Double-refrigerating-system unit and operation control method thereof

Abstract

The invention provides a double-refrigerating-system unit and an operation control method thereof, and belongs to the field of refrigerating and air conditioner control. Specifically, input ends and output ends of two groups of evaporators are respectively and symmetrically communicated with a group of three-way valves so as to effectively isolate two groups of refrigerants in a single refrigeration mode, so that self-adaptive mutual switching between a single refrigeration mode and a double refrigeration mode is realized, and the energy efficiency in the single refrigeration mode is obviously improved on the premise of ensuring that the two groups of refrigerants are not subjected to crosstalk and mixing. Comprising two sets of equipment assemblies which can operate and be controlled independently, and each set of equipment assembly is formed by sequentially connecting a compressor, an evaporator, a condenser and a throttling device through a refrigerant circulation pipeline; a refrigerant inlet of the first evaporator is connected with a first three-way valve, and a first refrigerant outlet of the first three-way valve is communicated with a refrigerant inlet of the second evaporator in an open state; a refrigerant outlet of the second evaporator is connected with a second three-way valve, and a first refrigerant outlet of the second three-way valve is communicated with a refrigerant outlet of the first evaporator in an open state.

Description

Technical Field

[0001] This application relates to the field of refrigeration and air conditioning control, specifically proposing a dual-refrigeration system unit that can adaptively switch between single or dual refrigeration modes, and also proposing a novel operation control method that uses two evaporators to improve energy efficiency in single refrigeration mode according to load changes. Background Technology

[0002] Currently, dual-refrigeration system units typically have two sets of independently operating and control equipment components, as shown in the appendix. Figure 1 As shown (of course, the structural forms may vary between different manufacturers; this diagram is only for illustrating the system composition), each equipment component includes an evaporator, a condenser, a compressor, and a throttling device, etc.; the refrigeration cycle is as follows: Figure 2 As shown, the two refrigeration systems operate independently without interfering with each other. When the system load is high, both sets of equipment components operate independently; when the system load is low, only one set of refrigeration systems can operate, while the other set of refrigeration systems is in a stopped state.

[0003] Existing dual-refrigeration system units have low operating efficiency in single-refrigeration mode, primarily because one set of evaporators is idle and not in operation. To improve system energy efficiency by using both sets of evaporators simultaneously, the technical challenge of preventing refrigerant crosstalk and mixing between the two sets of components must first be addressed. Specifically, when one set of components is not operating, its evaporator stores the refrigerant required for that refrigeration system; while the other set of components, after passing through a throttling device, sends its refrigerant into both evaporators. This inevitably leads to refrigerant mixing. The mixed refrigerant then enters one of the compressors in the operating set, resulting in a decrease in refrigerant in the idle set and an increase in refrigerant in the operating set. This affects the overall operating efficiency of the unit in dual-refrigeration mode and may even impact the compressor's lifespan. Furthermore, these problems become particularly complex when switching between single-refrigeration and dual-refrigeration systems. When switching from single-cooling to dual-cooling mode, it is necessary to ensure that the refrigerant of the running equipment components does not enter the non-running equipment components; when switching from dual-cooling to single-cooling mode, it is necessary to ensure that the refrigerant of the non-running equipment components does not enter the running equipment components.

[0004] Therefore, to solve the aforementioned technical challenges, comprehensive innovations and safeguards must be proposed for the overall operation and control process of the system unit (including but not limited to the initial startup of the unit, the switching from single-cooling to dual-cooling mode during operation, the switching from dual-cooling to single-cooling mode, and the shutdown phase). In view of this, this application is hereby submitted. Summary of the Invention

[0005] The dual-refrigeration system unit and its operation control method described in this application aim to solve the problems existing in the prior art by symmetrically connecting a set of three-way valves at the input and output ends of the two sets of evaporators. This effectively isolates the two sets of refrigerants in single-refrigeration mode, thereby realizing adaptive switching between single-refrigeration and dual-refrigeration modes. Under the premise of ensuring that the refrigerants in the two sets of equipment components operate independently, without crosstalk or mixing, the energy efficiency in single-refrigeration mode is significantly improved.

[0006] To achieve the above-mentioned objectives, the dual refrigeration system unit includes two sets of independently operable and controllable equipment components. Each set of equipment components includes a compressor and an evaporator, a condenser and a throttling device connected in sequence through a refrigerant circulation pipeline. A first three-way valve is connected to the refrigerant inlet of the first evaporator, and the first refrigerant outlet of the first three-way valve is connected to the refrigerant inlet of the second evaporator when it is open. A second three-way valve is connected to the refrigerant outlet of the second evaporator, and the first refrigerant outlet of the second three-way valve is connected to the refrigerant outlet of the first evaporator when it is open.

[0007] Furthermore, the first evaporator and the second evaporator are two relatively independent devices, or two relatively enclosed sets of pipe channels in the same evaporator, each with its own refrigerant flow; the first condenser and the second condenser are two relatively independent devices, or two relatively enclosed sets of pipe channels in the same condenser, each with its own refrigerant flow.

[0008] Based on the above-mentioned dual-refrigeration system unit, this application also proposes the following dual-refrigeration system unit operation control method: In the two sets of independently operating and controlled equipment components, a controllable open and closed channel is established between the refrigerant inlet and refrigerant outlet of the two sets of evaporators; in the single refrigeration operation mode, the refrigerant flows through the two sets of evaporators in the operating and non-operating equipment components at the same time; in the low-load single refrigeration system operation mode, the refrigerant uses the two evaporators to exchange heat and circulate at the same time.

[0009] Furthermore, before switching from single-cooling to dual-cooling operation mode, the refrigerant inside the two sets of evaporators in the separately operating equipment components is transferred to the condenser or other liquid storage device in the system pipeline, thereby ensuring that the refrigerant in the two sets of refrigeration systems does not mix.

[0010] Furthermore, before switching from dual-cooling to single-cooling operation mode, the refrigerant in the subsequent non-operating equipment group is transferred to the condenser or other liquid storage device in the system pipeline, thereby ensuring that the refrigerant in the two refrigeration systems does not mix.

[0011] The aforementioned dual-refrigeration system operation control method includes the following implementation stages: Phase 1: Before system unit startup; The valve core of the first three-way valve moves to between the first refrigerant outlet and the second refrigerant outlet, with both outlets in the open state, allowing refrigerant to flow simultaneously from both channels; the valve core of the second three-way valve moves to the second refrigerant outlet and closes it, allowing refrigerant to flow in one direction, while the refrigerant flowing through the second evaporator will still flow back to the first compressor; the first throttling device and the second throttling device remain in the closed state. Phase Two: Initial Start-up of the System Units; The system unit starts up in cooling-only mode upon initial startup; While the first compressor and the first throttling device are running, the second compressor remains stopped, and the first three-way valve, the second three-way valve, and the second throttling device remain at their default settings before the system unit was started. The low-temperature liquid refrigerant after passing through the first throttling device is divided into two channels by the valve body of the first three-way valve and enters the first evaporator and the second evaporator respectively. After heat exchange in the second evaporator, one channel of refrigerant passes through the second three-way valve and merges with the other channel of refrigerant after heat exchange in the first evaporator, and they both enter the first compressor. The high-temperature gaseous refrigerant after compression enters the first condenser, and after heat exchange, it enters the first throttling device to form a refrigeration cycle. After running for a period of time, the system determines whether the unit's outlet water temperature has reached the preset first threshold; if so, it continues to operate in single cooling mode; if not, it proceeds to the following stage three. Phase 3: Switch from single-cooling to dual-cooling operation mode; First, the first compressor continues to run, and the first throttling device is closed. The refrigerant that has passed through the first evaporator and the second evaporator is stored in the first condenser under the suction of the first compressor. After a few seconds, the refrigerant in the second evaporator is emptied, and the refrigerant circulating in the single refrigeration operation mode is concentrated in the first condenser. Then, the valve core in the first three-way valve moves to the first refrigerant outlet and closes it, cutting off the passage between the first three-way valve and the second evaporator; the valve core in the second three-way valve moves to the first refrigerant outlet and closes it, cutting off the passage between the first evaporator and the second three-way valve. Finally, the second compressor is started, and the first and second throttling devices are opened simultaneously, allowing the equipment components of the two refrigeration systems to operate independently. When the system load decreases, the first compressor continues to operate at its current operating frequency, while the second compressor operates at a reduced frequency. After operating for a period of time, when the system load continues to decrease, it transitions to the following stage four. Phase 4: Switching from dual-cooling to single-cooling operation mode; First, the second throttling device is closed, and the refrigerant in the second evaporator is stored in the second condenser under the suction of the second compressor; the second compressor continues for a period of time to empty the refrigerant in the second evaporator. Then, the valve core in the second three-way valve moves to the second refrigerant outlet and closes it; the valve core of the first three-way valve moves between the first refrigerant outlet and the second refrigerant outlet, with both outlets in the open state, allowing refrigerant to flow simultaneously from both channels. Secondly, after the first three-way valve and the second three-way valve have completed their operation, the second compressor stops. Finally, the second throttling device remains closed and the first throttling device remains open. The low-temperature liquid refrigerant flowing through the first throttling device enters the first evaporator and the second evaporator respectively through the two channels of the first three-way valve body. After heat exchange in the second evaporator, one path of refrigerant merges with the other path of refrigerant after heat exchange in the first evaporator through the second three-way valve and enters the first compressor together to form a refrigeration cycle. As the system load continues to decrease, the first compressor operates at a reduced frequency. Phase 5: After running for a period of time, the system determines whether the unit's outlet water temperature has reached the preset second threshold. If not, the first compressor continues to operate at reduced frequency. If so, the first compressor and the first throttling device are shut down, and the first three-way valve and the second three-way valve remain unchanged from the previous moment. At this time, the first throttling device, the first three-way valve, and the second three-way valve are in the same state as the unit before the start-up of the system in Phase 1.

[0012] In summary, this application has the following beneficial effects and advantages compared with the prior art: 1. This application can adaptively switch between single cooling and dual cooling modes according to the real-time load changes of the system, and can also make full use of the evaporator of another set of non-operating equipment components in the single cooling mode, which significantly improves the system operating efficiency in the single cooling mode.

[0013] 2. When switching between single and dual cooling modes, this application can ensure that the refrigerant in the two sets of equipment components does not crosstalk or mix into each other's pipelines, which is conducive to the balance of operating efficiency of each set of equipment components, while protecting core components such as compressors from damage. Attached Figure Description

[0014] The present application will now be further described in conjunction with the following figures; Figure 1 This is a schematic diagram of the structure of an existing dual-refrigeration system unit; Figure 2 This is a schematic diagram of the operation of an existing dual-refrigeration system unit; Figure 3 This is a schematic diagram of the structure and operation of the dual-cooling system unit described in this application under dual-cooling mode; Figure 4 This is a schematic diagram of operation in single cooling mode; Figures 5 to 7These are comparative diagrams showing the three-way valve in different open and closed states; Figure 8 This is a schematic diagram showing the refrigerant stored in the first condenser when switching from single-cooling to dual-cooling mode. Figure 9 This is a schematic diagram showing the refrigerant stored in the second condenser when switching from dual-cooling to single-cooling mode. In the above figures, the first compressor 11, the second compressor 12, the first evaporator 21, and the second evaporator 22 are... First condenser 31, second condenser 32, first throttling device 41, second throttling device 42, first three-way valve 51, second three-way valve 52, valve core 53, refrigerant inlet 54, first refrigerant outlet 55, second refrigerant outlet 56, first liquid storage tank 61, second liquid storage tank 62, electrical control device 7. Detailed Implementation

[0015] The technical solution proposed in this application will be clearly and completely described below with reference to the accompanying drawings. For those skilled in the art, the described embodiments are merely a part of, and not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the following embodiments without inventive effort should fall within the protection scope of this application.

[0016] Furthermore, although certain terms are used in this description, such as “first,” “second,” “upper,” “lower,” “left,” and “right,” those skilled in the art will understand that these terms are merely for the convenience of explanation and are not intended to provide specific or restrictive descriptions of the technical solutions.

[0017] Example 1, such as Figures 3 to 9 As shown, this application proposes a dual refrigeration system unit comprising two sets of equipment components that can be operated and controlled independently. Each set of equipment components includes a compressor and an evaporator, a condenser and a throttling device connected in sequence through a refrigerant circulation pipeline.

[0018] Specifically, the first set of equipment components is controlled by the electrical control device 7, and includes a first compressor 11, a first condenser 31, a first throttling device 41 and a first evaporator 21 in the direction of refrigerant flow. The refrigerant flows back to the first compressor 11 via the first evaporator 21. The second set of equipment components is also controlled by the electrical control device 7. According to the refrigerant flow direction, it includes the second compressor 12, the second condenser 32, the second throttling device 42, and the second evaporator 22. The refrigerant flows back to the second compressor 12 through the second evaporator 22. To improve the flexibility and energy efficiency of the design of the above-mentioned dual refrigeration system unit, the first evaporator 21 and the second evaporator 22 are two relatively independent devices, or two relatively closed pipeline channels in the same evaporator, each with its own refrigerant flow. Based on the same design concept, the first condenser 31 and the second condenser 32 are two relatively independent devices, or two relatively closed sets of pipeline channels in the same condensing device, each flowing with refrigerant. The first throttling device 41 and the second throttling device 42 throttle the refrigerant to reduce its flow rate and temperature. When the refrigeration system is shut down, the first throttling device 41 and the second throttling device 42 are normally closed, and the refrigerant in the pipeline does not flow.

[0019] The first three-way valve 51 is connected to the refrigerant inlet of the first evaporator 21, and the first refrigerant outlet 55 of the first three-way valve 51 is connected to the refrigerant inlet of the second evaporator 22 when it is open. A second three-way valve 52 is connected to the refrigerant outlet of the second evaporator 22, and the first refrigerant outlet 55 of the second three-way valve 52 is connected to the refrigerant outlet of the first evaporator 21 when it is open. The first three-way valve 51 and the second three-way valve 52 are provided inside the valve body with a refrigerant inlet 54 for one-way refrigerant flow, a first refrigerant outlet 55, and a second refrigerant outlet 56, as well as a valve core 53 for opening or closing the first refrigerant outlet 55 and the second refrigerant outlet 56; inside the valve body, the valve core 53 switches between the first refrigerant outlet 55 and the second refrigerant outlet 56 to change the flow direction of the refrigerant when it passes through the valve body.

[0020] like Figures 5 to 7 As shown, both the first three-way valve 51 and the second three-way valve 52 have three refrigerant flow modes, the first of which is as follows: Figure 5 The valve core 53 moves to the second refrigerant outlet 56 and closes it, at which point the refrigerant flows unidirectionally from A to C; the second type... Figure 6 The valve core 53 moves to the first refrigerant outlet 55 and closes it, at which point the refrigerant flows unidirectionally from A to B; the third type is as follows: Figure 7 The valve core 53 moves to the space between the first refrigerant outlet 55 and the second refrigerant outlet 56, with both outlets in the open state. At this time, the refrigerant flows unidirectionally from A→B and A→C simultaneously.

[0021] Based on the system architecture of the aforementioned dual-refrigeration system unit, this application proposes the following dual-refrigeration system operation control method: In the two independently operating and controlled equipment components, controllable open and closed channels are established between the refrigerant inlets and outlets of the two evaporators. In single-refrigeration operation mode, the refrigerant flows simultaneously through both evaporators in the operating and non-operating equipment components. This allows for full utilization of the evaporator of the other non-operating equipment component in low-load single-refrigeration system operation mode, achieving simultaneous heat exchange through two evaporators when the single compressor is running, significantly improving the efficiency of the single refrigeration unit under low-load conditions.

[0022] To more effectively avoid the problems of refrigerant crosstalk and mixing, before switching from single-cooling to dual-cooling operation mode, the refrigerant inside the evaporator (first evaporator 21) of the separately operating equipment component is transferred to the condenser (first condenser 31) in the system pipeline, thereby ensuring that the refrigerants in the two refrigeration systems do not mix.

[0023] Before switching from dual-cooling to single-cooling operation mode, the refrigerant in the non-operating equipment components (the system pipeline where the second compressor 12 is located) is transferred to the condenser (second condenser 32) or other liquid storage device to ensure that the refrigerant in the two refrigeration systems does not mix.

[0024] The aforementioned dual-refrigeration system operation control method includes the following implementation stages: Phase 1: Before system unit startup; like Figure 7 As shown, the valve core 53 of the first three-way valve 51 moves to between the first refrigerant outlet 55 and the second refrigerant outlet 56, with both outlets in the open state. The refrigerant can flow simultaneously from both channels A→C and A→B. That is, the refrigerant in the equipment assembly where the first compressor 11 is located can simultaneously enter the first evaporator 21 and the second evaporator 22 of the two equipment assemblies. The first throttling device 41 and the second throttling device 42 remain in the closed state. like Figure 5 As shown, the valve core 53 of the second three-way valve 52 moves to the second refrigerant outlet 56 and closes it. At this time, the refrigerant can flow unidirectionally from A to C; that is, the refrigerant flowing through the second evaporator 22 will still flow back to the first compressor 11. Phase Two: Initial Start-up of the System Units; The system unit starts up in cooling-only mode upon initial startup; While the first compressor 11 and the first throttling device 41 are running, the second compressor 12 remains stopped, and the first three-way valve 51, the second three-way valve 52, and the second throttling device 42 (which is closed at this time) still maintain the default settings before the system unit started. like Figure 4As shown, the low-temperature liquid refrigerant after passing through the first throttling device 41 is divided into two channels, A→B and A→C, by the valve body of the first three-way valve 51 and enters the first evaporator 21 and the second evaporator 22 respectively. After heat exchange in the second evaporator 22, one channel of refrigerant merges with the other channel of refrigerant after heat exchange in the first evaporator 21 through the A→C channel of the valve body of the second three-way valve 22, and they both enter the first compressor 1. The compressed high-temperature gaseous refrigerant enters the first condenser 31, and after heat exchange, it enters the first throttling device 41 to form a refrigeration cycle. After running for a period of time, the system determines whether the unit's outlet water temperature has reached the preset first threshold; if so, it continues to operate in single cooling mode; if not, it proceeds to the following stage three. Phase 3: Switch from single-cooling to dual-cooling operation mode; First, such as Figure 8 As shown, the first compressor 1 continues to run, the first throttling device 41 is closed, and the refrigerant passing through the first evaporator 21 and the second evaporator 22 is stored in the first condenser 31 under the suction of the first compressor 11; After several seconds, the refrigerant in the second evaporator 22 is emptied, and the refrigerant circulating in the single refrigeration operation mode is concentrated in the first condenser 31. This effectively prevents the refrigerant from the original first refrigeration system from entering the second refrigeration system in the dual refrigeration operation mode, thereby avoiding the mixing of the refrigerants in the first and second refrigeration systems, which could lead to uneven distribution in the subsequent dual refrigeration operation mode, affecting the unit's operating efficiency and even the compressor's service life. Then, as Figure 6 As shown, the valve core 53 in the first three-way valve 51 moves to the first refrigerant outlet 55 and closes it, that is, it blocks the C channel, cutting off the channel between the first three-way valve 51 and the second evaporator 22; at this time, the refrigerant flows unidirectionally from A to B. Similarly, the valve core 53 in the second three-way valve 52 moves to the first refrigerant outlet 55 and closes it, that is, blocks the C channel, cutting off the passage between the first evaporator 21 and the second three-way valve 52; at this time, the refrigerant flows unidirectionally from A to B. Finally, the second compressor 12 is started, and the first throttling device 41 and the second throttling device 42 are opened simultaneously, allowing the components of the two refrigeration systems to operate independently; the refrigeration cycle proceeds as follows. Figure 3 As shown; When the system load decreases, the first compressor 11 continues to operate at its current operating frequency, while the second compressor 12 operates at a reduced frequency. After operating for a period of time, when the system load continues to decrease, it transitions to the following stage four. Phase 4: Switching from dual-cooling to single-cooling operation mode; First, such as Figure 9As shown, when the second throttling device 42 is closed, the refrigerant in the second evaporator 22 is stored in the second condenser 32 under the suction of the second compressor 12. The second compressor 12 continues for a period of time to empty the refrigerant in the second evaporator 22, thus avoiding the problem of refrigerant originally belonging to the second refrigeration system entering the first refrigeration system when switching to single refrigeration operation mode, which would cause the refrigerants of different systems to mix and affect the unit's operating efficiency. At the same time, closing the second throttling device 42 can also prevent the refrigerant originally belonging to the first refrigeration system from flowing back to the second condenser 32 through the A→C channel of the first three-way valve when switching to single refrigeration operation mode. Then, as Figure 5 As shown, the valve core 53 in the second three-way valve 52 moves to the second refrigerant outlet 56 and closes it, at which point the refrigerant flows unidirectionally from A to C; as Figure 7 As shown, the valve core 53 of the first three-way valve 51 moves to the space between the first refrigerant outlet 55 and the second refrigerant outlet 56, with both outlets in the open state, allowing refrigerant to flow simultaneously from both channels A→C and A→B. Secondly, after the first three-way valve 51 and the second three-way valve 52 have completed their operation, the second compressor 12 stops. Finally, as Figure 4 As shown, the second throttling device 42 remains closed and the first throttling device 41 remains open. The low-temperature liquid refrigerant flowing through the first throttling device 41 enters the first evaporator 21 and the second evaporator 22 respectively through the A→B and A→C channels of the first three-way valve 51. After heat exchange in the second evaporator 22, one path of refrigerant merges with the other path of refrigerant after heat exchange in the first evaporator 21 through the A→C channel of the second three-way valve 52, and they both enter the first compressor 1 to form a refrigeration cycle. As the system load continues to decrease, the first compressor 11 operates at a reduced frequency. Phase 5: After running for a period of time, the system determines whether the unit's outlet water temperature has reached the preset second threshold. If not, the first compressor 11 continues to operate at a reduced frequency. If so, the first compressor 11 is shut down and the first throttling device 41 is stopped. The first three-way valve 51 and the second three-way valve 52 remain unchanged from the previous moment. At this time, the first throttling device 41, the first three-way valve 51, and the second three-way valve 52 are in the same state as before the unit started in Phase 1.

[0025] It should be noted that those skilled in the art can make changes and modifications to the above-described embodiments. Therefore, this application is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on this application shall fall within the protection scope of this application.

Claims

1. A dual-refrigeration system unit, characterized in that: It includes two sets of independently operable and controllable equipment components. Each set of equipment components consists of a compressor and evaporator, a condenser and a throttling device connected in sequence through a refrigerant circulation pipeline. A first three-way valve is connected to the refrigerant inlet of the first evaporator, and the first refrigerant outlet of the first three-way valve is connected to the refrigerant inlet of the second evaporator when it is open. A second three-way valve is connected to the refrigerant outlet of the second evaporator. When the first refrigerant outlet of the second three-way valve is open, it connects to the refrigerant outlet of the first evaporator.

2. The dual-refrigeration system unit according to claim 1, characterized in that: The first evaporator and the second evaporator are two relatively independent devices, or two relatively enclosed sets of pipelines in the same evaporator, each with its own refrigerant flow. The first condenser and the second condenser are two relatively independent devices, or two relatively enclosed sets of pipelines in the same condensing device, each with its own refrigerant flow.

3. The operation control method for a dual-refrigeration system unit as described in claim 1 or 2, characterized in that: In the two sets of independently operating and controlled equipment components, a controllable open and closed channel is established between the refrigerant inlet and refrigerant outlet of the two sets of evaporators; in the single refrigeration operation mode, the refrigerant flows through the two sets of evaporators in the operating and non-operating equipment components at the same time; in the low-load single refrigeration system operation mode, the refrigerant uses the two evaporators to exchange heat and circulate at the same time.

4. The dual-refrigeration system operation control method according to claim 3, characterized in that: Before switching from single-cooling to dual-cooling operation mode, the refrigerant inside the two sets of evaporators in the separately operating equipment components is transferred to the condenser or other liquid storage device in the system pipeline, thereby ensuring that the refrigerant in the two sets of refrigeration systems does not mix.

5. The dual-refrigeration system operation control method according to claim 3, characterized in that: Before switching from dual-cooling to single-cooling operation mode, the refrigerant in the subsequent non-operating equipment group is transferred to the condenser or other liquid storage device in the system pipeline to ensure that the refrigerant in the two refrigeration systems does not mix.

6. The dual-refrigeration system operation control method according to claim 3, characterized in that: Including the following implementation phases, Phase 1: Before system unit startup; The valve core of the first three-way valve moves to between the first refrigerant outlet and the second refrigerant outlet, with both outlets in the open state, allowing refrigerant to flow simultaneously from both channels; the valve core of the second three-way valve moves to the second refrigerant outlet and closes it, allowing refrigerant to flow in one direction, while the refrigerant flowing through the second evaporator will still flow back to the first compressor; the first throttling device and the second throttling device remain in the closed state. Phase Two: Initial Start-up of the System Units; The system unit starts up in cooling-only mode upon initial startup; While the first compressor and the first throttling device are running, the second compressor remains stopped, and the first three-way valve, the second three-way valve, and the second throttling device remain at their default settings before the system unit was started. The low-temperature liquid refrigerant after passing through the first throttling device is divided into two channels by the valve body of the first three-way valve and enters the first evaporator and the second evaporator respectively. After heat exchange in the second evaporator, one channel of refrigerant passes through the second three-way valve and merges with the other channel of refrigerant after heat exchange in the first evaporator, and they both enter the first compressor. The high-temperature gaseous refrigerant after compression enters the first condenser, and after heat exchange, it enters the first throttling device to form a refrigeration cycle. After running for a period of time, the system determines whether the unit's outlet water temperature has reached the preset first threshold; if so, it continues to operate in single cooling mode; if not, it proceeds to the following stage three. Phase 3: Switch from single-cooling to dual-cooling operation mode; First, the first compressor continues to run, and the first throttling device is closed. The refrigerant that has passed through the first evaporator and the second evaporator is stored in the first condenser under the suction of the first compressor. After a few seconds, the refrigerant in the second evaporator is emptied, and the refrigerant circulating in the single refrigeration operation mode is concentrated in the first condenser. Then, the valve core in the first three-way valve moves to the first refrigerant outlet and closes it, cutting off the passage between the first three-way valve and the second evaporator; the valve core in the second three-way valve moves to the first refrigerant outlet and closes it, cutting off the passage between the first evaporator and the second three-way valve. Finally, the second compressor is started, and the first and second throttling devices are opened simultaneously, allowing the equipment components of the two refrigeration systems to operate independently. When the system load decreases, the first compressor continues to operate at its current operating frequency, while the second compressor operates at a reduced frequency. After operating for a period of time, when the system load continues to decrease, it transitions to the following stage four. Phase 4: Switching from dual-cooling to single-cooling operation mode; First, the second throttling device is closed, and the refrigerant in the second evaporator is stored in the second condenser under the suction of the second compressor; the second compressor continues for a period of time to empty the refrigerant in the second evaporator. Then, the valve core in the second three-way valve moves to the second refrigerant outlet and closes it; the valve core of the first three-way valve moves between the first refrigerant outlet and the second refrigerant outlet, with both outlets in the open state, allowing refrigerant to flow simultaneously from both channels. Secondly, after the first three-way valve and the second three-way valve have completed their operation, the second compressor stops. Finally, the second throttling device remains closed and the first throttling device remains open. The low-temperature liquid refrigerant flowing through the first throttling device enters the first evaporator and the second evaporator respectively through the two channels of the first three-way valve body. After heat exchange in the second evaporator, one path of refrigerant merges with the other path of refrigerant after heat exchange in the first evaporator through the second three-way valve and enters the first compressor together to form a refrigeration cycle. As the system load continues to decrease, the first compressor operates at a reduced frequency. Phase 5: After running for a period of time, the system determines whether the unit's outlet water temperature has reached the preset second threshold. If not, the first compressor continues to operate at reduced frequency. If so, the first compressor and the first throttling device are shut down, and the first three-way valve and the second three-way valve remain unchanged from the previous moment. At this time, the first throttling device, the first three-way valve, and the second three-way valve are in the same state as the unit before the start-up of the system in Phase 1.

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