Thermal cycle experiment system and method for stagnation pipeline

Abstract

The invention discloses a stagnation pipeline thermal cycle experiment system and method, and the system comprises a heating pipeline (3a) and an experiment pipeline (3b) which are connected in parallel, and the experiment pipeline (3b) comprises a main pipe (1) and a branch pipe (2); the branch pipe (2) comprises a first pipe section, a second pipe section and a third pipe section, the branch pipe (2) is connected to the main pipe (1) through the first pipe section, the first pipe section is connected to one end of the second pipe section, and the third pipe section is connected to the other end of the second pipe section; the pipe diameter D1 of the main pipe (1) is greater than the pipe diameter D2 of the branch pipe (2); the experimental method comprises the following steps: adjusting the water temperature and pressure of experimental water in the system to target values through the heating pipeline (3a); the experimental water is controlled to flow into the main pipe (1) and the branch pipe (2), and the experimental parameters under different conditions can be obtained through rapid adjustment by the simple and convenient experimental system, so that the thermal cycle experimental system for the stagnation pipeline has higher adaptability and practicability.

Description

Technical Field

[0001] The invention relates to the field of nuclear power pipeline thermal cycle experiments, and in particular to a stagnant pipeline thermal cycle experiment system and method. Background Art

[0002] During the operation of a nuclear power plant, the heat generated by the reactor needs to be transmitted through a piping system. The movement of fluids in these pipes may become very complicated due to the special structure of the pipes, such as the thermal cycle phenomenon induced by turbulent penetration in the downward horizontal stagnation branch pipe. This phenomenon is characterized by a thermal fluctuation state of reciprocating motion of the cold and hot interface. After this temperature fluctuation is transmitted to the pipe wall, it will form a periodic enhancement and weakening of the thermal stratification phenomenon, and then generate local fatigue loads at key locations of the pipe, aggravating the initiation of pipe cracks, shortening the life of key pipes, and posing a potential threat to the safety of nuclear power facility operation. Since the thermal cycle phenomenon is a dynamic feature and is difficult to monitor directly in engineering, it is necessary to carry out targeted experiments during the research process to measure the influence of parameters such as mainstream velocity, mainstream temperature, and main-branch pipe diameter ratio on the thermal cycle phenomenon.

[0003] At present, there are relevant measures for the experiment of thermal stratification phenomenon of wave tubes. However, there is a lack of flexibility in adjusting parameters such as pipe diameter ratio, temperature difference, flow rate, etc., and there is less strain data collection. Secondly, the existing heat dissipation devices often cannot effectively consider the complex heat dissipation of thermal cycles. When the pipeline is subjected to thermal cycle experiments, there is no more comprehensive monitoring system or method for the temperature and deformation state of the pipeline to accurately obtain the pipeline condition data during the experiment. At present, digital image correlation (DIC) technology is mainly used for pipeline deformation detection. There are the following problems, including that DIC technology has certain requirements for ambient light and surface texture. In outdoor or unsatisfactory lighting conditions, additional lighting equipment may be required to ensure image quality; DIC technology requires good texture features on the surface of the object to be measured so as to track feature points in the image. For pipelines with smooth surfaces or unclear textures, additional surface treatment may be required, such as spraying random speckles, to improve measurement accuracy; DIC technology mainly uses a single camera and can only measure two-dimensional deformation data, but cannot measure three-dimensional deformation.

[0004] Patent document CN116066654B discloses a pipeline system for eliminating thermal fatigue of nuclear power pipelines, including a main pipeline and a branch pipeline connected to the main pipeline, wherein the branch pipeline includes a vertical pipe section and a horizontal pipe section, wherein the vertical pipe section is connected to the main pipeline, and the horizontal pipe section is connected to an end of the vertical pipe section away from the main pipeline, wherein the horizontal pipe section has a sensitive area. An axial heat transfer system for alleviating thermal stratification effect of nuclear power plant pipelines includes: a heat pipe device, which is axially extended along the lower outer wall surface of the main pipeline and the branch pipeline, and is used to transport heat to the sensitive area to eliminate or alleviate the thermal stratification effect; a temperature measuring device, which is arranged on the periphery of the horizontal pipe section located in the sensitive area, and is used to detect the temperature of the sensitive area. The pipeline system for eliminating thermal fatigue of nuclear power pipelines is used to reduce the occurrence of thermal stratification, thermal cycling and thermal shock of nuclear power plant pipelines, and can reduce the probability of pipeline fatigue. However, the problem of monitoring in combination with pipeline temperature, deformation state and strain in current pipeline thermal fatigue tests is not solved.

[0005] In the patent document CN116221525A, an axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines is disclosed, including a main pipeline and a branch pipeline connected to the main pipeline, the branch pipeline including a vertical pipe section and a transverse pipe section, the vertical pipe section is connected to the main pipeline, the transverse pipe section is connected to an end of the vertical pipe section away from the main pipeline, the transverse pipe section has a sensitive area, and the axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines includes a heat pipe device, the heat pipe device is axially extended along the lower outer wall surface of the main pipeline and the branch pipeline, and is used to transport heat to the sensitive area to eliminate or alleviate the thermal stratification effect; the probability of pipeline fatigue occurrence can be reduced and the availability of nuclear power units can be improved, but the problem of monitoring in combination with pipeline temperature, deformation state and strain in the current pipeline thermal fatigue test is not solved.

[0006] In summary, the above two existing patents do not solve the problem of monitoring the pipeline temperature, deformation state and strain in the current pipeline thermal fatigue test. Summary of the invention

[0007] Based on the above technical problems, the present invention proposes a stagnant pipeline thermal cycle test system and method to solve the problem of monitoring the pipeline temperature, deformation state and strain in the current pipeline thermal fatigue test.

[0008] To achieve the above object, the present invention proposes a stagnant pipeline thermal cycle experimental system.

[0009] A stagnant pipeline thermal cycle experimental system comprises a heating pipeline and an experimental pipeline, wherein the heating pipeline and the experimental pipeline are arranged in parallel, and the experimental pipeline comprises a main pipe and a branch pipe;

[0010] The branch pipe includes a first pipe section, a second pipe section and a third pipe section, the branch pipe is connected to the main pipe through the first pipe section, the first pipe section is connected to one end of the second pipe section, and the third pipe section is connected to the other end of the second pipe section;

[0011] The pipe diameter D of the main pipe 1 Greater than the diameter D of the branch pipe 2 .

[0012] Furthermore, the diameter-reducing section is provided at both ends of the main pipe, and the distance between the outlet of the diameter-reducing section at the inflow end of the main pipe and the center position of the contact surface between the branch pipe and the main pipe is 10D. 1 -20D 1 The distance between the inlet of the reducing section at the outflow end of the main pipe and the center of the contact surface between the branch pipe and the main pipe is 5D 1 -10D 1 .

[0013] Furthermore, the first pipe section is connected perpendicularly to the main pipe, the second pipe section is arranged parallel to the main pipe, and the second pipe section is an L-shaped pipe section.

[0014] Furthermore, the branch pipe includes a plurality of temperature measuring points and a plurality of thermocouples, and the plurality of temperature measuring points are arranged at different radial angles of the branch pipe; each of the thermocouples is arranged corresponding to a temperature measuring point;

[0015] The thermocouple is inserted into the wall of the branch pipe along the radial direction of the branch pipe and is 1mm-3mm away from the inner wall of the branch pipe.

[0016] Furthermore, the plurality of temperature measurement points are arranged on the same measurement section of the branch pipe and are arranged at radial positions of the branch pipe at intervals of 44°-46°, and the branch pipe includes the plurality of measurement sections.

[0017] Furthermore, the branch pipe includes a plurality of high-temperature speckle spraying points, and the plurality of high-temperature speckle spraying points are arranged in the second pipe section.

[0018] Furthermore, the branch pipe includes a cooling flange, and the cooling flange is disposed at an end of the third pipe segment that is not connected to the second pipe segment.

[0019] Furthermore, it also includes a water cooler and an electric valve, the water cooler is connected to the cooling flange through a pipeline, and the electric valve is arranged in the pipeline between the water cooler and the cooling flange.

[0020] Furthermore, it also includes a cooling air duct, which is arranged outside the branch pipe.

[0021] Furthermore, it also includes a heat-insulating layer, which is filled between the cooling air duct and the branch pipe, and the thickness of the heat-insulating layer is 5mm-15mm.

[0022] Furthermore, it also includes a blower, which is connected to the cooling air duct through a hose.

[0023] Furthermore, the pipe diameter D of the main pipe 1 The range is 15cm-40cm;

[0024] The diameter D of the branch pipe 2 The range is 3cm-20cm.

[0025] Furthermore, it also includes a water tank, which is connected to the heating pipeline and the experimental pipeline.

[0026] Furthermore, it also includes a heating pipe section, and the heating pipe section and the heating pipeline form a heating circuit.

[0027] Furthermore, the heating pipe section also includes a filter, a variable frequency pump, a flow meter, an electric heater and a voltage stabilizer, wherein the filter is arranged upstream of the variable frequency pump to prevent impurities from entering the variable frequency pump;

[0028] The filter, the variable frequency pump, the flow meter, the electric heater and the voltage stabilizer are sequentially connected and arranged on the heating pipe section.

[0029] Furthermore, the experimental pipeline also includes a speed meter, which is arranged at an upstream position of the main pipe in the experimental pipeline.

[0030] To achieve the above objectives, the present invention also proposes an experimental method using the above stagnant pipe thermal cycle system.

[0031] A stagnant pipeline thermal cycle test method, characterized by comprising:

[0032] S1: Adjust the water temperature and pressure of the experimental water in the system to the target value through the heating pipeline;

[0033] S2: Control the experimental water to flow into the main pipe and the branch pipe.

[0034] Furthermore, the step S1 includes:

[0035] The water temperature and pressure of the experimental water in the system are adjusted to the target values ​​by an electric heater and a pressure regulator.

[0036] Furthermore, the step S2 includes:

[0037] Close the electric regulating valve of the heating pipeline, open the electric regulating valve of the experimental pipeline, allow the experimental water to flow into the main pipe and the branch pipe, and detect the flow rate of the experimental pipeline by a speed meter;

[0038] According to the experimental parameters, the electric regulating valve of the experimental pipeline is adjusted to input different waveforms and openings of the experimental water. The flow rate y is calculated as follows:

[0039] y=F(x,T)

[0040] Wherein x is the opening of the electric regulating valve of the experimental pipeline, T is time, a flow curve is obtained according to the flow rate, and the output waveform and opening of the electric regulating valve of the experimental pipeline are adjusted according to the flow curve.

[0041] Furthermore, the step S2 further includes:

[0042] Start the blower, electric valve, and water cooler, and set the two strain monitoring lenses at different positions 30cm-50cm away from the second pipe section, so that the two strain monitoring lenses can both capture the high-temperature speckle spraying point, obtain temperature data through thermocouples, turn on the two strain monitoring lenses to capture the second pipe section, capture the deformation position of the high-temperature speckle spraying point to obtain three-dimensional strain field data.

[0043] Based on the above technical solution, the present invention has at least the following beneficial effects:

[0044] 1. The present invention proposes a stagnant pipe thermal cycle test system and method, adjusts the flow system and replaces the test section pipe. The test system of the present invention can simulate thermal cycle phenomena under different working conditions, including different main pipe temperatures, pipe diameters, main-branch pipe diameter ratios, flow rates and other variables. The present invention improves the flexibility of the pipeline thermal cycle test, enables the test system to adapt to a wide range of experimental needs, improves the experimental efficiency and system availability, and also saves economic costs. The stagnant pipe thermal cycle test method proposed by the present invention can be quickly adjusted to obtain experimental parameters for different situations through a simple experimental system, and is more adaptable and practical.

[0045] 2. The present invention proposes a stagnant pipeline thermal cycle experimental system and method. By setting temperature measuring points on the outside of multiple cross sections of the branch pipe in the experimental system, setting strain measuring points at the bend, and arranging a non-contact strain measurement system, the experimental system can effectively measure the temperature and strain information during the experiment. Through multiple sets of strain monitoring lenses, scattered spots can be captured through an optical measurement system to obtain a three-dimensional strain field. This precise data acquisition capability makes the experimental results more reliable and provides accurate data support for subsequent analysis and research.

[0046] 3. The present invention proposes a stagnant pipe thermal cycle experimental system and method. By wrapping the cooling air duct on the outside of the branch pipe insulation cotton and controlling the heat exchange conditions through experimental water at the end of the branch pipe, the experimental device can effectively deal with complex thermal cycle phenomena and ensure the heat dissipation boundary conditions of the branch pipe, thereby effectively controlling the thermal cycle phenomenon during the experiment. This ability to adjust the heat dissipation conditions not only improves the accuracy of the experiment, but also enhances the safety of the experiment, because it can effectively prevent local overheating or pressure abnormalities caused by thermal cycles, and protect the safety of the experimental device and operators. The design of the experimental device allows for adjustment of multiple parameters to simulate different working conditions, which increases the flexibility and adaptability of the experiment, allowing the experimental device to operate stably under different experimental conditions, further ensuring the safety and reliability of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0048] Figure 1 A schematic structural diagram of a stagnant pipeline thermal cycle experimental system according to an embodiment is shown;

[0049] Figure 2 A schematic diagram of the structure of a branch pipeline portion of an embodiment is shown.

[0050] The above-mentioned drawings include the following reference numerals:

[0051] 1. Main pipe; 2. Branch pipe; 3a. Heating pipeline; 3b. Experimental pipeline; 4. Check valve; 5a. Water tank; 5b. Electric regulating valve for water tank; 6. Filter; 7. Frequency conversion pump; 8. Flow meter; 9. Electric heater; 10. Voltage stabilizer; 11. Electric regulating valve for heating pipeline; 12. Electric regulating valve for experimental pipeline; 13. Speed ​​meter; 14. Cooling flange; 15. Cooling air duct; 16. Blower; 17. Electric valve; 18. Water cooler; 19. Strain monitoring lens;

[0052] 2a, temperature measurement point; 2b, thermocouple; 2c, high temperature speckle spraying point. DETAILED DESCRIPTION

[0053] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0054] The present invention is further described in detail below in conjunction with specific embodiments, and these embodiments cannot be understood as limiting the scope of protection claimed by the present invention. The term "including" when used indicates the existence of a feature, but does not exclude the existence or addition of one or more other features; the orientation or position relationship indicated by the terms "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; in addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

[0055] In the description, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0056] Example

[0057] The present invention provides a stagnant pipeline thermal cycle experimental system, such as Figure 1 The example shown includes a heating pipeline and an experimental pipeline, wherein the heating pipeline is arranged in parallel with the experimental pipeline, and the experimental pipeline includes a main pipe and a branch pipe;

[0058] The branch pipe includes a first pipe section, a second pipe section and a third pipe section, the branch pipe is connected to the main pipe through the first pipe section, the first pipe section is connected to one end of the second pipe section, and the third pipe section is connected to the other end of the second pipe section;

[0059] The diameter D1 of the main pipe is larger than the diameter D2 of the branch pipe.

[0060] Furthermore, the structure of the branch pipe 2 is as follows: Figure 2 As shown, the first pipe segment of the branch pipe 2 is vertically connected to the main pipe 1, the other end of the first pipe segment is connected to the second pipe segment, the third pipe segment is connected to the first pipe segment through the second pipe segment, the bending angle of the second pipe segment is 90°, the length of the first pipe segment is 0.5m, the length of the third pipe segment is 1.2m, and the main structure of the branch pipe 2 is composed of the first pipe segment, the second pipe segment and the third pipe segment.

[0061] Furthermore, a cooling flange 14 is provided at the end of the third pipe section, and a multi-layer guide plate is provided inside the cooling flange 14, and a water inlet and a water outlet are provided on both sides of the cooling flange 14, respectively, for connecting to a water cooler 18, so as to control the temperature of the water in the branch pipe 2 when it flows into the water cooler 18 through the cooling flange 14 and is maintained between 35°C and 80°C.

[0062] Furthermore, a heat-insulating cotton is provided on the outside of the branch pipe 2, a cooling air duct 15 is provided on the outside of the heat-insulating cotton to wrap the branch pipe 2, a blower 16 is provided outside the branch pipe 2, and the blower 16 is connected to the cooling air duct 15 through a hose.

[0063] Furthermore, two strain monitoring lenses 19 are respectively arranged outside the second pipe section, so that the two groups of strain monitoring lenses 19 can photograph and detect as many high-temperature speckle spraying points 2c on the second pipe section as possible.

[0064] To achieve the above object, the present invention further proposes a stagnant pipe thermal cycle test method, using the stagnant pipe thermal cycle test system described above, comprising the following steps:

[0065] S1: Adjust the water temperature and pressure of the experimental water in the system to the target value by heating the pipeline 3a;

[0066] S2: Control the experimental water to flow into the main pipe 1 and the branch pipe 2.

[0067] Furthermore, the step S1 includes:

[0068] The water temperature and pressure of the experimental water in the system are adjusted to the target values ​​by the electric heater 9 and the voltage stabilizer 10.

[0069] Furthermore, the heating pipeline electric regulating valve 11 of the heating pipeline 3a is opened, the experimental pipeline electric regulating valve 12 of the experimental pipeline 3b is closed, the frequency conversion pump 7 is adjusted, and the loop flow is observed through the flow meter 8. Preferably, the water temperature in the heating pipeline 3a is increased to 300°C and the pressure is increased to 9Mpa through the electric heater 9 and the voltage stabilizer 10. The electric heater 9 and the voltage stabilizer 10 work alternately to ensure that all parts in the system are stable and do not boil.

[0070] Furthermore, the step S2 includes:

[0071] By opening the electric regulating valve 12 of the experimental pipeline, the experimental water is allowed to flow into the main pipe 1 and the branch pipe 2, and the temperature boundary outside the branch pipe 2 is kept stable by the water cooler 18 and the blower 16.

[0072] Furthermore, by adjusting the experimental pipeline regulating valve 12, a sine wave, a triangular wave, a square wave or a trapezoidal wave is input into the experimental water according to the experimental parameter requirements. At the same time, a flow curve is obtained according to the opening and time of the experimental pipeline regulating valve 12, and then the experimental pipeline regulating valve 12 is further adjusted according to the obtained flow curve.

[0073] Furthermore, the step S2 further includes:

[0074] The two strain monitoring lenses are respectively set at different positions 40 cm away from the second pipe section, so that the two strain monitoring lenses can collect images of the high-temperature speckle spraying points 2c on the second pipe section, start the blower 16, open the electric valve 17, and obtain the temperature data of each temperature measuring point 2a on different cross sections through the thermocouple 2b on the experimental pipe section. The second pipe section is photographed by setting the strain 2 lenses 19 at different angles to capture the high-temperature speckle spraying points 2c to obtain three-dimensional strain field data.

[0075] Furthermore, when it is necessary to conduct experiments under different experimental conditions, after the experimental pipeline 3b is no longer draining water, the main pipe 1 and the branch pipe 2 are removed, and the pipe diameter ratio of the main pipe 1 to the branch pipe 2 is adjusted by replacing the main pipe 1 and the branch pipe 2 with different pipe diameters. Preferably, the pipe diameter D of the main pipe 1 is 1 is 20cm, the diameter of branch pipe 2 is D 2 10cm, D 1 With D 2 The ratio is 2:1.

[0076] In summary, it can be seen from the above description that the above embodiments of the present invention achieve the following technical effects:

[0077] 1. The present invention proposes a stagnant pipe thermal cycle test system and method, adjusts the flow system and replaces the test section pipe. The test system of the present invention can simulate thermal cycle phenomena under different working conditions, including different main pipe temperatures, pipe diameters, main-branch pipe diameter ratios, flow rates and other variables. The present invention improves the flexibility of the pipeline thermal cycle test, enables the test system to adapt to a wide range of experimental needs, improves the experimental efficiency and system availability, and also saves economic costs. The stagnant pipe thermal cycle test method proposed by the present invention can be quickly adjusted to obtain experimental parameters for different situations through a simple experimental system, and is more adaptable and practical.

[0078] 2. The present invention proposes a stagnant pipeline thermal cycle experimental system and method. By setting temperature measuring points on the outside of multiple cross sections of the branch pipe in the experimental system, setting strain measuring points at the bend, and arranging a non-contact strain measurement system, the experimental system can effectively measure the temperature and strain information during the experiment. Through multiple sets of strain monitoring lenses, scattered spots can be captured through an optical measurement system to obtain a three-dimensional strain field. This precise data acquisition capability makes the experimental results more reliable and provides accurate data support for subsequent analysis and research.

[0079] 3. The present invention proposes a stagnant pipe thermal cycle experimental system and method. By wrapping the cooling air duct on the outside of the branch pipe insulation cotton and controlling the heat exchange conditions through experimental water at the end of the branch pipe, the experimental device can effectively deal with complex thermal cycle phenomena and ensure the heat dissipation boundary conditions of the branch pipe, thereby effectively controlling the thermal cycle phenomenon during the experiment. This ability to adjust the heat dissipation conditions not only improves the accuracy of the experiment, but also enhances the safety of the experiment, because it can effectively prevent local overheating or pressure abnormalities caused by thermal cycles, and protect the safety of the experimental device and operators. The design of the experimental device allows for adjustment of multiple parameters to simulate different working conditions, which increases the flexibility and adaptability of the experiment, allowing the experimental device to operate stably under different experimental conditions, further ensuring the safety and reliability of the experiment.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0081] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0082] It should be noted that, in the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Claims

1. A stagnant pipeline thermal cycle experimental system, characterized in that: It includes a heating pipeline (3a) and a test pipeline (3b), The heating pipeline (3a) is arranged in parallel with the experimental pipeline (3b), and the experimental pipeline (3b) includes a main pipe (1) and a branch pipe (2); The branch pipe (2) comprises a first pipe section, a second pipe section and a third pipe section, the branch pipe (2) is connected to the main pipe (1) via the first pipe section, the first pipe section is connected to one end of the second pipe section, and the third pipe section is connected to the other end of the second pipe section; The pipe diameter D1 of the main pipe (1) is greater than the pipe diameter D2 of the branch pipe (2).

2. The system according to claim 1, characterized in that: The main pipe (1) comprises a reducing section, The reducing section is arranged at both ends of the main pipe (1); the distance between the outlet of the reducing section at the inflow end of the main pipe (1) and the center position of the contact surface between the branch pipe (2) and the main pipe (1) is 10D1-20D1, and the distance between the inlet of the reducing section at the outflow end of the main pipe (1) and the center position of the contact surface between the branch pipe (2) and the main pipe (1) is 5D1-10D1.

3. The system according to claim 1, characterized in that: The first pipe section is connected perpendicularly to the main pipe (1), the third pipe section is arranged parallel to the main pipe (1), and the second pipe section is an L-shaped pipe section.

4. The system according to claim 1, characterized in that: The branch pipe (2) comprises a plurality of temperature measuring points (2a) and a plurality of thermocouples (2b). The plurality of temperature measuring points (2a) are arranged at different radial angles of the branch pipe (2); each of the thermocouples (2b) is arranged corresponding to a temperature measuring point (2a); The thermocouple (2b) is inserted into the wall of the branch pipe (2) along the radial direction of the branch pipe (2) and is located 1 mm to 3 mm away from the inner wall of the branch pipe (2).

5. The system according to claim 4, characterized in that: The plurality of temperature measuring points (2a) are arranged on the same measuring section of the branch pipe (2) and are arranged at radial positions of the branch pipe (2) at intervals of 44°-46°. The branch pipe (2) includes the plurality of measuring sections.

6. The system according to claim 1, characterized in that: The branch pipe (2) comprises a plurality of high-temperature speckle spraying points (2c), A plurality of high-temperature speckle spraying points (2c) are arranged on the second pipe section.

7. The system according to claim 1, characterized in that: The branch pipe (2) comprises a cooling flange (14), The cooling flange (14) is disposed at an end of the third pipe section that is not connected to the second pipe section.

8. The system according to claim 7, characterized in that: It also includes a water cooler (18) and an electric valve (17), The water cooler (18) is connected to the cooling flange (14) via a pipeline, and the electric valve (17) is arranged in the pipeline between the water cooler (18) and the cooling flange (14).

9. The system according to claim 1, characterized in that: It also includes a cooling air duct (15), The cooling air duct (15) is arranged outside the branch pipe (2).

10. The system according to claim 9, characterized in that: It also includes an insulation layer. The thermal insulation layer is filled between the cooling air duct (15) and the branch pipe (2), and the thickness of the thermal insulation layer is 5 mm-15 mm.

11. The system according to claim 9, characterized in that: Also includes a blower (16), The blower (16) is connected to the cooling air duct (15) via a hose.

12. The system according to claim 1, characterized in that: The diameter D1 of the main pipe (1) ranges from 15 cm to 40 cm; The diameter D2 of the branch pipe (2) ranges from 3 cm to 20 cm.

13. The system according to claim 1, characterized in that: It also includes a water storage tank (5a), The water storage tank (5a) is connected to the heating pipeline (3a) and the experimental pipeline (3b).

14. The system according to claim 1, characterized in that: Also includes heating pipe section, The heating pipe section and the heating pipeline (3a) form a heating circuit.

15. The system according to claim 14, characterized in that: The heating pipe section further comprises a filter (6), a variable frequency pump (7), a flow meter (8), an electric heater (9) and a voltage stabilizer (10). The filter (6) is arranged upstream of the variable frequency pump (7) to prevent impurities from entering the variable frequency pump (7); The filter (6), the variable frequency pump (7), the flow meter (8), the electric heater (9) and the voltage stabilizer (10) are sequentially connected and arranged on the heating pipe section.

16. The system according to claim 1, characterized in that: The experimental pipeline also includes a speed meter (13), The velocity meter (13) is arranged at an upstream position of the main pipe (1) in the experimental pipeline.

17. An experimental method using the stagnant pipe thermal cycle experimental system as claimed in claim 1, characterized in that: include: S1: Adjust the water temperature and pressure of the experimental water in the system to the target values ​​through the heating pipeline (3a); S2: Control the experimental water to flow into the main pipe (1) and the branch pipe (2).

18. The method according to claim 17, characterized in that: The step S1 includes: The water temperature and pressure of the experimental water in the system are adjusted to target values ​​by means of an electric heater (9) and a voltage stabilizer (10).

19. The method according to claim 17, characterized in that: The step S2 includes: The electric regulating valve (11) of the heating pipeline is closed, and the electric regulating valve (12) of the experimental pipeline is opened to allow the experimental water to flow into the main pipe (1) and the branch pipe (2), and the flow rate of the experimental pipeline (3b) is detected by a speed meter (13); According to the experimental parameters, the electric regulating valve (12) of the experimental pipeline is adjusted to input different waveforms and openings of the experimental water. The flow rate y is calculated as follows: y=F(x,T) Wherein x is the opening of the experimental pipeline electric regulating valve (12), T is time, a flow curve is obtained according to the flow rate, and the output waveform and opening of the experimental pipeline electric regulating valve (12) are adjusted according to the flow curve.

20. The method according to claim 17, characterized in that: The step S2 further includes: The blower (16), the electric valve (17), and the water cooler (18) are started, and two strain monitoring lenses (19) are respectively set at different positions 30 cm to 50 cm away from the second pipe section so that the two strain monitoring lenses (19) can both photograph the high-temperature speckle spraying point (2c), and temperature data is obtained through the thermocouple (2b). The two strain monitoring lenses (19) are turned on to photograph the second pipe section, and the deformation position of the high-temperature speckle spraying point (2c) is captured to obtain three-dimensional strain field data.

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