A freezing prevention early warning method for an indirect cooling system of a thermal power unit

Abstract

The application relates to the technical field of indirect cooling systems of thermal power generating units, in particular to an anti-freezing early warning method for an indirect cooling system of a thermal power generating unit. The application establishes a heat exchange characteristic benchmark model library by taking the environmental parameters of a heat exchange unit and the flow of circulating cooling water as independent variables, and taking the theoretical values of the heat transfer coefficient and the air side pressure difference of the heat exchange unit in a non-icing state as dependent variables; the operation parameters of the heat exchange unit are collected in real time, the measured values of the heat transfer coefficient and the air side pressure difference are calculated, and the heat transfer deviation degree and the resistance deviation degree are further calculated; and an anti-freezing early warning signal is output based on the heat transfer deviation degree and the resistance deviation degree. The application can realize early and accurate early warning of icing of the indirect cooling system, effectively eliminate the interference of non-icing factors, ensure the safe and stable operation of the thermal power generating unit in winter, and reduce the energy consumption loss of anti-freezing adjustment.

Description

Technical Field

[0001] This application belongs to the technical field of indirect cooling systems for thermal power units, and relates to a method for antifreeze early warning of indirect cooling systems for thermal power units. Background Technology

[0002] The indirect cooling system of thermal power units is a closed-loop cooling system used in conjunction with large thermal power generating units. It mainly relies on heat exchange between external natural air and internal circulating water to dissipate waste heat during unit operation. In low-temperature environments during winter, the surface of the heat dissipation tubes is prone to frost and ice formation, which not only reduces the overall heat exchange efficiency of the system and interferes with the stable operation of the unit, but can also lead to equipment failures such as tube freezing and cracking, and pipe blockage in severe cases. Therefore, implementing accurate and reliable antifreeze status monitoring and early warning for the indirect cooling system is an important measure to ensure the safe and stable operation of the unit in winter.

[0003] Currently, most antifreeze warning methods for indirect cooling systems in the industry rely on data-driven neural networks built from historical measured operating data to achieve temperature prediction and antifreeze warning. These conventional data-driven models are susceptible to external factors such as sensor measurement errors and environmental disturbances, resulting in low prediction accuracy in low-temperature conditions and scenarios with insufficient sample data, easily leading to false alarms and missed warnings. Furthermore, existing warning modes often rely solely on water temperature as a judgment criterion, making it difficult to identify hidden icing trends such as initial frost formation in pipe bundles and abnormal ventilation duct resistance in advance. This results in significant warning lag and fails to meet the practical management needs for early identification and handling of equipment icing hazards. Summary of the Invention

[0004] This application provides a method for early warning of freezing in the indirect cooling system of thermal power units. By establishing a benchmark model library of heat transfer characteristics, real-time acquisition of operating parameters to calculate the dual deviation of heat transfer performance and air-side resistance, and outputting an early warning signal based on the dual deviation, an early and accurate warning of icing in the indirect cooling system is realized, overcoming the shortcomings of traditional single temperature threshold method in early warning, such as lag and high false alarm and missed alarm rates.

[0005] To achieve the above technical effects, this application provides a method for anti-freezing early warning of an indirect cooling system for thermal power units. The indirect cooling system includes a heat exchange unit for exchanging heat between the circulating cooling water and air of the thermal power unit. The anti-freezing early warning method includes: establishing a heat exchange characteristic benchmark model library with the environmental parameters of the heat exchange unit and the flow rate of the circulating cooling water as independent variables, and the theoretical values ​​of the heat transfer coefficient and the air-side pressure difference of the heat exchange unit in a non-icing state as dependent variables; calculating the measured values ​​of the heat transfer coefficient and the air-side pressure difference of the heat exchange unit based on the real-time collected operating parameters of the heat exchange unit; calculating the heat transfer deviation of the heat exchange unit based on the measured and theoretical values ​​of the heat transfer coefficient; calculating the resistance deviation of the heat exchange unit based on the measured and theoretical values ​​of the air-side pressure difference; and outputting an anti-freezing early warning signal based on the heat transfer deviation and the resistance deviation.

[0006] This application's technical solution overcomes the core limitation of traditional single-temperature threshold early warning systems. Traditional methods rely solely on monitoring the outlet temperature of circulating cooling water to determine icing, only detecting anomalies after icing has progressed to a certain extent and heat exchange capacity has significantly decreased, resulting in a noticeable early warning lag. This application establishes a comprehensive heat exchange characteristic benchmark model library under all operating conditions, directly quantifying the actual heat exchange capacity changes of the heat exchange unit. This enables the identification of anomalies in the early stages of icing, before an observable drop in outlet water temperature occurs, achieving early warning of icing. Furthermore, a dual-parameter joint judgment mechanism combining heat transfer performance and air-side resistance is employed, cross-validating the icing state from two independent dimensions: heat transfer capacity and flow resistance characteristics. A decrease in the heat transfer coefficient reflects increased thermal resistance due to icing on the fin surface, while an increase in air-side pressure difference reflects a reduction in airflow area due to icing. These two factors corroborate each other, effectively eliminating interference from non-icing factors such as sudden changes in ambient temperature, fluctuations in cooling water flow, and sensor drift, significantly reducing the false alarms and missed alarms commonly found in traditional methods.

[0007] Ultimately, the technical solution of this application achieves a dual improvement in safety and economy. In terms of safety, accurate early warning can effectively prevent serious accidents such as freezing and cracking of heat exchange units and leakage of circulating water systems, ensuring the continuous and stable operation of thermal power units in winter. In terms of economy, the precise early warning mechanism significantly reduces unnecessary excessive anti-freeze adjustments, avoiding increased unit coal consumption due to blindly closing louvers and increasing cooling water flow, effectively reducing energy losses from winter anti-freeze adjustments.

[0008] In some embodiments of this application, the indirect cooling system includes multiple heat exchange units, and the method for outputting the antifreeze warning signal includes: performing a deviation consistency check on the heat transfer deviation of multiple heat exchange units under the same wind field conditions; and outputting a corresponding antifreeze warning signal based on the heat transfer deviation, resistance deviation, and deviation consistency check results of the heat exchange units.

[0009] In some embodiments of this application, the deviation consistency verification result includes identifying isolated icing units. The method for performing deviation consistency verification includes: calculating the average value of the heat transfer deviation of all heat exchange units under the same wind field conditions; calculating the difference between the heat transfer deviation of a single heat exchange unit and the average value; defining the difference as the residual of the heat exchange unit; preset a residual threshold; when the residual of a heat exchange unit exceeds the residual threshold and the resistance deviation of the heat exchange unit shows an upward trend, the heat exchange unit is determined to be the isolated icing unit; and outputting a corresponding antifreeze warning signal based on the identification result of the isolated icing unit.

[0010] In some embodiments of this application, the method for determining whether the two heat exchange units are under the same wind field conditions includes: setting a wind speed deviation threshold and a wind direction deviation threshold; when the difference between the ambient wind speeds of any two heat exchange units does not exceed the wind speed deviation threshold, and the angle difference between the ambient wind directions of the two heat exchange units does not exceed the wind direction deviation threshold, the two heat exchange units are determined to be under the same wind field conditions.

[0011] In some embodiments of this application, the heat transfer deviation is the ratio of the measured value to the theoretical value of the heat transfer coefficient, and the resistance deviation is the ratio of the measured value to the theoretical value of the air-side pressure difference; the method for outputting an anti-freezing warning signal further includes: presetting a first heat transfer deviation threshold, a second heat transfer deviation threshold, and a third heat transfer deviation threshold, wherein the first heat transfer deviation threshold is greater than the second heat transfer deviation threshold, and the second heat transfer deviation threshold is greater than the third heat transfer deviation threshold; presetting a first resistance deviation threshold, and presetting a first duration threshold; when the duration for which the heat transfer deviation of the heat exchange unit is lower than the first heat transfer deviation threshold exceeds the first duration threshold. When the heat exchange unit experiences micro-frost, a Level 1 antifreeze warning signal is output. This Level 1 antifreeze warning signal includes a warning signal indicating micro-frost formation on the heat exchange unit. When the heat transfer deviation of the heat exchange unit is lower than the second heat transfer deviation threshold and the resistance deviation is higher than the first resistance deviation threshold, or when the heat exchange unit is determined to be an isolated icing unit, a Level 2 antifreeze warning signal is output. This Level 2 antifreeze warning signal includes a warning signal indicating localized icing on the heat exchange unit. When the heat transfer deviation of the heat exchange unit is lower than the third heat transfer deviation threshold, a Level 3 antifreeze warning signal is output. This Level 3 antifreeze warning signal includes a warning signal indicating a risk of large-area icing on the heat exchange unit.

[0012] In some embodiments of this application, the heat exchange unit is an independently controlled heat dissipation sector. The air inlet side of the heat dissipation sector is provided with louvers for adjusting the air intake volume, and the heat dissipation sector is provided with an antifreeze bypass valve for bypassing the circulating cooling water. The antifreeze warning method further includes performing antifreeze adjustment measures according to the classification of the antifreeze warning signal: preset a first opening degree and a second opening degree; when a first-level antifreeze warning signal is output, the opening degree of the louvers of the corresponding heat dissipation sector is reduced to the first opening degree; when a second-level antifreeze warning signal is output, the opening degree of the louvers of the corresponding heat dissipation sector is reduced to the second opening degree, and the flow rate of the circulating cooling water is increased; when a third-level antifreeze warning signal is output, the louvers of the corresponding heat dissipation sector are closed, and the antifreeze bypass valve is opened.

[0013] In some embodiments of this application, the heat exchange unit includes a radiator for exchanging heat between the circulating cooling water and the outside air; the measured value of the heat transfer coefficient of the heat exchange unit is calculated using the following formula:

[0014] In the formula, This is the measured value of the heat transfer coefficient of the heat exchange unit. The effective heat exchange area of ​​the radiator is... This is the structural correction factor for the heat sink. The logarithmic mean temperature difference The heat exchange capacity of the heat exchange unit; The logarithmic mean temperature difference The calculation formula is: In the formula, The inlet temperature of the circulating cooling water for the heat exchange unit. The outlet temperature of the circulating cooling water in the heat exchange unit. The ambient air temperature of the heat exchange unit; The heat exchange unit has a heat exchange capacity of [number] times. The calculation formula is: In the formula, The mass flow rate of the circulating cooling water in the heat exchange unit is [value missing]. The specific heat capacity at constant pressure of circulating cooling water, The inlet temperature of the circulating cooling water for the heat exchange unit. The outlet temperature of the circulating cooling water in the heat exchange unit.

[0015] In some embodiments of this application, the antifreeze warning method further includes: presetting a monitoring duration; after implementing the antifreeze adjustment measures, continuously monitoring the heat transfer deviation and resistance deviation of the heat exchange unit within the monitoring duration; when the monitoring duration expires, if the heat transfer deviation of the heat exchange unit is still lower than the first heat transfer deviation threshold, or the resistance deviation is still trending upward, implementing antifreeze adjustment measures corresponding to a higher level of antifreeze warning.

[0016] In some embodiments of this application, the antifreeze warning method further includes: during the monitoring period, when the heat transfer deviation of the heat exchange unit is higher than the first heat transfer deviation threshold and the resistance deviation is lower than the first resistance deviation threshold, the theoretical values ​​of the heat transfer coefficient and the theoretical values ​​of the air-side pressure difference in the heat exchange characteristic benchmark model library are updated based on the environmental parameters of the heat exchange unit at the current time, the flow rate of the circulating cooling water, the measured value of the heat transfer coefficient and the measured value of the air-side pressure difference.

[0017] In some embodiments of this application, the method for establishing a heat transfer characteristic benchmark model library includes: collecting the operating parameters and environmental parameters of the heat transfer unit under non-icing conditions, calculating the measured values ​​of the heat transfer coefficient and the air-side pressure difference of the heat transfer unit; based on the independent variable and its corresponding measured values ​​of the heat transfer coefficient and the air-side pressure difference, fitting the functional relationship between the theoretical value of the heat transfer coefficient and the independent variable, and the functional relationship between the theoretical value of the air-side pressure difference and the independent variable; and storing the functional relationships in the heat transfer characteristic benchmark model library.

[0018] The anti-freezing early warning method for the indirect cooling system of a thermal power unit provided in this application also has at least the following beneficial effects: 1. Precise identification of localized icing: By verifying the consistency of deviations between adjacent heat exchange units under the same wind field conditions and calculating residuals, early localized icing of a single heat exchange unit can be accurately identified and targeted warnings can be triggered, solving the problem that traditional methods cannot detect localized icing.

[0019] 2. Tiered Intelligent Response: A three-tiered early warning mechanism is adopted to implement differentiated antifreeze regulation measures based on the severity of icing, and the regulation effect is monitored in real time and automatically upgraded, so as to minimize the energy loss of antifreeze regulation while ensuring safety.

[0020] 3. Adaptive Model Update: By defining the critical moment for recovery to normal as the benchmark for model update, the benchmark model is self-learning and can adapt to long-term performance degradation such as heat sink dust accumulation and aging. No manual periodic calibration is required, and the early warning accuracy continues to improve with running time.

[0021] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more apparent, specific embodiments of this application are given below. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is the main control flowchart for the antifreeze early warning system of the indirect cooling system of thermal power units in this application. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0025] The prefixes such as "first" and "second" used in this application embodiment are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this application embodiment does not constitute a limitation on the described objects. The description of the described objects is given in the claims or the context of the embodiments, and should not constitute unnecessary restrictions due to the use of such prefixes. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0026] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B; the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0027] In the embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0028] Indirect cooling systems for thermal power units are closed-loop cooling systems used in conjunction with large thermal power generating units. They primarily rely on external natural air and internal circulating water to exchange heat, thus dissipating waste heat from unit operation. The system mainly consists of heat dissipation tube bundles, circulating water pipelines, airflow regulating louvers, and temperature and pressure monitoring sensors. By adjusting the intake airflow to match the cooling heat exchange intensity, it meets the cooling requirements of the unit under different load conditions. Compared with traditional wet cooling systems, indirect cooling systems have significant water-saving advantages, with a water saving rate of over 85%. Therefore, they have been widely used in water-scarce areas of northern my country and have become the mainstream cooling method for large thermal power generating units.

[0029] However, indirect cooling systems face severe freeze protection challenges when operating in low-temperature winter environments. Since the heat exchange tubes are directly exposed to outdoor air, the circulating water inside the tubes is highly susceptible to freezing when the ambient temperature drops below 0°C. Initially, micro-frost forms on the inner walls of the tubes, reducing heat exchange efficiency. As the ice layer thickens, it can cause localized blockages in the tubes, reducing the circulating water flow and further exacerbating the freezing process. In severe cases, it can lead to tube cracking, causing unplanned shutdowns of thermal power units, resulting in significant economic losses and safety hazards. Therefore, freeze protection has become a core task for the winter operation of indirect cooling systems.

[0030] To address the problems existing in the prior art, this application provides a method for early warning of freezing in the indirect cooling system of thermal power units. The method aims to establish a benchmark model library of heat transfer characteristics, employ a dual-parameter joint judgment mechanism of heat transfer performance and air-side resistance, and identify localized icing by combining deviation consistency verification under the same wind field conditions. It also enables self-learning updates of the early warning model, effectively solving the technical problems of traditional methods such as delayed early warning, high false alarm and missed alarm rates, inability to identify localized icing in individual heat exchange units, and lack of adaptive capability. This method achieves early, accurate, and graded early warning of icing in the indirect cooling system, ensuring the safe and stable operation of thermal power units in winter while minimizing the impact of antifreeze regulation on the unit's economic efficiency.

[0031] The indirect cooling system for thermal power units described in this embodiment includes an indirect cooling tower radiator, which is divided into multiple independently controlled heat exchange units along the circumference. Each heat exchange unit is an independent heat dissipation sector. Each heat dissipation sector has louvers on its inlet side for adjusting the airflow, and an anti-freeze bypass valve for bypassing the circulating cooling water. Each heat exchange unit includes a radiator for exchanging heat between the circulating cooling water and the outside air, as well as a temperature sensor, a flow sensor, and a differential pressure sensor installed on the corresponding pipeline on the inlet and outlet sides of the radiator.

[0032] To ensure clarity and logical consistency throughout the document, the following definitions are provided for some of the terms used in this specification: Operating parameters: These refer to all measurable parameters that can reflect the operating status and environmental conditions of the heat exchange unit, and are divided into two categories: environmental parameters and equipment status parameters.

[0033] Environmental parameters: These refer to the external environmental conditions of the heat exchange unit, including ambient temperature, ambient wind speed, and ambient wind direction.

[0034] Equipment status parameters: These refer to the operating status parameters of the heat exchange unit itself, including circulating cooling water flow rate, circulating cooling water inlet temperature, circulating cooling water outlet temperature, and air-side pressure difference.

[0035] Air-side pressure difference: refers to the static pressure difference generated between the air inlet side and the air outlet side of the radiator when air flows through the radiator of the heat exchange unit. It is directly measured by differential pressure sensors installed on the air inlet side and the air outlet side of the radiator of each heat exchange unit.

[0036] Measured value: refers to the actual operating value obtained by direct measurement through sensors or by calculation through measurement parameters.

[0037] Theoretical value: refers to the baseline value obtained from the heat transfer characteristic benchmark model library under the non-icing condition.

[0038] The anti-freezing early warning method for the indirect cooling system of a thermal power unit provided in this embodiment specifically includes the following steps: Step 1: Establish a benchmark model library for heat transfer characteristics.

[0039] After the unit is put into operation for the first time or after a major overhaul, under non-icing environmental conditions (ambient temperature above 5°C), the operating parameters of the heat exchange unit under different operating conditions are collected to establish a benchmark model library of heat exchange characteristics.

[0040] The heat exchange characteristic benchmark model library uses the environmental parameters of the heat exchange unit and the flow rate of the circulating cooling water as independent variables, and the theoretical values ​​of the heat transfer coefficient and the air-side pressure difference of the heat exchange unit under non-icing conditions as dependent variables.

[0041] The specific method for establishing the heat transfer characteristic benchmark model library is as follows: Data acquisition should be conducted under non-icing conditions in the heat exchange unit. To ensure that the acquired data accurately reflects the inherent heat exchange characteristics of the heat exchange unit, data acquisition should be carried out under stable operating conditions, i.e., when the unit load fluctuation does not exceed the preset range and the circulating water system parameters remain constant.

[0042] In this step, a synchronous acquisition method is used to obtain all parameters at the same time. That is, for each heat exchange unit, its operating parameters and environmental parameters are collected simultaneously at the same time point. Through synchronous acquisition, multiple sets of one-to-one corresponding parameter groups can be obtained. Each parameter group contains: a set of independent variables collected at the same time, namely environmental parameters and circulating cooling water flow rate, as well as all operating parameters collected at the same time for calculating the corresponding measured values ​​of that set of independent variables.

[0043] The continuous data acquisition time reaches the set duration to ensure that the collected parameter sets cover all typical operating conditions of the indirect cooling system during winter. After acquisition, all parameter sets are preprocessed to remove abnormal parameter sets caused by sensor failures, data transmission errors, sudden changes in operating conditions, etc., to ensure the accuracy of the modeling data.

[0044] Then, the measured values ​​corresponding to each set of parameters are calculated. For each set of preprocessed parameters, the measured value of the heat transfer coefficient corresponding to the independent variable is calculated based on the circulating cooling water inlet temperature, circulating cooling water outlet temperature, and circulating cooling water flow rate collected at the same time in that set of parameters; at the same time, the measured value of the air-side pressure difference corresponding to the independent variable is directly obtained based on the air-side pressure difference collected at the same time in that set of parameters.

[0045] Through the above calculations, multiple sets of one-to-one mapping relationships can be obtained, that is, each set of independent variables uniquely corresponds to a measured value of the heat transfer coefficient and a measured value of the air-side pressure difference at the same time.

[0046] Based on the one-to-one correspondence between the obtained sets of independent variables and the measured values ​​of the heat transfer coefficient, a multivariate nonlinear regression method or a high-dimensional interpolation algorithm is used for fitting to obtain the functional relationship between the theoretical value of the heat transfer coefficient and the independent variables. At the same time, based on the one-to-one correspondence between the obtained sets of independent variables and the measured values ​​of the air-side pressure difference, the same fitting method is used to obtain the functional relationship between the theoretical value of the air-side pressure difference and the independent variables.

[0047] Among them, the multivariate nonlinear regression method is suitable for scenarios with large data volume and uniform working condition distribution, and the model has strong generalization ability; the high-dimensional interpolation algorithm is suitable for scenarios with small data volume and discrete working condition points, and the local fitting accuracy is high; the appropriate fitting method can be selected according to the actual data situation.

[0048] Finally, the two fitted functional relationships are stored in the heat transfer characteristic benchmark model library. During subsequent real-time system operation, only the independent variables at the current moment need to be input. By calling the corresponding functional relationships in the benchmark model library, the theoretical values ​​of the heat transfer coefficient and the air-side pressure difference under the non-icing state at that moment can be quickly obtained, and then the deviation can be calculated and icing judgment can be made.

[0049] The technical solution in this step establishes a benchmark model under icing-free conditions, providing an accurate reference standard for subsequent icing judgment and eliminating the impact of performance differences caused by manufacturing and installation errors between different heat exchange units.

[0050] Step 2: Real-time parameter acquisition and deviation calculation.

[0051] The system collects the operating parameters of each heat exchange unit in real time, with a collection frequency of 1 second.

[0052] Based on the collected operating parameters, the measured values ​​of the heat transfer coefficient and air-side pressure difference for each heat exchange unit are calculated, and then the heat transfer deviation and resistance deviation are calculated.

[0053] 2.1 Calculation of heat exchange.

[0054] The heat exchange capacity of the heat exchange unit is calculated using the following formula: ; In the formula, For the heat exchange unit's heat exchange capacity, This refers to the mass flow rate of the circulating cooling water in the heat exchange unit. The specific heat capacity at constant pressure of circulating cooling water, The inlet temperature of the circulating cooling water for the heat exchange unit. This refers to the outlet temperature of the circulating cooling water in the heat exchange unit.

[0055] 2.2 Calculation of logarithmic mean temperature difference.

[0056] The logarithmic mean temperature difference of the heat exchange unit is calculated using the following formula: ; In the formula, The logarithmic mean temperature difference The inlet temperature of the circulating cooling water for the heat exchange unit. The outlet temperature of the circulating cooling water in the heat exchange unit. The ambient air temperature of the heat exchange unit.

[0057] 2.3 Calculation of heat transfer coefficient.

[0058] The measured value of the heat transfer coefficient of the heat exchange unit is calculated using the following formula: ; In the formula, This is the measured value of the heat transfer coefficient of the heat exchange unit. The effective heat exchange area of ​​the radiator. This is the structural correction factor for the radiator. The logarithmic mean temperature difference This refers to the amount of heat exchanged by the heat exchange unit.

[0059] 2.4 Deviation Calculation The heat transfer deviation is the ratio of the measured value to the theoretical value of the heat transfer coefficient, and the calculation formula is: ; In the formula, For heat transfer deviation, This is the measured value of the heat transfer coefficient. This is the theoretical value of the heat transfer coefficient.

[0060] The technical solution in this step uses deviation rather than absolute value for judgment, eliminating the influence of operating condition fluctuations on icing judgment. When icing occurs in the heat exchange unit, the ice layer increases thermal resistance, causing a decrease in the heat transfer coefficient. At the same time, it blocks the air flow channel, causing an increase in the air-side pressure difference. Therefore, the two deviation values ​​can accurately reflect the severity of icing.

[0061] Step 3: Deviation consistency verification and isolated icing unit identification.

[0062] Since the indirect cooling tower is arranged circumferentially, the heat exchange units at different locations are exposed to different wind conditions, resulting in variations in their heat exchange performance. Therefore, this embodiment performs a deviation consistency check on heat exchange units operating under the same wind conditions.

[0063] 3.1 Determination of identical wind field conditions Preset wind speed deviation thresholds and wind direction deviation thresholds. For example, the wind speed deviation threshold is set to 1 m / s and the wind direction deviation threshold is set to 15°.

[0064] When the difference between the ambient wind speeds of any two heat exchange units does not exceed the wind speed deviation threshold, and the angle difference between the ambient wind directions of the two heat exchange units does not exceed the wind direction deviation threshold, the two heat exchange units are determined to be under the same wind field conditions.

[0065] All heat exchange units under the same wind field conditions are divided into a verification group.

[0066] Furthermore, considering that the degree of dust accumulation on the radiator surface and the amount of solar radiation received by heat exchange units at different locations may vary, in order to eliminate the interference of non-icing factors on the deviation consistency verification results and improve the accuracy of identifying isolated icing units, heat exchange units under the same wind field conditions and located in adjacent positions can also be divided into a verification group.

[0067] 3.2 Residual calculation and identification of isolated icing units.

[0068] Calculate the average heat transfer deviation of all heat exchange units within each verification group using the following formula: ; In the formula, The average value of the heat transfer deviation of all heat exchange units in the verification group is n, where n is the number of heat exchange units in the verification group. Let be the heat transfer deviation of the i-th heat exchange unit.

[0069] The difference between the heat transfer deviation of a single heat exchange unit and the average value of the group is calculated using the following formula: ; In the formula, It is the difference between the heat transfer deviation of the i-th heat exchange unit and the average value of the group.

[0070] The obtained difference is defined as the residual of the heat exchange unit, and a residual threshold is preset, for example, 0.05; when the residual of a heat exchange unit exceeds the residual threshold and the resistance deviation of the heat exchange unit shows an upward trend, the heat exchange unit is determined to be an isolated icing unit.

[0071] Heat exchange units under the same wind field conditions should theoretically have similar heat transfer performance. If the heat transfer performance of a certain heat exchange unit is significantly lower than that of other units in the same group, and the air-side resistance increases simultaneously, the influence of environmental factors can be ruled out, and it can be accurately determined that local icing has occurred in that unit. This method can effectively identify icing phenomena in individual units that cannot be detected by traditional methods, providing an early warning 15-30 minutes in advance.

[0072] Step 4: Tiered early warning and tiered adjustment.

[0073] A first heat transfer deviation threshold, a second heat transfer deviation threshold, and a third heat transfer deviation threshold are preset, wherein the first heat transfer deviation threshold is greater than the second heat transfer deviation threshold, and the second heat transfer deviation threshold is greater than the third heat transfer deviation threshold. For example, the first heat transfer deviation threshold is 0.95, the second heat transfer deviation threshold is 0.90, and the third heat transfer deviation threshold is 0.80.

[0074] A first resistance deviation threshold is preset, for example, 1.10.

[0075] A preset first duration threshold is set, for example, to 30 seconds.

[0076] Based on the heat transfer deviation, resistance deviation, and isolated icing unit identification results, a three-level antifreeze warning signal is output, and corresponding antifreeze adjustment measures are implemented.

[0077] 4.1 Level I Freezing Warning.

[0078] When the heat transfer deviation of the heat exchange unit is below the first heat transfer deviation threshold for a duration exceeding the first duration threshold, a first-level antifreeze warning signal is output. The first-level antifreeze warning signal includes a warning signal indicating that micro-frost has occurred on the heat exchange unit.

[0079] When a Level 1 antifreeze warning signal is output, the opening degree of the louvers of the corresponding heat exchange unit is reduced to the first opening degree. For example, the first opening degree is 50%.

[0080] The Level 1 warning targets the earliest stage of icing—micro-frost. At this stage, the ice layer is extremely thin, and reducing the air intake by decreasing the louver opening can effectively prevent the ice layer from developing, with minimal impact on the unit's economic efficiency.

[0081] 4.2 Level II Freezing Warning.

[0082] A level-two antifreeze warning signal will be output when any of the following conditions are met: The heat transfer deviation of the heat exchange unit is lower than the second heat transfer deviation threshold, and the resistance deviation is higher than the first resistance deviation threshold; or, the heat exchange unit is determined to be an isolated icing unit.

[0083] The Level 2 antifreeze warning signal includes a warning signal indicating that local icing has occurred in the heat exchange unit.

[0084] When a level-two antifreeze warning signal is output, the opening degree of the louvers of the corresponding heat exchange unit is reduced to the second opening degree, and the flow rate of the circulating cooling water is increased. For example, the second opening degree is 20%, and the flow rate of the circulating cooling water is increased by 10%.

[0085] Level 2 warning targets the localized icing stage, where ice has formed and begun to block some airflow channels. By further reducing the louver opening and increasing the cooling water flow rate, the pipe wall temperature can be increased, melting the existing ice.

[0086] 4.3 Level III Freezing Warning.

[0087] When the heat transfer deviation of the heat exchange unit falls below the third heat transfer deviation threshold, a level-three anti-freeze warning signal is output. The level-three anti-freeze warning signal includes a warning signal indicating that there is a risk of large-area icing on the heat exchange unit.

[0088] When a Level 3 antifreeze warning signal is output, the louvers of the corresponding heat exchange unit will be completely closed, and the antifreeze bypass valve of the heat exchange unit will be opened, so that the circulating cooling water can flow back directly without passing through the radiator, thus preventing the tube bundle from freezing and cracking.

[0089] Level 3 warning targets the stage of severe icing risk, at which point emergency measures must be taken to protect equipment safety. Closing the louvers and opening the anti-freeze bypass valve can quickly shut off the heat exchange process, preventing the ice layer from thickening further and causing the tube bundle to freeze and crack.

[0090] Step 5: Monitoring the adjustment effect and model self-learning.

[0091] The preset monitoring duration is 10 minutes, for example.

[0092] After implementing the above antifreeze adjustment measures, the heat transfer deviation and resistance deviation of the heat exchange unit are continuously monitored during the monitoring period.

[0093] 5.1 Handling ineffective adjustments.

[0094] When the monitoring period expires, if the heat transfer deviation of the heat exchange unit is still lower than the first heat transfer deviation threshold, or if the resistance deviation is still on the rise, it indicates that the current antifreeze adjustment measures are ineffective, and the antifreeze adjustment measures corresponding to the higher-level antifreeze warning will be implemented.

[0095] 5.2 Model self-learning update.

[0096] During the monitoring period, if the heat transfer deviation of the heat exchange unit is higher than the first heat transfer deviation threshold and the resistance deviation is lower than the first resistance deviation threshold, it indicates that the antifreeze adjustment measures have taken effect and the heat exchange unit has returned to normal operation.

[0097] At this point, based on the environmental parameters of the heat exchange unit at the current moment, the flow rate of the circulating cooling water, the measured value of the heat transfer coefficient, and the measured value of the air-side pressure difference, the theoretical values ​​of the heat transfer coefficient and the theoretical values ​​of the air-side pressure difference under the corresponding operating conditions in the heat exchange characteristic benchmark model library are updated.

[0098] It should be noted that, because monitoring is continuous within the monitoring period, the "current moment" mentioned here specifically refers to the critical moment when the operating state of the heat exchange unit recovers from abnormal to normal, that is, the moment when the heat transfer deviation first exceeds the first heat transfer deviation threshold and the resistance deviation first falls below the first resistance deviation threshold. The reason for choosing this moment for model update is that at this time, the icing of the heat exchange unit has been completely eliminated, and it has not yet been significantly affected by long-term slow-changing factors such as dust accumulation on the radiator surface and performance aging. Its operating parameters can most realistically reflect the icing-free baseline performance of the heat exchange unit under this operating condition.

[0099] Furthermore, the specific update method is as follows: First, based on the environmental parameters of the heat exchange unit and the circulating cooling water flow rate at the current moment, the corresponding operating point is located in the heat exchange characteristic benchmark model library; then, using the same algorithm as when the heat exchange characteristic benchmark model library was established, the theoretical values ​​of the heat transfer coefficient and the theoretical values ​​of the air-side pressure difference at this operating point are progressively weighted and updated, thereby avoiding the impact of single measurement errors or instantaneous operating condition fluctuations on the model stability. If the current operating condition exceeds the original coverage of the heat exchange characteristic benchmark model library, the measured values ​​of the operating parameters at the current moment are directly added to the heat exchange characteristic benchmark model library as new samples, expanding its applicable operating condition range.

[0100] Once the adjustment measures take effect, it indicates that the current operating parameters are the true parameters for the non-icing state under that operating condition. The technical solution in this step updates the benchmark model library with these operating parameters, which can gradually correct the deviation between the theoretical model and actual operation, adapt to performance changes such as radiator dust accumulation and aging, and continuously improve the early warning accuracy over time. This self-learning mechanism requires no manual intervention and can automatically achieve continuous model optimization.

[0101] This embodiment provides an apparatus for implementing the above-mentioned method for antifreeze early warning of indirect cooling system of thermal power unit. The antifreeze early warning apparatus for indirect cooling system of thermal power unit includes: a data acquisition module, a reference model module, a calculation module, a deviation consistency verification module, an early warning generation module, and an antifreeze adjustment execution module.

[0102] The data acquisition module is used to collect all operating parameters of each heat exchange unit in real time, and its hardware components include: A platinum resistance temperature sensor is installed on the circulating cooling water inlet branch pipe of each heat exchange unit to measure the circulating cooling water inlet temperature. A platinum resistance temperature sensor is installed on the circulating cooling water outlet branch pipe of each heat exchange unit to measure the circulating cooling water outlet temperature. An electromagnetic mass flow meter is installed on the circulating cooling water inlet branch pipe of each heat exchange unit to measure the mass flow rate of the circulating cooling water. Micro differential pressure sensors installed on the air inlet and outlet sides of the radiator in each heat exchange unit are used to measure the air pressure difference. Platinum resistance temperature sensors are evenly arranged along the circumference of the cooling tower to measure the ambient air temperature at the location of each heat exchange unit. Ultrasonic wind speed and direction sensors are evenly arranged along the circumference of the indirect cooling tower to measure the ambient wind speed and direction at the location of each heat exchange unit. An industrial-grade data acquisition unit is used to convert the analog signals output by the aforementioned sensors into digital signals and transmit them to the computing module via an industrial Ethernet network.

[0103] The benchmark model module stores a library of benchmark models for heat transfer characteristics. Its hardware consists of an industrial-grade solid-state drive array, installed on a dedicated server in the power plant's control room. The module stores the following: The functional relationship between the heat transfer coefficient of each heat exchange unit and the independent variables (ambient temperature, ambient wind speed, ambient wind direction, and circulating cooling water flow rate); The functional relationship between the air-side pressure difference and the independent variable in each heat exchange unit; All preset threshold parameters include: first heat transfer deviation threshold, second heat transfer deviation threshold, third heat transfer deviation threshold, first resistance deviation threshold, first duration threshold, wind speed deviation threshold, wind direction deviation threshold, residual threshold, monitoring duration, and update weight.

[0104] The calculation module is used to calculate the measured values ​​of heat transfer coefficients, air-side pressure differences, heat transfer deviations, and resistance deviations for each heat exchange unit based on the operating parameters transmitted by the data acquisition module. Its hardware consists of a multi-core central processing unit (CPU) of a server, employing a real-time operating system to ensure a calculation latency of less than 100ms, meeting the real-time requirements of industrial control.

[0105] The deviation consistency verification module is used to verify the deviation consistency of multiple heat exchange units under the same wind field conditions and identify isolated icing units. It is deployed on the same industrial control server as the calculation module, sharing the server's central processing unit, memory, and other computing resources, and executes the verification logic according to a preset verification cycle.

[0106] The early warning generation module is used to output corresponding three-level anti-freezing early warning signals based on the heat transfer deviation, resistance deviation, and isolated icing unit identification results. Its hardware components include: The display interface of the host computer in the central control room is used to display the operating status, warning level and warning information of each heat exchange unit; An audible and visual alarm is used to provide an audible and visual alert when a level two or higher anti-freeze warning signal is output. The communication interface with the power plant's distributed control system (DCS) is used to upload early warning signals to the DCS system.

[0107] The antifreeze adjustment execution module is used to execute corresponding antifreeze adjustment measures based on the antifreeze warning signal output by the warning generation module. Its hardware components include: Each heat exchange unit has an electric actuator for adjusting the opening degree of the louvers; The electric actuator of the antifreeze bypass valve in each heat exchange unit is used to control the opening and closing of the antifreeze bypass valve; A frequency converter for circulating water pumps is used to regulate the total flow rate of circulating cooling water.

[0108] The antifreeze adjustment module communicates with the aforementioned actuators through the DCS system to issue adjustment commands and provide feedback on the execution status.

[0109] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for anti-freezing early warning of an indirect cooling system for a thermal power unit, wherein the indirect cooling system includes a heat exchange unit for exchanging heat between the circulating cooling water and air of the thermal power unit, characterized in that, include: Using the environmental parameters of the heat exchange unit and the flow rate of the circulating cooling water as independent variables, and the theoretical values ​​of the heat transfer coefficient of the heat exchange unit in the non-icing state and the theoretical values ​​of the air-side pressure difference as dependent variables, a benchmark model library for heat exchange characteristics is established. Based on the real-time collected operating parameters of the heat exchange unit, the measured values ​​of the heat transfer coefficient and the air-side pressure difference of the heat exchange unit are calculated. Based on the measured and theoretical values ​​of the heat transfer coefficient, the heat transfer deviation of the heat exchange unit is calculated. Based on the measured and theoretical values ​​of the air-side pressure difference, the resistance deviation of the heat exchange unit is calculated. Based on the heat transfer deviation and the resistance deviation, an antifreeze warning signal is output.

2. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 1, characterized in that, The indirect cooling system includes multiple heat exchange units, and the method for outputting the antifreeze warning signal includes: The heat transfer deviation of multiple heat exchange units under the same wind field conditions is checked for consistency. Based on the heat transfer deviation, resistance deviation, and deviation consistency verification results of the heat exchange unit, a corresponding antifreeze warning signal is output.

3. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 2, characterized in that, The deviation consistency verification result includes the identification of isolated icing units, and the method for performing the deviation consistency verification includes: Calculate the average heat transfer deviation of all the heat exchange units under the same wind field conditions, calculate the difference between the heat transfer deviation of a single heat exchange unit and the average value, and define the difference as the residual of the heat exchange unit. Preset residual threshold; When the residual of a heat exchange unit exceeds the residual threshold and the resistance deviation of the heat exchange unit shows an upward trend, the heat exchange unit is determined to be the isolated icing unit. Based on the identification results of the isolated icing unit, a corresponding antifreeze warning signal is output.

4. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 3, characterized in that, Methods for determining whether two people are under the same wind field conditions include: Preset wind speed deviation threshold and wind direction deviation threshold; When the difference between the ambient wind speeds of any two heat exchange units does not exceed the wind speed deviation threshold, and the angle difference between the ambient wind directions of the two heat exchange units does not exceed the wind direction deviation threshold, the two heat exchange units are determined to be under the same wind field conditions.

5. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 3, characterized in that, The heat transfer deviation is the ratio of the measured value to the theoretical value of the heat transfer coefficient, and the resistance deviation is the ratio of the measured value to the theoretical value of the air-side pressure difference. The method for outputting antifreeze warning signals also includes: A first heat transfer deviation threshold, a second heat transfer deviation threshold, and a third heat transfer deviation threshold are preset, wherein the first heat transfer deviation threshold is greater than the second heat transfer deviation threshold, and the second heat transfer deviation threshold is greater than the third heat transfer deviation threshold; a first resistance deviation threshold and a first duration threshold are preset. When the heat transfer deviation of the heat exchange unit is lower than the first heat transfer deviation threshold for a duration exceeding the first duration threshold, a first-level antifreeze warning signal is output; the first-level antifreeze warning signal includes a warning signal indicating that micro-frost has occurred in the heat exchange unit. When the heat transfer deviation of the heat exchange unit is lower than the second heat transfer deviation threshold and the resistance deviation is higher than the first resistance deviation threshold, or when the heat exchange unit is determined to be an isolated icing unit, a secondary antifreeze warning signal is output; the secondary antifreeze warning signal includes a warning signal indicating that the heat exchange unit has localized icing. When the heat transfer deviation of the heat exchange unit is lower than the third heat transfer deviation threshold, a level three antifreeze warning signal is output; the level three antifreeze warning signal includes a warning signal indicating that there is a risk of large-area icing in the heat exchange unit.

6. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 5, characterized in that, The heat exchange unit is an independently controlled heat dissipation sector. The air inlet side of the heat dissipation sector is equipped with louvers for adjusting the air intake volume, and the heat dissipation sector is equipped with an antifreeze bypass valve for bypassing the circulating cooling water. The anti-freezing early warning method also includes implementing anti-freezing adjustment measures based on the classification of the anti-freezing early warning signal: Preset the first opening and the second opening; When a Level 1 antifreeze warning signal is output, the opening of the louvers in the corresponding heat dissipation sector will be reduced to the first opening. When a level 2 antifreeze warning signal is output, the opening of the louvers in the corresponding heat dissipation sector is reduced to the second opening, and the flow rate of the circulating cooling water is increased; When a Level 3 antifreeze warning signal is output, the louvers of the corresponding heat dissipation sector will be closed, and the antifreeze bypass valve will be opened.

7. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 6, characterized in that, The heat exchange unit includes a radiator for exchanging heat between the circulating cooling water and the outside air. The measured value of the heat transfer coefficient of the heat exchange unit is calculated using the following formula: ； In the formula, This is the measured value of the heat transfer coefficient of the heat exchange unit. The effective heat exchange area of ​​the radiator is... This is the structural correction factor for the heat sink. The logarithmic mean temperature difference The heat exchange capacity of the heat exchange unit; The logarithmic mean temperature difference The calculation formula is: ； In the formula, The inlet temperature of the circulating cooling water for the heat exchange unit. The outlet temperature of the circulating cooling water in the heat exchange unit. The ambient air temperature of the heat exchange unit; The heat exchange unit has a heat exchange capacity of [number] times. The calculation formula is: ； In the formula, The mass flow rate of the circulating cooling water in the heat exchange unit is [value missing]. The specific heat capacity at constant pressure of circulating cooling water, The inlet temperature of the circulating cooling water for the heat exchange unit. The outlet temperature of the circulating cooling water in the heat exchange unit.

8. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 6, characterized in that, Also includes: Preset monitoring duration; After implementing the antifreeze adjustment measures, the heat transfer deviation and resistance deviation of the heat exchange unit are continuously monitored during the monitoring period. When the monitoring period expires, if the heat transfer deviation of the heat exchange unit is still lower than the first heat transfer deviation threshold, or if the resistance deviation is still on an upward trend, then a higher level of antifreeze warning and corresponding antifreeze adjustment measures will be implemented.

9. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to claim 8, characterized in that, Also includes: During the monitoring period, when the heat transfer deviation of the heat exchange unit is higher than the first heat transfer deviation threshold and the resistance deviation is lower than the first resistance deviation threshold, the theoretical values ​​of the heat transfer coefficient and the theoretical values ​​of the air-side pressure difference in the heat exchange characteristic benchmark model library are updated based on the environmental parameters of the heat exchange unit at the current time, the flow rate of the circulating cooling water, the measured value of the heat transfer coefficient and the measured value of the air-side pressure difference.

10. The method for anti-freezing early warning of the indirect cooling system of a thermal power unit according to any one of claims 1-9, characterized in that, The method for establishing a benchmark model library of heat transfer characteristics includes: Under the condition that the heat exchange unit is free of ice, the operating parameters and environmental parameters of the heat exchange unit are collected, and the measured values ​​of the heat transfer coefficient and the air-side pressure difference of the heat exchange unit are calculated. Based on the measured values ​​of the independent variable and its corresponding heat transfer coefficient, and the measured value of the air-side pressure difference, the functional relationship between the theoretical value of the heat transfer coefficient and the independent variable, and the functional relationship between the theoretical value of the air-side pressure difference and the independent variable are obtained by fitting. The aforementioned functional relationship is stored in the heat transfer characteristic benchmark model library.

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