Frost-proof natural cooling water chiller and control method and control device thereof

Abstract

The present disclosure provides a natural cooling water chiller with anti-freezing function and a control method and device thereof, and relates to the field of air conditioners. The natural cooling water chiller comprises a liquid pump, an air cooler provided with a fan, a heat exchanger comprising a first inlet and a first outlet on a water solution circulation side to which anti-freezing liquid is added and a second inlet and a second outlet on a chilled water circulation side to which anti-freezing liquid is not added, and an opening-adjustable bypass valve. The first outlet of the heat exchanger is communicated with the inlet of the liquid pump, and the bypass valve is connected between the communication path between the outlet of the liquid pump and the inlet of the air cooler and the communication path between the outlet of the air cooler and the first inlet of the heat exchanger. By adjusting at least one of the opening of the bypass valve or the frequency of the fan, the freezing problem of the water without anti-freezing liquid on the user side of the natural cooling water chiller can be prevented when the ambient temperature is lower than 0℃.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of air conditioners, and in particular to a natural cooling water chiller with anti-freezing function and a control method and control device thereof. BACKGROUND

[0002] With the vigorous promotion of energy-saving technology, the use of natural cold sources is increasingly valued. Natural cooling water chillers with surface coolers can use natural cold sources for refrigeration when the outdoor ambient temperature is lower than the chilled water outlet temperature of the water chiller. For example, in some areas, the lowest winter temperature can reach below -30℃, and the winter temperature always remains below 0℃. These areas can use natural cold sources for refrigeration. However, since the inlet and outlet water of the user side of the natural cooling water chiller is not water added with anti-freezing liquid, freezing problems may occur when the ambient temperature is lower than 0℃, and accidents such as cracking of the heat exchanger may occur, affecting the reliability of the water chiller. SUMMARY

[0003] One of the technical problems to be solved by the embodiments of the present disclosure is the freezing problem of the water without anti-freezing liquid added on the user side of the natural cooling water chiller when the ambient temperature is lower than 0℃.

[0004] Some embodiments of the present disclosure provide a natural cooling water chiller with anti-freezing function, comprising:

[0005] a liquid pump;

[0006] a surface cooler provided with a fan;

[0007] a heat exchanger comprising a first inlet and a first outlet located on the circulation side of the water solution added with anti-freezing liquid and a second inlet and a second outlet located on the circulation side of the chilled water without anti-freezing liquid added;

[0008] a bypass valve with adjustable opening degree;

[0009] wherein the first outlet of the heat exchanger is in communication with the inlet of the liquid pump, the outlet of the liquid pump is in communication with the inlet of the surface cooler, the outlet of the surface cooler is in communication with the first inlet of the heat exchanger, and the bypass valve is connected between the communication path between the outlet of the liquid pump and the inlet of the surface cooler and the communication path between the outlet of the surface cooler and the first inlet of the heat exchanger.

[0010] In some embodiments, the natural cooling water chiller further comprises:

[0011] a first temperature sensor arranged at the first inlet of the heat exchanger; and

[0012] a control device configured to control at least one of the opening degree of the bypass valve or the frequency of the fan based on the temperature detected by the first temperature sensor;

[0013] The control device is electrically connected with the first temperature sensor, the bypass valve and the fan respectively.

[0014] In some embodiments, the natural cooling water chiller further comprises:

[0015] A second temperature sensor is arranged at a second outlet of the heat exchanger.

[0016] A heater is arranged on the heat exchanger; and

[0017] A control device is configured to control the heater to be turned on or turned off based on a temperature detected by the second temperature sensor.

[0018] The control device is electrically connected with the second temperature sensor and the heater respectively.

[0019] In some embodiments, the liquid pump is a constant frequency liquid pump.

[0020] In some embodiments, the fan is a frequency-adjustable variable frequency fan.

[0021] Some embodiments of the present disclosure provide a control method for a freeze-proof natural cooling water chiller, comprising:

[0022] Obtaining a working state of the natural cooling water chiller;

[0023] According to the working state of the natural cooling water chiller, detecting a first temperature of a first inlet of the heat exchanger located on a water solution circulation side to which antifreeze is added, or detecting a second temperature of a second outlet of the heat exchanger located on a chilled water circulation side to which antifreeze is not added;

[0024] According to the working state of the natural cooling water chiller and the first temperature, controlling at least one of an opening degree of the bypass valve or a frequency of the fan; or

[0025] According to the working state of the natural cooling water chiller and the second temperature, controlling a heater arranged on the heat exchanger to be turned on or turned off.

[0026] In some embodiments, according to the working state of the natural cooling water chiller and the first temperature, controlling at least one of the opening degree of the bypass valve or the frequency of the fan, comprises:

[0027] When the natural cooling water chiller enters a starting state, controlling the opening degree of the bypass valve to be at a maximum opening degree;

[0028] If the first temperature is continuously detected to be greater than an upper threshold value within a preset time, controlling the bypass valve to decrease the opening degree;

[0029] If the first temperature is continuously detected to be less than a lower threshold value within a preset time, turning off the liquid pump and controlling the natural cooling water chiller to enter a standby state;

[0030] If the first temperature is continuously detected to be not greater than the upper threshold value and not less than the lower threshold value within a preset time, the current operating state of each device in the natural cooling chiller is kept unchanged.

[0031] In some embodiments, the at least one of the opening of the bypass valve or the frequency of the fan is controlled according to the working state of the natural cooling chiller and the first temperature, and further comprising:

[0032] After the opening of the bypass valve is controlled to be reduced, if the first temperature is continuously detected to be still greater than the upper threshold value within a preset time and the bypass valve has been reduced to the minimum opening, the fan is started;

[0033] After the opening of the bypass valve is controlled to be reduced, if the first temperature is continuously detected to be not greater than the upper threshold value within a preset time, the current operating state of each device in the natural cooling chiller is kept unchanged.

[0034] In some embodiments, the at least one of the opening of the bypass valve or the frequency of the fan is controlled according to the working state of the natural cooling chiller and the first temperature, and further comprising:

[0035] After the fan is started, if the first temperature is continuously detected to be still greater than the upper threshold value within a preset time, the frequency of the fan is controlled to be increased;

[0036] After the fan is started, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, the fan is stopped and the opening of the bypass valve is kept unchanged;

[0037] After the fan is started, if the first temperature is continuously detected to be not greater than the upper threshold value and not less than the lower threshold value within a preset time, the current operating state of each device in the natural cooling chiller is kept unchanged.

[0038] In some embodiments, the at least one of the opening of the bypass valve or the frequency of the fan is controlled according to the working state of the natural cooling chiller and the first temperature, and further comprising:

[0039] After the frequency of the fan is controlled to be increased, if the first temperature is continuously detected to be still greater than the upper threshold value within a preset time, the frequency of the fan is controlled to continue to be increased until the maximum frequency of the fan is reached;

[0040] After the frequency of the fan is controlled to be increased, if the first temperature is continuously detected to be not greater than the upper threshold value within a preset time, the current operating state of each device in the natural cooling chiller is kept unchanged.

[0041] In some embodiments, the at least one of the opening of the bypass valve or the frequency of the fan is controlled according to the working state of the natural cooling chiller and the first temperature, and comprising:

[0042] When the natural cooling water chiller is in the running state, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, and the fan is in the open state, the frequency of the fan is controlled to decrease;

[0043] When the natural cooling water chiller is in the running state, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, and the fan is in the open state, the frequency of the fan is controlled to decrease;

[0044] In some embodiments, according to the working state of the natural cooling water chiller and the first temperature, at least one of the opening of the bypass valve or the frequency of the fan is controlled, further comprising:

[0045] After the opening of the bypass valve is controlled to increase, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, the bypass valve is controlled to continue to increase the opening until the bypass valve is increased to the maximum opening;

[0046] After the bypass valve is increased to the maximum opening, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, the liquid pump is closed, and the natural cooling water chiller is controlled to enter the standby state.

[0047] In some embodiments, according to the working state of the natural cooling water chiller and the second temperature, the heater mounted on the heat exchanger is controlled to be turned on or turned off, comprising:

[0048] When the natural cooling water chiller is in the standby state or the shutdown state, if the second temperature is continuously detected to be less than the temperature threshold value within a preset time, the heater mounted on the heat exchanger is controlled to be turned on.

[0049] Some embodiments of the present disclosure propose a control device of a freeze-proof natural cooling water chiller, comprising:

[0050] a memory; and

[0051] a processor coupled to the memory, the processor being configured to execute the control method of the freeze-proof natural cooling water chiller based on instructions stored in the memory.

[0052] Some embodiments of the present disclosure propose a control device of a freeze-proof natural cooling water chiller, comprising:

[0053] a state acquisition module configured to acquire a working state of the natural cooling water chiller;

[0054] a temperature detection module configured to detect a first temperature of a first inlet of a heat exchanger located on a side of a water solution circulating with added antifreeze, or detect a second temperature of a second outlet of the heat exchanger located on a side of chilled water circulating without added antifreeze, according to the working state of the natural cooling water chiller;

[0055] The control module is configured to control at least one of the opening degree of the bypass valve or the frequency of the fan according to the working state of the natural cooling water chiller and the first temperature, or control the heater mounted on the heat exchanger to be turned on or turned off according to the working state of the natural cooling water chiller and the second temperature.

[0056] Some embodiments of the present disclosure provide a non-transitory computer-readable storage medium having stored thereon a computer program, which, when executed by a processor, implements the steps of the control method of the anti-freezing natural cooling water chiller.

[0057] The anti-freezing natural cooling water chiller, the control method and the control device provided by the embodiments of the present disclosure can prevent the water without anti-freezing liquid from freezing at the user side of the natural cooling water chiller when the ambient temperature is lower than 0℃. BRIEF DESCRIPTION OF DRAWINGS

[0058] The drawings needed to be used in the embodiments or related technical descriptions will be briefly introduced below. According to the detailed description below with reference to the drawings, the present disclosure can be more clearly understood.

[0059] Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor based on these drawings.

[0060] Figure 1 The schematic diagram of the anti-freezing natural cooling water chiller according to some embodiments of the present disclosure.

[0061] Figure 2 The flowchart of the control method of the anti-freezing natural cooling water chiller according to some embodiments of the present disclosure.

[0062] Figure 3 The flowchart of the control method of the natural cooling water chiller in the start-up state according to some embodiments of the present disclosure.

[0063] Figure 4 The flowchart of the control method of the natural cooling water chiller in the running state according to some embodiments of the present disclosure.

[0064] Figure 5 The flowchart of the control method of the natural cooling water chiller in the standby state or the shutdown state according to some embodiments of the present disclosure.

[0065] Figure 6 The schematic diagram of the control device of the anti-freezing natural cooling water chiller according to some embodiments of the present disclosure.

[0066] Figure 7This is a schematic diagram of the control device for an antifreeze natural cooling chiller unit according to other embodiments of this disclosure. Detailed Implementation

[0067] The technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings.

[0068] Figure 1 This is a schematic diagram of a freeze-proof natural cooling chiller unit according to some embodiments of this disclosure.

[0069] like Figure 1 As shown, the antifreeze natural cooling chiller unit of this embodiment includes: a liquid pump 1; a surface cooler 2 equipped with a fan 3; and a heat exchanger 4, including a circulating side of the aqueous solution where antifreeze is added (i.e., Figure 1 The first inlet and first outlet of the heat exchanger 4 shown on the right side (i.e., the side without added antifreeze) and the chilled water circulation side (i.e., Figure 1 The heat exchanger 4 shown in the diagram has a second inlet and a second outlet on the left side; and a bypass valve 5 with an adjustable opening. Furthermore, the antifreeze natural cooling chiller unit also includes: a first temperature sensor 6, installed at the first inlet of the heat exchanger 4; a second temperature sensor 7, installed at the second outlet of the heat exchanger 4; a heater 8 mounted on the heat exchanger 4; and a control device 9, etc. Additionally, a chilled water pump can be installed on the passage of the second inlet of the heat exchanger 4 located on the chilled water circulation side without added antifreeze. Figure 1 Not shown in the image.

[0070] The first outlet of heat exchanger 4 is connected to the inlet of liquid pump 1, the outlet of liquid pump 1 is connected to the inlet of surface cooler 2, and the outlet of surface cooler 2 is connected to the first inlet of heat exchanger 4. A bypass valve 5 is connected across the communication path between the outlet of liquid pump 1 and the inlet of surface cooler 2, and between the outlet of surface cooler 2 and the first inlet of heat exchanger 4. Control device 9 is electrically connected to the first temperature sensor 6, bypass valve 5, fan 3, second temperature sensor 7, and heater 8, respectively.

[0071] Among them, the liquid pump 1 is, for example, a fixed-frequency liquid pump, which reduces control complexity and lowers cost. The surface cooler 2 is a heat exchanger, whose inner side (i.e., Figure 1 The left side shown in the image is an aqueous solution with added antifreeze, and its outer side (i.e., Figure 1(The right side shown in the diagram) represents air, used for natural cooling. Fan 3 is, for example, a frequency-adjustable variable frequency fan, whose frequency can be changed according to the antifreeze control requirements. Bypass valve 5 is an electrically adjustable flow regulating valve, whose flow rate can be adjusted by changing its opening according to the antifreeze control requirements. First temperature sensor 6 and second temperature sensor 7 are sensors capable of sensing temperature. First temperature sensor 6 senses the temperature at the first inlet of heat exchanger 4 on the side where antifreeze is added to the aqueous solution circulation, referred to as the first temperature, denoted as T1. Second temperature sensor 7 senses the temperature at the second outlet of heat exchanger 4 on the side where no antifreeze is added to the chilled water circulation, referred to as the second temperature, denoted as T2. Heater 8 is, for example, an electric heater. Control device 9 can execute antifreeze control logic, for example, controlling at least one of the opening degree of bypass valve 5 or the frequency of fan 3 based on the temperature detected by first temperature sensor 6, or controlling heater 8 to turn on or off based on the temperature detected by second temperature sensor 7, according to the antifreeze control requirements.

[0072] In some embodiments, the opening degree of the bypass valve 5 is adjustable and can be manually operated by the user or intelligently controlled by the control device 9. The control device 9, in addition to... Figure 6-7 Besides the implementation shown in the embodiment, it can also be implemented using hardware such as comparators and triggers. The comparator compares the temperature sensed by the temperature sensor with a threshold value and sends the comparison result to the trigger. Based on different comparison results, the trigger sends different control signals to the bypass valve 5 or the fan 3. The bypass valve 5 adjusts its opening degree according to the different control signals, and the fan 3 adjusts its frequency according to the different control signals. Each temperature sensor can be configured with one trigger.

[0073] Adding antifreeze to an aqueous solution can prevent freezing. The concentration of the antifreeze is determined based on its composition and the actual conditions at the installation location of the naturally cooled chiller unit, where freezing does not occur under the lowest ambient temperature throughout the year. Antifreeze includes, but is not limited to, ethylene glycol antifreeze.

[0074] The antifreeze aqueous solution circulation includes a main circulation for refrigeration purposes and a bypass circulation for antifreeze purposes.

[0075] The main cycle includes: the liquid pump 1 pumps out an aqueous solution containing antifreeze (such as an aqueous solution of ethylene glycol), which passes through the surface cooler 2 and is cooled by the low-temperature air in the ambient environment. Then it flows to the heat exchanger 4, where it exchanges heat with the chilled water on the other side that does not contain antifreeze. The cooling capacity of the aqueous solution containing antifreeze (such as an aqueous solution of ethylene glycol) is transferred to the chilled water that does not contain antifreeze, thus lowering the temperature of the chilled water and achieving the purpose of preparing low-temperature chilled water. After the heat exchange, the heated aqueous solution containing antifreeze (such as an aqueous solution of ethylene glycol) flows out of the heat exchanger 4 and flows back through the liquid pump 1 to start the next cycle.

[0076] The bypass circulation includes: when the bypass valve 5 has a certain opening, a part of the antifreeze solution (such as ethylene glycol solution) pumped out from the liquid pump 1 is shunted through the bypass valve 5 on the bypass circuit, and mixed with the antifreeze solution (such as ethylene glycol solution) flowing out of the surface cooler 2 cooled by the low-temperature air of the external environment, and then flows to the heat exchanger 4 for heat exchange. After heat exchange, the heated antifreeze solution (such as ethylene glycol solution) flows out of the heat exchanger 4 and then flows through the liquid pump 1 again, starting the next cycle.

[0077] The "antifreeze" referred to in the present disclosure means preventing the freezing of the chilled water without antifreeze on the left side of the heat exchanger 4. If the temperature of the antifreeze solution on the right side of the heat exchanger 4 is much lower than 0℃, the heat exchange capacity of the heat exchanger is strong, which causes the chilled water without antifreeze on the left side to be excessively cooled and the temperature to be reduced to below 0℃, resulting in freezing and cracking of the heat exchanger 4. Therefore, the antifreeze control logic of the present disclosure is to control the temperature of the antifreeze solution on the right side of the heat exchanger 4 not to be too low, so as to prevent the chilled water without antifreeze on the left side of the heat exchanger 4 from freezing.

[0078] The control parameters used in the antifreeze control logic of the present disclosure are described as follows.

[0079] A1: the maximum frequency of the variable frequency fan, unit Hz.

[0080] A2: the minimum frequency of the variable frequency fan, unit Hz.

[0081] B: the frequency adjustment step of the fan, unit Hz, that is, the frequency amplitude that can be adjusted by the control device each time the fan frequency is adjusted.

[0082] C: the interval time of the control device detecting the first temperature T1 and the second temperature T2, for example, seconds, that is, the control device reads the value of the first temperature T1 and the value of the second temperature T2 every C seconds after the unit is started.

[0083] D1: the lower threshold value of the first temperature T1, which is the critical range to ensure that the chilled water does not freeze.

[0084] D2: the upper threshold value of the first temperature T1. D1 < D2. The values of D1 and D2 are related to the type, heat exchange area, heat exchange capacity, and water flow on both sides of the heat exchanger.

[0085] D3: the temperature threshold value of the second temperature T2. D3 > 0℃. For example, D3 is in the range of 3-4℃. D1 is less than D3, and the difference between D1 and D3 is, for example, between 2-10℃.

[0086] F: the maximum opening of the bypass valve 5, which is 100, unit %.

[0087] G: The adjustment step of bypass valve 5, in percentage, that is, the range of adjustment of bypass valve 5 by the control device each time.

[0088] Figure 2 This is a schematic flowchart illustrating a control method for a freeze-resistant natural cooling chiller unit according to some embodiments of the present disclosure. This control method is executed, for example, by a control device 9 of the freeze-resistant natural cooling chiller unit.

[0089] like Figure 2 As shown, the control method of the antifreeze natural cooling chiller unit in this embodiment includes steps S210-S240.

[0090] In step S210, the operating status of the natural cooling chiller unit is obtained.

[0091] The operating states of a natural cooling chiller unit (hereinafter referred to as "the unit") include: start-up state, running state, standby state, and shutdown state. Start-up state: The unit starts up after receiving a start-up command. Running state: The liquid pump is on after the unit is started. Standby state: The liquid pump is off after the unit is started, provided no fault or protection is detected. Shutdown state: The liquid pump is off after the unit is started, provided a fault or protection is detected.

[0092] In step S220, based on the operating state of the natural cooling chiller unit, the first temperature of the first inlet of the heat exchanger located on the side of the aqueous solution circulation with added antifreeze is detected, or the second temperature of the second outlet of the heat exchanger located on the side of the chilled water circulation without added antifreeze is detected.

[0093] In step S230, at least one of the following is controlled: the opening degree of the bypass valve or the frequency of the fan, based on the operating state of the natural cooling chiller unit and the first temperature.

[0094] When the first temperature is relatively low, for example, when the first temperature is less than the lower threshold, it indicates that the first temperature is relatively low and the chilled water on the left side of the heat exchanger without antifreeze is at risk of freezing. To prevent the chilled water on the left side of the heat exchanger from freezing, the opening of the bypass valve should be increased, or the frequency of the fan should be reduced to increase the temperature of the antifreeze solution on the right side of the heat exchanger.

[0095] When the first temperature is relatively high, for example, when the first temperature is greater than the upper limit threshold, it indicates that the first temperature is relatively high and it is difficult to achieve the purpose of preparing low-temperature chilled water. The opening of the bypass valve can be reduced, or the frequency of the fan can be increased to reduce the temperature of the antifreeze solution on the right side of the heat exchanger. The heat exchange capacity of the heat exchanger can be used to achieve the purpose of preparing low-temperature chilled water.

[0096] At step S240, according to the working state of the natural cooling water chiller and the second temperature, the heater assembled on the heat exchanger is controlled to be turned on or turned off.

[0097] When the second temperature is relatively low, for example, the second temperature is less than the temperature threshold, it indicates that the chilled water without antifreeze on the left side of the heat exchanger has the risk of freezing, and the heater assembled on the heat exchanger is controlled to be turned on to increase the second temperature, so as to prevent the chilled water without antifreeze on the left side of the heat exchanger from freezing.

[0098] When the second temperature is not less than the temperature threshold, that is, the risk of freezing has been eliminated, the heater assembled on the heat exchanger can be controlled to be turned off.

[0099] It should be noted that the working state of the natural cooling water chiller is different, and the specific antifreeze control logic is also different. For example, when the natural cooling water chiller is in the starting state or the running state, the first temperature is detected in step S220, and step S230 is executed; when the natural cooling water chiller is in the standby state and the shutdown state, the second temperature is detected in step S220, and step S240 is executed. But not limited to the examples. For example, when the natural cooling water chiller is in the starting state or the running state, the second temperature can also be detected in step S220 and step S240 can also be executed according to needs. Examples of antifreeze control logic in various working states will be described in detail later.

[0100] The above examples control the temperature of the water solution with antifreeze on the right side of the heat exchanger not to be too low by controlling at least one of the opening degree of the bypass valve or the frequency of the fan, so as to prevent the chilled water without antifreeze on the left side of the heat exchanger from freezing; in addition, by controlling the heater assembled on the heat exchanger to be turned on or turned off, the purpose of preventing the chilled water without antifreeze on the left side of the heat exchanger from freezing is achieved.

[0101] Figure 3 The flowchart of the control method of the natural cooling water chiller in the starting state of some embodiments of the present disclosure is shown. The control method is executed by the antifreeze natural cooling water chiller control device 9, for example.

[0102] The control method of the natural cooling water chilling unit in the start-up state mainly includes: ① the unit is in the start-up state, and the liquid pump, bypass valve and fan are executed according to the start-up anti-freezing control logic. ② after the unit is started, the chilled water pump and liquid pump are started, and the opening degree of the bypass valve is kept maximum, and after a period of operation, the temperature of the glycol water solution is increased due to the lower outdoor temperature of the water solution added with the anti-freezing liquid (the glycol water solution is taken as an example in the following). ③ due to the full opening of the bypass valve, most of the flow of the glycol water solution passes through the bypass circuit where the bypass valve is located, and the flow passing through the surface cooler is small, and the heat exchange amount of the surface cooler is small, so the first temperature T1 is relatively high, and then the opening degree of the bypass valve is gradually reduced, the flow and heat exchange amount of the surface cooler are increased, and the first temperature T1 is gradually reduced, in the process, the first temperature T1 is controlled in a reasonable range to ensure that the chilled water without the anti-freezing liquid on the left side of the heat exchanger will not freeze, until the bypass valve is closed. ④ the next step is to start the fan, and the fan is initially operated at the minimum frequency, the first temperature T1 is controlled in a reasonable range to ensure that the chilled water without the anti-freezing liquid on the left side of the heat exchanger will not freeze, and the frequency of the fan is gradually increased to increase the air volume until the first temperature T1 reaches the critical range of the chilled water without freezing, or the frequency of the fan is operated to the highest frequency.

[0103] As shown in Figure 3 The control method of the natural cooling water chilling unit in the start-up state includes steps S301-S330.

[0104] In step S301, the natural cooling water chilling unit receives a start-up command.

[0105] In step S302, the control device controls the chilled water pump on the side of the chilled water without the anti-freezing liquid and the liquid pump on the side of the water solution added with the anti-freezing liquid to be opened, and controls the opening degree of the bypass valve to be at the maximum opening degree F, and the control device detects the value of the first temperature T1 every C seconds.

[0106] In step S303, the control device judges the interval of the first temperature T1.

[0107] In step S304a, whether the first temperature T1 is greater than the upper threshold D2 is continuously detected within a preset time (such as x seconds, and the value of x can be set), if yes, it is indicated that the first temperature T1 is relatively high, and it is difficult to achieve the purpose of preparing low-temperature chilled water, step S305 is executed, and if not, step S304b is executed.

[0108] In step S304b, whether the first temperature T1 is less than the lower threshold D1 is continuously detected within a preset time (such as x seconds, and the value of x can be set), if yes, it is indicated that the first temperature T1 is relatively low, and freezing problem may occur, step S309 is executed, and if not, step S304c is executed.

[0109] In step S304c, if the first temperature T1 is continuously detected to be not greater than the upper threshold D2 and not less than the lower threshold D1 within a preset time (e.g., x seconds, the value of x can be set), the first temperature T1 is in a proper range, i.e., the purpose of preparing low-temperature chilled water can be achieved and freezing problem does not occur. Then step S311 is executed.

[0110] In step S305, the opening of the bypass valve is adjusted to reduce the first temperature T1, and the adjustment is performed by G each time.

[0111] In step S306, the control device determines the interval in which the first temperature T1 is located.

[0112] In step S307, it is continuously detected whether the first temperature T1 is greater than the upper threshold D2 within a preset time (e.g., x seconds, the value of x can be set), if yes, step S308 is executed, and if no, step S313 is executed.

[0113] In step S308, it is determined whether the opening of the bypass valve is the minimum opening (e.g., 0), if no, step S305 is continuously executed, and if yes, step S315 is executed.

[0114] In step S309, the liquid pump is closed, and the natural cooling chiller is controlled to enter a standby state.

[0115] In step S310, the start-up anti-freezing control logic (1) is exited, wherein (1) represents the first path of the exit of the start-up anti-freezing control logic.

[0116] In step S311, the current running state of each device in the natural cooling chiller is maintained. At this time, the chilled water pump and the liquid pump are opened, and the opening of the bypass valve is the maximum. Then step S312 is executed.

[0117] In step S312, the start-up anti-freezing control logic (2) is exited, wherein (2) represents the second path of the exit of the start-up anti-freezing control logic.

[0118] In step S313, the current running state of each device in the natural cooling chiller is maintained. At this time, the chilled water pump and the liquid pump are opened, and the opening of the bypass valve is reduced by G from the maximum opening. Then step S314 is executed.

[0119] In step S314, the start-up anti-freezing control logic (3) is exited, wherein (3) represents the third path of the exit of the start-up anti-freezing control logic.

[0120] In step S315, the fan is started, and runs at the minimum frequency A2.

[0121] In step S316, the control device determines the interval in which the first temperature T1 is located.

[0122] In step S317a, it is continuously detected whether the first temperature Tl is greater than the upper threshold D2 within a preset time (e.g. x seconds, the value of x can be set). If yes, step S318 is executed, and if no, step S317b is executed.

[0123] In step S317b, it is continuously detected whether the first temperature Tl is less than the lower threshold Dl within a preset time (e.g. x seconds, the value of x can be set). If yes, step S323 is executed, and if no, step S317c is executed.

[0124] In step S317c, it is continuously detected whether the first temperature Tl is neither greater than the upper threshold D2 nor less than the lower threshold Dl within a preset time (e.g. x seconds, the value of x can be set). Then step S325 is executed.

[0125] In step S318, the frequency of the fan is increased, and the adjustment amplitude is B each time.

[0126] In step S319, the control device judges the interval in which the first temperature Tl is located.

[0127] In step S320, it is continuously detected whether the first temperature Tl is greater than the upper threshold D2 within a preset time (e.g. x seconds, the value of x can be set). If yes, step S321 is executed, and if no, step S327 is executed.

[0128] In step S321, it is judged whether the frequency of the fan is the maximum frequency Al. If no, step S322 is executed, and if yes, step S329 is executed.

[0129] In step S322, the frequency of the fan is increased, and the adjustment amplitude is B each time. Then step S319 is continuously executed.

[0130] In step S323, the fan is turned off, and the liquid pump is kept on and the opening degree of the bypass valve is kept unchanged.

[0131] In step S324, the start-up anti-freezing control logic (4) is exited, wherein (4) represents the fourth path of the exit of the start-up anti-freezing control logic.

[0132] In step S325, the current running state of each device in the natural cooling water chilling unit is kept unchanged. At this time, the chilled water pump and the liquid pump are turned on, the opening degree of the bypass valve is minimum, and the fan is operated at the minimum frequency. Then step S326 is executed.

[0133] In step S326, the start-up anti-freezing control logic (5) is exited, wherein (5) represents the fifth path of the exit of the start-up anti-freezing control logic.

[0134] In step S327, the current operating state of each device in the natural cooling chiller unit is maintained unchanged. At this time, the chilled water pump and the liquid pump are turned on, the bypass valve opening is minimum, and the frequency of the fan is increased by several B from the minimum frequency. Then step S328 is executed.

[0135] In step S328, the startup anti-freezing control logic (6) is exited, where (6) represents the sixth path of exiting the startup anti-freezing control logic.

[0136] In step S329, the current operating state of each device in the natural cooling chiller unit is maintained unchanged. At this time, the chilled water pump and the liquid pump are turned on, the bypass valve opening is minimum, and the fan operates at the maximum frequency. Then step S330 is executed.

[0137] In step S330, the startup anti-freezing control logic (7) is exited, where (7) represents the seventh path of exiting the startup anti-freezing control logic.

[0138] The above embodiment prevents the freezing of the chilled water without antifreeze on the left side of the heat exchanger during the startup of the chiller unit. During the startup, the bypass valve opening is maximum, so that the water solution with antifreeze on the right side of the heat exchanger has the highest temperature and the lowest risk of freezing. Subsequently, the bypass valve opening or the frequency of the fan is gradually increased to achieve the purpose of preparing low-temperature chilled water, while ensuring that the chilled water without antifreeze on the left side of the heat exchanger does not freeze.

[0139] After the startup state ends, the natural cooling chiller unit enters the operating state, i.e., enters the natural cooling operation process. If anti-freezing is required during this period, the control logic of the embodiment shown in Figure 4 is performed.

[0140] Figure 4 A flowchart of a control method for a natural cooling chiller unit in the operating state of some embodiments of the present disclosure is shown. The control method is executed, for example, by the control device 9 of the anti-freezing natural cooling chiller unit.

[0141] The control method for the natural cooling chiller unit in the operating state mainly includes: ①According to the control logic shown in Figure 3 , if the fan is in the open state, the bypass valve opening is minimum, and the liquid pump is in the open state. ②In the case of a constant-frequency water pump, the heat transfer amount of the cooling radiator and the value of the first temperature T1 are adjusted by adjusting the frequency of the fan and the opening of the bypass valve, and finally the value of the second temperature T2 is controlled.

[0142] As shown in Figure 4 , the control method for the natural cooling chiller unit in the operating state includes steps S401-S413.

[0143] At step S401, the natural cooling water chilling unit is in running state, and the control device detects the value of the first temperature Tl every C seconds.

[0144] At step S402, the control device judges the interval in which the first temperature Tl is located.

[0145] At step S403, it is continuously detected whether the first temperature Tl is less than the lower threshold Dl within a preset time (such as x seconds, the value of x can be set), if not, step S404 is executed, and if yes, it is indicated that the first temperature Tl is relatively low, and freezing problem can occur, and step S405 is executed.

[0146] At step S404, the running state anti-freezing control logic is not entered or exited.

[0147] At step S405, the running state anti-freezing control logic is executed. Then step S406 is executed.

[0148] At step S406, the control device judges whether the fan is in the open state, if yes, step S407 is executed, and if not, step S408 is executed.

[0149] At step S407, the frequency of the fan is reduced, and the adjustment amplitude is B each time, and then step S402 is continuously executed.

[0150] At step S408, the control device judges whether the opening degree of the bypass valve is the maximum opening degree, if yes, step S409 is executed, and if not, step S410 is executed.

[0151] At step S409, the liquid pump is closed, and the natural cooling water chilling unit is controlled to enter the standby state.

[0152] At step S410, the opening degree of the bypass valve is increased, and the adjustment amplitude is G each time.

[0153] At step S411, the control device judges the interval in which the first temperature Tl is located.

[0154] At step S412, it is continuously detected whether the first temperature Tl is less than the lower threshold Dl within a preset time (such as x seconds, the value of x can be set), if not, step S413 is executed, and if yes, step S408 is executed.

[0155] At step S413, the running state anti-freezing control logic is exited.

[0156] The above embodiment prevents freezing of the chilled water without antifreeze on the left side of the heat exchanger during operation of the unit. When the natural cooling water chiller is in the running state, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, the frequency of the fan is reduced, or the opening of the bypass valve is increased, thereby increasing the temperature of the water solution with antifreeze on the right side of the heat exchanger, and preventing freezing of the chilled water without antifreeze on the left side of the heat exchanger.

[0157] Figure 5 The flowchart of the control method of the natural cooling water chiller in the standby state or the shutdown state of some embodiments of the present disclosure. The control method is executed by the antifreeze natural cooling water chiller control device 9, for example.

[0158] The natural cooling water chiller, in the standby state, the liquid pump and the fan are not running, and the chilled water pump is in the open state; in the shutdown state, the liquid pump and the fan are not running, and the chilled water pump is in the closed state.

[0159] As shown in Figure 5 The control method of the natural cooling water chiller in the standby state or the shutdown state includes steps S501-S505.

[0160] In step S501, the natural cooling water chiller is in the standby state or the shutdown state, and the control device detects the value of the second temperature T2 every C seconds.

[0161] In step S502, the control device determines the interval of the second temperature T2.

[0162] In step S503, it is continuously detected whether the second temperature T2 is less than the temperature threshold value D3 within a preset time (such as x seconds, the value of x can be set). If not, step S504 is executed, and if yes, it means that the second temperature T2 is relatively low, and freezing problem may occur, and step S505 is executed.

[0163] In step S504, the antifreeze control logic in the standby state or the shutdown state is not executed.

[0164] In step S505, the control device controls the heater mounted on the heat exchanger to be turned on, and can also issue an antifreeze alarm signal.

[0165] After the heater is turned on for a period of time, if the second temperature T2 is continuously detected to be not less than the temperature threshold value D3 within a preset time (such as x seconds, the value of x can be set), the heater can be turned off.

[0166] The above embodiment prevents freezing of the chilled water without antifreeze on the left side of the heat exchanger during standby or shutdown of the unit, according to the antifreeze needs, by turning on the heater mounted on the heat exchanger.

[0167] Figure 6 Schematic diagram of a control device of a freeze-proof natural cooling water chiller unit according to some embodiments of the present disclosure.

[0168] As shown in Figure 6 , the control device 9 of the freeze-proof natural cooling water chiller unit comprises a memory 610 and a processor 620 coupled to the memory 610, the processor 620 being configured to perform the control method of the freeze-proof natural cooling water chiller unit according to any one of the embodiments based on instructions stored in the memory 610.

[0169] For example, the working state of the natural cooling water chiller unit is acquired; the first temperature of the first inlet of the heat exchanger on the water solution circulation side to which the freeze-proof liquid is added is detected, or the second temperature of the second outlet of the heat exchanger on the chilled water circulation side to which the freeze-proof liquid is not added is detected according to the working state of the natural cooling water chiller unit; at least one of the opening degree of the bypass valve or the frequency of the fan is controlled according to the working state of the natural cooling water chiller unit and the first temperature; or the heater mounted on the heat exchanger is turned on or off according to the working state of the natural cooling water chiller unit and the second temperature.

[0170] The memory 610 may, for example, include a system memory, a fixed non-volatile storage medium, etc. The system memory, for example, stores an operating system, an application program, a Boot Loader, and other programs, etc.

[0171] Figure 7 Schematic diagram of a control device of a freeze-proof natural cooling water chiller unit according to some embodiments of the present disclosure.

[0172] As shown in Figure 7 , the control device 9 of the freeze-proof natural cooling water chiller unit comprises modules 710-730.

[0173] The state acquisition module 710 is configured to acquire the working state of the natural cooling water chiller unit.

[0174] The temperature detection module 720 is configured to detect the first temperature of the first inlet of the heat exchanger on the water solution circulation side to which the freeze-proof liquid is added, or detect the second temperature of the second outlet of the heat exchanger on the chilled water circulation side to which the freeze-proof liquid is not added according to the working state of the natural cooling water chiller unit.

[0175] The control module 730 is configured to control at least one of the opening degree of the bypass valve or the frequency of the fan according to the working state of the natural cooling water chiller unit and the first temperature; or control the heater mounted on the heat exchanger to be turned on or off according to the working state of the natural cooling water chiller unit and the second temperature. The specific control logic is described in the foregoing embodiments, which will not be described here again.

[0176] In some embodiments, the control module 730, when controlling at least one of the opening degree of the bypass valve or the frequency of the fan according to the working state of the free cooling chiller unit and the first temperature, is configured to:

[0177] when the free cooling chiller unit enters the starting state, control the opening degree of the bypass valve to be at the maximum opening degree;

[0178] if the first temperature is continuously detected to be greater than the upper threshold value within a preset time, control the bypass valve to decrease the opening degree;

[0179] if the first temperature is continuously detected to be less than the lower threshold value within a preset time, turn off the liquid pump, and control the free cooling chiller unit to enter the standby state;

[0180] if the first temperature is continuously detected to be not greater than the upper threshold value and not less than the lower threshold value within a preset time, keep the current running state of each device in the free cooling chiller unit unchanged.

[0181] In some embodiments, the control module 730, when controlling at least one of the opening degree of the bypass valve or the frequency of the fan according to the working state of the free cooling chiller unit and the first temperature, is further configured to:

[0182] controlling at least one of the opening degree of the bypass valve or the frequency of the fan according to the working state of the free cooling chiller unit and the first temperature, further comprises:

[0183] after controlling the bypass valve to decrease the opening degree, if the first temperature is continuously detected to be still greater than the upper threshold value within a preset time and the bypass valve has decreased to the minimum opening degree, turn on the fan;

[0184] after controlling the bypass valve to decrease the opening degree, if the first temperature is continuously detected to be not greater than the upper threshold value within a preset time, keep the current running state of each device in the free cooling chiller unit unchanged.

[0185] In some embodiments, the control module 730, when controlling at least one of the opening degree of the bypass valve or the frequency of the fan according to the working state of the free cooling chiller unit and the first temperature, is further configured to:

[0186] after turning on the fan, if the first temperature is continuously detected to be still greater than the upper threshold value within a preset time, control the frequency of the fan to increase;

[0187] after turning on the fan, if the first temperature is continuously detected to be less than the lower threshold value within a preset time, turn off the fan and keep the opening degree of the bypass valve unchanged;

[0188] After the fan is turned on, if the first temperature is continuously detected to be not greater than the upper threshold and not less than the lower threshold within a preset time, the current operating state of each device in the natural cooling water chilling unit is kept unchanged.

[0189] In some embodiments, the control module 730, when controlling at least one of the opening of the bypass valve or the frequency of the fan according to the working state of the natural cooling water chilling unit and the first temperature, is further configured to:

[0190] After the frequency of the fan is controlled to increase, if the first temperature is continuously detected to be still greater than the upper threshold within a preset time, the frequency of the fan is controlled to continue to increase until the maximum frequency of the fan is reached.

[0191] After the frequency of the fan is controlled to increase, if the first temperature is continuously detected to be not greater than the upper threshold within a preset time, the current operating state of each device in the natural cooling water chilling unit is kept unchanged.

[0192] In some embodiments, the control module 730, when controlling at least one of the opening of the bypass valve or the frequency of the fan according to the working state of the natural cooling water chilling unit and the first temperature, is configured to:

[0193] When the natural cooling water chilling unit is in the running state, if the first temperature is continuously detected to be less than the lower threshold and the fan is in the turned-on state within a preset time, the frequency of the fan is controlled to decrease.

[0194] When the natural cooling water chilling unit is in the running state, if the first temperature is continuously detected to be less than the lower threshold and the fan is in the turned-off state within a preset time, the opening of the bypass valve is controlled to increase.

[0195] In some embodiments, the control module 730, when controlling at least one of the opening of the bypass valve or the frequency of the fan according to the working state of the natural cooling water chilling unit and the first temperature, is further configured to:

[0196] After the opening of the bypass valve is controlled to increase, if the first temperature is continuously detected to be still less than the lower threshold within a preset time, the opening of the bypass valve is controlled to continue to increase until the bypass valve is increased to the maximum opening.

[0197] After the bypass valve is increased to the maximum opening, if the first temperature is continuously detected to be still less than the lower threshold within a preset time, the liquid pump is turned off, and the natural cooling water chilling unit is controlled to enter the standby state.

[0198] In some embodiments, the control module 730, when controlling the heater arranged on the heat exchanger to be turned on or turned off according to the working state of the natural cooling water chiller and the second temperature, is configured to: when the natural cooling water chiller is in the standby state or the shutdown state, if the second temperature is continuously detected to be less than the temperature threshold within a preset time, control the heater arranged on the heat exchanger to be turned on.

[0199] The embodiments of the present disclosure provide a non-transitory computer readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the steps of the control method of the anti-freezing natural cooling water chiller according to any one of the embodiments.

[0200] Those skilled in the art will understand that the embodiments of the present disclosure can be provided as a method, a system, or a computer program product. Therefore, the present disclosure can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present disclosure can take the form of a computer program product implemented on one or more computer-usable non-transitory storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0201] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and a combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks Figure 1 The functions specified in a flow or multiple flows and / or blocks

[0202] These computer program instructions can also be stored in a computer-readable memory capable of directing the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a product including instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks Figure 1 The functions specified in a flow or multiple flows and / or blocks

[0203] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a means for implementing the functions specified in the flowcharts and / or block diagrams.Figure 1 one or more processes and / or functions specified in one or more blocks Figure 1 Figure 1 one or more processes and / or functions specified in one or more blocks

[0204] The above description is merely illustrative of the application and not restrictive.

Claims

1. A freeze-resistant natural cooling chiller unit, characterized in that, include: Liquid pump; A surface cooler equipped with a fan; A heat exchanger includes a first inlet and a first outlet located on the circulating side of an aqueous solution with added antifreeze, and a second inlet and a second outlet located on the circulating side of chilled water without added antifreeze, wherein the aqueous solution with added antifreeze and the chilled water without added antifreeze exchange heat in the heat exchanger. The first temperature sensor is installed at the first inlet of the heat exchanger to detect the first temperature. An adjustable bypass valve; The heat exchanger’s first outlet is connected to the liquid pump’s inlet, the liquid pump’s outlet is connected to the surface cooler’s inlet, the surface cooler’s outlet is connected to the heat exchanger’s first inlet, and the bypass valve is connected across the connection path between the liquid pump’s outlet and the surface cooler’s inlet and the connection path between the surface cooler’s outlet and the heat exchanger’s first inlet. The controller is configured to control at least one of the following based on the operating state of the natural cooling chiller unit and a first temperature: the opening degree of the bypass valve and the frequency of the fan, to ensure that the temperature of the antifreeze-added aqueous solution is not lower than a threshold value, preventing the chilled water without antifreeze from freezing. This includes: when the natural cooling chiller unit enters the start-up state, controlling the bypass valve to its maximum opening degree; if the first temperature is continuously detected to be greater than an upper threshold value within a preset time, controlling the bypass valve to reduce its opening degree; if the first temperature is continuously detected to be less than a lower threshold value within a preset time, shutting off the liquid pump and controlling the natural cooling chiller unit to enter a standby state; if the first temperature is continuously detected to be neither greater than the upper threshold value nor less than the lower threshold value within a preset time, maintaining the current operating state of each device in the natural cooling chiller unit unchanged; after controlling the bypass valve to reduce its opening degree, if the first temperature is still continuously detected to be greater than the upper threshold value within a preset time and the bypass valve has already reduced to its maximum opening degree, then... At a small opening, the fan is started at the minimum frequency. After the bypass valve is reduced in opening, if the first temperature is continuously detected as not exceeding the upper threshold within a preset time, the current operating state of each device in the natural cooling chiller unit remains unchanged. After the fan is started at the minimum frequency, if the first temperature is continuously detected as still exceeding the upper threshold within a preset time, the fan frequency is increased. After the fan is started at the minimum frequency, if the first temperature is continuously detected as less than the lower threshold within a preset time, the fan is shut down, and the bypass valve opening remains unchanged. After the fan is started at the minimum frequency, if the first temperature is continuously detected as not exceeding the upper threshold and not less than the lower threshold within a preset time, the current operating state of each device in the natural cooling chiller unit remains unchanged. When the natural cooling chiller unit is in operation, if the first temperature is continuously detected as less than the lower threshold within a preset time and the fan is not turned on, the bypass valve opening is increased.

2. The antifreeze natural cooling chiller unit according to claim 1, characterized in that, Also includes: The control device is configured to control at least one of the opening degree of the bypass valve and the frequency of the fan based on the first temperature detected by the first temperature sensor. The control device is electrically connected to the first temperature sensor, the bypass valve, and the fan, respectively.

3. The antifreeze natural cooling chiller unit according to claim 1, characterized in that, Also includes: The second temperature sensor is located at the second outlet of the heat exchanger. Heaters mounted on heat exchangers; as well as The control device is configured to control the heater to turn on or off based on a second temperature detected by the second temperature sensor; The control device is electrically connected to the second temperature sensor and the heater, respectively.

4. The antifreeze natural cooling chiller unit according to any one of claims 1-3, characterized in that, The liquid pump is a fixed-frequency liquid pump; The fan is a frequency-adjustable variable frequency fan.

5. A control method for a freeze-proof natural cooling chiller unit according to any one of claims 1-4, characterized in that, include: Obtain the operating status of the natural cooling chiller unit; Based on the operating status of the natural cooling chiller unit, the first temperature of the first inlet of the heat exchanger located on the circulating side of the aqueous solution with added antifreeze is detected; Based on the operating status of the natural cooling chiller unit and a first temperature, at least one of the following is controlled: the opening degree of the bypass valve and the frequency of the fan, to ensure that the temperature of the antifreeze-added aqueous solution is not lower than a threshold, preventing the chilled water without antifreeze from freezing. This includes: when the natural cooling chiller unit enters the start-up state, controlling the bypass valve opening to its maximum; if the first temperature is continuously detected to be higher than the upper threshold within a preset time, controlling the bypass valve opening to decrease; if the first temperature is continuously detected to be lower than the lower threshold within a preset time, shutting down the liquid pump and controlling the natural cooling chiller unit to enter a standby state; if the first temperature is continuously detected to be neither higher than the upper threshold nor lower than the lower threshold within a preset time, maintaining the current operating status of each device in the natural cooling chiller unit unchanged; after controlling the bypass valve to decrease its opening, if the first temperature is still continuously detected to be higher than the upper threshold within a preset time and the bypass valve has already decreased to its minimum opening... The system operates as follows: First, the fan is turned on at the minimum frequency. Then, after the bypass valve is reduced in opening, if the first temperature is continuously detected as not exceeding the upper threshold within a preset time, the current operating state of each device in the natural cooling chiller unit remains unchanged. Next, after the fan is turned on at the minimum frequency, if the first temperature is continuously detected as still exceeding the upper threshold within a preset time, the fan frequency is increased. Then, after the fan is turned on at the minimum frequency, if the first temperature is continuously detected as less than the lower threshold within a preset time, the fan is turned off, and the bypass valve opening remains unchanged. Finally, after the fan is turned on at the minimum frequency, if the first temperature is continuously detected as not exceeding the upper threshold and not less than the lower threshold within a preset time, the current operating state of each device in the natural cooling chiller unit remains unchanged. When the natural cooling chiller unit is in operation, if the first temperature is continuously detected as less than the lower threshold within a preset time and the fan is not turned on, the bypass valve opening is increased.

6. The control method according to claim 5, characterized in that, Also includes: After the frequency of the control fan is increased, if the first temperature is still greater than the upper limit threshold after a preset time, the frequency of the control fan will continue to increase until the maximum frequency of the fan is reached. After the frequency of the control fan is increased, if the first temperature is continuously detected to be no greater than the upper limit threshold within a preset time, the current operating state of each device in the natural cooling chiller unit remains unchanged.

7. The control method according to claim 5, characterized in that, Also includes: When the natural cooling chiller is in operation, if the first temperature is continuously detected to be lower than the lower threshold within a preset time and the fan is on, the frequency of the fan will be reduced.

8. The control method according to claim 7, characterized in that, Also includes: After the bypass valve is opened, if the first temperature is still lower than the lower threshold value after a preset time, the bypass valve is opened further until it reaches the maximum opening. After the bypass valve is increased to its maximum opening, if the first temperature is still lower than the lower threshold value continuously within a preset time, the liquid pump is shut down and the natural cooling chiller unit is controlled to enter standby mode.

9. The control method according to claim 5, characterized in that, Also includes: The system detects the second temperature at the second outlet of the heat exchanger on the chilled water circulation side without antifreeze, and controls the heater mounted on the heat exchanger to turn on or off based on the operating status of the natural cooling chiller unit and the second temperature, including: When the natural cooling chiller is in standby or shutdown state, if the second temperature is continuously detected to be lower than the temperature threshold within a preset time, the heater installed on the heat exchanger will be turned on.

10. A control device for a freeze-proof natural cooling chiller unit, comprising: Memory; as well as A processor coupled to the memory, the processor being configured to execute the control method of the antifreeze natural cooling chiller unit according to any one of claims 5-9 based on instructions stored in the memory.

11. A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the control method for an antifreeze natural cooling chiller unit as described in any one of claims 5-9.

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