A heat exchange experimental device with variable tube bundle arrangement

Abstract

The present invention relates to a variable tube bundle arrangement heat exchange experimental device, wherein a natural circulation unit, a forced circulation unit, a convection heat exchange cooling unit and a tube bundle arrangement heating platform are sequentially connected in series through pipelines to form a circulation loop, and a plurality of pressure gauges, temperature sensors and electromagnetic flow meters for collecting pressure, temperature and flow are arranged in the pipelines. Bypass pipelines are respectively arranged in parallel at both ends of the natural circulation unit and the forced circulation unit, and the tube bundle arrangement heating platform comprises a tube bundle arrangement bracket, a heating power supply arranged at the bottom of the tube bundle arrangement bracket and a transparent heating experimental section at the top. The device can be used to study the heat transfer flow mechanism of different tube bundle arrangements, as well as the boiling heat transfer mechanism and local heat transfer characteristics of the heating section under two circulation conditions. It is helpful for understanding and in-depth research on the heat transfer mechanism. In addition, the data of the entire system is detected in real time to ensure data recording of the entire process of experimental data.

Description

Technical Field

[0001] The invention relates to a heat exchange experimental device, in particular to a heat exchange experimental device with variable tube bundle arrangement. Background Art

[0002] In the design process of nuclear power plants, in order to improve the safety of equipment and enhance the ability to handle accident conditions, the passive principle is widely used in the construction of engineering equipment. Natural circulation is one of the passive means and plays an important role in nuclear power accident conditions. Natural circulation refers to a method of energy transmission in a closed system that relies solely on the buoyancy formed by the density difference between the cold and hot fluids to drive the circulation of fluids. It does not rely on any external force, but relies on the pressure difference generated by the density difference between the riser and the downcomer to drive the natural circulation flow.

[0003] The instability of natural circulation flow will restrict the application of the natural circulation principle. Most of the research on heat transfer characteristics under flow oscillation conditions at home and abroad is concentrated on forced circulation, and the research under natural circulation is incomplete. At present, the design of heat exchangers is still based on the empirical relationship of single-tube heat exchange, while the heat transfer mechanism and influencing factors of tube bundle boiling heat transfer are different from those of single tubes. What are the effects of natural circulation and forced circulation on the heat transfer mechanism of single tubes and tube bundles, what are the influencing factors, whether the heat transfer phenomenon and heat transfer mechanism are different for cooling water flowing through heat exchange tubes with different tube bundle arrangements, and what are the single-phase flow and two-phase flow phenomena when different heat exchange tube bundles are arranged in natural circulation and forced circulation? These issues need in-depth research.

[0004] The existing condensation heat exchange experimental device that can realize the coupling of autothermal circulation and forced circulation, such as the device disclosed in Chinese patent CN103196945A, is mainly a device for studying the heat exchange between steam and low-temperature saturated temperature wall. By heating non-condensable gas to change the gas composition, the characteristics of condensation heat exchange under natural circulation and forced circulation are studied. However, the device does not study the mechanism of tube bundle heat exchange. At present, there is no experimental platform for designing natural circulation and forced circulation coupling for different tube bundle arrangement styles. In addition, the heat exchange method of the device is complicated, and the use process and adjustment are cumbersome. Summary of the invention

[0005] The purpose of the present invention is to provide a variable tube bundle arrangement heat exchange experimental device, which can be used to study different tube bundle arrangements and realize variable tube bundle arrangement experiments coupling natural circulation and forced circulation.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A variable tube bundle arrangement heat exchange experimental device comprises a natural circulation unit and a forced circulation unit, and also comprises a convection heat exchange cooling unit and a tube bundle arrangement heating platform. The natural circulation unit, the forced circulation unit, the convection heat exchange cooling unit and the tube bundle arrangement heating platform are sequentially connected in series through pipelines to form a circulation loop. A plurality of pressure gauges, temperature sensors and electromagnetic flow meters for collecting pressure, temperature and flow are arranged in the pipelines. Bypass pipelines are respectively arranged in parallel at both ends of the natural circulation unit and the forced circulation unit. The tube bundle arrangement heating platform comprises a tube bundle arrangement bracket, a heating power supply arranged at the lower part of the tube bundle arrangement bracket and a transparent heating experimental section at the upper part.

[0008] Furthermore, the natural circulation unit comprises a natural circulation water tank, and an upward interface and a downward interface are provided at the lower part of the natural circulation water tank, and the upward interface and the downward interface are connected to the circulation loop of the device through a pipeline provided with a flow regulating valve.

[0009] Furthermore, an electric heater and a temperature measuring thermocouple are provided inside the natural circulation water tank.

[0010] Furthermore, the forced circulation unit includes a flow regulating valve, a forced circulation water tank and a forced circulation pump which are sequentially connected through pipelines.

[0011] Furthermore, the convection heat exchange cooling unit includes a cooling water pool, a cooling water circulation pump, a flow regulating valve, an electromagnetic flow meter and a heat exchange pipeline which are sequentially connected through pipelines.

[0012] Furthermore, the convection heat exchange cooling unit is provided in plurality in the circulation loop of the device as required.

[0013] Furthermore, a pressure stabilizing tank is provided in the circulation loop of the device.

[0014] Furthermore, an automatic exhaust valve is provided in the circulation loop of the device.

[0015] Furthermore, the transparent heating experimental section is made of heat-resistant glass.

[0016] Furthermore, the tube bundle arrangement heating platform is provided with a panel with a replaceable tube bundle arrangement, and the shape of the panel is set according to needs.

[0017] More specifically, the present invention comprises:

[0018] 1. A natural circulation pipeline valve is provided on the connecting pipelines between the natural circulation unit and the heating section, the top heat exchange section and the descending heat exchange section. A forced circulation pipeline valve is provided on the connecting pipelines between the forced circulation unit and the heating section, the top heat exchange section and the descending heat exchange section. By switching between the natural circulation pipeline valve and the forced circulation pipeline valve, the heat exchange characteristics of natural circulation and forced circulation can be compared under the conditions of the same heating power of the heating section and the same tube bundle arrangement.

[0019] 2. The natural circulation water tank is equipped with an electric heating device, which can control the initial temperature of the cooling water in the natural circulation unit.

[0020] 3. The heating test section adopts heat-resistant glass, which is convenient for observing and analyzing the experimental phenomena in the heating section.

[0021] 4. Temperature sampling points are arranged at different heights in the heating test section to observe the temperature distribution at different positions of the tube bundle heat exchange.

[0022] 5. Tube bundle arrangement The heating platform can be installed with a single heating tube or multiple heating tube bundles to realize experimental research on different numbers of heating tube bundles.

[0023] 6. The tube bundle arrangement heating platform is a replaceable tube bundle arrangement enclosure to study the effects of different tube bundle arrangements on heat exchange capacity.

[0024] 7. An insulation layer is set on the outside of the pipelines of the natural circulation unit, forced circulation unit, and convection heat exchange cooling unit to reduce heat exchange to the external environment and improve the accuracy of the experimental data.

[0025] 8. The power control system can control the power of the electric heating rod in the heating test section.

[0026] 9. The data measurement system includes temperature measurement system and pressure measurement system.

[0027] The temperature measurement system consists of thermocouples at the following locations. The temperature measurement system mainly measures: the inlet and outlet temperatures of the heating test section, the temperature distribution in the heating test section, the inlet and outlet temperatures of the top heat exchange section, the temperature of the self-heating circulation water tank, the inlet and outlet temperatures of the descending heat exchange section, the temperature of the natural circulation pipeline, and the outlet temperature of the forced circulation pump. The pressure measurement system consists of pressure gauges at the following locations. The pressure measurement system mainly measures: the inlet and outlet pressures of the heating test section, the inlet and outlet pressures of the top heat exchange section, the inlet and outlet temperature of the descending heat exchange section, the pressure of the natural circulation pipeline, and the pressure of the surge tank.

[0028] The specific working process of this device is:

[0029] The experimental device includes a natural circulation unit, a forced circulation unit, a convection heat exchange cooling unit, a tube bundle arrangement heating platform, a power control system and a data measurement and acquisition instrument. Driven by the density difference between the cold and hot sections, the cooling water in the circulating water tank flows downward along the natural circulation pipeline through the descending heat exchange section, enters the flow regulating valve, the pressure regulating tank, and the electromagnetic flowmeter in turn, flows upward through the heating experimental section, enters the top heat exchange section to complete the heat exchange, and finally returns to the circulating water tank; the circulating pump draws cooling water from the forced circulation water tank, passes through the flow regulating valve, the pressure regulating tank, the electromagnetic flowmeter, the visual heating section, the top heat exchange section, and the descending heat exchange section to complete the heat exchange, and then returns to the forced circulation water tank; the convection heat exchange cooling unit consists of a cooling water circulation pump, a cooling water pool, a flow regulating valve, an electromagnetic flowmeter, and a heat exchange pipeline. The circulating pump draws water out and flows through the flow regulating valve, the flowmeter, the heat exchange pipeline, and finally flows back to the cooling water pool.

[0030] Compared with the prior art, the variable tube bundle arrangement experimental device provided by the present invention can realize the coupling of natural circulation and forced circulation, and can realize the study of the heat transfer flow mechanism of a single tube under natural circulation and forced circulation conditions; the study of boiling heat transfer mechanism and local heat transfer characteristics of the heating section under natural circulation and forced circulation conditions with different tube bundle arrangement styles; can realize the visual observation of experimental phenomena in the heating experimental section, and the measurement of temperature distribution, which is helpful for understanding the experimental scheme; can realize the influence of different initial temperatures of cooling water in natural circulation on the heat transfer characteristics of the tube bundle. The device is provided with a convection heat exchange cooling unit, including a top heat exchange section and a descending heat exchange section, which is more accurate in controlling the water temperature and is conducive to realizing the steady-state operation of natural circulation and forced circulation. For example, when the top heat exchange meets the temperature control requirements, the descending heat exchange section can be regarded as a descending section and does not participate in the heat exchange. When the water temperature of the top heat exchange section does not meet the experimental requirements, the circulating pump of the descending heat exchange section is turned on to realize the control of the water temperature of the descending heat exchange section to meet the temperature control requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the schematic diagram of the experimental device.

[0032] Figure 2 This is a schematic diagram of the internal structure of a natural circulation water tank;

[0033] Figure 3a This is a schematic diagram of the internal structure of the first type of replaceable tube bundle arrangement heating platform;

[0034] Figure 3b This is a schematic diagram of the internal structure of the second type of replaceable tube bundle arrangement heating platform;

[0035] Figure 3c This is a schematic diagram of the internal structure of the third type of replaceable tube bundle arrangement heating platform;

[0036] In the figure: high-precision voltage and current stabilizing power supply 1, tube bundle arrangement bracket 2, heating test section 3, top heat exchange section 4, top heat exchange pipeline 5, electromagnetic flowmeter 6, flow regulating valve 7, cooling water circulation pump 8, cooling water pool 9, natural circulation pipeline valve 10, natural circulation water tank 11, forced circulation pipeline valve 12, automatic exhaust valve 13, descending section heat exchange pipeline 14, descending section 15, electromagnetic flowmeter 16, flow regulating valve 17, cooling water circulation pump 18, pool 19, forced circulation water tank 20, forced circulation pump 21, main pipeline flow regulating valve 22, pressure regulating tank control valve 23, pressure regulating tank 24, electromagnetic flowmeter 25, electric heater 26, upstream interface 27, downstream interface 28, thermocouple temperature measurement interface 29, heating platform 30, tube bundle enclosure 31, heating tube bundle 32, tube bundle enclosure 33, heating platform 34, heating tube bundle 35, heating platform 36, tube bundle enclosure 37, heating tube bundle 38. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process.

[0038] Combination Figure 1 The main structure of this experiment mainly includes a high-precision voltage and current stabilizing power supply 1, a tube bundle arrangement bracket 2, a heating experiment section 3, a top heat exchange section 4, a top heat exchange pipeline 5, an electromagnetic flowmeter 6, a flow regulating valve 7, a cooling water circulation pump 8, a cooling water pool 9, a natural circulation pipeline valve 10, a natural circulation water tank 11, a forced circulation pipeline valve 12, an automatic exhaust valve 13, a descending section heat exchange pipeline 14, a descending section 15, an electromagnetic flowmeter 16, a flow regulating valve 17, a cooling water circulation pump 18, a water pool 19, a forced circulation water tank 20, a forced circulation pump 21, a main line flow regulating valve 22, a pressure regulating tank control valve 23, a pressure regulating tank 24, an electromagnetic flowmeter 25, as well as pressure measuring instruments and temperature measuring elements.

[0039] Combination Figure 2 The natural circulation water tank is mainly composed of an electric heater 26, a natural circulation pipeline upstream interface 27, a natural circulation pipeline downstream interface 28, and a thermocouple temperature measurement interface 29.

[0040] Combination Figure 3a The first type of replaceable tube bundle arrangement heating platform is composed of a heating platform 30, a tube bundle enclosure 31, and a heating tube bundle 32. Figure 3b The second replaceable tube bundle arrangement heating platform is composed of a tube bundle enclosure 33, a heating platform 34, and a heating tube bundle 35. Figure 3c The third type of replaceable tube bundle arrangement heating platform consists of a heating platform 36 , a tube bundle enclosure 37 , and a heating tube bundle 38 .

[0041] For the natural circulation heat exchange experiment of a single heat exchange tube, the technical scheme is as follows: for the natural circulation heat exchange experiment, first control the cooling water in the natural circulation water tank 11 to the required temperature of the experiment, fill the experimental device with water, close the forced circulation pipeline valve 12, open the natural circulation pipeline valve 10, close the pressure regulating tank control valve 23, open the automatic exhaust valve 13, exhaust the air in the pipeline through the exhaust valve, observe the pressure at each test point, and when the pressure is stable, open the pressure regulating tank control valve 23, and use the pressure regulating tank 24 to control the natural circulation loop pressure to be stable. In the experimental stage, start the power control system 1, heat the heat exchange tube placed on the tube bundle arrangement heating platform 2, and the cooling water in the natural circulation water tank 11, driven by the density difference between the cold and hot sections, flows through the descending section 15, the pressure regulating tank 24, the electromagnetic flowmeter 25, flows upward through the visual heating experimental section 3, the top heat exchange section 4, and finally flows back to the self-heating circulation water tank 11. The cooling water circulation pump 8 draws water from the cooling water pool 9, flows through the flow regulating valve 7, the electromagnetic flowmeter 6, realizes heat exchange with the top heat exchange section in the top heat exchange pipeline 5, and finally flows back to the cooling water pool 9. By adjusting the flow regulating valve 7, the temperature of the top heat exchange section is controlled. When the temperature of the top heat exchange section does not meet the control requirements, the cooling circulation water pump 18 is started to draw the cooling water in the pool 19 through the electromagnetic flowmeter, the descending heat exchange pipeline 15, and finally flows back to the pool 19. When the system parameters, temperature and pressure are stable and the experimental phenomena are stable, the measured data are read and analyzed through the data measurement and acquisition instrument.

[0042] For the forced circulation heat exchange experiment of a single heat exchange tube, the technical scheme is: first fill the experimental device with water, close the natural circulation pipeline valve 10, open the forced circulation pipeline valve 12, close the pressure regulating tank control valve 23, open the automatic exhaust valve 13, exhaust the air in the pipeline through the exhaust valve, open the forced circulation pump 21, extract the cooling water from the forced circulation water tank 20, flow through the flow regulating valve 22, the electromagnetic flowmeter 25, flow upward through the visualized heating experimental section 3, the top heat exchange section 4, the automatic exhaust valve 13, the descending section 14, and finally flow back to the forced circulation water tank 20. Observe the pressure at each test point. When the pressure is stable, open the pressure regulating tank control valve 23, and use the pressure regulating tank 24 to control the pressure stability of the forced circulation loop. In the experimental stage, start the power control system 1 to heat the heat exchange tube placed on the tube bundle arrangement heating platform 2, and the heating tube heats the heating test section 3. The cooling water is drawn from the forced circulation water tank 20, flows through the flow regulating valve 22, the electromagnetic flowmeter 25, flows upward through the visualized heating experimental section 3, the top heat exchange section 4, the automatic exhaust valve 13, the descending section 14, and finally flows back to the forced circulation water tank 20. The cooling water mass flow rate of the forced circulation unit is fed back in time by the electromagnetic flowmeter 25, and the flow rate is adjusted and controlled by the flow regulating valve 22. The cooling water circulation pump 8 draws water from the cooling water pool 9, flows through the flow regulating valve 7, the electromagnetic flowmeter 6, and realizes heat exchange with the top heat exchange section in the top heat exchange pipeline 5, and finally flows back to the cooling water pool 9. The temperature of the top heat exchange section is controlled by adjusting the flow regulating valve 7. When the temperature of the top heat exchange section does not meet the control requirements, the cooling circulation water pump 18 is started to draw the cooling water in the water pool 19 and flow through the electromagnetic flowmeter and the descending heat exchange pipeline 15, and finally flows back to the water pool 19. When the system parameter temperature and pressure are stable and the experimental phenomenon is stable, the measured data is read and analyzed through the data measurement and acquisition instrument.

[0043] For the variable tube bundle arrangement heat exchange experiment, the technical scheme is: the variable tube bundle arrangement heat exchange experiment natural circulation experiment is the same as scheme 1, and the forced circulation experiment scheme is the same as scheme 2. By replacing the tube bundle arrangement bracket 2 and changing the tube bundle arrangement mode, the present invention designs three different styles of tube bundle enclosures, tube bundle enclosure 31, tube bundle enclosure 33, and tube bundle enclosure 37. By replacing the tube bundle enclosures and applying the technical scheme, the heat exchange characteristics of tube bundles with different tube bundle arrangement styles can be studied.

[0044] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. It should also be noted that the experimental device needs to be improved and adjusted according to specific requirements. Those skilled in the art may improve the technical solution of the present invention without departing from the principle and scope of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A variable tube bundle arrangement heat exchange experimental device, comprising a natural circulation unit and a forced circulation unit, characterized in that: It also includes a convection heat exchange cooling unit and a tube bundle arrangement heating platform, wherein the natural circulation unit, the forced circulation unit, the convection heat exchange cooling unit and the tube bundle arrangement heating platform are sequentially connected in series through pipelines to form a circulation loop, and the pipelines are provided with a plurality of pressure gauges, temperature sensors and electromagnetic flowmeters for collecting pressure, temperature and flow, and bypass pipelines are respectively arranged in parallel at both ends of the natural circulation unit and the forced circulation unit, and the tube bundle arrangement heating platform includes a tube bundle arrangement bracket, a heating power supply arranged at the lower part of the tube bundle arrangement bracket and a transparent heating experimental section at the upper part; The natural circulation unit comprises a natural circulation water tank, an upper interface and a lower interface are provided at the lower part of the natural circulation water tank, and the upper interface and the lower interface are connected to the circulation loop of the device through a pipeline provided with a flow regulating valve; An electric heater and a temperature measuring thermocouple are provided inside the natural circulation water tank; The tube bundle arrangement heating platform is provided with a panel with a replaceable tube bundle arrangement mode, and the shape of the panel is set according to needs; The tube bundle arrangement heating platform is equipped with a single heating tube or multiple heating tube bundles to realize experimental research on different numbers of heating tube bundles; The tube bundle arrangement heating platform is a replaceable tube bundle arrangement enclosure to study the effects of different tube bundle arrangements on heat exchange capacity.

2. The variable tube bundle arrangement heat exchange experimental device according to claim 1, characterized in that: The forced circulation unit comprises a flow regulating valve, a forced circulation water tank and a forced circulation pump which are sequentially connected through pipelines.

3. The variable tube bundle arrangement heat exchange experimental device according to claim 1, characterized in that: The convection heat exchange cooling unit comprises a cooling water pool, a cooling water circulation pump, a flow regulating valve, an electromagnetic flow meter and a heat exchange pipeline which are sequentially connected through pipelines.

4. The variable tube bundle arrangement heat exchange experimental device according to claim 3 is characterized in that: The counter-flow heat exchange cooling unit may be provided in a plurality in the circulation loop of the device as required.

5. The variable tube bundle arrangement heat exchange experimental device according to claim 1, characterized in that: A pressure stabilizing tank is provided in the circulation loop of the device.

6. The variable tube bundle arrangement heat exchange experimental device according to claim 1, characterized in that: An automatic exhaust valve is provided in the circulation loop of the device.

7. The variable tube bundle arrangement heat exchange experimental device according to claim 1, characterized in that: The transparent heating experimental section is made of heat-resistant glass.

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