Low-grade energy efficient ejector and compression coupled refrigeration system and method of operation thereof

Abstract

The application belongs to the technical field of refrigeration. In order to solve the problems of over-compression and under-compression of the compressor and the problem of too high exhaust temperature of the existing refrigeration system, a low-grade energy efficiency injection and compression coupled refrigeration system and its operation method are provided. The system includes a low-grade energy system and an injection and compression coupled refrigeration system. The low-grade energy system includes a heat storage water tank, a heater and a generator. The injection and compression coupled refrigeration system includes a condenser, an economizer, an evaporator, a compressor, a gas-gas ejector, a working medium pump, two expansion valves, four regulating valves and six switching valves. The system is driven by different heaters to work the generator. According to the relationship between the required pressure ratio of the system and the pressure ratio provided by the compressor, different system modes are switched, so as to meet the required refrigeration capacity, avoid the problems of over-compression and under-compression of the compressor, and improve the performance of the refrigeration system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of refrigeration, and particularly relates to a low-grade energy efficient ejector and compression coupled refrigeration system and a running method thereof. BACKGROUND

[0002] Air conditioning refrigeration energy consumption is a major part of building energy consumption and building carbon emissions. By utilizing renewable energy, industrial waste heat and other auxiliary driving air conditioning refrigeration systems, air conditioning refrigeration energy consumption can be greatly reduced. In small and medium capacity refrigeration air conditioning systems, scroll compressors are usually used. When the working condition changes, the scroll compressor often faces the situation that the compression ratio (internal pressure ratio) of the compressor and the required pressure ratio (external pressure ratio) of the system, i.e. the ratio of condensing pressure and evaporating pressure, are inconsistent, resulting in over-compression or under-compression loss, and also possibly causing the exhaust temperature to be too high, resulting in system performance degradation and increased carbon emissions. SUMMARY

[0003] In order to solve the above technical problems, the present application provides a low-grade energy efficient ejector and compression coupled refrigeration system and a running method thereof which can avoid over-compression and under-compression of the compressor.

[0004] The first aspect of the present application provides a low-grade energy efficient ejector and compression coupled refrigeration system, comprising a low-grade energy system and an ejector and compression coupled refrigeration system.

[0005] The low-grade energy system comprises a heat storage water tank, a heater and a generator, the heat storage water tank and the heater are connected to form a heating circuit, and the heat storage water tank and the generator are connected to form a generation circuit.

[0006] The ejector and compression coupled refrigeration system comprises a condenser, the outlet pipeline of the condenser is divided into three paths, the first path is sequentially connected with a working medium pump and an inlet of the generator, the second path is sequentially connected with a first expansion valve and an economizer, and the third path is sequentially connected with the economizer, a second expansion valve, an evaporator, a compressor and a second inlet of the condenser.

[0007] The outlet pipeline of the generator is sequentially connected with a primary flow inlet of the gas-gas ejector and a first inlet of the condenser.

[0008] The compressor is provided with a medium-pressure supplementary exhaust port and a low-pressure supplementary exhaust port, a pipeline connected with the medium-pressure supplementary exhaust port comprises a medium-pressure exhaust pipeline and a medium-pressure supplementary gas pipeline, the medium-pressure supplementary exhaust port is connected with the secondary flow inlet of the gas-gas ejector through the medium-pressure exhaust pipeline, and the medium-pressure supplementary exhaust port is connected with the economizer through the medium-pressure supplementary gas pipeline.

[0009] Optionally, the medium-pressure exhaust pipeline is sequentially connected with a sixth switch valve, a fourth adjusting valve, a second switch valve and the secondary flow inlet of the gas-gas ejector.

[0010] The medium-pressure supplementary gas pipeline is sequentially connected with a fifth switch valve, a third adjusting valve, a third switch valve and the gaseous refrigerant outlet pipeline of the economizer.

[0011] The low-pressure exhaust pipeline is sequentially connected with a fourth switch valve, a first adjusting valve and the inlet of the compressor.

[0012] The low-pressure supplementary gas pipeline is sequentially connected with a first switch valve, a second adjusting valve and the gaseous refrigerant outlet pipeline of the economizer.

[0013] The second aspect of the present application provides a running method of an ejector and compression coupled refrigeration system with low-grade energy efficiency, which is completed based on the ejector and compression coupled refrigeration system with low-grade energy efficiency in any of the above aspects, and comprises the following steps:

[0014] S1, according to whether the gas-gas ejector works, the running method is divided into two levels, the first level is that the heat provided by the heater cannot drive the gas-gas ejector to work, and the second level is that the heat provided by the heater can drive the gas-gas ejector to work.

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

[0016] S3, when the system runs at the first level, the low-grade energy system stops running, the ejector and compression coupled refrigeration system runs to realize compression refrigeration, medium pressure air supplement and low pressure exhaust, when the system is at the second level, the low-grade energy system runs, the liquid refrigerant in the generator absorbs the heat of the hot water to become high temperature and high pressure vapor, thereby entering the ejector and compression coupled refrigeration system to complete the cycle, realizing supercooling, low pressure air supplement and medium pressure exhaust.

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

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

[0019] When the system is at the second mode and the third mode of the second level, the medium pressure exhaust pipeline and the low pressure air supplement pipeline are opened.

[0020] Optionally, when the system is at the first level, 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, the liquid refrigerant of the outlet pipeline of the condenser enters the evaporator after being throttled by the second expansion valve to evaporate and absorb heat, the vapor generated by the evaporator is sucked into the compressor, and after being compressed by the compressor, the vapor enters the condenser to condense, complete the cycle and realize compression refrigeration.

[0021] Optionally, when the system is at the first level, 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 degree of the first regulating valve is increased, and the opening degree of the third regulating valve is reduced to reduce the medium pressure air supplement amount and increase the low pressure exhaust amount.

[0022] Optionally, when the system is at the first level, the 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 degree of the first regulating valve is reduced, and the opening degree of the third regulating valve is increased to increase the medium pressure air supplement amount and reduce the low pressure exhaust amount.

[0023] Optionally, when the system is in the second level, the first mode, the second switch valve and the third switch valve are opened, and the first switch valve, the fourth switch valve, the fifth switch valve and the sixth switch valve are closed, the refrigerant in the generator enters the gas-gas ejector, sucks the vapor from the economizer, mixes and pressurizes in the gas-gas ejector, and then enters the condenser, and the condensed liquid refrigerant completes the circulation through three paths through the outlet pipeline of the condenser, so that supercooling and enthalpy reduction are realized.

[0024] Optionally, when the system is in the second level, the second mode, the first switch valve, the second switch valve and the sixth switch valve are opened, the third switch valve, the fourth switch valve and the fifth switch valve are closed, the opening degree of the second regulating valve is reduced, and the opening degree of the fourth regulating valve is increased, so that the low-pressure air supplement is reduced and the medium-pressure air exhaust is increased.

[0025] Optionally, when the system is in the second level, the third mode, the first switch valve, the second switch valve and the sixth switch valve are opened, the third switch valve, the fourth switch valve and the fifth switch valve are closed, the opening degree of the second regulating valve is increased, and the opening degree of the fourth regulating valve is reduced, so that the low-pressure air supplement is increased and the medium-pressure air exhaust is reduced.

[0026] Compared with the prior art, the technical scheme provided by the embodiment of the application has the following beneficial effects:

[0027] The low-grade energy efficiency coupling refrigeration system and the operation method thereof provided by the embodiment of the application, by opening holes in the low-pressure and medium-pressure sections of the fixed volume ratio compressor, i.e., by arranging a medium-pressure air supplement and exhaust port and a low-pressure air supplement and exhaust port on the compressor, and by connecting the medium-pressure air supplement and exhaust port and the low-pressure air supplement and exhaust port with the air supplement and exhaust pipeline of the refrigeration system, according to the supply condition of the low-grade energy, by controlling the opening and closing of the multiple switch valves, by adjusting the opening degree of the regulating valve on the air supplement and exhaust pipeline, by controlling the air supplement and exhaust states of the low-pressure air supplement and exhaust port and the medium-pressure air supplement and exhaust port of the compressor, and by adjusting the air supplement and exhaust amounts, the adjustment of the pressure ratio of the fixed volume ratio compressor is realized, the pressure ratio inside the compressor is consistent with the pressure ratio outside the compressor, the problems of over-compression or under-compression during the operation of the compressor under the variable working condition are avoided, and the performance of the refrigeration system is improved.

[0028] The system drives the suction of the secondary flow inlet of the gas-gas ejector or the intermediate suction hole of the compressor by the low-grade energy, so that the refrigerant in the economizer is evaporated, the refrigerant flowing from the condenser to the evaporator is supercooled and the enthalpy is reduced, the enthalpy difference between the inlet and the outlet of the evaporator is increased, and the performance of the refrigeration system is improved.

[0029] The system is coupled with the electric drive and heat driven refrigeration system by the two-stage compressor compensation gas volume adjustment and the low-grade energy driven gas-gas ejector, so that the efficiency and energy saving and carbon reduction are realized, and the performance of the refrigeration system is improved. BRIEF DESCRIPTION OF DRAWINGS

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

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced hereinafter. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0032] Figure 1 The heater described in the embodiments of the present application is a schematic diagram of a low-grade energy efficiency injection and compression coupled refrigeration system of a solar heat collector;

[0033] Figure 2 The heater described in the embodiments of the present application is a schematic diagram of a low-grade energy efficiency injection and compression coupled refrigeration system of a waste heat source.

[0034] 1, condenser; 2, economizer; 3, evaporator; 4, compressor; 5, gas-gas ejector; 6, generator; 7, working medium 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, circulating water pump of generation; 22, heat storage water tank; 23, circulating water pump of heat collection; 24, solar heat collector; 25, circulating water pump of waste heat. DETAILED DESCRIPTION

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced hereinafter. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0036] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other different ways from those described here; obviously, the examples in the specification are only a part of the embodiments of the present application, not all the embodiments.

[0037] Embodiment one

[0038] ReferenceFigure 1 As shown, the embodiment provides a low-grade energy efficiency injection and compression coupled refrigeration system, which comprises a low-grade energy system and an injection and compression coupled refrigeration system.

[0039] Wherein, the heater is a solar collector 24, and the low-grade energy system further comprises a heat collection circulating water pump 23 and a generation circulating water pump 21. The low-grade energy system comprises a heating circuit and a generation circuit. The heat storage water tank 22, the solar collector 24 and the heat collection circulating water pump 23 are connected to form the heating circuit, and the heat storage water tank 22, the generator 6 and the generation circulating water pump 21 are connected to form the generation circuit. In the heating circuit, the water in the heat storage water tank 22 is heated by the heat collection circulating water pump 23 into the heat collector 24. When the solar energy is sufficient, the solar energy absorbed by the heat collector 24 can make the water temperature in the heat storage water tank 22 reach the required temperature of the generator 6. At this time, the gas-gas ejector 5 is started. For the generation circuit, the water heated and warmed in the solar collector 24 enters the heat storage water tank 22. When the temperature of the upper layer of the heat storage water tank 22 reaches the required temperature of the generator 6, the generation circulating water pump 21 is started. The heat collection circulating water pump 23 and the generation circulating water pump 21 can respectively provide power for the water circulation in the heating circuit and the generation circuit, so as to ensure that the water can be stably circulated in the system according to the set flow.

[0040] The injection and compression coupled refrigeration system comprises a condenser 1. The outlet pipeline of the condenser 1 is divided into three routes. The first route is sequentially connected with a working medium pump 7 and an inlet of a generator 6. The second route is sequentially connected with a first expansion valve 8, an economizer 2 and a secondary flow inlet of a gas-gas ejector 5. The third route is sequentially connected with the economizer 2, a second expansion valve 9, an evaporator 3, a compressor 4 and a second inlet of the condenser 1. An outlet pipeline of the generator 6 is sequentially connected with a primary flow inlet of the gas-gas ejector 5 and a first inlet of the condenser 1. The compressor 4 is provided with a medium-pressure supplement and exhaust port and a low-pressure supplement and exhaust port. The pipeline connected with the medium-pressure supplement and exhaust port comprises a medium-pressure exhaust pipeline and a medium-pressure supplement pipeline. The medium-pressure supplement and exhaust port is connected with the secondary flow inlet of the gas-gas ejector 5 through the medium-pressure exhaust pipeline and connected with the economizer 2 through the medium-pressure supplement pipeline. The pipeline connected with the low-pressure supplement and exhaust port comprises a low-pressure exhaust pipeline and a low-pressure supplement pipeline. The low-pressure supplement and exhaust port is connected with the inlet of the compressor 4 through the low-pressure exhaust pipeline and connected with the economizer 2 through the low-pressure supplement pipeline. The medium-pressure exhaust pipeline is sequentially connected with a sixth switch valve 19, a fourth adjusting valve 13, a second switch valve 15 and the secondary flow inlet of the gas-gas ejector 5. The medium-pressure supplement pipeline is sequentially connected with a fifth switch valve 18, a third adjusting valve 12, a third switch valve 16 and a gaseous refrigerant outlet pipeline of the economizer 2. The low-pressure exhaust pipeline is sequentially connected with a fourth switch valve 17, a first adjusting valve 10 and the inlet of the compressor 4. The low-pressure supplement pipeline is sequentially connected with a first switch valve 14, a second adjusting valve 11 and the gaseous refrigerant outlet pipeline of the economizer 2.

[0041] The inlet of the compressor 4 is provided with a drying filter, which can prevent water or impurities from entering the compressor 4. The outlet of the compressor 4 is provided with an oil separator, which can prevent the lubricating oil carried by the refrigerant gas in the compressor 4 from entering the system, ensuring the oil return of the compressor 4 and realizing the normal work 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 also can help to reduce the fluctuation and pressure change of the refrigerant, thereby improving the working efficiency of the system and prolonging the service life of the equipment.

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

[0044] The embodiment also provides a running method of the injection and compression coupled refrigeration system with low-grade energy efficiency, which is completed based on the injection and compression coupled refrigeration system with low-grade energy efficiency and includes the following steps.

[0045] S1, according to whether the gas-gas ejector 5 works, the running method is divided into two levels, the first level is that the heat provided by the heater cannot drive the gas-gas ejector 5 to work, and the second level is that the heat provided by the heater can drive the gas-gas ejector 5 to work, the system efficiency is higher, the refrigeration capacity is stronger, and the electricity saving and carbon reduction effect is better in the second level;

[0046] S2, the compression ratio of the compressor 4 is an internal compression ratio, the required compression ratio of the system is an external compression ratio, the first level and the second level are both set to three modes according to the ratio of the internal compression ratio to the external compression ratio, the first mode is that the internal compression ratio is equal to the external compression ratio, the second mode is that the internal compression ratio is greater than the external compression ratio, and the third mode is that the internal compression ratio is less than the external compression ratio;

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

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

[0049] Specifically, when the required pressure ratio of the system is consistent with the pressure ratio of the compressor 4, i.e., the internal pressure ratio is equal to the external pressure ratio, at night or in a harsh environment, the low-grade energy system cannot provide enough heat for the generator 6 to drive the gas-gas ejector 5 to work, and the low-grade energy system is not put into use. For the ejector-compression coupled refrigeration system, the gas-gas ejector 5 is not put into use. In this case, the system can realize compression refrigeration. At this time, the liquid refrigerant in the condenser 1 outlet pipeline is throttled by the second expansion valve 9 and then enters the evaporator 3 to evaporate and absorb heat. The vapor is sucked into the compressor 4 and becomes high-temperature and high-pressure vapor after compression. The vapor enters the condenser 1 to condense, completing the cycle. When the outdoor solar radiation intensity increases, the low-grade energy system can provide heat for the generator 6 to drive the gas-gas ejector 5 to work normally, and the low-grade energy system is put into use. In this case, 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, realizing 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 vapor. The vapor expands and depressurizes in the gas-gas ejector 5, and absorbs the low-pressure vapor generated from the economizer 2. After mixing and pressurizing, the two fluids leave the gas-gas ejector 5 and enter the condenser 1. The liquid refrigerant condensed in the condenser 1 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, completing the cycle. The second path is throttled by the first expansion valve 8 and then enters the economizer 2 to evaporate and absorb heat. The vapor is then sucked into the gas-gas ejector 5. The third path is throttled by the second expansion valve 9 after the enthalpy reduction of the economizer 2, and then enters the evaporator 3 to evaporate and absorb heat. The vapor is sucked into the compressor 4 and becomes high-temperature and high-pressure vapor after compression. The vapor enters the condenser 1 to complete the cycle.

[0050] Generally, when the ratio of the internal pressure ratio to the external pressure ratio is 0.95-1.05, the overcompression and undercompression losses are small. At this time, it is considered that the internal and external pressure ratios are consistent. In order to avoid frequent switching of the system mode, the first mode of the first level or the second level is used for operation.

[0051] The system requires a pressure ratio less than the pressure ratio of the compressor 4, that is, the inner pressure ratio is greater than the outer pressure ratio. When there is no solar energy or the solar radiation intensity is weak, the low-grade energy system cannot provide enough heat for the generator 6 to work. The low-grade energy system and the solar hot water circuit are not used in the generator circuit. For the ejector and compression coupled refrigeration system, the gas-gas ejector 5 is not used. In this case, 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 supply and low-pressure air exhaust. At this time, the steam generated by the compressor 4 is divided into two paths. The first path is the low-pressure steam generated by the intermediate compression of the compressor 4, which passes through the fourth switching valve 17 and the first regulating valve 10 to enter the compressor 4 for compression to complete the cycle. The second path is the high-temperature and high-pressure steam, which passes through the condenser 1 to condense. The subcooled liquid generated at the outlet of the condenser 1 is divided into two paths. The first path passes through the economizer 2 to reduce the enthalpy, and then passes through the second expansion valve 9 to enter the evaporator 3 to evaporate and absorb heat after throttling. The gaseous refrigerant enters the compressor 4 for compression to complete the cycle. The second path is the liquid refrigerant, which passes through the first expansion valve 8 to enter the economizer 2 to evaporate and absorb heat after throttling. 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 and exhaust port of the compressor 4 to complete the cycle. In this case, by increasing the opening degree of the first regulating valve 10 and reducing the opening degree of the third regulating valve 12, the low-pressure air exhaust is increased and the medium-pressure air supply is reduced to prevent over-compression.

[0052] When the solar radiation intensity is enhanced, the low-grade energy system can provide heat for the generator 6 to drive the gas ejector 5 to work normally, the solar hot water circuit and the generation circuit in the low-grade energy system are put into use, and the gas ejector 5 is put into use for the ejector and compression coupled refrigeration system. In this working 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, so that the system realizes low-pressure air supplement and medium-pressure air exhaust. At this time, the liquid refrigerant in the generator 6 in the system absorbs the heat of hot water to become high-temperature and high-pressure steam, which enters the gas ejector 5 to expand and be drawn into the medium-pressure steam generated by the intermediate compression of the compressor 4, mixes and pressurizes, and then leaves the gas ejector 5 and enters the condenser 1. The liquid refrigerant condensed is divided into three paths. The first path is pressurized by the working medium pump 7 and then returns to the generator 6 to evaporate, completing the cycle. The second path is throttled by the first expansion valve 8 and then enters the economizer 2 to evaporate and absorb heat, and the low-pressure steam generated is drawn into the low-pressure air exhaust port of the compressor 4 through the second regulating valve 11 and the first switching valve 14, completing the cycle. The third path is dehumidified by the economizer 2, flows through the second expansion valve 9, is throttled, and then enters the evaporator 3 to evaporate and absorb heat. The steam is sucked into the compressor 4, and the steam outlet of the compressor 4 is divided into two paths. The first path is high-temperature and high-pressure steam after compression of the compressor 4, which enters the condenser 1 to complete the cycle. The second path is medium-pressure steam after compression of the compressor 4, which is drawn into the gas ejector 5 through the sixth switching valve 19, the fourth regulating valve 13 and the second switching valve 15. In this working condition, the opening degree of the second regulating valve 11 is reduced, and the opening degree of the fourth regulating valve 13 is increased, so as to reduce the low-pressure air supplement and increase the medium-pressure air exhaust, thereby preventing over-compression.

[0053] When the required pressure ratio of the system is greater than the pressure ratio of the compressor 4, i.e. the inner pressure ratio is less than the outer pressure ratio, the solar water heating circuit and the generation circuit in the low-grade energy system are not put into use when there is no solar energy or the solar radiation intensity is weak, and the low-grade energy system cannot provide enough heat for the driver gas ejector 5 to work, and the gas ejector 5 is not put into use in the ejector and compression coupled refrigeration system. Under this working 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 supplement and low-pressure air exhaust. At this time, the steam generated by the compressor 4 is divided into two paths. The first path is the low-pressure steam generated by the intermediate compression of the compressor 4, which passes through the fourth switching valve 17 and the first regulating valve 10 to enter the compressor 4 for compression to complete the cycle. The second path is the high-temperature and high-pressure steam, which passes through the condenser 1 to be condensed. The supercooled liquid generated at the outlet of the condenser 1 is divided into two paths. The first path passes through the economizer 2 to be supercooled and dehumidified, and then passes through the second expansion valve 9 to be throttled and enter the evaporator 3 to be evaporated and absorb heat. The gaseous refrigerant enters the compressor 4 to be compressed to complete the cycle. The second path is the liquid refrigerant, which passes through the first expansion valve 8 to be throttled and enter the economizer 2 to be evaporated and absorb heat. 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 supplement and exhaust port of the compressor 4 to complete the cycle. Under this working condition, the opening degree of the first regulating valve 10 is reduced and the opening degree of the third regulating valve 12 is increased to reduce the low-pressure exhaust and increase the medium-pressure supplement, thereby preventing under-compression.

[0054] When the solar radiation intensity increases, the low-grade energy system can provide heat for the generator 6 to drive the gas ejector 5 to work normally, and the solar hot water circuit and the generation circuit in the low-grade energy system are put into use. For the ejector and compression coupled refrigeration system, the gas ejector 5 is put into use. In this working 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, so as to realize low-pressure air supplement and medium-pressure air exhaust. At this time, the liquid refrigerant in the generator 6 in the system absorbs the heat of the hot water to become high-temperature and high-pressure steam, which enters the gas ejector 5 to expand and reduce pressure, and then absorbs the medium-pressure steam generated from the intermediate compression of the compressor 4. After mixing and pressure increasing, the two fluids leave the gas ejector 5 and enter the condenser 1. The liquid refrigerant after condensation is divided into three paths. The first path is pressurized by the working medium pump 7 and then 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 the low-pressure steam generated enters the low-pressure air supplement and exhaust port of the compressor 4 through the second regulating valve 11 and the first switching valve 14, completing the cycle. The third path enters the evaporator 3 to evaporate and absorb heat after the enthalpy is reduced by the economizer 2 and throttling by the second expansion valve 9. The steam is sucked into the compressor 4. The steam outlet of the compressor 4 is divided into two paths. The first path is high-temperature and high-pressure steam after compression by the compressor 4, which enters the condenser 1 to complete the cycle. The second path is medium-pressure steam after compression by the compressor 4, which is sucked into the gas ejector 5 through the sixth switching valve 19, the fourth regulating valve 13 and the second switching valve 15. In this working condition, by increasing the opening degree of the second regulating valve 11 and reducing the opening degree of the fourth regulating valve 13, the low-pressure air supplement is increased and the medium-pressure air exhaust is reduced, so as to prevent under-compression.

[0055] Embodiment Two

[0056] With reference to Figure 2 The embodiment provides a low-grade energy enhanced ejector and compression coupled refrigeration system, which comprises a low-grade energy system and an ejector and compression coupled refrigeration system.

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

[0058] The low-grade energy system comprises a heating loop and a generating loop. The heat storage water tank 22, the waste heat source 20 and the waste heat circulating pump 25 form the heating loop, and the heat storage water tank 22, the generator 6 and the generating circulating pump 21 form the generating loop. In the heating loop, the water heated by the waste heat source 20 enters the heat storage water tank 22, the upper hot water of the heat storage water tank 22 is sent into the generator 6 by the generating circulating pump 21 to heat the refrigerant therein, and the water is cooled by heat release and then enters the bottom of the heat storage water tank 22. The low-temperature hot water at the bottom of the heat storage water tank 22 is returned to the waste heat source 20 by the waste heat circulating pump 25, heated again and then enters the upper part of the heat storage water tank 22.

[0059] The connection relationship of each component in the ejector and compression coupled refrigeration system in the embodiment is the same as that in the first embodiment, and thus is not repeated. The ejector and compression coupled refrigeration system in the embodiment can switch the system mode according to whether the waste heat source 20 can provide heat for the generator 6 to normally operate the gas-gas ejector 5 and the size relationship between the required pressure ratio of the system and the pressure ratio of the compressor 4, and the cycle process is the same as that in the first embodiment, and thus is not repeated.

[0060] Based on the above-described ejector and compression refrigeration system using low-grade energy in stages, the low-grade energy system and the ejector and compression coupled refrigeration system cooperate with each other, can effectively realize the switching between the solar energy and the waste heat source 20, so that the system can well operate whether there is solar energy or not, and the heat storage water tank 22 can further improve the utilization rate of solar energy.

[0061] By using the solar energy or the waste heat source 20 as the driving energy of the gas-gas ejector 5, the water in the heat storage water tank 22 is heated to the required temperature of the generator 6, the gas-gas ejector 5 is driven to operate, and the economizer 2 is cooperated to reduce the enthalpy value of the liquid refrigerant at the outlet of the condenser 1. At the same time, when the compressor 4 is over-compressed, the intermediate exhaust gas of the compressor 4 is sucked by the gas-gas ejector 5, the pressure ratio of the compressor 4 is adjusted, the exhaust gas temperature of the compressor 4 is reduced, and thus the performance of the system is significantly improved. The system also adjusts the intermediate exhaust pressure of the compressor 4 to exhaust or supplement the gas according to the intensity of the low-grade energy and the internal and external pressure ratios, adjusts the pressure ratio and capacity of the compressor 4, reduces the inlet enthalpy value of the evaporator 3, fully utilizes the solar energy and the waste heat source 20 of different intensities, realizes energy saving and carbon reduction, and increases efficiency.

[0062] It has to be noted that, in the present document, the terms "first", "second", etc. merely serve the purpose of distinguishing between two entities or operations, without necessarily requiring or implying any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "containing" or any other transitional term, do not exclude other elements or steps, but merely specify the presence of the stated elements or steps. The term "comprising" does not exclude that other elements can be added. Further, the term "comprising" or "including" shall not exclude any possibility of including other elements, steps or actions, whether or not these elements, steps or actions are listed in the claims.

[0063] The foregoing is merely illustrative of the principles of this application and various modifications can be made by those skilled in the art without departing from the spirit and scope of the application. The above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the application should, therefore, be determined not with reference to the above description, but instead with reference to the appended claims, along with their full scope of equivalents.

Claims

1. A low-grade energy-efficient injection and compression coupled refrigeration system, characterized in that, This includes low-grade energy systems and injection-compression coupled refrigeration systems; The low-grade energy system includes a hot water storage tank (22), a heater, and a generator (6). 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 includes a condenser (1). The outlet pipe of the condenser (1) is divided into three paths. The first path is connected in sequence to the working fluid pump (7) and the inlet of the generator (6). The second path is connected in sequence to the first expansion valve (8), the economizer (2), and the secondary flow inlet of the gas-gas injector (5). The third path is connected in sequence to the economizer (2), the second expansion valve (9), the evaporator (3), the compressor (4), and the second inlet of the condenser (1). The outlet pipe of the generator (6) is sequentially connected to the primary inlet of the gas injector (5) and the first inlet of the condenser (1); The compressor (4) is provided with a medium-pressure exhaust port and a low-pressure exhaust port. The pipeline connected to the medium-pressure exhaust port includes a medium-pressure exhaust pipeline and a medium-pressure gas supply pipeline. The medium-pressure exhaust port is connected to the secondary inlet of the gas injector (5) through the medium-pressure exhaust pipeline. The medium-pressure exhaust port is connected to the economizer (2) through the medium-pressure gas supply pipeline. The pipeline connected to the low-pressure exhaust port includes a low-pressure exhaust pipeline and a low-pressure gas supply pipeline. The low-pressure exhaust port is connected to the inlet of the compressor (4) through the low-pressure exhaust pipeline. The low-pressure exhaust port is connected to the economizer (2) through the low-pressure gas supply pipeline.

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

3. A method for operating a low-grade energy-efficient injection-compression coupled refrigeration system, based on the low-grade energy-efficient injection-compression coupled refrigeration system described in any one of claims 1 or 2, characterized in that... Includes the following steps: S1. Based on whether the gas injector (5) is working, the operation method is divided into two levels. The first level is when the heat provided by the heater cannot drive the gas injector (5) to work, and the second level is when the heat provided by the heater can drive the gas injector (5) to work. S2. The pressure ratio of the compressor (4) is the internal pressure ratio, and the required pressure ratio of the system is the external pressure ratio. According to the ratio of the internal pressure ratio and the external pressure ratio, the first level and the second level are both 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. 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 gas 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 the 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 gas replenishment, and medium-pressure exhaust.

4. The operation method of 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 pipe, the medium-pressure air supply pipe, the low-pressure exhaust pipe and the low-pressure air supply pipe are all in the closed state; When the system is in the second and third modes of the first level, the medium-pressure air supply line and the low-pressure exhaust line are opened. When the system is in the second mode and the third mode of the second level, the medium-pressure exhaust pipe and the low-pressure air supply pipe are opened.

5. The operation method of 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 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. The liquid refrigerant in the outlet pipe of the condenser (1) is throttled by the second expansion valve (9) and enters the evaporator (3) to evaporate and absorb heat. The vapor generated by the evaporator (3) is drawn 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 operation method of 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 and increase the low pressure exhaust volume.

7. The operation method of 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 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 and reduce the low pressure exhaust volume.

8. The operation method of the low-grade energy-enhancing 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-gas ejector (5) and draws in the vapor from the economizer (2). After mixing and pressurizing in the gas-gas ejector (5), the refrigerant enters the condenser (1). The condensed liquid refrigerant completes the circulation through the outlet pipe of the condenser (1) via three paths, thereby achieving subcooling and enthalpy reduction.

9. The operation method of the low-grade energy-enhancing injection and compression coupled refrigeration system according to claim 4, characterized in that, When the system is in the second level and 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 gas supply and increase the medium-pressure exhaust.

10. The operation method of 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 or 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 gas supply and decrease the medium-pressure exhaust.

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