Cooling tower cooling water return water temperature optimization control system and control method

Abstract

This invention discloses a cooling tower cooling water return temperature optimization control system and method. The system includes a water circuit formed by a cooling tower, a condenser, and a water pump. The pipe between the water pump and the cooling tower is a return water pipe. A cooling tower fan is installed on the cooling tower, and a frequency converter is installed on the cooling tower fan. A temperature sensor is installed on the return water pipe to detect the real-time return water temperature. The system also includes a controller and outdoor temperature and humidity sensors to detect outdoor temperature and humidity. The controller controls the cooling tower fan to operate at an optimized frequency value, thereby keeping the return water temperature within the deviation range of the optimized temperature setpoint in real time. Using this control system and method, this invention can optimize the cooling water return temperature in real time according to changes in outdoor wet-bulb temperature, while ensuring the safe and stable operation of the central air conditioning system and meeting the user's cooling capacity requirements, thus maximizing energy savings during system operation.

Description

Technical Field

[0001] This invention relates to the field of building energy conservation control technology, and in particular to a cooling tower cooling water return temperature optimization control system and control method. Background Technology

[0002] In central air conditioning and air compressor cooling water systems, refrigerant transfers heat load to cooling water through heat exchange in the condenser. The cooling water then exchanges heat with outdoor air in the cooling tower, dissipating heat and returning to room temperature. The outlet temperature of the cooling tower is the return temperature of the cooling water. Therefore, the cooling tower fan speed affects the heat exchange efficiency between the cooling tower and outdoor air, further influencing the return temperature of the cooling water. Current technology controls the cooling water based on its near-wet-bulb temperature, typically using a setpoint equal to the wet-bulb temperature plus a constant. However, this constant cannot account for variations in the air conditioning system load, resulting in suboptimal control, energy waste, and potential impacts on system stability. Low wet-bulb temperatures lead to excess cooling tower energy consumption. Higher setpoints and cooling tower frequencies result in higher energy consumption. High wet-bulb temperatures can cause excessively high return water temperatures. Furthermore, higher wet-bulb temperatures and higher setpoints can cause excessively high condenser-side pressure in the refrigeration unit or air compressor, potentially leading to system shutdown. In practice, most conventional cooling tower fans are not controlled, or the fan frequency is controlled based on a fixed 3°C optimal approximation, which is the difference between the cooling water return temperature setpoint and the outdoor wet-bulb temperature.

[0003] Meanwhile, as the cooling tower's cooling water system operates in real time, its cooling effect changes according to the outdoor ambient temperature. For example, when the outdoor wet-bulb temperature is low, the cooling water return temperature is also low. This reduces the cooling water's evaporation capacity, increasing the required airflow and resulting in higher energy consumption compared to a cooling tower operating at normal temperatures. Therefore, optimizing the cooling water return temperature control strategy is crucial for reducing system energy consumption.

[0004] Given the aforementioned technical background, cooling tower return water systems are characterized by fixed proximity, inability to respond promptly to changes in the outdoor environment, and a lack of energy-saving measures, thus failing to fully meet the needs of building energy conservation and consumption reduction. Summary of the Invention

[0005] To overcome the above technical problems, the purpose of this invention is to provide a cooling tower cooling water return temperature optimization control system and control method. This control system and control method can optimize the cooling water return temperature in real time according to the changes in outdoor wet-bulb temperature, while ensuring the safe and stable operation of the cooling tower system and meeting the user's cooling capacity requirements. This maximizes the energy saving during system operation and is applicable to air compressor systems and central air conditioning systems.

[0006] This invention provides the following technical solution:

[0007] A cooling tower cooling water return temperature optimization control system includes a water circuit formed by connecting a cooling tower (1), a condenser (8) and a water pump (7). The pipeline between the water pump (7) and the cooling tower (1) is a return water pipe (9). A cooling tower fan (2) is provided on the cooling tower (1), and a cooling tower fan frequency converter (3) is provided on the cooling tower fan (2). A temperature sensor (6) is provided on the return water pipe (9) to detect the real-time return water temperature of the return water pipe (9).

[0008] It also includes a control box (5) and a temperature and humidity sensor (4) installed outdoors for detecting outdoor temperature and humidity. The temperature and humidity sensor (4), the cooling tower fan frequency converter (3), and the temperature sensor (6) are all electrically connected to the control box (5).

[0009] The controller (5) includes an outdoor wet-bulb temperature calculation module (10), a cooling water return temperature optimization module (11), and a cooling water return temperature control module (12);

[0010] The outdoor wet-bulb temperature calculation module (10) calculates the real-time outdoor wet-bulb temperature value based on the real-time outdoor temperature and humidity signal collected by the temperature and humidity sensor (4), and transmits the real-time outdoor wet-bulb temperature value to the cooling water return temperature optimization module (11).

[0011] The cooling water return temperature optimization module (11) calculates the optimized temperature setpoint based on the received real-time outdoor wet-bulb temperature value and transmits the optimized temperature setpoint to the cooling water return temperature control module (12).

[0012] The cooling water return temperature control module (12) calculates the optimized operating frequency value by comparing the optimized temperature setpoint and the real-time return water temperature value, and transmits the optimized operating frequency value to the cooling tower fan inverter (3) to adjust the cooling tower fan (2) to operate according to the optimized operating frequency value, thereby adjusting the return water temperature of the return water pipe (9) to maintain it at the optimized return water temperature setpoint.

[0013] According to the above implementation method, the optimized temperature setpoint is the optimized temperature setpoint of the cooling water return water; the controller calculates and obtains the optimized operating frequency value, and controls the transmission of this optimized operating frequency value to the cooling tower fan frequency converter via an electrical signal. The cooling tower fan frequency converter sets the frequency according to the optimized operating frequency value, adjusts the speed of the cooling tower fan, and thus adjusts the return water temperature of the return water pipe to maintain it at the optimized return water temperature setpoint. At this time, the total energy consumption of the cooling tower fan and the chiller unit is minimized, thereby saving energy.

[0014] Further, the cooling water return temperature optimization module (11) calculates the optimized temperature set value according to an optimized temperature algorithm. The optimized temperature algorithm includes the calculation of an optimized approximation degree and the calculation of an optimized temperature set value. The optimized approximation degree is calculated according to the following formula:

[0015] T = a * ln(Twet0) + b

[0016] where T is the optimized approximation degree, a is the gain coefficient, b is the increment coefficient, T is the optimized approximation degree, and Twet0 is the virtual wet bulb temperature; the virtual wet bulb temperature Twet0 is determined by the real-time outdoor wet bulb temperature Twet, and the range of the virtual wet bulb temperature Twet0 is 6°C - 35°C. The determination method is as follows:

[0017] If Twet <= 6°C, then Twet0 = 6°C;

[0018] If Twet >= 35°C, then Twet0 = 35°C;

[0019] If 6°C < Twet < 35°C, then Twet0 = Twet;

[0020] The optimized temperature set value Tw,set is the sum of the calculated optimized approximation degree T and the virtual wet bulb temperature Twet0, that is: Tw,set = T + Twet0.

[0021] According to the above embodiments, the difference between the return water temperature set value Tw,set of the cooling tower system and the outdoor wet bulb temperature Twet0 is a dynamic value. The resulting effect is that when the outdoor wet bulb temperature is low, the difference between the return water temperature set value and the outdoor wet bulb temperature is large, and the return water temperature is not too low, so the cooling tower fan does not need to operate at a high frequency, resulting in a beneficial energy-saving effect; when the outdoor wet bulb temperature is high, the difference between the return water temperature set value and the outdoor wet bulb temperature is small, and the return water temperature set value is pulled down as much as possible. On the premise of meeting the heat dissipation requirements, the return water temperature is ensured to be within a reasonable range to ensure the stable operation of the system. Calculating according to the above algorithm model, the optimized temperature set value is obtained. The cooling water return temperature optimization module calculates the optimized approximation degree according to the outdoor wet bulb temperature value. When the outdoor wet bulb temperature is lower than 6°C and higher than 35°C, the optimized approximation degree is a fixed value; when the outdoor wet bulb temperature is between 6°C and ~35°C, the optimized approximation degree changes in real time with the real-time outdoor wet bulb temperature value.

[0022] Further, the value range of the gain coefficient a is -7 to -5; the value range of the increment coefficient b is 22 to 26.

[0023] According to the above implementation method, a is the gain coefficient, which usually takes a value range of -7 to -5, and preferably defaults to -6.4; b is the increment coefficient, which usually takes a value range of 22 to 26, and preferably defaults to 24; T is the optimization approximation degree; and Twet0 is the virtual wet-bulb temperature.

[0024] Furthermore, the range of the optimized temperature setting value is from the upper temperature value to the lower temperature value; when the calculated optimized temperature setting value is greater than the upper temperature value, the optimized temperature setting value is equal to the upper temperature value; when the calculated optimized temperature setting value is less than the lower temperature value, the temperature setting value is equal to the lower temperature value.

[0025] Furthermore, when used to cool a central air conditioning system, the upper temperature limit is 36°C and the lower temperature limit is 18°C; when used to cool an air compressor system, the upper temperature limit is 28°C and the lower temperature limit is 22°C.

[0026] In the above embodiments, the upper and lower temperature limits differ due to the different application conditions of the central air conditioning and air compressor systems.

[0027] This invention also provides a control method for a cooling tower cooling water return temperature optimization control system, characterized by comprising the following steps:

[0028] S1: The temperature and humidity sensor (4) detects the real-time outdoor temperature and humidity values ​​and transmits them to the controller (5) via electrical signals. The outdoor wet-bulb temperature calculation module (10) in the controller (5) calculates the outdoor wet-bulb temperature value based on the outdoor temperature and humidity values ​​and inputs it to the cooling water return temperature optimization module (11) to proceed to step S2.

[0029] S2: The cooling water return temperature optimization module (11) calculates the optimized temperature setpoint based on the outdoor wet-bulb temperature value through the optimized temperature algorithm, and inputs it to the cooling water return temperature control module (12) to proceed to step S3.

[0030] S3: The cooling water return temperature control module (12) determines whether the real-time cooling water return temperature value detected by the temperature sensor (6) is within the deviation range of the optimized temperature setting value. If yes, the optimized operating frequency value remains unchanged from the previous optimized operating frequency value, and proceeds to step S4; if no, the cooling water return temperature control module (12) calculates the optimized operating frequency value through the PID algorithm and proceeds to step S4.

[0031] S4: The optimized operating frequency value is sent to the cooling tower fan inverter (3) via an electrical signal. The cooling tower fan inverter (3) adjusts the speed of the cooling tower fan (2) according to the optimized operating frequency value, thereby controlling the cooling water return temperature to maintain it within the deviation range of the optimized temperature setting value.

[0032] According to the above implementation method, when the real-time cooling water return temperature is within the deviation range of the optimized temperature setting value, the optimized operating frequency value remains unchanged from the previous optimized operating frequency value. If the cooling tower fan is being started for the first time, the previous optimized operating frequency value is the preset default operating frequency value for the cooling tower fan. When the real-time cooling water return temperature is not within the deviation range of the optimized temperature setting value, the controller calculates the operating frequency of the cooling tower fan based on the real-time system return water temperature and outdoor temperature and humidity values, and controls the cooling tower fan speed through the cooling tower fan inverter to adjust the cooling tower air volume in real time, thereby maintaining the system cooling water return temperature at the set value and reducing the energy consumption during system operation.

[0033] Furthermore, in step S3, the deviation range of the optimized temperature setting value is between ±0.2℃ of the optimized temperature setting value.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention provides a cooling tower cooling water return temperature optimization control system and control method. The control system is equipped with an intelligent controller, which includes three modules and adopts a hierarchical design of control strategy. It can make full use of the safe and reliable performance of the intelligent controller, not only to achieve energy-saving operation of the system, but also to ensure the reliability and safety of the system during operation.

[0036] The optimized approximation degree is no longer a fixed value of 3℃, but is calculated by a corresponding algorithm, improving the accuracy and reliability of the optimized approximation degree, thereby improving the accuracy of the cooling water return temperature setpoint calculation. The optimized cooling water return temperature setpoint can be automatically adjusted according to changes in the outdoor wet-bulb temperature, improving the automation level of the entire system and reducing the system's response time to environmental changes. The cooling water return temperature control module in the controller calculates the optimized operating frequency of the cooling tower fan and sends the optimized frequency signal to the fan inverter. The operating frequency of the cooling tower fan is adjusted according to the optimized frequency, ensuring the system's cooling capacity requirements while reducing system energy consumption, achieving energy-saving operation of the cooling tower cooling water system.

[0037] This invention is novel in concept, reasonable and reliable in design, and highly intelligent. It can effectively save energy consumption during system operation and solve the problems of high energy consumption, lack of energy-saving measures, and inability to fully meet the needs of building energy conservation and consumption reduction when the outdoor wet-bulb temperature is too high or too low. It is applicable to central air conditioning systems and air compressor systems. Attached Figure Description

[0038] Figure 1 The control principle diagram of the control system provided by the present invention.

[0039] Figure 2 A comparison chart of the optimized cooling water return temperature setting and the outdoor wet-bulb temperature provided by this invention.

[0040] Figure 3 A diagram illustrating the control method provided by this invention.

[0041] Figure 4 A schematic diagram of a controller according to an embodiment of the present invention is provided.

[0042] The numbers in the attached diagram are:

[0043] 1. Cooling tower; 2. Cooling tower fan; 3. Cooling tower fan frequency converter; 4. Temperature and humidity sensor; 5. Controller; 6. Temperature sensor; 7. Water pump; 8. Condenser; 9. Return water pipe; 10. Outdoor wet-bulb temperature calculation module; 11. Cooling water return temperature optimization module; 12. Cooling water return temperature control module. Detailed Implementation

[0044] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0045] The present invention will be further described below with reference to the accompanying drawings.

[0046] like Figure 1As shown in one embodiment, the cooling tower cooling water return temperature optimization control system in this embodiment adjusts the operating frequency of the cooling tower fan according to the measured real-time cooling water return temperature, outdoor temperature, and outdoor humidity values ​​during the operation of the cooling tower system, combined with a corresponding control algorithm. The control system includes a cooling tower 1, a cooling tower fan 2, a cooling tower fan frequency converter 3, a temperature and humidity sensor 4, a controller 5, a temperature sensor 6, a water pump 7, a condenser 8, and a return water pipe 9. Specifically, the cooling tower 1, condenser 8, and water pump 7 are connected sequentially via water pipes. The water pump 7 and cooling tower 1 are connected via the return water pipe 9 to form a water loop. The cooling tower fan 2 is mounted on the cooling tower 1, and the fan frequency converter 3 is mounted on the cooling tower fan 2. The temperature sensor 6 is installed on the return water pipe 9 to collect the return water temperature of the system's return water pipeline. The temperature and humidity sensor 4 is installed outdoors to collect outdoor temperature and humidity. The controller 5 collects operating data of the system, including the outdoor temperature and humidity values ​​collected by the outdoor temperature and humidity sensor 4, and the return water pipe temperature value collected by the temperature sensor 6.

[0047] like Figure 4 The controller 5 includes an outdoor wet-bulb temperature calculation module 10, a cooling water return temperature optimization module 11, and a cooling water return temperature control module 12.

[0048] The outdoor wet-bulb temperature calculation module 10 calculates the real-time outdoor wet-bulb temperature value based on the real-time outdoor temperature and humidity signal collected by the temperature and humidity sensor 4, and transmits the real-time outdoor wet-bulb temperature value to the cooling water return temperature optimization module 11 via an electrical signal. The cooling water return temperature optimization module 11 calculates the optimized temperature setpoint based on the received real-time outdoor wet-bulb temperature value, and transmits the optimized temperature setpoint to the cooling water return temperature control module 12 via an electrical signal. The cooling water return temperature control module 12 calculates the optimized operating frequency value based on the difference between the optimized temperature setpoint and the real-time return water temperature using an optimized frequency algorithm, and transmits the optimized operating frequency value to the cooling tower fan inverter 3 to adjust the fan speed of the cooling tower 1, thereby adjusting the return water temperature of the return water pipe 9 to maintain it at the optimized temperature setpoint. The controller 5 is also used to control the issuance of frequency conversion commands, including sending the calculated optimized operating frequency value to the cooling tower fan inverter 3 via an electrical signal to control the cooling tower fan 2 to operate according to the frequency of the optimized operating frequency signal, so as to adjust the return water temperature of the return water pipe 9.

[0049] The controller 5 is selected from any of the existing microcontrollers, CPUs, PLCs or PID controllers. The outdoor wet-bulb temperature calculation module 10, the cooling water return temperature optimization module 11 and the cooling water return temperature control module 12 are selected from the runnable program modules stored in the controller 5.

[0050] Based on the above control system, when calculating the optimized temperature setpoint, the cooling water return temperature optimization module 11 first calculates the outdoor wet-bulb temperature value through the outdoor wet-bulb temperature calculation module 10 and transmits it to the cooling water return temperature optimization module 11; then, according to the outdoor wet-bulb temperature value, it uses the formula T=a*ln(Twet0)+b

[0051] Determine the optimization approximation degree T. 'a' is the gain coefficient, typically ranging from -7 to -5, with a preferred default of -6.4; 'b' is the increment coefficient, typically ranging from 22 to 26, with a preferred default of 24; T is the optimization approximation degree; and Twet0 is the virtual wet-bulb temperature. When the real-time outdoor wet-bulb temperature is less than or equal to 6℃, the virtual wet-bulb temperature value is fixed at 6℃, and the optimization approximation degree defaults to 12.5℃; when the real-time outdoor wet-bulb temperature is greater than or equal to 35℃, the virtual wet-bulb temperature value is fixed at 35℃, and the optimization approximation degree defaults to 1.2℃; when the real-time outdoor wet-bulb temperature is greater than 6℃ but less than 35℃, the virtual wet-bulb temperature value is the same as the real-time outdoor wet-bulb temperature value.

[0052] After detecting the real-time outdoor wet-bulb temperature and the optimized approximation, the optimized setpoint for the cooling water return temperature can be determined using the formula Tw,set = T + Twet0. When the real-time outdoor wet-bulb temperature is less than or equal to 6℃, the virtual wet-bulb temperature is fixed at 6℃, the optimized approximation is set to 12.5℃ by default, and the cooling water return temperature setpoint is 18.5℃. When the real-time outdoor wet-bulb temperature is greater than or equal to 35℃, the virtual wet-bulb temperature is fixed at 35℃, the optimized approximation is set to 1.2℃ by default, and the calculated cooling water return temperature setpoint is 36.2℃. When the real-time outdoor wet-bulb temperature is greater than 6℃ but less than 35℃, the virtual wet-bulb temperature is the same as the real-time outdoor wet-bulb temperature, and the optimized approximation and cooling water return temperature setpoints change with the outdoor wet-bulb temperature.

[0053] The optimized temperature setpoint has a certain range. When the calculated optimized temperature setpoint is higher than the upper limit, such as 36℃, the optimized temperature setpoint is output at the upper limit; when the calculated optimized temperature setpoint is lower than the lower limit, such as 18℃, the optimized temperature setpoint is output at the lower limit.

[0054] In practical applications, the cooling tower cooling water return temperature optimization control system provided by this invention has different upper and lower temperature limits when used to cool central air conditioning and air compressor systems. Specifically, when used to cool central air conditioning systems, the upper temperature limit is 36°C and the lower temperature limit is 18°C; when used to cool air compressor systems, the upper temperature limit is 22°C and the lower temperature limit is 28°C.

[0055] When used in central air conditioning systems, the upper temperature limit is 36℃ and the lower limit is 18℃. This is because the industry design specifications for central air conditioning systems clearly stipulate that the cooling water supply temperature is 32℃ and the return temperature is 37℃. These design parameters determine the heat dissipation capacity of the cooling tower and the condenser-side pressure level of the central air conditioning chiller. In actual central air conditioning systems, the cooling side is an open system, and the cooling towers are placed outdoors. Due to the influence of cooling water quality and outdoor dust, scale easily forms on the surface of the cooling tower fins, which reduces the cooling tower's heat dissipation capacity.

[0056] The upper limit of the return water temperature setting corresponds to this extreme high temperature weather. Setting the maximum value to 36℃ can meet the needs of most actual projects. When the maximum setting value is too high, exceeding 36℃, the actual cooling water temperature will exceed 36℃, the pressure on the condenser side of the host will be too high, and the host will be at risk of shutting down. When the maximum setting value is too low, under extreme high temperature conditions, the cooling tower will have difficulty reaching the set value due to its limited heat dissipation capacity, and the energy consumption of the cooling tower will increase.

[0057] The lower limit for the return water temperature setting corresponds to the weather during transitional seasons and low-load operation of the central air conditioning system. Setting the minimum value too low will result in an excessively low actual cooling water return temperature, leading to excessively low condenser-side pressure on the central air conditioning chiller. Since central air conditioning chillers are generally closed-loop compressor systems, excessively low condenser-side pressure is detrimental to the return flow of lubricating oil. Setting the minimum value at 18℃ ensures stable operation of the refrigeration system while achieving maximum energy savings.

[0058] When used in air compressor systems, the upper temperature limit is 28℃ and the lower limit is 22℃. This is because air compressor systems typically operate year-round, requiring high system stability. The heat discharged during operation is large and relatively stable, and cooling water is used to lower the temperature of the air compressor lubricating oil and the compressor system itself. Setting the upper limit of the return water temperature to 28℃ ensures that during most of the hottest months in July and August, the outdoor wet-bulb temperature will exceed 28℃. At this time, the cooling tower will operate at its set temperature of 28℃ at full frequency, which is beneficial for the stable operation of the air compressor system.

[0059] The viscosity of air compressor lubricating oil is greatly affected by temperature. The lubricating oil temperature should not be too low. The lower limit of the return water temperature is set to 22℃. When the outdoor wet-bulb temperature is below 22℃ during the transition season, the cooling tower will operate at a low frequency at the set temperature of 22℃. This will meet the heat dissipation requirements of the air compressor, achieve energy saving of the cooling tower system, and avoid the lubricating oil temperature from being too low.

[0060] Figure 2 A comparison chart of the optimized cooling water return temperature setpoint for the central air conditioning system and the outdoor wet-bulb temperature calculated by the cooling water return temperature optimization module 11.

[0061] The difference between the optimal cooling water return temperature setpoint Tw,set and the outdoor wet-bulb temperature Twet0, i.e., the optimal approximation T, is a dynamic value. The lower the outdoor wet-bulb temperature, the greater the difference between the optimal cooling water return temperature setpoint and the outdoor wet-bulb temperature. As the outdoor wet-bulb temperature decreases, the cooling water return temperature also decreases, reducing the evaporation capacity of the cooling water and thus the heat exchange efficiency between the cooling water and the outdoor air. If the cooling water return temperature were to achieve the same approximation as at high temperatures, more cooling tower fan energy would be required. Therefore, the optimal cooling water approximation is not constant but changes with the outdoor wet-bulb temperature.

[0062] Figure 3 The diagram illustrates the steps of a method for controlling this control system. The control method based on the above control system includes the following steps:

[0063] S1: Temperature and humidity sensor 4 detects real-time outdoor temperature and humidity values ​​and transmits them to controller 5 via electrical signals. Outdoor wet-bulb temperature calculation module 10 in controller 5 calculates the outdoor wet-bulb temperature value based on the outdoor temperature and humidity values ​​and inputs it into cooling water return temperature optimization module 11, proceeding to step S2.

[0064] S2: The cooling water return temperature optimization module 11 in the controller 5 calculates the optimized temperature setpoint based on the outdoor wet-bulb temperature value through the optimized temperature algorithm, and inputs it to the cooling water return temperature control module 12, and proceeds to step S3.

[0065] S3: The cooling water return temperature control module 12 determines whether the real-time cooling water return temperature value detected by the temperature sensor 6 is within the deviation range of the optimized temperature set value. If so, the optimized operating frequency value remains unchanged from the previous optimized operating frequency value, and proceeds to step S4; if not, the cooling water return temperature control module 12 calculates the optimized operating frequency value through the PID algorithm, and proceeds to step S4.

[0066] S4: The optimized operating frequency value is sent to the cooling tower fan inverter 3 via an electrical signal. The cooling tower fan inverter 3 adjusts the speed of the cooling tower fan 2 according to the optimized operating frequency value, thereby controlling the cooling water return temperature to keep it within the deviation range of the optimized temperature setting value.

[0067] When the detected cooling water return temperature is greater than the calculated optimal temperature setpoint, the PID algorithm calculates a larger optimal operating frequency value for the cooling tower based on the deviation value, and then sends the optimal operating frequency signal to the cooling tower fan inverter to increase the cooling tower fan speed, thereby reducing the cooling water return temperature. When the detected cooling water return temperature is less than the calculated optimal temperature setpoint, the PID algorithm calculates a smaller optimal operating frequency value for the cooling tower based on the deviation value, and then sends the optimal operating frequency signal to the cooling tower fan inverter to decrease the cooling tower fan speed, thereby increasing the cooling water return temperature.

[0068] During the control process, a frequency control dead zone is set in the frequency optimization algorithm. The dead zone range is generally from -0.2℃ to 0.2℃. That is, when the detected cooling water return temperature deviates from the calculated optimized temperature setpoint between -0.2℃ and 0.2℃, the PID algorithm does not perform calculations, and the cooling tower operating frequency remains unchanged from the previous moment.

[0069] The PID algorithm used in the frequency optimization algorithm of this invention is a commonly used algorithm. The specific algorithm formula is not the subject of this invention, so it will not be described in this specification.

[0070] Through the above control system and control method, the cooling water return temperature control of cooling tower 1 is based on the optimized cooling water return temperature setpoint and the real-time cooling water return temperature of the system to control the operating frequency of the cooling tower fan, so that the fan operates at the optimized operating frequency, saving energy consumption of the cooling tower while meeting the user's cooling capacity requirements, and realizing energy-saving operation of the system; effectively improving the intelligence level of the cooling water system operation and improving indoor thermal comfort.

[0071] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An optimized control system for the return water temperature of cooling water in a cooling tower, which comprises a water circuit formed by connecting a cooling tower (1), a condenser (8) and a water pump (7). The pipeline between the water pump (7) and the cooling tower (1) is a return water pipe (9). A cooling tower fan (2) is provided on the cooling tower (1), and a cooling tower fan frequency converter (3) is provided on the cooling tower fan (2). A temperature sensor (6) for detecting the real-time return water temperature of the return water pipe (9) is provided on the return water pipe (9). It is characterized in that: It further comprises a controller (5) and a temperature and humidity sensor (4) installed outdoors for detecting the outdoor temperature and humidity. The temperature and humidity sensor (4), the cooling tower fan frequency converter (3) and the temperature sensor (6) are all electrically connected to the controller (5); The controller (5) comprises an outdoor wet bulb temperature calculation module (10), a cooling water return water temperature optimization module (11) and a cooling water return water temperature control module (12); The outdoor wet bulb temperature calculation module (10) calculates the real-time outdoor wet bulb temperature value according to the real-time outdoor temperature and humidity signals collected by the temperature and humidity sensor (4), and transmits the real-time outdoor wet bulb temperature value to the cooling water return water temperature optimization module (11); The cooling water return water temperature optimization module (11) calculates an optimized temperature set value according to the received real-time outdoor wet bulb temperature value, and transmits the optimized temperature set value to the cooling water return water temperature control module (12); The cooling water return water temperature control module (12) compares the optimized temperature set value with the real-time return water temperature value, calculates an optimized operation frequency value through an optimized frequency algorithm, and transmits the optimized operation frequency value to the cooling tower fan frequency converter (3) to adjust the cooling tower fan (2) to operate according to the optimized operation frequency value, thereby adjusting the return water temperature of the return water pipe (9) to maintain it at the optimized temperature set value; The cooling water return water temperature optimization module (11) calculates the optimized temperature set value according to an optimized temperature algorithm. The optimized temperature algorithm includes the calculation of an optimized approximation degree and the calculation of an optimized temperature set value. The optimized approximation degree is calculated according to the following formula: ， Where, T is the optimized approximation degree, a is the gain coefficient, b is the increment coefficient, T is the optimized approximation degree, and Twet0 is the virtual wet bulb temperature; the virtual wet bulb temperature Twet0 is determined by the real-time outdoor wet bulb temperature Twet, and the range of the virtual wet bulb temperature Twet0 is 6°C - 35°C. The determination method is as follows: If Twet <= 6°C, then Twet0 = 6°C; If Twet >= 35°C, then Twet0 = 35°C; If 6°C < Twet < 35°C, then Twet0 = Twet; The optimized temperature set value Tw,set is the sum of the calculated optimized approximation degree T and the virtual wet bulb temperature Twet0, that is: Tw,set = T + Twet0; The value range of the gain coefficient a is -7 to -5; the value range of the increment coefficient b is 22 to 26.

2. The control system of claim 1, wherein: The range of the optimized temperature setting value is from the upper temperature value to the lower temperature value; when the calculated optimized temperature setting value is greater than the upper temperature value, the optimized temperature setting value is equal to the upper temperature value; when the calculated optimized temperature setting value is less than the lower temperature value, the temperature setting value is equal to the lower temperature value.

3. The control system of claim 2, wherein: When used to cool a central air conditioning system, the upper temperature limit is 36°C and the lower temperature limit is 18°C; when used to cool an air compressor system, the upper temperature limit is 28°C and the lower temperature limit is 22°C.

4. The control method for the control system according to any one of claims 1 to 3, characterized in that: Includes the following steps: S1: The temperature and humidity sensor (4) detects the real-time outdoor temperature and humidity values ​​and transmits them to the controller (5) via electrical signals. The outdoor wet-bulb temperature calculation module (10) in the controller (5) calculates the outdoor wet-bulb temperature value based on the outdoor temperature and humidity values ​​and inputs it to the cooling water return temperature optimization module (11) to proceed to step S2. S2: The cooling water return temperature optimization module (11) calculates the optimized temperature setpoint based on the outdoor wet-bulb temperature value through the optimized temperature algorithm, and inputs it to the cooling water return temperature control module (12) to proceed to step S3; S3: The cooling water return temperature control module (12) determines whether the real-time cooling water return temperature value detected by the temperature sensor (6) is within the deviation range of the optimized temperature setting value. If yes, the optimized operating frequency value remains unchanged from the previous optimized operating frequency value, and proceeds to step S4; if no, the cooling water return temperature control module (12) calculates the optimized operating frequency value through the PID algorithm and proceeds to step S4. S4: The optimized operating frequency value is sent to the cooling tower fan frequency converter (3) via an electrical signal. The cooling tower fan frequency converter (3) adjusts the speed of the cooling tower fan (2) according to the optimized operating frequency value, thereby controlling the cooling water return temperature to maintain it within the deviation range of the optimized temperature setting value.

5. The control method according to claim 4, characterized in that: In step S3, the deviation range of the optimized temperature setting value is between ±0.2℃.

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