WO2024004558A1

WO2024004558A1 - Refrigeration device, and refrigeration device control method

Info

Publication number: WO2024004558A1
Application number: PCT/JP2023/021218
Authority: WO
Inventors: 剛吉田
Original assignee: 株式会社前川製作所
Priority date: 2022-06-30
Filing date: 2023-06-07
Publication date: 2024-01-04
Also published as: JP2024005797A

Abstract

A refrigeration device according to an embodiment of the present disclosure comprises: a low-stage compressor for compressing a refrigerant; a high-stage compressor for compressing the refrigerant that has been compressed by the low-stage compressor; a flash tank capable of accepting the refrigerant that has been compressed by the high-stage compressor; and a liquid injection flow passage for supplying refrigerant liquid in the flash tank into the refrigerant that has been compressed by the low-stage compressor and discharged from the low-stage compressor.

Description

Refrigeration equipment and refrigeration equipment control method

The present disclosure relates to a refrigeration device and a method of controlling the refrigeration device.

A refrigeration system is known that includes a low-stage compressor and a high-stage compressor and is configured to perform two-stage compression. In such a refrigeration system, in order to increase the efficiency of the high-stage compressor, it is necessary to suppress the degree of superheating of the refrigerant sucked into the high-stage compressor. Therefore, in order to suppress the degree of superheating of the refrigerant sucked into the high-stage compressor, a configuration is known in which an intercooler is provided to cool the refrigerant discharged from the low-stage compressor (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2009-133585

However, when providing such an intercooler, there are problems such as securing an installation location and heat radiation space, and an increase in cost, and especially in the case of an air-cooled type, there is also the problem of noise. Furthermore, when the outside air temperature is high, there is a possibility that the refrigerant discharged from the low stage compressor cannot be sufficiently cooled.

In view of the above-mentioned circumstances, at least one embodiment of the present disclosure provides a method for efficiently suppressing the degree of superheating of refrigerant sucked into a high-stage compressor in a refrigeration system configured to perform two-stage compression. purpose.

(1) A refrigeration device according to at least one embodiment of the present disclosure includes:
a low stage compressor for compressing refrigerant;
a high stage compressor for compressing the refrigerant after being compressed by the low stage compressor;
a flash tank capable of receiving the refrigerant after being compressed by the high-stage compressor;
a liquid injection flow path for supplying refrigerant liquid in the flash tank to the refrigerant after being compressed by the low-stage compressor and discharged from the low-stage compressor;
Equipped with.

(2) A method for controlling a refrigeration device according to at least one embodiment of the present disclosure includes:
A method for controlling a refrigeration device, the method comprising:
The refrigeration device includes:
a low stage compressor for compressing refrigerant;
a high stage compressor for compressing the refrigerant after being compressed by the low stage compressor;
a flash tank capable of receiving the refrigerant after being compressed by the high-stage compressor;
a liquid injection flow path for supplying refrigerant liquid in the flash tank to the refrigerant after being compressed by the low stage compressor;
a first expansion valve provided in the liquid injection flow path;
Equipped with
a suction temperature detection step of detecting the suction temperature of the refrigerant sucked into the high-stage compressor;
a suction pressure detection step of detecting the suction pressure of the refrigerant sucked into the high-stage compressor;
a suction superheat degree calculation step of calculating a suction superheat degree of the refrigerant sucked into the high-stage compressor based on the detected suction temperature and the detected suction pressure;
an opening degree adjusting step of adjusting the opening degree of the first expansion valve so that the calculated suction superheat degree becomes a preset target value;
Equipped with.

According to at least one embodiment of the present disclosure, in a refrigeration system configured to perform two-stage compression, the degree of superheat of refrigerant sucked into a high-stage compressor can be efficiently suppressed.

FIG. 1 is a system diagram of a refrigeration device according to an embodiment. 1 is an example of a Mollier diagram of a refrigeration system according to an embodiment that uses CO ₂ refrigerant. It is a flowchart which shows the flow of the process performed in a control apparatus for adjusting the opening degree of a 1st expansion valve.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, and are merely illustrative examples. do not have.
For example, expressions expressing relative or absolute positioning such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""centered,""concentric," or "coaxial" are strictly In addition to representing such an arrangement, it also represents a state in which they are relatively displaced with a tolerance or an angle or distance that allows the same function to be obtained.
For example, expressions such as "same,""equal," and "homogeneous" that indicate that things are in an equal state do not only mean that things are exactly equal, but also have tolerances or differences in the degree to which the same function can be obtained. It also represents the existing state.
For example, expressions expressing shapes such as squares and cylinders do not only refer to shapes such as squares and cylinders in a strict geometric sense, but also include uneven parts and chamfers to the extent that the same effect can be obtained. Shapes including parts, etc. shall also be expressed.
On the other hand, the expressions "comprising,""comprising,""comprising,""containing," or "having" one component are not exclusive expressions that exclude the presence of other components.

FIG. 1 is a system diagram of a refrigeration system according to an embodiment. The refrigeration system 1 according to one embodiment is, for example, a two-stage compression two-stage expansion type refrigeration system that uses CO ₂ refrigerant. In the refrigeration apparatus 1 according to one embodiment, a low stage compressor 11, a high stage compressor 12, and a flash tank 13 are provided in a refrigerant circulation path 30. In the refrigeration system 1 according to one embodiment, for example, two low stage compressors 11 are provided in parallel to the refrigerant circulation path 30. In the refrigeration system 1 according to one embodiment, for example, two high-stage compressors 12 are provided in parallel to the refrigerant circulation path 30.

In the refrigeration system 1 according to one embodiment, an accumulator 14 is provided in a refrigerant flow path 31 that connects the outlet of the low-stage compressor 11 and the inlet of the high-stage compressor 12.
In the refrigeration system 1 according to one embodiment, a condenser 15 that operates as a gas cooler is provided in a refrigerant flow path 32 that connects the outlet of the high-stage compressor 12 and the inlet of the flash tank 13. In the refrigeration system 1 according to one embodiment, a heat exchanger 17 is provided in the refrigerant circulation path 30 for exchanging heat between the liquid phase part of the flash tank 13 and the refrigerant that has passed through the evaporator 16 as a cooling load, for example. There is.

In the refrigeration system 1 according to one embodiment, the low-stage compressor 1 The refrigerant flow path 31a connects the outlet of the accumulator 14 to the refrigerant flow path 31a.
The refrigeration apparatus 1 according to one embodiment includes a flash gas flow path 36 that connects the gas phase portion of the flash tank 13 and a refrigerant flow path 31a that connects the outlet of the low stage compressor 11 and the accumulator 14. .

In the refrigeration apparatus 1 according to one embodiment, a first expansion valve 41 is provided in the liquid injection flow path 35, and a second expansion valve (high-stage An expansion valve) 42 is provided. The refrigeration apparatus 1 according to one embodiment has a refrigerant flow path 34 b that connects the heat exchanger 17 and the evaporator 16 among the refrigerant flow paths 34 for supplying the refrigerant liquid in the flash tank 13 to the evaporator 16 . A third expansion valve (low stage expansion valve) 43 is provided. In the refrigeration apparatus 1 according to one embodiment, a fourth expansion valve 44 is provided in the flash gas flow path 36.

In the refrigeration system 1 according to one embodiment, an oil separator 21 for separating refrigerant gas and refrigerating machine oil is provided in a refrigerant flow path 32a that connects the outlet of the high-stage compressor 12 and the condenser 15. . In the refrigeration system 1 according to one embodiment, the refrigeration oil separated by the oil separator 21 is configured to be returned to the low-stage compressor 11 and the high-stage compressor 12 via an oil tank (not shown). .

The refrigeration system 1 according to one embodiment includes a control device 50 for controlling each part of the refrigeration system 1. The control device 50 includes a processor 51 that executes various calculation processes, and a memory 53 that non-temporarily or temporarily stores various data processed by the processor 51. The processor 51 is realized by a CPU, GPU, MPU, DSP, various other arithmetic devices, or a combination thereof. The memory 53 is realized by ROM, RAM, flash memory, or a combination thereof.
In the following description, the control content of the control device 50 will be mainly explained regarding adjustment of the opening degree of the first expansion valve 41. Note that the control contents of the control device 50 will be described in detail later.
The refrigeration system 1 according to one embodiment includes various sensors for controlling each part of the refrigeration system 1. Various sensors for controlling each part of the refrigeration system 1 include, for example, a suction temperature sensor 55 for detecting the suction temperature Ti of the refrigerant sucked into the high-stage compressor 12; A suction pressure sensor 57 is included to detect the suction pressure Pi of the refrigerant.

In the refrigeration system 1 according to the embodiment configured as described above, the refrigerant compressed by the low stage compressor 11 and the high stage compressor 12 is cooled by the condenser 15. The refrigerant cooled by the condenser 15 is depressurized through the second expansion valve 42 and then sent to the flash tank 13 where it is separated into a gas phase and a liquid phase.
The refrigerant liquid forming the liquid phase in the flash tank 13 exits the flash tank 13 and exchanges heat with the refrigerant returning from the evaporator 16 in the heat exchanger 17 to heat the refrigerant. The refrigerant liquid sent from the flash tank 13 to the heat exchanger 17 exits the heat exchanger 17, passes through the third expansion valve 43, is depressurized, is vaporized via the evaporator 16 and the heat exchanger 17, and is transferred to the lower stage. It is supplied to the compressor 11.

In the refrigeration apparatus 1 according to the embodiment, as described above, the refrigerant liquid in the flash tank 13 is supplied to the refrigerant after being compressed by the low stage compressor 11 and discharged from the low stage compressor 11. An injection flow path 35 is provided.
In order to increase the efficiency of the high-stage compressor 12, it is necessary to suppress the degree of superheating of the refrigerant sucked into the high-stage compressor 12. Therefore, it is conceivable to use a heat exchanger for cooling the refrigerant sucked into the high-stage compressor 12. However, when providing such a heat exchanger, problems arise such as securing an installation location and increasing costs.
As a result of intensive study by the inventors, the refrigerant liquid in the flash tank 13 is supplied to the refrigerant after being compressed in the low stage compressor 11 and discharged from the low stage compressor 11. It has been found that the degree of superheating of the refrigerant being sucked can be effectively suppressed.
According to the refrigeration system 1 according to the embodiment, there is no installation space for installing a heat exchanger for cooling the refrigerant sucked into the high-stage compressor 12, and there is no need to pay the cost for installing the heat exchanger. The degree of superheating of the refrigerant sucked into the high-stage compressor 12 can be efficiently suppressed regardless of the temperature conditions of the outside air. Thereby, the efficiency of the high-stage compressor 12 can be improved at low cost.

In the refrigeration system 1 according to the embodiment, the liquid injection channel 35 is a channel through which the liquid phase part of the flash tank 13 and the refrigerant after being compressed by the low stage compressor 11 flow through the low stage compressor 11. The refrigerant flow path 31 connecting the outlet of the high-stage compressor 12 and the inlet of the high-stage compressor 12 may be provided so as to communicate with each other. A downstream end 35d of the liquid injection channel 35 is preferably connected to the refrigerant channel 31.
Thereby, the refrigerant liquid in the flash tank 13 can be supplied to the refrigerant after being compressed by the low stage compressor 11 with a simple configuration.
Note that the upstream end 35u of the liquid injection channel 35 is connected to the flash tank 13 and the heat exchanger 17 in the refrigerant channel 34 for supplying the refrigerant liquid in the flash tank 13 to the evaporator 16, as shown in FIG. It may be connected to the refrigerant flow path 34a that connects the flash tank 13, or it may be directly connected to the flash tank 13.

The refrigeration apparatus 1 according to one embodiment may include a first expansion valve 41 provided in the liquid injection channel 35.
Thereby, the refrigerant liquid in the flash tank 13 can be supplied to the refrigerant compressed by the low-stage compressor 11 with good controllability.

The refrigeration device 1 according to one embodiment may include a second expansion valve 42 provided in the refrigerant flow path 32b, which is a flow path connecting the condenser 15 and the flash tank 13.
Thereby, the discharge pressure of the high stage compressor 12 can be adjusted.
Furthermore, in the refrigeration system 1 according to the embodiment, a flash gas flow path 36 connecting the gas phase portion of the flash tank 13 and the refrigerant flow path 31a connecting the outlet of the low stage compressor 11 and the accumulator 14 is provided. It is preferable to include a fourth expansion valve 44.
Since the pressure in the flash tank 13 can be adjusted by the fourth expansion valve 44, the supply of the refrigerant liquid in the flash tank 13, which is supplied to the refrigerant after being compressed by the low stage compressor 11, is stabilized. Thereby, the degree of superheat of the refrigerant supplied to the high-stage compressor 12 can be stably suppressed.

The refrigeration apparatus 1 according to one embodiment includes an accumulator 14 as a gas-liquid separator provided in a refrigerant flow path 31, which is a flow path through which refrigerant after being compressed by the low stage compressor 11 flows. good. The liquid injection flow path 35 is preferably provided so as to communicate the liquid phase portion of the flash tank 13 and the refrigerant flow path 31 . The downstream end 35 d of the liquid injection flow path 35 is preferably connected to the refrigerant flow path 31 a between the low stage compressor 11 and the accumulator 14 in the refrigerant flow path 31 .
This can prevent the refrigerant liquid in the flash tank from being supplied to the high stage compressor in a liquid state.

The refrigeration device 1 according to one embodiment may include a flash gas flow path 36 for supplying refrigerant gas in the gas phase in the flash tank 13 to the refrigerant compressed by the low stage compressor 11. .
Thereby, the refrigerant gas generated within the flash tank 13 can be returned to the high stage compressor 12.

In the refrigeration apparatus 1 according to one embodiment, the flash gas flow path 36 is preferably provided so as to communicate the gas phase portion of the flash tank 13 and the refrigerant flow path 31. A downstream end 36 d of the flash gas flow path 36 is preferably connected to a refrigerant flow path 31 a between the low stage compressor 11 and the accumulator 14 in the refrigerant flow path 31 .
Thereby, even if the refrigerant liquid is included in the refrigerant flowing through the flash gas passage 36, it is possible to prevent the refrigerant liquid from being supplied to the high-stage compressor 12 in a liquid state.

In the refrigeration apparatus 1 according to one embodiment, the refrigerant is preferably a CO ₂ refrigerant. The reason for this will be explained below.
FIG. 2 is an example of a Mollier diagram of the refrigeration system 1 according to an embodiment that uses CO ₂ refrigerant.
In the CO ₂ refrigerant, in the Mollier diagram shown in FIG. 2, as the specific enthalpy increases at a certain pressure, the slope of the isentropic line Ei shown by the plurality of thin solid lines in FIG. 2 becomes smaller. Therefore, even if the suction pressure of the refrigerant sucked into the high-stage compressor 12 is the same and the discharge pressure of the refrigerant discharged from the high-stage compressor 12 is the same, the refrigerant sucked into the high-stage compressor 12 The difference between the specific enthalpy of the refrigerant discharged from the high-stage compressor 12 becomes smaller as the specific enthalpy of the refrigerant sucked into the high-stage compressor 12 becomes smaller.
By supplying the refrigerant liquid in the flash tank 13 to the refrigerant compressed by the low stage compressor 11, the amount of refrigerant sucked into the high stage compressor 12 increases. The difference between the specific enthalpy of the refrigerant sucked into the compressor 12 and the specific enthalpy of the refrigerant discharged from the high-stage compressor 12 becomes smaller.
As a result of intensive study by the inventors, the power consumption of the high stage compressor 12 is almost the same when the refrigerant liquid in the flash tank 13 is supplied to the refrigerant after being compressed by the low stage compressor 11 and when it is not supplied. It turned out that there was no difference.
Thereby, the degree of superheat of the refrigerant sucked into the high-stage compressor 12 can be efficiently suppressed while suppressing an increase in the power consumption of the high-stage compressor 12.

In FIG. 2, point n is the critical point of _CO2 , line X on the left side of point n is a saturated liquid line, and line Y on the right side of point n is a saturated vapor line. Point a is the state quantity of the refrigerant at the inlet of the low stage compressor 11, and point b is the state quantity of the refrigerant at the outlet of the low stage compressor 11. Point c is the state quantity of the refrigerant at the inlet of the high stage compressor 12, and point d is the state quantity of the refrigerant at the outlet of the high stage compressor 12. Point e is the state quantity of the refrigerant at the outlet of the condenser 15 as a gas cooler, and point f is the state quantity of the refrigerant in the gas-liquid mixed state at the outlet of the second expansion valve 42. The g point is the state quantity of the liquid phase part of the flash tank 13, and the h point is the state quantity of the gas phase part after gas-liquid separation in the flash tank 13. Point i is the state quantity of the refrigerant after leaving the flash tank 13 and passing through the heat exchanger 17, point j is the state quantity of the refrigerant at the outlet of the third expansion valve 43, and point k is the state quantity of the refrigerant at the outlet of the evaporator 16. It is the state quantity of the refrigerant. Point l is the state quantity of the refrigerant at the outlet of the fourth expansion valve 44, and point m is the state quantity of the refrigerant at the outlet of the first expansion valve 41.

In the refrigeration system 1 according to one embodiment, the liquid injection flow path 35 and the flash gas flow path 36 meet at point b, that is, the refrigerant flow path 31a between the low stage compressor 11 and the accumulator 14. The specific enthalpy h of the refrigerant at point c, that is, the inlet of the high-stage compressor 12, is lower than point b.
Note that, for convenience of understanding, the same locations in FIG. 1 are also given symbols a to m.

(Regarding adjustment of the opening degree of the first expansion valve 41)
As described above, the control device 50 according to one embodiment is a control device for controlling each part of the refrigeration device 1, and also adjusts the opening degree of the first expansion valve 41. The control device 50 calculates the suction superheat degree of the refrigerant sucked into the high-stage compressor 12 based on the suction temperature detected by the suction temperature sensor 55 and the suction pressure detected by the suction pressure sensor 57, The opening degree of the first expansion valve 41 is adjusted so that the calculated suction superheat degree becomes a preset target value.
Thereby, as will be described later, the suction superheat degree of the refrigerant sucked into the high-stage compressor 12 can be stably suppressed.

FIG. 3 is a flowchart showing the flow of processing performed in the control device 50 to adjust the opening degree of the first expansion valve 41. A program for executing the processing shown in the flowchart of FIG. 3 is read by the processor 51 from the memory 53 and executed.

The method for controlling the refrigeration apparatus 1 according to one embodiment includes a suction temperature detection step S10, a suction pressure detection step S20, a suction superheat degree calculation step S30, and an opening adjustment step S40.

The suction temperature detection step S10 is a step of detecting the suction temperature Ti of the refrigerant sucked into the high-stage compressor 12. In the suction temperature detection step S10, the processor 51 acquires the refrigerant suction temperature Ti detected by the suction temperature sensor 55.
The suction pressure detection step S20 is a step of detecting the suction pressure Pi of the refrigerant sucked into the high-stage compressor 12. In the suction pressure detection step S20, the processor 51 acquires the refrigerant suction pressure Pi detected by the suction pressure sensor 57.

The suction superheat degree calculation step S30 is a step of calculating the suction superheat degree of the refrigerant sucked into the high-stage compressor 12 based on the detected suction temperature Ti and the detected suction pressure Pi. In the suction superheat degree calculation step S30, the processor 51 determines whether the high-stage compressor 12 Calculate the suction superheat degree of the refrigerant sucked into the

Opening degree adjustment step S40 is a step of adjusting the opening degree of the first expansion valve 41 so that the calculated suction superheat degree becomes a preset target value. In the opening adjustment step S40, the processor 51 sets the refrigerant suction superheat degree calculated in the suction superheat degree calculation step S30 to the target value of the suction superheat degree that is set in advance and stored in the memory 53. The opening degree of the first expansion valve 41 is calculated, and a control signal for driving an actuator (not shown) of the first expansion valve 41 to achieve the calculated opening degree is output.
In the first expansion valve 41, an actuator (not shown) adjusts the opening degree of the first expansion valve 41 by receiving the control signal. Thereby, the opening degree of the first expansion valve 41 is adjusted so that the degree of suction superheat of the refrigerant sucked into the high-stage compressor 12 becomes the target value of the degree of suction superheat.
According to the method for controlling the refrigeration system 1 according to the embodiment, the suction superheat degree of the refrigerant sucked into the high-stage compressor 12 can be stably suppressed. Thereby, the efficiency of the high-stage compressor 12 can be stably improved.

The present disclosure is not limited to the embodiments described above, and also includes forms in which modifications are made to the embodiments described above, and forms in which these forms are appropriately combined.

The contents described in each of the above embodiments can be understood as follows, for example.
(1) The refrigeration apparatus 1 according to at least one embodiment of the present disclosure includes a low-stage compressor 11 for compressing refrigerant, and a high-stage compressor for compressing the refrigerant after being compressed by the low-stage compressor 11. A flash tank 13 that can receive the refrigerant compressed by the high stage compressor 12, and a flash tank that can receive the refrigerant compressed by the low stage compressor 11 and discharged from the low stage compressor 11. A liquid injection flow path 35 for supplying the refrigerant liquid in 13 is provided.

According to the configuration (1) above, there is no need to install a heat exchanger for cooling the refrigerant sucked into the high-stage compressor 12, and there is no need to pay the cost for installing the heat exchanger. The degree of superheating of the refrigerant sucked into the machine 12 can be efficiently suppressed. Thereby, the efficiency of the high-stage compressor 12 can be improved at low cost.

(2) In some embodiments, in the configuration of (1) above, the liquid injection flow path 35 is a flow path through which the refrigerant after being compressed by the liquid phase part of the flash tank 13 and the low stage compressor 11 flows. (refrigerant channel 31). The downstream end 35d of the liquid injection channel 35 is preferably connected to the channel (refrigerant channel 31).

According to the configuration (2) above, the refrigerant liquid in the flash tank 13 can be supplied to the refrigerant after being compressed by the low stage compressor 11 with a simple configuration.

(3) In some embodiments, the configuration of (1) or (2) above may include a first expansion valve 41 provided in the liquid injection channel 35.

According to the configuration (3) above, the refrigerant liquid in the flash tank 13 can be stably supplied to the refrigerant after being compressed by the low stage compressor 11.

(4) In some embodiments, in any of the configurations (1) to (3) above, a condenser for cooling the refrigerant after being compressed by the high-stage compressor 12, and a condenser 15. It is preferable to include a second expansion valve 42 provided in the flow path (refrigerant flow path 32b) that connects the flash tank 13.

According to the configuration (4) above, the discharge pressure of the high-stage compressor 12 can be adjusted.

(5) In some embodiments, in any of the configurations (1) to (4) above, the refrigerant is provided in the flow path (refrigerant flow path 31) through which the refrigerant after being compressed by the low stage compressor 11 flows. It is preferable to include a gas-liquid separator (accumulator 14). The liquid injection flow path 35 is preferably provided so as to communicate the liquid phase portion of the flash tank 13 and the flow path (refrigerant flow path 31). The downstream end 35d of the liquid injection channel 35 is connected to the channel (refrigerant channel 31a) between the low stage compressor 11 and the gas-liquid separator (accumulator 14) in the channel (refrigerant channel 31). It would be good to be connected.

According to the configuration (5) above, it is possible to prevent the refrigerant liquid in the flash tank 13 from being supplied to the high-stage compressor 12 in a liquid state.

(6) In some embodiments, in any of the configurations (1) to (5) above, for supplying refrigerant gas in the flash tank 13 to the refrigerant after being compressed by the low stage compressor 11. A flash gas flow path 36 may be provided.

According to the configuration (6) above, the refrigerant gas generated in the flash tank 13 can be returned to the high-stage compressor 12. Furthermore, the degree of superheating of the refrigerant sucked into the high-stage compressor 12 can be suppressed by the refrigerant gas generated within the flash tank 13.

(7) In some embodiments, in the configuration of (6) above, a gas-liquid separator ( It is preferable to include an accumulator 14). The flash gas flow path 36 is preferably provided so as to communicate the gas phase portion of the flash tank 13 and the flow path (refrigerant flow path 31). The downstream end 36d of the flash gas flow path 36 is connected to the flow path (refrigerant flow path 31a) between the low-stage compressor 11 and the gas-liquid separator (accumulator 14) in the flow path (refrigerant flow path 31). It would be good to be connected.

According to the configuration (7) above, even if refrigerant liquid is included in the refrigerant flowing through the flash gas flow path 36, it is possible to prevent the refrigerant liquid from being supplied to the high-stage compressor 12 in a liquid state.

(8) In some embodiments, in any of the configurations (1) to (7) above, the refrigerant may be a CO ₂ refrigerant.

According to the configuration (8) above, the degree of superheat of the refrigerant sucked into the high-stage compressor 12 can be efficiently suppressed while suppressing an increase in the power consumption of the high-stage compressor 12.

(9) In some embodiments, in any of the configurations (1) to (8) above, the first expansion valve 41 provided in the liquid injection flow path 35 and the refrigerant sucked into the high-stage compressor 12 A suction temperature sensor 55 for detecting the suction temperature Ti of the refrigerant, a suction pressure sensor 57 for detecting the suction pressure Pi of the refrigerant sucked into the high-stage compressor 12, and adjusting the opening degree of the first expansion valve 41. It is preferable to include a control device 50 for controlling. The control device 50 calculates the suction superheat degree of the refrigerant sucked into the high-stage compressor 12 based on the suction temperature Ti detected by the suction temperature sensor 55 and the suction pressure Pi detected by the suction pressure sensor 57. However, it is preferable that the opening degree of the first expansion valve 41 is adjusted so that the calculated suction superheat degree becomes a preset target value.

According to the configuration (9) above, the degree of suction superheat of the refrigerant sucked into the high-stage compressor 12 can be stably suppressed.

(10) A method for controlling the refrigeration apparatus 1 according to at least one embodiment of the present disclosure is a method for controlling the refrigeration apparatus 1. The refrigeration system 1 includes a low stage compressor 11 for compressing refrigerant, a high stage compressor 12 for compressing the refrigerant after being compressed by the low stage compressor 11, and a refrigerant compressed by the high stage compressor 12. A flash tank 13 that can receive the refrigerant after being compressed by the low-stage compressor 11, a liquid injection flow path 35 for supplying the refrigerant liquid in the flash tank 13 to the refrigerant after being compressed by the low stage compressor 11, and a liquid injection flow path. A first expansion valve 41 provided at 35 is provided. A method for controlling a refrigeration system 1 according to at least one embodiment of the present disclosure includes a suction temperature detection step S10 for detecting a suction temperature Ti of refrigerant sucked into the high-stage compressor 12; The suction pressure detection step S20 detects the suction pressure Pi of the refrigerant, and the degree of suction superheat of the refrigerant sucked into the high-stage compressor 12 is calculated based on the detected suction temperature Ti and the detected suction pressure Pi. and an opening adjustment step S40 for adjusting the opening degree of the first expansion valve 41 so that the calculated suction superheat degree becomes a preset target value.

According to the method (10) above, the degree of suction superheat of the refrigerant sucked into the high-stage compressor 12 can be stably suppressed regardless of the outside temperature, so that the efficiency of the high-stage compressor 12 can be stably improved. .

1 Refrigeration device 11 Low stage compressor 12 High stage compressor 13 Flash tank 14 Accumulator 15 Condenser 16 Evaporator 35 Liquid injection channel 36 Flash gas channel 41 First expansion valve 42 Second expansion valve (high stage expansion valve)
43 Third expansion valve (low stage expansion valve)
44 Fourth expansion valve 50 Control device 55 Suction temperature sensor 57 Suction temperature sensor

Claims

a low stage compressor for compressing refrigerant;
a high stage compressor for compressing the refrigerant after being compressed by the low stage compressor;
a flash tank capable of receiving the refrigerant after being compressed by the high-stage compressor;
a liquid injection flow path for supplying refrigerant liquid in the flash tank to the refrigerant after being compressed by the low-stage compressor and discharged from the low-stage compressor;
Refrigeration equipment equipped with.
The liquid injection flow path is provided so as to communicate the liquid phase part of the flash tank with a flow path through which the refrigerant after being compressed by the low stage compressor flows,
The downstream end of the liquid injection flow path is connected to the flow path,
The refrigeration device according to claim 1.
a first expansion valve provided in the liquid injection flow path;
Equipped with
The refrigeration device according to claim 1 or 2.
a condenser for cooling the refrigerant after being compressed by the high-stage compressor;
a second expansion valve provided in a flow path connecting the condenser and the flash tank;
Equipped with
The refrigeration device according to claim 1 or 2.
a gas-liquid separator provided in a flow path through which the refrigerant after being compressed by the low-stage compressor flows;
Equipped with
The liquid injection flow path is provided so as to communicate the liquid phase part of the flash tank with the flow path,
A downstream end of the liquid injection flow path is connected to a flow path between the low-stage compressor and the gas-liquid separator among the flow paths.
The refrigeration device according to claim 1 or 2.
a flash gas flow path for supplying refrigerant gas in the flash tank to the refrigerant after being compressed by the low stage compressor;
Equipped with
The refrigeration device according to claim 1 or 2.
a gas-liquid separator provided in a flow path through which the refrigerant after being compressed by the low-stage compressor flows;
Equipped with
The flash gas flow path is provided to communicate the gas phase part of the flash tank and the flow path,
A downstream end of the flash gas flow path is connected to a flow path between the low-stage compressor and the gas-liquid separator among the flow paths.
The refrigeration device according to claim 6.
the refrigerant is a CO2 refrigerant;
The refrigeration device according to claim 1 or 2.
a first expansion valve provided in the liquid injection flow path;
a suction temperature sensor for detecting the suction temperature of the refrigerant sucked into the high-stage compressor;
a suction pressure sensor for detecting the suction pressure of the refrigerant sucked into the high-stage compressor;
a control device for adjusting the opening degree of the first expansion valve;
Equipped with
The control device determines the suction superheat degree of the refrigerant sucked into the high-stage compressor based on the suction temperature detected by the suction temperature sensor and the suction pressure detected by the suction pressure sensor. The refrigeration system according to claim 1 or 2, wherein the refrigeration system is configured to adjust the opening degree of the first expansion valve so that the calculated suction superheat degree becomes a preset target value.
A method for controlling a refrigeration device, the method comprising:
The refrigeration device includes:
a low stage compressor for compressing refrigerant;
a high stage compressor for compressing the refrigerant after being compressed by the low stage compressor;
a flash tank capable of receiving the refrigerant after being compressed by the high-stage compressor;
a liquid injection flow path for supplying refrigerant liquid in the flash tank to the refrigerant after being compressed by the low stage compressor;
a first expansion valve provided in the liquid injection flow path;
Equipped with
a suction temperature detection step of detecting the suction temperature of the refrigerant sucked into the high-stage compressor;
a suction pressure detection step of detecting the suction pressure of the refrigerant sucked into the high-stage compressor;
a suction superheat degree calculation step of calculating a suction superheat degree of the refrigerant sucked into the high-stage compressor based on the detected suction temperature and the detected suction pressure;
an opening degree adjusting step of adjusting the opening degree of the first expansion valve so that the calculated suction superheat degree becomes a preset target value;
A method for controlling a refrigeration device comprising: