EP4628732A1

EP4628732A1 - Refrigeration heat pump unit

Info

Publication number: EP4628732A1
Application number: EP25167525.2A
Authority: EP
Inventors: Kai DENG; Jun Cao; Jiedong LI; Qunyi MA
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2024-04-01
Filing date: 2025-03-31
Publication date: 2025-10-08
Also published as: US20250305728A1; CN120799754A

Abstract

There is provided a refrigeration heat pump unit (100), including a refrigerant circuit formed by a centrifugal compressor (1), a condenser (2), a throttling device, and an evaporator (3). The centrifugal compressor (1) includes a housing (10), a first motor (11), a second motor (12), a first compression chamber (13), a second compression chamber (14), a first impeller (15), a second impeller (16), and a controller (4). The first motor (11) is disposed inside the housing (10). The second motor (12) is disposed inside the housing (10) and disposed opposite to the first motor (11). The first compression chamber (13) is disposed at an end portion of the housing (10) close to the first motor (11) and includes a first suction port (131) and a first discharge port (132). The second compression chamber (14) is disposed at an end portion of the housing (10) close to the second motor (12) and includes a second suction port (141) and a second discharge port (142). The first impeller (15) is driven by the first motor (11), and the second impeller (16) is driven by the second motor (12). The controller (4) is configured to turn on the first motor (11) and turn off the second motor (12) in response to a first working condition, turn off the first motor (11) and turn on the second motor (12) in response to a second working condition, and turn on the first motor (11) and the second motor (12) in response to a third working condition.

Description

Technical Field

This application relates to the technical field of refrigeration heat pumps, in particular to a refrigeration heat pump unit with a centrifugal compressor.

Background Art

A centrifugal refrigeration heat pump unit generally requires high compression ratio, and therefore requires more than three stages of impellers to meet a high compression ratio requirement. In the prior art, a multi-stage centrifugal compressor for a centrifugal refrigeration heat pump unit is provided, in which a plurality of impellers are mounted on a rotating shaft, such a structure allows a plurality of impellers to operate at the same rotation speed, so that it is difficult to achieve a high-efficiency design in a double-working condition (cold water preparation and hot water preparation) application.

Summary of the Invention

This application aims to provide a refrigeration heat pump unit to at least solve or alleviate some of the problems existing in the prior art.
This application provides a refrigeration heat pump unit, including a refrigerant circuit formed by a centrifugal compressor, a condenser, a throttling device, and an evaporator. The centrifugal compressor includes a housing, a first motor, a second motor, a first compression chamber, a second compression chamber, a first impeller, a second impeller, and a controller. The first motor is disposed inside the housing. The second motor is disposed inside the housing and disposed opposite to the first motor. The first compression chamber is disposed at an end portion of the housing close to the first motor and includes a first suction port and a first discharge port, the first suction port communicating with an outlet of the evaporator. The second compression chamber is disposed at an end portion of the housing close to the second motor and includes a second suction port and a second discharge port, the second suction port communicating with the first discharge port, and the second discharge port communicating with an inlet of the condenser. The first impeller is disposed inside the first compression chamber and is driven by the first motor. The second impeller is disposed inside the second compression chamber and is driven by the second motor. The controller is configured to turn on the first motor and turn off the second motor in response to a first working condition, turn off the first motor and turn on the second motor in response to a second working condition, and turn on the first motor and the second motor in response to a third working condition.
In a refrigeration heat pump unit according to an optional technical solution, there are at least two first impellers and/or at least two second impellers.
In a refrigeration heat pump unit according to an optional technical solution, a rotation speed of the first motor and a rotation speed of the second motor are able to be controlled independently of each other.
In a refrigeration heat pump unit according to an optional technical solution, the first motor and the second motor are coaxially disposed, the first impeller is directly fixed to an output shaft of the first motor, and the second impeller is directly fixed to an output shaft of the second motor.
In a refrigeration heat pump unit according to an optional technical solution, the centrifugal compressor further includes a first bypass flow path, a second bypass flow path, a first switching device, and a second switching device. The first bypass flow path is located between the first suction port and the first discharge port and bypasses the first impeller. The second bypass flow path is located between the second suction port and the second discharge port and bypasses the second impeller. The first switching device selectively communicates with the first bypass flow path or communicates with a compression flow path, the compression flow path being located between the first suction port and the first discharge port and passing through the first impeller. The second switching device selectively communicates with the second bypass flow path or communicates with a compression flow path, the compression flow path being located between the second suction port and the second discharge port and passing through the second impeller.
In a refrigeration heat pump unit according to an optional technical solution, the controller is configured to: turn on the first motor and turn off the second motor in response to the first working condition, causing the first switching device to selectively communicate with the compression flow path, the compression flow path being located between the first suction port and the first discharge port and passing through the first impeller, and causing the second switching device to selectively communicate with the second bypass flow path; turn off the first motor and turn on the second motor in response to the second working condition, causing the first switching device to selectively communicate with the first bypass flow path, and causing the second switching device to selectively communicate with the compression flow path, the compression flow path being located between the second suction port and the second discharge port and passing through the second impeller; and turn on the first motor and the second motor in response to the third working condition, causing the first switching device to selectively communicate with the compression flow path, the compression flow path being located between the first suction port and the first discharge port and passing through the first impeller, and causing the second switching device to selectively communicate with the compression flow path, the compression flow path being located between the second suction port and the second discharge port and passing through the second impeller.
In a refrigeration heat pump unit according to an optional technical solution, the first switching device includes a first bypass valve and a first variable guide vane, the first bypass valve being disposed in the first bypass flow path, and the first variable guide vane being disposed corresponding to the first suction port. The second switching device includes a second bypass valve and a second variable guide vane, the second bypass valve is disposed in the second bypass flow path, and the second variable guide vane is disposed corresponding to the second suction port.
In a refrigeration heat pump unit according to an optional technical solution, the first bypass valve is a one-way valve that allows unidirectional flow from the first suction port to the first discharge port, and the second bypass valve is a one-way valve that allows unidirectional flow from the second suction port to the second discharge port.
In a refrigeration heat pump unit according to an optional technical solution, the controller is configured to: turn on the first motor and turn off the second motor, and open the first variable guide vane and close the second variable guide vane in response to the first working condition; turn off the first motor and turn on the second motor, and close the first variable guide vane and open the second variable guide vane in response to the second working condition; and turn on the first motor and the second motor, and open the first variable guide vane and the second variable guide vane in response to the third working condition.

Descriptions of the Drawings

Certain exemplary embodiments will now be described in greater detail by way of example only and with reference to the accompanying drawings in which:

FIG. 1 shows a schematic diagram of a refrigeration unit according to a first embodiment of this application;
FIG. 2 shows a schematic diagram of a refrigeration unit according to a second embodiment of this application, and a refrigerant flow direction under a first working condition;
FIG. 3 shows a schematic diagram of the refrigeration unit according to the second embodiment of this application, and a refrigerant flow direction under a second working condition;
FIG. 4 shows a schematic diagram of the refrigeration unit according to the second embodiment of this application, and a refrigerant flow direction under a third working condition;
FIG. 5 shows a schematic diagram of a refrigeration unit according to some embodiments of this application; and
FIG. 6 shows a schematic diagram of a refrigeration unit according to some embodiments of this application.

List of Reference Numerals:

Refrigeration heat pump unit 100, centrifugal compressor 1, housing 10, first motor 11, second motor 12, first compression chamber 13, first suction port 131, first discharge port 132, second compression chamber 14, second suction port 141, second discharge port 142, first impeller 15, second impeller 16, first bypass flow path 171, second bypass flow path 172, first switching device 181, first bypass valve (one-way valve) 1811, first variable guide vane 1812, second switching device 182, second bypass valve (one-way valve) 1821, second variable guide vane 1822, connecting pipe 19, condenser 2, evaporator 3, and controller 4.

Detailed Description

It should be noted that working principles, features, advantages, and the like of a refrigeration heat pump unit according to this application will be explained below by way of embodiments. However, it should be understood that all descriptions are only given for exemplification and therefore these embodiments should not be understood as forming any limitation on this application.
In addition, for any single technical feature described or implicit in the embodiments mentioned herein, or any single technical feature illustrated or implicit in the drawings, this application still allows any combination or deletion between these technical features (or their equivalents) without any technical obstacles, thereby obtaining more other embodiments of this application that may not be directly mentioned herein.

As shown in FIG. 1, a refrigeration heat pump unit 100 in this embodiment includes a refrigerant circuit formed by a centrifugal compressor 1, a condenser 2, a throttling device (not shown), and an evaporator 3. The centrifugal compressor 1 includes a housing 10, a first motor 11, a second motor 12, a first compression chamber 13, a second compression chamber 14, a first impeller 15, a second impeller 16, and a controller 4.
The first motor 11 and the second motor 12 are both disposed inside the housing 10, and the second motor 12 is disposed opposite to the first motor 11. The first motor 11 and the second motor 12 are both motors with independent output shafts and bearings. By allowing the first motor 11 and the second motor 12 to share one housing 10, a structure of the centrifugal compressor 1 may be designed in a more compact form, which facilitates cost reduction in manufacturing the centrifugal compressor 1. By disposing such that the first motor 11 and the second motor 12 are opposite to each other, that is, an output end of the first motor 11 and an output end of the second motor 12 face in two substantially opposite directions, respectively, a structure layout of the centrifugal compressor 1 can be more reasonable, which also facilitates pipe connection in the refrigeration heat pump unit 100.
The first compression chamber 13 is disposed at an end portion of the housing 10 close to the first motor 11, and includes a first suction port 131 and a first discharge port 132, the first suction port 131 communicating with an outlet of the evaporator 3. The second compression chamber 14 is disposed at an end portion of the housing 10 close to the second motor 12 and includes a second suction port 141 and a second discharge port 142, the second suction port 141 communicating with the first discharge port 132, and the second discharge port 142 communicating with an inlet of the condenser 2. The first impeller 15 is disposed inside the first compression chamber 13 and is driven by the first motor 11, and the second impeller 16 is disposed inside the second compression chamber 14 and is driven by the second motor 12.
The controller 4 is configured to turn on the first motor 11 and turn off the second motor 12 in response to a first working condition, turn off the first motor 11 and turn on the second motor 12 in response to a second working condition, and turn on the first motor 11 and the second motor 12 in response to a third working condition. That is, the first motor 11 and the second motor 12 may be alternatively or simultaneously turned on according to the working condition. In this manner, on one hand, the normalized part load value (NPLV) of the refrigeration heat pump unit 100 is improved, and on the other hand, the operation reliability of the refrigeration heat pump unit 100 is improved through a redundant design.
In addition, it may be understood that in a multi-stage centrifugal compressor 1, blades of different levels of impellers may differ in geometry, size, number, and the like. Specifically, referring to FIG. 1, levels of a first impeller 15a, a first impeller 15b, a second impeller 16a, and a second impeller 16b are gradually increased in this order, so that designs between the respective impellers are generally different. Since designs of the first impeller 15 and the second impeller 16 are different, the centrifugal compressor 1 has different processing effects on a refrigerant between a case where the first motor 11 is separately turned on to drive the first impeller 15 and a case where the second motor 12 is separately turned on to drive the second impeller 16, so that the centrifugal compressor 1 is allowed to operate efficiently in a larger range of working conditions.
In this embodiment, as shown in FIG. 1, a first variable guide vane 1812 is disposed upstream of the first impeller 15a, that is, at a position corresponding to the first suction port 131, and a second variable guide vane 1822 is disposed upstream of the second impeller 16a, that is, at a position corresponding to the second suction port 141. By adjusting opening angles of the first variable guide vane 1812 and the second variable guide vane 1822, flow rates of the refrigerant entering the first compression chamber 13 and the second compression chamber 14 can be adjusted in response to a change of a load.
In other embodiments, other structures that may be used to adjust a flow rate of a refrigerant entering a compression chamber may be used instead of the first variable guide vane 1812 and the second variable guide vane 1822 in this embodiment.
In this embodiment, as shown in FIG. 1, there are two first impellers 15, and there are two second impellers 16.
In other embodiments, as shown in FIG. 5, there are two first impellers 15 and one second impeller 16.
In other embodiments, as shown in FIG. 6, there are one first impeller 15 and two second impellers 16.
In this embodiment, as shown in FIG. 1, the first motor 11 and the second motor 12 are coaxially disposed, the first impeller 15 is directly fixed to an output shaft of the first motor 11, and the second impeller 16 is directly fixed to an output shaft of the second motor 12. By directly fixing the first impeller 15 and the second impeller 16 to the output shafts of the first motor 11 and the second motor 12, respectively, a lift of the centrifugal compressor 1 can be increased under a working condition requiring a high compression ratio, so as to meet the requirements of the specific working condition.
In other embodiments, the output shaft of the first motor 11 and the output shaft of the second motor 12 may be staggered from each other to match arrangement of a unit.
In other embodiments, the output shaft of the first motor 11 is connected to a rotating shaft provided with the first impeller 15 through a transmission mechanism, thereby driving the first impeller 15. Similarly, the output shaft of the second motor 12 is connected to a rotating shaft provided with the second impeller 16 through a transmission mechanism, thereby driving the second impeller 16. By disposing the transmission mechanism, a rotation speed of the impeller can be adjusted without changing a motor frequency.
In this embodiment, a rotation speed of the first motor 11 and a rotation speed of the second motor 12 are able to be controlled independently of each other. In this manner, it is advantageous to allow both the first motor 11 and the second motor 12 to work at a more suitable rotation speed, thereby more flexibly meeting requirements under more working conditions.
In other embodiments, according to an application scenario of a refrigeration heat pump system, the rotation speed of the first motor 11 and the rotation speed of the second motor 12 may be controlled in a linkage manner, thereby simplifying operation of the controller 4 to ensure a stable operation of the unit.
Operations of a refrigeration heat pump system in this embodiment under some working conditions will be described below with reference to FIG. 1.
Under the first working condition, which may be, for example, a high-load low-lift working condition for preparing cold water, the controller 4 turns on the first motor 11 and turns off the second motor 12. After exiting from the outlet of the evaporator 3, the refrigerant first enters the first compression chamber 13 through the first suction port 131 and is compressed and accelerated by the first impeller 15, then exits the first compression chamber 13 through the first discharge port 132, then enters the condenser 2 for heat exchange after sequentially passing through the connecting pipe 19 and the second compression chamber 14, and then exits the condenser 2, and enters the evaporator 3 after being throttled for heat exchange to absorb heat to prepare the cold water. Since the second motor 12 is in a turned-off state, the refrigerant is not compressed and accelerated after entering the second compression chamber 14, but simply flows through the second compression chamber 14, in other words, the second compression chamber 14 only functions as a passage.
Under the second working condition, which may be, for example, a low-load low-lift working condition for preparing cold water, the controller 4 turns off the first motor 11 and turns on the second motor 12. After exiting from the outlet of the evaporator 3, the refrigerant first sequentially passes through the first compression chamber 13 and the connecting pipe 19, then enters the second compression chamber 14 through the second suction port 141 and is compressed and accelerated by the second impeller 16, then exits the second compression chamber 14 through the second discharge port 142 and enters the condenser 2 for heat exchange, and then exits the condenser 2, and enters the evaporator 3 after being throttled for heat exchange to absorb heat to prepare the cold water. Since the first motor 11 is in a turned-off state, the refrigerant is not compressed and accelerated after entering the first compression chamber 13, but simply flows through the first compression chamber 13, in other words, the first compression chamber 13 only functions as a passage.
Under the third working condition, which may be, for example, a high-lift working condition for preparing hot water, the controller 4 turns on the first motor 11 and the second motor 12. The refrigerant first enters the first compression chamber 13 through the first suction port 131 and is compressed and accelerated by the first impeller 15, passes through the connecting pipe 19, then enters the second compression chamber 14 through the second suction port 141 and is compressed and accelerated by the second impeller 16, then exits the second compression chamber 14 through the second discharge port 142 and enters the condenser 2 for heat exchange to prepare the hot water, and then exits the condenser 2, and enters the evaporator 3 after being throttled for heat exchange.
It should be noted that the above descriptions of the load, the lift, and the application corresponding to the first working condition, the second working condition, and the third working condition are merely examples. It can be understood that when to turn on the first motor 11, when to turn on the second motor 12, and when to turn on the first motor 11 and the second motor 12 simultaneously can be set according to an application scenario and an operating condition of the unit. Whether to turn on the first motor 11 or the second motor 12 is not directly related to high or low of the load, high or low of the lift, preparation of hot water or cold water. For example, when the first motor 11 needs to be serviced, it is directly selected to turn on the second motor 12 to ensure operation of the unit.

The same reference numerals in the second embodiment of this application as those in the first embodiment refer to the same structures, which will not be repeated here.
In this embodiment, as shown in FIGS. 2 to 6, the centrifugal compressor 1 further includes a first bypass flow path 171, a second bypass flow path 172, a first switching device 181, and a second switching device 182. The first bypass flow path 171 is located between the first suction port 131 and the first discharge port 132 and bypasses the first impeller 15. The second bypass flow path 172 is located between the second suction port 141 and the second discharge port 142 and bypasses the second impeller 16. The first switching device 181 selectively communicates with the first bypass flow path 171 or communicates with a compression flow path, the compression flow path being located between the first suction port 131 and the first discharge port 132 and passing through the first impeller 15. The second switching device 182 selectively communicates with the second bypass flow path 172 or communicates with a compression flow path, the compression flow path being located between the second suction port 141 and the second discharge port 142 and passing through the second impeller 16.
In this embodiment, as shown in FIGS. 2 to 6, the first switching device 181 includes a first bypass valve 1811 and a first variable guide vane 1812, the first bypass valve 1811 being disposed in the first bypass flow path 171, and the first variable guide vane 1812 being disposed corresponding to the first suction port 131. The second switching device 182 includes a second bypass valve 1821 and a second variable guide vane 1822, the second bypass valve 1821 is disposed in the second bypass flow path 172, and the second variable guide vane 1822 is disposed corresponding to the second suction port 141.
In this embodiment, the controller 4 is configured to: turn on the first motor 11 and turn off the second motor 12 in response to the first working condition, causing the first switching device 181 to selectively communicate with the compression flow path, the compression flow path being located between the first suction port 131 and the first discharge port 132 and passing through the first impeller 15, and causing the second switching device 182 to selectively communicate with the second bypass flow path 172; turn off the first motor 11 and turn on the second motor 12 in response to the second working condition, causing the first switching device 181 to selectively communicate with the first bypass flow path 171, and causing the second switching device 182 to selectively communicate with the compression flow path, the compression flow path being located between the second suction port 141 and the second discharge port 142 and passing through the second impeller 16; and turn on the first motor 11 and the second motor 12 in response to the third working condition, causing the first switching device 181 to selectively communicate with the compression flow path, the compression flow path being located between the first suction port 131 and the first discharge port 132 and passing through the first impeller 15, and causing the second switching device 182 to selectively communicate with the compression flow path, the compression flow path being located between the second suction port 141 and the second discharge port 142 and passing through the second impeller 16.
In this embodiment, when the refrigerant does not need to be compressed and accelerated by the first impeller 15, the refrigerant is avoided to pass through the first impeller 15, but directly reaches a position of the first discharge port 132 through the first bypass flow path 171, thereby avoiding a problem of refrigerant flow loss caused by factors such as collision with the first impeller 15. Similarly, when the refrigerant does not need to be compressed and accelerated by the second impeller 16, the refrigerant is avoided to pass through the second impeller 16, but directly reaches a position of the second discharge port 142 through the second bypass flow path 172, thereby avoiding a problem of refrigerant flow loss caused by factors such as collision with the second impeller 16.
In this embodiment, as shown in FIGS. 2 to 4, the first bypass valve 1811 is a one-way valve 1811 that allows unidirectional flow from the first suction port 131 to the first discharge port 132, and the second bypass valve 1821 is a one-way valve 1821 that allows unidirectional flow from the second suction port 141 to the second discharge port 142. That is, the first bypass valve 1811 and the second bypass valve 1821 can only that allows unidirectional flow (along pointing of arrow) from an impeller inlet side to an impeller outlet side, and thus a backflow of the refrigerant on a relatively high-pressure side due to the disposition of the first bypass flow path 171 or the second bypass flow path 172 can be prevented. In addition, since the first bypass valve 1811 and the second bypass valve 1821 are both one-way valves, the first bypass valve 1811 and the second bypass valve 1821 can automatically open and close in response to a state change of the first variable guide vane 1812 and the second variable guide vane 1822, instead of being controlled by way of electric control, thereby simplifying a control mode for the first bypass valve 1811 and the second bypass valve 1821, and facilitating improvement of the operation reliability of the unit.
In other embodiments, the first bypass valve 1811 and the second bypass valve 1821 may both be electrically controlled valves.
Operations of the refrigeration heat pump system in this embodiment under some working conditions will be described below with reference to FIGS. 2 to 4.
Under the first working condition, the controller 4 turns on the first motor 11 and turns off the second motor 12, and opens the first variable guide vane 1812 and closes the second variable guide vane 1822. In this case, a pressure at the first discharge port 132 is higher than a pressure at the first suction port 131, so that the one-way valve 1811 remains in a closed state. Since the second variable guide vane 1822 is in a closed state, a high-pressure refrigerant can impact the one-way valve 1821, and then cause the one-way valve 1821 to be conducted. A dotted arrow in FIG. 2 shows a flow direction of the refrigerant, and as shown in FIG. 2, after exiting from the outlet of the evaporator 3, the refrigerant first enters the first compression chamber 13 through the first suction port 131 and is compressed and accelerated by the first impeller 15, then exits the first compression chamber 13 through the first discharge port 132, then enters the condenser 2 for heat exchange after sequentially passing through the connecting pipe 19 and the one-way valve 1821, and then exits the condenser 2, and enters the evaporator 3 after being throttled for heat exchange.
Under the second working condition, the controller 4 turns off the first motor 11 and turns on the second motor 12, and closes the first variable guide vane 1812 and opens the second variable guide vane 1822. In this case, a pressure at the second suction port 141 drops, and the one-way valve 1811 is automatically conducted. A pressure at the second discharge port 142 is higher than the pressure at the second suction port 141, so that the one-way valve 1821 remains in the closed state. A dotted arrow in FIG. 3 shows a flow direction of the refrigerant, and as shown in FIG. 3, after exiting from the outlet of the evaporator 3, the refrigerant first sequentially passes through the first bypass flow path 171 and the connecting pipe 19, then enters the second compression chamber 14 through the second suction port 141 and is compressed and accelerated by the second impeller 16, then exits the second compression chamber 14 through the second discharge port 142 and enters the condenser 2 for heat exchange, and then exits the condenser 2, and enters the evaporator 3 after being throttled for heat exchange.
Under the third working condition, the controller 4 turns on the first motor 11 and the second motor 12, and opens the first variable guide vane 1812 and the second variable guide vane 1822. In this case, the pressure at the first discharge port 132 is higher than the pressure at the first suction port 131, so that the one-way valve 1811 remains in the closed state. The pressure at the second discharge port 142 is higher than the pressure at the second suction port 141, so that the one-way valve 1821 remains in the closed state. A dotted arrow in FIG. 4 shows a flow direction of the refrigerant, and as shown in FIG. 4, the refrigerant first enters the first compression chamber 13 through the first suction port 131 and is compressed and accelerated by the first impeller 15, then enters the second compression chamber 14 through the second suction port 141 after passing through the connecting pipe 19 and is compressed and accelerated by the second impeller 16, then exits the second compression chamber 14 through the second discharge port 142 and enters the condenser 2 for heat exchange, and then exits the condenser 2, and enters the evaporator 3 after being throttled for heat exchange.
The above embodiments are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions and improvements made within the scope of the invention as set out in the appended claims shall be included in the protection scope of this application.

Claims

A refrigeration heat pump unit (100), comprising a refrigerant circuit formed by a centrifugal compressor (1), a condenser (2), a throttling device, and an evaporator (3), wherein
the centrifugal compressor (1) includes:
a housing (10);

a first motor (11) disposed inside the housing;

a second motor (12) disposed inside the housing and disposed opposite to the first motor;

a first compression chamber (13) disposed at an end portion of the housing close to the first motor and including a first suction port (131) and a first discharge port (132), the first suction port communicating with an outlet of the evaporator (3);

a second compression chamber (14) disposed at an end portion of the housing (10) close to the second motor (12) and including a second suction port (141) and a second discharge port (142), the second suction port communicating with the first discharge port (132), and the second discharge port (142) communicating with an inlet of the condenser (2);

a first impeller (15) disposed inside the first compression chamber (13) and driven by the first motor (11); and

a second impeller (16) disposed inside the second compression chamber (14) and driven by the second motor (12), and

the refrigeration heat pump unit (100) further comprises a controller (4),

the controller (4) being configured to turn on the first motor (11) and turn off the second motor (12) in response to a first working condition, turn off the first motor (11) and turn on the second motor (12) in response to a second working condition, and turn on the first motor (11) and the second motor (12) in response to a third working condition.
The refrigeration heat pump unit (100) according to claim 1, wherein there are at least two first impellers (15) and/or at least two second impellers (16).
The refrigeration heat pump unit (100) according to claim 1 or 2, wherein a rotation speed of the first motor (11) and a rotation speed of the second motor (12) are able to be controlled independently of each other.
The refrigeration heat pump unit (100) according to claim 1, 2 or 3, wherein the first motor (11) and the second motor (12) are coaxially disposed, the first impeller (15) is directly fixed to an output shaft of the first motor (11), and the second impeller (16) is directly fixed to an output shaft of the second motor (12).
The refrigeration heat pump unit (100) according to any preceding claim, wherein the centrifugal compressor (1) further includes:
a first bypass flow path (171) located between the first suction port (131) and the first discharge port (132) and bypassing the first impeller (15);

a second bypass flow path (172) located between the second suction port (141) and the second discharge port (142) and bypassing the second impeller (16);

a first switching device (181) selectively communicating with the first bypass flow path (171) or communicating with a compression flow path, the compression flow path being located between the first suction port (131) and the first discharge port (132) and passing through the first impeller (15); and

a second switching device (182) selectively communicating with the second bypass flow path (172) or communicating with a compression flow path, the compression flow path being located between the second suction port (141) and the second discharge port (142) and passing through the second impeller (16).
The refrigeration heat pump unit (100) according to claim 5, wherein the controller (4) is configured to:
turn on the first motor (11) and turn off the second motor (12) in response to the first working condition, causing the first switching device (181) to selectively communicate with the compression flow path, the compression flow path being located between the first suction port (131) and the first discharge port (132) and passing through the first impeller (15), and causing the second switching device (182) to selectively communicate with the second bypass flow path (172);

turn off the first motor (11) and turn on the second motor (12) in response to the second working condition, causing the first switching device (181) to selectively communicate with the first bypass flow path (171), and causing the second switching device (182) to selectively communicate with the compression flow path, the compression flow path being located between the second suction port (141) and the second discharge port (142) and passing through the second impeller (16); and

turn on the first motor (11) and the second motor (12) in response to the third working condition, causing the first switching device (181) to selectively communicate with the compression flow path, the compression flow path being located between the first suction port (131) and the first discharge port (132) and passing through the first impeller (15), and causing the second switching device (182) to selectively communicate with the compression flow path, the compression flow path being located between the second suction port (141) and the second discharge port (142) and passing through the second impeller (16).
The refrigeration heat pump unit (100) according to claim 5 or 6, wherein
the first switching device (181) includes a first bypass valve (1811) and a first variable guide vane (1812), the first bypass valve (1811) being disposed in the first bypass flow path (171), and the first variable guide vane (1812) being disposed corresponding to the first suction port (131), and

the second switching device (182) includes a second bypass valve (1821) and a second variable guide vane (1822), the second bypass valve (1821) being disposed in the second bypass flow path (172), and the second variable guide vane (1822) being disposed corresponding to the second suction port (141).
The refrigeration heat pump unit (100) according to claim 7, wherein
the first bypass valve (1811) is a one-way valve that allows unidirectional flow from the first suction port (131) to the first discharge port (132), and

the second bypass valve (1821) is a one-way valve that allows unidirectional flow from the second suction port (141) to the second discharge port (142).
The refrigeration heat pump unit (100) according to claim 7 or 8, wherein the controller (4) is configured to:
turn on the first motor (11) and turn off the second motor (12), and open the first variable guide vane (1812) and close the second variable guide vane (1822) in response to the first working condition;

turn off the first motor (11) and turn on the second motor (12), and close the first variable guide vane (1812) and open the second variable guide vane (1822) in response to the second working condition; and

turn on the first motor (11) and the second motor (12), and open the first variable guide vane (1812) and the second variable guide vane (1822) in response to the third working condition.