Large nuclear reactor molten pool natural-convection heat transfer test system and method

[0027] The present invention will be described in detail below in conjunction with the drawings and specific embodiments:

[0028] Such as figure 1 with figure 2 As shown, the present invention is a large-scale nuclear reactor melting pool natural convection heat transfer test system and method. The test system includes a large-scale nuclear reactor melting pool natural convection heat transfer test piece 1, a molten salt heating furnace 2 that provides a high-temperature melt, and The nitrogen source 3 connected to the test piece and the molten salt furnace, and the cooling water system; the first centrifugal pump 502 drives the water in the cooling water tank 4 to take away the decay heat source through the cooling channel of the test piece 1, and the heated cooling water passes through the plate heat exchange After the cooling of the device 7 and the cooling tower 8 return to the initial water temperature, return to the cooling water tank 4; until the temperature of the melting pool reaches a steady state, the test ends, and the waste liquid in the test piece 1 is discharged into the waste liquid pool 13; Including matching power distribution equipment 14, instrument control equipment 15, and data measurement acquisition equipment 16.

[0029] The large-scale nuclear reactor melting pool natural convection heat transfer test piece 1 includes an internal heating system and a cooling channel. A first thermocouple 101 and a first pressure gauge 111 are installed in the test piece 1 to monitor the temperature and pressure changes in the test piece 1 . The molten salt heating furnace 2 of the high-temperature melt is connected to the test piece 1 through the high-temperature molten salt submerged pump 501, the first high-temperature ball valve 901 and the corresponding molten salt pipeline in sequence, and a second thermocouple 102 and a high-temperature electromagnetic flowmeter are installed on the pipeline 121 is used to measure the molten salt temperature and flow rate at the molten salt injection port of test piece 1. When molten salt is used as a molten material, nitrogen is supplemented for high-temperature anti-oxidation protection. The nitrogen source 3 passes through the first nitrogen pressure reducing valve 902 and the second nitrogen pressure reducing valve 903, and the corresponding nitrogen pipes and test piece 1 and molten salt heating furnace 2 respectively. Connected, the first vortex flowmeter 122 and the second vortex flowmeter 123 are installed on the pipeline to measure the nitrogen flow.

[0030] In the cooling water circuit, the cooling water tank 4 is connected to the lower water inlet of the test piece 1 through the first ball valve 904, the first filter 601, the first centrifugal pump 502 and the corresponding pipeline in turn, and a second thermometer 104 is installed on the water tank for monitoring The water temperature in the water tank changes. There is a tee on the downstream pipe of the first centrifugal pump 502, and the vertical branch of the tee is connected to the cooling water tank 4 through the pipe and the second ball valve 905 to form a bypass loop to assist in adjusting the flow of cooling water; A third pressure gauge 113, a first electromagnetic flowmeter 124, and a third thermocouple 105 are sequentially installed on the downstream pipeline to obtain pipeline pressure, cooling water flow, and inlet temperature, respectively. The cooling water heated by the test piece 1 is cooled by the plate heat exchanger 7 and the cooling tower 8 to return to the initial water temperature and then return to the cooling water tank 4. The primary side water inlet of the plate heat exchanger 7 is connected to the cooling water outlet on the upper part of the test piece 1 through a pipe and a third ball valve 906, and a fourth thermocouple 106 is installed on the pipe to obtain the cooling water outlet temperature; in the plate heat exchanger The primary side water outlet of 7 is connected to the cooling water tank 4 through a pipe and the fourth ball valve 907 to form a closed circuit on the primary side. The secondary side water flow direction of the plate heat exchanger 7 and the primary side flow direction are countercurrent, and the secondary side water outlet is connected to the water inlet of the cooling tower 8 through the fifth ball valve 908 and the second electromagnetic flowmeter 125 in turn; the outlet of the cooling tower 8 The water inlet is connected to the secondary side water inlet of the plate heat exchanger 7 through the second filter 602, the second centrifugal pump 503, the sixth ball valve 909 and the corresponding pipes in sequence to form a secondary side closed loop. Install the fifth thermocouple 107, the second electromagnetic flowmeter 125 and the fourth pressure gauge 114 on the secondary circuit pipeline to obtain the secondary circuit cooling water temperature, flow rate and pipeline pressure respectively. In addition, there is a three-way on the downstream pipeline of the third ball valve 906, and the vertical branch of the three-way is connected to the seventh ball valve 910 through the pipeline to the upstream of the fourth ball valve 907 to form a bypass circuit to assist in adjusting the flow of cooling water.

[0031] As a preferred embodiment of the present invention, the cooling water system is designed with multiple valves and bypass lines to facilitate water flow adjustment and ensure that the temperature of the cooling water inlet at the test piece 1 is measured and the temperature of the third thermocouple 105 remains constant. , Reduce the influence of cooling water temperature fluctuation on the heat transfer characteristics of the melting pool.

[0032] As a preferred embodiment of the present invention, the surfaces of the high-temperature test piece, molten salt furnace, and molten salt inlet and outlet pipes of the test system are all covered with an insulating layer. The thermal insulation layer includes an aluminum silicate plate coating layer fixed with thin iron wires, a glass cloth wrapped around the aluminum silicate plate coating layer, and aluminum foil paper pasted on the glass cloth cloth. The function of the fine iron wire is to fix and compress the aluminum silicate plate, the function of the glass cloth is to reduce the contact between people and the aluminum silicate plate, and the function of the aluminum foil paper is to paste the glass cloth to further cover the aluminum silicate plate and improve the cleanliness of the test site. The maximum temperature of this test system can reach 350℃, and the thickness of the aluminum silicate plate coating should be greater than 150mm. The heating wire is wound around the molten salt inlet pipe and the sewage pipe to preheat the pipe before and after the test, and the heating wire is wrapped in the insulation cotton.

[0033] Such as image 3 As shown, as a preferred embodiment of the present invention, the power distribution equipment 14 mainly includes a power distribution cabinet, transmission lines, and electrical equipment connected in sequence. The power supply capacity of the power distribution equipment 14 meets the requirements of the test system, providing the test system with heating power for heating rods, heating power for molten salt furnace, heating power for pipe preheating wires, power power for molten salt submerged pumps and centrifugal pumps, Working power supply for instrument control equipment and data acquisition equipment, working power supply for lighting equipment, etc.

[0034] Such as Figure 4 As shown, as a preferred embodiment of the present invention, the instrument control equipment 15 mainly includes display instruments for various parts of the test circuit, a molten salt furnace startup control platform, a molten salt pump centrifugal pump startup control platform, and a heating system startup control platform. Components include pressure regulator, temperature gauge, pressure gauge, flow meter and valve controller. The electric heating power is adjusted by the pressure regulator, the state of the melting pool and cooling water is displayed by the thermometer and pressure gauge, the flow of molten salt, nitrogen and cooling water is displayed by the flow meter, and the valve opening is adjusted by the valve controller.

[0035] Such as Figure 5 As shown, the data measurement and acquisition equipment 16 mainly includes thermocouples, flow meters and pressure sensors, junction boxes, acquisition cards, measurement modules, signal conditioners, computer drive software and data acquisition software. Thermocouples, flow meters and pressure sensors convert physical parameters into electrical signals, pass through the junction box, and transmit to the signal conditioner for filtering and setting. The measurement module and data acquisition card convert the electrical signals into digital signals and provide them to the computer's drive software And data acquisition software, and then a special program compiled by LabView processes and displays the signals of all sensors.

[0036] The test method for natural convection heat transfer in the molten pool of the large nuclear reactor of the present invention, the specific test operation process is as follows: the molten salt heating furnace 2 heats and melts the nitrate at 350°C, the molten salt level reaches the position of the feeding port, and the nitrogen protection is turned on during the heating process , Turn on the cooling of the motor of the pump 501 under the high-temperature molten salt liquid. In the actual heating process, it is necessary to add materials to the molten salt furnace one by one, and add new materials after the melting volume of the solid salt decreases. In addition, due to the low heat conduction efficiency, low power is used in the initial stage of heating, and the power is gradually increased to avoid excessively high central temperature of the heating rod. During the heating process and test process of the molten salt furnace, sufficient nitrogen supply should be ensured. Multiple nitrogen cylinders can be selected to jointly supply nitrogen. The first nitrogen pressure reducing valve 902 and the second nitrogen pressure reducing valve 903 are used to control the nitrogen flow. Turn on the data measurement and acquisition system 16 to start recording data; after the molten salt is prepared, check the opening and closing of all valves, turn on the first centrifugal pump 502 and the second centrifugal pump 503, and run the cooling water circuit to reach a steady state until the inlet and outlet water temperature is constant ; Turn on the molten salt feeding pipeline to preheat until 250℃; adjust the pressure regulator, turn on the heating system of test piece 1 to the required power, turn on the nitrogen protection of the test section; turn on the high-temperature molten salt liquid pump 501, and inject the test piece 1 Molten salt, monitor the temperature change of the molten pool displayed by the collection system, when the molten salt reaches the specified height, turn off the molten salt submerged pump 501 and preheating heating wire; monitor data collection in real time, adjust the heating power and cooling water flow until the system reaches a steady state ; Switch the heating power to the next working condition and adjust the cooling water flow until steady state; the starting point of the sewage pipe is connected to the bottom of the test piece 1, and the outlet directly leads to the waste liquid tank 13. Before the end of the test, turn on the sewage pipe to preheat to 250 ℃, open the second high-temperature ball valve 911 for sewage discharge, the molten salt in test piece 1 is directly discharged into the waste liquid pool 13 by gravity; then the heating system of test piece 1 is turned off, but test piece 1 needs to continue to be cooled until the temperature drops to 100℃ Only then can the first centrifugal pump 502 and the second centrifugal pump 503 be turned off.