Local flow concentration narrow rectangular channel boiling critical test section and test method under motion condition

Abstract

The application discloses a narrow rectangular channel boiling critical test section under motion condition with local heat flow concentration, which adopts direct current power single-side electric heating and comprises a compression glass window, compression bolts, an outer glass window, an inner glass window, a rectangular narrow slit flow channel, a heating plate assembly, upper and lower pressure bearing shells, a flow channel inlet, a flow channel outlet, an inlet electrode assembly and an outlet electrode assembly. The test section changes the regional resistance by adjusting the thickness of the heating plate part area, thereby changing the regional distribution voltage and power, and realizes the heat flow local concentration effect. The compression glass assembly, the outer window, the air gap and the inner window jointly form a visual window for observing the experimental phenomena. The test device can complete the visual test of the rectangular narrow slit channel boiling critical under the condition of the middle-low pressure heat flow local concentration.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of boiling criticality characteristics in rectangular narrow channel, in particular to a boiling critical test section and test method of narrow rectangular channel under motion condition with local heat flux concentration. BACKGROUND

[0002] The dispersion type plate fuel element has higher safety and higher efficiency compared with the traditional rod fuel element. However, in the preparation process of the dispersion type plate fuel element, the nuclear fission particle dispersion may have certain uneven deposition and aggregation deviation, so that the local reactivity increases under the condition of the same neutron flux, and the local heat flux concentration phenomenon is formed correspondingly, and the boiling criticality phenomenon may occur in the heat flux concentration area in advance. It is urgent to carry out the critical boiling mechanism research of the plate fuel element in the rectangular narrow channel under the local heat flux concentration, and to reveal the influence mechanism of key working condition parameters such as pressure, mass flow rate, subcooling degree and surface roughness on the CHF, so as to provide technical support for the accurate formulation of the thermal safety criterion of the dispersion type fuel element in the full range of working conditions. SUMMARY

[0003] The purpose of the present application is to provide a boiling critical test section and test method of narrow rectangular channel under motion condition with local heat flux concentration, and to provide an experimental device and method for the flow boiling characteristics research of the rectangular narrow channel under the local heat flux concentration.

[0004] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0005] A boiling critical test section of narrow rectangular channel under motion condition with local heat flux concentration, the test section adopts single-side electric heating of direct current power supply, is placed on a six-degree-of-freedom motion platform, and completes the research on the influence of critical heat flux density under static and motion conditions; comprising a compression window glass 1, a compression bolt 2, an outer glass window 3, an inner glass window 4, a rectangular narrow flow channel 5, an upper pressure-bearing shell 6, a lower pressure-bearing shell 7, a flow channel outlet 8, an outlet electrode assembly 9, an inlet electrode assembly 10, a flow channel inlet 11 and an Inconel625 heating plate 12;

[0006] The compression window glass 1, the compression bolt 2, the outer glass window 3 and the inner glass window 4 jointly constitute a visual glass assembly, the compression bolt 2 fixes the visual glass assembly with the upper pressure-bearing shell 6, a gas gap is arranged between the outer glass window 3 and the inner glass window 4, and through holes are arranged in the corners and connected with the rectangular narrow flow channel 5, deionized water working medium is introduced, the gas gap and the pressure on both sides of the rectangular narrow flow channel 5 are balanced, the outer glass window 3 meets the pressure-bearing requirement, and the inner glass window 4 meets the temperature-bearing requirement; the inner glass window 4 is fixed by bolts on both sides in the upper pressure-bearing shell 6, and the lower part directly contacts with the rectangular narrow flow channel 5;

[0007] The rectangular narrow slit flow channel 5 is arranged between the upper pressure shell 6 and the lower pressure shell 7, the Inconel 625 heating plate 12 is embedded on the upper side of the lower pressure shell 7, the Inconel 625 heating plate 12 is in contact with the rectangular narrow slit flow channel 5, and the deionized water working medium in the rectangular narrow slit flow channel 5 is heated; the flow channel inlet 11 and the flow channel outlet 8 are distributed in the lower pressure shell 7 and are communicated with both ends of the rectangular narrow slit flow channel 5 respectively, the flow channel inlet and outlet are respectively provided with inlet and outlet chamber cylinders, the structure sizes of the inlet and outlet chamber cylinders are the same, and the inlet and outlet effects of the test section are reduced; the outlet electrode assembly 9 and the inlet electrode assembly 10 are used for conducting the current provided by the direct-current power supply; the test section further comprises a thermocouple arrangement temperature measuring hole for measuring the temperature of the Inconel 625 heating plate 12.

[0008] The Inconel 625 heating plate 12 has a total length of 800 mm, a width of 60 mm and a thickness of 3.3 mm, two grooves with a size of 30*20*2.7 mm are arranged at a distance of 200 mm from the flow channel outlet, the reduced groove thickness increases the groove area resistance, increases the distributed resistance and power, and realizes the heat flux concentration effect.

[0009] The upper pressure shell 6 and the lower pressure shell 7 are 316L stainless steel shells.

[0010] The outlet electrode assembly 9 and the inlet electrode assembly 10 are conductive copper columns, and the copper columns are fixed with nickel plates welded on both sides of the Inconel 625 heating plate.

[0011] The Inconel 625 heating plate 12 is respectively welded with non-heating area conductive nickel plates at both ends.

[0012] The outlet electrode assembly 9 and the inlet electrode assembly 10 have the same structure, the main body is a solid copper column, the diameter of the solid copper column is matched with the required conductive amount of the test section; the copper column is wrapped with a sleeve and a sealing ring, and plays a sealing and isolation role.

[0013] The test method of the test section for the local heat flow concentration narrow rectangular channel boiling under the motion condition, at the beginning of the test, the working medium enters the rectangular narrow slit flow channel 5 from the flow channel inlet 11, and at the same time, the working medium enters the air gap between the outer glass window 3 and the inner glass window 4; after the working medium flows stably, the direct-current power supply is used to conduct current heating through the outlet electrode assembly 9 and the inlet electrode assembly 10, the electric heating power is gradually increased, and the temperature of the Inconel 625 heating plate 12 is ensured to rise gently, when the temperature of the inner wall surface of the Inconel 625 heating plate 12 suddenly increases, the direct-current power supply is cut off according to a reduction amplitude of 20% of the current power, so as to prevent the test section from being damaged; after the temperature of the test section decreases to room temperature, the inlet pressure, the mass flow rate and the subcooling degree parameters are adjusted according to the working condition table, the heating power is adjusted by repeating the above steps, and the experiments under different working conditions are completed.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] 1) Two recesses are arranged on the Inconel 625 heating plate 12, the thickness of the recess area is reduced to increase the resistance of the recess area, the voltage and power distributed in the area are increased, the surface heat flux density of the area between the two recesses is increased, and the heat flux density concentration effect is realized.

[0016] 2) The press window glass 1, the press bolt 2, the outer glass window 3 and the inner glass window 4 jointly constitute the visual glass assembly, the air gap arranged between the outer glass window and the inner glass window reduces the harsh requirement that the glass material must simultaneously satisfy the high temperature and high pressure resistance, and the safety of the test is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic view of the test section of the present application heat flow local concentration under the rectangular narrow slit channel.

[0018] Figure 2 It is a three-dimensional structure diagram of the Inconel 625 heating plate.

[0019] Figure 3 It is a diagram of the Inconel 625 heating plate and the surface thermocouple arrangement. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below with reference to the accompanying drawings.

[0021] As Figure 1The application is a narrow rectangular channel boiling critical test section under motion condition, which is mainly composed of a compression window glass 1, a compression bolt 2, an outer glass window 3, an inner glass window 4, a narrow rectangular channel 5, an upper pressure-bearing shell 6, a lower pressure-bearing shell 7, a channel outlet 8, an outlet electrode assembly 9, an inlet electrode assembly 10, a channel inlet 11 and an Inconel625 heating plate 12. The test section is placed on a two-ton six-degree-of-freedom motion platform, which can complete the related research on the influence of critical heat flux density under static and motion conditions. The compression window glass 1, the compression bolt 2, the outer glass window 3 and the inner glass window 4 together constitute a visual glass assembly, the compression bolt 2 fixes the visual glass assembly with the upper pressure-bearing shell 6, and the outer glass window 3 and the inner glass window 4 are provided with an air gap, and the corners are provided with through holes connected with the narrow rectangular channel 5, and the deionized water working medium is introduced, which is used for balancing the pressure on both sides of the air gap and the narrow rectangular channel 5, so that the outer glass window 3 mainly meets the pressure-bearing requirement, and the inner glass window 4 mainly meets the temperature-bearing requirement. The inner glass window 4 is fixed on both sides of the upper pressure-bearing shell 6 by bolts, and the lower part directly contacts with the narrow rectangular channel 5. The upper pressure-bearing shell 6 and the lower pressure-bearing shell 7 are provided with the narrow rectangular channel 5, the Inconel625 heating plate 12 is embedded on the upper side of the lower pressure-bearing shell 7, and the Inconel625 heating plate 12 contacts with the narrow rectangular channel 5, so as to heat the deionized water working medium in the narrow rectangular channel 5. The channel inlet 11 and the channel outlet 8 are distributed in the lower pressure-bearing shell 7 and communicate with both ends of the narrow rectangular channel 5, respectively, and the inlet and outlet chambers are provided with inlet and outlet chamber cylinders, respectively, which have the same structure size and can be used to reduce the inlet and outlet effects of the test section. In addition to the above main components, the test section also includes a thermocouple arrangement temperature measuring hole for measuring the temperature of the Inconel625 heating plate 12.

[0022] The test section can carry out boiling critical test of narrow rectangular channel under static and motion conditions, and deionized water is used as the flowing working medium, which enters from the channel inlet 11, then passes through the narrow rectangular channel 5 and flows out from the channel outlet 8.

[0023] The inlet and outlet chambers of the test section are provided with inlet and outlet chamber cylinders, respectively, which are used to reduce the turbulence of the working medium entering the narrow rectangular channel and reduce the inlet and outlet effects of the test section.

[0024] As Figure 2As shown in the drawings, as a preferred embodiment of the present application, the Inconel 625 heating plate 12 is generally 800 mm long, 60 mm wide, and 3.3 mm thick, and two grooves are arranged at a distance of 200 mm from the outlet of the flow passage. The groove size is 30*20*2.7 mm, and by arranging the grooves, the thickness of the local area of the plate is reduced, and by the resistance calculation formula, the resistance of the groove area is increased, the voltage and power distributed in the area are increased, thereby increasing the surface heat flux density of the area between the two grooves, and the heat flux density concentration effect is realized.

[0025] As shown in the drawings, Figure 3 As shown in the drawings, as a preferred embodiment of the present application, two 100*60*3.3 mm non-heating area conductive nickel plates are welded at both ends of the Inconel 625 heating plate 12. The arrangement of the non-heating area can make the deionized water working medium enter the heating area to reach the fully developed stage. Under the test condition of a temperature lower than 400 DEG C, the resistance of the Inconel 625 heating plate is much larger than that of the non-heating area conductive nickel plate, so most of the heating power of the direct current power supply will act on the Inconel 625 heating plate, so that the critical boiling phenomenon occurs in the heating area. A solid copper column is welded at the center of each conductive nickel plate, and the diameter of the copper column is matched with the direct current power supply parameters of the test loop. Twelve rows of temperature measuring holes are arranged on the back of the heating plate for inserting thermocouples to measure the wall temperature. The first three rows of temperature measuring holes are arranged at an interval of 60 mm, and the temperature measuring holes are arranged on the center line of the heating plate along the fluid flow direction; four groups of single temperature measuring holes are arranged at the center of the local heat flow concentration area and 34 mm, 60 mm and 110 mm away from the end of the heating plate, and the temperature measuring holes are arranged on the center line of the heating plate along the fluid flow direction. Three thermocouple temperature measuring holes are arranged at a distance of 8 mm from the outlet of the test section and 40 mm from the center of the groove, and each group of adjacent temperature measuring holes has a spacing of 20 mm. Two grooves are arranged in the upper and lower pressure shells respectively.

[0026] As a preferred embodiment of the present application, the upper and lower pressure shells 6 and 7 are 316L stainless steel shells, which have excellent corrosion resistance and high temperature resistance, and can avoid large deformation of the upper and lower shells at high temperature.

[0027] As shown in the drawings, Figure 1 The test method of the test section for the local heat flow concentration narrow rectangular channel boiling critical test under motion conditions of the present application comprises the following steps:

[0028] (1) Keep the inlet and outlet parameters of the test section stable, i.e. the inlet pressure, the inlet flow rate and the inlet subcooling degree. At the beginning of the test, the working fluid enters the rectangular narrow channel 5 from the inlet 11, and at the same time, the working fluid enters the air gap between the outer glass window 3 and the inner glass window 4. After the working fluid flow is stable, the direct current power source is used to conduct current through the outlet electrode assembly 9 and the inlet electrode assembly 10 to heat.

[0029] (2) When the critical power is approached, the power of the test section is gradually increased, and at the same time, the power increasing rate is reduced. The power is adjusted every 10 minutes and the data is recorded. The adjustment amplitude is not more than 2% of the current power.

[0030] (3) Pay attention to the flow channel image taken by the high-speed camera, and be ready to trigger the high-speed camera at any time to capture the bubble movement characteristics when the critical heat flux occurs.

[0031] (4) When the temperature of the inner wall of the Inconel 625 heating plate 12 rises at a speed of 5-15 ℃ / s and does not fall back for more than 3s, it is considered that the boiling criticality occurs. The computer criticality judgment program confirms it, and the direct current power source is cut off according to the program setting at a reduction amplitude of 20% of the current power to prevent the test section from being damaged by thermal fatigue. When the wall temperature exceeds 20-50 ℃ or exceeds the set upper limit temperature, the direct current power source can also be manually cut off to prevent the test section from being burned by heat, ensuring the safety of the experiment.

[0032] (5) Adjust the inlet pressure, mass flow rate and subcooling degree parameters according to the working condition table, repeat the above steps to adjust the heating power, until all the critical heat flux working condition tests are completed.

Claims

1. A narrow rectangular channel boiling critical test section with local heat flux concentration under motion conditions, characterized in that: The test section is placed on a six-degree-of-freedom motion platform and heated by a direct current power supply on one side to complete the research on the influence of critical heat flux density under static and motion conditions; the test section comprises a pressed window glass (1), a pressed bolt (2), an outer glass window (3), an inner glass window (4), a rectangular narrow slit flow channel (5), an upper pressure-bearing shell (6), a lower pressure-bearing shell (7), a flow channel outlet (8), an outlet electrode assembly (9), an inlet electrode assembly (10), a flow channel inlet (11) and an Inconel625 heating plate (12); The pressed window glass (1), the pressed bolt (2), the outer glass window (3) and the inner glass window (4) jointly form a visual glass assembly, the pressed bolt (2) fixes the visual glass assembly to the upper pressure-bearing shell (6), an air gap is arranged between the outer glass window (3) and the inner glass window (4), and through holes are arranged in the corners and connected to the rectangular narrow slit flow channel (5) to pass deionized water working medium, so as to balance the pressure on both sides of the air gap and the rectangular narrow slit flow channel (5), so that the outer glass window (3) meets the pressure-bearing requirement and the inner glass window (4) meets the temperature-bearing requirement; the inner glass window (4) is fixed to the upper pressure-bearing shell (6) by bolts on both sides and directly contacts the rectangular narrow slit flow channel (5) at the lower part. The upper pressure-bearing shell (6) and the lower pressure-bearing shell (7) are provided with the rectangular narrow slit flow channel (5), the Inconel625 heating plate (12) is embedded on the upper side of the lower pressure-bearing shell (7), the Inconel625 heating plate (12) contacts the rectangular narrow slit flow channel (5) to heat the deionized water working medium in the rectangular narrow slit flow channel (5); the flow channel inlet (11) and the flow channel outlet (8) are arranged in the lower pressure-bearing shell (7) and communicate with both ends of the rectangular narrow slit flow channel (5), respectively, and inlet and outlet chamber cylinders are arranged at the flow channel inlet and outlet, respectively, which have the same structure and size and are used to reduce the inlet and outlet effects of the test section; the outlet electrode assembly (9) and the inlet electrode assembly (10) are used to conduct the current provided by the direct current power supply; the test section further comprises a thermocouple arrangement temperature measuring hole for measuring the temperature of the Inconel625 heating plate (12). Non-heating area conductive nickel plates are welded at both ends of the Inconel625 heating plate (12).

2. The test section of claim 1, wherein: The Inconel625 heating plate (12) has a total length of 800 mm, a width of 60 mm and a thickness of 3.3 mm, and two grooves at a distance of 200 mm from the flow channel outlet have a size of 30*20*2.7 mm; reducing the groove thickness increases the groove area resistance, increases the distributed resistance and power, and realizes the heat flux density concentration effect.

3. The test section of claim 1, wherein: The upper pressure-bearing shell (6) and the lower pressure-bearing shell (7) are 316L stainless steel shells.

4. The test section of claim 1, wherein: The outlet electrode assembly (9) and the inlet electrode assembly (10) are conductive copper columns, and the copper columns are fixed to the nickel plates welded on both sides of the Inconel625 heating plate.

5. A test section for local pool boiling heat transfer in narrow rectangular channels under motion conditions according to claim 1, characterized in that: The outlet electrode assembly (9) and the inlet electrode assembly (10) have the same structure, the main body is a solid copper column, the diameter of the solid copper column matches the required conductive amount of the test section, and the copper column is covered with a sleeve and a sealing ring to play a sealing and isolation role.

6. A test method for a narrow rectangular channel boiling critical test section with local heat flux concentration under motion conditions according to any one of claims 1 to 5, characterized in that: At the beginning of the experiment, the working fluid enters the rectangular narrow channel (5) from the inlet (11), and at the same time, the working fluid enters the air gap between the outer glass window (3) and the inner glass window (4); after the working fluid flow is stable, the direct current power is used to conduct current heating through the outlet electrode assembly (9) and the inlet electrode assembly (10), the electric heating power is gradually increased, the temperature of the Inconel 625 heating plate (12) is ensured to rise smoothly, when the temperature of the inner wall of the Inconel 625 heating plate (12) increases suddenly, the direct current power is cut off according to the reduction amplitude of 20% of the current power, so as to prevent the damage of the test section; after the temperature of the test section decreases to room temperature, the inlet pressure, mass flow rate and subcooling degree parameters are adjusted according to the working condition table, the above steps are repeated to adjust the heating power, and the experiment under different working conditions is completed.

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