Supercritical Carbon Dioxide Experimental Device for Simultaneously Measuring the Performance of Multiple Heat Exchangers

Abstract

A supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers provided by the present invention includes a carbon dioxide gas cylinder, a cooler, a liquid storage tank, a booster pump, a buffer tank, and a high-pressure section heater connected in sequence along the medium flow direction. The outlet of the high-pressure section heater is connected to the cold-side inlet of a regenerator, and the cold-side outlet of the regenerator is sequentially connected to a high-pressure section cooler and a low-pressure section heater. The low-pressure section heater is connected to the hot-side inlet of the regenerator, the hot-side outlet of the regenerator is connected to a low-pressure section cooler, and the low-pressure section cooler is connected to the inlet of a first cooler. A pressure reducing valve is provided at the inlet of the high-pressure section heater, back pressure valves are provided at the inlet of the low-pressure section heater and the outlet of the low-pressure section cooler, and a liquid level gauge is provided outside the liquid storage tank. The present invention has the ability to carry out material corrosion experiments and heat transfer experiments between different working fluids and supercritical carbon dioxide. It is an experimental device with high integration and high efficiency, which can save experimental costs and improve research efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of performance testing of supercritical carbon dioxide cycle heat exchangers. Specifically, it relates to a supercritical carbon dioxide experimental device that can simultaneously measure the performance of multiple heat exchangers. Background Art

[0002] The supercritical carbon dioxide Brayton cycle is an important development direction in the future in the fields of solar energy, nuclear energy, distributed energy, and ship power, etc. due to its high thermal efficiency and medium density, and the relatively small sizes of equipment such as compressors and heat exchangers, making the system more compact. Among them, the design and optimization of heat exchangers are one of the main technical obstacles to improving the cycle efficiency and net power output. At least three heat exchangers, namely a heater, a recuperator, and a cooler, are required in a simple Brayton cycle. Since the operating parameters and heat transfer conditions of the heater, the recuperator, and the cooler are different, their structural characteristics need to be designed and optimized separately. Therefore, corresponding experimental devices need to be designed to carry out research on the performance of supercritical carbon dioxide multi-heat exchangers.

[0003] The document with the publication number CN111537253A discloses an experimental platform and method for the performance of a highly efficient and compact heat exchanger for water-carbon dioxide heat transfer to achieve experiments on supercritical carbon dioxide coolers. The document with the publication number CN113406141A discloses a supercritical carbon dioxide microchannel heat transfer experimental system that can complete experiments on supercritical carbon dioxide heaters with different heat flux densities and flow directions. However, both of the above two devices can only study the performance of single supercritical carbon dioxide heat exchangers. The document with the publication number CN113155503A discloses a supercritical carbon dioxide heat transfer performance test platform for a printed circuit board type heat exchanger, which can have the ability to carry out heat transfer performance test experiments of water-supercritical carbon dioxide and supercritical carbon dioxide-supercritical carbon dioxide, but cannot simultaneously carry out performance tests of multiple heat exchangers and must conduct experiments multiple times. If the existing experimental devices are used to study the performance of supercritical carbon dioxide heat exchangers, multiple sets of experimental devices must be used or experiments must be conducted multiple times to complete the performance studies of supercritical carbon dioxide heaters, recuperators, and coolers. At this time, the experimental cost is high, the utilization rate of carbon dioxide is low, and the economy and environmental protection are poor. Therefore, it is necessary to provide an experimental device that can simultaneously measure the performance of multiple heat exchangers in the supercritical carbon dioxide cycle. An experimental device and related methods with high integration and high efficiency are of great significance for saving experimental costs, improving research efficiency, promoting the design and optimization of the structure of supercritical carbon dioxide heat exchangers, and realizing the supercritical carbon dioxide Brayton cycle power conversion technology. The present invention provides a supercritical carbon dioxide experimental device that can simultaneously measure the performance of multiple heat exchangers. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention provides a supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers. A plurality of heat exchangers are connected in this set of experimental device, so that heat exchanger experiments under different working condition parameters can be carried out simultaneously, completing the structural design and optimization of heaters, recuperators and coolers in the supercritical carbon dioxide Brayton cycle. At the same time, it has the ability to carry out material corrosion experiments and heat transfer experiments between different working fluids and supercritical carbon dioxide, which can save experimental costs, improve research efficiency, and has high economic efficiency and environmental protection.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers, including a carbon dioxide gas cylinder, a cooler, a liquid storage tank, a booster pump, a buffer tank, and a high-pressure section heater connected in sequence along the medium flow direction. The outlet of the high-pressure section heater is connected to the cold-side inlet of the recuperator, and the cold-side outlet of the recuperator is sequentially connected to the high-pressure section cooler and the low-pressure section heater. The low-pressure section heater is connected to the hot-side inlet of the recuperator, the hot-side outlet of the recuperator is connected to the low-pressure section cooler, and the low-pressure section cooler is connected to the inlet of the first cooler; a pressure reducing valve is provided at the inlet of the high-pressure section heater, back pressure valves are provided at the inlet of the low-pressure section heater and the outlet of the low-pressure section cooler, and a liquid level gauge is provided outside the liquid storage tank; a mass flow meter is provided at the outlet of the liquid storage tank and / or the outlet of the low-pressure section cooler; the recuperator adopts a water-carbon dioxide, molten salt-carbon dioxide, oil-carbon dioxide, carbon dioxide-carbon dioxide or air-carbon dioxide heat exchanger; the mass flow meter adopts a mass flow meter with adjustable flow rate.

[0006] It also includes a swing experimental platform, which includes a slot-type bracket, a heat exchanger fixing support, a servo motor, a swing connecting rod, and a base; two heat exchanger fixing brackets are slidably arranged on the vertical support rod of the slot-type bracket, the servo motor is fixed on the base, the slot-type bracket is fixed on the swing connecting rod through fasteners, and the output shaft of the servo motor is connected to the swing connecting rod.

[0007] Thermocouples are arranged on the high-pressure section heater, the low-pressure section heater, the high-pressure section cooler, the low-pressure section cooler, and the recuperator.

[0008] It is divided into a low-temperature high-pressure section and a high-temperature low-pressure section. The high-pressure section adopts 1 to 12 heaters, the low-pressure section adopts 1 to 8 heaters, and the swing experimental platform adopts 1 to 8 heaters. The multiple heaters are connected in series.

[0009] Valves are provided at both the hot-side inlet and the cold-side inlet of the recuperator, bypass pipelines are provided in front of the valves, valves are provided on the bypass pipelines, and the bypass pipelines are respectively connected to the inlets of the high-pressure section cooler and the low-pressure section cooler.

[0010] The cooling method of the first cooler adopts compression refrigeration, absorption refrigeration or semiconductor refrigeration to cool carbon dioxide into liquid; water is used as the cooling medium for both the high-pressure stage cooler and the low-pressure stage cooler.

[0011] The outer wall of the liquid storage tank is provided with heat insulation material, and the liquid level gauge adopts a liquid level with liquid storage function; a filter is set at the outlet of the liquid storage tank.

[0012] The high-pressure stage heater and the low-pressure stage heater adopt oil bath heating, water bath heating, burner heating, resistance wire heating, concentrating solar heating, trough solar heating, tower solar heating or dish solar heating.

[0013] A pressure relief branch is set at the outlet of the low-pressure stage cooler, and a ball valve is set on the pressure relief branch.

[0014] A high-temperature and high-pressure reactor is connected in series in the high-pressure stage heater or the low-pressure stage heater.

[0015] One-way valves are set on the pipeline from the low-pressure stage cooler to the first cooler and at the inlet of the buffer tank; ball valves are set on the pipeline from the carbon dioxide gas cylinder to the first cooler, at the inlet of the liquid storage tank and at the inlet of the booster pump.

[0016] Temperature and pressure transmitters are set on the pipeline before the inlet of the booster pump, on the outlet pipeline of the buffer tank and on the inlet and outlet pipelines of the regenerator; temperature transmitters are set at the outlets of both the high-pressure stage cooler and the low-pressure stage cooler; a pressure transmitter is set behind the back pressure valve on the outlet pipeline of the low-pressure stage cooler.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] Using the experimental device of a supercritical carbon dioxide cycle loop provided by the present invention, which can measure the performance of multiple heat exchangers simultaneously, by connecting multiple heat exchangers in the loop, namely multiple series-connected heaters, a recuperator and a cooler, and setting a pressure reducing valve and a back pressure valve in the whole loop, it is possible to conduct heat exchanger experiments under different operating conditions simultaneously, analyze the heat transfer and pressure drop characteristics of multiple heat exchangers, thereby enabling the structural design and optimization of heaters, recuperators and coolers in the supercritical carbon dioxide Brayton cycle, improving the utilization rate of carbon dioxide in the loop, saving experimental costs and enhancing experimental efficiency; the mass flowmeter is placed at the front end of the circulation loop, that is, between the liquid storage tank and the booster pump, and at this time, the flow rate of the loop can be controlled and measured by the mass flowmeter; placed at the rear end of the circulation loop, that is, between the low-pressure section cooler and the cooler, at this time, the mass flowmeter only measures the flow rate in the loop, or mass flowmeters are set at both the liquid storage tank and the outlet of the low-pressure section cooler; the experimental device of the present invention has the ability to carry out material corrosion experiments and heat transfer experiments between different working fluids and supercritical carbon dioxide; it is of great significance for promoting the design optimization of the structure of supercritical carbon dioxide heat exchangers and the realization of supercritical carbon dioxide Brayton cycle power conversion technology.

[0019] Furthermore, it includes a swing experimental platform, which can simulate the marine swing environment and can analyze the heat transfer characteristics of the heat exchanger under the marine swing conditions. Brief Description of the Drawings

[0020] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0021] Figure 1 is a schematic diagram of a supercritical carbon dioxide cycle loop experimental platform that can measure the performance of multiple heat exchangers simultaneously;

[0022] Figure 2 is a schematic diagram of the swing structure in the experimental platform;

[0023] Figure 3 is a schematic diagram of a supercritical carbon dioxide cycle loop experimental platform that can measure the performance of multiple heat exchangers simultaneously with a bypass;

[0024] Figure 4 is a schematic diagram of another implementation manner of the swing structure in the experimental platform;

[0025] Figure 5 is a schematic diagram of the partial structure of the swing structure in the experimental platform;

[0026] In the figure: 1. Carbon dioxide gas cylinder; 2. First cooler; 3. Liquid storage tank; 4. Filter; 5. Mass flowmeter; 6. Booster pump; 7. Buffer tank; 8. High-pressure section heater; 9. Regenerator; 10. High-pressure section cooler; 11. Low-pressure section heater; 12. Low-pressure section cooler; 13. Swing test platform; 20. Liquid level gauge; 14. Groove-type support; 15. Heat exchanger fixed support; 17. Servo motor; 19. Swing connecting rod; 21. Servo motor fixing plate; 16. First fastening bolt; 18. Second fastening bolt; 22. Third fastening bolt; 23. Base. Detailed implementation manners

[0027] In order to elaborate in detail the technical content, structural features, achieved objectives and effects of the present invention, the following detailed description is provided in conjunction with the accompanying drawings and specific implementation manners:

[0028] Example 1, as Figure 1As shown in the figure, a supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers includes a supercritical carbon dioxide circulation loop, and multiple heat exchangers are connected to the loop. The supercritical carbon dioxide circulation loop includes a carbon dioxide gas cylinder 1, a first cooler 2, a liquid storage tank 3, a liquid level gauge 20, a filter 4, a mass flowmeter 5, a booster pump 6, a buffer tank 7, and a high-pressure section heater 8 connected in sequence. The high-pressure section heater 8 is connected to the cold-side inlet of the regenerator 9 through pipeline I. The cold-side outlet of the regenerator 9 is connected to the high-pressure section cooler 10 through pipeline II. The high-pressure section cooler 10 is connected to the low-pressure section heater 11 through pipeline III. The low-pressure section heater 11 is connected to the regenerator 9 through pipeline IV. The hot-side outlet of the regenerator 9 is connected to the low-pressure section cooler 12 through pipeline V. The low-pressure section cooler 12 is connected to the inlet of the first cooler 2 and enters the liquid storage tank 3. The liquid storage tank 3 is connected to the inlet of the liquid booster pump 6, thus forming a supercritical carbon dioxide circulation loop. The carbon dioxide gas cylinder 1 provides low-pressure gaseous carbon dioxide for the test loop. The low-pressure gaseous carbon dioxide is first cooled to liquid carbon dioxide in the first cooler 2 and enters the liquid storage tank 3. The liquid storage tank 3 is externally connected with a liquid level gauge 20, which can display the storage amount of liquid carbon dioxide in the tank. And an external device is used to refrigerate the closed external space of the liquid storage tank 3 and the liquid level gauge 20 to ensure low temperature in the tank, so as to buffer and stabilize the loop flow and prevent the loss of gas carbon dioxide to the booster pump. The liquid carbon dioxide enters the mass flowmeter 5 to measure the flow rate after passing through the filter 4, and then is pressurized in the booster pump 6 and enters the buffer tank 7. The buffer tank 7 can effectively slow down the fluctuation of the operating parameters of the supercritical carbon dioxide fluid in the circulation loop caused by the operating state of the booster pump, make the flow of the entire circulation loop more stable, and improve the test accuracy. Then, the pressure of the liquid supercritical carbon dioxide is reduced to the inlet pressure of the cold side of the regenerator 9 through the pressure reducing valve V5, and then heated by the high-pressure section heater 8. The function of the high-pressure section cooler 10 is to make the fluid temperature not exceed the maximum bearing temperature of the back pressure valve V7. After the fluid passes through the back pressure valve V7, the pressure is reduced to the inlet pressure of the hot side of the regenerator 9 and enters the low-pressure section heater 11 for heating. The low-pressure section cooler 12 preliminarily cools the fluid, and then the pressure is reduced through the back pressure valve V8. When the ball valve V9 of the pressure relief branch is in the closed state, the fluid is cooled to liquid by the first cooler 2 and flows into the booster pump 6, thus forming a closed circulation loop. When the ball valve V9 of the pressure relief branch is in the open state, the fluid is discharged through the ball valve V9 to form an open cycle.

[0029] Based on Example 1 with other settings unchanged, the mass flowmeter 5 is arranged at the outlet of the low-pressure section cooler 12.

[0030] It is also possible to simultaneously arrange the mass flowmeter 5 at the outlet of the liquid storage tank 3 and the outlet of the low-pressure section cooler 12, and control the flow mode by controlling whether the mass flowmeter 5 is turned on to control the flow or not control the flow of a certain section.

[0031] Optional embodiment, the regenerator 9 is not connected to the experimental loop, refer to Figure 3 , valves V12 and V14 are respectively arranged at the hot-side inlet and the cold-side inlet of the regenerator. Bypass pipes are arranged in front of valves V12 and V14, and valves V12 and V13 are respectively arranged on the bypass pipes. The bypass pipes are respectively connected to the inlets of the high-pressure section cooler and the low-pressure section cooler; the regenerator can be selectively connected to the experimental loop. As Figure 3 shown, when the ball valve V11 is opened, V12 is closed, V13 is opened, and V14 is closed, the regenerator is not connected to the experimental loop; when the ball valve V11 is closed, V12 is opened, V13 is closed, and V14 is opened, the regenerator is connected to the experimental loop.

[0032] Refer to Figure 2 , Figure 4 and Figure 5 , in an optional embodiment, the present invention further provides a swing experimental platform 13, which includes a slot-type bracket 14, two heat exchanger fixing supports 15, two servo motors 17, a swing connecting rod 19, a base 23, a servo motor fixing plate 21 and fasteners; the heat exchanger fixing support can adopt a clamp-type support, and the structural parts of the equipment are installed in the clamp and fastened by the first fastening bolt 16. Two heat exchanger fixing supports 15 are slidably arranged on the vertical support rod of the slot-type bracket 14, and the heat exchanger can be connected to the slot-type bracket 14 through the two heat exchanger fixing supports 15; the position on the slot-type bracket 14 is changed and fixed through the groove, so as to change the swing radius, and the position can also be changed into a vertical or inclined state. The servo motor 17 is fixed on the base 23 through the servo motor fixing plate 21 and the third fastening bolt 22, and the slot-type bracket 14 is fixed on the swing connecting rod 19 through the second fastening bolt 18; the output shaft of the servo motor 17 is connected to the swing connecting rod 19; the servo motor 17 drives the swing connecting rod 19 and the slot-type bracket 14 to perform periodic swing movements together, and the swing angle and swing period can be controlled by the servo motor; in addition, when the heights of the two heat exchange fixing brackets are different, the swing working condition experiments at different inclination angles can also be studied.

[0033] During the experiments of the supercritical carbon dioxide heater, supercritical carbon dioxide cooler, supercritical carbon dioxide - supercritical carbon dioxide recuperator, and heat transfer experiment under the rocking condition of supercritical carbon dioxide, thermocouples are arranged on the high - pressure section heater 8, low - pressure section heater 11, high - pressure section cooler 10, low - pressure section cooler 12, and recuperator 9, which can monitor and record the temperature changes at various positions of the high - pressure section heater 8, low - pressure section heater 11, high - pressure section cooler 10, low - pressure section cooler 12, and recuperator 9. Temperature transmitters and pressure transmitters are arranged at the inlets and outlets. The flow rate in the loop is recorded by the mass flowmeter 5, and the heat transfer efficiency is calculated numerically, so that multiple heat exchanger experiments can be carried out simultaneously to analyze their heat transfer and pressure drop characteristics.

[0034] For the experimental device of the present invention, different cold - side and hot - side media of the recuperator can be selected to carry out heat transfer characteristic experiments of different media and supercritical carbon dioxide, including water - supercritical carbon dioxide heat transfer experiment, supercritical water - supercritical carbon dioxide heat transfer experiment, molten salt - supercritical carbon dioxide heat transfer experiment, oil - supercritical carbon dioxide heat transfer experiment, supercritical carbon dioxide - supercritical carbon dioxide heat transfer experiment, and air - supercritical carbon dioxide heat transfer experiment. At the same time, the temperature, pressure, and flow rate changes of the working fluids on both sides are recorded, so as to analyze the heat transfer and pressure drop characteristics of the heat exchanger.

[0035] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers, characterized in that, It includes a carbon dioxide gas cylinder (1), a first cooler (2), a liquid storage tank (3), a booster pump (6), a buffer tank (7), and a high-pressure section heater (8) connected in sequence along the medium flow direction. The outlet of the high-pressure section heater (8) is connected to the cold-side inlet of a regenerator (9). The cold-side outlet of the regenerator (9) is sequentially connected to a high-pressure section cooler (10) and a low-pressure section heater (11). The low-pressure section heater (11) is connected to the hot-side inlet of the regenerator (9). The hot-side outlet of the regenerator (9) is connected to a low-pressure section cooler (12). The low-pressure section cooler (12) is connected to the inlet of the first cooler (2); a pressure reducing valve is provided at the inlet of the high-pressure section heater (8), back pressure valves are provided at the inlet of the low-pressure section heater (11) and the outlet of the low-pressure section cooler (12), and a liquid level gauge (20) is provided outside the liquid storage tank (3); a mass flow meter (5) is provided at the outlet of the liquid storage tank (3) and / or the outlet of the low-pressure section cooler (12); the regenerator (9) is a water-carbon dioxide, molten salt-carbon dioxide, oil-carbon dioxide, carbon dioxide-carbon dioxide, or air-carbon dioxide heat exchanger; the mass flow meter (5) is a mass flow meter with adjustable flow; it further includes a swing test platform (13), and the swing test platform (13) includes a slot-type bracket (14), a heat exchanger fixing support (15), a servo motor (17), a swing connecting rod (19), and a base (23); two heat exchanger fixing supports (15) are slidably provided on the vertical support rods of the slot-type bracket (14), the servo motor (17) is fixed on the base (23), the slot-type bracket (14) is fixed on the swing connecting rod (19) through a fastener (18), and the output shaft of the servo motor (17) is connected to the swing connecting rod (19); it is divided into a low-temperature high-pressure section and a high-temperature low-pressure section. The high-pressure section uses 1 to 12 heaters, the low-pressure section uses 1 to 8 heaters, and the swing test platform uses 1 to 8 heaters. The multiple heaters are connected in series.

2. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, characterized in that Thermocouples are arranged on the high-pressure section heater (8), the low-pressure section heater (11), the high-pressure section cooler (10), the low-pressure section cooler (12), and the regenerator (9).

3. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, wherein Valves are provided at both the hot-side inlet and the cold-side inlet of the regenerator (9). Bypass pipes are provided in front of the valves, valves are provided on the bypass pipes, and the bypass pipes are respectively connected to the inlets of the high-pressure section cooler (10) and the low-pressure section cooler (12).

4. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, characterized in that, The cooling method of the first cooler (2) is a compression refrigeration method, an absorption refrigeration method, or a semiconductor refrigeration method, and is used to cool carbon dioxide into a liquid state; both the high-pressure section cooler (10) and the low-pressure section cooler (12) use water as a cooling medium.

5. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, characterized in that, The outer wall of the liquid storage tank (3) is provided with a heat-insulating material. The liquid level gauge (20) is a liquid level with a liquid storage function; a filter (4) is provided at the outlet of the liquid storage tank (3).

6. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, characterized in that, The high-pressure section heater (8) and the low-pressure section heater (11) use an oil bath heating method, a water bath heating method, a burner heating method, a resistance wire heating method, a concentrating solar heating method, a trough solar heating method, a tower solar heating method, or a dish solar heating method.

7. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, wherein A pressure relief branch is provided at the outlet of the low-pressure stage cooler (12), and a ball valve is provided on the pressure relief branch.

8. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, wherein, The high-pressure stage heater (8) or the low-pressure stage heater (11) is connected in series with a high-temperature and high-pressure reactor.

9. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, characterized in that, Check valves are provided on the pipeline from the low-pressure stage cooler (12) to the first cooler (2) and at the inlet of the buffer tank (7); ball valves are provided on the pipeline from the carbon dioxide gas cylinder (1) to the first cooler (2), at the inlet of the liquid storage tank (3), and at the inlet of the booster pump (6).

10. The supercritical carbon dioxide experimental device capable of simultaneously measuring the performance of multiple heat exchangers according to claim 1, wherein, Temperature and pressure transmitters are provided on the pipeline before the inlet of the booster pump (6), on the outlet pipeline of the buffer tank (7), and on the inlet and outlet pipelines of the regenerator (9); temperature transmitters are provided at the outlets of the high-pressure stage cooler (10) and the low-pressure stage cooler; a pressure transmitter is provided behind the back pressure valve on the outlet pipeline of the low-pressure stage cooler.

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