Dual-injector enhanced transcritical co2 refrigeration system with t-junction and working method

Abstract

The application discloses a kind of dual-injector synergistic transcritical CO2 refrigeration system and working method combined with T-shaped pipe, the system includes low-pressure stage compressor, high-pressure stage compressor, gas cooler, first ejector, first expansion valve, first T-shaped pipe, high-temperature stage evaporator, second ejector, second T-shaped pipe, second expansion valve, regenerator, low-temperature stage evaporator;Although T-shaped pipe gas-liquid separation effect is not high, the first T-shaped pipe is enriched with gas phase refrigerant in the present application, which reduces the suction superheat of high-pressure stage compressor;The first T-shaped pipe is enriched with liquid phase refrigerant, which is fully condensed and supercooled in the regenerator, reducing the dryness of the refrigerant at the inlet of the high-temperature stage evaporator, increasing the refrigerating capacity of the high-temperature stage evaporator and improving the refrigeration performance of the system;The second T-shaped pipe is enriched with gas phase refrigerant, which prevents the low-pressure stage compressor from sucking liquid after passing through the regenerator, ensuring the stable operation of the low-pressure stage compressor and further improving the performance of the system.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration and cryogenic technology, specifically relating to a transcritical CO2 refrigeration system with dual ejectors combined with a T-tube and its working method. Background Technology

[0002] Statistics show that 20% of global electricity consumption is used for refrigeration, and this demand is projected to increase nearly tenfold by 2050, with supermarkets consuming up to 60% of that energy. Currently, the main refrigerants used in supermarket refrigeration systems in my country are R22, R134a, R404A, and ammonia. With global restrictions on refrigerants with high GWP and high ODP, the use of the natural refrigerant CO2 is becoming increasingly important.

[0003] Transcritical CO2 two-stage compression refrigeration systems offer significant advantages in supermarket refrigeration. However, in existing transcritical CO2 two-stage compression refrigeration systems, the large pressure difference between the inlet and outlet of the expansion valve leads to substantial throttling losses. Therefore, reducing throttling losses is one of the effective solutions to improve the operating efficiency of transcritical CO2 refrigeration systems. The large pressure difference between high and low pressures and the high upper limit of recoverable expansion work in transcritical CO2 refrigeration systems make them ideally suited for the function of ejectors.

[0004] Ejectors, as a commonly used expansion work recovery device, are widely used in the refrigeration field due to their high reliability (no moving parts) and low cost. Existing research shows that applying ejectors to CO2 systems can not only recover some expansion work but also improve system efficiency. Currently, most applications of ejectors in CO2 systems focus on single-stage transcritical CO2 refrigeration systems, and often involve the use of a single ejector. However, existing technologies still have significant room for improvement in system configuration and performance enhancement. Summary of the Invention

[0005] To address the deficiencies and shortcomings of the existing technology, the present invention aims to provide a transcritical CO2 refrigeration system and its operating method that combines a T-tube with dual ejectors. The system comprises two ejectors, two T-tubes, and a regenerator in a two-stage CO2 compression refrigeration system. The ejectors recover part of the expansion work and increase the compressor's suction pressure, thus reducing the compressor's power consumption. Compared to existing gas-liquid separators, although the gas-liquid separation effect of the T-tube is not high, its structure is simple and low-cost. Furthermore, applying the T-tube to this practical system can turn its disadvantages into advantages. The fluid rich in the gas phase outlet of the first T-tube reduces the suction superheat of the high-pressure stage compressor, thereby reducing the power consumption of the high-pressure stage compressor. The CO2 refrigerant rich in the liquid phase in the first T-tube condenses into a subcooled liquid refrigerant after passing through the regenerator, effectively reducing the dryness of the refrigerant at the inlet of the high-temperature stage evaporator, increasing the cooling capacity of the high-temperature stage evaporator, and thus improving the system's coefficient of performance (COP). In addition, the CO2 refrigerant rich in the gas phase in the second T-tube passes through the regenerator, preventing liquid from being drawn into the low-pressure stage compressor, ensuring the stable operation of the low-pressure stage compressor, and further improving the system performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A transcritical CO2 refrigeration system with dual ejectors and T-tube configuration includes a high-pressure compressor 102. The outlet of the high-pressure compressor 102 is connected to the inlet of a gas cooler 103. The outlet of the gas cooler 103 is connected to the primary flow inlet of a first ejector 104. The outlet of the first ejector 104 is connected to the inlet of a first T-tube 105. The outlet of the first T-tube 105, rich in liquid CO2 refrigerant, is split into two paths after passing through a regenerator 112. These paths are connected to the inlet of a first expansion valve 106 and the primary flow inlet of a second ejector 108, respectively. The outlet of the first expansion valve 106 is connected to the inlet of a high-temperature evaporator 107, and the outlet of the high-temperature evaporator 107 is connected to the inlet of the first ejector 108. 4. The secondary flow inlet is connected; the outlet of the second ejector 108 is connected to the inlet of the second T-tube 109, the outlet of the second T-tube 109 rich in liquid CO2 refrigerant is connected to the inlet of the second expansion valve 110, the outlet of the second expansion valve 110 is connected to the inlet of the low-temperature evaporator 111, and the outlet of the low-temperature evaporator 111 is connected to the secondary flow inlet of the second ejector 108; the outlet of the second T-tube 109 rich in gaseous CO2 refrigerant is connected to the inlet of the low-pressure compressor 101 after passing through the regenerator 112, and the outlet of the low-pressure compressor 101 is connected to the outlet of the first T-tube 105 rich in gaseous CO2 refrigerant, and then connected to the inlet of the high-pressure compressor 102 to form the entire circulation system.

[0008] The first T-tube 105 and the second T-tube 109 serve to separate the refrigerant gas and liquid phases. The outlets of the first T-tube 105 and the second T-tube 109 each include a two-phase refrigerant outlet rich in gas and a two-phase CO2 refrigerant outlet rich in liquid. The fluid from the CO2-rich outlet of the first T-tube 105 can effectively reduce the exhaust temperature of the low-pressure stage compressor 101, thereby reducing the superheat of the refrigerant entering the suction port of the high-pressure stage compressor 102. This helps reduce the power consumption of the high-pressure stage compressor 102 and improves system performance. Furthermore, the fluid from the CO2-rich outlet of the first T-tube 105 reacts with the CO2-rich fluid from the second T-tube 109 in the regenerator 112. The fluid at the refrigerant outlet undergoes heat exchange, causing the fluid from the first T-tube 105, rich in liquid CO2 refrigerant, to become subcooled liquid CO2 refrigerant after passing through the regenerator 112, while the fluid from the second T-tube 109, rich in gaseous refrigerant, becomes superheated gaseous refrigerant. The regenerator 112 serves two purposes: firstly, it prevents liquid from being carried into the low-pressure stage compressor 101, ensuring its stable operation; secondly, it causes the refrigerant entering the first expansion valve 106 to further condense into a subcooled liquid state. Therefore, the dryness of the refrigerant decreases before entering the high-temperature stage evaporator 107, increasing the heat absorption per unit mass of refrigerant in the high-temperature stage evaporator 107 and further improving the system performance.

[0009] The transcritical high-pressure refrigerant fluid from the gas cooler 103 all enters the primary fluid inlet of the first ejector 104, entraining the superheated gaseous refrigerant from the outlet of the high-temperature evaporator 107. The work-capacity of the first ejector 104 recovers some of the expansion work. The fluid from the outlet of the first T-tube 105, rich in liquid CO2 refrigerant, enters the regenerator 112 and becomes subcooled liquid CO2 refrigerant. Part of the subcooled liquid CO2 refrigerant enters the primary fluid inlet of the second ejector 108, entraining the superheated gaseous CO2 refrigerant from the outlet of the low-temperature evaporator 111. The work-capacity of the second ejector 108 recovers some of the expansion work. Simultaneously, the pressure-boosting effect of the second ejector 108 increases the suction pressure of the low-pressure compressor 101, reducing the power consumption of the low-pressure compressor 101.

[0010] The operating method of the T-tube combined dual-ejector enhanced transcritical CO2 refrigeration system is as follows: High-temperature transcritical high-pressure superheated gaseous CO2 refrigerant, compressed by the high-pressure stage compressor 102, enters the gas cooler 103. After being cooled in the gas cooler 103, the transcritical high-pressure room-temperature gaseous CO2 refrigerant serves as the working fluid of the first ejector 104. Within the nozzle of the first ejector 104, it expands into a low-pressure, high-speed fluid, which then entrains the superheated gaseous CO2 refrigerant from the outlet of the high-temperature stage evaporator 107. The two fluids are fully mixed in the mixing section of the first ejector 104, and then decelerated and pressurized in the diffuser section of the first ejector 104 to become a gas-liquid two-phase mixed refrigerant before being discharged from the first ejector 104. The pressurized gas-liquid two-phase mixed refrigerant enters the first T-tube 105, where the fluid from the outlet of the first T-tube 105, rich in liquid refrigerant, enters the regenerator 112 and condenses into subcooled liquid CO2 refrigerant. A portion of the subcooled liquid CO2 refrigerant is cooled by isenthalpic throttling through the first expansion valve 106 and then enters the high-temperature evaporator 107 for a heat-absorbing evaporation refrigeration process; the other portion... The subcooled liquid CO2 refrigerant enters the nozzle of the second ejector 108 as the working fluid. After expanding in the nozzle, it becomes a low-pressure, high-speed fluid, which then entrains the superheated gaseous refrigerant from the outlet of the low-temperature evaporator 111. The two fluids are fully mixed in the mixing section of the second ejector 108, and then decelerated and pressurized in the diffuser section to become a gas-liquid two-phase mixed refrigerant before exiting the second ejector 108. The pressurized gas-liquid two-phase mixed refrigerant enters the second T-tube 109, which is rich in... The liquid CO2 refrigerant outlet fluid passes through the second expansion valve 110 for isenthalpic throttling and cooling, then enters the low-temperature evaporator 111 for heat absorption and evaporation refrigeration. The fluid from the outlet of the second T-tube 109, rich in gaseous CO2 refrigerant, passes through the regenerator 112 for heat exchange and becomes superheated gaseous CO2 refrigerant. It then enters the low-pressure compressor 101 for compression and is discharged from the low-pressure compressor 101. It mixes with the fluid from the outlet of the first T-tube 105, rich in gaseous CO2 refrigerant, and then enters the suction port of the high-pressure compressor 102, completing the refrigeration cycle of the entire system.

[0011] The system of this invention operates at five different pressures: the working pressure of the gas cooler 103, the outlet pressure of the first ejector 104, the working pressure of the high-temperature evaporator 107, the outlet pressure of the second ejector 108, and the working pressure of the low-temperature evaporator 111. The working pressures of the low-temperature evaporator 111, the high-temperature evaporator 107, and the gas cooler 103 are determined by the operating conditions set by the refrigeration system. The outlet pressure of the first ejector 104 is related to the opening degree of the first expansion valve 106 and the pressure boost ratio and ejection ratio of the first ejector 104. The outlet pressure of the second ejector 108 is related to the opening degree of the second expansion valve 110 and the pressure boost ratio and ejection ratio of the second ejector 108. By adjusting the opening degrees of the first expansion valve 106 and the second expansion valve 110, the refrigerant flow rate into the high-temperature evaporator 107 and the low-temperature evaporator 111 can be controlled, and the ejection ratio and pressure boost ratio of the first ejector 104 and the second ejector 108 can also be adjusted.

[0012] Compared to existing transcritical two-stage CO2 compression refrigeration systems, this invention proposes a dual-ejector enhanced transcritical CO2 refrigeration system and its operating method incorporating T-tubes. The CO2 two-stage compression refrigeration system is equipped with two ejectors, two T-tubes, and a regenerator. The ejectors recover part of the expansion work and increase the compressor's suction pressure, reducing the compressor's power consumption. Compared to existing gas-liquid separators, although the gas-liquid separation effect of the T-tube is not high, its structure is simple and low-cost, and applying the T-tube to this practical system can turn its disadvantages into advantages. The fluid rich in the gas phase outlet in the first T-tube reduces the suction superheat of the high-pressure stage compressor, thereby reducing the power consumption of the high-pressure stage compressor. The CO2 refrigerant rich in the liquid phase in the first T-tube condenses into subcooled liquid CO2 refrigerant after passing through the regenerator, effectively reducing the dryness of the refrigerant at the inlet of the high-temperature stage evaporator, increasing the cooling capacity of the high-temperature stage evaporator, and thus improving the system's coefficient of performance (COP). Furthermore, the CO2 refrigerant, rich in gaseous phase, passes through the regenerator in the second T-tube, preventing liquid carryover in the low-pressure compressor and ensuring its stable operation, thus further improving system performance. This technology plays a positive role in enhancing the performance and energy efficiency of CO2 refrigeration systems, bringing better economic and environmental benefits. In summary, this invention is an economical, effective, and feasible innovative solution that can effectively improve the performance of transcritical CO2 refrigeration systems and promote the development of transcritical CO2 refrigeration technology. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the refrigeration system of the present invention.

[0014] Figure 2 This is a cyclic pressure-enthalpy diagram (Ph diagram) of the working process of the refrigeration system of the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] By rationally arranging the system configuration, and simultaneously configuring ejectors, T-tubes, and regenerators in a CO2 two-stage compression refrigeration system, the ability of ejectors to recover expansion work can be effectively utilized.

[0017] like Figure 1 As shown, this invention relates to a transcritical CO2 refrigeration system with dual ejectors and a T-tube configuration, comprising a high-pressure stage compressor 102. The outlet of the high-pressure stage compressor 102 is connected to the inlet of a gas cooler 103. The outlet of the gas cooler 103 is connected to the primary flow inlet of a first ejector 104. The outlet of the first ejector 104 is connected to the inlet of a first T-tube 105. The outlet of the first T-tube 105, rich in liquid CO2 refrigerant, is split into two paths after passing through a regenerator 112. These paths are connected to the inlet of a first expansion valve 106 and the primary flow inlet of a second ejector 108, respectively. The outlet of the first expansion valve 106 is connected to the inlet of a high-temperature stage evaporator 107, and the outlet of the high-temperature stage evaporator 107 is connected to the inlet of the first ejector 108. The secondary flow inlet of the second ejector 104 is connected; the outlet of the second ejector 108 is connected to the inlet of the second T-tube 109, the outlet of the second T-tube 109 rich in liquid CO2 refrigerant is connected to the inlet of the second expansion valve 110, the outlet of the second expansion valve 110 is connected to the inlet of the low-temperature stage evaporator 111, and the outlet of the low-temperature stage evaporator 111 is connected to the secondary flow inlet of the second ejector 108; the outlet of the second T-tube 109 rich in gaseous CO2 refrigerant is connected to the inlet of the low-pressure stage compressor 101 after passing through the regenerator 112, and the outlet of the low-pressure stage compressor 101 is connected to the outlet of the first T-tube 105 rich in gaseous CO2 refrigerant, and then connected to the inlet of the high-pressure stage compressor 102, forming the entire circulation system.

[0018] like Figure 2 The diagram shown is a pressure-enthalpy diagram (also known as a Ph diagram) of the transcritical CO2 refrigeration system with dual ejectors and T-tube enhancement according to the present invention. Figure 2The working process of the refrigeration system shown is as follows: The high-temperature transcritical high-pressure superheated gaseous CO2 refrigerant (point 4 in the figure), after being compressed by the high-pressure stage compressor 102, enters the gas cooler 103. The transcritical high-pressure room-temperature gaseous CO2 refrigerant, cooled in the gas cooler 103, acts as the working fluid of the first ejector 104 (point 5 in the figure) and enters the nozzle of the first ejector 104 (point 5' in the figure). After expanding in the nozzle of the first ejector 104, it becomes a low-pressure high-speed fluid, which then entrains the superheated gaseous CO2 refrigerant from the outlet of the high-temperature stage evaporator 107 (point 11 in the figure). The two fluids are fully mixed in the mixing section of the first ejector 104 (point 6 in the figure). After passing through the diffuser section of the first ejector 104 (point 6 in the figure), the refrigerant is decelerated and pressurized to become a gas-liquid two-phase mixed refrigerant before exiting the first ejector 104. The pressurized gas-liquid two-phase mixed refrigerant (point 6 in the figure) enters the first T-tube 105, where the fluid from the outlet of the first T-tube 105, rich in liquid CO2 refrigerant (point 8 in the figure), enters the regenerator 112 and condenses into subcooled liquid CO2 refrigerant (point 9 in the figure). Part of the subcooled liquid CO2 refrigerant is cooled by isenthalpic throttling through the first expansion valve 106 (point 10 in the figure) and then enters the high-temperature evaporator 107 for endothermic evaporation (point 11 in the figure) for a refrigeration process. The other part of the subcooled liquid CO2 refrigerant is used as the second... The working fluid of ejector 108 enters the nozzle of the second ejector 108, expands in the nozzle and becomes a low-pressure, high-speed fluid (point 9' in the figure), which then entrains the superheated gaseous CO2 refrigerant from the outlet of the low-temperature evaporator 111 (point 15 in the figure). The two fluids are fully mixed in the mixing section of the second ejector 108 (point 12' in the figure), and then decelerate and pressurize in the diffuser section of the second ejector 108 to become a gas-liquid two-phase mixed refrigerant before being discharged from the second ejector 108. The pressurized gas-liquid two-phase mixed refrigerant (point 12 in the figure) enters the second T-tube 109, and the fluid at the outlet of the second T-tube 109, which is rich in liquid CO2 refrigerant (point 12 in the figure), is then discharged. The refrigerant (at point 13) is enthalpy-dependent cooling via the second expansion valve 110 (at point 14 in the figure) then enters the low-temperature evaporator 111 for heat absorption and evaporation (at point 15 in the figure), completing the refrigeration process. The fluid from the outlet of the second T-tube 109, rich in gaseous CO2 refrigerant (at point 16 in the figure), becomes superheated gaseous CO2 refrigerant after heat exchange in the regenerator 112 (at point 1 in the figure). It then enters the low-pressure compressor 101 for compression and is discharged from the low-pressure compressor 101. It mixes with the fluid from the outlet of the first T-tube 105, rich in gaseous CO2 refrigerant (at point 7 in the figure), and then enters the suction port of the high-pressure compressor 102 (at point 3 in the figure), completing the refrigeration cycle of the entire system.

[0019] like Figure 2 As shown, the system of the present invention operates at five different pressures, namely the working pressure P of the gas cooler 103. gcThe outlet pressure P of the first injector 104 io High-temperature evaporator 107 working pressure P h-e The outlet pressure P of the second injector 108 suc and the low-temperature stage evaporator 111 working pressure P l-e The operating pressures of the low-temperature evaporator 111, the high-temperature evaporator 107, and the gas cooler 103 are determined by the operating conditions set by the refrigeration system. The outlet pressure of the first ejector 104 is related to the opening degree of the first expansion valve 106 and the pressure boost ratio and ejection ratio of the first ejector 104. The outlet pressure of the second ejector 108 is related to the opening degree of the second expansion valve 110 and the pressure boost ratio and ejection ratio of the second ejector 108. The refrigerant flow rate entering the high-temperature evaporator 107 and the low-temperature evaporator 111 can be controlled by adjusting the opening degree of the first expansion valve 106 and the second expansion valve 110, and the ejection ratio and pressure boost ratio of the first ejector 104 and the second ejector 108 can also be adjusted.

[0020] Compared to existing transcritical two-stage CO2 compression refrigeration systems, this invention proposes a dual-ejector enhanced transcritical CO2 refrigeration system and its operating method incorporating T-tubes. The system utilizes two ejectors, two T-tubes, and a regenerator within the two-stage CO2 compression refrigeration system. The ejectors recover some expansion work and increase the compressor's suction pressure, reducing compressor power consumption. While the T-tube's gas-liquid separation efficiency is not as high as existing gas-liquid separators, its simple structure and low cost allow its disadvantages to be transformed into advantages in this practical system. The fluid rich in the gas phase outlet of the first T-tube reduces the suction superheat of the high-pressure stage compressor, thereby lowering its power consumption. The liquid-rich CO2 refrigerant in the first T-tube condenses into subcooled liquid CO2 refrigerant after passing through the regenerator, effectively reducing the refrigerant dryness at the high-temperature stage evaporator inlet, increasing the refrigeration capacity of the high-temperature stage evaporator, and thus improving the system's coefficient of performance (COP). In addition, the CO2 refrigerant rich in the gas phase in the second T-tube passes through the regenerator, preventing liquid from being drawn into the low-pressure stage compressor, ensuring the stable operation of the low-pressure stage compressor, and further improving the system performance.

Claims

1. A transcritical CO2 refrigeration system with dual ejectors combined with a T-tube, characterized in that: The transcritical CO2 refrigeration system with dual ejectors and T-tube configuration includes a high-pressure stage compressor (102). The outlet of the high-pressure stage compressor (102) is connected to the inlet of a gas cooler (103). The outlet of the gas cooler (103) is connected to the primary flow inlet of the first ejector (104). The outlet of the first ejector (104) is connected to the inlet of the first T-tube (105). The outlet of the first T-tube (105), rich in liquid CO2 refrigerant, is divided into two paths after passing through a regenerator (112). These paths are connected to the inlet of the first expansion valve (106) and the primary flow inlet of the second ejector (108), respectively. The outlet of the first expansion valve (106) is connected to the inlet of the high-temperature stage evaporator (107), and the outlet of the high-temperature stage evaporator (107) is connected to the first ejector (104). The secondary flow inlet is connected; the outlet of the second ejector (108) is connected to the inlet of the second T-tube (109), the outlet of the second T-tube (109) rich in liquid CO2 refrigerant is connected to the inlet of the second expansion valve (110), the outlet of the second expansion valve (110) is connected to the inlet of the low-temperature evaporator (111), and the outlet of the low-temperature evaporator (111) is connected to the secondary flow inlet of the second ejector (108); the outlet of the second T-tube (109) rich in gaseous CO2 refrigerant passes through the regenerator (112) and is connected to the inlet of the low-pressure compressor (101); the outlet of the low-pressure compressor (101) is connected to the outlet of the first T-tube (105) rich in gaseous CO2 refrigerant, and then connected to the inlet of the high-pressure compressor (102) to form the entire circulation system; The first T-tube (105) and the second T-tube (109) serve to separate the refrigerant gas and liquid phases. The outlets of the first T-tube (105) and the second T-tube (109) each include a two-phase CO2 refrigerant outlet rich in gas and a two-phase CO2 refrigerant outlet rich in liquid. The fluid from the gas-phase refrigerant outlet of the first T-tube (105) can effectively reduce the exhaust temperature of the low-pressure stage compressor (101), thereby reducing the superheat of the refrigerant entering the suction port of the high-pressure stage compressor (102), which helps reduce the power consumption of the high-pressure stage compressor (102) and improves system performance. Furthermore, the fluid from the liquid-phase CO2 refrigerant outlet of the first T-tube (105) reacts with the gas-phase CO2 refrigerant from the second T-tube (109) in the regenerator (112). The fluid at the refrigerant outlet undergoes heat exchange, causing the fluid from the first T-tube (105) rich in liquid CO2 refrigerant to become subcooled liquid CO2 refrigerant after passing through the regenerator (112), while the fluid from the second T-tube (109) rich in gaseous CO2 refrigerant becomes superheated gaseous CO2 refrigerant. The regenerator (112) serves two purposes: firstly, it prevents liquid from being drawn into the low-pressure stage compressor (101), ensuring the stable operation of the low-pressure stage compressor (101); secondly, it causes the CO2 refrigerant entering the first expansion valve (106) to further condense into subcooled liquid, thus reducing the dryness of the refrigerant before entering the high-temperature stage evaporator (107), increasing the heat absorption per unit mass of refrigerant in the high-temperature stage evaporator (107), and further improving the system performance. The fluid from the outlet of the first T-tube (105) rich in liquid CO2 refrigerant enters the regenerator (112) and becomes subcooled liquid refrigerant. Part of the subcooled liquid CO2 refrigerant enters the primary fluid inlet of the second ejector (108) and ejects the superheated gaseous CO2 refrigerant from the outlet of the low-temperature evaporator (111). By utilizing the work capacity of the second ejector (108), part of the expansion work is recovered. At the same time, by utilizing the pressure boosting effect of the second ejector (108), the suction pressure of the low-pressure stage compressor (101) is increased, and the power consumption of the low-pressure stage compressor (101) is reduced.

2. The transcritical CO2 refrigeration system with dual ejectors combined with a T-tube as described in claim 1, characterized in that: All the transcritical high-pressure refrigerant fluid of the gas cooler (103) enters the primary fluid inlet of the first ejector (104), which ejects the superheated gaseous carbon dioxide refrigerant from the outlet of the high-temperature evaporator (107) and recovers part of the expansion work by utilizing the work capacity of the first ejector (104).

3. The operating method of the transcritical CO2 refrigeration system with dual ejectors combined with a T-tube as described in claim 1 or 2, characterized in that: The high-temperature transcritical high-pressure superheated gaseous CO2 refrigerant, compressed by the high-pressure stage compressor (102), enters the gas cooler (103). After being cooled in the gas cooler (103), the transcritical high-pressure room-temperature gaseous CO2 refrigerant becomes the working fluid of the first ejector (104). It expands in the nozzle of the first ejector (104) and becomes a low-pressure, high-speed fluid, which then ejects the superheated gaseous CO2 refrigerant from the outlet of the high-temperature stage evaporator (107). The two fluids are fully mixed in the mixing section of the first ejector (104) before passing through the second stage evaporator (107). The diffuser section of the first ejector (104) decelerates and pressurizes to become a gas-liquid two-phase mixed refrigerant, which is then discharged from the first ejector (104). The pressurized gas-liquid two-phase mixed CO2 refrigerant enters the first T-tube (105), where the fluid from the liquid refrigerant outlet of the first T-tube (105) enters the regenerator (112) and condenses into subcooled liquid CO2 refrigerant. A portion of the subcooled liquid CO2 refrigerant is cooled by isenthalpic throttling through the first expansion valve (106) and enters the high-temperature evaporator (107) for heat absorption and evaporation refrigeration. The other portion of the subcooled liquid CO2 refrigerant is used as the second ejector ( The working fluid of the second ejector (108) enters the nozzle of the second ejector (108), expands in the nozzle of the second ejector (108) and becomes a low-pressure, high-speed fluid, which then entrains the superheated gaseous CO2 refrigerant from the outlet of the low-temperature evaporator (111). The two fluids are fully mixed in the mixing section of the second ejector (108) and then decelerated and pressurized in the diffuser section of the second ejector (108) to become a gas-liquid two-phase mixed CO2 refrigerant before being discharged from the second ejector (108). The pressurized gas-liquid two-phase mixed refrigerant enters the second T-tube (109), which is rich in liquid CO2. The fluid from the refrigerant outlet is cooled by isenthalpic throttling through the second expansion valve (110) and then enters the low-temperature evaporator (111) for heat absorption and evaporation. The fluid from the outlet of the second T-tube (109) rich in gaseous CO2 refrigerant is heated by heat exchange in the regenerator (112) and becomes superheated gaseous CO2 refrigerant. It enters the low-pressure compressor (101) for compression and is discharged from the low-pressure compressor (101). It mixes with the fluid from the outlet of the first T-tube (105) rich in gaseous CO2 refrigerant and then enters the suction port of the high-pressure compressor (102) to complete the refrigeration cycle of the entire system.

4. The operating method of the transcritical CO2 refrigeration system with dual ejectors combined with a T-tube according to claim 3, characterized in that: The working method involves five different working pressures: the working pressure of the gas cooler (103), the outlet pressure of the first ejector (104), the working pressure of the high-temperature evaporator (107), the outlet pressure of the second ejector (108), and the working pressure of the low-temperature evaporator (111). The working pressures of the low-temperature evaporator (111), the high-temperature evaporator (107), and the gas cooler (103) are determined by the operating conditions set by the refrigeration system. The outlet pressure of the first ejector (104) is related to the operating pressure of the first expansion valve (108). The opening degree of the first ejector (106) is related to the pressure ratio and ejection ratio of the first ejector (104); the outlet pressure of the second ejector (108) is related to the opening degree of the second expansion valve (110) and the pressure ratio and ejection ratio of the second ejector (108); by adjusting the opening degree of the first expansion valve (106) and the second expansion valve (110), the refrigerant flow rate entering the high-temperature stage evaporator (107) and the low-temperature stage evaporator (111) is controlled, and the ejection ratio and pressure ratio of the first ejector (104) and the second ejector (108) are also adjusted.

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