Axial heat transfer system for alleviating thermal stratification effect of nuclear power plant pipelines

Abstract

The present invention discloses an axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines, which is used to alleviate the thermal stratification effect of nuclear power plant pipelines. The nuclear power plant pipelines include a main pipeline and a branch pipeline connected to the main pipeline. The branch pipeline includes a vertical pipe section and a horizontal pipe section. The vertical pipe section is connected to the main pipeline, and the horizontal pipe section is connected to one end of the vertical pipe section away from the main pipeline. The horizontal pipe section has a sensitive area. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines includes: a heat pipe device, which is axially extended along the outer wall surfaces of the lower sides of the main pipeline and the branch pipeline and is used to transfer heat to the sensitive area to eliminate or alleviate the thermal stratification effect; a temperature measuring device, which is arranged on the outer periphery of the horizontal pipe section located in the sensitive area and is used to detect the temperature of the sensitive area. It can reduce the occurrence of pipeline thermal stratification, thermal cycling and thermal shock, can reduce the probability of pipeline fatigue occurrence so as to improve the unit availability, reduce the risk of radioactive substance release, and enhance the operation safety level of the unit.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power technology, and in particular to an axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines. Background Art

[0002] Abbreviation and Definition of Key Terms:

[0003] Thermal stratification: The temperature gradient distribution phenomenon in a pipeline or container caused by the fluid density difference. The generalized concept of thermal stratification also includes thermal cycling and thermal striping phenomena.

[0004] Thermal cycling: The temperature fluctuation phenomenon at a certain point on the inner wall of a pipeline or container caused by the change of the stratified water level, the change of the fluid temperature, or the penetration of turbulence.

[0005] Thermal striping, the high-frequency fluctuation of the cyclic temperature over time caused by the interfacial wave at the stratified interface.

[0006] During the operation of a nuclear power plant, there will be many complex thermohydraulic phenomena. Especially on the stagnant pipelines connected to the reactor coolant system, one end of these pipelines is connected to the reactor coolant system pipeline and is disturbed by high-speed fluid, while the other end is in a stagnant state for a long time due to being closed (usually a valve is set). Under the combined action of factors such as turbulence penetration, valve leakage, and environmental heat dissipation, complex thermohydraulic phenomena such as thermal stratification, thermal cycling, and thermal striping will occur. The long-term existence of these phenomena will cause thermal stress and thermal fatigue effects on the system pipelines, and even pose a threat to the safety of the nuclear power plant. Experience feedback shows that cracks or even leaks have been found in the sensitive parts of the pipelines during the ten-year overhaul of foreign nuclear power plants. Therefore, these thermohydraulic phenomena should be fully considered in the design, operation, and maintenance processes of nuclear power plants.

[0007] In the existing design of nuclear power plant units, there are mainly two technical solutions for reducing the pipeline thermal fatigue caused by thermal stratification, thermal cycling, and thermal striping: one is to set up fatigue monitoring of pipelines in sensitive areas and valve leakage monitoring; the other is to conduct volume inspection during the unit overhaul to verify the integrity of the pressure boundary.

[0008] Due to the certain long-term and hidden nature of the pipeline defect problems caused by the thermal stratification effect, according to the experience feedback of foreign nuclear power plants, cracks have appeared locally in pipelines with intact reference point inspections after ten years of operation and maintenance. In view of this technical feature, the existing technologies have the following problems:

[0009] - Whether it is setting up monitoring or conducting regular inspections, it is necessary to accurately locate the sensitive positions, and a large amount of screening, analysis, and test work needs to be done in the early stage.

[0010] - The prior art is based on "after-the-fact" solutions, where subsequent maintenance, mitigation, or replacement work is carried out only after a problem is discovered. This poses challenges to the plant availability and safety. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide an axial heat transfer system for mitigating the thermal stratification effect in nuclear power plant pipelines.

[0012] The technical solution adopted by the present invention to solve its technical problem is: constructing an axial heat transfer system for mitigating the thermal stratification effect in nuclear power plant pipelines, which is used to mitigate the thermal stratification effect in nuclear power plant pipelines. The nuclear power plant pipelines include a main pipeline and at least one branch pipeline connected and communicating with the main pipeline. The branch pipeline includes a vertical pipe section and a horizontal pipe section. The vertical pipe section is connected to the main pipeline, and the horizontal pipe section is connected to one end of the vertical pipe section far from the main pipeline. The horizontal pipe section has a sensitive area. The axial heat transfer system for mitigating the thermal stratification effect in nuclear power plant pipelines includes:

[0013] A heat pipe device, which is axially extended along the outer wall surfaces of the lower sides of the main pipeline and the branch pipeline, and is used to transfer heat to the sensitive area to eliminate or mitigate the thermal stratification effect;

[0014] A temperature measuring device, which is arranged on the outer periphery of the horizontal pipe section located in the sensitive area and is used to detect the temperature of the sensitive area.

[0015] In some embodiments, the axial heat transfer system for mitigating the thermal stratification effect in nuclear power plant pipelines includes a heat insulation layer arranged on the outer periphery of the nuclear power plant pipelines;

[0016] Both the heat pipe device and the temperature measuring device are arranged in the heat insulation layer.

[0017] In some embodiments, the manufacturing material of the heat insulation layer is at least one of rock wool, aluminum silicate wool, glass wool, or foam glass.

[0018] In some embodiments, the heat pipe device has a heat absorption section, an intermediate section, and a heat release section connected in sequence;

[0019] The heat release section is arranged on the outer periphery of the horizontal pipe section located in the sensitive area, and the outer periphery of the intermediate section is provided with a heat insulation layer.

[0020] In some embodiments, the manufacturing material of the heat insulation layer is at least one of rock wool, aluminum silicate wool, glass wool, or foam glass.

[0021] In some embodiments, the heat pipe device includes multiple heat pipes.

[0022] In some embodiments, the heat required to heat the cold fluid in the stratified fluid is calculated by the following formula:

[0023] Q 1 = c·m·ΔT

[0024] where c is the specific heat of water; ΔT is the temperature difference between the hot and cold fluid streams, ΔT = T 热流体 - T 冷流体 ; m is the mass of water in the heated pipe, ρ 冷流体 : cold fluid density; d is the diameter of the stratified pipe; L is the length of the stratified pipe;

[0025] The heat absorption of the heat pipe is calculated by the following formula:

[0026] Q 2 = K·A·ΔT m ·t;

[0027] where K is the heat transfer coefficient, determined according to the heat pipe material; A is the total heat transfer area; ΔT m : logarithmic mean temperature difference, ΔT max = T 热流体 - T 1 ; ΔT min = T 冷流体 - T 1 ; T 1 : saturated temperature of the fluid in the heat pipe; t is the heating time;

[0028] The number of heat pipes installed is calculated by the following formula:

[0029]

[0030]

[0031] where Q 2 = η·Q 1 , η is the heat loss coefficient, taking 0.98; F is the heat transfer area of a single heat pipe.

[0032] In some embodiments, the heat pipe is a round pipe or a square pipe.

[0033] In some embodiments, the temperature measuring device includes a plurality of temperature measuring units, and the plurality of temperature measuring units are arranged along the axial direction and / or the circumferential direction of the transverse pipe section on the outer periphery of the transverse pipe section located in the sensitive area.

[0034] In some embodiments, the plurality of temperature measuring units are symmetrically arranged along the axial direction of the transverse pipe section on the upper and lower outer surfaces of the transverse pipe section located in the sensitive area.

[0035] In some embodiments, the temperature measuring unit includes a thermocouple or a thermal resistor.

[0036] In some embodiments, the temperature measuring device is communicatively connected to the main control of the power plant.

[0037] Implementing the present invention has the following beneficial effects: The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines is used to reduce the occurrence of pipeline thermal stratification, thermal cycling, and thermal shock, can reduce the probability of pipeline fatigue occurrence, thereby improving the unit availability rate, reducing the risk of radioactive substance release, and enhancing the operation safety level of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the present invention, the present invention will be further described below in conjunction with the drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:

[0039] Figure 1 is a schematic diagram of the axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines in some embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings. In the following description, it should be understood that the orientation or positional relationships indicated by "front", "rear", "upper", "lower", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", "tail", etc. are based on the orientation or positional relationships shown in the drawings and are constructed and operated in a specific orientation, and are only for the convenience of describing the technical solution, rather than indicating that the device or element referred to must have a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0041] It should also be noted that, unless otherwise clearly specified and limited, terms such as "installation", "connection", "linkage", "fixation", "setting" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. When a component is referred to as "on" or "under" another component, the component can be "directly" or "indirectly" located above the other component, or there may also be one or more intermediate components. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures, technologies, etc. are presented in order to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0043] Please refer to Figure 1 , the present invention shows an axial heat transfer system 50 for alleviating the thermal stratification effect of nuclear power plant pipelines, which is used to alleviate the thermal stratification effect of nuclear power plant pipelines. The nuclear power plant pipelines include a main pipeline 10 and at least one branch pipeline 20 connected and communicated with the main pipeline 10. The branch pipeline 20 includes a vertical pipe section 21 and a horizontal pipe section 22. The vertical pipe section 21 is connected to the main pipeline 10, and the horizontal pipe section 22 is connected to one end of the vertical pipe section 21 away from the main pipeline 10. The horizontal pipe section 22 has a sensitive area. Specifically, one end of the horizontal pipe section 22 away from the vertical pipe section 21 is connected to a cold pipe 40 through an isolation valve 30. The fluid in the horizontal pipe section 22 is in a low-speed or stagnant state. Due to the combined influence of the heat dissipation of the wall surface of the branch pipeline 20 and the cold fluid on the isolation valve 30 side, natural convection occurs in this part of the fluid region, and this region is the sensitive area. Among them, the hot fluid flows upward and the cold fluid flows downward, and thermal stratification occurs in the fluid in the horizontal pipeline 22. Among them, the label A is the interface between the hot and cold fluids, which is a virtual interface for facilitating the understanding of the thermal stratification phenomenon.

[0044] The axial heat transfer system 50 for alleviating the thermal stratification effect of nuclear power plant pipelines includes:

[0045] The heat pipe device 51 is axially extended along the outer wall surface of the lower side of the main pipeline 10 and the branch pipeline 20, and is used to transfer heat to the sensitive area to eliminate or alleviate the thermal stratification effect;

[0046] The temperature measuring device 52 is arranged on the outer periphery of the transverse pipe section 22 in the sensitive area and is used to detect the temperature of the sensitive area.

[0047] Understandably, the axial heat transfer system 50 for alleviating the thermal stratification effect of nuclear power plant pipelines is used to reduce the occurrence of pipeline thermal stratification, thermal cycling and thermal shock, can reduce the probability of pipeline fatigue occurrence, thereby improving the unit availability, reducing the risk of radioactive substance release, and enhancing the operation safety level of the unit.

[0048] In some embodiments, the axial heat transfer system 50 for alleviating the thermal stratification effect of nuclear power plant pipelines includes a heat insulation layer 53 arranged on the outer periphery of the nuclear power plant pipeline, and both the heat pipe device 51 and the temperature measuring device 52 are arranged in the heat insulation layer 53.

[0049] Preferably, the manufacturing material of the heat insulation layer 53 is at least one of rock wool, aluminum silicate wool, glass wool or foam glass. Of course, the heat insulation layer 53 can also be made of other heat insulation materials, and specific limitations are not made here.

[0050] In some embodiments, the heat pipe device 51 has a heat absorption section 511, an intermediate section 512 and a heat release section 513 connected in sequence. The heat absorption section 511 can be arranged on the outer surface of the main pipeline 10, such as the lower surface of the main pipeline 10. At least part of the heat absorption section 511 can be arranged on the outer side surface of the vertical pipe section 21. The intermediate section 512 can be arranged on the lower side of the turning point between the vertical pipe section 21 and the transverse pipe section 22, and the heat release section 513 is arranged on the outer periphery of the transverse pipe section 22 in the sensitive area.

[0051] Furthermore, a heat insulation layer 54 is arranged on the outer periphery of the intermediate section 512. Preferably, the manufacturing material of the heat insulation layer 54 is at least one of rock wool, aluminum silicate wool, glass wool or foam glass. Of course, the manufacturing material of the heat insulation layer 54 can also be other materials, and specific limitations are not made here.

[0052] In some other embodiments, the heat insulation layer 54 can be a heat insulation sleeve.

[0053] In some embodiments, the heat pipe device 51 includes multiple heat pipes. Heat Pipe: A component that fills a heat transfer working medium into a vacuum pipeline and transfers heat by evaporation and condensation. Preferably, the heat pipe is a round pipe or a square pipe. In order to increase the heat transfer area of the heat pipe, the heat pipe can be selected as square or flattened circular. Of course, the heat pipe can also be selected as a pipe with other structures according to requirements.

[0054] In some embodiments, the heat required to heat the cold fluid in the stratified fluid is calculated by the following formula:

[0055] Q 1 = c·m·ΔT

[0056] where, c: specific heat of water; ΔT: temperature difference between the hot and cold fluids, ΔT = T 热流体 - T 冷流体 ; m: mass of water in the heated pipe, ρ 冷流体 : density of the cold fluid; d: diameter of the stratified pipe; L: length of the stratified pipe; Note: Assume that half of the stratified fluid is hot fluid and half is cold fluid.

[0057] The heat absorption of the heat pipe is calculated by the following formula:

[0058] Q 2 = K·A·ΔT m ·t;

[0059] where, K: heat transfer coefficient, determined according to the heat pipe material; A: total heat transfer area; ΔT m : logarithmic mean temperature difference, ΔT max = T 热流体 - T 1 ; ΔT min = T 冷流体 - T 1 ; T 1 : saturation temperature of the fluid inside the heat pipe; t: heating time (assuming the heating time, the number of heat pipes is determined by iterative calculation according to the layout of the stratified pipes and the number of heat pipes).

[0060] The number of heat pipes installed is calculated by the following formula:

[0061]

[0062]

[0063] where, Q 2 = η·Q 1 , η: heat loss coefficient, taking 0.98; F: heat transfer area of a single heat pipe, selected according to the heat pipe form. To increase the heat transfer area of the heat pipe, the heat pipe can be square or flat round.

[0064] In some embodiments, the temperature measuring device 52 includes a plurality of temperature measuring units 521, and the plurality of temperature measuring units 521 are arranged along the axial direction and / or the circumferential direction of the transverse pipe section 22 on the outer periphery of the transverse pipe section 22 located in the sensitive area.

[0065] Preferably, multiple temperature measuring units 521 are symmetrically arranged along the axial direction of the transverse pipe section 22 on the upper and lower outer surfaces of the transverse pipe section 22 located in the sensitive area. For example, six temperature measuring units 521 can be set. Three temperature measuring units 521 are arranged on the outer periphery of the upper side of the transverse pipe section 22, and the other three temperature measuring units 521 are arranged on the outer periphery of the lower side of the transverse pipe section 22. The temperature measuring units 521 arranged up and down are symmetrically arranged along the transverse pipe section 22 to improve the accuracy of temperature detection. Of course, the number and arrangement position of the temperature measuring units 521 can be selected according to actual needs and are not specifically limited here.

[0066] In some embodiments, the temperature measuring unit 521 includes a thermocouple or a thermal resistor. Understandably, the temperature measuring unit 521 preferably uses a thermocouple. Understandably, the arrangement position of the thermocouple / thermal resistor is determined by thermal engineering calculations according to the different positions and arrangement forms of the branch pipeline 20. In order to accurately obtain the temperature difference between the upper and lower wall surfaces of the branch pipeline 20, multiple groups of thermocouples / thermal resistors can be arranged on the upper and lower wall surfaces of the branch pipeline 20.

[0067] In some embodiments, the temperature measuring device 52 is communicatively connected to the main control of the power plant to transmit the detected temperature information to the main control console of the power plant, and then feedback the measured temperature to the operation and maintenance personnel to monitor the development and elimination of its thermal stratification.

[0068] Understandably, the axial heat transfer system 50 for alleviating the thermal stratification effect of nuclear power plant pipelines includes a heat pipe device 51 and a temperature measuring device 52 arranged along the axial direction of the nuclear power plant pipeline. The above components are all arranged inside the thermal insulation layer 53, and an additional heat insulation layer 54 is provided for other pipeline parts of the heat pipe device 51 except for the two end regions. During the operation of the nuclear power plant, hot fluid flows in the main pipeline 10. Affected by turbulent penetration and temperature heat transfer, part of the hot fluid enters the branch pipeline 20. In the transverse pipe section 22 of the branch pipeline 20, the fluid is in a low-speed or stagnant state. Due to the heat dissipation of the wall surface of the branch pipeline 20 and the combined influence of the cold fluid on the side of the isolation valve 30, natural convection occurs in this part of the fluid region. Among them, the hot fluid flows upward and the cold fluid flows downward, and thermal stratification occurs in the fluid in the branch pipeline 20. Due to the presence of the heat pipe device 51, a temperature difference is generated at both ends of the heat pipe device 51 (one end contacts the mainstream or the hot fluid close to the mainstream, and the other end contacts the bottom of the pipeline in the sensitive area). Due to the characteristics of the heat pipe, the working medium in the heat pipe evaporates and absorbs heat at the hot end and condenses and releases heat at the cold end. So that heat is continuously transported from the hot end to the cold end, thereby heating this part of the sensitive area. The thermocouples / thermal resistors arranged on the branch pipeline 20 measure the temperature in real time and feedback the measured temperature to the operation and maintenance personnel to monitor the development and elimination of its thermal stratification.

[0069] Since the cold fluid in the branch pipeline 20 is on the lower wall surface of the branch pipeline 20, the heat pipe device 51 (composed of a heat pipe bundle) is arranged on the lower wall surface of the branch pipeline 20, so as to facilitate the heat conduction of the heat pipe device 51.

[0070] Understandably, the axial heat transfer system 50 for mitigating the thermal stratification effect of nuclear power plant pipelines can utilize the heat of the reactor coolant system itself and heat the pipelines in relevant sensitive areas in a passive manner, eliminating or mitigating the thermal stratification phenomenon from the heat transfer mechanism, thereby eliminating the thermal stress and thermal fatigue effect, providing guarantee for the safe operation of nuclear power plants and preventing radioactive release.

[0071] Understandably, the above embodiments only express the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, and these all belong to the protection scope of the present invention; therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. An axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines, which is used to alleviate the thermal stratification effect of nuclear power plant pipelines. The nuclear power plant pipelines include a main pipeline (10) and at least one branch pipeline (20) connected and communicated with the main pipeline (10). The branch pipeline (20) includes a vertical pipe section (21) and a horizontal pipe section (22). The vertical pipe section (21) is connected to the main pipeline (10), and the horizontal pipe section (22) is connected to one end of the vertical pipe section (21) far from the main pipeline (10). The horizontal pipe section (22) has a sensitive area. Characterized in that, The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines includes: A heat pipe device (51), which is axially extended along the outer wall surfaces of the lower sides of the main pipeline (10) and the branch pipeline (20) for transporting heat to the sensitive area to eliminate or alleviate the thermal stratification effect. The heat pipe device (51) has a heat absorption section (511), an intermediate section (512), and a heat release section (513) connected in sequence. The heat release section (513) is arranged on the outer periphery of the horizontal pipe section (22) in the sensitive area, and a heat insulation layer (54) is arranged on the outer periphery of the intermediate section (512). A temperature measuring device (52), which is arranged on the outer periphery of the horizontal pipe section (22) in the sensitive area for detecting the temperature of the sensitive area.

2. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 1, Characterized in that, The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines includes a heat insulation layer (53) arranged on the outer periphery of the nuclear power plant pipelines; Both the heat pipe device (51) and the temperature measuring device (52) are arranged in the heat insulation layer (53).

3. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 2, Characterized in that, The manufacturing material of the heat insulation layer (53) is at least one of rock wool, aluminum silicate wool, glass wool, or foam glass.

4. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 1, Characterized in that, The manufacturing material of the heat insulation layer (54) is at least one of rock wool, aluminum silicate wool, glass wool, or foam glass.

5. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 1, Characterized in that, The heat pipe device (51) includes multiple heat pipes.

6. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 5, Characterized in that, The heat required for heating the cold fluid in the stratified fluid is calculated by the following formula: Q 1 = c·m·ΔT where, c: specific heat of water; ΔT: temperature difference between the hot and cold fluid, ΔT = T 热流体 - T 冷流体 ; m: mass of water in the heated pipe, ρ 冷流体 : density of the cold fluid; d: diameter of the stratified pipe; L: length of the stratified pipe; The heat absorption of the heat pipe is calculated by the following formula: Q 2 = K·A·ΔT m ·t; Among them, K: heat transfer coefficient, determined according to the heat pipe material; A: total heat transfer area; ΔT m : logarithmic mean temperature difference, ΔT max = T 热流体 - T 1 ; ΔT min = T 冷流体 - T 1 ; T 1 : saturated temperature of the fluid inside the heat pipe; t: heating time; The number of heat pipes arranged is calculated by the following formula: Among them, Q 2 = η·Q 1 , where η is the heat loss coefficient, taking 0.98; F: the heat transfer area of a single heat pipe.

7. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 5, Characterized in that, The heat pipe is a round pipe or a square pipe.

8. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 1, Characterized in that, The temperature measuring device (52) includes a plurality of temperature measuring units (521), and the plurality of temperature measuring units (521) are arranged on the outer periphery of the transverse pipe section (22) located in the sensitive area along the axial direction and / or the circumferential direction of the transverse pipe section (22).

9. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 8, characterized in that the plurality of temperature measuring units (521) are symmetrically arranged along the axial direction of the transverse pipe section (22) on the upper and lower outer surfaces of the transverse pipe section (22) located in the sensitive area.

10. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to claim 8, characterized in that the temperature measuring unit (521) includes a thermocouple or a thermal resistor.

11. The axial heat transfer system for alleviating the thermal stratification effect of nuclear power plant pipelines according to any one of claims 1 to 10, characterized in that the temperature measuring device (52) is communicatively connected to the main control of the power plant.

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