CN114623617A - Refrigeration cycle method of transcritical carbon dioxide two-stage compression cold-hot combined supply system - Google Patents

Refrigeration cycle method of transcritical carbon dioxide two-stage compression cold-hot combined supply system Download PDF

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Publication number
CN114623617A
CN114623617A CN202210522179.1A CN202210522179A CN114623617A CN 114623617 A CN114623617 A CN 114623617A CN 202210522179 A CN202210522179 A CN 202210522179A CN 114623617 A CN114623617 A CN 114623617A
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temperature
working medium
low
pressure
medium
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郭东奇
刘冲
吕一帆
潘利生
费洪磊
刘宏斌
王宇航
杨东江
贾海生
杨永明
李菊花
李景晓
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China Energy Engineering Group Shanxi Electric Power Engineering Co Ltd
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China Energy Engineering Group Shanxi Electric Power Engineering 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
    • F25B40/00—Subcoolers, desuperheaters or superheaters
    • F25B40/02—Subcoolers
    • 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
    • F25B41/30—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
    • 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
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/06—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using expanders

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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)
  • Heat-Pump Type And Storage Water Heaters (AREA)

Abstract

The invention discloses a refrigeration cycle method of a transcritical carbon dioxide two-stage compression cold-hot combined supply system, belongs to the technical field of low-temperature refrigeration, and enables transcritical CO to be subjected to refrigeration cycle2The cycle efficiency and the practical use performance of the cycle are greatly improved, and the invention aims at the common working media adopted by the heat pump cycle, namely high ODP and GWP values and transcritical CO2The system has the advantages that the problem of low system circulation efficiency is caused by the reasons that the single-stage compression exhaust temperature is too high, the irreversible loss of large-temperature-difference heat exchange of the air cooler is too large, the throttling loss is large due to too large throttling pressure difference and the like in circulation, the system comprises a cold-heat combined supply main circulation system and an additional mechanical supercooling circulation system, the performance of the circulation system is fully improved from all aspects, and efficient refrigeration and heat supply are realized; the transcritical CO is subjected to three aspects of pressurization of a low-temperature system, reduction of outlet temperature of an air cooler and recovery throttling loss2Optimizing in circulation to make transcritical CO2The circulating efficiency of circulation is greatly improved.

Description

Refrigeration cycle method of transcritical carbon dioxide two-stage compression cold-hot combined supply system
Technical Field
The invention relates to a low-temperature refrigeration system, in particular to a high-energy-efficiency trans-critical carbon dioxide two-stage compression cold and heat combined supply system which is mainly used in the refrigeration and heat supply fields at various evaporation temperatures, such as the fields of commercial refrigeration, refrigeration houses, ice yards, regional heat supply and the like.
Background
With the continuous improvement of national economic level, the energy environmental problem faced by China is increasingly severe, and especially under the background of carbon peak reaching and carbon neutralization, the environmental problem faced by China is more prominent; the existing technical routes of the district heating coal-fired boiler and the thermal power cogeneration existLow energy efficiency of system and CO emission2The development of the defect is limited to a certain extent; for the refrigeration air-conditioning industry, the existing equipment has the problems of high power consumption, easy ozone layer damage caused by common refrigerants and greenhouse effect generation in the using process; the development of a new refrigeration technology with energy conservation, environmental protection and low carbon is urgently needed to realize the timely replacement of the prior art; CO 22As a specific NH3The safer natural refrigerant has an ODP (Ozone depletion Potential) value of 0 and a GWP (Global Warming Potential) of 1, has better low-temperature fluidity, heat exchange performance and high-temperature heating performance, and is regarded as one of the most ideal alternative working media of the refrigerant; CO compared to conventional refrigeration systems2The refrigeration cycle has the characteristics of safety, no toxicity, large refrigerating capacity per unit volume, more compact system equipment, higher system energy efficiency at low evaporation temperature and the like, and is suitable for industries with refrigeration and freezing low-temperature refrigeration requirements, such as business super, cold storage and the like; when it is mixed with CO2Transcritical CO as a single refrigerant2The Chinese patent with publication No. CN110030756A discloses a transcritical CO with ejector2The combined cooling and heating system is characterized in that a throttle valve connected with an outlet of the air cooler and an inlet of the evaporator in the system is replaced by an ejector, and cooling heat generated by the air cooler is recovered for hot water supply; chinese patent publication No. CN207350986U discloses a transcritical CO system for supercooling a working medium at an outlet of a gas cooler by using an auxiliary system of an evaporative cooler while recovering medium and low temperature expansion work by using an expander2A refrigeration system; the Chinese patent with publication number CN211041462U discloses a transcritical CO recycling waste heat of an air cooler and reducing the temperature of working media at the outlet of the air cooler by using mechanical supercooling circulation2A refrigeration cycle; the technical schemes all have the problem that the use efficiency of the system cannot be comprehensively improved.
Disclosure of Invention
The invention provides a transcritical carbon dioxide two-stage compression cold-heat combined supply systemThe refrigeration cycle of (2) is performed so that the transcritical CO is maintained2The efficiency and the actual performance of circulation are promoted by a wide margin to under the normal cold and hot confession mode, the system carries out high-efficient multi-temperature-zone refrigeration, utilizes the cooling heat to produce high-temperature water simultaneously and supplies heat.
The invention solves the technical problems by the following technical scheme:
the general concept of the invention is: the invention aims at the common working medium ODP and GWP values adopted by the heat pump cycle and trans-critical CO2During circulation, the problem of low system circulation efficiency is caused by the reasons that the single-stage compression exhaust temperature is overhigh, the irreversible loss of large-temperature-difference heat exchange of the air cooler is overhigh, the throttling loss is large due to overhigh throttling pressure difference and the like, and the transcritical CO with high circulation efficiency is provided2The double-stage compression combined cooling and heating system and the method comprise a main cooling and heating circulation system and an additional mechanical supercooling circulation system, fully improve the performance of the circulation system and realize high-efficiency refrigeration and heating; the transcritical CO is subjected to three aspects of pressurization of a low-temperature system, reduction of outlet temperature of an air cooler and recovery throttling loss2Optimizing in circulation to make transcritical CO2The circulating efficiency and the actual use performance of the circulation are greatly improved.
A high-energy-efficiency transcritical carbon dioxide two-stage compression cold and heat combined supply system comprises a high-pressure compressor, a main circulating air cooler, a subcooler, an expander, a liquid storage device, a medium-temperature evaporator, an ejector, a low-temperature evaporator, a gas-liquid separator, a low-pressure compressor and a circulating working medium CO2The expander and the high-pressure compressor are coaxially arranged; the output port of the high-pressure compressor is communicated with the working medium input port of the main circulation air cooler through a pipeline, the working medium output port of the main circulation air cooler is communicated with the working medium input port of the subcooler through a pipeline, the working medium output port of the subcooler is communicated with the working medium input port of the expander through a pipeline, the working medium output port of the expander is communicated with the working medium input port at the upper end of the liquid storage device through a pipeline, two output pipelines are connected in parallel on the liquid output port at the bottom of the liquid storage device, the first output pipeline is communicated with the working medium input port of the medium-temperature evaporator, and the first output pipeline is communicated with the working medium input port of the medium-temperature evaporatorA second regulating valve and a first expansion valve are connected in series on the output pipeline, a working medium output port of the intermediate temperature evaporator is communicated with a working medium input port at the lower end of the liquid storage device through a pipeline, a gas output port of the liquid storage device is communicated with an input port of the high-pressure compressor through a pipeline, and a first regulating valve is arranged on a communicating pipeline between the gas output port of the liquid storage device and the input port of the high-pressure compressor; on a liquid output port at the bottom of the liquid storage device, a second path of output pipeline connected in parallel is communicated with a main flow input port of the ejector, an output port of the ejector is communicated with a working medium input port of the gas-liquid separator through a pipeline, a liquid working medium output port of the gas-liquid separator is communicated with a working medium input port of the low-temperature evaporator through a pipeline, a third regulating valve and a second expansion valve are connected in series on a pipeline between the liquid working medium output port of the gas-liquid separator and the working medium input port of the low-temperature evaporator, and the working medium output port of the low-temperature evaporator is communicated with a secondary flow input port of the ejector through a pipeline; the gas working medium output port of the gas-liquid separator is communicated with the input port of the low-pressure compressor through a pipeline, and the output port of the low-pressure compressor is communicated with the input port of the high-pressure compressor through a pipeline; the main circulation air cooler is respectively provided with a main circulation cold water input pipeline and a main circulation hot water output pipeline.
The subcooler is provided with a low-temperature working medium input port and a low-temperature working medium output port, the low-temperature working medium output port of the subcooler is communicated with the working medium input port of the auxiliary compressor through a pipeline, the working medium output port of the auxiliary compressor is communicated with the working medium input port of the auxiliary air cooler through a pipeline, and the working medium output port of the auxiliary air cooler is communicated with the low-temperature working medium input port of the subcooler through a third expansion valve; an auxiliary circulating cold water input pipeline and an auxiliary circulating hot water output pipeline are arranged on the auxiliary air cooler.
A refrigeration cycle method of a transcritical carbon dioxide two-stage compression combined cooling and heating system comprises a high-pressure compressor, a main circulation air cooler, a subcooler, an expander, a liquid storage device, a medium-temperature evaporator, an ejector, a low-temperature evaporator, a gas-liquid separator, a low-pressure compressor and a medium-temperature and medium-pressure circulating working medium CO2Which isIs characterized in that:
a first output pipeline is connected in parallel to a liquid output port at the bottom of the liquid storage device, the other end of the first output pipeline is communicated with a working medium input port of the medium temperature evaporator, a second regulating valve and a first expansion valve are connected in series to the first output pipeline, and the working medium output port of the medium temperature evaporator is communicated with the working medium input port at the lower end of the liquid storage device;
a gas outlet of the liquid accumulator is communicated with an input port of the high-pressure compressor through a pipeline, and a first regulating valve is arranged on the communicating pipeline;
a third regulating valve and a second expansion valve are connected in series on a pipeline between a liquid working medium output port of the gas-liquid separator and a working medium input port of the low-temperature evaporator;
opening the first regulating valve, the second regulating valve and the third regulating valve to obtain the gaseous CO at medium temperature and medium pressure2Working medium is compressed to high-temperature high-pressure supercritical state by a high-pressure compressor, then conveyed to a main circulation gas cooler for cooling, still becomes medium-temperature high-pressure gas after cooling because the cooling process is still in the supercritical state, and then is cooled again to low-temperature high-pressure gas by a subcooler, and supercritical CO2The working medium cools down and can heat the cold water to a high temperature for hot water supply; supercritical CO at low temperature and high pressure2After entering an expansion machine for doing work, reducing the pressure into low-temperature medium-pressure gas and low-temperature medium-pressure liquid, dividing the low-temperature medium-pressure gas and the low-temperature medium-pressure liquid into two paths to flow out through a liquid storage device, wherein the low-temperature medium-pressure gas is low-temperature gaseous CO2The working medium is delivered to a working medium input port of the high-pressure compressor from a gas output port of the liquid storage device, and is mixed with medium-temperature medium-pressure gas at an outlet of the low-pressure compressor, and then the mixture enters the high-pressure compressor, the low-temperature medium-pressure liquid working medium is divided into two paths and enters a subcritical state, one path of the low-temperature medium-pressure liquid working medium absorbs environment latent heat in the medium-temperature evaporator, and then the environment latent heat is changed from a liquid state to a gas state, enters the liquid storage device, is converged with the original gas working medium, and is then delivered back to the high-pressure compressor, and medium-temperature refrigeration cycle is completed; the other path of low-temperature medium-pressure liquid working medium enters an ejector to inject the working medium with lower outlet pressure of the low-temperature evaporator, the two paths of fluid are mixed and then enter a gas-liquid separator in a two-phase state, the gas working medium enters a low-pressure compressor, and the liquid working medium flows into the low-temperature evaporator to continuously absorb heat to the environmentAnd completing the low-temperature refrigeration cycle.
The subcooler is provided with a low-temperature working medium input port and a low-temperature working medium output port, the low-temperature working medium output port of the subcooler is communicated with the working medium input port of the auxiliary compressor through a pipeline, the working medium output port of the auxiliary compressor is communicated with the working medium input port of the auxiliary air cooler through a pipeline, the working medium output port of the auxiliary air cooler is communicated with the low-temperature working medium input port of the subcooler through a third expansion valve, and the auxiliary air cooler is provided with an auxiliary circulating cold water input pipeline and an auxiliary circulating hot water output pipeline; working medium output from the low-temperature working medium output port of the subcooler sequentially flows through the auxiliary compressor, the auxiliary air cooler and the third expansion valve to complete mechanical supercooling circulation; the low-temperature low-pressure circulating working medium absorbs latent heat of the circulating working medium of the main circulating system in the subcooler and changes from liquid state to gas state, the circulating working medium is compressed to high-temperature high-pressure gas state by the auxiliary compressor, then enters the auxiliary air cooler to be condensed into low-temperature high-pressure liquid state at medium pressure, and the generated cooling heat can heat cold water in an auxiliary circulating cold water input pipeline and join with hot water heated by the main circulating air cooler for hot water supply, the low-temperature high-pressure working medium flows into the subcooler for heat absorption after being throttled and depressurized by the third expansion valve, and the mechanical subcooling cycle is repeatedly completed.
The invention discloses a high-cycle-efficiency trans-critical CO2A double-stage compression combined cooling and heating system and a working method thereof design a transcritical CO2The circulating system mainly adopts combined cooling and heating supply and assists in mechanical supercooling, and solves the problem of transcritical CO2In the refrigeration cycle, the exhaust temperature is overhigh due to overlarge compressor pressure ratio in the single-stage compression process, the irreversible heat exchange loss is larger due to larger average heat exchange temperature difference of an air cooler, the throttling loss is overlarge due to overlarge pressure difference of a working medium in the isenthalpic throttling process, and the like, and the stepped utilization of energy is realized by using the cooling heat generated by the air cooler for the supply of high-temperature hot water; the improvement of the circulating system can greatly improve the comprehensive energy efficiency and has certain significance for increasing the utilization rate of carbon dioxide, reducing the greenhouse effect and promoting the carbon neutralization.
Drawings
FIG. 1 is a schematic structural view of the present invention;
fig. 2 is a schematic view of the auxiliary mechanical subcooling cycle of the present invention.
Detailed Description
The invention is described in detail below with reference to the accompanying drawings:
a high-energy-efficiency transcritical carbon dioxide two-stage compression cold and heat combined supply system comprises a high-pressure compressor 1, a main circulation air cooler 2, a subcooler 3, an expander 4, a liquid storage device 5, a medium-temperature evaporator 6, an ejector 7, a low-temperature evaporator 8, a gas-liquid separator 9, a low-pressure compressor 10 and a circulating working medium CO2The expander 4 is coaxially arranged with the high-pressure compressor 1; an output port of the high-pressure compressor 1 is communicated with a working medium input port of the main circulation gas cooler 2 through a pipeline, a working medium output port of the main circulation gas cooler 2 is communicated with a working medium input port of the subcooler 3 through a pipeline, a working medium output port of the subcooler 3 is communicated with a working medium input port of the expander 4 through a pipeline, a working medium output port of the expander 4 is communicated with a working medium input port at the upper end of the liquid storage device 5 through a pipeline, two output pipelines are connected in parallel on a liquid output port at the bottom of the liquid storage device 5, a first output pipeline is communicated with a working medium input port of the medium-temperature evaporator 6, a second regulating valve 11-2 and a first expansion valve 12-1 are connected in series on the first output pipeline, a working medium output port of the medium-temperature evaporator 6 is communicated with a working medium input port at the lower end of the liquid storage device 5 through a pipeline, and a gas output port of the liquid storage device 5, the gas storage device is communicated with an input port of the high-pressure compressor 1 through a pipeline, and a first regulating valve 11-1 is arranged on a communication pipeline between a gas output port of the liquid storage device 5 and the input port of the high-pressure compressor 1; on the liquid outlet at the bottom of the liquid storage device 5, a second output pipeline connected in parallel is communicated with a main flow inlet of the ejector 7, an outlet of the ejector 7 is communicated with a working medium inlet of the gas-liquid separator 9 through a pipeline, a liquid working medium outlet of the gas-liquid separator 9 is communicated with a working medium inlet of the low-temperature evaporator 8 through a pipeline, and a third regulating valve 11-3 and a second expansion valve 11-3 are connected in series on the pipeline between the liquid working medium outlet of the gas-liquid separator 9 and the working medium inlet of the low-temperature evaporator 812-2, a working medium output port of the low-temperature evaporator 8 is communicated with a secondary flow input port of the ejector 7 through a pipeline; the gas outlet of the gas-liquid separator 9 is communicated with the inlet of the low-pressure compressor 10 through a pipeline, and the outlet of the low-pressure compressor 10 is communicated with the inlet of the high-pressure compressor 1 through a pipeline; the main circulation air cooler 2 is provided with a main circulation cold water input pipeline 15 and a main circulation hot water output pipeline 16.
A low-temperature working medium input port and a low-temperature working medium output port are arranged on the subcooler 3, the low-temperature working medium output port of the subcooler 3 is communicated with the working medium input port of the auxiliary compressor 14 through a pipeline, the working medium output port of the auxiliary compressor 14 is communicated with the working medium input port of the auxiliary gas cooler 13 through a pipeline, and the working medium output port of the auxiliary gas cooler 13 is communicated with the low-temperature working medium input port of the subcooler 3 through a third expansion valve 12-3; an auxiliary circulating cold water input pipeline 17 and an auxiliary circulating hot water output pipeline 18 are arranged on the auxiliary air cooler 13.
A refrigeration cycle method of a transcritical carbon dioxide two-stage compression combined cooling and heating system comprises a high-pressure compressor 1, a main cycle air cooler 2, a subcooler 3, an expander 4, a liquid storage device 5, a medium-temperature evaporator 6, an ejector 7, a low-temperature evaporator 8, a gas-liquid separator 9, a low-pressure compressor 10 and a medium-temperature and medium-pressure cycle working medium CO2The method is characterized in that:
a first output pipeline is connected in parallel to a liquid output port at the bottom of the liquid storage device 5, the other end of the first output pipeline is communicated with a working medium input port of the medium temperature evaporator 6, a second regulating valve 11-2 and a first expansion valve 12-1 are connected in series to the first output pipeline, and the working medium output port of the medium temperature evaporator 6 is communicated with a working medium input port at the lower end of the liquid storage device 5;
a gas outlet of the liquid accumulator 5 is communicated with an input port of the high-pressure compressor 1 through a pipeline, and a first regulating valve 11-1 is arranged on the communicating pipeline;
a third regulating valve 11-3 and a second expansion valve 12-2 are connected in series on a pipeline between a liquid working medium output port of the gas-liquid separator 9 and a working medium input port of the low-temperature evaporator 8;
the first regulating valve 11-1 and the second regulating valve 1 are opened1-2 and a third regulating valve 11-3, medium-temperature and medium-pressure gaseous CO2Working medium is compressed to high-temperature high-pressure supercritical state by the high-pressure compressor 1, then conveyed to the main circulation gas cooler 2 for cooling, and is still in supercritical state in the cooling process, so that the cooled medium-temperature high-pressure gas is still medium-temperature high-pressure gas, and is then cooled again to low-temperature high-pressure gas by the subcooler 3, and the supercritical CO is supercritical2The working medium cools down and can heat the cold water to a high temperature for hot water supply; supercritical CO at low temperature and high pressure2After entering the expansion machine 4 for doing work and being decompressed into low-temperature medium-pressure gas and low-temperature medium-pressure liquid, the low-temperature medium-pressure gas CO flows out in two ways through the liquid storage device 52The working medium is delivered to a working medium input port of the high-pressure compressor 1 from a gas output port of the liquid storage device 5, and is mixed with the medium-temperature medium-pressure gas at the outlet of the low-pressure compressor 10, and then enters the high-pressure compressor 1, the low-temperature medium-pressure liquid working medium is divided into two paths and enters a subcritical state, wherein one path of the low-temperature medium-pressure liquid working medium absorbs environment latent heat in the medium-temperature evaporator 6, changes the environment latent heat from a liquid state to a gas state, enters the liquid storage device 5, is converged with the original gas working medium, and then is delivered back to the high-pressure compressor 1, and medium-temperature refrigeration cycle is completed; the other path of low-temperature medium-pressure liquid working medium enters the ejector 7, the working medium with lower outlet pressure of the low-temperature evaporator is ejected, the two paths of fluid are mixed and then enter the gas-liquid separator 9 in a two-phase state, the gaseous working medium enters the low-pressure compressor 10, and the liquid working medium flows into the low-temperature evaporator 8 to continuously absorb heat to the environment, so that the low-temperature refrigeration cycle is completed.
A low-temperature working medium input port and a low-temperature working medium output port are arranged on the subcooler 3, the low-temperature working medium output port of the subcooler 3 is communicated with a working medium input port of the auxiliary compressor 14 through a pipeline, a working medium output port of the auxiliary compressor 14 is communicated with a working medium input port of the auxiliary gas cooler 13 through a pipeline, a working medium output port of the auxiliary gas cooler 13 is communicated with a low-temperature working medium input port of the subcooler 3 through a third expansion valve 12-3, and an auxiliary circulating cold water input pipeline 17 and an auxiliary circulating hot water output pipeline 18 are arranged on the auxiliary gas cooler 13; working medium output from a low-temperature working medium output port of the subcooler 3 sequentially flows through the auxiliary compressor 14, the auxiliary air cooler 13 and the third expansion valve 12-3 to complete mechanical supercooling circulation; the low-temperature low-pressure circulating working medium absorbs latent heat of the circulating working medium of the main circulating system in the subcooler 3 and changes from liquid state to gas state, the circulating working medium is compressed to high-temperature high-pressure gas state by the auxiliary compressor 14, then enters the auxiliary air cooler 13 to be condensed at medium pressure to low-temperature high-pressure liquid state, meanwhile, the generated cooling heat can heat cold water in the auxiliary circulating cold water input pipeline 17, the cold water is converged with hot water heated by the main circulating air cooler to be supplied with hot water, the low-temperature high-pressure working medium flows into the subcooler 3 to absorb heat after being throttled and depressurized by the third expansion valve 12-3, and the mechanical subcooling cycle is repeatedly completed.

Claims (2)

1. A refrigeration cycle method of a transcritical carbon dioxide two-stage compression combined cooling and heating system comprises a high-pressure compressor (1), a main cycle air cooler (2), a subcooler (3), an expander (4), a liquid storage device (5), a medium-temperature evaporator (6), an ejector (7), a low-temperature evaporator (8), a gas-liquid separator (9), a low-pressure compressor (10) and a medium-temperature and medium-pressure cycle working medium CO2The method is characterized in that:
a first output pipeline is connected in parallel to a liquid output port at the bottom of the liquid reservoir (5), the other end of the first output pipeline is communicated with a working medium input port of the medium temperature evaporator (6), a second regulating valve (11-2) and a first expansion valve (12-1) are connected in series to the first output pipeline, and the working medium output port of the medium temperature evaporator (6) is communicated with the working medium input port at the lower end of the liquid reservoir (5);
a gas outlet of the liquid storage device (5) is communicated with an input port of the high-pressure compressor (1) through a pipeline, and a first regulating valve (11-1) is arranged on the communicating pipeline;
a third regulating valve (11-3) and a second expansion valve (12-2) are connected in series on a pipeline between a liquid working medium output port of the gas-liquid separator (9) and a working medium input port of the low-temperature evaporator (8);
opening a first regulating valve (11-1), a second regulating valve (11-2) and a third regulating valve (11-3), and obtaining the gaseous CO at the medium temperature and the medium pressure2The working medium is compressed to a high-temperature high-pressure supercritical state by the work of the high-pressure compressor (1), and then is conveyed to the main circulation air cooler (2) for carrying outCooling, because the temperature reduction process is still in a supercritical state, the gas is still medium-temperature high-pressure gas after cooling, and then is cooled again to be low-temperature high-pressure gas through a subcooler (3), and supercritical CO2The working medium cools down and can heat the cold water to a high temperature for hot water supply; supercritical CO at low temperature and high pressure2After entering an expander (4) to do work, the gas is decompressed into low-temperature medium-pressure gas and low-temperature medium-pressure liquid, and then is divided into two paths to flow out through a liquid storage device (5), and low-temperature medium-pressure gaseous CO2The working medium is delivered to a working medium input port of the high-pressure compressor (1) from a gas output port of the liquid storage device (5), mixed with medium-temperature medium-pressure gas at an outlet of the low-pressure compressor (10), and then enters the high-pressure compressor (1), the low-temperature medium-pressure liquid working medium is divided into two paths and enters a subcritical state, one path of the low-temperature medium-pressure liquid working medium changes the environment latent heat absorbed in the medium-temperature evaporator (6) from liquid state to gas state, enters the liquid storage device (5), is converged with the original gas state working medium, and then is delivered back to the high-pressure compressor (1), and medium-temperature refrigeration cycle is completed; and the other path of low-temperature medium-pressure liquid working medium enters the ejector (7) to inject the working medium with lower outlet pressure of the low-temperature evaporator, the two paths of fluid are mixed and then enter the gas-liquid separator (9) in a two-phase state, the gaseous working medium enters the low-pressure compressor (10), and the liquid working medium flows into the low-temperature evaporator (8) to continuously absorb heat to the environment, so that the low-temperature refrigeration cycle is completed.
2. The refrigeration cycle method of a transcritical carbon dioxide two-stage compression combined cooling and heating system as recited in claim 1, wherein a low-temperature working medium input port and a low-temperature working medium output port are provided on the subcooler (3), the low-temperature working medium output port of the subcooler (3) is communicated with the working medium input port of the auxiliary compressor (14) through a pipeline, the working medium output port of the auxiliary compressor (14) is communicated with the working medium input port of the auxiliary air cooler (13) through a pipeline, the working medium output port of the auxiliary air cooler (13) is communicated with the low-temperature working medium input port of the subcooler (3) through a third expansion valve (12-3), and an auxiliary cycle cold water input pipeline (17) and an auxiliary cycle hot water output pipeline (18) are provided on the auxiliary air cooler (13); working medium output from a low-temperature working medium output port of the subcooler (3) sequentially flows through the auxiliary compressor (14), the auxiliary air cooler (13) and the third expansion valve (12-3) to complete mechanical supercooling circulation; the low-temperature low-pressure circulating working medium absorbs latent heat of the circulating working medium of the main circulating system in the subcooler (3) and changes from liquid state to gas state, the circulating working medium is compressed to high-temperature high-pressure gas state by the auxiliary compressor (14), then enters the auxiliary air cooler (13) to be condensed to low-temperature high-pressure liquid state at medium pressure, meanwhile, the generated cooling heat can heat cold water in the auxiliary circulating cold water input pipeline (17), and the cold water is heated by the main circulating air cooler and converged with hot water for hot water supply, the low-temperature high-pressure working medium flows into the subcooler (3) to absorb heat after throttling and pressure reduction by the third expansion valve (12-3), and the mechanical subcooling cycle is repeatedly completed.
CN202210522179.1A 2022-05-14 2022-05-14 Refrigeration cycle method of transcritical carbon dioxide two-stage compression cold-hot combined supply system Pending CN114623617A (en)

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