Regulation method and system for realizing precise heat exchange of industrial circulating water heat exchange equipment

Abstract

This invention relates to industrial fluid control and heat exchange technology, aiming to provide a control method and system for achieving precise heat exchange in industrial circulating water heat exchange equipment. It includes: selecting a portion of the heat exchange equipment in the circulating water system as the control targets, prioritizing their operation in a climate-adaptive temperature difference control mode, and dynamically setting the optimal target temperature difference between the primary-side supply water and the primary-side return water. To maximize energy efficiency, if an abnormal state of insufficient heat exchange occurs, the primary side flow rate is increased while maintaining a regulatory margin. If the valve opening exceeds the threshold, the flow rate is switched to flow priority mode. If this is ineffective, the pressure and flow rate of the primary side circulating water main are changed by adjusting the operating frequency of the circulating water pump until the secondary side outlet water temperature and the regulating valve opening both fall back to the set range. Compared with existing technologies, this invention achieves intelligent control, precise energy saving, system linkage for strong protection, and high integration with multi-functional valves.

Description

Control methods and systems for achieving precise heat exchange in industrial circulating water heat exchange equipment Technical Field

[0001] This invention belongs to the field of industrial fluid control and heat exchange technology, specifically relating to a control method and system for achieving precise heat exchange in industrial circulating water heat exchange equipment. Background Technology

[0002] In industrial circulating water cooling systems in industries such as metallurgy and chemicals, heat exchangers are the core equipment for achieving process cooling. Their operating efficiency and energy consumption directly affect the safety, economy, and carbon emission intensity of the entire production system. To maximize energy efficiency, precise temperature control of the heat exchanger is required. A common practice is to install electric or pneumatic regulating valves on the return water pipeline of the primary side (circulating water side) of the heat exchanger, adjusting the water flow to match the changing heat load of the process medium on the secondary side. Existing regulation schemes typically only adjust based on the temperature changes of the primary and secondary sides of the controlled object (a single piece of equipment). However, due to the strong coupling between various nodes in the fluid distribution network, the circulating water system operates inefficiently for extended periods under conditions of "high flow rate and small temperature difference."

[0003] Firstly, there is the challenge of accurate flow measurement, as precise flow control relies on accurate sensing of instantaneous flow. Currently, the industry commonly uses a solution of installing an independent flow meter (such as an electromagnetic flow sensor or ultrasonic flow sensor) in addition to the regulating valve. This not only significantly increases the costs of hardware procurement, installation, and wiring, but more importantly, mainstream flow sensors, to ensure measurement accuracy, generally require sufficiently long straight pipe sections upstream and downstream (e.g., 10D upstream and 5D downstream, where D is the pipe diameter) to eliminate flow distortion caused by pumps, elbows, and other turbulent components. However, the inlet and outlet pipe layouts of heat exchangers in industrial settings are usually compact and complex, making it difficult to meet this ideal installation condition. This results in most flow meters exhibiting significant "inaccurate flow measurement" in practical applications, with low reliability of their measurements, failing to provide reliable feedback for closed-loop control.

[0004] Secondly, the inherent flaw in the control strategy stems from the persistent problem of high energy consumption due to "large flow rate, small temperature difference." Lacking effective, reliable, and economical real-time flow sensing, control systems often resort to using only the secondary outlet temperature or the primary supply / return water temperature difference as the sole control objective. When heat exchanger efficiency decreases due to scaling, traditional PID controllers passively and continuously increase valve openings to compensate for insufficient heat exchange. This lagging feedback control easily leads the system into the unfavorable condition of "large flow rate, small temperature difference," where the circulating water flow is large, but the heat it carries is not effectively exchanged, resulting in a very small inlet / outlet temperature difference. This means that a significant amount of work done by the pump is wasted on driving the fluid "idling." Under this condition, the energy consumption of the circulating water pumping station can be more than 30% higher than the ideal design calculations, resulting in enormous energy and water waste.

[0005] Third, the flow velocity in the circulating water system varies greatly with changes in ambient temperature throughout the season. Most mainstream flow sensors only have a range ratio of 1:5 to 1:10, leading to inaccurate flow measurements. Furthermore, installing an independent flow sensor for each heat exchanger inevitably introduces more wiring, interfaces, and potential points of failure, increasing system installation costs and maintenance complexity.

[0006] In summary, existing technologies for controlling circulating water networks using heat exchangers are trapped in a vicious cycle: improving control accuracy requires flow measurement, but independent measurement methods are unreliable due to cost, accuracy, installation conditions, or their own energy efficiency issues; ultimately, because precise flow control cannot be achieved, the heat exchange system is forced to operate in a high-energy-consumption state of "high flow rate, small temperature difference" for extended periods. Therefore, the industry urgently needs a new technological solution that can fundamentally solve these problems: a high-performance regulating valve that integrates high-precision, low-resistance flow measurement functions, and based on this, a precise heat exchange measurement and control technology for heat exchange equipment. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a control method and system for achieving precise heat exchange in industrial circulating water heat exchange equipment.

[0008] To solve the technical problem, the solution of the present invention is:

[0009] A method for regulating precise heat exchange in industrial circulating water heat exchange equipment is provided, comprising:

[0010] (1) Install regulating valves on the primary side return water pipelines of each heat exchanger in the industrial circulating water system, and use multiple sensors to obtain real-time operating data of the system and temperature and humidity data of the external environment;

[0011] (2) Using the selected heat exchange equipment as the object of precise heat exchange control, when the circulating water system is running stably and the secondary side outlet water temperature of the controlled object is within the process requirement range, it is operated in the climate adaptive temperature difference control mode, and the optimal target temperature difference between the primary side supply water and the primary side return water is dynamically set. To maximize energy efficiency;

[0012] (3) If the secondary outlet water temperature of the controlled object is found to be higher than the upper limit of the set range and exceeds the preset deviation range for a certain period of time, it is judged to be an abnormal state of insufficient heat exchange; and handled as follows:

[0013] Prioritize maintaining the climate-adaptive temperature difference control mode, by adjusting the optimal target temperature difference. Optimize valve opening to increase the primary flow rate of the controlled object while maintaining adjustment margin;

[0014] If the valve opening exceeds the maximum threshold of the preset range, switch to flow priority mode; by forcibly increasing the valve opening, more circulating water flows through, so that the secondary side outlet water temperature drops to the set range;

[0015] If the secondary side outlet water temperature cannot be reduced even at maximum flow rate, the pressure and flow rate of the primary side circulating water main pipe are changed by adjusting the operating frequency of the circulating water pump until the secondary side outlet water temperature and the opening of the regulating valve both fall back to the set range.

[0016] This invention further provides a system for achieving precise heat exchange in industrial circulating water heat exchange equipment, comprising:

[0017] The heat exchange equipment is connected to the circulating water main and the process side pipelines through primary and secondary side pipelines, respectively; when there are multiple heat exchange equipment, they are operated in parallel, and at least one heat exchange equipment is selected as the control object for precise heat exchange.

[0018] The regulating valve is installed on the primary side return water pipe of the heat exchange equipment, and its valve body is connected to the actuator through a rotating shaft.

[0019] The circulating water pump is installed on the return water main of the primary circulating water.

[0020] An outdoor temperature and humidity sensor is installed in the outdoor environment near the cooling tower of the circulating water system.

[0021] Multiple temperature sensors are installed on the primary and secondary side pipelines of the controlled object, respectively;

[0022] At least two pressure sensors are installed on both sides of the valve body of the regulating valve that is matched with the controlled object;

[0023] The flow meter is installed on the return main pipe of the primary circulating water.

[0024] The power meter is installed in the motor control module of the circulating water pump;

[0025] The intelligent controller is connected to various sensors, the motor control module of the water pump, and the actuator of the regulating valve via signal lines. The actuator of the regulating valve is either a separate design or built into the actuator. The intelligent controller includes at least one processor and a memory communicatively connected to the at least one processor. The memory stores instructions that are executed by the at least one processor to cause the at least one processor to perform the aforementioned control method for achieving precise heat exchange in industrial circulating water heat exchange equipment.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. Intelligent control, precise energy saving.

[0028] This invention can automatically identify the operating status of the precise heat exchange control object (heat exchange equipment), enabling it to intelligently switch between "climate adaptive" and "flow priority" modes, effectively eliminating high-energy-consuming conditions of "large flow rate and small temperature difference", and automatically optimizing operating parameters according to seasonal changes to achieve high efficiency and energy saving throughout the year.

[0029] 2. System coordination ensures strong support.

[0030] When the valve's adjustment capacity is insufficient, the linkage mechanism between the circulating water pump and the control valve can be automatically triggered. Through system-level collaboration, the cooling capacity is improved, maximizing the stable operation of the production process and far exceeding the reliability of the adjustment mode of a single heat exchanger.

[0031] 3. Highly integrated, one valve for multiple uses.

[0032] This invention, through an innovative butterfly valve + guide plate design, enables the regulating valve itself to possess both high-precision flow measurement and excellent regulation characteristics. It utilizes the pressure difference between the valve and its upstream and downstream sides to achieve instantaneous flow calculation. This eliminates the need for a separate flow meter, fundamentally solving the problems of high cost, complex installation, and inaccurate measurement in traditional solutions, as well as the difficulty in arranging installation locations on-site in actual production facilities. Attached Figure Description

[0033] Figure 1 is a schematic diagram of the structure of the precision heat exchange system and the sensor arrangement diagram of the present invention.

[0034] Figure 2 is a schematic diagram of the structure of the guide plate installed on the butterfly valve.

[0035] Figure 3 is a three-dimensional structural diagram of the deflector.

[0036] Figure 4 is a flowchart of the present invention for achieving precise heat exchange through flow restriction and climate compensation.

[0037] In the diagram: 1. Primary water supply pipe; 2. Primary water return pipe; 3. Secondary water inlet pipe; 4. Secondary water outlet pipe; 5. First temperature sensor; 6. Second temperature sensor; 7. Third temperature sensor; 8. Fourth temperature sensor; 9. First pressure sensor; 10. Second pressure sensor; 11. Regulating valve; 12. Intelligent controller; 13. Circulating water main flow meter; 14. Circulating water pump total power meter; 15. Outdoor temperature and humidity sensor; 16. Circulating water pump; 17. Rotating shaft; 18. Bushing; 19. Butterfly plate; 20. Guide plate; 801. Guide plate body; 802. Guide hole; 803. Mounting hole. Detailed Implementation

[0038] The specific implementation scheme of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] Part One: A System for Achieving Precise Heat Exchange in Industrial Circulating Water Heat Exchange Equipment

[0040] 1. In industrial production processes, heat exchange equipment is typically required for different devices to meet the heat exchange needs of the process side. In large-scale production units, the number of such equipment can reach dozens or even hundreds. For example, in a 5 million tons / year combined atmospheric and vacuum distillation and catalytic cracking oil refining unit, the total number of heat exchangers of various types is approximately 80-120. Therefore, to achieve intensive heat exchange, the primary side of the heat exchange equipment in the unit is usually connected to the same circulating water system, using a unit consisting of one or more parallel water pumps and a cooling tower as supporting equipment.

[0041] Because numerous factors, such as medium type, temperature differences, and flow rate variations, affect the heat exchange efficiency of various heat exchange devices in a production unit, not all heat exchange devices need to be precisely controlled. In reality, the importance of heat exchange devices can be determined based on the process conditions, and the industrial circulating water system manufacturer can identify or conduct on-site surveys to select several or more heat exchange devices as control targets. There are two main considerations: one is that the process-side heat exchange requirements are high, potentially directly impacting product quality or production safety; the other is that the heat exchange / circulation water volume is large, accounting for a significant portion of the overall energy consumption in the circulating water system, or that there is substantial energy-saving potential (currently operating under "high flow rate, small temperature difference" conditions). Heat exchange devices with low process-side temperature regulation requirements, small heat exchange / circulation water volume, or intermittent use that has little impact on the overall system flow / pressure are generally considered unimportant and do not need to be controlled. By "differentiating treatment" and "precise control" of heat exchange devices, the investment benefits can be maximized on key heat exchange equipment, which is conducive to its widespread application in real-world scenarios.

[0042] 2. Based on the above innovative ideas, this invention proposes a system for achieving precise heat exchange in industrial circulating water heat exchange equipment:

[0043] As shown in Figure 1, the system includes one or more heat exchangers, regulating valves, circulating water pumps, outdoor temperature and humidity sensors, flow meters, power meters, and multiple temperature sensors, at least two pressure sensors, and an intelligent controller installed on the heat exchangers.

[0044] The heat exchange equipment has its inlet and outlet connected to the primary side supply water pipe 1, primary side return water pipe 2, secondary side inlet water pipe 3, and secondary side outlet water pipe 4, respectively, which are connected to the circulating water main pipe and the process side pipeline. A regulating valve is installed on the primary side return water pipe 2 of each heat exchanger, and the valve body is connected to an actuator via a rotating shaft. As an optional example, the heat exchange equipment is a shell-and-tube heat exchanger, specifically any of the following: shell-and-tube heat exchanger, plate heat exchanger, spiral plate heat exchanger, coaxial tube heat exchanger, finned tube heat exchanger, jacketed heat exchanger, serpentine tube heat exchanger, or heat pipe heat exchanger.

[0045] As shown in Figure 1, the system consists of multiple heat exchangers operating in parallel. One (or several) heat exchangers are selected as the control targets for precise heat exchange. To further achieve precise control, this invention proposes to select a newly designed regulating valve 11, whose valve body is a butterfly valve with a guide plate 20, as shown in Figures 3 and 4. The butterfly valve includes a valve body, a rotating shaft 17, a butterfly plate 19, and guide plates 20. One end of the rotating shaft 17 is connected to the electric drive output of the actuator, and the other end is fixedly installed at the center of the butterfly plate 19. A pair of guide plates 20 are symmetrically installed on both sides of the butterfly plate 19. The main body 801 of the guide plate is a semi-cylindrical structure with a through guide hole 802 perpendicular to the rotating shaft 17. The main body of the guide plate 20 fits the surface of the butterfly plate 19, and the mounting surface has a concave curved surface structure adapted to the shape of the middle part of the butterfly plate 19. It is fixed by screws inserted into the mounting holes 803. There are 1 to 2 guide holes 802, and their cross-sections are circular, elliptical, or square. Through the appropriate combination of the end face area of ​​the guide plate 20 and the cross-section of the guide hole, the regulating valve 11 can utilize the pressure difference before and after the valve while maintaining sufficient flow capacity. The system provides precisely calibrated equal percentage flow regulation characteristics. Furthermore, the structure of the baffle 20 effectively reduces fluid resistance during valve opening and closing, significantly lowering the required drive torque for the actuator. The intelligent controller 12 is connected via signal lines to the outdoor temperature and humidity sensor 15, various temperature sensors, pressure sensors, flow meter 13, the motor control module of the circulating water pump 16, and the actuator of the regulating valve 11. The intelligent controller 12 can be designed as a separate unit from the regulating valve actuator or integrated into the actuator housing. To reduce equipment costs, other heat exchange equipment not selected for precise heat exchange regulation in the circulating water system is fitted with V-port ball valves or seat valves with equal percentage regulation characteristics.

[0046] The circulating water pump 16 can be a single pump or a pump unit composed of multiple pumps connected in parallel. The motor control module of the circulating water pump 16 integrates a power meter 14 and a frequency converter control module, enabling precise control of flow rate and pressure by adjusting the pump's operating frequency and speed. The circulating water pump 16 and flow meter 13 are installed on the return water main of the primary circulating water. An outdoor temperature and humidity sensor 15 is installed in the outdoor environment near the cooling tower reached by the return water main of the primary circulating water. The heat exchanger (HE1) is equipped with four temperature sensors and two pressure sensors. The second temperature sensor 6 is installed on the valve wall on the axial side of the inlet flow channel of the control valve 11. The first temperature sensor 5, the third temperature sensor 7, and the fourth temperature sensor 8 are respectively installed on the primary side supply pipe 1, the secondary side inlet pipe 3, and the secondary side outlet pipe 4. The first pressure sensor 9 and the second pressure sensor 10 are installed at the front and rear ends of the regulating valve 11, respectively, and the pressure difference between them is expressed as... .

[0047] It is understandable that if the circulating water system has only one heat exchange device and is used as the object of precise heat exchange control, the way to obtain flow data can be to install a flow meter only on the return water main of the primary circulating water, or to use only a butterfly valve with a guide plate as a regulating valve.

[0048] For the scheme using a 20mm butterfly valve with a baffle plate, the instantaneous flow rate of the primary circulating cooling water of a single heat exchanger can be calculated using the following formula:

[0049]

[0050] in: To determine the instantaneous flow rate of the circulating cooling water on the primary side via the regulating valve, m 3 / h; This represents the maximum flow capacity of the control valve at 100% opening. This is the inherent flow characteristic function of the valve, calibrated before leaving the factory; This indicates the pressure difference between the valve and its upstream and downstream sides.

[0051] When multiple heat exchangers operate in parallel, the primary side circulating water return main pipe collects the flow rates from multiple primary side return water pipes. That is, flow meter 13 measures the sum of the instantaneous flow rates of the primary side return water from multiple heat exchangers (including controlled and uncontrolled devices):

[0052]

[0053] in: The current circulating water main flow rate is in meters (m). 3 / h. m is the instantaneous flow rate of the primary circulating cooling water through each controlled and uncontrolled object. 3 / h; n is the total number of heat exchangers.

[0054] 3. Based on common understanding, the intelligent controller 12 includes at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions that are executed by the at least one processor, and the instructions are executed by the at least one processor to cause the at least one processor to perform the control method for achieving precise heat exchange in industrial circulating water heat exchange equipment as described in this invention.

[0055] The applicant believes that, after carefully reading the application documents and accurately understanding the implementation principles and objectives of this invention, and in conjunction with existing known technologies, those skilled in the art can fully implement this invention using their software programming skills. For example, in addition to implementing the control method provided by this invention using purely computer-readable program code, the same function can also be achieved by logically programming the method steps. This part will not be elaborated upon further in this invention.

[0056] Part Two: Scheduling Methods for Precise Heat Exchange in Industrial Circulating Water Heat Exchange Equipment

[0057] 1. Utilize multiple sensors to acquire real-time operating data of the circulating water system and external environmental temperature and humidity data TH1.

[0058] Taking the circulating water system shown in Figure 1 as an example, the real-time operating data includes at least: the opening degree TV1 of regulating valve 11, the pressure P1 before regulating valve and the pressure P2 after regulating valve, the primary side supply water temperature T1 and return water temperature T2, the secondary side inlet water temperature T3 and outlet water temperature T4, the primary side circulating water flow rate F, and the primary side circulating water pump operating power W.

[0059] 2. When the circulating water system is operating stably and the secondary side outlet water temperature of the heat exchange equipment is within the process requirement range, the heat exchange equipment, which is the object of precise heat exchange regulation, is operated in the climate adaptive temperature difference control mode. The optimal target temperature difference between the primary side supply water and the primary side return water is dynamically set. This is to maximize the energy efficiency of heat exchange equipment. Specifically:

[0060] (1) First, under stable and highest priority process parameters (secondary side outlet water pipe temperature sensor data) Under normal conditions, the system operates in "climate adaptive temperature difference control" mode to maximize the energy efficiency of the heat exchange equipment.

[0061] Among them, the climate-adaptive temperature difference control mode refers to the control mode based on the outdoor wet-bulb temperature. Dynamically set the optimal target temperature difference on the primary side In summer, a relatively small temperature difference is set to ensure cooling capacity; in winter, a relatively large temperature difference is set to save energy consumption of the circulating water pump.

[0062] Ambient temperature detected by an ambient temperature and humidity sensor (°C) and relative humidity (%), the outdoor wet-bulb temperature is calculated using the following approximate formula. :

[0063]

[0064] Primary side optimal target temperature difference It is based on the wet-bulb temperature The linear relationship is calculated to obtain:

[0065]

[0066] Where 'a' is a negative coefficient (because wet-bulb temperature) The higher the temperature difference, the better the primary side's optimal target temperature difference. The lower the value, the better. b is a coefficient used as a reference value (related to the design temperature difference on the primary side of the heat exchanger). related).

[0067] The specific values ​​of coefficients a and b are determined through system debugging and optimization, specifically in three stages:

[0068] ① Initial value setting

[0069] First, determine The upper and lower limits can generally be set to [ [This refers to the highest wet-bulb temperature in summer.] hour, Lowest wet-bulb temperature in winter hour, .

[0070] Then there is,

[0071]

[0072]

[0073] Taking a specific project as an example, the design temperature difference on the primary side of the heat exchanger... At wet-bulb temperature At 30℃, At wet-bulb temperature At 10℃, ;

[0074] but, .

[0075] ②On-site adjustment

[0076] Different wet-bulb temperature ranges (e.g., wet-bulb temperature) Within 10℃; 10℃~20℃; 20~30℃), select several stable working days respectively, at which time the secondary side load is relatively stable. At a fixed wet-bulb temperature... Below, minor changes to the existing (For example, ±0.5℃), record the system average efficiency η during this period, η = heat exchange / pump power, i.e.

[0077]

[0078]

[0079] in: The real-time heat exchange capacity of the heat exchange equipment is expressed in kW; ρ is the density of the primary circulating cooling water, expressed in kg / m³. 3 Take 1000 kg / m 3 ; The constant-pressure specific heat capacity of the primary circulating cooling water, in units ; The temperature difference between the primary supply and return water of the current controlled object is ℃; The total operating power of the primary circulating water pump is kW; The current circulating water main flow rate is in meters (m). 3 / h. This indicates the primary circulating water pump power allocated to the currently regulated object. This refers to the instantaneous flow rate of the primary circulating cooling water of the currently controlled object.

[0080] Draw the current The average efficiency η of the lower system varies with The changing relationship curve (referred to as the climate compensation curve in this invention), the peak value of the curve corresponds to That is, the The optimal setting under different conditions. Repeat the above steps to obtain multiple sets. Linear regression fitting is performed on the data points to obtain optimized a and b.

[0081] ② Online optimization.

[0082] After accumulating sufficient data through long-term operation of the circulating water system, the values ​​of coefficients a and b are automatically fine-tuned through on-site tuning calculations, so that the climate compensation curve always tracks the actual optimal performance point of the controlled object and adapts to disturbances such as aging of heat exchange equipment and changes in circulating water quality.

[0083] 3. If the secondary outlet water temperature of the controlled object is found to be higher than the upper limit of the set range and exceeds the preset deviation range for a certain period of time, it is judged to be an abnormal state of insufficient heat exchange.

[0084] When monitoring data from the secondary side outlet water pipe temperature sensor When the fluctuation exceeds its set upper limit, that is... For a period of time (e.g.) If the temperature remains above 1.5℃ for 5 minutes, it is considered an abnormal state of "insufficient heat exchange." In this case, the system's operating status should be diagnosed, and the root cause of the problem analyzed. This represents the degree to which the current heat exchanger's process temperature can deviate, for example, by 1.5℃.

[0085] The specific steps are as follows:

[0086] (1) Prioritize maintaining the climate adaptive temperature difference control mode, and adjust the optimal target temperature difference. Optimize valve opening to increase primary flow while maintaining adjustment margin;

[0087] First, examine the current valve opening. If the current valve opening is less than 85%, it indicates that there is still room for flow adjustment. Therefore, first optimize and adjust the "climate adaptive temperature difference control" parameters. The temperature is typically set to decrease by 0.5℃.

[0088] (2) If the valve opening exceeds the maximum threshold of the preset range, switch to flow priority mode; by forcibly increasing the valve opening, more circulating water flows through the heat exchange equipment, so that the secondary side outlet water temperature drops to the set range;

[0089] If the valve opening is between 85% and 95%, it means that the current valve opening is already large. At this time, the system will automatically switch from "climate adaptive temperature difference control mode" to "flow priority mode".

[0090] The control objective of the "flow priority" mode is to maintain a high set flow rate. (e.g., heat exchanger design flow rate) forces more circulating water to flow through the heat exchanger, prioritizing the secondary side temperature. Revert to the set value.

[0091] (3) If the secondary side outlet water temperature cannot be reduced even under the maximum flow rate, the pressure and flow rate of the primary side are changed by adjusting the operating power of the primary side circulating water pump until the secondary side outlet water temperature and the opening of the regulating valve both fall back to the set range.

[0092] If the current valve opening is already greater than 95%, its adjustment margin is only 5%. At this point, relying solely on the valve itself, its capacity is nearing its limit. Even if the valve is opened to 100%, the flow rate increase is limited and cannot compensate for the heat exchange deficit caused by severe scaling or a sudden increase in load.

[0093] Therefore, the determination of the status of the circulating water pumps in the circulating water pumping station is triggered by whether the frequency of the currently operating circulating water pump is lower than its maximum frequency and whether the system pipeline pressure is within the allowable range.

[0094] ① If the conditions are met, a command is sent to the water pump inverter to gradually increase the frequency (1Hz per step). As the circulating water pump frequency increases, the pressure and flow distribution in the circulating water system will change, and the valve opening will slowly return to below 85%. Simultaneously, the secondary side temperature is continuously monitored. Check if the value is within the normal range. If it is, maintain the current state. If the problem persists, iterate through the "small step frequency increase - valve opening optimization" steps again until the secondary side temperature... It is within the normal range or has reached the upper limit of the circulating water pump frequency.

[0095] ② If not satisfied, maintain the "flow priority" mode until the valve opening reaches 100%, and generate a clear alarm message in the control system: the maximum cooling capacity of the heat exchange equipment can no longer meet the current process load, and process adjustment or equipment maintenance is required immediately.

[0096] 4. Status of heat exchange equipment not subject to control

[0097] The above mainly describes the process of precise heat exchange control for selected heat exchange equipment. Its core is based on the parameters of a single heat exchange equipment (flow rate Q, heat exchange capacity). ) and circulating water system parameters (total flow rate) Outdoor wet-bulb temperature Ts, total power of circulating water pump set ), calculate the efficiency of a single device Values ​​and their optimal control temperature difference Ultimately, the climate compensation curve will always track the system's actual optimal performance point to adapt to disturbances such as aging heat exchange equipment and changes in circulating water quality.

[0098] In this process, the heat exchange equipment, which is not a controlled object, has a small energy consumption ratio or a relatively small flow rate in the circulating water system. Therefore, it only needs to use a V-port ball valve or a seat valve with equal percentage adjustment characteristics to make its own adjustment strategy to adapt to the flow and pressure fluctuations in the circulating water system. It does not need to track the changes in flow data in real time like the controlled object.

[0099] In actual production, the degree of scaling and energy consumption changes of each heat exchanger vary due to different usage levels. Moreover, under normal conditions, scaling of heat exchangers is a slow process, and the circulating water pump set is not constantly adjusted. Therefore, for changes in the pipe network characteristic curve (pipe network resistance) caused by changes in the opening of the regulating valve of the controlled object, the non-controlled object can suppress fluctuations through self-adjustment and achieve stable operation.

[0100] For example, in a circulating water system with 5 heat exchangers, if 2 of them, which are controlled, experience increased flow demand due to scaling (and their valve openings have reached their maximum values), while the flow demand of the other 3 remains unchanged, the circulating water pump will adjust its flow rate (i.e., implement a frequency increase), resulting in an increase in the overall flow rate of the network. While meeting the increased flow demand of the 2 scaled heat exchangers (with valve openings restored to 85% of the set value), the opening of the valves for the other 3 non-controlled heat exchangers will be reduced accordingly to ensure that their flow rates remain within the set value range.

[0101] A specific example:

[0102] This embodiment uses a shell-and-tube circulating water heat exchanger (HE1) in a chemical plant production unit as an example. This heat exchanger is used to cool high-temperature process materials (shell side, secondary side) from 80°C to 45°C, while circulating cooling water flows through the tubes (primary side). The original heat exchange system suffered from insufficient cooling capacity in summer and high pump energy consumption in winter.

[0103] 1. System Configuration

[0104] The control valve 11 is model ZTAT46.100 (DN100) and is driven by an electric actuator. The core feature of this valve is that its butterfly plate is equipped with a guide plate structure as shown in Figures 2 and 3, which enables it to have equal percentage regulation characteristics and pressure differential-based flow self-measurement function. The dimensionless constant for its flow calculation is calibrated by the manufacturer at the factory.

[0105] Sensor group: Temperature sensors are installed on the primary and secondary sides of the heat exchanger, and pressure sensors are installed before and after the regulating valve 11. Flow meter 13 is installed on the circulating water return main pipe, power meter 14 is installed on the circulating water pump, and outdoor temperature and humidity sensor 15 is installed behind the cooling tower.

[0106] Controller and Data: All the sensor signals mentioned above are connected to the intelligent controller 12 built into the valve actuator through signal lines to obtain the corresponding monitoring signals.

[0107] 2. Parameter initialization

[0108] Before the system is put into operation, key parameters should be initialized and set:

[0109] Control objective: Secondary side outlet temperature setpoint Allowable deviation .

[0110] Initial values ​​for the climate compensation curve: Based on design data and experience, the initial relationship is set as follows: That is: when the summer wet-bulb temperature... At 30℃, the target temperature difference =4℃; when the winter wet-bulb temperature At 10℃, the target temperature difference =6℃.

[0111] Mode switching threshold: Valve opening intervention threshold: =85%, =95%.

[0112] 3. Regulation and Operation Process

[0113] The intelligent control process of the system during a complete operating cycle is as follows, referring to the control flowchart in Figure 4.

[0114] S1: Stable Operation and Energy Efficiency Optimization (Climate Adaptive Mode)

[0115] After the system starts up, the controller continuously collects data from all sensors. It calculates the instantaneous flow rate Q and the actual temperature difference ΔT on the primary side.

[0116] Assuming the current wet-bulb temperature =25℃, the system calculates the target temperature difference based on the climate compensation curve. .

[0117] controller with To achieve the desired effect, the valve opening is adjusted using a PID algorithm to stabilize the actual temperature difference near the set value. At this point, the system operates in its high-efficiency range.

[0118] S2: Anomaly Diagnosis and Intelligent Decision-Making

[0119] Due to water quality issues, scale gradually formed on the walls of the heat exchange tubes. One day, the system detected a temperature difference on the secondary side. Sustained above 46.5℃ (i.e. If the temperature reaches +1.5℃ for 5 minutes, the "insufficient heat exchange" diagnosis will be triggered.

[0120] Diagnostic execution:

[0121] The controller checks the current valve opening φ=88% (exceeding the 85% warning threshold). It automatically switches from "Climate Adaptive Mode" to "Flow Priority Mode".

[0122] S3: Process Assurance (Flow Priority Mode)

[0123] In this mode, the control objective becomes maintaining a high safe flow rate. =48m³ / h (design flow rate).

[0124] The controller directly uses the flow rate Q as feedback, increasing the valve opening to 92% to stabilize the flow rate. nearby.

[0125] As the flow rate increases and the heat exchange increases, after about 10 minutes... It gradually dropped and stabilized within the safe range of 45.5℃.

[0126] 4. Implementation Effect Analysis

[0127] After implementing the precise heat exchange method of the present invention in this embodiment, the following significant effects were achieved:

[0128] Energy saving effect: During normal operation in spring and autumn, the average energy consumption of the circulating water pump was reduced by about 15% through climate compensation optimization, which further improved the stability of the heat exchanger process operation.

[0129] It is understood that the above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. For example, the valve may also employ a pneumatic actuator; the control algorithm may be deployed on an edge computing gateway or a cloud server; the present invention is also applicable to heating systems or other media heat exchange scenarios. Any equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for controlling precise heat exchange in industrial circulating water heat exchange equipment, characterized in that, include: (1) Install regulating valves on the primary side return water pipelines of each heat exchanger in the industrial circulating water system, and use multiple sensors to acquire real-time operating data of the system and temperature and humidity data of the external environment; (2) Take the selected heat exchanger as the object of precise heat exchange control, and when the circulating water system is running stably and the secondary side outlet water temperature of the object of control is within the process requirement range, make it run in the climate adaptive temperature difference control mode, and dynamically set the optimal target temperature difference between the primary side supply water and the primary side return water. To maximize energy efficiency; (3) If the secondary outlet water temperature of the controlled object is found to be higher than the upper limit of the set range and exceeds the preset deviation level for a certain period of time, it is judged to be an abnormal state of insufficient heat exchange; and it is handled in the following manner: prioritize the operation of the climate adaptive temperature difference control mode, and adjust the optimal target temperature difference. Optimize valve opening to increase the primary flow rate of the controlled object while maintaining adjustment margin; If the valve opening exceeds the maximum threshold of the preset range, switch to flow priority mode; force the valve opening to increase the flow of more circulating water, so that the secondary side outlet water temperature drops to the set range; if the secondary side outlet water temperature still cannot be reduced under the maximum flow rate, change the pressure and flow rate of the primary side circulating water main by adjusting the operating frequency of the circulating water pump, until the secondary side outlet water temperature and the regulating valve opening both fall back to the set range.

2. The method according to claim 1, characterized in that, The real-time operating data of the system includes at least: the total flow rate of primary circulating water, the operating power of the primary circulating water pump, and the opening degree of the regulating valve of the controlled object, the pressure before and after the valve, the primary water supply and return temperature, and the secondary water inlet and outlet temperature.

3. The method according to claim 1, characterized in that, The optimal target temperature difference It is obtained through the following linear relationship: ； In the formula, It is the outdoor wet-bulb temperature; It refers to the ambient temperature, in °C. It represents the relative humidity of the environment; %; a is a negative coefficient, and b is a coefficient used as a reference value.

4. The method according to claim 3, characterized in that, In the linear relationship, the specific values ​​of a and b are determined as follows: (1) Initial value setting: the upper and lower limits are set as [ If a and b are constant, then the initial values ​​of a and b are: ； In the formula, It is the highest wet-bulb temperature in summer. It is the highest wet-bulb temperature in winter; Corresponding to ， The optimal target temperature difference at that time; (2) On-site setting: Select relatively stable working days for the secondary side load of the circulating water system in different wet-bulb temperature ranges; at a certain fixed wet-bulb temperature Below, minor changes to the existing Record the average efficiency η of the controlled object during this period; plot the current wet-bulb temperature. The average efficiency η varies with The changing relationship curve is the climate compensation curve, and the peak value of the curve corresponds to... That is the The optimal setting value is as follows; at different fixed wet-bulb temperatures. Repeat the above steps to obtain multiple sets of data points and perform linear regression fitting to obtain the optimized coefficients a and b; (3) Online optimization: After the circulating water system has accumulated sufficient data through long-term operation, the values ​​of coefficients a and b are automatically fine-tuned by on-site tuning calculation, so that the climate compensation curve always tracks the actual optimal performance point of the controlled object and adapts to the disturbances caused by equipment aging and water quality changes.

5. The method according to claim 4, characterized in that, The average efficiency η of the controlled object is calculated according to the following formula: ； ;in: The real-time heat exchange capacity of the heat exchange equipment is measured in kW. The total operating power of the primary circulating water pump is kW; The current total primary circulating water flow rate, m 3 / h; The instantaneous flow rate (m) of the primary circulating cooling water of the currently controlled object. 3 / h; This represents the primary circulating water pump power allocated to the currently regulated object; ρ is the density of the primary circulating cooling water, taken as 1000 kg / m³. 3 ; The specific heat capacity at constant pressure of the primary circulating cooling water. ； The temperature difference between the primary and return water of the heat exchanger is expressed in °C.

6. The method according to claim 5, characterized in that, As a heat exchanger subject to precise heat exchange control, the matching regulating valve is a butterfly valve with a guide vane. Through an appropriate combination of the end face area of ​​the guide vane and the cross-section of the guide orifice, the regulating valve, while maintaining sufficient flow capacity, possesses the characteristic of equal percentage flow regulation that can be precisely calibrated using the pressure difference before and after the valve. During the control process, the instantaneous flow rate is calculated using the following formula. ： ;in: To determine the instantaneous flow rate of the circulating cooling water on the primary side via the regulating valve, m 3 / h; This represents the maximum flow capacity of the control valve at 100% opening. This is the inherent flow characteristic function of the valve, calibrated before leaving the factory; This indicates the pressure difference between the valve and its upstream and downstream sides.

7. The method according to claim 1, characterized in that, When adjusting the operating power of the primary circulating water pump, first determine whether the pump frequency is lower than its maximum frequency and whether the pressure in the primary pipeline is within the allowable range. If the above conditions are met, gradually increase the pump frequency in steps, while monitoring the valve opening recovery and the secondary outlet water temperature. If the temperature falls back to the normal range, maintain the current operating state. If the temperature still does not fall back, iterate again to increase the frequency and optimize the valve opening until the secondary outlet water temperature is within the normal range or the circulating water pump frequency reaches its upper limit. If the above conditions are not met, maintain the flow priority mode until the valve opening reaches 100%. At the same time, generate a clear alarm message indicating that the maximum cooling capacity of the controlled object cannot meet the current process load, and process-side adjustments or equipment maintenance are required immediately.

8. A system for achieving precise heat exchange in industrial circulating water heat exchange equipment, characterized in that, include: The heat exchanger is connected to the circulating water main and process side pipelines via primary and secondary side pipes, respectively. Multiple heat exchangers operate in parallel, with at least one selected as the object for precise heat exchange control. A regulating valve is installed on the primary side return water pipe of the heat exchanger, its body connected to an actuator via a rotating shaft. A circulating water pump is installed on the primary side return water main. An outdoor temperature and humidity sensor is installed in the outdoor environment near the cooling tower of the circulating water system. Multiple temperature sensors are installed on the primary and secondary side pipelines of the controlled object, respectively. At least two pressure sensors are installed on both sides of the regulating valve body of the controlled object. A flow meter is installed... The device is installed on the return water main of the primary circulating water; a power meter is installed in the motor control module of the circulating water pump; an intelligent controller is connected to each sensor, the motor control module of the water pump, and the actuator of the regulating valve via signal lines; the actuator of the regulating valve is either a separate design or built into the actuator; the intelligent controller includes at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions to be executed by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the control method for achieving precise heat exchange in industrial circulating water heat exchange equipment as described in any one of claims 1 to 7.

9. The system according to claim 8, characterized in that, The circulating water pump is a single pump or a pump unit composed of multiple pumps connected in parallel, and a frequency conversion control unit is integrated in the motor control module of the circulating water pump; the heat exchange equipment is a shell-and-tube heat exchanger, specifically any of the following: shell and tube heat exchanger, plate heat exchanger, spiral plate heat exchanger, coaxial tube heat exchanger, finned tube heat exchanger, jacketed heat exchanger, serpentine tube heat exchanger, or heat pipe heat exchanger.

10. The system according to claim 8, characterized in that, At least one heat exchanger is selected as the control object for precise heat exchange. The valve body of the regulating valve for this control object is a butterfly valve with a guide plate. The butterfly valve includes a valve body, a rotating shaft, a butterfly plate, and a guide plate. One end of the rotating shaft is connected to the electric drive output end of the actuator, and the other end is fixedly installed at the center of the butterfly plate. A pair of guide plates are symmetrically installed on both sides of the butterfly plate. The main body of the guide plate is a semi-cylindrical structure with a through guide hole perpendicular to the rotating shaft. The main body of the guide plate fits against the surface of the butterfly plate and is fixed by screws inserted into the mounting holes. There are 1 to 2 guide holes, and their cross-sections are circular, elliptical, or square. Through an appropriate combination of the end face area of ​​the guide plate and the cross-section of the guide hole, the regulating valve can have the characteristic of equal percentage flow regulation that can be accurately calibrated by using the pressure difference before and after the valve while maintaining sufficient flow capacity. For other heat exchangers in the circulating water system that are not selected as the control objects for precise heat exchange, the matching regulating valve is a V-port ball valve or a seat valve with equal percentage regulation characteristics.

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