Dirt growth simulation and boiling heat transfer test device for heat transfer pipe of steam generator

Abstract

The invention provides a steam generator heat transfer pipe dirt growth simulation and boiling heat transfer test device. The device comprises a simulation heat transfer pipe system, a reaction kettle system and a sliding thermocouple system, dirt growth speed regulation and control of a compact layer and a sparse layer of the heat transfer tube are realized through direct electric heating and increase of Fe ion concentration, and the problems of slow growth and large difference between dirt pore distribution and a power station in a traditional dirt experiment are solved; measurement of data at multiple positions in the circumferential direction of multiple heights is achieved through fine control of the sliding thermocouple, the reliability and repeatability of the data are verified through mutual verification of the data, and the repeatability and reliability of the data can be analyzed under the same working condition in combination with dirt observation and sampling analysis after an experiment. And a reliable coupling relationship between dirt growth and boiling heat transfer characteristics is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power plant simulation experiments, in particular to a steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device. Background Art

[0002] The steam generator of a pressurized water reactor (PWR) connects the primary and secondary circuits and is a key heat exchanger for transferring energy from the primary to the secondary circuit. Corrosion products such as Fe₃O₄ generated by carbon steel piping in the secondary circuit continuously migrate into the steam generator. Because these Fe compounds do not evaporate, they are almost always deposited inside the steam generator, forming a fouling layer on the outer walls of the heat transfer tubes, tube sheets, and support plates. This leads to reduced heat transfer performance and corrosion at the bottom of the deposits, negatively impacting the economics and safety of the nuclear power unit. Directly measuring the fouling morphology of steam generators in operating nuclear power units is difficult. Therefore, it is necessary to develop a device to simulate fouling growth and conduct heat transfer experiments on the simulated fouling to determine its impact on the heat transfer performance of the heat transfer tubes. Designing a coupled experimental setup for fouling growth and boiling on the heat transfer tube surface not only helps understand the fouling morphology of the heat transfer tubes but also helps predict fouling growth and the evolution of thermal performance. This not only allows for timely fouling removal to ensure unit output performance, but also facilitates operation and maintenance management, reducing operation and maintenance costs, and is of great significance for steam generator operation and maintenance.

[0003] Experiments on scale growth and boiling heat transfer in steam generator heat transfer tubes typically use indirect heating rods to simulate the energy transfer process between the hot fluid inside the tube and the fluid outside. Fixed thermocouples are placed inside the rods to measure the temperature at specific locations within the rods, and the temperature distribution is obtained using a cylindrical two-dimensional energy transfer method. This method accelerates scale growth by increasing the Fe ion concentration, but it is unable to control the growth rate of scale in the dense and sparse layers of the heat transfer tubes. This results in slow growth and significant discrepancies between the scale pore distribution and the actual scale. Furthermore, this method is limited by the size of the indirect heating rods, requiring only a very small number of thermocouples. Furthermore, because scale growth locations are somewhat random, the distribution at the same height is not uniform. The fixed thermocouple measurement method generates a small amount of data, making it difficult to verify the credibility and reliability of the data in a single experiment. This results in large random errors in the scale heat transfer performance results, making it difficult to obtain a reliable coupling relationship between scale growth and boiling heat transfer characteristics. Repeated experiments are often required to improve measurement accuracy and reliability, but this is costly.

[0004] Patent document CN114965191A discloses a heat transfer tube scaling behavior simulation system, comprising: an autoclave having a first water inlet, a second water inlet, a first water outlet, and a second water outlet on its top; two first connecting pipes, one of which is inserted into the first water inlet and the other into the first water outlet; a sample assembly comprising a heat transfer tube sample, a support plate sample, and a second connecting pipe. The heat transfer tube sample is placed in the autoclave. The upper ends of the two heat transfer tube samples are connected to the lower ends of the two first connecting pipes in a one-to-one correspondence. One end of the second connecting pipe is connected to the lower end of one heat transfer tube sample, and the other end is connected to the lower end of the other heat transfer tube sample. Each heat transfer tube sample is connected to a support plate sample. A first circuit is used to simulate the primary water circuit of a pressurized water reactor nuclear power plant; and a second circuit is used to simulate the secondary water circuit of a pressurized water reactor nuclear power plant. However, this patent does not fully solve the existing technical problems and does not meet the requirements of the present invention. Summary of the Invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device.

[0006] The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device provided by the present invention comprises: a simulated heat transfer tube system, a reactor system and a sliding thermocouple system;

[0007] The simulated heat transfer tube system includes: a first copper electrode, a simulated heat transfer tube, a second copper electrode, an insulating flange, and a heating power supply; the first copper electrode is connected to the upper end of the simulated heat transfer tube by welding, and the lower end of the simulated heat transfer tube is connected to the second copper electrode by welding; the heating power supply is connected to the first and second copper electrodes via a copper plate or a thick copper wire; the first and second copper electrodes are welded to the insulating flange;

[0008] The reactor system includes: a fluid outlet, an insulating ceramic grid, a simulated insulating grid, a reactor, a rectifier insulating ceramic grid, a fluid inlet, a lower groove, an upper groove and bolts; both ends of the reactor are provided with a cover plate, the lower cover plate of the reactor is welded with bolts, which are connected to the insulating flange in the simulated heat transfer tube to fix the simulated heat transfer tube; the upper cover plate of the reactor has a hole, through which the simulated heat transfer tube passes, and the side wall of the hole is provided with an O-ring groove, which is sealed by an O-ring after the simulated heat transfer tube is installed; the fluid outlet is located at the upper end of the reactor, and the fluid inlet is located at the lower end of the reactor; the upper groove is located at the upper end of the reactor, lower than the fluid outlet; the lower groove is located at the lower end of the reactor, higher than the fluid inlet; the simulated insulating grid is fixed to the reactor by welding; the insulating ceramic grid is embedded in the upper groove; the rectifier insulating ceramic grid is embedded in the lower groove; after the simulated heat transfer tube is installed, it will pass through the hole of the rectifier insulating ceramic grid, the simulated insulating grid, the insulating ceramic grid and the reactor upper cover plate;

[0009] The sliding thermocouple system includes: a sliding plate and displacement sensor module, a thermocouple extension wire, a guide tube, a thermocouple, a fixed bracket, a stepper motor and an insulating tube; the guide tube is tightly installed in the insulating tube with an interference fit, and the insulating tube and the guide tube are installed in the simulated heat transfer tube. The insulating tube moves up and down in the simulated heat transfer tube with the guide tube; the thermocouple is connected to the external data acquisition system via the thermocouple extension wire; the thermocouple extension wire passes through the guide tube and fixes the thermocouple on the guide tube; the guide tube is welded or screwed to the sliding plate and displacement sensor module; the sliding plate and displacement sensor module are respectively connected to the fixed bracket and the stepper motor. Under the support of the fixed bracket, the sliding plate and the displacement sensor module are driven by the stepper motor to achieve vertical sliding. The sliding plate and the displacement sensor module slide up and down with the guide tube and the thermocouple to achieve surface temperature measurement at any height position in the heat transfer tube.

[0010] Preferably, the heating power supply is a DC power supply, one end of the heating power supply is a low voltage of 0V, connected to the first copper electrode; the other end of the heating power supply is a high voltage, connected to the second copper electrode.

[0011] Preferably, the solution fluid enters the reactor from the fluid inlet, flows inside the reactor, and then flows out from the fluid outlet, simulating the heat transfer tube transferring energy to the fluid in the reactor through the outer surface. As the fluid flows and heat transfers, impurities in the fluid will be deposited on the surface of the heat transfer tube to form scale. Direct electric heating and increasing ion concentration can be used to control the growth rate of scale in the dense layer and sparse layer of the heat transfer tube.

[0012] Preferably, the reactor is made of stainless steel and has a cylindrical structure.

[0013] Preferably, the guide tube is a stainless steel round tube, and four elastic compression plates inclined outward are welded to the lower end.

[0014] Preferably, the thermocouples are 4 N-type insulated thermocouples with a diameter of 1 mm. The 4 N-type insulated thermocouples are evenly distributed circumferentially on the 4 elastic compression plates at the lower end of the guide tube. The ends of the insulated thermocouples are tightly attached to the inner surface of the heat transfer tube under the action of the elastic compression plates, thereby realizing the measurement of the inner surface temperature of the heat transfer tube.

[0015] Preferably, after the position of the thermocouple is fixed, high-temperature glue is injected into the guide tube to fix the thermocouple extension wire in the guide tube.

[0016] Preferably, the guide tube is longer than the insulating tube, and both ends of the guide tube have a section outside the insulating tube, and the length of the lower end of the guide tube outside the insulating tube is 2 mm; the elastic compression plate on the lower end of the guide tube is outside the insulating tube and extends obliquely outward, and the maximum horizontal distance from the elastic compression plate to the axis of the guide tube is 0.25 mm smaller than the radius of the insulating tube.

[0017] Preferably, the insulating tube is made of ceramic material, and the diameter of the insulating tube is 0.5 mm smaller than the inner diameter of the simulated heat transfer tube.

[0018] Preferably, when the device conducts a boiling heat transfer experiment, the heating power and the fluid inlet state are maintained at set values ​​under the same operating conditions. The fluid inlet state includes flow rate, temperature, pressure, subcooling, pH value, and impurity content. The experiment starts by simulating a clean and fouling-free state of the heat transfer tube, and gradually grows fouling. The experiment is stopped when the fouling thickness reaches tens or hundreds of microns. Thermocouple temperature measurement is performed at regular time intervals. Each measurement data is measured by using a sliding thermocouple system to achieve temperature measurement at four circumferential positions at different heights.

[0019] During the experiment, the heating power of the heat transfer tube and the fluid inlet state parameters were measured simultaneously. Based on the heating power and the temperature inside the heat transfer tube, the outer surface temperature of the heat transfer tube at four locations at different circumferential heights was calculated using the one-dimensional cylindrical heat conduction equation. The fluid temperature at different heights inside the heat transfer tube was also calculated based on the fluid inlet temperature and heating power. Furthermore, the heat transfer coefficient at four locations at different circumferential heights was calculated based on the heat flux density, fluid temperature, and the outer surface temperature of the heat transfer tube. This heat transfer coefficient was compared with the heat transfer coefficient of the heat transfer tube when it was clean and free of dirt. The change in the fouling thermal resistance at different heights of the heat transfer tube over time was determined to characterize the boiling heat transfer characteristics caused by the fouling of the heat transfer tube.

[0020] After the experiment, the experimental device was disassembled, the heat transfer tube was taken out, and the surface dirt at different heights and around the heat transfer tube corresponding to the temperature measurement position was observed and sampled for analysis to obtain the dirt weight, dirt thickness at different positions, and microstructure information, and to obtain the coupling relationship between dirt growth and boiling heat transfer characteristics.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention can analyze the repeatability and reliability of data by mutual verification of height and circumferential data, combined with observation and sampling analysis of fouling after the experiment. Compared with the traditional fixed thermocouple measurement method, the measurement method of the present invention obtains a large amount of data, can verify the credibility and reliability of the data in a single experiment, reduce the measurement error of fouling heat transfer performance, and can obtain a reliable coupling relationship between fouling growth and boiling heat transfer characteristics;

[0023] (2) By direct electric heating and increasing the Fe ion concentration, the growth rate of the dense layer and sparse layer of the heat transfer tube can be controlled, solving the problems of slow growth in traditional fouling experiments and large differences in the pore distribution of fouling and power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0025] Figure 1 It is a sliding measurement device for steam generator heat transfer tube fouling growth simulation and boiling heat transfer test;

[0026] Figure 2 for Figure 1 A partial enlarged view of

[0027] In the figure: 1-sliding plate and displacement sensor module; 2-thermocouple extension wire; 3-guide tube; 4-first copper electrode; 5-fluid outlet; 6-insulating ceramic grid element; 7-simulated heat transfer tube; 8-simulated insulating grid; 9-reactor; 10-thermocouple; 11-rectifier insulating ceramic grid element; 12-second copper electrode; 13-fluid inlet; 14-insulating flange; 15-heating power supply; 16-fixing bracket; 17-stepping motor; 18-insulating tube; 19-O-ring; 20-lower groove; 21-upper groove; 22-bolt; 23-O-ring groove. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0029] Example

[0030] like Figure 1 and Figure 2As shown, this embodiment provides a steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device with sliding measurement, including: a simulated heat transfer tube system, a reactor system and a sliding thermocouple system;

[0031] The simulated heat transfer tube system includes: a first copper electrode 4, a simulated heat transfer tube 7, a second copper electrode 12, an insulating flange 14, and a heating power supply 15; the first copper electrode 4 is connected to the upper end of the simulated heat transfer tube 7 by welding, and the lower end of the simulated heat transfer tube 7 is connected to the second copper electrode 12 by welding; the heating power supply 15 is connected to the first copper electrode 4 and the second copper electrode 12 via a copper plate or a thick copper wire; the first copper electrode 4 and the second copper electrode 12 are welded to the insulating flange 14;

[0032] The reactor system includes: a fluid outlet 5, an insulating ceramic grid element 6, a simulated insulating grid 8, a reactor 9, a rectifier insulating ceramic grid element 11, a fluid inlet 13, a lower groove 20, an upper groove 21 and bolts 22; the reactor 9 has a cover plate at both ends, and the lower cover plate of the reactor 9 is welded with bolts 22, which are connected to the insulating flange 14 in the simulated heat transfer tube 7 to fix the simulated heat transfer tube; the upper cover plate of the reactor 9 has a hole, and the simulated heat transfer tube 7 passes through the hole. The side wall of the hole is provided with an O-ring groove 23, which is sealed by an O-ring 19 after the simulated heat transfer tube 7 is installed; the fluid outlet 5 The reactor 9 is placed at the upper end, and the fluid inlet 13 is placed at the lower end of the reactor 9; the upper groove 21 is placed at the upper end of the reactor 9, lower than the fluid outlet 5; the lower groove 20 is placed at the lower end of the reactor 9, higher than the fluid inlet 13; the simulated insulating grid 8 is fixed to the reactor 9 by welding; the insulating ceramic grid element 6 is embedded in the upper groove 21; the rectifier insulating ceramic grid element 11 is embedded in the lower groove 20; after installation, the simulated heat transfer tube 7 will pass through the holes of the rectifier insulating ceramic grid element 11, the simulated insulating grid 8, the insulating ceramic grid element 6, and the upper cover plate of the reactor 9;

[0033] The sliding thermocouple system includes: a sliding plate and displacement sensor module 1, a thermocouple extension wire 2, a guide tube 3, a thermocouple 10, a fixing bracket 16, a stepper motor 17 and an insulating tube 18; the guide tube 3 is tightly installed in the insulating tube 18 with an interference fit, and the insulating tube 18 and the guide tube 3 are installed in the simulated heat transfer tube 7. The insulating tube 18 moves up and down with the guide tube 3 in the simulated heat transfer tube 7; the thermocouple 10 is connected to the external data collection system through the thermocouple extension wire 2; the thermocouple extension wire 2 passes through the guide tube 17. The guide tube 3 is provided with a thermocouple 10, and the guide tube 3 is fixed to the thermocouple 10. The guide tube 3 is connected to the sliding plate and the displacement sensor module 1 by welding or screws. The sliding plate and the displacement sensor module 1 are connected to the fixed bracket 16 and the stepper motor 17 respectively. The sliding plate and the displacement sensor module 1 are supported by the fixed bracket 16 and driven by the stepper motor 17 to slide in the vertical direction. The sliding plate and the displacement sensor module 1 slide up and down with the guide tube 3 and the thermocouple 10, so as to realize the surface temperature measurement at any height position in the heat transfer tube.

[0034] One end of the simulated heat transfer tube 7 is at 0V and can be connected to the reactor without insulation, while the other end carries a higher voltage and is connected to the reactor through an insulating flange 14.

[0035] The heating power supply 15 is a DC power supply. One end of the heating power supply 15 is a low voltage 0V and is connected to the first copper electrode 4 ; the other end of the heating power supply 15 is a high voltage and is connected to the second copper electrode 12 .

[0036] The solution fluid enters the reactor 9 from the fluid inlet 13, flows within the reactor 9, and then flows out from the fluid outlet 5, simulating the heat transfer tube 7 transferring energy to the fluid in the reactor 9 through its outer surface. As the fluid flows and heat transfers, impurities in the fluid will deposit on the surface of the heat transfer tube, forming scale. Direct electrical heating and increasing ion concentration can be used to control the growth rate of scale in the dense and sparse layers of the heat transfer tube.

[0037] The reactor 9 is made of stainless steel and has a cylindrical structure.

[0038] The guide tube 3 is a stainless steel round tube, and four elastic pressing pieces inclined outward are welded to the lower end.

[0039] The thermocouples 10 are four N-type insulated thermocouples with a diameter of 1 mm. The four N-type insulated thermocouples are evenly distributed circumferentially on the four elastic compression plates at the lower end of the guide tube 3. The ends of the insulated thermocouples are tightly attached to the inner surface of the heat transfer tube under the action of the elastic compression plates, thereby realizing the measurement of the inner surface temperature of the heat transfer tube.

[0040] After the position of the thermocouple 10 is fixed, high-temperature glue is injected into the guide tube 3 to fix the thermocouple extension wire 2 in the guide tube 3.

[0041] The guide tube 3 is longer than the insulating tube 18. Both ends of the guide tube 3 have a section outside the insulating tube 18, and the length of the lower end of the guide tube 3 outside the insulating tube 18 is 2 mm; the elastic compression piece on the lower end of the guide tube 3 is outside the insulating tube 18 and extends obliquely outward. The maximum horizontal distance from the elastic compression piece to the axis of the guide tube 3 is 0.25 mm smaller than the radius of the insulating tube 18.

[0042] The insulating tube 18 is made of ceramic material, and its diameter is 0.5 mm smaller than the inner diameter of the simulated heat transfer tube 7 .

[0043] When conducting boiling heat transfer experiments, the device maintains the heating power and fluid inlet conditions at set values ​​under the same operating conditions. The fluid inlet conditions include flow rate, temperature, pressure, subcooling, pH value, and impurity content. The experiment starts with simulating a clean, fouling-free state on the heat transfer tube, gradually growing fouling and stopping when the fouling reaches a thickness of tens or hundreds of microns. Thermocouple temperature measurement is performed at regular intervals. Each measurement data is measured by a sliding thermocouple system to achieve temperature measurements at four circumferential positions at different heights.

[0044] During the experiment, the heating power of the heat transfer tube and the fluid inlet state parameters were measured simultaneously. Based on the heating power and the temperature inside the heat transfer tube, the outer surface temperature of the heat transfer tube at four locations at different circumferential heights was calculated using the one-dimensional cylindrical heat conduction equation. The fluid temperature at different heights inside the heat transfer tube was also calculated based on the fluid inlet temperature and heating power. Furthermore, the heat transfer coefficient at four locations at different circumferential heights was calculated based on the heat flux density, fluid temperature, and the outer surface temperature of the heat transfer tube. This heat transfer coefficient was compared with the heat transfer coefficient of the heat transfer tube when it was clean and free of dirt. The change in the fouling thermal resistance at different heights of the heat transfer tube over time was determined to characterize the boiling heat transfer characteristics caused by the fouling of the heat transfer tube.

[0045] After the experiment, the experimental device was disassembled, the heat transfer tube was taken out, and the surface dirt at different heights and around the heat transfer tube corresponding to the temperature measurement position was observed and sampled for analysis to obtain the dirt weight, dirt thickness at different positions, and microstructure information, and to obtain the coupling relationship between dirt growth and boiling heat transfer characteristics.

[0046] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device 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 this application.

[0047] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device, characterized in that: include: Simulate heat transfer tube systems, reactor systems, and sliding thermocouple systems; The simulated heat transfer tube system comprises: a first copper electrode (4), a simulated heat transfer tube (7), a second copper electrode (12), an insulating flange (14) and a heating power supply (15); the first copper electrode (4) is connected to the upper end of the simulated heat transfer tube (7) by welding, and the lower end of the simulated heat transfer tube (7) is connected to the second copper electrode (12) by welding; the heating power supply (15) is connected to the first copper electrode (4) and the second copper electrode (12) by a copper plate or a thick copper wire; the first copper electrode (4) and the second copper electrode (12) are connected to the insulating flange (14) by welding; The reactor system comprises: a fluid outlet (5), an insulating ceramic grid element (6), a simulated insulating grid (8), a reactor (9), a rectifying insulating ceramic grid element (11), a fluid inlet (13), a lower groove (20), an upper groove (21) and bolts (22); both ends of the reactor (9) are provided with cover plates, and bolts (22) are welded on the lower cover plate of the reactor (9) and connected to the insulating flange (14) in the simulated heat transfer tube (7) to fix the simulated heat transfer tube; the upper cover plate of the reactor (9) has a hole, and the simulated heat transfer tube (7) passes through the hole, and the side wall of the hole is provided with an O-ring groove (23), and after the simulated heat transfer tube (7) is installed, the hole is sealed by an O-ring (19); the fluid outlet (5) The reactor (9) is placed at the upper end, and the fluid inlet (13) is placed at the lower end of the reactor (9); the upper groove (21) is placed at the upper end of the reactor (9), lower than the fluid outlet (5); the lower groove (20) is placed at the lower end of the reactor (9), higher than the fluid inlet (13); the simulated insulating grid (8) is fixed in the reactor (9) by welding; the insulating ceramic grid element (6) is embedded in the upper groove (21); the rectifying insulating ceramic grid element (11) is embedded in the lower groove (20); after installation, the simulated heat transfer pipe (7) will pass through the holes of the rectifying insulating ceramic grid element (11), the simulated insulating grid element (8), the insulating ceramic grid element (6) and the upper cover plate of the reactor (9); The sliding thermocouple system comprises: a sliding plate and displacement sensor module (1), a thermocouple extension wire (2), a guide tube (3), a thermocouple (10), a fixing bracket (16), a stepping motor (17) and an insulating tube (18); the guide tube (3) is tightly installed in the insulating tube (18) by interference fit, the insulating tube (18) and the guide tube (3) are installed in the simulated heat transfer tube (7), and the insulating tube (18) moves up and down with the guide tube (3) in the simulated heat transfer tube (7); the thermocouple (10) is connected to an external acquisition system through the thermocouple extension wire (2); the thermocouple extension wire (2) The guide tube (3) is passed through, and a thermocouple (10) is fixed on the guide tube (3); the guide tube (3) is welded or screwed to the sliding plate and displacement sensor module (1); the sliding plate and displacement sensor module (1) are respectively connected to a fixed bracket (16) and a stepper motor (17); the sliding plate and displacement sensor module (1) are supported by the fixed bracket (16) and driven by the stepper motor (17) to achieve vertical sliding; the sliding plate and displacement sensor module (1) slide up and down with the guide tube (3) and the thermocouple (10), thereby achieving surface temperature measurement at any height position in the heat transfer tube.

2. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: The heating power supply (15) is a DC power supply. One end of the heating power supply (15) is a low voltage of 0V and is connected to the first copper electrode (4); the other end of the heating power supply (15) is a high voltage and is connected to the second copper electrode (12).

3. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: The solution fluid enters the reactor (9) from the fluid inlet (13), flows in the reactor (9), and then flows out from the fluid outlet (5), simulating the heat transfer tube (7) transferring energy to the fluid in the reactor (9) through the outer surface. As the fluid flows and heat transfers, impurities in the fluid will be deposited on the surface of the heat transfer tube to form dirt. The growth rate of the dirt in the dense layer and the sparse layer of the heat transfer tube is regulated by direct electric heating and increasing the ion concentration.

4. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: The reaction kettle (9) is made of stainless steel and has a cylindrical structure.

5. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: The guide tube (3) is a stainless steel round tube, and four elastic pressing pieces inclined outward are welded to the lower end.

6. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 5, characterized in that: The thermocouples (10) are four N-type insulated thermocouples with a diameter of 1 mm. The four N-type insulated thermocouples are evenly distributed circumferentially on four elastic compression plates at the lower end of the guide tube (3). The ends of the insulated thermocouples are tightly attached to the inner surface of the heat transfer tube under the action of the elastic compression plates, thereby achieving measurement of the inner surface temperature of the heat transfer tube.

7. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 6, characterized in that: After the position of the thermocouple (10) is fixed, high-temperature glue is injected into the guide tube (3) to fix the thermocouple extension wire (2) in the guide tube (3).

8. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: The guide tube (3) is longer than the insulating tube (18), and both ends of the guide tube (3) have a section outside the insulating tube (18), and the length of the lower end of the guide tube (3) outside the insulating tube (18) is 2 mm; the elastic compression piece on the lower end of the guide tube (3) is outside the insulating tube (18) and extends obliquely outward, and the maximum horizontal distance of the elastic compression piece from the axis of the guide tube (3) is 0.25 mm smaller than the radius of the insulating tube (18).

9. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: The insulating tube (18) is made of ceramic material, and the diameter of the insulating tube (18) is 0.5 mm smaller than the inner diameter of the simulated heat transfer tube (7).

10. The steam generator heat transfer tube fouling growth simulation and boiling heat exchange test device according to claim 1, characterized in that: When conducting boiling heat transfer experiments, the device maintains the heating power and fluid inlet conditions at set values ​​under the same operating conditions. The fluid inlet conditions include flow rate, temperature, pressure, subcooling, pH value, and impurity content. The experiment starts with simulating a clean, fouling-free state on the heat transfer tube, gradually growing fouling and stopping when the fouling reaches a thickness of tens or hundreds of microns. Thermocouple temperature measurement is performed at regular intervals. Each measurement data is measured by a sliding thermocouple system to achieve temperature measurements at four circumferential positions at different heights. During the experiment, the heating power of the heat transfer tube and the fluid inlet state parameters were measured simultaneously. Based on the heating power and the temperature inside the heat transfer tube, the outer surface temperature of the heat transfer tube at four locations at different circumferential heights was calculated using the one-dimensional cylindrical heat conduction equation. The fluid temperature at different heights inside the heat transfer tube was also calculated based on the fluid inlet temperature and heating power. Furthermore, the heat transfer coefficient at four locations at different circumferential heights was calculated based on the heat flux density, fluid temperature, and the outer surface temperature of the heat transfer tube. This heat transfer coefficient was compared with the heat transfer coefficient of the heat transfer tube when it was clean and free of dirt. The change in the fouling thermal resistance at different heights of the heat transfer tube over time was determined to characterize the boiling heat transfer characteristics caused by the fouling of the heat transfer tube. After the experiment, the experimental device was disassembled, the heat transfer tube was taken out, and the surface dirt at different heights and around the heat transfer tube corresponding to the temperature measurement position was observed and sampled for analysis to obtain the dirt weight, dirt thickness at different positions, and microstructure information, and to obtain the coupling relationship between dirt growth and boiling heat transfer characteristics.

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