Steam-water vapor-liquid two-phase countercurrent comprehensive test system and test method

Abstract

The invention discloses a steam-water vapor-liquid two-phase countercurrent comprehensive test system and test method. The test system comprises a test body, a water supply branch, a steam supply branch and a condensation loop. According to the invention, steam-water is used as a test working medium, a steam-liquid two-phase countercurrent test is carried out based on an actual power plant surge pipe structure model, and the two-phase countercurrent limiting characteristic mechanism research of the steam-water working medium under the saturation condition is carried out by adjusting the steam flow and the liquid level of an upper pressure-bearing container.

Description

Technical Field

[0001] The present invention relates to the technical field of test loop design in the application and scientific research fields of the nuclear industry, and particularly relates to a steam-water vapor-liquid two-phase countercurrent comprehensive test system and a test method. Background Art

[0002] Gas-liquid two-phase countercurrent (Counter-Current Flow, CCF) is a very complex two-phase flow phenomenon, which widely exists in the practical applications of industrial systems, such as in the nuclear power plant system, oil and gas pipeline system, refrigeration system, condensation reflux system, and in simple or complex channel structures such as inside pipes, between tube bundles, and in pebble beds in the packing tower system. It usually shows that the gas phase flows upward under forced flow, while the liquid phase flows downward by gravity. When the gas phase velocity is low, the liquid phase can flow downward completely smoothly; as the gas phase increases, when the downward flowing liquid phase is partially or completely unable to flow downward due to the hindrance of the gas phase, the two-phase countercurrent limitation (Counter-Current Flow Limitation, CCFL) phenomenon appears. After a nuclear reactor accident or abnormal condition, CCFL is likely to occur in any channel where a two-phase countercurrent state of "steam flowing upward due to pressure difference and water flowing downward by gravity" appears, thus greatly affecting the safety performance of the nuclear reactor system. Therefore, in the safety analysis of nuclear reactor accidents, accurate prediction of the steam-water two-phase countercurrent phenomenon under different structures and conditions is crucial.

[0003] Under accident conditions of the AP series nuclear power plants, during the ADS injection stage, steam in the reactor core and the hot leg will be discharged into the in-containment refueling water storage tank (IRWST) in the containment through the surge line, the pressurizer, and the ADS relief pipeline. During this process, the condensate water in the pressurizer flows downward along the surge line by gravity, thus forming a two-phase countercurrent phenomenon in the surge line. When the relative velocity of the gas-liquid two-phase reaches a certain value, the two-phase countercurrent limitation phenomenon will be caused, that is, part or all of the liquid flowing downward along the surge line is entrained by the upward gas. The two-phase countercurrent limitation phenomenon will affect the drainage rate of the pressurizer and have an adverse impact on the water inventory in the reactor core in the later stage of the accident. The two-phase countercurrent limitation phenomenon is not only closely related to the gas-liquid two-phase velocity, but also related to the flow channel structure, the boundary conditions at the inlet and outlet of the flow channel, the inclination angle of the flow channel, the fluid physical properties, etc. So far, for the understanding of the mechanism of two-phase countercurrent limitation, especially for the mechanism of two-phase countercurrent limitation in the surge line, there is still a lack of reliable test data to support it. A two-phase countercurrent test device in the surge line is of great significance for studying the mechanism of the two-phase countercurrent limitation phenomenon in the surge line.

[0004] In the existing technology, there are already experimental devices for gas-liquid two-phase countercurrent flow in pipes. Chinese Patent CN 105181027A discloses a gas-liquid two-phase reverse flow detection device in a pipe. It includes an air supply part, a water supply part, a high-level water tank, a low-level water tank, a detection part, a data acquisition part and a data processing part. The air supply part is used for conveying gas and measuring the gas flow rate, the water supply part is used for providing liquid, the high-level water tank and the low-level water tank are connected through an exhaust pipe, and a gas-liquid two-phase countercurrent flow is formed in the exhaust pipe. This invention focuses on the two-phase countercurrent phenomenon of air-water in a horizontal pipe and cannot reveal the evolution mechanism of steam-water two-phase countercurrent flow in the surge pipe of a pressurized water reactor under accident conditions. Summary of the Invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a steam-water vapor two-phase countercurrent comprehensive test system and test method, which can simulate the steam-water CCFL characteristics in the surge pipe of a pressurized water reactor during a small break accident according to the test purpose, provide verification for the safety assessment under power plant accident conditions, develop a CCFL model suitable for the AP series surge pipes, and provide a useful model and visual flow pattern data for predicting the occurrence of CCFL phenomena in the surge pipe under small break accident conditions of AP series nuclear power plants. Record the visual test process through high-speed photography equipment to help understand and describe important test phenomena, and further verify, supplement or correct the existing research on the CCFL mechanism.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A steam-water vapor two-phase countercurrent comprehensive test system includes a test body 100, a water supply branch 200, a steam supply branch 300 and a condensation circuit 400; the steam generated by the steam supply branch 300 flows into the horizontal pipe section 130 after passing through the lower pressure container 140, then flows upward through the surge pipe test section 120 into the upper pressure container 110, and flows into the condensation circuit 400 through the exhaust pipeline; after the saturated water generated by the water supply branch 200 is injected into the upper pressure container 110, it flows downward through the surge pipe test section 120 under the action of gravity, forms a steam-water two-phase countercurrent phenomenon with the upward flowing steam in the surge pipe test section 120, and finally flows into the lower pressure container 140 through the horizontal pipe section 130;

[0008] The test body 100 includes an upper pressure-bearing container 110, a surge tube test section 120, a horizontal tube section 130, and a lower pressure-bearing container 140; the upper pressure-bearing container 110 is connected to the water supply branch 200 through a first stop valve 111 for introducing saturated water and forming a stable liquid level; it is connected to the condensation circuit 400 through a second stop valve 112 for discharging condensed steam; a first pressure sensor 113 installed on the top of the upper pressure-bearing container 110 is used to measure the steam chamber pressure, and a first differential pressure sensor 114 installed on the side of the upper pressure-bearing container 110 is used to measure the pressure difference between the steam chamber in the upper pressure-bearing container 110 and the fixed liquid level, and the liquid level height in the upper pressure-bearing container 110 is obtained according to the pressure difference; the surge tube test section 120 is connected to the upper pressure-bearing container 110 and the horizontal tube section 130 through flanges. The surge tube test section 120 presents a three-dimensional spiral structure, which is processed and manufactured in sections using 304 stainless steel materials, and is connected in sections using flanges in the middle to maintain the same structure as the surge tube of the AP series power plant. The vertical tube part is processed and manufactured using a visual toughened glass light tube with flanges, connected to the inclined tube part through flanges, and sealed with a PTFE gasket; a second differential pressure sensor 121 installed on the vertical tube part of the upper pressure-bearing container 110 and the surge tube test section 120 is used to measure the pressure difference change between the steam chamber and the lower end of the vertical tube, a third differential pressure sensor 122 installed at both ends of the inclined tube of the surge tube test section 120 is used to measure the pressure difference change at the inclined tube, and a fourth differential pressure sensor 123 installed between the surge tube test section 120 and the horizontal tube section 130 is used to measure the pressure difference change at the T-shaped tube. The horizontal tube section 130 is connected to the lower pressure-bearing container 140 through a third stop valve 131, and a second pressure sensor 132 installed on the horizontal tube section 130 is used to measure the outlet pressure of the lower pressure-bearing container 140; a fifth pressure sensor 141 installed on the top of the lower pressure-bearing container 140 is used to measure the steam chamber pressure of the lower pressure-bearing container 140, and a fourth differential pressure sensor 142 installed at the upper and lower ends of the lower pressure-bearing container 140 is used to measure the pressure difference between the steam chamber in the lower pressure-bearing container 140 and the fixed liquid level, and the liquid level height in the lower pressure-bearing container 140 is obtained according to the pressure difference;

[0009] The water supply branch 200 includes a first water tank 210, a heater 211, a first filter 214, a high-temperature pump 215, a large-range mass flow meter 219, a small-range mass flow meter 220, a regenerator 222, a preheating section 223, thermocouples and valves on the pipeline; the first water tank 210 is connected to the first filter 214 in front of the inlet of the high-temperature pump through a fourth stop valve 213, and the heater 211 installed inside the first water tank 210 is used to heat the deionized water in the first water tank, and the first thermocouple 212 installed on the side of the first water tank is used to measure the temperature change of the internal water; the inlet of the high-temperature pump 215 is connected to the first filter 214 and is connected to the parallel mass flow meters through a fifth stop valve 216; the sixth stop valve 217 is connected to the large range

[0010] The flowmeter 219 is connected, and the seventh stop valve 218 is connected to the small-range mass flowmeter 220. Two mass flowmeters are used to measure the water flow rates of large and small ranges. The parallel mass flowmeters are connected to the inlet of the regenerator 222 through the eighth stop valve 221; the outlet of the regenerator 222 is connected to the inlet of the preheating section 223. The second thermocouple 224 installed at the outlet of the preheating section 223 is used to measure the temperature of the water at the outlet of the preheating section 223.

[0011] The steam supply branch 300 is used to provide the steam flow rate required for the test, and includes a second water tank 311, a second filter 313, a first feed water pump 314, an electric heating boiler 316, a steam-water separator 319, a large-range vortex flowmeter 325, a small-range vortex flowmeter 326, thermocouples and valves on the pipeline; the second water tank 311 is connected to the second filter 313 in front of the inlet of the first feed water pump through the ninth stop valve 312; the inlet of the first feed water pump 314 is connected to the second filter 313, and the outlet is connected to the electric heating boiler 316 through the tenth stop valve 315; the outlet of the electric heating boiler 316 is connected to the steam-water separator 319 through a pressure reducing valve 318. The first steam trap 317 installed on the drain pipeline at the bottom of the electric heating boiler 316 is used to drain the remaining water in the electric heating boiler after the test; the steam-water separator 319 is connected to the parallel gas vortex flowmeters through the eleventh stop valve 322. The second steam trap 320 installed on the drain pipeline at the bottom of the steam-water separator 319 is used to discharge the separated liquid water. The twelfth stop valve 321 installed on the bypass pipeline at the outlet of the steam-water separator 319 is used to adjust the steam flow rate entering the test section; the thirteenth stop valve 323 is connected to the large-range vortex flowmeter 325, and the fourteenth stop valve 324 is connected to the small-range vortex flowmeter 326. Two vortex flowmeters are used to measure the gas flow rates of large and small ranges. The parallel vortex flowmeters are connected to the lower pressure-bearing container 140 through the fifteenth stop valve 328. The third thermocouple 327 installed on the steam supply pipeline is used to measure the temperature of the steam entering the lower pressure-bearing container 140.

[0012] The condensation circuit 400 includes a third water tank 410, a third filter 412, a second feed water pump 413, a condenser 414, a cooling water tower 416 and valves; the third water tank 410 is connected to the third filter 412 in front of the inlet of the second feed water pump through the sixteenth stop valve 411; the inlet of the second feed water pump 413 is connected to the third filter 412, and the outlet is connected to the secondary side inlet of the condenser 414; the primary side inlet of the condenser 414 is connected to the secondary side outlet of the regenerator 222. The primary side outlet of the condenser 414 is connected to the first water tank 210 through the seventeenth stop valve 415. The secondary side outlet of the condenser 414 is connected to the inlet of the cooling tower 416; the outlet of the cooling tower 416 is connected to the third water tank 410 through the eighteenth stop valve 417.

[0013] The test system uses a NI data acquisition system to collect thermal parameters and control the DC power supply of instruments and equipment. The measured voltage or current signals of all thermal parameters of the test system are input into the NI data acquisition system. After signal conversion and conditioning, they are collected into the computer through a data acquisition card to output the analog signals to be collected. At the same time, it is checked whether the output values of the meter heads of the acquisition equipment are consistent.

[0014] Preferably, all the steam supply branches 300 are wrapped with heat insulation cotton, and the entire steam supply branch circuit is preheated before the test. Heating wires are evenly wound outside the entire steam supply branch circuit to keep the pipeline warm and heated.

[0015] Preferably, in the visual vertical glass tube part of the oscillating tube test section 120, high-speed imaging equipment is used to record images and photos of the visual test process to help study the mechanism of the occurrence of the CCFL phenomenon.

[0016] Preferably, to fully meet the steam demand of the test, the test electric heating boiler 316 can generate steam with a certain degree of superheat, and the pressure grade of the steam-water separator 319 is above 1 MPa. Before use, tests and various commissioning works should be carried out on the alarm or protection device.

[0017] Preferably, the preheating section 223 adopts three-stage heating, all of which are two-point direct electric heating, and the material is 316L stainless steel.

[0018] Preferably, the electric heating boiler 316 is used as the steam supply source in the main pipe two-phase flow, and the heating power is adjusted by its internal multi-stage heating rods.

[0019] The test method of the steam-water-vapor two-phase countercurrent comprehensive test system is to study the influence of various parameters on the CCFL phenomenon of the oscillating tube by changing the test liquid phase inlet flow rate, that is, the liquid level of the upper pressure-bearing container 110, and the vapor phase inlet flow rate. For the inlet temperature parameter, the steam and water are the saturation temperatures at the corresponding pressures. Before the test starts, check whether the water levels of all water tanks and related equipment are normal. 1) First, open the water supply branch 200 to inject normal temperature saturated water into the upper pressure-bearing container 110 and keep the preset water level in the upper pressure-bearing container 110 unchanged; 2) Then open the steam supply branch 300 to make a two-phase stable countercurrent state form in the oscillating tube test section 120; 3) After a stable preset time in the oscillating tube test section 120, gradually increase the vapor phase flow rate to start the test.

[0020] The test process includes a flooding process and a deflooding process. 1) After the test starts, a preset amount of steam is first introduced, and then saturated water at a preset flow rate is supplied to the upper pressure vessel 110 from the water supply branch 200 under pressure, so that the water level in the upper pressure vessel 110 remains unchanged at the preset level; 2) Then, steam at a preset flow rate is supplied to the lower pressure vessel 140 from the steam supply branch 300, so as to form a two-phase countercurrent flow state in the wavy tube test section 120; 3) In the initial stage of the test, the vapor phase flow rate provided is small, and a stable two-phase countercurrent state will be formed in the wavy tube test section 120. At this time, the water flow rate flowing into the wavy tube test section 120 from the upper pressure vessel 110 is equal to the water flow rate flowing from the wavy tube test section 120 into the lower pressure vessel 140; 4) After further increasing the steam flow rate, an unstable two-phase countercurrent flow of vapor and liquid appears at a certain position in the wavy tube test section 120, accompanied by wavy or agitated flow, and an obvious pressure drop mutation occurs at this position. It is considered that the CCFL phenomenon occurs at this position, which is called the CCFL starting point; 5) After increasing the steam flow rate again, the water flow rate flowing downward along the wavy tube test section 120 will further decrease until it finally becomes zero. At this time, the water flow rate entering the lower pressure vessel 140 is 0, that is, the liquid backflow critical point is reached; 6) Then, adjust the water flow rate to another working condition and repeat the above steps; or at the given flow rate above, gradually decrease the steam flow rate and observe the deflooding hysteresis effect in the wavy tube test section 120 until the countercurrent phenomenon disappears.

[0021] The steam-water two-phase countercurrent test system of the present invention has the following characteristics:

[0022] 1. Using steam-water as the two-phase countercurrent test working medium, designing and manufacturing a wavy tube test section 120 with the same structure as that of an actual power plant. The CCFL model obtained from test data analysis can be directly used for power plant simulation calculations;

[0023] 2. Selecting toughened glass with high strength and thick thickness for the vertical section of the wavy tube test section 120 to meet the test pressure requirements and visualization research requirements. The change of the two-phase countercurrent flow pattern in the visualization test section is tracked and recorded by a high-speed camera, providing a research basis for the evolution of the two-phase countercurrent mechanism;

[0024] 3. Designing a stable steam supply source, installing a pressure reducing valve 318 on the pipeline of the steam supply branch 400, and adjusting the opening of the pressure reducing valve 318 and the heating power of the electric heating boiler to obtain a steam flow with a specified pressure and specified flow rate. Description of the Drawings

[0025] Figure 1 It is a diagram of the steam-water vapor-liquid two-phase countercurrent comprehensive test system of the present invention. Detailed Embodiment

[0026] As Figure 1As shown in the figure, a steam-water two-phase countercurrent comprehensive test system of the present invention has a loop pipeline made of 1Cr18Ni9Ti stainless steel. The test system includes a test body 100, a water supply branch 200, a steam supply branch 300, and a condensation loop 400. The steam generated by the steam supply branch 400 flows into the horizontal pipe section 130 after passing through the lower pressure-bearing container 140, then flows upward through the fluctuating pipe test section 120 into the upper pressure-bearing container 110, and flows into the condensation loop 400 through the exhaust pipeline. After the saturated water generated by the water supply branch 200 is injected into the upper pressure-bearing container 110, it flows downward under the action of gravity through the fluctuating pipe test section 120, forming a steam-water two-phase countercurrent phenomenon with the upward-flowing steam in the fluctuating pipe test section 120, and finally flows into the lower pressure-bearing container 140 through the horizontal pipe section 130.

[0027] The test body 100 includes an upper pressure-bearing container 110, a fluctuating pipe test section 120, a horizontal pipe section 130, and a lower pressure-bearing container 140. The upper pressure-bearing container 110 is connected to the water supply branch 200 through a first stop valve 111 for introducing saturated water and forming a stable liquid level; it is connected to the condensation loop 400 through a second stop valve 112 for discharging condensed steam. The first pressure sensor 113 installed on the top of the upper pressure-bearing container 110 is used to measure the steam chamber pressure, and the first differential pressure sensor 114 installed on the side of the upper pressure-bearing container 110 is used to measure the pressure difference between the steam chamber in the upper pressure-bearing container 110 and the fixed liquid level, and the liquid level height in the upper pressure-bearing container 110 is obtained according to the pressure difference. The fluctuating pipe test section 120 is connected to the upper pressure-bearing container 110 and the horizontal pipe section 130 through flanges. The fluctuating pipe test section 120 presents a three-dimensional spiral structure, which is fabricated by segmented processing using 304 stainless steel material, and is connected by flanges in the middle to keep the same structure as the fluctuating pipe of the AP series power plant pressurizer. In particular, the vertical pipe part is fabricated using a visual toughened glass light pipe with flanges, connected to the inclined pipe part through a flange, and sealed with a PTFE gasket. The second differential pressure sensor 121 installed between the upper pressure-bearing container 110 and the vertical pipe part of the fluctuating pipe test section 120 is used to measure the pressure difference change between the steam chamber and the lower end of the vertical pipe. The third differential pressure sensor 122 installed at both ends of the inclined pipe of the fluctuating pipe test section 120 is used to measure the pressure difference change at the inclined pipe. The fourth differential pressure sensor 123 installed between the fluctuating pipe test section 120 and the horizontal pipe section 130 is used to measure the pressure difference change at the T-shaped pipe. The horizontal pipe section 130 is connected to the lower pressure-bearing container 140 through a third stop valve 131. The second pressure sensor 132 installed on the horizontal pipe section 130 is used to measure the outlet pressure of the lower pressure-bearing container 140. The fifth pressure sensor 141 installed on the top of the lower pressure-bearing container 140 is used to measure the steam chamber pressure of the lower pressure-bearing container 140, and the fourth differential pressure sensor 142 installed at the upper and lower ends of the lower pressure-bearing container 140 is used to measure the pressure difference between the steam chamber in the lower pressure-bearing container 140 and the fixed liquid level, and the liquid level height in the lower pressure-bearing container 140 is obtained according to the pressure difference.

[0028] The water supply branch 200 includes equipment such as a first water tank 210, a heater 211, a first filter 214, a high-temperature pump 215, a large-range mass flowmeter 219, a small-range mass flowmeter 220, a regenerator 222, a preheating section 223, thermocouples and valves on the pipeline, etc. The first water tank 210 is connected to the first filter 214 in front of the inlet of the high-temperature pump through a fourth stop valve 213. The heater 211 installed inside the first water tank 210 is used to heat the deionized water in the first water tank. The first thermocouple 212 installed on the side of the first water tank is used to measure the temperature change of the internal water. The inlet of the high-temperature pump 215 is connected to the first filter 214 and is connected to the parallel mass flowmeters through a fifth stop valve 216. A sixth stop valve 217 is connected to the large-range mass flowmeter 219, and a seventh stop valve 218 is connected to the small-range mass flowmeter 220. Two mass flowmeters are used to measure the water flow in large and small ranges. The parallel mass flowmeters are connected to the inlet of the regenerator 222 through an eighth stop valve 221. The outlet of the regenerator 222 is connected to the inlet of the preheating section 223. The second thermocouple 224 installed at the outlet of the preheating section 223 is used to measure the temperature of the water at the outlet of the preheating section 223. During the test, first heat the water in the first water tank 210 to 70 - 80 °C. The hot water is pumped out from the heated first water tank 210 by the high-temperature pump 215, enters the regenerator 222 for heat regeneration through the liquid flowmeter, and is finally heated to the saturated state by the preheating section 223 and injected into the upper pressure vessel 110 of the test body 100 through the water supply pipeline. The processing material of the first water tank 210 is 304 stainless steel, which is mainly used to store deionized water and preheat it. Before the heated deionized water enters the pressure vessel, the preheating section 223 is used to further preheat the water. The preheating section 223 adopts three-stage heating, all of which are two-point direct electric heating, and the material is 316L stainless steel.

[0029] The steam supply branch 300 is mainly used to provide the steam flow required for the test, and mainly includes a second water tank 311, a second filter 313, a first feed water pump 314, an electric heating boiler 316, a steam-water separator 319, a large-range vortex flowmeter 325, a small-range vortex flowmeter 326, thermocouples and valves on the pipeline, etc. The second water tank 311 is connected to the second filter 313 before the inlet of the first feed water pump through a ninth stop valve 312; the inlet of the first feed water pump 314 is connected to the second filter 313, and the outlet is connected to the electric heating boiler 316 through a tenth stop valve 315; the outlet of the electric heating boiler 316 is connected to the steam-water separator 319 through a pressure reducing valve 318, and a first steam trap 317 installed on the drain pipeline at the bottom of the electric heating boiler 316 is used to drain the remaining water in the electric heating boiler after the test; the steam-water separator 319 is connected to the parallel gas vortex flowmeter through an eleventh stop valve 322, a second steam trap 320 installed on the drain pipeline at the bottom of the steam-water separator 319 is used to discharge the separated liquid water, and a twelfth stop valve 321 installed on the bypass pipeline at the outlet of the steam-water separator 319 can be used to adjust the steam flow entering the test section; a thirteenth stop valve 323 is connected to the large-range vortex flowmeter 325, a fourteenth stop valve 324 is connected to the small-range vortex flowmeter 326, two vortex flowmeters are used to measure the gas flow of large and small ranges, the parallel vortex flowmeter is connected to the lower pressure bearing container 140 through a fifteenth stop valve 328, and a third thermocouple 327 installed on the steam supply pipeline is used to measure the steam temperature entering the lower pressure bearing container 140. During the test, steam is generated by the electric heating boiler 316 and separated by the steam-water separator 319. The gas enters the lower pressure bearing container 140 in the test body 100 through the steam supply pipeline. The electric heating boiler 316 is used as the steam supply source in the main pipe two-phase flow, and its power is adjusted by multiple heating rods in the electric heating boiler. The outlet exhaust pipe of the electric heating boiler 316 is connected to the pressure reducing valve 318 to control the steam discharge pressure in the test section and maintain the pressure in the test section. During the heating process of the electric heating boiler 316, since the pipeline before the water vapor pipeline enters the steam-water separator 319 is relatively long, if the water vapor flow is small at the beginning, more wet steam is likely to be generated when passing through this pipe section. To make the water vapor entering the test section be superheated steam, when the water vapor volume is small and the temperature is low, the generated water vapor is directly discharged to the outside through the steam trap 320 beside the steam-water separator 319 until the water vapor discharged from the steam trap 320 no longer contains water and the water vapor flow is large enough, then the steam trap 320 is closed, and the water vapor is introduced into the gas path measurement section.

[0030] The condensation loop 400 includes equipment such as a third water tank 410, a third filter 412, a second feed water pump 413, a condenser 414, a cooling water tower 416, and valves. The third water tank 410 is connected to the third filter 412 in front of the inlet of the second feed water pump through a sixteenth stop valve 411; the inlet of the second feed water pump 413 is connected to the third filter 412, and the outlet is connected to the secondary side inlet of the condenser 414; the primary side inlet of the condenser 414 is connected to the secondary side outlet of the recuperator 222, and the primary side outlet of the condenser 414 is connected to the first water tank 210 through a seventeenth stop valve 415, and the secondary side outlet of the condenser 414 is connected to the inlet of the cooling water tower 416; the outlet of the cooling water tower 416 is connected to the third water tank 410 through an eighteenth stop valve 417. The cooling water is pumped out by the second feed water pump 413 and enters the condenser 414 to exchange heat and condense the steam from the test body 100, then enters the cooling water tower 416 to release heat, and finally flows into the third water tank 410 to complete the condensation loop circulation.

[0031] The test system uses a NI data acquisition system to collect thermal parameters and control the DC power supply of instruments and equipment. Input the measured voltage or current signals of all thermal parameters of the test system into the NI data acquisition system. After signal conversion and conditioning, the signals are collected into the computer through a data acquisition card to output the analog signals to be collected. At the same time, check whether the output values of the meter heads of the acquisition equipment are consistent.

[0032] Preferably, since the condensation of steam will greatly affect the accuracy of test data, the entire steam supply branch 300 is wrapped with heat insulation cotton, and the entire steam supply branch loop is preheated before the test. In addition, heating wires are evenly wound outside the entire steam supply branch loop to keep the pipeline warm and heated.

[0033] Preferably, in the visual vertical glass tube part of the fluctuating tube test section 120, high-speed imaging equipment can be used to record images and photos of the visual test process to help study the mechanism of the occurrence of the CCFL phenomenon.

[0034] Preferably, to fully meet the steam demand of the test, the test electric heating boiler 316 can generate steam with a certain degree of superheat, and tests and various commissioning works should be carried out on the alarm or protection device before use.

[0035] Test method of the steam-water two-phase countercurrent comprehensive test system. By changing the test liquid phase inlet flow rate (the liquid level of the upper pressure vessel 110) and the vapor phase inlet flow rate, the influence of various parameters on the CCFL phenomenon in the oscillating tube is studied. For the inlet temperature parameter, the steam and water are the saturation temperatures at the corresponding pressures. Before the test starts, check whether the water levels in all water tanks and related equipment are normal. 1) First, open the water supply branch 200 according to the regulations to inject normal temperature saturated water into the upper pressure vessel 110 and keep a certain water level in the upper pressure vessel 110 unchanged; 2) Then, open the steam supply branch 300 according to the requirements of the regulations to form a stable two-phase countercurrent state in the oscillating tube test section 120; 3) After the oscillating tube test section 120 has been stable for a period of time, gradually increase the vapor phase flow rate to start the test.

[0036] The test process includes the flooding process and the de-flooding process. 1) After the test starts, first introduce a certain amount of steam, and then the water supply branch 200 supplies saturated water at a certain flow rate to the upper pressure vessel 110 to keep a certain water level in the upper pressure vessel 110 unchanged; 2) Then, the steam supply branch 300 supplies steam at a certain flow rate to the lower pressure vessel 140 to form a vapor-liquid two-phase countercurrent flow state in the oscillating tube test section 120; 3) In the initial stage of the test, when the supplied vapor phase flow rate is small, a stable two-phase countercurrent state will be formed in the oscillating tube test section 120. At this time, the water flow rate flowing into the oscillating tube test section 120 from the upper pressure vessel 110 is equal to the water flow rate flowing from the oscillating tube test section 120 into the lower pressure vessel 140; 4) After further increasing the steam flow rate, an unstable vapor-liquid two-phase countercurrent flow appears at a certain position in the oscillating tube test section 120, accompanied by wavy (or agitated) flow, and there is an obvious sudden change in pressure drop at this position. It is considered that the CCFL phenomenon occurs at this position (referred to as the CCFL onset point, also known as the onset of flooding); 5) After increasing the steam flow rate again, the water flow rate flowing downward along the oscillating tube test section 120 will further decrease until it finally becomes zero. At this time, the water flow rate entering the lower pressure vessel 140 is 0, that is, the liquid backflow critical point (zero liquid penetration) is reached; 6) Then adjust the water flow rate to another working condition and repeat the above steps; or at the given flow rates above, gradually decrease the steam flow rate and observe the de-flooding hysteresis effect in the oscillating tube test section 120 until the countercurrent phenomenon disappears.

Claims

1. A steam-water vapor-liquid two-phase countercurrent comprehensive test system, characterized in that: It includes a test body (100), a water supply branch (200), a steam supply branch (300), and a condensation circuit (400); the steam generated by the steam supply branch (300) flows through the lower pressure-bearing container (140) and then into the horizontal pipe section (130), and then flows upward through the fluctuating pipe test section (120) into the upper pressure-bearing container (110), and flows into the condensation circuit (400) through the exhaust pipeline; after the saturated water generated by the water supply branch (200) is injected into the upper pressure-bearing container (110), it flows downward through the fluctuating pipe test section (120) under the action of gravity, and forms a steam-water two-phase countercurrent phenomenon with the upward-flowing steam in the fluctuating pipe test section (120), and finally flows into the lower pressure-bearing container (140) through the horizontal pipe section (130); The test body (100) includes an upper pressure-bearing container (110), a fluctuating tube test section (120), a horizontal tube section (130), and a lower pressure-bearing container (140); the upper pressure-bearing container (110) is connected to the water supply branch (200) through a first stop valve (111) for introducing saturated water and forming a stable liquid level; it is connected to the condensation circuit (400) through a second stop valve (112) for discharging condensed steam; a first pressure sensor (113) installed on the top of the upper pressure-bearing container (110) is used to measure the steam chamber pressure, and a first differential pressure sensor (114) installed on the side of the upper pressure-bearing container (110) is used to measure the pressure difference between the steam chamber in the upper pressure-bearing container (110) and the fixed liquid level, and the liquid level height in the upper pressure-bearing container (110) is obtained according to the pressure difference; the fluctuating tube test section (120) is connected to the upper pressure-bearing container (110) and the horizontal tube section (130) through flanges. The fluctuating tube test section (120) presents a three-dimensional spiral structure, which is processed and manufactured in sections using (304) stainless steel material, and is connected in sections using flanges in the middle to keep it consistent with the fluctuating tube structure of the AP series power plant. The vertical tube part is processed and manufactured using a visual toughened glass tube with flanges, and is connected to the inclined tube part through a flange and sealed with a PTFE gasket; a second differential pressure sensor (121) installed on the vertical tube part of the upper pressure-bearing container (110) and the fluctuating tube test section (120) is used to measure the pressure difference change between the steam chamber and the lower end of the vertical tube, a third differential pressure sensor (122) installed at both ends of the inclined tube of the fluctuating tube test section (120) is used to measure the pressure difference change at the inclined tube, and a fourth differential pressure sensor (123) installed between the fluctuating tube test section (120) and the horizontal tube section (130) is used to measure the pressure difference change at the T-shaped tube. The horizontal tube section (130) is connected to the lower pressure-bearing container (140) through a third stop valve (131), and a second pressure sensor (132) installed on the horizontal tube section (130) is used to measure the outlet pressure of the lower pressure-bearing container (140); a fifth pressure sensor (141) installed on the top of the lower pressure-bearing container (140) is used to measure the steam chamber pressure of the lower pressure-bearing container (140), and a fourth differential pressure sensor (142) installed at the upper and lower ends of the lower pressure-bearing container (140) is used to measure the pressure difference between the steam chamber in the lower pressure-bearing container (140) and the fixed liquid level, and the liquid level height in the lower pressure-bearing container (140) is obtained according to the pressure difference; The water supply branch (200) includes a first water tank (210), a heater (211), a first filter (214), a high-temperature pump (215), a large-range mass flowmeter (219), a small-range mass flowmeter (220), a regenerator (222), a preheating section (223), thermocouples and valves on the pipeline; the first water tank (210) is connected to the first filter (214) in front of the inlet of the high-temperature pump through a fourth stop valve (213), the heater (211) installed inside the first water tank (210) is used to heat the deionized water in the first water tank, and the first thermocouple (212) installed on the side of the first water tank is used to measure the temperature change of the internal water; the inlet of the high-temperature pump (215) is connected to the first filter (214) and is connected to the parallel mass flowmeters through a fifth stop valve (216); a sixth stop valve (217) is connected to the large-range mass flowmeter (219), and a seventh stop valve (218) is connected to the small-range mass flowmeter (220). Two mass flowmeters are used to measure the water flow in large and small ranges. The parallel mass flowmeters are connected to the inlet of the regenerator (222) through an eighth stop valve (221); the outlet of the regenerator (222) is connected to the inlet of the preheating section (223), and the second thermocouple (224) installed at the outlet of the preheating section (223) is used to measure the temperature of the water at the outlet of the preheating section (223); The steam supply branch (300) is used to provide the steam flow required for the test and includes a second water tank (311), a second filter (313), a first feed pump (314), an electric heating boiler (316), a steam-water separator (319), a large-range vortex flowmeter (325), a small-range vortex flowmeter (326), thermocouples and valves on the pipeline; the second water tank (311) is connected to the second filter (313) in front of the inlet of the first feed pump through a ninth stop valve (312); the inlet of the first feed pump (314) is connected to the second filter (313), and the outlet is connected to the electric heating boiler (316) through a tenth stop valve (315); The outlet of the electric heating boiler (316) is connected to the steam-water separator (319) through a pressure reducing valve (318). The first steam trap (317) installed on the blowdown pipeline at the bottom of the electric heating boiler (316) is used to drain the remaining water in the electric heating boiler after the test ends; the steam-water separator (319) is connected to the parallel gas vortex flowmeter through the eleventh stop valve (322). The second steam trap (320) installed on the blowdown pipeline at the bottom of the steam-water separator (319) is used to discharge the separated liquid water. The twelfth stop valve (321) installed on the bypass pipeline at the outlet of the steam-water separator (319) is used to adjust the steam flow rate entering the test section; the thirteenth stop valve (323) is connected to the large-range vortex flowmeter (325), and the fourteenth stop valve (324) is connected to the small-range vortex flowmeter (326). Two vortex flowmeters are used to measure the gas flow rates of large and small ranges. The parallel vortex flowmeters are connected to the lower pressure-bearing vessel (140) through the fifteenth stop valve (328). The third thermocouple (327) installed on the steam supply pipeline is used to measure the steam temperature entering the lower pressure-bearing vessel (140). The condensation circuit (400) includes a third water tank (410), a third filter (412), a second feed water pump (413), a condenser (414), a cooling water tower (416) and valves; the third water tank (410) is connected to the third filter (412) in front of the inlet of the second feed water pump through the sixteenth stop valve (411); the inlet of the second feed water pump (413) is connected to the third filter (412), and the outlet is connected to the secondary side inlet of the condenser (414); the primary side inlet of the condenser (414) is connected to the secondary side outlet of the regenerator (222). The primary side outlet of the condenser (414) is connected to the first water tank (210) through the seventeenth stop valve (415). The secondary side outlet of the condenser (414) is connected to the inlet of the cooling tower (416); the outlet of the cooling tower (416) is connected to the third water tank (410) through the eighteenth stop valve (417). The test system uses the NI data acquisition system to collect thermal parameters and control the DC power supply of the instruments and equipment; all the measured voltage or current signals of the thermal parameters of the test system are input into the NI data acquisition system. After signal conversion and conditioning, they are collected into the computer through the data acquisition card to output the analog signals to be collected, and at the same time, check whether the output values of the meter heads of the acquisition equipment are consistent.

2. The steam-water two-phase countercurrent comprehensive test system according to claim 1, wherein: All the steam supply branches (300) are wrapped with heat insulation cotton, and the entire steam supply branch circuit is preheated before the test. Heating wires are evenly wound around the outside of the entire steam supply branch circuit to heat and insulate the pipeline.

3. The steam-water two-phase countercurrent comprehensive test system according to claim 1, wherein: In the visual vertical glass tube part of the fluctuating tube test section (120), high-speed imaging equipment is used to record images and photos of the visual test process to help study the mechanism of the occurrence of the CCFL phenomenon.

4. The steam-water two-phase countercurrent comprehensive test system according to claim 1, characterized in that: To fully meet the steam demand of the test, the test electric heating boiler (316) can generate steam with a certain degree of superheat, and the pressure grade of the steam-water separator (319) is above 1 MPa; before use, tests and various commissioning works shall be carried out on the alarm or protection device.

5. The steam-water two-phase countercurrent comprehensive test system according to claim 1, characterized in that: The preheating section (223) adopts three-stage heating, all of which are two-point direct electric heating, and the material is 316L stainless steel.

6. The steam-water two-phase countercurrent comprehensive test system according to claim 1, characterized in that: The electric heating boiler (316) serves as the steam supply source in the main pipe two-phase flow, and the heating power is adjusted by its internal multi-stage heating rods.

7. The test method of the steam-water two-phase countercurrent comprehensive test system according to any one of claims 1 to 6, characterized in that: By changing the test liquid phase inlet flow rate, i.e., the liquid level of the upper pressure-bearing vessel (110), and the vapor phase inlet flow rate, the influence of each parameter on the CCFL phenomenon of the oscillating tube is studied. For the inlet temperature parameter, the steam and water are the saturation temperatures at the corresponding pressures; before the test starts, check whether the water levels of all water tanks and related equipment are normal. 1) First, open the water supply branch (200) to inject normal temperature saturated water into the upper pressure-bearing vessel (110) and keep the preset water level in the upper pressure-bearing vessel (110) unchanged; 2) Then open the steam supply branch (300) to form a stable two-phase countercurrent state in the oscillating tube test section (120); 3) After a stable preset time in the oscillating tube test section (120), gradually increase the vapor phase flow rate to start the test. The test process includes the flooding process and the de-flooding process. 1) After the test starts, first introduce a preset amount of steam, and then the water supply branch (200) supplies saturated water at a preset flow rate to the upper pressure-bearing vessel (110) to keep the preset water level in the upper pressure-bearing vessel (110) unchanged; 2) Then, the steam supply branch (300) supplies steam at a preset flow rate to the lower pressure-bearing vessel (140) to form a vapor-liquid two-phase countercurrent flow state in the oscillating tube test section (120); 3) In the initial stage of the test, when the supplied vapor phase flow rate is small, a stable two-phase countercurrent state will be formed in the oscillating tube test section (120). At this time, the water flow rate flowing into the oscillating tube test section (120) through the upper pressure-bearing vessel (110) is equal to the water flow rate flowing from the oscillating tube test section (120) into the lower pressure-bearing vessel (140); 4) After further increasing the steam flow rate, an unstable vapor-liquid two-phase countercurrent flow appears at a certain position in the oscillating tube test section (120), accompanied by wavy or agitated flow, and there is an obvious sudden change in pressure drop at this position, then it is considered that the CCFL phenomenon occurs at this position, which is called the CCFL starting point; 5) After increasing the steam flow rate again, the water flow rate flowing downward along the oscillating tube test section (120) will further decrease until it finally becomes zero. At this time, the water flow rate entering the lower pressure-bearing vessel (140) is 0, that is, the liquid backflow critical point is reached; 6) Then adjust the water flow rate to another working condition and repeat the above steps; or at the given flow rate above, gradually reduce the steam flow rate and observe the de-flooding hysteresis effect in the oscillating tube test section (120) until the countercurrent phenomenon disappears.

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