Low-grade energy synergistic injection and compression coupling refrigerating system and operation method thereof

Abstract

The invention belongs to the technical field of refrigeration. In order to solve the problems that an existing refrigerating system cannot solve the problems of over-compression and under-compression of a compressor and the exhaust temperature is too high, the low-grade energy synergistic injection and compression coupling refrigerating system and the operation method thereof are provided, and the system comprises a low-grade energy system and an injection and compression coupling refrigerating system body. The low-grade energy system comprises a heat storage water tank, heaters and a generator, and the injection and compression coupling refrigeration system comprises a condenser, an economizer, an evaporator, a compressor, a gas-gas injector, a working medium pump, two expansion valves, four regulating valves and six switching valves. According to the relationship between the pressure ratio required by the system and the pressure ratio provided by the compressor, different system modes are switched, so that the refrigerating capacity meeting the requirement is achieved, the problems of over-compression and under-compression of the compressor are avoided, and the performance of the refrigerating system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of refrigeration technology, and in particular relates to a low-grade energy efficiency-enhancing injection and compression coupling refrigeration system and an operation method thereof. Background Art

[0002] Air conditioning and refrigeration energy consumption is the main part of building energy consumption and building carbon emissions. By using renewable energy, industrial waste heat and other auxiliary driving air conditioning and refrigeration systems, air conditioning and refrigeration energy consumption can be greatly reduced. In small and medium-capacity refrigeration and air conditioning systems, scroll compressors are usually used. When the working conditions change, the scroll compressor often faces the situation where the compressor's pressure ratio (internal pressure ratio) is inconsistent with the system's required pressure ratio (external pressure ratio), that is, the ratio of condensing pressure to evaporating pressure, resulting in over-compression or under-compression losses, and may also cause the exhaust temperature to be too high, resulting in a decrease in system performance and increased carbon emissions. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a low-grade energy-efficient injection and compression coupling refrigeration system and an operating method thereof, which can avoid over-compression and under-compression of the compressor.

[0004] A first aspect of the present invention provides an injection and compression coupled refrigeration system for improving the efficiency of low-grade energy, comprising a low-grade energy system and an injection and compression coupled refrigeration system;

[0005] The low-grade energy system comprises a hot water storage tank, a heater and a generator, wherein the hot water storage tank and the heater are connected to form a heating loop, and the hot water storage tank and the generator are connected to form a generating loop;

[0006] The injection and compression coupled refrigeration system comprises a condenser, wherein the outlet pipeline of the condenser is divided into three paths, wherein the first path is sequentially connected to the inlet of the working fluid pump and the generator, the second path is sequentially connected to the first expansion valve and the economizer, and the third path is sequentially connected to the economizer, the second expansion valve, the evaporator, the compressor and the second inlet of the condenser;

[0007] The outlet pipeline of the generator is connected in sequence to the primary flow inlet of the gas-to-gas ejector and the first inlet of the condenser;

[0008] The compressor is provided with a medium-pressure air supply and exhaust port and a low-pressure air supply and exhaust port, the pipeline connected to the medium-pressure air supply and exhaust port includes a medium-pressure exhaust pipeline and a medium-pressure air supply pipeline, the medium-pressure air supply and exhaust port is connected to the secondary flow inlet of the gas-to-gas injector through the medium-pressure exhaust pipeline, the medium-pressure air supply and exhaust port is connected to the economizer through the medium-pressure air supply pipeline, the pipeline connected to the low-pressure air supply and exhaust port includes a low-pressure exhaust pipeline and a low-pressure air supply pipeline, the low-pressure air supply and exhaust port is connected to the inlet of the compressor through the low-pressure exhaust pipeline, and the low-pressure air supply and exhaust port is connected to the economizer through the low-pressure air supply pipeline.

[0009] Optionally, the medium-pressure exhaust pipeline is sequentially connected with a sixth switching valve, a fourth regulating valve, a second switching valve and a secondary inlet of the gas-to-gas injector;

[0010] The medium-pressure air supply pipeline is sequentially connected with a fifth switching valve, a third regulating valve, a third switching valve, and a gaseous refrigerant outlet pipeline of the economizer;

[0011] The low-pressure exhaust pipeline is sequentially connected to a fourth switching valve, a first regulating valve and an inlet of the compressor;

[0012] The low-pressure air supply pipeline is sequentially connected to the first switching valve, the second regulating valve and the gas refrigerant outlet pipeline of the economizer.

[0013] A second aspect of the present invention provides an operating method of a low-grade energy efficiency-enhanced injection and compression coupled refrigeration system, which is based on any of the above-mentioned low-grade energy efficiency-enhanced injection and compression coupled refrigeration systems and comprises the following steps:

[0014] S1. According to whether the gas-gas injector is working, the operation method is divided into two levels, the first level is that the heat provided by the heater cannot drive the gas-gas injector to work, and the second level is that the heat provided by the heater can drive the gas-gas injector to work;

[0015] S2, the pressure ratio of the compressor is the internal pressure ratio, the pressure ratio required by the system is the external pressure ratio, and the first level and the second level are set to three modes according to the ratio of the internal pressure ratio to the external pressure ratio, the first mode is that the internal pressure ratio is equal to the external pressure ratio, the second mode is that the internal pressure ratio is greater than the external pressure ratio, and the third mode is that the internal pressure ratio is less than the external pressure ratio;

[0016] S3. When the system is operating at the first level, the low-grade energy system stops running, and the injection and compression coupled refrigeration system operates to achieve compression refrigeration, medium-pressure air replenishment and low-pressure exhaust. When the system is at the second level, the low-grade energy system operates, and the liquid refrigerant in the generator absorbs the heat of hot water and becomes high-temperature and high-pressure steam, thereby entering the injection and compression coupled refrigeration system to complete the cycle, achieving subcooling enthalpy reduction, low-pressure air replenishment and medium-pressure exhaust.

[0017] Optionally, when the system is in the first mode of the first level and the second level, the medium-pressure exhaust pipeline, the medium-pressure air supply pipeline, the low-pressure exhaust pipeline and the low-pressure air supply pipeline are all in a closed state;

[0018] When the system is in the second mode and the third mode of the first level, the medium-pressure air supply pipeline and the low-pressure exhaust pipeline are opened;

[0019] When the system is in the second mode and the third mode of the second level, the medium-pressure exhaust line and the low-pressure supplementary air line are opened.

[0020] Optionally, when the system is in the first level and the first mode, the first switching valve, the second switching valve, the third switching valve, the fourth switching valve, the fifth switching valve and the sixth switching valve are all closed, and the liquid refrigerant in the outlet pipeline of the condenser enters the evaporator to evaporate and absorb heat after being throttled by the second expansion valve. The vapor generated by the evaporator is sucked into the compressor, compressed by the compressor, and then enters the condenser to condense, completing the cycle and realizing compression refrigeration.

[0021] Optionally, when the system is in the first level and the second mode, the third switching valve, the fourth switching valve and the fifth switching valve are opened, the first switching valve, the second switching valve and the sixth switching valve are closed, the opening of the first regulating valve is increased, and the opening of the third regulating valve is reduced to reduce the medium-pressure air supply volume and increase the low-pressure exhaust volume.

[0022] Optionally, when the system is in the first level, third mode, the third switching valve, the fourth switching valve and the fifth switching valve are opened, the first switching valve, the second switching valve and the sixth switching valve are closed, the opening of the first regulating valve is reduced, and the opening of the third regulating valve is increased to increase the medium-pressure air supply volume and reduce the low-pressure exhaust volume.

[0023] Optionally, when the system is in the second level and the first mode, the second switching valve and the third switching valve are opened, and the first switching valve, the fourth switching valve, the fifth switching valve and the sixth switching valve are closed. The refrigerant in the generator enters the gas-to-gas ejector, draws the vapor from the economizer, mixes and pressurizes in the gas-to-gas ejector, and then enters the condenser. The condensed liquid refrigerant completes the cycle through three routes through the outlet pipe of the condenser, thereby achieving subcooling and enthalpy reduction.

[0024] Optionally, when the system is in the second level and the second mode, the first switching valve, the second switching valve and the sixth switching valve are opened, the third switching valve, the fourth switching valve and the fifth switching valve are closed, the opening of the second regulating valve is reduced, and the opening of the fourth regulating valve is increased to reduce low-pressure air supply and increase medium-pressure exhaust.

[0025] Optionally, when the system is in the second level, third mode, the first switching valve, the second switching valve and the sixth switching valve are opened, and the third switching valve, the fourth switching valve and the fifth switching valve are closed, the opening of the second regulating valve is increased, and the opening of the fourth regulating valve is reduced to increase low-pressure air supply and reduce medium-pressure exhaust.

[0026] Compared with the prior art, the technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0027] An embodiment of the present invention provides a low-grade energy efficiency-enhanced injection and compression coupling refrigeration system and an operation method thereof. The system opens holes in the low-pressure and medium-pressure sections of a fixed volumetric ratio compressor, that is, a medium-pressure supply and exhaust port and a low-pressure supply and exhaust port are arranged on the compressor, and the medium-pressure supply and exhaust port and the low-pressure supply and exhaust port are respectively connected to supply and exhaust pipes of the refrigeration system. According to the supply of low-grade energy, the opening and closing of multiple switching valves are controlled to adjust the opening of the regulating valve on the supply and exhaust pipe to control the supply and exhaust states of the low-pressure supply and exhaust port and the medium-pressure supply and exhaust port of the compressor. By adjusting the supply and exhaust volume, the pressure ratio of the fixed volumetric ratio compressor is adjusted, so that the internal pressure ratio of the compressor is consistent with the external pressure ratio, avoiding over-compression or under-compression problems when the compressor changes its operating conditions, thereby improving the performance of the refrigeration system.

[0028] The system uses low-grade energy to drive the secondary flow inlet of the gas-to-gas ejector or the suction of the intermediate suction port of the compressor, so that the refrigerant in the economizer evaporates, and the refrigerant flowing from the condenser to the evaporator is supercooled to reduce the enthalpy, thereby increasing the inlet and outlet enthalpy difference of the evaporator and improving the performance of the refrigeration system.

[0029] The system achieves energy efficiency and carbon reduction by coupling the electrically driven and thermally driven refrigeration systems through two-stage compressor exhaust volume regulation and coordination with the gas-to-gas ejector driven by low-grade energy, thereby improving the performance of the refrigeration system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 A schematic diagram of a low-grade energy efficiency injection and compression coupling refrigeration system in which the heater is a solar collector according to an embodiment of the present invention;

[0033] Figure 2 It is a schematic diagram of a low-grade energy efficiency injection and compression coupling refrigeration system in which the heater is the waste heat source according to an embodiment of the present invention.

[0034] Among them, 1. condenser; 2. economizer; 3. evaporator; 4. compressor; 5. gas-to-gas ejector; 6. generator; 7. working fluid pump; 8. first expansion valve; 9. second expansion valve; 10. first regulating valve; 11. second regulating valve; 12. third regulating valve; 13. fourth regulating valve; 14. first switching valve; 15. second switching valve; 16. third switching valve; 17. fourth switching valve; 18. fifth switching valve; 19. sixth switching valve; 20. waste heat source; 21. generating circulating water pump; 22. heat storage tank; 23. heat collecting circulating water pump; 24. solar collector; 25. waste heat circulating water pump. DETAILED DESCRIPTION

[0035] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0037] Embodiment 1

[0038] Reference Figure 1 As shown, this embodiment provides an injection and compression coupled refrigeration system for improving the efficiency of low-grade energy, including a low-grade energy system and an injection and compression coupled refrigeration system.

[0039] Among them, the heater is a solar collector 24, and the low-grade energy system also includes a heat collection circulation water pump 23 and a generating circulation water pump 21. The low-grade energy system includes a heating circuit and a generating circuit. The hot water storage tank 22, the solar collector 24 and the heat collection circulation water pump 23 are connected to form a heating circuit. The hot water storage tank 22, the generator 6 and the generating circulation water pump 21 are connected to form a generating circuit. In the heating circuit, the water in the hot water storage tank 22 enters the collector 24 through the heat collection circulation water pump 23 for heating. When the solar energy is sufficient, the solar energy absorbed by the collector 24 can make the water temperature in the hot water storage tank 22 reach the temperature required by the generator 6. At this time, the gas-gas injector 5 is started. For the generating circuit, the water that absorbs heat and heats up in the solar collector 24 enters the hot water storage tank 22. When the temperature of the upper layer of the hot water storage tank 22 reaches the temperature required by the generator 6, the generating circulation water pump 21 is turned on. The heat collection circulation water pump 23 and the generating circulation water pump 21 can provide power for the water circulation in the heating circuit and the generating circuit respectively to ensure that the water can circulate stably in the system according to the set flow rate.

[0040] The injection and compression coupling refrigeration system includes a condenser 1, and the outlet pipeline of the condenser 1 is divided into three routes. The first route is connected to the inlet of the working fluid pump 7 and the generator 6 in sequence, the second route is connected to the first expansion valve 8, the economizer 2 and the secondary flow inlet of the gas-to-gas injector 5 in sequence, and the third route is connected to the economizer 2, the second expansion valve 9, the evaporator 3, the compressor 4 and the second inlet of the condenser 1 in sequence; the outlet pipeline of the generator 6 is connected to the primary flow inlet of the gas-to-gas injector 5 and the first inlet of the condenser 1 in sequence; the compressor 4 is provided with a medium-pressure air supply port and a low-pressure air supply port, and the pipelines connected to the medium-pressure air supply port include a medium-pressure exhaust pipeline and a medium-pressure air supply pipeline, the medium-pressure air supply port is connected to the secondary flow inlet of the gas-to-gas injector 5 through the medium-pressure exhaust pipeline, and the medium-pressure air supply port is connected to the low-pressure air supply pipeline through the medium-pressure air supply pipeline. The low-pressure air supply port is connected to the economizer 2, and the pipeline connected to the low-pressure air supply port includes a low-pressure exhaust pipeline and a low-pressure air supply pipeline. The low-pressure air supply port is connected to the inlet of the compressor 4 through the low-pressure exhaust pipeline, and the low-pressure air supply port is connected to the economizer 2 through the low-pressure air supply pipeline, wherein the medium-pressure exhaust pipeline is connected with the sixth switching valve 19, the fourth regulating valve 13, the second switching valve 15 and the secondary flow inlet of the gas-gas injector 5 in sequence; the medium-pressure air supply pipeline is connected with the fifth switching valve 18, the third regulating valve 12, the third switching valve 16, and the gaseous refrigerant outlet pipeline of the economizer 2 in sequence; the low-pressure exhaust pipeline is connected with the fourth switching valve 17, the first regulating valve 10 and the inlet of the compressor 4 in sequence; the low-pressure air supply pipeline is connected with the first switching valve 14, the second regulating valve 11 and the gaseous refrigerant outlet pipeline of the economizer 2 in sequence.

[0041] Among them, a drying filter is provided at the inlet of the compressor 4, which can prevent moisture or impurities from entering the compressor 4. An oil separator is provided at the outlet of the compressor 4, which can prevent the lubricating oil carried in the refrigerant gas in the compressor 4 from entering the system, thereby ensuring the oil return of the compressor 4 and realizing the normal operation of the system.

[0042] The outlet of the condenser 1 is provided with a liquid accumulator, which can be used to store and balance the refrigerant to ensure the performance and stability of the refrigeration system, and can also help reduce the fluctuation and pressure change of the refrigerant, thereby improving the working efficiency of the system and extending the service life of the equipment.

[0043] The injection and compression coupled refrigeration system uses pure refrigerant or mixed refrigerant as the working fluid, thereby reducing the power consumption of the working fluid pump 7 and improving the thermodynamic performance and operational reliability of the system.

[0044] This embodiment also provides an operation method of a low-grade energy efficiency-enhanced injection and compression coupled refrigeration system, which is based on the above-mentioned low-grade energy efficiency-enhanced injection and compression coupled refrigeration system and includes the following steps:

[0045] S1. According to whether the gas-gas injector 5 is working, the operation method is divided into two levels. The first level is that the heat provided by the heater cannot drive the gas-gas injector 5 to work, and the second level is that the heat provided by the heater can drive the gas-gas injector 5 to work. In the second level, the system efficiency is higher, the cooling capacity is stronger, and the power saving and carbon reduction effect is better;

[0046] S2, the pressure ratio of compressor 4 is the internal pressure ratio, and the pressure ratio required by the system is the external pressure ratio. According to the ratio of the internal pressure ratio to the external pressure ratio, the first level and the second level are set to three modes. The first mode is that the internal pressure ratio is equal to the external pressure ratio, the second mode is that the internal pressure ratio is greater than the external pressure ratio, and the third mode is that the internal pressure ratio is less than the external pressure ratio;

[0047] S3. When the system is running at the first level, the low-grade energy system stops running, and the injection and compression coupled refrigeration system runs to realize traditional compression refrigeration, medium-pressure air replenishment and low-pressure exhaust. When the system is at the second level, the low-grade energy system runs, and the liquid refrigerant in the generator 6 absorbs the heat of hot water and becomes high-temperature and high-pressure steam, thereby entering the injection and compression coupled refrigeration system to complete the cycle, realizing supercooling enthalpy reduction, low-pressure air replenishment and medium-pressure exhaust.

[0048] Furthermore, when the system is in the first mode of the first level and the second mode, the medium-pressure exhaust pipeline, the medium-pressure air supply pipeline, the low-pressure exhaust pipeline and the low-pressure air supply pipeline are all in a closed state; when the system is in the second mode and the third mode of the first level, the medium-pressure air supply pipeline and the low-pressure exhaust pipeline are opened; when the system is in the second mode and the third mode of the second level, the medium-pressure exhaust pipeline and the low-pressure air supply pipeline are opened.

[0049] Specifically, when the pressure ratio required by the system is consistent with the pressure ratio of the compressor 4, that is, the internal pressure ratio is equal to the external pressure ratio, when the low-grade energy system cannot provide the generator 6 with sufficient heat to drive the gas-to-gas injector 5 to work at night or in harsh environments, the low-grade energy system is not put into use. For the injection and compression coupled refrigeration system, the gas-to-gas injector 5 is not put into use. Under this condition, the system can achieve compression refrigeration. At this time, the liquid refrigerant in the outlet pipeline of the condenser 1 enters the evaporator 3 after throttling by the second expansion valve 9 to evaporate and absorb heat. The vapor is sucked into the compressor 4, and becomes high-temperature and high-pressure vapor after compression, and enters the condenser 1 for condensation, completing the cycle; when the outdoor solar radiation intensity increases, the low-grade energy system can provide the generator 6 with heat to drive the gas-to-gas injector 5 to work normally, and the low-grade energy system is put into use. Under this condition, the second switching valve 15 and the third switching valve 15 are opened. Switch valve 16, close the first switch valve 14, the fourth switch valve 17, the fifth switch valve 18, and the sixth switch valve 19 to achieve supercooling and enthalpy reduction. At this time, the liquid refrigerant in the generator 6 absorbs the heat of the hot water and becomes high-temperature and high-pressure steam, enters the gas-to-gas ejector 5 to expand and reduce the pressure, and inhales the low-pressure steam generated by the economizer 2. The two fluids are mixed and pressurized, then leave the gas-to-gas ejector 5 and enter the condenser 1. The condensed liquid refrigerant is divided into three paths. The first path is pressurized by the working fluid pump 7 and returns to the generator 6 to evaporate, completing the cycle. The second path enters the economizer 2 to evaporate and absorb heat after throttling by the first expansion valve 8, and then is inhaled by the gas-to-gas ejector 5. The third path passes through the second expansion valve 9 after the economizer 2 reduces the enthalpy, and enters the evaporator 3 after throttling to evaporate and absorb heat. The steam is inhaled by the compressor 4, and becomes high-temperature and high-pressure steam after compression and enters the condenser 1 to complete the cycle.

[0050] Generally speaking, when the ratio of the internal pressure ratio to the external pressure ratio is within the range of 0.95 to 1.05, the over-compression and under-compression losses are small. At this time, it is considered that the internal and external pressure ratios are consistent. To avoid frequent switching of system modes, the first mode of the first level or the second level mentioned above is adopted for operation.

[0051] The pressure ratio required by the system is less than the pressure ratio of the compressor 4, that is, the internal pressure ratio is greater than the external pressure ratio. When there is no solar energy or the solar radiation intensity is weak, the low-grade energy system cannot provide the generator 6 with sufficient heat to drive the gas-to-gas injector 5 to work, and the solar hot water circuit and the generating circuit in the low-grade energy system are not put into use. For the injection and compression coupled refrigeration system, the gas-to-gas injector 5 is not put into use. Under this condition, the third switching valve 16, the fourth switching valve 17, and the fifth switching valve 18 are opened, and the first switching valve 14, the second switching valve 15, and the sixth switching valve 19 are closed to realize medium-pressure air replenishment and low-pressure exhaust. At this time, the steam generated by the compressor 4 is divided into two paths. The first path compressor The low-pressure steam generated by the intermediate compression passes through the fourth switching valve 17 and the first regulating valve 10, enters the compressor 4 for compression, and completes the cycle. The second high-temperature and high-pressure steam passes through the condenser 1 for condensation. The supercooled liquid generated at the outlet of the condenser 1 is divided into two paths. The first path passes through the economizer 2 for supercooling and enthalpy reduction, passes through the second expansion valve 9, enters the evaporator 3 after throttling to evaporate and absorb heat, and the gaseous refrigerant enters the compressor 4 for compression, and completes the cycle. The second path of liquid refrigerant passes through the first expansion valve 8, enters the economizer 2 after throttling to evaporate and absorb heat, and the generated steam passes through the third switching valve 16, the third regulating valve 12, and the fifth switching valve 18 to enter the medium-pressure air supply port of the compressor 4, and completes the cycle. Under this working condition, by increasing the opening of the first regulating valve 10 and reducing the opening of the third regulating valve 12, the low-pressure exhaust volume is increased and the medium-pressure air supply volume is reduced to prevent over-compression.

[0052] When the intensity of solar radiation increases and the low-grade energy system can provide heat for the generator 6 to drive the normal operation of the gas-to-gas injector 5, the solar hot water circuit and the generating circuit in the low-grade energy system are put into use. For the injection and compression coupled refrigeration system, the gas-to-gas injector 5 is put into use. Under this condition, the first switching valve 14, the second switching valve 15, and the sixth switching valve 19 are opened, and the third switching valve 16, the fourth switching valve 17, and the fifth switching valve 18 are closed to realize low-pressure air replenishment and medium-pressure exhaust of the system. At this time, the liquid refrigerant in the generator 6 in the system absorbs the heat of the hot water and becomes high-temperature and high-pressure steam, which enters the gas-to-gas injector 5 to expand and reduce the pressure, and inhales the medium-pressure steam generated by the intermediate compression of the compressor 4. The two fluids are mixed and pressurized, and then leave the gas-to-gas injector 5 and enter the condenser. 1. The condensed liquid refrigerant is divided into three paths. The first path is pressurized by the working fluid pump 7 and then returns to the generator 6 to evaporate and complete the cycle. The second path enters the economizer 2 after throttling through the first expansion valve 8 to evaporate and absorb heat. The low-pressure steam generated passes through the second regulating valve 11 and the first switching valve 14 and enters the low-pressure air supply and exhaust port of the compressor 4 to complete the cycle. The third path passes through the economizer 2 to reduce enthalpy, flows through the second expansion valve 9, and enters the evaporator 3 after throttling to evaporate and absorb heat. The steam is sucked into the compressor 4. The steam outlet of the compressor 4 is divided into two paths. The first path is the high-temperature and high-pressure steam compressed by the compressor 4. Enter the condenser 1 to complete the cycle. The second path is the medium-pressure steam generated by the compressor 4 after compression. Pass through the sixth switching valve 19, the fourth regulating valve 13, and the second switching valve 15, and is sucked into the gas-gas ejector 5. Under this working condition, by reducing the opening of the second regulating valve 11 and increasing the opening of the fourth regulating valve 13, the low-pressure air supply volume is reduced, the medium-pressure exhaust volume is increased, and over-compression is prevented.

[0053] The pressure ratio required by the system is greater than the pressure ratio of the compressor 4, that is, the internal pressure ratio is less than the external pressure ratio. When there is no solar energy or the solar radiation intensity is weak, the low-grade energy system cannot provide the generator 6 with sufficient heat to drive the gas-to-gas injector 5 to work, and the solar hot water circuit and the generating circuit in the low-grade energy system are not put into use. For the injection and compression coupled refrigeration system, the gas-to-gas injector 5 is not put into use. Under this condition, the third switching valve 16, the fourth switching valve 17, and the fifth switching valve 18 are opened, and the first switching valve 14, the second switching valve 15, and the sixth switching valve 19 are closed to realize medium-pressure air replenishment and low-pressure exhaust. At this time, the steam generated by the compressor 4 is divided into two paths. The first path compressor The low-pressure steam generated by the intermediate compression passes through the fourth switching valve 17 and the first regulating valve 10, enters the compressor 4 for compression, and completes the cycle. The second high-temperature and high-pressure steam passes through the condenser 1 for condensation. The supercooled liquid generated at the outlet of the condenser 1 is divided into two paths. The first path passes through the economizer 2 for supercooling and enthalpy reduction, passes through the second expansion valve 9, enters the evaporator 3 after throttling to evaporate and absorb heat, and the gaseous refrigerant enters the compressor 4 for compression, and completes the cycle. The second path of liquid refrigerant passes through the first expansion valve 8, enters the economizer 2 after throttling to evaporate and absorb heat, and the generated steam passes through the third switching valve 16, the third regulating valve 12, and the fifth switching valve 18 to enter the medium-pressure air supply port of the compressor 4, and completes the cycle. Under this working condition, by reducing the opening of the first regulating valve 10 and increasing the opening of the third regulating valve 12, the low-pressure exhaust volume is reduced and the medium-pressure air supply volume is increased to prevent under-compression.

[0054] When the intensity of solar radiation increases and the low-grade energy system can provide heat for the generator 6 to drive the normal operation of the gas-to-gas injector 5, the solar hot water circuit and the generating circuit in the low-grade energy system are put into use. For the injection and compression coupled refrigeration system, the gas-to-gas injector 5 is put into use. Under this condition, the first switching valve 14, the second switching valve 15, and the sixth switching valve 19 are opened, and the third switching valve 16, the fourth switching valve 17, and the fifth switching valve 18 are closed to realize low-pressure air replenishment and medium-pressure exhaust of the system. At this time, the liquid refrigerant in the generator 6 in the system absorbs the heat of the hot water and becomes high-temperature and high-pressure steam, which enters the gas-to-gas injector 5 to expand and reduce the pressure, and inhales the medium-pressure steam generated by the intermediate compression of the compressor 4. The two fluids are mixed and pressurized, and then leave the gas-to-gas injector 5 and enter the condenser 1. , the condensed liquid refrigerant is divided into three paths. The first path is pressurized by the working fluid pump 7 and then returns to the generator 6 to evaporate and complete the cycle. The second path enters the economizer 2 after throttling through the first expansion valve 8 to evaporate and absorb heat. The low-pressure steam generated passes through the second regulating valve 11 and the first switching valve 14 and enters the low-pressure replenishment and exhaust port of the compressor 4 to complete the cycle. The third path passes through the economizer 2 to reduce enthalpy, flows through the second expansion valve 9, and enters the evaporator 3 after throttling to evaporate and absorb heat. The steam is sucked into the compressor 4. The steam outlet of the compressor 4 is divided into two paths. The first path is the high-temperature and high-pressure steam compressed by the compressor 4, which enters the condenser 1 to complete the cycle. The second path is the medium-pressure steam generated by the compressor 4 after compression, which passes through the sixth switching valve 19, the fourth regulating valve 13, and the second switching valve 15 and is sucked into the gas-gas ejector 5. Under this working condition, by increasing the opening of the second regulating valve 11 and reducing the opening of the fourth regulating valve 13, the low-pressure replenishment volume is increased, the medium-pressure exhaust volume is reduced, and under-compression is prevented.

[0055] Embodiment 2

[0056] Reference Figure 2 As shown, this embodiment provides an injection and compression coupled refrigeration system for improving the efficiency of low-grade energy, including a low-grade energy system and an injection and compression coupled refrigeration system.

[0057] The difference between this embodiment and the first embodiment is that the heater is a waste heat source 20 , and the circulating water pump is a waste heat circulating water pump 25 .

[0058] Among them, the low-grade energy system includes a heating circuit and a generating circuit. The hot water storage tank 22, the waste heat source 20 and the waste heat circulating water pump 25 are connected to form a heating circuit. The hot water storage tank 22, the generator 6 and the generating circulating water pump 21 are connected to form a generating circuit. In the heating circuit, the water heated by the waste heat source 20 enters the hot water storage tank 22, and the upper hot water in the hot water storage tank 22 is sent to the generator 6 by the generating circulating water pump 21 to heat the refrigerant therein. After the water releases heat and cools down, it enters the bottom of the hot water storage tank 22. The hot water with low temperature at the bottom of the hot water storage tank 22 returns to the waste heat source 20 through the waste heat circulating water pump 25 for heating and then enters the upper part of the hot water storage tank 22 again.

[0059] The connection relationship of each component in the injection and compression coupled refrigeration system in this embodiment is the same as that in the first embodiment, so it will not be repeated; for the injection and compression coupled refrigeration system in this embodiment, the mode of the system can be switched according to whether the waste heat source 20 can provide the generator 6 with heat to drive the gas-to-gas injector 5 to work normally and the relationship between the pressure ratio required by the system and the pressure ratio of the compressor 4. The cycle process is the same as that in the first embodiment, so it will not be repeated.

[0060] Based on the above-mentioned injection and compression refrigeration system for graded utilization of low-grade energy, the low-grade energy system and the injection and compression coupled refrigeration system cooperate with each other, which can effectively realize the switching between solar energy and waste heat source 20, so that the system can operate well regardless of the presence or absence of solar energy, and the hot water storage tank 22 can further improve the utilization rate of solar energy.

[0061] By using solar energy or waste heat source 20 as the driving energy source of the gas-to-gas ejector 5, the water in the hot water storage tank 22 is heated to the temperature required by the generator 6, driving the operation of the gas-to-gas ejector 5, and cooperating with the economizer 2 to reduce the enthalpy of the liquid refrigerant at the outlet of the condenser 1. At the same time, when the compressor 4 is over-compressed, the gas-to-gas ejector 5 is used to suck the intermediate exhaust gas of the compressor 4, adjust the pressure ratio of the compressor 4, and reduce the exhaust gas temperature of the compressor 4, thereby significantly improving the performance of the system. The system also uses different intermediate exhaust gas pressures for exhaust or gas replenishment of the compressor 4 according to the intensity of low-grade energy and the internal and external pressure ratio, adjusts the pressure ratio and capacity of the compressor 4, reduces the inlet enthalpy of the evaporator 3, and makes full use of solar energy and waste heat sources 20 of different intensities to achieve efficiency improvement, energy saving and carbon reduction.

[0062] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0063] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but should conform to the widest scope consistent with the principles and novel features invented herein.

Claims

1. A low-grade energy efficiency injection and compression coupled refrigeration system, characterized in that: Includes low-grade energy systems and ejection and compression coupled refrigeration systems; The low-grade energy system comprises a hot water storage tank (22), a heater and a generator (6), wherein the hot water storage tank (22) and the heater are connected to form a heating circuit, and the hot water storage tank (22) and the generator (6) are connected to form a generating circuit; The injection and compression coupled refrigeration system comprises a condenser (1), wherein the outlet pipeline of the condenser (1) is divided into three routes, wherein the first route is sequentially connected to a working fluid pump (7) and an inlet of the generator (6), the second route is sequentially connected to a first expansion valve (8), an economizer (2), and a secondary flow inlet of a gas-to-gas ejector (5), and the third route is sequentially connected to the economizer (2), a second expansion valve (9), an evaporator (3), a compressor (4), and a second inlet of the condenser (1); The outlet pipeline of the generator (6) is connected in sequence to the primary flow inlet of the gas-gas ejector (5) and the first inlet of the condenser (1); The compressor (4) is provided with a medium-pressure air supply port and a low-pressure air supply port. The pipeline connected to the medium-pressure air supply port includes a medium-pressure exhaust pipeline and a medium-pressure air supply pipeline. The medium-pressure air supply port is connected to the secondary flow inlet of the gas-gas injector (5) through the medium-pressure exhaust pipeline. The medium-pressure air supply port is connected to the economizer (2) through the medium-pressure air supply pipeline. The pipeline connected to the low-pressure air supply port includes a low-pressure exhaust pipeline and a low-pressure air supply pipeline. The low-pressure air supply port is connected to the inlet of the compressor (4) through the low-pressure exhaust pipeline. The low-pressure air supply port is connected to the economizer (2) through the low-pressure air supply pipeline.

2. The low-grade energy efficient injection and compression coupled refrigeration system according to claim 1 is characterized in that: The medium-pressure exhaust pipeline is sequentially connected to a sixth switching valve (19), a fourth regulating valve (13), a second switching valve (15) and a secondary inlet of the gas-to-gas injector (5); The medium-pressure air supply pipeline is sequentially connected to a fifth switching valve (18), a third regulating valve (12), a third switching valve (16), and a gaseous refrigerant outlet pipeline of the economizer (2); The low-pressure exhaust pipeline is sequentially connected to a fourth switching valve (17), a first regulating valve (10) and an inlet of the compressor (4); The low-pressure air supply pipeline is sequentially connected to a first switching valve (14), a second regulating valve (11) and a gaseous refrigerant outlet pipeline of the economizer (2).

3. A method for operating a low-grade energy efficient injection and compression coupled refrigeration system, based on the low-grade energy efficient injection and compression coupled refrigeration system according to any one of claims 1 or 2, characterized in that: The following steps are involved: S1. According to whether the gas-gas injector (5) is working, the operation method is divided into two levels, the first level is that the heat provided by the heater cannot drive the gas-gas injector (5) to work, and the second level is that the heat provided by the heater can drive the gas-gas injector (5) to work; S2, the pressure ratio of the compressor (4) is the internal pressure ratio, the pressure ratio required by the system is the external pressure ratio, and the first level and the second level are set to three modes according to the ratio of the internal pressure ratio to the external pressure ratio, the first mode is that the internal pressure ratio is equal to the external pressure ratio, the second mode is that the internal pressure ratio is greater than the external pressure ratio, and the third mode is that the internal pressure ratio is less than the external pressure ratio; S3. When the system is operating at the first level, the low-grade energy system stops operating, and the injection and compression coupled refrigeration system operates to achieve compression refrigeration, medium-pressure air replenishment and low-pressure exhaust. When the system is at the second level, the low-grade energy system operates, and the liquid refrigerant in the generator (6) absorbs the heat of hot water and becomes high-temperature and high-pressure steam, thereby entering the injection and compression coupled refrigeration system to complete the cycle, achieving subcooling enthalpy reduction, low-pressure air replenishment and medium-pressure exhaust.

4. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 3, characterized in that: When the system is in the first mode of the first level and the second level, the medium-pressure exhaust pipeline, the medium-pressure air supply pipeline, the low-pressure exhaust pipeline and the low-pressure air supply pipeline are all in a closed state; When the system is in the second mode and the third mode of the first level, the medium-pressure air supply pipeline and the low-pressure exhaust pipeline are opened; When the system is in the second mode and the third mode of the second level, the medium-pressure exhaust line and the low-pressure supplementary air line are opened.

5. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 4, characterized in that: When the system is in the first level and the first mode, the first switching valve (14), the second switching valve (15), the third switching valve (16), the fourth switching valve (17), the fifth switching valve (18) and the sixth switching valve (19) are all closed, and the liquid refrigerant in the outlet pipeline of the condenser (1) enters the evaporator (3) to evaporate and absorb heat after being throttled by the second expansion valve (9). The vapor generated by the evaporator (3) is sucked into the compressor (4), compressed by the compressor (4), and then enters the condenser (1) to condense, completing the cycle and realizing compression refrigeration.

6. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 4, characterized in that: When the system is in the first level and the second mode, the third switching valve (16), the fourth switching valve (17) and the fifth switching valve (18) are opened, the first switching valve (14), the second switching valve (15) and the sixth switching valve (19) are closed, the opening of the first regulating valve (10) is increased, and the opening of the third regulating valve (12) is decreased, so as to reduce the medium-pressure air supply volume and increase the low-pressure exhaust volume.

7. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 4, characterized in that: When the system is in the first level, the third mode, the third switching valve (16), the fourth switching valve (17) and the fifth switching valve (18) are opened, the first switching valve (14), the second switching valve (15) and the sixth switching valve (19) are closed, the opening of the first regulating valve (10) is reduced, and the opening of the third regulating valve (12) is increased, so as to increase the medium-pressure air supply volume and reduce the low-pressure exhaust volume.

8. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 4, characterized in that: When the system is in the second level and the first mode, the second switching valve (15) and the third switching valve (16) are opened, and the first switching valve (14), the fourth switching valve (17), the fifth switching valve (18) and the sixth switching valve (19) are closed. The refrigerant in the generator (6) enters the gas-to-gas ejector (5), draws the vapor from the economizer (2), mixes and pressurizes in the gas-to-gas ejector (5), and then enters the condenser (1). The condensed liquid refrigerant completes the circulation through three routes through the outlet pipe of the condenser (1), thereby achieving subcooling and enthalpy reduction.

9. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 4, characterized in that: When the system is in the second level and the second mode, the first switching valve (14), the second switching valve (15) and the sixth switching valve (19) are opened, the third switching valve (16), the fourth switching valve (17) and the fifth switching valve (18) are closed, the opening of the second regulating valve (11) is reduced, and the opening of the fourth regulating valve (13) is increased, so as to reduce the low-pressure air supply and increase the medium-pressure exhaust.

10. The method for operating the low-grade energy efficient injection and compression coupled refrigeration system according to claim 4, characterized in that: When the system is in the second level, the third mode, the first switching valve (14), the second switching valve (15) and the sixth switching valve (19) are opened, the third switching valve (16), the fourth switching valve (17) and the fifth switching valve (18) are closed, the opening of the second regulating valve (11) is increased, and the opening of the fourth regulating valve (13) is decreased, so as to increase the low-pressure air supply and reduce the medium-pressure exhaust.

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