CN109028629B - Carbon dioxide secondary refrigerant refrigerating system and refrigerating method thereof - Google Patents

Carbon dioxide secondary refrigerant refrigerating system and refrigerating method thereof Download PDF

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Publication number
CN109028629B
CN109028629B CN201810603098.8A CN201810603098A CN109028629B CN 109028629 B CN109028629 B CN 109028629B CN 201810603098 A CN201810603098 A CN 201810603098A CN 109028629 B CN109028629 B CN 109028629B
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Prior art keywords
carbon dioxide
refrigerant
defrosting
outlet
evaporator
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CN109028629A (en
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张小明
庞成兵
魏建国
张志�
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SHANDONG SHENZHOU REFRIGERATION EQUIPMENT CO LTD
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SHANDONG SHENZHOU REFRIGERATION EQUIPMENT CO LTD
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/002—Lubrication
    • F25B31/004—Lubrication oil recirculating arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B39/00—Evaporators; Condensers
    • F25B39/02—Evaporators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F25B41/22—Disposition of valves, e.g. of on-off valves or flow control valves between evaporator and compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/02—Defrosting cycles
    • F25B47/022—Defrosting cycles hot gas defrosting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2339/00—Details of evaporators; Details of condensers
    • F25B2339/02—Details of evaporators
    • F25B2339/024—Evaporators with refrigerant in a vessel in which is situated a heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/13—Pump speed control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2513—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2519—On-off valves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Defrosting Systems (AREA)

Abstract

The invention discloses a carbon dioxide secondary refrigerant refrigerating system which comprises a refrigerant circulation loop, a carbon dioxide circulation loop, a defrosting circulation loop and a lubricating oil cooling circulation loop. The carbon dioxide secondary refrigerant refrigerating system fully utilizes the waste heat of the compressor and the cold energy of the refrigerant, and has low energy consumption and low cost. The invention improves the flooded evaporator, so that the required installation space is small, and the heat exchange efficiency between the refrigerant and the secondary refrigerant is high; and the maintenance unit is provided, and multiple measures are taken to prevent the system from being too high in pressure, so that the safety and stability are improved. The invention can be used in various application environments such as workshops, refrigeration houses, ice boxes and the like. Also disclosed herein are methods of refrigerating the carbon dioxide coolant refrigeration system.

Description

Carbon dioxide secondary refrigerant refrigerating system and refrigerating method thereof
Technical Field
The invention relates to the technical field of refrigeration systems, in particular to a carbon dioxide secondary refrigerant refrigeration system and a refrigeration method thereof.
Background
In recent years, environmental problems such as ozone layer destruction and greenhouse effect are more and more prominent, which has a great influence on the refrigeration industry. Currently, CFC refrigerants have been disabled and HFC and HCFC refrigerants are also being phased out, so it is imperative to employ new environmental protection refrigerants and refrigeration systems.
Natural working substance CO2 is a preferred target for refrigerant research because of its good environmental index, such as non-toxic, nonflammable, ozone Depletion Potential (ODP) of 0, global Warming Potential (GWP) of only 1, and its good chemical stability, without decomposition of toxic gases even at high temperatures.
At present, a plurality of NH are applied 3 /CO 2 But the system uses CO at the low temperature side 2 A compressor, resulting in a lower coefficient of performance (COP) of the system. CN204421413U and CN205227902U are disclosed as CO 2 NH as coolant 3 Refrigeration system, CO 2 At the quilt NH 3 After cooling, the ammonia reaches the refrigeration evaporator through pump circulation to cool the cooling room, so that the problems of potential safety hazards caused by ammonia as a refrigerant are solved, and the energy consumption of the system is reduced.
Carbon dioxide coolant refrigeration systems still suffer from certain drawbacks. Firstly, the defrosting method of the refrigeration evaporator mainly comprises electric defrosting, water defrosting and hot air defrosting, wherein the electric defrosting consumes a large amount of electric energy, and ice blockage or incomplete defrosting is easy to occur when the water defrosting mode is used in a low-temperature environment. The existing hot gas defrosting method needs to additionally add a device and equipment for providing hot gas, and is more complex in control system and higher in cost.
At present, the flooded evaporator is widely used due to high heat transfer efficiency and energy conservation. However, the flooded evaporator mostly adopts gravity to realize refrigerant liquid supply, and a higher machine room needs to be built, so that equipment cost is increased. And the refrigerant gasified by heating is sucked by the compressor to provide internal circulation, so that the temperature distribution of the refrigerant in the flooded evaporator is uneven, and the heat exchange with the refrigerating medium is not facilitated.
Accordingly, there is a need for a carbon dioxide coolant refrigeration system that improves both the defrost method and the refrigerant liquid supply and increases the heat transfer efficiency.
Disclosure of Invention
The present invention addresses the deficiencies of the prior art described above by providing a carbon dioxide coolant refrigeration system that includes a refrigerant circulation loop, a carbon dioxide circulation loop, a defrost circulation loop and a lube oil cooling circulation loop,
the refrigerant circulation loop comprises a compressor, an oil separator, a condenser, a siphon pipe, a refrigerant reservoir, an electronic expansion valve, a flooded evaporator and a pressure regulating valve, wherein the top end refrigerant outlet of the flooded evaporator is connected to the compressor through a pressure regulating valve pipeline, the outlet pipeline of the compressor is connected to the oil separator, the refrigerant outlet of the oil separator is connected to the condenser through a three-way valve pipeline, the condenser is connected to the refrigerant reservoir through the siphon pipe pipeline, and the refrigerant reservoir is connected to the refrigerant inlet of the flooded evaporator through the electronic expansion valve;
the carbon dioxide circulation loop comprises a flooded evaporator, a carbon dioxide liquid reservoir, a carbon dioxide pump and a refrigeration evaporator, wherein an outlet pipeline of a carbon dioxide condensing pipe in the flooded evaporator is connected to an inlet of the carbon dioxide liquid reservoir, an outlet of the carbon dioxide liquid reservoir is connected with the carbon dioxide pump, the carbon dioxide pump is connected to the refrigeration evaporator through a cold carbon dioxide liquid supply electromagnetic valve pipeline, and an outlet of the refrigeration evaporator is connected to an inlet of a carbon dioxide condensing pipe in the flooded evaporator through a carbon dioxide discharge electromagnetic valve pipeline;
the defrosting circulation loop is provided with a defrosting refrigerant side and a carbon dioxide side, the defrosting refrigerant side comprises an oil separator, a refrigerant defrosting electromagnetic valve, a defrosting heat exchanger and a refrigerant liquid storage device, a refrigerant inlet pipeline of the defrosting heat exchanger is connected with an outlet of the refrigerant defrosting electromagnetic valve, a refrigerant outlet pipeline of the defrosting heat exchanger is connected with an inlet of the refrigerant liquid storage device, a top gas outlet of the refrigerant liquid storage device is connected with an inlet pipeline of the condenser, the carbon dioxide side comprises a carbon dioxide liquid storage device, a defrosting heat exchanger, a carbon dioxide defrosting electromagnetic valve, a refrigerating evaporator and a flooded evaporator, an outlet pipeline of the carbon dioxide liquid storage device is connected to a carbon dioxide inlet of the defrosting heat exchanger, a carbon dioxide outlet of the defrosting heat exchanger is connected to the refrigerating evaporator through the carbon dioxide defrosting electromagnetic valve pipeline, and an outlet pipeline of the refrigerating evaporator is connected to an inlet of a carbon dioxide condensing pipe of the flooded evaporator;
the lube oil cooling circuit having a lube oil cooling refrigerant side and a lube oil side, the lube oil cooling refrigerant side including a condenser, a siphon pipe and an oil cooler, the siphon pipe line being connected to a refrigerant inlet of the oil cooler, a refrigerant outlet line of the oil cooler being connected to an inlet of the condenser, the lube oil side including a compressor, an oil separator and the oil cooler, a lube oil outlet line of the oil separator being connected to a lube oil inlet of the oil cooler, a lube oil outlet line of the oil cooler being connected to a lube oil inlet of the compressor,
in the flooded evaporator, the carbon dioxide coolant of the carbon dioxide circulation loop flows in a carbon dioxide condenser tube, which is immersed in the refrigerant from the refrigerant circulation loop, whereby heat exchange of carbon dioxide with the refrigerant occurs;
the refrigerant circulation loop and the defrost refrigerant side of the defrost circulation loop are communicated by a line between a three-way valve between an oil separator and a condenser and a refrigerant defrost solenoid valve and by a line between a refrigerant outlet of a defrost heat exchanger and a refrigerant reservoir inlet, the carbon dioxide circulation loop and the carbon dioxide side of the defrost circulation loop are communicated by a line between a carbon dioxide reservoir outlet and a carbon dioxide inlet of a defrost heat exchanger and by a line between a carbon dioxide outlet of a defrost heat exchanger and a refrigeration evaporator;
the refrigerant circulation circuit communicates with a lubricant-cooling refrigerant side of the lubricant-cooling circulation circuit through a line between a siphon tube and a refrigerant inlet of an oil cooler, and communicates through a line between a refrigerant outlet of the oil cooler and an inlet of a condenser,
the refrigerant circulating pump is arranged outside the flooded evaporator, an inlet of the refrigerant circulating pump is connected with a refrigerant outlet at the bottom of the flooded evaporator, and an outlet of the refrigerant circulating pump is connected with a sprayer at the inner top of the flooded evaporator.
Further, a liquid level controller is arranged in the flooded evaporator, 4 liquid level sensors are arranged on the liquid level controller from bottom to top, and the liquid level controller is electrically connected with and controls the electronic expansion valve and the refrigerant circulating pump through a control system.
Further, the flooded evaporator is provided with an oil return ejector, an oil return port of the oil return ejector extends into the flooded evaporator, an air inlet of the oil return ejector is connected to a refrigerant outlet of the oil separator through an oil return ejection electromagnetic valve, and an air outlet of the oil return ejector is connected to an inlet of the pressure regulating valve.
Further, the carbon dioxide liquid reservoir is provided with a maintenance unit, and the maintenance unit is used for preventing the pressure in the carbon dioxide liquid reservoir from being too high during shutdown.
Further, the refrigeration evaporator is provided with a hot carbon dioxide gas supply decompression solenoid valve, a cold carbon dioxide gas supply liquid solenoid valve, a carbon dioxide discharge solenoid valve and a carbon dioxide differential pressure valve, wherein an inlet of the hot carbon dioxide gas supply decompression solenoid valve is connected with an outlet of the carbon dioxide defrosting solenoid valve, an inlet of the cold carbon dioxide gas supply liquid solenoid valve is connected with an outlet of the carbon dioxide pump, an outlet of the hot carbon dioxide gas supply decompression solenoid valve and the cold carbon dioxide gas supply liquid solenoid valve is connected with an inlet of the refrigeration evaporator, an inlet of the carbon dioxide discharge solenoid valve and the carbon dioxide differential pressure valve are connected with an outlet of the refrigeration evaporator, and an outlet of the carbon dioxide discharge solenoid valve and the carbon dioxide differential pressure valve are connected with a carbon dioxide inlet of the flooded evaporator.
Further, the refrigeration evaporator is provided with a sensor which is electrically connected with a control system,
under a refrigeration working condition, the control system opens the cold carbon dioxide liquid supply electromagnetic valve and the carbon dioxide discharge electromagnetic valve, and closes the hot carbon dioxide gas supply decompression electromagnetic valve and the carbon dioxide differential pressure valve;
under defrosting working conditions, the control system closes the cold carbon dioxide liquid supply electromagnetic valve and the carbon dioxide discharge electromagnetic valve, and opens the hot carbon dioxide gas supply decompression electromagnetic valve and the carbon dioxide differential pressure valve.
Further, the refrigerant reservoir top outlet is connected to the inlet line of the condenser.
When the number of the refrigeration evaporators is more than one, the refrigeration evaporators are in parallel connection.
Further, the shell of the flooded evaporator is provided with an outer wall and an inner wall, a plurality of air outlet holes are formed in the inner wall, an air outlet cavity is formed between the outer wall and the inner wall, and the air outlet cavity is communicated with a refrigerant outlet at the top end of the flooded evaporator.
In the carbon dioxide coolant refrigeration system of the present invention, the refrigerant is preferably ammonia.
The invention also provides a refrigerating method of the carbon dioxide secondary refrigerant, which comprises a refrigerant cycle, a carbon dioxide cycle, a defrosting cycle and a lubricating oil cooling cycle,
in the refrigerant circulation, refrigerant is compressed into high-temperature high-pressure refrigerant gas, the gas enters an oil separator and is separated from lubricating oil carried by a compressor, the refrigerant gas after separation enters a condenser to be condensed and liquefied, the refrigerant gas enters a refrigerant liquid storage device through a siphon pipe and then enters a flooded evaporator after being depressurized by an electronic expansion valve, the refrigerant liquid is subjected to heat exchange with carbon dioxide secondary refrigerant in the flooded evaporator to become refrigerant gas, and the refrigerant gas returns to the compressor through a pressure regulating valve to complete the circulation;
in the carbon dioxide circulation, the carbon dioxide secondary refrigerant is condensed into liquid by a refrigerant in the flooded evaporator and then enters a carbon dioxide liquid storage device, then enters the refrigeration evaporator through a carbon dioxide pump to exchange heat with cold, absorbs heat and changes phase into gas, and returns to the flooded evaporator to be condensed again, so that the circulation is completed;
in the defrosting cycle, before part of high-temperature and high-pressure refrigerant gas from an oil separator enters a condenser on the side of a defrosting refrigerant, the refrigerant gas enters a defrosting heat exchanger through a three-way valve and a refrigerant defrosting electromagnetic valve, carbon dioxide liquid is heated and then returns to a refrigerant liquid storage device, on the side of carbon dioxide, part of carbon dioxide liquid from the carbon dioxide liquid storage device enters the defrosting heat exchanger to be heated by the refrigerant gas, then enters a refrigeration evaporator through a carbon dioxide defrosting electromagnetic valve to defrost, carbon dioxide returns to a flooded evaporator to be condensed again, and the condensed carbon dioxide liquid reaches the carbon dioxide liquid storage device to complete the cycle;
in the lubricating oil cooling cycle, a part of the refrigerant liquid from the condenser leaves from the siphon pipe on the lubricating oil cooling refrigerant side, enters the oil cooler to heat the lubricating oil separated in the oil separator, then the refrigerant returns to the condenser to be condensed again to complete the cycle, on the lubricating oil side, the lubricating oil from the compressor is separated from the refrigerant in the oil separator and then enters the oil cooler to exchange heat with the refrigerant liquid, the cooled lubricating oil returns to the compressor to complete the cycle,
the refrigerant cycle interacts with the carbon dioxide cycle in the flooded evaporator by heat exchange;
a part of refrigerant in the refrigerant cycle enters a defrosting refrigerant side of the defrosting cycle, a part of carbon dioxide in the carbon dioxide cycle enters a carbon dioxide side of the defrosting cycle, and the part of refrigerant and the part of carbon dioxide are subjected to heat exchange in the defrosting heat exchanger;
a part of the refrigerant in the refrigerant cycle enters the lubricant-cooling refrigerant side in the lubricant-cooling cycle, and heat exchange occurs with the lubricant in the oil cooler.
It should be noted that when the high temperature and pressure refrigerant gas generated by the compressor enters the condenser at a high velocity, the negative pressure generated in the line drives the refrigerant gas from the oil cooler and the refrigerant reservoir back to the condenser.
The beneficial effects of the invention are as follows:
the defrosting heat exchanger utilizes high-temperature and high-pressure refrigerant gas generated by the compressor to heat the carbon dioxide secondary refrigerant and defrost the refrigeration evaporator, thereby fully utilizing the redundant heat of the refrigerant without utilizing additional defrosting media, and reducing the energy consumption and the cost.
In addition, the circulating pump is arranged outside the flooded evaporator, so that the refrigerant used for soaking the condensing tube in the flooded evaporator can be circulated, the temperature distribution of the refrigerant is more uniform, and the heat transfer efficiency with the carbon dioxide secondary refrigerant is higher. And the negative pressure generated by the circulating pump drives the refrigerant to enter the flooded evaporator from the refrigerant liquid reservoir, so that the whole refrigerant circulation is driven, a higher machine room is not required to be built, the refrigerant circulation is driven by utilizing the gravity effect, and a large amount of cost and space are saved. The top in the flooded evaporator is also provided with a spraying device, so that the circulating refrigerant can be uniformly sprayed to a carbon dioxide condensing tube which is not soaked in the refrigerant, and the heat exchange rate is improved.
Drawings
FIG. 1 is a schematic diagram of a carbon dioxide coolant refrigeration system of the present invention.
In the figure, 1, a compressor; 2. an oil separator; 3. a condenser; 4. an oil cooler; 5. a siphon tube; 6. a refrigerant reservoir; 7. a flooded evaporator; 8. an electronic expansion valve; 9. a refrigerant circulation pump; 10. a carbon dioxide reservoir; 11. a carbon dioxide pump; 12. a hot carbon dioxide gas supply pressure reducing solenoid valve; 13. a cold carbon dioxide liquid supply electromagnetic valve; 14. a refrigeration evaporator; 15. a carbon dioxide discharge solenoid valve; 16. a carbon dioxide differential pressure valve; 17. maintaining a unit; 18. a defrosting heat exchanger; 19. a carbon dioxide defrosting electromagnetic valve; 20. a refrigerant defrosting solenoid valve; 21. an oil return ejector; 22. an oil return injection electromagnetic valve; 23. a liquid level controller; 24. a pressure regulating valve; 25. and an oil return port.
Detailed Description
In order to better understand the present invention, a specific example will be used to describe the technical solution of the present invention in detail, but the present invention is not limited thereto.
Example 1
This example illustrates a carbon dioxide coolant refrigeration system employing ammonia as the refrigerant and carbon dioxide as the coolant.
Referring to fig. 1, the refrigeration system includes a refrigerant circulation circuit, a carbon dioxide circulation circuit, a defrosting circulation circuit, and a lubricating oil cooling circulation circuit.
The refrigerant cycle circuit includes 2 compressors 1, an oil separator 2, a condenser 3, a siphon 5, a refrigerant reservoir 6, an electronic expansion valve 8, a flooded evaporator 7, and a pressure regulating valve 24 in parallel. The top end refrigerant outlet of the flooded evaporator 7 is connected to the compressor 1 through a pressure regulating valve 24 line, the outlet line of the compressor 1 is connected to the oil separator 2, the refrigerant outlet of the oil separator 2 is connected to the condenser 3 through a three-way valve line, the condenser 3 is connected to the refrigerant reservoir 6 through a siphon 5 line, and the refrigerant reservoir 6 is connected to the refrigerant inlet of the flooded evaporator 7 through an electronic expansion valve 8.
The carbon dioxide circulation loop comprises a flooded evaporator 7, a carbon dioxide reservoir 10, a carbon dioxide pump 11 and 4 refrigeration evaporators 14 connected in parallel. The outlet pipeline of the carbon dioxide condensing pipe in the flooded evaporator 7 is connected to the inlet of the carbon dioxide reservoir 10, the outlet of the carbon dioxide reservoir 10 is connected with the carbon dioxide pump 11, the carbon dioxide pump 11 is connected to the refrigeration evaporator 14 through the pipeline of the cold carbon dioxide liquid supply electromagnetic valve 13, and the outlet of the refrigeration evaporator 14 is connected to the inlet of the carbon dioxide condensing pipe in the flooded evaporator 7 through the pipeline of the carbon dioxide discharge electromagnetic valve 15.
In the flooded evaporator 7, the carbon dioxide coolant of the carbon dioxide circulation loop flows in a carbon dioxide condensing tube, which is immersed in the liquid ammonia from the refrigerant circulation loop, whereby heat exchange of carbon dioxide and liquid ammonia occurs;
the defrosting circulation loop comprises a defrosting heat exchanger 18, a carbon dioxide defrosting electromagnetic valve 19, a refrigerant defrosting electromagnetic valve 20, a refrigeration evaporator 14, a hot carbon dioxide air supply decompression electromagnetic valve 12 and a carbon dioxide differential pressure valve 16 at two ends of the refrigeration evaporator. The defrosting heat exchanger 18, the refrigerant defrosting solenoid valve 20, the oil separator 2 and the refrigerant reservoir 6 constitute a defrosting refrigerant side. The refrigerant inlet line of the defrosting heat exchanger 18 is connected with the outlet of the refrigerant defrosting electromagnetic valve 20, the inlet of the refrigerant defrosting electromagnetic valve 20 is connected with the three-way valve line between the oil separator 2 and the condenser 3, the refrigerant outlet line of the defrosting heat exchanger 18 is connected with the inlet of the refrigerant liquid reservoir 6, and the top gas outlet of the refrigerant liquid reservoir 6 is connected with the inlet line of the condenser 3. The defrosting heat exchanger 18 and the carbon dioxide defrosting electromagnetic valve 19 form a carbon dioxide side together with the refrigeration evaporator 14, the hot carbon dioxide air supply decompression electromagnetic valve 12, the carbon dioxide differential pressure valve 16, the flooded evaporator 7 and the carbon dioxide reservoir 10. The outlet pipeline of the carbon dioxide liquid storage device 10 is connected to the carbon dioxide inlet of the defrosting heat exchanger 18, the carbon dioxide outlet of the defrosting heat exchanger 18 is connected to the refrigeration evaporator 14 through a carbon dioxide defrosting electromagnetic valve 19 and a hot carbon dioxide air supply pressure reducing electromagnetic valve 12 pipeline, and the outlet of the refrigeration evaporator 14 is connected to the inlet of the carbon dioxide condensing pipe of the flooded evaporator 7 through a carbon dioxide differential pressure valve 16 pipeline.
The refrigeration evaporator 14 is provided with a sensor, which is electrically connected to the control system. Under refrigeration working conditions, the control system opens the cold carbon dioxide liquid supply electromagnetic valve 13 and the carbon dioxide discharge electromagnetic valve 15 to enable condensed carbon dioxide secondary refrigerant to enter the refrigeration evaporator 14 to exchange heat with cold for refrigeration, and simultaneously closes the hot carbon dioxide gas supply decompression electromagnetic valve 12 and the carbon dioxide differential pressure valve 16; under defrosting operation, the control system closes the cold carbon dioxide liquid supply electromagnetic valve 13, closes the carbon dioxide discharge electromagnetic valve 15 after the residual cold carbon dioxide in the refrigeration evaporator 14 is discharged, and opens the hot carbon dioxide gas supply decompression electromagnetic valve 12 and the carbon dioxide pressure difference valve 16.
The lubricating oil cooling circulation circuit includes an oil cooler 4. The oil cooler 4 constitutes a lubricating oil cooling refrigerant side with the condenser 3 and the siphon 5. The siphon 5 is connected in line to the refrigerant inlet of the oil cooler 4 and the refrigerant outlet line of the oil cooler 4 is connected to the inlet of the condenser 3. The oil cooler 4 constitutes the lubricating oil side with the oil separator 2 and the compressor 1. The oil outlet line of the oil separator 2 is connected to the oil inlet of the oil cooler 4, and the oil outlet line of the oil cooler 4 is connected to the oil inlet of the compressor 1.
Further, a refrigerant circulating pump 9 is arranged outside the flooded evaporator 7, and a top sprayer is arranged in the flooded evaporator 7. An inlet line of the refrigerant circulation pump 9 is connected to a refrigerant outlet at the bottom of the flooded evaporator 7, and an outlet line of the refrigerant circulation pump 9 is connected to an inlet of the top shower. The refrigerant circulation pump 9 recirculates the liquid ammonia at the bottom of the flooded evaporator 7 to the top of the flooded evaporator 7 and sprays the liquid ammonia onto the heat exchange tubes exposed in the headspace of the flooded evaporator 7, so as to help the temperature of the liquid ammonia in the evaporator to be evenly distributed, and improve the heat exchange efficiency. In addition, the shell of the flooded evaporator 7 is provided with an outer wall and an inner wall, a plurality of air outlet holes are arranged on the inner wall, an air outlet cavity is arranged between the outer wall and the inner wall, and the air outlet cavity is communicated with a refrigerant outlet at the top end of the flooded evaporator 7. The gas generated by heating the liquid ammonia in the evaporator in the heat exchange process can enter the air outlet cavity through the air outlet hole and leave the evaporator through the refrigerant outlet through the air outlet cavity. Therefore, bubbles in the liquid ammonia can not obstruct the descending speed of the sprayed liquid ammonia due to ascending in the evaporator, and the spraying heat exchange efficiency of the evaporator is improved.
In addition, a liquid level controller 23 is provided in the flooded evaporator 7, liquid level sensors are disposed at 4 positions a, b, c, and d from bottom to top of the liquid level controller 23, respectively, and the liquid level controller 23 is electrically connected to control the electronic expansion valve 8 and the refrigerant circulation pump 9 through a control system. The normal liquid level should be between the positions b and c, the electronic expansion valve 8 should be opened to supply liquid when the liquid level falls to the position a or b, and the refrigerant circulation pump 9 should also be stopped if the liquid level falls to the position a. When the liquid level rises to the position c, the electronic expansion valve 8 can be closed to stop supplying liquid, and when the liquid level rises to the position d, the electronic expansion valve 8 or other devices can possibly fail, and the machine should be stopped for maintenance or the liquid ammonia in the evaporator 7 should be waited for gasification and discharge. The presence of the liquid level controller improves the safety and continuity of the overall system operation.
In addition, the flooded evaporator 7 is provided with an oil return ejector 21, an oil return port 25 of the oil return ejector 21 extends into the flooded evaporator 7, an air inlet of the oil return ejector 21 is connected to a refrigerant outlet of the oil separator 2 through an oil return ejection electromagnetic valve 22, and an air outlet of the oil return ejector 21 is connected to an inlet of a pressure regulating valve 24. The high-speed high-pressure gas generated by the compressor 1 rapidly flows through the oil return ejector 21, and negative pressure is generated in the oil return ejector to suck lubricating oil in the liquid ammonia in the flooded evaporator 7. Therefore, the oil return ejector can prevent lubricating oil from influencing heat exchange in the evaporator, improve the recovery rate of the lubricating oil and save the cost.
The carbon dioxide reservoir 10 is provided with a maintenance unit 17, and the maintenance unit 17 has a dedicated generator, a compressor, a condenser, and a safety valve. The maintenance unit 17 can start a special generator when the refrigeration system is powered off, and the compressor and the condenser of the maintenance unit are used for maintaining the liquid state of the carbon dioxide in the carbon dioxide liquid storage device 10, so that the problem of safety caused by the fact that the temperature of the carbon dioxide rises and gasifies due to power off and the pressure is too high is prevented, and the safety valve of the maintenance unit 17 can also discharge a part of gas when the pressure is too high so as to maintain the safety pressure in the system, thereby obviously improving the safety of the refrigeration system.
Example 2
This example illustrates a carbon dioxide coolant refrigeration process that includes a refrigerant cycle, a carbon dioxide cycle, a defrost cycle, and a lube oil cooling cycle.
In the refrigerant cycle, the liquid ammonia in the flooded evaporator 7 is vaporized and then sucked into the compressor 1 through the refrigerant outlet at the top end, and the compressor 1 compresses the ammonia gas into high-temperature and high-pressure ammonia gas. The ammonia gas enters the oil separator 2 and is separated from the oil carried out of the compressor 1, and the separated oil leaves the oil separator 2 and enters the oil cooler 4. The high-temperature high-pressure ammonia leaves the oil separator 2 and enters the condenser 3 to be condensed into liquid ammonia. Liquid ammonia enters a refrigerant reservoir 6 through a siphon 5, is depressurized through an electronic expansion valve 8, and enters a flooded evaporator 7 for condensing carbon dioxide as a coolant. After that, the ammonia which is converted into gas by the heat absorption phase change is returned to the compressor 1 through the refrigerant outlet at the top end of the flooded evaporator 7, thereby completing the cycle.
In the carbon dioxide cycle, carbon dioxide condensed into liquid by ammonia in the flooded evaporator 7 enters the carbon dioxide reservoir 10, then enters the refrigeration evaporator 14 through the cold carbon dioxide liquid supply solenoid valve 13 under the action of the carbon dioxide pump 11, exchanges heat with cold, and is cooled by phase change into gas. The carbon dioxide gas leaves the refrigeration evaporator 14 through the carbon dioxide discharge electromagnetic valve 15 and returns to the carbon dioxide condensation pipe of the flooded evaporator 7 to exchange heat with ammonia again, thus completing the cycle.
If the sensor in the refrigeration evaporator 14 detects that frosting occurs in the refrigeration evaporator 14, a signal is sent to the control system, which closes the carbon dioxide pump 11 and the cold carbon dioxide supply solenoid valve 13 so that carbon dioxide no longer enters the refrigeration evaporator 14. After a period of time, the cold carbon dioxide is discharged from the refrigeration evaporator 14, the carbon dioxide discharge solenoid valve 15 is closed, and the hot carbon dioxide supply pressure reducing solenoid valve 12 and the carbon dioxide pressure difference valve 16 are opened, so that the carbon dioxide heated by the hot ammonia gas in the defrosting heat exchanger 18 enters the refrigeration evaporator 14 to be defrosted.
In the defrosting cycle, on the defrosting refrigerant side, a part of high-temperature and high-pressure ammonia gas from the oil separator 2 enters the defrosting heat exchanger 18 through the three-way valve and the refrigerant defrosting electromagnetic valve 20 before entering the condenser 3, heats carbon dioxide liquid from the carbon dioxide liquid reservoir 10, turns the ammonia gas into a gas-liquid mixture, and leaves the defrosting heat exchanger 18 to reach the refrigerant liquid reservoir 6. The pressure differential between the refrigerant inlet and outlet ends of the defrosting heat exchanger 18 drives this cycle. The liquid in the gas-liquid mixture of ammonia will enter the flooded evaporator 7 and the gas will return from the top gas outlet of the refrigerant reservoir 6 to the condenser 3 for re-condensation.
On the carbon dioxide side, carbon dioxide liquid enters a defrosting heat exchanger 18 from a carbon dioxide liquid reservoir 10, is heated by high-temperature high-pressure ammonia gas to become hot carbon dioxide, and then enters the refrigeration evaporator 14 to be defrosted through a carbon dioxide defrosting electromagnetic valve 19 and a hot carbon dioxide air supply decompression electromagnetic valve 12 under the action of pressure difference of cold carbon dioxide in the refrigeration evaporator 14. The flow of hot carbon dioxide into the refrigeration evaporator 14 may be set by the hot carbon dioxide supply pressure reducing solenoid valve 12. The carbon dioxide is then returned to the flooded evaporator 7 via the carbon dioxide differential pressure valve 16 for recondensing. The carbon dioxide differential pressure valve 16 maintains the carbon dioxide exiting the refrigeration evaporator 14 in a low pressure vapor-liquid mixture to avoid excessive system pressure.
In the lubricating oil cooling cycle, on the lubricating oil cooling refrigerant side, a part of the liquid ammonia condensed in the condenser 3 leaves from the siphon pipe 5, enters the oil cooler 4 to heat the lubricating oil from the oil separator 2, and then returns to the condenser 3 to be condensed again. On the lubricating oil side, the lubricating oil separated from the ammonia gas in the oil separator 2 enters the oil cooler 4, is cooled by the liquid ammonia on the lubricating oil cooling refrigerant side, and then returns to the compressor 1 to complete the cycle.
When the high-temperature and high-pressure ammonia gas generated by the compressor 1 enters the condenser 3 at a high speed, negative pressure is generated at the inlet of the condenser 3, and the ammonia gas from the oil cooler 4 and the refrigerant reservoir 6 is driven back into the condenser 3.
Maintaining the pressure in the carbon dioxide reservoir 10 at 13 kg.f/cm 2 The temperature was kept below-31 ℃.
The invention improves the carbon dioxide secondary refrigerant refrigerating system, fully utilizes the waste heat of the compressor and the cold energy of the refrigerant, and has low energy consumption and low cost; the improved flooded evaporator requires small installation space, and the heat exchange efficiency between the refrigerant and the secondary refrigerant is high;
in addition, the oil cooler utilizes a part of condensed refrigerant liquid to cool lubricating oil, so that the energy consumption can be saved, and the cost can be reduced.
In addition, the refrigerant gas from the oil cooler and the refrigerant reservoir is driven back to the condenser by the pressure difference generated by the high-pressure refrigerant gas, so that additional driving pumps and other devices are not required, and the cost can be further reduced.
In addition, the plurality of refrigeration evaporators are connected in parallel, so that frosting can be performed on the frosted refrigeration evaporators alone, and the rest refrigeration evaporators can continue to operate without stopping the whole refrigeration system.
The foregoing is only a preferred embodiment of the invention and is not intended to limit the scope of the invention, as any modifications, equivalent substitutions and improvements made within the spirit and principles of the invention fall within the scope of the invention.

Claims (8)

1. A carbon dioxide refrigerating medium refrigerating system is characterized by comprising a refrigerating medium circulation loop, a carbon dioxide circulation loop, a defrosting circulation loop and a lubricating oil cooling circulation loop,
the refrigerant circulation loop comprises a compressor (1), an oil separator (2), a condenser (3), a siphon pipe (5), a refrigerant liquid storage device (6), an electronic expansion valve (8), a flooded evaporator (7) and a pressure regulating valve (24), wherein a top end refrigerant outlet of the flooded evaporator (7) is connected to the compressor (1) through a pressure regulating valve (24) pipeline, an outlet pipeline of the compressor (1) is connected to the oil separator (2), a refrigerant outlet of the oil separator (2) is connected to the condenser (3) through a three-way valve pipeline, the condenser (3) is connected to the refrigerant liquid storage device (6) through the siphon pipe (5) pipeline, and the refrigerant liquid storage device (6) is connected to a refrigerant inlet of the flooded evaporator (7) through the electronic expansion valve (8);
the carbon dioxide circulation loop comprises a flooded evaporator (7), a carbon dioxide liquid storage device (10), a carbon dioxide pump (11) and a refrigeration evaporator (14), wherein an outlet pipeline of a carbon dioxide condensation pipe in the flooded evaporator (7) is connected to an inlet of the carbon dioxide liquid storage device (10), an outlet of the carbon dioxide liquid storage device (10) is connected with the carbon dioxide pump (11), the carbon dioxide pump (11) is connected to the refrigeration evaporator (14) through a pipeline of a cold carbon dioxide liquid supply electromagnetic valve (13), and an outlet of the refrigeration evaporator (14) is connected to an inlet of a carbon dioxide condensation pipe in the flooded evaporator (7) through a pipeline of a carbon dioxide discharge electromagnetic valve (15);
the defrosting circulation loop is provided with a defrosting refrigerant side and a carbon dioxide side, the defrosting refrigerant side comprises an oil separator (2), a refrigerant defrosting electromagnetic valve (20), a defrosting heat exchanger (18) and a refrigerant liquid storage device (6), a refrigerant inlet pipeline of the defrosting heat exchanger (18) is connected with an outlet of the refrigerant defrosting electromagnetic valve (20), an inlet of the refrigerant defrosting electromagnetic valve (20) is connected with a three-way valve pipeline between the oil separator (2) and the condenser (3), a refrigerant outlet pipeline of the defrosting heat exchanger (18) is connected with an inlet of the refrigerant liquid storage device (6), a top end gas outlet of the refrigerant liquid storage device (6) is connected with an inlet pipeline of the condenser (3), the carbon dioxide side comprises a carbon dioxide liquid storage device (10), the defrosting heat exchanger (18), a carbon dioxide defrosting electromagnetic valve (19), a refrigerating evaporator (14) and a full liquid evaporator (7), an outlet pipeline of the carbon dioxide liquid storage device (10) is connected with a carbon dioxide inlet of the defrosting heat exchanger (18), and a carbon dioxide outlet of the defrosting heat exchanger (18) is connected with a carbon dioxide outlet pipeline of the carbon dioxide evaporator (14) through the carbon dioxide defrosting electromagnetic valve (19) to a carbon dioxide outlet pipeline of the refrigerating evaporator (14);
the lubricating oil cooling circulation circuit has a lubricating oil cooling refrigerant side including a condenser (3), a siphon (5) and an oil cooler (4), the siphon (5) being connected to a refrigerant inlet of the oil cooler (4), a refrigerant outlet line of the oil cooler (4) being connected to an inlet of the condenser (3), and a lubricating oil side including a compressor (1), an oil separator (2) and the oil cooler (4), a lubricating oil outlet line of the oil separator (2) being connected to a lubricating oil inlet of the oil cooler (4), a lubricating oil outlet line of the oil cooler (4) being connected to a lubricating oil inlet of the compressor (1),
in the flooded evaporator (7), the carbon dioxide coolant of the carbon dioxide circulation loop flows in a carbon dioxide condensation tube, which is immersed in the refrigerant from the refrigerant circulation loop, whereby heat exchange of carbon dioxide with the refrigerant occurs;
the refrigerant circulation loop and the defrosting refrigerant side of the defrosting circulation loop are communicated through a pipeline between a three-way valve between an oil separator (2) and a condenser (3) and a refrigerant defrosting electromagnetic valve (20) and are communicated through a pipeline between a refrigerant outlet of a defrosting heat exchanger (18) and an inlet of a refrigerant reservoir (6), the carbon dioxide circulation loop and the carbon dioxide side of the defrosting circulation loop are communicated through a pipeline between an outlet of a carbon dioxide reservoir (10) and a carbon dioxide inlet of the defrosting heat exchanger (18) and are communicated through a pipeline between a carbon dioxide outlet of the defrosting heat exchanger (18) and a refrigerating evaporator (14);
the refrigerant circulation circuit and the lubricant cooling refrigerant side of the lubricant cooling circulation circuit are communicated by a line between a siphon pipe (5) and a refrigerant inlet of an oil cooler (4) and by a line between a refrigerant outlet of the oil cooler (4) and an inlet of a condenser (3),
the refrigerant circulating pump (9) is arranged outside the flooded evaporator (7), an inlet of the refrigerant circulating pump (9) is connected with a refrigerant outlet at the bottom of the flooded evaporator (7), and an outlet of the refrigerant circulating pump (9) is connected with a sprayer at the inner top of the flooded evaporator (7);
a liquid level controller (23) is arranged in the flooded evaporator (7), 4 liquid level sensors are arranged on the liquid level controller (23) from bottom to top, and the liquid level controller (23) is electrically connected with and controls the electronic expansion valve (8) and the refrigerant circulating pump (9) through a control system;
the full-liquid evaporator (7) is provided with an oil return ejector (21), an oil return port (25) of the oil return ejector (21) stretches into the full-liquid evaporator (7), an air inlet of the oil return ejector (21) is connected to a refrigerant outlet of the oil separator (2) through an oil return injection electromagnetic valve (22), and an air outlet of the oil return ejector (21) is connected to an inlet of the pressure regulating valve (24).
2. A carbon dioxide coolant refrigeration system of claim 1, wherein the carbon dioxide reservoir (10) is provided with a maintenance unit (17).
3. A carbon dioxide brine refrigeration system according to claim 1, wherein the refrigeration evaporator (14) is provided with a hot carbon dioxide supply pressure reducing solenoid valve (12), a cold carbon dioxide supply liquid solenoid valve (13), a carbon dioxide discharge solenoid valve (15) and a carbon dioxide differential pressure valve (16), an inlet of the hot carbon dioxide supply pressure reducing solenoid valve (12) is connected to an outlet of a carbon dioxide defrosting solenoid valve (19), an inlet of the cold carbon dioxide supply liquid solenoid valve (13) is connected to an outlet of the carbon dioxide pump (11), an outlet of the hot carbon dioxide supply pressure reducing solenoid valve (12) and the cold carbon dioxide supply liquid solenoid valve (13) is connected to an inlet of the refrigeration evaporator (14), an inlet of the carbon dioxide discharge solenoid valve (15) and the carbon dioxide differential pressure valve (16) are connected to an outlet of the refrigeration evaporator (14), and an outlet of the carbon dioxide discharge solenoid valve (15) and the carbon dioxide differential pressure valve (16) are connected to a carbon dioxide inlet of the flooded evaporator (7).
4. A carbon dioxide coolant refrigeration system as set forth in claim 3 wherein said refrigeration evaporator (14) is provided with a sensor, said sensor being electrically connected to a control system,
under the refrigeration working condition, the control system opens the cold carbon dioxide liquid supply electromagnetic valve (13) and the carbon dioxide discharge electromagnetic valve (15), and closes the hot carbon dioxide gas supply decompression electromagnetic valve (12) and the carbon dioxide differential pressure valve (16);
under defrosting working conditions, the control system closes the cold carbon dioxide liquid supply electromagnetic valve (13) and the carbon dioxide discharge electromagnetic valve (15), and opens the hot carbon dioxide gas supply decompression electromagnetic valve (12) and the carbon dioxide differential pressure valve (16).
5. A carbon dioxide coolant refrigeration system as claimed in claim 1, 3 or 4, wherein when the number of said refrigeration evaporators (14) is greater than one, said refrigeration evaporators (14) are in a parallel relationship.
6. A carbon dioxide coolant refrigeration system as set forth in claim 1 wherein the shell of the flooded evaporator (7) has an outer wall and an inner wall, the inner wall having a plurality of air outlet holes, an air outlet chamber being provided between the outer wall and the inner wall, the air outlet chamber being in communication with the refrigerant outlet at the top of the flooded evaporator (7).
7. A carbon dioxide coolant refrigeration system as recited in claim 1 wherein said refrigerant is ammonia.
8. A refrigerating method of carbon dioxide secondary refrigerant is characterized by comprising a refrigerant cycle, a carbon dioxide cycle, a defrosting cycle and a lubricating oil cooling cycle,
in the refrigerant circulation, refrigerant is compressed into high-temperature high-pressure refrigerant gas through a compressor (1), the gas enters an oil separator (2) and is separated from lubricating oil carried by the compressor (1), the refrigerant gas after separation enters a condenser (3) to be condensed and liquefied, the refrigerant gas enters a refrigerant liquid storage device (6) through a siphon tube (5), and then enters a flooded evaporator (7) after being depressurized through an electronic expansion valve (8), the refrigerant liquid is subjected to heat exchange with carbon dioxide secondary refrigerant in the flooded evaporator (7) to be changed into refrigerant gas, and the refrigerant gas returns to the compressor (1) through a pressure regulating valve (24) to complete the circulation;
in the carbon dioxide circulation, a carbon dioxide secondary refrigerant is condensed into liquid by a refrigerant in a flooded evaporator (7) and then enters a carbon dioxide liquid storage device (10), then enters a refrigeration evaporator (14) through a carbon dioxide pump (11), exchanges heat with cold, absorbs heat and changes phase into gas, and returns to the flooded evaporator (7) for condensation again to complete the circulation;
in the defrosting cycle, part of high-temperature and high-pressure refrigerant gas from an oil separator (2) enters a defrosting heat exchanger (18) through a three-way valve and a refrigerant defrosting electromagnetic valve (20) before entering a condenser (3) on the side of defrosting refrigerant, carbon dioxide liquid is heated and then returns to a refrigerant liquid storage device (6), part of carbon dioxide liquid from a carbon dioxide liquid storage device (10) enters the defrosting heat exchanger (18) on the side of carbon dioxide and is heated by the refrigerant gas, then enters a refrigerating evaporator (14) through a carbon dioxide defrosting electromagnetic valve (19) for defrosting, carbon dioxide returns to a flooded evaporator (7) for re-condensation, and the condensed carbon dioxide liquid reaches the carbon dioxide liquid storage device (10) to complete the cycle;
in the lubricating oil cooling cycle, on the lubricating oil cooling refrigerant side, a part of refrigerant liquid from the condenser (3) leaves from the siphon pipe (5) and enters the oil cooler (4) to heat lubricating oil separated in the oil separator (2), then the refrigerant returns to the condenser (3) to be condensed again to complete the cycle, on the lubricating oil side, lubricating oil from the compressor (1) is separated from the refrigerant in the oil separator (2) and then enters the oil cooler (4) to be subjected to heat exchange with the refrigerant liquid, the cooled lubricating oil returns to the compressor (1) to complete the cycle, and the refrigerant cycle and the carbon dioxide cycle interact through heat exchange in the flooded evaporator (7);
a portion of the refrigerant in the refrigerant cycle enters a defrost refrigerant side of the defrost cycle, a portion of the carbon dioxide in the carbon dioxide cycle enters a carbon dioxide side of the defrost cycle, and the portion of the refrigerant and the portion of the carbon dioxide are in heat exchange in the defrost heat exchanger (18);
a part of the refrigerant in the refrigerant cycle enters the lubricant cooling refrigerant side in the lubricant cooling cycle, and heat exchange with the lubricant occurs in the oil cooler (4).
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