JP2023011324A - Refrigerating device - Google Patents

Abstract

To realize both an environmental property and compression performance in a refrigerating device.SOLUTION: A refrigerating device 1 includes a three-stage type screw compressor 10 for compressing a refrigerant in three stages. The three-stage type screw compressor 10 comprises a motor 11 that is a drive source, a first stage compression part 12 mechanically connected to the motor 11, a second stage compression part 13 mechanically connected to the first stage compression part 12 via a first joint 18, and a third stage compression part 14 mechanically connected to the second stage compression part 13 via a second joint 19. The first stage compression part 12, the second stage compression part 13, and the third stage compression part 14 comprise a common rotating shaft. The global warming potential of the refrigerant is 1500 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to refrigeration equipment.

The environmental friendliness of refrigerants used in refrigeration systems is evaluated by an index value called global warming potential (GWP). A larger value of GWP is worse, and a smaller value is better. GWP is required to be 1500 or less from the viewpoint of prevention of global warming.

In general refrigeration equipment, R404A is often used as a refrigerant for low-temperature applications. The compression ratio of the refrigerant depends on the saturation pressure of the refrigerant at the evaporating temperature and the saturation pressure of the refrigerant at the condensing temperature. Since R404A has a relatively high saturation pressure at the evaporation temperature, the compression ratio of R404A is small and high compression efficiency can be exhibited. However, R404A has a very high GWP of 3920, which is not preferable from an environmental point of view.

JP 2012-167608 A

R448A, R513A, etc. are available as refrigerants to replace R404A. R448A has a GWP of 1387 and R513A has a GWP of 631. Both have a smaller GWP than R404A and are more environmentally friendly. However, refrigerants with a relatively small GWP, such as R448A or R513A, tend to have a large compression ratio. If a refrigerant with a large compression ratio is used in a general two-stage screw compressor, leakage of the refrigerant occurs between the tooth profiles of the screw rotor, and there is a risk that the intended compression performance cannot be ensured.

An object of the present invention is to achieve both environmental friendliness and compression performance in a refrigeration system.

A first aspect of the present invention is a refrigeration system including a three-stage screw compressor that compresses a refrigerant in three stages, the three-stage screw compressor comprising: a motor as a drive source; a first stage compression section mechanically connected, a second stage compression section mechanically connected to the first stage compression section via a first joint, and a second stage compression section mechanically connected to the second compression section via a second joint a third stage compression section mechanically connected to the refrigerant through the A refrigeration system having a global warming potential of 1500 or less is provided.

According to this configuration, since a refrigerant having a global warming potential (GWP) of 1500 or less is used, it is excellent in environmental friendliness. Moreover, even if a refrigerant with a small GWP of 1500 or less is used, a sufficient compression performance can be ensured compared to a general two-stage screw compressor because a three-stage screw compressor is used. Therefore, in the refrigeration system, both environmental performance and compression performance can be achieved. Further, since the motor, the first stage compression section, the second stage compression section, and the third stage compression section are mechanically connected, they can be driven by a single drive source (motor). In particular, since they have a common rotating shaft, the structure of the three-stage screw compressor can be simplified.

The refrigeration system includes a first bypass pipe that fluidly connects a suction port of the first stage compression section and a suction port of the second stage compression section, and a first solenoid valve provided in the first bypass piping. and the compression ratios of the first stage compression section and the second stage compression section, ie, the mechanically determined compression ratios, may each be fixed.

If the compression ratios of the first-stage compression section and the second-stage compression section are fixed and the operation is started without any ingenuity, there will be a capacity difference between the first-stage compression section and the second-stage compression section. , the refrigerant may stagnate at the suction port of the second stage compression section. This retention can be eliminated by making the compression ratios of the first stage compression section and the second stage compression section variable and adjusting the capacities. However, a configuration that makes the compression ratio variable, as exemplified by a slide valve, is complicated and difficult to adopt. Therefore, in the above configuration, the compression ratios of both the first-stage compression section and the second-stage compression section are fixed, and the refrigerant that may stay in the suction port of the second-stage compression section is discharged to the first stage by opening the first electromagnetic valve. 1 bypass line to the suction port of the first stage compression section. As a result, in the first stage compression section and the second stage compression section, it is possible to suppress the retention of the refrigerant at the suction port of the second stage compression section with a simple configuration without adopting a complicated configuration for varying the compression ratio. .

The refrigeration system includes: a second bypass pipe that fluidly connects a suction port of the first stage compression section and a suction port of the third stage compression section; and a second electromagnetic valve provided in the second bypass piping. and wherein the compression ratios of the first stage compression section, the second stage compression section, and the third stage compression section may each be fixed.

Assuming that the compression ratios of the first, second and third stage compression sections are fixed and the operation is started without any modification, the first stage compression section and the third stage compression section Since there is a capacity difference between the parts, there is a risk that the refrigerant will stagnate at the suction port of the third stage compression part. The stagnation can be eliminated by making the compression ratios of the first, second, and third stage compression sections variable and adjusting their capacities. However, a configuration that makes the compression ratio variable, as exemplified by a slide valve, is complicated and difficult to adopt. Therefore, in the above configuration, while fixing the compression ratios of the first-stage compression section, the second-stage compression section, and the third-stage compression section, the refrigerant that can stay in the suction port of the third-stage compression section is By opening the valve, it can flow through the second bypass line to the suction port of the first stage compression section. As a result, the suction port of the third-stage compression section can be adjusted with a simple configuration without adopting a complicated configuration for varying the compression ratio in the first-stage compression section, the second-stage compression section, and the third-stage compression section. stagnation of the refrigerant can be suppressed.

The first joint and the second joint may each be a spline joint.

According to this configuration, power can be easily transmitted by a spline joint having a simple and low-cost structure.

The refrigerating device includes a condenser for condensing the refrigerant discharged from the three-stage screw compressor, a condenser for cooling the refrigerant condensed by the condenser, and a second-stage compression section and a third-stage compression section for cooling the refrigerant condensed by the condenser. a first economizer fluidly connected between a section and a first economizer for further cooling the refrigerant cooled by the first economizer and fluidly between the first stage compression section and the second stage compression section; and a second economizer connected to.

According to this configuration, the coefficient of performance (COP) of the refrigeration system can be improved by cooling the refrigerant with the first economizer and the second economizer.

The refrigeration system may further include a third economizer that further cools the refrigerant cooled by the second economizer and that is fluidly connected to the internal space of the first stage compression section.

According to this configuration, the COP of the refrigeration system can be further improved by cooling the refrigerant with the third economizer. Here, the internal space of the first-stage compression section refers to a closed space that is not in communication with the suction port and the discharge port of the first-stage compression section.

The refrigeration system may further include an inverter that adjusts the rotation speed of the motor.

According to this configuration, the driving amount of the three-stage screw compressor can be adjusted by controlling the inverter.

According to the present invention, the refrigerating apparatus uses a three-stage screw compressor that compresses a refrigerant having a global warming potential of 1500 or less in three stages, so that both environmental friendliness and compression performance can be achieved.

1 is a schematic configuration diagram of a refrigeration system according to a first embodiment of the present invention; FIG. Sectional drawing of a three-stage screw compressor. The schematic block diagram of the refrigeration apparatus which concerns on 2nd Embodiment. The schematic block diagram of the refrigeration apparatus which concerns on 3rd Embodiment. The schematic block diagram of the refrigeration apparatus which concerns on 4th Embodiment. The schematic block diagram of the refrigeration apparatus which concerns on 5th Embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
1 and 2, the refrigeration system 1 includes a three-stage screw compressor 10, an oil separation reservoir 20, a condenser 30, an expansion valve 40, and an evaporator 50 in a refrigerant flow path 2. have.

A refrigerant having a global warming potential (GWP) of 1500 or less flows through the refrigerant flow path 2 . A refrigerant with a GWP of 1500 or less can be, for example, R448A or R513A.

The three-stage screw compressor 10 has a motor 11 , a first stage compression section 12 , a second stage compression section 13 and a third stage compression section 14 . The first stage compression section 12, the second stage compression section 13, and the third stage compression section 14 are connected in series and compress the refrigerant in three stages.

The motor 11 is a drive source that drives the first stage compression section 12 , the second stage compression section 13 and the third stage compression section 14 . Motor 11 is housed in casing 15 . The motor 11 includes a rotor 11a sharing a rotating shaft 16 with a first-stage screw rotor 12a, a second-stage screw rotor 13a, and a third-stage screw rotor 14a, which will be described later, and a stator 11b surrounding the rotor 11a. have.

An inverter 17 is electrically connected to the motor 11 . The inverter 17 is controlled by a control device (not shown). By controlling the inverter 17, the rotation speed of the motor 11 can be adjusted, that is, the driving amount of the three-stage screw compressor 10 can be adjusted. Note that the inverter 17 is not an essential component and may be omitted as necessary.

A first stage compression section 12 is mechanically connected to the motor 11 . The mode of connection is not particularly limited.

The first stage compression section 12 is formed by housing a pair of male and female first stage screw rotors 12 a in a first stage rotor chamber R<b>1 formed inside a casing 15 . The first stage compression section 12 sucks the refrigerant from a suction port 12b fluidly connected to the refrigerant flow path 2 on the upstream side, compresses it in the first stage rotor chamber R1, and discharges it from a discharge port 12c. The discharge port 12 c is fluidly connected to a first intermediate chamber R 12 defined within the casing 15 between the first stage compression section 12 and the second stage compression section 13 .

A second stage compression section 13 is mechanically connected to the first stage compression section 12 via a first joint 18 . In this embodiment, the first joint 18 is a spline joint.

The second stage compression section 13 is formed by housing a pair of male and female second stage screw rotors 13 a in a second stage rotor chamber R<b>2 formed inside the casing 15 . The second stage compression section 13 sucks the refrigerant from a suction port 13b fluidly connected to the first intermediate chamber R12 on the upstream side, compresses it in the second stage rotor chamber R2, and discharges it from a discharge port 13c. The discharge port 13 c is fluidly connected to a second intermediate chamber R 23 defined within the casing 15 between the second stage compression section 13 and the third stage compression section 14 .

A third stage compression section 14 is mechanically connected to the second stage compression section 13 via a second joint 19 . In this embodiment, the second joint 19 is a spline joint.

The third stage compression section 14 is formed by accommodating a pair of male and female third stage screw rotors 14 a in a third stage rotor chamber R<b>3 formed inside the casing 15 . The third stage compression section 14 sucks the refrigerant from a suction port 14b fluidly connected to the second intermediate chamber R23 on the upstream side, compresses it in the third stage rotor chamber R3, and discharges it from a discharge port 14c. The discharge port 14c is fluidly connected to the refrigerant channel 2 on the downstream side.

The first stage screw rotor 12a is rotatably supported by bearings 12d and 12e, the second stage screw rotor 13a is rotatably supported by bearings 13d and 13e, and the third stage screw rotor 14a is rotatably supported by bearings 14d and 14e. supported by The casing 15 is formed with an oil passage 3 for supplying oil to the bearings 12d, 12e, 13e and 14e. Although details are not shown, the oil may be directly or indirectly supplied to the bearings 13d, 14d, the first joint 18, and the second joint 19 as well.

The male rotor of the first stage screw rotor 12a, the male rotor of the second stage screw rotor 13a, and the male rotor of the third stage screw rotor 14a rotate coaxially. That is, the first-stage compression section 12 , the second-stage compression section 13 , and the third-stage compression section 14 have a common rotating shaft 16 .

The oil separation reservoir 20 is fluidly connected to the three-stage screw compressor 10 via the refrigerant flow path 2 . The oil separation reservoir 20 separates and stores oil from the oil-containing refrigerant discharged from the three-stage screw compressor 10 . The oil separation reservoir 20 has a separator 21 that separates oil from the oil-containing refrigerant and a tank 22 that stores the oil separated by the separator 21 . Oil stored in the tank 22 is supplied to the three-stage screw compressor 10 via the oil flow path 3 .

Condenser 30 is fluidly connected with oil separation reservoir 20 . The condenser 30 cools and condenses the refrigerant from which the oil is separated in the oil separation reservoir 20 .

Expansion valve 40 is fluidly connected to condenser 30 . The expansion valve 40 expands the refrigerant condensed in the condenser 30 and depressurizes it.

Evaporator 50 is fluidly connected to condenser 30 and three stage screw compressor 10 . The evaporator 50 evaporates the refrigerant decompressed by the expansion valve 40 . The decompressed refrigerant is supplied to the three-stage screw compressor 10 .

The condenser 30, the expansion valve 40, and the evaporator 50 can be of known types used in general refrigeration cycles.

According to this embodiment, since a refrigerant having a GWP of 1500 or less is used, it is excellent in environmental friendliness. Moreover, even if a refrigerant with a small GWP of 1500 or less is used, the three-stage screw compressor 10 is used, so sufficient compression performance can be ensured compared to a general two-stage screw compressor. Therefore, in the refrigeration system 1, both environmental friendliness and compression performance can be achieved. Further, since the motor 11, the first stage compression section 12, the second stage compression section 13, and the third stage compression section 14 are mechanically connected, they can be driven by one drive source (motor 11). In particular, since they have a common rotating shaft 16, the structure of the three-stage screw compressor 10 can be simplified.

(Second embodiment)
The refrigeration system 1 of the second embodiment shown in FIG. 3 has a first economizer 60 and a second economizer 70, also called subcoolers. The configuration other than this is substantially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

In this embodiment, a first economizer 60 and a second economizer 70 are provided between the condenser 30 and the expansion valve 40 in the refrigerant flow path 2 .

First economizer 60 further cools the refrigerant cooled in condenser 30 . The first economizer 60 has a heat exchanger 61 and an expansion valve 62 . In the first economizer 60 , the expansion valve 62 expands a portion of the refrigerant cooled by the condenser 30 , and the heat exchanger 61 exchanges heat between the refrigerant before and after expansion. As a result, the refrigerant before expansion (the refrigerant condensed in the condenser 30) is cooled, and the refrigerant after expansion is heated. The first economizer 60 is fluidly connected to the second intermediate chamber R23 between the second stage compression section 13 and the third stage compression section 14, and the expanded refrigerant is supplied to the second intermediate chamber R23. be.

Second economizer 70 further cools the refrigerant cooled by first economizer 60 . The second economizer 70 has a heat exchanger 71 and an expansion valve 72 . In the second economizer 70 , the expansion valve 72 partially expands the refrigerant cooled by the first economizer 60 , and the heat exchanger 71 exchanges heat between the refrigerant before and after the expansion. As a result, the refrigerant before expansion (the refrigerant cooled by the first economizer 60) is cooled, and the refrigerant after expansion is heated. The second economizer 70 is fluidly connected to the first intermediate chamber R12 between the first stage compression section 12 and the second stage compression section 13, and the expanded refrigerant is supplied to the first intermediate chamber R12. be.

According to this embodiment, by cooling the refrigerant with the first economizer 60 and the second economizer 70, the coefficient of performance (COP) of the refrigeration system 1 can be improved.

(Third Embodiment)
The refrigeration system 1 of the third embodiment shown in FIG. 4 has a third economizer 80, also called a supercooler. The configuration other than this is substantially the same as the second embodiment. Therefore, the description of the parts shown in the first and second embodiments may be omitted.

In this embodiment, a third economizer 80 is provided between the second economizer 70 and the expansion valve 40 in the refrigerant flow path 2 .

Third economizer 80 further cools the refrigerant cooled by second economizer 70 . The third economizer 80 has a heat exchanger 81 and an expansion valve 82 . In the third economizer 80 , the expansion valve 82 expands part of the refrigerant cooled by the second economizer 70 , and the heat exchanger 81 exchanges heat between the refrigerant before and after expansion. As a result, the refrigerant before expansion (the refrigerant cooled by the second economizer 70) is cooled, and the refrigerant after expansion is heated. The third economizer 80 is fluidly connected to the internal space S of the first stage compression section, and the expanded refrigerant is supplied to the internal space S. Here, the internal space S is a closed space that is not in communication with the suction port 12b and the discharge port 12c of the first stage compression section 12 in the first stage rotor chamber R1.

According to this embodiment, the COP of the refrigeration system 1 can be further improved by cooling the refrigerant with the third economizer 80 .

(Fourth embodiment)
A refrigeration system 1 of the fourth embodiment shown in FIG. 5 has a first bypass pipe 4 and a first solenoid valve 4a. The configuration other than this is substantially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

In this embodiment, a first bypass pipe 4 is provided that fluidly connects the suction port 12b of the first stage compression section 12 and the suction port 13b of the second stage compression section 13 . The first bypass pipe 4 is provided with a first electromagnetic valve 4a. Opening and closing of the first solenoid valve 4a is controlled by a control device (not shown). The first solenoid valve 4a is normally closed and opened when the three-stage screw compressor 10 starts operating.

Further, in this embodiment, the compression ratios of the first stage compression section 12 and the second stage compression section 13 are fixed.

According to this embodiment, it is possible to suppress the retention of the refrigerant in the suction port 13b of the second stage compression section 13 when the operation is started. If the compression ratios of the first-stage compression section 12 and the second-stage compression section 13 are fixed and the operation is started without any ingenuity, the capacities of the first-stage compression section 12 and the second-stage compression section 13 will be Due to the difference, the refrigerant may stay in the suction port 13 b of the second stage compression section 13 . The retention can be eliminated by making the compression ratios of the first stage compression section 12 and the second stage compression section 13 variable and adjusting the capacities. However, the configuration that makes the compression ratio variable is complicated and difficult to adopt. Therefore, in this embodiment, while the compression ratios of the first stage compression section 12 and the second stage compression section 13 are both fixed, the refrigerant that can stay in the suction port 13b of the second stage compression section 13 is removed by the first solenoid valve. By opening 4 a , the gas can flow through the first bypass pipe 4 to the suction port 12 b of the first stage compression section 12 . As a result, in the first-stage compression section 12 and the second-stage compression section 13, the refrigerant at the suction port 13b of the second-stage compression section 13 does not need to adopt a complicated construction for varying the compression ratio. Stagnation can be suppressed.

(Fifth embodiment)
A refrigeration system 1 of the fifth embodiment shown in FIG. 6 has a second bypass pipe 5 and a second solenoid valve 5a. The configuration other than this is substantially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

In this embodiment, a second bypass pipe 5 is provided that fluidly connects the suction port 13b of the second stage compression section 13 and the suction port 14b of the third stage compression section 14 . The second bypass pipe 5 is provided with a second solenoid valve 5a. Opening and closing of the second solenoid valve 5a is controlled by a control device (not shown). The second solenoid valve 5a is normally closed and opened when the three-stage screw compressor 10 starts operating.

Further, in the present embodiment, the compression ratios of the first compression section 12, the second compression section 13, and the third compression section 14 are fixed.

According to this embodiment, it is possible to suppress the retention of the refrigerant in the suction port 14b of the third stage compression section 14 when the operation is started. If the compression ratios of the first-stage compression section 12, the second-stage compression section 13, and the third-stage compression section 14 are fixed and the operation is started without any ingenuity, the second-stage compression section 13 and Since the third stage compression section 14 has a capacity difference, the refrigerant may stay in the suction port 14 b of the third stage compression section 14 . The stagnation can be eliminated by making the compression ratios of the second-stage compression section 13 and the third-stage compression section 14 variable and adjusting the capacities. However, a configuration that makes the compression ratio variable, as exemplified by a slide valve, is complicated and difficult to adopt. Therefore, in the above configuration, while the compression ratios of the first-stage compression section 12, the second-stage compression section 13, and the third-stage compression section 14 are fixed, the refrigerant that can stay in the suction port 14b of the third-stage compression section 14 can flow to the suction port 13b of the second stage compression section 13 through the second bypass pipe 5 by opening the second electromagnetic valve 5a. As a result, in the second stage compression section 13 and the third stage compression section 14, the refrigerant at the suction port 14b of the third stage compression section 14 can be supplied with a simple configuration without adopting a complicated configuration for varying the compression ratio. retention can be suppressed.

As described above, specific embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention. For example, an embodiment of the present invention may be an appropriate combination of the contents of individual embodiments.

REFERENCE SIGNS LIST 1 refrigerating device 2 refrigerant flow path 3 oil flow path 4 first bypass pipe 4a first solenoid valve 5 second bypass pipe 5a second solenoid valve 10 three-stage screw compressor 11 motor 11a rotor 11b stator 12 first stage Compression part 12a First stage screw rotor 12b Suction port 12c Discharge port 12d, 12e Bearing 13 Second stage compression part 13a Second stage screw rotor 13b Suction port 13c Discharge port 13d, 13e Bearing 14 Third stage compression part 14a Third stage Screw rotor 14b Suction port 14c Discharge port 14d, 14e Bearing 15 Casing 16 Rotating shaft 17 Inverter 18 First joint 19 Second joint 20 Oil separation reservoir 21 Separator 22 Tank 30 Condenser 40 Expansion valve 50 Evaporator 60 First economizer 61 Heat exchanger 62 Expansion valve 70 Second economizer 71 Heat exchanger 72 Expansion valve 80 Third economizer 81 Heat exchanger 82 Expansion valve R1 First stage rotor chamber R2 Second stage rotor chamber R3 Third stage rotor chamber R12 First intermediate Chamber R23 Second intermediate chamber S Internal space

Claims (7)

A refrigeration system including a three-stage screw compressor that compresses a refrigerant in three stages,
The three-stage screw compressor is
a motor as a drive source;
a first stage compression section mechanically connected to the motor;
a second stage compression section mechanically connected to the first stage compression section via a first joint;
a third stage compression section mechanically connected to the second stage compression section via a second joint,
the first stage compression section, the second stage compression section, and the third stage compression section have a common rotating shaft;
The refrigeration system, wherein the global warming potential of the refrigerant is 1500 or less. a first bypass pipe that fluidly connects the suction port of the first stage compression section and the suction port of the second stage compression section;
and a first solenoid valve provided in the first bypass pipe,
2. The refrigeration system according to claim 1, wherein the compression ratios of said first stage compression section and said second stage compression section are each fixed. a second bypass pipe that fluidly connects the suction port of the first stage compression section and the suction port of the third stage compression section;
a second solenoid valve provided in the second bypass pipe,
3. The refrigeration system according to claim 1, wherein compression ratios of said first stage compression section, said second stage compression section, and said third stage compression section are each fixed. 4. The refrigerator according to any one of claims 1 to 3, wherein said first joint and said second joint are spline joints respectively. a condenser for condensing the refrigerant discharged from the three-stage screw compressor;
a first economizer cooling the refrigerant condensed by the condenser and fluidly connected between the second stage compression section and the third stage compression section;
from claim 1, further comprising: a second economizer further cooling the refrigerant cooled by the first economizer and fluidly connected between the first stage compression section and the second stage compression section; 5. A refrigeration system according to any one of claims 4 to 5. 6. The refrigeration system according to claim 5, further comprising a third economizer that further cools the refrigerant cooled by the second economizer and that is fluidly connected to the internal space of the first stage compression section. The refrigeration system according to any one of claims 1 to 6, further comprising an inverter that adjusts the rotation speed of said motor.

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