Fuel irradiation test device suitable for various media and control method thereof

Abstract

The application discloses a fuel irradiation test device suitable for various media, which comprises a built-in circulation loop and a natural circulation loop, the built-in circulation loop comprises an electric heating device, a test section, a built-in heat exchanger and a built-in circulation pipeline, the outlet of the electric heating device is communicated with the inlet of the test section, the outlet of the test section is communicated with the hot medium inlet of the built-in heat exchanger, and the hot medium outlet of the built-in heat exchanger is communicated with the inlet of the electric heating device through the built-in circulation pipeline; the inlet of the natural circulation loop is communicated with the cold medium outlet of the built-in heat exchanger, and the outlet of the natural circulation loop is communicated with the cold medium inlet of the built-in heat exchanger; the fuel irradiation test device can be suitable for various media at the same time, the cost of building multiple test loops for different media is avoided, the built-in circulation loop and the natural circulation loop are combined, the operation environment of a prototype reactor is simulated, wide-range thermal regulation conditions are realized, and the operation environment of different reactors can be more accurately simulated.

Description

Technical Field

[0001] This invention relates to the field of fuel irradiation technology for research reactors, and specifically to a fuel irradiation test apparatus and its control method applicable to various media. Background Technology

[0002] With the continuous development of nuclear energy technology, the design and research of fourth-generation nuclear reactors has gradually become a research focus. Among them, fuel elements, as the core components of the reactor core, are particularly crucial for performance testing and verification. In this regard, fuel and material irradiation testing has become a reliable research method, which can simulate and study the operating performance of fuel elements in actual or near-actual reactor environments.

[0003] In existing technologies, in-reactor irradiation devices are frequently used for such tests, utilizing gas temperature control systems to assist the testing process. However, due to the thermal properties of the gas, these devices have relatively weak cooling capabilities during accidents. Furthermore, the irradiation test conditions for different reactor fuel assemblies, such as inlet and outlet temperatures and fuel power, vary, posing greater challenges to fuel irradiation testing.

[0004] In this context, in fourth-generation reactors involving gaseous media (e.g., He), liquid metal media (e.g., LBE), and molten salt media (e.g., fluoride salts), due to the significant differences in their thermal properties, it is necessary to construct separate test loops for each medium. This not only increases the occupancy of the research reactor building but also increases the difficulty of maintaining and managing the different medium loops.

[0005] Currently, there is a lack of fuel irradiation test facilities that can adapt to multiple media and are more economical and efficient in design. A fuel irradiation test facility that can simulate various reactor operating environments, has a wide range of thermal regulation conditions, and simplifies the design of external test loops is of great significance for promoting the research and development of fourth-generation nuclear reactors.

[0006] Therefore, developing a fuel irradiation test device suitable for multiple media to meet the current needs of nuclear energy research has significant practical value and research significance. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that existing test devices cannot meet the requirements of irradiation tests on a variety of different media. The purpose is to provide a fuel irradiation test device and its control method that are applicable to a variety of media, and are suitable for irradiation tests on fuels and materials of various media, taking into account the thermal requirements such as power and temperature of different media.

[0008] This invention is achieved through the following technical solution:

[0009] A fuel irradiation test apparatus suitable for various media includes: an internal circulation loop and a natural circulation loop, wherein the internal circulation loop is disposed inside the apparatus and the natural circulation loop is disposed outside the apparatus;

[0010] The built-in circulation loop includes: an electric heating device, a test section, an internal heat exchanger, and a built-in circulation pipeline. The outlet of the electric heating device is connected to the inlet of the test section, the outlet of the test section is connected to the heat medium inlet of the internal heat exchanger, and the heat medium outlet of the internal heat exchanger is connected to the inlet of the electric heating device through the built-in circulation pipeline.

[0011] The inlet of the natural circulation loop is connected to the cold medium outlet of the internal heat exchanger, and the outlet of the natural circulation loop is connected to the cold medium inlet of the internal heat exchanger.

[0012] Furthermore, the built-in circulation loop also includes a media quality control system, the inlet and outlet of which are both connected to the built-in circulation pipeline, and the inlet of which is located upstream of the outlet.

[0013] Specifically, the natural circulation loop includes: a natural heat dissipation component, a valve group control system, and an external circulation loop. The inlet of the natural heat dissipation component is connected to the cold medium outlet of the internal heat exchanger, the outlet of the natural heat dissipation component is connected to the inlet of the valve group control system, the first outlet of the valve group control system is connected to the cold medium inlet of the internal heat exchanger, the second outlet of the valve group control system is connected to the inlet of the external circulation loop, and the outlet of the external circulation loop is connected to the cold medium inlet of the internal heat exchanger.

[0014] Optionally, the natural heat dissipation component is disposed within the research reactor cooling medium and exchanges heat with the research reactor cooling medium.

[0015] Optionally, the valve group control system includes: an inlet control valve connected to the natural heat dissipation component, a first outlet control valve connected to the internal heat exchanger, and a second outlet control valve connected to the external circulation loop.

[0016] Specifically, the natural heat dissipation component includes an outer spiral tube and an outer straight tube, which are arranged in parallel. The inlet of the outer spiral tube and the inlet of the outer straight tube are both connected to the cold medium outlet of the internal heat exchanger, and the outlet of the outer spiral tube and the outlet of the outer straight tube are both connected to the valve group control system.

[0017] Optionally, the valve group control system includes: a first inlet control valve connected to the outer spiral pipe, a second inlet control valve connected to the outer straight pipe, a first outlet control valve connected to the inner heat exchanger, and a second outlet control valve connected to the external circulation loop.

[0018] Furthermore, the test apparatus also includes an irradiation medium injection system, a leak detection system, a radioactivity detection system, and an instrumentation and control system;

[0019] The irradiation medium injection system is used to replenish the irradiation medium after a breach in the built-in circulation loop.

[0020] The leak detection system is used for leak detection at rupture points within the device;

[0021] The radioactivity detection system is used to detect radioactivity, and is equipped with targeted radioactivity detection based on the characteristics of the medium, in conjunction with the leak detection system to complete leak detection;

[0022] The instrumentation and control system is used to measure and control various parameters during the test, and provides data security signals for loop operation.

[0023] A control method for a fuel irradiation test apparatus applicable to various media, including a control method under accident conditions and a control method under non-accident conditions;

[0024] The control method under the accident conditions includes: connecting the outer spiral tube in the natural circulation assembly to the loop through the valve group control system; and disconnecting the external circulation loop from the loop through the valve group control system.

[0025] The control method under non-accident conditions includes: controlling the flow rate of the external spiral tube and / or external straight tube through the valve group control system, and selectively connecting to the external circulation loop for heat exchange through the valve group control system.

[0026] The control methods under non-accident operating conditions specifically include:

[0027] Obtain the real-time temperature at the outlet of the heat medium of the internal heat exchanger;

[0028] Connect the outer straight pipe to the circuit and determine whether the real-time temperature meets the set temperature. If it does, maintain the set temperature; otherwise,

[0029] Then, connect the outer straight pipe and the outer spiral pipe in parallel to the circuit, and determine whether the real-time temperature meets the set temperature. If it does, maintain the set temperature; otherwise,

[0030] If the temperature is below the set temperature, the flow rate of the outer spiral tube is reduced and the flow rate of the outer straight tube is increased; if the temperature is above the set temperature, the flow rate of the outer straight tube is reduced and the flow rate of the outer spiral tube is increased.

[0031] If the flow rate of the external straight pipe is adjusted to 0 and the real-time temperature is higher than the set temperature, then the external circulation loop is connected to the loop.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] The present invention sets up an internal circulation loop and a natural circulation loop. The internal circulation loop is located inside the device and includes an electric heating device, a test section, an internal heat exchanger, and an internal circulation pipeline. The natural circulation loop is located outside the device and includes a natural heat dissipation component, a valve group control system, and an external circulation loop.

[0034] This invention provides a fuel irradiation test apparatus applicable to multiple media (such as gas, liquid metal and molten salt), simplifying the need to set up multiple test apparatuses for different media and avoiding the cost of building multiple test loops for different media.

[0035] By combining built-in and natural circulation loops, the prototype reactor operating environment can be simulated, achieving a wide range of thermal regulation conditions. This allows for more accurate simulation of the operating environments of different reactors, improving research efficiency. Attached Figure Description

[0036] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0037] Figure 1 This is a schematic diagram of a fuel irradiation test apparatus applicable to various media according to the present invention.

[0038] Reference numerals: 1-Media quality control system, 2-Electric heating device, 3-Test section, 4-Internal heat exchanger, 5-Built-in circulation pipeline, 101-External circulation loop, 102-Valve group control system; 103-External straight pipe, 104-External spiral pipe. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0041] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0042] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] Example 1

[0045] A fuel irradiation test apparatus suitable for various media includes: an internal circulation loop and a natural circulation loop, wherein the internal circulation loop is disposed inside the apparatus and the natural circulation loop is disposed outside the apparatus;

[0046] The built-in circulation loop includes: an electric heating device 2, a test section 3, an internal heat exchanger 4, and a built-in circulation pipeline 5. The outlet of the electric heating device 2 is connected to the inlet of the test section 3, the outlet of the test section 3 is connected to the heat medium inlet of the internal heat exchanger 4, and the heat medium outlet of the internal heat exchanger 4 is connected to the inlet of the electric heating device 2 through the built-in circulation pipeline 5.

[0047] In this embodiment, the internal heat exchanger 4 is installed inside the device housing to form a closed loop within the device housing, providing irradiation test medium conditions. The natural circulation loop is coupled to the built-in circulation loop through the internal heat exchanger 4, serving as a heat sink for the device and removing heat from within the device.

[0048] The built-in electric heating device 2 has the function of regulating the thermal conditions of the test, so that the medium meets the test inlet temperature requirements.

[0049] The built-in circulation loop process is as follows: the medium reaches the corresponding medium irradiation inlet temperature condition through the electric heating device 2 and enters the test section 3; it enters the internal heat exchanger 4 from the outlet of the test section 3, and after heat exchange, it returns to the test section 3 through the electric heating device 2.

[0050] Based on the corresponding medium thermal conditions, the built-in circulation loop is designed with an internal heat exchanger 4 and an electric heating device 2. Through the built-in circulation pipeline 5, a closed loop is formed, continuously exporting the heat released by the fuel element to the external circulation loop 101. Under long-term operating conditions, the irradiated medium is quality controlled by the medium quality control system 1 to ensure the medium quality conditions.

[0051] The inlet of the natural circulation loop is connected to the cold medium outlet of the internal heat exchanger 4, and the outlet of the natural circulation loop is connected to the cold medium inlet of the internal heat exchanger 4.

[0052] The natural circulation loop includes a natural heat dissipation assembly, a valve group control system 102, and an external circulation loop 101. The inlet of the natural heat dissipation assembly is connected to the cold medium outlet of the internal heat exchanger 4, and the outlet of the natural heat dissipation assembly is connected to the inlet of the valve group control system 102. The first outlet of the valve group control system 102 is connected to the cold medium inlet of the internal heat exchanger 4, and the second outlet of the valve group control system 102 is connected to the inlet of the external circulation loop 101. The outlet of the external circulation loop 101 is connected to the cold medium inlet of the internal heat exchanger 4. The natural heat dissipation assembly is disposed within the research reactor cooling medium and exchanges heat with the research reactor cooling medium.

[0053] The natural heat dissipation assembly includes an outer spiral tube 104 and an outer straight tube 103, which are connected in parallel. The inlet of both the outer spiral tube 104 and the outer straight tube 103 is connected to the cold medium outlet of the internal heat exchanger 4, and the outlet of both the outer spiral tube 104 and the outer straight tube 103 is connected to the valve group control system 102. This parallel connection allows for fine-tuning of the heat exchange process under normal operating conditions by adjusting the parallel flow rate.

[0054] The natural circulation loop mainly consists of pipelines and valve group control system 102. The natural circulation loop is controlled by the parallel outer spiral pipe 104 and outer straight pipe 103 through the valve group control system 102. The heat removal of the entire device is divided into two parts: one part is removed to the research reactor cooling medium, and the other part is removed to the external circulation loop 101.

[0055] The natural circulation loop process is as follows: After internal heat exchange, the heat of test section 3 is discharged and flows out of the device at the bottom of the sample to conduct heat exchange of the reactor medium. According to the operating conditions (including the accident conditions of the irradiation test loop itself), the medium is controlled by valve group control system 102 to pass through the outer spiral tube 104 and the outer straight tube 103 to control the heat discharged to the reactor cooling medium. Finally, the remaining heat is discharged through the external circulation loop 101.

[0056] The outer spiral tube 104 establishes natural circulation under accident conditions to ensure long-term cooling of the device. Under non-accident conditions, the outer spiral tube 104 is connected in parallel with the straight tube to regulate the power matching between the test device and the external circulation loop 101.

[0057] By combining the built-in electric heating device 2 with the natural circulation loop, heat is exported through heat exchange between the natural circulation loop and the research reactor, and through heat exchange between the internal heat exchanger 4 and the external circulation loop 101, thereby improving the matching between the total power of the in-reactor device and the power of the external circulation loop 101. It is suitable for different media and different power requirements. Under different fuel and material power conditions, the power is supplemented by the electric heating device 2 to form thermal conditions that meet the irradiation test. The device follows the requirements of supplementing the heat exchange power of the external circulation loop 101 by heat exchange with the research reactor bypass flow.

[0058] In addition, the built-in circulation loop also includes a medium quality control system 1, the inlet and outlet of which are both connected to the built-in circulation pipeline 5, with the inlet of the medium quality control system 1 located upstream of its outlet. The quality status of the irradiated medium is monitored and controlled in real time according to the test cycle.

[0059] The advantages of this embodiment include:

[0060] The high-temperature section (internal heat exchanger 4 and test section 3) is located only within the built-in circulation loop, and the natural circulation loop and the external circulation loop 101, including the medium quality control system 1, have relatively low temperatures; this reduces the design difficulty and safety requirements of the complex loop system.

[0061] The built-in electric heating and natural circulation loop design can regulate the thermal conditions of fuel irradiation tests under normal operating conditions, while reducing the coupling degree between the power of the in-core test section 3 and the power of the external loop. Only one circulation loop needs to be built for the external heat exchange cycle. Under extreme accident conditions, long-term cooling capabilities can be established through electric heating and the research of lead-bismuth media to establish natural circulation.

[0062] Compared to in-reactor irradiation devices, the designed medium quality control system 1 can periodically perform quality control on lead-bismuth media, molten salt media, gaseous media, etc., under long-term operating conditions, providing longer-term irradiation test conditions.

[0063] Example 2

[0064] The valve group control system 102 has different structures for different situations, and this embodiment provides two structures.

[0065] If the valve group control component has only one inlet, the valve group control system 102 includes: an inlet control valve connected to the natural heat dissipation component, a first outlet control valve connected to the internal heat exchanger 4, and a second outlet control valve connected to the external circulation loop 101.

[0066] If the valve group control assembly has two inlets, the valve group control system 102 includes: a first inlet control valve connected to the outer spiral pipe 104, a second inlet control valve connected to the outer straight pipe 103, a first outlet control valve connected to the internal heat exchanger 4, and a second outlet control valve connected to the external circulation loop 101.

[0067] The test apparatus also includes an irradiation medium injection system, a leak detection system, a radioactivity detection system, and an instrumentation and control system;

[0068] The irradiation medium injection system is used to replenish the irradiation medium after a breach in the built-in circulation loop.

[0069] The leak detection system is used for leak detection at rupture points within the device;

[0070] The radioactivity detection system is used to detect radioactivity, and is equipped with targeted radioactivity detection based on the characteristics of the medium, in conjunction with the leak detection system to complete leak detection;

[0071] The instrumentation and control system is used to measure and control various parameters during the test, and provides data security signals for loop operation.

[0072] Example 3

[0073] A control method for a fuel irradiation test apparatus applicable to various media, including a control method under accident conditions and a control method under non-accident conditions;

[0074] The control method under the accident condition includes: connecting the outer spiral pipe 104 in the natural circulation assembly to the loop through the valve group control system 102; and disconnecting the external circulation loop 101 from the loop through the valve group control system 102.

[0075] The control method under non-accident conditions includes: controlling the flow rate of the external spiral pipe 104 and / or the external straight pipe 103 through the valve group control system 102, and selectively connecting to the external circulation loop 101 for heat exchange through the valve group control system 102.

[0076] The control methods under non-accident operating conditions specifically include:

[0077] Obtain the real-time temperature at the outlet of the heat medium of the internal heat exchanger 4;

[0078] Connect the outer straight pipe 103 to the circuit and determine whether the real-time temperature meets the set temperature. If it does, maintain the set temperature; otherwise,

[0079] Then, connect the outer straight pipe 103 and the outer spiral pipe 104 in parallel to the circuit, and determine whether the real-time temperature meets the set temperature. If it does, maintain the set temperature; otherwise,

[0080] If the temperature is below the set temperature, the flow rate of the outer spiral tube 104 is reduced and the flow rate of the outer straight tube 103 is increased; if the temperature is above the set temperature, the flow rate of the outer straight tube 103 is reduced and the flow rate of the outer spiral tube 104 is increased.

[0081] If the flow rate of the outer straight pipe 103 is adjusted to 0 and the real-time temperature is higher than the set temperature, then the external circulation loop 101 will be connected to the loop.

[0082] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0084] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A fuel irradiation test apparatus suitable for various media, characterized in that, include: The device includes a built-in circulation loop and a natural circulation loop, wherein the built-in circulation loop is located inside the device and the natural circulation loop is located outside the device. The built-in circulation loop includes: an electric heating device (2), a test section (3), an internal heat exchanger (4), and a built-in circulation pipeline (5). The outlet of the electric heating device (2) is connected to the inlet of the test section (3), the outlet of the test section (3) is connected to the heat medium inlet of the internal heat exchanger (4), and the heat medium outlet of the internal heat exchanger (4) is connected to the inlet of the electric heating device (2) through the built-in circulation pipeline (5). The inlet of the natural circulation loop is connected to the cold medium outlet of the internal heat exchanger (4), and the outlet of the natural circulation loop is connected to the cold medium inlet of the internal heat exchanger (4). The natural circulation loop includes: a natural heat dissipation component, a valve group control system (102), and an external circulation loop (101). The inlet of the natural heat dissipation component is connected to the cold medium outlet of the internal heat exchanger (4), the outlet of the natural heat dissipation component is connected to the inlet of the valve group control system (102), the first outlet of the valve group control system (102) is connected to the cold medium inlet of the internal heat exchanger (4), the second outlet of the valve group control system (102) is connected to the inlet of the external circulation loop (101), and the outlet of the external circulation loop (101) is connected to the cold medium inlet of the internal heat exchanger (4).

2. The fuel irradiation test apparatus suitable for multiple media according to claim 1, characterized in that, The built-in circulation loop further includes a media quality control system (1), the inlet of the media quality control system (1) and the outlet of the media quality control system (1) are both connected to the built-in circulation pipeline (5), and the inlet of the media quality control system (1) is located upstream of the outlet of the media quality control system (1).

3. The fuel irradiation test apparatus suitable for multiple media according to claim 1, characterized in that, The natural heat dissipation component is disposed within the cooling medium of the research reactor and exchanges heat with the cooling medium of the research reactor.

4. The fuel irradiation test apparatus suitable for multiple media according to claim 1, characterized in that, The valve group control system (102) includes: an inlet control valve connected to the natural heat dissipation component, a first outlet control valve connected to the internal heat exchanger (4), and a second outlet control valve connected to the external circulation loop (101).

5. A fuel irradiation test apparatus suitable for multiple media according to claim 3, characterized in that, The natural heat dissipation assembly includes an outer spiral tube (104) and an outer straight tube (103), which are arranged in parallel. The inlet of the outer spiral tube (104) and the inlet of the outer straight tube (103) are both connected to the cold medium outlet of the internal heat exchanger (4), and the outlet of the outer spiral tube (104) and the outlet of the outer straight tube (103) are both connected to the valve group control system (102).

6. A fuel irradiation test apparatus suitable for multiple media according to claim 5, characterized in that, The valve group control system (102) includes: a first inlet control valve connected to the outer spiral pipe (104), a second inlet control valve connected to the outer straight pipe (103), a first outlet control valve connected to the internal heat exchanger (4), and a second outlet control valve connected to the external circulation loop (101).

7. A fuel irradiation test apparatus suitable for multiple media according to claim 6, characterized in that, It also includes irradiation medium injection systems, leak detection systems, radioactivity detection systems, and instrumentation and control systems; The irradiation medium injection system is used to replenish the irradiation medium after a breach in the built-in circulation loop. The leak detection system is used for leak detection at rupture points within the device; The radioactivity detection system is used to detect radioactivity, and is equipped with targeted radioactivity detection based on the characteristics of the medium, in conjunction with the leak detection system to complete leak detection; The instrumentation and control system is used to measure and control various parameters during the test, and provides data security signals for loop operation.

8. A control method for a fuel irradiation test apparatus applicable to multiple media, characterized in that, Based on the fuel irradiation test apparatus as described in claim 7, the control method includes a control method under accident conditions and a control method under non-accident conditions. The control method under the accident conditions includes: connecting the outer spiral tube (104) in the natural circulation assembly to the loop through the valve group control system (102); and disconnecting the external circulation loop (101) from the loop through the valve group control system (102). The control method under non-accident conditions includes: adjusting the flow rate of the outer spiral pipe (104) and / or the outer straight pipe (103) through the valve group control system (102), and selectively connecting to the external circulation loop (101) for heat exchange through the valve group control system (102).

9. The control method for a fuel irradiation test apparatus applicable to multiple media according to claim 8, characterized in that, Control methods under non-accident operating conditions specifically include: Obtain the real-time temperature at the outlet of the heat medium of the internal heat exchanger (4); Connect the outer straight pipe (103) to the circuit and determine whether the real-time temperature meets the set temperature. If it does, maintain the set temperature; otherwise, The outer straight pipe (103) and the outer spiral pipe (104) are then connected in parallel to the circuit, and it is determined whether the real-time temperature meets the set temperature. If it does, the temperature is maintained; otherwise, If the temperature is below the set temperature, the flow rate of the outer spiral tube (104) is reduced and the flow rate of the outer straight tube (103) is increased; if the temperature is above the set temperature, the flow rate of the outer straight tube (103) is reduced and the flow rate of the outer spiral tube (104) is increased. If the flow rate of the outer straight pipe (103) is adjusted to 0 and the real-time temperature is higher than the set temperature, then the external circulation loop (101) will be connected to the loop.

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