Two-phase boiling structure measurement system under inclined downward heating flow boiling condition

Abstract

The invention provides a system for measuring a two-phase boiling structure under an obliquely downward heating flow boiling condition, and relates to the technical field of nuclear safety experiment equipment, and the system comprises a cooling water flow channel which is communicated with a cooling water circulation system; the cooling water runner is provided with a measuring area, and the heater is fixedly arranged on the outer surface of the cooling water runner and corresponds to the heating surface; the probe mechanism is fixedly arranged on the outer surface of the cooling water flow channel, a probe can move in the direction close to or away from the heating surface, and the probe can be inserted into the measuring area to obtain the void fraction. The heater simulates the temperature of the molten pool and heats the outer surface of the cooling water runner so as to form a heating surface in the cooling water runner, the heating surface is used for simulating the outer wall surface of the lower sealing head, when cooling water flows along the cooling water runner, heat of the heating surface can be taken away, and scene simulation that the cooling water cools the outer wall surface of the lower sealing head is achieved. The probe is inserted into the cooling water flow channel, the void fraction of different section depths is obtained, and then the liquid film thickness is indirectly obtained.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear safety experimental equipment, in particular to a two-phase boiling structure measurement system under inclined downward heating flow boiling conditions. Background Art

[0002] When a serious accident occurs in a nuclear reactor, the fuel assemblies and structural materials in the core melt, and the molten material falls into the lower head to form a molten pool. At this time, water needs to be injected into the reactor cavity to submerge the lower head and cool the outer wall of the lower head to prevent the pressure vessel from failing. Therefore, whether the external cooling can remove the heat generated by the molten pool in the reactor is crucial to avoid the failure of the pressure vessel.

[0003] Critical heat flux (CHF) refers to the maximum heat flux value at which the liquid can maintain a stable boiling state on the heat exchange surface during the heat transfer process. It can intuitively reflect the heat exchange effect between the cooling water and the outer wall of the lower head. The thickness of the liquid film near the wall is an important parameter affecting the critical heat flux. Currently, there is no device or method that can directly measure the thickness of the liquid film near the wall. In order to study the critical heat flux on the downward inclined surface (the lower head has a downward inclined curved outer wall), how to provide a liquid film thickness measurement device and obtain the variation law of the liquid film thickness under different conditions is a problem that technicians in this field urgently need to solve. Summary of the invention

[0004] The object of the present invention is to provide a two-phase boiling structure measurement system under inclined downward heating flow boiling conditions to solve the problems existing in the prior art.

[0005] To achieve the above object, the present invention provides a two-phase boiling structure measurement system under inclined downward heating flow boiling conditions, comprising:

[0006] A cooling water flow channel is connected to a cooling water circulation system, and the cooling water flow channel is arranged obliquely;

[0007] A heater, wherein the cooling water flow channel has a measuring area, the measuring area has a heating surface, the heater is fixedly arranged on the outer surface of the cooling water flow channel and corresponds to the heating surface, and the heater is used to adjust the temperature of the heating surface;

[0008] The probe mechanism is fixedly arranged on the outer surface of the cooling water flow channel. The probe mechanism has a probe. The probe can move in a direction close to or away from the heating surface, and the probe can be inserted into the measurement area to obtain the cavitation fraction.

[0009] Furthermore, the cooling water circulation system comprises:

[0010] A water tank, wherein the water inlet end of the cooling water flow channel is connected to the water tank through a water pump, the water outlet end of the cooling water flow channel is connected to a condenser, and the condenser is connected to the water tank.

[0011] Furthermore, it also includes:

[0012] A flow meter is arranged between the water inlet end of the cooling water flow channel and the water pump;

[0013] A shunt branch, the water tank and the water pump are connected through a first pipeline, the water pump and the flow meter are connected through a second pipeline, one end of the shunt branch is connected to the first pipeline, and the other end is connected to the second pipeline; a first flow regulating valve is provided near the water pump on the first pipeline, and a second flow regulating valve is provided on the shunt branch.

[0014] Furthermore, it also includes:

[0015] A pressure controller, connected to the water tank and used to control the water pressure entering the cooling water flow channel;

[0016] An exhaust valve is communicated with the water tank and is used for adjusting the air pressure in the water tank.

[0017] Furthermore, a first mounting hole and a second mounting hole are defined in the heater, a heating rod is arranged in the first mounting hole, the heating rod corresponds to the heating surface, and a thermocouple is arranged in the second mounting hole; a current and voltage sensor is arranged in the heater, and the current and voltage sensor is electrically connected to the heating rod.

[0018] Furthermore, the measuring area is made of transparent material, and image data of the measuring area is collected by a high-speed camera.

[0019] Furthermore, the probe mechanism comprises:

[0020] A housing, wherein a receiving cavity is defined in the housing;

[0021] A probe outer cylinder is arranged in the accommodating cavity, one end of the probe is fixedly arranged in the probe outer cylinder, and the other end of the probe extends outward from the rear end of the shell and extends into the measuring area in a sealed manner;

[0022] A movable dial indicator is fixedly connected to the probe outer cylinder, and its operating end extends from the head end of the shell to the outside. When the movable dial indicator rotates, the movable dial indicator drives the probe to move in a direction close to or away from the heating surface through the probe outer cylinder;

[0023] A sealing piston, fixedly disposed on the outer surface of the probe outer cylinder and capable of sliding along the inner wall of the accommodating cavity;

[0024] The piston spring is sleeved outside the probe, one end of the piston spring is fixedly connected to the probe outer cylinder, and the other end is fixedly connected to the outer surface of the measuring area.

[0025] Furthermore, it also includes a rotating bracket, the output end of which is fixedly connected to the cooling water channel for adjusting the inclination angle of the cooling water channel.

[0026] Furthermore, it also includes a water temperature sensor, which is arranged close to the water inlet and outlet of the cooling water flow channel.

[0027] The present invention discloses the following technical effects:

[0028] 1. The temperature of the molten pool is simulated by the heater, and the outer surface of the cooling water channel is heated to form a heating surface in the cooling water channel. The heating surface is used to simulate the outer wall of the lower head. When the cooling water flows along the cooling water channel, it can take away the heat of the heating surface, realizing the scene simulation of cooling the outer wall of the lower head by the cooling water. In this process, the probe is inserted into the cooling water channel to obtain the cavitation share of different cross-sectional depths, and then the liquid film thickness is indirectly obtained.

[0029] 2. The probe can achieve precise movement by moving the dial indicator, and can measure the cavitation fraction with high precision, thus improving the measurement accuracy. At the same time, the measurement area is made of transparent material, and the high-speed camera can collect image data of the measurement area to obtain the bubble image. The bubble image can be used to verify the cavitation fraction measured by the probe.

[0030] 3. The cooling water channel is installed on a rotating bracket, which can adjust the inclination of the cooling water channel. In addition, the cooling water flow, water pressure, heating power of the heater, and current and voltage of the heating rod can all be adjusted to obtain the change law of liquid film thickness under different experimental conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a schematic diagram of the structure of the present invention;

[0033] Figure 2 is a schematic diagram of the probe mechanism;

[0034] Figure 3 is the cross-sectional cavitation fraction distribution diagram;

[0035] Among them, 1. cooling water flow channel; 101. measuring area; 2. heater; 3. probe mechanism; 301. shell; 302. probe outer tube; 303. probe; 304. moving dial indicator; 305. sealing piston; 306. piston spring; 4. water tank; 5. water pump; 6. condenser; 7. flow meter; 8. diversion branch; 9. first pipeline; 10. second pipeline; 11. first flow regulating valve; 12. second flow regulating valve; 13. pressure controller; 14. exhaust valve; 15. high-speed camera; 16. rotating bracket. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The embodiment of the present invention discloses a two-phase boiling structure measurement system under the condition of inclined downward heating flow boiling, wherein the cooling water flow channel 1 is connected to the cooling water circulation system, and the cooling water flow channel 1 is inclined; the cooling water flow channel 1 has a measurement area 101, and the measurement area 101 has a heating surface, and the heater 2 is fixedly arranged on the outer surface of the cooling water flow channel 1 by screws and corresponds to the heating surface, the cooling water flow channel 1 is made of a heat-conducting material, and the heater 2 is used to adjust the temperature of the heating surface; the probe mechanism 3 is fixedly arranged on the outer surface of the cooling water flow channel 1, and specifically, in this embodiment, the probe mechanism 3 is located on the bottom surface of the measurement area 101, and the heater 2 is located on the top surface of the measurement area 101, and the two positions are directly opposite. The probe mechanism 3 has a probe 303, and the probe 303 can move in a direction close to or away from the heating surface, and the probe 303 can be inserted into the measurement area 101 and obtain the cavitation share.

[0039] In this embodiment, the cooling water circulation system includes: a water tank 4, the water inlet end of the cooling water channel 1 is connected to the water tank 4 through a water pump 5, the water outlet end of the cooling water channel 1 is connected to the condenser 6, and the condenser 6 is connected to the water tank 4 for adjusting the water temperature entering the cooling water channel 1.

[0040] In this embodiment, the flowmeter 7 is arranged between the water inlet end of the cooling water flow channel 1 and the water pump 5; the water tank 4 and the water pump 5 are connected through a first pipeline 9, the water pump 5 and the flowmeter 7 are connected through a second pipeline 10, one end of the diversion branch 8 is connected to the first pipeline 9, and the other end is connected to the second pipeline 10; a first flow regulating valve 11 is provided on the first pipeline 9 near the water pump 5, and a second flow regulating valve 12 is provided on the diversion branch 8.

[0041] In this embodiment, the pressure controller 13 is connected to the water tank 4 for controlling the water pressure entering the cooling water flow channel 1 ; the exhaust valve 14 is connected to the water tank 4 for adjusting the air pressure in the water tank 4 .

[0042] In this embodiment, a first mounting hole and a second mounting hole are defined in the heater 2. A heating rod is arranged in the first mounting hole. The heating rod is generally laid flat along the lower surface of the heater 2 and corresponds to the heating surface. The heating area is large, which is conducive to more realistic simulation of the outer wall surface of the lower head. A thermocouple is arranged in the second mounting hole; a current and voltage sensor is arranged in the heater 2, and the current and voltage sensor is electrically connected to the heating rod. The heating power can be monitored by the current and voltage sensor, and different heating surface heat flux densities can be simulated by adjusting the heating power.

[0043] In this embodiment, the measuring area 101 is made of a transparent, heat-conductive material, and image data of the measuring area 101 is collected by a high-speed camera 15 .

[0044] In this embodiment, the probe mechanism 3 includes: a housing 301, in which a receiving chamber is defined; a probe outer cylinder 302 is arranged in the receiving chamber, one end of the probe 303 is fixedly arranged in the probe outer cylinder 302, and the other end extends from the rear end of the housing 301 to the outside and extends into the measuring area 101 in a sealed manner; a movable dial indicator 304 is fixedly connected to the probe outer cylinder 302, and its operating end extends from the head end of the housing 301 to the outside. When the movable dial indicator 304 rotates, the movable dial indicator 304 drives the probe 303 to move in a direction close to or away from the heating surface through the probe outer cylinder 302; a sealing piston 305 is fixedly arranged on the outer surface of the probe outer cylinder 302 and can slide along the inner side wall of the receiving chamber. In this embodiment, an insulating glue is filled between the probe 303 and the probe outer cylinder 302 to play a fixing and sealing role. The sealing piston 305 is used to seal the probe outer cylinder 302 and the flow channel 1 to prevent cooling water leakage. The piston spring 306 is sleeved outside the probe 303, and one end of the piston spring 306 is fixedly connected to the probe outer cylinder 302, and the other end is fixedly connected to the outer surface of the measuring area 101. In the above scheme, the mobile dial indicator 304 is used to accurately adjust the distance between the probe 303 and the heating surface. The principle of accurately adjusting the moving distance of the probe 303 is to convert the tiny physical displacement into the deflection of the pointer through a mechanical structure, and use the precise scale on the dial to read the measurement result. This design enables the dial indicator to perform high-precision measurements. The mobile dial indicator 304 adopts the existing technology and will not be repeated here. The probe outer cylinder 302 is made of stainless steel material, which can prevent the probe 303 from vibrating or breaking due to impact, thereby ensuring the stability and reliability of the measurement process.

[0045] In this embodiment, the output end of the rotating bracket 16 is fixedly connected to the cooling water channel 1, and is used to adjust the inclination angle of the cooling water channel 1 and simulate the various slopes of the curved outer wall of the lower head tilted downward. The water temperature sensor is arranged near the water inlet and outlet of the cooling water channel 1, and is used to monitor the water temperature changes at the water inlet and outlet of the cooling water channel 1. The water temperature sensor, current and voltage sensor, thermocouple and other sensing elements are all sent to the data acquisition system through the signal processing device, and the power of the heating rod can be adjusted by the control center. In addition, in order to ensure that the various structures do not produce motion interference when the rotating bracket 16 rotates, the various pipelines connected to the cooling water channel 1 are made of flexible materials. The rotating bracket 16 can be driven by a rotating motor to drive the cooling water channel 1 to rotate along the vertical plane to change the inclination angle.

[0046] The specific working process is as follows:

[0047] Install and seal all components. Send preheated cooling water into the water tank 4 through an external hot water boiler to reach a preset water level, and start the water pump 5 to circulate the cooling water between the cooling water flow channel 1 and the water tank 4. The water flow entering the cooling water flow channel 1 is adjusted by the first flow regulating valve 11 and the second flow regulating valve 12.

[0048] The heating rod is controlled to reach a preset power. When the temperature of the heating surface is stable (the heating rod starts to work for a period of time), the distance between the probe 303 and the heating surface is adjusted using the movable dial indicator 304 to detect the cavitation fraction at different positions and obtain the liquid film thickness according to the cavitation fraction.

[0049] According to the experimental needs, the power of the heating plate, the inclination of the cooling water channel 1, the flow rate and water pressure of the cooling water are adjusted to obtain the corresponding liquid film thickness under different experimental conditions, and the variation law of the liquid film thickness under different conditions is obtained to evaluate the influence of the liquid film thickness change on the critical heat flux density and develop a critical heat flux density prediction model.

[0050] Figure 3 The cross-sectional cavitation fraction distribution diagram obtained by actual measurement in this embodiment is shown in FIG. 1 . The measurement conditions are as follows: the inclination angle θ = 45°, the inlet water temperature T in =100℃, flow rate G=1m 3 / h, heating heat flux q"=0.6MW / m 3 . Figure 3 The average cavitation fraction measurement results of each measuring point are also given, where y is the distance to the heated wall, α is the average cavitation fraction measured at this position, and α is determined by the time it takes for the bubble to pass through the probe (Δt i ) and divided by the total measurement time (t ave )get.

[0051]

[0052] Through the sudden change of the cavitation fraction on the cross section, the boiling structure of liquid film layer-large bubble-mainstream can be clearly identified; by further changing the measurement conditions, the variation pattern of the boiling structure and the thickness of the liquid film near the wall can be obtained.

[0053] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0054] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A two-phase boiling structure measurement system under inclined downward heating flow boiling conditions, characterized in that: include: A cooling water flow channel (1) is connected to a cooling water circulation system, and the cooling water flow channel (1) is arranged at an angle; A heater (2), the cooling water flow channel (1) having a measuring area (101), the measuring area (101) having a heating surface, the heater (2) being fixedly arranged on the outer surface of the cooling water flow channel (1) and corresponding to the heating surface, the heater (2) being used to adjust the temperature of the heating surface; A probe mechanism (3) is fixedly arranged on the outer surface of the cooling water flow channel (1), and the probe mechanism (3) has a probe (303). The probe (303) can move in a direction close to or away from the heating surface, and the probe (303) can be inserted into the measurement area (101) and obtain the cavitation fraction.

2. A two-phase boiling structure measurement system under inclined downward heating flow boiling conditions according to claim 1, characterized in that: The cooling water circulation system comprises: A water tank (4), wherein the water inlet end of the cooling water flow channel (1) is connected to the water tank (4) via a water pump (5), the water outlet end of the cooling water flow channel (1) is connected to a condenser (6), and the condenser (6) is connected to the water tank (4).

3. A two-phase boiling structure measurement system under inclined downward heating flow boiling conditions according to claim 2, characterized in that: Also includes: A flow meter (7) is arranged between the water inlet end of the cooling water flow channel (1) and the water pump (5); A shunt branch (8), the water tank (4) and the water pump (5) are connected via a first pipeline (9), the water pump (5) and the flow meter (7) are connected via a second pipeline (10), one end of the shunt branch (8) is connected to the first pipeline (9), and the other end is connected to the second pipeline (10); a first flow regulating valve (11) is provided near the water pump (5) on the first pipeline (9), and a second flow regulating valve (12) is provided on the shunt branch (8).

4. A two-phase boiling structure measurement system under inclined downward heating flow boiling conditions according to claim 2, characterized in that: Also includes: A pressure controller (13) connected to the water tank (4) and used for controlling the water pressure entering the cooling water flow channel (1); The exhaust valve (14) is communicated with the water tank (4) and is used to adjust the air pressure in the water tank (4).

5. The two-phase boiling structure measurement system under the condition of inclined downward heating flow boiling according to claim 1 is characterized in that: The heater (2) defines a first mounting hole and a second mounting hole, wherein a heating rod is disposed in the first mounting hole and corresponds to the heating surface, and a thermocouple is disposed in the second mounting hole; a current and voltage sensor is disposed in the heater (2) and is electrically connected to the heating rod.

6. The two-phase boiling structure measurement system under the condition of inclined downward heating flow boiling according to claim 1 is characterized in that: The measuring area (101) is made of a transparent material, and image data of the measuring area (101) is collected by a high-speed camera (15).

7. The two-phase boiling structure measurement system under the condition of inclined downward heating flow boiling according to claim 1 is characterized in that: The probe mechanism (3) comprises: A housing (301), wherein a receiving cavity is defined in the housing (301); A probe outer cylinder (302) is disposed in the accommodating cavity, one end of the probe (303) is fixedly disposed in the probe outer cylinder (302), and the other end extends from the rear end of the housing (301) to the outside and extends into the measuring area (101) in a sealed manner; A movable dial indicator (304) is fixedly connected to the probe outer tube (302), and its operating end extends from the head end of the housing (301) to the outside. When the movable dial indicator (304) rotates, the movable dial indicator (304) drives the probe (303) to move in a direction close to or away from the heating surface through the probe outer tube (302); A sealing piston (305) is fixedly arranged on the outer surface of the probe outer cylinder (302) and is capable of sliding along the inner wall of the accommodating cavity; The piston spring (306) is sleeved outside the probe (303), one end of the piston spring (306) is fixedly connected to the probe outer tube (302), and the other end is fixedly connected to the outer surface of the measuring area (101).

8. The two-phase boiling structure measurement system under the condition of inclined downward heating flow boiling according to claim 1 is characterized in that: It also comprises a rotating bracket (16), the output end of which is fixedly connected to the cooling water flow channel (1) and is used to adjust the inclination angle of the cooling water flow channel (1).

9. The two-phase boiling structure measurement system under the condition of inclined downward heating flow boiling according to claim 1 is characterized in that: It also comprises a water temperature sensor, which is arranged close to the water inlet and outlet of the cooling water flow channel (1).

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