JP2019066068A - Refrigeration system - Google Patents

Abstract

To provide a refrigeration system that can properly control conveyance pressure at the time of high-ambient temperature or low-ambient temperature and allows stable operation.SOLUTION: A refrigeration system 1 in which a compressor 10, a gas cooler 25, a throttle mechanism 27, an evaporator 41 and an accumulator 50 are sequentially connected with refrigerant piping includes bypass piping 51 for connecting an entrance side of the evaporator 41 to the accumulator 50. A bypass throttle mechanism 52 is provided in a middle part of the bypass piping 51.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, a compressor subunit performing two-stage compression of the refrigerant sent from the evaporator and a compressor subunit performing one-stage compression of the refrigerant returned from the economizer heat exchanger are installed to increase the efficiency of the refrigeration system A technique that has been made is disclosed (see, for example, Patent Document 1).

JP 2009-539058 gazette

In the above-mentioned prior art, since the compressor subunit which performs two-stage compression of the refrigerant sent from the evaporator is provided, it is possible to properly cope with one evaporator.
However, in the refrigeration system, since the amount of refrigerant enclosed differs depending on the installation store etc., when the transfer pressure exceeds the critical pressure during operation at high ambient temperature or at start-up at high ambient temperature, Control can not immediately return to stable operation.
In addition, when operating at low ambient temperature, the refrigeration system has a low load, so the load is low, and even at the minimum rotation speed of the compressor, the refrigeration capacity is sufficient and the number of start / stop times increases. The frequent occurrence of the start and stop causes extra power for starting, and the internal temperature of the load side temporarily rises. Furthermore, if the low pressure is operated at a low pressure to prevent the start and stop of the compressor, a deviation between the evaporation temperature and the temperature setting in the storage, frost formation and the like are easily generated.
The present invention has been made in view of the above-mentioned point, and it is possible to properly control the transfer pressure at high or low outside air temperature, and to provide a refrigeration system capable of performing stable operation. With the goal.

  In order to achieve the above object, the refrigeration system of the present invention is a refrigeration system in which a compressor, a condenser, a throttle mechanism, an evaporator, and an accumulator are sequentially connected by a refrigerant pipe, the inlet side of the evaporator and the accumulator And a bypass throttling mechanism provided at a middle portion of the bypass piping.

  According to this, by opening and closing the throttling mechanism for bypass, part of the refrigerant on the inlet side of the evaporator can be sent to the accumulator via the bypass piping, so the internal pressure of the accumulator is lower than the critical pressure Therefore, 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 conveyance pressure of the refrigerant can be properly maintained. Become.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a refrigeration cycle diagram showing an embodiment of a refrigeration system of the present invention. FIG. 2 is a block diagram showing a control configuration of the present embodiment. The flowchart which shows the operation | movement at the time of the high external temperature in this embodiment. The flowchart which shows the operation | movement at the time of the low external temperature in this embodiment.

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

A second aspect of the invention is provided with a control device, wherein the control device controls the bypass throttle mechanism to open when the refrigerant conveyance pressure becomes equal to or higher than a critical pressure, and the refrigerant conveyance pressure is a predetermined pressure. When it becomes below, it controls so that the throttling mechanism for bypass is closed.
According to this, according to the conveyance pressure of the refrigerant, the internal pressure of the accumulator can be maintained lower than the critical pressure, the liquid refrigerant can be stored inside the accumulator, and the conveyance pressure of the refrigerant is properly maintained. It becomes possible.

In a third aspect of the invention, the bypass throttling mechanism is configured by a motorized valve capable of controlling the opening degree, and the control device is configured to open the bypass throttling mechanism when the refrigerant transfer pressure becomes equal to or higher than a critical pressure. The opening degree of the bypass throttle mechanism is controlled to be closed when the refrigerant conveyance pressure becomes lower than a predetermined pressure.
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 properly maintained.

In a fourth aspect of the invention, the bypass throttle mechanism is configured by an electromagnetic on-off valve, and the control device controls the bypass throttle mechanism to open when the refrigerant conveyance pressure becomes equal to or higher than a critical pressure. The control device controls the bypass throttle mechanism to be closed when the transport pressure of the refrigerant becomes lower than a predetermined pressure.
According to this, the internal pressure of the accumulator can be controlled in accordance with the transport pressure of the refrigerant, and the transport pressure of the refrigerant can be properly maintained.

According to a fifth aspect of the invention, the control device is controlled to open the bypass throttle mechanism when there is a difference between the low pressure and the low pressure setting value with the minimum number of drive revolutions of the compressor. Do.
According to this, the evaporator side can maintain the driving | operation of the extent which does not carry out a thermo stop, and can reduce the frequency | count of start / stop of a compressor.

In a sixth aspect of the invention, the bypass throttling mechanism is configured by a motor-operated valve capable of controlling the opening degree, and the control device sets the low pressure and the low pressure with a minimum drive rotational speed of the compressor. 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 and the setting value of the low pressure.
According to this, the operation on the evaporator side can be finely controlled to the extent that the thermo stop does not occur, and the number of times of start / stop of the compressor can be reduced.

Hereinafter, embodiments of the present invention will be described 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. In addition, as a refrigeration system to which this invention is applied, it is not limited to this, A various refrigeration system is applicable.

  As shown in FIG. 1, the refrigeration system 1 includes, for example, a refrigerator 2 installed in facilities such as a convenience store and a supermarket, and a showcase 3 as a cooling device for displaying and cooling refrigerated and frozen products. There is. In addition, in this embodiment, although a carbon dioxide refrigerant is used as a refrigerant, it is not limited to this, A various refrigerant can be used.

The refrigerator 2 also includes a compressor 10 that is compressed by the two stages of the low pressure stage compression mechanism 11 and the 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 sucks the refrigerant sent from the evaporator 20 of the showcase 3 and compresses it to an intermediate pressure by the low pressure stage compression mechanism 11 and discharges it from the first discharge port 14 It is done.
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 side of the compressor 10 via the refrigerant pipe 60. It is connected to the suction port 15. An intercooler fan 23 is disposed in the intercooler 22.
Then, the refrigerant discharged from the first discharge port 14 of the compressor 10 flows into the intercooler 22 through the refrigerant pipe 60, and the intercooler 22 exchanges heat with the outside air by operating the intercooler fan 23 for cooling. And is returned to the second suction port 15 of the compressor 10.

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

Further, an intermediate cooler 26 is connected to the gas cooler 25 via a refrigerant pipe 62, and a throttle mechanism 27 for decompressing 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 gas cooler fan 28 and cooling the refrigerant, but since the carbon dioxide refrigerant is not condensed, the critical pressure is exceeded. In this state, the high pressure gas is sent to the throttling 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 addition, in this embodiment, although the example which provided two showcases 3 is shown, it is not limited to this, Installation of arbitrary numbers is possible.
The showcase 3 is provided with a showcase throttling mechanism 40 and an evaporator 20.
Then, the refrigerant sent via the refrigerant pipe 64 by the evaporator 20 is subjected to heat exchange with the air in the storage, and cooling of the interior of the showcase 3 is performed.
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.

In addition, a gas refrigerant return pipe 30 for taking out the gas refrigerant separated by the intermediate cooler 26 is connected to the upper portion of the intermediate cooler 26, and a gas return throttle mechanism is connected to the middle portion of the gas refrigerant return pipe 30. 36 are provided. A liquid refrigerant return pipe 31 for taking out the liquid refrigerant separated by the intercooler 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 respectively merge, 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 such that the refrigerant flows in the opposite flow direction, and in the internal heat exchanger 32, they are taken out from the intercooler 26 The heat exchange between the refrigerant gas or liquid refrigerant and the refrigerant sent from the intercooler 26 is efficiently performed.
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 and expand the refrigerant to an intermediate pressure level. The refrigerant flowing through the refrigerant pipe 63 and the depressurized refrigerant flowing through the merging pipe are subjected to heat exchange to cool the refrigerant flowing through the refrigerant pipe 63. 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 in an appropriate range.

Further, in the present embodiment, a bypass pipe 51 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 configured by 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 small point of enthalpy, but is not limited to this. For example, as long as the conveyance pressure of the refrigerant is an intermediate pressure, such as at the outlet side of the gas cooler, it may be connected to any position. Further, in the present embodiment, the bypass throttle mechanism 52 is configured by the motor-operated valve, but may be configured by a solenoid valve that performs only opening and closing.

  Further, in the vicinity of the first suction port 13 of the compressor 10, 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 respectively provided. An outside air temperature sensor 57 for detecting the outside air temperature is provided outside the refrigerator.

Next, a control configuration of the present 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 according to the present embodiment includes the compressor 10, the intercooler fan 23, the gas cooler fan 28, the throttle mechanism 27, the gas return throttle mechanism 36, the liquid return throttle mechanism 37, and the bypass throttle. A control device 70 is provided to drive and control the mechanism 52 and the throttle mechanism 40 for the showcase.
The control device 70 centrally controls each part of the refrigeration system, and includes a CPU as an operation execution unit, a ROM that stores a basic control program executable by the CPU, predetermined data, and the like, a RAM, and other peripherals. It has a circuit etc.
Further, detection signals from the refrigerant pressure sensor 56, the refrigerant temperature sensor 55, and the outside air temperature sensor 57 are input to the control device 70.

  The control device 70 includes the compressor 10, the intercooler fan 23, the gas cooler fan 28, the throttle mechanism 27, the gas return throttle mechanism 36, the liquid return throttle mechanism 37, the bypass throttle mechanism 52, and the showcase throttle mechanism By performing drive control of each 40, 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 control device 70 receives detection values of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55 and the outside air temperature sensor 57, and the control device 70 detects detection values of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55 and the outside air temperature sensor 57. The opening control of the bypass throttle mechanism 52 is performed based on the above.
Specifically, if the outside air temperature detected by the outside air temperature sensor 57 or the refrigerant transfer pressure detected by the refrigerant pressure sensor 56 is below the critical pressure and above the predetermined pressure, control in the normal operation mode is performed. .
When performing the normal operation mode, the controller 70 closes the bypass throttle mechanism 52, and the compressor 10 according to the outside air temperature detected by the outside air temperature sensor 57 or the conveyance pressure of the refrigerant 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 are respectively performed.

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

Further, when the outside air temperature detected by the outside air temperature sensor 57 or the conveyance pressure of the refrigerant detected by the refrigerant pressure sensor 56 is less than a predetermined pressure, the bypass throttling 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 equal to or higher than a predetermined pressure. Here, the determination as to whether or not the pressure is lower than or equal to the predetermined pressure is made, for example, based on whether or not the pressure is lower than 6.5 MPa. The set value of the predetermined pressure is set to be surely lower than the critical pressure in consideration of the variation of 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 in the high outside air temperature mode is switched to the control in the normal operation mode.

Further, the control device 70 performs the control in the low outside air temperature mode based on the difference between the low pressure of the refrigerant and the set value of the low pressure, which is the minimum number of rotations of the compressor 10.
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 of the refrigerant and the setting value of the low pressure. That is, the control device 70 controls the throttling mechanism 52 for bypass so as to widen as the difference between the low pressure of the refrigerant and the setting value of the low pressure increases, and the difference between the low pressure of the refrigerant and the setting value of the low pressure is Control to close as it gets smaller.

When the outside air temperature is low, the load on the showcase 3 decreases and the rotation speed of the compressor 10 decreases. However, the refrigerant flowing through the bypass pipe 51 is controlled by opening the bypass throttle mechanism 52 in the low outside air temperature mode. Increase the volume, limit the amount of refrigerant sent to showcase 3 and reduce the refrigeration capacity. Thereby, the driving | operation of the extent which the showcase 3 does not carry out a thermo stop can be maintained, and the frequency | count of start / stop of the compressor 10 can be reduced.
Then, when the driving rotational speed of the compressor 10 becomes equal to or more than the minimum rotational speed, the control device 70 performs control to close the bypass throttle mechanism 52 and switches to 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 a specified value, It is preferable to stop the compressor 10.

Next, the operation of the present embodiment will be described.
In this embodiment, by operating the compressor 10, the refrigerant sent from the evaporator through the first suction port 13 of the compressor 10 is sucked, and this refrigerant is compressed to an intermediate pressure by the low pressure stage compression mechanism 11. Then, the ink 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 through the refrigerant pipe 60, and is cooled by heat exchange with the outside air by the intercooler fan 23 in the intercooler 22. It is returned to the second suction port 15.

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

The liquid refrigerant sent from the lower part of the intercooler 26 is sent to the internal heat exchanger 32, and the refrigerant sent from the intercooler 26 in the internal heat exchanger 32 and the throttle mechanism for gas sent from the intercooler 26 Alternatively, the liquid throttling mechanism exchanges heat with the refrigerant depressurized to the intermediate pressure level.
Further, the refrigerant after heat exchange with the refrigerant sent from the intercooler 26 by the internal heat exchanger 32 is sent to the compressor 10 from the second suction port 15 and the temperature of the refrigerant discharged from the compressor 10 Maintain in the appropriate range.

The refrigerant cooled by the internal heat exchanger 32 is sent to the showcase 3, decompressed by the showcase throttling mechanism 40, and sent to the evaporator 20. Thereby, cooling of the showcase 3 is performed.
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 FIG. 3 and FIG.
First, the operation in the case of control in the high outside air temperature mode will be described with reference to the flowchart shown in FIG.
The control device 70 acquires detection values of the refrigerant pressure sensor 56, the refrigerant temperature sensor 55, and the outside air temperature sensor 57, and determines whether the transfer pressure is equal to or higher than a critical pressure (ST1). When it is determined that the outside air temperature detected by the outside air temperature sensor 57 or the transfer 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 determines that the outside air temperature is high. The operation according to the mode is performed (ST2).

When performing the high outside air temperature control mode, 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 judged that the conveyance pressure of the refrigerant is not above the critical pressure (ST1: NO), control is performed 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 controller 70 determines whether the transport pressure of the refrigerant is less than or equal to a predetermined pressure (ST4), and if it is determined that the transport pressure is less than or equal to the predetermined pressure (ST4: YES), the throttle mechanism 52 for bypass is used. Close (ST5).

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

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

When these controls are performed and it is determined that the difference between the low pressure and the set value of the low pressure is lost (ST18), the control device 70 controls the throttle mechanism 52 for bypass to close (ST19).
When it is determined that the driving rotational speed of the compressor 10 is not the minimum (ST11: NO), and when it is determined that there is no difference between the low pressure and the low pressure setting (ST12: NO), the normal operation mode The control according to is performed (ST20), and drive control of each device such as the compressor 10 is performed based on the detection value by each sensor (ST21).

As described above, according to the present embodiment, in the refrigeration system 1 in which the compressor 10, the gas cooler 25 (condenser), the throttling mechanism 27, the evaporator 41, and the accumulator 50 are sequentially connected by refrigerant piping, the evaporator is A bypass pipe 51 connecting the inlet side of the fuel pump 41 and the accumulator 50 is provided, and a bypass throttle mechanism 52 is provided in the middle of the bypass pipe 51.
Thus, 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 through the bypass pipe 51, so that the internal pressure of the accumulator 50 becomes the critical pressure. The lower temperature can be maintained, and the liquid refrigerant can be stored inside the accumulator 50. As a result, it is possible to maintain the transport pressure of the refrigerant properly.

Further, according to the present embodiment, the control device 70 is provided, and the control device 70 performs control to open the bypass throttle mechanism 52 when the transport pressure of the refrigerant reaches the critical pressure or more, and transport of the refrigerant. When the pressure becomes 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 conveyance pressure of the refrigerant, the liquid refrigerant can be stored inside the accumulator 50, and the conveyance pressure of the refrigerant is properly maintained. It becomes possible.

Further, according to the present embodiment, the bypass throttle mechanism 52 is configured by an electric valve capable of controlling the opening degree, and the controller 70 controls the bypass throttle when the refrigerant conveyance pressure 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 throttle mechanism for bypass 52 is controlled to be closed when the transport pressure of the refrigerant becomes lower than a predetermined pressure.
Thus, 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 properly maintained.

Further, according to the present embodiment, the bypass throttle mechanism 52 is configured by the electromagnetic on-off valve, and the control device 70 opens the bypass throttle mechanism 52 when the refrigerant conveyance pressure becomes equal to or higher than the critical pressure. While controlling, when the conveyance pressure of the refrigerant becomes equal to or less than a predetermined pressure, the throttling mechanism 52 for bypass is controlled to be closed.
Thus, the internal pressure of the accumulator 50 can be controlled in accordance with the transport pressure of the refrigerant, and the transport pressure of the refrigerant can be properly maintained.

Further, according to the present embodiment, the control device 70 opens the bypass throttle mechanism 52 when the driving rotational speed of the compressor 10 is minimum and there is a difference between the low pressure and the low pressure setting value. To control.
Thereby, the evaporator side can maintain the driving | operation of the extent which does not carry out a thermo stop, and can reduce the frequency | count of start / stop of the compressor 10. FIG.

Further, according to the present embodiment, the bypass throttle mechanism 52 is configured by the motor-operated valve capable of controlling the opening degree, and the control device 70 has the minimum number of drive rotations of the compressor 10 and low pressure and low pressure. When there is a difference from the set value of pressure, control is performed to open the opening degree of the bypass throttle mechanism 52 according to the difference between the low pressure and the set value of low pressure.
As a result, the operation on the evaporator side can be finely controlled such that the thermo stop does not occur, and the number of times of start / stop of the compressor 10 can be reduced.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention.

  As described above, the refrigeration system according to the present invention can be suitably used as a refrigeration system that can appropriately control the transfer pressure at high or low outside air temperature and can perform stable operation. .

DESCRIPTION OF SYMBOLS 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 Intercooler Fan 25 Gas cooler 26 Intercooler 27 Throttle 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 air temperature sensor 70 control device

Claims (6)

In a refrigeration system in which a compressor, a condenser, a throttle mechanism, an evaporator, and an accumulator are sequentially connected by refrigerant piping,
A bypass pipe connecting an inlet side of the evaporator and the accumulator;
A refrigeration system characterized in that a bypass throttle mechanism is provided in the middle of the bypass pipe. Equipped with a controller
The control device controls the bypass throttle mechanism to open when the refrigerant transfer pressure becomes equal to or higher than a critical pressure, and the bypass throttle when the refrigerant conveyance pressure becomes equal to or lower than a predetermined pressure. The refrigeration system according to claim 1, wherein the mechanism is controlled to close. The bypass throttle mechanism is composed of a motorized valve capable of controlling the opening degree,
The control device controls the opening of the bypass throttle mechanism to open when the refrigerant conveyance pressure becomes equal to or higher than the critical pressure, and when the refrigerant conveyance pressure becomes equal to or lower than a predetermined pressure. The refrigeration system according to claim 2, wherein the opening degree of the bypass throttle mechanism is controlled to be closed. The bypass throttle mechanism is constituted by an electromagnetic on-off valve.
The control device controls the bypass throttle mechanism to be open when the refrigerant transport pressure becomes equal to or higher than a critical pressure, and the bypass throttle mechanism when the refrigerant transport pressure becomes equal to or lower than a predetermined pressure. The refrigeration system according to claim 2, characterized in that the control unit is controlled to be closed.   The control device is characterized in that the bypass throttle mechanism is controlled to open when the driving rotational speed of the compressor is minimum and there is a difference between the low pressure and the low pressure setting value. The refrigeration system according to claim 1. The bypass throttle mechanism is composed of a motorized valve capable of controlling the opening degree,
When the driving rotational speed of the compressor is minimum and there is a difference between the low pressure and the set value of the low pressure, the control device performs the bypass according to the difference between the low pressure and the set value of the low pressure. The refrigeration system according to claim 5, characterized in that control is performed to open the opening degree of the throttle mechanism.

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