Nuclear reactor secondary side passive system high-pressure steam condensation experiment device and method

Abstract

The invention discloses a nuclear reactor secondary side passive system high pressure steam condensation experiment device and method, the experiment device can carry out a superheated steam condensation experiment and a saturated steam condensation experiment under high temperature and high pressure, and the experiment device comprises a shield pump, a water storage tank, a voltage stabilizer, a mass flow meter, a three-stage preheater, a condensation experiment section, a condenser and the like. The third-stage preheater is used for heating the single-phase water into single-phase superheated steam; the condensation experiment section is a double-pipe heat exchanger, a steam channel is arranged in the inner pipe, and cooling water is arranged outside the pipe; thermocouples are arranged at different depths of the pipe wall of the steam channel to measure the temperature distribution of the pipe wall, and the condensation heat transfer coefficient of the local position can be obtained according to the temperature distribution; the invention further provides an experimental method. The experimental device can complete the steam condensation heat exchange test in the inclined pipe under various inclination angles.

Description

Technical Field

[0001] This invention relates to the field of experimental technology for the heat transfer characteristics of condensers in passive emergency waste heat removal systems of nuclear reactors, specifically to an experimental apparatus and method for high-pressure steam condensation in a passive secondary system of a nuclear reactor. Background Technology

[0002] Passive residual heat removal systems play a crucial role as key safety facilities ensuring the effective removal of residual heat after an accident. In the event of an accident, the once-through steam generator rapidly produces a large amount of superheated steam. This high-temperature, high-pressure steam is then guided into the heat transfer tubes of the condenser. The outer wall of the heat transfer tubes is in direct contact with the cooling medium in the cooling water tank. Through an efficient heat exchange process, the heat released by the steam is transferred to the water in the cooling water tank, causing the steam to gradually condense into liquid water, thus achieving the removal of reactor residual heat. After entering the condenser, the superheated steam undergoes four stages: hot steam cooling, superheated steam condensation, saturated steam condensation, and condensate cooling. Steam condensation within the heat transfer tubes is a critical physical process affecting the system's operating characteristics, necessitating research into the high-temperature, high-pressure steam condensation mechanism to provide key technical support for system operating characteristic and safety analysis. Summary of the Invention

[0003] The purpose of this invention is to provide an experimental apparatus and method for high-pressure steam condensation in a passive secondary system of a nuclear reactor, providing an experimental apparatus and method for studying the high-temperature and high-pressure steam condensation mechanism of a passive waste heat removal system.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A high-pressure steam condensation experimental device for a passive secondary system of a nuclear reactor includes a water storage tank 2, a shielded pump 3, a flow meter 4, a first preheater 5, a second preheater 6, a third preheater 7, a condensation experimental section 8, and a condenser 9 connected in sequence by pipelines; a pressure regulator 1 connected to the pipelines for controlling the experimental pressure; and a cooling water pump 10 and a cooling tower 11 connected to the condensation experimental section 8. The condensation test section includes an inner tube 12, an outer sleeve 13, a fixing component 14, a high-pressure flange 15, a cooling water inlet 16, and a cooling water outlet 17. Multiple fixing components 14 are arranged along the axial direction of the outer sleeve 13. The inside of the inner tube is a steam channel, and the annular channel between the inner tube 12 and the outer sleeve 13 is a cooling water channel. The inner tube 12 is connected to the third preheater 7 and the condenser 9 through the high-pressure flange 15. The cooling water inlet 16 is connected to the cooling water pump 10, and the cooling water outlet 17 is connected to the cooling tower 11, continuously providing cooling water to the condensation test section 8. Temperature measuring holes 18 of different depths are opened at the same cross section of the inner tube 12 wall.

[0005] Deionized water flows out from storage tank 2, passes through shielded pump 3, flow meter 4, first preheater 5, second preheater 6, third preheater 7, condensation test section 8, and condenser 9, and returns to storage tank 2.

[0006] The first preheater 5, the second preheater 6, and the third preheater 7 adopt a three-point heating method, and the preheaters are directly welded to the pipeline, which avoids the sealing problem of the high-pressure insulating flange at high temperature.

[0007] A three-stage preheater is used. The first preheater 5 heats deionized water from room temperature to subcooled water with a subcooling degree of 20°C. The second preheater 6 and the third preheater 7 heat the subcooled water to single-phase superheated steam, providing working fluid for the condensation test section 8. This reduces the heat flux density of the preheating section and improves the safety of the experiment.

[0008] Temperature measuring holes 18 at different depths are opened at the same cross section of the inner tube 12 wall. The temperature distribution at different depths of the wall is obtained by arranging thermocouples. The local heat flux density and heat transfer coefficient are calculated based on the temperature difference at different depths at the same cross section, so as to study the high-pressure steam condensation heat transfer characteristics in the inclined tube at different inclination angles.

[0009] The experimental method for a high-pressure steam condensation experimental device for a passive secondary system of a nuclear reactor includes the following steps: Step (1): Turn on the data acquisition system, store experimental data in real time, and monitor the outlet steam pressure and temperature of the third preheater 7; Step (2): Fill the loop with water until it is full, start the shielded pump 3, and adjust the loop flow rate and the pressure of the pressure regulator 1 to achieve the water flow rate and pressure conditions required for the experimental conditions. Step (3): Start the cooling water pump 10, put the first preheater 5 into operation, and slowly increase the power of the preheating section in a step-by-step manner. Control the subcooling of the outlet of the first preheater 5 to 20°C to ensure the safety of the first preheater 5 during the experiment. Step (4): Put in the second preheater 6 and the third preheater 7, and slowly increase the heating power in a stepwise manner. Since the pressure may rise during the heating process, it is necessary to slowly release nitrogen from the pressure regulator 1 to control the experimental pressure during the heating process, and monitor the fluid temperature at the outlet of the third preheater 7 in real time. According to the experimental requirements, steam condensation experiments in two working fluid states can be carried out: Saturated steam condensation experiment: Slowly adjust the power of the second preheater 6 and the third preheater 7 until the outlet fluid temperature of the third preheater (7) reaches the saturation temperature corresponding to the pressure of the experimental device. Determine that the working medium entering the condensation test section 8 is saturated steam. Keep the heating power stable and pass the saturated steam into the inner tube 12 of the condensation test section 8. Under the action of cooling water, the saturated steam undergoes phase change condensation on the wall of the inner tube 12. Use the temperature measuring hole 18 on the wall of the inner tube 12 to collect data and calculate the saturated steam condensation heat transfer coefficient. Superheated steam condensation experiment: Adjust the power of the second preheater 6 and the third preheater 7 until the outlet fluid temperature of the third preheater 7 is higher than the saturation temperature corresponding to the pressure of the experimental device, and reach the target superheat set in the experiment. Then, introduce the superheated steam into the inner tube 12 of the condensation test section 8. Under the action of cooling water, the superheated steam gradually condenses on the wall of the inner tube 12. Use the temperature measuring hole 18 on the wall of the inner tube 12 to collect data and calculate the superheated steam condensation heat transfer coefficient. Step (5): After the data recording is completed, the power of the second preheater 6 and the third preheater 7 is gradually reduced in a stepwise manner. After the parameters stabilize, the system pressure, flow rate and the power of the first preheater 5 are slowly adjusted to the next operating point. Step (6): Repeat steps (4)-(5) until all operating points are completed; Step (7): After the experiment is completed, turn off the first preheater 5, the second preheater 6, and the third preheater 7, and keep the water circulation system running until the overall temperature of the circuit reaches room temperature. Then, drain the nitrogen gas in the voltage regulator 1 and the deionized water in the circuit. The experiment is over.

[0010] Compared with the prior art, the present invention has the following advantages: 1) The preheater adopts a three-point heating system and can be directly welded to the pipeline, avoiding the sealing problem of the high-pressure insulating flange at high temperature.

[0011] 2) The use of a three-stage preheater increases the heat exchange area, effectively reduces the heat flux density of the preheating section, and improves the safety of the experiment.

[0012] 3) Temperature measuring holes 18 at different depths are opened at the same cross section of the inner tube 12. By arranging thermocouples, the temperature distribution at different depths at the same cross section of the wall can be obtained. Based on the temperature difference at different depths at the same cross section, the local heat flux density and heat transfer coefficient can be calculated to obtain the distribution characteristics of the wall temperature and heat transfer coefficient of the inclined tube at different inclination angles, thus avoiding the error caused by calculating the heat flux density using the average temperature rise of the fluid. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of an experimental apparatus for high-pressure steam condensation in a passive secondary system of a nuclear reactor, according to the present invention.

[0014] Figure 2 This is a schematic diagram of the condensation test section of a high-pressure steam condensation experimental device for a passive secondary system of a nuclear reactor according to the present invention.

[0015] Figure 3 This is a schematic diagram of the temperature measurement point arrangement in the condensation test section of a high-pressure steam condensation experimental device for a passive secondary system of a nuclear reactor according to the present invention. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings.

[0017] like Figure 1 As shown, this invention discloses an experimental apparatus for high-pressure steam condensation in a passive secondary system of a nuclear reactor. The apparatus includes a pressurizer 1, a water storage tank 2, a shielded pump 3, a flow meter 4, a first preheater 5, a second preheater 6, a third preheater 7, a condensation experimental section 8, a condenser 9, a cooling water pump 10, and a cooling tower 11. The water storage tank 2, shielded pump 3, flow meter 4, first preheater 5, second preheater 6, third preheater 7, condensation experimental section 8, and condenser 9 are sequentially connected via pipelines. The pressurizer 1, connected to the pipelines, is used to control the experimental pressure. The cooling water pump 10 and cooling tower 11 are connected to the condensation experimental section 8.

[0018] like Figure 2 As shown, the condensation test section includes an inner pipe 12, an outer sleeve 13, a fixing component 14, a high-pressure flange 15, a cooling water inlet 16, and a cooling water outlet 17. The interior of the inner pipe 12 is a steam passage, and the annular passage between the inner pipe 12 and the outer sleeve 13 is a cooling water passage. The inner pipe 12 is connected to the third preheater 7 and the condenser 9 through the high-pressure flange 15. The cooling water inlet 16 is connected to the cooling water pump 10, and the cooling water outlet 17 is connected to the cooling tower 11, continuously providing cooling water to the condensation test section 8.

[0019] like Figure 3 As shown, temperature measuring holes 18 of different depths are opened at the same cross section of the inner tube 12 wall.

[0020] Deionized water flows out from storage tank 2, passes through shielded pump 3, flow meter 4, first preheater 5, second preheater 6, third preheater 7, condensation test section 8, and condenser 9, and returns to storage tank 2.

[0021] The first preheater 5, the second preheater 6, and the third preheater 7 adopt a three-point heating method, and the preheaters are directly welded to the pipeline, which avoids the sealing problem of the high-pressure insulating flange at high temperature.

[0022] A three-stage preheater is used. The first preheater 5 heats deionized water from room temperature to subcooled water with a subcooling degree of 20°C. The second preheater 6 and the third preheater 7 heat the subcooled water to single-phase superheated steam, providing working fluid for the condensation test section 8. This reduces the heat flux density of the preheating section and improves the safety of the experiment.

[0023] like Figure 3As shown, temperature measuring holes 18 of different depths are opened at the same cross section of the inner tube 12. By arranging thermocouples, the temperature distribution at different depths of the wall can be obtained. Based on the temperature difference at different depths at the same cross section, the local heat flux density and heat transfer coefficient can be calculated to study the high-pressure steam condensation heat transfer characteristics in the inclined tube at different inclination angles.

[0024] The experimental method for a high-pressure steam condensation experimental device for a passive secondary system of a nuclear reactor comprises the following steps: Step (1): Turn on the data acquisition system, store experimental data in real time, and monitor the outlet steam pressure and temperature of the third preheater 7.

[0025] Step (2): Fill the loop with water until it is full, start the shielded pump 3, and adjust the loop flow rate and the pressure of the regulator 1 to achieve the water flow rate and pressure conditions required for the experimental conditions.

[0026] Step (3): Start the cooling water pump 10, put the first preheater 5 into operation, and slowly increase the power of the preheating section in a step-by-step manner. Control the subcooling of the outlet of the first preheater 5 at 20°C to ensure the safety of the first preheater 5 during the experiment.

[0027] Step (4): Put in the second preheater 6 and the third preheater 7, and slowly increase the heating power in a stepwise manner. Since the pressure may rise during the heating process, it is necessary to slowly release nitrogen from the pressure regulator 1 to control the experimental pressure during the heating process, and monitor the fluid temperature at the outlet of the third preheater 7 in real time. According to the experimental requirements, steam condensation experiments in two working fluid states can be carried out: Saturated steam condensation experiment: Slowly adjust the power of the second preheater 6 and the third preheater 7 until the outlet fluid temperature of the third preheater (7) reaches the saturation temperature corresponding to the pressure of the experimental device. Determine that the working medium entering the condensation test section 8 is saturated steam. Keep the heating power stable and pass the saturated steam into the inner tube 12 of the condensation test section 8. Under the action of cooling water, the saturated steam undergoes phase change condensation on the wall of the inner tube 12. Use the temperature measuring hole 18 on the wall of the inner tube 12 to collect data and calculate the saturated steam condensation heat transfer coefficient. Superheated steam condensation experiment: Adjust the power of the second preheater 6 and the third preheater 7 until the outlet fluid temperature of the third preheater 7 is higher than the saturation temperature corresponding to the pressure of the experimental device, and reach the target superheat set in the experiment. Then, introduce the superheated steam into the inner tube 12 of the condensation test section 8. Under the action of cooling water, the superheated steam gradually condenses on the wall of the inner tube 12. Use the temperature measuring hole 18 on the wall of the inner tube 12 to collect data and calculate the superheated steam condensation heat transfer coefficient. Step (5): After the data recording is completed, the power of the second preheater 6 and the third preheater 7 is gradually reduced in a stepwise manner. After the parameters stabilize, the system pressure, flow rate and the power of the first preheater 5 are slowly adjusted to the next operating point.

[0028] Step (6): Repeat steps (4)-(5) until all operating points are completed.

[0029] Step (7): After the experiment is completed, turn off the first preheater 5, the second preheater 6, and the third preheater 7, and keep the water circulation system running until the overall temperature of the circuit reaches room temperature. Then, drain the nitrogen gas in the voltage regulator 1 and the deionized water in the circuit. The experiment is over.

[0030] The above content provides a further detailed explanation of the present invention in conjunction with specific principles. It should not be construed that the specific implementation of the present invention is limited to this. For those skilled in the art, any simple deductions or substitutions made without departing from the concept of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nuclear reactor secondary side passive system high pressure steam condensation experimental device, characterized in that: The experimental device comprises, which are connected in sequence by pipelines, a water storage tank (2), a shield pump (3), a flow meter (4), a first preheater (5), a second preheater (6), a third preheater (7), a condensation experimental section (8), a condenser (9), a pressure stabilizer (1) connected with the pipelines for controlling the experimental pressure, a cooling water pump (10) and a cooling tower (11) connected with the condensation experimental section (8); The condensation experimental section comprises an inner tube (12), an outer sleeve (13), fixing members (14), a high-pressure flange (15), a cooling water inlet (16) and a cooling water outlet (17), wherein the fixing members (14) are arranged along the outer sleeve (13) in multiple numbers in the axial direction, the inner tube is a steam passage, the annular passage between the inner tube (12) and the outer sleeve (13) is a cooling water passage, wherein the inner tube (12) is connected with the third preheater (7) and the condenser (9) through the high-pressure flange (15); the cooling water inlet (16) is connected with the cooling water pump (10), and the cooling water outlet (17) is connected with the cooling tower (11) to continuously provide cooling water for the condensation experimental section (8); the inner tube (12) is provided with temperature measuring holes (18) of different depths at the same section of the wall surface.

2. The experimental device for condensing high-pressure steam of a passive system in a secondary side of a nuclear reactor according to claim 1, characterized in that: Deionized water flows out from the water storage tank (2), passes through the shield pump (3), the flow meter (4), the first preheater (5), the second preheater (6), the third preheater (7), the condensation experimental section (8) and the condenser (9) and returns to the water storage tank (2).

3. The experimental device for condensing high-pressure steam of a passive system in a secondary side of a nuclear reactor according to claim 1, characterized in that: The first preheater (5), the second preheater (6) and the third preheater (7) adopt a three-point heating method, and the preheaters are directly welded with the pipelines to avoid the sealing problem of the high-pressure insulation flange under high temperature.

4. The experimental device for condensing high-pressure steam of a passive system in a secondary side of a nuclear reactor according to claim 1, characterized in that: The three-stage preheaters are adopted, wherein the first preheater (5) heats the deionized water from room temperature to supercooled water with a supercooling degree of 20℃, and the second preheater (6) and the third preheater (7) heat the supercooled water to single-phase superheated steam to provide the working medium for the condensation experimental section (8) and reduce the heat flux density of the preheating section, thereby improving the safety of the experiment.

5. The experimental device for condensing high-pressure steam of a passive system in a secondary side of a nuclear reactor according to claim 1, characterized in that: The inner tube (12) is provided with temperature measuring holes (18) of different depths at the same section of the wall surface, the temperature distribution at different depths of the wall surface is obtained by arranging thermocouples, and the local heat flux density and the heat transfer coefficient are calculated according to the temperature difference at different depths at the same section to study the high-pressure steam condensation heat transfer characteristics in the inclined tube under different inclination angles.

6. The experimental method of a high-pressure steam condensation experimental device for a nuclear reactor secondary side passive system according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: Step (1): turn on the data acquisition system to store the experimental data in real time and monitor the outlet steam pressure and temperature of the third preheater (7); Step (2): fill the loop with water to the full water state, start the shield pump (3), adjust the loop flow and the pressure of the pressure stabilizer (1) to reach the water flow and pressure conditions required by the experimental conditions; Step (3): start the cooling water pump (10), put in the first preheater (5), slowly increase the preheating section power in steps, and control the outlet supercooling degree of the first preheater (5) to be 20℃ to ensure the safety of the first preheater (5) during the experiment; Step (4): Put into the second preheater (6) and the third preheater (7), and slowly increase the heating power in steps. Since pressure may rise during heating, nitrogen in the pressure stabilizer (1) needs to be slowly discharged to control the experimental pressure during heating, and the fluid temperature at the outlet of the third preheater (7) needs to be monitored in real time. According to the experimental requirements, steam condensation experiments of two working conditions are carried out: Saturated steam condensation experiment: Slowly adjust the power of the second preheater (6) and the third preheater (7) until the fluid temperature at the outlet of the third preheater (7) reaches the saturated temperature corresponding to the pressure of the experimental device. Saturated steam is introduced into the inner tube (12) of the condensation experiment section (8), and under the action of cooling water, saturated steam undergoes phase change and condensation on the wall surface of the inner tube (12). Data are collected using the temperature measurement hole (18) on the wall of the inner tube (12), and the saturated steam condensation heat transfer coefficient is calculated; Superheated steam condensation experiment: Slowly adjust the power of the second preheater (6) and the third preheater (7) until the fluid temperature at the outlet of the third preheater (7) is higher than the saturated temperature corresponding to the pressure of the experimental device, and the target superheat degree is reached. Superheated steam is introduced into the inner tube (12) of the condensation experiment section (8), and under the action of cooling water, superheated steam gradually condenses on the wall surface of the inner tube (12). Data are collected using the temperature measurement hole (18) on the wall of the inner tube (12), and the superheated steam condensation heat transfer coefficient is calculated; Step (5): After the data recording is completed, the power of the second preheater (6) and the third preheater (7) is slowly reduced in steps. After the parameters are stable, the system pressure, flow rate, and the power of the first preheater (5) are slowly adjusted to the next working condition point; Step (6): Repeat steps (4) - (5) until all working condition points are completed; Step (7): After the experiment is completed, turn off the first preheater (5), the second preheater (6), and the third preheater (7). Keep the water circulation system running until the overall temperature of the loop reaches room temperature. Empty the nitrogen in the pressure stabilizer (1) and the deionized water in the loop. The experiment is completed.

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