KR102532023B1 - Supercritical refrigeration system and control method of same - Google Patents

Abstract

A cooling system according to the present invention includes a compressor provided to compress a refrigerant; a gas cooler provided to cool the refrigerant compressed in the compressor to liquefy; a flash tank provided to store the refrigerant cooled in the gas cooler; an expansion valve provided to expand the liquid refrigerant transferred from the flash tank; an evaporator provided to evaporate the refrigerant expanded by the expansion valve; a gas-liquid separator provided to separate a part of the liquid phase and a part of the gas phase of the refrigerant that has passed through the evaporator and transfer the part of the gas phase to the compressor; a circulation line provided to deliver the refrigerant compressed by the compressor to the gas-liquid separator; a circulation valve disposed in the circulation line to control opening and closing of the circulation line; a tank level acquisition unit installed inside the flash tank to obtain a level of the liquid refrigerant stored in the flash tank; and a processor electrically connected to the tank level acquisition unit and the circulation valve, wherein the processor: When the water level obtained by the tank level acquisition unit is less than or equal to a predetermined reference tank level, the circulation valve is set to a predetermined opening degree. Opening degree is controlled to open.

Description

Supercritical cooling system and its control method {SUPERCRITICAL REFRIGERATION SYSTEM AND CONTROL METHOD OF SAME}

The present invention relates to a supercritical cooling system and a control method thereof.

The cooling system refers to a system that performs cooling using a cooling cycle. A supercritical cooling system is a cooling system that uses a supercritical fluid such as carbon dioxide as a refrigerant. In the cooling system, a flash tank is installed in the refrigerant passage between the gas cooler and the evaporator, the refrigerant from the gas cooler is reduced by an expansion valve, and the gas-liquid mixture is sent to the flash tank to separate the gas and liquid phases. It is practiced to supply the separated gaseous refrigerant to a compressor, in particular a parallel compressor, bypassing the evaporator. Thereby, the area|region in which the pressure-resistant piping for high-pressure refrigerant is arrange|positioned can be reduced and cost reduction can be aimed at.

It can expand the operating application range of the cooling system while avoiding liquid compression and abnormal overheating due to liquid back of the compressor. 1 is a diagram conceptually showing the configuration of an existing cooling system. A conventional cooling system disclosed by Japanese Unexamined Patent Publication No. 2021-105474, which is a prior document shown in FIG. 1, has a flash tank 101 having a gas phase and a liquid phase, and a liquid phase from the flash tank 101 An evaporator 102 in which the refrigerant is induced, a compressor 108 for compressing the refrigerant gas after passing through the device, a first refrigerant flow path 103 connecting the evaporator 102 and the compressor 108, and a flash tank 101 A second refrigerant passage 104 for connecting the gas phase of the flash tank 101 and the first refrigerant passage 103, a heat exchanger 105 for heat exchange between the liquid phase of the flash tank 101 and the refrigerant passing through the evaporator, and the second refrigerant A first expansion valve 106 installed in the flow path 104, a sensor 109 for detecting a pressure or temperature correlated with the evaporation temperature of the refrigerant in the evaporator 102, and the sensor 109 and a control unit 107 for performing opening degree control of the first expansion valve 106 based on the target pressure of the flash tank 101 set based on the detection result.

According to this method, since the pressure of the flash tank 101 can be controlled to a target pressure at which liquid back or abnormal overheating of the compressor 108 does not occur, while avoiding liquid back or abnormal overheating of the compressor 108, The driving range can be expanded.

However, even if this method is followed, when there is a large amount of liquid refrigerant among the refrigerants separated in the flash tank 101, the liquid refrigerant is taken out of the flash tank 101 by the flow of the gaseous refrigerant and the compressor 108 In spite of the above configuration, liquid refrigerant does not evaporate sufficiently in the process of passing through the liquid refrigerant after the flash tank 101, and thus liquid back may occur in the compressor 108.

2 is a diagram conceptually showing the configuration of a cooling system (S) having a plurality of evaporators (E). As shown in FIG. 2 , when a plurality of evaporators E are connected to one cooling system S, an environment in which a small load frequently occurs may be provided. In this case, as in the conventional cooling system, when the amount of bypassed refrigerant is adjusted by measuring the superheat from the temperature and pressure of the refrigerant related to the evaporator (E), control to adjust the amount of refrigerant from the measured value must occur frequently. Therefore, it is often out of the control range of the expansion valve, making stable superheat control difficult, and failure of each component constituting the cooling cycle is likely to occur due to frequent control changes.

According to the existing cooling system disclosed by Japanese Patent Laid-open Publication No. 2021-188881, the cooling system may include a plurality of compressors including a main compressor and a parallel compressor. A plurality of compressors can be configured so that the cooling system can easily respond to various loads, but when a plurality of evaporators are connected as in the example described in FIG. Frequent heat (rapid on/off cycles) may occur, which may shorten the life of the entire cooling system.

Due to the above problems, when fresh food is stored in a refrigerator using a cooling cycle, quality deterioration may occur.

Japanese Unexamined Patent Publication No. 2021-105474 (published on July 26, 2021) Japanese Unexamined Patent Publication No. 2021-188881 (published on December 13, 2021)

The present invention has been made to solve these problems, and aims at solving at least one of the following problems.

An object of the present invention is to provide a cooling system that effectively prevents liquid back to a compressor and a control method thereof.

An object of the present invention is to provide a cooling system and a control method thereof that rapidly treat liquid in a gas-liquid separator so that operation is performed in a steady state.

An object of the present invention is to provide a cooling system in which the frequency of compressor heat is reduced and a control method thereof.

A cooling system according to an embodiment of the present invention includes a compressor configured to compress a refrigerant; a gas cooler provided to cool the refrigerant compressed in the compressor to liquefy; a flash tank provided to store the refrigerant cooled in the gas cooler; an expansion valve provided to expand the liquid refrigerant transferred from the flash tank; an evaporator provided to evaporate the refrigerant expanded by the expansion valve; a gas-liquid separator provided to separate a part of the liquid phase and a part of the gas phase of the refrigerant that has passed through the evaporator and transfer the part of the gas phase to the compressor; a circulation line provided to deliver the refrigerant compressed by the compressor to the gas-liquid separator; a circulation valve disposed in the circulation line to control opening and closing of the circulation line; a tank level acquisition unit installed inside the flash tank to obtain a level of the liquid refrigerant stored in the flash tank; a gas-liquid separation level acquisition unit installed inside the gas-liquid separator to obtain a level of the liquid refrigerant stored in the gas-liquid separator; and a processor electrically connected to the tank level acquisition unit, the circulation valve, the gas-liquid separation level acquisition unit, and the expansion valve, wherein the processor: determines that the water level acquired by the tank level acquisition unit is a predetermined criterion. When the tank water level is lower than the tank level, the circulation valve is controlled to open at a predetermined standard opening degree, and when the water level obtained by the gas-liquid separation level acquisition unit is higher than the predetermined standard gas-liquid separation level, the expansion valve is controlled to be closed.

According to an embodiment of the present invention, a control method for controlling a refrigeration system including a compressor, a gas cooler, a flash tank, an expansion valve, an evaporator, and a gas-liquid separator in order based on a flow direction of a refrigerant includes a liquid phase stored in the flash tank. Obtaining the level of the refrigerant of the; transferring the refrigerant compressed by the compressor to the gas-liquid separator when the obtained water level of the flash tank is equal to or less than a predetermined reference tank water level; obtaining a level of the liquid refrigerant stored in the gas-liquid separator; and closing the expansion valve when the obtained water level of the gas-liquid separator is equal to or greater than a predetermined standard gas-liquid separation water level.

Accordingly, at least one of the following effects can be achieved.

Liquid back to the compressor can be effectively prevented.

The operation of the gas-liquid separator can be maintained in a normal state by promptly processing the liquid.

Since the frequency of compressor estrus is reduced, the operating application range of stable refrigeration operation can be widened.

1 is a diagram conceptually showing the configuration of an existing cooling system.
2 is a diagram conceptually showing the configuration of a cooling system having a plurality of evaporators.
3 is a diagram conceptually showing the configuration of a cooling system according to an embodiment of the present invention.
4 is a flowchart illustrating a control method of a cooling system according to an embodiment of the present invention.
5 is a flowchart illustrating a control method for continuously controlling a compressor to operate in a cooling system according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing an embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function hinders understanding of the embodiment of the present invention, the detailed description will be omitted.

Also, terms such as first, second, A, B, (a), and (b) may be used to describe components of an embodiment of the present invention. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. When an element is described as being “connected,” “coupled to,” or “connected” to another element, that element may be directly connected or connected to the other element, but there may be another element between the elements. It should be understood that may be "connected", "coupled" or "connected".

3 is a diagram conceptually showing the configuration of a cooling system according to an embodiment of the present invention.

Referring to the drawings, a cooling system according to an embodiment of the present invention includes a compressor 20, a gas cooler 30, a flash tank 40, an expansion valve 60, an evaporator 70, and a gas-liquid separator 80. , a circulation line 12, a circulation valve 13, a tank level acquisition unit 41 and a processor P. The compressor 20, gas cooler 30, flash tank 40, expansion valve 60, evaporator 70 and gas-liquid separator 80 may be arranged in the above-described order on the main line 11, The refrigerant flows along the main line 11 in the above-described order and can be processed by each component. The cooling system according to an embodiment of the present invention may perform a supercritical cycle in which cooling is performed using a supercritical fluid as a refrigerant, but the cooling cycle performed by the cooling system is not limited thereto. In one embodiment of the present invention, the line refers to a component forming a flow path through which a refrigerant can flow. The line may be composed of a pipe, a flexible hose, or the like, but a configuration forming a flow path is not limited thereto.

The compressor 20 is a device for compressing gaseous refrigerant. The compressor 20 may be a screw, scroll, or reciprocating compressor 20 that is connected to a device that generates rotational force such as an electric motor or a turbine and uses the rotational force to compress the refrigerant, but the type is not limited thereto. . In one embodiment of the present invention, the electric motor 22 is connected to the compressor 20 to operate the compressor 20, and the inverter 23 is disposed for controlling the electric motor 22, but the compressor 20 ) The configuration for driving is not limited thereto.

The compressor 20 may be connected to the gas-liquid separator 80 and the gas cooler 30 to compress and discharge the gaseous refrigerant discharged from the gas-liquid separator 80 to the gas cooler 30 .

The gas cooler 30 is a device that cools the refrigerant compressed in the compressor 20 in order to make it easy to liquefy. The gas cooler 30 may cool the refrigerant by exchanging heat between the outside air and the refrigerant. Therefore, the gas cooler 30 may include at least one of a plate heat exchanger and a fin-tube heat exchanger, which are heat exchangers that enable heat exchange between different media, but the type of heat exchanger used for the gas cooler 30 is suitable for this. Not limited.

A cooling system according to an embodiment of the present invention may include a high-pressure expansion valve 14 . The high-pressure expansion valve 14 is disposed between the gas cooler 30 and the flash tank 40 to expand the refrigerant discharged from the gas cooler 30 and delivered to the flash tank 40 .

A cooling system according to an embodiment of the present invention may include a parallel compressor 21 . The parallel compressor 21 may be disposed in parallel with the compressor 20 to compress and discharge the refrigerant. The parallel compressor 21 may receive the gaseous refrigerant of the flash tank 40 and compress it to join the compressed refrigerant discharged from the compressor 20 . Similar to the compressor 20, various methods may be used as the parallel compressor 21.

The flash tank 40 stores the refrigerant cooled by the gas cooler 30 therein. In the flash tank 40, the refrigerant may be separated into a liquid phase and a gas phase. Accordingly, the flash tank 40 may be a flash tank, but the type is not limited thereto.

A cooling system according to an embodiment of the present invention may include a supercooling heat exchanger 50 . A part of the liquid refrigerant discharged from the flash tank 40 and another part passing through the supercooling expansion valve 51 may exchange heat in the supercooling heat exchange unit 50 . Among them, a part that does not pass through the supercooled expansion valve 51 is transferred to the expansion valve 60 and the evaporator 70, and may meet the other part after passing through the evaporator 70. The supercooling heat exchange unit 50 may include at least one of a plate heat exchanger and a fin-tube heat exchanger, which are heat exchangers that enable heat exchange between different media, but the type of heat exchanger used as the supercooling heat exchange unit 50 is It is not limited to this.

The expansion valve 60 may expand the liquid refrigerant transferred from the flash tank 40 . The expansion valve 60 may be an electronic expansion valve 60 whose opening and closing is controlled by an electrical signal, but its type is not limited thereto.

The evaporator 70 evaporates the refrigerant expanded by the expansion valve 60. The evaporator 70 may heat the refrigerant by exchanging heat with a refrigerant such as outside air or air inside a refrigerating compartment. Therefore, the evaporator 70 may include at least one of an air cooler, a plate heat exchanger, and a fin-tube heat exchanger, which are heat exchangers that enable heat exchange between different media, but the type of heat exchanger used as the evaporator 70 It is not limited to this.

When a part of the liquid phase remains in the refrigerant that has passed through the evaporator 70, the gas-liquid separator 80 separates a part of the liquid phase and a part of the gas phase of the refrigerant. A part of the gas phase of the refrigerant separated in the gas-liquid separator 80 may be transferred to the compressor 20 . The gas-liquid separator 80 may be an accumulator capable of gas-liquid separation, but its type is not limited thereto.

A cooling system according to an embodiment of the present invention may include a gas-liquid separation level acquisition unit 81 . The gas-liquid separation level acquisition unit 81 may be installed inside the gas-liquid separator 80 to obtain the level of the liquid refrigerant stored in the gas-liquid separator 80 . The gas-liquid separation level acquisition unit 81 may be a level switch, but means for measuring the level of the refrigerant in the gas-liquid separator 80 is not limited thereto.

A cooling system according to an embodiment of the present invention may include an inlet temperature acquisition unit 24 . The inlet temperature acquisition unit 24 may acquire the temperature of the gaseous refrigerant transferred from the gas-liquid separator 80 to the compressor 20 . The inlet temperature acquisition unit 24 may include a thermistor, a thermocouple, or the like, but means for measuring the temperature is not limited thereto.

A cooling system according to an embodiment of the present invention may include an inlet pressure acquisition unit 25 . The inlet pressure acquisition unit 25 may acquire the pressure of the gaseous refrigerant transferred from the gas-liquid separator 80 to the compressor 20 . The inlet pressure acquisition unit 25 may include a capacitive pressure sensor, a strain gauge, or the like, but a means for measuring the pressure is not limited thereto.

The circulation line 12 is a line connecting one point of the main line 11 and another point. The circulation line 12 connects two parts of the main line 11 to deliver the refrigerant compressed in the compressor 20 to the gas-liquid separator 80. Accordingly, the circulation line 12 may connect a location on the downstream side of the compressor 20 on the main line 11 with a location on the upstream side of the gas-liquid separator 80 based on the flow direction of the refrigerant. The circulation line 12 may be directly connected to the gas-liquid separator 80.

The circulation valve 13 is disposed in the circulation line 12 to control opening and closing of the circulation line 12 . The circulation valve 13 may be an electric valve or a solenoid valve having an adjustable opening, but the type is not limited thereto.

The tank level acquisition unit 41 is installed inside the flash tank 40 to obtain the level of the liquid refrigerant stored in the flash tank 40 . The tank level acquisition unit 41 may include a level transmitter, but the means used for acquiring the level is not limited thereto.

The processor P is a component including an element capable of performing logic operations for performing control commands, and may include a central processing unit (CPU) or the like. The processor P is connected to various components of the cooling system according to an embodiment of the present invention, can transmit a signal according to a control command to each component, and information obtained by being connected to various sensors or acquisition units. can be delivered in the form of a signal. Since the processor P may be electrically connected to each component, it may be connected with a wire or may have a communication module capable of wirelessly communicating with each other.

The cooling system further includes a memory, so that control commands executed by the processor P may be stored and utilized in the memory. The memory may be a device such as a hard disk drive (HDD), a solid state drive (SSD), a server, a volatile medium, or a non-volatile medium, but the type is not limited thereto. In addition, data and the like required for the processor P to perform tasks may be further stored in the memory.

4 is a flowchart illustrating a control method of a cooling system according to an embodiment of the present invention.

Hereinafter, the control method of the cooling system will be described focusing on the operation of the processor P. The tank level acquisition unit 41 may acquire the level of the liquid refrigerant stored in the flash tank 40 (S11). The processor P receives the refrigerant level of the flash tank 40 obtained from the tank level acquisition unit 41 and compares it with a predetermined standard tank level (S12). When the obtained water level is greater than the reference tank water level, the existing operating state may be maintained because an excessive amount of liquid refrigerant from the flash tank 40 is not transferred to the evaporator 70 . The reference tank water level may be 0 m.

If the obtained water level is below the standard tank level, an excessive amount of liquid refrigerant from the flash tank 40 is being transferred to the evaporator 70, so the refrigerant does not evaporate sufficiently in the evaporator 70 or the expansion valve 60 It can be seen that a large amount of liquid refrigerant will be transferred to the gas-liquid separator 80 due to the abnormal opening of ). Therefore, when the obtained water level is below the standard tank level, the processor P opens the circulation valve 13 so that the high-temperature gaseous refrigerant compressed in the compressor 20 is transferred to the gas-liquid separator 80 (S13). The processor P may open the circulation valve 13 at a reference opening degree, which is a predetermined opening degree. Therefore, the high-temperature and high-pressure refrigerant compressed and discharged from the compressor 20 along the circulation line 12 is transferred to the gas-liquid separator 80, whereby the liquid refrigerant in the gas-liquid separator 80 can be evaporated. The liquid refrigerant is evaporated, and the liquid in the gas-liquid separator 80 is quickly treated to prevent the liquid back phenomenon, and the normal operation can be quickly returned. The standard opening degree may be 30% when the maximum opening degree is 100%.

When the water level obtained by the tank level acquisition unit 41 is equal to or less than the reference tank level, the processor P may control the operation speed of the compressor 20 to be smaller than a predetermined normal speed (S14). As the load of the compressor 20 is reduced and the amount of refrigerant absorbed by the compressor 20 is reduced, the occurrence of a liquid back phenomenon can be prevented. The operating speed may refer to a rotational speed at which the compressor 20 rotates, and may be expressed in units of revolutions per minute (rpm) or hertz (Hz). The normal speed may be 65 Hz, and the driving speed reached by decreasing according to the above control may be 30 Hz.

With the above-described control, even if a temporary problem occurs, the cooling cycle can be operated while maintaining an operating state close to normal. However, if the liquid refrigerant accumulates in the gas-liquid separator 80 despite the above control, it is possible to predict that a problem such as a liquid compression phenomenon has occurred and take the next step.

The gas-liquid separation level acquisition unit 81 may acquire the level of the liquid refrigerant stored in the gas-liquid separator 80 (S21). The processor P may receive the obtained water level from the gas-liquid separation level acquisition unit 81 and compare it with a reference gas-liquid separation level (S22). If the obtained water level is less than the reference gas-liquid separation water level, which is a predetermined water level, no separate action may be taken because the normal operating state is returned. The processor P closes the expansion valve 60 when the water level obtained by the gas-liquid separation level acquisition unit 81 is equal to or greater than the reference gas-liquid separation level (S23). When the expansion valve 60 is closed, the processor P may open the circulation valve 13 at an opening degree greater than the reference opening degree so that the continuous operation of the compressor 20 can occur with a minimum load or more (S24). . When the expansion valve 60 is closed, the processor P may further reduce the operating speed of the compressor 20 (S25). By blocking the expansion valve 60, the transfer of refrigerant from the flash tank 40 to the evaporator 70 is blocked, and the liquid refrigerant remaining in the gas-liquid separator 80 is the high-temperature and high-pressure refrigerant compressed in the compressor 20. It evaporates, and the compressor 20 is operated at a low load to prevent liquid back from occurring as much as possible. When the above conditions are satisfied, the expansion valve 60 may be closed at step S23, or the opening degree thereof may only be decreased.

When the expansion valve 60 is closed, the level of the refrigerant in the gas-liquid separator 80 returns to normal and the degree of superheat meets the standard, it is determined that the normal state is established and the refrigeration cycle can be returned to its original state.

With the expansion valve 60 closed, the gas-liquid separation level acquisition unit 81 may obtain the level of the liquid refrigerant stored in the gas-liquid separator 80 (S31). With the expansion valve 60 closed, the inlet temperature acquisition unit 24 may acquire the temperature of the refrigerant discharged from the gas-liquid separator 80 (S32). With the expansion valve 60 closed, the inlet pressure acquisition unit 25 may acquire the pressure of the refrigerant discharged from the gas-liquid separator 80 (S33). The processor P may calculate the degree of superheat from the obtained temperature and pressure of the refrigerant (S34).

The processor may compare the obtained water level of the gas-liquid separator 80 and the calculated degree of superheat with the reference gas-liquid separation level and the reference degree of superheat (S35). If it is less than the predetermined reference gas-liquid separation level and the superheat calculated from the temperature obtained by the inlet temperature acquisition unit 24 and the pressure acquired by the inlet pressure acquisition unit 25 is greater than or equal to the predetermined reference superheat degree, the expansion valve 60 ) can be opened (S36). When the processor P opens the expansion valve 60, the circulation valve 13 is closed to block the transfer of the high-temperature gaseous refrigerant compressed in the compressor 20 to the gas-liquid separator 80 (S37). ). When the processor P opens the expansion valve 60, the operating speed of the compressor 20 may be set to a normal speed (S38). Therefore, the cooling system can return to a normal state, continue to operate, and return to the initial stage of the cycle.

5 is a flow chart illustrating a control method for continuously operating the compressor 20 in a cooling system according to an embodiment of the present invention. The processor P may control the circulation valve 13 to be opened when the pressure acquired by the inlet pressure acquisition unit 25 is equal to or less than a predetermined stop pressure, even if the operation is performed in a normal state. When the cooling load is insignificant, the load delivered to the compressor 20 is less than the minimum load, and operation may be stopped regardless of other conditions. The compressor 20 does not operate below the minimum load, but if a minute load occurs frequently, the operation of turning on and off the compressor 20 may be frequently repeated, so the refrigerant discharged from the compressor 20 is returned to the compressor 20 It is introduced to match the inlet pressure greater than the stop pressure, which is the minimum load, so that the compressor 20 continues to operate without stopping. Therefore, frequent heating of the compressor 20 can be reduced.

Specifically, the processor P may compare the inlet pressure, which is the pressure obtained by the inlet pressure acquisition unit 25, with the stop pressure in the situation where the compressor is operating (S41). When the pressure obtained by the inlet pressure acquisition unit 25 is greater than the stop pressure, the operation of the compressor 20 continues as it is because there is no problem in operation (S41).

When the pressure obtained by the inlet pressure acquisition unit 25 is equal to or less than the stop pressure, the processor P may compare the operating time of the compressor 20 with a predetermined minimum load operating time (S43). If the operating time of the compressor 20 is shorter than the minimum load operating time, it is not yet known whether a problem has occurred in the compressor 20 or a temporary error, so the operation of the compressor 20 continues (S41). . When the operating time of the compressor 20 is equal to or longer than the minimum load operating time, the processor P may open the circulation valve 13 so that an abnormality occurs in the compressor 20 or the compressor 20 does not stop (S44).

After the circulation valve 13 is opened, the processor P checks how long the circulation valve 13 has been open, and compares the opening time of the circulation valve 13 with a predetermined standard opening time (S45 ). If the opening time of the circulation valve 13 is shorter than the reference opening time, the circulation valve 13 may remain open (S44). However, if the opening time of the circulation valve 13 is longer than the reference opening time, the circulation valve 13 has been open for a sufficiently long time, so the processor P closes the circulation valve 13 to check whether the system has returned to a normal state. It can (S46).

After the circulation valve 13 is closed, the processor P may compare the inlet pressure of the compressor 20 with the stop pressure (S47). If the inlet pressure of the compressor 20 is greater than the stop pressure, since the compressor 20 is in a normal operating state, the processor P can maintain the compressor 20 operating state. If the inlet pressure of the compressor 20 is less than the stop pressure, the compressor 20 cannot operate normally, so the processor P can stop the compressor 20 (S48).

After the compressor 20 is stopped, the processor P may compare the inlet pressure of the compressor 20 with a predetermined operating pressure (S49). The operating pressure may be a pressure value greater than the stop pressure. If the inlet pressure is smaller than the operating pressure, the compressor 20 may be maintained in a stopped state (S48). If the inlet pressure is higher than the operating pressure, since the compressor 20 is in a normal operating state, the processor P may cause the compressor 20 to start operating again (S41).

In the above, even though all components constituting the embodiment of the present invention have been described as being combined or operated as one, the present invention is not necessarily limited to these embodiments. That is, within the scope of the object of the present invention, all of the components may be selectively combined with one or more to operate. In addition, terms such as "comprise", "comprise" or "having" described above mean that the corresponding component may be present unless otherwise stated, and thus exclude other components. It should be construed as being able to further include other components. All terms, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs, unless defined otherwise. Commonly used terms, such as terms defined in a dictionary, should be interpreted as being consistent with the contextual meaning of the related art, and unless explicitly defined in the present invention, they are not interpreted in an ideal or excessively formal meaning.

The above description is merely an example of the technical idea of the present invention, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed according to the claims below, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

11: main line
12: circulation line
13: circulation valve
14: high pressure expansion valve
20: Compressor
21: parallel compressor
22: electric motor
23: Inverter
24: inlet temperature acquisition unit
25: inlet pressure acquisition unit
30: gas cooler
40 : Flash Tank
41: tank level acquisition unit
50: supercooling heat exchange unit
51: supercooling expansion valve
60: expansion valve
70: evaporator
80: gas-liquid separator
81: gas-liquid separation level acquisition unit
P: processor

Claims (12)

a compressor provided to compress the refrigerant;
a gas cooler provided to cool the refrigerant compressed in the compressor to liquefy;
a flash tank provided to store the refrigerant cooled in the gas cooler;
an expansion valve provided to expand the liquid refrigerant transferred from the flash tank;
an evaporator provided to evaporate the refrigerant expanded by the expansion valve;
a gas-liquid separator provided to separate a part of the liquid phase and a part of the gas phase of the refrigerant that has passed through the evaporator and transfer the part of the gas phase to the compressor;
a circulation line provided to transfer the refrigerant compressed by the compressor to the gas-liquid separator;
a circulation valve disposed in the circulation line to control opening and closing of the circulation line;
a tank level acquisition unit installed inside the flash tank to obtain a level of the liquid refrigerant stored in the flash tank;
a gas-liquid separation level acquisition unit installed inside the gas-liquid separator to obtain a level of the liquid refrigerant stored in the gas-liquid separator; and
A processor electrically connected to the tank level acquisition unit, the circulation valve, the gas-liquid separation level acquisition unit, and the expansion valve;
The processor:
When the water level obtained by the tank level acquisition unit is less than or equal to a predetermined reference tank water level, controlling the circulation valve to open at a reference opening degree, which is a predetermined opening degree;
When the water level obtained by the gas-liquid separation level acquisition unit is equal to or greater than a predetermined reference gas-liquid separation level, the cooling system controls the expansion valve to be closed. According to claim 1,
The compressor is electrically connected to the processor,
The processor:
When the water level obtained by the tank level acquisition unit is equal to or less than a predetermined reference tank level, the cooling system controls an operating speed of the compressor to be smaller than a predetermined normal speed. delete According to claim 1,
When the expansion valve is closed, the processor:
The cooling system according to claim 1 , wherein the circulation valve is opened at an opening degree greater than the reference opening degree, and the operating speed of the compressor is controlled to decrease. According to claim 1,
an inlet temperature acquisition unit provided to obtain a temperature of the refrigerant discharged from the gas-liquid separator; and
Further comprising an inlet pressure acquisition unit provided to obtain a pressure of the refrigerant discharged from the gas-liquid separator,
With the expansion valve closed, the processor electrically connected to the inlet temperature acquisition unit and the inlet pressure acquisition unit:
When the water level obtained by the gas-liquid separation water level acquisition unit is less than the predetermined reference gas-liquid separation water level, and the superheat calculated from the temperature obtained by the inlet temperature acquisition unit and the pressure obtained by the inlet pressure acquisition unit is greater than or equal to the predetermined reference superheat degree, The refrigeration system comprising closing the circulation valve, controlling the operating speed of the compressor to a predetermined normal speed, and controlling the expansion valve to open. According to claim 1,
Further comprising an inlet pressure acquisition unit electrically connected to the processor and provided to obtain a pressure of the refrigerant flowing into the compressor,
The processor:
Controlling the circulation valve to open when the pressure obtained by the inlet pressure acquisition unit is equal to or less than a predetermined stop pressure, the cooling system. In the control method for controlling a refrigeration system having a compressor, a gas cooler, a flash tank, an expansion valve, an evaporator, and a gas-liquid separator in order based on the flow direction of the refrigerant,
obtaining a level of the liquid refrigerant stored in the flash tank;
transferring the refrigerant compressed by the compressor to the gas-liquid separator when the obtained water level of the flash tank is equal to or less than a predetermined reference tank water level;
obtaining a level of the liquid refrigerant stored in the gas-liquid separator; and
and closing the expansion valve when the obtained water level of the gas-liquid separator is equal to or greater than a predetermined reference gas-liquid separation water level. According to claim 7,
and operating the compressor at a speed lower than a predetermined normal speed when the obtained water level of the flash tank is equal to or less than a predetermined reference tank water level. delete According to claim 7,
further obtaining a level of the liquid refrigerant stored in the gas-liquid separator in a state in which the expansion valve is closed;
obtaining a temperature of the refrigerant discharged from the gas-liquid separator in a state in which the expansion valve is closed;
obtaining a pressure of the refrigerant discharged from the gas-liquid separator in a state in which the expansion valve is closed;
Calculating a degree of superheat from the obtained temperature and pressure of the refrigerant; and
When the level of the further obtained refrigerant is less than the reference gas-liquid separation level and the calculated superheat degree is greater than or equal to a predetermined reference superheat degree, the expansion valve is opened, and the refrigerant compressed in the compressor is transferred to the gas-liquid separator Further comprising the step of blocking the cooling system control method. According to claim 10,
When the further obtained level of the refrigerant is less than the reference gas-liquid separation level, the calculated superheat degree is greater than or equal to a predetermined reference superheat degree, and the operating speed of the compressor is operated at a speed lower than a predetermined normal speed, the compressor Further comprising the step of returning the operating speed of the normal speed, the cooling system control method. According to claim 7,
obtaining a pressure of the refrigerant flowing into the compressor; and
When the obtained pressure of the refrigerant flowing into the compressor is equal to or less than a predetermined stop pressure, further comprising transferring the refrigerant compressed in the compressor to the gas-liquid separator.

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