Turbo refrigerator and method for operating the same

Abstract

The purpose of the present disclosure is to suppress equipment introduction cost / equipment maintenance cost of a turbo refrigerator, to use a low-GWP refrigerant, and to make it possible to realize a use temperature of more than 100°C. A turbo refrigerator 1 according to 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. The refrigerant sealed in a refrigerant circulation circuit 11 formed by sequentially connecting the turbo compressor, the condenser, the expansion valve, and the evaporator is HCFO-1233ydZ, HCFO-1233ydE, or a mixture thereof, and a bearing that supports the rotary shaft (19) of the turbo compressor is a magnetic bearing (21).

Description

Centrifugal chiller and its operating method

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

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

[0003] JP 2019-73624 A International Publication No. 2019 / 039510

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

[0005] The refrigerants described in Patent Document 1, for example, HFO-1234ze(E), have 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 applied, which increases the cost of introducing the equipment.

[0006] The refrigerants described in Patent Document 1, such as HCFO-1233zd(E) and HFO-1336mzz(E), have boiling points of 18°C ​​and 33°C, respectively, and are not subject to 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 are subject to the Industrial Safety and Health Act.

[0007] The refrigerant (heat cycle working medium) described in Patent Document 2 is used in combination with lubricating oil. Centrifugal chillers that use lubricating oil require periodic maintenance such as replacing bearings, lubricating oil, and oil filters.

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

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

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

[0011] An 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 an operating method thereof.

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

[0013] The turbo chiller according to the present disclosure includes 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] A method for operating a turbo chiller according to the present disclosure includes: 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 passes that exchanges heat with the refrigerant in the evaporator, wherein HCFO-1233yd(Z), HCFO-1233yd(E), or a mixture thereof is sealed within the refrigerant circulation circuit, and the heat exchange medium at a temperature above 40°C is supplied to the heat exchange path.

[0015] A method for operating a turbo chiller according to the present disclosure is 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, and the temperature of the heat exchange medium at an outlet of the heat exchange path is controlled to be less than 48°C.

[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, thereby reducing equipment maintenance costs.

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

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

[0019] 1 is a schematic configuration diagram illustrating a turbo chiller according to an embodiment of the present disclosure. FIG.

[0020] Hereinafter, an 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] A schematic configuration diagram of a turbo chiller according to this embodiment is shown in Figure 1. The turbo chiller 1 includes 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 within 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, and the boiling point of HCFO-1233yd(E) is 48°C, and the global warming potential (GWP) of these refrigerants 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 the turbo compressor may have only one impeller, making it a single-stage compressor.

[0026] The refrigerant intake ports (not shown) of the impellers 13 a, 13 b of the turbo compressor 3 are provided with inlet guide vanes (not shown) that control the intake refrigerant flow rate, 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 metal such as an aluminum alloy, and can be opened and closed for maintenance and other purposes.

[0028] The rotating shaft 19 of the turbo compressor 3 is rotatably supported by a magnetic bearing 21. By employing 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, 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 electric motor 15 from the impellers 13a, 13b. 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, for example, a disk may be fixed to the end of the rotating shaft 19 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 on either side of the disk. The disk is positioned in the thrust direction while 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 between them. The rotational output of the rotor 23 is transmitted to the impellers 13 a, 13 b 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 includes a first heat exchange path 27 therein. The first heat exchange path 27 may be, for example, a heat transfer tube inserted into the condenser 5.

[0033] In the condenser 5, the (gas) refrigerant guided from the turbo compressor 3 and the first heat exchange medium M flowing in the first heat exchange path 27 are mixed. １ By this heat exchange, the refrigerant is cooled and the first heat exchange medium M １ is heated.

[0034] Heated first heat exchange medium M １ The refrigerant flows through the first heat exchange path 27 toward the outside of the condenser 5, and after heat is removed in a cooling tower (not shown), it is guided back to the condenser 5. The flow of the refrigerant supplied to the condenser 5 and the first heat exchange medium M supplied to the first heat exchange path 27 are １ It is best to make the flow countercurrent to the flow of the 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, the (liquid) refrigerant expanded by the expansion valve 7 and the second heat exchange medium M flowing in the second heat exchange path 29 are mixed. ２ By this heat exchange, the refrigerant is heated and evaporated, and the second heat exchange medium M ２ is cooled.

[0038] Cooled second heat exchange medium M ２ The second fluid flows through the second heat exchange path 29 toward the outside of the evaporator 9 and is introduced into a device (not shown) provided outside the turbo chiller 1 where it is 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 again within the evaporator 9.

[0039] The second heat exchange medium M at the inlet of the second heat exchange path 29 ２ The temperature of the second heat exchange medium M (evaporator inlet temperature) is designed to exceed 40°C. ２ This turbo chiller 1 is also suitable for use in areas where the outside air temperature is high.

[0040] When the turbo chiller 1 is a heat pump, the refrigerant absorbs heat from the heat source in the evaporator 9 and releases the heat in the condenser 5. ２ By operating the evaporator 9 so that the refrigerant is supplied 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 second heat exchange medium M at the outlet of the second heat exchange path 29 ２ The temperature of the second heat exchange medium M (evaporator outlet temperature) may be less than 48°C. ２ By operating the turbo chiller 1 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. This type of turbo chiller 1 does not require application of the Industrial Safety and Health Act, so the cost of introducing the equipment can be reduced.

[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 includes 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, wherein the refrigerant sealed in a refrigerant circulation circuit (11) 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 a bearing that supports a rotating shaft (19) of the turbo compressor is a magnetic bearing (21).

[0044] By using magnetic bearings to support the rotating shaft of the turbo compressor, lubrication oil is no longer necessary.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] As the operating temperature of a turbo chiller increases, the viscosity of the lubricating oil decreases, resulting in a decrease in lubricating performance. However, 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] HCFO-1233yd(Z), HCFO-1233yd(E) or a mixture thereof has a global warming potential (GWP) of less than 1, and therefore poses a small burden on the environment.

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

[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 according to the first aspect has a heat exchange medium (second heat exchange medium M) therein that exchanges heat with the refrigerant. ２ ) flows through a heat exchange path (second heat exchange path 29), and the temperature of the heat exchange medium at the inlet of the heat exchange path is higher 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 turbo 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 according to the first aspect described above has a heat exchange path therein through which a heat exchange medium flows that exchanges 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 to a temperature lower than the boiling point of the refrigerant (less than 48°C), the evaporator pressure can be made lower than atmospheric pressure, which eliminates the need for compliance with the Industrial Safety and Health Act and reduces the cost of introducing equipment.

[0053] A fourth aspect of the present disclosure provides a method for operating a turbo chiller including 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 passes that exchanges heat with the refrigerant in the evaporator, wherein HCFO-1233yd(Z), HCFO-1233yd(E), or a mixture thereof is sealed within the refrigerant circulation circuit, and the heat exchange medium at a temperature 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 including 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, and the temperature of the heat exchange medium at an outlet of the heat exchange path is controlled to be less than 48°C.

[0055] REFERENCE SIGNS LIST 1 turbo chiller 3 turbo compressor 5 condenser 7 expansion valve 9 evaporator 11 refrigerant circulation circuit 13a, 13b impeller 15 electric motor 17 casing 19 rotating shaft 21 magnetic bearing 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 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 led from the condenser; and an evaporator that evaporates the refrigerant led from the expansion valve; wherein the refrigerant sealed in a refrigerant circulation circuit formed by the turbo compressor, condenser, expansion valve, and evaporator connected in sequence is HCFO-1233yd(Z), HCFO-1233yd(E), or a mixture thereof; and wherein the bearing that supports the rotating shaft of the turbo compressor is a magnetic bearing.

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

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

4. 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 the 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, and the heat exchange medium at a temperature above 40°C is supplied 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 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, and the temperature of the heat exchange medium at the outlet of the heat exchange path is controlled to be less than 48°C.

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