Ultralow-temperature heat pump with oil-free carbon dioxide as refrigerant and refrigerating and heating method of ultralow-temperature heat pump

Abstract

The invention discloses an ultralow-temperature heat pump with oil-free carbon dioxide as a refrigerant and a refrigerating and heating method of the ultralow-temperature heat pump. The heat pump comprises a storage tank, a supercharger, a first air energy main machine, a second air energy main machine and a secondary refrigerant heat exchanger; a second port of the first air energy main machine is connected with the supercharger and the storage tank through a first branch pipeline. A second port of the second air energy main machine is connected with the supercharger and the storage tank through a second branch pipeline. An outlet of the supercharger is connected with the secondary refrigerant heat exchanger and the first air energy main machine. An outlet of the secondary refrigerant heat exchanger is connected with the first air energy main machine, the second air energy main machine and the supercharger. And a first pressure sensor, a second pressure sensor, a third pressure sensor and a fourth pressure sensor are respectively arranged between the secondary refrigerant heat exchanger and the supercharger, between the supercharger and the secondary refrigerant heat exchanger, and between the first branch pipeline and the second branch pipeline. According to the invention, the pressure change in the pipeline can be detected, and the pressure at the corresponding position can be kept stable through adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and in particular to an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant and a cooling and heating method thereof. Background Art

[0002] The main artificial refrigeration methods include phase change refrigeration, gas expansion refrigeration, vortex tube refrigeration, and thermoelectric refrigeration, each with its own unique characteristics. There are two main methods for artificial heating. One is the traditional heat pump method of adding electric auxiliary heating in low-temperature environments, which is energy-inefficient in low-temperature environments. The other is a refrigerant that absorbs low-grade thermal energy from the environment, increases its enthalpy, and vaporizes into a low-temperature gas refrigerant. A booster compressor then isentropically compresses the refrigerant into a refrigerant with high-grade thermal energy. The high-grade refrigerant then releases this heat energy to the refrigerant, raising its temperature. This is called heat pump heating.

[0003] There are also many heat pump (air conditioning) systems for cooling and heating in the prior art, such as an air-energy central air-conditioning refrigerant circulation system and its cooling and heating method disclosed in application publication number CN116772321A, wherein the air-energy central air-conditioning refrigerant circulation system specifically discloses: a storage tank, a booster, a first air-energy evaporator, a second air-energy evaporator and a refrigerant heat exchanger; the first air-energy evaporator and the second air-energy evaporator are located in an air-energy main unit; the outlet of the storage tank is connected to the first port of the first air-energy evaporator, the first port of the second air-energy evaporator and the low-pressure inlet end of the booster through a pipeline; a first reflux pipeline is connected between the second port of the first air-energy evaporator and the first port of the second air-energy evaporator; in the first A second reflux pipe is also connected between the second port of the second air energy evaporator and the first port of the first air energy evaporator; the second port of the first air energy evaporator and the second port of the second air energy evaporator are respectively connected to the low-pressure inlet end of the booster through pipes; the high-pressure outlet end of the booster is respectively connected to the inlet of the storage tank, the inlet of the refrigerant heat exchanger and the second port of the first air energy evaporator through pipes, and a first expansion valve is provided at the inlet of the refrigerant heat exchanger; the first port of the first air energy evaporator is connected to the inlet of the refrigerant heat exchanger through a pipe; the outlet of the refrigerant heat exchanger is respectively connected to the first port of the first air energy evaporator, the first port of the second air energy evaporator and the low-pressure inlet end of the booster through pipes.

[0004] However, the aforementioned air-to-energy central air conditioning refrigerant circulation system still has some drawbacks. For example, pressure fluctuations at the booster inlet can easily affect the stability of the CO2 system during circulation and shorten the booster's service life. Furthermore, CO2 pressure fluctuations at the inlet of the refrigerant heat exchanger can affect the stability of the refrigerant temperature during heat exchange, leading to significant improvements in system stability and refrigerant temperature stability. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant and a cooling and heating method thereof. By arranging a first pressure sensor, a second pressure sensor, a third pressure sensor and a fourth pressure sensor on the corresponding pipeline, the pressure change of carbon dioxide in the pipeline can be detected in real time, so that the quality of carbon dioxide in the system can be adjusted in time through the storage tank in the corresponding heating mode and cooling mode, and the pressure at the booster inlet, the inlet end of the refrigerant heat exchanger and the second port of the first air energy host or the second port of the second air energy host can be maintained at the set value by adjusting the speed of the booster, thereby making the overall operation of the system more stable, the booster life longer, and the temperature of the refrigerant more stable.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] An ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant, comprising a storage tank, a booster, a first air energy main unit, a second air energy main unit and a refrigerant heat exchanger;

[0008] The storage tank is used to store carbon dioxide; the outlet of the storage tank is connected to the inlet of the supercharger through a pipeline, and the inlet is connected to the outlet of the supercharger through a pipeline;

[0009] A first return pipe is connected between the second port of the first air energy host and the first port of the second air energy host; a second return pipe is also connected between the second port of the second air energy host and the first port of the first air energy host;

[0010] The second port of the first air energy main unit is connected to the inlet of the supercharger and the outlet of the storage tank respectively through a first branch pipe; the second port of the second air energy main unit is connected to the inlet of the supercharger and the outlet of the storage tank respectively through a second branch pipe, and the second port of the second air energy main unit is also connected to the inlet of the refrigerant heat exchanger through a pipe;

[0011] The outlet of the booster is connected to the inlet of the refrigerant heat exchanger and the first port of the first air energy host through pipelines; the inlet and outlet of the refrigerant heat exchanger are respectively provided with an expansion valve for use in cooling mode and a proportional valve for use in heating mode; the gaseous carbon dioxide is converted into supercritical high-temperature superfluid carbon dioxide after being pressurized by the booster; in cooling mode, the high-temperature superfluid carbon dioxide can be sequentially input into the first air energy host and the second air energy host to cool down and become superfluid carbon dioxide at room temperature; in heating mode, the high-temperature superfluid carbon dioxide can be input into the refrigerant heat exchanger to release heat;

[0012] The outlet of the refrigerant heat exchanger is connected to the first port of the first air energy host, the first port of the second air energy host and the inlet of the supercharger through pipelines respectively; in the cooling mode, the superfluid carbon dioxide at room temperature is throttled and expanded by the expansion valve to become low-temperature carbon dioxide, and the low-temperature carbon dioxide absorbs the heat of the refrigerant in the refrigerant heat exchanger to become gaseous carbon dioxide and then input into the inlet of the supercharger to realize circulation; in the heating mode, the high-temperature superfluid carbon dioxide releases heat to the refrigerant in the refrigerant heat exchanger and can be input into the first air energy host or the second air energy host and switch after running for a certain period of time, and the air entering first The fan of one air energy host is in a closed state and the fan of another air energy host is in an open state, or high-temperature superfluid carbon dioxide can be simultaneously input into the first air energy host and the second air energy host after releasing heat to the refrigerant in the refrigerant heat exchanger; when the fan of the first air energy host or the second air energy host is in a closed state, carbon dioxide can be used to defrost the surface of the heat exchanger; when the fan of the first air energy host or the second air energy host is in an open state, carbon dioxide is reduced in pressure and cooled to below the ambient temperature, and then absorbs heat from the air and heats up to become gaseous carbon dioxide, which is input into the inlet of the booster to realize circulation;

[0013] A first pressure sensor is provided on the pipeline between the outlet of the refrigerant heat exchanger and the inlet of the booster, so as to measure the carbon dioxide pressure at the inlet of the booster in the cooling mode;

[0014] A second pressure sensor is provided on the pipeline between the outlet of the booster and the inlet of the brine heat exchanger, for measuring the carbon dioxide pressure at the inlet of the brine heat exchanger;

[0015] A third pressure sensor is provided on the first branch pipe for measuring the carbon dioxide pressure of the second port of the first air energy host in heating mode;

[0016] A fourth pressure sensor is provided on the second branch pipe for measuring the carbon dioxide pressure of the second port of the second air energy host in heating mode.

[0017] The following technical solutions are also included:

[0018] Furthermore, a first electric ball valve and a second electric ball valve are respectively provided at the inlet and outlet of the storage tank to control the mass flow of carbon dioxide, while maintaining the carbon dioxide pressure at the inlet of the booster at a set value and maintaining the carbon dioxide pressure at the inlet of the refrigerant heat exchanger at a set value.

[0019] Furthermore, in the heating mode, the carbon dioxide pressure setting value at the inlet of the booster is between 0.5 MPa and 4 MPa, and the carbon dioxide pressure setting value at the inlet of the refrigerant heat exchanger is between 7.5 MPa and 13 MPa; in the cooling mode, the carbon dioxide pressure setting value at the inlet of the booster is between 0.5 MPa and 5.5 MPa, and the carbon dioxide pressure setting value at the inlet of the refrigerant heat exchanger is between 7.5 MPa and 13 MPa.

[0020] Furthermore, a third electric ball valve is provided on the first branch pipe; a fourth electric ball valve is also provided on the second branch pipe; a fifth electric ball valve and a sixth electric ball valve are provided on the first return pipe and the second return pipe, respectively; a seventh electric ball valve is provided on the pipe between the outlet of the booster and the inlet of the refrigerant heat exchanger; an eighth electric ball valve is provided on the pipe between the outlet of the refrigerant heat exchanger and the first port of the first air energy host; a ninth electric ball valve is provided on the pipe between the outlet of the refrigerant heat exchanger and the first port of the second air energy host; a tenth electric ball valve is provided on the pipe between the outlet of the refrigerant heat exchanger and the inlet of the booster; an eleventh electric ball valve is provided on the pipe between the outlet of the booster and the first port of the first air energy host; and a twelfth electric ball valve is provided on the pipe between the second port of the second air energy host and the inlet of the refrigerant heat exchanger.

[0021] Furthermore, the number of the brine heat exchanger is one or at least two arranged in parallel; the expansion valve and the proportional valve are correspondingly arranged at the inlet and outlet of each brine heat exchanger.

[0022] Furthermore, the carbon dioxide stored in the storage tank is pure carbon dioxide without additives.

[0023] The present invention also provides a cooling and heating method using an ultra-low temperature heat pump with oil-free carbon dioxide as a refrigerant, which uses the ultra-low temperature heat pump with oil-free carbon dioxide as a refrigerant and comprises the following steps:

[0024] (1) Startup mode:

[0025] S101, the refrigerant heat exchanger is closed, and the booster is set to a fixed speed;

[0026] S102. During the startup mode operation, when the carbon dioxide pressure sensed by the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor is lower than a set value, the first electric ball valve is opened and the carbon dioxide in the storage tank is input to the inlet of the booster; when the carbon dioxide pressure sensed by the second pressure sensor is higher than the set value, the second electric ball valve is opened and the carbon dioxide is recovered from the storage tank; when the carbon dioxide pressure sensed by the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor reaches the set value, the startup mode is completed, i.e., carbon dioxide refrigerant balance is achieved; the first electric ball valve and the second electric ball valve are closed;

[0027] S103, after the start-up mode is completed, the refrigerant heat exchanger starts the cooling mode or the heating mode;

[0028] (2) Refrigeration mode:

[0029] S201, the fans of the first air energy unit and the second air energy unit are both in the on state. After passing through the supercharger, the carbon dioxide is converted into high-temperature superfluid carbon dioxide. The high-temperature superfluid carbon dioxide first enters the first air energy unit and the second air energy unit in sequence, and is converted into normal-temperature superfluid carbon dioxide by releasing heat to the ambient air. The normal-temperature superfluid carbon dioxide is output from the second port of the second air energy unit, passes through the second pressure sensor and is throttled and expanded by the expansion valve and cooled before entering the refrigerant heat exchanger;

[0030] S202: The cooled carbon dioxide enters the refrigerant heat exchanger, absorbs heat from the refrigerant through the outer surface of the refrigerant heat exchanger, and heats up to become gaseous carbon dioxide. The refrigerant releases heat to the carbon dioxide, thereby cooling the refrigerant.

[0031] S203, the gaseous carbon dioxide discharged from the refrigerant heat exchanger is input to the inlet of the supercharger through the first pressure sensor, and is pressurized by the supercharger to become high-temperature superfluid carbon dioxide, thereby realizing a carbon dioxide refrigeration cycle;

[0032] S204: During the carbon dioxide refrigeration cycle, the carbon dioxide pressure sensed by the first pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the first electric ball valve; the carbon dioxide pressure sensed by the second pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the second electric ball valve;

[0033] S205, repeat the above steps S201-S204;

[0034] (2) Heating mode:

[0035] S301: The carbon dioxide after passing through the supercharger is converted into high-temperature superfluid carbon dioxide, which enters the brine heat exchanger through the expansion valve. The high-temperature superfluid carbon dioxide releases heat to the brine through the surface of the brine heat exchanger in the brine heat exchanger, thereby heating the brine.

[0036] S302: When the ambient temperature is greater than 2°C, the carbon dioxide that has released heat in the refrigerant heat exchanger enters the first air energy unit and the second air energy unit at the same time. After the pressure and temperature of the first and second air energy units are reduced, they absorb heat from the air and become gaseous carbon dioxide. The carbon dioxide then passes through the third and fourth pressure sensors and enters the inlet of the supercharger to complete the cycle.

[0037] S303. When the ambient temperature is lower than 2°C, the carbon dioxide that has released heat in the refrigerant heat exchanger enters the first air energy unit and the second air energy unit or the second air energy unit and the first air energy unit in sequence. The waste heat of the carbon dioxide can be used to defrost the evaporator of the first air energy unit that enters first, and the fan of the air energy unit is in the off state at this time. Then, after flowing into the second air energy unit, the carbon dioxide is reduced in pressure to become carbon dioxide below the ambient temperature. Then, the carbon dioxide absorbs the heat of the air in the air energy unit and becomes gaseous carbon dioxide. At this time, the fan of the second air energy unit is in the on state. Then, the gaseous carbon dioxide is discharged and enters the inlet of the booster after passing through the third pressure sensor or the fourth pressure sensor accordingly.

[0038] After running for a period of time, the carbon dioxide that has released heat in the refrigerant heat exchanger switches its entry order into the two air energy hosts, and the on and off modes of the fans of the two air energy hosts are also switched accordingly;

[0039] S304: During the carbon dioxide heating cycle, the carbon dioxide pressure sensed by the third pressure sensor or the fourth pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the first electric ball valve; the carbon dioxide pressure sensed by the second pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the second electric ball valve;

[0040] S305. Repeat the above steps S301-S304.

[0041] Furthermore, in step S201 of the cooling mode, the flow of the superfluid carbon dioxide in the refrigerant heat exchanger can be controlled by adjusting the expansion valve; in step S301 of the heating mode, the flow of the superfluid carbon dioxide entering the refrigerant heat exchanger can be controlled by adjusting the proportional valve.

[0042] The beneficial effects of the present invention are:

[0043] (1) The carbon dioxide refrigerant in the present invention is a supercritical fluid before entering the inlet of the refrigerant heat exchanger, which can greatly reduce the friction resistance when the high-pressure carbon dioxide flows, thereby effectively reducing the energy consumption of the supercharger.

[0044] (2) The present invention can instantly detect the pressure change of carbon dioxide in the pipeline by arranging the first pressure sensor, the second pressure sensor, the third pressure sensor and the fourth pressure sensor on the corresponding pipeline, so that the quality of carbon dioxide in the system can be timely adjusted through the storage tank in the corresponding heating mode and cooling mode, and the pressure at the booster inlet, the inlet end of the refrigerant heat exchanger and the second port of the first air energy host or the second port of the second air energy host can be maintained at the set value by adjusting the speed of the booster, thereby making the overall operation of the system more stable, the life of the booster longer, and the temperature of the refrigerant more stable.

[0045] (3) In heating mode, the present invention employs a series-connected dual air-energy unit structure. During operation, one air-energy unit uses the waste heat of the carbon dioxide refrigerant for defrosting, while the other air-energy unit absorbs heat from the air to increase the enthalpy of the carbon dioxide refrigerant and vaporize it. After a period of operation, the order in which the carbon dioxide flows into the two air-energy units is switched, ensuring that one air-energy unit in the system is always in a heating state, absorbing heat from the air. Because this ensures that one air-energy unit is always in normal heating operation, the normal operation of the heating function can be guaranteed while defrosting, and the system will not stop heating during defrosting, thereby improving the thermal stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the framework of an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant according to the present invention;

[0047] Figure 2 This is a schematic diagram of the operation principle of an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant in cooling mode according to the present invention;

[0048] Figure 3 This is a first operating principle diagram of an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant in a heating mode according to the present invention;

[0049] Figure 4 yes Figure 3 The operating principle diagram after switching the modes of the two air energy hosts.

[0050] Reference numerals:

[0051] 1. Storage tank; 2. Booster; 3. First air energy main unit; 31. First port of the first air energy main unit; 32. Second port of the first air energy main unit; 4. Second air energy main unit; 41. First port of the second air energy main unit; 42. Second port of the second air energy main unit; 5. Refrigerant heat exchanger; 6. First return pipe; 7. Second return pipe; 8. Expansion valve; 9. Proportional valve; 10. First pressure sensor; 11. Second pressure sensor; 12. Third pressure sensor; 13. Fourth pressure sensor; 14. First electric ball valve; 15. Second electric ball valve; 16. Third electric ball valve; 17. Fourth electric ball valve; 18. Fifth electric ball valve; 19. Sixth electric ball valve; 20. Seventh electric ball valve; 21. Eighth electric ball valve; 22. Ninth electric ball valve; 23. Tenth electric ball valve; 24. Eleventh electric ball valve; 25. Twelfth electric ball valve; 26. First branch pipeline; 27. Second branch pipeline. DETAILED DESCRIPTION

[0052] The invention will be further described below with reference to the accompanying drawings and specific embodiments. The following description is merely illustrative and does not limit the scope of protection of the invention.

[0053] Example 1:

[0054] refer to Figure 1 , an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant, comprising: a storage tank 1, a booster 2, a first air energy main unit 3, a second air energy main unit 4 and a refrigerant heat exchanger 5.

[0055] The storage tank 1 is used to store carbon dioxide and provide carbon dioxide refrigerant for the heat pump. Moreover, the refrigerant described below is illustrated using carbon dioxide as an example. In this heat pump, the two air energy main units serve as the outdoor unit, while the refrigerant heat exchanger 5 serves as the indoor unit. The first air energy main unit 3 and the second air energy main unit 4 each include a fan with adjustable air volume, and the air energy main units are also correspondingly equipped with an ambient air temperature probe, a refrigerant pressure sensor, a refrigerant temperature sensor, etc. However, since these are all existing technologies, they will not be elaborated here.

[0056] The brine heat exchanger 5 is equipped with a heat exchanger, a pressure sensor, a temperature sensor, etc. The brine transfers heat and cold with the refrigerant through the tube wall of the heat exchanger. The inlet and outlet of the booster 2 are also equipped with pressure sensors.

[0057] Carbon dioxide is an emerging natural working fluid. In terms of its impact on the environment, it is the most environmentally friendly cooling and heating working fluid besides water and air. In addition, carbon dioxide also has excellent safety and chemical stability.

[0058] The outlet of the storage tank 1 is connected to the inlet of the booster 2 through a pipeline, and the inlet is connected to the outlet of the booster 2 through a pipeline for outputting carbon dioxide.

[0059] A first return pipe 6 is connected between the second port 32 of the first air energy unit and the first port 41 of the second air energy unit for conveying the carbon dioxide outputted by the first air energy unit 3 to the second air energy unit 4. A second return pipe 7 is connected between the second port 42 of the second air energy unit and the first port 31 of the first air energy unit for conveying the carbon dioxide outputted by the second air energy unit 4 to the first air energy unit 3. Therefore, the provision of the first return pipe 6 and the second return pipe 7 is mainly used for the mutual flow of carbon dioxide between the two air energy units, so that the waste heat of the carbon dioxide can be used to defrost the air energy unit that enters first.

[0060] The second port 32 of the first air energy unit is connected to the inlet of the booster 2 and the outlet of the storage tank 1 via the first branch pipe 26. The second port 42 of the second air energy unit is connected to the inlet of the booster 2 and the outlet of the storage tank 1 via the second branch pipe 27. The second port 42 of the second air energy unit is also connected to the inlet of the refrigerant heat exchanger 5 via a pipe. Therefore, with the above arrangement, carbon dioxide can be input into the booster 2, the storage tank 1, and the refrigerant heat exchanger 5 respectively.

[0061] The outlet of the booster 2 is connected to the inlet of the refrigerant heat exchanger 5 and the first port 31 of the first air energy unit via pipes. The inlet and outlet of the refrigerant heat exchanger 5 are respectively provided with an expansion valve 8 for use in cooling mode and a proportional valve 9 for use in heating mode. After being pressurized by the booster 2, the gaseous carbon dioxide is converted into supercritical, high-temperature superfluid carbon dioxide. In cooling mode, the high-temperature superfluid carbon dioxide can be sequentially fed into the first and second air energy units 3 and 5 to cool down and become superfluid carbon dioxide at room temperature. In heating mode, the high-temperature superfluid carbon dioxide can be fed into the refrigerant heat exchanger 5 via the expansion valve 8 to release heat. Therefore, the carbon dioxide output routes of the booster 2 are different in different modes.

[0062] The outlet of the refrigerant heat exchanger 5 is connected to the first port 31 of the first air energy host, the first port 41 of the second air energy host and the inlet of the supercharger 2 through pipelines respectively; in the cooling mode, the superfluid carbon dioxide at room temperature is throttled and expanded by the expansion valve 8 to become low-temperature carbon dioxide, and the low-temperature carbon dioxide absorbs the heat of the refrigerant in the refrigerant heat exchanger 5 to become gaseous carbon dioxide and then input to the inlet of the supercharger 2, thereby realizing the cycle; in the heating mode, the high-temperature superfluid carbon dioxide releases heat to the refrigerant in the refrigerant heat exchanger 5 and can be input to the first air energy host 3 or the second air energy host. The air energy host 4 is switched after running for a certain period of time, and the fan of the air energy host that enters first is in the closed state, while the fan of the other air energy host is in the open state; when the fan of the first air energy host 3 or the second air energy host 4 is in the closed state, the carbon dioxide can use the waste heat to defrost the surface of the heat exchanger. When the fan of the first air energy host or the second air energy host 4 is in the open state, the carbon dioxide is depressurized and cooled to below the ambient temperature, and then absorbs heat from the air and heats up to become gaseous carbon dioxide. The gaseous carbon dioxide is input to the inlet of the booster 2 to realize circulation;

[0063] Therefore, the output carbon dioxide can be input into two air energy hosts. The input order of the two air energy hosts will not be limited in the heating mode. It is only necessary to ensure that the carbon dioxide is input into the two air energy hosts in sequence and the fan of the air energy host that is input first is turned off and the fan of the other air energy host is turned on.

[0064] A first pressure sensor 10 is provided on the pipe between the outlet of the refrigerant heat exchanger 5 and the inlet of the booster 2, for measuring the carbon dioxide pressure at the inlet of the booster 2 in the cooling mode; a second pressure sensor 11 is provided on the pipe between the outlet of the booster 2 and the inlet of the refrigerant heat exchanger 5, for measuring the carbon dioxide pressure at the inlet of the refrigerant heat exchanger 5; a third pressure sensor 12 is provided on the first branch pipe 26, for measuring the carbon dioxide pressure of the second port 32 of the first air energy host in the heating mode; a fourth pressure sensor 13 is provided on the second branch pipe 27, for measuring the carbon dioxide pressure of the second port 42 of the second air energy host in the heating mode.

[0065] Preferably, a first electric ball valve 14 and a second electric ball valve 15 are respectively provided at the inlet and outlet of the storage tank 1 to control the mass flow rate of carbon dioxide, while maintaining the carbon dioxide pressure at the inlet of the stable booster 2 at a set value, and maintaining the carbon dioxide pressure at the inlet of the refrigerant heat exchanger 5 at a set value.

[0066] In heating mode, the carbon dioxide pressure setting value at the inlet of the booster 2 is between 0.5MPa and 4MPa, and the carbon dioxide pressure setting value at the inlet of the refrigerant heat exchanger 5 is between 7.5MPa and 13MPa; in cooling mode, the carbon dioxide pressure setting value at the inlet of the booster 2 is between 0.5MPa and 5.5MPa, and the carbon dioxide pressure setting value at the inlet of the refrigerant heat exchanger 5 is between 7.5MPa and 13MPa.

[0067] A third electric ball valve 16 is also provided on the first branch pipe 26 .

[0068] A fourth electric ball valve 17 is also provided on the second branch pipe 27 .

[0069] A fifth electric ball valve 18 and a sixth electric ball valve 19 are respectively provided on the first return pipe 6 and the second return pipe 7; in heating mode, carbon dioxide can enter the second air energy host 4 after passing through the first air energy host 3 and the fifth electric ball valve 18, or can enter the first air energy host 3 after passing through the second air energy host 4 and the sixth electric ball valve 19; in cooling mode, the refrigerant can enter the second air energy host 4 after passing through the first air energy host 3 and the fifth electric ball valve 18.

[0070] A seventh electric ball valve 20 is provided on the pipe between the outlet of the supercharger 2 and the inlet of the brine heat exchanger 5 .

[0071] An eighth electric ball valve 21 is provided on the pipe between the outlet of the refrigerant heat exchanger 5 and the first port 31 of the first air energy main unit; a ninth electric ball valve 22 is provided on the pipe between the outlet of the refrigerant heat exchanger 5 and the first port 41 of the second air energy main unit; and a tenth electric ball valve 23 is provided on the pipe between the outlet of the refrigerant heat exchanger 5 and the inlet of the booster 2.

[0072] An eleventh electric ball valve 24 is provided on the pipeline between the outlet of the supercharger 2 and the first port 31 of the first air energy main unit.

[0073] A twelfth electric ball valve 25 is provided on the pipeline between the second port 42 of the second air energy main unit and the inlet of the refrigerant heat exchanger 5 .

[0074] It can be seen that each of the above-mentioned electric ball valves can control the switches on the corresponding pipelines accordingly.

[0075] Preferably, the number of refrigerant heat exchangers 5 can be one or at least two arranged in parallel, that is, the number of refrigerant heat exchangers 5 can be one, two, three or four, etc., and the refrigerant heat exchangers 5 are arranged in parallel so that people can increase or decrease the number of refrigerant heat exchangers 5 at any time to increase or decrease the cooling capacity or heating capacity.

[0076] In this embodiment, the number of the brine heat exchangers 5 is selected to be two.

[0077] In order to prevent the refrigerant from flowing back and affecting the operation, the ultra-low temperature heat pump with oil-free carbon dioxide as the refrigerant is also provided with a one-way valve (not marked in the figure), which is specifically set at the inlet of the storage tank 1 and the outlet of the booster 2. For details, please refer to Figure 1 The positions shown are not described in detail here.

[0078] In this application, the carbon dioxide stored in the storage tank 1 is pure carbon dioxide without additives, so that the carbon dioxide circulation system will not be affected by the carbonization of additives at high temperatures and affect the stability of the heat pump, and solve various faults caused by poor oil return of oil-containing refrigerants.

[0079] Regarding the use of refrigerant, the refrigerant on the refrigerant heat exchanger 5 can be a gaseous refrigerant or a liquid refrigerant, for example: the gaseous refrigerant is air, nitrogen or argon, and the liquid refrigerant is water, salt water, ethylene glycol or propylene glycol solution.

[0080] Example 2:

[0081] refer to Figure 2-Figure 4 The present invention also provides a cooling and heating method using an ultra-low temperature heat pump with oil-free carbon dioxide as a refrigerant, which uses the ultra-low temperature heat pump with oil-free carbon dioxide as a refrigerant, comprising the following steps:

[0082] (1) Startup mode:

[0083] S101, the refrigerant heat exchanger 5 is closed, and the booster 2 is set to a fixed speed;

[0084] S102. During the startup mode operation, when the carbon dioxide pressure sensed by the first pressure sensor 10, the second pressure sensor 11, the third pressure sensor 12, and the fourth pressure sensor 13 is lower than a set value, the first electric ball valve 14 is opened and the carbon dioxide in the storage tank 1 is input to the inlet of the booster 2. When the carbon dioxide pressure sensed by the second pressure sensor 11 is higher than the set value, the second electric ball valve 15 is opened and the carbon dioxide is recovered from the storage tank 1. When the carbon dioxide pressure sensed by the first pressure sensor 10, the second pressure sensor 11, the third pressure sensor 12, and the fourth pressure sensor 13 reaches the set value, the startup mode is completed, i.e., carbon dioxide refrigerant balance is achieved. The first electric ball valve 14 and the second electric ball valve 15 are closed.

[0085] S103, after the start-up mode is completed, the refrigerant heat exchanger 5 starts the cooling mode or the heating mode;

[0086] (2) Refrigeration mode:

[0087] like Figure 2 As shown, S201, the fan of the first air energy host 3 and the fan in the second air energy host 4 are all in the open state. In addition, after being pressurized by the supercharger 2, the carbon dioxide is converted into high-temperature superfluid carbon dioxide. The high-temperature superfluid carbon dioxide first enters the first air energy host 3 and the second air energy host 4 in sequence, and is converted into superfluid carbon dioxide at room temperature by releasing heat to the ambient air. The superfluid carbon dioxide at room temperature is output from the second port 42 of the second air energy host, passes through the second pressure sensor 11 and the expansion valve 8, and is throttled, expanded, and cooled before entering the refrigerant heat exchanger 5; therefore, at this time, the eleventh electric ball valve 24, the fifth electric ball valve 18, and the twelfth electric ball valve 25 are open;

[0088] S202: The cooled carbon dioxide enters the refrigerant heat exchanger 5, absorbs the heat of the refrigerant through the outer surface of the refrigerant heat exchanger 5, and heats up to become gaseous carbon dioxide. The refrigerant releases heat to the carbon dioxide, thereby cooling the refrigerant.

[0089] S203: The gaseous carbon dioxide discharged from the refrigerant heat exchanger 5 is input to the inlet of the supercharger 2 via the first pressure sensor 10 and pressurized by the supercharger 2 to become high-temperature superfluid carbon dioxide, thereby completing the carbon dioxide refrigeration cycle; therefore, the tenth electric ball valve 23 is open at this time;

[0090] S204: During the carbon dioxide refrigeration cycle, the carbon dioxide pressure sensed by the first pressure sensor 10 can be maintained at a set value by adjusting the speed of the booster 2 or adjusting the first electric ball valve 14; the carbon dioxide pressure sensed by the second pressure sensor 11 can be maintained at a set value by adjusting the speed of the booster 2 or the second electric ball valve 15;

[0091] S205, repeat the above steps S201-S204;

[0092] (3) Heating mode:

[0093] S301: After passing through the booster 2, the carbon dioxide is converted into high-temperature superfluid carbon dioxide and enters the brine heat exchanger 5 through the expansion valve 8. The high-temperature superfluid carbon dioxide releases heat to the brine through the surface of the brine heat exchanger 5, thereby heating the brine.

[0094] S302, when the ambient temperature is greater than 2°C, the carbon dioxide that has released heat in the refrigerant heat exchanger 5 enters the first air energy host 3 and the second air energy host 4 at the same time, and after the pressure and temperature of the first air energy host 3 and the second air energy host 4 are reduced, they absorb heat in the air and become gaseous carbon dioxide, which then passes through the third pressure sensor 12 and the fourth pressure sensor 13 respectively and enters the inlet of the supercharger 2 to complete the cycle;

[0095] S303, such as Figure 3 and Figure 4 As shown, when the ambient temperature is lower than 2°C, the carbon dioxide that has released heat in the refrigerant heat exchanger 5 enters the first air energy unit 3 and the second air energy unit 4 or the second air energy unit 4 and the first air energy unit 3 in sequence (specifically, this is achieved through the first return pipe 6 with the fifth electric ball valve 18 and the second return pipe 7 with the sixth electric ball valve 19). In the first air energy unit that enters first, the waste heat of the carbon dioxide can be used to defrost its evaporator, and at this time, the fan of the air energy unit is in the closed state. Then, after flowing into the second air energy unit, the carbon dioxide is depressurized to become carbon dioxide below the ambient temperature. Then, the carbon dioxide absorbs the heat of the air in the air energy unit and becomes gaseous carbon dioxide. At this time, the fan of the second air energy unit is in the open state. Then, the gaseous carbon dioxide is discharged and enters the inlet of the booster 2 after passing through the third pressure sensor 12 or the fourth pressure sensor 13 respectively. Of course, according to the flow direction of the carbon dioxide, the fourth electric ball valve 17 and the third electric ball valve 16 need to be opened accordingly.

[0096] After running for a period of time, for example, after the air energy host has been used for 20 minutes to 120 minutes, the carbon dioxide that has completed heat release in the refrigerant heat exchanger 5 switches the order of entry into the two air energy hosts, and the on and off modes of the fans of the two air energy hosts are also switched accordingly; that is, if the carbon dioxide first enters the first air energy host 3 and the second air energy host 4 in sequence, then the fan of the first air energy host 3 is turned off and the fan of the second air energy host 4 is turned on. After running for a period of time, the carbon dioxide needs to be switched to the order of entering the second air energy host 4 and the first air energy host 3 in sequence. At this time, the fan of the first air energy host 3 is turned on and the fan of the second air energy host 4 is turned off, thereby realizing the functional switching of defrosting and heat absorption and gasification, ensuring that the two air energy hosts can obtain effective defrosting effect, and the heating capacity remains stable during defrosting;

[0097] S304. During the heating cycle of carbon dioxide, the carbon dioxide pressure sensed by the third pressure sensor 12 or the fourth pressure sensor 13 can be maintained at a set value by adjusting the speed of the supercharger 2 or adjusting the first electric ball valve 14; the carbon dioxide pressure sensed by the second pressure sensor 11 can be maintained at a set value by adjusting the speed of the supercharger 2 or adjusting the second electric ball valve 15. Specifically, when carbon dioxide passes through the third pressure sensor 12, the carbon dioxide pressure sensed by the third pressure sensor 12 can be maintained at a set value by adjusting the speed of the supercharger 2 or adjusting the first electric ball valve 14. Similarly, when carbon dioxide passes through the fourth pressure sensor 13, the carbon dioxide pressure sensed by the fourth pressure sensor 13 can be maintained at a set value by adjusting the speed of the supercharger 2 or adjusting the first electric ball valve 14.

[0098] S305. Repeat the above steps S301-S304.

[0099] More specifically, adjusting the rotation speed of the booster 2 as described above can correspondingly increase or decrease the circulation volume of the refrigerant, while adjusting the first electric ball valve 15 and the second electric ball valve 16 can correspondingly output and recover carbon dioxide.

[0100] In addition, in step S201 of the cooling mode, the flow rate of the superfluid carbon dioxide in the refrigerant heat exchanger 5 can be controlled by adjusting the expansion valve 8; in step S301 of the heating mode, the flow rate of the superfluid carbon dioxide entering the refrigerant heat exchanger 5 can be controlled by adjusting the proportional valve 9.

[0101] It can be seen that for the switching use of each electric ball valve mentioned above, during operation, when the corresponding pipeline is needed, the electric ball valve on the pipeline is opened, and other electric ball valves that are not needed are closed accordingly to avoid affecting the circulation of carbon dioxide. In addition, the use of each valve has been partially reflected in the above description, and no further details will be given here.

[0102] To sum up, the present invention can instantly detect the pressure changes of carbon dioxide in the pipeline by arranging the first pressure sensor 10, the second pressure sensor 11, the third pressure sensor 12 and the fourth pressure sensor 13 on the corresponding pipeline, so that the quality of carbon dioxide in the system can be timely adjusted through the storage tank 1 in the corresponding heating mode and cooling mode, and the pressure at the inlet of the booster 2, the inlet end of the refrigerant heat exchanger 5 and the second port 31 of the first air energy host or the second port 44 of the second air energy host can be maintained at the set value by adjusting the speed of the booster 2, thereby making the overall operation of the system more stable, the life of the booster 2 longer, and the temperature of the refrigerant more stable.

[0103] The present invention is not limited to the above-mentioned embodiments. If various changes or modifications of the present invention do not depart from the spirit and scope of the present invention, and if these changes and modifications fall within the scope of the claims of the present invention and equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. An ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant, characterized by: It includes a storage tank, a booster, a first air energy main unit, a second air energy main unit and a refrigerant heat exchanger; The storage tank is used to store carbon dioxide; the outlet of the storage tank is connected to the inlet of the supercharger through a pipeline, and the inlet is connected to the outlet of the supercharger through a pipeline; A first return pipe is connected between the second port of the first air energy host and the first port of the second air energy host; a second return pipe is also connected between the second port of the second air energy host and the first port of the first air energy host; The second port of the first air energy main unit is connected to the inlet of the supercharger and the outlet of the storage tank respectively through a first branch pipe; the second port of the second air energy main unit is connected to the inlet of the supercharger and the outlet of the storage tank respectively through a second branch pipe, and the second port of the second air energy main unit is also connected to the inlet of the refrigerant heat exchanger through a pipe; The outlet of the booster is connected to the inlet of the refrigerant heat exchanger and the first port of the first air energy host through pipelines; the inlet and outlet of the refrigerant heat exchanger are respectively provided with an expansion valve for use in cooling mode and a proportional valve for use in heating mode; the gaseous carbon dioxide is converted into supercritical high-temperature superfluid carbon dioxide after being pressurized by the booster; in cooling mode, the high-temperature superfluid carbon dioxide can be sequentially input into the first air energy host and the second air energy host to cool down and become superfluid carbon dioxide at room temperature; in heating mode, the high-temperature superfluid carbon dioxide can be input into the refrigerant heat exchanger to release heat; The outlet of the refrigerant heat exchanger is connected to the first port of the first air energy host, the first port of the second air energy host and the inlet of the supercharger through pipelines respectively; in the cooling mode, the superfluid carbon dioxide at room temperature is throttled and expanded by the expansion valve to become low-temperature carbon dioxide, and the low-temperature carbon dioxide absorbs the heat of the refrigerant in the refrigerant heat exchanger to become gaseous carbon dioxide and then input into the inlet of the supercharger to realize circulation; in the heating mode, the high-temperature superfluid carbon dioxide releases heat to the refrigerant in the refrigerant heat exchanger and can be input into the first air energy host or the second air energy host and switch after running for a certain period of time, and the air entering first The fan of one air energy host is in a closed state and the fan of another air energy host is in an open state, or high-temperature superfluid carbon dioxide can be simultaneously input into the first air energy host and the second air energy host after releasing heat to the refrigerant in the refrigerant heat exchanger; when the fan of the first air energy host or the second air energy host is in a closed state, carbon dioxide can be used to defrost the surface of the heat exchanger; when the fan of the first air energy host or the second air energy host is in an open state, carbon dioxide is reduced in pressure and cooled to below the ambient temperature, and then absorbs heat from the air and heats up to become gaseous carbon dioxide, which is input into the inlet of the booster to realize circulation; A first pressure sensor is provided on the pipeline between the outlet of the refrigerant heat exchanger and the inlet of the booster, so as to measure the carbon dioxide pressure at the inlet of the booster in the cooling mode; A second pressure sensor is provided on the pipeline between the outlet of the booster and the inlet of the brine heat exchanger, for measuring the carbon dioxide pressure at the inlet of the brine heat exchanger; A third pressure sensor is provided on the first branch pipe for measuring the carbon dioxide pressure of the second port of the first air energy host in heating mode; A fourth pressure sensor is provided on the second branch pipe for measuring the carbon dioxide pressure of the second port of the second air energy host in heating mode.

2. The ultra-low temperature heat pump using oil-free carbon dioxide as refrigerant according to claim 1, characterized in that: A first electric ball valve and a second electric ball valve are respectively provided at the inlet and outlet of the storage tank to control the mass flow of carbon dioxide, while maintaining the carbon dioxide pressure at the inlet of the booster at a set value and maintaining the carbon dioxide pressure at the inlet of the refrigerant heat exchanger at a set value.

3. The ultra-low temperature heat pump using oil-free carbon dioxide as refrigerant according to claim 2, characterized in that: In the heating mode, the carbon dioxide pressure setting value at the inlet of the booster is between 0.5MPa and 4MPa, and the carbon dioxide pressure setting value at the inlet of the refrigerant heat exchanger is between 7.5MPa and 13MPa; in the cooling mode, the carbon dioxide pressure setting value at the inlet of the booster is between 0.5MPa and 5.5MPa, and the carbon dioxide pressure setting value at the inlet of the refrigerant heat exchanger is between 7.5MPa and 13MPa.

4. The ultra-low temperature heat pump using oil-free carbon dioxide as refrigerant according to claim 2, characterized in that: A third electric ball valve is also provided on the first pipeline; A fourth electric ball valve is also provided on the second pipeline; A fifth electric ball valve and a sixth electric ball valve are respectively provided on the first return pipe and the second return pipe; A seventh electric ball valve is provided on the pipeline between the outlet of the supercharger and the inlet of the refrigerant heat exchanger; An eighth electric ball valve is provided on the pipeline between the outlet of the refrigerant heat exchanger and the first port of the first air energy host; A ninth electric ball valve is provided on the pipeline between the outlet of the refrigerant heat exchanger and the first port of the second air energy host; A tenth electric ball valve is provided on the pipeline between the outlet of the refrigerant heat exchanger and the inlet of the supercharger; An eleventh electric ball valve is provided on the pipeline between the outlet of the supercharger and the first port of the first air energy host; A twelfth electric ball valve is provided on the pipeline between the second port of the second air energy main unit and the inlet of the refrigerant heat exchanger.

5. The ultra-low temperature heat pump using oil-free carbon dioxide as refrigerant according to claim 1, characterized in that: The number of the brine heat exchanger is one or at least two arranged in parallel; the expansion valve and the proportional valve are correspondingly arranged at the inlet and outlet of each brine heat exchanger.

6. The ultra-low temperature heat pump using oil-free carbon dioxide as refrigerant according to claim 1, characterized in that: The carbon dioxide stored in the storage tank is pure carbon dioxide without additives.

7. A cooling and heating method of an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant, characterized in that: The ultra-low temperature heat pump using the oil-free carbon dioxide as a refrigerant as claimed in claim 2 comprises the following steps: (1) Startup mode: S101, the refrigerant heat exchanger is closed, and the booster is set to a fixed speed; S102. During the startup mode operation, when the carbon dioxide pressure sensed by the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor is lower than a set value, the first electric ball valve is opened and the carbon dioxide in the storage tank is input to the inlet of the booster; when the carbon dioxide pressure sensed by the second pressure sensor is higher than the set value, the second electric ball valve is opened and the carbon dioxide is recovered from the storage tank; when the carbon dioxide pressure sensed by the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor reaches the set value, the startup mode is completed, i.e., carbon dioxide refrigerant balance is achieved; the first electric ball valve and the second electric ball valve are closed; S103, after the start-up mode is completed, the refrigerant heat exchanger starts the cooling mode or the heating mode; (2) Refrigeration mode: S201, the fans of the first air energy unit and the second air energy unit are both in the on state. After passing through the supercharger, the carbon dioxide is converted into high-temperature superfluid carbon dioxide. The high-temperature superfluid carbon dioxide first enters the first air energy unit and the second air energy unit in sequence, and is converted into normal-temperature superfluid carbon dioxide by releasing heat to the ambient air. The normal-temperature superfluid carbon dioxide is output from the second port of the second air energy unit, passes through the second pressure sensor and is throttled and expanded by the expansion valve and cooled before entering the refrigerant heat exchanger; S202: The cooled carbon dioxide enters the refrigerant heat exchanger, absorbs heat from the refrigerant through the outer surface of the refrigerant heat exchanger, and heats up to become gaseous carbon dioxide. The refrigerant releases heat to the carbon dioxide, thereby cooling the refrigerant. S203, the gaseous carbon dioxide discharged from the refrigerant heat exchanger is input to the inlet of the supercharger through the first pressure sensor, and is pressurized by the supercharger to become high-temperature superfluid carbon dioxide, thereby realizing a carbon dioxide refrigeration cycle; S204: During the carbon dioxide refrigeration cycle, the carbon dioxide pressure sensed by the first pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the first electric ball valve; the carbon dioxide pressure sensed by the second pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the second electric ball valve; S205, repeat the above steps S201-S204; (2) Heating mode: S301: The carbon dioxide after passing through the supercharger is converted into high-temperature superfluid carbon dioxide, which enters the brine heat exchanger through the expansion valve. The high-temperature superfluid carbon dioxide releases heat to the brine through the surface of the brine heat exchanger in the brine heat exchanger, thereby heating the brine. S302: When the ambient temperature is greater than 2°C, the carbon dioxide that has released heat in the refrigerant heat exchanger enters the first air energy unit and the second air energy unit at the same time. After the pressure and temperature of the first and second air energy units are reduced, they absorb heat from the air and become gaseous carbon dioxide. The carbon dioxide then passes through the third and fourth pressure sensors and enters the inlet of the supercharger to complete the cycle. S303. When the ambient temperature is lower than 2°C, the carbon dioxide that has released heat in the refrigerant heat exchanger enters the first air energy unit and the second air energy unit or the second air energy unit and the first air energy unit in sequence. The waste heat of the carbon dioxide can be used to defrost the evaporator of the first air energy unit that enters first, and the fan of the air energy unit is in the off state at this time. Then, after flowing into the second air energy unit, the carbon dioxide is reduced in pressure to become carbon dioxide below the ambient temperature. Then, the carbon dioxide absorbs the heat of the air in the air energy unit and becomes gaseous carbon dioxide. At this time, the fan of the second air energy unit is in the on state. Then, the gaseous carbon dioxide is discharged and enters the inlet of the booster after passing through the third pressure sensor or the fourth pressure sensor accordingly. After running for a period of time, the carbon dioxide that has released heat in the refrigerant heat exchanger switches its entry order into the two air energy hosts, and the on and off modes of the fans of the two air energy hosts are also switched accordingly; S304: During the carbon dioxide heating cycle, the carbon dioxide pressure sensed by the third pressure sensor or the fourth pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the first electric ball valve; the carbon dioxide pressure sensed by the second pressure sensor may be maintained at a set value by adjusting the speed of the booster or adjusting the second electric ball valve; S305. Repeat the above steps S301-S304.

8. The cooling and heating method of an ultra-low temperature heat pump using oil-free carbon dioxide as a refrigerant according to claim 7, characterized in that: In step S201 of the cooling mode, the flow rate of the superfluid carbon dioxide in the refrigerant heat exchanger can be controlled by adjusting the expansion valve; In step S301 of the heating mode, the flow rate of the superfluid carbon dioxide entering the brine heat exchanger can be controlled by adjusting the proportional valve.

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