WO2024106482A1 - Refrigeration system - Google Patents

Abstract

The present disclosure discloses a refrigeration system capable of improving the efficiency of a two-stage compression refrigeration system employing a low-stage compressor and a high-stage compressor, by switching a switching means in accordance with an operating condition.　A refrigeration system according to the present disclosure comprises a refrigeration cycle circuit in which an outdoor unit 10 including a low-stage compressor 11, a high-stage compressor 12, an outdoor heat exchanger 15, an accumulator 13 disposed between the low-stage compressor 11 and the high-stage compressor 12, and an oil separator disposed on a discharge side of the high-stage compressor 12, an indoor unit 20 including an indoor heat exchanger 22, and a cooling apparatus 30 including a cooling heat exchanger 31 are connected, together, the refrigeration system being provided with an intercooler 65 disposed between the low-stage compressor 11 and the accumulator 13, and a three-way valve 67 for switching a refrigerant from the low-stage compressor 11 to the accumulator or the intercooler 65.

Description

Refrigeration System

This disclosure relates to a refrigeration system.

Patent Document 1 discloses a refrigeration system that includes a two-stage compressor, an intercooler, a gas cooler, and an intermediate heat exchanger connected to the gas cooler, in which the intermediate heat exchanger exchanges heat between a refrigerant from the gas cooler and a refrigerant diverted from a high-pressure side refrigerant flow path and reduced in pressure by an expansion valve, and the refrigerant that has passed through the expansion valve and has been heat exchanged in the intermediate heat exchanger is caused to flow into a high-stage side suction port of the second stage of the two-stage compressor.
Patent Document 2 discloses a heat source unit and a refrigeration device that prevent gas refrigerant in a gas-liquid separator from being stopped from being sent to an intermediate flow path during high outdoor air temperatures. In this heat source unit and refrigeration device, a control unit executes a first operation of increasing the rotation speed of the third compressor when a first condition is satisfied that an intermediate pressure corresponding to the pressure in the intermediate flow path is higher than a predetermined value during operation of the first compressor, the second compressor, and the third compressor.

JP 2013-167386 A JP 2022-039365 A

A first aspect of the present disclosure provides a refrigeration system that can increase the efficiency of a two-stage compression refrigeration system using a low-stage compressor and a high-stage compressor by switching a switching means depending on operating conditions.
A second aspect of the present disclosure provides a refrigeration system including a refrigeration circuit with a simple configuration, and capable of improving refrigeration capacity.

A first aspect of the refrigeration system of the present disclosure comprises a refrigeration cycle circuit connecting a low-stage compressor, a high-stage compressor, an outdoor heat exchanger, an outdoor unit having an oil separator arranged on the discharge side of the high-stage compressor, an indoor unit having an indoor heat exchanger, and a refrigeration equipment having a refrigeration heat exchanger, an intercooler arranged between the low-stage compressor and the high-stage compressor, and a switching means for switching the refrigerant from the low-stage compressor to the suction side of the high-stage compressor or the intercooler.
In addition, this specification includes all the contents of Japanese Patent Application No. 2022-183979 filed in Japan on November 17, 2022.

A refrigeration system of a second aspect of the present disclosure includes a refrigeration circuit provided with a plurality of compressors, a heat source side heat exchanger, a plurality of user side heat exchangers, and a gas-liquid separator, the plurality of compressors being composed of a low stage compressor and a high stage compressor, the plurality of user side heat exchangers being composed of a first user side heat exchanger and a second user side heat exchanger having a refrigerant evaporation temperature lower than that of the first user side heat exchanger, the refrigeration circuit being provided with a switching mechanism that causes the refrigerant discharged from the high stage compressor and flowing through at least one of the heat source side heat exchanger and the first user side heat exchanger to flow to the gas-liquid separator, and a throttling mechanism that adjusts the pressure of the refrigerant being provided between the heat source side heat exchanger, the first user side heat exchanger, and the gas-liquid separator.
In addition, this specification includes all the contents of Japanese Patent Application No. 2023-142103 filed in Japan on September 1, 2023.

According to the first aspect of the present disclosure, by switching the switching means depending on the operating conditions, it is possible to increase the efficiency of a two-stage compression refrigeration system using a low-stage compressor and a high-stage compressor.
According to the second aspect of the present disclosure, a refrigeration circuit having a simple configuration is provided, and stable operation can be achieved.

FIG. 1 is a circuit diagram of a refrigeration system showing an operation during cooling operation in the first embodiment. FIG. 2 is a block diagram showing a control configuration according to the first embodiment. FIG. 3 is a diagram showing a refrigeration circuit of a refrigeration system according to a second embodiment. FIG. 4 is a block diagram of a refrigeration system according to a second embodiment. FIG. 5 is a circuit diagram showing a refrigeration circuit of a refrigeration system in a heating operation according to a second embodiment. FIG. 6 is a circuit diagram showing a refrigeration circuit of a refrigeration system in a heating operation according to a second embodiment. FIG. 7 is a circuit diagram showing a refrigeration circuit of a refrigeration system in a heating operation according to a second embodiment. FIG. 8 is a ph diagram showing the state of the refrigerant in the refrigeration circuit in the second embodiment. FIG. 9 is a flowchart showing the operation of the refrigeration system in the second embodiment. FIG. 10 is a circuit diagram showing a refrigeration circuit of a refrigeration system in a refrigerant recovery and vacuum pumping operation according to the second embodiment. FIG. 11 is a circuit diagram showing a refrigeration circuit of a refrigeration system during a refrigerant charging operation in accordance with a second embodiment. FIG. 12 is a circuit diagram showing a refrigeration circuit of a refrigeration system in an adjustment operation according to the second embodiment.

(Knowledge and other information that forms the basis of this disclosure)
At the time when the inventors came up with the idea of the refrigeration system of the first aspect of the present disclosure, there was technology in which refrigerant discharged from the low-stage side of the compressor was heat exchanged in an intercooler and returned to the high-stage side of the compressor.

When using such conventional technology, it is better to install an intercooler to improve efficiency in the summer, but the inventors discovered a problem that when trying to utilize exhaust heat in the winter, the intercooler causes heat to escape, making it impossible to fully utilize the exhaust heat.In order to solve this problem, the inventors came up with the subject matter of the present disclosure.
The present disclosure provides a refrigeration system that can increase the efficiency of a two-stage compression refrigeration system using a low-stage compressor and a high-stage compressor by switching a switching means depending on operating conditions.

Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming more redundant than necessary and to facilitate understanding by those skilled in the art.
It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to the drawings.
[1-1-1. Configuration of refrigeration system]
FIG. 1 is a diagram showing a refrigeration cycle circuit of a refrigeration system 1 according to a first embodiment.
As shown in FIG. 1 , the refrigeration system 1 includes an outdoor unit 10 , an indoor unit 20 , and a cooling device 30 .
The indoor unit 20 provides air conditioning within a store, such as a convenience store or supermarket, and the refrigeration equipment 30 provides cooling within refrigerated showcases and freezer showcases that serve as cooling storage facilities installed within the store.

The outdoor unit 10 includes a low stage compressor 11 and two high stage compressors 12, 12. The two high stage compressors 12 are connected in parallel to the low stage compressor 11.
An accumulator 13 is disposed between the low stage compressor 11 and the high stage compressor 12 .
That is, the refrigerant discharged from the low-stage compressor 11 is separated into gas and liquid by the accumulator 13 , and only the gas refrigerant is sent to the high-stage compressor 12 .

An oil separator 14 is connected to the discharge side of the high-stage compressor 12. An outdoor heat exchanger 15 is connected to the oil separator 14 via a refrigerant pipe 40.
A first heating pipe 41 that is connected to the refrigerant pipe 40 between the indoor unit 20 and the accumulator 13 is connected to the refrigerant pipe 40 between the oil separator 14 and the outdoor heat exchanger 15 .
In addition, a first outdoor return pipe 42 is connected to the refrigerant piping 40 between the oil separator 14 and the outdoor heat exchanger 15, and is connected to the refrigerant piping 40 between the cooling equipment 30 and the low-stage compressor 11.

A first switching mechanism 50 is provided between the oil separator 14 and the outdoor heat exchanger 15. The first switching mechanism 50 includes a first cooling valve 51 that opens and closes the refrigerant pipe 40 between the oil separator 14 and the outdoor heat exchanger 15, a first heating valve 52 that is provided in the middle of the first heating pipe 41 and opens and closes the first heating pipe 41, and an outdoor refrigerant return valve 53 that is provided in the middle of the first outdoor return pipe 42 and opens and closes the first outdoor return pipe 42.

The gas-liquid separator 16 is connected to the outdoor heat exchanger 15 via a refrigerant pipe 40. The gas-liquid separator 16 is connected to a cold-use heat exchanger 31 of the cold-use equipment 30 via the refrigerant pipe 40 and a cold-use inlet-side expansion mechanism 32. The cold-use heat exchanger 31 is connected to the low-stage compressor 11 via a cold-use outlet-side pressure adjustment mechanism 33.
A second cooling pipe 43 that is connected to the indoor heat exchanger 22 via an indoor expansion mechanism 21 is connected to the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16 .
A second heating pipe 44 that is connected to the indoor heat exchanger 22 is connected to the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16 .
A second outdoor return pipe 45 is connected to the refrigerant piping 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16, and is connected to the refrigerant piping 40 between the cold-installed heat exchanger 31 and the gas-liquid separator 16.

A second switching mechanism 54 is provided between the outdoor heat exchanger 15 and the gas-liquid separator 16. The second switching mechanism 54 includes a second cooling valve 55 for opening and closing the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16, a third cooling valve 56 provided in the middle of the second cooling pipe 43 for opening and closing the second cooling pipe 43, and a second heating valve 57 provided in the middle of the second heating pipe 44 for opening and closing the second heating pipe 44.
A refrigerant return expansion mechanism 58 that controls the flow rate of the second outdoor return pipe 45 is provided in the middle of the second outdoor return pipe 45 .
A check valve 59 is provided downstream of each of the second cooling valve 55, the third cooling valve 56, and the second heating valve 57.

The indoor heat exchanger 22 is connected to the high-stage compressor 12 via a refrigerant pipe 40 , an on-off valve 23 , and an accumulator 13 .
Furthermore, in this embodiment, a gas refrigerant return pipe 60 is provided to send the gas refrigerant from the gas-liquid separator 16 to the suction side of the accumulator 13. A gas refrigerant flow rate control valve 61 is provided in the middle of the gas refrigerant return pipe 60.

In the present embodiment, an intercooler 65 is provided between the low-stage compressor 11 and the accumulator 13 .
A bypass pipe 66 that bypasses the intercooler 65 is provided in the refrigerant piping between the low-stage compressor 11 and the accumulator 13. A three-way valve 67 is provided at a connection between the bypass pipe 66 and the refrigerant piping as a switching means for switching whether the refrigerant sent from the low-stage compressor 11 is sent to the accumulator 13 or the intercooler 65.

[1-2. motion]
Next, the operation of this embodiment will be described.
First, the cooling operation will be described.
When the cooling operation is performed, as shown in FIG. 1, the first cooling valve 51 is opened, and the second cooling valve 55 and the third cooling valve 56 are opened. The first high-load valve 52, the second heating valve 57, the first high-load valve, the outdoor return valve, and the outdoor return expansion mechanism are all closed.
In addition, the three-way valve 67 is switched so that the refrigerant sent from the low-stage compressor 11 is sent to the intercooler 65 .
In this state, by driving the low stage compressor 11 and each high stage compressor 12, the refrigerant compressed by the low stage compressor 11 is sent to the intercooler 65 and cooled by the intercooler 65. The cooled refrigerant is sent to each high-stage compressor 12 via the accumulator 13, where it is further compressed and discharged toward the oil separator 14.

The refrigerant that has passed through the oil separator 14 is sent through a first cooling valve 51 to the outdoor heat exchanger 15, where it exchanges heat with outside air.
The refrigerant after heat exchange is sent to the gas-liquid separator 16 via the second cooling valve 55 and to the indoor heat exchanger 22 via the third cooling valve 56 .
In the indoor heat exchanger 22, the refrigerant exchanges heat with the indoor air to cool the indoor air. The refrigerant that has exchanged heat with the indoor air is returned to each high-stage compressor 12 via the accumulator 13.

Meanwhile, a portion of the refrigerant from the gas-liquid separator 16 is sent to the refrigeration heat exchanger 31 via the refrigeration inlet expansion mechanism 32, where it undergoes heat exchange to cool the refrigeration equipment 30. The refrigerant that has undergone heat exchange in the refrigeration heat exchanger 31 is returned to the low-stage compressor 11 via the refrigeration inlet expansion mechanism 32.

Next, the operation when performing the heating operation will be described.
2 is a circuit diagram of the refrigeration system 1 showing the operation of the heating mode, in which the flow of the refrigerant is indicated by arrows.
As shown in FIG. 2, when heating operation is performed, the first heating valve 52 and the second heating valve 57 are opened, and the first cooling valve 51, the second cooling valve 55, the third cooling valve 56 and the outdoor refrigerant return valve 53 are closed.
In addition, the three-way valve 67 is switched so that the refrigerant sent from the low-stage compressor 11 is sent directly to the accumulator 13 via the bypass pipe 66 without passing through the intercooler 65 .

In this state, by driving the low-stage compressor 11 and each high-stage compressor 12, the refrigerant compressed by the low-stage compressor 11 is sent to each high-stage compressor 12 via the accumulator 13, further compressed by each high-stage compressor 12, and discharged toward the oil separator 14.
The refrigerant that has passed through the oil separator 14 is sent to the indoor heat exchanger 22 through the first heating valve 52, where it exchanges heat with indoor air to heat the indoor air.

The refrigerant that has exchanged heat in the indoor heat exchanger 22 is sent to the gas-liquid separator 16 via the second heating valve 57, and then sent to the cold-setting heat exchanger 31 via the cold-setting inlet expansion mechanism 32, where it undergoes heat exchange and cools the cold-setting equipment 30.
The refrigerant that has exchanged heat in the cold-setting heat exchanger 31 is returned to the low-stage compressor 11 via the cold-setting outlet side pressure adjustment mechanism 33 .
That is, the refrigeration system 1 of the present disclosure is configured such that during heating, the indoor heat exchanger 22 functions as a gas cooler or a radiator, and the outdoor heat exchanger 15 is not used.

In this embodiment, a gas refrigerant return pipe 60 is provided to send the gas refrigerant from the gas-liquid separator 16 to the suction side of the accumulator 13. During cooling operation, the opening of the gas refrigerant flow control valve 61 is controlled to control the return amount of the gas refrigerant from the gas-liquid separator 16, thereby generating a differential pressure of the refrigerant sent to the indoor heat exchanger 22.
This makes it possible to control the pressure by adding a specified value to the evaporation temperature of the indoor heat exchanger 22, which has a high evaporation temperature. Therefore, by using carbon dioxide (R744), a natural refrigerant with high environmental friendliness, the efficiency of the air conditioning temperature range, which is a weak point, can be improved, and the efficiency of the entire refrigeration system can be improved.

Furthermore, in this embodiment, during cooling operation, the refrigerant sent from the low-stage compressor 11 is sent to the intercooler 65, cooled by the intercooler 65, and then sent to each high-stage compressor 12 via the accumulator 13. Therefore, during cooling operation, the compression efficiency of the high-stage compressors can be improved.
On the other hand, during heating operation, the refrigerant sent from the low-stage compressor 11 is sent directly to the accumulator 13 without passing through the intercooler 65, so that the heat pump with a two-stage compression refrigerant circuit can achieve high efficiency in utilizing exhaust heat during heating operation.

[1-3. Effects, etc.]
As described above, in this embodiment, the system comprises an outdoor unit 10 having a low-stage compressor 11, a high-stage compressor 12, an outdoor heat exchanger 15, an accumulator 13 arranged between the low-stage compressor 11 and the high-stage compressor 12, an oil separator arranged on the discharge side of the high-stage compressor 12, an indoor unit 20 having an indoor heat exchanger 22, and a cooling equipment 30 having a cooling heat exchanger 31, a refrigeration cycle circuit connecting the above, an intercooler 65 arranged between the low-stage compressor 11 and the accumulator 13, and a three-way valve 67 (switching means) that switches the refrigerant from the low-stage compressor 11 to the accumulator 13 or the intercooler 65.
As a result, by switching the three-way valve 67 depending on the operating conditions, the efficiency of the two-stage compression refrigeration system using the low stage compressor 11 and the high stage compressor 12 can be improved.

In addition, in this embodiment, during cooling operation, the three-way valve 67 (switching means) switches so as to send the refrigerant from the low-stage compressor 11 to the intercooler 65 .
As a result, during cooling operation, the refrigerant sent from the low-stage compressor 11 is sent to the intercooler 65, cooled by the intercooler 65, and then sent to the high-stage compressor 12, thereby improving the compression efficiency of the high-stage compressor 12.

In addition, in this embodiment, during heating operation, the three-way valve 67 (switching means) switches so as to send the refrigerant from the low-stage compressor 11 directly to the accumulator 13 .
As a result, during heating operation, the refrigerant sent from the low-stage compressor 11 is sent directly to the accumulator 13 without passing through the intercooler 65, thereby making it possible to achieve high efficiency in utilizing exhaust heat during heating operation.

(Embodiment 2)
(Knowledge and other information that forms the basis of this disclosure)
At the time when the inventors came up with the idea of the refrigeration system of the second aspect of the present disclosure, there was a refrigeration system that had a low-stage compressor, a high-stage compressor, multiple user-side heat exchangers, and a heat source-side heat exchanger shared with these user-side heat exchangers in one refrigeration circuit, and each user-side heat exchanger operated in a different evaporation temperature range. As a result, in this refrigeration system, for example, air conditioning of a conditioned space and cooling of the inside of a refrigerator are performed simultaneously.
Among such refrigeration systems, there is known one that includes a gas-liquid separator. In such refrigeration systems, the refrigerant delivered from the compressor is made to flow through the gas-liquid separator into the utilization-side heat exchanger, thereby improving the refrigeration capacity.

In the above-mentioned refrigeration system, there is an operation in which the utilization side heat exchanger is switched between cooling and heating. In either operation of such a refrigeration system, the refrigerant discharged from the compressor is made to flow through the utilization side heat exchanger via a gas-liquid separator, and therefore the configuration of the refrigeration circuit of the refrigeration system may become complicated. The inventors have found a problem, and have come to constitute the subject of the present disclosure in order to solve the problem.
In view of the above, the present disclosure provides a refrigeration system that includes a refrigeration circuit with a simple configuration and that can improve the refrigeration capacity.

Hereinafter, a second embodiment corresponding to the second aspect of the present disclosure will be described with reference to the drawings.
[2-1-1. Configuration of refrigeration system]
Fig. 3 is a circuit diagram showing the refrigeration system 101 in the first embodiment. In Fig. 3, for convenience of explanation, the opening and closing device in the open state is shown in white, and the opening and closing device in the closed state and the expansion mechanism are shown in black. In Fig. 3, for convenience of explanation, the pipes through which the refrigerant flows are shown in thick lines, and the pipes through which the refrigerant does not flow are shown in thin lines. In the subsequent circuit diagrams, the opening and closing device and the pipes are shown in the same manner as in Fig. 3.
As shown in FIG. 3, the refrigeration system 101 includes an outdoor unit 110, an indoor unit 120, and a cooling equipment 130, which are connected to each other by refrigerant piping to form a refrigeration circuit 2 that functions as a flow path through which the refrigerant flows.
In this embodiment, the refrigerant used in the refrigeration circuit 2 is, for example, carbon dioxide (R744), a natural refrigerant that is non-flammable and non-toxic.

The indoor unit 120 includes a user-side heat exchanger, an indoor heat exchanger 122. The indoor unit 120 conditions the air inside a store, which is a space to be conditioned, based on a temperature setting set by a user in a store such as a convenience store or a supermarket.
The refrigeration equipment 130 includes a refrigeration heat exchanger 132, which is a user-side heat exchanger. The refrigeration equipment 130 cools the inside of a refrigerated showcase or a freezer showcase, which is a cooling storage facility installed in a store, based on a set temperature set by a user.

In the refrigeration system 101, when the set temperature of the indoor unit 120 is set, the rotation frequency of each compressor and the airflow rate of the fans 118 and 128 are determined based on the temperature difference between the set temperature and the temperature in the conditioned space in which the indoor unit 120 is installed. Furthermore, in the refrigeration system 101, when the set temperature of the indoor unit 120 is set, the opening degree of the throttle valve provided in the indoor unit 120 is determined so that the degree of superheat of the refrigerant at each of the inlet and outlet sides of the indoor heat exchanger 122 becomes a specified value. In this way, the refrigeration system 101 operates so that the conditioned space becomes the set temperature.

Similarly, in the refrigeration system 101, when the set temperature of the refrigeration equipment 130 is set, the rotation frequency of each compressor and the airflow rate of the fans 118 and 138 are determined based on the temperature difference between the set temperature and the temperature inside the showcase. Furthermore, in the refrigeration system 101, when the set temperature of the refrigeration equipment 130 is set, the opening degree of the throttle valve provided in the refrigeration equipment 130 is determined so that the degree of superheat of the refrigerant at each of the inlet and outlet sides of the refrigeration heat exchanger 132 becomes a specified value. In this way, the refrigeration system 101 operates so that the temperature inside the showcase becomes the set temperature.
Hereinafter, the operation in which the refrigeration system 101 conditions the air in the conditioned space and cools the inside of the showcase will be referred to as a first operation mode.

The outdoor unit 110 functions as a so-called heat source device. The outdoor unit 110 is formed by sequentially connecting a plurality of compressors, a first switching mechanism 150, an outdoor heat exchanger 115, a second switching mechanism 154, and a gas-liquid separator 116.
The outdoor heat exchanger 115 corresponds to the "heat source side heat exchanger" in this disclosure.

In this embodiment, the outdoor unit 110 is provided with a mechanism in which a low-stage compressor 111 and two high- stage compressors 112, 112 are configured as a two-stage compressor. The two high- stage compressors 112, 112 are both connected in series to the low-stage compressor 111. The two high- stage compressors 112, 112 are connected in parallel to each other downstream of the low-stage compressor 111.
Each of the compressors is a rotary compressor having a compression mechanism driven by, for example, a motor. Each of the high stage compressors 112 is driven to discharge the refrigerant at a higher discharge pressure than the low stage compressor 111.

An accumulator 113 is disposed between the low-stage compressor 111 and the high-stage compressor 112. The accumulator 113 functions as a flow divider that distributes the oil sent from the oil separator 114 approximately evenly to each of the high-stage compressors 112.

An oil separator 114 is connected to the discharge side of the high-stage compressor 112. A first switching mechanism 150 is connected to the oil separator 114. That is, the first switching mechanism 150 is connected to the discharge pipe of the high-stage compressor 112 via the oil separator 114.

The first switching mechanism 150 is a mechanism that switches the refrigerant sent from the high-stage compressor 112 in the refrigeration circuit 2 so that it flows through one of multiple flow paths.

The first switching mechanism 150 includes a pipe 140 that connects the oil separator 114 and the outdoor heat exchanger 115. A first cooling valve 151 is provided in the pipe 140. The first cooling valve 151 is located in the pipe 140 between the high-stage compressor 112 and the outdoor heat exchanger 115. The first cooling valve 151 is an opening/closing device that opens and closes the pipe 140. In this embodiment, the first cooling valve 151 is an opening/closing device that can be switched between an open state in which refrigerant can flow through the pipe 140, and a closed state in which refrigerant does not flow through the pipe 140.

In the piping 140, one end of the first heating piping 141 is connected between the oil separator 114 and the first cooling valve 151. The first heating piping 141 is provided with a first heating valve 152. The first heating valve 152 is an opening and closing device that opens and closes the first heating piping 141.

The other end of the first heating pipe 141 is connected to a pipe 171 that connects the indoor heat exchanger 122 of the indoor unit 120 and the suction side of the high-stage compressor 112. As a result, the discharge side of the high-stage compressor 112 is connected to the indoor heat exchanger 122 via the first heating pipe 141.
An on-off valve 123 is provided in the pipe 171 between the point where the other end of the first heating pipe 141 is connected and the accumulator 113. The on-off valve 123 is an on-off device that opens and closes the pipe 171.

In the piping 140, one end of the first outdoor return piping 142 is connected between the first cooling valve 151 and the outdoor heat exchanger 115. The first outdoor return piping 142 is provided with an outdoor refrigerant return valve 153. The outdoor refrigerant return valve 153 is an opening and closing device that opens and closes the first outdoor return piping 142. The other end of the first outdoor return piping 142 is connected between the cooling heat exchanger 132 of the cooling equipment 130 and the suction side of the low-stage compressor 111.

A cooling outlet pressure adjustment mechanism 133 is provided in the piping 172 between the point where the other end of the first outdoor return piping 142 is connected and the cooling heat exchanger 132. The cooling outlet pressure adjustment mechanism 133 is an opening/closing device that can change the opening degree from fully closed to fully open. The cooling outlet pressure adjustment mechanism 133 functions as a so-called throttle valve that can change the pressure of the refrigerant flowing through the piping 172 by adjusting the opening degree.

In this manner, the first switching mechanism 150 is connected to the outdoor heat exchanger 115 , the indoor heat exchanger 122 , the cold-use heat exchanger 132 , and the low-stage compressor 111 .
The first switching mechanism 150 switches the flow path of the refrigerant in the refrigeration circuit 2 by opening and closing a first cooling valve 151, a first heating valve 152, and an outdoor refrigerant return valve 153, and causes the refrigerant discharged from the high-stage compressor 112 to flow to either the outdoor heat exchanger 115 or the indoor heat exchanger 122.

For example, when the refrigeration system 101 performs a cooling operation, the refrigerant discharged from the high-stage compressor 112 flows into the outdoor heat exchanger 115 .
When the refrigeration system 101 performs a heating operation, the refrigerant discharged from the high-stage compressor 112 flows to the indoor heat exchanger 122. When the refrigeration system 101 performs a heating operation and the amount of heating heat becomes excessive, the refrigerant discharged from the high-stage compressor 112 flows to both the outdoor heat exchanger 115 and the indoor heat exchanger 122.

As described above, the first switching mechanism 150 includes the first cooling valve 151 , the first heating valve 152 , and the outdoor refrigerant return valve 153 .
In this embodiment, the first cooling valve 151, the first heating valve 152, and the outdoor refrigerant return valve 153 are electrically operated on-off valves that are opened and closed by an actuator or the like.
Therefore, the first switching mechanism 150 can switch the flow path of the refrigerant in the refrigeration circuit 2 without stopping the low stage compressor 111 and the high stage compressor 112. In other words, the refrigeration system 101 can switch operations related to air conditioning and cooling inside the showcase without stopping the low stage compressor 111 and the high stage compressor 112.
In the first switching mechanism 150, the first cooling valve 151, the first heating valve 152, and the outdoor refrigerant return valve 153 may be opening/closing devices whose opening degree can be adjusted from fully closed to fully open.
The first switching mechanism 150 corresponds to the "other switching mechanism" of the present disclosure.

A second switching mechanism 154 is provided on the piping 140 on the opposite side of the first switching mechanism 150 with the outdoor heat exchanger 115 interposed therebetween. That is, the second switching mechanism 154 is connected to the outdoor heat exchanger 115 via the piping 140.
The second switching mechanism 154 connects the outdoor heat exchanger 115, the indoor heat exchanger 122, the cold-installed heat exchanger 132, and the gas-liquid separator 116 to one another. The second switching mechanism 154 is a mechanism that switches the refrigerant to flow through any one of a plurality of flow paths that connect the outdoor heat exchanger 115, the indoor heat exchanger 122, the cold-installed heat exchanger 132, and the gas-liquid separator 116 to one another.

The second switching mechanism 154 is formed by connecting the ends of the first to fourth pipes 173, 174, 175, and 176 at connection parts A, B, C, and D in a ring shape.
A throttling mechanism 55 is disposed in the first pipe 173. A refrigerant return expansion mechanism 58 that controls the flow rate is disposed in the second pipe 174.
A check valve 159 is disposed in the third pipe 175. A check valve 159 is disposed in the fourth pipe 176. In this embodiment, the check valve 159 is a so-called automatic valve that is opened and closed by the flow of the refrigerant.

The throttling mechanism 155 and the refrigerant return expansion mechanism 158 are flow control valves whose opening can be changed from fully closed to fully open. The throttling mechanism 155 can change the pressure of the refrigerant flowing through the first pipe 173 by adjusting its opening. The refrigerant return expansion mechanism 158 can change the pressure of the refrigerant flowing through the second pipe 174 by adjusting its opening. In other words, the throttling mechanism 155 and the refrigerant return expansion mechanism 158 function as so-called throttling valves.

In the third pipe 175, the check valve 159 is disposed so that the refrigerant flows only from the connection portion B toward the connection portion C. In the fourth pipe 176, the check valve 159 is disposed so that the refrigerant flows only from the connection portion C toward the connection portion D.
The throttling mechanism 155, the refrigerant return expansion mechanism 158, and the check valve 159 correspond to the "valve body" in this disclosure.

A pipe 140 in which the outdoor heat exchanger 115 is provided is connected to a connection portion A between the throttling mechanism 155 and the refrigerant return expansion mechanism 158 .
A connection part B between the refrigerant return expansion mechanism 158 and the check valve 159 of the third pipe 175 is connected to a middle part of the pipe 77 connecting the gas-liquid separator 116 and the cold-installed heat exchanger 132. In the pipe 177, a cold-installed inlet-side expansion mechanism 31 is provided between the point where the connection part B is connected and the cold-installed heat exchanger 132.

A connection part C between the check valve 159 of the third pipe 175 and the check valve 159 of the fourth pipe 176 is connected to the indoor heat exchanger 122 via the pipe 78. An indoor expansion mechanism 121 of the indoor unit 120 is provided between one end of the pipe 178 to which the connection part C is connected and the indoor heat exchanger 122. The indoor expansion mechanism 121 is an opening/closing device capable of changing the opening degree from fully closed to fully open. The indoor expansion mechanism 121 functions as a so-called throttle valve that can change the pressure of the refrigerant flowing through the pipe 178 by adjusting the opening degree. The indoor expansion mechanism 121 and the throttle mechanism 155 correspond to the "throttle mechanism" in this disclosure.
A connection portion D between the check valve 159 of the fourth pipe 176 and the throttle mechanism 155 is connected to the gas-liquid separator 116 via a pipe 179 .

As described above, the gas-liquid separator 116 is connected to the outdoor heat exchanger 115, the indoor heat exchanger 122, and the cold-installed heat exchanger 132 via the second switching mechanism 154. As a result, when the refrigeration system 101 performs the first operation mode, the refrigerant flows into the gas-liquid separator 116 from the pipe 179 and flows out from the pipe 177. That is, the pipe 179 functions as an inlet-side pipe of the gas-liquid separator 116, and the pipe 177 functions as an outlet-side pipe of the gas-liquid separator 116.
The second switching mechanism 154 corresponds to the "switching mechanism" of the present disclosure.

Next, the utilization side heat exchanger provided in the refrigeration system 101 will be described.
When the indoor unit 120 performs cooling operation, the indoor heat exchanger 122 functions as an evaporator. In the refrigeration system 101, the rotational frequency of each compressor and the airflow rate of the blowers 118 and 128 are determined based on the temperature difference between the set temperature of the indoor unit 120 and the temperature in the space to be conditioned in which the indoor unit 120 is installed. Furthermore, the opening degree of the indoor expansion mechanism 121 is determined so that the degree of superheat of the refrigerant at each of the inlet side and outlet side of the indoor heat exchanger 122 becomes a specified value. As a result, the refrigeration system 101 operates so that the space to be conditioned becomes the set temperature. In this embodiment, the evaporation temperature zone of the indoor heat exchanger 122 is, for example, 3°C to 6°C.

The refrigeration heat exchanger 132 functions as an evaporator. In the refrigeration system 101, the rotational frequency of each compressor and the airflow rate of the blowers 118 and 138 are determined based on the temperature difference between the set temperature of the refrigeration equipment 130 and the temperature inside the showcase. Furthermore, the opening degree of the refrigeration inlet expansion mechanism 131 is determined so that the degree of superheat of the refrigerant at each of the inlet and outlet sides of the refrigeration heat exchanger 132 is a specified value. As a result, the refrigeration system 101 operates so that the temperature inside the showcase is the set temperature.

The refrigeration equipment 130 of this embodiment can select and set the temperature zone within the cabinet from among, for example, the refrigeration temperature zone (3°C to 6°C), a temperature zone slightly higher than the refrigeration temperature zone (3°C to 8°C), a partial temperature zone (-3°C to -1°C), and a freezing temperature zone (-20°C to -18°C). Therefore, the evaporation temperature zone of the refrigeration heat exchanger 132 is set lower than the temperature zone within the cabinet.

When the refrigeration equipment 130 is set to the refrigeration temperature range, the evaporation temperature range of the refrigeration heat exchanger 132 is, for example, from -5°C to 0°C.
When the cooling equipment 130 is set to the partial temperature zone, the evaporation temperature zone of the cooling heat exchanger 132 is, for example, from -12°C to -8°C.
When the refrigeration equipment 130 is set to the freezing temperature range, the evaporation temperature range of the refrigeration heat exchanger 132 is, for example, from -140°C to -20°C.

In this way, two user-side heat exchangers with different evaporation temperature zones are provided in the refrigeration system 101. Of these two user-side heat exchangers with different evaporation temperature zones, the indoor heat exchanger 122 is connected to the inlet side of the high-stage compressor 112, and the cold-use heat exchanger 132, which has a lower evaporation temperature zone than the indoor heat exchanger 122, is connected to the inlet side of the low-stage compressor 111.
The indoor heat exchanger 122 corresponds to the "first use-side heat exchanger" in this disclosure, and the cold-use heat exchanger 132 corresponds to the "first use-side heat exchanger" in this disclosure.

Next, the gas-liquid separator 116 will be described.
The gas-liquid separator 116 is a so-called flash tank that separates the gas-liquid two-phase refrigerant flowing thereinto into a gas refrigerant and a liquid refrigerant.
In the present embodiment, when the refrigeration system 101 performs cooling operation, the refrigerant flowing from the exterior heat exchanger 115 flows into the gas-liquid separator 116 via the second switching mechanism 154. During the cooling operation of the refrigeration system 101, the refrigerant flowing from the second switching mechanism 154 into the gas-liquid separator 116 is depressurized by the throttling mechanism 155.

When the refrigeration system 101 performs heating operation, the refrigerant flowing from the indoor heat exchanger 122 flows into the gas-liquid separator 116 via the second switching mechanism 154. During the heating operation of the refrigeration system 101, the refrigerant flowing from the second switching mechanism 154 into the gas-liquid separator 116 is depressurized by the indoor expansion mechanism 121.
In this way, when the refrigeration system 101 performs the first operation mode, the refrigerant flows into the gas-liquid separator 116 in a state where the pressure has been adjusted by the throttling mechanism 155 or the indoor expansion mechanism 121 via the second switching mechanism 154. That is, when the first operation mode is performed, the refrigeration system 101 is provided with the second switching mechanism 154, so that the pressure of the refrigerant flowing into the gas-liquid separator 116 can be adjusted with a simple circuit configuration.

A gas refrigerant return pipe 160 is connected to the gas-liquid separator 116, and the gas refrigerant return pipe 160 is connected to pipe 171 and then to the accumulator 113. A gas refrigerant flow control valve 161 is connected to the gas refrigerant return pipe 160. This gas refrigerant flow control valve 161 is an opening/closing device whose opening can be changed from fully closed to fully open. In the refrigeration system 101, the flow rate of gas refrigerant flowing through the gas refrigerant return pipe 160 is adjusted by the opening of the gas refrigerant flow control valve 161.

In this embodiment, a portion of the gas refrigerant separated in the gas-liquid separator 116 has its flow rate adjusted by the gas refrigerant flow control valve 161 , is sent to the accumulator 113 , and is returned to the suction side of the high-stage compressor 112 .
In this manner, in the gas-liquid separator 116, a portion of the gas refrigerant separated in the gas-liquid separator 116 is separated from the liquid refrigerant and flows out of the gas-liquid separator 116, thereby cooling the liquid refrigerant to a saturation temperature corresponding to the pressure of the gas-liquid separator 116. That is, in the refrigeration system 101, the gas-liquid separator 116 functions as a heat exchanger that cools the liquid refrigerant, and it is possible to increase the refrigeration capacity of the refrigeration system 101.

In addition, in the refrigeration system 101, by controlling the opening degree of the gas refrigerant flow control valve 161 and adjusting the return amount of the gas refrigerant, a pressure difference is generated before and after the indoor expansion mechanism 121. That is, in the refrigeration system 101, it is possible to generate a refrigerant pressure difference between the inlet and outlet of the indoor unit 120 in the refrigeration circuit 102.
This prevents the flow of the refrigerant from being stagnate, particularly when performing cooling operation, in the refrigeration system 101. In the refrigeration system 101, in the indoor heat exchanger 122 in which the evaporation temperature of the refrigerant is high, it becomes possible to control the refrigerant flowing through the indoor heat exchanger 122 at a pressure value obtained by adding a specified pressure value to the pressure value at which the refrigerant evaporates.

An internal heat exchanger 164 is provided midway between the gas refrigerant return pipe 160 and the pipe 177. The internal heat exchanger 164 is a so-called economizer heat exchanger. This internal heat exchanger 164 is disposed in the pipe 177 between the gas-liquid separator 116 and the connection part B, and is disposed in the gas refrigerant return pipe 160 between the gas refrigerant flow rate control valve 161 and the accumulator 113.
The internal heat exchanger 164 houses the pipe 177 and the gas refrigerant return pipe 160 inside at the above-mentioned position, and exchanges heat between the liquid refrigerant flowing through the pipe 177 and the gas refrigerant flowing through the gas refrigerant return pipe 160.

As a result, in the refrigeration system 101, the liquid refrigerant is cooled by the gas refrigerant in the internal heat exchanger 164. The liquid refrigerant is then more reliably brought into a supercooled state, and the degree of supercooling increases. Therefore, even if the temperature of the liquid refrigerant in the gas-liquid separator 116 does not drop to the saturation temperature in the gas-liquid separator 116, the temperature of the liquid refrigerant is lowered to below the saturation temperature by being cooled in the internal heat exchanger 164. The refrigeration system 101 is then able to ensure the degree of supercooling of the liquid refrigerant, and is able to improve operating efficiency.

The refrigeration circuit 102 is provided with a connection pipe 166. The connection pipe 166 connects the internal heat exchanger 164 and connection part B in the pipe 177, and the gas refrigerant flow control valve 161 and the internal heat exchanger 164 in the gas refrigerant return pipe 160. A portion of the liquid refrigerant that has been heat exchanged with the gas refrigerant in the internal heat exchanger 164 flows through this connection pipe 166. The liquid refrigerant that flows through this connection pipe 166 is mixed with the gas refrigerant before it is heat exchanged with the liquid refrigerant in the internal heat exchanger 164.

That is, in the internal heat exchanger 164, heat is exchanged between the liquid refrigerant and the mixed refrigerant of the liquid refrigerant and the gas refrigerant that has been cooled by heat exchange with the gas refrigerant in the internal heat exchanger 164.
This makes it possible to increase the degree of subcooling of the liquid refrigerant in the internal heat exchanger 164. Therefore, in the refrigeration system 101, it is possible to improve the operating efficiency.

A liquid refrigerant flow control valve 165 is provided in the connecting pipe 166. This liquid refrigerant flow control valve 165 is an opening/closing device whose opening can be changed from fully closed to fully open. In the refrigeration system 101, the flow rate of the liquid refrigerant flowing through the connecting pipe 166 is adjusted by the opening of the liquid refrigerant flow control valve 165.

Next, the service valve 190 will be described.
In the refrigeration system 101, a service valve 190 is provided in the piping 172. In the piping 172, the service valve 190 is provided between the outlet side of the cold-installation heat exchanger 132 and the cold-installation outlet-side pressure adjustment mechanism 133. In this embodiment, the service valve 190 is provided in the cold-installation equipment 130.
The service valve 190 has three connection ports: pipe connection ports 192, 194, and an external connection port 196. The pipe connection ports 192, 194 and the external connection port 196 are all valve bodies that can be opened and closed.
The piping connection port 192 is connected to the piping 172 located on the side of the outlet side pressure adjustment mechanism for cooling 133. The piping connection port 194 is connected to the piping 172 located on the outlet side of the cooling heat exchanger 132. In this embodiment, the piping connection ports 192 and 194 are normally open.

The external connection port 196 is provided to allow communication between the pipe 172 and the outside, and is formed so that external equipment can be connected. In this embodiment, for example, a manifold gauge, a refrigerant recovery device 150, a vacuum unit 152, a refrigerant sealing unit 154, etc. are connected (Figures 10 and 11). The external connection port 196 is closed when no external equipment is connected. The external connection port 196 may be capable of being opened and closed manually by an operator.

In the refrigeration system 101, the service valve 190 is provided between the outlet side of the cooling heat exchanger 132 and the cooling outlet pressure adjustment mechanism 133, so that a connection port for an external device can be provided without significantly changing the layout structure of the refrigeration circuit 102. In addition, the service valve 190 is provided at a location close to the connection location between the outdoor unit 110 and the cooling device 130, so that the refrigeration system 101 can improve the workability when connecting an external device to the refrigeration system 101.
The service valve 190 corresponds to the "connection port" in this disclosure.

[2-1-2. Configuration related to refrigeration system control]
FIG. 4 is a block diagram of the refrigeration system 101.
3 and 4, the refrigeration system 101 is provided with a plurality of refrigerant pressure sensors 180. The refrigerant pressure sensors 180 are provided at predetermined locations of the refrigeration circuit 102 that includes the outdoor unit 110, the indoor unit 120, and the cooling equipment 130. The refrigerant pressure sensors 180 detect the pressure of the refrigerant flowing through those locations.

3, the refrigerant pressure sensor 180 is provided in the pipe 177, between the gas-liquid separator 116 and the internal heat exchanger 164. The refrigerant pressure sensor 180 is also provided in the gas refrigerant return pipe 160, between the gas refrigerant flow rate control valve 161 and the accumulator 113.
Furthermore, the refrigerant pressure sensor 180 is provided in the pipe 171, between the connection point of the pipe 171 and the first heating pipe 141, and the indoor heat exchanger 122. Moreover, the refrigerant pressure sensor 180 is provided in the pipe 172, between the cooling outlet side pressure adjustment mechanism 133 and the suction side of the low stage compressor 111.
The refrigerant pressure sensor 180 is provided on a refrigerant pipe that connects the discharge side of the high-stage compressor 112 and the oil separator 114 .

As shown in Figures 3 and 4, the refrigeration system 101 is provided with multiple refrigerant temperature sensors 182. The refrigerant temperature sensors 182 are provided at predetermined locations in the refrigeration circuit 102, which includes the outdoor unit 110, the indoor unit 120, and the cooling equipment 130. The refrigerant temperature sensors 182 detect the temperature of the refrigerant flowing through those locations.

3, the refrigerant temperature sensor 182 is provided on a refrigerant pipe located on the suction side and a refrigerant pipe located on the discharge side in each of the high-stage compressors 112. In addition, the refrigerant temperature sensor 182 is provided on the pipe 172 located on the suction side of the low-stage compressor 111, between the cooling outlet side pressure adjustment mechanism 133 and the suction side of the low-stage compressor 111.
Furthermore, the refrigerant temperature sensor 182 is provided on each of the refrigerant pipes connected to the inlet side and outlet side of each of the indoor heat exchanger 122 and the cold-set heat exchanger 132 .

4, the refrigeration system 101 includes a space temperature sensor 127. The space temperature sensor 127 is disposed in a space to be conditioned of the indoor unit 120, and detects the temperature of the space to be conditioned.
The refrigeration system 101 includes an internal temperature sensor 137. The internal temperature sensor 137 is disposed inside a refrigerated showcase or a freezer showcase included in the refrigeration equipment 130, and detects the internal temperature.

The outdoor unit 110, indoor unit 120, and cooling equipment 130 are provided with blowers 118, 128, and 138, respectively. Each blower 118, 128, and 138 flows air through the outdoor heat exchanger 115, indoor heat exchanger 122, and cooling equipment 132, respectively, promoting heat exchange between the air and the refrigerant flowing through each of the outdoor heat exchanger 115, indoor heat exchanger 122, and cooling equipment 132.

The outdoor unit 110 is equipped with an outdoor unit communication unit 206 that communicates with the indoor unit 120 via control wiring. The outdoor unit communication unit 206 is composed of communication hardware such as connectors and communication circuits that comply with a specified communication standard.

The outdoor unit 110 includes a control device 200. The outdoor unit I/F 205 includes communication hardware conforming to a predetermined communication standard, such as a connector and a communication circuit. The outdoor unit I/F 205 communicates with the low stage compressor 111, the high stage compressor 112, the blower 118, the refrigerant pressure sensor 180, the refrigerant temperature sensor 182, and an outdoor unit communication unit 206. The outdoor unit I/F 205 communicates with the first cooling valve 151, the first heating valve 152, the outdoor refrigerant return valve 153, the throttling mechanism 155, the refrigerant return expansion mechanism 158, the on-off valve 123, the gas refrigerant flow rate control valve 161, the liquid refrigerant flow rate control valve 165, and the service valve 190.
Furthermore, the outdoor unit I/F 205 communicates with an indoor unit I/F 215 , a space temperature sensor 127 , and a cooling device I/F 225 .

The outdoor unit 110 includes a control device 200. The control device 200 includes a control unit 201 and a storage unit 203.
The control unit 201 is a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) that operates based on a program stored in advance in the storage unit 203. The control unit 201 may be configured with a single processor or may be configured with multiple processors. Note that a DSP (digital signal processor) or the like may be used as the control unit 201. Also, a control circuit such as an LSI (large scale integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programming Gate Array) may be used as the control unit 201.

The control unit 201 is capable of receiving various signals from each unit included in the outdoor unit 110 , the indoor unit 120 , and the cooling equipment 130 via the outdoor unit I/F 205 .
The control unit 201 is connected via the outdoor unit I/F 205 to each part of the outdoor unit 110, such as the memory unit 203 and the low-stage compressor 111, the indoor unit 120, and the cooling equipment 130, either wired or wirelessly, and controls each part.

The control unit 201 reads the computer program stored in the memory unit 203 and operates according to the read computer program, thereby functioning as an operation control unit 201a and a determination unit 201b.

The operation control unit 201a controls various devices such as the low-stage compressor 111, the high-stage compressor 112, and the opening and closing devices of the outdoor unit 110. The operation control unit 201a transmits control signals to the indoor unit 120 and the cooling equipment 130 via the outdoor unit I/F 205, and causes the refrigeration system 101 to operate in a coordinated manner.

The operation control unit 201a is capable of changing the rotation speed of the compression mechanism included in each of the compressors, and is also capable of changing the discharge pressure of the refrigerant.
The operation control unit 201a can adjust the opening degree of the gas refrigerant flow control valve 161, the throttling mechanism 155, the indoor expansion mechanism 121, the cooling-use inlet expansion mechanism 131, the cooling-use outlet pressure adjustment mechanism 133, and the refrigerant return expansion mechanism 158. The operation control unit 201a can switch the opening and closing devices provided in each of the first switching mechanism 150 and the second switching mechanism 154, and the opening and closing valve 123 to either an open state or a closed state.

The determination unit 201b compares the detection values of the refrigerant pressure sensors 180 and the detection values of the refrigerant temperature sensors 182 with data such as reference temperatures and reference pressures included in the setting data 103a stored in the memory unit 203.
The operation control unit 201a controls each part of the refrigeration system 101 based on the determination by this determination unit 201b.

The storage unit 203 includes a memory device such as a random access memory (RAM) or a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. The storage unit 203 also stores computer programs, databases, tables, and the like used for various operations of the refrigeration system 101. These computer programs, and the like may be installed in the storage unit 203 from a computer-readable portable recording medium using a known setup program, and the like. The portable recording medium is, for example, a semiconductor storage device including a CD-ROM (compact disc read only memory), a DVD-ROM (digital versatile disc read only memory), a USB (Universal Serial Bus) memory, or an SSD (Solid State Drive). The computer program, etc. may be installed from a predetermined server, etc.
Furthermore, the memory unit 203 may be provided with a volatile memory area and may constitute a work area for the control unit 201 .

Setting data 203a is stored in the storage unit 203. The setting data 203a includes data on the set temperature of the indoor unit 120 and data on the set temperature of the cooling equipment 130.
The setting data 203 a includes data such as the rotation speed that is a specified value for each compressor, and a reference pressure value that is a specified value indicating a differential pressure at a predetermined point in the refrigeration circuit 102 .

The setting data 203a includes data related to the first operating mode. Specifically, the setting data 203a includes information on the opening and closing, or the opening degree, of each of the valve bodies provided in the refrigeration circuit 102 when the first operating mode is performed. The control unit 201 controls each part of the refrigeration circuit 102 according to the data related to the first operating mode. In this way, the refrigeration system 101 performs the first operating mode.

The setting data 203a includes a second operation mode. The second operation mode is an operation mode of the refrigeration system 101 that is performed in conjunction with the operation of an external device connected to the external connection port 196. The setting data 203a includes information on the opening/closing or opening degree of each of the valve bodies provided in the refrigeration circuit 102 when the second operation mode is performed. The control unit 201 controls each part of the refrigeration circuit 102 according to the data related to the second operation mode. As a result, the refrigeration system 101 performs the second operation mode.
In the present embodiment, the setting data 203a includes three operation modes as the second operation mode: a refrigerant recovery/vacuum drawing mode, a refrigerant charging mode, and an adjustment operation mode.

The outdoor unit I/F 205 includes communication hardware such as a communication interface circuit and a connector that allows the outdoor unit 110 to communicate with each device via a cable or the like in accordance with a predetermined communication protocol. The outdoor unit I/F 205 sends data received from each device to the control device 200, and also transmits data received from the control device 200 to each device.

The control device 200 includes an operation panel 232. An operator is provided on the operation panel 232. When the operator is operated, the control device 200 transmits a signal to the outdoor unit 110 to switch the operation mode of the refrigeration system 101 from the first operation mode to the second operation mode. In this embodiment, the control device 200 switches to and executes one of three second operation modes, a refrigerant recovery/vacuum drawing mode, a refrigerant charging mode, and an adjustment operation mode, in accordance with the operation of the operation panel 232.

The control device 200 is provided with a display panel 234. The display panel 234 performs a predetermined screen display in accordance with a signal transmitted from the outdoor unit 110. In the present embodiment, the display panel 234 can display, for example, an operating status when the first operation mode or the second operation mode is executed, or the presence or absence of a malfunction in each part of the refrigeration system 101, and notify an operator of the same.
The control device 200 corresponds to a "control unit" in this disclosure. The operation panel 232 corresponds to an "operation unit" in this disclosure. The display panel 234 corresponds to a "display unit" in this disclosure.

The indoor unit 120 includes an indoor unit control device 210 and an indoor unit I/F 215. The indoor unit control device 210 includes an indoor unit control unit 211 and an indoor unit memory unit 213.

The indoor unit control unit 211 is a processor such as a CPU or an MPU, similar to the control unit 201. The indoor unit control unit 211 controls various devices such as the blower 128 mounted in the indoor unit 120 by operating according to a computer program stored in the indoor unit storage unit 213. The indoor unit control unit 211 also receives output signals from various sensors mounted in the indoor unit 120, such as the space temperature sensor 127.
The indoor unit storage unit 213, like the storage unit 203, has storage devices such as RAM and ROM, and stores computer programs and the like used for various operations of the indoor unit 120.

The indoor unit I/F 215 includes communication hardware such as a communication interface circuit and connectors that allow the indoor unit 120 to communicate with each device. The indoor unit I/F 215 sends data received from the space temperature sensor 127 and each device to the indoor unit control device 210, and also transmits data received from the indoor unit control device 210 to each device.

The refrigeration equipment 130 includes a refrigeration equipment control device 220 and a refrigeration equipment I/F 225. The refrigeration equipment control device 220 includes a refrigeration equipment control unit 221 and a refrigeration equipment memory unit 223.

The refrigeration equipment control unit 221 is a processor such as a CPU or an MPU, similar to the control unit 201. The refrigeration equipment control unit 221 controls various devices such as the blower 138 mounted on the refrigeration equipment 130 by operating according to a computer program stored in the refrigeration equipment storage unit 223. The refrigeration equipment control unit 221 also receives output signals from various sensors mounted on the refrigeration equipment 130, such as the inside temperature sensor 137.
The refrigeration equipment storage unit 223, like the storage unit 203, has storage devices such as RAM and ROM, and stores computer programs and the like used for various operations of the refrigeration equipment 130.

The refrigeration equipment I/F 225 includes communication hardware such as a communication interface circuit and connectors that allow the refrigeration equipment 130 to communicate with each device. The refrigeration equipment I/F 225 sends data received from the internal temperature sensor 137 and each device to the refrigeration equipment control device 220, and also transmits data received from the refrigeration equipment control device 220 to each device.

The operation control unit 201a and the determination unit 201b may be provided not only in the control unit 201 but also in the indoor unit control unit 211 or the cooling equipment control unit 221. For example, the operation control unit 201a and the determination unit 201b may be provided by a processor provided in another location of the refrigeration system 101. For example, the operation control unit 201a and the determination unit 201b may be provided by a processor provided in a server device or the like provided outside the refrigeration system 101. Such a server device may be capable of controlling each part of the refrigeration system 101 via a network consisting of, for example, a public line network, a dedicated line, other communication lines, and various communication facilities.

[2-2. Operation of the refrigeration system]
Next, the operation of this embodiment will be described.

[2-2-1. Cooling operation]
First, the operation of the refrigeration system 101 when performing cooling operation will be described.
During cooling operation, as shown in FIG. 3, the outdoor heat exchanger 115 is used as a gas cooler or a radiator, and the indoor heat exchanger 122 and the cold-setting heat exchanger 132 are used as evaporators.
When performing cooling operation, in the first switching mechanism 150, the control device 200 opens the first cooling valve 151 and closes the remaining first heating valve 152 and the outdoor refrigerant return valve 153. In addition, in the second switching mechanism 154, the control device 200 opens the throttling mechanism 155 and closes the refrigerant return expansion mechanism 158.
In this state, by driving each of the low-stage compressor 111 and the high-stage compressor 112, the refrigerant compressed by the low-stage compressor 111 is sent to each of the high-stage compressors 112, and is further compressed by each of the high-stage compressors 112 and discharged toward the oil separator 114.

The refrigerant that has passed through the oil separator 114 is sent through the first cooling valve 151 of the first switching mechanism 150 to the outdoor heat exchanger 115, where it exchanges heat with outside air.
The refrigerant after heat exchange is sent from connection part A of second switching mechanism 154 via throttling mechanism 155 to gas-liquid separator 116. The liquid refrigerant separated in gas-liquid separator 116 passes through piping 177, is heat exchanged with gas refrigerant in internal heat exchanger 164, and then reaches connection part B of second switching mechanism 154. One of the refrigerants branched at connection part B is sent through piping 178 to indoor heat exchanger 122 via check valve 159 provided in piping 175 and indoor expansion mechanism 121 of indoor unit 120.
In the indoor heat exchanger 122, the refrigerant exchanges heat with the indoor air to cool the indoor air. The refrigerant that has exchanged heat with the indoor air passes through a pipe 171, and is returned to the suction side of each of the high-stage compressors 112 via an on-off valve 123 and an accumulator 113.

The other refrigerant branched off at connection point B is sent to the refrigeration heat exchanger 132 via the refrigeration inlet expansion mechanism 131 of the refrigeration equipment 130, where it undergoes heat exchange to cool the refrigeration equipment 130. The refrigerant that has undergone heat exchange in the refrigeration heat exchanger 132 is returned to the low-stage compressor 111 via the refrigeration outlet pressure adjustment mechanism 133.

In the cooling operation of the refrigeration system 101 described above, the refrigerant discharged from the high-stage compressor 112 and dissipating heat while maintaining its high pressure in the outdoor heat exchanger 115 is reduced in pressure by the throttling mechanism 155 to an intermediate pressure and is sent to the gas-liquid separator 116.

[2-2-2. Heating operation]
Next, the operation of the refrigeration system 101 when performing heating operation will be described.
Fig. 5 is a circuit diagram of the refrigeration system 101 showing the operation of the heating mode. In Fig. 5, the flow of the refrigerant is indicated by arrows in the drawing, and the refrigerant pipes through which the refrigerant flows are indicated by thick lines.
In the refrigeration system 101, the heating operation is performed by using the indoor heat exchanger 122 as a gas cooler or a radiator, and the cold-use heat exchanger 132 as an evaporator.
5, when performing heating operation, in the first switching mechanism 150, the control device 200 opens the first heating valve 152 and closes the remaining first cooling valve 151 and the outdoor refrigerant return valve 153. In addition, in the second switching mechanism 154, the control device 200 closes the throttling mechanism 155 and the refrigerant return expansion mechanism 158.

In this state, by driving each of the low-stage compressor 111 and the high-stage compressor 112, the refrigerant compressed by the low-stage compressor 111 is sent to each high-stage compressor 112, further compressed by each of the high-stage compressors 112, and discharged toward the oil separator 114.
The refrigerant that has passed through the oil separator 114 passes through the first heating valve 152 of the first switching mechanism 150 and is sent to the indoor heat exchanger 122, where it exchanges heat with the indoor air, heating the indoor air.

The refrigerant that has exchanged heat in the indoor heat exchanger 122 passes through the indoor expansion mechanism 121, reaches connection C of the second switching mechanism 154, and is sent to the gas-liquid separator 116 via the check valve 159 and throttling mechanism 155 provided in the piping 176. The refrigerant separated in the gas-liquid separator 116 passes through the piping 177, reaches connection B of the second switching mechanism 154, and is sent to the cold-setting heat exchanger 132 via the cold-setting inlet expansion mechanism 131. This refrigerant exchanges heat in the cold-setting heat exchanger 132, and cools the cold-setting equipment 130.

The refrigerant that has exchanged heat in the cold-setting heat exchanger 132 passes through a pipe 172 and is returned to the suction side of the low-stage compressor 111 via the cold-setting outlet side pressure adjustment mechanism 133 .
In the refrigeration system 101 of the present disclosure, during heating operation, the indoor heat exchanger 122 functions as a gas cooler or a radiator, and the outdoor heat exchanger 115 is not used. That is, the refrigeration system 101 can operate without using the outdoor heat exchanger 115 by performing heat exchange in the cold-installed heat exchanger 132 using the refrigerant whose heat is radiated in the indoor heat exchanger 122.
In the refrigeration system 101 of the present disclosure, during heating operation, liquid refrigerant flows only through the cooling equipment 130, and therefore the opening degree of the gas refrigerant flow control valve 161 is smaller than during cooling operation.

[2-2-3. Heating operation when the heat exhausted from the cooling equipment is insufficient]
Next, an operation in a case where a heating operation is performed when the amount of heat exhausted to the cooling equipment 130 is insufficient will be described.
FIG. 6 is a circuit diagram of the refrigeration system 101 showing the heating operation when the amount of heat exhausted to the cooling equipment 130 is insufficient.
As shown in Figure 6, when heating at full capacity is performed, the control device 200 opens the first heating valve 152, the outdoor refrigerant return valve 153, and the refrigerant return expansion mechanism 158, and closes the first cooling valve 151 and the throttling mechanism 155.

In this state, by driving the low-stage compressor 111 and each high-stage compressor 112, the refrigerant compressed by the low-stage compressor 111 is sent to each high-stage compressor 112, further compressed by each high-stage compressor 112, and discharged toward the oil separator 114.
The refrigerant that has passed through the oil separator 114 is sent to the indoor heat exchanger 122 through the first heating valve 152, where it exchanges heat with indoor air to heat the indoor air.

The refrigerant that has exchanged heat in the indoor heat exchanger 122 is sent to the gas-liquid separator 116 via a check valve 159 provided in the piping 176, and then sent to the refrigeration heat exchanger 132 via the refrigeration inlet side expansion mechanism 131. The refrigerant exchanges heat in the refrigeration heat exchanger 132, cooling the refrigeration equipment 130, and the refrigerant that has exchanged heat in the refrigeration heat exchanger 132 is adjusted via the refrigeration outlet side pressure adjustment mechanism 133 so that its pressure is the same as that of the refrigerant sent from the first outdoor return piping 142, and is returned to the low-stage compressor 111. This is the operation when the outside air temperature is lower than the temperature inside the refrigeration equipment 130.
On the other hand, a portion of the refrigerant from the gas-liquid separator 116 is sent to the outdoor heat exchanger 115 via a refrigerant return expansion mechanism 158 , and is returned to the low-stage compressor 111 after heat exchange in the outdoor heat exchanger 115 .
This allows the exhaust heat from the cooling heat exchanger 132 and the heat pumped up by the outdoor heat exchanger 115 to be used as heat for the indoor heat exchanger 122, thereby increasing the heating capacity when the amount of heat exhausted to the cooling equipment 130 is insufficient.

Conventionally, when the outdoor air temperature becomes lower than the temperature inside the cooling equipment 130, it is necessary to lower the evaporation temperature of the cooling equipment 130 in order to pump heat from the outdoor heat exchanger 115. However, if the evaporation temperature of the cooling equipment 130 is lowered, there is a risk that the temperature will become lower than the set temperature of the cooling equipment 130.
Therefore, in this embodiment, by controlling the opening degree of the cooling outlet side pressure adjustment mechanism 133, the pressure can be balanced with the refrigerant sent from the outdoor heat exchanger 115, and a decrease in the evaporation temperature of the cooling equipment 130 can be suppressed.

[2-2-4. Heating operation when large capacity is required for cooling equipment and heating heat is not required]
Next, a heating operation in the case where a large capacity is required in the cooling equipment 130 but a heating heat quantity is not required will be described.
FIG. 7 is a circuit diagram of the refrigeration system 101 showing a heating operation when a large capacity is required in the cooling equipment 130 and a heating heat quantity is not required.
As shown in FIG. 7 , when a large capacity is required in the cooling equipment 130 but no heating heat is required, the control device 200 opens the first cooling valve 151, the throttling mechanism 155, the first heating valve 152, and the check valve 159 provided in the piping 176, and closes the refrigerant return valve and the check valve 159 provided in the piping 175.

In this state, by driving the low-stage compressor 111 and each high-stage compressor 112, the refrigerant compressed by the low-stage compressor 111 is sent to each high-stage compressor 112, further compressed by each high-stage compressor 112, and discharged toward the oil separator 114.
The refrigerant that has passed through the oil separator 114 is sent to the outdoor heat exchanger 115 through the first cooling valve 151, where it exchanges heat with outside air.
The refrigerant after heat exchange is sent to the gas-liquid separator 116 via a throttling mechanism 155 .

On the other hand, the refrigerant that has passed through the oil separator 114 is sent to the indoor heat exchanger 122 through the first heating valve 152, where it exchanges heat with indoor air to heat the indoor air.
The refrigerant that has exchanged heat in the indoor heat exchanger 122 is combined with the refrigerant sent from the outdoor heat exchanger 115 via a check valve 159 provided in the pipe 176 , and is sent to the gas-liquid separator 116 .

The refrigerant from the gas-liquid separator 116 is sent to the refrigeration heat exchanger 132 via an inlet expansion mechanism for the refrigeration equipment 130. Heat exchange is performed in the refrigeration heat exchanger 132 to cool the refrigeration equipment 130, and the refrigerant that has undergone heat exchange in the refrigeration heat exchanger 132 is returned to the low-stage compressor 111 via a refrigeration outlet pressure adjustment mechanism 133.
On the other hand, a portion of the refrigerant from the gas-liquid separator 116 is sent to the outdoor heat exchanger 115 via a refrigerant return expansion mechanism 158 , and is returned to the low-stage compressor 111 after heat exchange in the outdoor heat exchanger 115 .
As a result, during heating operation, the exhaust heat from the cooling equipment 130 can be dissipated by the outdoor heat exchanger 115 and the indoor heat exchanger 122, thereby increasing the cooling capacity of the cooling equipment 130 and making it possible to remove frost that has adhered to the outdoor heat exchanger 115.

In this way, in the refrigeration system 101, when performing heating operation, the usage state of the outdoor heat exchanger 115 can be switched between a state in which it is not used, a state in which it is used as an evaporator, and a state in which it is used as a condenser, depending on the load on the indoor unit 120 and the cooling equipment 130. Therefore, in the refrigeration system 101, stable heating operation can be performed depending on the load on the indoor unit 120 and the cooling equipment 130.

[2-2-5. State of refrigerant in the refrigeration circuit]
Fig. 8 is a ph diagram showing the state of the refrigerant in the refrigeration circuit 102. In Fig. 6, the vertical axis p represents pressure (MPa), and the horizontal axis h represents enthalpy (kJ/kg).
Here, the refrigerant of the refrigeration system 101 when performing cooling operation will be described.
On the suction side of the low-stage compressor 111, the refrigerant is in a state of being located at point P1 in Fig. 8. The refrigerant is the refrigerant that has evaporated in the cold-installed heat exchanger 132, and is a gas refrigerant at point P1. Hereinafter, for convenience of explanation, the pressure at point P1 will be referred to as the low pressure.

When the low-pressure refrigerant is drawn into the low-stage compressor 111 and adiabatically compressed, the refrigerant is positioned at point P2 in Fig. 8. For ease of explanation, the pressure at point P2 will be referred to as the medium pressure in the following description. In this embodiment, the differential pressure between the low pressure and the medium pressure is, for example, 1.0 MPa.
This refrigerant is mixed with the refrigerant evaporated in the indoor heat exchanger 122 and the gas refrigerant flowing through the gas refrigerant return pipe 160. The mixed refrigerants are maintained at a medium pressure while decreasing in temperature, and reach a state located at point P3 in FIG.

When the refrigerant in the state of being positioned at point P3 is adiabatically compressed, the refrigerant reaches a state of being positioned at point P4 in Fig. 8. For convenience of explanation, the pressure at point P4 will hereinafter be referred to as the high pressure.
When this refrigerant is discharged from the high-stage compressor 112, heat is dissipated in the outdoor heat exchanger 115 while the pressure is kept high. As a result, the refrigerant reaches a state located at point P5 in FIG.

The refrigerant at point P5 is decompressed by the throttling mechanism 155, and reaches point P6 in FIG. 8. At point P6, the refrigerant has a pressure value higher than the medium pressure. For ease of explanation, the pressure at point P2 will be referred to as the medium pressure below. In this embodiment, the pressure difference between the medium pressure and the medium pressure is, for example, 0.5 MPa.

As described above, in the refrigeration system 101, in both cooling and heating operation, low-pressure liquid refrigerant decompressed by the throttling mechanism 155 or the indoor expansion mechanism 121 flows into the gas-liquid separator 116. This allows the refrigeration system 101 to adjust the pressure of the refrigerant entering the gas-liquid separator 116 when performing the first operating mode.

The refrigerant in a state positioned at point P6 is separated into liquid refrigerant and gas refrigerant by the gas-liquid separator 116. Of these refrigerants, the gas refrigerant is discharged from the gas-liquid separator 116 via the gas refrigerant return pipe 160.
As the gas refrigerant is separated and discharged from the gas-liquid separator 116, the liquid refrigerant is cooled to a state indicated by point P7 on the saturated liquid line, as shown in FIG.

As described above, the gas refrigerant return pipe 160 is connected to the suction side of the high-stage compressor 112. That is, the gas refrigerant is sucked by the high-stage compressor 112 and discharged from the gas-liquid separator 116. As a result, in the refrigeration system 101, the liquid refrigerant stored in the gas-liquid separator 116 is cooled to a state of point P7 on the saturated liquid line.
The refrigeration system 101 includes one low stage compressor 111 and two high stage compressors 112. That is, in the refrigeration system 101, the capacity of the high stage compressor 112 is larger than that of the low stage compressor 111. By drawing in gas refrigerant by these high stage compressors 112, the refrigeration system 101 can cool the liquid refrigerant in the gas-liquid separator 116 to a state of point P7 on the saturated liquid line even when the outside air temperature of the conditioned space or the cooling equipment 130 is high, for example, in summer.
In this manner, the refrigeration system 101 can stably perform the first operation mode even when the ambient temperature of the utilization side heat exchanger is high.

The liquid refrigerant exchanges heat with the gas refrigerant in the internal heat exchanger 164, and reaches a state located at point P8 in FIG. 8. At point P8, the liquid refrigerant is in a subcooled state. The gas refrigerant that has exchanged heat with the liquid refrigerant in the internal heat exchanger 164 reaches a state located at point P11 in FIG. 8.

The liquid refrigerant flowing out from the internal heat exchanger 164 branches off at connection point B and flows to the indoor unit 120 and the cooling equipment 130. The liquid refrigerant flowing into the indoor unit 120 is decompressed to medium pressure by the indoor expansion mechanism 121, and reaches a state located at point P9 in FIG. 8. After this, the liquid refrigerant flowing into the indoor unit 120 evaporates in the indoor heat exchanger 122, and reaches a state located at point P3 in FIG. 8. The refrigerant flows out from the indoor unit 120 and is sent to the suction side of the high-stage compressor 112. The gas refrigerant flowing out from the internal heat exchanger 164 is also sent to the suction side of the high-stage compressor 112.

The liquid refrigerant flowing into the refrigeration equipment 130 is decompressed to a medium pressure by the refrigeration inlet side expansion mechanism 131, and reaches a state located at point P10 in Fig. 8. After this, the liquid refrigerant flowing into the refrigeration equipment 130 evaporates in the refrigeration heat exchanger 132, and reaches a state located at point P1 in Fig. 8. The refrigerant flows out of the refrigeration equipment 130 and is sent to the suction side of the low stage compressor 111.
As shown in FIG. 8, a refrigeration system 101 of the present embodiment is a system that performs a two-stage compression, two-stage expansion cycle by including a refrigeration circuit 102 .

In this way, in the refrigeration system 101, by controlling the opening degree of the gas refrigerant flow control valve 161 and adjusting the return amount of the gas refrigerant, the inlet side of the indoor heat exchanger 122 becomes a medium pressure and the outlet side of the indoor heat exchanger 122 becomes an intermediate pressure. That is, in the refrigeration system 101, it is possible to generate a refrigerant pressure difference between the inlet side and the outlet side of the indoor expansion mechanism 121 in the refrigeration circuit 102.
As a result, in the refrigeration system 101, in the indoor heat exchanger 122, where the evaporation temperature of the refrigerant is high, it is possible to control the refrigerant flowing through the indoor heat exchanger 122 at a pressure value obtained by adding a specified pressure value to the pressure value at which the refrigerant evaporates.
Therefore, in the refrigeration system 101, carbon dioxide (R744), a natural refrigerant with high environmental friendliness, is used, which can improve the efficiency of the air conditioning temperature range and can improve the efficiency of the entire refrigeration system.

As described above, in the refrigeration system 101, the refrigerant pressure is adjusted by the throttling mechanism 155, the indoor expansion mechanism 121, and the gas refrigerant flow control valve 161, and the refrigerant temperature is adjusted by the gas-liquid separator 116, so that the refrigerant state changes shown in FIG. 8 can be stably performed. Therefore, in the refrigeration system 101, the refrigerant pressure and temperature can be adjusted according to the load on the indoor unit 120 and the cooling equipment 130 due to the outside air temperature, etc., and stable operation can be performed.

Furthermore, in the refrigeration system 101, the liquid refrigerant separated in the gas-liquid separator 116 exchanges heat with the gas refrigerant in the internal heat exchanger 164. This causes the liquid refrigerant sent to the indoor unit 120 and the cooling equipment 130 to be supercooled. Therefore, even if the temperature of the liquid refrigerant fluctuates due to external heat radiation or heat capacity of the gas-liquid separator 116, or fluctuations in the operating load of the refrigeration system 101, the liquid refrigerant is prevented from rising to a temperature at which flash gas is generated, for example. And, in the refrigeration system 101, it is possible to achieve stable evaporation of the refrigerant in the indoor heat exchanger 122 and the cooling heat exchanger 132.

In addition, in the refrigeration system 101, a portion of the liquid refrigerant that has been heat exchanged with the gas refrigerant in the internal heat exchanger 164 is mixed with the gas refrigerant before heat exchange with the liquid refrigerant via the connecting pipe 166. As a result, in the internal heat exchanger 164, heat exchange occurs between the liquid refrigerant and the mixed refrigerant of the liquid refrigerant and gas refrigerant that has been cooled by heat exchange with the gas refrigerant in the internal heat exchanger 164. As a result, the degree of subcooling of the liquid refrigerant is increased in the internal heat exchanger 164, and the operating efficiency of the refrigeration system 101 can be improved.

[2-2-6. Operation of the refrigeration system in cooling operation]
FIG. 9 is a flow chart showing the operation of the refrigeration system 101.
Next, the operation relating to pressure control of the refrigeration system 101 during cooling operation will be described.
9, the determination unit 201b acquires a detection value of the refrigerant pressure sensor 180 provided on the discharge side of the indoor heat exchanger 122 and a detection value of the refrigerant pressure sensor 180 provided on the discharge side of the cold-installed heat exchanger 132. The determination unit 201b calculates a differential pressure between the medium pressure and the low pressure from these acquired detection values. The determination unit 201b compares the calculated value with data of a reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA1).

If the calculated value is greater than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA1: YES), the determination unit 201b acquires the detection value of the refrigerant pressure sensor 180 provided in the pipe 177 through which the liquid refrigerant discharged from the gas-liquid separator 116 flows. The determination unit 201b calculates the pressure difference between the intermediate pressure and the intermediate pressure from the detection value and the detection value of the refrigerant pressure sensor 180 provided on the discharge side of the indoor heat exchanger 122. The determination unit 201b then compares the calculated value with the data of the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA2).

If the calculated value is greater than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA2: YES), the operation control unit 201a drives each of the compressors and the fans 118, 28, and 38 so that the temperature reaches the setting temperature of the indoor unit 120 (step SA3).

In step SA1, if the calculated pressure difference between the medium pressure and the low pressure is equal to or less than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA1: NO), the operation control unit 201a adjusts the opening degree of the gas refrigerant flow control valve 161 and the throttling mechanism 155 to increase the medium pressure (step SA4).
In the refrigeration system 101, the intermediate pressure increases by increasing the opening degree of the throttling mechanism 155 or decreasing the opening degree of the gas refrigerant flow control valve 161.

Then, the determination unit 201b acquires the detection value of the refrigerant pressure sensor 180 provided on the discharge side of the indoor heat exchanger 122 and the detection value of the refrigerant pressure sensor 180 provided on the discharge side of the cold-air heat exchanger 132. The determination unit 201b calculates the differential pressure between the medium pressure and the low pressure from these acquired detection values, and compares this calculated value with the data of the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA5).

If the calculated pressure difference between the medium pressure and the low pressure is equal to or less than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA5: NO), the operation control unit 201a performs step SA4 again.
If both calculated values of the pressure difference between the medium pressure and the low pressure are greater than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA1: YES), the determination unit 201b performs step SA2.

As a result, in the refrigeration system 101, a pressure difference of a predetermined value or more is generated between the suction side and the discharge side of each of the low-stage compressor 111 and the high-stage compressor 112. Therefore, in the refrigeration system 101, poor compression is suppressed in each of the low-stage compressor 111 and the high-stage compressor 112.

As described above, in the refrigeration system 101 of this embodiment, an internal heat exchanger 164 is provided to exchange heat between the liquid refrigerant flowing from the gas-liquid separator 116 to the indoor heat exchanger 122 and the cold-installed heat exchanger 132 and the gas refrigerant discharged from the gas-liquid separator 116. Furthermore, the gas refrigerant discharged from the gas-liquid separator 116 is mixed with a portion of the liquid refrigerant that has exchanged heat with the gas refrigerant discharged from the gas-liquid separator 116 in the internal heat exchanger 164 via the connecting piping 166. As a result, in the refrigeration system 101, the liquid refrigerant becomes colder, improving the refrigeration capacity of the indoor unit 120 through which the liquid refrigerant flows.

When the set temperature of the indoor unit 120 is higher than a predetermined value relative to the temperature of the liquid refrigerant, the refrigeration system 101 reduces the opening of the indoor expansion mechanism 121 to restrict the flow rate of the liquid refrigerant flowing to the indoor unit 120. As a result, the refrigeration system 101 reduces the intermediate pressure, which is the pressure of the refrigerant flowing out of the indoor heat exchanger 122, in other words, the pressure of the refrigerant sucked into each of the high-stage compressors 112.

In step SA2, if the calculated pressure difference between the medium pressure and the intermediate pressure is less than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA2: NO), the operation control unit 201a reduces the rotation frequency of the high-stage compressor 112 (step SA6).

Then, the determination unit 201b determines whether the reduced rotational frequency of the high-stage compressor 112 is greater than a specified value included in the setting data 203a stored in the memory unit 203 (step SA7).

If the rotation frequency is greater than the specified value (step SA7: YES), the determination unit 201b again acquires the detection value of the refrigerant pressure sensor 180 provided in the pipe 177 through which the liquid refrigerant discharged from the gas-liquid separator 116 flows. The determination unit 201b calculates the pressure difference between the medium pressure and the intermediate pressure from the detection value and the detection value of the refrigerant pressure sensor 180 provided on the discharge side of the indoor heat exchanger 122. The determination unit 201b compares the calculated value with the reference pressure value data included in the setting data 203a stored in the memory unit 203 (step SA8).

If the calculated value is greater than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA8: YES), the operation control unit 201a drives each of the compressors and the fans 118, 28, and 38 so that the temperature reaches the setting temperature of the indoor unit 120 (step SA3).

If the calculated pressure difference between the medium pressure and the intermediate pressure is equal to or less than the reference pressure value included in the setting data 203a stored in the memory unit 203 (step SA8: NO), the operation control unit 201a again reduces the rotation frequency of the high-stage compressor 112 (step SA6).

If the rotational frequency of the high-stage compressor 112 is lower than the specified value in step SA7 (step SA7: YES), the operation control unit 201a reduces the opening of the liquid refrigerant flow control valve 165 (step SA9). After this, the operation control unit 201a drives each of the compressors and the fans 118, 28, and 38 so that the temperature of the indoor unit 120 becomes the set temperature (step SA3).

In this way, in the refrigeration system 101, by controlling the rotational frequency of the high-stage compressor 112, it is possible to maintain the pressure difference between the medium pressure and the low pressure at or below a predetermined value. This makes it possible for the refrigeration system 101 to improve the refrigeration efficiency of the indoor unit 120 while suppressing the input to the high-stage compressor 112. Therefore, in the refrigeration system 101, it is possible to improve the efficiency of cooling operation while saving energy.

In addition, the refrigeration system 101 reduces the opening of the liquid refrigerant flow control valve 165 when the rotation frequency becomes smaller than a specified value. As a result, in the refrigeration system 101, the flow rate at which the liquid refrigerant that has exchanged heat with the gas refrigerant discharged from the gas-liquid separator 116 in the internal heat exchanger 164 is mixed with the gas refrigerant discharged from the gas-liquid separator 116 is suppressed. As a result, the flow rate of the liquid refrigerant sent to the indoor unit 120 is reduced, and a decrease in the intermediate pressure is suppressed. And, in the refrigeration system 101, the operation of each of the high stage compressors 112 is suppressed from being stopped.

In the cooling operation of the above-mentioned refrigeration system 101, the refrigerant discharged from the high-stage compressor 112 and radiating heat while maintaining its pressure at high pressure in the outdoor heat exchanger 115 is reduced in pressure by the throttling mechanism 155 to an intermediate pressure and is sent to the gas-liquid separator 116.
On the other hand, in the heating operation of the refrigeration system 101, the refrigerant discharged from the high-stage compressor 112 dissipates heat while maintaining its pressure at a high pressure in the indoor heat exchanger 122. The refrigerant is reduced in pressure by the indoor expansion mechanism 121 to an intermediate pressure, and is sent to the gas-liquid separator 116.

In heating operation of the refrigeration system 101 when the amount of heat exhausted to the cooling equipment 130 is insufficient, the refrigerant discharged from the high-stage compressor 112 and dissipating heat while maintaining its pressure at high in the outdoor heat exchanger 115 is reduced in pressure by the throttling mechanism 155 to an intermediate pressure and sent to the gas-liquid separator 116. Similarly, the refrigerant discharged from the high-stage compressor 112 and dissipating heat while maintaining its pressure at high in the indoor heat exchanger 122 is reduced in pressure by the indoor expansion mechanism 121 to an intermediate pressure and sent to the gas-liquid separator 116.

In heating operation of the refrigeration system 101 when a large capacity is required in the cooling equipment 130 and a heating heat amount is not required, the refrigerant discharged from the high-stage compressor 112 and radiating heat while maintaining a high pressure in the indoor heat exchanger 122 is reduced in pressure by the indoor expansion mechanism 121 to an intermediate pressure and sent to the gas-liquid separator 116. In addition, a portion of the liquid refrigerant flowing out of the gas-liquid separator 116 is reduced in pressure from the intermediate pressure to a low pressure by the refrigerant return expansion mechanism 158 and sent to the outdoor heat exchanger 115.

As described above, the refrigeration system 101 is equipped with the first switching mechanism 150. This allows the refrigeration system 101 to switch between cooling operation and heating operation. In addition, by being equipped with the first switching mechanism 150, when performing heating operation, the refrigeration system 101 can switch between a state in which the outdoor heat exchanger 115 is not used as a condenser and a state in which it is used as a condenser, depending on the surplus or deficiency of heat.

As described above, the refrigeration system 101 is equipped with a second switching mechanism 154. As a result, in both cases where the indoor heat exchanger 122 functions as an evaporator and where the indoor heat exchanger 122 functions as a condenser, the refrigerant discharged from each of the high-stage compressors 112 can be sent to the heat exchanger functioning as an evaporator via the gas-liquid separator 116. This allows the refrigeration system 101 to increase its refrigeration capacity.

Specifically, when the indoor unit 120 is performing cooling operation, the refrigerant sent out from each of the high-stage compressors 112 flows into the gas-liquid separator 116 by the second switching mechanism 154, and then is flowed to the indoor heat exchanger 122 and the cold-setting heat exchanger 132.
When the indoor unit 120 is performing heating operation, the refrigerant sent out from each of the high-stage compressors 112 flows into the gas-liquid separator 116 by the second switching mechanism 154, and is then directed to the cooling heat exchanger 132 or the outdoor heat exchanger 115 depending on the amount of heating heat required.

Furthermore, by providing the first switching mechanism 150 and the second switching mechanism 154, the refrigeration system 101 can switch the state of the outdoor heat exchanger 115 between a state in which it is not used, a state in which it is used as a condenser, and a state in which it is used as an evaporator, depending on the surplus or deficiency of the amount of heat during heating operation. As a result, during heating operation, the refrigeration system 101 can adjust the surplus or deficiency of the amount of heating heat in the indoor unit 120 by switching the state of the outdoor heat exchanger, using the cooling exhaust heat of the cooling heat exchanger 132.

In this way, by being equipped with the first switching mechanism 150 and the second switching mechanism 154, the refrigeration system 101 can increase the refrigeration capacity and adjust the amount of heating heat to be insufficient or excessive, while suppressing an increase in the number of valve bodies and opening/closing devices to be controlled. In other words, the refrigeration system 101 can increase the refrigeration capacity and adjust the amount of heating heat to be insufficient or excessive, using the refrigeration circuit 102 with a simple configuration.

[2-2-7. Operations related to refrigerant recovery]
FIG. 10 is a circuit diagram showing the refrigeration circuit 102 of the refrigeration system 101 during the refrigerant recovery and vacuum drawing operation.
Next, the operation relating to refrigerant recovery will be described.
10 , when an operator performs a refrigerant recovery/vacuuming operation on refrigeration system 101, first, refrigerant recovery device 150 or vacuuming unit 152 is connected to external connection port 196 of service valve 190 via connection piping 156. External connection port 196 is released by the operator after connection piping 156 is connected.

Then, the operator operates the operation panel 232 to select the refrigerant recovery/vacuum drawing mode. This causes a specified signal to be sent from the operation panel 232 to the control device 200. When the control unit 201 receives this signal, it opens all opening and closing devices provided in the refrigeration system 101 fully. When all opening and closing devices are fully open, the control device 200 displays a screen on the display panel 234 indicating that the refrigeration system 101 is operating in the refrigerant recovery/vacuum drawing mode. The operator then drives the refrigerant recovery device 150 or the vacuum drawing unit 152 to recover the refrigerant from the refrigeration circuit 102.

[2-2-8. Operations related to refrigerant charging]
FIG. 11 is a circuit diagram showing the refrigeration circuit 102 of the refrigeration system 101 during the refrigerant charging operation.
Next, the operation relating to charging of the refrigerant will be described.
11 , when an operator performs a refrigerant charging operation on the refrigeration system 101, first, the refrigerant charging unit 154 is connected to the external connection port 196 of the service valve 190 via the connection pipe 156. After the connection pipe 156 is connected, the external connection port 196 is released by the operator.

Next, the operator operates the operation panel 232 to select the refrigerant charging mode. This causes a predetermined signal to be sent from the operation panel 232 to the control device 200. Upon receiving the signal, the control unit 201 fully closes each of the first cooling valve 151, the first heating valve 152, the outdoor refrigerant return valve 153, the opening/closing valve 123, the throttling mechanism 155, the refrigerant return expansion mechanism 158, the gas refrigerant flow control valve 161, the liquid refrigerant flow control valve 165, the indoor expansion mechanism 121, and the cooling outlet side pressure adjustment mechanism 133. Upon receiving the signal, the control unit 201 fully opens each of the check valves 159 provided on the pipes 175 and 76 and the cooling inlet side expansion mechanism 131. Upon completing the control of these opening/closing devices, the control device 200 displays a screen on the display panel 234 indicating that the refrigeration system 101 is performing the refrigerant charging mode. Thereafter, the operator drives the refrigerant charging unit 154 to send the refrigerant to the refrigeration circuit 102 .
As a result, in the refrigeration circuit 102 , the refrigerant is stored in the cold-installed heat exchanger 132 and the gas-liquid separator 116 .

FIG. 12 is a circuit diagram showing the refrigeration circuit 102 of the refrigeration system 101 in the regulated operation.
When the refrigeration system 101 performs cooling operation after the refrigerant is charged, the external connection port 196 is closed by an operator as shown in FIG.
Next, the operator operates the operation panel 232 to select the adjustment operation mode. As a result, a predetermined signal is transmitted from the operation panel 232 to the control device 200. When the control unit 201 receives the signal, it fully closes each of the first heating valve 152, the outdoor refrigerant return valve 153, the refrigerant return expansion mechanism 158, the check valve 159 provided in the piping 176, and the cooling outlet side pressure adjustment mechanism 133. When the control unit 201 receives the signal, it fully opens each of the first cooling valve 151, the opening/closing valve 123, the throttling mechanism 155, the check valve 159 provided in the piping 176, the gas refrigerant flow control valve 161, the liquid refrigerant flow control valve 165, the indoor expansion mechanism 121, and the cooling inlet side expansion mechanism 131. When the control of these opening/closing devices is completed, the control device 200 displays a screen on the display panel 234 indicating that the refrigeration system 101 is performing the adjustment operation mode. After this, the worker drives each of the high stage compressors 112 and the indoor unit 120 while stopping the cooling equipment 130 and the low stage compressor 111. As a result, in the refrigeration circuit 102, refrigerant is sent out to the outdoor heat exchanger 115 and the indoor heat exchanger 2F2. In this case, the indoor expansion mechanism 121 is opened so that the intermediate pressure refrigerant flowing from the gas-liquid separator 116 becomes a low pressure refrigerant. As a result, in the refrigeration system 101, high pressure refrigerant, medium pressure refrigerant, and intermediate pressure refrigerant are generated.

[2-3. Effects, etc.]
As described above, in this embodiment, the refrigeration system 101 includes a refrigeration circuit 102 connecting an outdoor unit 110 having a plurality of compressors, an outdoor heat exchanger 115, and a gas-liquid separator 116, an indoor unit 120 having an indoor heat exchanger 122, and a refrigeration equipment 130 having a refrigeration heat exchanger 132.
The multiple compressors are composed of a low-stage compressor 111 and a high-stage compressor 112, and the indoor heat exchanger 122, which has a high evaporation temperature of the refrigerant, is connected to the high-stage compressor 112, and the cold-air heat exchanger 132, which has a low evaporation temperature of the refrigerant, is connected to the low-stage compressor 111.
The refrigeration circuit 102 includes a second switching mechanism 154 that causes the refrigerant discharged from the high-stage compressor 112 and flowing through at least one of the outdoor heat exchanger 115 and the indoor heat exchanger 122 to flow to the gas-liquid separator 116. A throttling mechanism 155 that adjusts the pressure of the refrigerant, and an indoor expansion mechanism 121 are provided between the outdoor heat exchanger 115, the indoor heat exchanger 122, and the gas-liquid separator 116.

As a result, in the refrigeration system 101, the refrigeration circuit 102 is formed with a simple configuration, and the refrigerant can be sent to the evaporator via the gas-liquid separator 116 whether the cooling operation is being performed or the heating operation is being performed. Therefore, the refrigeration system 101 can improve the refrigeration capacity with a simple circuit configuration.

As in the present embodiment, the second switching mechanism 154 includes pipes 173 to 76 that connect the outdoor heat exchanger 115, the indoor heat exchanger 122, the cold-installed heat exchanger 132, and the gas-liquid separator 116 to one another. Each of the pipes 173 to 76 may be provided with a throttling mechanism 155 that adjusts the flow of the refrigerant, a refrigerant return expansion mechanism 158, and a check valve 159.
As a result, in the refrigeration system 101, the refrigerant that is heat exchanged by the gas-liquid separator 116 can be sent to any one of the outdoor heat exchanger 115, the indoor heat exchanger 122, and the cold-air heat exchanger 132 depending on the operation of the indoor unit 120 and the cold-air equipment 130. Therefore, the refrigeration system 101 can increase the refrigeration capacity of the indoor unit 120 and the cold-air equipment 130.

As in the present embodiment, the second switching mechanism 154 may include a check valve 159 and a throttle mechanism 155 as a valve body.
As a result, in the refrigeration system 101, the refrigerant that is heat exchanged by the gas-liquid separator 116 can be sent to any one of the outdoor heat exchanger 115, the indoor heat exchanger 122, and the cold-air heat exchanger 132 depending on the operation of the indoor unit 120 and the cold-air equipment 130. Therefore, the refrigeration system 101 can increase the refrigeration capacity of the indoor unit 120 and the cold-air equipment 130.

As in this embodiment, the first switching mechanism 150 may be a mechanism that switches between any of a flow path through which the refrigerant discharged from the high-stage compressor 112 flows to the outdoor heat exchanger 115, a flow path through which the refrigerant discharged from the high-stage compressor 112 flows to the indoor heat exchanger 122, and a flow path through which the refrigerant discharged from the high-stage compressor 112 flows to both the outdoor heat exchanger 115 and the indoor heat exchanger 122.
This allows the refrigeration system 101 to include a more simply configured refrigeration circuit 102. In addition, in the refrigeration system 101, operation can be switched without stopping the compressor.

As in this embodiment, the first switching mechanism 150 may be provided with a first cooling valve 151 located between the discharge side of the high-stage compressor 112 and the outdoor heat exchanger 115, and an outdoor refrigerant return valve 153 located downstream of the first cooling valve 151 and between the discharge side of the high-stage compressor 112 and the suction side of the low-stage compressor 111.
As a result, the refrigeration system 101 can switch between any one of a flow path in which the refrigerant discharged from the high-stage compressor 112 flows to the outdoor heat exchanger 115, a flow path in which the refrigerant discharged from the high-stage compressor 112 flows to the indoor heat exchanger 122, and a flow path in which the refrigerant discharged from the high-stage compressor 112 flows to both the outdoor heat exchanger 115 and the indoor heat exchanger 122. Therefore, the refrigeration system 101 can be provided with a refrigeration circuit 102 with a simpler configuration.

As in this embodiment, the refrigeration system 101 includes a control device 200 that controls each part of the refrigeration circuit 102. The control device 200 includes an operation panel 232 that can be operated by an operator. The control device 200 includes, as operation modes of the refrigeration circuit 102, a first operation mode in which the refrigerant flowing through the indoor heat exchanger 122 and the cold-setting heat exchanger 132 is adjusted to a predetermined temperature, and a second operation mode in which an operation is performed in accordance with the operation of an external device connected to the refrigeration circuit 102. The control device 200 may switch between the first operation mode and the second operation mode in accordance with an operation on the operation panel 232.
As a result, in the refrigeration system 101, it is possible to switch between the first operation mode and the second operation mode by operating the operation panel 232. Therefore, in the refrigeration system 101, an operator can easily switch between the operation modes.

As in the present embodiment, the control device 200 may be provided with a plurality of second operating modes, and may switch between each of the second operating modes in accordance with an operation on the operation panel 232 .
As a result, in the refrigeration system 101, an operator can perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging by operating the operation panel 232. As a result, in the refrigeration system 101, an operator can easily perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging.

As in this embodiment, the control device 200 may include a display panel 234 that displays the state of the refrigeration circuit 102 in each of the operation modes.
As a result, in refrigeration system 101, an operator can perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging by operating control device 200 while checking the state of refrigeration system 101. As a result, in refrigeration system 101, an operator can easily perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging.

As in the present embodiment, a service valve 190 to which an external device can be connected may be provided between the cold-installed heat exchanger 132 and the suction side of the low-stage compressor 111 .
As a result, in the refrigeration system 101, the service valve 190 is provided at a location close to a connection location between the outdoor unit 110 and the cooling equipment 130. Therefore, in the refrigeration system 101, it is possible to improve the workability when connecting an external device to the refrigeration system 101.

Other Embodiments
As described above, the first and second embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, it is also possible to combine the components described in the first and second embodiments to create new embodiments.
Therefore, other embodiments will be exemplified below.

In the above-described embodiment, the refrigeration system 101 is provided with the connection pipe 166, but the connection pipe 166 may be omitted.
In the above-described embodiment, the cooling-use outlet-side pressure adjustment mechanism 133 and the service valve 190 are provided in the cooling equipment 130. However, this is not limiting, and the cooling-use outlet-side pressure adjustment mechanism 133 and the service valve 190 may be provided in the outdoor unit 110. Furthermore, for example, the cooling-use outlet-side pressure adjustment mechanism 133 and the service valve 190 may be provided in the piping 172 between the outdoor unit 110 and the cooling equipment 130.

In the above-described embodiment, the refrigeration system 101 includes one indoor heat exchanger 122 and one cold-use heat exchanger 132. However, the present invention is not limited to this, and the refrigeration system 101 may include another cold-use heat exchanger 132 instead of the indoor heat exchanger 122. That is, in this refrigeration system 101, the indoor unit 120 may be omitted, and a plurality of cold-use devices 130 may be included.
In this case, the multiple cold-set heat exchangers 132 have different evaporation temperature zones. Among the multiple cold-set heat exchangers 132, the cold-set heat exchanger 132 having a higher evaporation temperature zone is connected to the inlet side of the high-stage compressor 112, and the cold-set heat exchanger 132 having a lower evaporation temperature zone is connected to the inlet side of the low-stage compressor 111.

For example, if the refrigeration system 101 includes a refrigeration equipment 130 set to the freezing temperature zone and a refrigeration equipment 130 set to the refrigeration temperature zone, the refrigeration heat exchanger 132 in the refrigeration equipment 130 set to the refrigeration temperature zone is connected to the inlet side of the high-stage compressor 112. In contrast, in the refrigeration equipment 130 set to the freezing temperature zone, the refrigeration heat exchanger 132 is connected to the inlet side of the low-stage compressor 111.

In the above-described embodiment, the utilization side heat exchangers connected to the inlet side of the high-stage compressor 112 may be arranged in parallel in multiple locations on the pipes 178 and 171. Similarly, the utilization side heat exchangers connected to the inlet side of the low-stage compressor 111 may be arranged in parallel in multiple locations on the pipes 177 and 172.

Furthermore, for example, multiple indoor heat exchangers 122 may be provided in parallel to each other in the pipes 178 and 171. In this case, an indoor expansion mechanism 121 may be provided on the inlet side of each of the indoor heat exchangers 122. In this case, the refrigeration system 101 includes multiple indoor units 120. Also in this case, one or more indoor heat exchangers 122 and one or more cold-use heat exchangers 132 may be provided in parallel in the pipes 178 and 171.

Plural cold-use heat exchangers 132 may be provided in parallel to each other in the pipes 177 and 172. In this case, a cold-use inlet expansion mechanism 131 may be provided on the inlet side of each of the cold-use heat exchangers 132. In this case, at least one of the cold-use heat exchangers 132 provided in parallel to each other in the pipes 177 and 172 may have a different evaporation temperature range from the other cold-use heat exchangers 132.

The control device 200 may include a touch panel that combines the functions of the operation panel 232 and the display panel 234 .
Furthermore, for example, the control device 200 may be provided in either the indoor unit 120 or the cooling equipment 130. Furthermore, for example, either the operation panel 232 or the display panel 234 may be provided integrally in either the outdoor unit 110, the indoor unit 120, or the cooling equipment 130.
Furthermore, for example, the control device 200 may be provided integrally with an operation terminal such as a remote control provided in the indoor unit 120 or the cooling equipment 130. The remote control is a terminal that operates the set temperatures of the indoor unit 120 or the cooling equipment 130, starts the indoor unit 120 or the cooling equipment 130, or the like.

Further, for example, the control device 200 may be a communication terminal such as a smartphone or tablet on which an app or program that transmits a predetermined signal to the outdoor unit 110 or each part of the refrigeration system 101 is installed. In this case, the control device 200 may be capable of communicating with the outdoor unit 110 and each part of the refrigeration system 101 via a network configured of a public line network, a dedicated line, other communication lines, and various communication facilities. The specific form of this network is not limited. The communication network may include at least one of a wireless communication circuit and a wired communication circuit.
Furthermore, for example, the control device 200 may be a server device in which an application or program that transmits a predetermined signal to the outdoor unit 110 and each part of the refrigeration system 101 is installed. The server device may be capable of communicating with the outdoor unit 110 and each part of the refrigeration system 101 via the above-mentioned network.

The components shown in FIG. 4 are merely examples, and the specific implementation form is not particularly limited. In other words, it is not necessary to implement hardware that corresponds to each component individually, and it is of course possible to implement a configuration in which one processor executes a program to realize the functions of each component. Also, some of the functions realized by software in the above-described embodiment may be hardware, or some of the functions realized by hardware may be software. In addition, the specific detailed configurations of other components such as the outdoor unit 110, indoor unit 120, and cooling equipment 130 may also be changed as desired without departing from the spirit of this disclosure.

The step units of the operation shown in FIG. 7 are divided according to the main processing content in order to facilitate understanding of the operation of each part of the refrigeration system 101, and the operation is not limited by the way in which the processing units are divided or their names. Depending on the processing content, the operation may be divided into more step units. Also, a step may be divided so that it contains even more processing. Also, the order of the steps may be changed as appropriate within the scope of the purpose of this disclosure.

The above-described embodiments are intended to illustrate the technology disclosed herein, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

(Additional Note)
The above description of the embodiments discloses the following techniques.
(Technology 1) A refrigeration system comprising: a refrigeration cycle circuit connecting an outdoor unit having a low-stage compressor, a high-stage compressor, an outdoor heat exchanger, and an oil separator arranged on the discharge side of the high-stage compressor, an indoor unit having an indoor heat exchanger, and a cooling equipment having a cooling heat exchanger, an intercooler arranged between the low-stage compressor and the high-stage compressor, and a switching means for switching the refrigerant from the low-stage compressor to the suction side of the high-stage compressor or to the intercooler.
With this configuration, the efficiency of a two-stage compression refrigeration system using a low-stage compressor and a high-stage compressor can be improved by switching the three-way valve depending on the operating conditions.

(Technology 2) The refrigeration system according to Technology 1, wherein during cooling operation, the switching means switches so as to send the refrigerant from the low-stage compressor to the intercooler.
With this configuration, during cooling operation, the refrigerant sent from the low-stage compressor is sent to the intercooler, cooled by the intercooler, and then sent to the high-stage compressor, thereby improving the compression efficiency of the high-stage compressor.

(Technology 3) A refrigeration system in which, during heating operation, the switching means switches so as to send refrigerant from the low-stage compressor directly to the suction side of the high-stage compressor.
With this configuration, during heating operation, the refrigerant sent from the low-stage compressor is sent directly to the high-stage compressor without passing through the intercooler, thereby making it possible to improve the efficiency of waste heat utilization during heating operation.

(Technology 4) A refrigeration system as described in Technology 1, in which an accumulator is disposed between the low-stage compressor and the high-stage compressor, and during heating operation, the switching means switches so as to send refrigerant from the low-stage compressor to the suction side of the high-stage compressor via the accumulator.
With this configuration, during heating operation, the refrigerant sent from the low-stage compressor is sent to the high-stage compressor via the accumulator without passing through the intercooler, thereby making it possible to improve the efficiency of utilizing exhaust heat during heating operation.

(Technology 5) A refrigeration system including a refrigeration circuit provided with a plurality of compressors, a heat source side heat exchanger, a plurality of user side heat exchangers, and a gas-liquid separator, the plurality of compressors being composed of low stage compressors and high stage compressors, the plurality of user side heat exchangers being composed of a first user side heat exchanger and a second user side heat exchanger having a refrigerant evaporation temperature lower than that of the first user side heat exchanger, the refrigeration circuit being provided with a switching mechanism that causes the refrigerant discharged from the high stage compressor and flowing through at least one of the heat source side heat exchanger and the first user side heat exchanger to flow to the gas-liquid separator, and a throttling mechanism that adjusts the pressure of the refrigerant being provided between the heat source side heat exchanger, the first user side heat exchanger, and the gas-liquid separator.
As a result, the refrigeration system forms a refrigeration circuit with a simple configuration, and can send refrigerant to the heat exchanger functioning as an evaporator via the gas-liquid separator in both cooling and heating operations, thereby improving the refrigeration capacity of the refrigeration system with a simple circuit configuration.

(Technology 6) A refrigeration system as described in Technology 5, wherein the switching mechanism includes piping that connects the heat source side heat exchanger, the first usage side heat exchanger, the second usage side heat exchanger, and the gas-liquid separator to each other, and each of the piping is provided with a valve body that adjusts the flow of the refrigerant.
As a result, in the refrigeration system, the refrigerant that is heat exchanged by the gas-liquid separator can be sent to any one of the heat source side heat exchanger, the first user side heat exchanger, and the second user side heat exchanger, thereby improving the refrigeration capacity of the refrigeration system.

(Technology 7) A refrigeration system according to Technology 6, wherein the switching mechanism includes a check valve as the valve body and the throttling mechanism.
As a result, in the refrigeration system, the refrigerant that is heat exchanged by the gas-liquid separator can be sent to any one of the utilization side heat exchanger, the first utilization side heat exchanger, and the second utilization side heat exchanger, thereby increasing the refrigeration capacity of the refrigeration system.

(Technology 8) The refrigeration system described in any one of Technology 5 to Technology 7, wherein the refrigeration circuit is provided with another switching mechanism that switches between a flow path through which the refrigerant discharged from the high-stage compressor flows to the heat source side heat exchanger, a flow path through which the refrigerant discharged from the high-stage compressor flows to the first use side heat exchanger, and a flow path through which the refrigerant discharged from the high-stage compressor flows to both the heat source side heat exchanger and the first use side heat exchanger.
This allows the refrigeration system to have a refrigeration circuit with a simpler configuration. In addition, the refrigeration system can switch between operations without stopping the compressor.

(Technology 9) A refrigeration system as described in Technology 8, in which the other switching mechanism includes a first cooling valve which is a valve body located between the discharge side of the high-stage compressor and the heat source side heat exchanger, and an outdoor refrigerant return valve which is a valve body located downstream of the first cooling valve and between the discharge side of the high-stage compressor and the suction side of the low-stage compressor.
This makes it possible for the refrigeration system to switch between a flow path in which the refrigerant discharged from the high-stage compressor flows to the heat source-side heat exchanger, a flow path in which the refrigerant discharged from the high-stage compressor flows to the first user-side heat exchanger, and a flow path in which the refrigerant discharged from the high-stage compressor flows to both the outdoor heat exchanger and the first user-side heat exchanger. Therefore, the refrigeration system can be provided with a refrigeration circuit with a simpler configuration.

(Technology 10) A refrigeration system as described in any one of Technology 5 to Technology 9, comprising a control unit that controls each part of the refrigeration circuit, the control unit having an operation unit that can be operated by an operator, the control unit having operation modes of the refrigeration circuit, a first operation mode in which a refrigerant flowing through the first use side heat exchanger and the second use side heat exchanger is adjusted to a predetermined temperature, and a second operation mode in which an operation is performed in conjunction with an operation of an external device connected to the refrigeration circuit, and the refrigeration system switches between the first operation mode and the second operation mode in accordance with an operation on the operation unit.
Thus, in the refrigeration system, the first operation mode and the second operation mode can be switched by operating the operation unit, so that an operator can easily switch the operation mode in the refrigeration system.

(Technology 11) A refrigeration system as described in Technology 10, wherein the control unit has a plurality of the second operating modes and switches between each of the second operating modes in accordance with an operation on the operating unit.
As a result, in the refrigeration system, an operator can perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging by operating the operation unit. As a result, in the refrigeration system, an operator can easily perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging.

(Technology 12) A refrigeration system according to Technology 10 or Technology 11, wherein the control unit is provided with a display unit that displays a state of the refrigeration circuit in each of the operating modes.
As a result, in the refrigeration system, an operator can perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging by operating the control unit while checking the state of the refrigeration system. Therefore, in the refrigeration system, an operator can easily perform tasks related to refrigerant recovery, vacuuming, and refrigerant charging.

(Technology 13) The refrigeration system according to any one of Technology 5 to Technology 12, wherein a connection port capable of connecting an external device is provided between the second utilization side heat exchanger and the suction side of the low stage compressor.
This makes it possible to improve the workability of the refrigeration system when connecting an external device to the refrigeration system.

The first aspect of the present disclosure can be suitably used as a refrigeration system that can increase the efficiency of a two-stage compression refrigeration system using a low-stage compressor and a high-stage compressor by switching the switching means depending on operating conditions.
The second aspect of the present disclosure can be suitably used as a refrigeration system that uses a natural refrigerant, can improve the efficiency of the air conditioning temperature zone, and can improve the efficiency of the entire system.

REFRIGERATION SYSTEM 10 Outdoor unit 11 Low stage compressor 12 High stage compressor 13 Accumulator 14 Oil separator 15 Outdoor heat exchanger 16 Gas-liquid separator 20 Indoor unit 21 Indoor expansion mechanism 22 Indoor heat exchanger 23 Opening/closing valve 30 Refrigeration equipment 31 Refrigeration heat exchanger 32 Refrigeration inlet side expansion mechanism 33 Refrigeration outlet side pressure adjustment mechanism 40 Refrigerant piping 41 First heating piping 42 First outdoor return piping 43 Second cooling piping 44 Second heating piping 45 Second outdoor return piping 50 First switching mechanism 51 First cooling valve 52 First heating valve 53 Outdoor refrigerant return valve 54 Second switching mechanism 55 Second cooling valve 56 Third cooling valve 57 Second heating valve 58 Refrigerant return expansion mechanism 59 Check valve 60 Gas refrigerant return piping 61 Gas refrigerant flow control valve 65 Intercooler 66 Bypass pipe 67 Three-way valve 101 Refrigeration system 102 Refrigeration circuit 110 Outdoor unit 111 Low stage compressor 112 High stage compressor 113 Accumulator 114 Oil separator 115 Outdoor heat exchanger (heat source side heat exchanger)
116 Gas- liquid separator 118, 128, 138 Blower 120 Indoor unit 121 Indoor expansion mechanism 122 Indoor heat exchanger (first use side heat exchanger)
123 Opening/closing valve 127 Space temperature sensor 130 Cooling equipment 131 Cooling inlet side expansion mechanism 132 Cooling heat exchanger (second user side heat exchanger)
133: Cooling outlet pressure adjustment mechanism 137: Internal temperature sensor 140: Pipe 141: First heating pipe 142: First outdoor return pipe 150: First switching mechanism (another switching mechanism)
151: First cooling valve; 152: First heating valve; 153: Outdoor refrigerant return valve; 154: Second switching mechanism (switching mechanism)
Description of the Reference Numerals 155 Throttling mechanism 158 Refrigerant return expansion mechanism 159 Check valve 160 Gas refrigerant return piping 161 Gas refrigerant flow control valve 164 Internal heat exchanger 165 Liquid refrigerant flow control valve 166 Connection piping 171 Pipe 172 Pipe 173 First pipe 174 Second pipe 175 Third pipe 176 Fourth pipe 177 Pipe 178 Pipe 179 Pipe 180 Refrigerant pressure sensor 182 Refrigerant temperature sensor 190 Service valve 192 Pipe connection port 194 Pipe connection port 196 External connection port 200 Control device 201 Control unit 201a Operation control unit 201b Determination unit 203 Memory unit 203a Setting data 205 Outdoor unit I/F
206 Outdoor unit communication unit 210 Indoor unit control device 211 Indoor unit control unit 213 Indoor unit memory unit 215 Indoor unit I/F
220 Refrigeration equipment control device 221 Refrigeration equipment control unit 223 Refrigeration equipment memory unit 225 Refrigeration equipment I/F
232 Operation panel 234 Display panel 250 Refrigerant recovery device 252 Vacuum drawing unit 254 Refrigerant injection unit 256 Connection pipes A, B, C, D Connection section

Claims (13)

1. a refrigeration cycle circuit connecting an outdoor unit having a low-stage compressor, a high-stage compressor, an outdoor heat exchanger, and an oil separator disposed on the discharge side of the high-stage compressor, an indoor unit having an indoor heat exchanger, and a cooling equipment having a cooling heat exchanger;
   A refrigeration system comprising: an intercooler disposed between the low-stage compressor and the high-stage compressor; and a switching means for switching refrigerant from the low-stage compressor to a suction side of the high-stage compressor or to the intercooler.
2. The refrigeration system according to claim 1 , wherein during a cooling operation, the switching means switches so that the refrigerant from the low stage compressor is sent to the intercooler.
3. The refrigeration system according to claim 1 , wherein during a heating operation, the switching means switches so that the refrigerant from the low-stage compressor is sent directly to the suction side of the high-stage compressor.
4. an accumulator is disposed between the low stage compressor and the high stage compressor;
   The refrigeration system according to claim 1 , wherein, during a heating operation, the switching means switches so that the refrigerant from the low-stage compressor is sent to the suction side of the high-stage compressor via the accumulator.
5. A plurality of compressors;
   A heat source side heat exchanger;
   A plurality of utilization side heat exchangers;
   A gas-liquid separator;
   A refrigeration circuit is provided with
   The plurality of compressors include
   A low stage compressor;
   A high-stage compressor;
   It is composed of
   The plurality of utilization side heat exchangers include
   A first utilization side heat exchanger;
   a second use-side heat exchanger having a refrigerant evaporation temperature lower than that of the first use-side heat exchanger;
   It is composed of
   The refrigeration circuit includes:
   a switching mechanism is provided that causes the refrigerant discharged from the high-stage compressor and flowing through at least one of the heat source side heat exchanger and the first usage side heat exchanger to flow into the gas-liquid separator;
   the heat source side heat exchanger and the first utilization side heat exchanger;
   The gas-liquid separator;
   In between,
   A refrigeration system in which a throttling mechanism is provided to adjust the pressure of the refrigerant.
6. The switching mechanism includes:
   The heat source side heat exchanger;
   The first utilization side heat exchanger;
   The second utilization side heat exchanger;
   The gas-liquid separator;
   a pipe connecting each of the
   The refrigeration system according to claim 5 , wherein each of the pipes is provided with a valve body for regulating the flow of the refrigerant.
7. The switching mechanism includes the valve body,
   A check valve;
   The throttle mechanism;
   The refrigeration system of claim 6 .
8. The refrigeration circuit includes:
   a flow path through which a refrigerant discharged from the high-stage compressor flows into the heat source-side heat exchanger;
   a flow path through which a refrigerant discharged from the high-stage compressor flows to the first utilization-side heat exchanger;
   a flow path through which a refrigerant discharged from the high-stage compressor flows to both the heat source side heat exchanger and the first utilization side heat exchanger;
   The refrigeration system according to any one of claims 5 to 7, further comprising another switching mechanism for switching to any one of the flow paths.
9. The other switching mechanism includes:
   a first cooling valve which is a valve body located between the discharge side of the high-stage compressor and the heat source side heat exchanger;
   an outdoor refrigerant return valve which is a valve body located downstream of the first cooling valve and between the discharge side of the high stage compressor and the suction side of the low stage compressor;
   The refrigeration system of claim 8 , further comprising:
10. A control unit for controlling each part of the refrigeration circuit,
    The control unit includes an operation unit that can be operated by an operator,
    The control unit sets the operation mode of the refrigeration circuit as follows:
    a first operation mode in which a refrigerant flowing through the first use-side heat exchanger and the second use-side heat exchanger is adjusted to a predetermined temperature;
    A second operation mode in which an operation is performed in association with an operation of an external device connected to the refrigeration circuit;
    Equipped with
    The refrigeration system according to claim 5 , wherein the first operation mode and the second operation mode are switched in accordance with an operation on the operation unit.
11. The refrigeration system according to claim 10 , wherein the control unit is configured to have a plurality of the second operation modes, and to switch between the second operation modes in accordance with an operation on the operation unit.
12. The refrigeration system according to claim 10 , wherein the control unit includes a display unit that displays a state of the refrigeration circuit in each of the operation modes.
13. The second utilization side heat exchanger;
    A suction side of the low stage compressor;
    The refrigeration system according to any one of claims 5 to 7, further comprising a connection port between the cooling unit and the cooling unit, the connection port being capable of connecting an external device.

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