CN117730234A - Refrigeration cycle device and control method for refrigeration cycle device - Google Patents
Refrigeration cycle device and control method for refrigeration cycle device Download PDFInfo
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- CN117730234A CN117730234A CN202180101054.5A CN202180101054A CN117730234A CN 117730234 A CN117730234 A CN 117730234A CN 202180101054 A CN202180101054 A CN 202180101054A CN 117730234 A CN117730234 A CN 117730234A
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- side refrigerant
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- 238000005057 refrigeration Methods 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims description 6
- 239000003507 refrigerant Substances 0.000 claims abstract description 235
- 239000000203 mixture Substances 0.000 claims abstract description 23
- 230000000717 retained effect Effects 0.000 claims description 3
- 238000009835 boiling Methods 0.000 description 10
- 238000001816 cooling Methods 0.000 description 9
- 239000007788 liquid Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 230000006837 decompression Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000012267 brine Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 2
- FXRLMCRCYDHQFW-UHFFFAOYSA-N 2,3,3,3-tetrafluoropropene Chemical compound FC(=C)C(F)(F)F FXRLMCRCYDHQFW-UHFFFAOYSA-N 0.000 description 1
- 238000004378 air conditioning Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
- F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
- Devices That Are Associated With Refrigeration Equipment (AREA)
Abstract
A refrigeration cycle device is provided with: a high-stage circuit having a 1 st compressor, a condenser, a 1 st pressure reducing device, and a cascade heat exchanger, wherein a high-stage side refrigerant circulates in the high-stage circuit; and a low-stage circuit having a 2 nd compressor, a cascade heat exchanger, a 2 nd pressure reducing device, and an evaporator, wherein the low-stage side refrigerant circulates in the low-stage circuit, the cascade heat exchanger exchanges heat between the high-stage side refrigerant and the low-stage side refrigerant, the low-stage side refrigerant is a non-azeotropic refrigerant mixture, and the pressure of the low-stage side refrigerant that remains in the low-stage circuit after the 2 nd compressor is stopped is maintained at a pressure that is lower than a pressure at which the low-stage side refrigerant can maintain incombustibility.
Description
Technical Field
The present disclosure relates to a refrigeration cycle apparatus including a binary refrigeration cycle and a control method of the refrigeration cycle apparatus.
Background
Conventionally, as a refrigeration cycle apparatus including a two-stage refrigeration cycle, a refrigeration apparatus including a low-stage circuit in which a low-stage side refrigerant circulates, a high-stage circuit in which a high-stage side refrigerant circulates, and a cascade condenser in which a low-stage side refrigerant and a high-stage side refrigerant exchange heat is known (for example, patent literature 1).
Prior art literature
Patent literature
Patent document 1: international publication No. 2014/030236
Disclosure of Invention
Problems to be solved by the invention
In the refrigeration cycle apparatus of patent document 1, a zeotropic refrigerant mixture is used as a low-stage side refrigerant circulating in a low-stage circuit. In this case, when the low-stage circuit is stopped, the refrigerant having a low boiling point among the refrigerants included in the zeotropic refrigerant mixture may be gasified and retained in the entire low-stage circuit, and the composition of the liquid refrigerant may vary. In particular, in the case where the low-stage circuit includes a welded portion of the pipe, when the gasified refrigerant leaks from the welded portion, the composition of the liquid refrigerant significantly fluctuates. In addition, when the refrigerant having a high boiling point among the refrigerants included in the zeotropic refrigerant mixture has flammability, the combustibility of the liquid refrigerant increases due to the composition fluctuation of the refrigerant, and the risk of flammability at the time of refrigerant leakage increases.
The present disclosure has been made to solve the above-described problems, and an object of the present disclosure is to provide a refrigeration cycle apparatus and a control method of the refrigeration cycle apparatus capable of suppressing a composition fluctuation of a refrigerant after a low-stage circuit is stopped.
Means for solving the problems
The refrigeration cycle device of the present disclosure includes: a high-stage circuit having a 1 st compressor, a condenser, a 1 st pressure reducing device, and a cascade heat exchanger, wherein a high-stage side refrigerant circulates in the high-stage circuit; and a low-stage circuit having a 2 nd compressor, a cascade heat exchanger, a 2 nd pressure reducing device, and an evaporator, wherein the low-stage side refrigerant circulates in the low-stage circuit, the cascade heat exchanger exchanges heat between the high-stage side refrigerant and the low-stage side refrigerant, the low-stage side refrigerant is a non-azeotropic refrigerant mixture, and the pressure of the low-stage side refrigerant that remains in the low-stage circuit after the 2 nd compressor is stopped is maintained at a pressure that is lower than a pressure at which the low-stage side refrigerant can maintain incombustibility.
In the method for controlling a refrigeration cycle device of the present disclosure, the refrigeration cycle device includes: a high-stage circuit having a 1 st compressor, a condenser, a 1 st pressure reducing device, and a cascade heat exchanger, wherein a high-stage side refrigerant circulates in the high-stage circuit; and a low-stage circuit having a 2 nd compressor, a cascade heat exchanger, a 2 nd pressure reducing device, and an evaporator, wherein the cascade heat exchanger causes the high-stage side refrigerant to exchange heat with the low-stage side refrigerant, and the low-stage side refrigerant is a non-azeotropic refrigerant mixture, and wherein the pressure of the low-stage side refrigerant that remains in the low-stage circuit after the 2 nd compressor is stopped is maintained at a pressure that is lower than a pressure at which the low-stage side refrigerant can maintain incombustibility.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present disclosure, after the 2 nd compressor is stopped, the pressure of the low-stage side refrigerant that remains in the low-stage circuit is maintained at a pressure that can maintain incombustibility of the low-stage side refrigerant, whereby the composition fluctuation of the refrigerant after the low-stage circuit is stopped can be suppressed.
Drawings
Fig. 1 is a schematic configuration diagram of a refrigeration cycle apparatus according to embodiment 1.
Fig. 2 is a graph showing a relationship between combustibility of the low-stage side refrigerant and the pressure P.
Fig. 3 is a flowchart showing the operation of the refrigeration cycle apparatus according to embodiment 1.
Fig. 4 is a flowchart showing the operation of the refrigeration cycle apparatus according to embodiment 2.
Fig. 5 is a schematic configuration diagram of a refrigeration cycle apparatus according to modification 1.
Fig. 6 is a schematic configuration diagram of the refrigeration cycle apparatus according to modification 2.
Detailed Description
Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same reference numerals are used to designate the same or corresponding parts. In the following drawings, the relationship between the sizes of the respective components may be different from the actual ones. In the following description, the level of temperature, pressure, and the like is not particularly determined based on the relationship with the absolute value, but is relatively determined in the state, operation, and the like of the system, the device, and the like.
Embodiment 1.
A refrigeration cycle apparatus 100 according to embodiment 1 will be described. The refrigeration cycle apparatus 100 includes two-stage refrigeration cycles in which refrigerant is circulated independently, and is used for cooling, refrigerating, hot water supply, air conditioning, and the like. In this embodiment, a case where the refrigeration cycle apparatus 100 is used as a refrigeration apparatus for cooling a refrigeration chamber or the like will be described as an example.
Fig. 1 is a schematic configuration diagram of a refrigeration cycle apparatus 100 according to embodiment 1. As shown in fig. 1, the refrigeration cycle apparatus 100 of the present embodiment includes a high-stage circuit 1, a low-stage circuit 2, and a control device 3. The high-stage circuit 1 is a high-temperature circuit for a high-stage side refrigerant cycle, and the low-stage circuit 2 is a low-temperature circuit for a low-stage side refrigerant cycle having a lower boiling point than the high-stage side refrigerant. The high-stage circuit 1 and the low-stage circuit 2 are provided with a cascade heat exchanger 14 in common, and heat exchange between the high-stage side refrigerant circulating in the high-stage circuit 1 and the low-stage side refrigerant circulating in the low-stage circuit 2 is performed by the cascade heat exchanger 14.
The high-order circuit 1 includes a 1 st compressor 11, a condenser 12, a 1 st pressure reducing device 13, and a cascade heat exchanger 14. The 1 st compressor 11, the condenser 12, the 1 st pressure reducing device 13, and the cascade heat exchanger 14 are connected in this order by piping. The high-stage side refrigerant circulating in the high-stage circuit 1 is, for example, an HFC-based refrigerant such as R134a, R32, or R410A, or an HFO-based refrigerant such as HFO-1234yf, or a mixed refrigerant.
The 1 st compressor 11 is, for example, a variable-frequency compressor capable of controlling the capacity. The 1 st compressor 11 sucks the high-stage-side refrigerant, compresses the high-stage-side refrigerant to a high-temperature and high-pressure state, and discharges the high-stage-side refrigerant, thereby circulating the high-stage-side refrigerant in the high-stage circuit 1.
The condenser 12 is, for example, a fin-tube heat exchanger. The condenser 12 exchanges heat between air and the high-stage side refrigerant, and condenses and liquefies the high-stage side refrigerant. The refrigeration cycle apparatus 100 includes a 1 st fan 15 for supplying air to the condenser 12. The 1 st fan 15 is, for example, a propeller fan, a cross flow fan, or the like capable of adjusting the air volume. The condenser 12 may be a plate heat exchanger or the like that exchanges heat between water or brine and the high-stage side refrigerant. In this case, the 1 st fan 15 may be omitted.
The 1 st pressure reducing device 13 is, for example, an electronic expansion valve capable of controlling the opening degree. The 1 st pressure reducing device 13 is connected to the condenser 12, and reduces the pressure of the high-stage side refrigerant flowing out of the condenser 12 to expand the high-stage side refrigerant. The 1 st pressure reducing device 13 may be a capillary tube or a temperature-sensitive expansion valve.
The cascade heat exchanger 14 is, for example, a plate heat exchanger. The cascade heat exchanger 14 includes a high-stage-side flow path 141 connected to the high-stage circuit 1 and a low-stage-side flow path 142 connected to the low-stage circuit 2, and exchanges heat between the high-stage-side refrigerant flowing through the high-stage-side flow path 141 and the low-stage-side refrigerant flowing through the low-stage-side flow path 142. The high-stage side flow path 141 of the cascade heat exchanger 14 functions as an evaporator, and evaporates and gasifies the high-stage side refrigerant. The low-stage-side flow path 142 of the cascade heat exchanger 14 functions as a condenser, and condenses and liquefies the low-stage-side refrigerant.
The low-stage circuit 2 includes a 2 nd compressor 21, a cascade heat exchanger 14, a 2 nd pressure reducing device 23, and an evaporator 24. The 2 nd compressor 21, the cascade heat exchanger 14, the 2 nd pressure reducing device 23, and the evaporator 24 are connected in this order by piping. The low-stage side refrigerant circulating in the low-stage circuit 2 is a non-azeotropic refrigerant mixture having a lower boiling point than the high-stage side refrigerant. By using a non-azeotropic refrigerant mixture, a lower evaporation temperature can be obtained that cannot be obtained with a single refrigerant. In the present embodiment, a low-side refrigerant containing CO is used 2 And R290 (propane). CO 2 Is a low boiling point refrigerant, R290 is a boiling point ratio CO 2 High boiling point refrigerants. By using CO 2 And natural refrigerants such as R290, the environmental load can be reduced. In addition, by mixing CO in the low-side refrigerant 2 Cooling capacity is improved, COP is improved and CO is increased by mixing R290 2 The three-phase point of (c) is lowered and can be used at a low temperature.
The 2 nd compressor 21 is, for example, a variable frequency compressor capable of controlling capacity. The 2 nd compressor 21 sucks the low-stage-side refrigerant, compresses the refrigerant to a high-temperature and high-pressure state, and discharges the refrigerant, thereby circulating the low-stage-side refrigerant in the low-stage circuit 2.
The 2 nd pressure reducing device 23 is, for example, an electronic expansion valve capable of controlling the opening degree. The 2 nd pressure reducing device 23 is connected to the low-stage side flow path 142 of the cascade heat exchanger 14, and reduces the pressure of the low-stage side refrigerant flowing out of the low-stage side flow path 142 to expand the refrigerant. The 2 nd pressure reducing device 23 may be a capillary tube or a temperature-sensitive expansion valve.
The evaporator 24 is, for example, a fin-tube heat exchanger. The evaporator 24 exchanges heat between the air and the low-stage side refrigerant, and evaporates and gasifies the low-stage side refrigerant. The refrigeration cycle apparatus 100 includes a 2 nd fan 25 for supplying air to the evaporator 24. The 2 nd fan 25 is, for example, a propeller fan or a cross flow fan capable of adjusting the air volume. The evaporator 24 may be, for example, a plate heat exchanger or the like that exchanges heat between water or brine and the low-stage side refrigerant. In this case, the 2 nd fan 25 may be omitted.
The refrigeration cycle device 100 further includes a pressure sensor 26, and the pressure sensor 26 detects the pressure P of the low-stage side refrigerant that stagnates in the low-stage circuit 2 when the low-stage circuit 2 is stopped. Since the pressure P of the low-stage side refrigerant at the time of stopping the low-stage circuit 2 becomes substantially uniform in the low-stage circuit 2, the pressure sensor 26 is provided at an arbitrary location in the low-stage circuit 2. In the example of fig. 1, the pressure sensor 26 is provided in a pipe connecting the low-stage side flow path 142 of the cascade heat exchanger 14 and the 2 nd pressure reducing device 23. The pressure P of the low-stage side refrigerant detected by the pressure sensor 26 is sent to the control device 3.
Instead of the pressure sensor 26, a sensor may be provided that detects another physical quantity (for example, condensation temperature) that can be converted into the pressure P of the low-stage side refrigerant, and the pressure P may be converted into the pressure P by the control device 3. The refrigeration cycle apparatus 100 may further include various sensors, not shown, such as an outside air temperature sensor that detects the outside air temperature, an indoor temperature sensor that detects the temperature in the cooling chamber, and a sensor that detects the temperature or pressure of the refrigerant in any place in the high-stage circuit 1 and the low-stage circuit 2.
The control device 3 controls the operation of the entire refrigeration cycle apparatus 100. The control device 3 is configured by a processing device including a memory storing data and programs necessary for control and a CPU executing the programs, or by dedicated hardware such as an ASIC or FPGA, or both. The control device 3 of the present embodiment controls the high-stage circuit 1 based on the pressure P of the low-stage side refrigerant detected by the pressure sensor 26 when the low-stage circuit 2 is stopped. The control device 3 controls the respective devices of the high-stage circuit 1 and the low-stage circuit 2, and the 1 st fan 15 and the 2 nd fan 25 based on the information received from the various sensors and the operation contents instructed from the user.
The operation of the refrigeration cycle apparatus 100 according to the present embodiment will be described based on the flow of the refrigerant circulating through each refrigerant circuit. First, the operation of the high-order circuit 1 will be described. When the start of the operation of the refrigeration cycle apparatus 100 is instructed, the 1 st compressor 11 and the 2 nd compressor 21 are driven. Then, the 1 st compressor 11 of the high-stage circuit 1 sucks in the high-stage side refrigerant, compresses the refrigerant to a high-temperature and high-pressure state, and discharges the refrigerant. The high-stage side refrigerant discharged from the 1 st compressor 11 flows into the condenser 12. The condenser 12 exchanges heat between the air supplied from the 1 st fan 15 and the high-stage side refrigerant, and condenses and liquefies the high-stage side refrigerant.
The high-stage side refrigerant condensed and liquefied by the condenser 12 passes through the 1 st pressure reducing device 13. The 1 st pressure reducing device 13 reduces the pressure of the condensed and liquefied high-stage side refrigerant. The high-stage side refrigerant decompressed by the 1 st decompressing device 13 flows into the high-stage side flow path 141 of the cascade heat exchanger 14. The high-stage-side refrigerant flowing into the high-stage-side flow path 141 exchanges heat with the low-stage-side refrigerant flowing through the low-stage-side flow path 142 of the cascade heat exchanger 14, and is vaporized. The high-stage side refrigerant evaporated and gasified by the cascade heat exchanger 14 is again sucked into the 1 st compressor 11.
Next, the operation of the low-stage circuit 2 will be described. The 2 nd compressor 21 of the low-stage circuit 2 sucks in the low-stage side refrigerant, compresses the refrigerant to a high-temperature and high-pressure state, and discharges the refrigerant. The low-stage side refrigerant discharged from the 2 nd compressor 21 flows into the low-stage side flow path 142 of the cascade heat exchanger 14. The low-stage-side refrigerant flowing into the low-stage-side flow path 142 exchanges heat with the high-stage-side refrigerant flowing through the high-stage-side flow path 141 of the cascade heat exchanger 14, and is condensed and liquefied.
The low-stage side refrigerant condensed and liquefied by the cascade heat exchanger 14 passes through the 2 nd pressure reducing device 23. The 2 nd pressure reducing device 23 reduces the pressure of the low-stage side refrigerant. The low-stage-side refrigerant decompressed by the 2 nd decompression device 23 flows into the evaporator 24. The evaporator 24 exchanges heat between the air supplied from the 2 nd fan 25 and the low-stage side refrigerant, and evaporates and gasifies the low-stage side refrigerant. At this time, the low-stage side refrigerant absorbs heat from the air to cool the refrigerating chamber. The low-stage side refrigerant evaporated and gasified by the evaporator 24 is again sucked into the 2 nd compressor 21.
When the stop of the refrigeration cycle apparatus 100 is instructed, the 1 st compressor 11 and the 2 nd compressor 21 are stopped, and the circulation of the refrigerant in the high-stage circuit 1 and the low-stage circuit 2 is stopped. At this time, when the refrigerant having a low boiling point among the low-stage side refrigerants that have remained in the entire low-stage circuit 2 is gasified, the composition of the liquid refrigerant in the low-stage circuit 2 changes. For example, as in the present embodiment, CO is used 2 When a refrigerant having a non-azeotropic mixture with R290 is used as the low-side refrigerant, CO having a boiling point lower than R290 2 By this vaporization, the ratio of R290 having combustibility in the liquid refrigerant increases.
The evaporator 24 of the low-stage circuit 2 is disposed in a room such as a refrigerating room, and is connected to the 2 nd compressor 21 through an extension pipe. Therefore, a welded portion connected to the extension pipe is provided on the suction side of the 2 nd compressor 21. Further, if CO gas leaks from the welded portion when the low-stage circuit 2 is stopped 2 The ratio of R290 having combustibility in the liquid refrigerant in the low-stage circuit 2 further increases. As a result, the low in the low-stage circuit 2The flammability of the meta-side refrigerant increases and the risk of flammability at refrigerant leakage increases.
Therefore, the control device 3 of the present embodiment continues the operation of the high-stage circuit 1 even after the low-stage circuit 2 is stopped, and controls the capacity of the high-stage circuit 1 so that the pressure P of the low-stage side refrigerant becomes equal to or lower than a pressure value at which the low-stage side refrigerant maintains incombustibility. Fig. 2 is a graph showing the relationship between the combustibility of the low-stage side refrigerant and the pressure P. Fig. 2 is a graph of the case where the low-stage side refrigerant is a zeotropic refrigerant mixture and the refrigerant having a relatively high boiling point has flammability, as in the present embodiment. As shown in fig. 2, the higher the pressure P of the low-stage side refrigerant, the higher the combustibility. Therefore, in order to keep the low-stage side refrigerant incombustible, it is necessary to set the pressure P of the low-stage side refrigerant to the threshold value P T The following is given. Threshold P T Is uniquely determined by the physical properties of the refrigerant constituting the low-stage side refrigerant. In the present embodiment, the threshold P is set in advance according to the low-stage side refrigerant T And stored in the control device 3. The control device 3 controls the capacity of the high-stage circuit 1 so that the pressure P of the low-stage side refrigerant detected by the pressure sensor 26 becomes a threshold value P T The following is given.
Fig. 3 is a flowchart showing the operation of the refrigeration cycle apparatus 100 according to embodiment 1. When the operation of the refrigeration cycle apparatus 100 is instructed by an instruction or the like from a user, the control device 3 drives the 1 st compressor 11 and the 2 nd compressor 21 (S1). Thereby, the high-stage side refrigerant circulates in the high-stage circuit 1, and the low-stage side refrigerant circulates in the low-stage circuit 2, thereby cooling the refrigerating chamber.
Then, the control device 3 determines whether to stop the operation of the refrigeration cycle apparatus 100 according to an instruction from the user or the like (S2). If the operation is not to be stopped (S2: NO), the operation of the high-stage circuit 1 and the low-stage circuit 2 is continued until a stop instruction is given.
On the other hand, when the operation is stopped (yes in S2), the control device 3 stops the 2 nd compressor 21 (S3). Thereby, the circulation of the low-stage side refrigerant in the low-stage circuit 2 is stopped. At this time, the operation of the 1 st compressor 11 is continued.
Then, the pressure P of the low-stage side refrigerant is detected by the pressure sensor 26 (S4). The control device 3 determines whether or not the pressure P of the low-stage side refrigerant detected by the pressure sensor 26 is a threshold value P T The following (S5). The pressure P of the refrigerant at the low-stage side is a threshold value P T In the following case (S5: yes), the routine proceeds to step S7 while maintaining the capability of the high-order circuit 1. On the other hand, the pressure P of the low-stage side refrigerant is higher than the threshold value P T If it is large (S5: NO), the control device 3 increases the capacity of the high-order circuit 1 (S6). Here, the control device 3 may increase the operation frequency of the 1 st compressor 11 by a predetermined fixed value, or may increase the pressure P and the threshold P with respect to the low-stage side refrigerant T The difference corresponds to a value.
By increasing the capacity of the high-stage circuit 1, the temperature of the high-stage side refrigerant flowing through the high-stage side flow path 141 of the cascade heat exchanger 14 decreases. Thereby, the temperature of the low-stage side refrigerant that exchanges heat with the high-stage side refrigerant in the cascade heat exchanger 14 decreases, and the pressure P of the low-stage side refrigerant decreases. By the pressure P of the low-stage side refrigerant being reduced, the gas density in the low-stage circuit 2 is reduced, and the mass of the gas refrigerant in the low-stage circuit 2 is reduced. That is, the pressure P of the low-stage-side refrigerant decreases, so that the low-boiling-point refrigerant (CO) that has remained in the entire low-stage circuit 2 after the low-stage circuit 2 has stopped 2 ) The amount of gas in (2) is reduced, and the variation in the composition of the liquid refrigerant in the low-stage circuit 2 can be suppressed to a minimum.
The control device 3 determines whether or not to start the operation of the refrigeration cycle apparatus 100 based on an instruction from the user or the like (S7). If the operation is not started (no in S7), the routine returns to step S4, and the subsequent processing is repeated. When the operation is started (yes in S7), the routine proceeds to step S1, and the 2 nd compressor 21 is driven to circulate the low-stage side refrigerant through the low-stage circuit 2.
As described above, in the refrigeration cycle apparatus 100 according to the present embodiment, the operation of the high-stage circuit 1 is continued even after the low-stage circuit 2 is stopped, and the high-stage circuit 1 is controlled so that the pressure P of the low-stage side refrigerant becomes the threshold P at which the incombustibility of the low-stage side refrigerant can be maintained T The following is given. From the following componentsThis can suppress the composition fluctuation of the low-stage side refrigerant that remains in the low-stage circuit 2 after the low-stage circuit 2 is stopped. As a result, even when a zeotropic refrigerant mixture including a flammable refrigerant is used as the low-stage side refrigerant, an increase in the risk of flammability at the time of refrigerant leakage can be suppressed. In addition, as in the present embodiment, a catalyst containing CO is used 2 In the case where the mixed refrigerant of (2) is used as the low-stage side refrigerant, CO can be reduced 2 Therefore, cooling below the freezing point (-56 ℃ C.) can also be achieved.
Embodiment 2.
A refrigeration cycle apparatus 100 according to embodiment 2 will be described. Fig. 4 is a flowchart showing the operation of the refrigeration cycle apparatus 100 according to embodiment 2. In this embodiment, the operation of the refrigeration cycle apparatus 100 is different from that of embodiment 1. The refrigeration cycle apparatus 100 has the same structure as that of embodiment 1.
As shown in fig. 4, when the operation of the refrigeration cycle apparatus 100 is instructed by an instruction from a user or the like, the control device 3 drives the 1 st compressor 11 and the 2 nd compressor 21 (S11). Thereby, the high-stage side refrigerant circulates in the high-stage circuit 1, and the low-stage side refrigerant circulates in the low-stage circuit 2.
Then, the control device 3 determines whether to stop the operation of the refrigeration cycle apparatus 100 according to an instruction from the user or the like (S12). If the operation is not to be stopped (S12: NO), the operation of the high-stage circuit 1 and the low-stage circuit 2 is continued until a stop instruction is given.
On the other hand, when the operation is stopped (yes in S12), the control device 3 performs the evacuation operation in the low-stage circuit 2 (S13). Specifically, the control device 3 turns off the 2 nd pressure reducing device 23 completely, and keeps the 2 nd compressor 21 continuously operating. Since the 2 nd pressure reducing device 23 is closed, the low-stage side refrigerant in the low-stage circuit 2 is recovered to the high-pressure side of the low-stage circuit 2, that is, from the discharge port of the 2 nd compressor 21 to the refrigerant inlet of the 2 nd pressure reducing device 23. Thereby, the low-pressure side of the low-stage circuit 2, that is, the space between the refrigerant outlet of the 2 nd pressure reducing device 23 and the suction port of the 2 nd compressor 21 becomes negative pressure (atmospheric pressure or lower).
After that, the control device 3 stops the 2 nd compressor 21 (S14). Thereby, the circulation of the low-stage side refrigerant in the low-stage circuit 2 is stopped. Further, a solenoid valve may be provided between the low-stage side flow path 142 of the cascade heat exchanger 14 and the 2 nd pressure reducing device 23, and the solenoid valve may be closed to perform the evacuation operation. In addition, a pressure sensor for detecting the low-pressure of the low-stage side refrigerant may be provided on the low-stage side of the low-stage circuit 2, that is, between the refrigerant outlet of the 2 nd pressure reducing device 23 and the suction port of the 2 nd compressor 21, and the 2 nd compressor 21 may be stopped when the low-pressure of the low-stage side refrigerant becomes equal to or lower than the atmospheric pressure. This can prevent a failure or the like from occurring due to the fact that the driving of the 2 nd compressor 21 is continued after the refrigerant is not present on the low-pressure side of the low-stage circuit 2.
The subsequent steps S15 to S18 are the same as those of steps S4 to S7 in embodiment 1, and the high-stage circuit 1 is controlled so that the pressure P of the low-stage side refrigerant becomes the threshold value P T The following is given. However, in the present embodiment, the pressure sensor 26 detects the pressure P of the low-stage side refrigerant recovered to the high-stage side of the low-stage circuit 2. That is, the pressure sensor 26 is provided between the discharge port of the 2 nd compressor 21 and the refrigerant inlet of the 2 nd pressure reducing device 23.
In the refrigeration cycle apparatus 100 of the present embodiment, the low-pressure side of the low-stage circuit 2 can be set to a negative pressure by performing the evacuation operation after the low-stage circuit 2 is stopped. This can prevent leakage of the gas refrigerant from the welded portion provided on the low-pressure side of the low-stage circuit 2. As a result, when the refrigeration cycle apparatus 100 is stopped, the composition fluctuation of the liquid refrigerant that is trapped in the low-stage circuit 2 can be further suppressed.
The embodiments are described above, but the present disclosure is not limited to the above embodiments, and various modifications and combinations can be made without departing from the gist of the present disclosure. For example, the low-stage side refrigerant is not limited to CO 2 And R290, or other non-azeotropic refrigerant. However, the low-stage side refrigerant contains CO 2 And flammable refrigerants, especially in the case of non-azeotropic mixtures of refrigerantsThe effects of the above embodiments can be obtained.
In the above embodiment, the control device 3 is used to control the entire refrigeration cycle apparatus 100, but the control device 3 may be provided in each of the high-stage circuit 1 and the low-stage circuit 2 to individually control the operations of the high-stage circuit 1 and the low-stage circuit 2.
In the above embodiment, the capacity of the high-order circuit 1 is controlled by controlling the operation frequency of the 1 st compressor 11, but the present invention is not limited to this. For example, the opening degree of the 1 st pressure reducing device 13 of the high-stage circuit 1 or the rotation speed of the 1 st fan 15 may be controlled instead of or in addition to the operation frequency of the 1 st compressor 11, thereby controlling the capacity of the high-stage circuit 1. In this case, the control device 3 compares the pressure P of the low-stage side refrigerant with the threshold P T When the opening degree of the 1 st pressure reducing device 13 and the rotation speed of the 1 st fan 15 are increased, the capacity of the high-order circuit 1 is increased.
The low-stage circuit 2 of the refrigeration cycle apparatus 100 may also include the accumulator 22. Fig. 5 is a schematic configuration diagram of a refrigeration cycle apparatus 100A according to modification 1. As shown in fig. 5, the low-stage circuit 2 of the refrigeration cycle apparatus 100A includes an accumulator 22 between the cascade heat exchanger 14 and the 2 nd pressure reducing device 23. The accumulator 22 temporarily stores the low-stage-side refrigerant flowing out of the low-stage-side flow path 142 of the cascade heat exchanger 14. The accumulator 22 stores the surplus refrigerant generated by the fluctuation of the cooling load.
Even when the refrigeration cycle apparatus 100A includes the accumulator 22, the operation of the high-stage circuit 1 is continued after the low-stage circuit 2 is stopped, and the high-stage circuit 1 is controlled so that the pressure P of the low-stage side refrigerant becomes a threshold P at which the low-stage side refrigerant can maintain incombustibility T The following is given. In the case where the refrigeration cycle apparatus 100A includes the accumulator 22, the high-stage circuit 1 may be controlled so that the high-pressure of the low-stage side refrigerant becomes a threshold P at which the low-stage side refrigerant can maintain incombustibility even during the operation of the low-stage circuit 2 T The following is given.
In the above embodiment, the construction is adopted in which the high-stage circuit 1 is controlled based on the pressure P of the low-stage side refrigerant detected by the pressure sensor 26 after the low-stage circuit 2 is stopped, but the present invention is not limited to this. For example, the control device 3 may control the high-stage circuit 1 based on the temperature of the low-stage side refrigerant corresponding to the pressure P of the low-stage side refrigerant. Alternatively, the low-stage circuit 2 may be provided with a pressure release device that is opened when the pressure or temperature increases to a reference value, and the pressure P of the low-stage side refrigerant that remains in the low-stage circuit 2 may be set to a pressure value equal to or lower than a pressure value at which the low-stage side refrigerant maintains incombustibility.
Fig. 6 is a schematic configuration diagram of a refrigeration cycle apparatus 100B according to modification 2. As shown in fig. 6, the refrigeration cycle apparatus 100B includes a pressure relief device 27. The pressure release device 27 is provided at an arbitrary position in the low-stage circuit 2. In addition, in the case of performing the evacuation operation as in embodiment 2, the pressure relief device 27 is provided on the high-pressure side of the low-stage circuit 2. The pressure relief device 27 is a pressure relief valve or fusible plug, and the pressure P or temperature of the low-stage side refrigerant becomes a threshold value P T In the above case, the valve or the plug is opened, and thereby the gas refrigerant is discharged to the outside, and the pressure P of the low-stage side refrigerant is lowered. As in the above embodiment, the threshold value P T Is a pressure value or a temperature at which the low-stage side refrigerant can maintain incombustibility. Thus, even after the low-stage circuit 2 is stopped, the pressure P of the low-stage side refrigerant can be maintained at a pressure value equal to or lower than a pressure value at which incombustibility of the low-stage side refrigerant can be maintained. In the case of the present modification, the high-order circuit 1 may be stopped after the low-order circuit 2 is stopped. Alternatively, the driving of the high-stage circuit 1 may be continued after the low-stage circuit 2 is stopped, and the pressure control by the pressure relief device 27 and the control of the high-stage circuit 1 by the pressure P of the low-stage side refrigerant may be performed in combination.
Description of the reference numerals
The cooling system comprises a 1-stage loop, a 2-stage loop, a 3-control device, an 11 st compressor, a 12 condenser, a 13 st decompression device, a 14-stage heat exchanger, a 15 st fan, a 21 st compressor, a 22 reservoir, a 23 nd decompression device, a 24-stage evaporator, a 25 nd fan, a 26-stage pressure sensor, a 27 decompression device, a 100, 100A and 100B cooling circulation device, a 141-stage high-stage side flow path and a 142-stage low-stage side flow path.
Claims (8)
1. A refrigeration cycle apparatus, wherein,
the refrigeration cycle device is provided with:
a high-stage circuit having a 1 st compressor, a condenser, a 1 st pressure reducing device, and a cascade heat exchanger, wherein a high-stage side refrigerant circulates in the high-stage circuit; and
a low-stage circuit having a 2 nd compressor, the cascade heat exchanger, a 2 nd pressure reducing device, and an evaporator, in which a low-stage side refrigerant circulates,
the cascade heat exchanger exchanges heat between the high-stage side refrigerant and the low-stage side refrigerant,
the low-side refrigerant is a non-azeotropic refrigerant mixture,
the pressure of the low-stage side refrigerant that remains in the low-stage circuit after the 2 nd compressor is stopped is maintained at a pressure that is not higher than a pressure at which the low-stage side refrigerant can maintain incombustibility.
2. The refrigeration cycle apparatus according to claim 1, wherein,
the refrigeration cycle apparatus further includes a control device,
the control device controls the high-stage circuit after the 2 nd compressor is stopped so that the pressure of the low-stage side refrigerant retained in the low-stage circuit becomes equal to or lower than a threshold value,
the threshold value is a pressure at which the low-stage side refrigerant can maintain incombustibility.
3. The refrigeration cycle apparatus according to claim 2, wherein,
the control device increases the capacity of the high-stage circuit when the pressure of the low-stage side refrigerant is greater than the threshold value.
4. A refrigeration cycle apparatus according to claim 2 or 3, wherein,
the control device increases the operating frequency of the 1 st compressor when the pressure of the low-stage side refrigerant is greater than the threshold value.
5. A refrigeration cycle apparatus according to any one of claims 2 to 4, wherein,
the control device performs the evacuation operation of the low-stage circuit before stopping the 2 nd compressor.
6. The refrigeration cycle apparatus according to claim 1, wherein,
the low-stage circuit has a pressure relief device that is opened when the pressure of the low-stage side refrigerant that has been retained in the low-stage circuit is equal to or higher than a threshold value,
the threshold value is a pressure at which the low-stage side refrigerant can maintain incombustibility.
7. A refrigeration cycle apparatus according to any one of claims 1 to 6, wherein,
the low-side refrigerant is a refrigerant containing CO 2 And a non-azeotropic mixed refrigerant of a flammable refrigerant.
8. A control method for a refrigeration cycle device is provided with:
a high-stage circuit having a 1 st compressor, a condenser, a 1 st pressure reducing device, and a cascade heat exchanger, wherein a high-stage side refrigerant circulates in the high-stage circuit; and
a low-stage circuit having a 2 nd compressor, the cascade heat exchanger, a 2 nd pressure reducing device, and an evaporator, in which a low-stage side refrigerant circulates,
wherein,
the cascade heat exchanger exchanges heat between the high-stage side refrigerant and the low-stage side refrigerant,
the low-side refrigerant is a non-azeotropic refrigerant mixture,
the pressure of the low-stage side refrigerant that remains in the low-stage circuit after the 2 nd compressor is stopped is maintained at a pressure that is not higher than a pressure at which incombustibility of the low-stage side refrigerant can be maintained.
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| PCT/JP2021/029053 WO2023012961A1 (en) | 2021-08-05 | 2021-08-05 | Refrigeration circuit device and control method for refrigeration circuit device |
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| EP (1) | EP4382828A1 (en) |
| JP (1) | JPWO2023012961A1 (en) |
| CN (1) | CN117730234A (en) |
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| JP2001019944A (en) * | 1999-07-09 | 2001-01-23 | Matsushita Electric Ind Co Ltd | Low-temperature working fluid and refrigerating cycle apparatus using the same |
| JP2004190917A (en) * | 2002-12-10 | 2004-07-08 | Sanyo Electric Co Ltd | Refrigeration device |
| JP2008215672A (en) * | 2007-03-01 | 2008-09-18 | Mac:Kk | Residual gas recovering method of refrigerating cycle using combustible refrigerant gas and its device |
| JP5854751B2 (en) * | 2011-10-12 | 2016-02-09 | 三菱電機株式会社 | Cooling system |
| JPWO2014030236A1 (en) | 2012-08-23 | 2016-07-28 | 三菱電機株式会社 | Refrigeration equipment |
| EP2910870B1 (en) * | 2012-09-21 | 2020-01-01 | Mitsubishi Electric Corporation | Refrigeration device and method for controlling same |
| JP5963969B2 (en) * | 2013-09-27 | 2016-08-03 | パナソニックヘルスケアホールディングス株式会社 | Refrigeration equipment |
| US10254016B2 (en) * | 2014-03-17 | 2019-04-09 | Mitsubishi Electric Corporation | Refrigeration cycle apparatus and method for controlling refrigeration cycle apparatus |
| WO2018198203A1 (en) * | 2017-04-25 | 2018-11-01 | 三菱電機株式会社 | Binary refrigeration device |
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| JPWO2023012961A1 (en) | 2023-02-09 |
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