JP7399322B2 - Refrigeration equipment outdoor unit and refrigeration equipment equipped with the same - Google Patents

Description

The present disclosure relates to an outdoor unit of a refrigeration system and a refrigeration system including the outdoor unit.

The refrigeration device has a defrost mode for melting frost that adheres to the cooler. As a defrosting method, for example, a reverse hot gas defrosting method is known in which the direction of refrigerant circulation is switched using a four-way valve so that high-temperature gas from a compressor is sent to a cooler that normally functions as an evaporator.

International Publication No. 2020/161803 (Patent Document 1) discloses a refrigeration device that performs defrosting using a reverse hot gas defrosting method in a low-temperature side circuit of a dual circuit. In the refrigeration device disclosed in Patent Document 1, the refrigerant amount adjustment mechanism supplies refrigerant from the liquid receiver to the low-temperature side circuit, thereby adjusting the amount of refrigerant circulating through the low-temperature side circuit to an amount suitable for defrosting. .

International Publication No. 2020/161803

However, the amount of refrigerant suitable for defrosting changes depending on the degree of progress of defrosting. Immediately after the start of defrosting, the amount of frost adhering to the cooler is large, so the amount of heat dissipated by the refrigerant in the cooler is large. As defrosting progresses, the amount of frost adhering to the cooler decreases, the temperature of the cooler increases, and the amount of heat dissipated by the refrigerant in the cooler decreases. Therefore, even if the amount of refrigerant is appropriate at the beginning of the defrosting period, the amount of refrigerant becomes excessive at the end of the defrosting period, and the pressure in the low temperature side circuit increases. When the pressure in the low-temperature side circuit rises to the design pressure, operation will be automatically stopped for protection, and there is a possibility that sufficient defrosting may not be achieved. Therefore, it is desirable to avoid a situation where the pressure increases too much during defrosting operation.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an outdoor unit of a refrigeration system and a refrigeration system that can suppress an increase in refrigerant pressure during defrosting operation.

The present disclosure relates to an outdoor unit of a refrigeration system having a freezing mode and a defrosting mode. The outdoor unit includes a first compressor and a second heat exchanger connected so that the first refrigerant circulates between the indoor unit and the first expansion valve and the first heat exchanger connected in series. The first compressor, the second heat exchanger, the first expansion valve, and the first heat exchanger constitute a first refrigerant circuit that uses the first refrigerant. The outdoor unit includes a second refrigerant circuit. The second refrigerant circuit includes a second compressor, a third heat exchanger, a second expansion valve, and a fourth heat exchanger, the second compressor, the third heat exchanger, the second expansion valve, and the fourth heat exchanger. The second refrigerant is circulated through the containers in order. The fourth heat exchanger exchanges heat between the second refrigerant and the first refrigerant flowing between the second heat exchanger and the first expansion valve. The outdoor unit further includes a four-way valve, a liquid receiver, a bypass flow path, and a control device. The four-way valve switches the circulation direction of the first refrigerant in the first refrigerant circuit to a positive direction in the order of the first compressor, the second heat exchanger, the first expansion valve, and the first heat exchanger in the refrigeration mode; In the defrosting mode, the first compressor, first heat exchanger, first expansion valve, and second heat exchanger are switched in the reverse order. The liquid receiver is installed between the fourth heat exchanger and the first expansion valve in the first refrigerant circuit. The bypass channel allows the first refrigerant to flow from the first expansion valve toward the second heat exchanger, bypassing the receiver in the defrosting mode. In the defrosting mode, the control device controls the second refrigerant circuit to lower the evaporation temperature of the second refrigerant in the fourth heat exchanger in response to the pressure of the first refrigerant circulating in the first refrigerant circuit exceeding a threshold value. control.

According to the present disclosure, in the defrosting mode, when the pressure of the first refrigerant in the bypass passage exceeds a threshold value, the evaporation temperature of the second refrigerant in the fourth heat exchanger is lowered. As a result, the pressure of the first refrigerant in the fourth heat exchanger decreases, and a portion of the refrigerant that has passed through the bypass channel flows into the liquid receiver. As a result, in the defrosting mode, the amount of the first refrigerant circulating in the first refrigerant circuit in the reverse direction is reduced, and an increase in the pressure of the refrigerant during the defrosting operation can be suppressed.

1 is a diagram showing the configuration of a refrigeration device according to Embodiment 1. FIG. FIG. 3 is a diagram showing the flow of refrigerant in the defrosting mode of the refrigeration apparatus according to the first embodiment. FIG. 2 is a diagram showing the configuration of a control device that controls a refrigeration device. 5 is a flowchart for explaining control executed by the control device in the first embodiment. 7 is a flowchart for explaining control executed by a control device in Embodiment 2. FIG.

Embodiments of the present invention will be described in detail below with reference to the drawings. Although a plurality of embodiments will be described below, it has been planned from the beginning of the application to appropriately combine the configurations described in each embodiment. In addition, the same reference numerals are attached to the same or corresponding parts in the figures, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is a diagram showing the configuration of a refrigeration system according to Embodiment 1. Referring to FIG. 1, refrigeration apparatus 100 includes an outdoor unit 101, an indoor unit 102, and pipes 27 and 31 that connect outdoor unit 101 and indoor unit 102.

Indoor unit 102 includes a first expansion valve 3 and a first heat exchanger 4. The first expansion valve 3 and the first heat exchanger 4 are connected in series. The first expansion valve 3 is, for example, a temperature expansion valve that is controlled based on the temperature of the refrigerant outlet of the first heat exchanger 4.

The outdoor unit 101 includes a first compressor 1 and a second heat exchanger 2. The first compressor 1, the second heat exchanger 2, the first expansion valve 3, and the first heat exchanger 4 constitute a first refrigerant circuit 103 on the low temperature side. The first refrigerant filled in the first refrigerant circuit 103 is, for example, CO ₂ .

The outdoor unit 101 further includes a second refrigerant circuit 104 on the high temperature side, a four-way valve 7, a refrigerant amount adjustment mechanism 10, a bypass passage 37, check valves 41 and 42, a temperature sensor 61, and a pressure sensor. 62 and a control device 50.

The second refrigerant circuit 104 includes a second compressor 211 , a third heat exchanger 212 , a second expansion valve 213 , and a fourth heat exchanger 214 . The second refrigerant circuit 104 circulates the second refrigerant in the order of the second compressor 211 , the third heat exchanger 212 , the second expansion valve 213 , and the fourth heat exchanger 214 . The second refrigerant is, for example, HF01234yf, R410A, _CO2 .

The fourth heat exchanger 214 is, for example, a cascade heat exchanger. The fourth heat exchanger 214 exchanges heat between the second refrigerant and the first refrigerant flowing between the second heat exchanger 2 and the first expansion valve 3 .

Refrigeration apparatus 100 has a freezing mode and a defrosting mode as operating modes. In the freezing mode, the refrigerant flows in the direction shown by the arrow in FIG. FIG. 2 is a diagram showing the flow of refrigerant in the defrosting mode of the refrigeration system according to the first embodiment.

The four-way valve 7 switches the circulation direction of the first refrigerant in the first refrigerant circuit 103 between freezing mode and defrosting mode. Note that the four-way valve may be composed of a plurality of valves.

The four-way valve 7 controls the circulation direction of the first refrigerant in the first refrigerant circuit 103 in the refrigeration mode shown in FIG. Switch to the positive direction of device 4. That is, in the refrigeration mode, the four-way valve 7 connects the inlet of the first compressor 1 to the first heat exchanger 4 and connects the outlet of the first compressor 1 to the second heat exchanger 2.

The four-way valve 7 controls the circulation direction of the first refrigerant in the first refrigerant circuit 103 in the defrosting mode shown in FIG. Switch in the opposite direction of the order of exchanger 2. That is, in the defrosting mode, the four-way valve 7 connects the suction port of the first compressor 1 to the second heat exchanger 2, and connects the discharge port of the first compressor 1 to the first heat exchanger 4.

The refrigerant amount adjustment mechanism 10 (see FIG. 1) is configured to adjust the amount of first refrigerant circulated in the defrosting mode.

The refrigerant amount adjustment mechanism 10 includes a liquid receiver 8, a refrigerant discharge channel 35, and a flow rate adjustment valve 45. The liquid receiver 8 is installed between the fourth heat exchanger 214 and the first expansion valve 3 in the first refrigerant circuit 103 . More specifically, the liquid receiver 8 is arranged between the fourth heat exchanger 214 and the first connection point 23. A bypass flow path 37 is connected to the first connection point 23 . The refrigerant discharge passage 35 connects between the outlet of the liquid receiver 8 and the suction port of the first compressor 1 . The flow rate adjustment valve 45 adjusts the flow rate of the first refrigerant flowing through the refrigerant discharge channel 35 .

As shown in FIG. 2, the bypass channel 37 bypasses the liquid receiver 8 and allows the first refrigerant to flow from the first expansion valve 3 toward the second heat exchanger 2 in the defrosting mode. Specifically, the bypass passage 37 connects the first connection point 23 between the outlet of the liquid receiver 8 and the first expansion valve 3 in the first refrigerant circuit 103 and the second heat exchanger in the first refrigerant circuit. 2 and a second connection point 26 between the fourth heat exchanger 214.

A third expansion valve 46 is provided in the bypass passage 37 . Furthermore, a check valve 43 is provided in the bypass passage 37 between the third expansion valve 46 and the second connection point 26 . The forward direction of the check valve 43 is the direction from the first connection point 23 to the second connection point 26 . Thereby, the refrigerant flow direction in the bypass channel 37 is restricted to the direction from the first connection point 23 to the second connection point 26 (that is, the direction from the third expansion valve 46 to the second heat exchanger 2). .

The check valve 41 is installed between the second connection point 26 and the fourth heat exchanger 214 in the first refrigerant circuit 103 . The forward direction of the check valve 41 is the direction from the second connection point 26 to the fourth heat exchanger 214.

The check valve 42 is installed between the outlet of the liquid receiver 8 and the first connection point 23 in the first refrigerant circuit 103 . The forward direction of the check valve 42 is the direction from the liquid receiver 8 toward the first connection point 23 .

When the four-way valve 7 is switched to the state shown in FIG. 4 flows toward heat exchanger 214. That is, the refrigerant circulates in the direction shown by the arrow in FIG.

When the four-way valve 7 is switched to the state shown in FIG. 2, the check valves 42 and 43 prevent the first refrigerant that has passed through the first expansion valve 3 from flowing from the first connection point 23 toward the receiver 8. It flows through the bypass channel 37. That is, the refrigerant circulates in the direction shown by the arrow in FIG.

The temperature sensor 61 and the pressure sensor 62 measure the temperature and pressure of the first refrigerant circulating in the first refrigerant circuit 103, respectively. Specifically, the temperature sensor 61 and the pressure sensor 62 respectively measure the temperature and pressure of the first refrigerant in the pipe that becomes a high pressure section in the defrosting mode. The piping that becomes a high pressure section in the defrosting mode is the piping between the first expansion valve 3 and the second heat exchanger 2. In this embodiment, temperature sensor 61 and pressure sensor 62 measure the temperature and pressure of the first refrigerant near the first connection point 23, respectively. The temperature sensor 61 and the pressure sensor 62 output measurement results to the control device 50.

FIG. 3 is a diagram showing the configuration of a control device 50 that controls the refrigeration system. As shown in FIG. 3, the control device 50 includes a processor 51, a memory 52, a communication interface (not shown), and the like. The processor 51 controls the operating frequency of the first compressor 1, the connection state of the four-way valve 7, the second refrigerant circuit 104, etc. according to data stored in the memory 52 and information obtained via the communication interface.

The memory 52 includes, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory. Note that the flash memory stores an operating system, application programs, and various data. Note that the control device 50 shown in FIG. 1 is realized by the processor 51 executing an operating system and application programs stored in the memory 52. When the application program is executed, various data stored in the memory 52 are referenced.

FIG. 4 is a flowchart for explaining control executed by the control device in the first embodiment. The processing in this flowchart is repeatedly executed during operation of the refrigeration apparatus 100 every time a certain period of time passes or every time a predetermined condition is satisfied. For example, when defrosting is performed at regular intervals, the control device 50 executes the process shown in the flowchart of FIG. 4 when a certain period of time has elapsed since the previous defrosting of the first heat exchanger 4. Note that the determination to shift to the defrosting mode may be made based on the detection of the refrigerant temperature or the state of frost adhesion to the first heat exchanger 4.

As shown in FIG. 4, when the conditions for switching to the defrosting mode are satisfied, the control device 50 switches the four-way valve 7 from the state shown in FIG. 1 to the state shown in FIG. 2 in step S1.

Then, in step S2, the control device 50 monitors the output of the pressure sensor 62 and determines whether the pressure P of the first refrigerant circulating in the first refrigerant circuit 103 is lower than the threshold Th1. The threshold Th1 is predetermined in consideration of the performance of the piping that constitutes the first refrigerant circuit 103, and is a design pressure or a value lower than the design pressure by a certain value.

If the pressure P is lower than the threshold Th1 (YES in S2), the control device 50 controls the operation of the second refrigerant circuit 104 in the normal operation mode (Step S3). In the normal operation mode, the first refrigerant circuit 103 is operated according to the target evaporation temperature set so that the pressure in the high pressure portion does not exceed the design pressure. Specifically, the control device 50 controls the operating frequency of the second compressor 211 or the opening degree of the second expansion valve 213 so that the evaporation temperature of the second refrigerant in the fourth heat exchanger 214 becomes the target evaporation temperature. Control.

If the pressure P is equal to or greater than the threshold Th1 (NO in S2), the control device 50 controls the second refrigerant circuit 104 in step S4 to lower the evaporation temperature of the second refrigerant in the fourth heat exchanger 214. Specifically, the control device 50 controls the operation of the second refrigerant circuit 104 in the increased speed operation mode. In the increased speed operation mode, the target evaporation temperature is set lower than in the normal operation mode. The control device 50 controls the operating frequency of the second compressor 211 or the opening degree of the second expansion valve 213 so that the evaporation temperature of the second refrigerant in the fourth heat exchanger 214 becomes the target evaporation temperature. That is, since the target evaporation temperature is set low, the control device 50 performs at least one of control to increase the operating frequency of the second compressor 211 and control to increase the opening degree of the second expansion valve 213. As a result, the evaporation temperature of the second refrigerant in the fourth heat exchanger 214 decreases.

As the evaporation temperature of the second refrigerant in the fourth heat exchanger 214 decreases, the pressure of the first refrigerant in the fourth heat exchanger 214 decreases in the first refrigerant circuit 103. As a result, the pressure P3 at the point 28 (see FIG. 2) between the check valve 41 and the fourth heat exchanger 214 in the first refrigerant circuit 103 becomes lower than the pressure P4 at the second connection point 26. As a result, a portion of the first refrigerant that has passed through the bypass channel 37 and reached the second connection point 26 flows into the liquid receiver 8 via the check valve 41 and the fourth heat exchanger 214. As the amount of refrigerant accumulated in the liquid receiver 8 increases, the amount of first refrigerant circulated decreases, and the pressure increase of the first refrigerant circulating through the first refrigerant circuit 103 is suppressed.

The processes of steps S2 to S4 are repeated until it is determined in step S5 that defrosting is complete. As a result, in the defrosting mode, a pressure increase caused by an excessive amount of first refrigerant being circulated is suppressed.

If it is determined that defrosting has been completed (YES in S5), in step S6, the control device 50 returns the four-way valve 7 to the freezing mode state of FIG. 1.

Embodiment 2.
FIG. 5 is a flowchart for explaining the control executed by the control device in the second embodiment. The flowchart shown in FIG. 5 differs from the flowchart shown in FIG. 4 in that it further includes steps S10 to S14.

When the four-way valve 7 is switched from the state shown in FIG. 1 to the state shown in FIG. 2 in step S1, in step S10, the control device 50 determines whether or not it has been determined NO in step S2 at least once since the transition to the defrosting mode. to judge.

If NO is not determined in step S2 even once (NO in step S10), the control device 50 monitors the outputs of the temperature sensor 61 and the pressure sensor 62, and detects an excess of the first refrigerant near the first connection point 23. It is determined whether the cooling degree SC is lower than a threshold Th2 (step S11). The value of the degree of supercooling when the amount of circulation of the first refrigerant is insufficient is set as the threshold Th2.

If the degree of supercooling SC is lower than the threshold Th2 (YES in step S11), the control device 50 opens the flow rate adjustment valve 45. As a result, the first refrigerant is supplied from the liquid receiver 8 to the first compressor 1 . As a result, the amount of circulation of the first refrigerant increases.

If the degree of subcooling SC is equal to or greater than the threshold Th2 (NO in step S11), the amount of circulation of the first refrigerant is sufficient, so the control device 50 closes the flow rate adjustment valve 45 (step S12).

Step S2 is executed after steps S11 and S12. Furthermore, if the determination in step S2 is NO at least once (YES in step S10), step S2 is also executed.

If YES in step S2, the control device 50 closes the flow rate adjustment valve 45 (step S14). After step S14, step S4 is executed. Steps S10 to S14 and S2 to S4 are repeatedly executed until defrosting is completed.

According to the second embodiment, when the circulating amount of the first refrigerant necessary for defrosting is insufficient, the flow rate adjustment valve 45 is opened to supply the first refrigerant from the liquid receiver 8 to the first compressor 1. is supplied. Therefore, the circulation amount of the first refrigerant is adjusted to be suitable for defrosting. In particular, at the beginning of the defrosting period, the amount of frost adhering to the first heat exchanger 4 is large, so the amount of heat released by the first refrigerant in the first heat exchanger 4 is large. Therefore, the amount of refrigerant required for defrosting increases. When the circulating amount of the first refrigerant is insufficient, the flow rate adjustment valve 45 is opened to increase the circulating amount of the first refrigerant. As a result, defrosting is performed efficiently.

On the other hand, at the end of the defrosting period, the amount of frost adhering to the first heat exchanger 4 decreases, the temperature of the first heat exchanger 4 increases, and the amount of the first refrigerant in the first heat exchanger 4 increases. The amount of heat dissipated is reduced. Therefore, the amount of refrigerant required for defrosting is reduced. At this time, by closing the flow rate adjustment valve 45, it is possible to prevent the first refrigerant from being supplied from the liquid receiver 8. Furthermore, by lowering the evaporation temperature of the second refrigerant in the fourth heat exchanger 214, the pressure P3 at point 28 in the first refrigerant circuit 103 becomes lower than the pressure P4 at the second connection point 26, and the second refrigerant passes through the bypass flow path 37. A part of the first refrigerant flows into the receiver 8 . As the amount of refrigerant accumulated in the liquid receiver 8 increases, the amount of first refrigerant circulated decreases, and pressure rise is suppressed.

In this specification, "more than" may be replaced with "more than" and "less than" may be replaced with "less than". Conversely, "more than" may be replaced with "more than" and "less than" may be replaced with "less than or equal to".

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments described above, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1 First compressor, 2 Second heat exchanger, 3 First expansion valve, 4 First heat exchanger, 7 Four-way valve, 8 Liquid receiver, 10 Refrigerant amount adjustment mechanism, 23 First connection point, 26 Second Connection point, 27, 31 Piping, 28 Point, 35 Refrigerant discharge channel, 37 Bypass channel, 41 to 43 Check valve, 45 Flow rate adjustment valve, 46 Third expansion valve, 50 Control device, 51 Processor, 52 Memory, 61 temperature sensor, 62 pressure sensor, 100 refrigeration device, 101 outdoor unit, 102 indoor unit, 103 first refrigerant circuit, 104 second refrigerant circuit, 211 second compressor, 212 third heat exchanger, 213 second expansion valve , 214 fourth heat exchanger.

Claims (6)

An outdoor unit of a refrigeration device having a freezing mode and a defrosting mode,
The first compressor and the second heat exchanger are connected to an indoor unit in which the first expansion valve and the first heat exchanger are connected in series so that the first refrigerant circulates between the first compressor and the second heat exchanger. the second heat exchanger, the first expansion valve, and the first heat exchanger constitute a first refrigerant circuit using the first refrigerant,
The outdoor unit includes a second compressor, a third heat exchanger, a second expansion valve, and a fourth heat exchanger, the second compressor, the third heat exchanger, the second expansion valve, and the fourth heat exchanger. a second refrigerant circuit that circulates a second refrigerant in order of four heat exchangers, and the fourth heat exchanger allows the second refrigerant to flow between the second heat exchanger and the first expansion valve. performing heat exchange with the first refrigerant,
The outdoor unit further includes:
In the refrigeration mode, the circulation direction of the first refrigerant in the first refrigerant circuit is a positive direction in the order of the first compressor, the second heat exchanger, the first expansion valve, and the first heat exchanger. a four-way valve that switches to reverse the order of the first compressor, the first heat exchanger, the first expansion valve, and the second heat exchanger in the defrosting mode;
In the first refrigerant circuit, a liquid receiver installed between the fourth heat exchanger and the first expansion valve;
In the defrosting mode, a bypass flow path that bypasses the liquid receiver and causes the first refrigerant to flow from the first expansion valve toward the second heat exchanger;
and a control device;
The control device lowers the evaporation temperature of the second refrigerant in the fourth heat exchanger in response to the pressure of the first refrigerant circulating in the first refrigerant circuit exceeding a threshold value in the defrosting mode. An outdoor unit that controls the second refrigerant circuit so as to control the second refrigerant circuit. The control device operates the second refrigerant circuit in an increased speed operation mode in response to the pressure of the first refrigerant circulating in the first refrigerant circuit exceeding the threshold value in the defrosting mode. The outdoor unit according to item 1. a refrigerant discharge channel connecting an outlet of the liquid receiver and an inlet of the first compressor;
a flow rate adjustment valve that adjusts the flow rate of the first refrigerant flowing through the refrigerant discharge flow path,
The outdoor device according to claim 1 or 2, wherein the control device closes the flow rate regulating valve in response to the pressure of the first refrigerant circulating in the first refrigerant circuit exceeding the threshold value in the defrosting mode. Machine. The bypass flow path connects a first connection point between the outlet of the liquid receiver and the first expansion valve in the first refrigerant circuit, and a connection point between the second heat exchanger and the fourth connection point in the first refrigerant circuit. a second connection point between the heat exchanger and the heat exchanger;
The outdoor unit is
In the first refrigerant circuit, a first non-return check is installed between the second connection point and the fourth heat exchanger, and the forward direction is a direction from the second connection point to the fourth heat exchanger. The outdoor unit according to any one of claims 1 to 3, further comprising a valve. a second check valve that is installed between the outlet of the liquid receiver and the first connection point, and whose forward direction is the direction from the liquid receiver to the first connection point;
The outdoor unit according to claim 4, further comprising: a third check valve that is installed in the bypass flow path and whose forward direction is a direction from the first connection point to the second connection point. The outdoor unit according to any one of claims 1 to 5,
A refrigeration device comprising the above-mentioned indoor unit.

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