A dual-temperature refrigeration system with adjustable mixed refrigerant components and its control method

Abstract

A dual-temperature refrigeration system with adjustable mixed refrigerant components and its control method. The dual-temperature refrigeration system includes a compressor, a condenser, a throttle valve, a flow regulating valve, two gas-liquid separators, a regenerator, a low-temperature evaporator, a high-temperature evaporator, a liquid storage tank and a control module. The dual-temperature refrigeration system uses a binary non-azeotropic mixed refrigerant, realizes two-stage separation of the mixed refrigerant by using two gas-liquid separators, and realizes the component regulation function of the evaporator through a bypass pipeline and the liquid storage tank, improving the operating efficiency of the system. To solve the shortcomings of the traditional dual-temperature refrigeration system, such as high compression ratio and exhaust temperature of the compressor and low energy efficiency of the system at the initial stage of startup, the present invention actively regulates the concentration of the low-boiling refrigerant at the suction port of the compressor at the initial stage of startup to improve the operating reliability of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of dual-temperature refrigeration, and particularly relates to a dual-temperature refrigeration system with adjustable mixed refrigerant components and a control method thereof. Background Art

[0002] When a dual-temperature refrigeration system uses a mixed refrigerant, it can effectively reduce the irreversible loss in the heat exchanger and improve the energy-saving efficiency of the system, and has been widely applied.

[0003] The refrigeration system using a mixed refrigerant faces problems of relatively high compression ratio and exhaust temperature at the initial stage of compressor startup. Actively regulating the content of high- and low-boiling point refrigerants in the system at the initial stage of compressor startup can solve this problem; when the external environment changes in the refrigeration system using a mixed refrigerant, the distribution of the mixed refrigerant in the system changes. For example, when the condenser in the system is insufficiently heated, the phase accumulation of the refrigerant will increase, and the ratio of the mixed refrigerant in the system deviates from the optimal concentration ratio under variable working conditions. Therefore, it is necessary to actively regulate the ratio of the mixed refrigerant in the system so that the component ratio of the mixed refrigerant in the system under variable working conditions is always close to the optimal ratio with the highest system performance, thereby improving the performance of the system. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned dual-temperature refrigeration system, the purpose of the present invention is to provide a dual-temperature refrigeration system with adjustable mixed refrigerant components and a control method thereof. By adjusting the opening degree of the third electronic expansion valve 11 in the bypass pipeline, the ratio of the mixed refrigerant in the system at the startup stage of the compressor 1 is adjusted to solve the problems of relatively high compression ratio and exhaust temperature at the initial stage of compressor 1 startup. The control module C1 adjusts the ratio of the mixed refrigerant in the high-temperature evaporator 7 and the low-temperature evaporator 6 by monitoring the change of the external environment temperature, so that the component ratio in the evaporator is always close to the optimal ratio with the highest system performance, and the operating efficiency of the system is improved.

[0005] To achieve the above technical purpose, the present invention adopts the following technical solutions:

[0006] A dual-temperature refrigeration system with adjustable mixed refrigerant components includes a compressor 1. The outlet of the compressor 1 is connected to the inlet of a condenser 2, and the outlet of the condenser 2 is connected to the inlet of a first gas-liquid separator 3. The gas-phase outlet of the first gas-liquid separator 3 is connected to the inlet of a second electronic expansion valve 10. Meanwhile, a bypass pipeline of the gas-phase outlet is connected to the inlet of a third electronic expansion valve 11, and the outlet of the third electronic expansion valve 11 is connected to the inlet of the compressor 1. The liquid-phase outlet of the first gas-liquid separator 3 is connected to the inlet of a first electronic expansion valve 9. The outlet of the first electronic expansion valve 9 is connected to the inlet of a second gas-liquid separator 4. The gas-phase outlet of the second gas-liquid separator 4 is connected to the outlet of the second electronic expansion valve 10. After merging, it is divided into two branches through a regenerator 8 and is respectively connected to the inlets of a fifth electronic expansion valve 15 and a sixth electronic expansion valve 16. The liquid-phase outlet of the second gas-liquid separator 4 is connected to the inlet of a fourth electronic expansion valve 12. The outlet of the fourth electronic expansion valve 12 is connected to the inlet of a high-temperature evaporator 7 through the regenerator 8. The outlet of the high-temperature evaporator 7 is connected to the inlet of the compressor 1. The outlet of the fourth electronic expansion valve 12 is simultaneously connected to the inlet of a first flow regulating valve 13. The outlet of the first flow regulating valve 13 is connected to the inlet of a liquid storage tank 5. The bottom outlet of the liquid storage tank 5 is connected to the inlet of a second flow regulating valve 14. The outlet of the second flow regulating valve 14 is connected to the inlet of a low-temperature evaporator 6. The side outlet of the liquid storage tank 5 is connected to the inlet of a third flow regulating valve 17. The outlet of the third flow regulating valve 17 is connected to the inlet of the compressor 1. The outlet of the fifth electronic expansion valve 15 is connected to the inlet of the low-temperature evaporator 6, and the outlet of the low-temperature evaporator 6 is connected to the inlet of the compressor 1. The outlet of the sixth electronic expansion valve 16 is connected to the inlet of the high-temperature evaporator 7. A control module C1 is connected to an ambient temperature sensor T, a pressure sensor P1, the third electronic expansion valve 11, the fourth electronic expansion valve 12, the first flow regulating valve 13, the second flow regulating valve 14, the fifth electronic expansion valve 15, the sixth electronic expansion valve 16, and the third flow regulating valve 17, and is used to collect the temperature signal of the ambient temperature sensor T and the pressure signal of the pressure sensor P1, and control the opening degrees of the third electronic expansion valve 11, the fourth electronic expansion valve 12, the first flow regulating valve 13, the second flow regulating valve 14, the fifth electronic expansion valve 15, the sixth electronic expansion valve 16, and the third flow regulating valve 17, wherein the pressure sensor P1 is arranged at the outlet of the compressor 1.

[0007] The control method of the dual-temperature refrigeration system with adjustable mixed refrigerant components is as follows. Before the compressor 1 starts, the system is in equilibrium with the external environment. The low-boiling refrigerant is in a gaseous state, and a large amount of the low-boiling refrigerant is stored in the first gas-liquid separator 3. After the compressor 1 starts, the control device C1 increases the opening degree of the flow regulating valve 17 to release the high-boiling refrigerant in the liquid storage device 5 into the suction port of the compressor, increasing the concentration of the high-boiling refrigerant in the system, thereby reducing the content of the low-boiling refrigerant in the system during the compressor startup stage. Thereafter, the control module C1 gradually increases the opening degree of the third electronic expansion valve 11 on the bypass pipeline, increasing the concentration of the low-boiling component in the system, which can effectively reduce the compression ratio and exhaust temperature during the compressor startup stage, ensuring that the exhaust pressure of the compressor is always less than the set value P0, and improving the dynamic operation characteristics of the system.

[0008] When the external environment changes, the control module C1 collects the ambient temperature t measured by the ambient temperature sensor T, and the control module C1 adjusts the opening degrees of the fourth electronic expansion valve 12 and the sixth electronic expansion valve 16 to adjust the mixing ratio of the refrigerant in the high-temperature evaporator 7, so that the mixing ratio of the refrigerant in the high-temperature evaporator 7 is always close to the optimal ratio with the highest system performance; the control module C1 adjusts the opening degrees of the fifth electronic expansion valve 15 and the second flow regulating valve 14 to adjust the mixing ratio of the refrigerant in the low-temperature evaporator 6, so that the mixing ratio of the refrigerant in the low-temperature evaporator 6 is always close to the optimal ratio with the highest system performance; when the external ambient temperature rises, the control module C1 reduces the content of the high-boiling refrigerant in the high-temperature evaporator 7 by adjusting the opening degree of the fourth electronic expansion valve 12, and increases the content of the low-boiling refrigerant in the high-temperature evaporator 7 by adjusting the opening degree of the sixth electronic expansion valve 16; the control module C1 increases the content of the low-boiling refrigerant in the low-temperature evaporator 6 by adjusting the opening degree of the fifth electronic expansion valve 15, and reduces the content of the high-boiling refrigerant in the low-temperature evaporator 6 by adjusting the opening degree of the second flow regulating valve 14; when the external ambient temperature drops, the control module C1 increases the content of the high-boiling refrigerant in the high-temperature evaporator 7 by adjusting the opening degree of the fourth electronic expansion valve 12, and reduces the content of the low-boiling refrigerant in the high-temperature evaporator 7 by adjusting the opening degree of the sixth electronic expansion valve 16; the control module C1 reduces the content of the low-boiling refrigerant in the low-temperature evaporator 6 by adjusting the opening degree of the fifth electronic expansion valve 15, and increases the content of the high-boiling refrigerant in the low-temperature evaporator 6 by adjusting the opening degree of the second flow regulating valve 14.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] 1. The present invention proposes a dual-temperature refrigeration system with adjustable mixed refrigerant components and its control method. By adjusting the mixing ratio of the refrigerant in the system at the initial stage of compressor startup, the problems of high compression ratio and exhaust temperature at the initial stage of compressor startup are solved.

[0011] 2. The present invention provides a dual-temperature refrigeration system with adjustable mixed refrigerant components and its control method, which actively adjusts the concentration ratio of the mixed refrigerant components in the evaporator according to the change of the external environmental temperature, so that the circulating concentration ratio of the components in the system is always close to the optimal ratio with the highest system performance. Description of the Drawings

[0012] Figure 1 It is a schematic diagram of a dual-temperature refrigeration system with adjustable mixed refrigerant components and its control method according to the present invention. Detailed Embodiments

[0013] The following will describe in detail the specific embodiments of the present invention with reference to the drawings.

[0014] As Figure 1As shown in the figure, a dual-temperature refrigeration system with adjustable mixed refrigerant components includes a compressor 1. The outlet of the compressor 1 is connected to the inlet of a condenser 2, and the outlet of the condenser 2 is connected to the inlet of a first gas-liquid separator 3. The gas-phase outlet of the first gas-liquid separator 3 is connected to the inlet of a second electronic expansion valve 10. Meanwhile, a bypass pipeline of the gas-phase outlet is connected to the inlet of a third electronic expansion valve 11, and the outlet of the third electronic expansion valve 11 is connected to the inlet of the compressor 1. The liquid-phase outlet of the first gas-liquid separator 3 is connected to the inlet of a first electronic expansion valve 9. The outlet of the first electronic expansion valve 9 is connected to the inlet of a second gas-liquid separator 4. The gas-phase outlet of the second gas-liquid separator 4 is connected to the outlet of the second electronic expansion valve 10. After merging, it is divided into two branches through a regenerator 8 and is respectively connected to the inlets of a fifth electronic expansion valve 15 and a sixth electronic expansion valve 16. The liquid-phase outlet of the second gas-liquid separator 4 is connected to the inlet of a fourth electronic expansion valve 12. The outlet of the fourth electronic expansion valve 12 is connected to the inlet of a high-temperature evaporator 7 through the regenerator 8. The outlet of the high-temperature evaporator 7 is connected to the inlet of the compressor 1. The outlet of the fourth electronic expansion valve 12 is simultaneously connected to the inlet of a first flow regulating valve 13. The outlet of the first flow regulating valve 13 is connected to the inlet of a liquid storage tank 5. The bottom outlet of the liquid storage tank 5 is connected to the inlet of a second flow regulating valve 14. The outlet of the second flow regulating valve 14 is connected to the inlet of a low-temperature evaporator 6. The side outlet of the liquid storage tank 5 is connected to the inlet of a third flow regulating valve 17. The outlet of the third flow regulating valve 17 is connected to the inlet of the compressor 1. The outlet of the fifth electronic expansion valve 15 is connected to the inlet of the low-temperature evaporator 6, and the outlet of the low-temperature evaporator 6 is connected to the inlet of the compressor 1. The outlet of the sixth electronic expansion valve 16 is connected to the inlet of the high-temperature evaporator 7. A control module C1 is connected to an ambient temperature sensor T, a pressure sensor P1, the third electronic expansion valve 11, the fourth electronic expansion valve 12, the first flow regulating valve 13, the second flow regulating valve 14, the fifth electronic expansion valve 15, the sixth electronic expansion valve 16, and the third flow regulating valve 17, and is used for collecting the temperature signal of the ambient temperature sensor T and the pressure signal of the pressure sensor P1, and controlling the opening degrees of the third electronic expansion valve 11, the fourth electronic expansion valve 12, the first flow regulating valve 13, the second flow regulating valve 14, the fifth electronic expansion valve 15, the sixth electronic expansion valve 16, and the third flow regulating valve 17, wherein the pressure sensor P1 is arranged at the outlet of the compressor 1.

[0015] The working process of the dual-temperature refrigeration system with adjustable mixed refrigerant components according to the present invention is as follows: As Figure 1As shown in the figure, the system uses a binary non-azeotropic mixture refrigerant. The high-temperature and high-pressure gaseous refrigerant compressed by the compressor 1 enters the first gas-liquid separator 3 after partial condensation in the condenser 2 to achieve the first-stage component separation. The gas phase is rich in low-boiling-point refrigerant, and the liquid phase is rich in high-boiling-point refrigerant. The bypass pipeline at the gas-phase outlet of the first gas-liquid separator 3 is depressurized by the third electronic expansion valve 11 and then enters the inlet of the compressor 1. Due to the mixing characteristics of the non-azeotropic refrigerant and the low separation efficiency of the gas-liquid separator, the liquid phase still contains some low-boiling-point refrigerant. The liquid phase is throttled by the first electronic expansion valve 9 and then enters the second gas-liquid separator 4 to further separate the low-boiling-point refrigerant, increasing the content of the low-boiling-point refrigerant in the gaseous refrigerant. The liquid-phase refrigerant in the second gas-liquid separator 4 contains a high concentration of high-boiling-point refrigerant. The high-boiling-point refrigerant is throttled and depressurized by the fourth electronic expansion valve 12 and then divided into two branches. One branch enters the regenerator 8 to cool the gaseous low-boiling-point refrigerant. The other branch is connected to the liquid storage tank 5 through the first flow regulating valve 13 to store some of the high-boiling-point refrigerant in the liquid storage tank 5. The gaseous refrigerant from the first gas-liquid separator 3 is depressurized by the second electronic expansion valve 10 and then merged with the gaseous refrigerant from the gas-phase outlet of the second gas-liquid separator 4. After being cooled by the regenerator 8, it is divided into two branches. One branch is throttled and depressurized by the fifth electronic expansion valve 15 and then enters the low-temperature evaporator 6. The other branch is throttled and depressurized by the sixth electronic expansion valve 16 and then enters the high-temperature evaporator 7. The bottom outlet of the liquid storage tank 5 is connected to the inlet of the low-temperature evaporator 6 through the second flow regulating valve 14. The side outlet of the liquid storage tank 5 is connected to the inlet of the compressor 1 through the third flow regulating valve 17. When the ambient temperature remains unchanged and the system operates stably, the third electronic expansion valve 11, the first flow regulating valve 13, the second flow regulating valve 14, the sixth electronic expansion valve 16, and the third flow regulating valve 17 are closed. The high-boiling-point refrigerant enters the compressor 1 after evaporation in the high-temperature evaporator 7. The low-boiling-point refrigerant enters the compressor 1 after evaporation in the low-temperature evaporator 6. When the ambient temperature changes, the control module C1 adjusts the opening degrees of the fifth electronic expansion valve 15 and the second flow regulating valve 14 respectively to make the component ratio of the mixture refrigerant in the low-temperature evaporator 6 close to the optimal ratio with the highest system performance under variable operating conditions in the system. The mixture refrigerant enters the low-temperature evaporator 6, evaporates, and then enters the compressor 1. By adjusting the fourth regulating electronic expansion valve 12 and the sixth electronic expansion valve 16, the component ratio of the mixture refrigerant in the high-temperature evaporator 7 is made to be close to the optimal ratio with the highest system performance under variable operating conditions in the system. The mixture refrigerant enters the high-temperature evaporator 7, evaporates, and then enters the compressor 1 again.

[0016] In the starting stage of the compressor 1 of the dual-temperature refrigeration system with adjustable mixed refrigerant components, the third flow regulating valve 17 is opened, and the opening degree of the third electronic expansion valve 11 is adjusted to gradually increase the content of the low-boiling refrigerant in the system, so as to solve the problems of high compression ratio and high exhaust temperature of the compressor 1 in the starting stage of the system; after the compressor 1 starts, the third electronic expansion valve 11 and the third flow regulating valve 17 are closed, and a part of the high-boiling refrigerant is stored in the liquid receiver 5.

[0017] A control method for a dual-temperature refrigeration system with adjustable mixed refrigerant components according to the present invention, the refrigeration system is applied to a dual-temperature refrigeration device, and the component concentration in the system is actively regulated according to the exhaust pressure and the change of the external environmental temperature in the starting stage of the compressor, so as to ensure the efficient operation of the system; use P to represent the exhaust pressure of the compressor 1, and use t to represent the environmental temperature, the control method includes two aspects:

[0018] 1. Before the compressor 1 starts, the system is in equilibrium with the external environment, the low-boiling refrigerant is in a gaseous state, and a large amount of low-boiling refrigerant is stored in the first gas-liquid separator 3. After the compressor 1 starts, the control module C1 increases the opening degree of the third flow regulating valve 17 to 80% to release the high-boiling refrigerant in the liquid receiver 5 into the compressor suction port, increasing the concentration of the high-boiling refrigerant in the system, thereby reducing the content of the low-boiling refrigerant in the system in the starting stage of the compressor. Thereafter, the control module C1 gradually increases the opening degree of the third electronic expansion valve 11 on the bypass pipeline to 80%, gradually increasing the concentration of the low-boiling component in the system, which can effectively reduce the compression ratio and exhaust temperature in the starting stage of the compressor, ensure that the exhaust pressure of the compressor is always less than the set value P0, and the value of P0 is 3 MPa, improving the dynamic operation characteristics of the system.

[0019] 2. When the external environment changes, the control module C1 collects the ambient temperature t measured by the ambient temperature sensor T. The control module C1 adjusts the opening degrees of the fourth electronic expansion valve 12 and the sixth electronic expansion valve 16 to regulate the mixing refrigerant component ratio in the high-temperature evaporator 7, so that the mixing refrigerant ratio in the high-temperature evaporator 7 is always close to the optimal concentration ratio with the highest system performance; the control module C1 adjusts the opening degrees of the fifth electronic expansion valve 15 and the second flow regulating valve 14 to regulate the mixing refrigerant component ratio in the low-temperature evaporator 6, so that the mixing refrigerant ratio in the low-temperature evaporator 6 is always close to the optimal concentration ratio with the highest system performance. When the external ambient temperature rises from 24°C to 32°C, the control module C1 reduces the content of the high-boiling refrigerant in the high-temperature evaporator 7 by decreasing the opening degree of the fourth electronic expansion valve 12, and increases the content of the low-boiling refrigerant in the high-temperature evaporator 7 by increasing the opening degree of the sixth electronic expansion valve 16, and the adjusted opening degree is 5% - 25%. The control module C1 increases the content of the low-boiling refrigerant in the low-temperature evaporator 6 by increasing the opening degree of the fifth electronic expansion valve 15, and reduces the content of the high-boiling refrigerant in the low-temperature evaporator 6 by decreasing the opening degree of the second flow regulating valve 14, and the adjusted opening degree is 5% - 25%. When the external ambient temperature drops from 24°C to 18°C, the control module C1 increases the content of the high-boiling refrigerant in the high-temperature evaporator 7 by increasing the opening degree of the fourth electronic expansion valve 12, and reduces the content of the low-boiling refrigerant in the high-temperature evaporator 7 by decreasing the opening degree of the sixth electronic expansion valve 16, and the adjusted opening degree is 5% - 25%. The control module C1 reduces the content of the low-boiling refrigerant in the low-temperature evaporator 6 by decreasing the opening degree of the fifth electronic expansion valve 15, and increases the content of the high-boiling refrigerant in the low-temperature evaporator 6 by increasing the opening degree of the second flow regulating valve 14, and the adjusted opening degree is 5% - 25%.

Claims

1. A dual-temperature refrigeration system with adjustable mixed refrigerant components, characterized in that: It includes a compressor (1), the outlet of the compressor (1) is connected to the inlet of a condenser (2), and the outlet of the condenser (2) is connected to the inlet of a first gas-liquid separator (3); the gas-phase outlet of the first gas-liquid separator (3) is connected to the inlet of a second electronic expansion valve (10), and at the same time, a bypass pipeline of the gas-phase outlet is connected to the inlet of a third electronic expansion valve (11), and the outlet of the third electronic expansion valve (11) is connected to the inlet of the compressor (1); the liquid-phase outlet of the first gas-liquid separator (3) is connected to the inlet of a first electronic expansion valve (9); the outlet of the first electronic expansion valve (9) is connected to the inlet of a second gas-liquid separator (4); the gas-phase outlet of the second gas-liquid separator (4) is connected to the outlet of the second electronic expansion valve (10), and after merging, it is branched into two paths through a regenerator (8) and is respectively connected to the inlets of a fifth electronic expansion valve (15) and a sixth electronic expansion valve (16); the liquid-phase outlet of the second gas-liquid separator (4) is connected to the inlet of a fourth electronic expansion valve (12); the outlet of the fourth electronic expansion valve (12) is connected to the inlet of a high-temperature evaporator (7) after passing through the regenerator (8); the outlet of the high-temperature evaporator (7) is connected to the inlet of the compressor (1); the outlet of the fourth electronic expansion valve (12) is simultaneously connected to the inlet of a first flow regulating valve (13); the outlet of the first flow regulating valve (13) is connected to the inlet of a liquid storage tank (5); the bottom outlet of the liquid storage tank (5) is connected to the inlet of a second flow regulating valve (14); the outlet of the second flow regulating valve (14) is connected to the inlet of a low-temperature evaporator (6); the side outlet of the liquid storage tank (5) is connected to the inlet of a third flow regulating valve (17); the outlet of the third flow regulating valve (17) is connected to the inlet of the compressor (1); the outlet of the fifth electronic expansion valve (15) is connected to the inlet of the low-temperature evaporator (6), and the outlet of the low-temperature evaporator (6) is connected to the inlet of the compressor (1); the outlet of the sixth electronic expansion valve (16) is connected to the inlet of the high-temperature evaporator (7); a control module (C1) is connected to an ambient temperature sensor (T), a pressure sensor (P1), the third electronic expansion valve (11), the fourth electronic expansion valve (12), the first flow regulating valve (13), the second flow regulating valve (14), the fifth electronic expansion valve (15), the sixth electronic expansion valve (16) and the third flow regulating valve (17), and is used for collecting the temperature signal of the ambient temperature sensor (T) and the pressure signal of the pressure sensor (P1), and controlling the opening degrees of the third electronic expansion valve (11), the fourth electronic expansion valve (12), the first flow regulating valve (13), the second flow regulating valve (14), the fifth electronic expansion valve (15), the sixth electronic expansion valve (16) and the third flow regulating valve (17), wherein the pressure sensor (P1) is arranged at the outlet of the compressor (1).

2. The dual-temperature refrigeration system with adjustable mixed refrigerant components according to claim 1, characterized in that: The system uses a binary non-azeotropic refrigerant mixture. The high-temperature and high-pressure gaseous refrigerant compressed by the compressor (1) enters the first gas-liquid separator (3) after partial condensation in the condenser (2) to achieve the first-stage component separation. The low-boiling-point refrigerant is rich in the gas phase, and the high-boiling-point refrigerant is rich in the liquid phase. The bypass pipeline at the gas-phase outlet of the first gas-liquid separator (3) is depressurized by the third electronic expansion valve (11) and then enters the inlet of the compressor (1). Due to the mixing characteristics of the non-azeotropic refrigerant and the low separation efficiency of the gas-liquid separator, the liquid phase still contains some low-boiling-point refrigerant. The liquid phase is throttled by the first electronic expansion valve (9) and then enters the second gas-liquid separator (4) to further separate the low-boiling-point refrigerant and increase the content of the low-boiling-point refrigerant in the gaseous refrigerant. The liquid-phase refrigerant in the second gas-liquid separator (4) contains a high concentration of high-boiling-point refrigerant. The high-boiling-point refrigerant is throttled and depressurized by the fourth electronic expansion valve (12) and then divided into two branches. One branch enters the regenerator (8) to cool the low-boiling-point gaseous refrigerant. The other branch is connected to the liquid storage tank (5) through the first flow regulating valve (13) to store some of the high-boiling-point refrigerant in the liquid storage tank (5). The gaseous refrigerant from the first gas-liquid separator (3) is depressurized by the second electronic expansion valve (10) and then merged with the gaseous refrigerant at the gas-phase outlet of the second gas-liquid separator (4). After being cooled by the regenerator (8), it is divided into two branches. One branch is throttled and depressurized by the fifth electronic expansion valve (15) and then enters the low-temperature evaporator (6). The other branch is throttled and depressurized by the sixth electronic expansion valve (16) and then enters the high-temperature evaporator (7). The bottom outlet of the liquid storage tank (5) is connected to the inlet of the low-temperature evaporator (6) through the second flow regulating valve (14). The side outlet of the liquid storage tank (5) is connected to the inlet of the compressor (1) through the third flow regulating valve (17). When the ambient temperature remains unchanged and the system operates stably, the third electronic expansion valve (11), the first flow regulating valve (13), the second flow regulating valve (14), the sixth electronic expansion valve (16), and the third flow regulating valve (17) are closed. The high-boiling-point refrigerant enters the compressor (1) after evaporation in the high-temperature evaporator (7). The low-boiling-point refrigerant enters the compressor (1) after evaporation in the low-temperature evaporator (6). When the ambient temperature changes, the control module (C1) adjusts the opening degrees of the fifth electronic expansion valve (15) and the second flow regulating valve (14) respectively to make the component ratio of the refrigerant mixture in the low-temperature evaporator (6) close to the optimal ratio with the highest system performance under variable working conditions. The refrigerant mixture enters the low-temperature evaporator (6), evaporates, and then enters the compressor (1). By adjusting the fourth electronic expansion valve (12) and the sixth electronic expansion valve (16), the component ratio of the refrigerant mixture in the high-temperature evaporator (7) is made close to the optimal ratio with the highest system performance under variable working conditions. The refrigerant mixture enters the high-temperature evaporator (7), evaporates, and then enters the compressor (1).

3. The dual-temperature refrigeration system with adjustable mixed refrigerant components according to claim 1, characterized in that: In the starting stage of the compressor (1) of the dual-temperature refrigeration system with adjustable mixed refrigerant components, the third flow regulating valve (17) is opened, and the opening degree of the third electronic expansion valve (11) is adjusted to gradually increase the content of the low-boiling refrigerant in the system, so as to solve the problems of high compression ratio and high exhaust temperature of the compressor (1) in the starting stage of the system; after the compressor (1) starts, the third electronic expansion valve (11) and the third flow regulating valve (17) are closed, and a part of the high-boiling refrigerant is stored in the liquid storage tank (5).

4. A control method for the dual-temperature refrigeration system with adjustable mixed refrigerant components according to any one of claims 1 to 3, characterized in that, The dual-temperature refrigeration system actively regulates the concentration of the mixed refrigerant components in the system according to the exhaust pressure in the starting stage of the compressor and the change of the external ambient temperature, so as to ensure the efficient operation of the system; P represents the exhaust pressure of the compressor (1), and t represents the ambient temperature. The control method is as follows: 1) Before the compressor (1) starts, the system is in equilibrium with the external environment, the low-boiling refrigerant is in a gaseous state, and a large amount of low-boiling refrigerant is stored in the first-stage gas-liquid separator (3); after the compressor (1) starts, the control module (C1) increases the opening degree of the third flow regulating valve (17) to release the high-boiling refrigerant in the liquid storage tank (5) into the suction port of the compressor (1), increasing the concentration of the high-boiling refrigerant in the system, thereby reducing the relative content of the low-boiling refrigerant in the system in the starting stage of the compressor. Thereafter, the control module (C1) controls the opening degree of the third electronic expansion valve (11) on the bypass pipeline to adjust the concentration of the low-boiling component in the system, effectively reducing the compression ratio and exhaust temperature in the starting stage of the compressor, ensuring that the exhaust pressure of the compressor is always less than the set value P0, and improving the dynamic operation characteristics of the system; 2), when the external environment changes, the control module (C1) collects the ambient temperature t measured by the ambient temperature sensor (T). The control module (C1) adjusts the opening degrees of the fourth electronic expansion valve (12) and the sixth electronic expansion valve (16) to regulate the mixing refrigerant component ratio in the high-temperature evaporator (7), so that the mixing refrigerant ratio in the high-temperature evaporator (7) is always close to the optimal ratio with the highest system performance; the control module (C1) adjusts the opening degrees of the fifth electronic expansion valve (15) and the second flow regulating valve (14) to regulate the mixing refrigerant component ratio in the low-temperature evaporator (6), so that the mixing refrigerant ratio in the low-temperature evaporator (6) is always close to the optimal ratio with the highest system performance; when the external ambient temperature rises, the control module (C1) reduces the content of the high-boiling-point refrigerant in the high-temperature evaporator (7) by adjusting the opening degree of the fourth electronic expansion valve (12), and increases the content of the low-boiling-point refrigerant in the high-temperature evaporator (7) by adjusting the opening degree of the sixth electronic expansion valve (16); the control module (C1) increases the content of the low-boiling-point refrigerant in the low-temperature evaporator (6) by adjusting the opening degree of the fifth electronic expansion valve (15), and reduces the content of the high-boiling-point refrigerant in the low-temperature evaporator (6) by adjusting the opening degree of the second flow regulating valve (14); when the external ambient temperature drops, the control module (C1) increases the content of the high-boiling-point refrigerant in the high-temperature evaporator (7) by adjusting the opening degree of the fourth electronic expansion valve (12), and reduces the content of the low-boiling-point refrigerant in the high-temperature evaporator (7) by adjusting the opening degree of the sixth electronic expansion valve (16); the control module (C1) reduces the content of the low-boiling-point refrigerant in the low-temperature evaporator (6) by adjusting the opening degree of the fifth electronic expansion valve (15), and increases the content of the high-boiling-point refrigerant in the low-temperature evaporator (6) by adjusting the opening degree of the second flow regulating valve (14).

Images