A method for evaluating performance of a condenser

Abstract

The application discloses a kind of condenser performance evaluation method, comprising the following steps: collecting the daily monitoring data of condenser and pre-processing, obtain the data after processing;According to the data after processing, the characteristic quantity of condenser is calculated;The characteristic quantity includes cleaning coefficient, four-layer thermal resistance, correction overall heat transfer coefficient;The maximum value Kmax of correction heat transfer overall heat transfer coefficient in all characteristic quantity data in a period of time is counted;And the daily correction overall heat transfer coefficient Kcheck with maximum value correction overall heat transfer coefficient Kmax is ratio, obtain the daily condenser cleaning coefficient correction factor Fcheck;The daily condenser cleaning coefficient correction factor Fcheck with cleaning coefficient Cf d Multiplied, obtain the real condenser cleaning coefficient Cf dr After correction every day;Real cleaning coefficient Cfdr and other data after processing every day, namely real dirt correction thermal resistance Rf-dailyr can be obtained;Real dirt correction thermal resistance is substituted into daily monitoring data, and daily real shell side correction thermal resistance Rs-checkr can be obtained.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant equipment performance monitoring and energy-saving technology, and in particular to a method for evaluating condenser performance based on modified heat transfer resistance. Background Technology

[0002] The condenser is an important component of the condensing steam turbine. As one of the most important pieces of equipment in the power plant's thermal system, its performance directly affects the thermal economy and safety of the entire system.

[0003] Various methods exist for monitoring condenser performance, primarily using HEI and ASME methods to calculate, correct, and analyze condenser performance under varying operating conditions. This allows for monitoring of the corrected pressure or overall heat transfer coefficient for condition-based performance monitoring, or for identifying the condition of parameters such as dissolved oxygen and terminal temperature difference. The HEI method is mainly used to evaluate condensers designed according to HEI standards; significant deviations from the design can introduce substantial errors. The ASME method, compared to HEI, can clearly calculate the heat transfer resistance of each layer, providing a better characterization of condenser performance changes from a heat transfer mechanism perspective. However, both methods fail to separate the effects of shell-side heat transfer performance from fouling heat transfer factors. This not only affects the performance evaluation of condensers but also hinders accurate monitoring and evaluation of changes in fouling influence. Therefore, a method for evaluating and monitoring condensers that can separate shell-side heat transfer performance changes from fouling thermal resistance, as well as a scheme for verifying the true performance of condensers, is urgently needed. Summary of the Invention

[0004] In view of this, in order to overcome the shortcomings of the prior art, the object of the present invention is to provide an improved method for evaluating condenser performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for evaluating condenser performance includes the following steps:

[0007] Collect daily monitoring data from the condenser and preprocess it to obtain processed data;

[0008] The characteristic parameters of the condenser are calculated based on the processed data; these characteristic parameters include the cleanliness factor, the four-layer thermal resistance, and the corrected overall heat transfer coefficient.

[0009] The maximum value Kmax of the corrected overall heat transfer coefficient among all characteristic data over a period of time is calculated; and the daily corrected overall heat transfer coefficient Kcheck is compared with the maximum value Kmax to obtain the daily condenser cleanliness coefficient correction factor Fcheck.

[0010] The daily condenser cleanliness factor correction factor Fcheck is compared with the cleanliness factor Cf. d Multiply by these to obtain the corrected daily actual condenser cleanliness coefficient Cf. dr ;

[0011] The true dirt-corrected thermal resistance Rf-dailyr can be obtained by using the actual daily cleanliness coefficient Cfdr and other pre-treated data; the true daily shell-side corrected thermal resistance Rs-checkr can be obtained by substituting the true dirt-corrected thermal resistance into the daily monitoring data.

[0012] According to some preferred embodiments of the present invention, the monitoring data includes condenser pressure, circulating water inlet temperature, circulating water outlet temperature, hot well outlet temperature, and hot well outlet dissolved oxygen.

[0013] According to some preferred embodiments of the present invention, the preprocessing is as follows: removing data anomalies (such as data points with a value of 0), excluding data points with dissolved oxygen exceeding the standard, and then taking the average value of each monitoring data point within the time period when dissolved oxygen is within the normal range.

[0014] According to some preferred embodiments of the present invention, the standard for exceeding the dissolved oxygen limit is greater than 5 ppb.

[0015] According to some preferred embodiments of the invention, the time period is greater than or equal to 12 months.

[0016] According to some preferred embodiments of the present invention, the corrected overall heat transfer coefficient is calculated by the following formula:

[0017]

[0018] In the formula, K is the overall heat transfer coefficient, and Rm is the pipe wall thermal resistance (m). 2 ℃) / kW; Ri is the internal thermal resistance of the tube (m) 2 ℃) / kW; do and di are the outer and inner diameters of the heat exchange tube, respectively, in meters; Rf is the fouling thermal resistance, in meters. 2 ℃) / kW; Rs is the shell-side thermal resistance, (m 2 ℃) / kW.

[0019] According to some preferred embodiments of the invention, the cleanliness factor is the design value Cf. d It is usually taken as 0.9.

[0020] According to some preferred embodiments of the invention, the four-layer thermal resistance includes internal thermal resistance, tube wall thermal resistance, fouling thermal resistance, and shell-side thermal resistance. The four-layer thermal resistance is calculated according to ASME PTC12.2 standard.

[0021] According to some preferred embodiments of the invention, the actual fouling-corrected thermal resistance Rf-dailyr and the actual shell-side corrected thermal resistance Rs-checkr are calculated according to the ASME PTC12.2 standard.

[0022] Due to the adoption of the above technical solutions, the advantages of this invention compared with the prior art are as follows: the condenser performance evaluation method of this invention realizes the separate and accurate evaluation of the effects of heat exchange and fouling on the condenser shell side, provides an accurate benchmark for condenser performance monitoring, has a clear principle, and is easy to calculate; thus, it provides a guarantee for the economical and safe operation of the condenser. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating the condenser performance evaluation method in a preferred embodiment of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] Current HEI condenser evaluation methods primarily assess condenser performance by calculating corrected pressure. However, when condenser performance fails to meet requirements, it's impossible to determine whether the issue stems from excessively high fouling thermal resistance or high shell-side thermal resistance, thus hindering the establishment of an accurate baseline for subsequent condenser performance monitoring. The ASME method mainly calculates the impact of various thermal resistances on condenser performance; however, it uses design values ​​for fouling thermal resistance or spurious values ​​derived from the HEI method when calculating each layer's thermal resistance, again failing to identify the underlying cause of the condenser performance problem. This application's solution achieves separate and accurate evaluation of the condenser shell-side heat transfer and fouling effects, providing an accurate baseline for condenser performance monitoring. Its principle is clear, and the calculations are convenient.

[0027] like Figure 1 As shown, the condenser performance evaluation method of the present invention includes the following steps:

[0028] Step 1: Collect daily monitoring data of the condenser and preprocess it to obtain processed data.

[0029] The monitoring data includes condenser pressure, circulating water inlet temperature, circulating water outlet temperature, hot well outlet temperature, and dissolved oxygen in the hot well outlet.

[0030] After startup, monitoring data is acquired for a fixed daily time period (≥2 hours) and preprocessed: abnormal data points, such as data with a value of 0, are removed; dissolved oxygen data is monitored to confirm that it is within the normal range (not exceeding 5 ppd). If dissolved oxygen exceeds the standard, that data set is removed, and data from the next time period is acquired. This yields the average values ​​of parameters such as condenser pressure and circulating water inlet and outlet temperatures for the fixed daily time period.

[0031] Step 2: Calculate the characteristic quantities of the condenser based on a set of data processed each day; the characteristic quantities include the cleanliness factor, the four-layer thermal resistance, and the corrected overall heat transfer coefficient.

[0032] The cleanliness factor is the design value Cf. d Generally, 0.9 is taken. The four thermal resistances are the internal thermal resistance, the tube wall thermal resistance, the fouling thermal resistance, and the shell side thermal resistance (calculated with reference to ASME PTC12.2 standard).

[0033] The overall heat transfer coefficient is calculated using the following formula:

[0034]

[0035] In the formula, K is the overall heat transfer coefficient, and Rm is the pipe wall thermal resistance (m). 2 ℃) / kW; Ri is the internal thermal resistance of the tube (m) 2 ℃) / kW; do and di are the outer and inner diameters of the heat exchange tube, respectively, in meters; Rf is the fouling thermal resistance, in meters. 2 ℃) / kW; Rs is the shell-side thermal resistance, (m 2 ℃) / kW.

[0036] Step 3: Collect all characteristic data over a period of time (e.g., 18 months) (one set of data per day, including cleanliness coefficient, four-layer thermal resistance, and corrected overall heat transfer coefficient), find the maximum value Kmax of the corrected overall heat transfer coefficient in the data; and compare the daily corrected overall heat transfer coefficient Kcheck with the maximum value Kmax to obtain the daily condenser cleanliness coefficient correction factor Fcheck.

[0037] F check =K check / K max (2)

[0038] Step 4: Compare the daily condenser cleanliness correction factor Fcheck with the cleanliness factor Cf. d Multiply by these to obtain the corrected daily actual condenser cleanliness coefficient Cf. dr .

[0039] Cf dr =Cf d *F check (3)

[0040] Step 5: Using the daily true cleanliness factor Cfdr and other monitoring data after pretreatment (condenser pressure, circulating water inlet temperature, circulating water outlet temperature), the daily true fouling-corrected thermal resistance Rf-dailyr can be calculated (refer to ASME PTC12.2 standard). Substituting the true fouling-corrected thermal resistance into the daily monitoring data, the daily true shell-side corrected thermal resistance Rs-checkr can be calculated (refer to ASME PTC12.2 standard). This result provides an accurate benchmark for the daily evaluation, analysis, and monitoring of condenser performance.

[0041] Existing technologies can only evaluate and monitor condenser performance under the combined effects of shell-side heat transfer and fouling, but cannot accurately and objectively evaluate the trend of fouling changes. This technology addresses the problem of evaluating the impact of fouling on condensers after separating the influence of shell-side thermal resistance. In the calculation method of this application, the overall heat transfer coefficient, tube internal thermal resistance, and tube wall thermal resistance are directly obtained. The fouling thermal resistance is set to a fixed value during calculation, and the shell-side thermal resistance is derived and corrected, thus coupling the effects of fouling thermal resistance and shell-side thermal resistance in the results. Compared to other schemes that can only consider the coupled effects of shell-side thermal resistance and fouling thermal resistance when evaluating condenser performance and cannot evaluate the actual design performance of the condenser during testing, this application's scheme achieves separate and accurate evaluation of the effects of condenser shell-side heat transfer and fouling accumulation, providing an accurate benchmark for condenser performance monitoring. The principle is clear and the calculation is convenient. This provides a guarantee for the economical and safe operation of condensers, saving manpower, financial resources, and material resources.

[0042] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for evaluating condenser performance, characterized in that, Includes the following steps: Collect daily monitoring data from the condenser and preprocess it to obtain processed data; The characteristic parameters of the condenser are calculated based on the processed data; these characteristic parameters include the cleanliness factor, the four-layer thermal resistance, and the corrected overall heat transfer coefficient. The maximum value of the corrected overall heat transfer coefficient Kmax among all characteristic data over a period of time is calculated. The daily corrected overall heat transfer coefficient Kcheck is then compared with the maximum corrected overall heat transfer coefficient Kmax to obtain the daily condenser cleanliness coefficient correction factor Fcheck. Multiply the daily condenser cleanliness factor correction factor Fcheck by the cleanliness factor Cfd to obtain the corrected daily true condenser cleanliness factor Cfdr. The true dirt-corrected thermal resistance Rf-dailyr can be obtained by using the daily true cleanliness factor Cfdr and other pre-treated data; the daily true shell-side corrected thermal resistance Rs-checkr can be obtained by substituting the true dirt-corrected thermal resistance into the daily monitoring data. The preprocessing involves removing abnormal data from the monitoring data and removing data corresponding to dissolved oxygen exceeding the standard. Then, the average value of each monitoring data is taken within the time period when dissolved oxygen is within the normal range. The time period is greater than or equal to 12 months; The monitoring data includes condenser pressure, circulating water inlet temperature, circulating water outlet temperature, hot well outlet temperature, and dissolved oxygen in the hot well outlet; the standard for exceeding the dissolved oxygen standard is greater than 5 ppb. The cleanliness factor is the design value Cfd; the four thermal resistances include the internal thermal resistance, the tube wall thermal resistance, the fouling thermal resistance, and the shell-side thermal resistance; the actual fouling-corrected thermal resistance Rf-dailyr and the actual shell-side corrected thermal resistance Rs-checkr are calculated according to the ASME PTC12.2 standard. In the evaluation method, the overall heat transfer coefficient, the internal thermal resistance of the tube and the thermal resistance of the tube wall are directly obtained during the calculation. The fouling thermal resistance is set to a fixed value during the calculation, the shell-side thermal resistance is derived, and the thermal resistance is corrected so that the effects of fouling thermal resistance and shell-side thermal resistance are coupled in the result. These results provide a benchmark for routine condenser performance evaluation, analysis, and monitoring.

2. The evaluation method according to claim 1, characterized in that, The corrected overall heat transfer coefficient is calculated using the following formula: （1）； In the formula, K is the overall heat transfer coefficient, and Rm is the pipe wall thermal resistance (m). 2 ℃) / kW; Ri is the internal thermal resistance of the tube (m) 2 ℃) / kW; do and di are the outer and inner diameters of the heat exchange tube, respectively, in meters; Rf is the fouling thermal resistance, in meters. 2 ℃) / kW; Rs is the shell-side thermal resistance, (m 2 ℃) / kW.

3. The evaluation method according to claim 1, characterized in that, The thermal resistance of the four layers was calculated according to the ASME PTC12.2 standard.

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