Turbo refrigerator and method for operating the same

Abstract

To reduce the equipment introduction cost / equipment maintenance cost of a turbo refrigerator, to apply a low GWP refrigerant, and to enable a service temperature of over 100°C.SOLUTION: A turbo refrigerator 1 according to the present disclosure comprises a turbo compressor 3 that compresses refrigerant, a condenser 5 that condenses the refrigerant discharged from the turbo compressor, an expansion valve 7 that expands the refrigerant guided from the condenser, and an evaporator 9 that evaporates the refrigerant guided from the expansion valve. The refrigerant sealed in a refrigerant circulation circuit 11, which is formed by sequentially connecting the turbo compressor, condenser, expansion valve, and evaporator, is HCFO-1233ydZ, HCFO-1233ydE, or a mixture thereof, and a bearing supporting a rotating shaft 19 of the turbo compressor is a magnetic bearing 21.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a turbo chiller and an operating method thereof. [Background technology]

[0002] In recent years, in response to global warming, refrigerants used in turbo chillers have been increasingly being replaced with refrigerants with low global warming potential (GWP) (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-73624 A [Patent Document 2] International Publication No. 2019 / 039510 Summary of the Invention [Problem to be solved by the invention]

[0004] For turbo chillers used in environments containing precision equipment such as data centers, there is a demand for the temperature of the chilled water used for heat exchange with the refrigerant in the evaporator to be between 20°C and 35°C to prevent condensation. Also, for turbo chillers (heat pumps) used in the distillation processes of chemical plants, there is a demand for the heat source water used for heat exchange with the refrigerant in the evaporator to be above 40°C.

[0005] The refrigerant described in Patent Document 1, for example, HFO-1234ze(E), has a low boiling point of −19° C. When such a low-boiling-point refrigerant is used in a turbo chiller, the High Pressure Gas Safety Act must be complied with, increasing the cost of introducing the equipment.

[0006] The refrigerants described in Patent Document 1, for example HCFO-1233zd(E) and HFO-1336mzz(E), have boiling points of 18°C ​​and 33°C, respectively, and do not require compliance with the High Pressure Gas Safety Act. However, in a turbo chiller using this refrigerant, if chilled water / heat source water with a temperature above 18°C ​​is used for heat exchange in the evaporator, the evaporator pressure will exceed atmospheric pressure. Such turbo chillers require compliance with the Industrial Safety and Health Act.

[0007] The refrigerant (heat cycle working medium) described in Patent Document 2 is used by mixing with lubricating oil. In turbo chillers that use lubricating oil, periodic maintenance such as replacement of bearings, lubricating oil, and oil filters is essential.

[0008] As the operating temperature of a turbo chiller increases, the viscosity of the lubricating oil decreases, and the lubricating performance decreases. For this reason, in Patent Document 2, it is difficult to set the operating temperature to above 100°C.

[0009] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a turbo chiller and an operating method thereof that reduce equipment installation costs.

[0010] Another object of the present disclosure is to provide a turbo chiller and an operating method thereof that can reduce equipment maintenance costs.

[0011] Another object of the present disclosure is to provide a turbo chiller that uses a low GWP refrigerant and can achieve an operating temperature of above 100°C, and a method for operating the same. [Means for solving the problem]

[0012] In order to solve the above problems, the turbo chiller and the operating method thereof disclosed herein employ the following measures.

[0013] The turbo chiller according to the present disclosure comprises a turbo compressor that compresses a refrigerant, a condenser that condenses the refrigerant discharged from the turbo compressor, an expansion valve that expands the refrigerant guided from the condenser, and an evaporator that evaporates the refrigerant guided from the expansion valve, wherein the refrigerant sealed in a refrigerant circulation circuit formed by sequentially connecting the turbo compressor, the condenser, the expansion valve, and the evaporator is HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof, and the bearing that supports the rotating shaft of the turbo compressor is a magnetic bearing.

[0014] The method of operating a turbo chiller according to the present disclosure is a method of operating a turbo chiller comprising: a turbo compressor that compresses a refrigerant, a condenser that condenses the refrigerant discharged from the turbo compressor, an expansion valve that expands the refrigerant guided from the condenser, an evaporator that evaporates the refrigerant guided from the expansion valve, a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence, a magnetic bearing that supports a rotating shaft of the turbo compressor, and a heat exchange path through which a heat exchange medium that exchanges heat with the refrigerant in the evaporator passes, wherein HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof is sealed within the refrigerant circulation circuit as a refrigerant, and the heat exchange medium at a temperature of above 40°C is supplied to the heat exchange path.

[0015] The method of operating a turbo chiller according to the present disclosure is a method of operating a turbo chiller comprising: a turbo compressor that compresses a refrigerant, a condenser that condenses the refrigerant discharged from the turbo compressor, an expansion valve that expands the refrigerant guided from the condenser, an evaporator that evaporates the refrigerant guided from the expansion valve, a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence, and a heat exchange path through which a heat exchange medium that exchanges heat with the refrigerant in the evaporator passes, wherein HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof is sealed within the refrigerant circulation circuit as a refrigerant, and the temperature of the heat exchange medium at an outlet of the heat exchange path is controlled to be less than 48°C. Effect of the Invention

[0016] According to the present disclosure, by using a magnetic bearing as the bearing that supports the rotating shaft of the turbo compressor, lubricating oil is not required, and therefore equipment maintenance costs can be reduced.

[0017] According to the present disclosure, by using HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof as a refrigerant, the cost of introducing equipment can be reduced.

[0018] According to the present disclosure, a turbo chiller is provided that can realize an operating temperature of over 100°C while using a low GWP refrigerant. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram illustrating a turbo chiller according to an embodiment of the present disclosure. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, one embodiment of a turbo chiller and an operating method thereof according to the present disclosure will be described with reference to the drawings.

[0021] In this specification, the term "turbo chiller" is a general term for a chiller equipped with a turbo compressor or a heat pump equipped with a turbo compressor.

[0022] FIG. 1 shows a schematic configuration diagram of a turbo chiller according to this embodiment. The turbo chiller 1 comprises a turbo compressor 3 that compresses a refrigerant, a condenser 5 that condenses the refrigerant compressed by the turbo compressor 3, an expansion valve 7 that expands the refrigerant condensed in the condenser 5, and an evaporator 9 that evaporates the refrigerant expanded by the expansion valve 7.

[0023] The turbo chiller 1 includes a refrigerant circulation circuit 11 in which a turbo compressor 3, a condenser 5, an expansion valve 7, and an evaporator 9 are connected in sequence.

[0024] A refrigerant is sealed in the refrigerant circulation circuit 11. The refrigerant is HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof. The boiling point of HCFO-1233yd(Z) is 54°C, the boiling point of HCFO-1233yd(E) is 48°C, and the global warming potential (GWP) is less than 1.

[0025] The turbo compressor 3 is a centrifugal two-stage compressor equipped with two impellers 13a, 13b, and is driven by an electric motor 15 whose rotation speed is controlled by an inverter device (not shown). The inverter device has its output controlled by a control unit (not shown). The number of impellers is not limited, and a single-stage compressor with one impeller may be used.

[0026] The refrigerant suction ports (not shown) of the impellers 13a, 13b of the turbo compressor 3 are provided with inlet guide vanes (not shown) that control the amount of suctioned refrigerant flow, making it possible to control the capacity of the turbo chiller 1.

[0027] The turbo compressor 3 and the electric motor 15 are housed in a sealed state in a casing 17. The casing 17 is made of a metal such as an aluminum alloy. The casing 17 can be opened and closed for maintenance and the like.

[0028] The rotating shaft 19 of the turbo compressor 3 is rotatably supported by a magnetic bearing 21. By adopting the magnetic bearing 21, it is possible to omit the installation of a lubricating oil system. Since there is no need to replace the bearings or lubricating oil, the equipment maintenance costs can be reduced.

[0029] A first radial magnetic bearing coil 21a of the magnetic bearing 21 is provided on the impellers 13a, 13b side of the electric motor 15, and a second radial magnetic bearing coil 21b of the magnetic bearing 21 is provided on the opposite side of the impellers 13a, 13b of the electric motor 15. The first radial magnetic bearing coil 21a and the second radial magnetic bearing coil 21b support the rotating shaft 19 in the radial direction.

[0030] Although not shown in the figures, for example, a disk may be fixed to the end of the rotating shaft 19 on the side opposite the impellers 13a and 13b (the second radial magnetic bearing coil 21b side), and multiple pairs of thrust magnetic bearing coils may be arranged at positions sandwiching both sides of the disk. The disk is positioned in the thrust direction while being levitated by the multiple pairs of thrust magnetic bearing coils. This allows the positions of the rotating shaft 19 and the impellers 13a and 13b in the thrust direction to be accurately determined.

[0031] The electric motor 15 includes a rotor 23 that rotates around a central axis, and a generally cylindrical stator 25 that is provided around the rotor 23 with a predetermined gap. The rotational output of the rotor 23 is transmitted to the impellers 13a, 13b via the rotary shaft 19.

[0032] The condenser 5 is a heat exchanger that condenses the high-temperature, high-pressure gas refrigerant guided from the turbo compressor 3. The condenser 5 is provided therein with a first heat exchange path 27. The first heat exchange path 27 may be, for example, a heat transfer tube inserted into the condenser 5.

[0033] In the condenser 5, heat exchange takes place between the (gas) refrigerant guided from the turbo compressor 3 and the first heat exchange medium M1 flowing through the first heat exchange path 27. Through this heat exchange, the refrigerant is cooled and the first heat exchange medium M1 is heated.

[0034] The heated first heat exchange medium M1 flows through the first heat exchange path 27 toward the outside of the condenser 5, and after heat is discharged in a cooling tower (not shown), is guided back to the condenser 5. The flow of the refrigerant supplied to the condenser 5 and the flow of the first heat exchange medium M1 supplied to the first heat exchange path 27 should be countercurrent to each other.

[0035] In the expansion valve 7, the liquid refrigerant condensed in the condenser 5 is expanded.

[0036] The evaporator 9 is a heat exchanger that evaporates the liquid refrigerant expanded by the expansion valve 7. The evaporator 9 includes a second heat exchange path 29 therein. The second heat exchange path 29 may be, for example, a heat transfer tube inserted into the evaporator 9.

[0037] In the evaporator 9, heat exchange takes place between the (liquid) refrigerant expanded by the expansion valve 7 and the second heat exchange medium M2 flowing in the second heat exchange path 29. Through this heat exchange, the refrigerant is heated and evaporated, and the second heat exchange medium M2 is cooled.

[0038] The cooled second heat exchange medium M2 flows through the second heat exchange path 29 towards the outside of the evaporator 9 and is introduced into a device (not shown) provided outside the turbo chiller 1 to be heated. The second fluid heated in the device outside the evaporator 9 flows back into the second heat exchange path 29 and exchanges heat with the refrigerant in the evaporator 9 again.

[0039] The temperature of the second heat exchange medium M2 at the inlet of the second heat exchange path 29 (evaporator inlet temperature) is designed to exceed 40° C. In this type of turbo chiller 1, waste heat from another source can be used as the second heat exchange medium M2. This type of turbo chiller 1 is also suitable for use in areas with high outside air temperatures.

[0040] When the turbo chiller 1 is a heat pump, the refrigerant absorbs heat from a heat source in the evaporator 9 and releases the heat in the condenser 5. By operating the turbo chiller 1 so as to supply the second heat exchange medium (heat source water) M2 at a temperature above 40°C to the second heat exchange path 29 of the evaporator 9, the amount of heat released in the condenser 5 can be increased.

[0041] The temperature of the second heat exchange medium M2 at the outlet of the second heat exchange path 29 (evaporator outlet temperature) may be less than 48° C. By operating the second heat exchange medium M2 so that the outlet temperature is controlled to be less than 48° C., the pressure inside the evaporator 9 can be maintained below atmospheric pressure. Such a turbo chiller 1 does not require application of the Industrial Safety and Health Act, thereby reducing the cost of introducing the equipment.

[0042] <Additional Notes> The turbo chiller and the operating method thereof described in the above-described embodiment can be understood, for example, as follows.

[0043] A turbo chiller (1) according to a first aspect of the present disclosure comprises a turbo compressor (3) that compresses a refrigerant, a condenser (5) that condenses the refrigerant discharged from the turbo compressor, an expansion valve (7) that expands the refrigerant guided from the condenser, and an evaporator (9) that evaporates the refrigerant guided from the expansion valve, in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence and the refrigerant sealed in a refrigerant circulation circuit (11) is HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof, and a bearing that supports a rotating shaft (19) of the turbo compressor is a magnetic bearing (21).

[0044] Using magnetic bearings to support the rotating shaft of the turbo compressor eliminates the need for lubricating oil. Since turbo chillers do not use lubricating oil, there is no need to change the lubricating oil, reducing the number of equipment maintenance items.

[0045] When the operating temperature of a turbo chiller becomes high, the viscosity of the lubricating oil decreases and the lubricating performance decreases. Because the turbo chiller according to the present disclosure does not use lubricating oil, the operating temperature of the turbo chiller can be set without being limited by the type of lubricating oil.

[0046] The global warming potential (GWP) of HCFO-1233yd(Z), HCFO-1233yd(E) or their mixtures is less than 1, posing a small burden on the environment.

[0047] The boiling points of HCFO-1233yd(Z), HCFO-1233yd(E) or mixtures thereof are 48°C or higher. When these refrigerants are used in a turbo chiller, the High Pressure Gas Safety Act does not apply. Therefore, the cost of introducing the equipment can be reduced compared to turbo chillers that use refrigerants such as HFO-1234yf that require the application of the High Pressure Gas Safety Act.

[0048] According to the above disclosure, a heat pump using a low GWP refrigerant with an operating temperature of over 100°C can be realized.

[0049] In a turbo chiller according to a second aspect of the present disclosure, the evaporator in the first aspect described above has a heat exchange path (second heat exchange path 29) inside through which a heat exchange medium (second heat exchange medium M2) that exchanges heat with the refrigerant flows, and the temperature of the heat exchange medium at the inlet of the heat exchange path is greater than 40°C.

[0050] When the temperature of the heat exchange medium exceeds 40°C, the temperature of the evaporator also exceeds 40°C. Because centrifugal chillers that use magnetic bearings do not use lubricating oil, a decrease in the viscosity of the lubricating oil does not pose a problem even if the temperature inside the evaporator exceeds 40°C.

[0051] In a turbo chiller according to a third aspect of the present disclosure, the evaporator in the first aspect above has a heat exchange path therein through which a heat exchange medium flows for exchanging heat with the refrigerant, and the temperature of the heat exchange medium at an outlet of the heat exchange path is less than 48°C.

[0052] By setting the temperature of the heat exchange medium at the outlet of the heat exchange path lower than the boiling point of the refrigerant (less than 48°C), the evaporator pressure can be made lower than atmospheric pressure. This makes it unnecessary to apply the Industrial Safety and Health Act, and reduces the cost of introducing the equipment.

[0053] A fourth aspect of the present disclosure provides a method for operating a turbo chiller comprising: a turbo compressor that compresses a refrigerant; a condenser that condenses the refrigerant discharged from the turbo compressor; an expansion valve that expands the refrigerant guided from the condenser; an evaporator that evaporates the refrigerant guided from the expansion valve; a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence; a magnetic bearing that supports a rotating shaft of the turbo compressor; and a heat exchange path through which a heat exchange medium that exchanges heat with the refrigerant in the evaporator passes, wherein HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof is sealed within the refrigerant circulation circuit as a refrigerant, and the heat exchange medium at a temperature of above 40°C is supplied to the heat exchange path.

[0054] A fifth aspect of the present disclosure provides a method for operating a turbo chiller comprising: a turbo compressor that compresses a refrigerant; a condenser that condenses the refrigerant discharged from the turbo compressor; an expansion valve that expands the refrigerant guided from the condenser; an evaporator that evaporates the refrigerant guided from the expansion valve; a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence; and a heat exchange path through which a heat exchange medium that exchanges heat with the refrigerant in the evaporator passes, wherein HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof is sealed within the refrigerant circulation circuit as a refrigerant, and the temperature of the heat exchange medium at an outlet of the heat exchange path is controlled to be less than 48°C. [Explanation of symbols]

[0055] 1. Turbo Refrigeration Unit 3. Turbo Compressor 5. Condenser 7 Expansion valve 9. Evaporator 11 Refrigerant circulation circuit 13a, 13b Impeller 15 Electric motor 17 Casing 19 Rotational Axis 21 Magnetic bearings 21a First radial magnetic bearing coil 21b Second radial magnetic bearing coil 23 Rotor 25 Stator 27 First heat exchange path 29 Second heat exchange path (heat exchange path)

Claims

1. a turbo compressor that compresses a refrigerant, a condenser that condenses the refrigerant discharged from the turbo compressor, an expansion valve that expands the refrigerant guided from the condenser, and an evaporator that evaporates the refrigerant guided from the expansion valve, the refrigerant sealed in a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence is HCFO-1233yd(Z), HCFO-1233yd(E), or a mixture thereof; A turbo chiller, wherein a bearing supporting a rotating shaft of the turbo compressor is a magnetic bearing.

2. The evaporator includes a heat exchange path therein through which a heat exchange medium that exchanges heat with the refrigerant flows, The turbo chiller according to claim 1 , wherein the temperature of the heat exchange medium at an inlet of the heat exchange path is greater than 40° C.

3. The evaporator includes a heat exchange path therein through which a heat exchange medium that exchanges heat with the refrigerant flows, The turbo chiller according to claim 1 , wherein the temperature of the heat exchange medium at an outlet of the heat exchange path is less than 48° C.

4. a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence; a magnetic bearing supporting a rotating shaft of the turbo compressor; and a heat exchange path through which a heat exchange medium passes that exchanges heat with the refrigerant in the evaporator, the method comprising the steps of: In the refrigerant circulation circuit, HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof is sealed as a refrigerant; A method for operating a turbo chiller, comprising: supplying the heat exchange medium at a temperature of more than 40°C to the heat exchange path.

5. A method for operating a turbo chiller comprising: a turbo compressor that compresses a refrigerant; a condenser that condenses the refrigerant discharged from the turbo compressor; an expansion valve that expands the refrigerant guided from the condenser; an evaporator that evaporates the refrigerant guided from the expansion valve; a refrigerant circulation circuit in which the turbo compressor, the condenser, the expansion valve, and the evaporator are connected in sequence; and a heat exchange path through which passes a heat exchange medium that exchanges heat with the refrigerant in the evaporator, the method comprising the steps of: In the refrigerant circulation circuit, HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof is sealed as a refrigerant; A method for operating a turbo chiller, comprising: controlling a temperature of the heat exchange medium at an outlet of the heat exchange path to be less than 48°C.

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