conditions of the compressor, The ratio A2 / A1 is 1.1 ≦ A2 / A1 ≦ 3.

  According to the present invention, when the oil charged in the compressor is oil that is incompatible with the refrigerant in the whole or part of the operating conditions of the compressor, A2 / A1 is 1.1 ≦ A2 / A1 ≦ Therefore, not only can both prevent liquid back and prevent oil from rising in the compressor, but A2 / A1 is too large and the liquid accumulated in the first accumulator during transient operation. The amount of refrigerant discharged is reduced, and the risk of the first accumulator overflowing or gas-low operation is avoided, while preventing liquid back and ensuring oil return. Therefore, even when an oil that is incompatible with the refrigerant, such as a polyalkylene glycol oil (PAG oil), is used as the lubricating oil for the compressor, it is possible to stably operate while ensuring oil return.

  Furthermore, the refrigerant circuit system of the present invention is the oil circuit system according to any one of the above-described refrigerant circuit systems, wherein an oil separator is provided in the refrigerant discharge pipe of the compressor, and the oil separated by the oil separator is returned to the compressor side. A return pipe is connected to a refrigerant pipe between the first accumulator and the second accumulator.

  According to the present invention, an oil separator is provided in the refrigerant discharge pipe of the compressor, and the oil return circuit for returning the oil separated by the oil separator to the compressor side is a refrigerant between the first accumulator and the second accumulator. Since it is connected to the pipe, the oil separated by the oil separator and returned to the compressor side through the oil return circuit is passed through the second oil return hole in which the opening area A2 of the second accumulator is increased. By returning, it can be easily returned to the compressor side. Therefore, it is possible to reliably prevent the oil from rising due to worsening of the return of oil, and even if equipment such as a liquid pool is installed in the oil return circuit, the equipment The liquid accumulator can be prevented from being backed by the second accumulator, and the reliability for preventing the liquid back can be ensured.

  According to the present invention, even when a large amount of liquid refrigerant that has accumulated in the refrigerant circuit is liquid-backed to the compressor side during system startup or transient operation, the volume V1 is large and The liquid refrigerant is reliably separated and held by the first accumulator in which the opening area A1 of the first oil return hole is reduced, and the liquid back to the compressor can be prevented. Further, even if a liquid back from the first accumulator occurs, since the liquid refrigerant can be separated and held by the second accumulator, liquid back to the compressor can be steadily prevented. On the other hand, since the liquid back can be basically prevented by the first accumulator, even if the opening area A2 of the second oil return hole of the refrigerant outlet pipe of the second accumulator is set to be large, the risk of the occurrence of the liquid back is Almost no oil can be steadily returned to the compressor through the enlarged second oil return hole, so that the reliability in preventing liquid back can be improved and the return of oil is reduced. Therefore, it is possible to reliably prevent the oil from rising from the compressor.

It is a schematic block diagram of the refrigerant circuit system which concerns on one Embodiment of this invention. It is an enlarged view of the principal part of the refrigerant circuit system shown in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a schematic configuration diagram of a refrigerant circuit system according to an embodiment of the present invention, and FIG. 2 shows an enlarged view of a main part thereof.
The refrigerant circuit system 1 of the present embodiment is applied to a supercritical vapor compression heat pump water heater using CO2 refrigerant, and includes a supercritical vapor compression heat pump (hereinafter simply referred to as a heat pump) 2 and an illustration not shown. And a water circulation system 3 connected to the hot water storage tank unit.

  The water circulation system path 3 on the hot water storage tank unit side includes a water supply side system path 3A connected to a water side flow path of a radiator (refrigerant / water heat exchanger) 11 in the heat pump 2 and the refrigerant / water heat exchanger 11. A hot water extraction side system path 3B for extracting the manufactured hot water is provided, and a water pump 4 and a flow rate control valve 5 are provided in the water supply side system path 3A.

  The heat pump 2 includes a two-stage compressor (compressor) 9 in which a low-stage compressor 7 and a high-stage compressor 8 are built in a sealed housing 6, and an oil separator 10 that separates lubricating oil in refrigerant gas. A radiator (refrigerant / water heat exchanger) 11 that radiates refrigerant gas, a first electronic expansion valve (intermediate pressure decompression means) 12 that decompresses the refrigerant to an intermediate pressure, and an intermediate pressure receiver with a gas-liquid separation function (Intermediate pressure gas-liquid separator) 13, an internal heat exchanger (intercooler) 14 for exchanging heat between the intermediate pressure refrigerant and the low pressure refrigerant sucked into the two-stage compressor 9, supercooling coils 15A and 15B, Second electronic expansion valves (main decompression means) 16A and 16B for decompressing the intermediate pressure refrigerant into a low-temperature and low-pressure gas-liquid two-phase refrigerant, and a plurality of evaporations for exchanging heat between the outside air blown from a blower (not shown) and the refrigerant (Air heat exchangers) 17A and 17B A first accumulator 18 and the second accumulator 19 connected in series is constituted by a refrigerant circuit 21 of the connected closed cycle through the refrigerant pipe 20 in this order.

  In the radiator 11 of the heat pump 2, the high-temperature and high-pressure refrigerant gas discharged from the two-stage compressor 9 is circulated in one refrigerant side flow path, and water is supplied to the other water side flow path via the water circulation system path 3. A refrigerant / water heat exchanger in which heat is exchanged between water and refrigerant gas by being circulated. And in this refrigerant | coolant / water heat exchanger 11, warm water is manufactured by heating water with the high-temperature / high pressure refrigerant gas.

  In the refrigerant circuit 21, an oil return circuit that returns the oil separated by the oil separator 10 provided in the refrigerant discharge pipe 20A from the two-stage compressor 9 to the refrigerant suction pipe 20B side of the two-stage compressor 9. 22 is connected. The oil return circuit 22 includes a double pipe heat exchanger 23 for exchanging heat between refrigerant and oil flowing through a gas injection circuit 31 described later, and a parallel circuit of an electromagnetic valve 24 and two capillary tubes 25A and 25B. The oil return amount adjusting mechanism 26 is provided.

  Further, the refrigerant circuit 21 has a high-temperature and high-pressure hot gas refrigerant discharged from the two-stage compressor 9 when frost is generated on the surfaces of the evaporators 17A and 17B during operation at a low outside temperature. A hot gas bypass circuit 27 is introduced between the refrigerant discharge pipe 20A and the refrigerant inlet side of the evaporators 17A and 17B. The hot gas bypass circuit 27 is provided with an electromagnetic valve 28 that opens and closes when frost generation is detected, a capillary tube 29 for adjusting the refrigerant flow rate, check valves 30A and 30B, and the like.

  Further, in the refrigerant circuit 21, the double-pipe heat exchanger provided in the oil return circuit 22 is supplied with the intermediate-pressure refrigerant gas separated by the intermediate-pressure receiver (intermediate-pressure gas-liquid separator) 13 having a gas-liquid separation function. A gas injection circuit 31 for injecting into the hermetic housing 6, which is an intermediate pressure gas atmosphere of the two-stage compressor 9, is provided via 23. The gas injection circuit 31 is provided with an electromagnetic valve 32 and a check valve 33 so that the gas injection circuit 31 can be opened and closed as necessary.

Further, in the present embodiment, as shown in FIG. 2, the first accumulator 18 and the second accumulator 19 arranged in series in the refrigerant suction pipe 20B of the two-stage compressor 9 are as follows. It is configured.
The first accumulator 18 provided on the upstream side in the refrigerant flow direction has a refrigerant inlet pipe 35 and a refrigerant outlet pipe 36 provided with a first oil return hole 37 with respect to the cylindrical sealed container 34. The second accumulator 19 that is connected and provided downstream is provided with a refrigerant inlet pipe 39 and a refrigerant outlet provided with a second oil return hole 41 with respect to the cylindrical sealed container 38. The pipe 40 is connected.

  Thus, the configuration itself of the first accumulator 18 and the second accumulator 19 is not particularly different from a known accumulator, but when the volume of the first accumulator 18 is V1 and the volume of the second accumulator 19 is V2. V1> V2, and the volume of the first accumulator 18 is larger than that of the second accumulator 19.

  Further, when the opening areas of the first oil return hole 37 and the second oil return hole 41 provided in the refrigerant outlet pipe 36 and the refrigerant outlet pipe 40 are A1 and A2, respectively, A1 <A2 and second The opening area A2 of the oil return hole 41 is made larger than the opening area A1 of the first oil return hole 37. That is, the first oil return hole 37 and the second oil return hole 41 are circular holes, the diameter of the first oil return hole 37 is d1 (opening area A1), and the diameter of the second oil return hole 41 is d2 (opening area A2). ), D1 <d2, so that the ratio A2 / A1 between the opening area A1 of the first oil return hole 37 and the opening area A2 of the second oil return hole 41 is at least “1.1 ≦ A2 / A1 ".

  Here, if the value of the ratio A2 / A1 becomes too large, the discharge amount of the liquid refrigerant accumulated in the first accumulator 18 during the transient operation decreases, and the first accumulator 18 overflows or gas-low operation is performed. Since there is a risk, it is desirable to set an upper limit value of the ratio A2 / A1. The upper limit is preferably set in consideration of the compatibility between the oil (lubricating oil) filled in the two-stage compressor (compressor) 9 and the refrigerant (CO2 refrigerant). When using oil with low compatibility, the oil separated in the accumulator is difficult to return to the two-stage compressor 9 side with respect to highly compatible oil, so the upper limit is set for the case of using highly compatible oil. It is desirable to keep it large.

  In the present embodiment, the oil used as the lubricating oil for the two-stage compressor (compressor) 9 is an oil that is compatible with the CO2 refrigerant over the entire operating conditions of the two-stage compressor 9, such as a polyol ester-based oil. In the case of (POE oil), the ratio A2 / A1 between the opening area A1 of the first oil return hole 37 and the opening area A2 of the second oil return hole 41 is set to 1.1 ≦ A2 / A1 ≦ 2. In the case where the oil is an oil incompatible with the CO2 refrigerant in the whole or part of the operating conditions of the two-stage compressor 9, for example, polyalkylene glycol oil (PAG oil), A2 / A1 is set to 1.1 ≦ A2. / A1 ≦ 3.

An oil return circuit 22 from the oil separator 10 is connected to the refrigerant suction pipe 20B connecting the first accumulator 18 and the second accumulator 19.
The second accumulator 19 is a small accumulator whose volume is relatively small as described above, and is integrally installed on the outer periphery of the hermetic housing 6 of the two-stage compressor 9 via a bracket or the like. It is good also as a structure.

With the configuration described above, according to the present embodiment, the following operational effects can be obtained.
In the refrigerant circuit system 1, when the supercritical vapor compression heat pump 2 using CO 2 refrigerant is operated, the high-temperature and high-pressure refrigerant gas compressed in two stages by the two-stage compressor 9 is contained in the refrigerant in the oil separator 10. After the oil is separated, it is introduced into a radiator (refrigerant / water heat exchanger) 11 where heat is exchanged with water circulated from the water supply side path 3A of the water circulation path 3 to the water side path. This water is heated and heated by heat radiation from the high-temperature and high-pressure refrigerant gas, and then returns to the hot water storage tank (not shown) via the hot water extraction side system path 3B until the amount of hot water stored in the hot water storage tank reaches a predetermined amount. Heat exchange between the refrigerant and water is continuously continued in the radiator (refrigerant / water heat exchanger) 11 and the hot water storage operation is terminated when the hot water storage amount reaches a predetermined amount.

  The refrigerant cooled by exchanging heat with water in the radiator 11 is depressurized by the first electronic expansion valve (intermediate pressure depressurizing means) 12 to reach the intermediate pressure receiver 13 where it is gas-liquid separated. The intermediate-pressure gas refrigerant separated by the intermediate-pressure receiver 13 passes through an electromagnetic valve 32, a check valve 33, and a double-pipe heat exchanger 23, and is intermediated in the hermetic housing 6 of the two-stage compressor 9 by the gas injection circuit 31. The refrigerant is injected into the pressurized refrigerant gas, sucked into the high stage compressor 8 and recompressed. By the economizer effect by this gas injection, the heating capability and the coefficient of performance (COP) by the heat pump 2 can be improved, and the hot water supply capability can be increased.

  On the other hand, the liquid refrigerant separated by the intermediate pressure receiver 13 is heat-exchanged with the low-pressure refrigerant gas evaporated by the evaporators 17A and 17B in the internal heat exchanger (intercooler) 14 and is supercooled, and then the supercooling coil. The pressure is reduced by the second electronic expansion valves (main pressure reducing means) 16A and 16B via 15A and 15B, and is converted into a low-temperature and low-pressure gas-liquid two-phase refrigerant and flows into the evaporators (air heat exchangers) 17A and 17B. The refrigerant that has flowed into the evaporators (air heat exchangers) 17A and 17B is heat-exchanged with the outside air blown by the blower, absorbs heat from the outside air, and is vaporized into gas.

  The refrigerant gasified in the evaporators 17A and 17B is heat-exchanged with the intermediate pressure liquid refrigerant in the internal heat exchanger 14 and is subjected to supercooling of the intermediate pressure liquid refrigerant, and then the first accumulator 18 and the second accumulator 19 are used. In the process of passing through, the liquid component (liquid refrigerant, oil) is separated, and only the gas refrigerant is sucked into the two-stage compressor 9 and recompressed. Thereafter, the same operation is repeated to provide hot water. During hot water storage operation, if frost is accumulated in the evaporators 17A and 17B, it is detected, the electromagnetic valve 28 is opened, and the hot gas refrigerant discharged from the two-stage compressor 9 is hot from the downstream of the oil separator 10. By introducing it into the evaporators 17A and 17B via the gas bypass circuit 27, the defrosting operation can be performed.

  Further, the oil separated from the refrigerant by the oil separator 10 is subjected to heat exchange with the intermediate pressure refrigerant gas by the double pipe heat exchanger 23 through the oil return circuit 22 and heated, and then the oil return amount is adjusted. The amount is adjusted via the mechanism 26 and returned to the refrigerant suction pipe 20 </ b> B between the first accumulator 18 and the second accumulator 19. This oil is once separated in the second accumulator 19 and then picked up little by little into the refrigerant gas flow through the second oil return hole 41 provided in the refrigerant outlet pipe 40 of the second accumulator 19. It will be returned to the stage compressor 9 side.

  Here, the first accumulator 18 and the second accumulator 19 are arranged in series in the refrigerant suction pipe 20B of the two-stage compressor 9, and their volumes V1, V2 are set to V1> V2, and the refrigerant outlet thereof Since the opening areas A1 and A2 of the first oil return hole 37 and the second oil return hole 41 provided in the pipe 36 and the refrigerant outlet pipe 40 are A1 <A2, when the refrigerant circuit system 1 is started up, Even during a transient operation or the like, even if a large amount of liquid refrigerant containing oil staying in the refrigerant circuit 21 is liquid-backed to the two-stage compressor 9 side, the volume V1 is increased and the first oil is increased. The first accumulator 18 on the upstream side in which the opening area A1 of the return hole 37 is small can be reliably separated and held, and liquid back to the two-stage compressor 9 can be prevented.

  As described above, the oil separated by the first accumulator 18 flows out into the second accumulator 19 on the downstream side through the first oil return hole 37 little by little. As described above, the liquid back from the refrigerant circuit 21 is basically prevented by the first accumulator 18. However, the liquid back to the downstream side of the first accumulator 18 or the oil separator 10 and the second Even if the refrigerant that has accumulated in the heavy pipe heat exchanger 23 is liquid-backed through the oil return circuit 22, the liquid is separated and held by the second accumulator 19, and is supplied to the two-stage compressor 9. Liquid back can be reliably prevented.

On the other hand, since liquid back can be basically prevented by the first accumulator 18, the opening area A2 of the second oil return hole 41 provided in the refrigerant outlet pipe 40 on the second accumulator 19 side is set to be large. However, there is almost no risk of the occurrence of liquid back, and the oil from the refrigerant circuit 21 and the oil return circuit 22 can be steadily returned to the two-stage compressor 9 through the larger second oil return hole 41. it can.
Thus, according to the present embodiment, it is possible to improve the reliability with respect to prevention of liquid back, and to reliably prevent oil from rising in the two-stage compressor 9 due to a decrease in oil return.

  In the present embodiment, the ratio A2 / A1 between the opening area A1 of the first oil return hole 37 of the first accumulator 18 and the second accumulator 19 and the opening area A2 of the second oil return hole 41 is at least 1. One or more. For this reason, the size of the second oil return hole 41 is made larger than that of the first oil return hole 37 by setting the size of the first oil return hole 37 to an appropriate size that can reliably prevent liquid back. However, even if the oil is easily returned with an area ratio of 1.1 times or more, liquid back can be prevented steadily. Accordingly, it is possible to achieve both prevention of liquid back and prevention of oil rising of the two-stage compressor 9.

  In particular, the area ratio A2 / A1 is not only 1.1 ≦ A2 / A1, but the ratio A2 / A1 is too large, and the discharge amount of the liquid refrigerant accumulated in the first accumulator 18 during transient operation In order to avoid the risk of the first accumulator 18 overflowing or gas-low operation, an upper limit is set for the value of A2 / A1, and the lubricating oil for the two-stage compressor (compressor) 9 is used. When an oil such as a polyol ester oil (POE oil) having compatibility with the refrigerant (CO2 refrigerant) is used throughout the operating conditions of the two-stage compressor 9, the ratio A2 / A1 is set to 1 1 ≦ A2 / A1 ≦ 2.

Also, as the lubricating oil for the two-stage compressor, an oil such as polyalkylene glycol oil (PAG oil) that is incompatible with the CO2 refrigerant is used throughout or part of the operating conditions of the two-stage compressor 9. In this case, the ratio A2 / A1 is set to 1.1 ≦ A2 / A1 ≦ 3.
For this reason, it is possible to achieve both prevention of liquid back and prevention of oil rising of the two-stage compressor 9, and also ensures oil returnability when using either POE oil or PAG oil. And can be operated stably.

  Further, an oil separator 10 is provided in the refrigerant discharge pipe 20A of the two-stage compressor 9, and an oil return circuit 22 for returning the oil separated by the oil separator 10 to the two-stage compressor 9 side is connected to the first accumulator 18 and the first accumulator 18. Since it is connected to the refrigerant suction pipe 20 </ b> B between the two accumulators 19, the oil separated by the oil separator 10 and returned to the two-stage compressor 9 side through the oil return circuit 22 is supplied to the opening of the second accumulator 19. By returning through the second oil return hole 41 having a larger area A2, it is possible to easily return to the two-stage compressor 9 side.

  As a result, it is possible to reliably prevent oil from rising in the two-stage compressor 9 due to worsening of the return of oil, and temporarily, a double pipe heat exchanger 23 that becomes a liquid pool in the oil return circuit 22. Even if such devices are installed, liquid back from the devices can be blocked by the second accumulator 19 and reliability for preventing liquid back can be ensured.

  In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, in the above embodiment, the example in which the refrigerant circuit system 1 is applied to a supercritical vapor compression heat pump water heater using CO2 refrigerant has been described. However, the refrigerant circuit system 1 of the present invention is not limited to a heat pump water heater. Needless to say, it can be widely applied to various refrigerators, air conditioners, heat pumps and the like. In addition, the refrigerant used is not limited to the CO 2 refrigerant, and other refrigerants such as an HFC refrigerant may be used, and can be similarly applied to a refrigerator, an air conditioner, a heat pump, and the like using those refrigerants.

  Furthermore, in the above-described embodiment, the example using the two-stage compressor 9 has been described. However, the present invention is not limited thereto, and may be applied to a refrigerator, an air conditioner, a heat pump, or the like using a single-stage compressor. Of course. In addition, the first oil return hole 37 of the first accumulator 18 and the second oil return hole 41 of the second accumulator 19 have been described as circular holes having diameters d1 and d2, respectively. As long as the opening area is A1 or A2, the hole may have any shape.

1 Refrigerant circuit system 9 Two-stage compressor (compressor)
10 Oil separator 18 First accumulator 19 Second accumulator 20 Refrigerant pipe 20A Refrigerant discharge pipe 20B Refrigerant intake pipe 22 Oil return circuit 36 Refrigerant outlet pipe 37 First oil return hole 40 Refrigerant outlet pipe 41 Second oil return hole V1 First accumulator Volume V2 Volume of the second accumulator d1 Diameter of the first oil return hole (opening area A1)
d2 Diameter of the second oil return hole (opening area A2)

Claims (5)

In the refrigerant circuit system in which the first accumulator and the second accumulator are provided in series along the refrigerant flow direction in the refrigerant suction pipe of the compressor.
The first accumulator and the second accumulator have V1> V2 when the volume of the first accumulator is V1, and the volume of the second accumulator is V2.
When the opening area of the first oil return hole provided in the refrigerant outlet pipe of the first accumulator is A1, and the opening area of the second oil return hole provided in the refrigerant outlet pipe of the second accumulator is A2. , A1 <A2.   The ratio A2 / A1 between the opening area A1 of the first oil return hole and the opening area A2 of the second oil return hole is at least 1.1 or more. Refrigerant circuit system.   When the oil charged in the compressor is an oil that is compatible with the refrigerant over the entire operating condition of the compressor, the ratio A2 / A1 is 1.1 ≦ A2 / A1 ≦ 2. The refrigerant circuit system according to claim 2.   When the oil charged in the compressor is oil that is incompatible with the refrigerant in the whole or part of the operating conditions of the compressor, the ratio A2 / A1 is 1.1 ≦ A2 / A1 ≦ 3. The refrigerant circuit system according to claim 2, wherein: An oil separator is provided in the refrigerant discharge pipe of the compressor, and an oil return circuit for returning the oil separated by the oil separator to the compressor side is provided in the refrigerant pipe between the first accumulator and the second accumulator. The refrigerant circuit system according to claim 1, wherein the refrigerant circuit system is connected.

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