System for critical heat flux test and method for controlling fluid inlet temperature of the test

Abstract

The embodiments of the present invention relate to the technical field of testing using thermal methods, and specifically to a system for critical heat flux density test and a method for controlling the fluid inlet temperature of the test. The system for critical heat flux density test provided by the embodiments of the present invention includes a test module, a first circulation pump, a preheater, a first heat exchanger, a second heat exchanger, a third heat exchanger and a coagulator. Using the system in the embodiments of the present invention, the flow medium required for the critical heat flux density test can be provided to the test module, and the flow medium flowing out of the test module can be converted from a vapor-liquid two-phase flow to a single-phase working medium, thereby realizing the circulation of the flow medium, and realizing precise control of the temperature of the flow medium at the inlet of the test module, and quickly and accurately adjusting the heat exchange power within a large power range, reducing the fluctuation of system parameters and reducing the thermal stress on the heat exchange tubes of the heat exchanger.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of testing using a thermal method, and more particularly to a system for a critical heat flux density test and a method for controlling a fluid inlet temperature of the test. Background Art

[0002] The statements herein merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] Critical heat flux (CHF) refers to the phenomenon in which the boiling heat transfer mechanism undergoes a sudden and drastic change, causing the heat transfer coefficient to drop sharply. When the heat flux of a fuel element reaches CHF, the fuel cladding temperature rises sharply, even reaching the burnout point, causing a serious accident. Therefore, critical heat flux (CHF) is an important limiting thermal-hydraulic parameter, its value directly affecting the safety and economics of the reactor. Currently, CHF values ​​are mainly predicted using empirical relationships obtained from critical heat flux tests. One of the key technologies for conducting critical heat flux tests is the precise control of the fluid temperature at the test module inlet.

[0004] The inventors discovered that during the critical heat flux test, the fluid exiting the test module is a high-temperature, high-pressure, vapor-liquid two-phase flow. This fluid needs to be cooled to a single-phase flow before it can be circulated into the first circulating pump. Furthermore, prior to the test, the fluid must be kept stable at the predetermined test temperature before entering the test module. This involves controlling the temperature of the fluid at the test module's inlet. Summary of the Invention

[0005] A brief overview of the present application is provided below to provide a basic understanding of certain aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to identify key or important portions of the present application, nor is it intended to limit the scope of the present application. Its purpose is simply to present certain concepts in a simplified form as a prelude to the more detailed description that will be discussed later.

[0006] In a first aspect, an embodiment of the present invention provides a system for critical heat flux density testing, comprising a test module, wherein a flow medium undergoes a critical heat flux density test within the test module. The system further comprises: a first circulation pump, a preheater, a first heat exchanger, a second heat exchanger, a third heat exchanger, and a coagulator, which are fluidically connected to each other. The first circulation pump is configured to provide power to the flow medium in the system; the preheater is fluidically connected to the test module and is configured to heat the flow medium flowing into the test module; the first heat exchanger and the second heat exchanger are configured in parallel, and the first heat exchanger and the second heat exchanger are respectively connected in parallel to the test module; the third heat exchanger is configured in series with the test module; the coagulator inlet is connected to the outlets of the test module, the first heat exchanger, and the second heat exchanger, and the outlet is connected to the inlet of the third heat exchanger. Among them, the flowing medium flows into the test module after being heated by the preheater, and the critical heat flux density test is carried out in the test module; after the critical heat flux density test, it flows out of the test module and flows to the coagulator; at the same time, the flowing medium flows into the first heat exchanger and the second heat exchanger from the outlet of the first circulation pump, and flows into the coagulator after heat exchange; the flowing medium is mixed into a single-phase medium in the coagulator, and then flows into the third heat exchanger for heat exchange; after heat exchange, it flows to the preheater for heating, and is ready to flow into the test module again for the critical heat flux density test.

[0007] In a second aspect, an embodiment of the present invention provides a method for controlling the fluid inlet temperature of a critical heat flux density test, wherein the method adopts the system of any embodiment of the first aspect of the present invention, and the method includes the following steps: S1, when the test module is in the initial heating stage, controlling the test module, the preheater, and the first, second, and third heat exchangers to heat the fluid pipeline of the system at a predetermined rate; S2: when the fluid inlet temperature entering the test module rises to a predetermined temperature, controlling the preheater and the first, second, and third heat exchangers to keep the fluid inlet temperature of the test module in a stable stage; S3: when the test module reaches a critical power, partially cutting off the heating power of the test module in manual or automatic mode, and controlling the first, second, and third heat exchangers to keep the fluid temperature and pressure at the test module inlet stable and prevent the fluid inlet temperature of the preheater from dropping too quickly; S4, after the test module test is completed, controlling the test module, the preheater, the first, second, and third heat exchangers to drop the fluid inlet temperature of the system at a predetermined rate.

[0008] In the system of the embodiments of the present invention, the preheater cooperates with the first, second, and third heat exchangers to convert the flowing medium exiting the test module from a two-phase vapor-liquid flow to a single-phase working medium, thereby achieving circulation of the flowing medium. Furthermore, the high-temperature, high-pressure flowing medium exiting the test module is first cooled to below the predetermined test temperature by heat exchange with the first, second, and third heat exchangers. The medium is then pumped into the preheater via a first circulation pump for precise temperature regulation before being re-flowed into the test module for testing. This achieves precise control of the flowing medium temperature at the inlet of the test module. Secondly, through the combined heat exchange of the first, second, and third heat exchangers, coupled with the regulation of the heat exchanger inlet flow by a regulating valve assembly, the heat exchange power can be quickly and accurately adjusted over a wide power range, while minimizing system parameter fluctuations. Finally, the fourth and fifth heat exchangers provide staged cooling of the first, second, and third heat exchangers, reducing thermal stress on the heat exchanger tubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other objects and advantages of the present invention will become apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, which will help to provide a comprehensive understanding of the present invention.

[0010] Figure 1 FIG. 4 is a schematic diagram of the layout of the main circuit of a system for critical heat flux density testing according to an embodiment of the present invention.

[0011] Figure 2 1 is a schematic diagram of the layout of the secondary circuit and the cooling circuit of a system for critical heat flux density testing according to one embodiment of the present invention.

[0012] Figure 3 is a flow chart of a method for controlling a fluid inlet temperature in a critical heat flux test according to one embodiment of the present invention.

[0013] Description of reference numerals:

[0014] 1. Bypass pipeline;

[0015] 10. Test module; 20. First circulation pump; 30. Preheater; 40. First heat exchanger; 50. Second heat exchanger; 60. Third heat exchanger; 70. Fourth heat exchanger; 80. Fifth heat exchanger; 90. Cooling tower; 100. Second circulation pump; 110. Third circulation pump; 120. Coagulator.

[0016] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0017] Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. For the sake of clarity and conciseness, not all features of an actual implementation are described in this specification. However, it should be understood that in the process of developing any such actual implementation, many implementation-specific decisions must be made in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary from implementation to implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is a routine task for those skilled in the art who benefit from the disclosure of this application.

[0018] It is also necessary to explain here that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show the device structure and / or processing steps that are closely related to the solution according to the present invention, while other details that are not closely related to the present invention are omitted.

[0019] An embodiment of the present invention provides a system for critical heat flux test, such as Figure 1 As shown, it includes a test module 10, in which a flow medium undergoes a critical heat flux test. The system also includes: a first circulation pump 20, a preheater 30, a first heat exchanger 40, a second heat exchanger 50, a third heat exchanger 60, and a coagulator 120, which are fluidically connected to each other. The first circulation pump 20 is configured to provide power to the flow medium in the system. The preheater 30 is fluidically connected to the test module 10 and is configured to heat the flow medium flowing into the test module 10. The first heat exchanger 40 and the second heat exchanger 50 are arranged in parallel, and the first heat exchanger 40 and the second heat exchanger 50 are respectively connected in parallel to the test module 10. The third heat exchanger 60 is arranged in series with the test module 10. The inlet of the coagulator 120 is connected to the outlets of the test module 10, the first heat exchanger 40, and the second heat exchanger 50, and the outlet is connected to the inlet of the third heat exchanger 60.

[0020] Among them, the flowing medium is heated by the preheater 30 and flows into the test module 10, and a critical heat flux density test is carried out in the test module 10. After the critical heat flux density test, it flows out of the test module 10 and flows to the coagulator 120; at the same time, the flowing medium flows from the outlet of the first circulation pump 20 into the first heat exchanger 40 and the second heat exchanger 50, and flows into the coagulator 120 after heat exchange; the flowing medium is mixed into a single-phase medium in the coagulator 120, and then flows into the third heat exchanger 60 for heat exchange; after heat exchange, it flows to the preheater 30 for heating, and is ready to flow into the test module 10 again for the critical heat flux density test.

[0021] The system provided by the embodiment of the present invention cooperates between the preheater 30 and the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 to enable the flow medium flowing out of the test module 10 to complete the conversion from a vapor-liquid two-phase flow to a single-phase working medium, thereby realizing the circulation of the flow medium. In addition, the high-temperature and high-pressure flow medium flowing out of the test module 10 is first heat exchanged by the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 to be cooled to below the predetermined test temperature, and then pumped into the preheater 30 by the first circulation pump 20 to accurately adjust its temperature, ready to flow into the test module 10 again for testing, thereby realizing precise control of the temperature of the flow medium at the inlet of the test module 10.

[0022] Specifically, if Figure 1 As shown, Figure 1 The loop connected by the black line represents the main loop of the system. Since the test module 10, first heat exchanger 40, and second heat exchanger 50 are connected in parallel, and the third heat exchanger 60 is connected in series with the test module 10, in the main loop, a portion of the fluid medium, heated by the first circulating pump 20 in the preheater 30, flows into the test module 10. After the critical heat flux density test is performed in the test module 10, the fluid exits the test module 10 as a vapor-liquid two-phase flow. Another portion of the fluid medium, driven by the first circulating pump 20, flows to the primary sides of the first and second heat exchangers 40 and 50 for heat exchange. The heat-exchanged fluid medium merges with the vapor-liquid two-phase flow exiting the test module 10 in the coagulator 120. The vapor-liquid two-phase flow releases heat under the action of the cooled fluid medium, forming a single-phase working medium. The fluid medium then flows to the primary side of the third heat exchanger 60 for further heat exchange, cooling it to below the predetermined test temperature. The cooled flow medium is pumped into the preheater 30 through the first circulation pump 20. The preheater 30 precisely adjusts the temperature of the flow medium and prepares it to flow into the test module 10 again for the critical heat flux density test, thereby converting the vapor-liquid two-phase flow out of the test module 10 into a single-phase working medium and achieving precise control of the test module inlet temperature.

[0023] It should be noted that the single-phase working medium is a single liquid cooling medium; the vapor-liquid two-phase flow is formed by the single-phase working medium absorbing heat and vaporizing through the liquid.

[0024] In some embodiments, the system is configured so that the flow rate of the flowing medium entering the first heat exchanger 40 and the second heat exchanger 50 is greater than the flow rate of the flowing medium entering the test module 10, so as to reduce the impact of the temperature change of the flowing medium in the test module 10 on the temperature and pressure of the main circuit, thereby ensuring the relative stability of the temperature and pressure of the main circuit.

[0025] In some embodiments, the control program of the test module 10 is provided with a rapid power cut-off function, which includes two modes: partial cut-off and full cut-off, so that when the test module 10 reaches the critical power, the heating power can be reduced quickly manually or automatically to protect the test module from being burned.

[0026] In some embodiments, the preheater 30 is configured so that the heating power can be manually or automatically controlled to facilitate precise control of the fluid temperature at the inlet of the test module 10. The manual control mode is configured to manually input a current value to control the heating power of the preheater 30; the automatic control mode is configured to adjust the heating power of the preheater 30 through an automatic control program. In the automatic control mode, the fluid temperature at the outlet of the preheater 30 predetermined for the test, i.e., the fluid temperature at the inlet of the test module 10, is input. The automatic control program calculates the heating power required to maintain the predetermined outlet temperature through heat balance based on the input temperature value, the real-time measured inlet temperature of the preheater 30, and the flow rate value, and adjusts the heating power of the preheater 30 in real time.

[0027] Since the heat exchange power of the critical heat flux density test varies widely, in order to achieve stable control of the inlet fluid temperature of the test module 10, multiple heat exchangers are set up in this embodiment for combined heat exchange, wherein the heat exchange power and heat exchange area of ​​a single heat exchanger are relatively small. Compared with the traditional method of using a heat exchanger with a larger heat exchange power for heat exchange, it is more conducive to meeting the heat exchange power requirements of the test with a larger variation range.

[0028] In some embodiments, the heat exchange power of the first heat exchanger 40 and the second heat exchanger 50 is set to be smaller than the heat exchange power of the third heat exchanger 60 to facilitate adjusting the heat exchange power for the critical heat flux test. For example, if the total heat exchange power of the heat exchangers is 12 MW, the heat exchange power of the first heat exchanger 40 and the second heat exchanger 50 can be set to 3 MW respectively, and the heat exchange power of the third heat exchanger 60 can be set to 6 MW.

[0029] In some embodiments, the total heating power of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60 can be determined by adding an appropriate margin to the sum of the maximum heating powers of the test module 10 and the preheater 30. For example, if the maximum heating power of the test module 10 is 10 MW and the maximum heating power of the preheater 30 is 1.5 MW, the total heating power of the heat exchangers can be set to 12 MW.

[0030] like Figure 1As shown, in some embodiments, a bypass line 1 is provided in the primary circuit of each of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60. The bypass line 1 is in fluid communication with the fluid inlet lines of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60. The fluid inlet lines of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60 are provided with regulating valves. The regulating valves cooperate with the bypass line 1 to precisely adjust the flow rate of the fluid entering the primary side of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60, thereby more accurately controlling the heat exchange efficiency of the heat exchangers.

[0031] To achieve stable control of the fluid temperature at the inlet of test module 10, the heat exchanger must be able to quickly and accurately adjust the heat exchange power to keep pace with transient changes in the heating power of test module 10, thereby ensuring relative stability of the loop temperature and pressure. In this embodiment, the amount of fluid entering the primary side of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60 is adjusted to control the heat exchange efficiency of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60, thereby achieving stable control of the fluid temperature and pressure in the main loop.

[0032] like Figure 2 As shown, in some embodiments, a fourth heat exchanger 70 and a fifth heat exchanger 80 are provided in the secondary side circuits of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60. A cooling circuit is provided in the secondary side circuits of the fourth heat exchanger 70 and the fifth heat exchanger 80, and the cooling circuit is provided with a cooling tower 90, which is in fluid communication with the fourth heat exchanger 70 and the fifth heat exchanger 80. The fourth heat exchanger 70 and the fifth heat exchanger 80 cool the fluid from the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60, and the fluid of the fourth heat exchanger 70 and the fifth heat exchanger 80 is cooled by the cooling tower 90.

[0033] Under high-temperature and high-pressure test conditions, heat exchangers are prone to experiencing large temperature differences across their heat exchange tubes, resulting in significant thermal stress on the tubes, which in turn affects the long-term operational stability of the test system and the safety of the test. In this embodiment, a fourth heat exchanger 70 and a fifth heat exchanger 80 are provided to cool the fluids from the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60. Simultaneously, the fluids from the fourth and fifth heat exchangers 70 and 80 are cooled by a cooling tower 90. This reduces the temperature difference across the heat exchange tubes of each heat exchanger, thereby alleviating the thermal stress on the heat exchange tubes and improving the long-term operational stability of the system and the safety of the test.

[0034] In this embodiment, the secondary sides of the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60, and the primary sides of the fourth heat exchanger 70 and the fifth heat exchanger 80 form a secondary circuit. Figure 2 , Figure 2 The loop connected by the green line represents the second loop of the above test system, and Figure 2 The circuit formed by the medium blue line represents the cooling circuit.

[0035] In some embodiments, the system may further include a second circulation pump 100 and a third circulation pump 110. The second circulation pump 100 is used to provide power for the flow medium in the secondary circuit, and the third circulation pump 110 is used to provide power for the flow medium in the cooling circuit.

[0036] Specifically, in the secondary circuit, the flow medium flows into the secondary sides of the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 under the action of the second circulation pump 100, and exchanges heat with the main circuit flow medium in the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60. After absorbing heat, the flow medium flows to the primary side of the fourth heat exchanger 70 and the fifth heat exchanger 80 for heat exchange. The cooled flow medium is ready to flow into the secondary sides of the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 again for heat exchange.

[0037] Furthermore, in the cooling circuit, the flow medium flows into the secondary side of the fourth heat exchanger 70 and the fifth heat exchanger 80 under the action of the third circulation pump 110, and exchanges heat with the secondary circuit flow medium in the fourth heat exchanger 70 and the fifth heat exchanger 80. After absorbing heat, the flow medium flows to the cooling tower 90 for cooling. The cooled flow medium is ready to flow into the secondary side of the fourth heat exchanger 70 and the fifth heat exchanger 80 again for heat exchange.

[0038] In some embodiments, the cooling power of the cooling tower 90 can be set to be the same as the heat exchange power of the secondary circuit.

[0039] In some embodiments, the total heat exchange power of the fourth heat exchanger 70 and the fifth heat exchanger 80 is set to match the heat exchange power of the main circuit, and the heat exchange power of the fourth heat exchanger 70 is set to be greater than that of the fifth heat exchanger 80 to facilitate adjustment of a wide range of heat exchange powers. For example, if the total heat exchange power of the heat exchangers is 12 MW, the heat exchange powers of the fourth heat exchanger 70 and the fifth heat exchanger 80 can be set to 8 MW and 4 MW, respectively.

[0040] In some embodiments, bypass lines are respectively provided in the primary side circuits of the fourth heat exchanger 70 and the fifth heat exchanger 80, and the bypass lines are connected to the fluid inlet lines of the fourth heat exchanger 70 and the fifth heat exchanger 80. The fluid inlet lines of the fourth heat exchanger 70 and the fifth heat exchanger 80 are provided with regulating valves, which cooperate with the bypass lines to accurately adjust the flow rate of the fluid entering the primary side of the fourth heat exchanger 70 and the fifth heat exchanger 80, thereby more accurately controlling the heat exchange efficiency of the heat exchanger.

[0041] In some embodiments, the operating temperature of the secondary circuit is set to be close to the average of the operating temperatures of the primary circuit and the cooling circuit to control the temperature difference across the heat exchange tubes of each heat exchanger, thereby further reducing the thermal stress on the heat exchange tubes of each heat exchanger and further ensuring the long-term stability of the system and the safety of the test. In this embodiment, the design temperatures of the primary circuit, the secondary circuit, and the cooling circuit are 360°C, 223°C, and 100°C, respectively. During system operation, the operating temperature of the primary circuit is in the range of 100°C-300°C, and the operating temperature of the cooling circuit is around 20°C. For example, if the operating temperature of the primary circuit is 300°C, the operating temperature of the secondary circuit can be controlled at 150°C, thereby controlling the temperature difference across the heat exchange tubes of each heat exchanger to below 150°C.

[0042] An embodiment of the present invention further provides a method for controlling the fluid inlet temperature of a critical heat flux test, wherein the method adopts a system of any embodiment of the present invention, such as Figure 3 As shown, the method includes the following steps S1 to S4.

[0043] S1: When the test module 10 is in the initial temperature increase stage, the test module 10, the preheater 30, and the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 are controlled to increase the temperature of the fluid pipeline of the system at a predetermined speed.

[0044] S2: When the inlet temperature of the fluid entering the test module 10 rises to a predetermined temperature, the preheater 30 and the first heat exchanger 40 , the second heat exchanger 50 and the third heat exchanger 60 are controlled to keep the inlet temperature of the fluid stable.

[0045] S3: When the test module 10 reaches a critical power, the heating power of the test module 10 is partially cut off in manual or automatic mode, and the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 are controlled to keep the fluid inlet temperature of the test module stable and prevent the fluid inlet temperature of the preheater 30 from dropping too quickly.

[0046] S4: After the test module 10 is finished, the test module 10, the preheater 30, and the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 are controlled to reduce the fluid inlet temperature of the system at a predetermined rate.

[0047] The method provided in an embodiment of the present invention controls the test module 10, the preheater 30, the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 respectively at different stages of the test to adapt to the test needs, thereby achieving precise control of the fluid temperature at the inlet of the test module 10.

[0048] In some embodiments, in step S1, the amount of flowing medium entering the inlet pipelines of the first heat exchanger 40 and the second heat exchanger 50 can be increased, and the amount of flowing medium entering the bypass pipeline 1 can be reduced to increase the flow rate of the fluid entering the primary side of the first heat exchanger 40 and the second heat exchanger 50, thereby improving the heat exchange power of the first heat exchanger 40 and the second heat exchanger 50, and thereby heating the fluid pipelines of the system.

[0049] In some embodiments, in step S1, the third heat exchanger 60 can be set as a heat exchanger for coarse adjustment of the heat exchange power, and the first heat exchanger 40 and the second heat exchanger 50 can be set as heat exchangers for fine adjustment of the heat exchange power to accurately control the fluid pipeline of the main loop of the system to heat up at a predetermined speed.

[0050] Specifically, in step S1, when the test module 10 is in the initial heating stage, the heating power of the preheater 30 is gradually increased through the manual control mode of the preheater 30, and the heating power of the test module 10 is gradually increased, the flow medium entering the inlet pipelines of the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60 is increased, and the flow medium entering the bypass pipeline 1 is reduced to increase the flow rate of the fluid entering the primary side of the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60, thereby improving the heating power of the first heat exchanger 40, the second heat exchanger 50 and the third heat exchanger 60. At the same time, the heating power is roughly adjusted by the third heat exchanger 60, and the heating power is fine-tuned by the first heat exchanger 40 and the second heat exchanger 50, so as to accurately control the fluid in the main circuit of the system to heat up at a predetermined speed. For example, the heating rate of the fluid in the main circuit of the system can be controlled to be below 1.5°C / min.

[0051] For example, regulating valves can be set on the inlet pipelines of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60 and the bypass pipeline 1, and the amount of flowing medium entering the inlet pipeline and the bypass pipeline 1 can be adjusted by increasing or decreasing the opening of the regulating valves.

[0052] In some embodiments, in step S2, the preheater 30 can be switched from a manual control mode to an automatic control mode, and its heating power can be controlled to maintain the fluid inlet temperature within a predetermined range. In this embodiment, by switching the control mode of the preheater 30, the preheater 30 can automatically fine-tune its heating power based on the input temperature value through the automatic control program in the automatic control mode, thereby facilitating precise control of the fluid inlet temperature.

[0053] In some embodiments, in step S2, the amount of flowing medium entering the inlet pipelines of the first heat exchanger 40 and the second heat exchanger 50 can be increased, and the amount of flowing medium entering the bypass pipeline 1 can be reduced to increase the flow rate of the fluid entering the primary side of the first heat exchanger 40 and the second heat exchanger 50, thereby improving the heat exchange power of the first heat exchanger 40 and the second heat exchanger 50.

[0054] Specifically, in step S2, when the inlet temperature of the fluid entering the test module 10 reaches a predetermined temperature, i.e., when the fluid inlet temperature of the test module 10 is in a stable control phase, the preheater 30 is switched from manual control mode to automatic control mode, causing it to automatically fine-tune the heating power to stabilize the fluid temperature at the inlet of the test module 10 within a predetermined range. For example, the fluid temperature at the inlet of the test module 10 can be controlled within a range of ±0.5°C of the predetermined temperature. At this point, the heating power of the test module 10 is increased in small stepwise increments, gradually approaching the critical power. For example, the increment of the heating power of the test module 10 can be 100 kW. While the heating power of the test module 10 is increasing in steps, the flow rate of the fluid entering the inlet pipes of the first heat exchanger 40 and the second heat exchanger 50 is gradually increased, while the flow rate of the fluid entering the bypass pipe 1 is reduced, thereby increasing the heating power of the first heat exchanger 40 and the second heat exchanger 50, thereby maintaining a stable fluid inlet temperature.

[0055] In some embodiments, in step S3, the heating power of the test module 10 can be quickly reduced, and the fluid inlet pipeline of the first heat exchanger 40 or the second heat exchanger 50 can be closed to quickly reduce the heat exchange power of the main circuit of the system, while keeping the temperature and pressure of the fluid pipeline of the main circuit relatively stable to avoid a rapid drop due to the reduction of the heating power of the test module 10.

[0056] Specifically, in step S3, when the test module 10 reaches critical power, its heating power needs to be rapidly reduced to prevent the heating element from burning out. At this point, the heating power of the test module 10 can be rapidly reduced through manual or automatic control mode. Simultaneously, the fluid inlet pipe to the first heat exchanger 40 or the second heat exchanger 50 is shut off, halting heat exchange in the first heat exchanger 40 or the second heat exchanger 50. This allows the heating power of the system's main circuit to rapidly decrease in tandem with the heating power of the test module 10, preventing an excessively rapid drop in the temperature and pressure of the main circuit, and thereby preventing an excessive drop in the inlet fluid temperature of the preheater 30.

[0057] For example, in step S3, when the test module 10 is at critical power, it is necessary to quickly reduce its heating power by 10%, and simultaneously quickly reduce the heat exchange power of the main circuit of the system by 10%.

[0058] In some embodiments, in step S4, the heating power of the test module 10 and the preheater 30 can be reduced, and the amount of fluid entering the fluid inlet pipelines of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60 can be reduced to reduce the heating power of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60, so that the fluid inlet temperature of the system drops at a predetermined rate.

[0059] Specifically, in step S4, after the test module 10 is tested, the temperature of the system's main circuit needs to be reduced to a predetermined temperature, for example, to below 100°C. At this time, the heating power of the test module 10 can be gradually reduced, and the heating power of the preheater 30 can be gradually reduced through the manual control mode of the preheater 30. At the same time, the amount of fluid entering the inlet pipes of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60 is reduced to reduce the flow rate of the fluid entering the primary side of the first heat exchanger 40, the second heat exchanger 50, and the third heat exchanger 60, thereby reducing their heat exchange power, lowering the temperature of the system's main circuit, and then controlling the system's fluid inlet temperature to decrease at a predetermined rate. For example, the cooling rate of the system's main circuit can be controlled to be below 1.5°C / min.

[0060] Regarding the embodiments of the present invention, it should also be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to obtain new embodiments.

[0061] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A system for critical heat flux density test, comprising a test module, wherein a flow medium is subjected to a critical heat flux density test in the test module, characterized in that Also included: a first circulation pump, a preheater, a first heat exchanger, a second heat exchanger, a third heat exchanger and a coagulator, which are in fluid communication with each other; The first circulation pump is configured to provide power to the flowing medium in the system; The preheater is in fluid communication with the test module and is configured to heat the flowing medium flowing into the test module; The first heat exchanger and the second heat exchanger are arranged in parallel, and the first heat exchanger and the second heat exchanger are respectively connected in parallel with the test module; The third heat exchanger and the test module are arranged in series; The inlet of the coagulator is in communication with the outlets of the test module, the first heat exchanger and the second heat exchanger, and the outlet of the coagulator is in communication with the inlet of the third heat exchanger; The flow medium is heated in the preheater and flows into the test module, where a critical heat flux test is performed. After the critical heat flux test, the flow medium flows out of the test module and flows into the coagulator. Simultaneously, the flow medium flows from the outlet of the first circulation pump into the first heat exchanger and the second heat exchanger, and flows into the coagulator after heat exchange. The flow medium is mixed into a single-phase medium in the coagulator, and then flows into the third heat exchanger for heat exchange. After heat exchange, the flow medium flows to the preheater for heating, and is ready to flow into the test module again for a critical heat flux test. A bypass pipeline is provided in the primary side circuit of the first heat exchanger, the second heat exchanger and the third heat exchanger, respectively, for regulating the flow rate of the fluid entering the first heat exchanger, the second heat exchanger and the third heat exchanger; A fourth heat exchanger and a fifth heat exchanger are provided in the secondary side circuits of the first heat exchanger, the second heat exchanger and the third heat exchanger. A cooling circuit is provided in the secondary side circuits of the fourth heat exchanger and the fifth heat exchanger. The cooling circuit is provided with a cooling tower. The cooling tower is in fluid communication with the fourth heat exchanger and the fifth heat exchanger. The fourth heat exchanger and the fifth heat exchanger cool the fluids from the first heat exchanger, the second heat exchanger, and the third heat exchanger, and the fluids in the fourth heat exchanger and the fifth heat exchanger are cooled by the cooling tower.

2. The system according to claim 1, wherein: The heat exchange power of the first heat exchanger and the second heat exchanger is set to be smaller than the heat exchange power of the third heat exchanger.

3. The system according to claim 1, wherein: The bypass line is in fluid communication with the lines at the fluid inlets of the first heat exchanger, the second heat exchanger, and the third heat exchanger.

4. A method for controlling the fluid inlet temperature of a critical heat flux test, wherein: The method adopts the system of any one of claims 1-3, characterized in that: S1: When the test module is in the initial temperature-raising stage, controlling the test module, the preheater, and the first, second, and third heat exchangers to heat the fluid pipelines of the system at a predetermined speed; S2: When the inlet temperature of the fluid entering the test module rises to a predetermined temperature, controlling the preheater and the first heat exchanger, the second heat exchanger, and the third heat exchanger to keep the inlet temperature of the fluid entering the test module in a stable stage; S3: When the test module reaches a critical power, partially cut off the heating power of the test module in a manual or automatic mode, and control the first heat exchanger, the second heat exchanger, and the third heat exchanger to keep the fluid inlet temperature of the test module stable and prevent the fluid inlet temperature of the preheater from dropping too quickly; S4: After the test module test is completed, controlling the test module, the preheater, and the first heat exchanger, the second heat exchanger, and the third heat exchanger to reduce the fluid inlet temperature of the system at a predetermined rate.

5. The method according to claim 4, characterized in that In step S1, the amount of flowing medium entering the inlet pipelines of the first heat exchanger and the second heat exchanger is increased, and the amount of flowing medium entering the bypass pipeline is reduced.

6. The method according to claim 5, characterized in that In step S1, the third heat exchanger is set as a heat exchanger for coarse adjustment of the heat exchange power, and the first heat exchanger and the second heat exchanger are set as heat exchangers for fine adjustment of the heat exchange power.

7. The method according to claim 4, characterized in that In step S2, the preheater is switched from a manual control mode to an automatic control mode, and its heating power is controlled so that the fluid inlet temperature remains stable within a predetermined range.

8. The method according to claim 5, characterized in that In step S2, the amount of flowing medium entering the inlet pipelines of the first heat exchanger and the second heat exchanger is increased, and the amount of flowing medium entering the bypass pipeline is reduced.

9. The method according to claim 4, characterized in that In step S3, the fluid inlet pipeline of the first heat exchanger or the second heat exchanger is closed.

10. The method according to claim 4, characterized in that In step S4, the preheater power adopts a manual control mode to reduce the heating power of the preheater and the test module, and reduce the amount of fluid entering the fluid entry pipeline of the first heat exchanger, the second heat exchanger, and the third heat exchanger to reduce the heating power of the first heat exchanger, the second heat exchanger, and the third heat exchanger.

Images