WO2019141019A1 - 一种跨临界二氧化碳复合热泵系统的控制方法 - Google Patents

一种跨临界二氧化碳复合热泵系统的控制方法 Download PDF

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Publication number
WO2019141019A1
WO2019141019A1 PCT/CN2018/120175 CN2018120175W WO2019141019A1 WO 2019141019 A1 WO2019141019 A1 WO 2019141019A1 CN 2018120175 W CN2018120175 W CN 2018120175W WO 2019141019 A1 WO2019141019 A1 WO 2019141019A1
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Prior art keywords
air
cooled
auxiliary
recombiner
main
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English (en)
French (fr)
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曹锋
王静
殷翔
李明佳
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Xian Jiaotong University
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Xian Jiaotong University
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Priority to US16/618,353 priority Critical patent/US11255579B2/en
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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
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H4/00—Fluid heaters characterised by the use of heat pumps
    • F24H4/02—Water heaters
    • 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
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary 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
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • 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
    • 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
    • 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
    • F25B49/022—Compressor control 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
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • 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
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by 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
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • 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
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/003—Indoor unit with water as a heat sink or heat source
    • 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
    • F25B2339/04—Details of condensers
    • F25B2339/047—Water-cooled condensers
    • 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
    • F25B2400/00—Component parts or details not otherwise provided for in this subclass
    • F25B2400/06—Several compression cycles arranged in parallel
    • 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
    • F25B2500/00—Problems to be solved
    • F25B2500/19—Calculation of parameters
    • 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
    • F25B2600/02—Compressor control
    • F25B2600/025—Compressor control by controlling speed
    • F25B2600/0253—Compressor control by controlling speed with variable speed
    • 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
    • F25B2600/11—Fan speed control
    • F25B2600/112—Fan speed control of evaporator fans
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2104—Temperatures of an indoor room or compartment
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2106—Temperatures of fresh outdoor air
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2116—Temperatures of a condenser
    • F25B2700/21161—Temperatures of a condenser of the fluid heated by the condenser
    • 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

Definitions

  • the invention belongs to the technical field of heat pumps, and in particular relates to a control method of a transcritical carbon dioxide composite heat pump system.
  • the heat pump can absorb the heat in the ambient air and transfer the heat to the circulating water through the working fluid circulation to play the role of heating.
  • Conventional heat pumps mostly use traditional working fluids such as R134a and R410a, which are less environmentally friendly and face a gradual elimination trend.
  • the critical temperature of CO 2 is very low, 31.1 ° C, so the CO 2 heat pump system generally uses a transcritical cycle.
  • the CO 2 transcritical cycle compressor has a higher exhaust gas temperature (up to 100 °C), and in the transcritical region, CO 2 has a large temperature slip during the cooling process. This temperature slip is exactly what is needed.
  • the variable temperature heat source is matched to heat the water to a very high temperature and maintain high efficiency, especially suitable for domestic hot water.
  • the difference between a CO 2 transcritical cycle system and a conventional subcritical cycle system is that in a conventional subcritical system, the temperature of the refrigerant remains constant in most areas of the condenser, and in the CO 2 transcritical cycle system. There is no two-phase zone in the supercritical pressure zone. The temperature and pressure are independent variables. The pressure change on the high pressure side also affects the cooling capacity, compressor power consumption and COP value.
  • the transcritical CO 2 heat pump cycle has a unique advantage in that the exothermic process temperature is high and there is a considerable temperature slip (about 80 to 100 ° C).
  • the research shows that: (1) When the evaporation temperature is 0 °C, the water temperature can be heated from 0 °C to 60 °C, and the heat pump COP can reach 4.3, which is 75% lower than that of electric water heaters and gas water heaters. In cold regions, the heat and efficiency of conventional air source heat pumps decrease rapidly with decreasing ambient temperature, and the use of heat pumps is limited.
  • the CO 2 heat pump system can maintain high heat supply and high water temperature in a low temperature environment, which greatly saves the energy consumed by the auxiliary heating equipment.
  • the performance of a transcritical carbon dioxide heat pump water heater is severely limited by the gas cooler outlet temperature, and the lower the gas cooler outlet temperature, the better the system performance.
  • the gas cooler outlet temperature of the transcritical carbon dioxide heat pump water heater can also be cooled by circulating water to a relatively low temperature, and the system performance is excellent at this time. .
  • the existing transcritical CO 2 composite heat pump returns two waters, the first return water enters the auxiliary gas cooler, and then returns to the water outlet, and the return water of the second loop enters the auxiliary evaporator, after cooling
  • the water enters the gas cooler of the main cycle and then returns to the water outlet.
  • the first road water is mixed with the second road water to supply water to the user.
  • the existing fixed-frequency heat pump system uses a fixed-frequency compressor, which has two loops and requires three heat exchangers of refrigerant and water.
  • the distribution and connection of the water path is extremely complicated and prone to failure. It can only be operated under design conditions (when the return water temperature in the water circulation system is sufficiently low (20 ° C or even lower than 20 ° C), the gas cooler outlet temperature of the transcritical carbon dioxide heat pump water heater can also be cooled to a relatively low temperature by circulating water. The temperature of the system, at this time, the performance of the system is excellent.)
  • the flow rate of the circuit during operation cannot be adjusted according to the change of working conditions. Especially for the main and auxiliary stage heat pump products, the fixed compressor flow ratio is difficult to adapt.
  • the object of the present invention is to provide a control method for a transcritical carbon dioxide composite heat pump system, which solves the problem that the performance of the existing transcritical CO 2 composite heat pump is severely restricted by the gas cooler outlet temperature, water distribution and connection complexity, and energy waste.
  • the existing fixed-frequency heat pump system adopts a fixed-frequency compressor, and the loop flow rate cannot be changed, especially for the main-sub-composite type composite heat pump products, and the fixed compressor flow ratio is difficult to adapt to the current situation of variable operating conditions, and the present invention
  • the heat pump is divided into main circuit and auxiliary circuit; under normal working conditions, when the return water temperature is low (30 ° C or lower than 30 ° C), the direct heat type heating mode is operated; when the return water temperature is high (higher than 30) °C), converted to a cyclic heating mode.
  • the two modes are alternately operated, which effectively improves the shortcomings of the existing system that cannot adapt to the variable working conditions, avoids the performance of the existing system under non-design conditions and the waste of energy, and still achieves the conditions under multiple working conditions. While maintaining high performance, due to the alternation of the two modes, the energy waste caused by the existing single operating mode of the system is avoided, and the number of heat exchangers is reduced, the structure of the system is simplified, and the probability of failure is reduced.
  • a method for controlling a transcritical carbon dioxide composite heat pump system comprising a CO 2 main road compressor, a gas cooled air cooled composite, a supercooled-evaporating composite, an evaporator, and a CO 2 auxiliary compressor;
  • the air-cooled-air-cooled recombiner comprises three paths of CO 2 main road, CO 2 auxiliary road and water path;
  • the supercooling-evaporation recombiner comprises two passages of CO 2 main road supercooling section and CO 2 auxiliary road evaporation section;
  • the transcritical carbon dioxide composite heat pump system comprises two circuits of a main circuit and an auxiliary circuit; a main circuit: an outlet of the CO 2 main circuit compressor is connected to an inlet of the CO 2 main path of the air-cooling-air-cooled recombiner, and is air-cooled- an outlet air-cooled CO 2 composite main road is connected supercooled - CO 2 recombiner evaporator passing cold leg main inlet subcooling - evaporator recombiner CO 2 outlet cooling section passing
  • the transcritical carbon dioxide composite heat pump system operates in a cyclic heating mode, and the control method includes:
  • the CO 2 main circuit compressor works, the main circuit opens, the CO 2 auxiliary compressor works, the auxiliary circuit opens; the fan is in the open state; the main circuit: the CO 2 working fluid is compressed by the state point a through the CO 2 main circuit compressor State point b, enters the CO 2 main road of the air-cooled-air-cooled recombiner, heats the circulating water in the waterway, and cools itself to a suitable temperature to reach the state point c, and then flows through the CO of the cold-evaporation recombiner 2 The main road passes through the cold section, exchanges heat with the CO 2 auxiliary road evaporation section, further cools down, reaches the state point d, and then enters the CO 2 main road expansion valve for expansion.
  • the expanded low-pressure working medium reaches the state point e and enters the evaporation.
  • the evaporator evaporates, absorbs heat, returns to the state point a, and finally returns to the inlet of the CO 2 main road compressor;
  • the auxiliary circuit the CO 2 working fluid reaches the state point g after being compressed by the CO 2 auxiliary compressor from the state point f, entering the air-cooled - CO 2 air-cooled recombiner roads in the circulating water to heat the water, and cool down to reach the state point itself H, CO 2 then enters the expansion valve roads expanded state reaches the point i, the low pressure after expansion Mass into the supercooled - CO 2 recombiner evaporator roads evaporator section, with CO 2 passing through the cold leg of the main heat exchanger, CO 2 is further cooled primary cooling zone passing, going to state their endothermic heat of vaporization point F, and finally back to the CO 2 compression aid Import of the machine.
  • the main CO 2 working medium is cooled and released in the CO 2 main road, and the auxiliary CO 2 working medium is cooled and released in the CO 2 auxiliary road, and the circulating water absorbs heat to reach the setting.
  • the temperature is fixed; in the supercooling-evaporation recombiner, the main CO 2 working fluid is further cooled and released in the supercooling section of the CO 2 main road, and the auxiliary CO 2 working fluid evaporates and absorbs heat in the CO 2 auxiliary road evaporation section, and the CO 2 auxiliary road evaporates.
  • the section exchanges heat with the CO 2 main road through the cold section to maintain heat balance.
  • the auxiliary road control method comprises: collecting the ambient temperature t- ring , the temperature t g of the CO 2 auxiliary road outlet of the air-cooling-air-cooling recombiner set by the user , the outlet auxiliary road and the air-cooling-air-cooling recombinator set by the user.
  • the temperature of the waterway outlet is returned to water
  • the exhaust pressure of the CO 2 auxiliary compressor is calculated by the formula.
  • CO 2 by adjusting the opening degree of the expansion valve roads to reach a given pressure
  • CO 2 auxiliary compressor is calculated according to the formula frequency f of the compressor motor 6, with the frequency of the compressor operating conditions vary;
  • Main road control method collecting ambient temperature t- ring , user-set air-cooled-air-cooled recombiner CO 2 main road outlet temperature t g, out main road and user-set air-cooled-air-cooled recombiner The temperature of the water outlet is returned to water ; then the optimal exhaust pressure P CO2 of the CO 2 main circuit compressor is calculated by the formula , and the main path is adjusted to achieve a given pressure by adjusting the opening of the CO 2 main expansion valve;
  • the air-cooled-air-cooled recombiner includes three inner tubes and one outer tube, two inner tubes serve as a CO 2 main circuit, and one inner tube serves as a CO 2 auxiliary circuit, between the outer tube and the three inner tubes.
  • the passage is a waterway; the three inner tubes are arranged in an equilateral triangle, and the spacing between the three inner tubes is the same, both are D L ; the diameters of the three inner tubes are all D 2 , and the diameter of the outer tube is D 1 ;
  • One end of the main circuit is combined with a pipe connected to the exhaust port of the CO 2 main circuit compressor on the outside of the air-cooled-air-cooled recombiner, and the other end of the two CO 2 main circuits is synthesized on the outside of the air-cooled-air-cooled recombiner a pipe connecting the exhaust port CO 2 main road supercooling section;
  • a fan is also mounted on the evaporator.
  • CO 2 auxiliary compressor uses an inverter compressor.
  • the transcritical carbon dioxide composite heat pump system operates in a circulating heating mode.
  • the present invention has the following beneficial effects:
  • the invention provides a transcritical CO 2 composite heat pump and a control method thereof, which adopts a control mode in which a heat pump is divided into a main circuit and an auxiliary circuit; so that under normal working conditions, when the return water temperature is low (30 ° C or lower) 30 °C), running the direct heating type heating mode; when the return water temperature is high (above 30 °C), it is converted into a circulating heating mode, so that the system can adapt to the variable working conditions and achieve energy saving. purpose.
  • the circulation type heating mode When the return water temperature is high (above 30 °C), the circulation type heating mode is operated, the main circuit compressor works, the main circuit is opened, the auxiliary circuit compressor is working, the auxiliary circuit is opened, the fan is in the open state; In the first subcooling-evaporation recombiner, the CO 2 of the auxiliary circuit evaporates and absorbs heat, and the CO 2 in the main circuit is cooled a second time, so that the CO 2 in the main circuit reaches a suitable outlet temperature, and a higher system is ensured. performance.
  • the circulating water circuit is a single circuit that is one in and one out, and the system is simple, reducing the failure rate.
  • the direct heat type heating mode and the circulation type heating mode are switched, so that the heat pump unit has a wider application range and higher performance.
  • CO 2 is an inert gas, non-toxic and non-irritating; good in safety and chemical stability, safe and non-toxic, non-flammable, and does not decompose to generate harmful gases even at high temperatures; its global warming potential index GWP is 1, CO 2 does not require industrial synthesis, it only needs to be extracted in the atmosphere, and it is convenient to use; at the same time, it has no destructive effect on the atmospheric ozone layer, and the ODP is zero. Moreover, the superior thermophysical properties of CO 2 itself and good migration characteristics are also suitable as refrigerants.
  • the heating method of the present invention adopts a CO 2 heat pump type, which has higher energy utilization rate and is more energy-saving.
  • CO 2 has a large latent heat of vaporization, high volume per unit volume, excellent flow and heat transfer characteristics, and can significantly reduce the size of the system, making the entire system very compact.
  • the transcritical CO 2 heat pump cycle has a unique advantage in that the exothermic process temperature is high and there is a considerable temperature slip (about 80 to 100 ° C).
  • Its heat pump COP can reach 4.3, which is more than 75% lower than that of electric water heaters and gas water heaters. In cold regions, the heat and efficiency of conventional air source heat pumps decrease rapidly with decreasing ambient temperature, and the use of heat pumps is limited.
  • the CO 2 heat pump system can maintain a high heat supply in a low temperature environment, which greatly saves the energy consumed by the auxiliary heating equipment.
  • the auxiliary circuit adopts the inverter compressor to enable the heat pump water heater system to operate stably and reliably for a long time under wider load and temperature conditions, reduce power consumption, and reduce the starting current of the compressor.
  • formula (1) is proposed for controlling the exhaust pressure of the compressor 6. To ensure the high performance of the entire system.
  • the temperature at the d in the cycle needs to be maintained at a suitable value.
  • the frequency of the compressor can be varied with the operating conditions, and the optimum of the compressor 6 is calculated by the formula (2).
  • the frequency by controlling the speed of the compressor 6, keeps the system operating efficiently.
  • the optimal exhaust pressure of the compressor 1 can be calculated by the formula (3), so that the main circuit can always maintain a higher efficiency operation.
  • the air-cooling-air-cooled recombiner with the highest heat exchange efficiency can be selected to improve the overall performance of the system.
  • FIG. 1 is a schematic structural view of a transcritical carbon dioxide composite heat pump system of the present invention
  • FIG. 2 is a schematic structural view of a transcritical carbon dioxide composite heat pump system in a direct heating type heating mode according to the present invention
  • FIG. 3 is a schematic diagram of a cycle of a transcritical carbon dioxide composite heat pump system in a direct heating type heating mode according to the present invention
  • FIG. 4 is a schematic structural view of a transcritical carbon dioxide composite heat pump system in a circulating heating mode according to the present invention
  • FIG. 5 is a schematic diagram of a cycle in a cyclic heating mode of a transcritical carbon dioxide composite heat pump system according to the present invention
  • FIG. 6 is a schematic view showing the internal piping arrangement of a gas-cooled-air-cooled recombiner of a transcritical carbon dioxide composite heat pump system according to the present invention
  • a transcritical carbon dioxide composite heat pump system of the present invention comprises a CO 2 main road compressor 1, an air-cooled-air-cooled recombiner 2, a supercooling-evaporating recombiner 3, an evaporator 5, and a CO 2 auxiliary compression. Machine 6.
  • the air-cooling-air-cooling recombiner 2 comprises three passages of a CO 2 main road 9, a CO 2 auxiliary road 10 and a water passage 11; the supercooling-evaporation recombiner 3 comprises a CO 2 main road supercooling section 12 and a CO 2 auxiliary road evaporation section 13 path.
  • the transcritical carbon dioxide composite heat pump system of the invention comprises two circuits of a main circuit and an auxiliary circuit;
  • the outlet of the CO 2 main circuit compressor 1 is connected to the inlet of the CO 2 main path 9 of the air-cooled-air-cooled recombiner 2, and the outlet of the CO 2 main path 9 of the air-cooled-air-cooled recombiner 2 is too cold-
  • the CO 2 main road of the evaporating recombiner 3 is imported from the supercooling section 12, the outlet of the CO 2 main road supercooling section 12 of the supercooling-evaporating recombiner 3 is connected to the inlet of the evaporator 5, and the outlet of the evaporator 5 is connected to the CO 2 main road compressor. Import of 1;
  • CO 2 auxiliary compressor outlet 6 is connected to air-cooling - air-cooled recombiner inlet of CO 2 10 2 roads, air cooling - air cooling exit of CO 2 2 multiplexer 10 is connected roads supercooling - evaporator recombiner roads 3 CO 2 inlet section 13 of the evaporator, the supercooling - evaporator outlet CO 2 roads composite evaporation stage 3 is connected to inlet 13 of CO 2 auxiliary compressor 6.
  • a CO 2 main path expansion valve 4 is disposed between the supercooling-evaporation recombiner 3 and the evaporator 5 on the main circuit; CO is disposed between the air-cooling-air-cooling recombiner 2 and the supercooling-evaporation recombiner 3 on the auxiliary circuit 2 auxiliary expansion valve 7.
  • a fan 8 is also mounted on the evaporator 5, and the appropriate heat transfer coefficient can be adjusted by changing the rotational speed of the fan.
  • the CO 2 auxiliary compressor 6 uses an inverter compressor.
  • the air-cooling-air-cooling recombiner 2 includes three inner tubes and one outer tube, two inner tubes serve as the CO 2 main circuit 9, and one inner tube serves as the CO 2 auxiliary circuit 10, the outer tube and The passage between the three inner tubes is the water path 11.
  • the three inner tubes are arranged in an equilateral triangle, and the tube spacing between the three inner tubes is the same, both are D L ; the diameters of the three inner tubes are all D 2 and the diameter of the outer tube is D 1 .
  • One end of the two CO 2 main circuits 9 is combined with a pipe connected to the exhaust port of the CO 2 main circuit compressor 1 outside the gas-cooled-air-cooled recombiner 2, and the other ends of the two CO 2 main circuits 9 are air-cooled - A pipe is connected to the outside of the air-cooled recombiner 2 to connect the CO 2 main path supercooling section 12.
  • the present invention sets two operating modes:
  • Direct heating type heating mode (return water temperature is 30 ° C or lower than 30 ° C): Please refer to Figure 2 and Figure 3, CO 2 main circuit compressor 1 works, main circuit is open; CO 2 auxiliary compressor 6 is closed, auxiliary The loop is closed; the fan is on.
  • the main circuit the CO 2 working fluid reaches the state point b after being compressed by the CO 2 main circuit compressor 1 from the state point a, enters the CO 2 main road 9 of the air-cooling-air-cooling recombiner 2, and circulates in the water path 11
  • the water is heated and cooled to a suitable temperature to reach the state point c, and then the state of the CO 2 main road supercooling section 12 flowing through the cold-evaporation recombiner 3 does not change, is still the state point c, and then enters the CO 2 main road expansion.
  • the valve 4 is expanded, and the expanded low-pressure working medium reaches the state point d, enters the evaporator 5 for evaporation, absorbs heat, returns to the state point a, and finally returns to the inlet of the CO 2 main circuit compressor 1.
  • Circulating heating mode (return water temperature is higher than 30 °C): Please refer to Figure 4 and Figure 5, CO 2 main circuit compressor 1 works, main circuit is open, CO 2 auxiliary compressor 6 is working, auxiliary circuit is open; fan is at Open state.
  • the main circuit the CO 2 working fluid reaches the state point b after being compressed by the CO 2 main circuit compressor 1 from the state point a, enters the CO 2 main road 9 of the air-cooling-air-cooling recombiner 2, and circulates in the water path 11
  • the water is heated and cooled to a suitable temperature to reach a state point c, and then flows through the CO 2 main road supercooling section 12 of the cold-evaporation recombiner 3, and exchanges heat with the CO 2 auxiliary road evaporation section to further cool down and reach a state.
  • Point d then enter the CO 2 main road expansion valve 4 for expansion, the expanded low-pressure working medium reaches the state point e, enters the evaporator 5 for evaporation, absorbs heat, returns to the state point a, and finally returns to the CO 2 main road The inlet of the compressor 1.
  • the auxiliary circuit the CO 2 working fluid reaches the state point g after being compressed by the CO 2 auxiliary compressor 6 from the state point f, enters the CO 2 auxiliary circuit 10 of the air-cooling-air-cooling recombiner 2, and performs the circulating water in the water path 11 Heating, and cooling down to the state point h, and then entering the CO 2 auxiliary expansion valve 7 for expansion to reach the state point i, the expanded low-pressure working medium enters the CO 2 auxiliary road evaporation section 13 of the supercooling-evaporation recombiner 3, and CO 2
  • the main road passes through the cold section 12 heat exchange, further cools the CO 2 main road supercooling section 12, the self-evaporation heat absorption reaches the state point f, and finally returns to the inlet of the CO 2 auxiliary compressor 6.
  • the main CO 2 working fluid is cooled and released in the CO 2 main road 9, and the auxiliary CO 2 working medium is cooled and released in the CO 2 auxiliary road 10, and the circulating water absorbs heat to achieve a suitable temperature. temperature.
  • the main CO 2 working fluid is further cooled and released in the CO 2 main road supercooling section 12 to reach a suitable temperature, and the auxiliary CO 2 working fluid evaporates and absorbs heat in the CO 2 auxiliary road evaporation section 13 , CO 2
  • the auxiliary road evaporation section 13 exchanges heat with the CO 2 main road supercooling section 12 to maintain heat balance.
  • Auxiliary road control When the return water temperature is high (greater than or equal to 30 ° C), the higher the exhaust pressure of the CO 2 auxiliary road, the greater the heat production, the better the running effect. From the perspective of the control principle, a fitting formula of the CO 2 auxiliary road exhaust pressure is proposed to control the exhaust pressure of the compressor 6. To ensure the high performance of the entire system.
  • auxiliary road temperature of CO 2 auxiliary road 10 outlet of air-cooling-air-cooling recombiner 2
  • t- ring ambient temperature
  • t return water air-cooling-air-cooling recombinator 2 waterway 11 outlet After the temperature
  • the exhaust pressure of the CO 2 auxiliary compressor 6 by adjusting the opening degree of the CO 2 auxiliary expansion valve 7, to achieve a given pressure, thereby ensuring a more efficient operation of the system.
  • the present invention proposes an adaptive frequency control formula for the CO 2 auxiliary compressor 6 when operating conditions change.
  • the temperature at d in the cycle needs to be kept at a suitable value.
  • the frequency of the compressor can be changed with the operating conditions to keep the system operating efficiently, and the following fitting formula is proposed.
  • the f compressor 6 (the motor frequency of the CO 2 auxiliary compressor 6) can be calculated according to the formula, and the frequency of the compressor can be varied with the operating conditions to keep the system operating efficiently.
  • Main road control When given t g, out main road (air-cooling-air-cooled recombinator 2 CO 2 main road 9 outlet temperature), t- ring (ambient temperature) t return water (air-cooled-air-cooled recombiner
  • the temperature of the outlet of the waterway 11 of 2 can be calculated by the formula P CO2, the main road (the optimal exhaust pressure of the CO 2 main circuit compressor 1), and the opening degree of the CO 2 main road expansion valve 4 is adjusted to achieve The pressure is set to ensure efficient operation of the system.
  • the present invention creatively proposes an optimal structural parameter of the air-cooled-air-cooled recombiner: when the air-cooled-air-cooled recombinator 2 is selected, it can be based on the parameter D 1 : the outer tube Diameter and formula, calculate D L : center distance between inner tubes, select the air-cooled-air-cooled composite that is most suitable for this system.

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Abstract

一种跨临界二氧化碳复合热泵系统的控制方法，包括CO 2主路压缩机（1）、气冷-气冷复合器（2）、过冷-蒸发复合器（3）、蒸发器（5）和CO 2辅助压缩机（6）；气冷-气冷复合器（2）包含CO 2主路（9）、CO 2辅路（10）和水路（11）三个通路；过冷-蒸发复合器（3）包含CO 2主路过冷段（12）和CO 2辅路蒸发段（13）两个通路。根据回水温度包括两种工作模式，使得机组应用范围更广，满足日常需要；只有一个制冷剂与水的换热器，相比较现有的临界CO 2复合热泵中的三个水和制冷剂的换热器，循环水路为一进一出的单一回路，系统简单，降低了故障率；辅助回路采用变频压缩机可以使热泵热水器系统能够在更宽负荷和温度条件下长时间稳定可靠运行，降低电能消耗，还可以降低压缩机的启动电流。

Description

一种跨临界二氧化碳复合热泵系统的控制方法 技术领域
本发明属于热泵技术领域，特别涉及一种跨临界二氧化碳复合热泵系统的控制方法。
背景技术
热泵可以吸收环境空气中的热量，通过工质循环，将热量传递给循环水，起到加热的作用。传统的热泵大多使用R134a，R410a等传统工质，环保性较差，面临逐渐淘汰的趋势。
前国际制冷学会主席G Lorentzen提出了CO 2跨临界循环理论，指出其在热泵领域将具有极其广阔的发展前景。CO 2的临界温度很低，为31.1℃，故CO 2热泵系统一般采用跨临界循环。CO 2跨临界循环压缩机排气温度较高(可达100℃以上)，且在跨临界区内，CO 2在冷却过程中存在较大的温度滑移，这种温度滑移正好与所需的变温热源相匹配，可以将水一次加热到很高的温度并保持极高的效率，尤其适合于家用生活热水领域。
CO 2跨临界循环系统与传统的亚临界循环系统之间的区别在于：在传统亚临界系统中，制冷剂在冷凝器中大部分区域内温度保持不变，而在CO 2跨临界循环系统中，超临界压力区内并无两相区存在，温度和压力为相互独立的变量，高压侧压力变化对制冷量、压缩机功耗和COP值也会产生影响。
跨临界CO 2热泵循环具有独特的优势，其放热过程温度较高且存在一个相当大的温度滑移(约80～100℃)。研究表明：(1)在蒸发温度为0℃时，水温可以从0℃加热到60℃，其热泵COP可达到4.3，比电热水器和燃气热水器能耗降低75％上。在寒冷地区，传统空气源热泵的制热量和效率随环境温度的降低下降很快，热泵的使用受到限制。而CO 2热泵系统在低温环境下能维持较高的供热量及很高的出水温度，大大节约辅助加热设备所耗费的能量。
跨临界二氧化碳热泵热水器的性能严重受制于气体冷却器出口温度，气体冷却器出口温 度越低，系统性能越好。当水循环系统中的回水温度足够低(20℃甚至低于20℃)时，跨临界二氧化碳热泵热水器的气体冷却器出口温度也能够被循环水冷却到相当低的温度，这个时候系统的性能优异。然而当回水温度高于25℃时(考虑到换热温差，气体冷却器出口二氧化碳温度可能达到30℃)，系统的性能随着回水温度的升高会剧烈下降，当回水温度高于40℃时二氧化碳热泵系统的性能极差，制热COP甚至在1.5以下。
现有的跨临界CO 2复合热泵回水分为两路，第一路回水进辅助循环的气体冷却器，然后回到出水口，第二路环的回水进辅助循蒸发器，冷却后的水进入主循环的气体冷却器，然后回到出水口。第一路出水与第二路出水混合后一起供水给用户。
现有的定频热泵系统采用定频压缩机，共两个回路，需要三个制冷剂与水的换热器，水路分布与连接会极其复杂，并容易出现故障。只能在设计工况下运行(当水循环系统中的回水温度足够低(20℃甚至低于20℃)时，跨临界二氧化碳热泵热水器的气体冷却器出口温度也能够被循环水冷却到相当低的温度，这个时候系统的性能优异)，导致运行时回路流量不能随着工况的改变而做出相应的调整，尤其针对主副级复合型的热泵产品，固定的压缩机流量比难以适应多变的运行工况，造成系统在非设计工况下的能源浪费或性能降低(当回水温度高于25℃时(考虑到换热温差，气体冷却器出口二氧化碳温度可能达到30℃)，系统的性能随着回水温度的升高会剧烈下降，当回水温度高于40℃时二氧化碳热泵系统的性能极差，制热COP甚至在1.5以下)。
发明内容
本发明的目的在于提供了一种跨临界二氧化碳复合热泵系统的控制方法，以解决现有跨临界CO 2复合热泵性能严重受制于气体冷却器出口温度、水路分布与连接复杂且能源浪费的问题，同时改善现有的定频热泵系统采用定频压缩机，回路流量不能改变，尤其针对主副级复合型的热泵产品，固定的压缩机流量比难以适应多变的运行工况的现状，本发明热泵分为 主回路和辅助回路；在一般工况下，回水温度较低时(30℃或者低于30℃)，运行直热型制热模式；当回水温度较高时(高于30℃)，转换为循环型制热模式。两种模式交替运行，有效的改善了已有系统对变工况无法适应的缺点，避免了现有系统在非设计工况下性能的低下以及对能源的浪费，达到在多工况条件下依然保持高的性能的同时，由于两种模式的交替，避免了已有的系统单一工作模式造成的能源浪费，而且减少了换热器的数量，简化了系统的结构，降低了出现故障的概率。
为了实现上述的目的，本发明采用的技术方案是：
一种跨临界二氧化碳复合热泵系统的控制方法，所述一种跨临界二氧化碳复合热泵系统，包括CO 2主路压缩机、气冷-气冷复合器、过冷-蒸发复合器、蒸发器和CO 2辅助压缩机；气冷-气冷复合器包含CO 2主路、CO 2辅路和水路三个通路；过冷-蒸发复合器包含CO 2主路过冷段和CO 2辅路蒸发段两个通路；所述一种跨临界二氧化碳复合热泵系统包含主回路和辅助回路两个回路；主回路：CO 2主路压缩机的出口连接气冷-气冷复合器的CO 2主路的进口，气冷-气冷复合器的CO 2主路的出口连接过冷-蒸发复合器的CO 2主路过冷段进口，过冷-蒸发复合器的CO 2主路过冷段的出口连接蒸发器的进口，蒸发器的出口连接CO 2主路压缩机的进口；辅助回路：CO 2辅助压缩机的出口连接气冷-气冷复合器的CO 2辅路的进口，气冷-气冷复合器CO 2辅路的出口连接过冷-蒸发复合器的CO 2辅路蒸发段的进口，过冷-蒸发复合器的CO 2辅路蒸发段的出口连接CO 2辅助压缩机的进口；主回路上过冷-蒸发复合器和蒸发器之间设置有CO 2主路膨胀阀；辅助回路上气冷-气冷复合器和过冷-蒸发复合器之间设置有CO 2辅助膨胀阀；
所述一种跨临界二氧化碳复合热泵系统工作在循环型制热模式下，所述控制方法包括：
CO 2主回路压缩机工作，主回路打开，CO 2辅助压缩机工作，辅助回路打开；风扇处于开启状态；主回路：CO 2工质由状态点a经过CO 2主路压缩机的压缩后达到状态点b，进入气冷-气冷复合器的CO 2主路中，对水路中的循环水进行加热，并且自身冷却到合适的温度达到 状态点c，然后流经过冷-蒸发复合器的CO 2主路过冷段，与CO 2辅路蒸发段进行换热，进一步冷却降温，达到状态点d，然后进入CO 2主路膨胀阀进行膨胀，膨胀后的低压工质达到状态点e，进入到蒸发器进行蒸发，吸收热量，回到状态点a，最后回到CO 2主路压缩机的进口；辅助回路：CO 2工质由状态点f经过CO 2辅助压缩机的压缩后达到状态点g，进入气冷-气冷复合器的CO 2辅路中，对水路中的循环水进行加热，并且自身冷却降温达到状态点h，接着进入CO 2辅路膨胀阀进行膨胀达到状态点i，膨胀后的低压工质进入过冷-蒸发复合器的CO 2辅路蒸发段，与CO 2主路过冷段换热，进一步冷却CO 2主路过冷段，自身蒸发吸热达到状态点f，最后回到CO 2辅助压缩机的进口。
进一步的，在气冷-气冷复合器中，主路CO 2工质在CO 2主路中冷却放热，辅路CO 2工质在CO 2辅路中冷却放热，循环水吸收热量，达到设定的温度；在过冷-蒸发复合器中，主路CO 2工质在CO 2主路过冷段进一步冷却放热，辅路CO 2工质在CO 2辅路蒸发段蒸发吸热，CO 2辅路蒸发段与CO 2主路过冷段换热，保持热量平衡。
进一步的，辅路控制控制方法：采集环境温度t 环、用户设定的气冷-气冷复合器的CO 2辅路出口的温度t g,out辅路和用户设定的气冷-气冷复合器的水路出口的温度t 回水，通过公式计算出CO 2辅助压缩机的排气压力
Figure PCTCN2018120175-appb-000001
通过调节CO 2辅路膨胀阀的开度来达到给定的压力；根据公式计算出CO 2辅助压缩机的电机频率f 压缩机6，使压缩机的频率随着工况进行变化；
Figure PCTCN2018120175-appb-000002
Figure PCTCN2018120175-appb-000003
主路控制控制方法：采集环境温度t 环、用户设定的气冷-气冷复合器的CO 2主路出口的温度t g,out主路和用户设定的气冷-气冷复合器的水路出口的温度t 回水；然后通过公式计算出CO 2主回路压缩机的最优排气压力P CO2,主路，通过调节CO 2主路膨胀阀的开度来达到给定的压力；
Figure PCTCN2018120175-appb-000004
进一步的，气冷-气冷复合器包括三个内管和一个外管，两个内管路作为CO 2主回路，一个内管路作为CO 2辅路，外管和三个内管之间的通路为水路；三个内管呈正三角形布置，三个内管间的管间距相同，均为D L；三个内管的直径相同均为D 2，外管的直径为D 1；两个CO 2主回路的一端在气冷-气冷复合器的外侧合成一个管子连接CO 2主回路压缩机的排气口，两个CO 2主回路的另一端在气冷-气冷复合器的外侧合成一个管子连接排气口CO 2主路过冷段；
三个内管间的管间距D L、三个内管的直径D 2和外管的直径D 1的关系为：
D L＝1.7D 2                     (4)
D 1/D 2＝3.7                    (5)
进一步的，蒸发器上还安装有风扇。
进一步的，CO 2辅助压缩机采用变频压缩机。
进一步的，用户设定的气冷-气冷复合器的水路出口的温度大于或等于30℃时，所述一种跨临界二氧化碳复合热泵系统工作在循环型制热模式下。
与现有的技术相比，本发明有以下有益效果：
本发明提供了一种跨临界CO 2复合热泵及其控制方法，采用将热泵分为主回路和辅助回路的控制方式；使得在一般工况下，回水温度较低时(30℃或者低于30℃)，运行直热型制热模式；当回水温度较高时(高于30℃)，转换为循环型制热模式，使系统适应多变工况的同时，还能达到节约能源的目的。
当回水温度较高时(高于30℃)，运行循环型制热模式，主路压缩机工作，主回路打开，辅助路压缩机工作，辅助回路打开，风扇处于开启状态；在辅助回路的第一过冷-蒸发复合器中，辅助回路的CO 2蒸发吸热，对主回路中的CO 2进行第二次降温，使主回路中的CO 2达到合适的出口温度，保证较高的系统性能。
进一步的，本发明中只有一个制冷剂与水的换热器，也就是气冷-气冷复合器。相比较现有的跨临界CO 2复合热泵中的三个水和制冷剂的换热器，本循环水路为一进一出的单一回路，系统简单，降低了故障率。
进一步的，根据实际中回水温度的不同，通过控制两个压缩机，进行直热型制热模式和循环型制热模式的转换，使热泵机组的应用范围更广，性能更高。
进一步的，CO 2属于惰性气体，无毒无刺激；良好的安全性和化学稳定性，安全无毒，不可燃，即便在高温下也不分解产生有害气体；其对全球变暖潜力指数GWP为1，CO 2不需要工业合成，只需要在大气中提取就可以，使用方便；同时，它对大气臭氧层无任何破环作用，ODP为0。并且，CO 2本身优越的热物理特性以及良好的迁移特性也适合其作为制冷工质。
进一步的，本发明制热方式采用CO 2热泵型式，能源利用率更高，更加节能。CO 2蒸发潜热较大，单位容积制冷量高，具有优良的流动和传热特性，可显著减小系统的尺寸，使整个系统非常紧凑。
进一步的，跨临界CO 2热泵循环具有独特的优势，其放热过程温度较高且存在一个相当大的温度滑移(约80～100℃)。其热泵COP可达到4.3，比电热水器和燃气热水器能耗降低75％以上。在寒冷地区，传统空气源热泵的制热量和效率随环境温度的降低下降很快，热泵的使用受到限制。而CO 2热泵系统在低温环境下能维持较高的供热量，大大节约辅助加热设备所耗费的能量。
进一步的，辅助回路采用变频压缩机可以使热泵热水器系统能够在更宽负荷和温度条件下长时间稳定可靠运行，降低电能消耗，还可以降低压缩机的启动电流。
进一步的，当回水温度较高时，CO 2辅路的排气压力越高，制热量越大，运行效果越好。从控制原理角度出发，提出公式(1)，用于控制压缩机6的排气压力。以保证整个系统的高 性能运转。
进一步的，循环中d处的温度需要保持为合适的值，为了均衡压缩机6的功耗，可以使压缩机的频率随着工况进行变化，通过公式(2)计算压缩机6的最优频率，通过控制压缩机6的转速，使系统保持高效运行。
进一步的，利用公式(3)可以计算出压缩机1的最优排气压力，可以让主回路始终保持较高效率的运行。
进一步的，利用公式(4)，(5)可以选用换热效率的最高的气冷-气冷复合器，提高系统的整体的性能。
附图说明
图1是本发明一种跨临界二氧化碳复合热泵系统的结构示意图；
图2是本发明一种跨临界二氧化碳复合热泵系统直热型制热模式下的结构示意图；
图3是本发明一种跨临界二氧化碳复合热泵系统直热型制热模式下的循环示意图；
图4是本发明一种跨临界二氧化碳复合热泵系统循环型制热模式下的结构示意图；
图5是本发明一种跨临界二氧化碳复合热泵系统循环型制热模式下的循环示意图；
图6是本发明一种跨临界二氧化碳复合热泵系统的气冷-气冷复合器的内部管路布置示意图；
其中：1、CO 2主路压缩机；2、气冷-气冷复合器；3、过冷-蒸发复合器；4、CO 2主路膨胀阀；5、蒸发器；6、CO 2辅助压缩机；7、CO 2辅助膨胀阀；8、风扇；9、CO 2主路；10、CO 2辅路；11、水路；12、CO 2主路过冷段；13、CO 2辅路蒸发段。
具体实施方式
下面结合附图对本发明作进一步详细说明。
请参阅图1，本发明一种跨临界二氧化碳复合热泵系统，包括CO 2主路压缩机1、气冷- 气冷复合器2、过冷-蒸发复合器3、蒸发器5和CO 2辅助压缩机6。
气冷-气冷复合器2包含CO 2主路9、CO 2辅路10和水路11三个通路；过冷-蒸发复合器3包含CO 2主路过冷段12和CO 2辅路蒸发段13两个通路。
本发明一种跨临界二氧化碳复合热泵系统包含主回路和辅助回路两个回路；
主回路：CO 2主路压缩机1的出口连接气冷-气冷复合器2的CO 2主路9的进口，气冷-气冷复合器2的CO 2主路9的出口连接过冷-蒸发复合器3的CO 2主路过冷段12进口，过冷-蒸发复合器3的CO 2主路过冷段12的出口连接蒸发器5的进口，蒸发器5的出口连接CO 2主路压缩机1的进口；
辅助回路：CO 2辅助压缩机6的出口连接气冷-气冷复合器2的CO 2辅路10的进口，气冷-气冷复合器2的CO 2辅路10的出口连接过冷-蒸发复合器3的CO 2辅路蒸发段13的进口，过冷-蒸发复合器3的CO 2辅路蒸发段13的出口连接CO 2辅助压缩机6的进口。
主回路上过冷-蒸发复合器3和蒸发器5之间设置有CO 2主路膨胀阀4；辅助回路上气冷-气冷复合器2和过冷-蒸发复合器3之间设置有CO 2辅助膨胀阀7。
蒸发器5上还安装有风扇8，通过改变风扇的转速，可以调节合适的换热系数。
CO 2辅助压缩机6采用变频压缩机。
请参阅图6所示，气冷-气冷复合器2包括三个内管和一个外管，两个内管路作为CO 2主回路9，一个内管路作为CO 2辅路10，外管和三个内管之间的通路为水路11。三个内管呈正三角形布置，三个内管间的管间距相同，均为D L；三个内管的直径相同均为D 2，外管的直径为D 1。两个CO 2主回路9的一端在气冷-气冷复合器2的外侧合成一个管子连接CO 2主回路压缩机1的排气口，两个CO 2主回路9的另一端在气冷-气冷复合器2的外侧合成一个管子连接CO 2主路过冷段12。
为了保证机组在回水温度改变时，能保证合适的CO 2的冷却温度，从而保证较高的系统 性能，本发明设置了两种运行模式：
直热型制热模式(回水温度为30℃或者低于30℃)：请参阅图2和图3，CO 2主回路压缩机1工作，主回路打开；CO 2辅助压缩机6关闭，辅助回路关闭；风扇处于开启状态。主回路：CO 2工质由状态点a经过CO 2主路压缩机1的压缩后达到状态点b，进入气冷-气冷复合器2的CO 2主路9中，对水路11中的循环水进行加热，并且自身冷却到合适的温度达到状态点c，然后流经过冷-蒸发复合器3的CO 2主路过冷段12状态不改变，依旧为状态点c，然后进入CO 2主路膨胀阀4进行膨胀，膨胀后的低压工质达到状态点d，进入到蒸发器5进行蒸发，吸收热量，回到状态点a，最后回到CO 2主路压缩机1的进口。
循环型制热模式(回水温度高于30℃)：请参阅图4和图5，CO 2主回路压缩机1工作，主回路打开，CO 2辅助压缩机6工作，辅助回路打开；风扇处于开启状态。主回路：CO 2工质由状态点a经过CO 2主路压缩机1的压缩后达到状态点b，进入气冷-气冷复合器2的CO 2主路9中，对水路11中的循环水进行加热，并且自身冷却到合适的温度达到状态点c，然后流经过冷-蒸发复合器3的CO 2主路过冷段12，与CO 2辅路蒸发段进行换热，进一步冷却降温，达到状态点d，然后进入CO 2主路膨胀阀4进行膨胀，膨胀后的低压工质达到状态点e，进入到蒸发器5进行蒸发，吸收热量，回到状态点a，最后回到CO 2主路压缩机1的进口。
辅助回路：CO 2工质由状态点f经过CO 2辅助压缩机6的压缩后达到状态点g，进入气冷-气冷复合器2的CO 2辅路10中，对水路11中的循环水进行加热，并且自身冷却降温达到状态点h，接着进入CO 2辅路膨胀阀7进行膨胀达到状态点i，膨胀后的低压工质进入过冷-蒸发复合器3的CO 2辅路蒸发段13，与CO 2主路过冷段12换热，进一步冷却CO 2主路过冷段12，自身蒸发吸热达到状态点f，最后回到CO 2辅助压缩机6的进口。
在气冷-气冷复合器2中，主路CO 2工质在CO 2主路9中冷却放热，辅路CO 2工质在CO 2辅路10中冷却放热，循环水吸收热量，达到合适的温度。在过冷-蒸发复合器3中，主路CO 2 工质在CO 2主路过冷段12进一步冷却放热，达到合适温度，辅路CO 2工质在CO 2辅路蒸发段13蒸发吸热，CO 2辅路蒸发段13与CO 2主路过冷段12换热，保持热量平衡。
辅路控制：当回水温度较高(大于或等于30℃)时，CO 2辅路的排气压力越高，制热量越大，运行效果越好。从控制原理角度出发，提出一个CO 2辅路排气压力的拟合公式，用于控制压缩机6的排气压力。以保证整个系统的高性能运转。当给定t g,out辅路(气冷-气冷复合器2的CO 2辅路10出口的温度)，t 环(环境温度)，t 回水(气冷-气冷复合器2的水路11出口的温度)后，通过公式计算出
Figure PCTCN2018120175-appb-000005
(CO 2辅助压缩机6的排气压力)，通过调节CO 2辅路膨胀阀7的开度来达到给定的压力，从而保证系统更高效的运行。本发明提出，在工况变化时，CO 2辅助压缩机6的适应性频率控制公式。循环中d处的温度需要保持为合适的值，为了均衡CO 2辅助压缩机6的功耗，可以使压缩机的频率随着工况进行变化，使系统保持高效运行，提出下面的拟合公式。可以根据公式计算出f 压缩机6(CO 2辅助压缩机6的电机频率)，可以使压缩机的频率随着工况进行变化，使系统保持高效运行。
Figure PCTCN2018120175-appb-000006
Figure PCTCN2018120175-appb-000007
主路控制：当给定t g,out主路(气冷-气冷复合器2的CO 2主路9出口的温度)，t 环(环境温度)t 回水(气冷-气冷复合器2的水路11出口的温度)，可以通过公式计算出P CO2,主路(CO 2主回路压缩机1的最优排气压力)，通过调节CO 2主路膨胀阀4的开度来达到给定的压力，从而保证系统的高效运行。
Figure PCTCN2018120175-appb-000008
为了保证CO 2与水充分换热，本发明创造性的提出了气冷-气冷复合器的结构最优参数：在选用气冷-气冷复合器2的时候，可以根据参数D 1：外管直径和公式，计算出D L：内管间 的中心距，选用最适合本系统的气冷-气冷复合器。
D L＝1.7D 2                   (4)
D 1/D 2＝3.7                  (5)。

Claims (7)

  1. 一种跨临界二氧化碳复合热泵系统的控制方法，其特征在于，所述一种跨临界二氧化碳复合热泵系统，包括CO 2主路压缩机(1)、气冷-气冷复合器(2)、过冷-蒸发复合器(3)、蒸发器(5)和CO 2辅助压缩机(6)；气冷-气冷复合器(2)包含CO 2主路(9)、CO 2辅路(10)和水路(11)三个通路；过冷-蒸发复合器(3)包含CO 2主路过冷段(12)和CO 2辅路蒸发段(13)两个通路；所述一种跨临界二氧化碳复合热泵系统包含主回路和辅助回路两个回路；
    主回路：CO 2主路压缩机(1)的出口连接气冷-气冷复合器(2)的CO 2主路(9)的进口，气冷-气冷复合器(2)的CO 2主路(9)的出口连接过冷-蒸发复合器(3)的CO 2主路过冷段(12)进口，过冷-蒸发复合器(3)的CO 2主路过冷段(12)的出口连接蒸发器(5)的进口，蒸发器(5)的出口连接CO 2主路压缩机(1)的进口；
    辅助回路：CO 2辅助压缩机(6)的出口连接气冷-气冷复合器(2)的CO 2辅路(10)的进口，气冷-气冷复合器(2)CO 2辅路(10)的出口连接过冷-蒸发复合器(3)的CO 2辅路蒸发段(13)的进口，过冷-蒸发复合器(3)的CO 2辅路蒸发段(13)的出口连接CO 2辅助压缩机(6)的进口；
    主回路上过冷-蒸发复合器(3)和蒸发器(5)之间设置有CO 2主路膨胀阀(4)；辅助回路上气冷-气冷复合器(2)和过冷-蒸发复合器(3)之间设置有CO 2辅助膨胀阀(7)；
    所述一种跨临界二氧化碳复合热泵系统工作在循环型制热模式下，所述控制方法包括：
    CO 2主回路压缩机工作，主回路打开，CO 2辅助压缩机工作，辅助回路打开；风扇处于开启状态；
    主回路：CO 2工质由状态点a经过CO 2主路压缩机的压缩后达到状态点b，进入气冷-气冷复合器的CO 2主路中，对水路中的循环水进行加热，并且自身冷却到合适的温度达到状态点c，然后流经过冷-蒸发复合器的CO 2主路过冷段，与CO 2辅路蒸发段进行换热，进一步冷却降温，达到状态点d，然后进入CO 2主路膨胀阀进行膨胀，膨胀后的低压工质达到状态点e， 进入到蒸发器进行蒸发，吸收热量，回到状态点a，最后回到CO 2主路压缩机的进口；
    辅助回路：CO 2工质由状态点f经过CO 2辅助压缩机的压缩后达到状态点g，进入气冷-气冷复合器的CO 2辅路中，对水路中的循环水进行加热，并且自身冷却降温达到状态点h，接着进入CO 2辅路膨胀阀进行膨胀达到状态点i，膨胀后的低压工质进入过冷-蒸发复合器的CO 2辅路蒸发段，与CO 2主路过冷段换热，进一步冷却CO 2主路过冷段，自身蒸发吸热达到状态点f，最后回到CO 2辅助压缩机的进口。
  2. 根据权利要求1所述的控制方法，其特征在于，在气冷-气冷复合器中，主路CO 2工质在CO 2主路中冷却放热，辅路CO 2工质在CO 2辅路中冷却放热，循环水吸收热量，达到设定的温度；在过冷-蒸发复合器中，主路CO 2工质在CO 2主路过冷段进一步冷却放热，辅路CO 2工质在CO 2辅路蒸发段蒸发吸热，CO 2辅路蒸发段与CO 2主路过冷段换热，保持热量平衡。
  3. 根据权利要求1所述的控制方法，其特征在于，辅路控制控制方法：采集环境温度t 环、用户设定的气冷-气冷复合器的CO 2辅路出口的温度t g,out辅路和用户设定的气冷-气冷复合器的水路出口的温度t 回水，通过公式(1)计算出CO 2辅助压缩机的排气压力
    Figure PCTCN2018120175-appb-100001
    通过调节CO 2辅路膨胀阀(7)的开度来达到给定的压力；根据公式(2)计算出CO 2辅助压缩机的电机频率f 压缩机6，使压缩机的频率随着工况进行变化；
    Figure PCTCN2018120175-appb-100002
    Figure PCTCN2018120175-appb-100003
    主路控制控制方法：采集环境温度t 环、用户设定的气冷-气冷复合器的CO 2主路出口的温度t g,out主路和用户设定的气冷-气冷复合器的水路出口的温度t 回水；然后通过公式(3)计算出CO 2主回路压缩机的最优排气压力P CO2,主路，通过调节CO 2主路膨胀阀的开度来达到给定的压力；
    Figure PCTCN2018120175-appb-100004
  4. 根据权利要求1所述的控制方法，其特征在于，气冷-气冷复合器(2)包括三个内管和一个外管，两个内管路作为CO 2主回路(9)，一个内管路作为CO 2辅路(10)，外管和三个内管之间的通路为水路(11)；三个内管呈正三角形布置，三个内管间的管间距相同，均为D L；三个内管的直径相同均为D 2，外管的直径为D 1；两个CO 2主回路(9)的一端在气冷-气冷复合器(2)的外侧合成一个管子连接CO 2主回路压缩机(1)的排气口，两个CO 2主回路(9)的另一端在气冷-气冷复合器(2)的外侧合成一个管子连接排气口CO 2主路过冷段(12)；
    三个内管间的管间距D L、三个内管的直径D 2和外管的直径D 1的关系为：
    D L＝1.7D 2           (4)
    D 1/D 2＝3.7                  (5)。
  5. 根据权利要求1所述的控制方法，其特征在于，蒸发器(5)上还安装有风扇(8)。
  6. 根据权利要求1所述的控制方法，其特征在于，CO 2辅助压缩机(6)采用变频压缩机。
  7. 根据权利要求1所述的控制方法，其特征在于，用户设定的气冷-气冷复合器的水路出口的温度大于或等于30℃时，所述一种跨临界二氧化碳复合热泵系统工作在循环型制热模式下。
PCT/CN2018/120175 2018-01-18 2018-12-11 一种跨临界二氧化碳复合热泵系统的控制方法 Ceased WO2019141019A1 (zh)

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