CN114364929A

CN114364929A - Outdoor unit and refrigeration cycle device

Info

Publication number: CN114364929A
Application number: CN201980099963.2A
Authority: CN
Inventors: 石川智隆; 有井悠介; 早坂素
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2019-09-09
Filing date: 2019-09-09
Publication date: 2022-04-15
Anticipated expiration: 2039-09-09
Also published as: WO2021048900A1; EP4030117A1; JPWO2021048900A1; ES2967450T3; EP4030117B1; JP7195449B2; EP4030117A4; DK4030117T3; FI4030117T3; CN114364929B

Abstract

The outdoor unit (2) is provided with a 1 st flow path (F1), a 2 nd flow path (F2), a 3 rd flow path (F3), and an opening/closing valve (78). The 1 st flow path (F1) is a flow path from the refrigerant inlet port (PI2) to the refrigerant outlet port (PO2), and forms a circulation flow path for circulating the refrigerant together with the load device (3). The compressor (10), the condenser (20), and the 2 nd expansion device (40) are disposed in the 1 st flow path (F1). The 2 nd flow path (F2) is configured to branch from the 1 st flow path (F1) and return the refrigerant passing through the condenser (20) to the compressor (10). The 3 rd expansion device (71) and the liquid receiver (73) are disposed in the 2 nd flow path (F2) in the order from the branch point of the 1 st flow path (F1) of the 2 nd flow path (F2). The 3 rd flow path (F3) connects the portion between the 2 nd expansion device (40) and the refrigerant outlet port (PO2) in the 1 st flow path (F1) and the refrigerant inlet of the liquid receiver (73). The on-off valve (78) is disposed in the 3 rd flow path (F3).

Description

Outdoor unit and refrigeration cycle device

Technical Field

The present invention relates to an outdoor unit and a refrigeration cycle apparatus.

Background

Japanese patent application laid-open No. 2014-01917 (patent document 1) discloses a refrigeration apparatus having an intermediate injection passage and a suction injection passage. In this refrigeration apparatus, a part of the refrigerant flowing from the condenser to the evaporator can be joined to a medium-pressure (intermediate pressure) refrigerant of the compressor by using the intermediate injection flow path, or joined to a low-pressure refrigerant sucked into the compressor by using the suction injection flow path. Therefore, when the operation efficiency is deteriorated in the intermediate injection passage, the discharge temperature of the compressor can be lowered by using the suction injection passage.

Documents of the prior art

Patent document 1: japanese patent laid-open publication No. 2014-01917

Disclosure of Invention

In the refrigeration apparatus described in japanese patent application laid-open No. 2014-01917 (patent document 1), when the flow of the refrigerant in the indoor unit is shut off due to the load device being stopped or the like and the evacuation (pump down) operation starts to be performed in the load device side, the pressure of the liquid pipe in the outdoor unit rises. For example, when a supercritical CO2 refrigerant or the like is used, the discharge pressure of the compressor is high, and therefore, the pressure of a part of the liquid pipe may exceed the design pressure.

An object of the present invention is to provide an outdoor unit and a refrigeration cycle apparatus improved so as to prevent a pressure exceeding a design pressure from being applied to a pipe.

The present disclosure relates to an outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a 1 st expansion device and an evaporator. The outdoor unit is provided with: a refrigerant outlet port and a refrigerant inlet port for connection with a load device; a 1 st flow path which is a flow path from the refrigerant inlet port to the refrigerant outlet port and forms a circulation flow path for circulating the refrigerant together with the load device; a compressor, a condenser and a 2 nd expansion device disposed in the 1 st flow path; a 2 nd flow path configured to branch from a portion between the condenser and the 2 nd expansion device of the 1 st flow path and return the refrigerant passing through the condenser to the compressor; a 3 rd expansion device and a liquid receiver which are arranged in the 2 nd flow path in order from the branch point of the 1 st flow path of the 2 nd flow path; a 3 rd flow path which connects a portion between the 2 nd expansion device and the refrigerant outlet port in the 1 st flow path with the refrigerant inlet of the liquid receiver; and an on-off valve disposed in the 3 rd flow path.

According to the outdoor unit and the refrigeration cycle apparatus including the outdoor unit of the present disclosure, even when the pressure abruptly increases due to, for example, the flow of the refrigerant being shut off on the load apparatus side, the pressure of the piping can be prevented from exceeding the design pressure.

Drawings

Fig. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to the present embodiment.

Fig. 2 is a flowchart for explaining control of the 3 rd expansion valve 71.

Fig. 3 is a flowchart for explaining the control of the flow rate adjustment valve 72.

Fig. 4 is a flowchart for explaining the control of the 2 nd expansion valve 40.

Fig. 5 is a flowchart for explaining control of the opening/closing valve 78.

(symbol description)

1: a refrigeration cycle device; 2: an outdoor unit; 3: a load device; 10: a compressor; 20: a condenser; 22: a fan; 28. 75, 76, 78: an opening and closing valve; 30: a heat exchanger; 40: a 2 nd expansion valve; 50: 1 st expansion valve; 60: an evaporator; 70: a throttling device; 71: a 3 rd expansion valve; 72: a flow rate regulating valve; 73: a liquid receiver; 74: a flow path switching unit; 77: a pressure reducing device; 80-85, 88, 89, 91, 92, 94, 96-98: piping; 93: an exhaust pipe; 100: a control device; 104: a memory; 110-113: a pressure sensor; 120-122: a temperature sensor; f1: a 1 st flow path; f2: a 2 nd flow path; f3: a 3 rd flow path; g1: a suction port; g2: a discharge port; g3: an intermediate pressure port (intermediate pressure port); h1: a 1 st path; h2: a 2 nd path; PI2, PI 3: a refrigerant inlet port; PO2, PO 3: a refrigerant outlet port.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but it is anticipated that the configurations described in the embodiments can be appropriately combined from the beginning of the application. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

Fig. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to the present embodiment. In fig. 1, the connection relationship and arrangement structure of each device in the refrigeration cycle apparatus are functionally shown, and the arrangement in the physical space is not necessarily shown.

Referring to fig. 1, the refrigeration cycle apparatus 1 includes an outdoor unit 2, a load device 3, and

pipes

84 and 88. The outdoor unit 2 has a refrigerant outlet port PO2 for connection with the load device 3 and a refrigerant inlet port PI 2. The load device 3 has a refrigerant outlet port PO3 for connection with the outdoor unit 2 and a refrigerant inlet port PI 3. The pipe 84 connects the refrigerant outlet port PO2 of the outdoor unit 2 and the refrigerant inlet port PI3 of the load device 3. The pipe 88 connects the refrigerant outlet port PO3 of the load device 3 and the refrigerant inlet port PI2 of the outdoor unit 2.

The outdoor unit 2 of the refrigeration cycle apparatus 1 is connected to a load device 3. The outdoor unit 2 includes: the compressor 10 includes a suction port G1, a discharge port G2, and a medium-pressure port G3, a condenser 20, a fan 22, a heat exchanger 30, a 2 nd expansion valve 40, and pipes 80 to 83, 89. The heat exchanger 30 includes the 1 st passage H1 and the 2 nd passage H2, and exchanges heat between the refrigerant flowing through the 1 st passage H1 and the refrigerant flowing through the 2 nd passage H2.

The load device 3 includes the 1 st expansion valve 50, the evaporator 60,

pipes

85, 86, 87, and the opening/closing valve 28. The evaporator 60 is configured to exchange heat between air and refrigerant. In the refrigeration cycle apparatus 1, the evaporator 60 evaporates the refrigerant by absorbing heat from air in the space to be cooled. The 1 st expansion valve 50 is, for example, a temperature expansion valve controlled independently of the outdoor unit 2. The 1 st expansion valve 50 may be an electronic expansion valve capable of reducing the pressure of the refrigerant. The on-off valve 28 is closed (closed) when the load device 3 stops operating, and cuts off the refrigerant.

The compressor 10 compresses a refrigerant sucked from a pipe 89 and discharges the refrigerant to a pipe 80. The compressor 10 can arbitrarily change the drive frequency by inverter control. The compressor 10 is provided with the intermediate pressure port G3, and the refrigerant from the intermediate pressure port G3 can flow into the compressor during the compression process. The compressor 10 is configured to adjust the rotation speed in accordance with a control signal from the control device 100. The capacity of the refrigeration cycle apparatus 1 can be adjusted by adjusting the rotation speed of the compressor 10 to adjust the circulation amount of the refrigerant. Various types of compressors can be employed in the compressor 10, for example, a rolling type, a rotary type, a screw type, or the like can be employed.

The condenser 20 is configured to exchange heat (dissipate heat) between the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 and outside air. By this heat exchange, the refrigerant is condensed to change to a liquid phase. The refrigerant discharged from the compressor 10 to the pipe 80 is condensed and liquefied in the condenser 20 and flows out to the pipe 81. In order to improve the efficiency of heat exchange, a fan 22 for feeding outside air is installed in the condenser 20. The fan 22 supplies the outside air heat-exchanged with the refrigerant in the condenser 20 to the condenser 20. The refrigerant pressure on the discharge side (high-pressure side pressure) of the compressor 10 can be adjusted by adjusting the rotation speed of the fan 22. The 2 nd expansion valve 40 is an electronic expansion valve capable of decompressing the refrigerant passing through the condenser 20 and the 1 st passage H1 of the heat exchanger 30.

Here, the refrigerant used in the refrigerant circuit of the refrigeration cycle apparatus 1 is CO₂However, in the case where a state in which it is difficult to ensure the degree of supercooling occurs, another refrigerant may be used.

In this specification, for the sake of easy explanation, CO in a supercritical state is used₂Such a case where the refrigerant cools is also referred to as a condenser 20. In the present specification, for the sake of easy description, the amount of decrease of the supercritical refrigerant from the reference temperature is also referred to as the supercooling degree.

The 1 st flow path F1 extending from the refrigerant inlet port PI2 to the refrigerant outlet port PO2 via the compressor 10, the condenser 20, the 1 st passage H1 of the heat exchanger 30, and the 2 nd expansion valve 40 forms a circulation flow path through which the refrigerant circulates together with the flow path of the load device 3 in which the 1 st expansion valve 50 and the evaporator 60 are disposed. Hereinafter, this circulation flow path is also referred to as a "main refrigerant circuit" of the refrigeration cycle.

The outdoor unit 2 further includes:

pipes

91, 92, and 94 for allowing the refrigerant to flow from a portion of the circulation flow path between the outlet of the 1 st passage H1 and the 2 nd expansion valve 40 to the inlet of the 2 nd passage H2; pipes 96 to 98 for allowing the refrigerant to flow from the outlet of the 2 nd passage H2 to the suction port G1 or the intermediate pressure port G3 of the compressor 10; and a flow path switching unit 74 capable of selecting either one of the suction port G1 and the intermediate pressure port G3 as a destination of the refrigerant flowing out of the outlet of the 2 nd passage H2. Hereinafter, the 2 nd flow path F2 that branches from the main refrigerant circuit and feeds the refrigerant to the compressor 10 via the 2 nd flow path H2 is also referred to as an "injection flow path".

The outdoor unit 2 further includes a liquid receiver (receiver) 73 disposed in the 2 nd flow path F2 and storing the refrigerant. The 3 rd expansion valve 71 is disposed between a pipe 91 branched from a portion between the outlet of the 1 st passage H1 and the 2 nd expansion valve 40 of the circulation flow path and a pipe 92 connected to the inlet of the liquid receiver 73. The outdoor unit 2 further includes: an exhaust pipe 93 connecting the gas discharge port of the liquid receiver 73 and the 2 nd passage H2 to discharge the refrigerant gas in the liquid receiver 73; an expansion device 70 disposed between the exhaust pipe 93 and a pipe 94 leading to a 2 nd passage H2; and a flow rate adjustment valve 72 that adjusts the flow rate of the refrigerant in the pipe 94 connected to the liquid refrigerant discharge port of the liquid receiver 73.

The pipe 91 branches from the main refrigerant circuit and allows the refrigerant to flow into the liquid receiver 73. The 3 rd expansion valve 71 is an electronic expansion valve capable of reducing the refrigerant at the high pressure portion of the main refrigerant circuit to an intermediate pressure. The liquid receiver 73 is a container as follows: the gas phase and the liquid phase of the refrigerant that has been depressurized and has become two phases can be separated in the container, and the refrigerant can be stored to adjust the circulation amount of the refrigerant in the main refrigerant circuit. The discharge pipe 93 connected to the upper portion of the liquid receiver 73 and the pipe 94 connected to the lower portion of the liquid receiver 73 are pipes for taking out the refrigerant separated into the gas refrigerant and the liquid refrigerant in the liquid receiver 73 in a separated state. The flow rate adjustment valve 72 can adjust the amount of refrigerant in the liquid receiver 73 by adjusting the circulation amount of the liquid refrigerant discharged from the pipe 94.

By providing the liquid receiver 73 in the injection flow path in this way, the degree of supercooling in the

pipes

82 and 83 as liquid pipes can be easily ensured. This is because, in general, since the liquid receiver 73 contains a gas refrigerant, the refrigerant temperature becomes a saturation temperature, and therefore, if the liquid receiver 73 is disposed in the pipe 82, the degree of supercooling cannot be ensured.

Further, if the liquid receiver 73 is provided in the intermediate-pressure portion, the intermediate-pressure liquid refrigerant can be stored in the liquid receiver 73 even when the high-pressure portion of the main refrigerant circuit has a high pressure and the refrigerant is in a supercritical state. Therefore, the design pressure of the container of the liquid receiver 73 can be made lower than that of the high-pressure portion, and the cost can be reduced by making the wall of the container thin.

The outdoor unit 2 further includes pressure sensors 110 to 112, temperature sensors 120 to 122, and a control device 100 for controlling the compressor 10, the 2 nd expansion valve 40, the 3 rd expansion valve 71, the flow rate adjustment valve 72, and the flow path switching unit 74.

The pressure sensor 110 detects a pressure PL of a suction port portion of the compressor 10, and outputs a detection value thereof to the control device 100. The pressure sensor 111 detects the discharge pressure PH of the compressor 10, and outputs a detection value thereof to the control device 100. The pressure sensor 112 detects the pressure P1 of the pipe 83 at the outlet of the 2 nd expansion valve 40, and outputs the detected value to the control device 100.

The outdoor unit 2 is provided with the 2 nd expansion valve 40 in the liquid pipe, and is capable of reducing the refrigerant pressure to a pressure lower than the design pressure (for example, 4MPa) of the load device 3 and then sending the refrigerant to the load device 3. Thereby, even if CO is used₂Etc. by using the supercritical refrigerant, it is also possible to use a general-purpose product having the same design pressure as the conventional one as the load device 3.

The temperature sensor 120 detects the discharge temperature TH of the compressor 10, and outputs the detected value to the control device 100. The temperature sensor 121 detects the refrigerant temperature T1 of the pipe 81 at the outlet of the condenser 20, and outputs the detected value to the control device 100. The temperature sensor 122 detects a refrigerant temperature T2 at the outlet of the 1 st passage H1 on the cooled side of the heat exchanger 30, and outputs the detected value to the control device 100.

The flow path switching unit 74 includes: the vacuum cleaner includes

pipes

97 and 98 into which the pipe 96 is bifurcated, a pressure reducing device 77 disposed between the

pipes

97 and 98, and opening/

closing valves

75 and 76 disposed in the

pipes

97 and 98, respectively.

The pipe 97 is connected between the pipe 96 and the intermediate pressure port G3, and the opening/closing valve 75 is provided in the pipe 97. The pressure reducing device 77 and the on-off valve 76 are disposed in series between the outlet of the 2 nd passage H2 and the suction port G1.

The on-off valve 75 and the on-off valve 76 can switch between the destination of the refrigerant in the 2 nd flow path F2 being the intermediate pressure port G3 and the suction port G1 of the compressor 10.

In the present embodiment, the 2 nd flow path F2 controls the discharge temperature TH of the compressor 10 by flowing the two-phase refrigerant, which has been depressurized, into the compressor 10. The refrigerant amount in the main refrigerant circuit can be adjusted by the liquid receiver 73 provided in the 2 nd flow path F2. The 2 nd flow path F2 also ensures supercooling of the refrigerant in the main refrigerant circuit by heat exchange in the heat exchanger 30. The controller 100 switches the destination of the refrigerant by the on-off valve 75 and the on-off valve 76 so that each purpose can be performed under each operating condition.

The outdoor unit 2 further includes: a 3 rd flow path F3 for connecting the pipe 83 and the pipe 92; and an on-off valve 78 provided in the 3 rd flow path F3. The on-off valve 78 is provided to avoid a sudden increase in the pressure P1 of the pipe 83 at the start of the evacuation operation, which will be described later.

The control device 100 includes a CPU (Central Processing Unit) 102, a Memory 104 (a ROM (Read Only Memory) and a RAM (Random Access Memory)), an input/output buffer (not shown) for inputting/outputting various signals, and the like. The CPU102 expands and executes a program stored in the ROM in the RAM or the like. The program stored in the ROM is a program describing a processing procedure of the control device 100. The control device 100 executes control of each device in the outdoor unit 2 in accordance with these programs. The control is not limited to the processing performed by software, and may be performed by dedicated hardware (electronic circuit).

(control during normal operation of the refrigeration cycle apparatus)

The control device 100 performs feedback control on the 3 rd expansion valve 71 so that the discharge temperature TH of the compressor 10 matches the target temperature.

Fig. 2 is a flowchart for explaining control of the 3 rd expansion valve 71. When the discharge temperature TH of the compressor 10 is higher than the target temperature (yes in S21), the controller 100 increases the opening degree of the 3 rd expansion valve 71 (S22). Accordingly, the refrigerant flowing into the intermediate-pressure port G3 or the suction port G1 via the liquid receiver 73 increases, and therefore the discharge temperature TH decreases.

On the other hand, when the discharge temperature TH of the compressor 10 is lower than the target temperature (no in S21 and yes in S23), the control device 100 decreases the opening degree of the 3 rd expansion valve 71 (S24). Accordingly, the refrigerant flowing into the intermediate-pressure port G3 or the suction port G1 via the liquid receiver 73 decreases, and the discharge temperature TH increases.

If the discharge temperature TH is equal to the target temperature (no in S21 and no in S23), the control device 100 maintains the opening degree of the 3 rd expansion valve 71 in the current state.

In this way, the controller 100 controls the opening degree of the 3 rd expansion valve 71 so that the discharge temperature TH of the compressor 10 approaches the target temperature.

Further, the controller 100 feedback-controls the flow rate adjustment valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 matches the target temperature in order to ensure the degree of subcooling SC of the refrigerant at the outlet of the condenser 20.

Fig. 3 is a flowchart for explaining the control of the flow rate adjustment valve 72. When the degree of supercooling SC determined from the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure (approximated by PH) of the condenser 20 is larger than the target value (yes in S31), the controller 100 decreases the opening degree of the flow rate adjustment valve 72 (S32). As a result, the amount of the liquid refrigerant discharged from the liquid receiver 73 decreases, and the amount of the liquid refrigerant in the liquid receiver 73 increases, so that the amount of the refrigerant circulating in the main refrigerant circuit decreases, and the refrigerant temperature T1 increases, and the degree of supercooling SC decreases.

On the other hand, if the degree of supercooling SC determined from the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure of the condenser 20 (approximated by PH) is smaller than the target value (no in S31 and yes in S33), the controller 100 increases the opening degree of the flow rate adjustment valve 72 (S34). As a result, the amount of the liquid refrigerant discharged from the liquid receiver 73 increases, and the amount of the liquid refrigerant accumulated in the liquid receiver 73 decreases, so that the amount of the refrigerant circulating in the main refrigerant circuit increases, and the refrigerant temperature T1 decreases, and therefore the degree of supercooling SC increases.

If the degree of subcooling SC is equal to the target value (no in S31 and no in S33), the control device 100 maintains the opening degree of the flow rate adjustment valve 72 in the current state.

In this way, the controller 100 controls the opening degree of the flow rate adjustment valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 approaches the target temperature.

In addition, the control device 100 uses CO₂In the case of the refrigerant, the control of the compressor 10 and the 2 nd expansion valve 40 is performed so as to use the supercritical region of the refrigerant. For example, in the case where the outside air temperature is higher than the supercritical temperature of the refrigerant in summer or the like, the control device 100 increases the pressure in the high-pressure portion of the main refrigerant circuit by increasing the rotation speed of the compressor 10 to be higher than in spring or autumn. The second expansion valve 40 reduces the pressure, so that the load device 3 can be used in common with a device used in a normal refrigerant. At this time, the 2 nd expansion valve 40 is controlled as follows.

The control device 100 performs feedback control of the 2 nd expansion valve 40 so that the pressure P1 matches the target pressure. The target pressure is set to be about the same as the pressure in the case of using a normal refrigerant such as R410.

Fig. 4 is a flowchart for explaining the control of the 2 nd expansion valve 40. When the pressure P1 is higher than the target pressure (yes in S41), the control device 100 decreases the opening degree of the 2 nd expansion valve 40 (S42). Thereby, the pressure P1 decreases because the decompression amount by the 2 nd expansion valve 40 increases.

On the other hand, in the case where the pressure P1 is lower than the target pressure (no in S41 and no in S43), the control device 100 increases the opening degree of the 2 nd expansion valve 40 (S44). As a result, the pressure P1 increases because the amount of pressure reduction by the 2 nd expansion valve 40 decreases.

If the pressure P1 is equal to the target pressure (no in S41 and no in S43), the control device 100 maintains the opening degree of the 2 nd expansion valve 40 in the current state.

Since the pressure P1 is controlled in this way, the pressure in the load device 3 can be set to be equal to or lower than the design pressure of a device used with a normal refrigerant, and can be shared with a load device of a conventional apparatus using a refrigerant such as R410A.

(switching control of injection flow path)

When the temperature sensor 120 detects an excessive increase in the discharge temperature TH of the compressor 10, the control device 100 opens the on-off valve 75 and closes the on-off valve 76, thereby increasing the injection amount into the compressor 10 and preventing the discharge temperature from further increasing.

At this time, if the intermediate pressure PM increases with an increase in the evaporation temperature or the like while the opening/closing valve 75 is open, the saturation temperature of the refrigerant increases, and therefore the temperature of the refrigerant passing through the 2 nd passage H2 of the heat exchanger 30 also increases, and the cooling in the heat exchanger 30 becomes insufficient, so that the degree of supercooling of the refrigerant in the 2 nd expansion valve 40 may not be ensured.

Therefore, the control device 100 monitors the refrigerant temperature T2 with the temperature sensor 122 in a state where the on-off valve 75 is open, and closes the on-off valve 75 and opens the on-off valve 76 when it detects that the degree of supercooling of the refrigerant cannot be ensured. This can join the refrigerant in the low-pressure side and the refrigerant in the 2 nd flow path F2 to reduce the intermediate pressure PM and ensure a temperature difference in the heat exchanger 30.

Since each device such as the liquid receiver 73 disposed in the 2 nd flow path F2 reduces the pressure in the main refrigerant circuit by the 3 rd expansion valve 71, the design pressure can be reduced, and therefore the manufacturing cost can be reduced. Even when the design pressure is reduced, when the pressure sensor 113 detects an increase in the intermediate pressure PM during operation due to overfilling of the refrigerant, an increase in the outside air temperature, or the like, a safety measure can be taken to release the pressure to the low-pressure side by opening the on-off valve 76.

(control during evacuation operation)

Next, control during the evacuation operation will be described. The evacuation operation is performed by providing an on-off valve 28 or the like to the pipe 85 through which the liquid refrigerant flows in the main refrigerant circuit, and operating the compressor 10 while the pipe 85 is shut off, thereby moving the refrigerant from the load device 3 to the outdoor unit 2 and storing the refrigerant. The evacuation operation is performed by, for example, closing the 2 nd expansion valve 40 before the operation is stopped, or operating the compressor 10 after the opening/closing valve 28 is closed.

In general, the signal instructing the start of the evacuation operation is not particularly transmitted from the load device 3 side to the outdoor unit 2, and the evacuation operation is executed by continuing the normal operation in the outdoor unit 2.

The structure in the evacuation operation is as follows: if the opening/closing valve 28 is closed and the pressure PL of the low pressure portion detected by the pressure sensor 110 is reduced to a set value, the control device 100 stops the compressor 10 to stop the evacuation. Since the compressor 10 is configured not to pass the refrigerant in the stopped state, the refrigerant does not flow back to the load device 3.

However, if the 1 st expansion valve 50 is closed or the on-off valve 28 is closed during the normal operation, the pressure P1 in the

pipes

83, 84, 85 rises rapidly. When the pressure P1 exceeds the design pressure of the

pipes

83, 84, 85 and the load device 3, there is a possibility that a problem such as leakage of the refrigerant may occur, and it is necessary to control the pressure P1 to a range not exceeding the design pressure.

Therefore, the control device 100 temporarily opens the on-off valve 78 to prevent a sudden increase in the pressure P1.

The control of the opening/closing valve 78 performed at the time of evacuation will be described below. Fig. 5 is a flowchart for explaining control of the opening/closing valve 78.

The control device 100 determines in step S51 whether the pressure P1 exceeds the design pressure. The design pressure here is a pressure that can be tolerated if it is short-lived, and may be set to be slightly lower than the actual design pressure.

If the pressure P1 does not exceed the design pressure in step S51 (no in S51), the control device 100 closes the opening/closing valve 78 in step S56 and advances the process to step S57 because the pressure P1 does not need to be decreased.

On the other hand, if it is detected in step S51 that pressure P1 exceeds the design pressure (yes in S51), control device 100 executes the processing of steps S52 to S55 to prevent a sudden increase in pressure P1.

In step S52, the control device 100 determines whether the pressure P1 of the pipe 83 is higher than the pressure P2 of the pipe 92 of the injection flow path.

If P1> P2 (no in S52), the pressure P1 in the pipe 83 does not decrease even if the opening/closing valve 78 is opened, so in step S53, the control device 100 opens the opening/closing valve 76 and closes the opening/closing valve 75 to decrease the pressure in the 2 nd flow path F2. Then, the process advances to step S54.

If P1> P2 (yes in S52), the pressure P1 in the pipe 83 can be reduced when the opening/closing valve 78 is opened, so the process proceeds to step S54 without executing the process of step S53.

Note that, although the pipe 96 and the intermediate pressure port G3 may be directly connected without the flow path switching unit 74, in this case, the processing of steps S52 and S53 is not executed, and if the determination of step S51 is yes, the processing may quickly proceed to step S54.

In step S54, the controller 100 opens the on-off valve 78 and closes the flow rate adjustment valve 72 to introduce the intermediate pressure in the 2 nd flow path F2 to the pipe 83, thereby lowering the pressure P1. This can prevent the pressure P1 from exceeding the design pressure of the

pipes

83 and 84 and the load device 3.

Although not necessarily required, the controller 100 preferably reduces the rotation speed of the compressor 10 and suppresses a further increase in the pressure P1 of the pipe 83 in step S55. When the pressure P1 suddenly rises temporarily, the process of step S55 may be executed, and then, when the pressure P1 falls, the process of step S56 may be followed to return the rotation speed of the compressor 10 to the original rotation speed in order to shorten the time of the evacuation operation.

Then, in step S57, the process temporarily returns to the main flow, and thereafter the process of the flowchart of fig. 5 is repeatedly executed.

Finally, the present embodiment is summarized again with reference to the drawings. As shown in fig. 1, the present disclosure relates to an outdoor unit 2 of a refrigeration cycle apparatus 1 configured to be connected to a load device 3 including a 1 st expansion valve 50 corresponding to a "1 st expansion device" and an evaporator 60. The outdoor unit 2 includes: a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connection to the load device 3, a 1 st flow path F1, a compressor 10, a condenser 20, a 2 nd expansion valve 40 corresponding to a "2 nd expansion device", a 2 nd flow path F2, a 3 rd expansion valve 71 corresponding to a "3 rd expansion device", a liquid receiver 73, a 3 rd flow path F3, and an opening/closing valve 78. The 1 st flow path F1 is a flow path from the refrigerant inlet port PI2 to the refrigerant outlet port PO2, and forms a circulation flow path for circulating the refrigerant together with the load device 3. The compressor 10, the condenser 20, and the 2 nd expansion valve 40 are disposed in the 1 st flow path F1. The 2 nd flow path F2 is configured to branch from a portion between the condenser 20 and the 2 nd expansion valve 40 in the 1 st flow path F1, and to return the refrigerant passing through the condenser 20 to the compressor 10. The 3 rd expansion valve 71 and the liquid receiver 73 are disposed in the 2 nd flow path F2 in this order from the branching point of the 1 st flow path F1 of the 2 nd flow path F2. The 3 rd flow path F3 connects the portion of the 1 st flow path F1 between the 2 nd expansion valve 40 and the refrigerant outlet port PO2 to the refrigerant inlet of the liquid receiver 73. The on-off valve 78 is disposed in the 3 rd flow path F3.

As shown in fig. 5, the opening/closing valve 78 is configured to open when the pressure P1 of the portion between the 2 nd expansion valve 40 and the refrigerant outlet port PO2 in the 1 st flow path F1 exceeds a threshold value corresponding to the design pressure (yes in S51).

Since the 3 rd flow path F3 and the opening/closing valve 78 are thus provided, even if the pressure P1 rises rapidly at the start of the evacuation operation, the pressure P1 can be rapidly reduced. Thereby, the supercritical region is used in the high-pressure partCO of₂For example, in the case of a refrigerant, piping and the load device 3 having a low design pressure can be used.

In addition, by disposing the liquid receiver 73 in the 2 nd flow path F2, even when CO in the supercritical region is used₂The refrigerant may be stored in the liquid receiver 73 in a liquid refrigerant state. Further, the super-cooling of the pipe portion through which the liquid refrigerant flows can be ensured, and the performance of the refrigeration cycle apparatus can be improved.

The outdoor unit 2 further includes a flow rate adjustment valve 72, and the flow rate adjustment valve 72 is disposed in the 2 nd flow path F2 and configured to adjust the discharge flow rate of the liquid refrigerant from the liquid receiver 73.

The outdoor unit 2 further includes a heat exchanger 30, and the heat exchanger 30 includes a 1 st path H1 and a 2 nd path H2, and is configured to exchange heat between the refrigerant flowing through the 1 st path H1 and the refrigerant flowing through the 2 nd path H2. The 1 st passage H1 of the heat exchanger 30 is disposed between the condenser 20 of the 1 st passage F1 and a branch point at which the pipe 91 branches off from the pipe 82, and the 2 nd passage H2 of the heat exchanger 30 is disposed between the flow rate adjustment valve 72 of the 2 nd passage F2 and the compressor 10.

The compressor 10 has a discharge port G2, a suction port G1, and a medium pressure port G3. The outdoor unit 2 further includes a flow path switching unit 74, and the flow path switching unit 74 is configured to be able to switch the destination of the refrigerant passing through the 2 nd flow path F2 to either the medium pressure port G3 or the suction port G1. As shown in fig. 5, the flow path switching unit 74 is configured to select the suction port G1 as the destination when the pressure P1 of the portion of the 1 st flow path F1 downstream of the 2 nd expansion valve 40 is lower than the pressure P2 of the liquid receiver 73 (no in S52).

With such a configuration, since the pressure of the liquid receiver 73 is reduced when the pressure of the liquid receiver 73 increases, an operating state in which the pressure of the liquid receiver 73 increases can be allowed, and the operating range can be expanded.

The outdoor unit 2 further includes: a pressure sensor 112 for detecting a pressure P1 in a portion of the 1 st flow path F1 downstream of the 2 nd expansion valve 40; and a control device 100 for controlling the compressor 10 and the on-off valve 78. As shown in fig. 5, when the pressure P1 detected by the pressure sensor 112 changes from a state lower than the threshold value to a state higher than the threshold value (yes in S51), the control device 100 is configured to open the on-off valve 78(S54) and reduce the rotation speed of the compressor 10 (S55).

By linking the on-off valve 78 and the compressor 10 in this way, the pressure P1 can be quickly reduced even if the pressure P1 rises sharply.

While the present embodiment has been described above by exemplifying a refrigeration apparatus including the refrigeration cycle device 1, the refrigeration cycle device 1 may be used in an air conditioner or the like.

It should be understood that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope.

Claims

1. An outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a 1 st expansion device and an evaporator, the outdoor unit comprising:

a refrigerant outlet port and a refrigerant inlet port for connection with the load device;

a 1 st flow path which is a flow path from the refrigerant inlet port to the refrigerant outlet port and forms a circulation flow path for circulating a refrigerant together with the load device;

a compressor, a condenser, and a 2 nd expansion device disposed in the 1 st flow path;

a 2 nd flow path configured to branch from a portion of the 1 st flow path between the condenser and the 2 nd expansion device and return the refrigerant passing through the condenser to the compressor;

a 3 rd expansion device and a liquid receiver which are arranged in the 2 nd flow path in the order from the branch point of the 1 st flow path in the 2 nd flow path;

a 3 rd flow path which connects a portion between the 2 nd expansion device and the refrigerant outlet port in the 1 st flow path and the refrigerant inlet of the liquid receiver; and

and an on-off valve disposed in the 3 rd flow path.

2. The outdoor unit of claim 1,

the opening/closing valve is configured to open when a pressure of a portion between the 2 nd expansion device and the refrigerant outlet port in the 1 st flow path exceeds a threshold value.

3. The outdoor unit of claim 1,

the outdoor unit further includes a flow rate adjustment valve that is disposed in the 2 nd flow path and adjusts a discharge flow rate of the liquid refrigerant from the liquid receiver.

4. The outdoor unit of claim 3,

the outdoor unit further includes a heat exchanger having a 1 st path and a 2 nd path, and configured to exchange heat between the refrigerant flowing through the 1 st path and the refrigerant flowing through the 2 nd path,

the 1 st passage of the heat exchanger is disposed between the condenser and the branch point of the 1 st passage,

the 2 nd passage of the heat exchanger is disposed between the flow rate adjustment valve of the 2 nd flow path and the compressor.

5. The outdoor unit of claim 1,

the compressor has:

a discharge port;

a suction port; and

a medium-voltage port is arranged at the middle part of the shell,

the outdoor unit further includes a flow path switching unit configured to be capable of switching a destination of the refrigerant passing through the 2 nd flow path to either the intermediate pressure port or the suction port,

the flow path switching unit is configured to select the suction port as the destination when a pressure in a portion of the 1 st flow path downstream of the 2 nd expansion device is lower than a pressure of the accumulator.

6. The outdoor unit of claim 1,

the outdoor unit further includes:

a pressure sensor that detects a pressure in a portion of the 1 st flow path downstream of the 2 nd expansion device; and

a control device for controlling the compressor and the on-off valve,

the control device is configured to open the on-off valve and reduce the rotation speed of the compressor when a detection value of the pressure sensor changes from a state lower than a threshold value to a state higher than the threshold value.

7. A refrigeration cycle device is provided with:

an outdoor unit according to any one of claims 1 to 6; and

the load device.