A method and system for preventing freezing of a section temperature of a circulating water pipeline in a cold region tunnel

Abstract

The present application belongs to the technical field of automatic temperature control, and relates to a kind of cold region tunnel circulating water pipeline section temperature freeze control method and system, to solve the problem that existing freeze control is difficult to take into account the difference in heat dissipation of pipe section, upstream heat supply capacity, circulating pump cooperative control and heat tracing energy consumption.The present application includes: dividing freeze control pipe section along the direction of water flow and establishing pipe section and heat tracing section association table;Obtain target pipe section water temperature, ambient temperature, upstream side collection point water temperature and circulating pump frequency;Calculate comprehensive heat dissipation coefficient, equivalent safe water temperature, remaining time and transport time within the safety test window;According to the heat supply condition, transport time and remaining time, select at least one of the corresponding heat tracing section in the upstream heat tracing section and the target pipe section, generate circulating pump variable frequency control instruction and segmented heat tracing scheduling instruction;When heat tracing is abnormal, select other heat tracing sections to participate in heat supply.The present application can realize on-demand segmented heat tracing and circulating pump cooperative control, reduce energy consumption and operation and maintenance cost.

Description

Technical Field

[0001] This invention belongs to the field of automatic temperature control technology in industrial processes, specifically relating to a method and system for segmented temperature antifreeze control of circulating water pipelines in cold-region tunnels. Background Technology

[0002] In cold and frigid regions, tunnels operating in winter expose water supply pipelines to prolonged low temperatures, making them susceptible to factors such as cold air intrusion, localized insulation degradation, temperature fluctuations at the tunnel entrance, and insufficient heat at the return water terminal. This poses risks of water freezing inside the pipes, pipe blockage, and valve freezing. Existing projects typically install insulation layers and heating tapes on the outside of the circulation pipelines to mitigate the risk of freezing.

[0003] Existing antifreeze control methods mostly employ fixed temperature threshold control or timed control. For example, heating is activated when the ambient temperature falls below a set value. To maintain continuous antifreeze operation, heating cables typically operate for extended periods during cold seasons, with some scenarios involving continuous 24-hour operation of the entire heating cable. While this method has simple control logic, for long or extra-long tunnels, the heat dissipation conditions differ significantly between the tunnel entrance on the shaded slope, the entrance on the sunny slope, the stable zone inside the tunnel, the pipe sections near the ventilation openings, and the return water end. The freezing risk varies at different locations. If all heating sections operate simultaneously for extended periods, it not only results in high energy consumption but also increases the cumulative energization time of the heating cables, subjecting the insulation materials and heating elements to continuous heat load and increasing the costs of inspection, replacement, and downtime maintenance. Conversely, if control is based solely on the water temperature at a single sampling point or a fixed temperature threshold, the freezing risk of locally high-heat-dissipation pipe sections may be underestimated, leading to delayed heating activation or missed detection of high-risk sections.

[0004] Furthermore, relying solely on increasing the circulation pump frequency for freeze protection control presents certain contradictions. When the water temperature upstream of the target pipe section is high, increasing the circulation pump frequency can shorten the heat transport time, allowing upstream heat to be delivered to the low-temperature pipe section more quickly. However, when the upstream water temperature is not high, blindly increasing the circulation pump frequency may cause the low-temperature water to diffuse rapidly within the system, thereby expanding the area affected by the low temperature. Existing technologies typically struggle to simultaneously determine the remaining time for the target pipe section to reach its low-temperature critical point, the heat transport time from the upstream heating section to the target pipe section, and whether the upstream water body has effective heat replenishment capabilities. Therefore, the coordinated control between the heating section's start-up location, start-up sequence, and circulation pump frequency is insufficient.

[0005] Meanwhile, existing electric heat tracing fault alarms mostly rely on whether the heat tracing current is abnormal. When the heat tracing operating current is significantly low, it can be determined that the heat tracing cable is broken, has poor contact, or has an abnormal power supply. However, when the heat tracing operating current is normal but the water temperature in the target pipe section is insufficient to recover, the existing control method is unable to further distinguish between different abnormal causes such as insulation layer failure, local cold air intrusion, abnormal heat dissipation in the pipeline, or pipeline leakage. This leads to inaccurate alarm location, and maintenance personnel cannot promptly determine whether to check the heat tracing electrical parts, the insulation structure, or the pipeline itself.

[0006] For the antifreeze retrofit of existing tunnel circulating water pipelines, the method of setting up point heating devices and matching circulating heat transfer control requires the addition of new heating equipment, control equipment, and related construction, resulting in a high retrofit investment. How to achieve on-demand segmented control while retaining the existing heating cables and pipelines, and reduce the workload of subsequent heating cable replacement and maintenance, is also an issue that needs to be considered when retrofitting existing pipelines.

[0007] Therefore, a segmented temperature antifreeze control method and system for circulating water pipelines in cold-region tunnels is needed. This system should be able to judge the water temperature change trend of different antifreeze control pipeline segments based on multi-point temperature acquisition, pipeline heat dissipation status, circulating pump operating frequency, and heat tracing section status, and dynamically generate heat tracing section scheduling instructions and circulating pump frequency conversion control instructions. Summary of the Invention

[0008] To address the aforementioned problems in the existing technology, namely the difficulty in simultaneously considering differences in heat dissipation between pipe sections, upstream heat replenishment capacity, coordinated control of circulating pumps, and heat tracing energy consumption in existing antifreeze control systems, this invention provides a segmented temperature antifreeze control method and system for circulating water pipelines in cold-region tunnels.

[0009] In a first aspect, this invention proposes a method for segmented temperature antifreeze control of circulating water pipelines in cold-region tunnels, comprising:

[0010] The pipeline between adjacent temperature acquisition points is divided into antifreeze control sections along the water flow direction. The upstream and downstream sides of the pipe sections are determined, and a correlation table between the pipe sections and the heat tracing sections is established.

[0011] Select the target pipe section and obtain the water temperature, ambient temperature, upstream sampling point water temperature, and circulation pump frequency of the target pipe section;

[0012] Within the safety test window, close the heat tracing section corresponding to the target pipe section, calculate the measured temperature drop rate based on the water temperature change of the target pipe section, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature and the ambient temperature.

[0013] The equivalent safe water temperature and the predicted temperature drop rate are calculated based on the comprehensive heat dissipation coefficient. The water temperature drops faster from the measured temperature drop rate and the predicted temperature drop rate. The remaining time for the target pipe section to reach the antifreeze critical temperature is then calculated.

[0014] The transport time is calculated based on the frequency of the circulating pump and the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section, and the heat replenishment conditions are determined based on the difference between the water temperature at the upstream sampling point and the water temperature in the target pipe section.

[0015] Based on the transport time, remaining time, and reheating conditions, select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section, and generate a circulating pump frequency conversion control command and a segmented heat tracing scheduling command.

[0016] Furthermore, the establishment of the association table between the antifreeze control pipe section and the heat tracing section includes:

[0017] Based on the location of adjacent temperature acquisition points, the layout of the heat tracing section, and the direction of circulating water flow, determine the starting point, ending point, length, upstream and downstream pipe sections, and calculate the water flow distance from the heat tracing section to the corresponding antifreeze control pipe section.

[0018] Write one heat tracing section covering the range of the antifreeze control pipe section into the heat tracing section field corresponding to the antifreeze control pipe section, or write multiple consecutive heat tracing sections covering the range of the antifreeze control pipe section into the heat tracing section field corresponding to the antifreeze control pipe section.

[0019] The heat tracing section located upstream of the antifreeze control pipe section along the direction of circulating water flow and connected to the waterway of the antifreeze control pipe section is written into the upstream support item of the antifreeze control pipe section.

[0020] Furthermore, the target pipe section water temperature is determined in the following way:

[0021] The lower of the starting and ending water temperatures of the antifreeze control pipe section is determined as the target pipe section water temperature; when the antifreeze control pipe section is close to a preset high heat dissipation position, the water temperature of the sampling point on the side close to the preset high heat dissipation position is determined as the target pipe section water temperature, and the preset high heat dissipation position includes at least one of the following: the entrance of the shady slope, the entrance door, the vent, and the end of the return water.

[0022] If the temperature at the sampling point exceeds the preset temperature range, or if the temperature change at the sampling point in multiple consecutive sampling cycles is greater than the temperature change at the upstream and downstream sampling points in the corresponding sampling cycles when the heating status, circulation pump frequency, and water supply operation status remain unchanged, the abnormal sampling point will be removed from the risk assessment input. A substitute water temperature will be formed based on the water temperature at the normal upstream and downstream sampling points and the historical water temperature change trend, and the substitute water temperature will be determined as the target pipe section water temperature.

[0023] Furthermore, the calculation of the overall heat dissipation coefficient includes:

[0024] The safety test window is the time period that simultaneously meets the requirements of system standby state, sensor effective state, water temperature safe state, circulating pump stable operation state, and ambient temperature stable state.

[0025] The system standby state is when no manual forced operation command or water supply operation command is received; the sensor effective state is when no sensor fault alarm is received; the water temperature safety state is when the water temperature of each antifreeze control pipe section is higher than the safety test threshold; the circulation pump stable operation state is when the circulation pump runs continuously at a preset base frequency; and the ambient temperature stable state is when the change in ambient temperature of the target pipe section does not exceed the preset temperature change threshold within the preset test duration.

[0026] Within the safety test window, the heat tracing section corresponding to the target pipe section is closed, and the measured temperature drop rate of the target pipe section under the condition of no heat tracing input is recorded. The measured temperature drop rate is the change in water temperature of the target pipe section per unit time, and a negative value indicates that the water temperature of the target pipe section has decreased.

[0027] When the water temperature of the target pipe section is higher than the ambient temperature of the target pipe section and the measured temperature drop rate is less than zero, the ratio of the absolute value of the measured temperature drop rate to the difference between the water temperature and the ambient temperature of the target pipe section is determined as the comprehensive heat dissipation coefficient of the target pipe section.

[0028] Furthermore, the step of correcting the target pipe section water temperature based on the comprehensive heat dissipation coefficient to obtain the equivalent safe water temperature includes:

[0029] Based on the range of the comprehensive heat dissipation coefficient of the target pipe section, the pre-stored insulation layer status of the target pipe section, and the location attributes of the target pipe section near the shady slope opening, doorway, air outlet, or return water end, match the wall temperature safety correction ratio.

[0030] The wall temperature correction amount is generated based on the correction relationship between the target pipe section water temperature, the target pipe section ambient temperature, and the wall temperature safety correction ratio.

[0031] The target pipe section water temperature is adjusted by subtracting the wall temperature correction amount to obtain the equivalent safe water temperature.

[0032] The low-temperature risk level is determined based on the comparison results between the equivalent safe water temperature and the preset safe temperature, preset warning temperature, and antifreeze critical temperature, as well as the measured temperature drop rate. Specifically, the preset safe temperature is higher than the preset warning temperature, and the preset warning temperature is higher than the antifreeze critical temperature. When the equivalent safe water temperature is higher than the preset safe temperature and the measured temperature drop rate is not less than zero, it is considered safe. When the equivalent safe water temperature is higher than the preset warning temperature but does not meet the safety conditions, it is considered a concern. When the equivalent safe water temperature is higher than the antifreeze critical temperature but not higher than the preset warning temperature, it is considered a warning. When the equivalent safe water temperature is not higher than the antifreeze critical temperature, it is considered a high-risk level.

[0033] Furthermore, the calculation of the predicted temperature drop rate and remaining time includes:

[0034] The predicted temperature drop rate is generated based on the comprehensive heat dissipation coefficient and the difference between the target pipe section water temperature and the target pipe section ambient temperature.

[0035] When at least one of the predicted temperature drop rate and the measured temperature drop rate is less than zero, the negative temperature drop rate with the smaller value is selected from the predicted temperature drop rate and the measured temperature drop rate as the remaining time to calculate the temperature drop rate.

[0036] When the equivalent safe water temperature is greater than the critical antifreeze temperature and the calculated temperature drop rate for the remaining time is less than zero, the difference between the equivalent safe water temperature and the critical antifreeze temperature is divided by the absolute value of the calculated temperature drop rate for the remaining time to obtain the remaining time.

[0037] When the equivalent safe water temperature is not greater than the critical antifreeze temperature, the remaining time is set to zero.

[0038] Furthermore, the step of selecting and activating at least one of the heat tracing section located upstream of the target pipe section and the corresponding heat tracing section of the target pipe section includes:

[0039] For target pipe sections with a low temperature risk level of warning, when the difference between the remaining time and the transportation time is not less than the preset minimum observation time and the heating conditions are met, the heat tracing section located upstream of the target pipe section is activated first and an observation window is set.

[0040] After the observation window ends, the difference between the equivalent safe water temperature at the end of the observation window and the equivalent safe water temperature at the beginning of the observation window is determined as the equivalent safe water temperature recovery range. When the equivalent safe water temperature recovery range is less than the preset recovery range threshold, the heat tracing section corresponding to the target pipe section is activated.

[0041] For target pipe sections with a low temperature risk level of warning, when the difference between the remaining time and the transportation time is less than the preset minimum observation time or the heating conditions are not met, the corresponding heat tracing section of the target pipe section will be activated.

[0042] For target pipe sections with a high-risk low-temperature risk level, the corresponding heat tracing section is directly activated; when there is a heat tracing section located upstream of the target pipe section that meets the heat replenishment conditions, the heat tracing section with the shortest transport time to the target pipe section is selected from the heat tracing sections to participate in the heat replenishment.

[0043] Furthermore, the generation of the circulating pump frequency conversion control command and the segmented heat tracing scheduling command includes:

[0044] Obtain the outlet water temperature and return water temperature; when a water supply operation command or a manual forced operation command is issued, generate an operation priority command, stop the safety test and the heat tracing section rotation control, and make the operation priority command override other circulation pump control commands;

[0045] When no priority operation command is generated, the low temperature risk level of each antifreeze control pipe section is safe or concerned, the return water temperature is higher than the preset return water temperature, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, the basic frequency command is generated.

[0046] When no priority operation instruction is generated, there is no high-risk target pipe section and only one warning target pipe section exists, the warning target pipe section meets the heat replenishment conditions, the transport time is less than the remaining time, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, an intermediate frequency instruction is generated.

[0047] A high-frequency operation command is generated when no priority operation command is generated and any of the following conditions are met: there is a high-risk target pipe section or multiple warning target pipe sections, and at least one target pipe section meets the heat replenishment conditions; the difference between the outlet water temperature and the return water temperature is not less than the preset circulation temperature difference.

[0048] When no priority operation command is generated, there is a warning or high-risk target pipe section, none of the target pipe sections meet the heat replenishment conditions, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, a command is generated to maintain the circulation pump frequency and increase the heat tracing level of the corresponding heat tracing section.

[0049] Furthermore, after generating the circulating pump frequency conversion control command and the segmented heat tracing scheduling command, the process also includes:

[0050] Record the target pipe section water temperature and heat tracing current before and after the start-up of the heat tracing section, and calculate the water temperature recovery range.

[0051] When the water temperature recovery range is less than the preset temperature rise reference range, if the heat tracing working current is lower than the preset current threshold, a heat tracing electrical abnormality prompt will be output and the corresponding heat tracing section will be removed from the heat replenishment candidate; if the heat tracing working current is within the preset normal current range, a target pipe section heat dissipation abnormality prompt will be output.

[0052] According to the heat tracing section association table, select other heat tracing sections located upstream of the target pipe section that meet the heat replenishment conditions and have a transport time less than the remaining time to participate in heat replenishment;

[0053] When the water temperature of the target pipe section is higher than the safety diagnostic threshold, reduce or shut down the output of the corresponding heat tracing section of the target pipe section and record the shutdown diagnostic temperature drop rate; when the shutdown diagnostic temperature drop rate is less than the predicted temperature drop rate, update the comprehensive heat dissipation coefficient according to the difference between the predicted temperature drop rate and the shutdown diagnostic temperature drop rate, and increase the wall temperature safety correction ratio.

[0054] In a second aspect, the present invention provides a segmented temperature antifreeze control system for circulating water pipelines in cold-region tunnels, comprising:

[0055] The pipe segment division and association module is used to divide the pipeline between adjacent temperature acquisition points into antifreeze control pipe segments along the water flow direction, determine the upstream and downstream sides of the pipe segments, and establish an association table between the pipe segments and the heat tracing sections.

[0056] The target data acquisition module is used to select the target pipe section and acquire the target pipe section's water temperature, ambient temperature, upstream sampling point water temperature, and circulating pump frequency.

[0057] The heat dissipation coefficient calculation module is used to close the heat tracing section corresponding to the target pipe section within the safety test window, calculate the measured temperature drop rate based on the water temperature change of the target pipe section, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature and the ambient temperature.

[0058] The risk time calculation module is used to calculate the equivalent safe water temperature and the predicted temperature drop rate based on the comprehensive heat dissipation coefficient. It selects the water temperature drop rate that drops faster from the measured temperature drop rate and the predicted temperature drop rate, and calculates the remaining time for the target pipe section to reach the antifreeze critical temperature.

[0059] The transport condition calculation module is used to calculate the transport time based on the circulation pump frequency and the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section, and to determine the heat replenishment conditions based on the difference between the water temperature at the upstream sampling point and the water temperature of the target pipe section.

[0060] The collaborative control module is used to select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section based on the transport time, remaining time, and heat replenishment conditions, and to generate frequency conversion control commands for the circulating pump and segmented heat tracing scheduling commands.

[0061] The beneficial effects of this invention are:

[0062] This invention divides the circulating water pipeline into multiple antifreeze control sections along the flow direction of the circulating water and establishes an association table between the antifreeze control sections and the heat tracing sections, enabling the controller to distinguish between the heat tracing section corresponding to the target section and the heat tracing section located upstream of the target section. Based on the remaining time, transport time, and reheating conditions, the controller selects and activates at least one of the heat tracing sections located upstream of the target section and the heat tracing section corresponding to the target section as needed. Heat tracing sections without reheating requirements do not need to operate simultaneously for extended periods. Compared to the method of continuous 24-hour operation of the entire heat tracing cable during low-temperature seasons, this invention reduces unnecessary energization time and energy consumption of heat tracing sections and lowers the possibility of missed local risks due to temperature control at a single acquisition point.

[0063] This invention closes the heat tracing section corresponding to the target pipe segment within the safety testing window. It calculates the comprehensive heat dissipation coefficient based on the measured temperature drop rate of the target pipe segment and the difference between the target pipe segment's water temperature and the ambient temperature. Furthermore, it corrects the target pipe segment's water temperature based on the comprehensive heat dissipation coefficient to obtain the equivalent safe water temperature. Therefore, this invention incorporates the actual heat dissipation capacity of the pipe segment, its insulation status, ambient temperature, and water temperature change trends into the low-temperature risk assessment process. This avoids the underestimation of risks at high-heat-dissipation locations such as slope openings, air vents, and return water terminals due to the simple use of the same fixed temperature threshold across different pipe segments, thus improving the accuracy and lead time of low-temperature risk assessment.

[0064] This invention calculates the remaining time for a target pipe section to reach its critical antifreeze temperature based on the equivalent safe water temperature, the measured temperature drop rate, and the predicted temperature drop rate. It also calculates the transport time based on the water flow distance from the upstream heating section to the target pipe section. By comparing the time margin between the remaining time and the transport time, and determining whether the temperature difference between the upstream sampling point and the target pipe section is not less than the preset supplementary heating temperature difference, this invention can determine whether the heat generated by the upstream heating section can reach and complete the observation and verification before the target pipe section reaches its low-temperature critical point. Therefore, when the time margin is sufficient and the supplementary heating conditions are met, the upstream heating section is activated first; when the time margin is insufficient or the supplementary heating conditions are not met, the corresponding heating section of the target pipe section is activated.

[0065] This invention determines whether the upstream water temperature of the target pipe section has effective heat replenishment capacity before the circulating pump frequency is increased, and determines whether to increase the circulating pump frequency based on the transport time and remaining time. When the upstream water temperature has heat replenishment capacity and the heat can reach the target pipe section in time, the circulating pump frequency is increased to accelerate heat transport; when the upstream water temperature is insufficient, the circulating pump frequency is maintained and the heating level of the target pipe section is increased to reduce the rapid diffusion of low-temperature water, so that the operating state of the circulating pump and the state of the heating section form a synergistic relationship.

[0066] This invention also identifies anomalies based on the target pipe section's water temperature recovery range after the heating section is started, the heating operating current, and the shutdown diagnostic temperature drop rate. When the heating operating current is too low and the temperature rise is insufficient, it outputs a warning indicating a broken heating cable, poor contact, or abnormal power supply. When the heating operating current is within the normal range but the temperature rise is insufficient, it outputs a warning indicating insulation layer failure, localized cold air intrusion, abnormal heat dissipation in the pipeline, or pipeline leakage, based on changes in the temperature drop rate. This provides a basis for maintenance personnel to troubleshoot heating electrical faults, insulation structure deterioration, and pipeline anomalies.

[0067] When a heat tracing section is identified as having an electrical fault, this invention removes that section from the heat replenishment candidates and selects other heat tracing sections located upstream of the target pipe section that meet the heat replenishment conditions and have a transport time shorter than the remaining time, based on the heat tracing section association table, to participate in the heat replenishment. By combining the cumulative running time of each heat tracing section to determine the start-up order under the same conditions, heat tracing sections with shorter cumulative running time are given priority to participate in heat replenishment. This balances the running time of each heat tracing section, reduces the continuous power supply of a single heat tracing section, delays the aging of the heat tracing tape, and reduces inspection, replacement, and maintenance costs. At the same time, it provides a time window for the maintenance of abnormal sections while maintaining the antifreeze protection of the circulating water pipeline.

[0068] In scenarios where existing pipelines are modified to have segmented heating cables, this invention can reuse existing pipelines and heating cables. By adding a circulation pump or connecting a temperature acquisition point, segmented switches, and controllers, the above-mentioned control can be implemented, reducing the equipment and construction investment required for setting up additional point heating devices, replacing the entire heating cable, or making large-scale pipeline modifications, thereby reducing the modification cost. Attached Figure Description

[0069] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0070] Figure 1 This is a schematic diagram of the main flow of the segmented temperature antifreeze control method for circulating water pipelines in cold regions provided in the first embodiment of the present invention;

[0071] Figure 2 This is a schematic diagram of the antifreeze control of circulating water pipeline in cold-region tunnels provided in an embodiment of the present invention;

[0072] Figure 3 This is a partial schematic diagram of a pipeline provided in an embodiment of the present invention;

[0073] Figure 4 This is a schematic diagram of the process for determining the water temperature of the target pipe section provided in an embodiment of the present invention;

[0074] Figure 5 This is a schematic diagram of the comprehensive heat dissipation coefficient calculation process provided in an embodiment of the present invention;

[0075] Figure 6 This is a schematic diagram of the calculation process for equivalent safe water temperature and remaining time provided in an embodiment of the present invention;

[0076] Figure 7 This is a schematic diagram of the process for calculating transport time and selecting heat tracing sections provided in an embodiment of the present invention;

[0077] Figure 8 This is a schematic diagram of the module architecture of the cold-region tunnel circulating water pipeline segmented temperature antifreeze control system provided in the second embodiment of the present invention. Detailed Implementation

[0078] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0079] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0080] In one application scenario, this embodiment can be applied to fire-fighting water supply circulation systems with circulation loops and circulation pumps in highway tunnels, railway tunnels, or urban rail transit tunnels in cold and frigid regions, as well as their electric heat tracing and antifreeze control.

[0081] See Figure 2 The circulating water pipeline in the cold-region tunnel includes a water supply pipe 10, a water supply pump 20, a circulating pump 30, a controller 40, and temperature acquisition points 50. The water supply pump 20 replenishes the circulating water pipeline via the water supply pipe 10 when the pressure at the far end of the pipeline is insufficient. The circulating pump 30 is set up independently of the water supply pump 20 and is used to drive the water in the pipe to flow in a preset circulation direction and provide the flow rate required for heat transport. Multiple heat tracing sections are arranged in segments along the circulating water pipeline. The controller 40 is connected to the temperature acquisition points 50, the circulating pump 30, and each heat tracing section, respectively, to collect water temperature at each location, obtain and control the operating status of the circulating pump 30, and determine the upstream and downstream sides of each antifreeze control pipe section according to the circulating water flow direction.

[0082] See Figure 3 The circulating water pipeline includes a steel pipe 60, a heat tracing cable 70 and an insulation layer 80 installed on the outside of the steel pipe 60. The heat tracing cable 70 is installed between the steel pipe 60 and the insulation layer 80. The controller 40 is connected to the heat tracing cable 70 and is used to control the start, stop or heat tracing level adjustment of the heat tracing cable 70 in the corresponding heat tracing section. Figure 3 The water flow direction in the diagram is used to indicate the flow direction of circulating water within a local pipe. This direction is related to... Figure 2 The direction of circulating water flow serves as the basis for subsequently determining the heat tracing section located upstream of the target pipe section, the corresponding heat tracing section of the target pipe section, and the transportation time.

[0083] In the scenario of retrofitting existing tunnel fire protection pipelines, the controller 40 can be connected to the existing circulating pump 30, heating cable 70, and their control interfaces. It can also supplement temperature acquisition points or sectional switches based on the existing temperature acquisition point 50 layout, thereby forming a sectional temperature antifreeze control system while retaining the existing pipelines, circulating pump 30, and heating cable 70. This retrofit method mainly involves adding or adjusting temperature acquisition, sectional switches, and control programs, reducing the equipment and construction investment required for replacing the entire heating cable 70, setting up additional point heating devices, or extensive pipeline modifications.

[0084] The first embodiment of this invention proposes a segmented temperature antifreeze control method for circulating water pipelines in cold-region tunnels, such as... Figure 1 As shown, it includes the following steps:

[0085] S10: Divide the pipeline between adjacent temperature acquisition points into antifreeze control sections along the water flow direction, determine the upstream and downstream sides of the pipe sections, and establish a correlation table between the pipe sections and the heat tracing sections.

[0086] S20: Select the target pipe section and obtain the target pipe section water temperature, ambient temperature, upstream sampling point water temperature and circulation pump frequency;

[0087] S30: Close the heat tracing section corresponding to the target pipe section within the safety test window, calculate the measured temperature drop rate based on the water temperature change of the target pipe section, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature and the ambient temperature.

[0088] S40: Calculate the equivalent safe water temperature and predicted temperature drop rate based on the comprehensive heat dissipation coefficient. Select the water temperature drop rate that drops faster from the measured temperature drop rate and the predicted temperature drop rate, and calculate the remaining time for the target pipe section to reach the antifreeze critical temperature.

[0089] S50: Calculate the transport time based on the circulation pump frequency and the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section, and determine the heat replenishment conditions based on the difference between the water temperature at the upstream sampling point and the water temperature of the target pipe section.

[0090] S60: Based on the transport time, remaining time, and reheating conditions, select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section, and generate a circulating pump frequency conversion control command and a segmented heat tracing scheduling command.

[0091] To more clearly explain the segmented temperature antifreeze control method for circulating water pipelines in cold-region tunnels according to the present invention, the following is in conjunction with... Figure 1 The steps in the embodiments of the present invention are described in detail below:

[0092] S10: Divide the pipeline between adjacent temperature acquisition points into antifreeze control sections along the direction of circulating water flow, determine the upstream and downstream sides of each antifreeze control section, and establish a correlation table between the antifreeze control section and the heat tracing section.

[0093] In this embodiment, the controller reads the sequential relationship between temperature sampling points according to the direction of circulating water flow, determining the side where the water flow arrives first as the upstream side of the corresponding antifreeze control pipe section, and the side where the water flow arrives later as the downstream side of the corresponding antifreeze control pipe section. The controller collects operational data according to a preset sampling period. The operational data includes water temperature at each sampling point, ambient temperature corresponding to each sampling point, outlet water temperature, return water temperature, circulating pump operating frequency, circulating pump start / stop status, on / off status of each heat tracing section, operating current of each heat tracing section, cumulative operating time of each heat tracing section, water supply operation status, and water replenishment status. For example, the sampling period can be set to 10 minutes. The controller writes the water temperature, ambient temperature, circulating pump frequency, and heat tracing status collected within the same sampling time into the same operation record, so that the subsequent calculation of temperature drop rate, comprehensive heat dissipation coefficient, and transport time has a unified time reference.

[0094] In this embodiment, step S10 includes:

[0095] Step S11: Based on the location of adjacent temperature acquisition points, the layout of the heat tracing section, and the direction of circulating water flow, determine the starting point, ending point, length, upstream section, and downstream section of the pipe segment, and calculate the water flow distance from the heat tracing section to the corresponding antifreeze control pipe segment.

[0096] Step S12: Write one heat tracing section covering the range of the antifreeze control pipe section into the heat tracing section field corresponding to the antifreeze control pipe section, or write multiple consecutive heat tracing sections covering the range of the antifreeze control pipe section into the heat tracing section field corresponding to the antifreeze control pipe section.

[0097] Step S13: The heat tracing section located upstream of the antifreeze control pipe section along the direction of circulating water flow and connected to the water passage of the antifreeze control pipe section is written into the upstream support item of the antifreeze control pipe section.

[0098] In step S11, the controller moves along Figure 2 The sequence of temperature acquisition points is read according to the circulating water flow direction. The pipeline between two adjacent temperature acquisition points is defined as an antifreeze control section, and the upstream and downstream sides of this antifreeze control section are determined according to the water flow direction. The pipe section length is derived from construction drawings, as-built measurement data, or pipeline parameters preset in the controller. The water flow distance from the heat tracing section to the corresponding antifreeze control section is taken as the distance from the center point of the heat tracing section to the center point of the antifreeze control section along the water flow direction, or as the distance from the downstream end of the heat tracing section to the risk assessment location of the antifreeze control section; the same distance definition method is used for the same project.

[0099] In step S12, when a heat tracing section covers the piping range of an antifreeze control pipe section, the controller writes the heat tracing section into the heat tracing section field corresponding to that antifreeze control pipe section. When multiple consecutive heat tracing sections cover the piping range of the same antifreeze control pipe section, the controller writes the multiple consecutive heat tracing sections into the heat tracing section field corresponding to that antifreeze control pipe section. When multiple short pipe sections share the same heat tracing section, the controller writes the same heat tracing section into the heat tracing section fields corresponding to the multiple short pipe sections respectively, and writes the risk assessment water temperature source of each short pipe section into the association table.

[0100] The association table includes at least the antifreeze control pipe section number, the pipe section start collection point, the pipe section end collection point, the pipe section length, the corresponding heat tracing section number, the upstream pipe section number, the downstream pipe section number, and the water flow distance from the heat tracing section to the corresponding antifreeze control pipe section.

[0101] In step S13, the controller determines the position of each heat tracing section relative to the target pipe section according to the direction of circulating water flow. If a heat tracing section is located upstream of the target pipe section, and the heated water in that section can enter the target pipe section with the circulating water, the controller adds the heat tracing section to the upstream support entry of the target pipe section. If a heat tracing section has a bypass, disconnection, out-of-operation branch, or a pipe section with opposite water flow direction to the target pipe section, the controller does not add the heat tracing section to the upstream support entry of the target pipe section. Through the association table, subsequent steps can simultaneously identify the heat tracing section corresponding to the target pipe section and the heat support heat tracing section located upstream of the target pipe section.

[0102] In this embodiment, a rotation field can be added to the association table based on the cumulative operating time of the heat tracing sections. The rotation field records the cumulative operating time, most recent start-up time, and most recent stop time of each heat tracing section. When multiple heat tracing sections can provide heat support to the target pipe section, the controller, provided that the transport time and heat replenishment conditions are met, prioritizes the heat tracing section with the shorter cumulative operating time to participate in the support. When the antifreeze requirement is met, heat tracing sections not selected for heat replenishment remain closed or have their heat tracing duty cycle reduced to decrease the continuous energization time of the entire pipeline's heat tracing tape. Rotation operation makes the cumulative operating time of each heat tracing section tend to be balanced, reducing the possibility of accelerated aging of a single heat tracing section due to long-term continuous energization. The rotation field does not change the basic association relationship between the antifreeze control pipe section and the heat tracing section; it only serves as a basis for the start-up order under the same conditions.

[0103] S20: Select the antifreeze control pipe section as the target pipe section, and obtain the water temperature of the target pipe section, the ambient temperature of the target pipe section, the water temperature of the upstream sampling point of the target pipe section, and the frequency of the circulating pump.

[0104] In this embodiment, the controller can sequentially select each antifreeze control pipe segment as the target pipe segment, or it can prioritize selecting antifreeze control pipe segments with lower ambient temperatures, higher historical low-temperature risks, or those close to the tunnel entrance as target pipe segments. After the target pipe segment is determined, the controller reads the water temperature of the target pipe segment, the ambient temperature at the location of the target pipe segment, the water temperature at the upstream sampling point of the target pipe segment, and the circulation pump frequency. Among them, the water temperature at the upstream sampling point of the target pipe segment is used to determine whether the upstream water body has the ability to replenish heat to the target pipe segment; the circulation pump frequency is used to calculate the circulating water flow rate and participates in the subsequent transport time calculation.

[0105] See Figure 4 In this embodiment, step S20 includes:

[0106] Step S21: Determine the lower of the starting water temperature and the ending water temperature of the antifreeze control pipe section as the target pipe section water temperature; when the antifreeze control pipe section is close to the preset high heat dissipation position, determine the water temperature of the sampling point on the side close to the preset high heat dissipation position as the target pipe section water temperature. The preset high heat dissipation position includes at least one of the following: the entrance of the shady slope, the door of the tunnel, the vent, and the end of the return water.

[0107] Step S22: If the temperature at the sampling point exceeds the preset temperature range, or if the temperature change at the sampling point in multiple consecutive sampling cycles exceeds the preset mutation threshold when the heating status, circulation pump frequency, and water supply operation status remain unchanged, the abnormal sampling point will be removed from the risk judgment input. A substitute water temperature will be formed based on the water temperature of the normal sampling points upstream and downstream and the historical water temperature change trend, and the substitute water temperature will be determined as the target pipe section water temperature.

[0108] In step S21, to avoid the risk of freezing being masked by localized high-temperature sampling points, the controller determines the lower of the starting and ending water temperatures of the anti-freeze control pipe section as the target pipe section water temperature. For pipe sections near the entrance of a shady slope, tunnel door, air vent, or the end of the return water supply, the controller determines the water temperature of the sampling point closest to the preset high heat dissipation position as the target pipe section water temperature. The controller can also simultaneously save the starting water temperature, ending water temperature, and average water temperature in the operation record for trend display and operation verification.

[0109] In step S22, the controller sets a preset temperature range for both the water temperature and the ambient temperature. When the temperature at a certain sampling point exceeds the corresponding preset temperature range, the sampling point is marked as an abnormal sampling point. Under the condition that the heating status, circulation pump frequency, and water supply operation status remain unchanged, the controller compares the temperature change at the sampling point with that of the upstream and downstream sampling points within the corresponding sampling period. If the difference between the temperature changes exceeds a preset mutation threshold for multiple consecutive sampling periods, the sampling point is removed from the risk assessment input. The alternative water temperature is obtained by interpolating the water temperature at the upstream normal sampling point, the water temperature at the downstream normal sampling point, and the historical temperature drop slope, and is used as the target pipe section water temperature for subsequent calculations of the equivalent safe water temperature and remaining time.

[0110] For example, if the starting water temperature of a certain antifreeze control pipe section is 6.0℃ and the ending water temperature is 5.2℃, and this pipe section is close to the entrance of a tunnel on a shady slope, then the controller will use 5.2℃ as the water temperature for risk assessment of this pipe section. If the pipe section is located in a stable temperature zone inside the tunnel, the controller can also use the average of 5.2℃ and 6.0℃ as the reference value for operation display, but 5.2℃ will still be given priority for low temperature risk assessment.

[0111] S30: Close the heat tracing section corresponding to the target pipe section within the safety test window, calculate the measured temperature drop rate based on the change in water temperature of the target pipe section over time, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature of the target pipe section and the ambient temperature of the target pipe section.

[0112] In this embodiment, the safety test window is used to estimate the heat dissipation capacity of the target pipe section without affecting the normal operation of the system and antifreeze safety. Within the safety test window, the controller closes the heat tracing section corresponding to the target pipe section, records the water temperature drop process of the target pipe section under conditions without heat tracing input, calculates the measured temperature drop rate, and calculates the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the target pipe section water temperature and the target pipe section ambient temperature. The comprehensive heat dissipation coefficient reflects the heat dissipation strength of the target pipe section under the current insulation state, environmental conditions, and water state. Subsequent steps use the comprehensive heat dissipation coefficient for equivalent safe water temperature correction, predicted temperature drop rate calculation, and abnormal heat dissipation identification.

[0113] See Figure 5 In this embodiment, step S30 includes:

[0114] Step S31: Determine the safe test window that simultaneously satisfies the system standby state, sensor effective state, water temperature safe state, circulating pump stable operation state, and ambient temperature stable state.

[0115] Step S32: The system standby state is when no manual forced operation command or water supply operation command is received; the sensor effective state is when no sensor fault alarm is received; the water temperature safety state is when the water temperature of each antifreeze control pipe section is higher than the safety test threshold; the circulation pump stable operation state is when the circulation pump runs continuously at a preset basic frequency; and the ambient temperature stable state is when the change in ambient temperature of the target pipe section does not exceed the preset temperature change threshold within the preset test duration.

[0116] Step S33: Close the heat tracing section corresponding to the target pipe section within the safety test window, and record the measured temperature drop rate of the target pipe section under the condition of no heat tracing input.

[0117] Step S34: When the water temperature of the target pipe section is higher than the ambient temperature of the target pipe section and the measured temperature drop rate is less than zero, the ratio of the absolute value of the measured temperature drop rate to the difference between the water temperature of the target pipe section and the ambient temperature of the target pipe section is determined as the comprehensive heat dissipation coefficient of the target pipe section.

[0118] In steps S31 and S32, the safety test threshold is set to a temperature value higher than the critical antifreeze temperature. For example, if the critical antifreeze temperature is 4℃, the safety test threshold is set to 7℃ or 8℃. The stable ambient temperature can be set to ensure that the ambient temperature variation of the target pipe section within the safety test window does not exceed 2℃. The circulating pump operates continuously at a preset base frequency, which can be a base frequency around 20Hz, to keep the circulating water flow state controllable. If a manual forced operation command, a water supply operation command, an abnormal water replenishment, a circulating pump malfunction, or the water temperature of the target pipe section approaches the critical antifreeze temperature occurs within the test window, the controller immediately stops the safety test and resumes antifreeze control.

[0119] In step S33, the controller calculates the temperature drop rate based on the water temperature change between two adjacent sampling periods, using the following formula:

[0120] ;

[0121] in, For the first The rate of water temperature change in each antifreeze control pipe section The target pipe section water temperature at the current sampling time. The target pipe section water temperature at the previous sampling time. This is the sampling time interval. When... A negative value indicates that the water temperature in the target pipe section is decreasing. To reduce the impact of fluctuations in a single sampling, the controller can use the average temperature drop rate over multiple consecutive sampling periods. For example, with a sampling period of 10 minutes, the controller can take the average temperature drop rate of the three sampling periods within the most recent 30 minutes as the measured temperature drop rate of the target pipe section.

[0122] In step S34, the formula for calculating the overall heat dissipation coefficient can be:

[0123] ;

[0124] in, For the first The overall heat dissipation coefficient of each antifreeze control pipe section, The target pipe section ambient temperature, This is the difference between the target pipe section water temperature and the target pipe section ambient temperature. When the target pipe section water temperature is higher than the ambient temperature and the target pipe section water temperature decreases, It is a positive value. The larger the value, the faster the target pipe section dissipates heat under the current insulation and environmental conditions. If If the value is too small, the calculation results will be unstable. The controller can temporarily not update the overall heat dissipation coefficient of the target pipe section and continue to use the historical overall heat dissipation coefficient for subsequent judgments.

[0125] For example, if the water temperature of a target pipe section drops from 7.4℃ to 7.1℃ within a 30-minute safety test window, the temperature drop rate is -0.6℃ / h; if the average ambient temperature during this period is -8℃, and the temperature difference between the target pipe section's water and the ambient temperature is approximately 15.2℃, then the overall heat dissipation coefficient is... Approximately The subsequent controller will Used for assessing low-temperature risks, predicting remaining time, and identifying abnormal heat dissipation in this pipe section.

[0126] In this embodiment, a reliability flag can also be set for the comprehensive heat dissipation coefficient. The reliability flag can be determined by the test window duration, ambient temperature fluctuation range, circulation pump frequency stability, actual shutdown status of the heat tracing section, and sensor status. If the safety test window duration is insufficient, the ambient temperature fluctuates significantly, or the circulation pump frequency changes noticeably, the controller will mark the comprehensive heat dissipation coefficient calculated this time as low reliability, using it only as a reference and not directly overwriting the historical comprehensive heat dissipation coefficient. If the safety test window meets the reliable data segment conditions, the controller will write the comprehensive heat dissipation coefficient calculated this time into the target pipe section parameter record for subsequent calculation of equivalent safe water temperature and remaining time.

[0127] S40: Correct the target pipe section water temperature based on the comprehensive heat dissipation coefficient to obtain the equivalent safe water temperature, generate the predicted temperature drop rate based on the comprehensive heat dissipation coefficient, and select the temperature drop rate with the faster water temperature drop rate from the measured temperature drop rate and the predicted temperature drop rate to calculate the remaining time for the target pipe section to reach the antifreeze critical temperature.

[0128] In this embodiment, the equivalent safe water temperature is used to reflect situations where the water temperature near the pipe wall may be lower than the water temperature at the sampling point or the water temperature at the center of the pipe. For pipe sections near the entrance of a shady slope, tunnel door, air vent, or the end of the return water supply, even if the water temperature at the sampling point has not yet fallen below the critical antifreeze temperature, the area near the pipe wall may be close to a freezing risk state due to strong heat dissipation. The controller uses the comprehensive heat dissipation coefficient and the difference between the target pipe section water temperature and the target pipe section ambient temperature to correct the target pipe section water temperature, thus obtaining the equivalent safe water temperature. Subsequently, the controller compares the measured temperature drop rate with the predicted temperature drop rate generated by the comprehensive heat dissipation coefficient, and selects the temperature drop rate with the faster corresponding water temperature drop rate as the remaining time to calculate the temperature drop rate.

[0129] See Figure 6 In this embodiment, step S40 includes:

[0130] Step S41: Match the wall temperature safety correction ratio based on the range of the comprehensive heat dissipation coefficient of the target pipe section, the pre-stored insulation layer status of the target pipe section, and the location attributes of the target pipe section near the shady slope opening, doorway, air outlet, or return water end.

[0131] Step S42: Generate the wall temperature correction amount based on the correction relationship between the target pipe section water temperature, the target pipe section ambient temperature, and the wall temperature safety correction ratio;

[0132] Step S43: Subtract and correct the target pipe section water temperature using the wall temperature correction amount to obtain the equivalent safe water temperature;

[0133] Step S44: Based on the comparison results of the equivalent safe water temperature with the preset safe temperature, the preset warning temperature and the antifreeze critical temperature, and the measured temperature drop rate, output the low temperature risk level as safe, attention, warning or high risk.

[0134] Step S45: Generate the predicted temperature drop rate based on the comprehensive heat dissipation coefficient and the difference between the target pipe section water temperature and the target pipe section ambient temperature.

[0135] Step S46: When at least one of the predicted temperature drop rate and the measured temperature drop rate is less than zero, select the negative temperature drop rate with the smaller value from the predicted temperature drop rate and the measured temperature drop rate as the remaining time to calculate the temperature drop rate.

[0136] Step S47: When the equivalent safe water temperature is greater than the critical antifreeze temperature and the calculated temperature drop rate for the remaining time is less than zero, divide the difference between the equivalent safe water temperature and the critical antifreeze temperature by the absolute value of the calculated temperature drop rate for the remaining time to obtain the remaining time.

[0137] Step S48: When the equivalent safe water temperature is not greater than the antifreeze critical temperature, set the remaining time to zero.

[0138] In step S41, the wall temperature safety correction ratio is denoted as: For pipe sections with good insulation inside the tunnel, A value of 0.02 to 0.05 can be used; for pipe sections near the shady slope entrance, doorway, vent, or those with a history of strong heat dissipation, A value of 0.05 to 0.10 can be used. The controller can pre-establish the correspondence between the comprehensive heat dissipation coefficient range, insulation layer status, pipe segment location attributes, and wall temperature safety correction ratio. For example, the target pipe segment is close to the opening of the shady slope and... When in a higher range, the controller selects a larger value. The target pipe section is located in a relatively stable temperature zone inside the tunnel and When in the lower range, the controller selects a smaller value. .

[0139] In steps S42 and S43, the equivalent safe water temperature can be calculated according to the following formula:

[0140] ;

[0141] in, For the first The equivalent safe water temperature of each antifreeze control pipe section For the target pipe section water temperature, The target pipe section ambient temperature, This is the wall temperature safety correction ratio. The larger and The larger the value, the greater the wall temperature correction, indicating that the low-temperature risk near the pipe wall carries a higher weight in risk assessment. The equivalent safe water temperature is used for low-temperature risk level assessment and remaining time calculation.

[0142] In step S44, the antifreeze critical temperature can be set to 4℃, the preset warning temperature can be set to 6℃, and the preset safe temperature can be set to 8℃. The preset safe temperature is higher than the preset warning temperature, and the preset warning temperature is higher than the antifreeze critical temperature. When the temperature is higher than the preset safety temperature and the measured temperature drop rate is not less than zero, the controller outputs a safety level; when When the temperature exceeds the preset warning level but does not meet safety requirements, the controller outputs a level of concern; when When the temperature exceeds the antifreeze critical temperature but does not exceed the preset warning temperature, the controller outputs a warning level; when... When the temperature is not higher than the critical antifreeze temperature, the controller outputs a high-risk level.

[0143] For example, the water temperature of a target pipe section is 5.8℃, the ambient temperature is -10℃, and this pipe section is near the entrance of a tunnel on a shady slope. The equivalent safe water temperature is:

[0144] .

[0145] Although the collected water temperature of 5.8℃ is not lower than 4℃, the equivalent safe water temperature is close to the critical temperature for freezing. At the same time, the pipe section is located in the area of ​​the tunnel entrance on the shady slope. If its temperature drop rate continues to decrease, the controller will determine it as a warning pipe section or a high-risk pipe section.

[0146] In step S45, the predicted temperature drop rate can be calculated using the following formula:

[0147] ;

[0148] in, For the first Predicted temperature drop rate for each antifreeze control pipe section The overall heat dissipation coefficient of the target pipe section, This represents the difference between the target pipe section's water temperature and its ambient temperature. The predicted temperature drop rate reflects the potential trend of temperature decrease in the target pipe section under the current overall heat dissipation coefficient and temperature difference. If historical heat dissipation capacity is strong and the current internal and external temperature difference is large, the predicted temperature drop rate will be greater.

[0149] In step S46, the controller reads the current measured temperature drop rate. and predicted rate of temperature drop The measured temperature drop rate was compared with the predicted temperature drop rate. When the measured temperature drop rate corresponds to a faster water temperature decrease, The remaining time is used to calculate the rate of temperature drop. When the predicted rate of temperature decrease is faster, Calculate the rate of temperature drop as the remaining time. Through this comparison, the controller simultaneously considers both short-term measured changes and the pipe section's heat dissipation capacity reflected by the comprehensive heat dissipation coefficient, avoiding deviations in risk time predictions from reality caused by single sampling fluctuations or single historical parameters.

[0150] In steps S47 and S48, the remaining time can be calculated using the following formula:

[0151] ;

[0152] in, The remaining time for the target pipe section to reach the critical temperature for freeze protection. For equivalent safe water temperature, This is the critical temperature for freeze protection. Calculate the rate of temperature drop for the remaining time. When If the value is not decreasing, the controller can temporarily disregard calculating the remaining emergency time and continue monitoring the target pipe section based on the return water temperature, ambient temperature trend, and overall heat dissipation coefficient. The remaining time serves as an important basis for subsequently selecting at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing section of the target pipe section.

[0153] For example, a target pipe section It is 5.0℃. The temperature is 4.0℃, and the current measured temperature drop rate is... ,based on The predicted rate of temperature drop is Then take The remaining time for the target pipe section to reach the critical antifreeze temperature is:

[0154] ;

[0155] Based on this, the controller determines that the target pipe section may reach the critical temperature for freezing in about 2 hours, and heat tracing needs to be scheduled in advance.

[0156] In this embodiment, step S40 may further include the following processing of candidate quantities for heat dissipation anomalies:

[0157] Step S491: When the difference between the measured temperature drop rate and the predicted temperature drop rate exceeds the deviation threshold, read the ambient temperature change amplitude, the circulation pump frequency change amplitude, and the state change record of the heat tracing section.

[0158] Step S492: When the ambient temperature change range, the circulation pump frequency change range, and the heat tracing section status change record are all within the reliable data segment conditions, write the difference into the heat dissipation anomaly candidate quantity.

[0159] Step S493: When the candidate quantity of heat dissipation anomaly accumulates within the continuous sampling window, the comprehensive heat dissipation coefficient of the target pipe section is written into the parameter to be updated and the temperature drop rate calculated in the remaining time is input into the remaining time calculation.

[0160] In step S491, the deviation threshold can be set to 0.2℃ / h. When the measured temperature drop rate is significantly faster or slower than the predicted temperature drop rate, the controller does not directly modify the overall heat dissipation coefficient, but instead reads the ambient temperature, circulating pump frequency, and heat tracing status change records within the same time period to determine whether the deviation is caused by changes in operating conditions.

[0161] In step S492, the reliable data segment conditions may include an ambient temperature change of no more than 2°C, a circulating pump frequency change of no more than 5Hz, and no on / off switching of the heat tracing section and no water supply operation command. If the above conditions are met, the difference between the measured temperature drop rate and the predicted temperature drop rate is more likely to reflect the change in the heat dissipation status of the target pipe section, and the controller writes the difference into the heat dissipation anomaly candidate quantity.

[0162] In step S493, the continuous sampling window can be 3 sampling periods or 30 minutes. When candidate quantities of heat dissipation anomalies continuously appear within the continuous sampling window, the controller marks the comprehensive heat dissipation coefficient of the target pipe section as a parameter that needs to be updated, and prioritizes the use of the temperature drop rate with the larger decrease in the remaining time calculation. If the deviation occurs only once or occurs synchronously with the change in the heat tracing status, the controller retains the historical comprehensive heat dissipation coefficient and waits for subsequent sampling verification.

[0163] S50: Calculate the flow rate based on the circulation pump frequency, and calculate the transport time based on the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section. When the difference between the water temperature at the sampling point upstream of the target pipe section and the water temperature of the target pipe section is not less than the preset heat replenishment temperature difference, it is determined that the heat replenishment condition is met.

[0164] In this embodiment, after the target pipe segment is identified as a concern, under warning, or high-risk segment, the controller reads the upstream support item from the association table of antifreeze control pipe segments and heat tracing sections. For each candidate heat tracing section located upstream of the target pipe segment, the controller reads the water flow distance from the candidate heat tracing section to the target pipe segment and calculates the current circulating water flow rate based on the circulation pump frequency. The transport time is used to represent the time required for the heat generated by the upstream heat tracing section to reach the target pipe segment with the circulating water. When the difference between the water temperature at the upstream sampling point and the water temperature of the target pipe segment is not less than the preset heat replenishment temperature difference, the controller determines that the heat replenishment condition is met; when the difference between the remaining time and the transport time is not less than the preset minimum observation time and the heat replenishment condition is met, the heat tracing section located upstream of the target pipe segment is activated first; when the time difference is less than the preset minimum observation time or the heat replenishment condition is not met, the heat tracing section corresponding to the target pipe segment is activated.

[0165] See Figure 7 In this embodiment, step S50 includes:

[0166] Step S51: Calculate the flow rate based on the circulation pump frequency, and calculate the transport time based on the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section.

[0167] Step S52: For the target pipe section with a low temperature risk level of warning, when the difference between the remaining time and the transportation time is not less than the preset minimum observation time and the heating conditions are met, the heat tracing section located upstream of the target pipe section is started first and the observation window is set.

[0168] Step S53: After the observation window ends, the difference between the equivalent safe water temperature at the end of the observation window and the equivalent safe water temperature at the beginning of the observation window is determined as the equivalent safe water temperature recovery range. When the equivalent safe water temperature recovery range is less than the preset recovery range threshold, the heat tracing section corresponding to the target pipe section is activated.

[0169] Step S54: For target pipe sections with a low temperature risk level of warning, if the difference between the remaining time and the transport time is less than the preset minimum observation time or the heat replenishment conditions are not met, the corresponding heat tracing section of the target pipe section is activated; for target pipe sections with a low temperature risk level of high risk, the corresponding heat tracing section of the target pipe section is activated directly; when there is a heat tracing section located upstream of the target pipe section that meets the heat replenishment conditions, the heat tracing section with the shortest transport time to the target pipe section is selected from the heat tracing sections to participate in the heat replenishment.

[0170] In step S51, the transport time can be calculated according to the following formula:

[0171] ;

[0172] in, Let be the transport time from the j-th heat tracing section to the i-th antifreeze control pipe section. Let be the water flow distance from the j-th heat tracing section to the i-th antifreeze control pipe section, and v be the current circulating water flow velocity. The circulating water flow velocity v is determined by the circulating pump frequency and the frequency-flow velocity correspondence calibrated on-site. The supplementary heating temperature difference is set based on the pipe length, heat tracing power, and on-site trial operation data.

[0173] In step S52, when the difference between the remaining time and the transport time is not less than the preset minimum observation time and the heat replenishment conditions are met, the heat generated by the heat tracing section located upstream of the target pipe section is sufficient to arrive and complete the observation verification before the target pipe section reaches the critical antifreeze temperature. The controller outputs a command to start the heat tracing section. The preset minimum observation time is at least one sampling cycle; the observation window starts from the expected arrival time of heat replenishment, lasts for one or more sampling cycles, and the end time of the observation window is not later than the expected time when the target pipe section reaches the critical antifreeze temperature.

[0174] In step S53, the recovery amplitude threshold can be set to 0.3℃ to 0.5℃. At the end of the observation window, the controller recalculates the equivalent safe water temperature of the target pipe section, and the difference between the equivalent safe water temperature at the end of the observation window and the equivalent safe water temperature at the beginning of the observation window is determined as the equivalent safe water temperature recovery amplitude. If the recovery amplitude is not less than the preset recovery amplitude threshold, the controller continues to operate the heat tracing section located upstream of the target pipe section and temporarily does not start the corresponding heat tracing section; if the recovery amplitude is less than the preset recovery amplitude threshold, the controller starts the corresponding heat tracing section of the target pipe section and writes the operating effect of the heat tracing section located upstream of the target pipe section into the historical record.

[0175] In step S54, when the remaining time of the target pipe section is zero, the difference between the remaining time and the transport time is less than the preset minimum observation time, or the equivalent safe water temperature is close to the antifreeze critical temperature and the measured temperature drop rate is less than zero, the controller does not wait for the upstream support observation results and directly starts the heat tracing section corresponding to the target pipe section. For high-risk target pipe sections, the controller selects the heat tracing section with the shortest transport time to the target pipe section from the heat tracing sections located upstream of the target pipe section that meet the heat replenishment conditions and participates in heat replenishment simultaneously. If the heat replenishment conditions are not met, the controller retains the heat tracing section corresponding to the target pipe section as the main control object and suppresses the direct increase of the circulating pump frequency due to the risk of the target pipe section in the subsequent frequency conversion control of the circulating pump.

[0176] For example, the fifth anti-freeze control section is an early warning section, predicting the remaining time. The heat transfer time is 40 minutes. The fourth heat tracing section is located upstream of the target pipe section. If the water temperature at the upstream sampling point is 1.2°C higher than the water temperature of the fifth antifreeze control pipe section, the controller will first activate the fourth heat tracing section and set a 50-minute observation window. If the equivalent safe water temperature of the fifth antifreeze control pipe section rises by more than 0.5°C after the observation window ends, the fifth heat tracing section will not be activated temporarily. If the equivalent safe water temperature at the end of the observation window rises by only 0.1°C or decreases compared to the beginning of the observation window, the controller will activate the fifth heat tracing section.

[0177] S60: Based on the transport time, remaining time, and reheating conditions, select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section, and generate a circulating pump frequency conversion control command and a segmented heat tracing scheduling command.

[0178] In this embodiment, the variable frequency control of the circulating pump and the heat tracing control are executed in concert. Before increasing the frequency of the circulating pump, the controller first determines whether increasing the circulation speed can effectively supplement the heat to the target pipe section. When the target pipe section meets the heat supplementation conditions and the transport time is less than the remaining time, increasing the frequency of the circulating pump can shorten the time for upstream heat to reach the target pipe section, and the controller generates a command to increase the frequency of the circulating pump. When the target pipe section does not meet the heat supplementation conditions or the transport time is not less than the remaining time, the controller maintains the frequency of the circulating pump and increases the heat tracing level of the corresponding heat tracing section of the target pipe section, so that heat is preferentially formed in the target pipe section or near the adjacent heat tracing section.

[0179] In some implementations, after determining the priority to start the heat tracing section located upstream of the target pipe section based on the transport time, remaining time, and heat replenishment conditions, the heat replenishment effect of the upstream heat tracing section is also verified.

[0180] In this embodiment, after selecting to activate at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing section based on the transport time, remaining time, and reheating conditions, the method further includes:

[0181] After activating the heat tracing section located upstream of the target pipe section, the arrival time of the heat replenishment for the target pipe section is determined based on the transport time.

[0182] Within the observation window after the arrival of the heat replenishment, the water temperature recovery range of the target pipe section, the water temperature change at the upstream sampling point of the target pipe section, and the frequency change record of the circulating pump are acquired.

[0183] When the water temperature recovery of the target pipe section reaches the preset recovery threshold, and the water temperature change at the upstream sampling point of the target pipe section and the frequency change record of the circulating pump meet the conditions for heat replenishment and transportation, the operation of the heat tracing section located upstream of the target pipe section is maintained and the start-up priority of the corresponding heat tracing section of the target pipe section is reduced.

[0184] When the water temperature recovery of the target pipe section does not reach the preset recovery threshold, or when the water temperature change at the upstream sampling point of the target pipe section does not meet the consistency condition of heat replenishment and transportation with the circulating pump frequency change record, the heat tracing section located upstream of the target pipe section will be stopped as the priority heat replenishment source for the target pipe section, and the corresponding heat tracing section of the target pipe section will be activated.

[0185] In some implementations, after selecting to start at least one of the heat tracing section located upstream of the target pipe section and the corresponding heat tracing section based on the transport time, remaining time, and heat replenishment conditions, the process further includes a heat replenishment arrival verification step.

[0186] Specifically, after activating the heat tracing section located upstream of the target pipe section, the controller does not directly assume that the upstream heat tracing section has effectively supplemented the heat to the target pipe section. Instead, it determines the arrival time of the supplemented heat to the target pipe section based on the water flow distance from the upstream heat tracing section to the target pipe section and the flow velocity calculated from the circulation pump frequency. The arrival time of the supplemented heat can be the sum of the activation time of the upstream heat tracing section and the transport time.

[0187] After the reheating is completed, the controller sets an observation window and reads the water temperature recovery range of the target pipe section, the water temperature change at the upstream sampling point of the target pipe section, and the frequency change of the circulating pump within the observation window. The observation window can be one or more sampling periods, or it can be set according to the length of the transport time. For example, when the transport time is short, the observation window can be set to one sampling period; when the transport time is long, the observation window can be set to two consecutive sampling periods after the transport time.

[0188] The aforementioned conditions for consistent heat replenishment and transport refer to the following: the water temperature at the upstream sampling point has already shown a temperature increase corresponding to the start of heat tracing; the circulation pump frequency is in a state capable of transporting upstream water to the target pipe section; and the water temperature in the target pipe section shows a recovery trend after the heat replenishment arrives. The controller simultaneously determines whether there is a temporal correspondence between the upstream water temperature change, the circulation pump transport status, and the target pipe section water temperature recovery.

[0189] When the water temperature recovery of the target pipe section reaches the preset recovery threshold, and the water temperature change at the upstream sampling point of the target pipe section and the frequency change record of the circulating pump meet the conditions for heat replenishment and transport, it indicates that the heat generated by the heat tracing section located upstream of the target pipe section can be transported to the target pipe section with the circulating water. The controller maintains the operation of the heat tracing section and reduces the start priority of the heat tracing section corresponding to the target pipe section to reduce unnecessary start-ups of the heat tracing section corresponding to the target pipe section.

[0190] When the water temperature recovery of the target pipe section fails to reach the preset recovery threshold, or when the water temperature change at the upstream sampling point of the target pipe section does not meet the consistency condition for heat replenishment and transport with the circulating pump frequency change record, it indicates that although the heat tracing section located upstream of the target pipe section has been activated, the heat it generates has failed to provide effective heat replenishment before the risk in the target pipe section continues to increase. At this time, the controller stops using the aforementioned heat tracing section as the priority heat source for the target pipe section and activates the corresponding heat tracing section. This avoids the situation where, after selecting the upstream heat tracing section solely based on the theoretical transport time, the target pipe section continues to cool down due to increased local heat dissipation, changes in water flow conditions, or insufficient upstream heat replenishment.

[0191] In this embodiment, step S60 includes:

[0192] Step S61: Obtain the outlet water temperature and return water temperature; when a water supply operation command or a manual forced operation command is issued, generate an operation priority command, stop the safety test and the heat tracing section rotation control, and make the operation priority command override other circulation pump control commands.

[0193] Step S62: When no priority operation command is generated, the low temperature risk level of each antifreeze control pipe section is safe or concerned, the return water temperature is higher than the preset return water temperature, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, a basic frequency command is generated.

[0194] Step S63: When no priority operation instruction is generated, there is no high-risk target pipe section and only one warning target pipe section exists, the warning target pipe section meets the heat replenishment conditions, the transport time is less than the remaining time, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, an intermediate frequency instruction is generated.

[0195] Step S64: When no priority operation instruction is generated and any of the following conditions are met, a high-frequency operation instruction is generated: there is a high-risk target pipe section or multiple warning target pipe sections, and at least one target pipe section meets the heat replenishment conditions; the difference between the outlet water temperature and the return water temperature is not less than the preset circulation temperature difference.

[0196] Step S65: When no priority operation instruction is generated, there is a warning or high-risk target pipe section, each target pipe section does not meet the heat replenishment conditions, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, an instruction to maintain the circulation pump frequency and increase the heat tracing level of the corresponding heat tracing section is generated.

[0197] Step S66: Record the target pipe section water temperature and heat tracing operating current before and after the start-up of the heat tracing section, and calculate the target pipe section water temperature recovery range.

[0198] Step S67: When the water temperature recovery range of the target pipe section is less than the preset temperature rise reference range and the heat tracing working current is lower than the preset current threshold, output a heat tracing electrical abnormality prompt and remove the corresponding heat tracing section from the heat replenishment candidate.

[0199] Step S68: When the water temperature recovery of the target pipe section is less than the preset temperature rise reference range and the heat tracing current is within the preset normal current range, output a heat dissipation abnormality prompt for the target pipe section.

[0200] Step S69: According to the heat tracing section association table, select heat tracing sections that meet the heat replenishment conditions and whose transport time is less than the remaining time from other heat tracing sections located upstream of the target pipe section to participate in heat replenishment.

[0201] Step S610: When the water temperature of the target pipe section is higher than the safe diagnostic threshold, reduce or turn off the output of the heat tracing section corresponding to the target pipe section within the preset diagnostic time, and record the shutdown diagnostic temperature drop rate.

[0202] Step S611: When the shutdown diagnosis temperature drop rate is less than the predicted temperature drop rate, update the comprehensive heat dissipation coefficient based on the difference between the predicted temperature drop rate and the shutdown diagnosis temperature drop rate, and increase the wall temperature safety correction ratio.

[0203] In step S61, the priority command causes the controller to stop actions related to energy saving, antifreeze parameter updates, or rotation control, while maintaining the operation of the circulating pump and necessary heat tracing protection directly related to the normal water supply of the system. If the circulating pump fails and stops operating, the controller switches to static water protection mode and controls the corresponding heat tracing section to operate intermittently or continuously according to the equivalent safe water temperature of each target pipe section.

[0204] In step S62, the base frequency is set to 20Hz. When the return water temperature is higher than the preset return water temperature and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, it indicates that the circulation loop is in a state that can maintain basic circulation. The base frequency command keeps the circulating water flowing at a low frequency and provides stable flow conditions for subsequent temperature acquisition and comprehensive heat dissipation coefficient updates.

[0205] In step S63, the intermediate frequency is set to 30Hz. Before generating the intermediate frequency command, the controller confirms that the target pipe section meets the heat replenishment conditions and that the transport time is less than the remaining time. The intermediate frequency command is used to accelerate the transfer of upstream heat to the target pipe section and to prevent the heat generated by the newly started heat tracing section from being quickly carried away before it has been transferred to the water body due to excessively high circulation pump frequency.

[0206] In step S64, the high-frequency operation is set to 40Hz to 45Hz. When there is a high-risk target pipe section or multiple warning target pipe sections and at least one target pipe section meets the heat replenishment conditions, the controller shortens the heat transport time through high-frequency operation; when the temperature difference between the outlet water and the return water is not less than the preset circulation temperature difference, the controller accelerates the transfer of heat from the outlet side to the return water side through high-frequency operation. The high-frequency operation command is set with a maximum holding time. After the maximum holding time is exceeded, the controller recalculates the low-temperature risk level and remaining time for each target pipe section.

[0207] In step S65, when none of the warning or high-risk target pipe sections meet the heat replenishment conditions, increasing the circulation pump frequency may accelerate the flow of low-temperature water within the system. At this time, the controller maintains the circulation pump's base frequency or current frequency and adjusts the heat tracing section corresponding to the target pipe section from intermittent operation to continuous operation, or adjusts the low duty cycle heat tracing to a higher duty cycle heat tracing. If adjacent heat tracing sections of the target pipe section have a short-distance heat replenishment effect, the controller can also synchronously start the adjacent heat tracing sections.

[0208] During the period when the priority operation command is in effect, the controller suspends safety testing and heat tracing section rotation control, allowing the water supply operation command or manual forced operation command to override other circulation pump control commands; at the same time, the heat tracing protection required to prevent local freezing is retained.

[0209] In step S66, when the heat tracing section starts, the controller records the start-up time, heat tracing section number, target pipe section number, target pipe section water temperature, target pipe section ambient temperature, circulation pump frequency, and heat tracing operating current. After a preset response time, the controller reads the target pipe section water temperature again and determines the difference between the two water temperatures as the target pipe section water temperature recovery range. The preset response time can be set to 30 minutes.

[0210] In step S67, the preset current threshold can be set to 80% of the nominal operating current. When the heat tracing operating current is lower than the preset current threshold and the water temperature recovery of the target pipe section is less than the preset temperature rise reference range, the controller outputs a heat tracing electrical abnormality prompt, marks the corresponding heat tracing section as an object to be inspected, and removes it from the heat replenishment candidates.

[0211] In step S68, the preset temperature rise reference range can be determined based on the ambient temperature range, the circulation pump frequency setting, the initial water temperature range, and the historical normal operation data corresponding to the heat tracing section number. When the heat tracing operating current is within the preset normal current range but the water temperature recovery range of the target pipe section is less than the preset temperature rise reference range, the controller outputs a heat dissipation abnormality warning for the target pipe section, and combines the comprehensive heat dissipation coefficient, ambient temperature changes, return water temperature changes, and water replenishment status to determine possible causes such as insulation layer failure, local cold air intrusion, abnormal heat dissipation, or pipe leakage.

[0212] In step S69, the controller searches for other effective heat tracing sections upstream of the target pipe section based on the association table between the antifreeze control pipe section and the heat tracing section, and selects heat tracing sections that meet the heat replenishment conditions and whose transport time is less than the remaining time to participate in heat replenishment. When there are multiple selectable heat tracing sections, the start-up order is determined according to the cumulative running time. When there is no alternative heat tracing section that meets the conditions, the controller maintains the necessary operation of the circulating pump and the output of the remaining effective heat tracing sections, while generating an alarm that requires timely maintenance.

[0213] In step S610, the controller performs a shutdown diagnosis only when the target pipe section water temperature is higher than the safety diagnostic threshold and the remaining time is greater than the diagnostic protection time. The preset diagnosis duration can be set to 10 minutes to 20 minutes. At the start of the diagnosis, the controller reduces or shuts down the output of the heat tracing section corresponding to the target pipe section and records the target pipe section water temperature. At the end of the diagnosis, the controller records the target pipe section water temperature again and calculates the shutdown diagnosis temperature drop rate.

[0214] In step S611, when the shutdown diagnostic temperature drop rate is less than the predicted temperature drop rate, it indicates that the actual water temperature drop rate of the target pipe section is faster than the water temperature drop rate predicted based on the current comprehensive heat dissipation coefficient. The controller updates the comprehensive heat dissipation coefficient based on the difference between the predicted temperature drop rate and the shutdown diagnostic temperature drop rate, and increases the wall temperature safety correction ratio, so that the equivalent safe water temperature and remaining time calculation for the next operating cycle improve the responsiveness to heat dissipation anomalies.

[0215] In step S611, the overall heat dissipation coefficient can be updated using a weighted average of old and new data:

[0216] ;

[0217] in, For the updated overall heat dissipation coefficient, The historical comprehensive heat dissipation coefficient, This represents the overall thermal efficiency obtained from this safety test or diagnostic. 0.8 and 0.2 are exemplary weights; when the test window is long, the environment is stable, and the data is reliable, the coefficients should be increased. The weight should be reduced when the test window is short or the environment fluctuates greatly. The weighting of the updated overall thermal coefficient is used in the calculation of the equivalent safe water temperature, predicted temperature drop rate, and remaining time for the next operating cycle. When the shutdown diagnostic temperature drop rate is less than the predicted temperature drop rate, the controller increases the wall temperature safety correction ratio based on the difference between the predicted temperature drop rate and the shutdown diagnostic temperature drop rate.

[0218] In this embodiment, step S60 may further include the following short-time shutdown diagnostic processing:

[0219] Step S612: When the water temperature of the target pipe section is higher than the safety diagnostic threshold, briefly reduce or shut down the output of the heat tracing section corresponding to the target pipe section and record the shutdown diagnostic temperature drop rate.

[0220] Step S613: Compare the shutdown diagnostic temperature drop rate with the predicted temperature drop rate obtained according to the comprehensive heat dissipation coefficient of the target pipe section.

[0221] Step S614: When the decrease in the temperature drop rate diagnosed by the shutdown is greater than the decrease in the predicted temperature drop rate and the heating current is within the preset normal current range, output a warning of insulation layer failure or local cold air intrusion; when the decrease in the temperature drop rate diagnosed by the shutdown is greater than the decrease in the predicted temperature drop rate and abnormal water supply, abnormal pressure, or sudden drop in return water temperature occurs simultaneously, output a warning of pipeline leakage.

[0222] In step S612, the controller performs a short-term shutdown diagnosis only when the equivalent safe water temperature of the target pipe section is higher than the safe diagnostic threshold and the remaining time is greater than the diagnostic protection time. The short-term shutdown time can be set from 10 min to 20 min. The controller records the target pipe section water temperature before shutdown, records the target pipe section water temperature again at the end of shutdown, and calculates the shutdown diagnostic temperature drop rate.

[0223] In step S613, if the decrease in the temperature drop rate diagnosed by the shutdown is greater than the decrease in the predicted temperature drop rate, it indicates that the actual heat dissipation rate of the target pipe section exceeds the heat dissipation rate predicted by the historical comprehensive heat dissipation coefficient and the current internal and external temperature difference. The controller writes the comparison result into the anomaly identification input and uses it to distinguish between insulation layer failure, cold air intrusion, or pipe leakage.

[0224] In step S614, a normal operating current for the heat tracing cable indicates that the power supply and energization status of the heat tracing cable are suitable for heating; insufficient temperature rise is more likely due to deterioration of the pipe section's heat dissipation conditions. If abnormal water supply, abnormal pressure, or a sudden drop in return water temperature occur simultaneously, the controller will record a pipe leakage warning in the maintenance inspection record. After the short-term shutdown diagnosis is completed, the controller will restore the output of the heat tracing section corresponding to the target pipe section according to the current risk level.

[0225] For example, after 30 minutes of operation, the historical normal temperature rise of the fifth heating section should be 0.6℃ to 1.0℃, but this time it only rose by 0.1℃. The controller read the operating current of the fifth heating section and found that the current was 95% of the nominal operating current, indicating that the heating cable was basically powered normally. At this time, the controller did not directly determine that the heating cable was faulty, but instead indicated that there was a risk of insulation failure or abnormal heat dissipation in the fifth antifreeze control section. Subsequently, while the water temperature was still higher than the safety diagnostic threshold, the controller performed a short-term shutdown diagnosis. If the rate of temperature drop after shutdown was significantly greater than the expected rate, the controller would then take action. The magnitude of the predicted temperature drop rate further confirms that there is an abnormal heat dissipation in the target pipe section.

[0226] In this embodiment, intermediate result recording and operation verification interfaces can also be set. The controller can cache the target pipe segment number, target pipe segment water temperature, target pipe segment ambient temperature, comprehensive heat dissipation coefficient, equivalent safe water temperature, calculated temperature drop rate with remaining time, remaining time, transport time, heat replenishment condition judgment result, heat tracing section number, circulating pump frequency command, and anomaly identification result in each sampling cycle. The cached records can be stored in the controller's local storage area or uploaded to the operation and maintenance platform for verifying the formation process of segmented heat tracing scheduling commands and circulating pump frequency conversion control commands. These records do not change the data stream from S10 to S60 and are only used for operation status verification and operation and maintenance checks.

[0227] In some implementations, the generation of the circulating pump frequency control command further includes a cryogenic diffusion risk suppression step.

[0228] The generated circulating pump frequency conversion control command includes:

[0229] When there is a target pipe section with a low temperature risk level of warning or high risk, read the water temperature at the upstream sampling point of the target pipe section, the water temperature at the downstream sampling point of the target pipe section, and the low temperature risk level of the adjacent antifreeze control pipe section.

[0230] When the target pipe section does not meet the heat replenishment conditions, and there is an adjacent antifreeze control pipe section downstream of the target pipe section with a low temperature risk level of warning or high risk, a circulation pump frequency increase suppression command is generated, and the heat tracing level of the heat tracing section corresponding to the target pipe section or the heat tracing section adjacent to the target pipe section is increased.

[0231] When the target pipe section meets the heat replenishment conditions and the transport time is less than the remaining time, the frequency increase suppression command of the circulating pump is released, and an intermediate frequency command or a high frequency operation command is generated according to the low temperature risk level of the target pipe section.

[0232] When the duration of the frequency increase suppression command of the circulating pump reaches the preset suppression time, the remaining time, transport time and heat replenishment conditions of the target pipe section are recalculated, and the frequency conversion control command of the circulating pump and the segmented heat tracing scheduling command are updated according to the recalculation results.

[0233] In some implementations, the generation of the circulating pump frequency control command includes a cryogenic diffusion risk suppression step.

[0234] Specifically, when there is a target pipe section with a low-temperature risk level of warning or high risk, the controller reads the water temperature at the upstream sampling point of the target pipe section, the water temperature at the downstream sampling point of the target pipe section, and the low-temperature risk level of the adjacent antifreeze control pipe section. Based on the above data, the controller determines whether increasing the circulation pump frequency will quickly transport the low-temperature water to the downstream risk pipe section, or whether it can effectively transport the higher-temperature water from the upstream to the target pipe section.

[0235] When the target pipe section does not meet the heating conditions, it indicates that the upstream water body does not yet have effective heating capacity. If there is an adjacent antifreeze control pipe section downstream of the target pipe section with a low temperature risk level of warning or high risk, increasing the circulation pump frequency may cause the low-temperature water near the target pipe section to flow downstream more quickly, increasing the temperature drop pressure of the downstream risk pipe section. Therefore, the controller generates a circulation pump frequency increase suppression command to maintain the circulation pump's base frequency or current frequency, and increases the heating level of the corresponding heating section of the target pipe section or the adjacent heating section of the target pipe section, so that the target pipe section can first restore the water temperature through local heating.

[0236] When the target pipe section meets the heat replenishment conditions and the transport time from the heat tracing section upstream of the target pipe section to the target pipe section is less than the remaining time for the target pipe section to reach the antifreeze critical temperature, it indicates that the upstream heat has transport accessibility. The controller releases the frequency increase suppression command of the circulating pump and generates an intermediate frequency command or a high frequency operation command according to the low temperature risk level of the target pipe section to accelerate the transport of higher temperature water from upstream to the target pipe section.

[0237] When the duration of the circulating pump frequency increase suppression command reaches the preset suppression time, the controller recalculates the remaining time, transport time, and heat replenishment conditions of the target pipe section, and updates the circulating pump frequency conversion control command and segmented heat tracing scheduling command based on the recalculation results. If the water temperature of the target pipe section recovers and the risk of the downstream adjacent pipe section decreases, the frequency increase suppression is lifted; if the target pipe section continues to cool, the heat tracing level of the target pipe section is further increased or the adjacent heat tracing section is activated to participate in heat replenishment.

[0238] In this way, the variable frequency control of the circulating pump simultaneously considers the upstream heating capacity and the downstream low-temperature diffusion risk. When the upstream water temperature is insufficient, the frequency of the circulating pump is suppressed to reduce the diffusion of low-temperature water; when the upstream water temperature has heating capacity, the frequency of the circulating pump is increased to improve heat transport efficiency.

[0239] The first embodiment will be described in detail with specific examples.

[0240] In one example, the circulating water pipeline in a cold-region tunnel is arranged with eight heat tracing sections along the water flow direction. The controller reads the water temperature and ambient temperature at each sampling point with a sampling period of 10 minutes. In step S10, the controller divides the pipeline between adjacent temperature sampling points into multiple anti-freezing control sections and establishes an association table between the anti-freezing control sections and the heat tracing sections. The fifth anti-freezing control section is close to the tunnel entrance on the shady slope, with a starting water temperature of 6.0℃ and an ending water temperature of 5.2℃. The controller uses 5.2℃ as the risk assessment water temperature for the fifth anti-freezing control section. The fourth heat tracing section is located upstream of the fifth anti-freezing control section, and the association table records that the water flow distance from the fourth heat tracing section to the center of the fifth anti-freezing control section is 120m.

[0241] In step S30, the controller shuts down the heat tracing section corresponding to the 5th antifreeze control pipe section within the safety test window. No manual forced operation command or water supply operation command is received within the safety test window, and no sensor fault alarm is received. The circulating pump runs continuously at the preset base frequency. The water temperature in the 5th antifreeze control pipe section drops from 7.4℃ to 7.1℃ within 30 minutes, with a temperature drop rate of [missing information]. During this period, the average ambient temperature of the fifth antifreeze control section was -8℃, and the difference between the target section water temperature and the target section ambient temperature was approximately 15.2℃. The controller operates according to... The calculated overall heat dissipation coefficient of the 5th antifreeze control pipe section is approximately .

[0242] In step S40, the controller selects the wall temperature safety correction ratio based on the location attributes of the 5th antifreeze control pipe section near the entrance of the shady slope and the overall heat dissipation coefficient. The value is 0.05. Current water temperature of the 5th antifreeze control section. The ambient temperature was 5.2℃. The effective safe water temperature is -10℃, and the equivalent safe water temperature is 5.2 - 0.05 × [5.2 - (-10)] = 4.44℃. The critical temperature for freezing is set to 4℃. The current measured temperature drop rate is -0.3℃ / h, and the predicted temperature drop rate is -0.039 × [5.2 - (-10)], approximately -0.59℃ / h. The controller uses -0.59℃ / h as the remaining time to calculate the temperature drop rate and calculates the remaining time as [4.44 - 4] / 0.59, approximately 0.75h. The controller designates the 5th freezing control section as the warning section.

[0243] In step S50, the controller reads the water flow distance of 120m from the 4th heating section to the 5th antifreeze control pipe section and determines the current flow rate based on the circulation pump frequency and the frequency-flow rate calibration relationship. At 30Hz, the circulating water flow rate is 3m / min, and the transport time for the heat generated in the 4th heating section to reach the 5th antifreeze control pipe section is 40min. The water temperature at the upstream sampling point of the 5th antifreeze control pipe section is 6.4℃, and the water temperature in the 5th antifreeze control pipe section is 5.2℃, with a temperature difference of 1.2℃, which is not less than the preset heat replenishment temperature difference. The remaining time is approximately 0.75h, and the difference between the remaining time and the transport time is approximately 5min, which is less than the preset minimum observation time corresponding to a 10min sampling cycle. Therefore, the controller does not wait for the upstream heat replenishment observation results and directly starts the heating section corresponding to the 5th antifreeze control pipe section, while simultaneously starting the 4th heating section to participate in heat replenishment.

[0244] In step S60, after activating the 5th and 4th heat tracing sections, the controller confirms that the 5th antifreeze control section meets the heat replenishment conditions, there are currently no multiple warning target sections or high-risk target sections, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference. It then generates a control command to adjust the circulation pump from the base frequency to the intermediate frequency. In subsequent sampling cycles, the controller recalculates the equivalent safe water temperature and remaining time for the 5th antifreeze control section. When the equivalent safe water temperature recovery amplitude is not less than the preset recovery amplitude threshold, the current heat tracing and circulation pump control status is maintained; when the equivalent safe water temperature recovery amplitude is less than the preset recovery amplitude threshold, the heat tracing level of the 5th heat tracing section is increased.

[0245] like Figure 8 As shown, the second embodiment of the present invention proposes a segmented temperature antifreeze control system for circulating water pipelines in cold-region tunnels. The system includes a pipeline segmentation and association module, a target data acquisition module, a heat dissipation coefficient calculation module, a risk time calculation module, a transport condition calculation module, and a collaborative control module.

[0246] The pipe segment division and association module is used to divide the pipeline between adjacent temperature acquisition points into antifreeze control pipe segments along the water flow direction, determine the upstream and downstream sides of the pipe segments, and establish an association table between the pipe segments and the heat tracing sections.

[0247] The target data acquisition module is used to select the target pipe section and acquire the target pipe section's water temperature, ambient temperature, upstream sampling point water temperature, and circulation pump frequency.

[0248] The heat dissipation coefficient calculation module is used to close the heat tracing section corresponding to the target pipe section within the safety test window, calculate the measured temperature drop rate based on the water temperature change of the target pipe section, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature and the ambient temperature.

[0249] The risk time calculation module is used to calculate the equivalent safe water temperature and the predicted temperature drop rate based on the comprehensive heat dissipation coefficient. It selects the water temperature drop rate that drops faster from the measured temperature drop rate and the predicted temperature drop rate, and calculates the remaining time for the target pipe section to reach the antifreeze critical temperature.

[0250] The transport condition calculation module is used to calculate the transport time based on the circulation pump frequency and the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section, and to determine the heat replenishment conditions based on the difference between the water temperature at the upstream sampling point and the water temperature of the target pipe section.

[0251] The collaborative control module is used to select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section based on the transport time, remaining time, and heat replenishment conditions, and to generate frequency conversion control commands for the circulating pump and segmented heat tracing scheduling commands.

[0252] In this embodiment, the pipe segment division and association module receives the location of temperature acquisition points, the layout location of the heat tracing sections, and the direction of circulating water flow, and outputs the antifreeze control pipe segment, the upstream and downstream sides of each pipe segment, and the association table between the pipe segment and the heat tracing section. The target data acquisition module receives temperature acquisition point data, ambient temperature data, and circulating pump operation data, and outputs the target pipe segment water temperature, ambient temperature, upstream acquisition point water temperature, and circulating pump frequency. The heat dissipation coefficient calculation module outputs the comprehensive heat dissipation coefficient based on the target pipe segment water temperature change and the difference between the water temperature and the ambient temperature. The risk time calculation module outputs the equivalent safe water temperature, predicted temperature drop rate, low temperature risk level, and remaining time. The transport condition calculation module outputs the transport time and the result of the heat replenishment condition judgment. The collaborative control module outputs the heat tracing section start-up result, the circulating pump frequency conversion control command, and the segmented heat tracing scheduling command based on the above results.

[0253] In some implementations, the collaborative control module is also used to determine whether the upstream heat tracing section has formed effective heat replenishment after starting the heat tracing section located upstream of the target pipe section, based on the arrival time of heat replenishment, the recovery range of the target pipe section water temperature, the change in water temperature at the upstream sampling point of the target pipe section, and the change in the frequency of the circulating pump; and to generate a circulating pump frequency increase suppression command when the water temperature at the upstream sampling point of the target pipe section does not meet the heat replenishment conditions and there is a low-temperature risk pipe section downstream.

[0254] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0255] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only the elements expressly listed, but also elements not expressly listed or inherent to such processes, methods, articles, or apparatus / devices.

[0256] The technical solution of the present invention has been described in conjunction with the embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions resulting from such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for segmented temperature antifreeze control of circulating water pipelines in cold-region tunnels, characterized in that, include: The pipeline between adjacent temperature acquisition points is divided into antifreeze control sections along the water flow direction. The upstream and downstream sides of the pipe sections are determined, and a correlation table between the pipe sections and the heat tracing sections is established. Select the target pipe section and obtain the water temperature, ambient temperature, upstream sampling point water temperature, and circulation pump frequency of the target pipe section; Within the safety test window, close the heat tracing section corresponding to the target pipe section, calculate the measured temperature drop rate based on the water temperature change of the target pipe section, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature and the ambient temperature. The equivalent safe water temperature and the predicted temperature drop rate are calculated based on the comprehensive heat dissipation coefficient. The water temperature drops faster from the measured temperature drop rate and the predicted temperature drop rate. The remaining time for the target pipe section to reach the antifreeze critical temperature is then calculated. The transport time is calculated based on the frequency of the circulating pump and the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section, and the heat replenishment conditions are determined based on the difference between the water temperature at the upstream sampling point and the water temperature in the target pipe section. Based on the transport time, remaining time, and reheating conditions, select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section, and generate a circulating pump frequency conversion control command and a segmented heat tracing scheduling command.

2. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 1, characterized in that, The establishment of the association table between the antifreeze control pipe section and the heat tracing section includes: Based on the location of adjacent temperature acquisition points, the layout of the heat tracing section, and the direction of circulating water flow, determine the starting point, ending point, length, upstream and downstream pipe sections, and calculate the water flow distance from the heat tracing section to the corresponding antifreeze control pipe section. Write one heat tracing section covering the range of the antifreeze control pipe section into the heat tracing section field corresponding to the antifreeze control pipe section, or write multiple consecutive heat tracing sections covering the range of the antifreeze control pipe section into the heat tracing section field corresponding to the antifreeze control pipe section. The heat tracing section located upstream of the antifreeze control pipe section along the direction of circulating water flow and connected to the waterway of the antifreeze control pipe section is written into the upstream support item of the antifreeze control pipe section.

3. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 1, characterized in that, The target pipe section water temperature is determined in the following way: The lower of the starting and ending water temperatures of the antifreeze control pipe section is determined as the target pipe section water temperature; when the antifreeze control pipe section is close to a preset high heat dissipation position, the water temperature of the sampling point on the side close to the preset high heat dissipation position is determined as the target pipe section water temperature, and the preset high heat dissipation position includes at least one of the following: the entrance of the shady slope, the entrance door, the vent, and the end of the return water. If the temperature at the sampling point exceeds the preset temperature range, or if the temperature change at the sampling point in multiple consecutive sampling cycles is greater than the temperature change at the upstream and downstream sampling points in the corresponding sampling cycles when the heating status, circulation pump frequency, and water supply operation status remain unchanged, the abnormal sampling point will be removed from the risk assessment input. A substitute water temperature will be formed based on the water temperature at the normal upstream and downstream sampling points and the historical water temperature change trend, and the substitute water temperature will be determined as the target pipe section water temperature.

4. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 1, characterized in that, The calculation of the overall heat dissipation coefficient includes: The safety test window is the time period that simultaneously meets the requirements of system standby state, sensor effective state, water temperature safe state, circulating pump stable operation state, and ambient temperature stable state. The system standby state is when no manual forced operation command or water supply operation command is received; the sensor effective state is when no sensor fault alarm is received; the water temperature safety state is when the water temperature of each antifreeze control pipe section is higher than the safety test threshold; the circulation pump stable operation state is when the circulation pump runs continuously at a preset base frequency; and the ambient temperature stable state is when the change in ambient temperature of the target pipe section does not exceed the preset temperature change threshold within the preset test duration. Within the safety test window, the heat tracing section corresponding to the target pipe section is closed, and the measured temperature drop rate of the target pipe section under the condition of no heat tracing input is recorded. The measured temperature drop rate is the change in water temperature of the target pipe section per unit time, and a negative value indicates that the water temperature of the target pipe section has decreased. When the water temperature of the target pipe section is higher than the ambient temperature of the target pipe section and the measured temperature drop rate is less than zero, the ratio of the absolute value of the measured temperature drop rate to the difference between the water temperature and the ambient temperature of the target pipe section is determined as the comprehensive heat dissipation coefficient of the target pipe section.

5. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 1, characterized in that, The process of correcting the target pipe section water temperature based on the comprehensive heat dissipation coefficient to obtain the equivalent safe water temperature includes: Based on the range of the comprehensive heat dissipation coefficient of the target pipe section, the pre-stored insulation layer status of the target pipe section, and the location attributes of the target pipe section near the shady slope opening, doorway, air outlet, or return water end, match the wall temperature safety correction ratio. The wall temperature correction amount is generated based on the correction relationship between the target pipe section water temperature, the target pipe section ambient temperature, and the wall temperature safety correction ratio. The target pipe section water temperature is adjusted by subtracting the wall temperature correction amount to obtain the equivalent safe water temperature. The low-temperature risk level is determined based on the comparison results between the equivalent safe water temperature and the preset safe temperature, preset warning temperature, and antifreeze critical temperature, as well as the measured temperature drop rate. Specifically, the preset safe temperature is higher than the preset warning temperature, and the preset warning temperature is higher than the antifreeze critical temperature. When the equivalent safe water temperature is higher than the preset safe temperature and the measured temperature drop rate is not less than zero, it is considered safe. When the equivalent safe water temperature is higher than the preset warning temperature but does not meet the safety conditions, it is considered a concern. When the equivalent safe water temperature is higher than the antifreeze critical temperature but not higher than the preset warning temperature, it is considered a warning. When the equivalent safe water temperature is not higher than the antifreeze critical temperature, it is considered a high-risk level.

6. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 1, characterized in that, The calculation of the predicted temperature drop rate and remaining time includes: The predicted temperature drop rate is generated based on the comprehensive heat dissipation coefficient and the difference between the target pipe section water temperature and the target pipe section ambient temperature. When at least one of the predicted temperature drop rate and the measured temperature drop rate is less than zero, the negative temperature drop rate with the smaller value is selected from the predicted temperature drop rate and the measured temperature drop rate as the remaining time to calculate the temperature drop rate. When the equivalent safe water temperature is greater than the critical antifreeze temperature and the calculated temperature drop rate for the remaining time is less than zero, the difference between the equivalent safe water temperature and the critical antifreeze temperature is divided by the absolute value of the calculated temperature drop rate for the remaining time to obtain the remaining time. When the equivalent safe water temperature is not greater than the critical antifreeze temperature, the remaining time is set to zero.

7. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 5, characterized in that, The selection and activation of at least one of the heat tracing section located upstream of the target pipe section and the corresponding heat tracing section of the target pipe section includes: For target pipe sections with a low temperature risk level of warning, when the difference between the remaining time and the transportation time is not less than the preset minimum observation time and the heating conditions are met, the heat tracing section located upstream of the target pipe section is activated first and an observation window is set. After the observation window ends, the difference between the equivalent safe water temperature at the end of the observation window and the equivalent safe water temperature at the beginning of the observation window is determined as the equivalent safe water temperature recovery range. When the equivalent safe water temperature recovery range is less than the preset recovery range threshold, the heat tracing section corresponding to the target pipe section is activated. For target pipe sections with a low temperature risk level of warning, when the difference between the remaining time and the transportation time is less than the preset minimum observation time or the heating conditions are not met, the corresponding heat tracing section of the target pipe section will be activated. For target pipe sections with a high-risk low-temperature risk level, the corresponding heat tracing section is directly activated; when there is a heat tracing section located upstream of the target pipe section that meets the heat replenishment conditions, the heat tracing section with the shortest transport time to the target pipe section is selected from the heat tracing sections to participate in the heat replenishment.

8. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 5, characterized in that, The generation of the circulating pump frequency conversion control command and the segmented heat tracing scheduling command includes: Obtain the outlet water temperature and return water temperature; when a water supply operation command or a manual forced operation command is issued, generate an operation priority command, stop the safety test and the heat tracing section rotation control, and make the operation priority command override other circulation pump control commands; When no priority operation command is generated, the low temperature risk level of each antifreeze control pipe section is safe or concerned, the return water temperature is higher than the preset return water temperature, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, the basic frequency command is generated. When no priority operation instruction is generated, there is no high-risk target pipe section and only one warning target pipe section exists, the warning target pipe section meets the heat replenishment conditions, the transport time is less than the remaining time, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, an intermediate frequency instruction is generated. A high-frequency operation command is generated when no priority operation command is generated and any of the following conditions are met: there is a high-risk target pipe section or multiple warning target pipe sections, and at least one target pipe section meets the heat replenishment conditions; the difference between the outlet water temperature and the return water temperature is not less than the preset circulation temperature difference. When no priority operation command is generated, there is a warning or high-risk target pipe section, none of the target pipe sections meet the heat replenishment conditions, and the difference between the outlet water temperature and the return water temperature is less than the preset circulation temperature difference, a command is generated to maintain the circulation pump frequency and increase the heat tracing level of the corresponding heat tracing section.

9. The method for segmented temperature antifreeze control of circulating water pipeline in cold-region tunnels according to claim 5, characterized in that, After generating the circulating pump frequency conversion control command and the segmented heat tracing scheduling command, the following is also included: Record the target pipe section water temperature and heat tracing current before and after the start-up of the heat tracing section, and calculate the water temperature recovery range. When the water temperature recovery range is less than the preset temperature rise reference range, if the heat tracing working current is lower than the preset current threshold, a heat tracing electrical abnormality prompt will be output and the corresponding heat tracing section will be removed from the heat replenishment candidate; if the heat tracing working current is within the preset normal current range, a target pipe section heat dissipation abnormality prompt will be output. According to the heat tracing section association table, select the heat tracing section that meets the heat replenishment conditions and has a transport time less than the remaining time from other heat tracing sections located upstream of the target pipe section to participate in heat replenishment; When the water temperature of the target pipe section is higher than the safety diagnostic threshold, reduce or shut down the output of the corresponding heat tracing section of the target pipe section and record the shutdown diagnostic temperature drop rate; when the shutdown diagnostic temperature drop rate is less than the predicted temperature drop rate, update the comprehensive heat dissipation coefficient according to the difference between the predicted temperature drop rate and the shutdown diagnostic temperature drop rate, and increase the wall temperature safety correction ratio.

10. A segmented temperature antifreeze control system for circulating water pipelines in cold-region tunnels, characterized in that, include: The pipe segment division and association module is used to divide the pipeline between adjacent temperature acquisition points into antifreeze control pipe segments along the water flow direction, determine the upstream and downstream sides of the pipe segments, and establish an association table between the pipe segments and the heat tracing sections. The target data acquisition module is used to select the target pipe section and acquire the target pipe section's water temperature, ambient temperature, upstream sampling point water temperature, and circulating pump frequency. The heat dissipation coefficient calculation module is used to close the heat tracing section corresponding to the target pipe section within the safety test window, calculate the measured temperature drop rate based on the water temperature change of the target pipe section, and calculate the comprehensive heat dissipation coefficient based on the measured temperature drop rate and the difference between the water temperature and the ambient temperature. The risk time calculation module is used to calculate the equivalent safe water temperature and the predicted temperature drop rate based on the comprehensive heat dissipation coefficient. It selects the water temperature drop rate that drops faster from the measured temperature drop rate and the predicted temperature drop rate, and calculates the remaining time for the target pipe section to reach the antifreeze critical temperature. The transport condition calculation module is used to calculate the transport time based on the circulation pump frequency and the water flow distance from the heat tracing section located upstream of the target pipe section to the target pipe section, and to determine the heat replenishment conditions based on the difference between the water temperature at the upstream sampling point and the water temperature of the target pipe section. The collaborative control module is used to select and start at least one of the heat tracing sections located upstream of the target pipe section and the corresponding heat tracing sections of the target pipe section based on the transport time, remaining time, and heat replenishment conditions, and to generate frequency conversion control commands for the circulating pump and segmented heat tracing scheduling commands.

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