Water chilling unit and control method thereof

Abstract

The embodiment of the invention provides a water chilling unit and a control method thereof, relates to the technical field of air conditioners, and is used for solving the problem that when the water chilling unit is started, as a refrigerant of an evaporator is migrated to a condenser, the evaporator lacks the refrigerant, and a compressor bearing breaks down. The water chilling unit comprises a refrigerant circulation loop; a liquid level detection device; one end of the first branch communicates with the condenser, and the other end communicates with the evaporator; the controller is configured to obtain the outdoor temperature, the chilled water temperature and the liquid level height detected by the liquid level detection device within the preset duration under the condition that the compressor is in the shutdown state; under the condition that the outdoor temperature is smaller than the chilled water temperature, the target frequency of a refrigerant pump is determined according to the temperature difference value between the outdoor temperature and the chilled water temperature and the liquid level height within the preset duration; and the refrigerant pump is controlled to operate at the target frequency, and the first electromagnetic valve is opened, so that the refrigerant in the condenser is conveyed into the evaporator through the first branch.

Description

TECHNICAL FIELD

[0001] The present application relates to the air conditioning technical field, and particularly relates to a water chiller and a control method thereof. BACKGROUND

[0002] The current water chiller can be applied to a place such as a data center for all-year refrigeration.

[0003] However, in the actual operation process of the refrigeration unit, when the outdoor temperature is lower than the water temperature on the evaporator side, a pressure difference between the outdoor and the outdoor may be caused. Under the action of the pressure difference, the refrigerant in the evaporator may migrate to the condenser, causing a lack of refrigerant in the evaporator. When the water chiller is started, the lack of refrigerant in the evaporator may cause a compressor bearing failure.

[0004] Therefore, how to solve the problem of the compressor bearing failure caused by the migration of the refrigerant in the evaporator to the condenser when the water chiller is started has become a technical problem to be solved. SUMMARY

[0005] The present application provides a water chiller and a control method thereof, which are used to solve the problem of the compressor bearing failure caused by the migration of the refrigerant in the evaporator to the condenser when the water chiller is started.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions.

[0007] In a first aspect, the present application provides a water chiller, which comprises: a refrigerant circulation loop, which circulates refrigerant in a loop composed of a compressor, a condenser and an evaporator; a liquid level detection device, which is arranged on the evaporator and is used to detect the liquid level of the refrigerant in the evaporator; a first branch, one end of the first branch being communicated with the condenser, the other end of the first branch being communicated with the evaporator, and a refrigerant pump and a first electromagnetic valve being arranged on the first branch; wherein the refrigerant pump is used to transport the refrigerant; and a controller, which is configured to: acquire an outdoor temperature, a chilled water temperature and the liquid level detected by the liquid level detection device within a preset time length, in a case that the compressor is in a shutdown state; determine a target frequency of the refrigerant pump according to a temperature difference between the outdoor temperature and the chilled water temperature and the liquid level within the preset time length, in a case that the outdoor temperature is less than the chilled water temperature; control the refrigerant pump to operate at the target frequency, and open the first electromagnetic valve, so as to transport the refrigerant in the condenser to the evaporator through the first branch.

[0008] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects: The present application provides a chiller that can adjust the target frequency of the refrigerant pump based on the temperature difference between the outdoor temperature and the chilled water temperature and the refrigerant liquid level in the evaporator within a preset time period when the outdoor temperature is lower than the chilled water temperature. By controlling the opening of the first solenoid valve, the refrigerant that has migrated to the condenser is redistributed to the evaporator through the first branch to replenish the refrigerant in the evaporator. In this way, when the chiller is restarted, compressor bearing failure caused by a lack of refrigerant in the evaporator can be avoided.

[0009] Furthermore, the refrigerant pump's target frequency can be adjusted based on the difference between the outdoor and chilled water temperatures, as well as the liquid level within a preset timeframe. This adjustment, based on the actual distribution and changes in the refrigerant within the chiller, prevents excessive refrigerant from migrating from the condenser to the evaporator due to excessive pump frequency, or insufficient refrigerant from migrating from the condenser to the evaporator due to insufficient pump frequency, ensuring even refrigerant distribution across the evaporator and condenser. This also reduces energy consumption.

[0010] In some embodiments, when the liquid level decreases within a preset time period, the controller is configured to determine the target frequency of the refrigerant pump based on the temperature difference between the outdoor temperature and the chilled water temperature and the preset time period, including: when the temperature difference is less than the first threshold and any liquid level within the preset time period is greater than the first liquid level threshold, the first frequency is determined as the target frequency of the refrigerant pump; when the temperature difference is less than the first threshold and any liquid level within the preset time period is greater than or equal to the second liquid level threshold and less than or equal to the first liquid level threshold, the third frequency is determined as the target frequency of the refrigerant pump; wherein the third frequency is greater than the first frequency.

[0011] In some embodiments, when the liquid level height remains unchanged within a preset time period, the controller is configured to determine the target frequency of the refrigerant pump based on the temperature difference between the outdoor temperature and the chilled water temperature and the preset time period, including: when the temperature difference is less than the first threshold and any liquid level height within the preset time period is greater than or equal to the second liquid level height threshold and less than or equal to the first liquid level height threshold, the second frequency is determined as the target frequency of the refrigerant pump; wherein the third frequency is greater than the second frequency, and the second frequency is greater than the first frequency.

[0012] In some embodiments, in the case that the liquid level height is unchanged or decreases within the preset time length, the controller is configured to determine the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature, the liquid level height, and the change information, including: in the case that the temperature difference is greater than or equal to the first threshold value and any liquid level height within the preset time length is greater than the first liquid level height threshold value, determining the second frequency as the target frequency of the refrigerant pump; in the case that the temperature difference is greater than or equal to the first threshold value and any liquid level height within the preset time length is greater than or equal to the second liquid level height threshold value and less than or equal to the first liquid level height threshold value, determining the third frequency as the target frequency of the refrigerant pump; in the case that the temperature difference is greater than or equal to the first threshold value and any liquid level height within the preset time length is less than the second liquid level height threshold value, determining the fourth frequency as the target frequency of the refrigerant pump; wherein the fourth frequency is greater than the third frequency.

[0013] In some embodiments, the chiller further includes: a second branch, one end of the second branch being in communication with the compressor and the other end of the second branch being in communication with the condenser; a third branch, one end of the third branch being in communication with the compressor and the other end of the third branch being in communication with the condenser, and the third branch being provided with the refrigerant pump and the second electromagnetic valve; and the controller is further configured to: in the case that the compressor is in the open state, detect the compression ratio of the chiller; in the case that the compression ratio is above the second threshold value, control the first electromagnetic valve to be closed, the second electromagnetic valve to be closed, and the refrigerant pump to be closed, so as to deliver the refrigerant into the compressor through the second branch; and in the case that the compression ratio is below the second threshold value, control the first electromagnetic valve to be closed, the second electromagnetic valve to be opened, and the refrigerant pump to be opened, so as to deliver the refrigerant into the compressor through the third branch.

[0014] In some embodiments, the chiller further includes: a second branch, one end of the second branch being in communication with the compressor and the other end of the second branch being in communication with the condenser; a third branch, one end of the third branch being in communication with the compressor and the other end of the third branch being in communication with the condenser, and the third branch being provided with the refrigerant pump and the second electromagnetic valve; and the controller is further configured to: in the case that the compressor is in the open state, detect the compression ratio of the chiller; in the case that the compression ratio is above the second threshold value, control the first electromagnetic valve to be closed, the second electromagnetic valve to be closed, and the refrigerant pump to be closed, so as to deliver the refrigerant into the compressor through the second branch; and in the case that the compression ratio is below the second threshold value, control the first electromagnetic valve to be closed, the second electromagnetic valve to be opened, and the refrigerant pump to be opened, so as to deliver the refrigerant into the compressor through the third branch.

[0015] In a second aspect, the embodiments of the present application provide a control method of a water chiller. The method is applied to the water chiller, and the method comprises the following steps: acquiring an outdoor temperature, a chilled water temperature, and a liquid level height detected by a liquid level detection device within a preset time length, when the compressor is in a shutdown state; determining a target frequency of a refrigerant pump according to a temperature difference between the outdoor temperature and the chilled water temperature and the liquid level height within the preset time length, when the outdoor temperature is less than the chilled water temperature; controlling the refrigerant pump to operate at the target frequency, and opening a first electromagnetic valve to transport refrigerant in a condenser to an evaporator through a first branch.

[0016] In a third aspect, the embodiments of the present application provide a controller. The controller comprises one or more processors and one or more memories. The one or more memories are configured to store computer program codes. The computer program codes comprise computer instructions. When the one or more processors execute the computer instructions, the controller performs any of the control methods of the water chiller provided in the second aspect.

[0017] In a fourth aspect, the embodiments of the present application provide a computer readable storage medium. The computer readable storage medium comprises computer instructions. When the computer instructions are executed on a computer, the computer performs any of the control methods of the water chiller provided in the second aspect.

[0018] In a fifth aspect, the embodiments of the present application provide a computer program product. The computer program product can be directly loaded into a memory and contains software codes. The computer program product can be loaded and executed by a computer to implement any of the control methods of the water chiller provided in the second aspect.

[0019] It should be noted that the computer instructions can be stored on the computer readable storage medium in whole or in part. The computer readable storage medium can be packaged together with the processor of the controller or packaged separately from the processor of the controller, and the present application does not limit the computer readable storage medium.

[0020] The beneficial effects of the second aspect to the fifth aspect of the present application are analyzed with reference to the beneficial effects of the first aspect, and will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the technical solutions of the present application, constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0022] Figure 1 A structure schematic diagram of a water chiller provided by the embodiments of the present application is shown in the accompanying drawings.

[0023] Figure 2Another structure schematic diagram of a water chiller provided by the embodiment of the present application is provided;

[0024] Figure 3 Another structure schematic diagram of a water chiller provided by the embodiment of the present application is provided;

[0025] Figure 4 Another structure schematic diagram of a water chiller provided by the embodiment of the present application is provided;

[0026] Figure 5 Another structure schematic diagram of a water chiller provided by the embodiment of the present application is provided;

[0027] Figure 6 A hardware configuration block diagram of a water chiller provided by the embodiment of the present application is provided;

[0028] Figure 7 A refrigeration cycle principle schematic diagram of a water chiller provided by the embodiment of the present application is provided;

[0029] Figure 8 A refrigerant migration schematic diagram when a water chiller is in a shutdown state provided by the embodiment of the present application is provided;

[0030] Figure 9 A cycle principle schematic diagram when a compressor is cooled provided by the embodiment of the present application is provided;

[0031] Figure 10 Another cycle principle schematic diagram when a compressor is cooled provided by the embodiment of the present application is provided;

[0032] Figure 11 A flow chart of a control method of a water chiller provided by the embodiment of the present application is provided;

[0033] Figure 12 A flow chart of another control method of a water chiller provided by the embodiment of the present application is provided;

[0034] Figure 13 A flow chart of another control method of a water chiller provided by the embodiment of the present application is provided;

[0035] Figure 14 A flow chart of another control method of a water chiller provided by the embodiment of the present application is provided;

[0036] Figure 15 A flow chart of another control method of a water chiller provided by the embodiment of the present application is provided;

[0037] Figure 16 A flow chart of another control method of a water chiller provided by the embodiment of the present application is provided;

[0038] Figure 17A structural schematic diagram of a control device of a water chilling unit is provided in the embodiments of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0040] It should be noted that all directional indications, such as upper, lower, left, right, front, back, and the like, used in the embodiments of the present application are only used to explain the relative position relationship, movement condition and the like between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0041] The terms "first", "second", and the like are used only for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0042] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "connected", "connected" should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or integrally connected. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, when describing the pipeline, the "connected" and "connected" used in the present application have the meaning of conducting. The specific meaning needs to be understood in conjunction with the context.

[0043] In the embodiments of the present application, the words such as "exemplary" or "for example" are used to represent as an example, illustration or description. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words such as "exemplary" or "for example" are intended to present the relevant concept in a specific manner.

[0044] In order to solve the problem of compressor bearing failure caused by the evaporator refrigerant migrating to the condenser when the chiller is turned on, the embodiment of the present application provides a control method for the chiller. When the outdoor temperature is lower than the chilled water temperature, the target frequency of the refrigerant pump can be adjusted based on the temperature difference between the outdoor temperature and the chilled water temperature, the liquid level of the refrigerant in the evaporator, and the change information of the liquid level within a preset time period. By controlling the opening of the first solenoid valve, the refrigerant migrating to the condenser is redistributed to the evaporator through the first branch to replenish the refrigerant in the evaporator. In this way, when the chiller is restarted, the compressor bearing failure caused by the lack of refrigerant in the evaporator can be avoided.

[0045] Furthermore, the refrigerant pump's target frequency can be adjusted based on the temperature difference between the outdoor temperature and the chilled water temperature, the refrigerant level in the evaporator, and any changes in the level over a preset time period. This adjustment, based on the actual distribution and changes in the refrigerant within the chiller, prevents excessive refrigerant from migrating from the condenser to the evaporator due to excessive pump frequency, or insufficient refrigerant from migrating from the condenser to the evaporator due to insufficient pump frequency, ensuring even refrigerant distribution across the evaporator and condenser. This also reduces energy consumption.

[0046] Figure 1 This is a schematic diagram of the structure of a chiller provided by this application according to an exemplary embodiment. Figure 1 As shown, the chiller 100 includes a compressor 101, a condenser 102, an evaporator 103, a throttling device 104, a liquid level detection device 105 and a controller 106 ( Figure 1 not shown).

[0047] In some embodiments, the chiller 100 may be an air-cooled magnetic levitation chiller.

[0048] In some embodiments, the compressor 101, condenser 102, throttling device 104 and evaporator 103 are sequentially connected to form a refrigerant circulation loop. In the embodiments of the present application, sequential connection only describes the sequential relationship between the various components, and other components may also be included between the various components. For example, Figure 2 As shown, a one-way valve 201 or the like may be provided on the pipeline between the compressor 101 and the condenser 102 .

[0049] In some embodiments, the compressor 101 is used to compress low-temperature and low-pressure liquid refrigerant into high-temperature and high-pressure gaseous refrigerant, and transmit the compressed refrigerant to the throttling device 104 .

[0050] In some embodiments, the compressor 101 can be a magnetic suspension compressor. The magnetic suspension compressor is a centrifugal compressor using magnetic bearings, which can compress the suction gas by centrifugal force of the gas and improve the refrigerant energy. Compared with the traditional centrifugal compressor, the magnetic suspension compressor is more energy-saving.

[0051] In some embodiments, the inlet of the condenser 102 is communicated with the compressor 101, and the outlet of the condenser 102 is communicated with the inlet of the evaporator 103, for condensing the high-temperature and high-pressure gaseous refrigerant discharged by the compressor 101 into high-temperature and high-pressure liquid refrigerant, to complete the heat dissipation process.

[0052] In some embodiments, the condenser 102 can be a finned condenser. The finned condenser can enable the gaseous refrigerant to realize the condensation heat exchange from gaseous state to liquid state under the high-speed suction of the fan.

[0053] In some embodiments, the inlet of the evaporator 103 is communicated with the outlet of the condenser 102, and the outlet of the evaporator 103 is communicated with the inlet of the compressor 101, for evaporating the liquid refrigerant into gaseous refrigerant to complete the heat absorption process.

[0054] In some embodiments, the evaporator 103 can be a flooded evaporator.

[0055] In some embodiments, the throttling device 104 is arranged between the condenser 102 and the evaporator 103, and the throttling device 104 has the function of expanding and decompressing the refrigerant flowing through the throttling device 104, which can be used to adjust the supply amount of the refrigerant in the pipeline.

[0056] In some embodiments, the throttling device 104 can be an electronic expansion valve.

[0057] In some embodiments, the liquid level detection device 105 is arranged on the evaporator 103, for detecting the liquid level of the refrigerant in the evaporator 103.

[0058] In some embodiments, the liquid level detection device 105 can be a liquid level meter or a liquid level sensor, and the specific type of the liquid level detection device 105 is not specially limited in the present application.

[0059] In some embodiments, the controller 106 can be a device capable of generating operation control signals to instruct the chiller to execute control instructions according to instruction operation codes and timing signals. Exemplarily, the controller can be a central processing unit (CPU), a general processor network processor (NP), a digital signal processing (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. The controller can also be other devices with processing functions, such as a circuit, a device, or a software module, and embodiments of the present application do not make any limitation in this regard.

[0060] In addition, the controller 106 controls the operation of each component inside the chiller 100, so that each component of the chiller 100 operates to achieve each predetermined function of the chiller.

[0061] In some embodiments, in order to solve the problem that, in the case that the chiller 100 is shut down, the refrigerant in the evaporator 103 will be transferred to the condenser 102 due to the temperature difference between the chilled water temperature in the evaporator 103 and the outdoor temperature, and the compressor 101 will have bearing failure due to the lack of refrigerant in the evaporator when the chiller 100 is started, as shown in FIG. 1, the chiller provided by embodiments of the present application can further include a first branch 301. The first branch 301 is provided with a refrigerant pump 302 and a first electromagnetic valve 303. Figure 3

[0062] In some embodiments, the inlet of the refrigerant pump 302 is in communication with the outlet of the condenser 102, and the outlet of the refrigerant pump 302 is connected to the first electromagnetic valve 303, for conveying refrigerant. The refrigerant pump 302 is usually driven by an electric motor, and converts energy into the power of the refrigerant pump 302 through a mechanical device, so as to push the refrigerant to flow. In some embodiments, since the refrigerant pump 302 is arranged on the first branch 301, the refrigerant pump 302 can be specifically used to convey the refrigerant discharged from the condenser to the evaporator through the first branch 301.

[0063] In some embodiments, the refrigerant pump 302 can be a variable frequency pump. The variable frequency pump has multiple frequency gears, for example, the variable frequency pump can have four frequency gears, which are a first frequency, a second frequency, a third frequency, and a fourth frequency in order from small to large. In this way, the controller 106 can adjust the frequency gear of the variable frequency pump based on actual demand, on the one hand, the refrigerant can be uniformly distributed in the evaporator 103 and the condenser 102, so as to avoid flow mutation. On the other hand, the energy consumption of the chiller can be reduced, and the chiller is more energy-saving.

[0064] ​In some embodiments, the first electromagnetic valve 303 is arranged between the refrigerant pump 302 and the evaporator 103, for controlling the connection and interruption of the first branch 301.

[0065] In some embodiments, as shown in FIG. 1, the first branch 301 can further be provided with a third check valve 401. Figure 4

[0066] In some embodiments, the third check valve 401 can be arranged between the refrigerant pump 302 and the first electromagnetic valve 303. The third check valve 401 has the function of preventing the backflow of refrigerant and isolating the protection of the compressor 101.

[0067] In some embodiments, in order to cool the compressor during the operation of the compressor, as shown in FIG. 1, the water chiller provided by the embodiments of the present application can further include a second branch 501 and a third branch 502. Figure 5

[0068] In some embodiments, the second branch 501 can be provided with a first check valve 503, and the third branch 502 can be provided with a refrigerant pump 504, a second check valve 505, and a second electromagnetic valve 506.

[0069] In some embodiments, the refrigerant pump 504 can be the same as the refrigerant pump 302 described above, and the second check valve 505 can be the same as the third check valve 401 described above. Hereinafter, the water chiller is exemplarily introduced with the refrigerant pump 504 being the same as the refrigerant pump 302 described above, and the second check valve 505 being the same as the third check valve 401 described above.

[0070] In some embodiments, the first check valve 503 is connected to the compressor 101 at one end and is communicated with the condenser 102 at the other end, for controlling the connection and interruption of the second branch 501.

[0071] In some embodiments, the refrigerant pump 504 (i.e., the refrigerant pump 302 described above) can be specifically used for conveying the refrigerant discharged from the condenser to the compressor 101 through the third branch, since the refrigerant pump 504 is further arranged on the third branch 502.

[0072] In some embodiments, the second check valve 505 (i.e., the third check valve 401 described above) can be further arranged between the refrigerant pump 504 and the second electromagnetic valve 506.

[0073] In some embodiments, the second electromagnetic valve 506 can be arranged between the second check valve 505 and the compressor 101, for controlling the connection and interruption of the third branch 502.

[0074] Figure 6 FIG. 1 is a hardware configuration block diagram of a water chiller provided by the embodiments of the present application. As shown in FIG. 1, the water chiller provided by the embodiments of the present application can include a compressor 101, a condenser 102, an evaporator 103, a first branch 301, a second branch 501, and a third branch 502. Figure 6 ​​As shown, the chiller 100 may further include: a communicator 601 and a memory 602 .

[0075] In some embodiments, the communicator 601 is used to establish a communication connection with other network entities, such as establishing a communication connection with a terminal device. The communicator 601 may include a radio frequency (RF) module, a cellular module, a wireless fidelity (WIFI) module, and a GPS module. Taking the RF module as an example, the RF module can be used to receive and transmit signals, in particular, to send received information to the controller 106 for processing; in addition, it can send signals generated by the controller 106. Typically, the RF circuit may include but is not limited to an antenna, at least one amplifier, a transceiver, a coupler, a low noise amplifier (LNA), a duplexer, etc.

[0076] In some embodiments, the memory 602 can be used to store software programs and data, such as historical operating status information of the chiller. The controller 106 executes various functions and data processing of the chiller 100 by running the software programs or data stored in the memory 602. The memory 602 may include a high-speed random access memory and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other volatile solid-state storage device. The memory 602 stores an operating system that enables the chiller 100 to run. In the present application, the memory 602 can store an operating system and various application programs, and can also store code for executing the control method of the chiller provided in the embodiments of the present application.

[0077] Those skilled in the art will understand that Figure 6 The hardware structure shown in the figure does not constitute a limitation on the chiller. The chiller may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0078] The following is an example of the working principle of the chiller. Figure 7 The present application provides a schematic diagram of the refrigeration cycle principle of a chiller according to an exemplary embodiment. Figure 7 As shown, the low-temperature, low-pressure gaseous refrigerant is compressed by the compressor 101 and converted into a high-temperature, high-pressure gaseous refrigerant. The compressed refrigerant enters the condenser 102, and is converted into a medium-temperature, high-pressure liquid refrigerant after heat exchange with the outdoor air in the condenser 102. The refrigerant flowing out of the condenser 102 is throttled and reduced in pressure by the throttling device 104 and is converted into a low-temperature, low-pressure gas-liquid two-phase refrigerant. The refrigerant after throttling and decompression is converted into a low-temperature, low-pressure gaseous refrigerant after heat exchange with the indoor air through the evaporator 103. The refrigerant flowing out of the evaporator 103 returns to the compressor 101 again.

[0079] Figure 8 Fig. 1 shows a schematic diagram of refrigerant migration when the water chiller is in a shutdown state according to an example embodiment of the present application. As shown in Fig. 1, when the water chiller is in a shutdown state, if the refrigerant in the evaporator 103 migrates to the condenser 102, the refrigerant pump 504 is turned on, and the first electromagnetic valve 303 is opened to connect the first branch 301. In this way, the refrigerant migrated to the condenser 102 can flow to the evaporator 103 through the first branch 301 under the drive of the refrigerant pump 504, so as to uniformly distribute the refrigerant between the evaporator 103 and the condenser 102. Figure 8

[0080] Figure 9 Fig. 2 shows a schematic diagram of a circulation principle when the compressor is cooled according to an example embodiment of the present application. As shown in Fig. 2, when the water chiller is in an on state, the water chiller normally performs the refrigeration cycle shown in Fig. 1 to perform refrigeration. Meanwhile, when the compression of the water chiller is small, the refrigerant pump 504 is turned on, and the second electromagnetic valve 506 is opened to connect the third branch 502. In this way, the refrigerant flowing out of the condenser 102 can flow to the compressor 101 through the third branch 502 under the drive of the refrigerant pump 504, so as to cool the motor of the compressor 101. Figure 9 Figure 7 Fig. 3 shows another schematic diagram of a circulation principle when the compressor is cooled according to an example embodiment of the present application. As shown in Fig. 3, when the water chiller is in an on state, the water chiller normally performs the refrigeration cycle shown in Fig. 1 to perform refrigeration. Meanwhile, when the compression of the water chiller is large, the refrigerant pump 504 is turned off, and the second electromagnetic valve 506 is closed to disconnect the third branch 502. In this way, the refrigerant flowing out of the condenser 102 can only flow to the compressor 101 through the second branch 501, so as to cool the motor of the compressor 101.

[0081] Figure 10 Figure 10 Figure 7 The embodiments provided by the present application will be described in detail below with reference to the accompanying drawings.

[0082] As shown in Fig. 4, the embodiment provided by the present application provides a control method of a water chiller, which comprises the following steps:

[0083] As shown in Fig. 4, the embodiment provided by the present application provides a control method of a water chiller, which comprises the following steps: Figure 11

[0084] S101, the controller acquires the outdoor temperature, the chilled water temperature, and the liquid level height detected by the liquid level detection device within a preset time length when the compressor is in a shutdown state.

[0085] ​​​​​It can be understood that when the water chiller is powered off or in standby mode, the compressor is in a powered-off state, and the guide vane of the compressor is not completely closed, which allows the refrigerant to flow through the compressor. If the outdoor temperature is less than the chilled water temperature, the pressure difference caused by the temperature difference between the outdoor temperature and the chilled water temperature will drive the refrigerant in the evaporator to migrate to the evaporator, causing a compressor bearing failure problem when the water chiller is turned on again due to the lack of refrigerant in the evaporator. Therefore, when it is detected that the compressor is powered off, the outdoor temperature, the chilled water temperature, the liquid level detected by the liquid level detection device, and the change information of the liquid level within a preset time period can be obtained.

[0086] In some embodiments, before obtaining the outdoor temperature, the chilled water temperature, and the liquid level within the preset time period, the controller can detect the operating state of the compressor. The operating state includes a powered-on state and a powered-off state.

[0087] In the case where it is detected that the compressor is in the powered-off state, the controller can execute Figure 12 、 Figure 13 、 Figure 14 The control method of the water chiller provided in the embodiments shown in the above can solve the problem that the refrigerant in the evaporator migrates to the evaporator, causing a compressor bearing failure problem when the water chiller is turned on again due to the lack of refrigerant in the evaporator.

[0088] In the case where it is detected that the compressor is in the powered-on state, the controller can execute the following Figure 15 The control method of the water chiller provided in the embodiments shown in the above can reduce the temperature during the operation of the compressor.

[0089] In some embodiments, after obtaining the outdoor temperature and the chilled water temperature, the size relationship between the outdoor temperature and the chilled water temperature can be determined first, and then whether the liquid level within the preset time period needs to be obtained can be determined based on the size relationship between the outdoor temperature and the chilled water temperature. Alternatively, the outdoor temperature, the chilled water temperature, and the liquid level within the preset time period can be directly obtained.

[0090] In an example, when the outdoor temperature is less than the chilled water temperature, the refrigerant migrates from the evaporator to the condenser, and at this time, the liquid level within the preset time period needs to be obtained, and then the refrigerant pump can be controlled based on the liquid level within the preset time period to migrate the refrigerant migrated to the condenser to the evaporator, that is, the following steps S102 and S103 are executed.

[0091] When the outdoor temperature is greater than or equal to the chilled water temperature, the refrigerant does not migrate from the evaporator to the condenser, and the refrigerant pump does not need to be turned on, so that the liquid level within the preset time period does not need to be obtained, thereby saving resources.

[0092] In another example, as long as it is detected that the compressor is in the shutdown state, the controller can obtain the outdoor temperature, the chilled water temperature, and the liquid level height within a preset time length.

[0093] S102, the controller determines the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature and the liquid level height within a preset time length, in a case where the outdoor temperature is less than the chilled water temperature.

[0094] It can be understood that, if the outdoor temperature is less than the chilled water temperature, it indicates that the pressure difference outside is less than the pressure difference inside, and under the driving of the pressure difference, the refrigerant in the evaporator can migrate to the condenser. However, in some cases, even if there is a pressure difference between the indoor and outdoor, the refrigerant in the evaporator will not migrate to the condenser. Therefore, the target frequency of the refrigerant pump can be further determined based on the temperature difference between the outdoor temperature and the chilled water temperature, and the liquid level height within a preset time length, and if the target frequency is determined to be 0, the refrigerant pump does not need to be turned on even if the outdoor temperature is less than the chilled water temperature.

[0095] In some embodiments, the controller can determine the change information of the liquid level height within a preset time length, such as the change information of the decrease of the liquid level height within a preset time length, based on the liquid level height within a preset time length. Further, the controller can determine the target frequency of the refrigerant pump based on the temperature difference, the liquid level height within a preset time length, and the change information of the liquid level height within a preset time length. The target frequency of the refrigerant pump can also be determined based on a neural network control method.

[0096] In one example, the controller can refer to the specific description in the embodiments shown in the following Figure 12 , Figure 13 , Figure 14 The specific process of determining the target frequency of the refrigerant pump based on the preset correspondence between the temperature difference, the liquid level height, and the change information and the frequency of the refrigerant pump is not described herein.

[0097] In another example, the controller can train a neural network model through a large amount of historical data (including the temperature difference, the liquid level height, the change information, and the frequency of the refrigerant pump), so that the neural network model can learn the complex nonlinear relationship between the temperature difference, the liquid level height, the change information, and the frequency of the refrigerant pump, and output the best target frequency of the refrigerant pump according to the current values of the temperature difference, the liquid level height, and the change information.

[0098] S103, the controller controls the refrigerant pump to operate at the target frequency, and turns on the first electromagnetic valve to deliver the refrigerant in the condenser to the evaporator through the first branch.

[0099] In some embodiments, the controller can send a control instruction to the refrigerant pump through the communicator, the control instruction comprising a target frequency of the refrigerant pump, the control instruction being used to instruct the refrigerant pump to operate at the target frequency.

[0100] For example, the specific delivery process of the refrigerant in the condenser to the evaporator can refer to the above-mentioned Figure 8 The embodiments shown in the present application will not be repeated here.

[0101] Based on Figure 11 The control method of the water chiller provided by the embodiments shown in the present application can adjust the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature, the liquid level height of the refrigerant in the evaporator, and the change information of the liquid level height within a preset time length, and re-distribute the refrigerant migrated to the condenser to the evaporator through the first branch by opening the first electromagnetic valve to supplement the refrigerant in the evaporator when the outdoor temperature is less than the chilled water temperature. In this way, when the water chiller is started again, the compressor bearing failure caused by the lack of refrigerant in the evaporator can be avoided.

[0102] In addition, the target frequency of the refrigerant pump can be adjusted according to the temperature difference between the outdoor temperature and the chilled water temperature, the liquid level height of the refrigerant in the evaporator, and the change information of the liquid level height within a preset time length. This adjustment method based on the actual distribution and actual change of the refrigerant in the water chiller can avoid the excessive amount of refrigerant migrated from the condenser to the evaporator caused by the excessively high frequency of the refrigerant pump, or the insufficient amount of refrigerant migrated from the condenser to the evaporator caused by the excessively low frequency of the refrigerant pump, and ensure the uniform distribution of the refrigerant in the evaporator and the condenser. At the same time, energy consumption can be reduced.

[0103] In some embodiments, in the case that the liquid level height decreases within the preset time length, that is, in the case that the change information of the liquid level height within the preset time length is the change information that the liquid level height decreases within the preset time length, in order to determine the target frequency of the refrigerant pump, as Figure 12 The control method of the water chiller provided by the embodiments of the present application can further comprise the following steps.

[0104] S201, the controller determines the first frequency as the target frequency of the refrigerant pump in the case that the temperature difference is less than the first threshold value and the liquid level height within the preset time length is greater than the first liquid level height threshold value.

[0105] It can be understood that if the liquid level height is greater than the first liquid level height threshold value, it means that the amount of refrigerant in the evaporator is relatively large, that is, the evaporator does not lack refrigerant, but since the liquid level height is still decreasing, the refrigerant in the evaporator is migrating to the condenser, and if no necessary measures are taken, the refrigerant in the evaporator will continue to decrease, thereby causing the evaporator to lack refrigerant, and therefore the refrigerant pump needs to be started.

[0106] If the temperature difference is less than the first threshold value, it indicates that the temperature difference between the chilled water temperature and the outdoor temperature is small, that is, the pressure difference between the outdoor and the evaporator side is small. Under the driving of the pressure difference, the flow rate of the refrigerant in the evaporator migrating to the condenser is small, and the flow of the refrigerant in the evaporator migrating to the condenser in the same time is small. Therefore, the refrigerant pump does not need too high frequency, and the refrigerant can be effectively re-migrated to the evaporator.

[0107] S202, the controller determines the third frequency as the target frequency of the refrigerant pump in the case that the temperature difference is less than the first threshold value, the liquid level height in the preset time length is greater than or equal to the second liquid level height threshold value and less than or equal to the first liquid level height threshold value.

[0108] The third frequency is greater than the first frequency.

[0109] It can be understood that, on the basis of the following step S301, since the liquid level height is decreasing, it indicates that the refrigerant in the evaporator is migrating to the condenser, that is, the case of step S202 is more serious than that of step S301. Therefore, the third frequency greater than the second frequency is determined as the target frequency of the refrigerant pump, so as to quickly migrate the refrigerant in the condenser to the evaporator.

[0110] In some embodiments, in the case that the liquid level height in the preset time length is unchanged, that is, in the case that the change information of the liquid level height in the preset time length is the change information that the liquid level height in the preset time length is unchanged, in order to determine the target frequency of the refrigerant pump, as shown in Figure 13 The control method of the water chiller provided by the embodiments of the present application can further include the following steps.

[0111] S301, the controller determines the second frequency as the target frequency of the refrigerant pump in the case that the temperature difference is less than the first threshold value, and the liquid level height in the preset time length is greater than or equal to the second liquid level height threshold value and less than or equal to the first liquid level height threshold value.

[0112] It can be understood that, on the basis of the above-mentioned step S201, if the liquid level height is unchanged, it indicates that the refrigerant in the evaporator is not migrating to the condenser. However, since the liquid level height is greater than or equal to the second liquid level height threshold value and less than or equal to the first liquid level height threshold value, it indicates that the amount of refrigerant in the evaporator is small, that is, the case of step S301 is more serious than that of step S201. Therefore, the second frequency greater than the first frequency is determined as the target frequency of the refrigerant pump, so as to quickly migrate the refrigerant in the condenser to the evaporator.

[0113] In some embodiments, the controller determines the sixth frequency as the target frequency of the refrigerant pump in the case that the temperature difference is less than the first threshold value and the liquid level height is greater than the first liquid level height threshold value. The sixth frequency is 0, that is, the refrigerant pump is controlled to be closed.

[0114] It can be understood that if the liquid level height is greater than the first liquid level height threshold, it indicates that the amount of refrigerant in the evaporator is relatively large, that is, the evaporator does not lack refrigerant. And the liquid level height does not change, and the refrigerant in the evaporator does not migrate to the condenser, so the refrigerant pump does not need to be started.

[0115] In some embodiments, as shown in Figure 14 The control method of the water chiller provided by the embodiments of the present application can further include the following steps.

[0116] S401, the controller determines the second frequency as the target frequency of the refrigerant pump in the case that the temperature difference is greater than or equal to the first threshold value, and the liquid level height in the preset time length is greater than the first liquid level height threshold.

[0117] It can be understood that, on the basis of the above step S201, since the temperature difference is greater than or equal to the first threshold value, it indicates that the pressure difference between the outdoor and the indoor is large, and under the driving of the pressure difference, the flow rate of the refrigerant in the evaporator migrating to the condenser becomes large, and the flow of the refrigerant in the evaporator migrating to the condenser in the same time is relatively large, that is, the case of step S401 is more serious than that of step S201. Therefore, the second frequency greater than the first frequency needs to be determined as the target frequency of the refrigerant pump to quickly migrate the refrigerant in the condenser to the evaporator.

[0118] S402, the controller determines the third frequency as the target frequency of the refrigerant pump in the case that the temperature difference is greater than or equal to the first threshold value, the liquid level height in the preset time length is greater than or equal to the second liquid level height threshold and less than or equal to the first liquid level height threshold.

[0119] The third frequency is greater than the second frequency.

[0120] It can be understood that, on the basis of the above step S401, since the liquid level height is greater than or equal to the second liquid level height threshold and less than or equal to the first liquid level height threshold, it indicates that the amount of refrigerant in the evaporator is relatively small, that is, the case of step S402 is more serious than that of step S041. Therefore, the third frequency greater than the second frequency needs to be determined as the target frequency of the refrigerant pump to quickly migrate the refrigerant in the condenser to the evaporator.

[0121] S403, the controller determines the fourth frequency as the target frequency of the refrigerant pump in the case that the temperature difference is greater than or equal to the first threshold value, and the liquid level height is less than the second liquid level height threshold.

[0122] The fourth frequency is greater than the third frequency.

[0123] It can be understood that, on the basis of the step S402, since the liquid level height is greater than or equal to the second liquid level height threshold and less than or equal to the first liquid level height threshold, it means that the amount of refrigerant in the evaporator is very small, that is, the case of step S403 is more serious than that of step S402. Therefore, the fourth frequency greater than the third frequency is determined as the target frequency of the refrigerant pump, so as to quickly migrate the refrigerant in the condenser to the evaporator.

[0124] In some embodiments, in the case that the water chiller is in the open state, the high operation of the motor of the compressor can cause the temperature of the motor cavity of the compressor to rise, thereby affecting the service life of the compressor and the like. Therefore, as shown in Figure 15 In order to reduce the temperature of the motor of the compressor, the embodiments of the present application also provide a control method of a water chiller, which comprises the following steps.

[0125] S501, the controller detects the compression ratio of the water chiller in the case that the compressor is in the open state.

[0126] In some embodiments, the controller can detect the discharge pressure of the compressor through the discharge pressure sensor, detect the suction pressure of the compressor through the suction pressure sensor, and then determine the compression ratio of the water chiller based on the ratio of the discharge pressure to the suction pressure.

[0127] S502, the controller controls the first electromagnetic valve to be closed, the second electromagnetic valve to be closed, and the refrigerant pump to be closed in the case that the compression ratio is above the second threshold, so that the refrigerant flows into the compressor through the second branch.

[0128] It can be understood that, if the compression ratio is above the second threshold, it means that the discharge pressure of the compressor can be relatively large, so that there can be greater driving force to promote the circulation of the refrigerant in the pipeline. Therefore, the refrigerant can be cooled only by the second branch with the first check valve without the aid of the refrigerant pump.

[0129] For example, for the cooling process in this case, reference can be made to the embodiments shown in the above Figure 10 The specific process of cooling the compressor is not described here.

[0130] S503, the controller controls the first electromagnetic valve to be closed, the second electromagnetic valve to be closed, and the refrigerant pump to be closed in the case that the compression ratio is below the second threshold, so that the refrigerant flows into the compressor through the third branch.

[0131] It can be understood that if the compression ratio is below the second threshold, it means that the exhaust pressure of the compressor can be relatively small, and there is no large driving force to drive the refrigerant to circulate in the pipeline. Therefore, the assistance of the refrigerant pump is needed to make the refrigerant pass through the third branch with the refrigerant pump to realize the cooling of the motor of the compressor.

[0132] For example, for the cooling process in this case, reference can be made to the above Figure 9 The specific process of cooling the compressor is not repeated here.

[0133] The complete flow of the control method of the water chiller provided by the embodiment of the application is exemplarily introduced below.

[0134] As Figure 16 shown, the flow starts.

[0135] Step a1, judge whether the detected compressor is in the shutdown state.

[0136] If yes, execute the following step a2.

[0137] If no, execute the following step a6.

[0138] Step a2, obtain the outdoor temperature, the chilled water temperature, and the liquid level height within the preset time length.

[0139] Judge whether the temperature difference between the outdoor temperature and the chilled water temperature is greater than 0℃.

[0140] If yes, execute the following step a3.

[0141] If no, the flow ends.

[0142] Step a3, judge whether the temperature difference between the outdoor temperature and the chilled water temperature is less than the first threshold.

[0143] If yes, execute the following step a4.

[0144] If no, execute the following step a5.

[0145] Step a4, according to the size relationship between the liquid level height within the preset time length and the first liquid level height threshold and the second liquid level height threshold, and the change information of the liquid level height within the preset time length, determine the target frequency of the refrigerant pump.

[0146] Step a5, according to the size relationship between the liquid level height within the preset time length and the first liquid level height threshold and the second liquid level height threshold, determine the target frequency of the refrigerant pump.

[0147] Step a6, the refrigeration unit is normally operated, and the motor cooling mode is started.

[0148] It is determined whether the detected compression ratio is less than a second threshold.

[0149] If yes, execute the following step a7.

[0150] If not, execute the following step a8.

[0151] Step a7: Control the first solenoid valve to close, the second solenoid valve to open, and the refrigerant pump to turn on, so as to deliver the refrigerant to the compressor through the third branch.

[0152] Step a8: Control the first solenoid valve to be closed, the second solenoid valve to be closed, and the refrigerant pump to be closed, so as to deliver the refrigerant to the compressor through the second branch.

[0153] Those skilled in the art will appreciate that in one or more of the above examples, the functions described herein can be implemented using hardware, software, firmware, or any combination thereof. When implemented using software, these functions can be stored in a computer-readable medium or transmitted as one or more instructions or codes on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of computer programs from one place to another. The storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0154] In the embodiments of the present invention, electronic products, etc., can be divided into functional modules according to the above-mentioned method examples. For example, each functional module can be divided according to each function, or two or more functions can be integrated into a processing module. The above-mentioned integrated modules can be implemented in the form of hardware or software functional modules. It should be noted that the division of modules in the embodiments of the present invention is schematic and is only a logical functional division. In actual implementation, other division methods may be used.

[0155] In the case of dividing each functional module into corresponding functional modules, Figure 17 A schematic diagram of a control device for a chiller provided in an embodiment of the present application is shown in FIG. Figure 17 As shown, the control device of the chiller (hereinafter referred to as the control device for ease of description) 1700 may include: an acquisition module 1701 , a determination module 1702 and a control module 1703 .

[0156] In some embodiments, the acquisition module 1701 is used to acquire the outdoor temperature, the chilled water temperature, and the liquid level height detected by the liquid level detection device within a preset time period when the compressor is in the off state.

[0157] In some embodiments, the determining module 1702 is configured to determine a target frequency of the refrigerant pump according to a temperature difference between the outdoor temperature and the chilled water temperature and the liquid level height within the preset time length, in a case that the outdoor temperature is less than the chilled water temperature.

[0158] In some embodiments, the control module 1703 is configured to control the refrigerant pump to operate at the target frequency, and open the first electromagnetic valve to transport the refrigerant in the condenser to the evaporator through the first branch.

[0159] In the case of an integrated unit, the control device 1700 can further include a storage module and a communication module.

[0160] In some embodiments, the storage module is configured to store program codes and data of the control device 1700. In some embodiments, the communication module can be a transceiver, a transceiver circuit, a communication interface, or the like.

[0161] The embodiments of the present application also provide a computer readable storage medium, which includes computer execution instructions, and when the computer execution instructions run on a computer, the computer is caused to execute the method provided by the above embodiments.

[0162] The embodiments of the present application also provide a computer program product, which can be directly loaded into a memory and contains software codes, and the computer program product can realize the method provided by the above embodiments after being loaded and executed by a computer.

[0163] From the above description of the embodiments, those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional modules is taken as an example for illustration, and in actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above.

[0164] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed in the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A water chiller, characterized by, The application relates to a refrigerant circulation system. The refrigerant circulation system comprises: a refrigerant circulation loop, in which refrigerant is circulated in a compressor, a condenser and an evaporator; a liquid level detection device arranged on the evaporator and used for detecting the liquid level of refrigerant in the evaporator; a first branch, one end of the first branch being connected to the condenser, the other end of the first branch being connected to the evaporator, and a refrigerant pump and a first electromagnetic valve being arranged on the first branch, wherein the refrigerant pump is used for conveying refrigerant; a controller configured to: when the compressor is in an off state, acquire an outdoor temperature, a chilled water temperature and a liquid level detected by the liquid level detection device within a preset time length; when the outdoor temperature is less than the chilled water temperature, determine a target frequency of the refrigerant pump according to a temperature difference between the outdoor temperature and the chilled water temperature and the liquid level within the preset time length; 2. The water chiller of claim 1, wherein control the refrigerant pump to operate at the target frequency and open the first electromagnetic valve, so as to convey refrigerant in the condenser to the evaporator through the first branch. when the liquid level within the preset time length decreases, the controller is configured to determine the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature and the liquid level within the preset time length, comprising: when the temperature difference is less than a first threshold value and any liquid level within the preset time length is greater than a first liquid level threshold value, a first frequency is determined as the target frequency of the refrigerant pump; when the temperature difference is less than the first threshold value and any liquid level within the preset time length is greater than or equal to a second liquid level threshold value and less than or equal to the first liquid level threshold value, a third frequency is determined as the target frequency of the refrigerant pump; 3. The water chiller of claim 2, wherein wherein the third frequency is greater than the first frequency. when the liquid level within the preset time length is unchanged, the controller is configured to determine the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature and the liquid level within the preset time length, comprising: when the temperature difference is less than the first threshold value and any liquid level within the preset time length is greater than or equal to the second liquid level threshold value and less than or equal to the first liquid level threshold value, a second frequency is determined as the target frequency of the refrigerant pump; 4. The water chiller of claim 3, wherein wherein the third frequency is greater than the second frequency and the second frequency is greater than the first frequency. when the liquid level within the preset time length is unchanged or decreases, the controller is configured to determine the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature and the liquid level within the preset time length, comprising: when the temperature difference is greater than or equal to the first threshold value and any liquid level within the preset time length is greater than the first liquid level threshold value, the second frequency is determined as the target frequency of the refrigerant pump. determining the third frequency as the target frequency of the refrigerant pump in a case that the temperature difference is greater than or equal to the first threshold value and any liquid level height in the preset time period is greater than or equal to a second liquid level height threshold value and less than or equal to the first liquid level height threshold value; determining a fourth frequency as the target frequency of the refrigerant pump in a case that the temperature difference is greater than or equal to the first threshold value and any liquid level height in the preset time period is less than the second liquid level height threshold value; wherein the fourth frequency is greater than the third frequency.

5. The water chiller according to any of claims 1-4, wherein The water chiller further comprises: a second branch, one end of the second branch being in communication with the compressor, and the other end of the second branch being in communication with the condenser; a third branch, one end of the third branch being in communication with the compressor, and the other end of the third branch being in communication with the condenser, and the refrigerant pump and a second electromagnetic valve being arranged on the third branch; The controller is further configured to: detect a compression ratio of the water chiller in a case that the compressor is in an open state; control the first electromagnetic valve to be closed, the second electromagnetic valve to be closed, and the refrigerant pump to be closed to deliver refrigerant into the compressor through the second branch in a case that the compression ratio reaches a second threshold value or above; control the first electromagnetic valve to be closed, the second electromagnetic valve to be opened, and the refrigerant pump to be opened to deliver refrigerant into the compressor through the third branch in a case that the compression ratio reaches the second threshold value or below.

6. A control method of a water chiller, characterized by, comprises: acquire an outdoor temperature, a chilled water temperature, and liquid level heights detected by a liquid level detection device in a preset time period in a case that the compressor is in a shutdown state; determine a target frequency of a refrigerant pump according to a temperature difference between the outdoor temperature and the chilled water temperature and the liquid level heights in the preset time period in a case that the outdoor temperature is less than the chilled water temperature; control the refrigerant pump to operate at the target frequency and open a first electromagnetic valve to deliver refrigerant in the condenser into the evaporator through a first branch.

7. The method of claim 6, wherein, In a case that the liquid level heights in the preset time period decrease, the determining of the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature and the liquid level heights in the preset time period comprises: determining a first frequency as the target frequency of the refrigerant pump in a case that the temperature difference is less than a first threshold value and any liquid level height in the preset time period is greater than a first liquid level height threshold value; determining a third frequency as the target frequency of the refrigerant pump in a case that the temperature difference is less than the first threshold value and any liquid level height in the preset time period is greater than or equal to a second liquid level height threshold value and less than or equal to the first liquid level height threshold value; wherein the third frequency is greater than the first frequency.

8. The method of claim 7, wherein, In a case that the liquid level heights in the preset time period are unchanged, the determining of the target frequency of the refrigerant pump according to the temperature difference between the outdoor temperature and the chilled water temperature and the liquid level heights in the preset time period comprises: In a case where the temperature difference is less than the first threshold value, and any liquid level height in the preset time period is greater than or equal to a second liquid level height threshold value and less than or equal to the first liquid level height threshold value, a second frequency is determined as the target frequency of the refrigerant pump. The third frequency is greater than the second frequency, and the second frequency is greater than the first frequency.

9. The method of claim 8, wherein, The method further comprises: In a case where the temperature difference is greater than or equal to the first threshold value, and any liquid level height in the preset time period is greater than the first liquid level height threshold value, the second frequency is determined as the target frequency of the refrigerant pump. In a case where the temperature difference is greater than or equal to the first threshold value, and any liquid level height in the preset time period is greater than or equal to a second liquid level height threshold value and less than or equal to the first liquid level height threshold value, the third frequency is determined as the target frequency of the refrigerant pump. In a case where the temperature difference is greater than or equal to the first threshold value, and any liquid level height in the preset time period is less than the second liquid level height threshold value, a fourth frequency is determined as the target frequency of the refrigerant pump. The fourth frequency is greater than the third frequency.

10. The method according to any one of claims 6-9, characterized in that, The method further comprises: In a case where the compressor is in an open state, a compression ratio of the water chiller is detected; In a case where the compression ratio is above a second threshold value, the first electromagnetic valve is controlled to be closed, the second electromagnetic valve is controlled to be closed, and the refrigerant pump is controlled to be closed, so as to deliver refrigerant into the compressor through a second branch; In a case where the compression ratio is below the second threshold value, the first electromagnetic valve is controlled to be closed, the second electromagnetic valve is controlled to be opened, and the refrigerant pump is controlled to be opened, so as to deliver refrigerant into the compressor through the third branch.

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