KR102128576B1 - Refrigerant cycle apparatus - Google Patents

Abstract

Refrigeration cycle device according to an embodiment of the present invention, the suction pipe connected to the suction side of the first compressor; A connecting pipe connecting the discharge side of the first compressor and the suction side of the second compressor; A condenser through which the refrigerant passed through the second compressor flows; A supercooler through which the condensed refrigerant is introduced and supercooled; A liquid pipe for guiding the supercooled refrigerant in the supercooler to an evaporator; A supercooling inlet pipe for introducing a part of the refrigerant branched from the liquid pipe and flowing through the liquid pipe into the supercooler; A supercooling expansion mechanism installed in the supercooling inlet pipe; A supercooling outlet pipe connected to the supercooler and through which the refrigerant introduced into the supercooling inlet pipe is discharged; A first bypass pipe communicating the supercooled outlet pipe with the suction pipe; A second bypass pipe communicating the supercooling outlet pipe with the connecting pipe; A first bypass valve installed in the first bypass pipe; A second bypass valve installed in the second bypass pipe; And a controller for controlling the opening degree of each of the supercooling expansion mechanism, the first bypass valve, and the second bypass valve.

Description

Refrigerant cycle apparatus

The present invention relates to a refrigeration cycle device, and more particularly, to a refrigeration cycle device in which refrigerant passages of a low pressure side compressor and a high pressure side compressor are connected in series so that refrigerants can be sequentially compressed in multiple stages.

In general, a refrigeration cycle device cools or heats ambient air using a refrigerant as a working fluid, such as an air conditioner or a refrigerator, whereby the refrigerant undergoes compression, condensation, expansion, and evaporation processes.

In the refrigeration cycle device, the refrigerant is compressed into a gas state of high temperature and high pressure by a compressor, and then discharges heat to the outside while passing through the condenser, and is converted into a low-temperature low-pressure two-phase refrigerant through an expansion process. Then, the two-phase refrigerant that has undergone the expansion process absorbs heat from the outside, evaporates in a gaseous state, and then flows back into the compressor.

The refrigeration cycle device may be divided into a single compression cycle in which the refrigerant undergoes one compression process or a multi-stage compression cycle in which two or more compression processes are performed. When performing a multi-stage compression cycle, compared to the case of a single compression cycle, the compression days for compressing at a set pressure are reduced, and at the same time, the compressor discharge temperature can be lowered, and the compression days are reduced, thereby increasing efficiency.

The problem to be solved by the present invention is to provide a refrigeration cycle device that prevents the discharge temperature of the low pressure side compressor from excessively rising under low load conditions.

Refrigeration cycle device according to an embodiment of the present invention, the suction pipe connected to the suction side of the first compressor; A connecting pipe connecting the discharge side of the first compressor and the suction side of the second compressor; A condenser through which the refrigerant passing through the second compressor flows; A supercooler through which the condensed refrigerant is introduced and supercooled; A liquid pipe guiding the refrigerant supercooled in the supercooler to an evaporator; A supercooling inlet pipe for introducing a portion of the refrigerant branched from the liquid pipe and flowing through the liquid pipe into the supercooler; A supercooling expansion mechanism installed in the supercooling inlet pipe; A supercooling outlet pipe which is connected to the supercooler and discharges refrigerant flowing into the supercooling inlet pipe; A first bypass pipe communicating the supercooled outlet pipe with the suction pipe; A second bypass pipe communicating the supercooled outlet pipe with the connecting pipe; A first bypass valve installed in the first bypass pipe; A second bypass valve installed in the second bypass pipe; And a controller that controls the opening degree of each of the supercooling expansion mechanism, the first bypass valve, and the second bypass valve.

The first bypass valve and the second bypass valve may be controlled to a maximum opening degree, respectively, until the first compressor and the second compressor are turned on and a set time elapses.

The controller may control the first bypass valve to a minimum opening degree and control the second bypass valve to a maximum opening degree when the set time elapses and the first compressor and the second compressor are turned on. .

The controller, if one of the first compressor and the second compressor is on and the other is off, after the set time has elapsed, controls the first bypass valve to the maximum opening, and the second bypass The valve can be controlled to a minimum opening.

The controller may control the first bypass valve and the second bypass valve to the maximum opening, respectively, when the set time elapses and the first compressor and the second compressor are in an off state.

When one of the first compressor and the second compressor is on and the other is off, the controller may control the opening degree of the supercooling expansion mechanism between a predetermined maximum opening degree and a first minimum introduction degree.

The evaporator may further include a refrigeration temperature sensor that senses the temperature of the space to be cooled or frozen.

The controller, if the first compressor and the second compressor is on and the difference between the desired temperature set by the user's input and the sensing temperature of the refrigeration temperature sensor is greater than or equal to a preset temperature difference, the opening degree of the supercooling expansion mechanism is determined. It can be controlled between the set maximum opening degree and the first maximum introduction degree.

The controller, if the first compressor and the second compressor is on and the difference between the desired temperature set by the user's input and the sensing temperature of the refrigeration temperature sensor is less than a preset temperature difference, the controller opens the opening degree of the supercooling expansion mechanism. Control between the maximum opening degree and the second maximum introduction degree, and the second maximum introduction degree may be larger than the first maximum introduction degree.

According to a preferred embodiment of the present invention, since the controller can control the opening degree of the supercooling expansion mechanism, the first bypass valve, and the second bypass valve, respectively, the first compressor (low pressure side compressor) and the second compressor (high pressure side compressor) ) Has the advantage of controlling each intake superheat.

In addition, the first and second compressors are controlled to the maximum opening degree until the first compressor and the second compressor are turned on and the set time has elapsed, so that the suction superheat of the first compressor and the second compressor is operated. It can be prevented from rising rapidly in the beginning.

In addition, when the set time elapses and the first compressor and the second compressor are turned on, the first bypass valve may be controlled to the minimum opening degree and the second bypass valve may be controlled to the maximum opening degree. Thereby, it is possible to prevent excessively high intake superheat and discharge temperature of the high-pressure side compressor (second compressor).

In addition, when the set time has elapsed and either one of the first compressor and the second compressor is on and the other is off, the first bypass valve can be controlled to the maximum opening degree and the second bypass valve can be controlled to the minimum opening degree. have. In this way, even if any of the first and second compressors is in operation, it is possible to easily control the intake superheat and discharge temperature of the operating compressor.

In addition, when the set time elapses and the first compressor and the second compressor are in an off state, the first bypass valve and the second bypass valve may be controlled to the maximum opening degree. Thereby, the refrigerant of the refrigeration cycle device can be spread evenly over the entire pipe.

In addition, if one of the first compressor and the second compressor is on and the other is off, the opening degree of the supercooling expansion mechanism can be controlled between the maximum opening degree and the first maximum introduction degree. This is because even if the opening degree of the supercooling expansion mechanism is controlled based on the discharge temperature of the compressor in operation, there is no fear that the discharge temperature of the compressor in suspension increases, thereby making it easier to control the discharge temperature and suction superheat of the compressor in operation. have.

In addition, if the first compressor and the second compressor are on and the difference between the desired temperature and the sensing temperature of the refrigeration temperature sensor is greater than or equal to the set temperature difference (normal load condition), the opening degree of the supercooling expansion mechanism can be controlled between the maximum opening degree and the first minimum introduction degree. Can. This is because there is no fear that the discharge temperature of the low pressure side compressor (the first compressor) increases excessively under the normal load condition, whereby the suction superheat and discharge temperature of the second compressor can be more easily controlled.

In addition, if the first compressor and the second compressor are on and the difference between the desired temperature and the sensing temperature of the refrigeration temperature sensor is less than the set temperature difference (low load condition), the opening degree of the supercooling expansion mechanism is the maximum opening degree and the first best introduction degree. A larger second best introduction can also be controlled between. Accordingly, there is an advantage that it is possible to prevent the discharge temperature of the low pressure side compressor (first compressor) from being excessively raised under low load conditions.

1 is a block diagram of a refrigeration cycle device according to an embodiment of the present invention.
Figure 2 is an example showing the flow of the refrigerant when the first compressor and the second compressor of the refrigeration cycle device according to an embodiment of the present invention is on.
3 is an example showing a flow of refrigerant when the first compressor is on and the second compressor is off, according to an embodiment of the present invention.
4 is a control block diagram of a refrigeration cycle device according to an embodiment of the present invention.
5 is a flowchart illustrating a control sequence of a first bypass valve and a second bypass valve of a refrigeration cycle device according to an embodiment of the present invention.
6 is a flowchart illustrating a control sequence of a supercooling expansion mechanism of a refrigeration cycle device according to an embodiment of the present invention.

Hereinafter, a specific embodiment of the present invention will be described in detail with the accompanying drawings.

1 is a configuration diagram of a refrigeration cycle device according to an embodiment of the present invention, and FIG. 2 shows a flow of refrigerant when the first and second compressors of the refrigeration cycle device according to an embodiment of the present invention are in an on state. 3 is an example of the flow of refrigerant when the first compressor of the refrigerating cycle device according to an embodiment of the present invention is in an on state and the second compressor is in an off state.

Refrigeration cycle device according to an embodiment of the present invention will be described as an example when used for refrigeration, such as food. However, the present invention is not limited thereto, and the refrigeration cycle device of the present invention can be used in an air conditioner.

The refrigeration cycle device according to an embodiment of the present invention may include an outdoor unit 1 and a refrigeration unit 2.

The refrigeration unit 2 may be configured to keep the internal temperature of the case low. As an example, the refrigeration unit 2 may include a showcase for keeping foods displayed on the inside cold.

The outdoor unit 1 may be disposed outdoors, or may be disposed in a separate machine room separated from the space in which the refrigeration unit 2 is disposed, and can bear the cooling load of the refrigeration unit 2.

The indoor unit 1 may include a first compressor 10, a second compressor 15, a condenser 30, a receiver 31, an accumulator 32, and a supercooler 33. . The refrigeration unit 2 may include an evaporator 50 and an expansion mechanism 42.

The first compressor 10 and the second compressor 15 may be connected in series with respect to the flow direction of the refrigerant. That is, the refrigerant may be sequentially compressed in multiple stages in the first compressor 10 and the second compressor 15. The first compressor 10 may be referred to as a low pressure side compressor, and the second compressor 15 may be referred to as a high pressure side compressor.

Each of the first compressor 10 and the second compressor 15 may be configured as an inverter compressor capable of controlling an operating frequency.

Between the first compressor (10) and the second compressor (15), an oil level tube (24) is installed to allow the first compressor (10) and the second compressor (15) to communicate with each other. The milk level tube 24 may be provided with a milk level expansion mechanism 25 for adjusting the opening degree of the milk level tube 24. The bacterial oil expansion mechanism 25 may include an electronic expansion valve (EEV). As a result, when a shortage of oil supply occurs in one of the compressors 10 and 15, it can be replenished from the other compressors 10 and 15, thereby preventing burnout of the compressors 10 and 15 due to insufficient flow.

The first connection pipe 14 may be connected to the discharge side of the first compressor 10. The refrigerant compressed and discharged from the first compressor 10 may flow to the first connection pipe 14.

A first discharge temperature sensor 13 for sensing the temperature of the refrigerant discharged from the first compressor 10 may be provided on the outlet side of the first compressor 10 among the first connection pipes 14.

A first oil separator 11 may be provided in the first connection pipe 14. The first oil separator 11 may be connected to the first compressor 10 by the first oil recovery pipe 12.

The first oil separator 11 may separate the oil mixed with the refrigerant discharged from the first compressor 10 and recover it to the first compressor 10 through the first oil recovery pipe 12.

A check valve 12A for preventing oil from flowing back to the first oil separator 11 may be installed in the first oil recovery pipe 12. In addition, a check valve 14A is installed on the outlet side of the first oil separator 11 among the first connection pipes 14 to prevent the refrigerant from flowing back to the first oil separator 11.

The first connecting pipe 14 is a second connecting pipe 20 connected to the suction side of the second compressor 15 and a bypass pipe connected to the condenser inlet pipe 19 by bypassing the second compressor 15 ( 21), respectively.

Among the first connection pipe 14, a portion adjacent to the connection portion of the second connection pipe 20 and the bypass pipe 21 is provided with a check valve 14B to prevent refrigerant from flowing back into the first connection pipe 14 Can be.

As illustrated in FIG. 2, when the second compressor 15 is in the on state, the refrigerant in the first connection pipe 14 is sucked through the second connection pipe 20 by the suction force of the second compressor 15. It can be sucked into the compressor (15). That is, the first connecting pipe 14 and the second connecting pipe 20 constitute a connecting pipe 14 and 20 connecting the discharge side of the first compressor 10 and the suction side of the second compressor 15. can do.

The second connection pipe 20 may be provided with a medium pressure sensor 20A that senses the pressure of the refrigerant passing through the second connection pipe 20. In addition, the second connection pipe 20 may be provided with an opening/closing valve 20B for opening and closing the second connection pipe 20.

When the second compressor 15 is turned on, the on-off valve 20B may be opened.

On the other hand, as shown in FIG. 3, when the second compressor 20 is in an off state, the on-off valve 20B may be closed. Therefore, the refrigerant of the first connection pipe 14 can be guided to the condenser inlet pipe 19 by bypassing the second compressor 15 through the bypass pipe 21 and flow to the condenser 30. .

A condenser inlet pipe 19 may be connected to the discharge side of the second compressor 15. The refrigerant sucked into the second compressor 15 through the second connection pipe 20 may be compressed in the second compressor 15 and discharged to the condenser inlet pipe 19.

A second discharge temperature sensor 16 for sensing the temperature of the refrigerant discharged from the second compressor 15 may be provided at the outlet side of the second compressor 15 among the condenser inlet pipe 19.

A second oil separator 17 may be provided in the condenser inlet pipe 19. The second oil separator 17 may be connected to the second compressor 15 by a second oil recovery pipe 18.

The second oil separator 17 may separate the oil mixed with the refrigerant discharged from the second compressor 15 and recover it to the second compressor 15 through the second oil recovery pipe 18.

A check valve 18A for preventing oil from flowing back to the second oil separator 17 may be installed in the second oil return pipe 18. In addition, a check valve 19A is installed on the outlet side of the second oil separator 17 among the condenser inlet pipe 19 to prevent the refrigerant from flowing back into the second oil separator 17.

The condenser inlet pipe 19 is connected to the inlet side of the condenser 30 to guide the refrigerant to the condenser 30.

The condenser inlet pipe 19 may be provided with a high pressure sensor 19B for sensing the pressure of the refrigerant passing through the condenser inlet pipe 19.

To the condenser inlet pipe 19, a hot gas pipe 45 for introducing a high-temperature and high-pressure gas phase refrigerant into the suction pipe 22 connected to the suction side of the first compressor 10 may be connected. When the hot gas pipe 45 needs to increase the low pressure of the refrigerant circulating in the refrigeration cycle device, some of the high temperature and high pressure gaseous refrigerant passing through the condenser inlet pipe 19 is directly introduced into the suction pipe 22. Can.

A hot gas valve 46 is installed in the hot gas pipe 45 to adjust the opening degree of the hot gas pipe 45. The hot gas valve 46 may include an electromagnetic expansion valve (EEV).

The condenser 30 can condense the refrigerant. When the condenser 30 is air-cooled, the refrigerant passing through the condenser 30 may be condensed by exchanging heat with air blown by the blowing fan 30A.

The condenser outlet pipe 26 may be connected to the outlet side of the condenser 30, and the condenser outlet pipe 26 may be connected to the inlet side of the receiver 31. That is, the refrigerant condensed in the condenser 30 may be introduced into the receiver 31 through the condenser outlet pipe 26. The receiver 31 may be configured to control the amount of refrigerant circulating in the refrigeration cycle device.

The refrigerant pipe 27 may be connected to the outlet side of the receiver 31, and the refrigerant pipe 27 may be connected to the supercooler 33. That is, the refrigerant discharged from the receiver 31 may flow to the supercooler 33 through the refrigerant pipe 27. The refrigerant pipe 27 may be provided with a check valve 27A for preventing the refrigerant from flowing back to the receiver 31.

The supercooler 130 may be formed of a double tube. The supercooler 130 guides the inner pipe (not shown) connecting the refrigerant pipe 27 and the liquid pipe 28 and flows the refrigerant in a direction opposite to the inner pipe surrounding the inner pipe to guide the supercooling outlet pipe 36 to be described later. It may include an appearance (not shown). However, it is of course possible to have a configuration in which the roles of the exterior and the inner tube are reversed.

A liquid pipe 28 communicating with the refrigerant pipe 27 through the inner pipe may be connected to the supercooler 130. That is, the refrigerant in the refrigerant pipe 27 may flow into the liquid pipe 28 through the inner pipe.

In the liquid pipe 28, the supercooling inlet pipe 29 is branched so that it can be connected to the external appearance of the supercooler 33. A supercooling expansion mechanism 34 for expanding and cooling the refrigerant may be installed in the supercooling inlet pipe 29. The supercooling expansion mechanism 34 may include an electromagnetic expansion valve (EEV).

In addition, between the supercooling expansion mechanism 34 and the supercooler among the supercooling inlet pipes 29, a supercooling inlet temperature sensor 29A passing through the supercooling expansion mechanism 34 and sensing the temperature of the supercooled refrigerant may be provided. .

Accordingly, a part of the refrigerant discharged from the inner pipe of the supercooler 33 to the liquid pipe 28 flows into the supercooling inlet pipe 29 and passes through the supercooling expansion mechanism 34 to expand and cool, and the supercooler 33 ) May cool the refrigerant passing through the exterior and passing through the inner tube. Therefore, the refrigerant flowing into the evaporator 50 to be described later through the liquid pipe 28 may be further cooled.

A supercooling outlet pipe 36 may be connected to the supercooler 130. Since the supercooling outlet pipe 36 communicates with the supercooling inlet pipe 29 through the exterior of the supercooler 33, the refrigerant flowing into the supercooler from the supercooling inlet pipe passes through the exterior and passes through the inner pipe. It can exchange heat and discharge to the supercooled outlet pipe.

The supercooling outlet pipe 36 may be provided with a supercooling outlet temperature sensor 36A that measures the temperature of the refrigerant discharged from the supercooler 33.

The supercooling outlet pipe 36 may be connected to the first bypass pipe 37 and the second bypass pipe 38, respectively. That is, the refrigerant in the supercooling outlet pipe 36 may be divided into the first bypass pipe 37 and the second bypass pipe 38 and flow.

The first bypass pipe 37 may be connected to the suction pipe 22 connected to the suction side of the first compressor 10. In addition, the second bypass pipe 38 may be connected to the first connection pipe 14 in communication with the suction side of the second compressor 15. It is of course possible to configure the second bypass pipe 38 to be connected to the second connecting pipe 20 connected to the suction side of the second compressor 15.

That is, when it is necessary to lower the suction superheat and discharge temperature of the first compressor 10, the first bypass pipe 37 bypasses the evaporator 50 with the supercooled refrigerant, thereby compressing the first compressor 10. It can be directly injected into the suction side. In addition, when the second bypass pipe 38 needs to lower the intake superheat and discharge temperature of the second compressor 15, the second compressor 15 by bypassing the supercooled refrigerant to the evaporator 50 It can be directly injected into the suction side.

A first bypass valve 39 for adjusting the opening degree of the first bypass pipe 37 may be installed in the first bypass pipe 37. A second bypass valve 40 for adjusting the opening degree of the second bypass pipe 38 may be installed in the second bypass pipe 38. The first bypass valve and the second bypass valve may each include an electromagnetic expansion valve (EEV).

Meanwhile, the liquid pipe 28 may be extended to the outside of the outdoor unit 2 and connected to the inlet side of the evaporator 50 of the refrigeration unit 2. The liquid pipe 28 may be provided with an expansion mechanism 42 for expanding the refrigerant. As a result, the refrigerant flowing through the liquid pipe 28 to the refrigerating unit 2 can be expanded while passing through the expansion mechanism 42 and evaporated in the evaporator 50 to cool the inside of the refrigerating unit 2.

The engine 41 may be connected to the outlet side of the evaporator 50. The engine 41 may extend outside the refrigeration unit 2 and be connected to the inlet side of the accumulator 32 of the outdoor unit 1. Thus, the refrigerant evaporated from the evaporator 50 may be introduced into the accumulator 32 through the engine 41.

When the refrigerant that is not evaporated as a gas among the refrigerants flowing from the engine 41 and remains in the liquid phase directly flows into the first compressor 10, the load on the first compressor 10 is increased to increase the first compressor 10 Will cause damage. To prevent this, the accumulator 32 filters the liquid refrigerant and only the refrigerant in the gas state can be introduced into the first compressor 10. Of the refrigerants introduced into the accumulator 32, the refrigerants that are not evaporated and remain in the liquid phase are relatively heavier than the gaseous refrigerant and are stored in the lower portion of the accumulator 32, and only the upper gaseous refrigerant is the first compressor 10. Flows into

The suction pipe 22 may be connected to the outlet side of the accumulator 32, and the suction pipe 22 may be connected to the suction side of the first compressor 10. Accordingly, the gaseous refrigerant discharged from the accumulator 32 may be sucked into the first compressor 10 through the suction pipe 22. As described above, the hot gas pipe 45 and the first bypass pipe 37 may be connected to the suction pipe 22.

The accumulator 32 may be provided with a low pressure sensor 44.

The oil return pipe 47 connected to the suction pipe 22 may be connected to the accumulator 32. The oil mixed with the refrigerant flowing from the accumulator 32 to the suction pipe 22 may be recovered to the accumulator 32 through the oil return pipe 47. In addition, an oil return valve 48 for controlling the opening degree of the oil return pipe 47 may be installed in the oil return pipe 47.

On the other hand, the refrigeration unit 2 may be provided with a refrigeration temperature sensor 51 for sensing the temperature in the refrigeration unit (2). The refrigeration temperature sensor 51 may sense the temperature of the space that is cooled or frozen by the evaporator 50. For example, when the refrigeration unit 2 includes a showcase in which food is stored, the refrigeration temperature sensor 51 may sense the temperature inside the showcase.

4 is a control block diagram of a refrigeration cycle device according to an embodiment of the present invention.

Refrigeration cycle device according to an embodiment of the present invention may further include a controller (60). The controller 60 may control the overall operation of the refrigeration cycle device.

The controller 60 may be disposed in any one of the outdoor unit 1 and the refrigeration unit 2, or may be included in a building control system that controls the entire building in which the refrigeration cycle device is disposed.

The controller 60 includes a first discharge temperature sensor 13, a second discharge temperature sensor 16, a suction temperature sensor 23, a high pressure sensor 19B, a medium pressure sensor 20A, a low pressure sensor 44, and a supercooling inlet Measurement values of the temperature sensor 29A, the supercooled outlet temperature sensor 26A, and the refrigeration temperature sensor 51 may be received, respectively. However, the present invention is not limited thereto, and the controller 60 may receive measurement values of additional sensors or measurement values of sensors excluding some of the sensors.

The controller 60 may receive the discharge temperature of the first compressor 10 measured by the first discharge temperature sensor 13. The controller 60 may receive the discharge temperature of the second compressor 15 measured by the second discharge temperature sensor 16. The controller 60 may receive the suction temperature of the first compressor 10 measured by the suction temperature sensor 23.

The controller 60 may receive the discharge pressure of the second compressor 15 from the high pressure sensor 19B, that is, the high pressure of the refrigeration cycle device. The controller 60 may receive the discharge pressure of the first compressor 10 from the medium pressure sensor 20A, that is, the medium pressure of the refrigeration cycle device. The controller 60 may receive the suction pressure of the first compressor 10 from the low pressure sensor 44, that is, the low pressure of the refrigeration cycle device.

The controller 60 may receive the temperature of the refrigerant flowing into the supercooler 33, measured by the supercooling inlet temperature sensor 29A. The controller 60 may receive the temperature of the refrigerant flowing out of the supercooler 33, measured by the supercooling outlet temperature sensor 36A.

The controller 60 may receive the temperature measured by the freezing temperature sensor 51. The controller may calculate the refrigeration load required by the evaporator 50 by comparing the temperature measured by the refrigeration temperature sensor 51 with the desired temperature. In this case, the desired temperature may mean a target temperature of a target space (eg, an inner space of a showcase) in which the freezing unit 2 freezes. The desired temperature can be set by user input.

In addition, the controller 60 may control the opening degree of the hot gas valve 46 to control the amount of high temperature and high pressure gaseous refrigerant flowing into the suction pipe 22 from the condenser inlet pipe 19 through the hot gas pipe 45. have. When the opening degree of the hot gas valve 46 increases, the low pressure of the refrigeration cycle device may increase.

The controller 60 may control the opening degree of the supercooling expansion mechanism 34 to cool the refrigerant that has passed through the supercooling expansion mechanism 34 and control the superheating degree of the supercooler 33.

As described above, the refrigerant passing through the supercooling expansion mechanism 34 may be expanded and cooled. Therefore, when the temperature of the refrigerant passing through the supercooling expansion mechanism 34 decreases, suction of the first compressor 10 by the refrigerant flowing through the first bypass pipe 37 toward the suction side of the first compressor 10 is performed. The superheat degree may be lowered, and the suction superheat degree of the second compressor 15 may be lowered by the refrigerant flowing through the second bypass pipe 38 to the suction side of the second compressor 15.

The controller 60 controls the opening degree of the first bypass valve 39, and the amount of refrigerant flowing into the suction pipe 22 through the first bypass pipe 37 among the refrigerant discharged from the supercooler 33 Can be adjusted. Therefore, when the opening degree of the first bypass valve 39 is increased, the suction superheat degree and the discharge temperature of the first compressor 10 may drop.

The controller 60 controls the opening degree of the second bypass valve 40, and the refrigerant flowing into the first connection pipe 14 through the second bypass pipe 38 among the refrigerant discharged from the supercooler 33 You can adjust the amount of. Therefore, when the opening degree of the second bypass valve 40 is increased, the suction superheat degree and the discharge temperature of the second compressor 15 may drop.

The controller 60 may control on/off and operation frequencies of the first compressor 10 and the second compressor 15, respectively.

The controller 60 may open or close the on-off valve 20B. The controller 60 may open the on-off valve 20B and turn on the second compressor 15, or close the on-off valve 20B and turn off the second compressor 15.

5 is a flowchart illustrating a control sequence of a first bypass valve and a second bypass valve of a refrigeration cycle device according to an embodiment of the present invention.

When the operation of the refrigeration cycle device is started, the controller 60 may turn on the first compressor 10 and the second compressor 12. In this case, the controller 60 may control the first bypass valve 39 and the second bypass valve 40 to each maximum opening degree (S11).

In addition, the controller 60 may determine whether a set time has elapsed since the first compressor 10 and the second compressor 15 were turned on (S12). In one example, the set time may be 10 seconds. After the first compressor 10 and the second compressor 15 are turned on, the controller 60 opens the first bypass valve 39 and the second bypass valve 40 to the maximum opening degree before the set time elapses. Can be maintained.

Therefore, the refrigerant that has passed through the supercooling expansion mechanism 34 and the supercooler 33 may be divided into the suction side of the first compressor 10 and the second compressor 15 and flow. Accordingly, it is possible to prevent the intake superheat of the first compressor 10 and the second compressor 15 from rapidly increasing in the initial stage of operation.

When the set time has elapsed since the first compressor 10 and the second compressor 15 were turned on, the controller 60 may be operated by the first compressor according to the operating states of the first compressor 10 and the second compressor 15. The opening degree of the pass valve 39 and the second bypass valve 40 can be adjusted.

In more detail, when the first compressor 10 and the second compressor 15 are in the on state, the controller 60 controls the first bypass valve 39 to the minimum opening degree and opens the second bypass valve 40. It can be controlled to the maximum opening degree (S13) (S14).

In more detail, if both the first compressor 10 and the second compressor 15 are in the on state, the refrigerant is first compressed in the first compressor 10 and then secondarily compressed in the second compressor 15. Can. Therefore, since the discharge temperature of the second compressor 15 may increase excessively, the first bypass valve 39 is controlled to a minimum opening degree to reduce the suction superheat and discharge temperature of the second compressor 15. 2 The bypass valve 40 can be controlled to the maximum opening degree.

When the first bypass valve 39 is controlled to the minimum opening degree and the second bypass valve 40 is controlled to the maximum opening degree, most of the refrigerant that has passed through the supercooling expansion mechanism 34 and the supercooler 33 are second. It can flow to the suction side of the second compressor (15) through the bypass pipe (38). Therefore, it is possible to prevent the intake superheat and discharge temperature of the second compressor 15 from becoming too high.

On the other hand, if only one of the first compressor 10 and the second compressor 15 is in the on state, the controller 60 controls the first bypass valve 39 to the maximum opening degree and the second bypass valve 40 It can be controlled to the minimum opening degree (S15) (S16).

For example, when the first compressor 10 is on and the second compressor 15 is off, the refrigerant sucked into the first compressor 10 through the suction pipe 22 is compressed in the first compressor 10. After being discharged to the first connection pipe 14, the second compressor 15 may be bypassed through the bypass pipe 21 to flow to the condenser inlet pipe 19. That is, since the refrigerant does not pass through the second compressor 15 and there is no need to control the degree of intake superheat of the second compressor 15, the first bypass valve 39 is controlled to the maximum opening degree and the second bypass valve (40) can be controlled to the minimum opening degree. Thus, most of the refrigerant that has passed through the supercooling expansion mechanism 34 and the supercooler 33 may flow to the suction side of the first compressor 10 through the first bypass pipe 37.

As another example, when the first compressor 10 is off and the second compressor 15 is on, the refrigerant in the suction pipe 22 is sucked into the first compressor 10 by the suction force of the second compressor 15. However, the refrigerant may be sucked into the second compressor 15 through the first connection pipe 14 and the second connection pipe 20 without being compressed by the first compressor 10. Thereafter, the refrigerant may be compressed in the second compressor 15 and discharged to the condenser inlet pipe 19. That is, since the refrigerant is not compressed in the first compressor 10, the refrigerant temperature of the suction pipe 20 can determine the degree of suction superheat of the second compressor 15. Therefore, the first bypass valve 39 is controlled to the maximum opening degree and the second bypass valve 40 is controlled to the minimum opening degree, and most of the refrigerant that has passed through the supercooling expansion mechanism 34 and the supercooler 33 is removed. Even if it flows through the 1 bypass pipe 37 to the suction side of the first compressor 10, the suction superheat of the second compressor 15 can be controlled thereby.

Meanwhile, when the first compressor 10 and the second compressor 15 are in an off state, the controller 60 may control the first bypass valve 39 and the second bypass valve 40 to the maximum opening degree. (S15)(S17). As a result, the refrigerant of the refrigeration cycle device can be spread evenly over the entire pipe including the first bypass pipe 37 and the second bypass pipe 38.

6 is a flowchart illustrating a control sequence of a supercooling expansion mechanism of a refrigeration cycle device according to an embodiment of the present invention.

The controller 60 may control the supercooling expansion mechanism 34 to the opening degree at which the refrigerant expands. When the opening degree of the supercooling expansion mechanism 34 increases, the amount of refrigerant flowing into the supercooler 33 increases, and the suction superheat and discharge temperature of the first compressor 10 and the second compressor 15 become relatively low. Can. On the other hand, when the opening degree of the supercooling expansion mechanism 34 decreases, the amount of refrigerant flowing into the supercooler 33 decreases, and the suction superheat and discharge temperature of the first compressor 10 and the second compressor 15 are relatively Can be a little lower.

The refrigeration load required by the evaporator 50 of the indoor unit 2 may be determined according to a difference between a measurement temperature of the refrigeration temperature sensor 51 and a desired temperature of the refrigeration unit 2. That is, if the difference between the desired temperature of the refrigeration unit 2 and the measurement temperature of the refrigeration temperature sensor 51 is large, the refrigeration load required by the evaporator 50 of the indoor unit 2 may be large. On the other hand, if the difference between the desired temperature of the refrigeration unit 2 and the measurement temperature of the refrigeration temperature sensor 51 is small, the refrigeration load required by the evaporator 50 of the indoor unit 2 may be small.

The controller 60 may feedback control the opening degree of the supercooling expansion mechanism 34 with respect to the measured temperature of the second discharge temperature sensor 16 according to the cooling load required by the evaporator 50. This is because the refrigerant discharged from the second compressor 15 forms a high pressure of the refrigeration cycle device.

In more detail, if the cooling load required by the evaporator 50 of the indoor unit 2 is large, the target discharge temperature tp of the second compressor 15 is increased. In this case, if the current discharge temperature of the second compressor 15, i.e., the measured temperature of the second discharge temperature sensor 16 is lower than the target discharge temperature tp, the controller 60 can control the supercooling expansion mechanism 34. The opening degree can be reduced. Thus, the amount of low-temperature refrigerant flowing into the suction side of the first compressor 10 and the second compressor 15 is reduced, and the discharge temperature of the second compressor 15 can be increased.

Conversely, if the cooling load required by the evaporator 50 of the indoor unit 2 is small, the target discharge temperature tp of the second compressor 15 is lowered. In this case, if the current discharge temperature of the second compressor 15, that is, the measured temperature of the second discharge temperature sensor 16 is higher than the target discharge temperature tp, the controller 60 opens the opening degree of the supercooling expansion mechanism 34. Can increase Accordingly, the amount of low-temperature refrigerant flowing into the suction side of the first compressor 10 and the second compressor 15 increases, and the discharge temperature of the second compressor 15 may drop.

On the other hand, the case where the difference (Δt) between the measured temperature of the refrigeration temperature sensor 51 and the desired temperature of the refrigeration unit 2 is greater than or equal to a preset temperature difference may be referred to as a general load condition. That is, the case where the target discharge temperature tp is equal to or greater than the preset discharge temperature ts may be referred to as a general load condition.

When the first compressor 10 and the second compressor 15 are in operation, under the normal load condition, the controller 60 expands supercooling according to the difference between the target discharge temperature tp and the second discharge temperature sensor 16. The opening/closing of the mechanism 34 can be increased or decreased between the predetermined maximum opening degree k1 and the first minimum opening degree k2 (S21) (S22) (S23). For example, the maximum opening degree k1 may be 460 pls and the first minimum opening degree k2 may be 20 pls.

A case where the difference (Δt) between the measured temperature of the refrigeration temperature sensor 51 and the desired temperature of the refrigeration unit 2 is smaller than a preset temperature difference can be referred to as a low load condition. That is, the case where the target discharge temperature tp is lower than the preset discharge temperature ts may be referred to as a low load condition.

When the first compressor 10 and the second compressor 15 are operating, under the low load condition, the controller 60 supercools according to the difference between the target discharge temperature tp and the second discharge temperature sensor 16. The opening and closing of the expansion mechanism 34 can be increased or decreased between the predetermined maximum opening degree k1 and the second minimum opening degree k3 (S21) (S22) (S24). The second minimum opening degree k3 may be greater than the first minimum opening degree k2. As an example, the second minimum opening degree k3 may be 30 pls.

Under low load conditions, since the refrigeration load required by the evaporator 50 is small, the opening degree of the supercooling expansion mechanism 34 may be reduced. In addition, as described with reference to FIG. 5, since both the first compressor 10 and the second compressor 15 are operating, the first bypass valve 39 is controlled to the minimum opening and the second bypass valve 40 is the maximum. Can be controlled by opening. By such control, the discharge temperature of the second compressor 15 may be lowered, but the amount of low-temperature refrigerant sucked into the first compressor 10 is reduced, so that the discharge temperature of the first compressor 10 may be excessively increased. have.

In order to prevent this concern, by changing the minimum opening degree of the supercooling expansion mechanism 34 under a low load condition to a second maximum introduction degree k3 larger than the first minimum introduction degree k2, the first compressor 10 is sucked. It is possible to secure a minimum amount of low-temperature refrigerant and prevent excessive rise in discharge temperature of the first compressor (10).

On the other hand, if only one of the first compressor 10 or the second compressor 15 is operating, the controller 60 may be concerned that the discharge temperature of the stopped compressor will rise even if it is controlled based on the discharge temperature of the operating compressor. none. Therefore, the controller 60 can control the opening degree of the supercooling expansion mechanism 34 between the maximum opening degree k1 and the first minimum introduction degree k2 as in the general load condition (S21) (S23).

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations 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 spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments.

The scope of protection of the present invention should be interpreted by the following claims, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present invention.

1: Outdoor unit 2: Refrigeration unit
10: first compressor 14: first connection pipe
15: second compressor 19: condenser inlet pipe
20: second connection piping 21: bypass piping
22: suction pipe 28: liquid pipe
29: supercooling inlet pipe 30: condenser
31: receiver 32: accumulator
33: supercooler 34: supercooling expansion mechanism
36: supercooled outlet piping 37: first bypass piping
38: second bypass piping 39: first bypass valve
40: second bypass valve 41: engine
42: expansion mechanism 50: evaporator
51: refrigeration temperature sensor 60: controller

Claims (8)

A suction pipe connected to the suction side of the first compressor;
A connecting pipe connecting the discharge side of the first compressor and the suction side of the second compressor;
A condenser through which the refrigerant passing through the second compressor flows;
A supercooler through which the condensed refrigerant is introduced and supercooled;
A liquid pipe guiding the refrigerant supercooled in the supercooler to an evaporator;
A supercooling inlet pipe for introducing a portion of the refrigerant branched from the liquid pipe and flowing through the liquid pipe into the supercooler;
A supercooling expansion mechanism installed in the supercooling inlet pipe;
A supercooling outlet pipe which is connected to the supercooler and discharges refrigerant flowing into the supercooling inlet pipe;
A first bypass pipe communicating the supercooled outlet pipe with the suction pipe;
A second bypass pipe communicating the supercooled outlet pipe with the connecting pipe;
A first bypass valve installed in the first bypass pipe;
A second bypass valve installed in the second bypass pipe; And
Refrigeration cycle device including a controller for controlling the opening degree of each of the supercooling expansion mechanism, the first bypass valve and the second bypass valve according to the operation state of the first compressor and the second compressor. According to claim 1,
The controller,
A refrigeration cycle device that controls the first bypass valve and the second bypass valve to their maximum opening, respectively, until the first compressor and the second compressor are turned on and a set time has elapsed. According to claim 2,
The controller,
When the set time elapses and the first compressor and the second compressor are turned on,
Control the first bypass valve to a minimum opening,
A refrigeration cycle device that controls the second bypass valve to a maximum opening degree. According to claim 2,
The controller,
If the set time has elapsed and one of the first compressor and the second compressor is on and the other is off,
Control the first bypass valve to the maximum opening,
A refrigeration cycle device that controls the second bypass valve to a minimum opening degree. According to claim 2,
The controller,
When the set time elapses and the first compressor and the second compressor are off,
A refrigeration cycle device that controls each of the first bypass valve and the second bypass valve to a maximum opening degree. According to claim 1,
The controller,
If one of the first compressor and the second compressor is on and the other is off,
A refrigeration cycle device for controlling the opening degree of the supercooling expansion mechanism between a preset maximum opening degree and a first maximum introduction degree. According to claim 1,
Further comprising a refrigeration temperature sensor for sensing the temperature of the space to be cooled or frozen by the evaporator,
The controller,
If the first compressor and the second compressor are on and the difference between the desired temperature set by the user's input and the sensing temperature of the refrigeration temperature sensor is greater than or equal to a preset temperature difference,
A refrigeration cycle device for controlling the opening degree of the supercooling expansion mechanism between a preset maximum opening degree and a first maximum introduction degree. The method of claim 7,
The controller,
If the first compressor and the second compressor are on and the difference between the desired temperature set by the user's input and the sensing temperature of the refrigeration temperature sensor is smaller than the preset temperature difference,
The opening degree of the supercooling expansion mechanism is controlled between the maximum opening degree and the second maximum introduction degree,
The second maximum introduction degree is greater than the first maximum introduction refrigeration cycle device.

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