Large-scale CO2 two-stage compressed air source heat pump system

Abstract

This invention relates to a large-temperature-span CO2 two-stage compressed air source heat pump system, belonging to the field of refrigeration and air conditioning technology. The system comprises high and low pressure compressors, an interstage air-cooled heat exchanger, a defrost receiver, a pre-subcooling heat exchanger, a post-subcooling heat exchanger, and a water pump, all connected by pipelines. Its key feature is that the large-temperature-span CO2 two-stage compression unit, consisting of two variable-frequency CO2 compressors (high and low pressure), is coupled with the pre-subcooling and post-subcooling units to form a subcooling-heating coupling path. It also forms an interstage cooling, overheat prevention, and pressure stabilization path with the interstage air-cooled heat exchanger. In conjunction with solenoid valves, the two evaporators provide three operating modes: refrigeration heat pump, sensible heat defrosting, and latent heat defrosting. The advantages of this invention are that it overcomes the shortcomings of long defrosting time and poor defrosting effect under large-temperature-span conditions in cold regions, increases the system's heating capacity, and improves system performance. Simultaneously, the system can adjust different supply water temperatures to meet users' multi-functional needs, expanding its application range and enabling widespread application under large-temperature-span conditions in cold regions. It has significant potential for promotion and energy saving.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration and air conditioning technology, and relates to a large-temperature-span CO2 two-stage compressed air source heat pump system, particularly a heat pump system that utilizes outdoor air source to operate under a large temperature span and provide users with the required hot water. Background Technology

[0002] Residential heating energy consumption is particularly prominent in building operation energy consumption, accounting for approximately 25% of my country's total building energy consumption. Centralized coal-fired heating suffers from high energy consumption, low efficiency, and severe environmental pollution. Traditional vapor compression cycle air source heat pumps, with their advantages of high efficiency, energy saving, and cost-effectiveness, have become the most suitable method for promotion and have been widely applied in Beijing and areas south of North my country. However, when used in cold regions, air source heat pumps face challenges such as low ambient temperature, large intake volume, small system working fluid circulation volume, high pressure ratio, high exhaust temperature, poor lubrication, and evaporator surface frosting, limiting their widespread application in these areas.

[0003] Comparative studies have shown that CO2 can improve the low-temperature performance of heat pumps and increase the seasonal energy efficiency of air-source heat pumps. At the same time, two-stage compression can improve problems such as high compressor pressure ratio and high exhaust temperature under low-temperature conditions when using CO2.

[0004] In terms of subcooling technology, as the degree of subcooling increases, the isenthalpic process of the system gradually approaches the isentropic process, thus reducing throttling losses, increasing the circulating cooling capacity, and improving system performance. Meanwhile, domestic and international scholars have proposed that two-stage compression technology with jet characteristics can effectively solve the low-temperature adaptability problem of air-source heat pumps and exhibits good integration characteristics with air-source heat pumps. Therefore, this invention combines the jet process with mechanical subcooling to improve the low-temperature cycle performance of air-source heat pump systems and enhance the overall heating efficiency of the system.

[0005] Traditional air-cooled heat pump units typically defrost via reverse circulation. This conventional four-way valve reversing defrosting method has several drawbacks: the reversing of the four-way valve leads to oil leakage, reducing system reliability and lifespan. Furthermore, the traditional defrosting process requires two valve switching cycles to re-establish balance, resulting in energy loss and prolonged defrosting time. Therefore, we have chosen interstage extraction defrosting, which ensures effective defrosting, maintains system stability, and extends system lifespan. Summary of the Invention

[0006] The purpose of this invention is to provide a large-temperature-span CO2 two-stage compressed air source heat pump system, which solves the shortcomings of traditional air source heat pumps with low performance and poor defrosting effect under large-temperature-span conditions in cold regions, and realizes the efficient and stable operation of the heat pump system during the heating season in cold regions.

[0007] The technical solution of the present invention is as follows:

[0008] The large-temperature-range CO2 two-stage compressed air source heat pump system provided by the present invention includes a CO2 two-stage compression cycle refrigerant circuit (A) consisting of a low-pressure compressor; a high-pressure compressor; a first evaporator; a second evaporator; a gas cooler; an interstage heat exchanger; an interstage air-cooled heat exchanger; an interstage mixing chamber; a defrost receiver; a first electronic expansion valve; a second electronic expansion valve; a third electronic expansion valve; a fourth electronic expansion valve; a first solenoid valve; a second solenoid valve; a third solenoid valve; a fourth solenoid valve; a fifth solenoid valve; a sixth solenoid valve; a seventh solenoid valve; an eighth solenoid valve; a ninth solenoid valve; and refrigerant connecting pipes; a subcooling and heating coupled cycle refrigerant circuit (B) consisting of a subcooling and heating compressor; a heating heat exchanger; a pre-subcooling heat exchanger; a post-subcooling heat exchanger; a fifth electronic expansion valve; a tenth solenoid valve; an eleventh solenoid valve; and refrigerant connecting pipes; and a hot water supply cycle circuit (C) consisting of a user heat exchange device; a water pump; a twelfth solenoid valve; a thirteenth solenoid valve; a fourteenth solenoid valve; and water connecting pipes.

[0009] The CO2 two-stage compression cycle refrigerant loop (A) includes a low-pressure compressor; a high-pressure compressor; a first evaporator; a second evaporator; a gas cooler; an interstage heat exchanger; an interstage air-cooled heat exchanger; an interstage mixing chamber; a first electronic expansion valve; a second electronic expansion valve; a first solenoid valve; a second solenoid valve; a third solenoid valve; a fourth solenoid valve; and refrigerant connecting pipes, forming a two-stage compression unit. The connection method of each device in the two-stage compression unit is as follows: the refrigerant pipe at the upper end of the low-pressure compressor is connected to the lower left port of the interstage mixing chamber; the refrigerant pipe at the upper right port of the interstage mixing chamber is connected to the high-pressure compressor; the refrigerant pipe at the upper end of the high-pressure compressor is connected to the lower left port of the gas cooler; and the refrigerant pipe at the upper left port of the gas cooler is connected via the fourth electronic expansion valve. The expansion valve is connected to the lower left port of the interstage heat exchanger. The refrigerant line at the upper left port of the interstage heat exchanger is connected to the upper port of the interstage mixing chamber. The refrigerant line at the lower right port of the interstage heat exchanger is connected to the refrigerant line of the gas cooler connected to the first electronic expansion valve. The refrigerant line at the upper right port of the interstage heat exchanger is connected to the second electronic expansion valve. The refrigerant line on the left side of the second electronic expansion valve is connected to the lower left end of the low-pressure compressor via the first solenoid valve, the first evaporator, and the second solenoid valve. The refrigerant line on the left end of the second evaporator is connected to the refrigerant line of the second electronic expansion valve connected to the first solenoid valve via the third solenoid valve. The refrigerant line on the right end of the second evaporator is connected to the refrigerant line of the lower left end of the low-pressure compressor connected to the second solenoid valve via the fourth solenoid valve.

[0010] The device of this invention adds an interstage air-cooled heat exchanger between the low-pressure compressor and the interstage mixing chamber to form an interstage cooling, overheat prevention, and pressure stabilization path. The interstage air-cooled heat exchanger is used to regulate the refrigerant temperature in the refrigerant line on the right side of the low-pressure compressor, preventing excessively high outlet temperatures of the low-pressure stage compressor and excessively high inlet temperatures and pressures of the high-pressure stage compressor.

[0011] The CO2 two-stage compression cycle refrigerant circuit (A) includes a low-pressure compressor, a first evaporator, a second evaporator, a defrost receiver, a third electronic expansion valve, a fourth electronic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve, a fourth solenoid valve, a fifth solenoid valve, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, a ninth solenoid valve, and refrigerant connecting pipes, forming an interstage suction defrost unit. In the interstage suction defrost unit, the second, third, fourth, and fifth solenoid valves are energized and open, while the first, sixth, seventh, eighth, and ninth solenoid valves are de-energized and closed. The third electronic expansion valve is energized and open, while the fourth electronic expansion valve is de-energized. When activated, it forms the sensible heat defrosting path for the first evaporator. The connections of the devices in this path are as follows: the refrigerant line on the right side of the third electronic expansion valve is connected to the refrigerant line connecting the low-pressure compressor and the interstage air-cooled heat exchanger; the refrigerant line on the left side of the third electronic expansion valve is connected to the left side of the first evaporator via the fifth solenoid valve; the refrigerant line on the right side of the first evaporator is connected to the lower left end of the low-pressure compressor via the second solenoid valve; the third, fourth, fifth, sixth, and eighth solenoid valves in the interstage defrosting unit are energized and open; the first, second, seventh, and ninth solenoid valves are de-energized and closed; the third electronic expansion valve is de-energized and closed; the fourth electronic expansion valve... When the valve is energized and opened, it forms the latent heat defrosting path for the first evaporator. The connections of the devices in the first evaporator latent heat defrosting path are as follows: the refrigerant line on the right side of the sixth solenoid valve is connected to the refrigerant line connecting the low-pressure compressor and the interstage air-cooled heat exchanger; the refrigerant line on the left side of the sixth solenoid valve is connected to the left side of the first evaporator via the fifth solenoid valve; the refrigerant line on the left side of the eighth solenoid valve is connected to the refrigerant line between the first evaporator and the second solenoid valve; the refrigerant line on the right side of the fifth solenoid valve is connected to the upper end of the defrost receiver; the refrigerant line at the lower end of the defrost receiver is connected to the lower end of the fourth electronic expansion valve; the refrigerant line at the upper end of the fourth electronic expansion valve is connected to the refrigerant line connecting the second electronic expansion valve and the first solenoid valve; interstage... In the air extraction defrosting unit, the first, second, fourth, and seventh solenoid valves are energized and open, while the third, fifth, sixth, eighth, and ninth solenoid valves are de-energized and closed. When the third electronic expansion valve is energized and open, and the fourth electronic expansion valve is de-energized and closed, a sensible heat defrosting path for the second evaporator is formed. The connection method of each device in the sensible heat defrosting path of the second evaporator is as follows: the refrigerant pipeline on the right side of the third electronic expansion valve is connected to the refrigerant pipeline connecting the low-pressure compressor and the interstage air-cooled heat exchanger; the refrigerant pipeline on the left side of the third electronic expansion valve is connected to the left side of the second evaporator via the seventh solenoid valve; and the refrigerant pipeline on the right side of the second evaporator is connected to the lower left end of the low-pressure compressor via the fourth solenoid valve.In the interstage defrosting unit, the first, second, sixth, seventh, and ninth solenoid valves are energized and open; the third, fourth, fifth, and eighth solenoid valves are de-energized and closed; the third electronic expansion valve is de-energized and closed; and the fourth electronic expansion valve is energized and open, forming the latent heat defrosting path for the second evaporator. The connections of the equipment in the sensible heat defrosting path for the second evaporator are as follows: the refrigerant line on the right side of the sixth solenoid valve is connected to the refrigerant line connecting the low-pressure compressor and the interstage air-cooled heat exchanger; the refrigerant line on the left side of the sixth solenoid valve is connected to the left side of the second evaporator via the seventh solenoid valve; the refrigerant line on the left side of the ninth solenoid valve is connected to the refrigerant line between the second evaporator and the fourth solenoid valve; the refrigerant line on the right side of the ninth solenoid valve is connected to the refrigerant line between the eighth solenoid valve and the defrost receiver; the refrigerant line at the lower end of the defrost receiver is connected to the lower end of the fourth electronic expansion valve; and the refrigerant line at the upper end of the fourth electronic expansion valve is connected to the refrigerant line connecting the second electronic expansion valve and the first solenoid valve.

[0012] In the subcooling-heating coupled refrigerant loop (B), a pre-subcooling heat exchanger is added between the gas cooler and the interstage heat exchanger, and a post-subcooling heat exchanger is added between the interstage heat exchanger and the second electronic expansion valve. When the tenth solenoid valve is energized and open, and the eleventh solenoid valve is de-energized and closed, a pre-subcooling unit is formed. The connection method of each device in the pre-subcooling unit is as follows: the refrigerant pipeline at the lower right port of the pre-subcooling heat exchanger is connected to the left side of the subcooling-heating compressor; the refrigerant pipeline at the upper end of the subcooling-heating compressor is connected to the upper left port of the heat exchanger; the refrigerant pipeline at the upper right port of the heat exchanger is connected to the lower end of the fifth electronic expansion valve; and the upper end of the fifth electronic expansion valve is connected to the... The refrigerant line is connected to the upper right port of the front subcooling heat exchanger via the tenth solenoid valve. When the tenth solenoid valve is closed and the eleventh solenoid valve is open, the rear subcooling unit is formed. The connection method of each device in the rear subcooling unit is as follows: the refrigerant line at the lower right port of the rear subcooling heat exchanger is connected to the refrigerant line connecting the front subcooling heat exchanger and the subcooling heating compressor; the refrigerant line at the upper right port of the heating heat exchanger is connected to the lower end of the fifth electronic expansion valve; the refrigerant line on the right side of the eleventh solenoid valve is connected to the refrigerant line connecting the fifth electronic expansion valve and the tenth solenoid valve; and the refrigerant line on the left side of the eleventh solenoid valve is connected to the upper right port of the rear subcooling heat exchanger.

[0013] In the hot water circulation loop (C), when the twelfth solenoid valve is energized and open, and the thirteenth and fourteenth solenoid valves are de-energized and closed, a heating series water supply circuit is formed. The connection method for each device in the heating series water supply circuit is as follows: the water connection pipe on the right side of the user's heat exchanger is connected to the left side of the water pump; the water connection pipe on the right side of the water pump is connected to the lower right port of the heating heat exchanger; the water connection pipe at the lower left port of the heating heat exchanger is connected to the upper right port of the gas cooler via the twelfth solenoid valve; and the water connection pipe at the lower right port of the gas cooler is connected to the left side of the user's heat exchanger. When the thirteenth and fourteenth solenoid valves are energized and open, and the twelfth solenoid valve is de-energized and closed, a heating series water supply circuit is formed. The connection method of each device in the combined water supply circuit and the parallel heating water supply circuit is as follows: the water connection pipe on the right side of the user's heat exchange device is connected to the left side of the water pump; the water connection pipe on the right side of the water pump is connected to the lower right port of the heating heat exchanger; the water connection pipe on the lower left port of the heating heat exchanger is connected to the connection pipe between the lower right port of the gas cooler and the user's heat exchange device via the thirteenth solenoid valve; the water connection pipe on the right side of the fourteenth solenoid valve is connected to the pipe connecting the water pump and the lower right port of the heating heat exchanger; the water connection pipe on the left side of the fourteenth solenoid valve is connected to the pipe between the twelfth solenoid valve and the upper right port of the gas cooler; and the water connection pipe on the lower right port of the gas cooler is connected to the left side of the user's heat exchange device.

[0014] In the above technical solution, the refrigerant working fluid in the CO2 two-stage compression cycle refrigerant circuit and the subcooling and heating coupled cycle refrigerant circuit is replaced according to the working environment; the circulating working fluid in the hot water supply circuit is replaced according to the working environment and its matching with the subcooling and heating coupled cycle refrigerant circuit.

[0015] The effects and benefits of this invention are as follows: The large-span CO2 two-stage compressed air source heat pump system employs two compressors (high and low pressure) and an interstage mixing chamber to achieve a two-stage compression heat pump cycle with primary CO2 refrigerant throttling and complete intermediate cooling. Utilizing the sensible heat defrosting and latent heat defrosting functions of the interstage extraction defrosting unit, it overcomes the shortcomings of long defrosting time and poor defrosting effect under large-span conditions in cold regions. Furthermore, the subcooling effect of the subcooling-heating coupling cycle further increases the system's heating capacity under large-span conditions in cold regions, improving system performance. Simultaneously, this system can also adjust different supply water temperatures to meet users' multi-functional needs, expanding its application range. This allows the device to be widely used under large-span conditions in cold regions, possessing significant potential for promotion and energy-saving significance. Attached Figure Description

[0016] The attached diagram is a schematic diagram of the structural principle of a large-scale CO2 two-stage compressed air source heat pump system.

[0017] In the diagram: 1-Low-pressure stage compressor; 2-High-pressure stage compressor; 3-First evaporator; 4-Second evaporator; 5-Gas cooler; 6-Interstage heat exchanger; 7-Interstage mixing chamber; 8-Interstage air-cooled heat exchanger; 9-Defrost receiver; 10-First electronic expansion valve; 11-Second electronic expansion valve; 12-Third electronic expansion valve; 13-Fourth electronic expansion valve; 14-First solenoid valve; 15-Second solenoid valve; 16-Third solenoid valve; 17-Fourth solenoid valve; 8-Fifth solenoid valve; 19-Sixth solenoid valve; 20-Seventh solenoid valve; 21-Eighth solenoid valve; 22-Ninth solenoid valve; 23-Subcooling and heating compressor; 24-Heating heat exchanger; 25-First subcooling heat exchanger; 26-Rear subcooling heat exchanger; 27-Fifth electronic expansion valve; 28-Tenth solenoid valve; 29-Eleventh solenoid valve; 30-User heat exchange device; 31-Water pump; 32-Twelfth solenoid valve; 33-Thirteenth solenoid valve; 34-Fourteenth solenoid valve. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0019] Two-stage compression heating mode:

[0020] The high-temperature, medium-pressure superheated gaseous refrigerant exiting the low-pressure compressor 1 enters the lower left inlet of the interstage mixing chamber 7 and mixes with the medium-temperature, medium-pressure gaseous and liquid refrigerant entering the upper inlet of the interstage mixing chamber 7. The saturated gaseous refrigerant then flows out from the upper outlet of the interstage mixing chamber 7 and enters the high-pressure compressor 2. Under the action of the high-pressure compressor 2, the refrigerant changes from a medium-pressure saturated gaseous refrigerant to a high-temperature, high-pressure superheated gaseous refrigerant. This high-temperature, high-pressure superheated gaseous refrigerant enters the gas cooler 5, where it is cooled by the hot water circulation loop to become a medium-temperature, high-pressure refrigerant. The cooled medium-temperature, high-pressure refrigerant then enters the interstage heat exchanger 6 in two ways: one path directly enters the lower right inlet of the interstage heat exchanger 6, and the other path is throttled by the first electronic expansion valve 10 to become a low-temperature, medium-pressure gaseous and liquid mixed refrigerant, which then enters the lower left inlet of the interstage heat exchanger 6. The two refrigerant paths then pass through the interstage heat exchanger 6... In the intermediate heat exchange, the medium-temperature, medium-pressure refrigerant entering the lower right inlet of the interstage heat exchanger 6 enters the second electronic expansion valve 11 through the upper right outlet. Another path leads to the medium-temperature, medium-pressure gaseous and liquid mixed refrigerant entering the lower left inlet of the interstage heat exchanger 6, which enters the interstage mixing chamber 7 through the upper left outlet. It mixes with the high-temperature, medium-pressure gaseous refrigerant discharged from the low-pressure compressor 1. The refrigerant entering the second electronic expansion valve 11 is throttled from medium-temperature, medium-pressure to low-temperature, low-pressure. Then, it enters the first evaporator 3 and the second evaporator 4 through the first solenoid valve 14 and the third solenoid valve 16, respectively, to absorb heat. After absorbing heat, the refrigerant changes from low-temperature, low-pressure to medium-temperature, low-pressure. The refrigerant entering the first evaporator 3 enters the left side of the low-pressure compressor 1 through the second solenoid valve 15, and the refrigerant entering the second evaporator 4 enters the left side of the low-pressure compressor 1 through the fourth solenoid valve 17.

[0021] In the hot water circulation loop C, the 12th solenoid valve 32 and the 13th solenoid valve 33 are closed when not energized, and the 14th solenoid valve 34 is energized and opened. The circulating working fluid water enters the gas cooler 5 for heat exchange through the 14th solenoid valve 34 under the action of the water pump 31, and finally enters the user heat exchange device 30. The water pipe on the right side of the user heat exchange device 30 is connected to the water pump 31.

[0022] Two-stage compression coupling with pre-mechanical subcooling heating mode:

[0023] In the CO2 two-stage compression cycle refrigerant loop A, the two-stage compression unit is turned on. The specific implementation method is the same as the two-stage compression heating mode, so it will not be described again.

[0024] In the subcooling-heating coupled refrigerant circuit B, the tenth solenoid valve 28 is energized and opened, while the eleventh solenoid valve 29 is de-energized and closed. After being throttled to a low-temperature, low-pressure state by the fifth electronic expansion valve 27, the refrigerant enters the pre-subcooling heat exchanger 25 via the tenth solenoid valve 28 to cool the CO2 two-stage compression cycle refrigerant circuit. The refrigerant then becomes a medium-temperature, low-pressure refrigerant. Subsequently, the refrigerant enters the subcooling-heating compressor 23 and is compressed into a high-temperature, high-pressure gaseous refrigerant. This compressed high-temperature, high-pressure gaseous refrigerant enters the heat exchanger 24 to exchange heat with the circulating working fluid in the hot water supply circuit. After heat exchange, it becomes a medium-temperature, high-pressure refrigerant. Finally, the refrigerant enters the fifth electronic expansion valve 27 for throttling, changing from a medium-temperature, high-pressure refrigerant to a low-temperature, low-pressure refrigerant.

[0025] In the hot water circulation loop C, the user can select different water supply paths for the opening and closing of the 12th solenoid valve 32, the 13th solenoid valve 33, and the 14th solenoid valve 34 as needed.

[0026] Heat-enhancing series water supply circuit: If the water supply temperature is below 50℃, the twelfth solenoid valve 32 is energized and opened, while the thirteenth solenoid valve 33 and the fourteenth solenoid valve 34 are de-energized and closed. The circulating working fluid water first enters the heat-enhancing heat exchanger 24 for heat exchange under the action of the water pump 32, and after being heated, it enters the gas cooler 5 for heat exchange again through the fourteenth solenoid valve 34, and finally enters the user heat exchange device 30. The water pipe on the right side of the user heat exchange device 30 is connected to the water pump 31.

[0027] Heating and parallel water supply path: If the water supply temperature is greater than 50℃, the thirteenth solenoid valve 33 and the fourteenth solenoid valve 34 are energized and opened, while the twelfth solenoid valve 32 is de-energized and closed. The circulating working fluid water is divided into two paths under the action of the water pump 32. One path enters the gas cooler 5 for heat exchange through the twelfth solenoid valve 32, and the other path enters the heating heat exchanger 24 for heat exchange. It then mixes with the circulating working fluid from the gas cooler 5 through the thirteenth solenoid valve 33 and enters the user heat exchange device 30. The water pipe on the right side of the user heat exchange device 30 is connected to the water pump 31.

[0028] Two-stage compression coupling followed by mechanical subcooling and defrosting heating mode:

[0029] First evaporator 3 Sensible heat defrosting mode:

[0030] In the CO2 two-stage compression cycle refrigerant circuit A, the two-stage compression unit and the sensible heat defrosting passage of the first evaporator 3 are opened. The specific implementation of the two-stage compression unit is the same as that of the two-stage compression heating mode, so it will not be described again. The specific implementation of the sensible heat defrosting passage of the first evaporator 3 is as follows: the second solenoid valve 15, the third solenoid valve 16, the fourth solenoid valve 17, and the fifth solenoid valve 18 are energized and opened; the first solenoid valve 14, the sixth solenoid valve 19, the seventh solenoid valve 20, the eighth solenoid valve 21, and the ninth solenoid valve 22 are not energized and closed; the third electronic expansion valve 12 is energized and opened; and the fourth electronic expansion valve 13 is not energized and closed. The high-temperature, medium-pressure gaseous refrigerant from the upper end of the low-pressure compressor is throttled by the third electronic expansion valve 12 and becomes a high-temperature, low-pressure gaseous refrigerant. It then enters the first evaporator 3 through the fifth solenoid valve 18 for defrosting. After defrosting, it mixes with the refrigerant from the second evaporator 4 through the second solenoid valve 15 in the refrigerant line below the fourth solenoid valve 17 and enters the low-pressure compressor 1 together.

[0031] In the subcooling-heating coupled refrigerant circuit B, the tenth solenoid valve 28 is closed without energization, and the eleventh solenoid valve 29 is opened with energization. After the refrigerant is throttled to a low-temperature, low-pressure state by the fifth electronic expansion valve 27, it enters the subcooling heat exchanger 26 via the eleventh solenoid valve 29 to cool the CO2 two-stage compression refrigerant circuit. The refrigerant then becomes a medium-temperature, low-pressure refrigerant and enters the subcooling-heating compressor 23, where it is compressed into a high-temperature, high-pressure refrigerant. The compressed high-temperature, high-pressure refrigerant then enters the heat exchanger 24 to exchange heat with the circulating working fluid in the hot water supply circuit. After heat exchange, it becomes a medium-temperature, high-pressure refrigerant. Finally, the refrigerant enters the fifth electronic expansion valve 27 for throttling, changing from a medium-temperature, high-pressure refrigerant to a low-temperature, low-pressure refrigerant, completing the cycle.

[0032] The specific implementation method of the water supply path in the hot water circulation loop C is the same as that in the hot water circulation loop C of the heating mode before two-stage compression coupling.

[0033] First evaporator 3 latent heat defrosting mode:

[0034] In the CO2 two-stage compression cycle refrigerant circuit A, the two-stage compression unit and the latent heat defrosting passage of the first evaporator 3 are opened. The specific implementation of the two-stage compression unit is the same as that of the two-stage compression heating mode, so it will not be described again. The specific implementation of the latent heat defrosting passage of the first evaporator 3 is as follows: the third solenoid valve 16, the fourth solenoid valve 17, the fifth solenoid valve 18, the sixth solenoid valve 19, and the eighth solenoid valve 21 are energized and opened; the first solenoid valve 14, the second solenoid valve 15, the seventh solenoid valve 20, and the ninth solenoid valve 22 are not energized and closed; the third electronic expansion valve 12 is not energized and closed; and the fourth electronic expansion valve 13 is energized and opened. The high-temperature, medium-pressure gaseous refrigerant from the top of the low-pressure compressor enters the first evaporator 3 for defrosting via the sixth solenoid valve 19 and the fifth solenoid valve 18. After defrosting, the refrigerant becomes a low-temperature, medium-pressure liquid refrigerant, which then enters the defrost receiver 9 via the eighth solenoid valve 21. After exiting the defrost receiver 9, the liquid refrigerant enters the fourth electronic expansion valve 13 and is throttled into a low-temperature, low-pressure liquid and gaseous mixture. This mixture is then mixed with the low-temperature, low-pressure liquid and gaseous refrigerant from the second electronic expansion valve 11 and enters the second evaporator 4 via the third solenoid valve 16.

[0035] The refrigerant cycle in the subcooling-heating coupled refrigerant circuit B is the same as the refrigerant cycle in the subcooling-heating coupled refrigerant circuit B in the sensible heat defrosting mode of the first evaporator 3.

[0036] The specific implementation method of the water supply path in the hot water circulation loop C is the same as that in the hot water circulation loop C of the heating mode before two-stage compression coupling.

[0037] Second evaporator 4 Sensible heat defrosting mode:

[0038] In the CO2 two-stage compression cycle refrigerant circuit A, the sensible heat defrosting passage of the two-stage compression unit and the second evaporator 4 is opened. The specific implementation of the two-stage compression unit is the same as that of the two-stage compression heating mode, so it will not be described again. The specific implementation of the sensible heat defrosting passage of the second evaporator 4 is as follows: the first solenoid valve 14, the second solenoid valve 15, the fourth solenoid valve 17, and the seventh solenoid valve 20 are energized and opened; the third solenoid valve 16, the fifth solenoid valve 18, the sixth solenoid valve 19, the eighth solenoid valve 21, and the ninth solenoid valve 22 are not energized and closed; the third electronic expansion valve 12 is energized and opened; and the fourth electronic expansion valve 13 is not energized and closed. The high-temperature, medium-pressure gaseous refrigerant from the upper end of the low-pressure compressor is throttled by the third electronic expansion valve 12 and becomes a high-temperature, low-pressure gaseous refrigerant. It then enters the second evaporator 4 through the seventh solenoid valve 20 for defrosting. After defrosting, it mixes with the refrigerant from the first evaporator 3 through the fourth solenoid valve 17 in the refrigerant line below the second solenoid valve 15 and enters the low-pressure compressor 1 together.

[0039] The refrigerant cycle in the subcooling-heating coupled refrigerant circuit B is the same as the refrigerant cycle in the subcooling-heating coupled refrigerant circuit B in the sensible heat defrosting mode of the first evaporator 3.

[0040] The specific implementation method of the water supply path in the hot water circulation loop C is the same as that in the hot water circulation loop C of the heating mode before two-stage compression coupling.

[0041] Second evaporator 4 latent heat defrosting mode:

[0042] In the CO2 two-stage compression refrigerant circuit A, the latent heat defrosting passage of the two-stage compression unit and the second evaporator 4 is opened. The specific implementation of the two-stage compression unit is the same as that of the two-stage compression heating mode, so it will not be described again. The specific implementation of the latent heat defrosting passage of the second evaporator 4 is as follows: the first solenoid valve 14, the second solenoid valve 15, the sixth solenoid valve 19, the seventh solenoid valve 20, and the ninth solenoid valve 22 are energized and opened; the third solenoid valve 16, the fourth solenoid valve 17, the fifth solenoid valve 18, and the eighth solenoid valve 21 are not energized and closed; the third electronic expansion valve 12 is not energized and closed; and the fourth electronic expansion valve 13 is energized and opened. The high-temperature, medium-pressure refrigerant from the top of the low-pressure compressor enters the second evaporator 4 for defrosting via the sixth solenoid valve 19 and the seventh solenoid valve 20. After defrosting, the refrigerant becomes a low-temperature, medium-pressure liquid refrigerant, which then enters the defrost receiver 9 via the ninth solenoid valve 22. After exiting the defrost receiver 9, the liquid refrigerant enters the fourth electronic expansion valve 13, where it is throttled into a low-temperature, low-pressure liquid and gaseous mixture. This mixture then mixes with the low-temperature, low-pressure liquid and gaseous refrigerant from the second electronic expansion valve 11 and enters the first evaporator 3 via the first solenoid valve 14.

[0043] The refrigerant cycle in the subcooling-heating coupled refrigerant circuit B is the same as the refrigerant cycle in the subcooling-heating coupled refrigerant circuit B in the sensible heat defrosting mode of the first evaporator 3.

[0044] The specific implementation method of the water supply path in the hot water circulation loop C is the same as that in the hot water circulation loop C of the heating mode before two-stage compression coupling.

[0045] The high-temperature, cross-CO2 two-stage compressed air source heat pump system of the present invention can operate efficiently and stably during the heating season by effectively controlling the system circulation process and coupling relationship between equipment, the heat and mass transfer and heat transport characteristics between refrigerant and related working fluids, and the defrosting mechanism under low-temperature conditions.

[0046] Obviously, the examples above are merely illustrative and not intended to limit the implementation. Those skilled in the art will recognize that many other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom remain within the scope of this invention.

Claims

1. A high-temperature, trans-CO2 two-stage compressed air source heat pump system, characterized in that: The system consists of a low-pressure compressor (1), a high-pressure compressor (2), a first evaporator (3), a second evaporator (4), a gas cooler (5), an interstage heat exchanger (6), an interstage air-cooled heat exchanger (7), an interstage mixing chamber (8), a defrost receiver (9), a first electronic expansion valve (10), a second electronic expansion valve (11), a third electronic expansion valve (12), a fourth electronic expansion valve (13), a first solenoid valve (14), a second solenoid valve (15), a third solenoid valve (16), a fourth solenoid valve (17), a fifth solenoid valve (18), a sixth solenoid valve (19), a seventh solenoid valve (20), an eighth solenoid valve (21), and a third solenoid valve (22). A CO2 two-stage compression cycle refrigerant circuit consisting of nine solenoid valves (22) and refrigerant connection pipelines (A); a subcooling and heating coupled cycle refrigerant circuit consisting of a subcooling and heating compressor (23), a heating heat exchanger (24), a front subcooling heat exchanger (25), a rear subcooling heat exchanger (26), a fifth electronic expansion valve (27), a tenth solenoid valve (28), an eleventh solenoid valve (29) and refrigerant connection pipelines (B); a hot water supply cycle circuit consisting of a user heat exchange device (30), a water pump (31), a twelfth solenoid valve (32), a thirteenth solenoid valve (33), a fourteenth solenoid valve (34) and water connection pipelines (C). The CO2 two-stage compression cycle refrigerant circuit (A) includes a low-pressure compressor (1), a high-pressure compressor (2), a first evaporator (3), a second evaporator (4), a gas cooler (5), an interstage heat exchanger (6), an interstage air-cooled heat exchanger (7), an interstage mixing chamber (8), a first electronic expansion valve (10), a second electronic expansion valve (11), a first solenoid valve (14), a second solenoid valve (15), a third solenoid valve (16), a fourth solenoid valve (17), and refrigerant connecting pipes forming a two-stage compression unit; the connection method of each device in the two-stage compression unit is as follows: the refrigerant pipe at the upper end of the low-pressure compressor (1) is connected to the lower left port of the interstage mixing chamber (8) via the interstage air-cooled heat exchanger (7), and the upper right port of the interstage mixing chamber (8) is connected to the refrigerant pipe at the upper end of the low-pressure compressor (1). The refrigerant line at the port is connected to the high-pressure compressor (2). The refrigerant line at the upper end of the high-pressure compressor (2) is connected to the lower left port of the gas cooler (5). The refrigerant line at the upper left port of the gas cooler (5) is connected to the lower left port of the interstage heat exchanger (6) via the first electronic expansion valve (10). The refrigerant line at the upper left port of the interstage heat exchanger (6) is connected to the upper port of the interstage mixing chamber (8). The refrigerant line at the lower right port of the interstage heat exchanger (6) is connected to the refrigerant line of the gas cooler (5) connected to the first electronic expansion valve (10). The refrigerant line at the upper right port of the interstage heat exchanger (6) is connected to the second electronic expansion valve (11). The refrigerant line on the left side of the second electronic expansion valve (11) is connected to the first solenoid valve (14) and the first evaporator. The refrigerant line of the second evaporator (4) is connected to the lower left end of the low-pressure compressor (1) via the third solenoid valve (16) to the refrigerant line connected to the second electronic expansion valve (11) and the first solenoid valve (14). The refrigerant line of the second evaporator (4) is connected to the lower left end of the low-pressure compressor (1) and the second solenoid valve (15) via the fourth solenoid valve (17). The CO2 two-stage compression cycle refrigerant circuit (A) includes the low-pressure compressor (1), the first evaporator (3), the second evaporator (4), the defrost receiver (9), the third electronic expansion valve (12), the fourth electronic expansion valve (13), the first solenoid valve (14), and the second solenoid valve (15). The interstage defrosting unit is composed of the third solenoid valve (16), the fourth solenoid valve (17), the fifth solenoid valve (18), the sixth solenoid valve (19), the seventh solenoid valve (20), the eighth solenoid valve (21), the ninth solenoid valve (22), and the refrigerant connection pipeline. In the interstage defrosting unit, the second solenoid valve (15), the third solenoid valve (16), the fourth solenoid valve (17), and the fifth solenoid valve (18) are energized and opened, the first solenoid valve (14), the sixth solenoid valve (19), the seventh solenoid valve (20), the eighth solenoid valve (21), and the ninth solenoid valve (22) are not energized and closed, the third electronic expansion valve (12) is energized and opened, and the fourth electronic expansion valve (13) is not energized and closed, thus forming the sensible heat defrosting passage of the first evaporator (3).The connection method of each device in the sensible heat defrosting passage of the first evaporator (3) is as follows: the refrigerant pipeline on the right side of the third electronic expansion valve (12) is connected to the refrigerant pipeline connecting the low-pressure compressor (1) and the interstage air-cooled heat exchanger (7); the refrigerant pipeline on the left side of the third electronic expansion valve (12) is connected to the left side of the first evaporator (3) via the fifth solenoid valve (18); the refrigerant pipeline on the right side of the first evaporator (3) is connected to the lower left end of the low-pressure compressor (1) via the second solenoid valve (15); the third solenoid valve (16), the fourth solenoid valve (17), and the third solenoid valve (18) in the interstage air extraction defrosting unit are connected to the refrigerant pipeline connecting the low-pressure compressor (1) and the interstage air extraction defrosting unit. When the fifth solenoid valve (18), the sixth solenoid valve (19), and the eighth solenoid valve (21) are energized and opened, and the first solenoid valve (14), the second solenoid valve (15), the seventh solenoid valve (20), and the ninth solenoid valve (22) are not energized and closed, and the third electronic expansion valve (12) is not energized and closed, and the fourth electronic expansion valve (13) is energized and opened, a latent heat defrosting passage for the first evaporator (3) is formed; the connection method of each device in the latent heat defrosting passage of the first evaporator (3) is as follows: the refrigerant pipeline on the right side of the sixth solenoid valve (19) is connected to the low-pressure compressor (1) and the interstage air-cooled heat exchanger. On the refrigerant line connected to the heater (7), the refrigerant line on the left side of the sixth solenoid valve (19) is connected to the left side of the first evaporator (3) via the fifth solenoid valve (18). The refrigerant line on the left side of the eighth solenoid valve (21) is connected to the refrigerant line between the first evaporator (3) and the second solenoid valve (15). The refrigerant line on the right side of the fifth solenoid valve (18) is connected to the upper end of the defrost receiver (9). The refrigerant line at the lower end of the defrost receiver (9) is connected to the lower end of the fourth electronic expansion valve (13). The refrigerant line at the upper end of the fourth electronic expansion valve (13) is connected to the second solenoid valve (15). The refrigerant pipeline connected to the sub-expansion valve (11) and the first solenoid valve (14); in the interstage defrosting unit, the first solenoid valve (14), the second solenoid valve (15), the fourth solenoid valve (17), and the seventh solenoid valve (20) are energized and opened, the third solenoid valve (16), the fifth solenoid valve (18), the sixth solenoid valve (19), the eighth solenoid valve (21), and the ninth solenoid valve (22) are not energized and closed, the third electronic expansion valve (12) is energized and opened, and the fourth electronic expansion valve (13) is not energized and closed, thus forming the sensible heat defrosting passage of the second evaporator (4); The connection method of each device in the sensible heat defrosting passage of the second evaporator (4) is as follows: the refrigerant pipeline on the right side of the third electronic expansion valve (12) is connected to the refrigerant pipeline connecting the low-pressure compressor (1) and the interstage air-cooled heat exchanger (7); the refrigerant pipeline on the left side of the third electronic expansion valve (12) is connected to the left side of the second evaporator (4) via the seventh solenoid valve (20); the refrigerant pipeline on the right side of the second evaporator (4) is connected to the lower left end of the low-pressure compressor (1) via the fourth solenoid valve (17); in the interstage air extraction defrosting unit, the first solenoid valve (14), the second solenoid valve (15), the sixth solenoid valve (19), the seventh solenoid valve (20), and the ninth solenoid valve (22) are energized and opened; the third solenoid valve (16), the fourth solenoid valve (17), the fifth solenoid valve (18), and the eighth solenoid valve (21) are not energized and closed; the third electronic expansion valve (12) is not energized and closed; and the fourth electronic expansion valve (13) is energized and opened, thus constituting... The latent heat defrosting passage of the second evaporator (4); the connection method of each device in the sensible heat defrosting passage of the second evaporator (4) is as follows: the refrigerant pipeline on the right side of the sixth solenoid valve (19) is connected to the refrigerant pipeline connected to the low-pressure compressor (1) and the interstage air-cooled heat exchanger (7); the refrigerant pipeline on the left side of the sixth solenoid valve (19) is connected to the left side of the second evaporator (4) via the seventh solenoid valve (20); the refrigerant pipeline on the left side of the ninth solenoid valve (22) is connected to the refrigerant pipeline between the second evaporator (4) and the fourth solenoid valve (17); the refrigerant pipeline on the right side of the ninth solenoid valve (22) is connected to the refrigerant pipeline between the eighth solenoid valve (21) and the defrost receiver (9); the refrigerant pipeline at the lower port of the defrost receiver (9) is connected to the lower end of the fourth electronic expansion valve (13); the refrigerant pipeline at the upper end of the fourth electronic expansion valve (13) is connected to the refrigerant pipeline connected to the second electronic expansion valve (11) and the first solenoid valve (14); In the aforementioned subcooling-heating coupled refrigerant loop (B), a front subcooling heat exchanger (25) is added between the gas cooler (5) and the interstage heat exchanger (6), and a rear subcooling heat exchanger (26) is added between the interstage heat exchanger (6) and the second electronic expansion valve (11); when the tenth solenoid valve (28) is energized and opened, and the eleventh solenoid valve (29) is not energized and closed, a front subcooling unit is formed; the connection method of each device in the front subcooling unit is as follows: the refrigerant pipeline at the lower right port of the front subcooling heat exchanger (25) is connected to the left side of the subcooling-heating compressor (23), the refrigerant pipeline at the upper port of the subcooling-heating compressor (23) is connected to the upper left port of the heat exchanger (24), and the refrigerant pipeline at the upper right port of the heat exchanger (24) is connected to the fifth electronic expansion valve (26). 7) The refrigerant pipeline at the upper end of the fifth electronic expansion valve (27) is connected to the upper right port of the front subcooling heat exchanger (25) via the tenth solenoid valve (28); when the tenth solenoid valve (28) is closed without power and the eleventh solenoid valve (29) is opened with power, the rear subcooling unit is formed; the connection method of each device in the rear subcooling unit is as follows: the refrigerant pipeline at the lower right port of the rear subcooling heat exchanger (26) is connected to the refrigerant pipeline of the front subcooling heat exchanger (25) and the subcooling heating compressor (23); the refrigerant pipeline at the upper right port of the heating heat exchanger (24) is connected to the lower end of the fifth electronic expansion valve (27); the refrigerant pipeline on the right side of the eleventh solenoid valve (29) is connected to the refrigerant pipeline of the fifth electronic expansion valve (27) and the tenth solenoid valve (28); the refrigerant pipeline on the left side of the eleventh solenoid valve (29) is connected to the upper right port of the rear subcooling heat exchanger (26); In the hot water circulation loop (C) described above, when the twelfth solenoid valve (32) is energized and opened, and the thirteenth solenoid valve (33) and the fourteenth solenoid valve (34) are de-energized and closed, a heating series water supply circuit is formed. The connection method of each device in the heating series water supply circuit is as follows: the water connection pipe on the right side of the user heat exchange device (30) is connected to the left side of the water pump (31), the water connection pipe on the right side of the water pump (31) is connected to the lower right port of the heating heat exchanger (24), the water connection pipe on the lower left port of the heating heat exchanger (24) is connected to the upper right port of the gas cooler (5) via the twelfth solenoid valve (32), and the water connection pipe on the lower right port of the gas cooler (5) is connected to the left side of the user heat exchange device (30). When the thirteenth solenoid valve (33) and the fourteenth solenoid valve (34) are energized and opened, and the twelfth solenoid valve (32) is de-energized and closed, a heating series water supply circuit is formed. The connection method of each device in the combined water supply path and the heating parallel water supply path is as follows: the water connection pipe on the right side of the user heat exchange device (30) is connected to the left side of the water pump (31), the water connection pipe on the right side of the water pump (31) is connected to the lower right port of the heating heat exchanger (24), the water connection pipe on the lower left port of the heating heat exchanger (24) is connected to the lower right port of the gas cooler (5) and the connection pipe of the user heat exchange device (30) via the thirteenth solenoid valve (33), the water connection pipe on the right side of the fourteenth solenoid valve (34) is connected to the pipe connecting the water pump (31) and the lower right port of the heating heat exchanger (24), the water connection pipe on the left side of the fourteenth solenoid valve (34) is connected to the pipe between the twelfth solenoid valve (32) and the upper right port of the gas cooler (5), and the water connection pipe on the lower right port of the gas cooler (5) is connected to the left side of the user heat exchange device (30).

2. The high-temperature-range CO2 two-stage compressed air source heat pump system according to claim 1, characterized in that: An interstage air-cooled heat exchanger (7) is added between the low-pressure compressor (1) and the interstage mixing chamber (8) to form an interstage cooling, overheat prevention, and pressure stabilization path.

3. The high-temperature-range CO2 two-stage compressed air source heat pump system according to claim 1, characterized in that, The refrigerant working fluid in the CO2 two-stage compression cycle refrigerant circuit and the subcooling-heating coupled cycle refrigerant circuit is replaced according to the working environment; the working fluid in the hot water supply circuit is replaced according to the working environment and its matching with the subcooling-heating coupled cycle refrigerant circuit.

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