An experimental device for studying the heat transfer characteristics of high-temperature and high-speed gas flow

Abstract

The purpose of the present invention is to provide a high-temperature and high-speed gas flow heat exchange characteristic research experimental device, including a compressor, a gas storage tank, a filter, a pressure reducing valve for stabilizing the pressure after the filter, a stop valve for flow regulation, a gas flow meter, a gas temperature sensor in the pipe, a pressure sensor, a preheater, an inlet section chamber and an outlet section chamber welded with a threaded base, a flow heat exchange experimental section, an outlet pressure regulating valve, and a PVC hose and a stainless steel pipe connecting various devices. The present invention adopts a modular design, which is more flexible than traditional experimental devices, has improved measurement accuracy, and has richer research phenomena. It can realize real-time and high-frequency data acquisition under transient operating conditions, can simulate the normal operation and accident working process of the reactor, and provide technical support for the study of transient operating characteristics of open nuclear power reactors.

Description

Technical Field

[0001] The invention relates to an experimental device, in particular to an experimental device for studying the heat transfer and friction resistance characteristics of gas media and the temperature response characteristics of heat exchangers under transient conditions. Background Art

[0002] Near-space is located in the area 20-100 kilometers above the earth's surface. Its altitude cannot meet the flight requirements of aircraft or spacecraft, and it is a blind spot for human space applications. The important significance of near-space in weather forecasting, electromagnetic communication, high-resolution wide-band imaging, etc. has attracted the attention of many countries in recent years. In order to meet the mission requirements of near-space exploration, the development of near-space aircraft is urgent. Nuclear-powered aircraft have the advantages of high power density, long endurance, large thrust, and wide coverage, and can be used as a near-space aircraft. Open-cycle reactors are used in nuclear-powered engines. High-temperature and high-speed air is used as a coolant to take away the heat generated by the core and as a propellant to generate thrust for the aircraft. As a new type of air-cooled reactor, it is different from conventional reactors in two aspects. One is that air is different from conventional coolants such as water, helium, and liquid metal. It is manifested in the compressibility of air, and its physical properties change with temperature and pressure. High-temperature and high-speed air parameters such as temperature, pressure, and speed have a great influence on air flow resistance and heat exchange performance with the core. If blockage and heat transfer deterioration occur, it will threaten the safe operation of the reactor. Secondly, the reactor has strong mobility, and its operating parameters change with the flight conditions. Compared with conventional reactors, the heat transfer characteristics of air under transient conditions and the temperature response characteristics of the reactor must be considered to ensure that the heat can be safely taken out. Experimental studies on air flow heat transfer at home and abroad mostly stopped around the 1960s. In recent years, most of the research on air flow heat transfer is external, and the research on flow heat transfer in the tube is insufficient; many studies mainly focus on the average heat transfer capacity of the entire pipeline under steady-state conditions, constant wall heat flux or temperature conditions. Less attention has been paid to the characteristics and mechanisms of the influence of transient conditions and heat flux (such as cosine distribution along the reactor axis), the flow of variable physical air and changes in thermal parameters (including temperature, pressure, velocity and heating power) on the flow heat transfer characteristics. In recent years, as scholars have paid more and more attention to new air-cooled reactors, it is of great significance to study the steady-state and transient flow heat transfer characteristics of air in the coolant channel, master its flow heat transfer mechanism, and provide guidance for the design of efficient and safe nuclear power engines. Summary of the invention

[0003] The purpose of the present invention is to provide a high-temperature and high-speed gas flow heat transfer characteristic research experimental device that can be quickly installed and can study the flow heat transfer characteristics of various gas working fluids under steady-state and transient conditions.

[0004] The object of the present invention is achieved in that:

[0005] The invention discloses an experimental device for studying the flow and heat exchange characteristics of high-temperature and high-speed gases, which is characterized by comprising a compressor, a gas storage tank, a filter, a pressure reducing valve, a stop valve, a gas flow meter, a gas temperature sensor, a pressure sensor, a preheater, an inlet section chamber, a flow and heat exchange experimental section, an outlet section chamber, and an outlet pressure regulating valve. The compressor, the gas storage tank, the filter, the pressure reducing valve, the stop valve, the gas flow meter, the gas temperature sensor, the pressure sensor, the preheater, the inlet section chamber, the flow and heat exchange experimental section, the outlet section chamber, and the outlet pressure regulating valve are connected in sequence through an experimental pipeline. The experimental pipeline comprises a PVC hose and a stainless steel pipe. The compressor and the gas storage tank are connected through the PVC hose. The filter is connected in series to the PVC hose at the outlet of the gas storage tank through a threaded quick connector. The pressure reducing valve has flanges at both ends. The flange on one side is connected to the upstream PVC hose, and the flange on the other side is connected to the downstream stainless steel pipe. The experimental pipelines behind it are all stainless steel pipes.

[0006] The present invention may also include:

[0007] 1. The stop valve has a flange and is connected in series at a position 10 times the pipe diameter away from the pressure reducing valve.

[0008] 2. The gas flow meter is connected to the experimental pipeline through a flange, and a straight pipe section of more than 10 times the pipe diameter is left upstream, and a straight pipe section of more than 5 times the pipe diameter is left downstream.

[0009] 3. The gas temperature sensor and pressure sensor have external threaded joints; first weld the internal threaded pipe seat to the experimental pipeline, then wrap the threaded joint with raw tape and screw it into the pipe seat.

[0010] 4. The inlet and outlet of the preheater are low inlet and high outlet and are connected to the experimental pipeline through flanges. The inlet section chamber after the preheater is at the same height as its outlet and is connected through flanges.

[0011] 5. The inlet section chamber and the outlet section chamber are both provided with 4 equally spaced and staggered baffles welded on the side of the box, and 4 threaded bases are welded on the top of the chamber.

[0012] 6. There are 4 threaded bases in the inlet section chamber and the outlet section chamber, which are welded on the side close to the flow heat transfer experimental section. Two threaded bases are connected to thermocouples, one threaded base is connected to a pressure sensor, and one threaded base is connected to a differential pressure sensor.

[0013] 7. A pair of thermocouples are arranged symmetrically every 5 cm on the flow heat transfer test section, and the entire flow heat transfer test section is wrapped with asbestos for insulation.

[0014] The advantages of the present invention are:

[0015] (1) High flexibility, capable of carrying out flow and heat transfer experiments of various working fluids. The use of reducers and flanges makes it easier to replace experimental sections with different pipe diameters.

[0016] (2) The measurement accuracy is improved by adding chambers at the inlet and outlet test sections to slow down the gas and improve the problem of inaccurate measurement of gas stagnation pressure and temperature caused by high-speed gas flow;

[0017] (3) The research phenomena are more abundant. The gas flow heat transfer characteristics at different temperatures, speeds, pressures and heating powers under steady-state conditions can be studied to simulate the normal operating conditions of nuclear power reactors and realize experimental demonstration and verification of flow heat transfer characteristics;

[0018] (4) Experimental research on flow and heat transfer under non-steady-state conditions can be carried out to achieve real-time and high-frequency data collection. By adjusting the valve opening to increase or decrease the flow rate, the reactor variable operation process or the reactor loss of flow accident process can be simulated. The power supply can be adjusted by programming methods to simulate the reactor power increase or decrease process and the introduction of positive or negative reactivity process, and the temperature response characteristics and laws of the coolant and reactor fuel can be obtained to understand the transient operation characteristics of the open nuclear power reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention;

[0020] Figure 2 This is the structural diagram of the flow heat transfer experimental section;

[0021] Figure 3 It is a schematic diagram of a conductive copper sheet;

[0022] Figure 4 The front view of the chamber of the inlet and outlet sections;

[0023] Figure 5 It is the left view of the chamber of the inlet and outlet sections;

[0024] Figure 6 It is a top view of the inlet and outlet chambers. DETAILED DESCRIPTION

[0025] The present invention is described in more detail below with reference to the accompanying drawings:

[0026] Combination Figure 1-6, the pipeline diagram of the experimental device for studying the flow and heat transfer characteristics of high-temperature and high-speed gas of the present invention is used to study the heat transfer characteristics and friction resistance characteristics of equal-section pipes under steady-state and transient conditions. The experimental device is an open pipeline, and the gas can be directly discharged into the atmosphere. The experimental device includes a compressor 1, a gas storage tank 2, a filter 3, a pressure reducing valve 4 for stabilizing the pressure after the filter, a stop valve 5 for flow regulation, a gas flow meter 6, a gas temperature sensor 7 in the pipe, a pressure sensor 8, a preheater 9, an inlet section chamber 10 and an outlet section chamber 16 welded with a threaded base, a flow and heat transfer experimental section 13, temperature instruments 11 and 15 for measuring the temperature and pressure of the inlet and outlet chambers, pressure instruments 12 and 14, and an outlet pressure regulating valve 17. The experimental components are all welded with flanges, the flanges are tightened by screws, and a high-temperature resistant metal gasket is padded in the middle to prevent air leakage.

[0027] The PVC hose connecting each device has a pressure resistance of 2.5MPa, and the stainless steel pipe is industrial 304 stainless steel, which can withstand gas pressure below 2.5MPa. The compressor 1 and the gas tank 2 are connected by a PVC hose with a flange. The filter 3 contains multiple stages and is connected in series to the PVC pipe at the outlet of the gas tank 2 through a threaded quick connector. The pressure reducing valve 4 has flanges at both ends, one end is connected to the upstream PVC hose, and the other end is connected to the downstream stainless steel pipe. All subsequent pipelines are stainless steel pipes. The stop valve 5 for flow regulation has a flange and is connected in series at a position 10 times the pipe diameter away from the pressure reducing valve. The gas flow meter 6 is connected to the pipeline through a flange, and a straight pipe section of more than 10 times the pipe diameter is left upstream, and a straight pipe section of more than 5 times the pipe diameter is left downstream. The gas temperature sensor 7 and the pressure sensor 8 in the pipe have external threaded joints; the internal threaded pipe seat is first welded to the experimental pipeline, and then the threaded joint is wrapped with raw tape and screwed into the pipe seat. The inlet and outlet of the preheater 9 are low-in and high-out and are connected to the experimental circuit through flanges. The inlet chamber 10 after the preheater 9 is at the same height as its outlet and is connected by a flange. After the inlet chamber 10 is a smooth 304 stainless steel experimental section 13, and after the experimental section 13 is an outlet chamber 16, which are connected by a reducer and are located at the same height. The outlet of the outlet chamber 16 is connected to the outlet pressure regulating valve 17 through a flange, and a pipeline is connected after the valve for gas discharge.

[0028] The inlet and outlet ends of the experimental equipment are welded with PN16 standard flanges, and anti-leakage and high-temperature resistant metal gaskets are installed between the flanges. The filter consists of a first-level solid particle filter, a first-level oil and gas filter, and a second-level water vapor filter. The pressure reducing valve is equipped with a pressure gauge, and its rear end is connected to the stop valve through a straight pipe with flanges at both ends. There are 4 equally spaced and staggered baffles inside the inlet and outlet chambers, which are welded on the side of the box, and 4 threaded bases are welded above the cavity. There are 4 threaded bases on the inlet and outlet chambers, which are welded on the side close to the experimental section, 2 of which are connected to thermocouples, 1 is connected to a pressure sensor, and 1 is connected to a differential pressure sensor. The experimental section is made of 304 stainless steel, with 304 material flanges welded at both ends, first connected to a conductive copper sheet, and then connected to the inlet and outlet chambers through flanges after multi-stage diameter reduction through a standard reducer. A pair of thermocouples are arranged at symmetrical positions every 5 cm on the experimental pipe section, and the entire experimental section is wrapped with asbestos for insulation. The conductive copper sheet is long and flat, with one end punched according to the DN15 flange and the other end evenly distributed with 4 threaded holes, sandwiched between the test section and the flange of the reducer. The reducer is 30 mm long and conical, with a larger diameter at one end and a smaller diameter at the other end, and flanges are welded at both ends. The outlet pressure regulating valve can be a gate valve, a stop valve or an electric regulating valve.

[0029] Combination Figure 2 The flow heat exchange experimental section structure diagram of the present invention, the experimental device includes an electrical insulating gasket 18, an experimental section flange 19, gradually expanding tubes 20 and 21, a conductive copper sheet 22, and gradually reducing tubes 23 and 24. The experimental section 13 includes a 304 stainless steel experimental section and a flange. The flange 19 is welded to the two ends of the 304 stainless steel experimental section by welding, and the three are required to be concentric circles. The gradually reducing tube and the gradually expanding tube are also connected by welding and flanges, and the flanges and pipelines are all in the form of concentric circles. According to the different temperature limits at different positions of the experimental pipeline, corresponding gaskets are used. Among them, a high temperature resistant metal gasket 25 is installed between the inlet section box 10 and the reducer 24, 23 for sealing; an electrical insulating gasket 18 is installed between the reducer 23 and the copper sheet to cut off the current; the outlet air temperature of the experimental section 13 is relatively high, and an electrical insulating mica gasket and a metal gasket are installed between the conductive copper sheet 22 and the flange of the gradually expanding tube 21; a metal gasket is installed between the gradually expanding tubes 20, 21 and the flange of the outlet box 16. This installation method avoids leakage in the experimental section and ensures that the flange connection is still reliable at high temperatures.

[0030] Combination Figure 3 It is a schematic diagram of the conductive copper sheet of the present invention, and the conductive copper sheet 27 includes a flange end 26 and a copper wire end 28. The flange end is drilled with 4 screw holes and a flow channel according to the DN15 flange plate, and the copper wire end is drilled with 4 screw holes to facilitate fixing the heating wire.

[0031] Combination Figure 4-6It is a schematic diagram of the inlet and outlet chambers of the present invention. The structures and processing methods of the two chambers are exactly the same, including the main view, top view and left view. The chamber includes a threaded base 29 and a spoiler 30 for the measurement channel. The threaded base 29 is connected to one side of the cavity by welding. There are 4 such bases in total; two of them are used as thermocouple measurement channels, equipped with armored thermocouples to measure the gas temperature in the box; one is a pressure sensor channel to measure the absolute pressure of the gas; and the last one is connected to a differential pressure sensor to measure the pressure difference between the inlet and outlet boxes. The spoiler 30 is a 304 stainless steel plate. In order to make the air disturbance uniform, the spoilers are arranged in an alternating manner. Two pieces are welded on the side walls at both ends of the inlet and outlet of the box, and two pieces are welded on the upper and lower walls in the middle of the box. When connected to the experimental pipeline, the end with the threaded base is close to the experimental section 13, so that the measured pressure and temperature parameters are as close as possible to the gas parameters of the experimental section.

Claims

1. An experimental device for studying the heat transfer characteristics of high-temperature and high-speed gas flow, characterized by: The invention comprises a compressor (1), a gas storage tank (2), a filter (3), a pressure reducing valve (4), a stop valve (5), a gas flow meter (6), a gas temperature sensor (7), a pressure sensor (8), a preheater (9), an inlet section chamber (10), a flow heat exchange experimental section (13), an outlet section chamber (16) and an outlet pressure regulating valve (17) which are sequentially connected through an experimental pipeline; The experimental pipeline comprises a PVC hose and a stainless steel pipe. The compressor (1) and the gas storage tank (2) are connected via the PVC hose. The filter (3) is connected in series to the PVC hose at the outlet of the gas storage tank (2) via a threaded quick connector. The pressure reducing valve (4) has flanges at both ends. The flange on one side is connected to the upstream PVC hose and the flange on the other side is connected to the downstream stainless steel pipe. The experimental pipelines behind it are all stainless steel pipes. The stop valve (5) is provided with a flange plate, which is connected in series at a position 10 times the pipe diameter away from the pressure reducing valve (4); the gas flow meter (6) is connected to the experimental pipeline through a flange, and a straight pipe section of more than 10 times the pipe diameter is left upstream, and a straight pipe section of more than 5 times the pipe diameter is left downstream; the gas temperature sensor (7) and the pressure sensor (8) are provided with external threaded joints, and the internal threaded pipe seat is first welded to the experimental pipeline, and then the threaded joint is wrapped with raw tape and screwed into the pipe seat; the inlet and outlet of the preheater (9) are in the form of low inlet and high outlet, and are connected to the experimental pipeline through flanges, and the inlet section chamber after the preheater (9) is at the same height as its outlet, and is connected to the experimental circuit through flanges; The filter (3) is composed of a first-level solid particle filter, a first-level oil and gas filter, and a second-level water vapor filter; the inlet section chamber (10) and the outlet section chamber (16) are both provided with four equidistantly arranged baffles, which are welded on the side of the box body; four threaded bases are welded on the upper side of the chamber, which are welded on the side close to the flow heat exchange experimental section (13); two threaded bases are connected to thermocouples, one threaded base is connected to a pressure sensor, and one threaded base is connected to a differential pressure sensor; the two ends of the flow heat exchange experimental section (13) are first connected to a conductive copper sheet, and then connected to the inlet and outlet sections of the chamber through a flange after multiple diameter reduction through a reducer; a pair of thermocouples are arranged at symmetrical positions every 5 cm on the flow heat exchange experimental section (13), and the entire flow heat exchange experimental section is wrapped with asbestos for thermal insulation; the conductive copper sheet is flat and long, and is sandwiched between the flow heat exchange experimental section (13) and the flange of the reducer; the reducer is conical, with a larger diameter at one end and a smaller diameter at the other end, and flanges are welded at both ends.

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