Transcritical carbon dioxide coupling circulation system, device and control method

Abstract

The invention discloses a transcritical carbon dioxide coupling circulation system and device and a control method, and relates to the technical field of refrigeration and heat energy. The system comprises a compressor unit for compressing input low-temperature and low-pressure gaseous CO2 into high-temperature and high-pressure transcritical CO2, and a first cooling device for cooling the high-temperature and high-pressure transcritical CO2; the first CO2 heat exchanger group is used for carrying out coupling heat exchange on the low-temperature low-pressure liquid CO2 and the high-temperature high-pressure liquid CO2; and the second CO2 heat exchanger group is used for carrying out coupling heat exchange on the low-temperature low-pressure liquid CO2 and the low-temperature high-pressure liquid CO2. According to the technical scheme, the refrigerating capacity and the refrigerating coefficient of the transcritical COcirculation system can be remarkably increased, the heat energy utilization rate can be increased in the heating aspect, and energy consumption is reduced. Wide application of the transcritical COC cycle technology in the field of refrigeration and heat supply is promoted, and good environmental protection benefits and social benefits are achieved.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration and thermal energy technology, and specifically relates to a transcritical carbon dioxide coupled cycle system, a transcritical carbon dioxide combined cooling and heating cycle device, and a transcritical carbon dioxide combined cooling and heating cycle control method. Background Technology

[0002] Carbon dioxide, as a natural working fluid, has advantages such as being environmentally friendly (ODP=0, GWP=1), safe and non-toxic, and having a large cooling capacity per unit volume, and its application in transcritical cycles is becoming increasingly widespread. In a transcritical carbon dioxide cycle system, the working fluid releases heat on the supercritical high-pressure side and absorbs heat on the subcritical low-pressure side, simultaneously producing a high-temperature heat source and a low-temperature cold source, achieving combined cooling and heating.

[0003] However, existing transcritical CO2 cycle systems have several problems. On the one hand, their cooling and heating efficiencies need improvement. During cooling, the throttling loss of CO2 is significant, resulting in low cooling capacity and coefficient of performance (COP). During heating, the heat exchange effect of the gas cooler is not ideal, failing to fully utilize the thermal energy of CO2. On the other hand, the system has poor adaptability, making it difficult to flexibly adjust to different operating conditions and load demands. For example, the system cannot operate efficiently and stably under different ambient temperatures in summer and winter. Summary of the Invention

[0004] The purpose of this invention is to provide a transcritical carbon dioxide coupled cycle system, device, and control method. By setting up two CO2 heat exchanger groups, high-temperature and high-pressure liquid CO2 exchanges heat with low-temperature and low-pressure liquid CO2 in the first CO2 heat exchanger group to form low-temperature and high-pressure liquid CO2 and low-temperature and low-pressure gaseous CO2, respectively. The low-temperature and low-pressure gaseous CO2 is then exchanged heat again with the low-temperature and high-pressure liquid CO2 in the second CO2 heat exchanger group to improve the compression efficiency. This solves the problems of low refrigeration and heating efficiency and poor adaptability in existing systems.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] This invention relates to a transcritical carbon dioxide coupled cycle system, comprising a compressor unit, a cooling and pressure reducing unit, a gas-liquid separator, a low-pressure oil separator, a first CO2 heat exchanger unit, and a second CO2 heat exchanger unit. The compressor unit compresses the input low-temperature, low-pressure gaseous CO2 into high-temperature, high-pressure transcritical CO2, and includes a first cooling device for cooling the high-temperature, high-pressure transcritical CO2. The first CO2 heat exchanger unit couples the low-temperature, low-pressure liquid CO2 with the high-temperature, high-pressure liquid CO2, and the second CO2 heat exchanger unit couples the low-temperature, low-pressure liquid CO2 with the low-temperature, high-pressure liquid CO2. The low-temperature, high-pressure liquid CO2 after heat exchange in the second CO2 heat exchanger unit is then cooled and pressure-reduced by the cooling and pressure reducing unit before entering the gas-liquid separator to output low-temperature, low-pressure liquid CO2 as a cold source.

[0007] The first CO2 heat exchanger group includes a high-temperature high-pressure manifold, a low-temperature high-pressure manifold, a low-temperature low-pressure manifold, a high-temperature low-pressure manifold, and several first heat exchanger groups arranged in parallel. The high-temperature high-pressure manifold is connected to the low-temperature high-pressure manifold through the heat exchanger group, and the low-temperature low-pressure manifold is connected to the high-temperature low-pressure manifold through the first heat exchanger group.

[0008] The second CO2 heat exchanger assembly includes a first input pipe, a second input pipe connected to the first input pipe, a first manifold, a second manifold, a third manifold, a fourth manifold, and several parallel second heat exchanger assemblies located at one end of the first input pipe; the second manifold is connected to the first manifold through the second heat exchanger assemblies, and the third manifold is connected to the fourth manifold through the second heat exchanger assemblies.

[0009] The first manifold is equipped with a first electric valve, and the second manifold is equipped with a second electric valve.

[0010] The cooling and pressure reducing unit includes several throttling valve groups connected in parallel, the number of which matches the total flow rate of the compressor unit.

[0011] The gas-liquid separator includes a third inlet pipe, a first outlet pipe, and a second outlet pipe.

[0012] The low-pressure oil separator has its output end connected to the air inlet of the first manifold and its outlet connected to the input end of the compressor unit.

[0013] The output end of the first cooling device is connected to the high-temperature and high-pressure manifold; the low-temperature and high-pressure manifold is connected to the third manifold of the second CO2 heat exchanger group; the fourth manifold is connected to the input end of the cooling and pressure reducing device group, and the output end of the cooling and pressure reducing device group is connected to the third input pipe; the first output pipe is connected to the low-temperature and low-pressure manifold.

[0014] Furthermore, it also includes a heat-using equipment end, a cold-using equipment end, an oil storage tank for supplying oil to the compressor unit, and a first high-pressure oil separator and a second high-pressure oil separator for separating oil from the high-temperature and high-pressure transcritical CO2 output by the compressor unit; the lubricating oil separated from the first high-pressure oil separator, the second high-pressure oil separator, and the low-pressure oil separator flows back into the oil storage tank.

[0015] Furthermore, the first cooling device is a series of closed cooling towers connected in parallel.

[0016] Furthermore, the compressor assembly comprises several compressors connected in parallel.

[0017] Furthermore, the first heat exchanger group consists of at least two heat exchangers connected in series; the second heat exchanger group consists of a single heat exchanger.

[0018] Furthermore, the gas-liquid separator also includes a third output pipeline and a liquid level switch controller. A first solenoid valve is also provided on the third output pipeline, and the first solenoid valve is electrically connected to the liquid level switch controller.

[0019] Furthermore, the cooling and pressure reducing device assembly also includes a fifth manifold and a sixth manifold, and several of the throttling valve assemblies are connected in parallel between the fifth manifold and the sixth manifold. The throttling valve assembly includes a solenoid valve and a pressure reducing device connected in series.

[0020] Furthermore, a sensor group is respectively installed on the pipeline of the first CO2 heat exchanger group and the pipeline of the second CO2 heat exchanger group. The sensor group includes a pressure sensor and a temperature sensor. A field control unit for controlling the first electric valve and the second electric valve is also installed on the first input pipeline.

[0021] A transcritical carbon dioxide combined cooling and heating cycle device, employing the aforementioned transcritical carbon dioxide combined cooling and heating cycle system.

[0022] A transcritical carbon dioxide combined cooling and heating cycle control method includes the following process:

[0023] S01 Start the compressor unit: The compressors start sequentially, with an interval set between 0.1 and 5 minutes;

[0024] S02 When the temperature collected by the temperature sensor on the first input pipeline is ≥25℃, the first electric valve is opened and the second electric valve is closed by the field control unit. The low-temperature and low-pressure gaseous CO2 in the first manifold enters the compressor unit for cyclic compression through the low-pressure oil separator.

[0025] When the temperature collected by the temperature sensor on the first input pipeline is <20℃, the first electric valve is closed and the second electric valve is opened by the field control unit, and heat is further exchanged through the second CO2 heat exchanger group until the temperature collected by the temperature sensor on the first input pipeline is ≥25℃.

[0026] S03 injects low-temperature, low-pressure gaseous CO2 through the second input pipeline. At this time, the temperature is <20℃. The low-temperature, low-pressure gaseous CO2 directly enters the low-pressure oil separator and then enters the compressor unit to be compressed into high-temperature, high-pressure transcritical CO2.

[0027] S04 The high-temperature and high-pressure transcritical CO2 enters the first cooling device after passing through the first high-pressure oil separator and the second high-pressure oil separator. Then it enters the first CO2 heat exchanger group in sequence, and finally enters the cooling and pressure reducing unit group after passing through the second CO2 heat exchanger group to output low-temperature and low-pressure transcritical CO2.

[0028] S05 Low-temperature and low-pressure transcritical CO2 enters the gas-liquid separator. When the liquid CO2 is lower than the highest liquid level of the level switch controller, the first solenoid valve is opened; when the liquid CO2 is higher than the highest liquid level of the level switch controller, the first solenoid valve (906) is closed.

[0029] The low-temperature, low-pressure transcritical CO2 output from the gas-liquid separator S06 enters the first CO2 heat exchanger group and exchanges heat with the high-temperature, high-pressure transcritical CO2. After that, it enters step S02 through the high-temperature, low-pressure manifold.

[0030] S07 completes the transcritical carbon dioxide cycle.

[0031] The present invention has the following beneficial effects:

[0032] 1. This invention employs two CO2 heat exchanger groups to perform a CO2 heat exchange cycle between hot and cold gas and liquid. This allows high-temperature, high-pressure liquid CO2 to exchange heat with low-temperature, low-pressure liquid CO2 in the first CO2 heat exchanger group, forming low-temperature, high-pressure liquid CO2 and low-temperature, low-pressure gaseous CO2 respectively. The low-temperature, low-pressure gaseous CO2 is then passed through the second CO2 heat exchanger group to exchange heat with the low-temperature, high-pressure liquid CO2 again, thereby improving the compression efficiency.

[0033] 2. The technical solution of this invention can significantly improve the cooling capacity and coefficient of performance of a transcritical CO2 cycle system, and in terms of heating, it can improve thermal energy utilization and reduce energy consumption. It helps promote the widespread application of transcritical CO2 cycle technology in the fields of refrigeration and heating, and has good environmental and social benefits.

[0034] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a diagram of a transcritical carbon dioxide coupled cycle system in this embodiment.

[0037] Figure 2 This is a diagram of the oil circuit system in Embodiment 2.

[0038] Figure 3 System diagram of the cooling and pressure reducing unit;

[0039] Figure 4 This is a system diagram of the first CO2 heat exchanger group;

[0040] Figure 5 This is a system diagram of the second CO2 heat exchanger group;

[0041] The attached diagram lists the components represented by each number as follows:

[0042] 1-Compressor unit, 2-First high-pressure oil separator, 3-Second high-pressure oil separator, 4-First cooling device, 5-Oil storage tank, 6-First CO2 heat exchanger group, 601-Low-temperature low-pressure manifold, 602-High-temperature low-pressure manifold, 603-High-temperature high-pressure manifold, 604-Low-temperature high-pressure manifold, 605-First heat exchanger group, 7-Second CO2 heat exchanger group, 701-First input pipeline, 702-First manifold, 703-Second manifold, 704-Third manifold, 705-Fourth manifold, 706-Second heat exchanger group 8-Heater group, 8-Cooling and pressure reducing unit group, 801-Pressure reducing unit, 802-Solenoid valve, 803-Fifth manifold, 804-Sixth manifold, 9-Gas-liquid separator, 901-Third input line, 902-First output line, 903-Second output line, 904-Third output line, 905-Level switch controller, 906-First solenoid valve, 10-Low-pressure oil separator, 11-First electric valve, 12-Second electric valve, 15-Second input line, 16-Pressure sensor, 17-Temperature sensor, 18-Field control unit. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 1 As shown, this embodiment is a transcritical carbon dioxide coupled cycle system, including a compressor unit 1 for compressing input low-temperature, low-pressure gaseous CO2 into high-temperature, high-pressure transcritical CO2, and a first cooling device 4 for cooling the high-temperature, high-pressure transcritical CO2. In this embodiment, the first cooling device 4 adopts four sets of parallel closed cooling towers; a first CO2 heat exchanger group 6 for coupling heat exchange between low-temperature, low-pressure liquid CO2 and high-temperature, high-pressure liquid CO2; a second CO2 heat exchanger group 7 for coupling heat exchange between low-temperature, low-pressure liquid CO2 and low-temperature, high-pressure liquid CO2; and a cooling and depressurizing device group 8 for cooling and depressurizing the low-temperature, high-pressure liquid CO2 after heat exchange in the second CO2 heat exchanger group 7, which then enters a gas-liquid separator 9 to output low-temperature, low-pressure liquid CO2 as a cold source.

[0046] The compressor unit consists of several compressors connected in parallel. The compressors are DORIN professional transcritical carbon dioxide compressors, and the start and stop of the compressors are controlled by DCS (Distributed Control System) commands.

[0047] The compressor unit 1 outputs high-temperature, high-pressure liquid CO2 at a pressure of 8.5–9.5 MPa and a temperature of 120°C, which serves as a heat source. After being cooled by the first cooling device 4, the high-temperature, high-pressure liquid CO2 is preliminarily cooled to a temperature of 8.5–9.5 MPa and 80°C.

[0048] Among them, after being cooled and depressurized by the cooling and depressurizing unit 8, the liquid CO2 that enters the gas-liquid separator 9 outputs low-temperature and low-pressure liquid CO2 with a pressure of 3.5-4MPa and a temperature of 0-5℃, which serves as a cold source.

[0049] Low-temperature, low-pressure liquid CO2 exchanges heat with high-temperature, high-pressure liquid CO2 in the first CO2 heat exchanger group 6 to form low-temperature, low-pressure gaseous CO2 with a pressure of 3.3–3.7 MPa and a temperature of 18–22 °C.

[0050] After passing through the first cooling device 4, the high-temperature and high-pressure liquid CO2 enters the first CO2 heat exchanger group 6 and exchanges heat with the low-temperature and low-pressure liquid CO2 to form low-temperature and high-pressure liquid CO2 with a pressure of 8-9 MPa and a temperature of 30-35℃.

[0051] Since the low-temperature, low-pressure gaseous CO2 needs to be returned to compressor unit 1 for compression again in the cycle process, in order to improve the system utilization efficiency, raising the low-temperature, low-pressure gaseous CO2 to above 25°C can maximize the efficiency of compressor unit 1 and reduce the energy loss of the entire system. Therefore, the low-temperature, low-pressure gaseous CO2 is exchanged with low-temperature, high-pressure liquid CO2 again through the second CO2 heat exchanger group 7 until the low-temperature, low-pressure gaseous CO2 is raised to above 25°C. After passing through the low-pressure oil separator 10, it is returned to compressor unit 1 for compression again in the cycle process.

[0052] like Figure 4The diagram shows a system where high-temperature, high-pressure liquid CO2 passes through a first cooling device 4 and then enters a first CO2 heat exchanger group 6 to exchange heat with low-temperature, low-pressure liquid CO2. The first CO2 heat exchanger group 6 includes a high-temperature, high-pressure manifold 603, a low-temperature, high-pressure manifold 604, a low-temperature, low-pressure manifold 601, a high-temperature, low-pressure manifold 602, and several first heat exchanger groups 605 connected in parallel. The high-temperature, high-pressure manifold 603 is connected to the low-temperature, high-pressure manifold 604 through the heat exchanger group 605, and the low-temperature, low-pressure manifold 601 is connected to the high-temperature, low-pressure manifold 602 through the first heat exchanger group 605. A sensor group is installed on each manifold, including a pressure sensor 16 and a temperature sensor 17, to collect temperature and pressure data before and after heat exchange on each manifold.

[0053] The first heat exchanger group 605 consists of at least two heat exchangers connected in series. In this embodiment, two heat exchangers are arranged in series vertically. This method can maximize the heat exchange efficiency.

[0054] like Figure 5 The diagram shows a system in which low-temperature, low-pressure gaseous CO2 exchanges heat again with low-temperature, high-pressure liquid CO2 through a second CO2 heat exchanger group 7. The second CO2 heat exchanger group 7 includes a first input pipe 701, a second input pipe 15 connected to the first input pipe 701, a first manifold 702, a second manifold 703, a third manifold 704, a fourth manifold 705, and several parallel second heat exchanger groups 706 located at one end of the first input pipe 701. The second manifold 703 is connected to the first manifold 702 through the second heat exchanger group 706, and the third manifold 704 is connected to the fourth manifold 705 through the second heat exchanger group 706. A sensor group is installed on each manifold, including a pressure sensor 16 and a temperature sensor 17, for collecting temperature and pressure data before and after heat exchange on each manifold.

[0055] The first input pipeline 701 is also equipped with a local control unit (LCU) for controlling the first electric valve 11 and the second electric valve 12. The local control unit 18 is used to monitor the pressure sensor 16 and temperature sensor 17 on the first input pipeline 701 in real time, and coordinates with the PLC system of the system to control the opening and closing of the first electric valve 11 and the second electric valve 12.

[0056] Sensor arrays are distributed at various critical locations within the system, such as the compressor inlet and outlet, and pipeline inlet and outlet, to monitor system parameters in real time. The controller is connected to the sensors and actuators (field control unit 18, level switch controller 905, etc.) via wires, receiving data from the sensors and sending control commands to the actuators. The actuators are connected to equipment such as the compressor, electric valves, and solenoid valves to control the operating status of the equipment.

[0057] The first manifold 702 is equipped with a first electric valve 11, and the second manifold 703 is equipped with a second electric valve 12; the second heat exchanger group 706 is a single heat exchanger, and since the temperature difference of heat exchange is relatively small, a single heat exchanger can achieve the heat exchange effect.

[0058] like Figure 3 The diagram shows the system connection between the cooling and pressure reducing unit 8 and the gas-liquid separator 9. The cooling and pressure reducing unit 8 includes a fifth manifold 803, a sixth manifold 804, and several throttling valve groups connected in parallel. The number of throttling valve groups is matched with the total flow rate of the compressor unit 1, and is generally set in a 1:2 ratio. However, the ratio is not limited to 1:2 depending on the flow rate of the compressor unit 1.

[0059] Several throttling valve groups are connected in parallel between the fifth manifold 803 and the sixth manifold 804. The throttling valve group includes a solenoid valve 802 and a pressure reducer 801 connected in series on the pipeline. Valves are also provided at the input and output ends of the pipeline, and are normally open in the working state.

[0060] The pressure reducer 801 uses a capillary device for pressure reduction, with the inlet made of stainless steel. The pressure reduction principle of the capillary is as follows: after high-pressure liquid carbon dioxide enters the capillary, the cross-sectional area of ​​the flow channel narrows, increasing the fluid velocity. This generates intense friction between the fluid and the capillary wall, causing the pressure to drop continuously. Due to the influence of flow friction resistance, the pressure drop changes linearly. The length of the capillary and the number of inner diameter turns result in different liquid supply capacities.

[0061] The gas-liquid separator 9 includes a third inlet pipe 901, a first outlet pipe 902, and a second outlet pipe 903; the second outlet pipe 903 returns the lubricating oil separated by the gas-liquid separator 9 to...

[0062] The output end of the first manifold 702 is connected to the air inlet of the low-pressure oil distributor 10, and the air outlet of the low-pressure oil distributor 10 is connected to the input end of the compressor unit 1.

[0063] The output end of the first cooling device 4 is connected to the high-temperature and high-pressure manifold 603; the low-temperature and high-pressure manifold 604 is connected to the third manifold 704 of the second CO2 heat exchanger group 7; the fourth manifold 705 is connected to the input end of the cooling and pressure reducing device group 8, and the output end of the cooling and pressure reducing device group 8 is connected to the third input pipe 901; the first output pipe 902 is connected to the low-temperature and low-pressure manifold 601.

[0064] Example 2, based on Example 1

[0065] like Figure 2 As shown, it also includes an oil storage tank 5 for supplying lubricating oil to the compressor unit 1, and a first high-pressure oil separator 2 and a second high-pressure oil separator 3 for separating oil from the high-temperature and high-pressure transcritical CO2 output by the compressor unit 1; the lubricating oil separated from the first high-pressure oil separator 2, the second high-pressure oil separator 3 and the low-pressure oil separator 10 flows back to the oil storage tank 5.

[0066] It also includes the heat-using equipment end, such as the flash drying system, which outputs high-temperature and high-pressure liquid CO2 from compressor unit 1 at a pressure of 8.5 to 9.5 MPa and a temperature of 120°C, as a heat source and outputs it to the flash drying system. After heat exchange and cooling, it enters the first cooling device 4.

[0067] It also includes the cooling equipment end, such as the heat exchanger arranged in a high-temperature environment through a multi-functional coupler. After being cooled and depressurized by the cooling and depressurizing unit 8, it enters the gas-liquid separator 9 to output low-temperature and low-pressure liquid CO2 with a pressure of 3.5-4 MPa and a temperature of 0-5℃, which serves as a cold source. It is connected to the distributed multi-functional coupler to cool the surrounding environment. After being heated by heat exchange, the low-temperature and low-pressure liquid CO2 becomes low-temperature and low-pressure gaseous CO2 with a pressure of 2.5-3.3 MPa and a temperature of 18-22℃, which directly enters the second CO2 heat exchanger group 7 for circulation.

[0068] Example 3, based on Example 2

[0069] The gas-liquid separator 9 also includes a third output pipe 904 and a level switch controller 905. A first solenoid valve 906 is also installed on the third output pipe 904, and the first solenoid valve 906 is electrically connected to the level switch controller 905. After cooling and depressurizing by the cooling and pressure reducing unit 8, the gas enters the gas-liquid separator 9 to output low-temperature, low-pressure liquid CO2, which also contains low-temperature, low-pressure gaseous CO2. When the level switch controller 905 cannot detect a signal of low-temperature, low-pressure liquid CO2, indicating an excess of low-temperature, low-pressure gaseous CO2, it controls the first solenoid valve 906 to open, sending the low-temperature, low-pressure gaseous CO2 into the second manifold 703 of the second CO2 heat exchanger unit 7 for circulation.

[0070] A transcritical carbon dioxide combined cooling and heating cycle control method includes the following process:

[0071] S01 Start compressor unit 1: The compressors start sequentially, with the interval set between 0.1 and 5 minutes. This is generally determined based on the compressor's own starting performance, and the interval is usually 20 seconds, 30 seconds, 40 seconds, etc.

[0072] S02 When the temperature collected by the temperature sensor 17 on the first input pipeline 701 is ≥25℃, the first electric valve 11 is opened and the second electric valve 12 is closed by the field control unit 18, and the low-temperature and low-pressure gaseous CO2 in the first manifold 702 enters the compressor unit 1 through the low-pressure oil separator 10 for cyclic compression.

[0073] When the temperature collected by the temperature sensor 17 on the first input pipeline 701 is <20℃, the first electric valve 11 is closed and the second electric valve 12 is opened by the field control unit 18, and the second CO2 heat exchanger group 7 further exchanges heat until the temperature collected by the temperature sensor 17 on the first input pipeline 701 is ≥25℃.

[0074] S03 Low-temperature and low-pressure gaseous CO2 is injected through the second input pipe 15. At this time, the temperature is <20℃. The low-temperature and low-pressure gaseous CO2 directly enters the low-pressure oil separator 10 and then enters the compressor unit 1 to be compressed into high-temperature and high-pressure transcritical CO2.

[0075] S04 The high-temperature and high-pressure transcritical CO2 enters the first cooling device 4 after passing through the first high-pressure oil separator 2 and the second high-pressure oil separator 3. Then it enters the first CO2 heat exchanger group 6 in sequence, and finally enters the cooling and pressure reducing device group 8 through the second CO2 heat exchanger group 7 to output low-temperature and low-pressure transcritical CO2.

[0076] S05 Low-temperature, low-pressure transcritical CO2 enters the gas-liquid separator 9. When the liquid CO2 is lower than the highest liquid level where the level switch controller 905 is located, the first solenoid valve 906 is opened; when the liquid CO2 is higher than the highest liquid level where the level switch controller 905 is located, the first solenoid valve 906 is closed.

[0077] The low-temperature, low-pressure transcritical CO2 output from the gas-liquid separator 9 enters the first CO2 heat exchanger group 6 and exchanges heat with the high-temperature, high-pressure transcritical CO2. After that, it enters step S02 through the high-temperature, low-pressure manifold 602.

[0078] S07 completes the transcritical carbon dioxide cycle.

[0079] Example 4, based on Example 3

[0080] In addition to the pressure reducer 801, which combines multi-stage throttling and heat recovery, an electronic expansion valve can be considered to replace the traditional pressure reducer 801. The electronic expansion valve can precisely adjust the refrigerant flow rate according to the real-time operating conditions of the system, improving the system's adjustment accuracy and response speed. Furthermore, by combining it with variable frequency technology, the opening degree of the electronic expansion valve can be dynamically adjusted according to the compressor's operating frequency, further optimizing system performance.

[0081] In addition to employing microchannel heat exchange technology and novel enhanced heat transfer tubes, heat exchangers can also explore the use of phase change materials (PCMs) to enhance heat transfer. PCMs are filled into specific locations within the heat exchanger, utilizing the latent heat generated during the phase change process to improve heat exchange efficiency. For example, in a heat exchanger, PCMs can be placed within the cooling medium channels. When CO2 gas releases heat, the PCMs absorb the heat and undergo a phase change, thereby improving the cooling effect.

[0082] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A transcritical carbon dioxide coupled cycle system, characterized in that: include The compressor unit (1) is used to compress the input low-temperature and low-pressure gaseous CO2 into high-temperature and high-pressure transcritical CO2, and the first cooling device (4) is used to cool the high-temperature and high-pressure transcritical CO2. The first CO2 heat exchanger group (6) includes a high-temperature high-pressure manifold (603), a low-temperature high-pressure manifold (604), a low-temperature low-pressure manifold (601), a high-temperature low-pressure manifold (602), and several first heat exchanger groups (605) arranged in parallel. The high-temperature high-pressure manifold (603) is connected to the low-temperature high-pressure manifold (604) through the heat exchanger group (605), and the low-temperature low-pressure manifold (601) is connected to the high-temperature low-pressure manifold (602) through the first heat exchanger group (605). The second CO2 heat exchanger group (7) includes a first input pipe (701), a second input pipe (15) connected to the first input pipe (701), a first manifold (702), a second manifold (703), a third manifold (704), a fourth manifold (705) and several parallel second heat exchanger groups (706) located at one end of the first input pipe (701); the second manifold (703) is connected to the first manifold (702) through the second heat exchanger group (706), and the third manifold (704) is connected to the fourth manifold (705) through the second heat exchanger group (706); The first manifold (702) is provided with a first electric valve (11), and the second manifold (703) is provided with a second electric valve (12). The cooling and pressure reducing unit (8) includes several throttling valve groups connected in parallel, the number of which matches the total flow rate of the compressor unit (1); The gas-liquid separator (9) includes a third input pipeline (901), a first output pipeline (902), and a second output pipeline (903); The low-pressure oil separator (10) has its output end connected to the air inlet of the first manifold (702) and its outlet connected to the input end of the compressor unit (1). The output end of the first cooling device (4) is connected to the high-temperature high-pressure manifold (603); the low-temperature high-pressure manifold (604) is connected to the third manifold (704) of the second CO2 heat exchanger group (7); the fourth manifold (705) is connected to the input end of the cooling and pressure reducing device group (8), and the output end of the cooling and pressure reducing device group (8) is connected to the third input pipe (901); the first output pipe (902) is connected to the low-temperature low-pressure manifold (601).

2. The transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, It also includes a heat-using equipment end, a cold-using equipment end, an oil storage tank (5) for supplying oil to the compressor unit (1), and a first high-pressure oil separator (2) and a second high-pressure oil separator (3) for separating oil from the high-temperature and high-pressure transcritical CO2 output by the compressor unit (1); the lubricating oil separated from the first high-pressure oil separator (2), the second high-pressure oil separator (3) and the low-pressure oil separator (10) flows back into the oil storage tank (5).

3. A transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, The first cooling device (4) is a series of closed cooling towers connected in parallel.

4. A transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, The compressor unit (1) includes several compressors connected in parallel.

5. A transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, The first heat exchanger group (605) consists of at least two heat exchangers connected in series; the second heat exchanger group (706) is a single heat exchanger.

6. A transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, The gas-liquid separator (9) also includes a third output pipeline (904) and a level switch controller (905). A first solenoid valve (906) is also provided on the third output pipeline (904), and the first solenoid valve (906) is electrically connected to the level switch controller (905).

7. A transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, The cooling and pressure reducing unit (8) also includes a fifth manifold (803) and a sixth manifold (804), and several of the throttling valve groups are connected in parallel between the fifth manifold (803) and the sixth manifold (804). The throttling valve group includes a solenoid valve (802) and a pressure reducing unit (801) connected in series.

8. A transcritical carbon dioxide coupled cycle system as described in claim 1, characterized in that, A sensor group is provided on the pipeline of the first CO2 heat exchanger group (6) and the pipeline of the second CO2 heat exchanger group (7). The sensor group includes a pressure sensor (16) and a temperature sensor (17). A field control unit (18) for controlling the first electric valve (11) and the second electric valve (12) is also provided on the first input pipeline (701).

9. An apparatus, characterized in that, The transcritical carbon dioxide combined cooling and heating cycle system as described in any one of claims 1-7 is adopted.

10. A transcritical carbon dioxide combined cooling and heating cycle control method, characterized in that, The process includes the following: S01 Start the compressor unit (1): The compressors are started sequentially, with an interval set between 0.1 and 5 minutes; S02 When the temperature collected by the temperature sensor (17) on the first input pipeline (701) is ≥25℃, the first electric valve (11) is opened and the second electric valve (12) is closed by the field control unit (18), and the low temperature and low pressure gaseous CO2 in the first manifold (702) enters the compressor unit (1) through the low pressure oil separator (10) for cyclic compression; When the temperature collected by the temperature sensor (17) on the first input pipeline (701) is <20℃, the first electric valve (11) is closed and the second electric valve (12) is opened by the field control unit (18), and the second CO2 heat exchanger group (7) further exchanges heat until the temperature collected by the temperature sensor (17) on the first input pipeline (701) is ≥25℃; S03 injects low-temperature, low-pressure gaseous CO2 through the second input pipe (15). At this time, the temperature is <20℃. The low-temperature, low-pressure gaseous CO2 directly enters the low-pressure oil separator (10) and then enters the compressor unit (1) to be compressed into high-temperature, high-pressure transcritical CO2. S04 The high-temperature and high-pressure transcritical CO2 enters the first cooling device (4) after passing through the first high-pressure oil separator (2) and the second high-pressure oil separator (3), and then enters the first CO2 heat exchanger group (6) in sequence. Finally, it enters the cooling and pressure reducing device group (8) after passing through the second CO2 heat exchanger group (7) to output low-temperature and low-pressure transcritical CO2. S05 Low-temperature and low-pressure transcritical CO2 enters the gas-liquid separator (9). When the liquid CO2 is lower than the highest liquid level of the liquid level switch controller (905), the first solenoid valve (906) is opened; when the liquid CO2 is higher than the highest liquid level of the liquid level switch controller (905), the first solenoid valve (906) is closed. The low-temperature, low-pressure transcritical CO2 output from the gas-liquid separator (9) enters the first CO2 heat exchanger group (6) and exchanges heat with the high-temperature, high-pressure transcritical CO2. After that, it enters step S02 through the high-temperature, low-pressure manifold (602). S07 completes the transcritical carbon dioxide cycle.

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