JP6945141B2 - Freezing system - Google Patents

Description

The present invention relates to a freezing system, and more particularly to a freezing system for cooling a showcase.

Conventionally, a compressor subsystem that performs two-stage compression of the refrigerant sent from the evaporator and a compressor subsystem that performs one-stage compression of the refrigerant returned from the economizer heat exchanger have been installed to improve the efficiency of the refrigeration system. Such a technique is disclosed (see, for example, Patent Document 1).

Special Table 2009-539058

In the conventional technique, since the compressor subunit that performs two-stage compression of the refrigerant sent from the evaporator is provided, it is possible to appropriately cope with one evaporator.
However, in the refrigeration system, the amount of refrigerant charged differs depending on the store where it is installed, so if the transport pressure exceeds the critical pressure during operation at high outside air temperature or when starting at high outside air temperature, the drive frequency of the compressor will be changed. Control cannot immediately return to stable operation.
Further, when operating at a low outside air temperature, the refrigerating system has a low load, so that the load is low, and even when operating at the minimum rotation speed of the compressor, the refrigerating capacity is excessive and the number of starts and stops increases. Due to the frequent occurrence of start and stop, extra power is required to start up, and the temperature inside the refrigerator on the load side rises temporarily. Further, if the compressor is operated while the low pressure is low in order to prevent the compressor from starting and stopping, a deviation between the evaporation temperature and the internal temperature setting and frost formation are likely to occur.
The present invention has been made in view of the above points, and provides a freezing system capable of appropriately controlling the transport pressure at high outside air temperature or low outside air temperature and performing stable operation. With the goal.

In order to achieve the above object, the refrigeration system of the present invention includes a compressor that is compressed by two stages of a low pressure stage compression mechanism and a high pressure stage compression mechanism, and an intercooler to which the refrigerant discharged from the low pressure stage compression mechanism is sent. A gas cooler in which the refrigerant from the intercooler is sent via the high-pressure stage compression mechanism, an intermediate cooler connected to the gas cooler via a throttle mechanism, and gas refrigerant and liquid refrigerant taken out from the intermediate cooler. An internal heat exchanger that exchanges heat with the refrigerant sent from the intermediate cooler, an evaporator connected to the internal heat exchanger, and a connection between the evaporator and the low-pressure stage compression mechanism of the compressor. comprising an accumulator that is, a control device, wherein the evaporator inlet side provided with a bypass pipe which connects the accumulator, the bypass throttle mechanism is provided in the middle portion of the bypass pipe, wherein the control device, the refrigerant Controls to open the bypass throttle mechanism when the transport pressure of the refrigerant exceeds the critical pressure, and controls to close the bypass throttle mechanism when the transport pressure of the refrigerant falls below a predetermined pressure. characterized in that it.

According to this, by opening and closing the bypass throttle mechanism, a part of the refrigerant on the inlet side of the evaporator can be sent to the accumulator via the bypass pipe, so that the internal pressure of the accumulator is lower than the critical pressure. It can be maintained and the liquid refrigerant can be stored inside the accumulator.

According to the present invention, the internal pressure of the accumulator can be maintained lower than the critical pressure, the liquid refrigerant can be stored inside the accumulator, and as a result, the transport pressure of the refrigerant can be properly maintained. Become.

The refrigerating cycle diagram which shows the embodiment of the refrigerating system of this invention. The block diagram which shows the control structure of this embodiment. The flowchart which shows the operation at the time of high outside temperature in this embodiment. The flowchart which shows the operation at the time of low outside temperature in this embodiment.

The first invention provides a refrigeration system in which a compressor, a condenser, a drawing mechanism, an evaporator, and an accumulator are sequentially connected by a refrigerant pipe, and includes a bypass pipe for connecting the inlet side of the evaporator and the accumulator. A bypass throttle mechanism was provided in the middle of the bypass pipe.
According to this, by opening and closing the bypass throttle mechanism, a part of the refrigerant on the inlet side of the evaporator can be sent to the accumulator via the bypass pipe, so that the internal pressure of the accumulator is lower than the critical pressure. It can be maintained and the liquid refrigerant can be stored inside the accumulator. As a result, it becomes possible to properly maintain the transport pressure of the refrigerant.

The second invention includes a control device, which controls the bypass throttle mechanism to open when the refrigerant transfer pressure becomes equal to or higher than the critical pressure, and the refrigerant transfer pressure is a predetermined pressure. When the following occurs, the bypass throttle mechanism is controlled to be closed.
According to this, the internal pressure of the accumulator can be maintained lower than the critical pressure according to the transport pressure of the refrigerant, the liquid refrigerant can be stored inside the accumulator, and the transport pressure of the refrigerant is properly maintained. It becomes possible.

In the third invention, the bypass throttle mechanism is composed of an electric valve capable of controlling the opening degree, and the control device opens the bypass throttle mechanism when the transport pressure of the refrigerant becomes equal to or higher than the critical pressure. It is controlled to open the degree, and when the transport pressure of the refrigerant becomes equal to or lower than a predetermined pressure, the opening degree of the bypass throttle mechanism is controlled to be closed.
According to this, the internal pressure of the accumulator can be finely controlled according to the transport pressure of the refrigerant, and the transport pressure of the refrigerant can be maintained appropriately.

In the fourth invention, the bypass throttle mechanism is composed of an electromagnetic on-off valve, and the control device opens and controls the bypass throttle mechanism when the transport pressure of the refrigerant becomes equal to or higher than the critical pressure. When the transport pressure of the refrigerant becomes equal to or lower than a predetermined pressure, the bypass throttle mechanism is controlled to be closed.
According to this, the internal pressure of the accumulator can be controlled according to the transport pressure of the refrigerant, and the transport pressure of the refrigerant can be maintained appropriately.

According to a fifth aspect of the present invention, the control device controls to open the bypass throttle mechanism when the drive rotation speed of the compressor is the minimum and there is a difference between the set value of the low pressure pressure and the low pressure pressure. do.
According to this, it is possible to maintain the operation to the extent that the evaporator side does not stop the thermostat, and it is possible to reduce the number of times the compressor is started and stopped.

In the sixth aspect of the present invention, the bypass throttle mechanism is composed of an electric valve capable of controlling the opening degree, and the control device has a minimum drive rotation speed of the compressor and sets low pressure and low pressure. When there is a difference from the value, the opening degree of the bypass throttle mechanism is controlled to be opened according to the difference between the low pressure pressure and the set value of the low pressure pressure.
According to this, it is possible to finely control the operation to the extent that the evaporator side does not stop the thermostat, and it is possible to reduce the number of times the compressor is started and stopped.

Hereinafter, embodiments of the present invention will be described with reference to the drawings with reference to the drawings.
FIG. 1 is a circuit diagram of a refrigeration cycle showing an embodiment of a refrigeration system according to the present invention. The freezing system to which the present invention is applied is not limited to this, and various freezing systems can be applied.

As shown in FIG. 1, the refrigerating system 1 includes, for example, a refrigerating machine 2 installed in a facility such as a convenience store or a supermarket, and a showcase 3 as a cooling device for displaying and cooling refrigerated / frozen products. There is. In this embodiment, a carbon dioxide refrigerant is used as the refrigerant, but the present invention is not limited to this, and various refrigerants can be used.

Further, the refrigerator 2 includes a compressor 10 that is compressed by two stages, a low-pressure stage compression mechanism 11 and a high-pressure stage compression mechanism 12.
The compressor 10 is provided with a first suction port 13 and a first discharge port 14 in the low-pressure stage compression mechanism 11, and is provided with a second suction port 15 and a second discharge port 16 in the high-pressure stage compression mechanism 12. There is.

The first suction port 13 of the compressor 10 is configured to suck the refrigerant sent from the evaporator 20 of the showcase 3, compress it to an intermediate pressure by the low pressure stage compression mechanism 11, and discharge it from the first discharge port 14. Has been done.
Further, the first discharge port 14 of the compressor 10 is connected to the inlet side of the intercooler 22 via the refrigerant pipe 60, and the outlet side of the intercooler 22 is connected to the second outlet side of the compressor 10 via the refrigerant pipe 60. It is connected to the suction port 15. A fan 23 for the intercooler is arranged in the intercooler 22.
Then, the refrigerant discharged from the first discharge port 14 of the compressor 10 flows into the intercooler 22 via the refrigerant pipe 60, and the intercooler 22 operates the intercooler fan 23 to exchange heat with the outside air for cooling. It is configured to be returned to the second suction port 15 of the compressor 10.

The second discharge port 16 of the compressor 10 is connected to the gas cooler 25 via the refrigerant pipe 61, respectively. Then, the compressor 10 is configured to be compressed to a required pressure by a second-stage compression mechanism, discharged from the second discharge port 16, and sent to the gas cooler 25.

Further, an intercooler 26 is connected to the gas cooler 25 via a refrigerant pipe 62, and a throttle mechanism 27 for reducing the pressure of the refrigerant sent from the gas cooler 25 is provided in the middle of the refrigerant pipe 62. ing.
The gas cooler 25 cools the refrigerant sent from the compressor 10 by exchanging heat with the outside air by operating the fan 28 for the gas cooler. However, since the carbon dioxide refrigerant does not condense, the critical pressure is exceeded. In this state, the high-pressure gas is sent to the drawing mechanism 27 as it is.

Further, an internal heat exchanger 32 is connected to the intercooler 26 via a refrigerant pipe 63.
Two showcases 3 are connected in parallel to the refrigerant pipe 64 on the outlet side of the internal heat exchanger 32. In this embodiment, an example in which two showcases 3 are provided is shown, but the present invention is not limited to this, and any number of showcases can be installed.
The showcase 3 is provided with a showcase drawing mechanism 40 and an evaporator 20.
Then, the evaporator 20 is configured to exchange heat between the refrigerant sent through the refrigerant pipe 64 and the air in the refrigerator to cool the inside of the showcase 3.
Further, the outlet side of the evaporator 20 is connected to the first suction port 13 of the compressor 10 via the accumulator 50 by the refrigerant pipe 65.

A gas refrigerant return pipe 30 for taking out the gas refrigerant separated by the intercooler 26 is connected to the upper part of the intercooler 26, and a gas return throttle mechanism is connected to the middle part of the gas refrigerant return pipe 30. 36 is provided. A liquid refrigerant return pipe 31 for taking out the liquid refrigerant separated by the intermediate cooler 26 is connected to the lower part of the intercooler 26, and a liquid return throttle mechanism 37 is provided in the middle of the liquid refrigerant return pipe 31. It is provided.
The gas refrigerant return pipe 30 and the liquid refrigerant return pipe 31 merge with each other, and the merge pipe 34 is connected to the internal heat exchanger 32. Inside the internal heat exchanger 32, the refrigerant pipe 63 and the merging pipe 34 are arranged so that the flow directions of the refrigerant are opposite, and are taken out from the intermediate cooler 26 in the internal heat exchanger 32. It is configured to efficiently exchange heat between the gas refrigerant or the liquid refrigerant and the refrigerant sent from the intermediate cooler 26.
The refrigerant pipe 35 on the outlet side of the internal heat exchanger 32 is connected to the second suction port 15 of the compressor 10.

The gas return throttle mechanism 36 and the liquid return throttle mechanism 37 decompress the refrigerant on the outlet side of the internal heat exchanger 32 to expand it to an intermediate pressure level, and the internal heat exchanger 32 reduces the refrigerant pipe 63. It is configured to cool the refrigerant flowing through the refrigerant pipe 63 by exchanging heat between the refrigerant flowing through the refrigerant pipe and the decompressed refrigerant flowing through the merging pipe. The decompressed refrigerant after heat exchange is sent from the second suction port 15 to the compressor 10, and the temperature of the refrigerant discharged from the compressor 10 is maintained within an appropriate range.

Further, in the present embodiment, a bypass pipe 51 for connecting the outlet side of the internal heat exchanger 32 and the accumulator 50 is provided, and a bypass throttle mechanism 52 is provided in the middle of the bypass pipe 51. There is. In the present embodiment, the bypass throttle mechanism 52 is composed of an electric valve capable of controlling the opening degree.
In the present embodiment, the bypass pipe 51 is connected to the outlet side of the internal heat exchanger, which is a point where the enthalpy is small, but the present invention is not limited to this. For example, if the transfer pressure of the refrigerant is an intermediate pressure, such as the outlet side of the gas cooler, the connection may be made to any of the locations. Further, in the present embodiment, the bypass throttle mechanism 52 is configured by an electric valve, but it may be configured by an electromagnetic valve that only opens and closes.

Further, a refrigerant temperature sensor 55 for detecting the temperature of the refrigerant and a refrigerant pressure sensor 56 for detecting the pressure of the refrigerant are provided in the vicinity of the first suction port 13 of the compressor 10. An outside air temperature sensor 57 for detecting the outside air temperature is provided outside the refrigerator.

Next, the control configuration of this embodiment will be described.
FIG. 2 is a block diagram showing a control configuration of the present embodiment.
As shown in FIG. 2, the refrigeration system of the present embodiment includes a compressor 10, an intercooler fan 23, a gas cooler fan 28, a throttle mechanism 27, a gas return throttle mechanism 36, a liquid return throttle mechanism 37, and a bypass throttle. A control device 70 for driving and controlling the mechanism 52 and the showcase diaphragm mechanism 40 is provided.
The control device 70 centrally controls each part of the refrigeration system, and is a CPU as an arithmetic execution unit, a ROM, a RAM, and other peripherals that store a basic control program and predetermined data that can be executed by the CPU. It has a circuit and so on.
Further, the control device 70 is configured to input detection signals of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55, and the outside air temperature sensor 57.

The control device 70 includes a compressor 10, an intercooler fan 23, a gas cooler fan 28, a throttle mechanism 27, a gas return throttle mechanism 36, a liquid return throttle mechanism 37, a bypass throttle mechanism 52, and a showcase throttle mechanism. By controlling the drive of each of the 40s, it is possible to operate in various operation modes. The operation mode includes a normal operation mode, a high outside air temperature mode, and a low outside air temperature mode.

The detection values of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55, and the outside temperature sensor 57 are input to the control device 70, and the control device 70 receives the detection values of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55, and the outside temperature sensor 57. The opening degree of the bypass throttle mechanism 52 is controlled based on the above.
Specifically, when the outside air temperature detected by the outside air temperature sensor 57 or the transport pressure of the refrigerant detected by the refrigerant pressure sensor 56 is equal to or lower than the critical pressure and equal to or higher than the predetermined pressure, control is performed in the normal operation mode. ..
When the normal operation mode is performed, the control device 70 closes the bypass throttle mechanism 52 and compresses the compressor 10 according to the outside temperature detected by the outside temperature sensor 57 or the transport pressure of the gas detected by the refrigerant pressure sensor 56. , The drive control of the intercooler fan 23 and the gas cooler fan 28, and the opening / closing control of the throttle mechanism 27, the gas return throttle mechanism 36, the liquid return throttle mechanism 37, and the showcase throttle mechanism 40, respectively.

Then, when the outside air temperature detected by the outside air temperature sensor 57 or the transport pressure of the refrigerant detected by the refrigerant pressure sensor 56 is equal to or higher than the critical pressure, the operation is performed in the high outside air temperature mode. Here, the judgment as to whether or not the pressure is equal to or higher than the critical pressure is determined by, for example, whether or not the pressure is equal to or higher than 7.38 MPa.
When the high outside air temperature control mode is performed, the control device 70 controls the bypass throttle mechanism 52 of the bypass pipe 51 so as to open a predetermined number of pulses.
As a result, a part of the refrigerant flowing out from the internal heat exchanger via the bypass pipe 51 is sent to the accumulator 50, and the internal pressure of the accumulator 50 can be maintained lower than the critical pressure, and the inside of the accumulator 50 can be maintained. Liquid refrigerant can be stored. As a result, it becomes possible to properly maintain the transport pressure of the refrigerant.

Further, when the outside air temperature detected by the outside air temperature sensor 57 or the transport pressure of the refrigerant detected by the refrigerant pressure sensor 56 is equal to or less than a predetermined pressure, the bypass throttle mechanism 52 of the bypass circuit is controlled to close a predetermined number of pulses. do. This control is performed until the transport pressure of the refrigerant is equal to or lower than the critical pressure and is equal to or higher than the predetermined pressure. Here, the determination as to whether or not the pressure is equal to or lower than the predetermined pressure is determined by, for example, whether or not the pressure is 6.5 MPa or less. The set value of the predetermined pressure is set so as to be surely lower than the critical pressure in consideration of the variation in the detected value of the refrigerant pressure sensor 56.
Then, when the transport pressure of the refrigerant is equal to or lower than the critical pressure and equal to or higher than the predetermined pressure, the control is switched from the control in the high outside air temperature mode to the control in the normal operation mode.

Further, the control device 70 controls the compressor 10 in the low outside air temperature mode based on the difference between the low pressure pressure of the refrigerant and the set value of the low pressure pressure, in which the drive rotation speed of the compressor 10 is the minimum rotation speed.
When the low outside air temperature mode is performed, the control device 70 controls the opening degree of the bypass throttle mechanism 52 based on the difference between the low pressure pressure of the refrigerant and the set value of the low pressure pressure. That is, the control device 70 controls the bypass throttle mechanism 52 so as to open larger as the difference between the low pressure pressure of the refrigerant and the set value of the low pressure pressure increases, and the difference between the low pressure pressure of the refrigerant and the set value of the low pressure pressure becomes larger. It is controlled to close as it becomes smaller.

At low outside air temperature, the load on the showcase 3 becomes small and the rotation speed of the compressor 10 becomes low. However, by controlling the bypass throttle mechanism 52 to open in the low outside air temperature mode, the refrigerant flowing through the bypass pipe 51 The amount is increased, the amount of refrigerant sent to the showcase 3 is limited, and the refrigerating capacity is reduced. As a result, the operation of the showcase 3 can be maintained to the extent that the thermostat does not stop, and the number of times the compressor 10 starts and stops can be reduced.
Then, when the drive rotation speed of the compressor 10 becomes equal to or higher than the minimum rotation speed, the control device 70 controls to close the bypass throttle mechanism 52, and switches to the control in the normal operation mode.

In order to prevent liquid back due to excessive return to the accumulator 50, the refrigerant temperature is detected by the refrigerant temperature sensor 55, and when the difference between the detected refrigerant temperature and the low pressure pressure saturation temperature becomes 0 or less than the specified value, It is preferable to stop the compressor 10.

Next, the operation of this embodiment will be described.
In the present embodiment, by operating the compressor 10, the refrigerant sent from the evaporator is sucked from the first suction port 13 of the compressor 10, and this refrigerant is compressed to an intermediate pressure by the low pressure stage compression mechanism 11. It is discharged from the first discharge port 14.
The refrigerant discharged from the first discharge port 14 of the compressor 10 flows into the intercooler 22 via the refrigerant pipe 60, is cooled by exchanging heat with the outside air by the intercooler fan 23 at the intercooler 22, and is cooled by the compressor 10. It is returned to the second suction port 15.

The refrigerant returned from the intercooler 22 is compressed to a required pressure by the compressor 10 in the second stage, discharged from the second discharge port 16, and sent to the gas cooler 25. The refrigerant sent from the compressor 10 is cooled by exchanging heat with the outside air by the gas cooler fan 28 in the gas cooler 25, and is sent to the intercooler 26 as a high-pressure refrigerant via the throttle mechanism 27.

The liquid refrigerant sent from the lower part of the intermediate cooler 26 is sent to the internal heat exchanger 32, and the refrigerant sent from the intermediate cooler 26 in the internal heat exchanger 32 and the gas throttle mechanism sent from the intermediate cooler 26. Alternatively, heat is exchanged with the refrigerant reduced to an intermediate pressure level by the liquid drawing mechanism.
Further, the refrigerant after heat exchange with the refrigerant sent from the intermediate cooler 26 by the internal heat exchanger 32 is sent from the second suction port 15 to the compressor 10, and the temperature of the refrigerant discharged from the compressor 10 is adjusted. Keep in the proper range.

Further, the refrigerant cooled by the internal heat exchanger 32 is sent to the showcase 3, decompressed by the showcase drawing mechanism 40, and sent to the evaporator 20. As a result, the showcase 3 is cooled.
The refrigerant after heat exchange by the evaporator 20 is sent to the accumulator 50, and after the refrigerant is separated into gas and liquid by the accumulator 50, only the gas refrigerant is returned to the first suction port 13 of the compressor 10.

Next, the operation of this embodiment will be described with reference to the flowcharts shown in FIGS. 3 and 4.
First, the operation in the case of controlling in the high outside air temperature mode will be described with reference to the flowchart shown in FIG.
The control device 70 acquires the detected values of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55, and the outside temperature sensor 57, and determines whether or not the transport pressure is equal to or higher than the critical pressure (ST1). Then, when it is determined that the outside air temperature detected by the outside air temperature sensor 57 or the transport pressure of the refrigerant detected by the refrigerant pressure sensor 56 is equal to or higher than the critical pressure (ST1: YES), the control device 70 raises the high outside air temperature. Operate according to the mode (ST2).

When the high outside air temperature control mode is performed, the control device 70 opens the bypass throttle mechanism 52 of the bypass circuit by a predetermined number of pulses (ST3).
On the other hand, when it is determined that the transport pressure of the refrigerant is not higher than the critical pressure (ST1: NO), it is controlled in the normal operation mode (ST6), and each device such as the compressor 10 is driven based on the detection value by each sensor. Control (ST7).

The control device 70 determines whether or not the transport pressure of the refrigerant is equal to or lower than the predetermined pressure (ST4), and if it determines that the transfer pressure is equal to or lower than the predetermined pressure (ST4: YES), sets the bypass throttle mechanism 52. Close (ST5).

Next, the operation in the case of controlling in the low outside air temperature mode will be described with reference to the flowchart shown in FIG.
The control device 70 determines whether or not the drive rotation speed of the compressor 10 is the minimum (ST11). When it is determined that the drive rotation speed of the compressor 10 is the minimum (ST11: YES), the control device 70 determines whether or not there is a difference between the set value of the low pressure pressure and the low pressure pressure (ST12).
When the control device 70 determines that there is a difference between the set value of the low pressure pressure and the low pressure pressure (ST12: YES), the control device 70 controls by the low outside air temperature mode (ST13).

Then, the control device 70 determines whether or not the difference between the low pressure pressure and the set value of the low pressure pressure is large (ST14), and when it is determined that the difference between the low pressure pressure and the set value of the low pressure pressure is large (ST14). : YES), the bypass throttle mechanism 52 is controlled to be wide open (ST15).
Further, the control device 70 determines whether or not the difference between the low pressure pressure and the set value of the low pressure pressure is small (ST16), and when it is determined that the difference between the low pressure pressure and the set value of the low pressure pressure is small (ST16). : YES), the control device 70 controls the bypass throttle mechanism 52 to open slightly (ST17).

When it is determined that the difference between the low pressure pressure and the set value of the low pressure pressure has disappeared by performing these controls (ST18), the control device 70 controls to close the bypass throttle mechanism 52 (ST19).
If it is determined that the drive speed of the compressor 10 is not the minimum (ST11: NO), or if it is determined that there is no difference between the low pressure pressure and the set value of the low pressure pressure (ST12: NO), the normal operation mode is used. (ST20), and each device such as the compressor 10 is driven and controlled based on the value detected by each sensor (ST21).

As described above, according to the present embodiment, in the refrigerating system 1 in which the compressor 10, the gas cooler 25 (condenser), the drawing mechanism 27, the evaporator 41, and the accumulator 50 are sequentially connected by a refrigerant pipe, the evaporator A bypass pipe 51 for connecting the inlet side of the 41 and the accumulator 50 is provided, and a bypass throttle mechanism 52 is provided in the middle of the bypass pipe 51.
As a result, by opening and closing the bypass throttle mechanism 52, a part of the refrigerant on the inlet side of the evaporator can be sent to the accumulator 50 via the bypass pipe 51, so that the internal pressure of the accumulator 50 is set to the critical pressure. It can be kept lower and the liquid refrigerant can be stored inside the accumulator 50. As a result, it becomes possible to properly maintain the transport pressure of the refrigerant.

Further, according to the present embodiment, the control device 70 is provided, and the control device 70 controls to open the bypass throttle mechanism 52 when the transport pressure of the refrigerant becomes equal to or higher than the critical pressure, and also transports the refrigerant. When the pressure becomes equal to or lower than a predetermined pressure, the bypass throttle mechanism 52 is controlled to be closed.
As a result, the internal pressure of the accumulator 50 can be maintained lower than the critical pressure according to the transport pressure of the refrigerant, the liquid refrigerant can be stored inside the accumulator 50, and the transport pressure of the refrigerant is properly maintained. It becomes possible.

Further, according to the present embodiment, the bypass throttle mechanism 52 is composed of an electric valve capable of controlling the opening degree, and the control device 70 uses the bypass throttle mechanism 70 when the transport pressure of the refrigerant becomes equal to or higher than the critical pressure. The opening degree of the mechanism 52 is controlled to be opened, and the opening degree of the bypass throttle mechanism 52 is controlled to be closed when the transport pressure of the refrigerant becomes equal to or lower than a predetermined pressure.
As a result, the internal pressure of the accumulator 50 can be finely controlled according to the transport pressure of the refrigerant, and the transport pressure of the refrigerant can be maintained appropriately.

Further, according to the present embodiment, the bypass throttle mechanism 52 is composed of an electromagnetic on-off valve, and the control device 70 opens the bypass throttle mechanism 52 when the transport pressure of the refrigerant becomes equal to or higher than the critical pressure. In addition to controlling, the bypass throttle mechanism 52 is controlled to be closed when the transport pressure of the refrigerant becomes equal to or lower than a predetermined pressure.
As a result, the internal pressure of the accumulator 50 can be controlled according to the transport pressure of the refrigerant, and the transport pressure of the refrigerant can be maintained appropriately.

Further, according to the present embodiment, the control device 70 opens the bypass throttle mechanism 52 when the drive rotation speed of the compressor 10 is the minimum and there is a difference between the low pressure pressure and the set value of the low pressure pressure. To control.
As a result, it is possible to maintain the operation to the extent that the evaporator side does not stop the thermostat, and the number of times of starting and stopping of the compressor 10 can be reduced.

Further, according to the present embodiment, the bypass throttle mechanism 52 is composed of an electric valve capable of controlling the opening degree, and the control device 70 has the minimum drive rotation speed of the compressor 10 and has low pressure and low pressure. When there is a difference from the set value of the pressure, the opening degree of the bypass throttle mechanism 52 is controlled to be opened according to the difference between the low pressure pressure and the set value of the low pressure pressure.
As a result, the operation of the evaporator side can be finely controlled to the extent that the thermostat does not stop, and the number of times of starting and stopping of the compressor 10 can be reduced.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

As described above, the freezing system according to the present invention can be suitably used as a freezing system capable of appropriately controlling the transport pressure at high outside air temperature or low outside air temperature and performing stable operation. ..

1 Refrigeration system 2 Refrigerator 3 Showcase 10 Compressor 11 Low pressure stage compression mechanism 12 High pressure stage compression mechanism 13 1st suction port 14 1st discharge port 15 2nd suction port 16 2nd discharge port 20 Evaporator 22 Intercooler 23 For intercooler Fan 25 Gas cooler 26 Intermediate cooler 27 Squeeze mechanism 28 Gas cooler fan 32 Internal heat exchanger 36 Gas return throttle mechanism 37 Liquid return throttle mechanism 40 Showcase throttle mechanism 41 Evaporator 50 Accumulator 51 Bypass piping 52 Bypass throttle mechanism 55 Refrigerant temperature sensor 56 Refrigerant pressure sensor 57 Outside temperature sensor 70 Control device

Claims (3)

A compressor that operates in two stages, a low-pressure stage compression mechanism and a high-pressure stage compression mechanism,
An intercooler to which the refrigerant discharged from the low-pressure stage compression mechanism is sent, and
A gas cooler in which the refrigerant from the intercooler is sent via the high-pressure stage compression mechanism, and
An intercooler connected to the gas cooler via a throttle mechanism,
An internal heat exchanger that exchanges heat between the gas refrigerant and liquid refrigerant taken out from the intercooler and the refrigerant sent from the intercooler.
The evaporator connected to the internal heat exchanger and
An accumulator connected between the evaporator and the low-pressure stage compression mechanism of the compressor, and
Equipped with a control device,
A bypass pipe for connecting the inlet side of the evaporator and the accumulator is provided.
A bypass throttle mechanism is provided in the middle of the bypass pipe.
The control device controls to open the bypass throttle mechanism when the refrigerant transport pressure becomes equal to or higher than the critical pressure, and when the refrigerant transport pressure becomes equal to or lower than a predetermined pressure, the bypass throttle mechanism is opened. A refrigeration system characterized by controlling the mechanism to close. The bypass throttle mechanism is composed of an electric valve capable of controlling the opening degree.
The control device controls to open the opening degree of the bypass throttle mechanism when the transport pressure of the refrigerant becomes equal to or higher than the critical pressure, and when the transfer pressure of the refrigerant becomes equal to or lower than a predetermined pressure, the above-mentioned control device is used. The refrigeration system according to claim 1, wherein the opening degree of the bypass throttle mechanism is controlled to be closed. The bypass throttle mechanism is composed of an electromagnetic on-off valve.
The control device opens the bypass throttle mechanism when the refrigerant transport pressure is equal to or higher than the critical pressure, and the bypass throttle mechanism is opened when the refrigerant transport pressure is equal to or lower than a predetermined pressure. The refrigeration system according to claim 1, wherein the refrigeration system is controlled to be closed.

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