Energy saving system for ship tube and shell heat exchanger based on temperature difference between tube side and shell side

Abstract

This invention discloses an energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side, relating to the field of energy-saving control technology for shipboard heat exchange equipment. It includes a thermal stress judgment and compensation module, used to acquire the metal wall temperature of the heat exchanger and the real-time temperature difference between the tube-side inlet and the shell-side inlet. Based on the metal wall temperature and the real-time temperature difference, it determines whether the heat exchanger is in an abnormal thermal stress state. If the heat exchanger is in an abnormal thermal stress state, it compensates for the dynamic frequency adjustment command based on the real-time temperature difference, generating a thermal stress suppression adjustment command. This invention, through the thermal stress judgment and compensation module, determines the abnormal thermal stress state based on the metal wall temperature and the real-time temperature difference between the tube and shell sides, clamps and compensates the frequency change rate to generate a thermal stress suppression adjustment command, effectively smoothing flow fluctuations and thermal shocks, avoiding alternating thermal stress damage to heat exchange components, and ensuring equipment operational safety and service life.

Description

Technical Field

[0001] This invention relates to the field of energy-saving control technology for ship heat exchange equipment, and particularly to an energy-saving system for ship shell-and-tube heat exchangers driven by the temperature difference between the tube side and the shell side. Background Technology

[0002] With the high-quality development of the global shipping industry, the International Maritime Organization (IMO) has continuously tightened its series of control rules on ship energy efficiency management and greenhouse gas emissions. Energy conservation, consumption reduction, safety, and reliability have become the core principles for the design and operation of modern ship power systems and auxiliary machinery systems. As the core heat exchange equipment in the main engine cooling system, lubrication system, and waste heat recovery system, the heat exchange efficiency, operating energy consumption, and structural reliability of the ship directly determine the overall energy efficiency level and navigation safety of the ship. During cross-sea navigation, the main engine load will be frequently and dynamically adjusted according to the navigation conditions, and the temperature of the external cooling water will also fluctuate significantly with the sea area and season, which will have a significant impact on the actual heat exchange conditions of the heat exchanger. How to make full use of the temperature difference characteristics between the tube side and the shell side to achieve efficient and energy-saving operation of the heat exchanger under complex and variable navigation conditions has become the core research direction for the current technological upgrading of ship heat exchange systems.

[0003] Currently, the control and energy-saving optimization technologies for circulating pumps in marine shell-and-tube heat exchangers are still mainly based on traditional fixed-frequency operation and single-parameter feedback regulation modes. In the traditional fixed-frequency operation mode, the circulating pump always operates at its rated power and cannot adjust its operating parameters according to changes in heat exchange conditions, resulting in serious energy waste. The gradually promoted single-loop variable frequency regulation technology mostly uses the outlet fluid temperature of the heat exchanger as the only feedback signal, and can only perform closed-loop regulation of the circulating pump frequency with lag based on the deviation of the outlet temperature. Some optimized technical solutions have also gradually introduced the correlation control logic of the main engine load, which adjusts the flow output of the circulating pump synchronously through changes in the main engine load, thereby improving the adaptability of the heat exchange system to changes in the main engine operating conditions to a certain extent. At the same time, natural circulation auxiliary technology driven by the temperature difference between the shell and tube sides is also being gradually applied in the field of marine heat exchange. By using the natural circulation head formed by the temperature difference between the hot and cold fluids, the driving power of the circulating pump is reduced, which has become an important development path for energy-saving technology in marine heat exchangers.

[0004] Existing energy-saving control technologies for ship shell-and-tube heat exchangers still suffer from several technical defects and application bottlenecks. Firstly, most existing frequency conversion control schemes based on temperature difference rely solely on the current real-time temperature difference as the sole control basis, failing to fully exploit the coupling characteristics between the timing of temperature difference changes on the shell-and-tube side and the load variation curve of the ship's main engine. This prevents the ability to anticipate changes in heat exchange conditions, resulting in a significant lag in the frequency adjustment of the circulating pump. Consequently, it is difficult to maintain stable heat exchange efficiency during changes in the main engine's operating conditions, and it also fails to maximize the energy-saving potential of temperature-difference-driven natural circulation. Secondly, existing technologies generally neglect the thermal stress impact on the heat exchanger's metal walls caused by sudden temperature changes on the shell-and-tube side and rapid fluctuations in circulation flow during energy-saving regulation. This leads to frequent adjustments of the circulating pump in pursuit of energy-saving effects. Operating parameters can easily lead to alternating thermal stress and thermal fatigue damage in core pressure-bearing components such as heat exchanger tube sheets and heat exchange tubes. This not only significantly shortens the service life of the equipment but may also cause serious malfunctions that threaten the safety of ship navigation, such as seal failure and heat exchange tube rupture. In addition, existing technologies often use fixed rated operating parameters for heat exchange efficiency control, failing to adapt to changes in water temperature in the ship's navigation area. Under different seasons and sea conditions, the heat exchange efficiency control benchmark is prone to mismatch with the actual environmental conditions. This makes it impossible to further explore the energy-saving potential of the circulating pump in low-temperature waters, and it is also difficult to ensure the cooling capacity and operational stability of the heat exchange system in high-temperature waters. Consequently, it is impossible to balance energy saving, heat exchange efficiency, and equipment operation safety under all ship navigation conditions.

[0005] Therefore, it is necessary to invent an energy-saving system for ship shell-and-tube heat exchangers driven by the temperature difference between the tube side and the shell side to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide an energy-saving system for shipboard shell-and-tube heat exchangers driven by the temperature difference between the tube side and the shell side, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side, comprising the following modules:

[0008] The temperature difference detection and initial command generation module is used to respond to the ship's main engine start signal, acquire the first fluid temperature at the tube-side inlet of the heat exchanger and the second fluid temperature at the shell-side inlet, and generate the initial frequency command for the temperature difference-driven circulating pump based on the temperature difference between the first fluid temperature and the second fluid temperature.

[0009] The coupling feature extraction module is used to obtain the temperature difference change rate sequence of the heat exchanger on the tube side and the shell side within a preset historical period, as well as the load change curve of the ship's main engine. It extracts temperature-load coupling features from the temperature difference change rate sequence and the load change curve, and generates multi-level coordinated heat exchange control parameters based on the temperature-load coupling features.

[0010] The efficiency calculation module is used to obtain the third fluid temperature at the tube-side outlet of the heat exchanger and the fourth fluid temperature at the shell-side outlet. Combining the first fluid temperature, the second fluid temperature and the real-time heat flux of the heat exchanger measured by the heat flux sensor, the module calculates the actual heat exchange efficiency of the heat exchanger under the current operating conditions.

[0011] The dynamic correction module is used to correct the initial frequency command of the temperature difference driven circulation pump according to the multi-level coordinated heat exchange control parameters and the temperature difference value when the actual heat exchange efficiency is lower than the preset efficiency threshold, and generate a dynamic frequency adjustment command.

[0012] The thermal stress judgment and compensation module is used to obtain the metal wall temperature of the heat exchanger and the real-time temperature difference between the tube-side inlet and the shell-side inlet. Based on the metal wall temperature and the real-time temperature difference, it determines whether the heat exchanger is in an abnormal thermal stress state. If the heat exchanger is in an abnormal thermal stress state, it compensates for the dynamic frequency adjustment command based on the real-time temperature difference and generates a thermal stress suppression adjustment command.

[0013] The feedforward correction and command generation module is used to obtain the water temperature of the ship, obtain the preset heat exchange efficiency of the heat exchanger under standard operating conditions as the heat exchange efficiency benchmark value, correct the heat exchange efficiency benchmark value according to the water temperature, fuse the corrected heat exchange efficiency benchmark value with the thermal stress suppression adjustment command, generate the target energy-saving control command, and send the target energy-saving control command to the frequency converter of the temperature difference driven circulation pump.

[0014] The technical effects and advantages of this invention are as follows:

[0015] 1. This invention uses a temperature difference detection and initial command generation module to collect the temperature difference between the inlet fluid on the pipe side and the shell side based on the ship's main engine start signal, and generates an initial frequency command by combining the rated power-frequency characteristic curve of the circulating pump. This fully utilizes the natural circulation characteristics driven by temperature difference, reduces the basic operating energy consumption of the circulating pump, and achieves precise initial control during the start-up phase of the heat exchange system.

[0016] 2. This invention uses a coupled feature extraction module to simultaneously analyze the temperature difference change rate sequence on the shell and tube side and the load change curve of the main unit, extracts the temperature-load coupling features and generates multi-level coordinated heat exchange control parameters, accurately identifies the response lag characteristics of temperature difference to load changes, provides data support for flow advance regulation, and solves the regulation lag problem of traditional control.

[0017] 3. This invention uses an efficiency calculation module to combine the four fluid temperatures at the inlet and outlet of the heat exchanger with the real-time heat flux, and adopts the efficiency-heat transfer unit number method to accurately calculate the actual heat exchange efficiency under the current operating conditions. This provides accurate efficiency feedback for frequency conversion regulation and ensures that the heat exchange system always remains within the target heat exchange efficiency range.

[0018] 4. This invention uses a dynamic correction module to adaptively correct the initial frequency command by combining multi-level collaborative heat exchange control parameters when the actual heat exchange efficiency is lower than a preset threshold, thereby generating a dynamic frequency adjustment command. This achieves closed-loop optimization of heat exchange efficiency under varying operating conditions of the main engine, improving the system's adaptability to complex navigation conditions.

[0019] 5. This invention uses a thermal stress judgment and compensation module to determine the abnormal state of thermal stress based on the real-time temperature difference between the metal wall temperature and the shell side. It performs clamping compensation on the frequency change rate to generate thermal stress suppression and adjustment commands, effectively smoothing out flow fluctuations and thermal shocks, avoiding alternating thermal stress damage to heat exchange components, and ensuring the safe operation and service life of the equipment.

[0020] 6. This invention introduces the ship's water temperature as a reference value for heat exchange efficiency through a feedforward correction and command generation module. It then weights and fuses efficiency constraints, safety constraints, and environmental adaptability to generate target energy-saving control commands, thereby achieving multi-objective collaborative optimization of heat exchange efficiency, energy-saving effect, and operational safety under different sea area navigation conditions. Attached Figure Description

[0021] Figure 1 This is a diagram of the overall system architecture of the present invention;

[0022] Figure 2 This is a structural diagram of the temperature difference detection and initial command generation module of the present invention;

[0023] Figure 3 This is a structural diagram of the coupling feature extraction module of the present invention;

[0024] Figure 4 This is a diagram showing the linkage between the dynamic correction and thermal stress compensation modules of this invention. Detailed Implementation

[0025] 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 are within the scope of protection of the present invention.

[0026] This invention provides, for example Figure 1 The energy-saving system for a ship's shell-and-tube heat exchanger, shown, based on the temperature difference between the tube side and the shell side, includes the following modules:

[0027] The temperature difference detection and initial command generation module is used to respond to the ship's main engine start signal, acquire the first fluid temperature at the tube-side inlet of the heat exchanger and the second fluid temperature at the shell-side inlet, and generate the initial frequency command for the temperature difference-driven circulating pump based on the temperature difference between the first fluid temperature and the second fluid temperature.

[0028] Furthermore, in the above technical solutions, such as Figure 2 As shown, the temperature difference detection and initial command generation module includes:

[0029] Pump characteristic acquisition unit, used to acquire the rated power-frequency characteristic curve of the temperature difference driven circulating pump;

[0030] The flow calculation unit is used to calculate the basic flow rate required to overcome the current temperature difference and achieve natural circulation based on the temperature difference between the first fluid temperature and the second fluid temperature, according to a preset temperature difference-demand flow rate mapping table.

[0031] The instruction mapping unit is used to query the rated power-frequency characteristic curve based on the basic demand flow and generate an initial frequency instruction that matches the basic demand flow.

[0032] It should be noted that the temperature difference detection and initial command generation module is bidirectionally connected to the ship's main engine control system, the first temperature sensor at the heat exchanger tube-side inlet, the second temperature sensor at the shell-side inlet, and the frequency converter controller of the temperature difference driven circulation pump. The specific implementation of the module in response to the ship's main engine start signal is as follows: when the trigger signal from the ship's main engine control system indicating that the main engine has started and entered the idling condition is received, the module immediately starts the temperature acquisition and initial command generation process. Before the main engine load enters the preset stable operating range, the module continuously updates the initial frequency command at a fixed sampling period until it receives the multi-level coordinated heat exchange control parameters output by the coupling feature extraction module, and then switches to the subsequent dynamic adjustment mode.

[0033] The first fluid temperature is the real-time temperature of the working fluid at the tube-side inlet of the heat exchanger, and the second fluid temperature is the real-time temperature of the cooling medium at the shell-side inlet of the heat exchanger. The first and second fluid temperatures are obtained as follows: the first fluid temperature raw data is collected by a Class A platinum resistance temperature sensor installed at the tube-side inlet, and the second fluid temperature raw data is collected by a Class A platinum resistance temperature sensor installed at the shell-side inlet. The module performs moving average filtering on both raw temperature data. The filtering window length is preset to 5 sampling points, and the sampling period is set to 100ms. After removing abnormal data that exceeds the preset temperature range, the effective first fluid temperature and effective second fluid temperature are obtained for calculation. The temperature difference value is the absolute value of the difference between the effective first fluid temperature and the effective second fluid temperature.

[0034] Furthermore, the detailed implementation methods of each unit under the temperature difference detection and initial command generation module are as follows:

[0035] The input terminal of the pump characteristic acquisition unit is communicatively connected to the equipment parameter storage module of the temperature difference driven circulating pump and the ship's engine room equipment management system. Its specific execution steps are as follows:

[0036] Step S101: Pre-store the factory-calibrated rated power-frequency characteristic curve of the temperature difference driven circulation pump. The characteristic curve has the operating frequency of the circulation pump as the horizontal axis and the output flow rate and shaft power of the circulation pump under rated operating conditions as the vertical axis. It includes the rated flow rate-frequency correspondence and rated power-frequency correspondence of the circulation pump in the full frequency range of 0~50Hz. The calibration conditions of the characteristic curve match the design rated operating conditions of the heat exchanger.

[0037] Step S102: When the main engine start signal is received, the current operating status parameters of the circulating pump are obtained from the ship's engine room equipment management system in real time, including the current power supply voltage and the cumulative running time of the equipment. If the circulating pump is in the first commissioning state or the cumulative running time exceeds the preset maintenance cycle, the characteristic curve online verification process is triggered. The most recent maintenance calibration data of the circulating pump is retrieved through the engine room equipment management system, and the pre-stored rated power-frequency characteristic curve is corrected to obtain the effective rated power-frequency characteristic curve under the current operating conditions.

[0038] Step S103: Output the effective rated power-frequency characteristic curve to the command mapping unit, and simultaneously output the effective frequency range and rated flow upper and lower limit parameters corresponding to the curve to the flow calculation unit as boundary constraints for the basic demand flow.

[0039] The flow calculation unit pre-stores a temperature difference-demand flow mapping table, and its specific execution steps are as follows:

[0040] Step S201: Receive the filtered effective first fluid temperature and effective second fluid temperature, and calculate the real-time temperature difference value under the current operating conditions;

[0041] Step S202: Retrieve a preset temperature difference-demand flow rate mapping table. The mapping table is pre-calibrated and constructed based on the heat exchanger's design structural parameters, pipeline resistance characteristics, and natural circulation head calculation formula. The horizontal axis of the mapping table represents the temperature difference range, and the vertical axis represents the basic demand flow rate required to overcome the circulation pipeline resistance, offset the natural circulation head deviation, and achieve stable heat exchange circulation under the corresponding temperature difference. The calibration logic of the mapping table is as follows: when the temperature difference increases, the natural circulation driving force of the heat exchanger increases, and the corresponding basic demand flow rate decreases accordingly; when the temperature difference decreases, the natural circulation driving force is insufficient, and the corresponding basic demand flow rate increases accordingly, ensuring that the output flow rate of the circulation pump can cover the minimum circulation flow rate requirement under the current temperature difference.

[0042] Step S203: Match the real-time temperature difference value with the temperature difference range in the mapping table. If the real-time temperature difference value is at the boundary point between two adjacent temperature difference ranges in the mapping table, then use the linear interpolation method to calculate the corresponding basic demand flow.

[0043] Step S204: Receive the rated flow upper and lower limit parameters output by the pump characteristic acquisition unit, perform boundary clamping processing on the calculated basic demand flow. If the basic demand flow exceeds the rated flow upper limit, limit the basic demand flow to the rated flow upper limit value; if the basic demand flow is lower than the rated flow lower limit, limit the basic demand flow to the rated flow lower limit value, and finally output the valid basic demand flow to the instruction mapping unit.

[0044] The output of the instruction mapping unit is communicatively connected to the frequency converter and dynamic correction module of the temperature difference driven circulating pump. Its specific execution steps are as follows:

[0045] Step S301: Receive the effective basic demand flow rate output by the flow calculation unit, retrieve the rated power-frequency characteristic curve output by the pump characteristic acquisition unit, and match the rated operating frequency corresponding to the basic demand flow rate from the curve.

[0046] Step S302: If the basic demand flow rate is between two adjacent flow rate calibration points on the characteristic curve, the corresponding accurate operating frequency is calculated using cubic spline interpolation to ensure that the frequency calculation error does not exceed ±0.1Hz.

[0047] Step S303: Based on the calculated operating frequency, generate an initial frequency command that conforms to the communication protocol of the frequency converter. The initial frequency command includes a frequency setting value, a command effective time, and a command priority identifier. The priority of the initial frequency command is lower than the adjustment commands output by the subsequent dynamic correction module and the thermal stress judgment and compensation module.

[0048] Step S304: The initial frequency command is synchronously sent to the frequency converter and the dynamic correction module. At the same time, the basic demand flow, real-time temperature difference value and acquisition timestamp corresponding to the initial frequency command are synchronously stored in the ship heat exchanger operation database as the historical data source of the coupled feature extraction module.

[0049] The coupling feature extraction module is used to obtain the temperature difference change rate sequence of the heat exchanger on the tube side and the shell side within a preset historical period, as well as the load change curve of the ship's main engine. It extracts temperature-load coupling features from the temperature difference change rate sequence and the load change curve, and generates multi-level coordinated heat exchange control parameters based on the temperature-load coupling features.

[0050] Furthermore, in the above technical solutions, such as Figure 3 As shown, the coupling feature extraction module includes:

[0051] The temperature difference analysis unit is used to perform time series analysis on the temperature difference change rate sequence, extract the peak time, trough time and corresponding change rate of the temperature difference change, and generate a temperature difference fluctuation feature vector.

[0052] The load analysis unit is used to perform synchronous time-series analysis on the load change curve of the ship's main engine, extract the inflection point time and load change rate of the load change, and generate a load fluctuation feature vector.

[0053] The coupled calculation unit is used to calculate the cross-correlation function of the temperature difference fluctuation feature vector and the load fluctuation feature vector in time series, and to determine the response lag time and synergistic influence coefficient of the temperature difference to the load change based on the peak value of the cross-correlation function.

[0054] The parameter generation unit is used to generate multi-level coordinated heat exchange control parameters for guiding flow advance adjustment based on the response lag time and the coordinated influence coefficient.

[0055] It should be noted that the coupling feature extraction module is bidirectionally connected to the ship's main engine control system, the temperature difference detection and initial command generation module, the ship's heat exchanger operation database, and the dynamic correction module. The module's startup trigger logic is as follows: when it receives a signal from the ship's main engine control system that the main engine load has entered a preset stable operating range, or when the initial frequency command output by the temperature difference detection and initial command generation module has been running for a preset initial stable duration (preferably 5 minutes), the module immediately starts the coupling feature extraction process. During the main engine operation, the temperature-load coupling features and multi-level collaborative heat exchange control parameters are updated in a preset update cycle (preferably 1 minute) to ensure that the parameters match the real-time operating conditions.

[0056] The preset historical time period is a 30-minute sliding time window tracing back from the current moment. The sampling period of the data within the window is consistent with the temperature sampling period of the temperature difference detection and initial command generation module, and is set to 100ms. The temperature difference change rate sequence between the pipe side and the shell side is an equal-time time sequence composed of the unit time change rate of the real-time temperature difference between the inlet and outlet of the pipe side and the shell side, calculated according to a fixed sampling period within the preset historical time period. The load change curve of the ship's main engine is a continuous time sequence curve of the percentage of the main engine output load changing with time during the same period and sampling period as the temperature difference change rate sequence. The main engine load data is obtained synchronously from the ship's main engine control system in real time, and the data synchronization error does not exceed one sampling period.

[0057] Furthermore, the detailed implementation methods of each unit under the coupling feature extraction module are as follows:

[0058] The input end of the temperature difference analysis unit is connected to the ship heat exchanger operation database, and the output end is connected to the coupled calculation unit. Its specific execution steps are as follows:

[0059] Step S101, Time Series Data Preprocessing: Retrieve real-time temperature difference data of the inlet and outlet of the tube side and shell side within a preset historical period from the ship heat exchanger operation database, calculate the temperature difference change rate of adjacent sampling points according to the sampling period, and construct an initial temperature difference change rate sequence; perform moving average filtering on the initial sequence, with the filtering window length preset to 5 sampling points, remove abnormal data that exceed the preset change rate range, and then perform zero mean normalization on the filtered sequence to eliminate the influence of dimensions and obtain the effective temperature difference change rate sequence;

[0060] Step S102, Temporal Feature Extraction: The sliding window extreme value detection method is used to perform temporal analysis on the effective temperature difference change rate sequence. The sliding window length is preset to 100 sampling points, and the step size is 1 sampling point. Within each sliding window, the peak time corresponding to the local maximum value and the valley time corresponding to the local minimum value of the sequence are identified. The rate of temperature difference increase corresponding to the peak time and the rate of temperature difference decrease corresponding to the valley time are calculated respectively. At the same time, the average rate of change and the fluctuation variance of the sequence in the preset historical period are calculated.

[0061] Step S103, Feature Vector Generation: The extracted peak time, valley time, peak increase rate of change, valley decrease rate of change, average change rate, and fluctuation variance are arranged in a preset dimension order to generate a temperature difference fluctuation feature vector aligned with the preset historical time period. The temperature difference fluctuation feature vector is output to the coupled calculation unit and simultaneously stored in the ship heat exchanger operation database.

[0062] The input terminal of the load analysis unit is bidirectionally connected to the ship's main engine control system and the ship's heat exchanger operation database, and its output terminal is connected to the coupled calculation unit. Its specific execution steps are as follows:

[0063] Step S201, Synchronous Time Series Data Acquisition: Retrieve real-time load data of the main engine from the ship's main engine control system that is in the same period and with the same sampling period as the temperature difference change rate sequence, construct the initial time series sequence of the main engine load, and ensure that the time axis of the load time series sequence and the temperature difference change rate sequence are completely aligned, with a time synchronization deviation of no more than 1 sampling period; Perform filtering and normalization processing on the initial load time series sequence that is consistent with the temperature difference change rate sequence to obtain the effective load change sequence;

[0064] Step S202, Synchronous Time Series Feature Extraction: The second-order difference inflection point detection method is used to perform synchronous time series analysis on the effective load change sequence. By calculating the second-order difference of the sequence, the load change inflection point corresponding to the zero crossing point of the second-order difference is identified, and the load increase inflection point and the load decrease inflection point are distinguished. The load increase change rate and load decrease change rate corresponding to each inflection point are calculated respectively. At the same time, the average load value and load fluctuation amplitude of the sequence in the preset historical period are calculated.

[0065] Step S203, Feature Vector Generation: The extracted inflection point time, load increase rate of change, load decrease rate of change, average load value, and load fluctuation amplitude are arranged in a preset dimension order to generate a load fluctuation feature vector that is simultaneously aligned with the temperature difference fluctuation feature vector. The load fluctuation feature vector is output to the coupled calculation unit and simultaneously stored in the ship heat exchanger operation database.

[0066] The input terminals of the coupled calculation unit are connected to the temperature difference analysis unit and the load analysis unit, respectively, and the output terminal is connected to the parameter generation unit. Its specific execution steps are as follows:

[0067] Step S301, cross-correlation function calculation: Receive the time-aligned temperature difference fluctuation feature vector and load fluctuation feature vector, take the load fluctuation feature vector as the reference sequence and the temperature difference fluctuation feature vector as the observation sequence, calculate the normalized cross-correlation function of the two sequences in time, the lag time range of the cross-correlation calculation is preset to -60s~+60s, the step size is 1 sampling period, and obtain the cross-correlation coefficient sequence corresponding to different lag times;

[0068] Step S302, Response Lag Time Determination: Identify the maximum peak value in the cross-correlation coefficient sequence. The lag time corresponding to this maximum peak value is the response lag time of the temperature difference between the tube side and the shell side to the change in the ship's main engine load. If the maximum peak value corresponds to a positive lag time, it indicates that the load change precedes the temperature difference change, which is consistent with the heat exchange lag characteristics of the ship's heat exchanger. If the maximum peak value corresponds to a negative lag time, the current coupling calculation is deemed invalid, and the data from the preset historical period is retrieved and the calculation is performed again.

[0069] Step S303, Determining the synergistic influence coefficient: The absolute value of the maximum peak value of the cross-correlation coefficient sequence is determined as the synergistic influence coefficient of temperature difference and load. The value range of the synergistic influence coefficient is 0~1. The closer the coefficient is to 1, the stronger the synergy between temperature difference change and load change, and the higher the degree of influence of load change on temperature difference fluctuation.

[0070] Step S304, Coupling Feature Output: The calculated response lag time and synergistic influence coefficient, together with the corresponding temperature difference fluctuation feature vector and load fluctuation feature vector, are output as temperature-load coupling features to the parameter generation unit.

[0071] The input end of the parameter generation unit is connected to the coupled calculation unit, and the output end is bidirectionally connected to the dynamic correction module and the ship heat exchanger operation database. Its specific execution steps are as follows:

[0072] Step S401, Coordination Level Classification: Based on the magnitude of the coordination influence coefficient, the degree of coordination between temperature and load is divided into three levels: when the coordination influence coefficient ≥ 0.7, it is a high coordination level; when 0.4 ≤ coordination influence coefficient < 0.7, it is a medium coordination level; when the coordination influence coefficient < 0.4, it is a low coordination level.

[0073] Step S402, Calibration of advance adjustment parameters: Taking the response lag time as the core, determine the advance time of flow advance adjustment. The advance time is equal to the response lag time to achieve advance compensation for temperature fluctuations caused by load changes. At the same time, according to the coordination level, the proportional adjustment coefficient, integral adjustment coefficient and derivative adjustment coefficient of the corresponding level are calibrated respectively. The higher the coordination level, the larger the adjustment coefficient and the faster the response speed of flow adjustment.

[0074] Step S403, Multi-level Coordination Parameter Generation: Combining the lead time, various adjustment coefficients, and the preset host load range division table, flow adjustment weights corresponding to different load ranges are generated, which together constitute multi-level coordinated heat exchange control parameters for guiding flow advance adjustment; the multi-level coordinated heat exchange control parameters include three core parameters: advance adjustment lead time, proportional-integral-derivative adjustment coefficients, and load-flow adjustment weight table, covering the host's 0~100% full load operating range;

[0075] Step S404, Parameter Output and Update: The generated multi-level coordinated heat exchange control parameters are output to the dynamic correction module in real time and simultaneously stored in the ship heat exchanger operation database. After the module completes the re-extraction of coupling features according to the preset update cycle, the multi-level coordinated heat exchange control parameters are updated in a rolling manner to ensure the adaptability of parameters to real-time operating conditions.

[0076] The efficiency calculation module is used to obtain the third fluid temperature at the tube-side outlet of the heat exchanger and the fourth fluid temperature at the shell-side outlet. Combining the first fluid temperature, the second fluid temperature and the real-time heat flux of the heat exchanger measured by the heat flux sensor, the module calculates the actual heat exchange efficiency of the heat exchanger under the current operating conditions.

[0077] Furthermore, in the above technical solution, the efficiency calculation module includes:

[0078] The heat calculation unit is used to calculate the actual heat absorption or release of the pipe-side fluid based on the difference between the temperature of the first fluid and the temperature of the third fluid; and to calculate the actual heat release or heat absorption of the shell-side fluid based on the difference between the temperature of the second fluid and the temperature of the fourth fluid.

[0079] The temperature difference calculation unit is used to obtain the heat exchange area of ​​the heat exchanger body and calculate the logarithmic mean temperature difference under the current operating conditions based on the temperature of the first fluid, the temperature of the second fluid, the temperature of the third fluid, and the temperature of the fourth fluid.

[0080] The efficiency calculation unit is used to calculate the actual heat exchange efficiency, which characterizes the heat exchange capacity under the current operating conditions, based on the real-time heat flux, the logarithmic mean temperature difference, and the heat exchange area, using the efficiency-number of heat transfer units method.

[0081] It is important to know that the efficiency calculation module is bidirectionally connected to the third temperature sensor installed at the tube-side outlet of the heat exchanger, the fourth temperature sensor installed at the shell-side outlet, the heat flux sensor deployed on the heat exchanger body, the temperature difference detection and initial command generation module, the dynamic correction module, and the ship heat exchanger operation database. The module starts synchronously when the ship's main engine starts and the temperature difference detection and initial command generation module starts working. It continuously performs heat exchange efficiency calculations throughout the entire operating cycle of the main engine. Its data sampling period is consistent with the temperature sampling period of the temperature difference detection and initial command generation module, which is set to 100ms. Moreover, the timestamps of all collected data are completely aligned with the timestamps of the first fluid temperature and the second fluid temperature obtained by the temperature difference detection and initial command generation module, with a time synchronization error of no more than one sampling period, ensuring the consistency and accuracy of the timing of the heat exchange efficiency calculation.

[0082] The third fluid temperature is the real-time temperature of the working fluid at the tube-side outlet of the heat exchanger, and the fourth fluid temperature is the real-time temperature of the cooling medium at the shell-side outlet of the heat exchanger. The third and fourth fluid temperatures are obtained as follows: the raw data of the third fluid temperature is collected by a Class A platinum resistance temperature sensor installed at the tube-side outlet, and the raw data of the fourth fluid temperature is collected by a Class A platinum resistance temperature sensor installed at the shell-side outlet. The module performs a moving average filtering process on both raw temperature data, which is consistent with the first and second fluid temperatures. The filtering window length is preset to 5 sampling points. After removing abnormal data that exceeds the preset temperature range, the effective third and fourth fluid temperatures used for calculation are obtained. The real-time heat flux is collected by a multi-point heat flux sensor array deployed on the metal wall of the core heat exchange area of ​​the heat exchanger. The sensor array contains at least 3 measuring points evenly distributed along the axial direction of the heat exchange tube. The module takes the arithmetic mean of the heat flux data collected from each measuring point, and after filtering with the same process as the temperature data, the effective real-time heat flux is obtained. The sampling period of the heat flux data is completely synchronized with the sampling period of the temperature data.

[0083] Furthermore, the detailed implementation methods of each unit under the efficiency calculation module are as follows:

[0084] The input terminals of the heat calculation unit are connected to the temperature difference detection and initial command generation module, the third temperature sensor, the fourth temperature sensor, and the ship heat exchanger operation database, respectively. The output terminals are connected to the temperature difference calculation unit and the efficiency solution unit. The specific execution steps are as follows:

[0085] Step S101, Basic parameter retrieval: Retrieve the isobaric specific heat capacity and design mass flow range of the tube-side working fluid, as well as the isobaric specific heat capacity and design mass flow range of the shell-side cooling medium, from the heat exchanger design parameter document pre-stored in the ship heat exchanger operation database; Simultaneously, obtain the effective first fluid temperature and effective second fluid temperature corresponding to the current sampling time, as well as the real-time mass flow rate of the tube-side fluid and the real-time mass flow rate of the shell-side fluid corresponding to the temperature difference driven circulation pump under the current operating conditions from the temperature difference detection and initial command generation module.

[0086] Step S102, Calculation of heat transfer in the pipe-side fluid: Based on the difference between the effective first fluid temperature and the effective third fluid temperature, combined with the isobaric specific heat capacity and real-time mass flow rate of the pipe-side fluid, the actual heat transfer of the pipe-side fluid is calculated according to the basic heat transfer formula. The calculation formula is as follows:

[0087] Q t =c t ×m t ×|T t1 -T t2 |,

[0088] In the formula, Q t c represents the actual heat transfer of the fluid on the pipe side. t The isobaric specific heat capacity of the working fluid on the pipe side, m t T represents the real-time mass flow rate of the fluid on the pipe side. t1 For the effective first fluid temperature, T t2 For the effective third fluid temperature; when T t2 >T t1 When the process is determined to be endothermic, Q t This represents the actual heat absorbed; when T t2 <T t1 When the process is determined to be exothermic, Q t This represents the actual heat released.

[0089] Step S103, Calculation of shell-side fluid heat: Based on the difference between the effective second fluid temperature and the effective fourth fluid temperature, combined with the isobaric specific heat capacity and real-time mass flow rate of the shell-side cooling medium, the actual heat transfer of the shell-side fluid is calculated according to the basic heat transfer formula. The calculation formula is as follows:

[0090] Q s =c s ×m s ×|T s1 -T s2 |,

[0091] In the formula, Q s c represents the actual heat transfer of the shell-side fluid. s The isobaric specific heat capacity of the shell-side cooling medium is given by ms, and the real-time mass flow rate of the shell-side fluid is given by T. s1 For the effective second fluid temperature, T s2 For the effective fourth fluid temperature; when T s2 <T s1 When the shell-side fluid is determined to be an exothermic process, Q s This represents the actual heat release; when T s2 >T s1 When the shell-side fluid is determined to be an endothermic process, Q s This represents the actual heat absorbed.

[0092] Step S104, Heat balance verification and valid data output: The calculated tube-side heat transfer Q... t Heat exchange with the shell side Q s Perform a thermal balance check and calculate the relative deviation between the two. The formula for calculating the relative deviation is: δ=|Q t -Q s | / max(Q t Q s)×100%; When the relative deviation δ≤5%, the heat calculation data is deemed valid, and the tube-side heat exchange, shell-side heat exchange, and four-way effective temperature data are synchronously output to the temperature difference calculation unit and efficiency solution unit; when the relative deviation δ>5%, the data is deemed abnormal, the calculation results are discarded, the effective heat data of the previous sampling time is retained, and a data abnormality alarm record is sent to the ship heat exchanger operation database.

[0093] The input end of the temperature difference calculation unit is communicatively connected to the heat calculation unit and the ship heat exchanger operation database, and the output end is connected to the efficiency solution unit. Its specific execution steps are as follows:

[0094] Step S201, Retrieve Design Parameters: Retrieve the nominal heat exchange area, number of shell passes, number of tube passes, flow arrangement form, and corresponding logarithmic mean temperature difference correction coefficient query chart of the heat exchanger body from the heat exchanger design parameter document stored in the ship heat exchanger operation database.

[0095] Step S202, Fluid end temperature difference calculation: Based on the four effective temperature data output by the heat calculation unit, calculate the fluid temperature difference at both ends of the heat exchanger. For the counter-flow arrangement of the heat exchanger, the formula for calculating the temperature difference at both ends is:

[0096] ΔT1=T t1 -T s2 ,

[0097] ΔT2=T t2 -T s1 ,

[0098] In the formula, ΔT1 is the temperature difference at the first end of the heat exchanger, ΔT2 is the temperature difference at the second end of the heat exchanger, and T... t1 For the effective first fluid temperature, T t2 For the effective third fluid temperature, T s1 For the effective second fluid temperature, T s2 The effective fourth fluid temperature; for a co-current arrangement, the temperature difference between the two ends is calculated using the formula: ΔT1 = T t1 -T s1 ΔT2=T t2 -T s2 ;

[0099] Step S203, Calculation of Ideal Logarithmic Mean Temperature Difference: Based on the temperature differences ΔT1 and ΔT2 at both ends, the logarithmic mean temperature difference under ideal counter-current conditions is calculated using the logarithmic mean temperature difference formula. The formula is as follows:

[0100] ΔT lm0 =(ΔT1-ΔT2) / ln(ΔT1 / ΔT2),

[0101] In the formula, ΔTlm0 Let ΔT1 be the ideal logarithmic mean temperature difference, and ln be the natural logarithm function. When the ratio of ΔT1 to ΔT2 is ≤ 2, the arithmetic mean temperature difference is used instead of the logarithmic mean temperature difference for simplified calculation. The formula for calculating the arithmetic mean temperature difference is: ΔT lm0 =(ΔT1+ΔT2) / 2, the simplified calculation error does not exceed 4%, which meets the accuracy requirements of engineering calculations;

[0102] Step S204, Actual Logarithmic Mean Temperature Difference Correction: Based on the number of shell-side and tube-side components and the flow arrangement of the heat exchanger, consult the preset logarithmic mean temperature difference correction coefficient lookup chart to obtain the correction coefficient ψ for the current operating condition. The value of the correction coefficient ψ ranges from 0 to 1. Multiply the ideal logarithmic mean temperature difference by the correction coefficient to obtain the actual logarithmic mean temperature difference under the current operating condition. The calculation formula is: ΔT lm =ψ×ΔT lm0 ;

[0103] Step S205, Valid data output: The nominal heat exchange area of ​​the heat exchanger and the calculated actual logarithmic mean temperature difference are simultaneously output to the efficiency solution unit, and the above data are stored in the ship heat exchanger operation database.

[0104] The input terminals of the efficiency calculation unit are communicatively connected to the heat calculation unit, the temperature difference calculation unit, the heat flux sensor, and the dynamic correction module, respectively, and the output terminal is connected to the dynamic correction module and the ship heat exchanger operation database. Its specific execution steps are as follows:

[0105] Step S301, Overall heat transfer coefficient calculation: Based on the effective real-time heat flux collected by the heat flux sensor and the actual logarithmic average temperature difference output by the temperature difference calculation unit, calculate the actual overall heat transfer coefficient of the heat exchanger under the current operating conditions. The calculation formula is as follows:

[0106] K=q / ΔT lm ,

[0107] In the formula, K is the actual overall heat transfer coefficient, q is the effective real-time heat flux, and ΔT is the total heat transfer coefficient. lm The actual logarithmic mean temperature difference is given. Simultaneously, based on the nominal heat exchange area A of the heat exchanger, the actual total heat flow under the current operating conditions is calculated, and the formula is verified as: Q = K × A × ΔT lm The actual total heat flow Q should deviate from the average value of the tube-side and shell-side heat exchange output by the heat calculation unit by no more than 5%; otherwise, the total heat transfer coefficient calculation is considered abnormal.

[0108] Step S302, Calculation of the number of heat transfer units and heat capacity ratio: The heat exchange efficiency is calculated using the efficiency-number of heat transfer units method (ε-NTU method). First, the number of heat transfer units (NTU) of the heat exchanger is calculated. The calculation formula is as follows:

[0109] NTU = K × A / Cmin ,

[0110] In the formula, C min The heat capacity flow rate is the smaller of the tube-side fluid heat capacity flow rate and the shell-side fluid heat capacity flow rate. The formula for calculating the heat capacity flow rate is: C t =c t ×m t C s =c s ×m s C min =min(C t C s ), where C t C represents the heat capacity flow rate of the fluid on the pipe side. s The heat capacity flow rate of the fluid on the shell side is given; simultaneously, the heat capacity ratio r is calculated using the formula: r = C min / C max C max The larger of the tube-side fluid heat capacity flow rate and the shell-side fluid heat capacity flow rate;

[0111] Step S303, Calculation of heat exchange efficiency and actual heat exchange efficiency: Based on the flow arrangement, number of shell passes, and number of tube passes of the heat exchanger, select the corresponding efficiency calculation formula. Combine the calculated NTU value and heat capacity ratio r to calculate the heat exchange efficiency ε under the current operating conditions. The heat exchange efficiency ε is the actual heat exchange efficiency of the heat exchanger under the current operating conditions, and its physical meaning is the ratio of the actual heat exchange to the theoretical maximum heat exchange, with a value range of 0~1. For the most commonly used 1-shell-pass, 2-tube-pass counter-current arrangement of marine shell-and-tube heat exchangers, the efficiency calculation formula is as follows:

[0112] ε=2 / [1+r+√(1+r 2 )×(1+exp(-NTU×√(1+r 2 ))) / (1-exp(-NTU×√(1+r 2 )))],

[0113] Step S304, Data Verification and Result Output: The calculated actual heat exchange efficiency is verified for reasonableness. When the actual heat exchange efficiency is within the range of 0.2 to 0.95, the calculation result is deemed valid, and the actual heat exchange efficiency is output to the dynamic correction module in real time. At the same time, parameters such as the total heat transfer coefficient, NTU value, heat capacity ratio, and heat exchange efficiency during the calculation process are synchronously stored in the ship heat exchanger operation database. When the actual heat exchange efficiency exceeds the above reasonable range, the calculation result is deemed abnormal, the current result is discarded, the valid heat exchange efficiency data at the previous sampling time is retained, and an efficiency calculation abnormality alarm record is sent to the ship heat exchanger operation database.

[0114] The dynamic correction module is used to correct the initial frequency command of the temperature difference driven circulation pump according to the multi-level coordinated heat exchange control parameters and the temperature difference value when the actual heat exchange efficiency is lower than the preset efficiency threshold, and generate a dynamic frequency adjustment command.

[0115] Furthermore, in the above technical solutions, such as Figure 4 As shown, the dynamic correction module includes:

[0116] The parameter extraction unit is used to extract the response lag time from the multi-level coordinated heat exchange control parameters.

[0117] The trend prediction unit is used to monitor the changing trend of the temperature difference value and predict the direction of load change based on the load fluctuation feature vector.

[0118] The adjustment generation unit is used to generate a dynamic frequency adjustment command for increasing or decreasing the flow rate in advance by performing proportional-integral-derivative adjustment on the initial frequency command according to the cooperative influence coefficient when the direction of change of the temperature difference value is consistent with the expected load change direction corresponding to the response lag time.

[0119] It should be noted that the dynamic correction module is bidirectionally connected to the efficiency calculation module, coupling feature extraction module, temperature difference detection and initial command generation module, thermal stress judgment and compensation module, ship heat exchanger operation database, and frequency converter controller of temperature difference driven circulation pump. The core triggering condition of the module is as follows: after receiving the actual heat exchange efficiency output in real time from the efficiency calculation module, it compares it with a preset efficiency threshold in real time. When the actual heat exchange efficiency is lower than the preset efficiency threshold, the frequency command correction process is immediately started. When the actual heat exchange efficiency is higher than or equal to the preset efficiency threshold, the module maintains a standby state, and the output dynamic frequency adjustment command is consistent with the initial frequency command, without performing any additional adjustment actions.

[0120] The preset efficiency threshold is pre-set based on the heat exchange efficiency benchmark value of the heat exchanger under standard operating conditions, with a default value of 85% of the benchmark value. It can be adaptively adjusted according to ship navigation conditions, heat exchanger maintenance status, and equipment service life, with an adjustment range of 70% to 95% of the benchmark value. The data sampling period of the module is consistent with that of the temperature difference detection and initial command generation module and the efficiency calculation module, set to 100ms. The timestamps of all input parameters are perfectly aligned, with a time synchronization error not exceeding one sampling period, ensuring the timing matching of adjustment actions with real-time operating conditions. The priority of the dynamic frequency adjustment command generated by the module is higher than the initial frequency command output by the temperature difference detection and initial command generation module, but lower than the thermal stress suppression adjustment command output by the thermal stress judgment and compensation module, ensuring that safety constraints take precedence over efficiency adjustment.

[0121] Furthermore, the detailed implementation methods of each unit under the dynamic correction module are as follows:

[0122] The input end of the parameter extraction unit is communicatively connected to the coupled feature extraction module and the ship heat exchanger operation database, and the output end is connected to the trend prediction unit and the adjustment generation unit. Its specific execution steps are as follows:

[0123] Step S101, core parameter retrieval: The latest generated multi-level synergistic heat exchange control parameters are obtained in real time from the coupling feature extraction module. The core response lag time, synergistic influence coefficient, load-flow regulation weight table, and proportional-integral-derivative regulation coefficient group are extracted from the parameters. At the same time, the temperature difference fluctuation feature vector and load fluctuation feature vector corresponding to the set of parameters are retrieved from the coupling feature extraction module.

[0124] Step S102, Parameter validity verification: The validity of the extracted response lag time is verified. The verification rule is: the value of the response lag time must be within the range of 0~60s and match the timing logic of the main engine load change, that is, the load change precedes the temperature difference change; if the response lag time exceeds the above range or the timing logic does not match, the parameter is determined to be invalid, and the previous set of valid multi-level coordinated heat exchange control parameters is retrieved from the ship heat exchanger operation database to complete the parameter replacement.

[0125] Step S103, parameter classification output: The valid response lag time is output to the trend prediction unit, the synergistic influence coefficient, proportional-integral-derivative adjustment coefficient group, and load-flow adjustment weight table are output to the adjustment generation unit, and all valid parameters are synchronously stored in the ship heat exchanger operation database.

[0126] The input end of the trend prediction unit is communicatively connected to the parameter extraction unit, the temperature difference detection and initial command generation module, the ship's main engine control system, and the ship's heat exchanger operation database, and its output end is connected to the adjustment generation unit. Its specific execution steps are as follows:

[0127] Step S201, Temperature Difference Trend Monitoring: Obtain the real-time temperature difference sequence of the pipe side and shell side inlet and outlet within the current moment and a preset historical window from the temperature difference detection and initial command generation module. The preset historical window is preferably twice the response lag time. Perform first-order linear fitting on the temperature difference sequence using the least squares method to obtain the slope of the temperature difference change. Determine the direction of temperature difference change based on the sign of the slope: when the slope is positive, the temperature difference is determined to be on an upward trend; when the slope is negative, the temperature difference is determined to be on a downward trend; when the absolute value of the slope is less than a preset slope threshold, the temperature difference is determined to be on a stable trend. Simultaneously calculate the confidence level of the temperature difference change trend. When the goodness of fit R... 2 When the value is ≥0.7, the trend prediction is considered valid;

[0128] Step S202, load change direction prediction: Obtain the real-time load sequence of the main engine at the current moment and the same period as the historical window from the ship's main engine control system. Combine the load fluctuation feature vector output by the parameter extraction unit, and use the time-series trend extrapolation method to predict the main engine load change direction within the future response lag time. Differentiate between three types of prediction results: load increase trend, load decrease trend, and load stability trend. Among them, the prediction logic of the load change direction is matched with the response characteristics of temperature difference fluctuation: when the predicted load is increasing, the expected shell-and-tube temperature difference will also be increasing; when the predicted load is decreasing, the expected shell-and-tube temperature difference will also be decreasing. This is how the expected load change direction corresponding to the response lag time is obtained.

[0129] Step S203, Trend Consistency Determination: The actual change direction of the monitored temperature difference value is compared with the expected change direction of the load. When the two change directions are completely consistent, it is determined to be a trend match, and a trend match signal is output to the adjustment generation unit. When the two change directions are opposite or one of them is a stable trend, it is determined to be a trend mismatch, and a trend mismatch signal is output to the adjustment generation unit. At this time, no advanced adjustment action is performed.

[0130] Step S204, trend data synchronization: The temperature difference change trend, load change prediction results, and consistency judgment results are synchronously output to the regulation generation unit, and the above data are stored in the ship heat exchanger operation database.

[0131] The input terminal of the adjustment generation unit is communicatively connected to the parameter extraction unit, trend prediction unit, temperature difference detection and initial command generation module, and efficiency calculation module. Its output terminal is connected to the thermal stress judgment and compensation module, the frequency converter controller of the temperature difference-driven circulating pump, and the ship heat exchanger operation database. The specific execution steps are as follows:

[0132] Step S301, Adjustment trigger determination: Receive the consistency determination result output by the trend prediction unit. When a trend matching signal is received and the actual heat exchange efficiency is continuously lower than the preset efficiency threshold for more than one sampling period, it is determined that the advance adjustment trigger condition is met, and the proportional-integral-derivative (PID) adjustment process is started. When a trend mismatch signal is received, only the conventional PID adjustment based on the heat exchange efficiency deviation is performed, and the advance adjustment action is not performed.

[0133] Step S302, adaptive matching of adjustment parameters: Based on the synergistic influence coefficients output by the parameter extraction unit, the preset PID adjustment coefficient set is adaptively corrected. The correction formula is as follows:

[0134] Kp'=Kp×α,

[0135] Ki' = Ki × α,

[0136] Kd'=Kd×α,

[0137] In the formula, Kp, Ki, and Kd are the preset baseline proportional coefficient, integral coefficient, and derivative coefficient, respectively; α is the synergistic influence coefficient; and Kp', Ki', and Kd' are the corrected actual adjustment coefficients. The higher the synergistic influence coefficient, the larger the corrected adjustment coefficient, and the faster the adjustment response speed, thus achieving adaptive adjustment that matches the degree of temperature-load synergy. At the same time, based on the current real-time load of the host, the load-flow adjustment weight table is queried to obtain the flow adjustment weight β under the current operating condition. The value of β ranges from 0.5 to 1.5 and is used for secondary correction of the adjustment range.

[0138] Step S303, Calculation of adjustment deviation: Using the preset efficiency threshold as the target value and the actual heat exchange efficiency as the feedback value, calculate the efficiency deviation e(t). The calculation formula is: e(t) = efficiency threshold - actual heat exchange efficiency. At the same time, combined with the changing trend of the temperature difference, an advance adjustment compensation is introduced. The compensation is calculated based on the response lag time. When the predicted load increases and the temperature difference increases, the compensation is positive, corresponding to an advance increase in flow rate; when the predicted load decreases and the temperature difference decreases, the compensation is negative, corresponding to an advance decrease in flow rate.

[0139] Step S304, PID regulation calculation and frequency command generation: Based on the corrected PID regulation coefficient, efficiency deviation e(t), and lead adjustment compensation, PID regulation calculation is performed to obtain the frequency regulation increment Δf. The calculation formula is as follows:

[0140] Δf=β×[Kp'×e(t)+Ki'× +Kd'×de(t) / dt]+Advanced adjustment compensation amount

[0141] The frequency adjustment increment Δf is superimposed on the frequency setting value of the initial frequency command to obtain the dynamic frequency setting value. At the same time, the rated operating frequency range of the circulating pump output by the pump characteristic acquisition unit is retrieved, and boundary clamping processing is performed on the dynamic frequency setting value. If the dynamic frequency setting value is higher than the upper limit of the rated frequency (preferably 50Hz), it is limited to the upper limit of the rated frequency. If the dynamic frequency setting value is lower than the lower limit of the rated frequency (preferably 10Hz), it is limited to the lower limit of the rated frequency to avoid the circulating pump operating in an inefficient or overloaded range.

[0142] Step S305, Dynamic frequency adjustment command output: Based on the clamped dynamic frequency setpoint, a dynamic frequency adjustment command conforming to the frequency converter communication protocol is generated. The command includes the dynamic frequency setpoint, command effective time, command priority identifier, and adjustment increment value. The dynamic frequency adjustment command is output to the thermal stress judgment and compensation module in real time and sent to the frequency converter, taking precedence over the initial frequency command. All parameters and command data during the adjustment process are synchronously stored in the ship heat exchanger operation database.

[0143] The thermal stress judgment and compensation module is used to obtain the metal wall temperature of the heat exchanger and the real-time temperature difference between the tube-side inlet and the shell-side inlet. Based on the metal wall temperature and the real-time temperature difference, it determines whether the heat exchanger is in an abnormal thermal stress state. If the heat exchanger is in an abnormal thermal stress state, it compensates for the dynamic frequency adjustment command based on the real-time temperature difference and generates a thermal stress suppression adjustment command.

[0144] Furthermore, in the above technical solutions, such as Figure 4 As shown, the thermal stress judgment and compensation module includes:

[0145] The threshold acquisition unit is used to acquire the allowable temperature difference threshold of the heat exchanger body at different metal wall temperatures;

[0146] The margin calculation unit is used to calculate the ratio of the real-time temperature difference to the allowable temperature difference threshold and generate a temperature difference margin coefficient.

[0147] The state determination unit is used to determine that the heat exchanger body is in an abnormal thermal stress state when the temperature difference margin coefficient exceeds the preset temperature difference safety threshold.

[0148] Furthermore, in the above technical solution, the thermal stress judgment and compensation module also includes:

[0149] The limit value calculation unit is used to calculate the required flow rate change limit value according to the temperature difference margin coefficient and the preset thermal stress suppression algorithm when it is determined that the thermal stress is in an abnormal state.

[0150] The clamping compensation unit is used to clamp the frequency change rate in the dynamic frequency adjustment command according to the flow rate change limit value, and generate a thermal stress suppression adjustment command for smoothing flow fluctuations and reducing thermal shock.

[0151] It is important to know that the thermal stress judgment and compensation module is bidirectionally connected to the wall temperature sensor array, temperature difference detection and initial command generation module, dynamic correction module, feedforward correction and command generation module, ship heat exchanger operation database, and frequency converter controller of temperature difference driven circulation pump deployed on the metal wall of the heat exchanger. The module starts synchronously when the ship's main engine starts and the temperature difference detection and initial command generation module starts working. It continuously performs thermal stress state monitoring and command compensation throughout the entire operating cycle of the main engine. Its data sampling period is consistent with all the aforementioned modules, set to 100ms. The timestamps of all collected data are completely aligned with the timestamps of the tube-side and shell-side temperature data, and the time synchronization error does not exceed one sampling cycle, ensuring the real-time performance and accuracy of thermal stress judgment.

[0152] The thermal stress suppression and adjustment command generated by the module has a higher priority than the initial frequency command output by the temperature difference detection and initial command generation module and the dynamic frequency adjustment command output by the dynamic correction module. It is the highest priority execution command in the system, ensuring that thermal stress safety constraints take precedence over heat exchange efficiency adjustment and energy-saving control. This avoids heat exchangers from fatigue damage, sealing failure, heat exchange tube rupture, and other faults caused by thermal shock and excessive thermal stress, thus ensuring the safe operation of the heat exchange system during ship navigation.

[0153] The metal wall temperature is collected by an array of wall temperature sensors installed on the metal walls of core pressure-bearing heat exchange components such as the heat exchanger tube sheet, heat exchange tubes, and shell. The sensor array includes at least four types of core measuring points: tube sheet measuring points, heat exchange tube inlet section measuring points, heat exchange tube mid-section measuring points, and shell measuring points. Each type of measuring point has at least two redundant measuring points. The sensors are Class A platinum resistance temperature sensors with a measurement accuracy of not less than ±0.2℃. The module takes the arithmetic mean of the wall temperature data collected from each measuring point, performs a moving average filtering process consistent with the inlet and outlet temperature data (the filtering window length is preset to 5 sampling points), and removes abnormal data that exceed the preset temperature range to obtain the effective metal wall temperature used for calculation. The real-time temperature difference between the tube-side inlet and the shell-side inlet is consistent with the temperature difference value output by the temperature difference detection and initial command generation module, and is the absolute value of the difference between the effective first fluid temperature and the effective second fluid temperature.

[0154] Furthermore, the detailed implementation methods of each unit under the thermal stress judgment and compensation module are as follows:

[0155] The input end of the threshold acquisition unit is communicatively connected to the ship heat exchanger operation database and the ship engine room equipment management system, and the output end is connected to the margin calculation unit and the status determination unit. Its specific execution steps are as follows:

[0156] Step S101, Retrieve Design Parameters and Material Properties: Retrieve the metal material grade, allowable thermal stress limit, material linear expansion coefficient, elastic modulus, connection form of heat exchange tubes and tube sheets, and rated operating temperature range and design temperature difference limit of the heat exchanger under design conditions from the heat exchanger design drawings, material mechanical property reports, and factory type test reports stored in the ship heat exchanger operation database.

[0157] Step S102, Allowable temperature difference threshold calibration: Based on the allowable thermal stress limit of the material and combined with the structural constraints of the heat exchanger, the allowable temperature difference threshold corresponding to different metal wall temperatures is pre-calibrated using the thermal stress-temperature difference conversion formula, and a metal wall temperature-allowable temperature difference threshold mapping table is constructed; the thermal stress-temperature difference conversion formula is:

[0158] [ΔT]=[σ]×(1-μ) / (E×α),

[0159] In the formula, [ΔT] is the allowable temperature difference threshold, [σ] is the allowable thermal stress limit of the metallic material at the corresponding wall temperature, μ is the Poisson's ratio of the material, E is the elastic modulus of the material at the corresponding wall temperature, and α is the linear expansion coefficient of the material; the temperature range of the mapping table covers the entire operating temperature range of the heat exchanger (preferably -20℃ to 200℃), the temperature interval is preset to 5℃, and a unique allowable temperature difference threshold is assigned to each temperature point;

[0160] Step S103, Threshold Online Correction and Validity Verification: When the main engine start signal is received, the latest maintenance report, hydrostatic test report, and wall thickness detection data of the heat exchanger are retrieved from the ship's engine room equipment management system. If the heat exchanger has corrosion thinning, weld repair, or other issues, the pre-stored allowable temperature difference threshold is reduced and corrected with a reduction factor of not less than 0.7 to ensure that the corrected threshold conforms to the current actual service status of the equipment. At the same time, the validity of the corrected allowable temperature difference threshold is verified. The verification rule is: the allowable temperature difference threshold shall not be lower than 50% of the design temperature difference limit and shall not be higher than 100% of the design temperature difference limit. If it exceeds the range, the threshold is deemed invalid, and the factory-calibrated design temperature difference limit is used as the default allowable temperature difference threshold.

[0161] Step S104, Threshold Matching and Output: Based on the effective metal wall temperature at the current sampling time, query the metal wall temperature-allowable temperature difference threshold mapping table. If the effective metal wall temperature is between two adjacent temperature points in the mapping table, calculate the corresponding accurate allowable temperature difference threshold using linear interpolation. Output the finally determined allowable temperature difference threshold to the margin calculation unit and the status determination unit in real time, and simultaneously store it in the ship heat exchanger operation database.

[0162] The input terminal of the margin calculation unit is communicatively connected to the threshold acquisition unit and the temperature difference detection and initial instruction generation module, and the output terminal is connected to the state determination unit and the limit value calculation unit. Its specific execution steps are as follows:

[0163] Step S201, Basic parameter acquisition: Synchronously acquire the real-time absolute value of the temperature difference between the tube-side inlet and the shell-side inlet at the current sampling time from the temperature difference detection and initial command generation module, and acquire the allowable temperature difference threshold corresponding to the current operating condition from the threshold acquisition unit.

[0164] Step S202, Calculation of temperature difference margin coefficient: Calculate the temperature difference margin coefficient according to the preset formula. The calculation formula is as follows:

[0165] K ΔT =|ΔT real | / [ΔT],

[0166] In the formula, K ΔT ΔT is the temperature margin coefficient. real The real-time temperature difference between the tube-side inlet and the shell-side inlet is [ΔT], which is the allowable temperature difference threshold under the current operating conditions. The physical meaning of the temperature difference margin coefficient is the proportion of the real-time temperature difference to the allowable temperature difference threshold. The larger the coefficient, the closer the heat exchanger is to the thermal stress over-limit state and the higher the risk of thermal shock.

[0167] Step S203, Data Validation: The calculated temperature margin coefficient is validated. The validation rules are as follows: When the real-time temperature difference is less than 1℃, it is determined to be a small temperature difference condition, and the temperature margin coefficient has no practical meaning. The default value of 0.1 is output. When the allowable temperature difference threshold is 0 or negative, the threshold is determined to be abnormal, and the effective allowable temperature difference threshold of the previous sampling time is retrieved and recalculated. When the temperature margin coefficient exceeds the reasonable range of 0 to 2, the calculation result is determined to be abnormal, the current result is discarded, and the effective temperature margin coefficient of the previous sampling time is retained.

[0168] Step S204, Valid data output: The valid temperature difference margin coefficient is output to the status judgment unit and the limit value calculation unit in real time, and the real-time temperature difference, allowable temperature difference threshold, and calculation process data are simultaneously stored in the ship heat exchanger operation database.

[0169] The input terminal of the state determination unit is communicatively connected to the margin calculation unit and the ship heat exchanger operation database, and the output terminal is connected to the limit value calculation unit, the ship engine room monitoring and alarm system, and the ship heat exchanger operation database. Its specific execution steps are as follows:

[0170] Step S301, Safety threshold retrieval: Retrieve the preset temperature difference safety threshold from the ship heat exchanger operation database. The temperature difference safety threshold is preset based on the heat exchanger's design life, fatigue strength, and ship navigation safety level. The default value is 0.8, which can be adjusted according to the equipment's service life and navigation conditions. The adjustment range is 0.6~0.9. At the same time, a backup warning threshold is preset, with a default value of 0.6, to trigger thermal stress warning in advance.

[0171] Step S302, State classification determination: Compare the effective temperature difference margin coefficient at the current sampling time with the preset threshold, and perform a three-level state determination:

[0172] Normal state: When the temperature difference margin coefficient is less than or equal to the warning threshold, the heat exchanger body is determined to be in a normal thermal stress state with no risk of thermal shock. No instruction compensation action is executed, and a normal state signal is output.

[0173] Warning status: When the warning threshold < temperature difference margin coefficient ≤ temperature difference safety threshold, the heat exchanger body is determined to be in a thermal stress warning state, and there is a potential risk of thermal shock. Warning information is sent to the ship's engine room monitoring and alarm system, but no forced compensation action is triggered. The change of margin coefficient is continuously monitored.

[0174] Abnormal state: When the temperature difference margin coefficient is greater than the temperature difference safety threshold, and this state continues for more than 3 consecutive sampling cycles, the heat exchanger body is determined to be in an abnormal thermal stress state, with a clear risk of thermal stress exceeding the limit and thermal shock damage. The abnormal thermal stress alarm signal is immediately sent to the ship's engine room monitoring and alarm system, and at the same time, the abnormal state trigger signal is output to the limit value calculation unit to start the instruction compensation process.

[0175] Step S303, Abnormal State Locking and Reset: When an abnormal thermal stress state is determined, the module performs state locking until the temperature difference margin coefficient is continuously lower than the warning threshold for 5 seconds, then the abnormal state lock can be released and the module can be reset to the normal state to avoid flow fluctuations caused by frequent start-stop compensation actions.

[0176] Step S304, Status signal output: The thermal stress status determination result and alarm signal are output to the limit value calculation unit and the ship's engine room monitoring and alarm system in real time. At the same time, the timestamp of the status change, the corresponding temperature difference margin coefficient, the real-time temperature difference, the metal wall temperature and other data are synchronously stored in the ship's heat exchanger operation database.

[0177] The input terminal of the limit value calculation unit is communicatively connected to the state determination unit, the margin calculation unit, and the dynamic correction module, and the output terminal is connected to the clamping compensation unit. Its specific execution steps are as follows:

[0178] Step S401, Compensation trigger determination: Receive the abnormal state trigger signal output by the state determination unit. When the trigger signal is received, immediately start the flow rate change limit value calculation process; when no trigger signal is received, the module maintains the standby state, outputs the default upper limit value of flow rate change (preferably 5Hz / s), and does not perform limit value correction.

[0179] Step S402, execution of the thermal stress suppression algorithm: Based on the temperature margin coefficient at the current sampling time, the required flow rate change limit value is calculated according to the preset thermal stress suppression algorithm. The core logic of the thermal stress suppression algorithm is: the larger the temperature margin coefficient, the higher the degree of thermal stress anomaly, the smaller the corresponding flow rate change limit value, and the smoother the frequency adjustment rate, thereby reducing the sudden change in wall temperature caused by flow rate mutations and suppressing thermal shock and thermal stress fluctuations; the algorithm calculation formula is:

[0180] R limit =R0×(1-(K ΔT -K safe ) / (K max -K safe )),

[0181] In the formula, R limit Here, R0 represents the flow rate change limit (unit: Hz / s), where R0 is the default upper limit for the flow rate change, and K... ΔT K represents the current temperature margin coefficient. safe K is the preset temperature difference safety threshold. max The preset upper limit of the margin coefficient (preferably 2.0); when the calculated R... limit When the flow rate is lower than the preset minimum limit (preferably 0.5 Hz / s), the minimum limit is taken as the final flow rate change limit to avoid stagnation in the frequency regulation of the circulating pump.

[0182] Step S403, Limit value validity verification: The calculated flow rate change limit value is verified for validity. The verification rule is: the limit value must be within the range of 0.5Hz / s to 5Hz / s. If it exceeds the range, the boundary value of the range is taken as the valid limit value. At the same time, combined with the current host load conditions, when the host is in a variable operating condition of rapid acceleration or deceleration, the limit value is corrected by the minimum magnitude to ensure that the adjustment rate can meet the basic heat exchange requirements. The corrected limit value shall not be lower than the minimum limit value.

[0183] Step S404, Limit value output: The valid flow rate change limit value is output to the clamping compensation unit in real time, and the parameters and algorithm execution data in the calculation process are synchronously stored in the ship heat exchanger operation database.

[0184] The input terminal of the clamping compensation unit is communicatively connected to the limit value calculation unit and the dynamic correction module, and the output terminal is connected to the feedforward correction and command generation module, the frequency converter of the temperature difference driven circulating pump, and the ship heat exchanger operation database. Its specific execution steps are as follows:

[0185] Step S501, Basic Instruction and Parameter Acquisition: Obtain the currently effective dynamic frequency adjustment instruction from the dynamic correction module, and extract the dynamic frequency setting value, frequency change rate, and instruction effective time from the instruction; obtain the flow rate change rate limit value under the current operating condition from the limit value calculation unit, wherein the flow rate change rate limit value corresponds to the upper limit of the frequency change rate of the frequency controller;

[0186] Step S502, frequency change rate clamping processing: compare the frequency change rate in the dynamic frequency adjustment command with the flow change rate limit value. If the frequency change rate in the original command is greater than the flow change rate limit value, clamp the frequency change rate according to the limit value and reduce the frequency change rate to the limit value; if the frequency change rate in the original command is less than or equal to the flow change rate limit value, retain the original frequency change rate unchanged.

[0187] Step S503, frequency setpoint smoothing: Based on the frequency change rate after clamping, the dynamic frequency setpoint is subjected to first-order inertial smoothing filtering to generate a smooth transition frequency adjustment sequence, avoiding sudden changes in flow rate caused by frequency step change, further smoothing the fluctuation range of fluid temperature on the tube shell side, and reducing the thermal shock of the metal wall; the time constant of the smoothing filter is negatively correlated with the flow rate change limit value. The smaller the limit value, the larger the time constant and the stronger the smoothing effect.

[0188] Step S504, Generating thermal stress suppression adjustment command: Based on the clamped and smoothed frequency setpoint and frequency change rate, a thermal stress suppression adjustment command conforming to the frequency converter communication protocol is generated. The command includes the smoothed frequency setpoint, the clamped frequency change rate, the command effective time, the highest priority identifier, and the thermal stress abnormal state marker.

[0189] Step S505, Command Output: The generated thermal stress suppression adjustment command is output to the feedforward correction and command generation module in real time, and is also sent directly to the frequency converter controller of the temperature difference driven circulation pump for execution with the highest priority; and all parameters in the command generation process and the command data before and after clamping compensation are synchronously stored in the ship heat exchanger operation database.

[0190] The feedforward correction and command generation module is used to obtain the water temperature of the ship, obtain the preset heat exchange efficiency of the heat exchanger under standard operating conditions as the heat exchange efficiency benchmark value, correct the heat exchange efficiency benchmark value according to the water temperature, fuse the corrected heat exchange efficiency benchmark value with the thermal stress suppression adjustment command, generate the target energy-saving control command, and send the target energy-saving control command to the frequency converter of the temperature difference driven circulation pump.

[0191] Furthermore, in the above technical solution, the feedforward correction and instruction generation module includes:

[0192] The reference correction unit is used to look up a preset water temperature-heat exchange efficiency correction coefficient table based on the water temperature and correct the heat exchange efficiency reference value.

[0193] The instruction fusion unit is used to take the corrected heat exchange efficiency benchmark value as a constraint condition and perform weighted fusion with the thermal stress suppression adjustment instruction to generate a target energy-saving control instruction that meets the heat exchange efficiency requirements, conforms to the thermal stress safety boundary, and adapts to changes in the external environment.

[0194] It is important to understand that the feedforward correction and command generation module is the core unit for generating and outputting the final control command of the system. It has bidirectional communication connections with the water temperature sensor deployed outside the ship, the ship navigation and navigation management system, the efficiency calculation module, the thermal stress judgment and compensation module, the ship heat exchanger operation database, the frequency converter controller of the temperature difference driven circulation pump, and the ship engine room monitoring system. The module starts synchronously when the ship's main engine starts and the temperature difference detection and initial command generation module starts working. It continuously performs environmental feedforward correction and final control command generation throughout the entire operating cycle of the main engine. Its data sampling period is consistent with all the aforementioned modules and is set to 100ms. The timestamps of all input parameters are completely aligned with the timestamps of the pipe-side, shell-side temperature data, and main engine load data, with a time synchronization error of no more than one sampling cycle, ensuring accurate matching of the final control command with real-time operating conditions and the external environment.

[0195] The core function of the module is to introduce feedforward correction based on the external environmental temperature of the ship's navigation waters, addressing the impact of cooling medium temperature variations in different sea areas and seasons on the heat exchanger's heat exchange efficiency benchmark. Simultaneously, it integrates heat exchange efficiency constraints, thermal stress safety constraints, and external environmental constraints from multiple dimensions to generate the final target energy-saving control command. This target energy-saving control command is the final execution command sent to the frequency converter, completely covering and replacing the previously output initial frequency command and dynamic frequency adjustment command. It also strictly retains the safety boundary constraints in the thermal stress suppression adjustment command, ensuring that thermal stress safety always takes precedence over energy-saving adjustment and efficiency optimization.

[0196] The water temperature is the real-time temperature of the cooling seawater outside the ship's navigating waters, collected by Class A platinum resistance temperature sensors deployed at the inlet of the ship's main seawater pipe or in the ballast tank area. The sensor measurement accuracy is no less than ±0.2℃. The module performs a moving average filtering process on the collected raw water temperature data, consistent with the inlet and outlet temperature data. The filter window length is preset to 5 sampling points. After removing abnormal data that exceed the preset temperature range (-2℃~35℃, covering the temperature range of all sea areas where ships navigate globally), the effective water temperature used for correction calculation is obtained. The heat exchange efficiency benchmark value is the calibrated rated heat exchange efficiency of the heat exchanger under standard operating conditions. The standard operating conditions are the rated operating conditions corresponding to the rated working pressure, rated flow rate, design inlet and outlet temperature difference, and standard ambient cooling temperature (25℃) specified in the heat exchanger design documents. The heat exchange efficiency benchmark value is extracted from the heat exchanger's factory type test report and design calculation sheet, and is pre-stored in the ship heat exchanger operation database. The value range is 0.7~0.9, which is completely consistent with the heat exchange efficiency definition calculated by the efficiency calculation module using the efficiency-number of heat transfer units method.

[0197] Furthermore, the detailed implementation methods of each unit under the feedforward correction and instruction generation module are as follows:

[0198] The input terminal of the reference correction unit is communicatively connected to the water temperature sensor, the ship navigation and navigation management system, and the ship heat exchanger operation database, and the output terminal is connected to the command fusion unit. Its specific execution steps are as follows:

[0199] Step S101, retrieve basic parameters: retrieve the heat exchange efficiency benchmark value of the heat exchanger under standard operating conditions and the preset water temperature-heat exchange efficiency correction coefficient table from the ship heat exchanger operation database, and at the same time obtain the effective water temperature at the current sampling time, synchronously obtain the current real-time load condition of the main engine from the ship main engine control system, and obtain the actual heat exchange efficiency under the current operating conditions from the efficiency calculation module.

[0200] Step S102, Pre-calibration explanation of the water temperature-heat transfer efficiency correction coefficient table: The water temperature-heat transfer efficiency correction coefficient table is pre-calibrated based on the heat transfer characteristics of the heat exchanger and the variation law of the physical properties of the cooling medium through bench tests. The horizontal axis of the correction coefficient table is the water temperature range, covering the entire sea area navigation temperature range from -2℃ to 35℃, with a preset temperature interval of 2℃. The vertical axis is the heat transfer efficiency correction coefficient for the corresponding temperature range. The calibration logic of the correction coefficient is as follows: When the water temperature is higher than the standard operating condition reference temperature of 25℃, the viscosity of the cooling seawater increases and the heat transfer coefficient decreases, and the theoretical maximum heat transfer efficiency of the heat exchanger under the same operating condition decreases, corresponding to a correction coefficient less than 1; when the water temperature is lower than the reference temperature of 25℃, the heat transfer performance of the cooling seawater improves, corresponding to a correction coefficient greater than 1; the value range of the correction coefficient is 0.7~1.2 to ensure that the corrected heat transfer efficiency reference value is always within the reasonable engineering range.

[0201] Step S103, Correction Coefficient Matching and Baseline Value Correction: Based on the effective water temperature at the current sampling time, query the preset water temperature-heat transfer efficiency correction coefficient table. If the effective water temperature is at the boundary point between two adjacent temperature intervals in the table, calculate the corresponding accurate correction coefficient using linear interpolation. Based on the matched correction coefficient, correct the heat transfer efficiency baseline value using the following formula:

[0202] η base '=η base ×f,

[0203] In the formula, η base 'η is the corrected baseline value for heat transfer efficiency. base is the original heat exchange efficiency baseline value under standard operating conditions, and f is the correction factor corresponding to the water temperature;

[0204] Step S104, Verification of the validity of the correction value and adjustment of the operating conditions: The validity of the corrected heat exchange efficiency benchmark value is verified. The verification rule is: the corrected heat exchange efficiency benchmark value shall not be lower than 70% of the original benchmark value and shall not be higher than 120% of the original benchmark value. If it exceeds the range, the boundary value of the corresponding range shall be taken as the valid correction benchmark value. At the same time, the adjustment is made in combination with the current host load conditions. When the host is in a low load condition below 25%, the corrected benchmark value is reduced by 0.9 times to avoid excessive pursuit of heat exchange efficiency under low load, which would lead to an increase in the energy consumption of the circulating pump. When the host is in a high load condition above 75%, the corrected benchmark value is amplified by 1.05 times to ensure heat exchange safety redundancy under high load.

[0205] Step S105, Valid data output: The corrected heat exchange efficiency benchmark value after verification and adaptation is output to the command fusion unit in real time, and the water temperature, correction coefficient, and benchmark value data before and after correction are synchronously stored in the ship heat exchanger operation database.

[0206] The input terminal of the instruction fusion unit is communicatively connected to the reference correction unit, the thermal stress judgment and compensation module, the dynamic correction module, the efficiency calculation module, and the ship heat exchanger operation database. Its output terminal is connected to the frequency converter controller of the temperature difference driven circulating pump, the ship engine room monitoring system, and the ship heat exchanger operation database. The specific execution steps are as follows:

[0207] Step S201, multi-source input parameter acquisition: Obtain the corrected heat exchange efficiency benchmark value from the benchmark correction unit; obtain the currently effective heat stress suppression adjustment command from the thermal stress judgment and compensation module, and extract the frequency setpoint, clamped frequency change rate, thermal stress state mark, and highest priority identifier from the command; obtain the currently effective dynamic frequency adjustment command from the dynamic correction module, and extract the dynamic frequency setpoint and PID adjustment parameters from the command; obtain the actual heat exchange efficiency under the current operating conditions from the efficiency calculation module; retrieve the rated operating frequency range, minimum safe operating frequency, maximum rated frequency, and minimum heat exchange flow rate corresponding to the current load of the main engine for the temperature difference driven circulating pump from the ship heat exchanger operation database;

[0208] Step S202, Operating Condition Classification Determination: Based on the thermal stress state marker in the thermal stress suppression and adjustment command, the current operating condition is determined in two levels, and a differentiated fusion strategy is executed:

[0209] Safety-priority operating condition: When the thermal stress state is marked as an abnormal state, it is determined to be a safety-priority operating condition. The thermal stress suppression adjustment command is the core constraint, and the corrected heat transfer efficiency benchmark value is only used as an auxiliary optimization constraint. Any fusion action is strictly prohibited from breaking the safety boundary of thermal stress suppression.

[0210] Efficiency optimization condition: When the thermal stress state is marked as normal or warning state, it is determined to be an efficiency optimization condition. The modified heat exchange efficiency benchmark value is used as the core constraint. Combined with the advanced adjustment characteristics of the dynamic frequency adjustment command and the safety boundary of the thermal stress warning, a weighted fusion is performed to take into account heat exchange efficiency, energy saving effect and operation safety.

[0211] Step S203, Weighted fusion calculation of target frequency setpoint: Based on the operating condition determination result, execute the corresponding weighted fusion algorithm to calculate the final target frequency setpoint.

[0212] For efficiency optimization conditions, the fusion calculation formula is as follows:

[0213] f target =w1×fdynamic +w2×f eff ,

[0214] In the formula, f target The target frequency setting value after fusion, f dynamic f is the dynamic frequency setting value in the dynamic frequency adjustment command. eff The frequency value corresponding to the target efficiency is calculated based on the corrected heat transfer efficiency benchmark value. w1 and w2 are dynamic weighting coefficients and satisfy w1+w2=1.

[0215] The adaptive matching rule for the dynamic weighting coefficients is as follows: when the actual heat exchange efficiency is ≥ 95% of the corrected benchmark heat exchange efficiency, w1 = 0.9 and w2 = 0.1, prioritizing the retention of the dynamic characteristics of proactive adjustment; when the actual heat exchange efficiency is in the range of 85% to 95% of the corrected benchmark value, w1 = 0.5 and w2 = 0.5, balancing dynamic adjustment and efficiency constraints; when the actual heat exchange efficiency is < 85% of the corrected benchmark value, w1 = 0.1 and w2 = 0.9, prioritizing ensuring that the heat exchange efficiency meets the benchmark requirements.

[0216] The target efficiency corresponds to the frequency value f. eff The target is the modified heat exchange efficiency benchmark value. It is calculated by interpolation using the rated power-frequency characteristic curve and flow-heat exchange efficiency mapping relationship of the circulating pump. The calculation is completely consistent with the generation logic of the initial frequency command.

[0217] For safety-priority operating conditions, the fusion calculation formula is as follows:

[0218] f target =w safe ×f thermal +w eff ×f eff ,

[0219] In the formula, fthermal is the frequency setting value in the thermal stress suppression adjustment command, and w safe w eff For fixed weighting coefficients, and satisfying w safe +w eff =1, where w safe ≥0.8, w eff ≤0.2, ensuring the absolute priority of thermal stress safety constraints, and only making minor efficiency optimizations without exceeding the safety boundary;

[0220] Step S204, Frequency Change Rate and Boundary Constraint Verification: Perform dual constraint verification on the fused target frequency setpoint and frequency change rate.

[0221] Frequency change rate constraint: Under efficiency optimization conditions, the smaller value between the frequency change rate in the dynamic frequency adjustment command and the maximum allowable change rate corresponding to the thermal stress warning state is taken as the final frequency change rate; under safety priority conditions, the frequency change rate after clamping in the thermal stress suppression adjustment command is strictly adopted, and no upward adjustment is made.

[0222] Frequency boundary constraints: The rated operating frequency range of the circulating pump is retrieved, and the target frequency setting value is clamped at the boundary. If the target frequency setting value is higher than the upper limit of the rated frequency (preferably 50Hz), it is limited to the upper limit of the rated frequency; if the target frequency setting value is lower than the lower limit of the rated frequency (preferably 10Hz), or lower than the lower limit of the frequency corresponding to the minimum heat exchange flow rate under the current load of the main unit, it is limited to the corresponding lower limit value. This avoids the circulating pump operating in an inefficient overload range and also prevents the sacrifice of heat exchange safety for energy saving.

[0223] Step S205, Target Energy-Saving Control Command Generation: Based on the verified target frequency setpoint and final frequency change rate, a target energy-saving control command conforming to the standard communication protocol of the ship frequency converter is generated. The command includes the target frequency setpoint, final frequency change rate, command effective time, command unique identifier, operating condition status flag, and cyclic redundancy check code. The command explicitly stipulates that after receiving the target energy-saving control command, the frequency converter immediately overwrites and stops executing the previous initial frequency command and dynamic frequency adjustment command, and strictly executes frequency adjustment according to the final command. If the command carries a thermal stress abnormality status flag, the frequency change rate is locked synchronously until the thermal stress abnormality status is resolved. During the locking period, no non-safety-related frequency adjustment requests are responded to.

[0224] Step S206, Command Output and Full-Process Data Archiving: The generated target energy-saving control command is sent to the frequency converter of the temperature difference driven circulation pump in real time, and simultaneously sent to the ship's engine room monitoring system for operation status display and alarm prompts; at the same time, all input parameters, fusion calculation process, verification rule execution status, and final command data during the command generation process are completely archived and stored in the ship's heat exchanger operation database for subsequent equipment operation status analysis, fault tracing, and control parameter self-optimization iteration.

[0225] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side, characterized in that, Includes the following modules: The temperature difference detection and initial command generation module is used to respond to the ship's main engine start signal, acquire the first fluid temperature at the tube-side inlet of the heat exchanger and the second fluid temperature at the shell-side inlet, and generate the initial frequency command for the temperature difference-driven circulating pump based on the temperature difference between the first fluid temperature and the second fluid temperature. The coupling feature extraction module is used to obtain the temperature difference change rate sequence of the heat exchanger on the tube side and the shell side within a preset historical period, as well as the load change curve of the ship's main engine. It extracts temperature-load coupling features from the temperature difference change rate sequence and the load change curve, and generates multi-level coordinated heat exchange control parameters based on the temperature-load coupling features. The efficiency calculation module is used to obtain the third fluid temperature at the tube-side outlet of the heat exchanger and the fourth fluid temperature at the shell-side outlet. Combining the first fluid temperature, the second fluid temperature and the real-time heat flux of the heat exchanger measured by the heat flux sensor, the module calculates the actual heat exchange efficiency of the heat exchanger under the current operating conditions. The dynamic correction module is used to correct the initial frequency command of the temperature difference driven circulation pump according to the multi-level coordinated heat exchange control parameters and the temperature difference value when the actual heat exchange efficiency is lower than the preset efficiency threshold, and generate a dynamic frequency adjustment command. The thermal stress judgment and compensation module is used to obtain the metal wall temperature of the heat exchanger and the real-time temperature difference between the tube-side inlet and the shell-side inlet. Based on the metal wall temperature and the real-time temperature difference, it determines whether the heat exchanger is in an abnormal thermal stress state. If the heat exchanger is in an abnormal thermal stress state, it compensates for the dynamic frequency adjustment command based on the real-time temperature difference and generates a thermal stress suppression adjustment command. The feedforward correction and command generation module is used to obtain the water temperature of the ship, obtain the preset heat exchange efficiency of the heat exchanger under standard operating conditions as the heat exchange efficiency benchmark value, correct the heat exchange efficiency benchmark value according to the water temperature, fuse the corrected heat exchange efficiency benchmark value with the thermal stress suppression adjustment command, generate the target energy-saving control command, and send the target energy-saving control command to the frequency converter of the temperature difference driven circulation pump.

2. The energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side according to claim 1, characterized in that, The temperature difference detection and initial command generation module includes: Pump characteristic acquisition unit, used to acquire the rated power-frequency characteristic curve of the temperature difference driven circulating pump; The flow calculation unit is used to calculate the basic flow rate required to overcome the current temperature difference and achieve natural circulation based on the temperature difference between the first fluid temperature and the second fluid temperature, according to a preset temperature difference-demand flow rate mapping table. The instruction mapping unit is used to query the rated power-frequency characteristic curve based on the basic demand flow and generate an initial frequency instruction that matches the basic demand flow.

3. The energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side according to claim 1, characterized in that, The coupling feature extraction module includes: The temperature difference analysis unit is used to perform time series analysis on the temperature difference change rate sequence, extract the peak time, trough time and corresponding change rate of the temperature difference change, and generate a temperature difference fluctuation feature vector. The load analysis unit is used to perform synchronous time-series analysis on the load change curve of the ship's main engine, extract the inflection point time and load change rate of the load change, and generate a load fluctuation feature vector. The coupled calculation unit is used to calculate the cross-correlation function of the temperature difference fluctuation feature vector and the load fluctuation feature vector in time series, and to determine the response lag time and synergistic influence coefficient of the temperature difference to the load change based on the peak value of the cross-correlation function. The parameter generation unit is used to generate multi-level coordinated heat exchange control parameters for guiding flow advance adjustment based on the response lag time and the coordinated influence coefficient.

4. The energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side according to claim 1, characterized in that, The efficiency calculation module includes: The heat calculation unit is used to calculate the actual heat absorption or release of the pipe-side fluid based on the difference between the temperature of the first fluid and the temperature of the third fluid; and to calculate the actual heat release or heat absorption of the shell-side fluid based on the difference between the temperature of the second fluid and the temperature of the fourth fluid. The temperature difference calculation unit is used to obtain the heat exchange area of ​​the heat exchanger body and calculate the logarithmic mean temperature difference under the current operating conditions based on the temperature of the first fluid, the temperature of the second fluid, the temperature of the third fluid, and the temperature of the fourth fluid. The efficiency calculation unit is used to calculate the actual heat exchange efficiency, which characterizes the heat exchange capacity under the current operating conditions, based on the real-time heat flux, the logarithmic mean temperature difference, and the heat exchange area, using the efficiency-number of heat transfer units method.

5. The energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side according to claim 3, characterized in that, The dynamic correction module includes: The parameter extraction unit is used to extract the response lag time from the multi-level coordinated heat exchange control parameters. The trend prediction unit is used to monitor the changing trend of the temperature difference value and predict the direction of load change based on the load fluctuation feature vector. The adjustment generation unit is used to generate a dynamic frequency adjustment command for increasing or decreasing the flow rate in advance by performing proportional-integral-derivative adjustment on the initial frequency command according to the cooperative influence coefficient when the direction of change of the temperature difference value is consistent with the expected load change direction corresponding to the response lag time.

6. The energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side according to claim 1, characterized in that, The thermal stress judgment and compensation module includes: The threshold acquisition unit is used to acquire the allowable temperature difference threshold of the heat exchanger body at different metal wall temperatures; The margin calculation unit is used to calculate the ratio of the real-time temperature difference to the allowable temperature difference threshold and generate a temperature difference margin coefficient. The state determination unit is used to determine that the heat exchanger body is in an abnormal thermal stress state when the temperature difference margin coefficient exceeds the preset temperature difference safety threshold.

7. The energy-saving system for a shipboard shell-and-tube heat exchanger driven by the temperature difference between the tube side and the shell side according to claim 6, characterized in that, The thermal stress judgment and compensation module also includes: The limit value calculation unit is used to calculate the required flow rate change limit value according to the temperature difference margin coefficient and the preset thermal stress suppression algorithm when it is determined that the thermal stress is in an abnormal state. The clamping compensation unit is used to clamp the frequency change rate in the dynamic frequency adjustment command according to the flow rate change limit value, and generate a thermal stress suppression adjustment command for smoothing flow fluctuations and reducing thermal shock.

8. The energy-saving system for a shipboard shell-and-tube heat exchanger based on the temperature difference between the tube side and the shell side as described in claim 1, characterized in that, The feedforward correction and instruction generation module includes: The reference correction unit is used to look up a preset water temperature-heat exchange efficiency correction coefficient table based on the water temperature and correct the heat exchange efficiency reference value. The instruction fusion unit is used to take the corrected heat exchange efficiency benchmark value as a constraint condition and perform weighted fusion with the thermal stress suppression adjustment instruction to generate a target energy-saving control instruction that meets the heat exchange efficiency requirements, conforms to the thermal stress safety boundary, and adapts to changes in the external environment.

Images