Turbokühler

Abstract

Turbo cooler (1), comprising: a closed cooling circuit (9) comprising a turbo compressor (2), a condenser (3), a decompression device (4) and an evaporator (7) connected in sequence by lines (8), and filled with a refrigerant, wherein the refrigerant is a low-pressure refrigerant R1233zd(E) with low global warming potential and low ozone depletion potential, the turbo compressor (2) has a direct drive configuration in which a rotating shaft (18) of a turbine wheel (15,17) is directly connected to a motor (19), the rotating shaft (18) is supported by a magnetic bearing (20,21,23,24), the turbo cooler (1) is configured such that a liquid refrigerant can be circulated from the cooling circuit (9) as a cooling and lubricating medium for the magnetic bearing (20, 21, 23, 24) and an air gap (19D) of the motor (19), and the turbo compressor (2) has a refrigerant injection port (19C) which is provided in a stator (19B) of the motor (19) such that the liquid refrigerant can be introduced through the refrigerant injection port (19C) into the air space (19D) of the motor (19), thereby cooling a rotor (19A) and the stator (19B) of the motor (19).

Description

[0001] The present invention relates to a turbo chiller with a reduced environmental impact using an R1233zd(E) refrigerant with a low global warming potential (GWP) and a low ozone depletion potential (ODP).

[0002] Currently, hydrofluorocarbon (HFC) refrigerants such as R134a are used in turbo chillers. HFC refrigerants have a zero ozone depletion potential (ODP) and a high global warming potential (GWP). Turbo chillers require routine maintenance, which includes replacing bearings, lubricating oil, an oil filter, and the like. While maintenance is performed after the refrigerant is recovered from the refrigeration cycle, unrecoverable refrigerant may remain in the chiller, and refrigerant may be contained in the lubricating oil. Consequently, some refrigerant may be released into the atmosphere. Although this does not violate regulations, it is undesirable from a global warming perspective.

[0003] Some conventional turbo coolers feature an oil-free configuration that eliminates the need for a lubrication system, a high-speed compressor that provides a high compression ratio and increases suction volume, increased motor speed that enables more compact motors and reduces bearing losses, and simplified components that improve reliability and reduce costs, all as a result of a direct-drive motor configuration in which the impeller's rotating shaft is directly connected to the motor, supported by magnetic bearings (see, for example, JP 2 809 346 B2 and JP 2013 - 122 331 A). However, many turbo coolers still feature a configuration in which the impeller's rotating shaft is driven via the motor shaft, which is connected by a speed-increasing gear unit.In such configurations, a lubrication system must also be installed to cool and lubricate the speed-increasing gear unit. Consequently, maintenance, such as replacing the lubricating oil or oil filter, is unavoidable.

[0004] Recently, R1233zd(E) refrigerant has gained attention as a refrigerant. R1233zd(E) refrigerant has a low GWP of 5 or less and an ODP of 0.00031, and reaches negative pressure at a saturation temperature of 18°C ​​or lower. R1233zd(E) refrigerant is a low-pressure, low-density refrigerant commonly and predominantly used as a urethane blowing agent. As part of an effort to reduce environmental impact, hydrochlorofluoroolefin (HCFO) refrigerant is being researched, including its application in coolers.

[0005] JP 2012 - 167 699 A describes a refrigerant compressor for a refrigeration machine with a magnetic bearing of a rotor that directly drives an impeller, and a closed cooling circuit with condenser, decompression device and evaporator.

[0006] US 2014 / 0 260 376 A1 describes a deep-freeze system with thermal storage and mentions in this context a number of refrigerants that can be used for this purpose.

[0007] EP 1 119 731 B1 describes an oil-free liquid cooler in which a liquid refrigerant is used to lubricate and cool rolling bearings with ceramic rolling elements. The liquid refrigerant is fed from a reservoir into an engine to cool it.

[0008] R1233zd(E) refrigerant has gained attention as a low-GWP HCFO refrigerant due to its desirable properties of low GWP and ODP, and consequently, low environmental impact. However, it is a low-pressure refrigerant and has a low density (approximately 1 / 5 that of R134a). Consequently, it has been considered unsuitable for use in chillers, air conditioners, and heat pumps that utilize scroll or rotary displacement compressors due to difficulties in ensuring adequate performance.

[0009] Centrifugal compressors are turbo compressors with the advantage of being suitable for high-flow refrigerant compression. These inventors focused on determining whether the properties of low-pressure R1233zd(E) refrigerant, which has a low density and achieves a negative pressure at a saturation temperature of 18°C ​​or less, could be utilized by applying it to a chiller equipped with a turbo compressor. As a result of diligent research, these inventors discovered a way to provide a turbo chiller with reduced environmental impact using the R1233zd(E) refrigerant, applying the R1233zd(E) refrigerant to a turbo chiller equipped with a turbo compressor with a specific configuration.

[0010] In view of the foregoing, an object of the present invention is to provide a turbo cooler having an oil-free configuration, which reduces the maintenance frequency and the release of refrigerant caused by maintenance, and which can achieve reduced environmental pollution by utilizing the properties of the low-pressure refrigerant R1233zd(E) that achieves a negative pressure at a saturation temperature of 18°C ​​or less.

[0011] The turbo cooler according to claim 1 of the present invention comprises a closed refrigeration cycle including a turbo compressor, a condenser, a decompression device, and an evaporator connected in order by piping, and filled with a refrigerant; wherein the refrigerant is a low-pressure, low-global warming potential, low-ozone depletion potential R1233zd(E) refrigerant; wherein the turbo compressor has a direct drive configuration in which the rotating shaft of an impeller is directly connected to a motor; and the rotating shaft is supported by a magnetic bearing.

[0012] According to this configuration, the refrigerant is a low-pressure, low-global-warming-potential (GWP) and low-ozone-depletion-potential (ODP) refrigerant, and the turbocompressor adopts a direct-drive configuration in which the impeller's rotating shaft is directly connected to the motor and supported by a magnetic bearing. Consequently, power loss in the speed-increasing gear unit and bearing losses of ball bearings are reduced, allowing the turbocompressor to achieve a higher rotation speed suitable for high-flow refrigerant compression. This compensates for the inherent problems associated with using R1233zd(E) refrigerant, which is believed to have difficulty ensuring suitable performance due to the low density of the low-pressure refrigerant and its high sonic velocity compared to conventional fluorocarbon refrigerants.By adopting an oil-free configuration without a speed-increasing gear unit or ball bearings that require oil lubrication, maintenance of lubrication systems, such as replacing lubricating oil and oil filters, can be eliminated. Consequently, the necessary performance can be ensured by using R1233zd(E) refrigerant, which is a low-pressure, low-density refrigerant. Furthermore, the turbo cooler can be designed with reduced environmental impact by reducing the maintenance frequency and maintenance-induced refrigerant release, and by utilizing the properties of a refrigerant that achieves negative pressure at a saturation temperature of 18°C ​​or lower, preventing refrigerant from being released into the atmosphere. Furthermore, the turbo cooler has high reliability at low cost due to a simplified configuration that eliminates the lubrication system.

[0013] The turbo cooler according to claim 2 of the present invention comprises a closed refrigeration cycle including a turbo compressor, a condenser, a decompression device, and an evaporator connected in sequence by piping, and filled with a refrigerant; wherein the refrigerant is a low-pressure refrigerant R1233zd(E) refrigerant with low global warming potential and low ozone depletion potential; the turbo compressor has a direct drive configuration in which the rotating shaft of an impeller is directly connected to a motor; and the rotating shaft is supported by an oil-free ceramic bearing.

[0014] According to this configuration, the refrigerant is a low-pressure, low-global-warming-potential (GWP) and low-OZP refrigerant, R1233zd(E). The turbocompressor adopts a direct-drive configuration in which a rotating shaft of an impeller is directly connected to a motor, and the rotating shaft is supported by an oil-free ceramic bearing. Consequently, power loss in the speed-increasing gear unit and bearing losses of ball bearings are reduced, allowing the turbocompressor to achieve a higher rotation speed suitable for high-flow refrigerant compression. This compensates for inherent problems with the use of R1233zd(E) refrigerant, which is believed to have difficulty ensuring suitable performance due to the low density of the low-pressure refrigerant and its high sonic velocity compared to conventional fluorocarbon refrigerants.By adopting an oil-free configuration without a speed-increasing gear unit requiring oil lubrication, maintenance such as replacing lubricating oil and an oil filter can be eliminated. Consequently, the required performance can be ensured by using R1233zd(E) refrigerant, which is a low-pressure, low-density refrigerant. Furthermore, the turbo cooler can be designed with reduced environmental impact because the maintenance frequency and maintenance-induced refrigerant release are significantly reduced, and the properties of a refrigerant that achieves negative pressure at a saturation temperature of 18°C ​​or lower are utilized, preventing refrigerant from being released into the atmosphere. Furthermore, the turbo cooler has high reliability at low cost due to a simplified configuration that eliminates the lubrication system.

[0015] The turbo cooler according to the invention further has a configuration wherein a liquid refrigerant is circulated from the refrigeration cycle as a cooling and lubricating medium for the magnetic bearing or a bearing housing of the ceramic bearing and an air gap of the motor.

[0016] According to this configuration, the liquid refrigerant from the cooling circuit can be circulated as a cooling and lubricating medium for the bearing housing and the air gap of the motor. By cooling and lubricating the ceramic bearings with the liquid refrigerant, the service life of the bearings can be extended and heat loss and fail-safe operations due to excessive temperature rise in the motor can be reduced by ensuring the cooling capacity of the liquid refrigerant that cools the high-speed motor. This configuration successfully cools and lubricates the oil-free ceramic bearing and the motor, improving their service life and performance, and thus providing the turbo cooler with high performance and reliability.

[0017] The turbo cooler according to a preferred embodiment further has a configuration wherein a spiral groove that allows the liquid refrigerant or the low-pressure gas refrigerant supplied to the air gap of the motor to flow axially outward is provided at least on an inner peripheral surface of the stator of the motor, an outer peripheral surface of the rotor, and an outer peripheral surface of a balancing ring provided on an end surface of the rotor.

[0018] According to this configuration, the spiral groove, which allows the liquid refrigerant or the low-pressure gas refrigerant supplied to the air gap of the motor to flow axially outward, is provided on at least one of the inner peripheral surface of the motor stator, the outer peripheral surface of the rotor, and the outer peripheral surface of the balancing ring provided on the end surface of the rotor. Accordingly, the refrigerant supplied to the air gap can be quickly discharged axially outward. Consequently, the cooling effect of the refrigerant on the motor can be further improved, and the engine performance can be further enhanced by reducing the ventilation loss of the motor due to the agitated refrigerant.

[0019] According to the present invention, power loss in the speed-increasing gear unit and bearing losses of ball bearings are reduced, enabling the turbocompressor to achieve a higher rotational speed suitable for high-flow refrigerant compression. This compensates for inherent problems with the use of R1233zd(E) refrigerant, which is believed to have difficulty ensuring suitable power due to the low density of the low-pressure refrigerant and its high sonic velocity compared to conventional HFC refrigerants. By adopting an oil-free configuration without a speed-increasing gear unit or ball bearings that require oil lubrication, and using oil-free ceramic bearings, maintenance of lubrication systems, such as replacing lubricating oil and an oil filter, can be eliminated.Furthermore, the turbo cooler can be designed with reduced environmental impact because the maintenance frequency and maintenance-induced refrigerant release are significantly reduced, and the properties of a refrigerant that achieves negative pressure at a saturation temperature of 18°C ​​or lower are utilized, preventing refrigerant from being released into the atmosphere. Furthermore, the turbo cooler offers high reliability at low cost due to a simplified configuration that eliminates the lubrication system. Fig. 1 is a configuration diagram illustrating a turbo cooler according to a first example for explaining features of the present invention. Fig. Figure 2 is a schematic configuration diagram showing a turbo compressor applied to the turbo cooler. Fig. 3 shows a schematic configuration illustrating a turbo compressor according to an embodiment of the present invention. Fig. 4 is an enlarged view of a portion of a drive motor for the turbo compressor shown in Fig. 3 is shown.

[0020] Hereinafter, a non-inventive example and embodiments of the present invention will be described with reference to the attached drawings.

[0021] An example to explain features of the present invention will now be given below with reference to Fig. 1 and Fig. 2 described.

[0022] Fig. 1 shows a configuration diagram of a turbo cooler according to the example. Fig. Figure 2 shows a schematic configuration diagram of a turbo compressor applied to the turbo cooler.

[0023] The turbo cooler 1, as in Fig. 1, is provided with a closed refrigeration circuit 9 in which a turbocompressor 2, a condenser 3, a first decompression device 4, a gas / liquid separator 5 serving as an exhaust gas preheater, a second decompression device 6 and an evaporator 7 are connected in order by a refrigerant line (line) 8.

[0024] The refrigeration cycle 9 of the present example is further connected to a known exhaust gas preheater cycle 10 configured to inject the gaseous refrigerant separated at the gas / liquid separator 5 into the intermediate-pressure refrigerant compressed at a lower-stage compression section 14 of the turbocompressor 2 via an intermediate port. The exhaust gas preheater cycle 10 here is a gas / liquid separation type provided with the gas / liquid separator 5. However, the exhaust gas preheater cycle 10 may be an intercooler type provided with an intercooler to provide heat exchange between a liquid refrigerant and a portion of the refrigerant condensed and liquefied at the condenser 3, which is branched and decompressed. Note that the exhaust gas preheater cycle 10 is not required in the present invention.

[0025] The refrigeration cycle 9 described above is filled with the required amount of R1233zd(E) refrigerant. R1233zd(E) refrigerant has a low global warming potential (GWP) of 5 or less and a low ozone depletion potential (ODP) of 0.00031, and reaches negative pressure at a saturation temperature of 18°C ​​or lower. R1233zd(E) refrigerant is a hydrochlorofluoroolefin (HCFO) refrigerant with a low GWP. R1233zd(E) refrigerant is a low-pressure, low-density refrigerant, approximately 1 / 5 the density of R134a, a hydrofluorocarbon (HFC) refrigerant used in conventional turbo chillers.

[0026] In the present example, the turbo compressor 2 installed in the turbo cooler 1 filled with R1233zd(E) has the following configuration.

[0027] Fig. 2 is a schematic configuration diagram of the turbo compressor 2. The turbo compressor 2 may be a known centrifugal compressor that compresses low-pressure gaseous refrigerant into high-pressure gaseous refrigerant via a rotating impeller and circulates the high-pressure gas through the refrigeration circuit 9.

[0028] The turbocompressor 2 of the present example has a direct-drive configuration in which a rotating shaft 18 is directly connected to a rotor 19A of a motor 19. Lower-stage and upper-stage impellers 15, 17 rotate around the rotating shaft 18, which is driven by the motor 19. The rotating shaft 18 is supported in a manner allowing free rotation by a pair of radial magnetic bearings 20, 21 arranged at the front and rear with respect to a casing 11, and by a pair of opposing magnetic thrust bearings 23, 24.

[0029] In other words, the turbo compressor 2 has the following configuration. The turbo compressor 2 is equipped with the casing 11, which includes a compressor housing 11A and a motor housing 11B connected to the compressor housing 11A. The low-pressure gas refrigerant evaporated at the evaporator 7 is admitted from a refrigerant suction port 12 and flows through an inlet vane 13. Thereafter, the low-pressure gas refrigerant is compressed in two stages: at the lower-stage compression section 14 with the lower-stage impeller 15 and at the upper-stage compression section 16 with the upper-stage impeller 17, and becomes a high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant is discharged from an outlet port of the scroll casing to a condenser 3 outside.The intermediate pressure refrigerant gas is injected from the exhaust gas preheater circuit 10 between the lower-stage compression section 14 and the upper-stage compression section 16 via the intermediate opening.

[0030] The lower-stage impeller 15 and the upper-stage impeller 17 are integrally connected to the rotating shaft 18 at the end to one side of the rotating shaft 18 and separated by a predetermined distance. The rotating shaft 18 is connected to a rotor 19B of the motor 19, thus the rotating shaft 18 of the impellers 15, 17 is directly connected to the motor 19. Furthermore, the motor 19 is provided with the rotor 19A and a stator 19B, is provided substantially centrally inside the motor housing 11B, and is configured to variably control the rotation speed via an inverter (not shown).

[0031] The previously described rotary shaft 18 is supported in a manner allowing free rotation by the pair of magnetic radial bearings 20, 21 provided at the front and rear of the motor 19. A thrust washer 22 is fixedly provided in the rear portion. The pair of magnetic thrust bearings 23, 24 are provided on opposite sides of the thrust washer 22 and also support the rotary shaft 18. Note that a magnetic attraction force is exerted on the pair of magnetic thrust bearings 23, 24 when current flows through the coil, and by centrally providing the thrust washer 22, the axial load received by the rotary shaft 18 is supported.

[0032] According to the configuration described above, the present example has the following actions and effects.

[0033] In the turbo cooler 1 described above, by driving the turbo compressor 2, the low-pressure gaseous refrigerant evaporated in the evaporator 7 is admitted from the suction port 12 and flows through the inlet vane 13. The low-pressure refrigerant is centrifugally compressed in two stages at the lower-stage compression section 14 and the upper-stage compression section 16, first from low pressure to intermediate pressure, then from intermediate pressure to high pressure via the lower-stage impeller 15 and the upper-stage impeller 17, which rotate at high speed. After being discharged into the spiral casing, the refrigerant is supplied to the external condenser 3.

[0034] At the condenser 3, the refrigerant exchanges heat with a cooling medium and is condensed and liquefied. The condensed and liquefied refrigerant flows through the first decompression device 4, the gas / liquid separator 5, which serves as an exhaust gas preheater, and the second decompression device 6, and is subcooled and reduced to a low pressure before being sent to the evaporator 7. The low-pressure liquid refrigerant, which has been sent to the evaporator 7, exchanges heat with a medium to be cooled, absorbs heat from the medium to be cooled, thereby cooling the medium to be cooled, and evaporates itself. The evaporated refrigerant is then fed to the turbocompressor 2 and recompressed, and the process repeats.

[0035] Furthermore, the exhaust gas preheater function for improving the cooling performance can be achieved by evaporating the liquid refrigerant separated at the gas / liquid separator 5 and subcooling the liquid refrigerant to be injected into the intermediate pressure gaseous refrigerant compressed at the lower-stage compression section 14 from the intermediate port of the turbocompressor 2 via the exhaust gas preheater circuit 10.

[0036] The refrigeration circuit 9 of the turbocompressor 1 is filled with R1233zd(E) refrigerant. R1233zd(E) refrigerant is a low-pressure, low-density refrigerant with a low global warming potential (GWP) and low ozone depletion potential (ODP). This refrigerant is considered to have difficulties related to ensuring adequate performance. However, in the present example, a turbocompressor 2 suitable for high-flow refrigerant compression has a configuration in which the rotating shaft 18 of the impellers 15, 17 are directly connected to the motor 19, and the rotating shaft 18 is supported by the magnetic radial bearings 20, 21 and the magnetic thrust bearings 23, 24.

[0037] Accordingly, power loss in the speed-increasing gear unit and bearing losses of ball bearings are reduced, allowing the turbocompressor 2 to achieve a higher rotational speed suitable for high-flow refrigerant compression. This compensates for inherent problems with the use of R1233zd(E) refrigerant, which is believed to have difficulty ensuring suitable power due to the low density of the low-pressure refrigerant and its high speed of sound compared to HFC refrigerants. An oil-free configuration without a speed-increasing gear unit or ball bearings, which require oil lubrication, eliminates the need for lubrication system maintenance, such as replacing lubricating oil and oil filters.

[0038] Consequently, a turbo cooler 1 can be provided in which necessary performance is ensured with the use of R1233zd(E) refrigerant, which is a low-pressure, low-density refrigerant. In addition, the turbo cooler 1 has a reduced environmental impact by reducing the maintenance frequency and maintenance-induced refrigerant release, and by utilizing the properties of a refrigerant that achieves a negative pressure at a saturation temperature of 18°C ​​or lower, preventing refrigerant from being released into the atmosphere. Furthermore, a highly reliable turbo cooler 1 can be provided at low cost due to a simplified configuration that eliminates a lubrication system.

[0039] Note that in the previously described example, an example of a turbocompressor 2 with two-stage compression was described. However, in the present invention, the turbocompressor 2 is not limited to two-stage compression and may have a single stage, or three or more stages. In other words, the turbocompressor 2 only needs to have a direct drive configuration in which the rotating shaft 18 of an impeller(s) is directly connected to the motor 19, and the rotating shaft 18 is supported by magnetic bearings.

[0040] Now, an embodiment of the present invention will be described with reference to Fig. 3 and Fig. 4 described.

[0041] The present embodiment differs from the example in that the rotary shaft 18 is supported in a manner allowing free rotation by oil-free ceramic bearings 25, 26. Other points are similar to the example, so their descriptions are omitted here.

[0042] In the present embodiment, the rotary shaft 18 is supported in a manner that allows free rotation by the oil-free ceramic sliding bearings or ball bearings 25, 26 (hereinafter referred to as ceramic bearings in the present invention) as shown in Fig. 3, instead of the magnetic radial bearings 20, 21 and the magnetic thrust bearings 23, 24.

[0043] The ceramic bearings 25, 26 are made of silicon nitride, have high durability and a long service life despite being oil-free. In the present embodiment, the ceramic bearings 25, 26 can be cooled and lubricated by liquid refrigerant extracted from the refrigeration circuit 9. In other words, a portion of high-pressure liquid refrigerant condensed and liquefied at the condenser 3 is extracted from the refrigeration circuit 9, or a quantity of low-pressure liquid refrigerant is extracted from the line or a device between the condenser 3 and the evaporator 7 via a refrigerant extraction line 27. The flow of the extracted liquid refrigerant is adjusted at a flow control valve 28 and supplied to bearing housings 25A, 26A of the ceramic bearings 25, 26. Thus, the ceramic bearings 25, 26 can be cooled and lubricated by the liquid refrigerant.

[0044] In the present embodiment, in addition to the ceramic bearings 25, 26, the motor 19 can also be cooled by the liquid refrigerant described above. In such a configuration, a portion of the liquid refrigerant supplied through the refrigerant extraction line 27 and the flow control valve 28 is introduced into an air gap 19D of the motor 19 through a refrigerant injection port 19C provided in the stator 19B of the motor 19, thereby allowing the rotor 19A and the stator 19B to be cooled. After cooling the ceramic bearings 25, 26 and the motor 19, the refrigerant is collected in a refrigerant sump 29 of the motor housing 11B before being returned to the low-pressure region of the refrigeration circuit 9, i.e., the evaporator 7 and the like, via a refrigerant outlet line 30.

[0045] Furthermore, in order to prevent a loss of ventilation at the motor 19 due to the rapid discharge of the liquid refrigerant which has entered the air gap 19D as shown in Fig. 4, spiral grooves 32A, 32B, 32C, which allow the liquid refrigerant introduced into the air space 19D to flow axially outward, are provided on at least one of the outer peripheral surface of the rotor 19A of the motor 19, the inner peripheral surface of the stator 19B, and the outer peripheral surface of the balancing ring 31 provided on the end surface of the rotor 19A. Note that, of the spiral grooves 32A, 32B, 32C, from a machining perspective, the spiral groove 32C is preferably provided on the outer peripheral surface of the balancing ring 31.

[0046] According to this embodiment, in which the rotating shaft 18 is supported by oil-free ceramic bearings 25, 26 in a similar manner to that of the example, power loss in the speed-increasing gear unit and bearing losses of ball bearings are reduced, enabling the turbocompressor 2 to achieve a higher rotation speed suitable for high-flow refrigerant compression, thereby compensating for inherent problems with the use of R1233zd(E) refrigerant, which is believed to have difficulty ensuring suitable power due to the low density of the low-pressure refrigerant and its high sonic speed compared to conventional HFC refrigerants. By implementing an oil-free configuration without a speed-increasing gear unit or ball bearings, which require oil lubrication, maintenance of lubrication systems, such as replacing lubricating oil and oil filters, can be eliminated.

[0047] Consequently, a turbo cooler 1 can be provided in which necessary performance is ensured with the use of R1233zd(E) refrigerant, which is a low-pressure, low-density refrigerant. In addition, the turbo cooler 1 has a reduced environmental impact by reducing the maintenance frequency and maintenance-induced refrigerant release, and by utilizing the properties of a refrigerant that achieves a negative pressure at a saturation temperature of 18°C ​​or lower, preventing refrigerant from being released into the atmosphere. Furthermore, a highly reliable turbo cooler 1 can be provided at low cost due to a simplified configuration that eliminates a lubrication system.

[0048] Furthermore, the liquid refrigerant, which serves as a cooling and lubricating medium for the bearing housings 25A, 26A of the ceramic bearings 25, 26 and the air gap 19D of the motor 19, can be circulated from the cooling circuit 9 through the refrigerant extraction line 27, the flow control valve 28, and the refrigerant outlet line 30. By cooling and lubricating the ceramic bearings 25, 26 with the liquid refrigerant, the durability of the ceramic bearings 25, 26 can be improved, and heat loss and fail-safe operations can be reduced by ensuring the cooling performance of the liquid refrigerant that cools the high-speed motor 19. This configuration cools and lubricates the oil-free ceramic bearings 25, 26 and the motor 19 with their improved durability and performance, providing the turbo cooler 1 with high performance and reliability.

[0049] Furthermore, in the above-described embodiment, the spiral grooves 32A, 32B, 32C, which allow the liquid refrigerant supplied to the air gap 19D of the motor 19 to flow axially outward, are provided on at least one of the inner peripheral surface of the stator 19B of the motor 19, the outer peripheral surface of the rotor 19A, and the outer peripheral surface of the balancing ring 31 provided on the end surface of the rotor 19A. Accordingly, the liquid refrigerant supplied into the air gap 19D can be quickly discharged to the outside via the spiral grooves 32A, 32B, 32C. Consequently, the cooling effect of the liquid refrigerant on the motor 19 can be further enhanced, and the engine performance can be further increased by reducing a ventilation loss of the motor 19 due to the agitated liquid refrigerant.

[0050] Furthermore, in the above-described embodiment, the motor 19 is cooled by supplying high-pressure liquid refrigerant or low-pressure liquid refrigerant from the refrigerant injection port 19C. However, instead of the liquid refrigerant, low-pressure gaseous refrigerant formed by evaporation at the evaporator 7 may be supplied to cool the motor 19. In a configuration in which low-pressure gaseous refrigerant is supplied as the cooling medium for the motor 19, the shaking loss due to the motor 19 can be reduced more than in configurations in which liquid refrigerant is supplied. Therefore, the motor 19 can be sufficiently cooled, thus enabling heat loss and the like to be reduced; and shaking loss can be further reduced, providing high power to the motor 19 and enabling higher speeds.

[0051] Note that the present invention is not limited to the invention according to the above-described embodiment. For example, in the above-described example and embodiment, an example of application of the refrigeration cycle 9 equipped with the exhaust gas preheater cycle 10 is described. However, a heat pump cycle of a turbo heat pump can be similarly applied. Furthermore, the example may have a configuration similar to the embodiment in which the magnetic bearings 20, 21, 23, 24 and the motor 19 can be cooled by the refrigerant (another embodiment). List of reference symbols 1 turbo cooler 2 turbo compressors 3 Capacitor 4 First decompression device 5 gas / liquid separators 6 Second decompression device 7 evaporators 8 Refrigerant line (line) 9 Cooling circuit 14 Lower-stage compression section 15 Lower-stage impeller 16 Upper-stage compression section 17 Upper-stage impeller 18 Rotating shaft 19 Engine 19A rotor 19B Stator 19C Refrigerant injection opening 19D Air gap 20, 21 Magnetic radial bearing 23, 24 Magnetic thrust bearing 25, 26 Ceramic bearing 25A, 26A bearing housing 27 Refrigerant extraction line 28 Flow control valve 29 Refrigerant sump 30 Refrigerant outlet line 31 balancing ring 32A, 32B, 32C spiral groove

Claims

[1] Turbo cooler (1), comprising: a closed refrigeration circuit (9) comprising a turbocompressor (2), a condenser (3), a decompression device (4) and an evaporator (7) connected in sequence by lines (8) and filled with a refrigerant, wherein the refrigerant is a low-pressure refrigerant R1233zd(E) with low global warming potential and low ozone depletion potential, the turbocompressor (2) has a direct drive configuration in which a rotating shaft (18) of an impeller (15, 17) is directly connected to a motor (19), the rotating shaft (18) is supported by a magnetic bearing (20,21,23,24), the turbo cooler (1) is configured so that a liquid refrigerant can be circulated from the cooling circuit (9) as a cooling and lubricating medium for the magnetic bearing (20, 21, 23, 24) and an air gap (19D) of the motor (19), and the turbo compressor (2) has a refrigerant injection port (19C) provided in a stator (19B) of the motor (19) so that the liquid refrigerant can be introduced through the refrigerant injection port (19C) into the air gap (19D) of the motor (19), thereby cooling a rotor (19A) and the stator (19B) of the motor (19). [2] Turbo cooler (1), comprising: a closed refrigeration circuit (9) comprising a turbocompressor (2), a condenser (3), a decompression device (4) and an evaporator (7) connected in sequence by lines (8) and filled with a refrigerant, wherein the refrigerant is a low-pressure refrigerant R1233zd(E) with low global warming potential and low ozone depletion potential, the turbocompressor (2) has a direct drive configuration in which a rotating shaft (18) of an impeller (15, 17) is directly connected to a motor (19), the rotating shaft (18) is supported by an oil-free ceramic bearing (25,26), the turbo cooler (1) is configured so that a liquid refrigerant can be circulated from the cooling circuit (9) as a cooling and lubricating medium for a bearing housing (25A, 25B) of the ceramic bearing (25, 26) and an air gap (19D) of the motor (19), and the turbo compressor (2) has a refrigerant injection port (19C) provided in a stator (19B) of the motor (19) so that the liquid refrigerant can be introduced through the refrigerant injection port (19C) into the air gap (19D) of the motor (19), thereby cooling a rotor (19A) and the stator (19B) of the motor (19). [3] Turbo cooler (1) according to claim 1 or 2, wherein a spiral groove (32A, 32B, 32C) allowing the liquid refrigerant supplied to the air gap (19D) of the motor (19) to flow axially outward is provided at least on an inner peripheral surface of the stator (19B) of the motor (19), an outer peripheral surface of the rotor (19A) of the motor (19), and an outer peripheral surface of a balancing ring (31) provided on an end surface of the rotor (19A).

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