US20090282848A1 - Refrigeration system - Google Patents

Refrigeration system Download PDF

Info

Publication number
US20090282848A1
US20090282848A1 US12/302,478 US30247807A US2009282848A1 US 20090282848 A1 US20090282848 A1 US 20090282848A1 US 30247807 A US30247807 A US 30247807A US 2009282848 A1 US2009282848 A1 US 2009282848A1
Authority
US
United States
Prior art keywords
heat exchanger
refrigerant
degree
expansion valve
heating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US12/302,478
Other languages
English (en)
Inventor
Masaaki Takegami
Kazuyoshi Nomura
Azuma Kondo
Yoshinari Oda
Kenji Tanimoto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Daikin Industries Ltd
Original Assignee
Daikin Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Daikin Industries Ltd filed Critical Daikin Industries Ltd
Assigned to DAIKIN INDUSTRIES, LTD. reassignment DAIKIN INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KONDO, AZUMA, NOMURA, KAZUYOSHI, ODA, YOSHINARI, TAKEGAMI, MASAAKI, TANIMOTO, KENJI
Publication of US20090282848A1 publication Critical patent/US20090282848A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/06—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the arrangements for the supply of heat-exchange fluid for the subsequent treatment of primary air in the room units
    • 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
    • F25B13/00—Compression machines, plants or systems, with reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F24F11/63—Electronic processing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
    • F24F5/001—Compression cycle 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
    • 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
    • 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
    • F25B2313/023—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple indoor units
    • F25B2313/0231—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple indoor units with simultaneous cooling and heating
    • 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
    • F25B2313/023—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple indoor units
    • F25B2313/0233—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple indoor units in parallel 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
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
    • F25B2313/02743—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using three four-way 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
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/031—Sensor arrangements
    • F25B2313/0314—Temperature sensors near the indoor 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
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/07—Details of compressors or related parts
    • F25B2400/075—Details of compressors or related parts with parallel compressors
    • F25B2400/0751—Details of compressors or related parts with parallel compressors the compressors having different capacities
    • 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—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/19—Pumping down refrigerant from one part of the cycle to another part of the cycle, e.g. when the cycle is changed from cooling to heating, or before a defrost cycle is started
    • 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—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/22—Refrigeration systems for supermarkets
    • 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
    • F25B2700/04—Refrigerant level

Definitions

  • This invention generally relates to a refrigeration system having a plurality of utilization side units and more particularly to the prevention of the accumulation of refrigerant (“refrigerant's falling-asleep” in the industry jargon) in a heating heat exchanger placed out of operation.
  • refrigerant refrigerant's falling-asleep
  • JP-A-1996-159590 shows a refrigeration system which includes a single heat source side unit having a compressor and a heat source side heat exchanger, and two utilization side units each having a utilization side heat exchanger (heating heat exchanger) and an expansion valve.
  • each expansion valve is opened at a predetermined degree of opening, thereby making it possible for each utilization side heat exchanger to individually carry out a space heating operation. More specifically, for example, in the case where these two utilization side units perform respective space heating operations at the same time, both the expansion valves are placed in the opened state so that refrigerant is fed to both the utilization side heat exchangers. As a result, heat is released from the refrigerant flowing through each utilization side heat exchanger to the indoor air and each utilization side heat exchanger performs a heating operation. As a result, indoor spaces respectively corresponding to the utilization side heat exchangers are heated.
  • thermo-off state a phenomenon of “refrigerant's falling-asleep”. More specifically, in such a phenomenon, refrigerant condenses in the utilization side heat exchanger placed in the out-of-operation state, resulting in the accumulation of condensed liquid refrigerant therein. And if, as described above, the refrigerant accumulates in large amounts within one of the utilization side heat exchangers, the supply of refrigerant to the other utilization side unit becomes scant. This gives rise to the problem that the other utilization side unit degrades in refrigeration capacity or heating capacity.
  • an object of the present invention is to ensure the prevention of any accumulation (“falling-asleep”) of refrigerant within a utilization side heat exchanger placed in the out-of-operation state.
  • the present invention provides, as a first aspect, a refrigeration system including a refrigerant circuit, the refrigerant circuit being configured such that a plurality of utilization side units ( 12 , 13 , 14 ) are connected in parallel to a heat source side unit ( 11 ) having a compressor ( 41 , 42 ) and a heat source side heat exchanger ( 44 ), wherein at least one of the plurality of utilization side units ( 12 , 13 , 14 ) includes a heating heat exchanger ( 71 ) capable of a heating operation in which heat is released from refrigerant and an expansion valve ( 72 ) associated with the heating heat exchanger.
  • the refrigeration system includes a degree-of-opening control means ( 101 ) for performing:
  • the plurality of utilization side units ( 12 , 13 , 14 ) are connected in parallel to the heat source side unit ( 11 ).
  • This arrangement constitutes a so-called multi-type refrigeration system.
  • a vapor compression refrigeration cycle is performed by the circulation of refrigerant.
  • Refrigerant is supplied to each of the utilization side units ( 12 , 13 , 14 ) where it evaporates or condenses, and by these utilization side units ( 12 , 13 , 14 ), indoor space heating/cooling or showcase storage compartment refrigeration is separately provided.
  • the degree-of-opening control means ( 101 ) when stopping the heating heat exchanger ( 71 ) capable of performing a heating operation in which heat is released from the refrigerant, the degree-of-opening control means ( 101 ) first performs a first control operation.
  • the degree of opening of the expansion valve ( 72 ) associated with the heating heat exchanger ( 71 ) is reduced to the fully closed degree or to an extremely small degree as close to the fully closed degree as possible.
  • no heating operation is carried out in the heating heat exchanger ( 71 ).
  • the degree-of-opening control means ( 101 ) of the present invention carries out a second control operation in order to prevent the occurrence of “refrigerant's falling-asleep” in the heating heat exchanger ( 71 ).
  • the index indicative of the accumulated amount of refrigerant within the heating heat exchanger ( 71 ) is detected by means of a given method. And based on the index detected, the degree of opening of the expansion valve ( 72 ) is adequately adjusted.
  • the degree-of-opening control means ( 101 ) provides control so that the degree of opening of the expansion valve ( 72 ) is increased.
  • the refrigerant accumulated within the heating heat exchanger ( 71 ) is expelled through the expansion valve ( 72 ) to outside the utilization side unit ( 12 ).
  • the present invention provides, as a second aspect according to the first aspect, a refrigeration system that is characterized in that the first control operation of the degree-of-opening control means ( 101 ) is an operation to place the expansion valve ( 72 ) in the fully closed state.
  • the degree-of-opening control means ( 101 ) performs a first control operation to place the expansion valve ( 72 ) in the fully closed state.
  • the present invention provides, as a third aspect according to either one of the first and second aspects, a refrigeration system that is characterized in that, in the second control operation of the degree-of-opening control means ( 101 ), either the degree of refrigerant subcooling on the inlet side of the heating heat exchanger ( 71 ) or the degree of refrigerant subcooling within the heating heat exchanger ( 71 ) serves as the index indicative of the accumulated amount of refrigerant within the heating heat exchanger ( 71 ).
  • the degree of refrigerant subcooling is used as the index indicative of the accumulated amount of refrigerant within the heating heat exchanger ( 71 ). That is, if refrigerant condenses and accumulates in liquid form within the heating heat exchanger ( 71 ) placed in the out-of-operation state, this liquid refrigerant further dissipates heat and then enters the subcooling state. Therefore, it is possible to observe the accumulated amount of refrigerant within the heating heat exchanger ( 71 ) by detecting the degree of refrigerant subcooling within the heating heat exchanger ( 71 ).
  • the present invention provides, as a fourth aspect according to the third aspect, a refrigeration system that is characterized in that, in the second control operation of the degree-of-opening control means ( 101 ), the expansion valve ( 72 ) is forcibly opened at a predefined degree of opening if the expansion valve ( 72 ) remains in the fully closed state for longer than a predetermined length of time.
  • the expansion valve ( 72 ) is forcibly opened if it has continuously been placed in the fully closed state, although the degree of opening of the expansion valve ( 72 ) is normally controlled based on the degree of refrigerant subcooling by the degree-of-opening control means ( 101 ) during the second control operation.
  • the degree of refrigerant subcooling on the inlet side of, or within the heating heat exchanger ( 71 ) is detected, it is impossible, in some cases, to accurately find the amount of refrigerant within the heating heat exchanger ( 71 ) due to the influence of the ambient temperature of the heating heat exchanger ( 71 ).
  • the saturated temperature corresponding to the pressure of high pressure gas, Pc, and the temperature of refrigerant on the inlet side of the heating heat exchanger ( 71 ), Th 1 are detected by the specific sensors, and if, when making a calculation of the degree of subcooling from the temperature difference (the difference between the temperatures Pc and Th 1 ), the ambient temperature of the heating heat exchanger ( 71 ) is relatively high, then the temperature, Th 1 , detected by the sensor, too, tends to be high. Therefore, under such a condition, the degree of refrigerant subcooling detected by the sensors decreases, although there actually is accumulated a large amount of refrigerant within the heating heat exchanger ( 71 ). As a result, there is the possibility that the expansion valve ( 72 ) will continuously remain in the fully closed state.
  • the expansion valve ( 72 ) is forcibly opened if, in the second control operation, the expansion valve ( 72 ) has continuously been in the fully closed state for longer than a predetermined length of time.
  • the degree of opening of the expansion valve ( 72 ) be as minimum as possible.
  • the accurate amount of refrigerant within the heating heat exchanger ( 71 ) can be detected with ease. That is, if the expansion valve ( 72 ) is forcibly opened, the continuous supply of refrigerant is provided to the heating heat exchanger ( 71 ). As a result, the refrigerant flowing in the heating heat exchanger ( 71 ) is less subject to the ambient temperature.
  • the degree of refrigerant subcooling is calculated having a low value, in spite of the occurrence of “refrigerant's falling asleep” within the heating heat exchanger ( 71 ). This therefore makes it possible that, after the forced opening of the expansion valve ( 72 ), the degree of opening of the expansion valve ( 72 ) can be adjusted properly by accurate detection of the amount of refrigerant within the heating heat exchanger ( 71 ).
  • the present invention provides, as a fifth aspect according to the first aspect, a refrigeration system that is characterized in that the utilization side units ( 13 , 14 ) other than the utilization side unit ( 12 ) that is provided with the heating heat exchanger ( 71 ) each include a respective refrigeration heat exchanger ( 81 , 91 ) capable of a refrigeration operation in which refrigerant absorbs heat from air; that the refrigerant circuit ( 20 ) is configured to be capable of a heat recovery operation in which refrigerant delivered out from the compressor dissipates heat in the heating heat exchanger ( 71 ), absorbs heat in the refrigeration heat exchanger ( 81 , 91 ), and then is drawn into the compressor ( 41 , 42 ); and that there is provided an operation control means ( 102 ) which provides control so that the heat recovery operation is temporarily carried out if, in the second control operation of the degree-of-opening control means ( 101 ), the index indicative of the accumulated amount of refrigerant within the heating heat exchanger ( 71 ) continues to
  • the refrigeration heat exchangers ( 81 , 91 ) are disposed respectively in the utilization side units ( 13 , 14 ) other than the utilization side unit ( 12 ) that is provided with the heating heat exchanger ( 71 ).
  • the refrigerant absorbs heat from air thereby to provide storage-compartment space refrigeration.
  • the refrigerant circuit ( 20 ) of the refrigeration system it is possible to perform a heat recovery operation by the feeding of refrigerant delivered out from the compressor ( 41 , 42 ) to the heating heat exchanger ( 71 ) and the refrigeration heat exchangers ( 81 , 91 ) in that order and then by the returning of refrigerant to the intake side of the compressor ( 41 , 42 ).
  • the operation control means ( 102 ) provides control so that the heat recovery operation is forcibly carried out in the refrigerant circuit ( 20 ). This causes the positive supply of refrigerant to the heating heat exchanger ( 71 ), thereby ensuring that the elimination of “refrigerant's falling-asleep” within the heating heat exchanger is accomplished.
  • the refrigerant discharged from within the heating heat exchanger ( 71 ) and flowing through the refrigeration heat exchanger ( 81 , 82 ) is used for the refrigeration operation of the refrigeration heat exchanger ( 81 , 82 ).
  • the degree of opening of the expansion valve ( 72 ) is reduced by a first control operation, which is followed by the execution of a second control operation to adjust the degree of opening of the expansion valve ( 72 ) based on the index indicative of the accumulated amount of refrigerant within the heating heat exchanger ( 71 ).
  • the degree of opening of the expansion valve ( 72 ) is increased, whereby the refrigerant accumulated within the heating heat exchanger ( 71 ) can be fed to the other utilization side units ( 13 , 14 ). That is, in accordance with the present invention, it is ensured that the elimination of “refrigerant's falling-asleep” within the heating heat exchanger ( 71 ) in the out-of-operation state is accomplished without fail, thereby making it possible to prevent the other utilization side units ( 13 , 14 ) from capacity degradation.
  • the degree of opening of the expansion valve ( 72 ) can be made small if the accumulated amount of refrigerant within the heating heat exchanger ( 71 ) is small. Therefore, it is avoided that an excess supply of refrigerant is provided to the heating heat exchanger ( 71 ) despite the fact that the elimination of “refrigerant's falling-asleep” within the heating heat exchanger ( 71 ) has already been accomplished. This makes it possible to satisfactorily ensure the supply of refrigerant to the other utilization side units ( 13 , 14 ). Accordingly, it becomes possible to still further effectively prevent the other utilization side units ( 13 , 14 ) from capacity degradation.
  • the first control operation is carried out to place the expansion valve ( 72 ) in the fully closed state, when stopping the heating heat exchanger ( 71 ). Therefore, in accordance with the present invention, it is possible to further increase the supply of refrigeration to the other utilization side units ( 13 , 14 ), thereby enhancing their capacity.
  • the third aspect of the present invention it is arranged such that, in the second control operation, the accumulated amount of refrigerant within the heating heat exchanger ( 71 ) is detected using the degree of refrigerant subcooling on the inlet side of or within the heating heat exchanger ( 71 ).
  • the accumulated amount of refrigerant within the heating heat exchanger ( 71 ) is detected using the degree of refrigerant subcooling on the inlet side of or within the heating heat exchanger ( 71 ).
  • the expansion valve ( 72 ) in view of the fact that the degree of refrigerant subcooling decreases due to the influence of the ambient temperature of the heating heat exchanger ( 71 ), the expansion valve ( 72 ) is opened if, in the second control operation, the expansion valve ( 72 ) continues to be in the fully closed state for longer than a predetermined length of time. Therefore, in accordance with the present invention, it is possible to avoid the occurrence of such a condition that the expansion valve ( 72 ) still remains in the closed state although refrigerant is actually “falling asleep” within the heating heat exchanger ( 71 ). This ensures that the elimination of “refrigerant's falling-asleep” within the heating heat exchanger ( 71 ) is accomplished without fail.
  • the degree of opening of the expansion valve ( 72 ) can further be controlled depending on the degree of refrigerant subcooling.
  • the temperature of refrigerant flowing on the inflow side of the heating heat exchanger ( 71 ) or through the inside of the heating heat exchanger ( 71 ) is less subject to the influence of the ambient temperature of the heating heat exchanger ( 71 ), whereby it becomes possible to accurately detect the amount of refrigerant within the heating heat exchanger ( 71 ).
  • the heat recovery operation is carried out in the refrigerant circuit ( 20 ) if the elimination of “refrigerant's falling-asleep” within the heating heat exchanger ( 71 ) still remains unaccomplished even after the execution of the second control operation by the degree-of-opening control means ( 101 ). Therefore, in accordance with the present invention, the elimination of “refrigerant's falling-asleep” within the heating heat exchanger ( 71 ) can be accomplished by the feed-in of refrigerant to the heating heat exchanger ( 71 ).
  • the refrigerant delivered out from the compressor ( 41 , 42 ) will not be fed into the heat source side heat exchanger ( 44 ) and others, but will be positively fed into the heating heat exchanger ( 71 ). Therefore, in accordance with the present invention, it is ensured that the refrigerant within the heating heat exchanger ( 71 ) is expelled outside.
  • refrigerant is evaporated in each of the refrigeration heat exchangers ( 81 , 91 ) while the accumulated refrigerant within the heating heat exchanger ( 71 ) is being expelled outside. That is, the present invention ensures that the elimination of “refrigerant's falling-asleep” within the heating heat exchanger ( 71 ) can be accomplished without the stop of the refrigeration operation by each of the refrigeration heat exchangers ( 81 , 91 ).
  • FIG. 1 is a plumbing diagram of a refrigerant circuit in a refrigeration system according to an embodiment of the present invention
  • FIG. 2 is a plumbing diagram illustrating the flow of refrigerant during the space cooling operation
  • FIG. 3 is a plumbing diagram illustrating the flow of refrigerant during the space heating operation
  • FIG. 4 is a plumbing diagram illustrating the flow of refrigerant immediately after the thermo-off operation of an indoor heat exchanger
  • FIG. 5 is a flowchart illustrating a second control operation by a degree-of-opening control means
  • FIG. 6 is a flowchart illustrating the operation of control by an operation control means.
  • FIG. 7 is a plumbing diagram illustrating the flow of refrigerant during the heat recovery operation.
  • a refrigeration system ( 10 ) is of the type for the installation in a convenience store or other facility.
  • the refrigeration system ( 10 ) provides, at the same time, refrigeration to a cold-storage compartment and a freeze-storage compartment and air conditioning to an indoor space.
  • the refrigeration system ( 10 ) includes an outdoor unit ( 11 ), an air conditioning unit ( 12 ), a cold-storage showcase ( 13 ), and a freeze-storage showcase ( 14 ).
  • the outdoor unit ( 11 ) is provided with an outdoor circuit ( 40 ) which constitutes a heat source side circuit.
  • the air conditioning unit ( 12 ) is provided with an air conditioning circuit ( 70 ) which constitutes a first utilization side circuit.
  • the cold-storage showcase ( 13 ) is provided with a cold-storage circuit ( 80 ) which constitutes a second utilization side circuit.
  • the freeze-storage showcase ( 14 ) is provided with a freeze-storage circuit ( 90 ) which constitutes a third utilization side circuit.
  • these utilization side circuits ( 70 , 80 , 90 ) are connected in parallel to the outdoor circuit ( 40 ) thereby to constitute a refrigerant circuit ( 20 ) which performs a vapor compression refrigeration cycle.
  • the outdoor circuit ( 40 ) and each utilization side circuit ( 70 , 80 , 90 ) are connected together by liquid side interunit piping ( 31 ), first gas side interunit piping ( 32 ), and second gas side interunit piping ( 33 ).
  • One end of the liquid side interunit piping ( 31 ) is connected to a liquid side closing valve ( 21 ) of the outdoor circuit ( 40 ).
  • the other end of the liquid side interunit piping ( 31 ) diverges into three branches, namely a first liquid branch pipe ( 31 a ), a second liquid branch pipe ( 31 b ), and a third liquid branch pipe ( 31 c ).
  • the first to third liquid branch pipes ( 31 a , 31 b , 31 c ) are connected to the air conditioning circuit ( 70 ), to the cold-storage circuit ( 80 ), and to the freeze-storage circuit ( 90 ), respectively.
  • One end of the first gas side interunit piping ( 32 ) is connected to a first gas side closing valve ( 22 ) of the outdoor circuit ( 40 ) and the other end thereof is connected to the air conditioning circuit ( 70 ).
  • One end of the second gas side interunit piping ( 33 ) is connected to a second gas side closing valve ( 23 ) of the outdoor circuit ( 40 ).
  • the other end of the second gas side interunit piping ( 33 ) diverges into two branches, namely a first gas branch pipe ( 33 a ) and a second gas branch pipe ( 33 b ).
  • the first and second gas branch pipes ( 33 a , 33 b ) are connected to the cold-storage circuit ( 80 ) and to the freeze-storage circuit ( 90 ), respectively.
  • the outdoor circuit ( 40 ) of the outdoor unit ( 11 ) includes three (first to third) compressors ( 41 , 42 , 43 ), an outdoor heat exchanger ( 44 ), a receiver ( 45 ), an outdoor expansion valve ( 46 ), and three (first to third) four-way selector valves ( 47 , 48 , 49 ).
  • the first to third compressors ( 41 , 42 , 43 ) are each formed by a respective scroll compressor of the high pressure dome type.
  • the first compressor ( 41 ) constitutes a compressor of the variable capacity type. That is, the first compressor ( 41 ) is configured such that its speed of rotation is made variable by inverter control.
  • the second and third compressors ( 42 , 43 ) each constitute a compressor of the fixed capacity type, that is, whose speed of rotation is fixed.
  • first intake pipe ( 51 ) Connected to the intake side of the first compressor ( 41 ) is one end of a first intake pipe ( 51 ). The other end of the first intake pipe ( 51 ) is connected to the second gas side closing valve ( 23 ).
  • second intake pipe ( 52 ) Connected to the intake side of the second compressor ( 42 ) is one end of a second intake pipe ( 52 ). The other end of the second intake pipe ( 52 ) is connected to the third four-way selector valve ( 49 ).
  • Connected to the intake side of the third compressor ( 43 ) is one end of a third intake pipe ( 53 ). The other end of the third intake pipe ( 53 ) is connected to the second four-way selector valve ( 48 ).
  • first delivery pipe ( 54 ) Connected to the delivery side of the first compressor ( 41 ) is one end of a first delivery pipe ( 54 ). The other end of the first delivery pipe ( 54 ) is connected through delivery piping ( 57 ) to the first four-way selector valve ( 47 ).
  • second delivery pipe ( 55 ) Connected to the delivery side of the second compressor ( 42 ) is one end of a second delivery pipe ( 55 ). The other end of the second delivery pipe ( 55 ) is connected to the delivery piping ( 57 ).
  • Connected to the delivery side of the third compressor ( 43 ) is one end of a third delivery pipe ( 56 ). The other end of the third delivery pipe ( 56 ) is connected in the middle of the delivery piping ( 57 ).
  • the outdoor heat exchanger ( 44 ) is a fin-and-tube heat exchanger of the cross fin type, and constitutes a heat source side heat exchanger. There is arranged in the vicinity of the outdoor heat exchanger ( 44 ) an outdoor fan ( 50 ). In the outdoor heat exchanger ( 44 ), the exchange of heat takes place between the outdoor air distributed by the outdoor fan ( 50 ) and the refrigerant.
  • One end of the outdoor heat exchanger ( 44 ) is connected to the first four-way selector valve ( 47 ).
  • the other end of the outdoor heat exchanger ( 44 ) is connected through a first liquid pipe ( 58 ) to the top of the receiver ( 45 ).
  • the bottom of the receiver ( 45 ) is connected through a second liquid pipe ( 59 ) to the liquid side closing valve ( 21 ).
  • first and second bypass pipes ( 60 , 61 ) are connected in the middle of the first liquid pipe ( 58 ).
  • the other ends of the first and second bypass pipes ( 60 , 62 ) are each connected to the second liquid pipe ( 59 ).
  • the outdoor expansion valve ( 46 ) is disposed in the first bypass pipe ( 60 ).
  • the outdoor expansion valve ( 46 ) is formed by an electronic expansion valve whose degree of opening is adjustable.
  • One end of a liquid injection pipe ( 62 ) is connected in the middle of the second bypass pipe ( 61 ).
  • the other end of the liquid injection pipe ( 62 ) is connected in the middle of the first intake pipe ( 51 ).
  • the liquid injection pipe ( 62 ) is provided with a flow control valve ( 63 ) whose degree of opening is adjustable.
  • Each of the first to third four-way selector valves ( 47 , 48 , 49 ) has four (first to fourth) ports.
  • the first four-way selector valve ( 47 ) its ports are connected as follows: the first port is connected to the delivery piping ( 57 ); the second port is connected to the fourth port of the second four-way selector valve ( 48 ); the third port is connected to the outdoor heat exchanger ( 44 ); and the fourth port is connected to the first gas side closing valve ( 22 ).
  • the second four-way selector valve ( 48 ) its ports are connected as follows: the first and second ports are connected to the third delivery pipe ( 56 ) and to the third intake pipe ( 53 ), respectively, while the third port is closed.
  • the third four-way selector valve ( 49 ) its ports are connected as follows: the second to fourth ports are connected to the second intake pipe ( 52 ), to the third intake pipe ( 53 ), and to the first intake pipe ( 51 ), respectively, while the first port is closed.
  • Each of the four-way selector valves ( 47 , 48 , 49 ) is selectively switchable between a first state (indicated by solid line in FIG. 1 ) and a second state (indicated by broken line in FIG. 1 ).
  • first state the first and third ports fluidly communicate with each other, while the second and fourth ports fluidly communicate with each other.
  • the first and fourth ports When in the second state, the first and fourth ports fluidly communicate with each other, while the second and third ports fluidly communicate with each other.
  • the first intake pipe ( 51 ) is provided with a first intake temperature sensor ( 111 ) and a first intake pressure sensor ( 112 ).
  • the third intake pipe ( 53 ) is provided with a second intake temperature sensor ( 113 ) and a second intake pressure sensor ( 114 ).
  • the first delivery pipe ( 54 ) is provided with a first high pressure switch ( 115 ).
  • the second delivery pipe ( 55 ) is provided with a second high pressure switch ( 116 ).
  • the third delivery pipe ( 56 ) is provided with a third high pressure switch ( 117 ).
  • the delivery piping ( 57 ) is provided with a first delivery temperature sensor ( 118 ) and a first delivery pressure sensor ( 119 ).
  • the third delivery pipe ( 56 ) is provided with a second delivery temperature sensor ( 120 ).
  • the outdoor heat exchanger ( 44 ) is provided, in its heat transfer tube, with an outdoor side refrigerant temperature sensor ( 121 ). In addition, there is disposed in the vicinity of the outdoor heat exchanger ( 44 ) an outdoor temperature sensor ( 122 ).
  • the outdoor circuit ( 40 ) is provided with a plurality of check valves configured to allow refrigerant to flow in one direction only while stopping the flow of refrigerant in the opposite direction. More specifically, a check valve (CV- 1 ) is disposed in piping between the first intake pipe ( 51 ) and the second intake pipe ( 52 ). A check valve (CV- 2 ) is disposed in piping between the second intake pipe ( 52 ) and the third intake pipe ( 53 ). In addition, the second delivery pipe ( 55 ) is provided with a check valve (CV- 3 ). The third delivery pipe ( 56 ) is provided with a fourth check valve (CV- 4 ). The first liquid pipe ( 58 ) is provided with a check valve (CV- 5 ).
  • the second liquid pipe ( 59 ) is provided with a check valve (CV- 6 ).
  • the second bypass pipe ( 61 ) is provided with a check valve (CV- 7 ).
  • the check valves (CV- 1 , CV- 2 , . . . ) are so configured as to permit only the flow of refrigerant in directions indicated by arrows assigned to the symbols representative of these valves in FIG. 1 .
  • the air conditioning circuit ( 70 ) of the air conditioning unit ( 12 ) is provided with an indoor heat exchanger ( 71 ) and an indoor expansion valve ( 72 ).
  • the indoor heat exchanger ( 71 ) is a fin-and-tube heat exchanger of the cross fin type, and constitutes a first utilization side heat exchanger.
  • the indoor heat exchanger ( 71 ) constitutes a heating heat exchanger capable of a heating operation in which heat is released from the refrigerant.
  • the indoor expansion valve ( 72 ) is formed by an electronic expansion valve whose degree of opening is adjustable by a pulse motor.
  • a first refrigerant temperature sensor ( 123 ) is disposed in piping between the first gas side interunit piping ( 32 ) and the indoor heat exchanger ( 71 ) and a second refrigerant temperature sensor ( 124 ) is disposed in the heat transfer tube of the indoor heat exchanger ( 71 ).
  • an indoor temperature sensor ( 125 ) is disposed in the vicinity of the indoor heat exchanger ( 71 ).
  • the cold-storage circuit ( 80 ) of the cold-storage showcase ( 13 ) is provided with a cold-storage heat exchanger ( 81 ) and a cold-storage expansion valve ( 82 ).
  • the cold-storage heat exchanger ( 81 ) is a fin-and-tube heat exchanger of the cross fin type, and constitutes a second utilization side heat exchanger.
  • the cold-storage heat exchanger ( 81 ) is a refrigeration heat exchanger in which refrigerant absorbs heat from air for the provision of refrigeration to the cold-storage compartment.
  • a first outlet refrigerant temperature sensor ( 126 ) is disposed on the outflow side of the cold-storage heat exchanger ( 81 ).
  • the cold-storage expansion valve ( 82 ) is formed by an expansion valve of the temperature sensing type whose degree of opening can be adjusted depending on the temperature detected by the first outlet refrigerant temperature sensor ( 126 ).
  • SV- 1 first solenoid valve
  • the freeze-storage circuit ( 90 ) of the freeze-storage showcase ( 14 ) is provided with a freeze-storage heat exchanger ( 91 ), a freeze-storage expansion valve ( 92 ), and a booster compressor ( 94 ).
  • the freeze-storage heat exchanger ( 91 ) is a fin-and-tube heat exchanger of the cross fin type, and constitutes a third utilization side heat exchanger.
  • the freeze-storage heat exchanger ( 91 ) is a refrigeration heat exchanger in which refrigerant absorbs heat from air for the provision of refrigeration to the freeze-storage compartment.
  • a second outlet refrigerant temperature sensor ( 128 ) is disposed on the outflow side of the freeze-storage heat exchanger ( 91 ).
  • the freeze-storage expansion valve ( 92 ) is formed by an expansion valve of the temperature sensing type whose degree of opening can be adjusted depending on the temperature detected by the second outlet refrigerant temperature sensor ( 128 ).
  • SV- 2 a second solenoid valve
  • SV- 2 a second solenoid valve
  • the booster compressor ( 94 ) is a scroll compressor of the high pressure dome type, and constitutes a compressor of the variable capacity type.
  • a fourth intake pipe ( 95 ) and a fourth deliver pipe ( 96 ) are connected to the intake side and to the delivery side of the booster compressor ( 94 ), respectively.
  • the fourth delivery pipe ( 96 ) is provided with a fourth high pressure switch ( 130 ), an oil separator ( 97 ), and a check valve (CV- 8 ).
  • Connected to the oil separator ( 97 ) is an oil return pipe ( 98 ) for the return of refrigeration oil separated from the refrigerant, to the intake side of the booster compressor ( 94 ).
  • the oil return pipe ( 98 ) is provided with a capillary tube ( 98 a ).
  • the freeze-storage circuit ( 90 ) is provided also with a third bypass pipe ( 99 ) by which the fourth intake pipe ( 95 ) and the fourth delivery pipe ( 96 ) are connected together.
  • the third bypass pipe ( 99 ) is provided with a check valve (CV- 9 ).
  • the third bypass pipe ( 99 ) is configured such that, for example, when the booster compressor ( 94 ) breaks down, the refrigerant flowing in the fourth intake pipe ( 95 ) is made to bypass the booster compressor ( 94 ) and be fed to the fourth delivery pipe ( 96 ).
  • the refrigeration system ( 10 ) is provided with a controller ( 100 ) for controlling the devices (targets for control) disposed in the refrigerant circuit ( 20 ).
  • the controller ( 100 ) is configured such that it can receive signals from the sensors disposed in the refrigerant circuit ( 20 ). And in response to the signals from the sensors, the controller ( 100 ) controls the operation of each compressor, the switching of each four-way selector valve and other operations.
  • the controller ( 100 ) is provided with a degree-of-opening control means ( 101 ) and an operation control means ( 102 ) both of which are features of the present invention.
  • the degree-of-opening control means ( 101 ) and the operation control means ( 102 ) together constitute a means for preventing the accumulation of refrigerant in the indoor heat exchanger ( 71 ) when the heating operation of the indoor heat exchanger ( 71 ) is stopped.
  • the operation of control by the degree-of-opening control means ( 101 ) and the operation of control by the operation control means ( 102 ) will fully be described hereinafter.
  • the following is a description of the running operation of the refrigeration system ( 10 ) according to the present embodiment.
  • the refrigeration system ( 10 ) it is possible to selectively perform a space cooling operation in which the air conditioning unit ( 12 ) provides indoor space cooling while simultaneously the storage compartment of each showcase ( 13 , 14 ) is being refrigerated, or a space heating operation in which the air conditioning unit ( 12 ) provides indoor space heating while simultaneously the storage compartment of each showcase ( 13 , 14 ) is being refrigerated.
  • FIG. 2 a typical space cooling operation of the refrigeration system ( 10 ) will be described below.
  • the first four-way selector valve ( 47 ), the second four-way selector valve ( 48 ), and the third four-way selector valve ( 49 ) are all placed in the first state.
  • the outdoor expansion valve ( 46 ) and the flow control valve ( 63 ) are fully closed and the first and second solenoid valves (SV- 1 , SV- 2 ) are opened.
  • the indoor expansion valve ( 72 ), the cold-storage expansion valve ( 82 ), and the freeze-storage expansion valve ( 92 ) are properly adjusted in their degree of opening.
  • the fans ( 50 , 73 , 83 , 93 ), the first to third compressors ( 41 , 42 , 43 ), and the booster compressor ( 94 ) are each placed in operation.
  • the refrigerant admitted to the first liquid branch pipe ( 31 a ) is pressure reduced during its passage through the indoor expansion valve ( 72 ), and then flows through the indoor heat exchanger ( 71 ).
  • the indoor heat exchanger ( 71 ) the refrigerant absorbs heat from the indoor air and evaporates. As a result, indoor space cooling is provided.
  • the refrigerant evaporated in the indoor heat exchanger ( 71 ) flows sequently through the first gas side interunit piping ( 32 ), then through the first four-way selector valve ( 47 ), then through the second four-way selector valve ( 48 ), and then through the third intake pipe ( 53 ), and is drawn into the third compressor ( 43 ).
  • the refrigerant admitted to the second liquid branch pipe ( 31 b ) is pressure reduced during its passage through the cold-storage expansion valve ( 82 ), and then flows through the cold-storage heat exchanger ( 81 ).
  • the refrigerant absorbs heat from the storage compartment air and evaporates.
  • the storage compartment of the cold-storage showcase ( 13 ) is refrigerated.
  • the storage compartment temperature is maintained at, for example, 5 degrees Centigrade.
  • the refrigerant evaporated in the cold-storage heat exchanger ( 81 ) flows into the first gas branch pipe ( 33 a ).
  • the refrigerant admitted to the third liquid branch pipe ( 31 c ) is pressure reduced during its passage through the freeze-storage expansion valve ( 92 ), and then flows through the freeze-storage heat exchanger ( 91 ).
  • the freeze-storage heat exchanger ( 91 ) the refrigerant absorbs heat from the storage compartment air and evaporates.
  • the storage compartment of the freeze-storage showcase ( 14 ) is refrigerated.
  • the storage compartment temperature is maintained at, for example, minus 10 degrees Centigrade.
  • the refrigerant evaporated in the freeze-storage heat exchanger ( 91 ) is compressed in the booster compressor ( 94 ), and then flows into the second gas branch pipe ( 33 b ).
  • the joined flow of refrigerant in the second gas side interunit piping ( 33 ) diverges again into the first and second intake pipes ( 51 , 52 ), the refrigerant diverged into the former of which is drawn into the first compressor ( 41 ) and the refrigerant diverged into the latter of which is drawn into the second compressor ( 42 ).
  • the first four-way selector valve ( 47 ) and the second four-way selector valve ( 48 ) are placed in the second state, while the third four-way selector valve ( 49 ) is placed in the first state.
  • the outdoor expansion valve ( 46 ) and the flow control valve ( 63 ) are fully closed, while the first and second solenoid valves (SV- 1 , SV- 2 ) are opened.
  • the indoor expansion valve ( 72 ), the cold-storage expansion valve ( 82 ), and the freeze-storage expansion valve ( 92 ) are properly adjusted in their degree of opening.
  • the fans ( 50 , 73 , 83 , 93 ), the first and second compressors ( 41 , 42 ), and the booster compressor ( 94 ) are all placed in operation.
  • One refrigerant flow passes through the second four-way selector valve ( 48 ) and flows through the outdoor heat exchanger ( 44 ) where it condenses. Thereafter, the condensed refrigerant flows, through the first liquid pipe ( 58 ), then through the receiver ( 45 ), and then through the second liquid pipe ( 59 ) in that order, into the liquid side interunit piping ( 31 ).
  • the other refrigerant flow passes through the first four-way selector valve ( 47 ) and then flows through the indoor heat exchanger ( 71 ).
  • the indoor heat exchanger ( 71 ) the refrigerant dissipates heat to the indoor air and condenses. As a result, indoor space heating is provided.
  • the refrigerant condensed in the indoor heat exchanger ( 71 ) is pressure reduced during its passage through the indoor expansion valve ( 72 ), and then flows into the first liquid branch pipe ( 31 a ).
  • the joined flow of refrigerant in the liquid side interunit piping ( 31 ) again diverges in two branches, namely the second liquid branch pipe ( 31 b ) and the third liquid branch pipe ( 31 c ).
  • the refrigerant admitted to the second liquid branch pipe ( 31 b ) is used to provide refrigeration of the storage compartment of the cold-storage showcase ( 13 ), as in the foregoing space cooling operation.
  • the refrigerant admitted to the third liquid branch pipe ( 31 c ) is used to provide refrigeration of the storage compartment of the freeze-storage showcase ( 14 ), as in the foregoing space cooling operation.
  • the flows of refrigerant used to provide refrigeration of the showcases ( 13 , 14 ) join together in the second gas side interunit piping ( 33 ).
  • the joined flow of refrigerant is drawn into the first and second compressors ( 41 , 42 ).
  • the heating operation by the indoor heat exchanger ( 71 ) may no longer be required in some cases, for example, when the room temperature reaches a user preset temperature. Therefore, in the refrigeration system ( 10 ), there is carried out a first control operation (thermo-off operation) to temporarily place the indoor heat exchanger ( 71 ) in the out-of-operation state if a given condition holds in the foregoing space heating operation.
  • a first control operation thermo-off operation
  • the degree-of-opening control means ( 101 ) of the controller ( 100 ) provides control of the degree of opening of the indoor expansion valve ( 72 ) so that the indoor expansion valve ( 72 ) is fully closed.
  • most of the refrigerant delivered out from both the first compressor ( 41 ) and the second compressor ( 42 ) is fed towards the outdoor heat exchanger ( 44 ), as shown in FIG. 5 .
  • the refrigerant after condensation in the outdoor heat exchanger ( 44 ) is fed, through the same distribution route as in the aforesaid space heating operation, to each showcase ( 13 , 14 ) where it is used to provide refrigeration of the storage compartment.
  • the indoor expansion valve ( 72 ) enters the fully closed state and no refrigerant will flow through the indoor heat exchanger ( 71 ). Consequently, in the indoor heat exchanger ( 71 ), there is no active exchange of heat between the refrigerant and the indoor air and, as a result, the indoor heat exchanger ( 71 ) is substantially placed in the out-of-operation state (thermo-off state). Thereafter, if a given condition holds (for example, if the room temperature falls lower than a preset temperature level by more than a predetermined value), this places the indoor heat exchanger ( 71 ) in the thermo-off state and the foregoing space heating operation resumes.
  • the indoor expansion valve ( 72 ) enters the fully closed state as described above.
  • the gas side of the indoor heat exchanger ( 71 ) still remains in fluid communication with the refrigerant circulation path. Therefore, after the thermo-off operation, refrigerant flows into the indoor heat exchanger ( 71 ) and gradually condenses to liquid form and this liquid refrigerant after condensation will accumulate in gradual degrees within the indoor heat exchanger ( 71 ). That is, in the indoor heat exchanger ( 71 ) in the thermo-off state, there is the possibility that the so-called “refrigerant's falling-asleep” may occur.
  • the degree-of-opening control means ( 101 ) of the present embodiment first provides control so that the indoor expansion valve ( 72 ) is placed in the fully closed state when thermo-offing the air conditioning unit ( 12 ) and, then, a degree-of-opening control operation (i.e., the second control operation) is performed to properly adjust the degree of opening of the indoor expansion valve ( 72 ), whereby the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) can be accomplished.
  • a degree-of-opening control operation i.e., the second control operation
  • Step S 1 a determination is made as to whether or not the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) is great. More specifically, in Step S 1 , the pressure difference, (Pc ⁇ Th 1 ), between Pc (the saturated temperature corresponding to the high pressure found from the values detected by the first delivery temperature sensor ( 118 ) and the first delivery pressure sensor ( 119 )) and Th 1 (the refrigerant temperature detected by the first refrigerant temperature sensor ( 123 )), is calculated. To sum up, in Step S 1 , the degree of refrigerant subcooling, (Pc ⁇ Th 1 ), in the vicinity of the inlet of the indoor heat exchanger ( 71 ) is calculated.
  • the degree of subcooling, (Pc ⁇ Th 1 ), of such refrigerant serves as an index indicative of the amount of refrigerant within the indoor heat exchanger ( 71 ).
  • Step S 1 makes a determination that the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) is great, and the control procedure moves to Step S 2 .
  • Step S 2 the current degree of opening of the indoor expansion valve ( 72 ) is increased by an amount corresponding to a predetermined number of pulses (for example, 352 pulses).
  • a predetermined number of pulses for example, 352 pulses.
  • Step S 1 it makes a determination as to whether or not the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) is accomplished.
  • Step S 3 makes a determination that very little refrigerant has accumulated within the indoor heat exchanger ( 71 ), and the control procedure moves to Step S 4 .
  • the indoor expansion valve ( 72 ) enters the fully closed state.
  • Step S 3 the temperature difference, (Pc ⁇ Th 2 ), between PC (the saturated temperature corresponding to the high pressure and Th 2 (the refrigerant temperature, detected by the second refrigerant temperature sensor ( 124 )) is calculated. That is, in Step S 3 , the degree of refrigerant subcooling, (Pc ⁇ Th 2 ), immediately before the outlet of the indoor heat exchanger ( 71 ) is also calculated.
  • Step S 1 or Step S 3 the indoor expansion valve ( 72 ) will remain in the fully closed state because the value of the degree of refrigerant subcooling becomes small although the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) is great.
  • Step S 5 makes a determination that the indoor expansion valve ( 72 ) continues to remain in the fully closed state for longer than t3 minutes (for example, 20 minutes), then the control procedure moves to Step S 6 on the assumption that there is the possibility that the amount of refrigerant within the indoor heat exchanger ( 71 ) may not have been detected accurately.
  • Step S 6 the degree of opening of the indoor expansion valve ( 72 ) is opened at a predetermined degree or opening (for example, 352 pulses). As a result, if there is an accumulation of refrigerant within the indoor heat exchanger ( 71 ), the refrigerant accumulated will be expelled promptly to outside the indoor heat exchanger ( 71 ).
  • Step S 6 the continuous supply of refrigerant to the indoor heat exchanger ( 71 ) is made.
  • the refrigerant flowing in the indoor heat exchanger ( 71 ) is less subject to the influence of the ambient temperature. Consequently, it is avoided that the value of the degree of refrigerant subcooling will become small due to the influence of the ambient temperature.
  • Steps S 1 , S 3 it becomes possible to control the degree of opening of the indoor expansion valve ( 72 ) by accurate detection of the amount of refrigerant within the indoor heat exchanger ( 71 ).
  • each of Steps S 1 -S 6 is repeatedly carried out so that the degree of opening of the indoor expansion valve ( 72 ) can be properly adjusted depending on the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) in the thermo-off state.
  • the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) is accomplished, whereby it is avoided that the cold-storage heat exchanger ( 81 ) and the freeze-storage heat exchanger ( 91 ) will deteriorate in their refrigeration capacity.
  • the head difference of the interunit piping (the first gas side interunit piping ( 32 )) extending from the outdoor unit ( 11 ) to the air conditioning unit ( 12 ) is great because the air conditioning unit ( 12 ) is installed relatively higher than the outdoor unit ( 11 ) of the refrigeration system ( 10 )
  • the refrigerant accumulated within the indoor heat exchanger ( 71 ) will not be sufficiently expelled outside because the refrigerant delivered out from each compressor ( 41 , 42 ) is supplied only to the outdoor heat exchanger ( 44 ) even when the degree of opening of the indoor expansion valve ( 72 ) is placed in the fully opened state (for example, 2000 pulses) by the degree-of-opening control operation.
  • the operation control means ( 102 ) of the controller ( 100 ) provides the following control.
  • Step S 11 makes a determination as to whether or not the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) still remains unaccomplished. More specifically, if the degree of refrigerant subcooling, (Pc ⁇ Th 1 ), on the inlet side of the indoor heat exchanger ( 71 ) continues to remain greater than T1 degrees Centigrade for longer than t4 minutes (for example 20 minutes), then Step S 11 makes a determination that the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) has not yet been accomplished, and the control procedure moves to Step S 12 . As a result, in the refrigeration system ( 10 ), the following heat recovery operation is carried out.
  • the first four-way selector valve ( 47 ) is placed in the second state and the second and third four-way selector valves ( 48 , 49 ) are placed in the first state.
  • the outdoor expansion valve ( 46 ) and the flow control valve ( 63 ) are fully closed, while the first and second solenoid valves (SV- 1 , SV- 2 ) are opened.
  • the indoor expansion valve ( 72 ), the cold-storage expansion valve ( 82 ), and the freeze-storage expansion valve ( 92 )) are properly adjusted in their degree of opening.
  • the fans ( 50 , 73 , 83 , 93 ), the first and second compressors ( 41 , 42 ), and the booster compressor ( 94 ) are all placed in operation.
  • the joined flow of refrigerant passes through the first four-way selector valve ( 47 ) and then flows through the indoor heat exchanger ( 71 ).
  • the indoor heat exchanger ( 71 ) the refrigerant accumulated therein is forced out by the high pressure refrigerant and expelled outside the indoor heat exchanger ( 71 ).
  • the heating operation is temporarily carried out in the indoor heat exchanger ( 71 ).
  • the refrigerant leaving the indoor heat exchanger ( 71 ) is pressure reduced during its passage through the indoor expansion valve ( 72 ) and then admitted to the first liquid branch pipe ( 31 a ).
  • the refrigerant admitted to the first liquid branch pipe ( 31 a ) diverges into two branches, namely the second liquid branch pipe ( 31 b ) and the third liquid branch pipe ( 31 c ).
  • the refrigerant admitted to the second liquid branch pipe ( 31 b ) is used to provide refrigeration of the storage compartment of the cold-storage showcase ( 13 ).
  • the refrigerant admitted to the third liquid branch pipe ( 31 c ) is used to provide refrigeration of the storage compartment of the freeze-storage showcase ( 14 ).
  • the flows of refrigerant used for the refrigeration of the showcases ( 13 , 14 ) join together in the second gas side interunit piping ( 33 ). Thereafter, the joined flow of refrigerant is drawn into the first and second compressors ( 41 , 42 ).
  • the heat recovery operation differs from the aforesaid space heating operation in that the refrigerant delivered from the first and second compressors ( 41 , 42 ) is supplied only towards the air conditioning unit ( 12 ). Consequently, even in the installation situation where the head difference between the outdoor unit ( 11 ) and the air conditioning unit ( 12 ) is great, it is ensured that the supply of high pressure refrigerant to the air conditioning unit ( 12 ) is provided without fail. As a result, the refrigerant accumulated within the indoor heat exchanger ( 71 ) is expelled outside without fail and is used to provide refrigeration of each showcase ( 13 , 14 ).
  • Step S 13 makes a determination as to whether or not the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) is accomplished. More specifically, if the degree of refrigerant subcooling within the indoor heat exchanger ( 71 ), (Pc ⁇ Th 2 ), continues to remain less than T2 degrees Centigrade for longer than t5 minutes (for example, 2 minutes), Step S 13 makes a determination that the elimination of “refrigerant's falling-asleep” is accomplished, and the control procedure moves to Step S 14 .
  • Step S 14 the heat recovery operation is brought to a stop and the indoor heat exchanger ( 71 ) again enters the thermo-off state.
  • Step S 14 makes a determination that the elimination of “refrigerant's falling-asleep” is accomplished without fail, and the control procedure moves to Step S 14 .
  • the degree-of-opening control operation in which the degree of opening of the indoor expansion valve ( 72 ) is adjusted based on the index (the degree of refrigerant subcooling) indicative of the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ), is carried out. More specifically, in the degree-of-opening control operation, as the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) increases, the degree of opening of the indoor expansion valve ( 72 ) is increased.
  • the refrigerant accumulated within the indoor heat exchanger ( 71 ) is properly expelled outside for forwarding to the cold-storage showcase ( 13 ) and to the freeze-storage showcase ( 14 ). Accordingly, it is ensured that the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) can be accomplished without fail, whereby it becomes possible to prevent the deterioration of refrigeration capacity in the storage compartment of each showcase ( 13 , 14 ).
  • the degree of opening of the expansion valve ( 72 ) is reduced if the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) is small. Consequently, in accordance with the aforesaid embodiment, it can be avoided that the excess supply of refrigerant is provided to the indoor heat exchanger ( 71 ) despite the fact that the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) has already been accomplished, thereby making it possible that the supply of refrigerant to be provided to each showcase ( 13 , 14 ) is satisfactorily secured. Accordingly, it becomes possible to more effectively prevent the capacity of refrigeration of the storage compartment of each showcase ( 13 , 14 ) from deterioration.
  • the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) is detected with the aid of the degree of refrigerant subcooling on the inlet side of or within the indoor heat exchanger ( 71 ). Consequently, in accordance with the foregoing embodiment, it is possible to relatively easily observe the occurrence of the “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ).
  • the indoor expansion valve ( 72 ) is opened if the indoor expansion valve ( 72 ) continues to remain in the fully closed state for longer than a predetermined length of time, in view of the fact that the degree of refrigerant subcooling decreases due to the influence of the ambient temperature of the indoor heat exchanger ( 71 ). Consequently, in accordance with the foregoing embodiment, it can be avoided that the indoor expansion valve ( 72 ) enters the state of remaining closed despite that fact that the “refrigerant's falling-asleep” is in fact occurring in the indoor heat exchanger ( 71 ). This makes it sure that the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) is accomplished without fail.
  • the degree of refrigerant subcooling is less subject to the influence of the ambient temperature of the indoor heat exchanger ( 71 ) in the subsequent degree-of-opening control operation, whereby the amount of refrigerant within the indoor heat exchanger ( 71 ) can be detected with accuracy. Consequently, in accordance with the present embodiment, it is possible to properly control the degree of opening of the expansion valve ( 72 ) depending on the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ).
  • the heat recovery operation is carried out in the refrigerant circuit ( 20 ) if the elimination of “refrigerant's falling-asleep” within the indoor heat exchanger ( 71 ) still remains unaccomplished even when the degree-of-opening control operation is performed by the degree-of-opening control means ( 101 ) after the execution of the thermo-off operation of the indoor heat exchanger ( 71 ).
  • the total amount of refrigerant delivered out from each compressor ( 41 , 42 ) is fed towards the indoor heat exchanger ( 71 ).
  • the foregoing embodiment may be configured as follows.
  • the number of air conditioning units ( 12 ) connected to the outdoor unit ( 11 ) is one.
  • a plurality of air conditioning units of such a type may be connected to the outdoor unit ( 11 ).
  • the elimination of “refrigerant's falling-asleep” in each indoor heat exchanger can be accomplished by the execution of the foregoing degree-of-opening control operation after the thermo-offing of the indoor heat exchanger of each air conditioning unit.
  • the fully closing of the indoor expansion valve ( 72 ) is carried out as the thermo-off operation of the indoor heat exchanger ( 71 ).
  • the degree of opening of the indoor expansion valve ( 72 ) may be reduced to a very small degree of opening.
  • the accumulation of refrigerant will gradually proceed within the indoor heat exchanger ( 71 ).
  • the foregoing degree-of-opening control operation is carried out to eliminate the “refrigerant's falling-asleep”.
  • the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) in the thermo-off state is found from the degree of refrigerant subcooling on the inflow side of or within the indoor heat exchanger ( 71 ).
  • the accumulated amount of refrigerant within the indoor heat exchanger ( 71 ) may be found by other than the above method.
  • the present invention finds its utility in the prevention of “refrigerant's falling-asleep” in a heating heat exchanger placed in the out-of-operation state in a refrigeration system having a plurality of utilization units.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Signal Processing (AREA)
  • Thermal Sciences (AREA)
  • Sustainable Development (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Fuzzy Systems (AREA)
  • Mathematical Physics (AREA)
  • Air Conditioning Control Device (AREA)
  • Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
US12/302,478 2006-05-26 2007-05-25 Refrigeration system Abandoned US20090282848A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2006-146923 2006-05-26
JP2006146923A JP4069947B2 (ja) 2006-05-26 2006-05-26 冷凍装置
PCT/JP2007/060688 WO2007139010A1 (fr) 2006-05-26 2007-05-25 Dispositif frigorifique

Publications (1)

Publication Number Publication Date
US20090282848A1 true US20090282848A1 (en) 2009-11-19

Family

ID=38778530

Family Applications (1)

Application Number Title Priority Date Filing Date
US12/302,478 Abandoned US20090282848A1 (en) 2006-05-26 2007-05-25 Refrigeration system

Country Status (7)

Country Link
US (1) US20090282848A1 (fr)
EP (1) EP2023061B1 (fr)
JP (1) JP4069947B2 (fr)
KR (1) KR20090009315A (fr)
CN (1) CN101449117B (fr)
TW (1) TW200809151A (fr)
WO (1) WO2007139010A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120055177A1 (en) * 2010-09-08 2012-03-08 Samsung Electronics Co., Ltd. Air conditioner and control method thereof
US20140208787A1 (en) * 2011-09-01 2014-07-31 Daikin Industries, Ltd. Refrigeration apparatus
US20140245766A1 (en) * 2012-01-24 2014-09-04 Mitsubishi Electric Corporation Air-conditioning apparatus
US20150343365A1 (en) * 2014-05-28 2015-12-03 Ingersoll-Rand Company Compressor system and oil separation system
US20160003499A1 (en) * 2014-07-07 2016-01-07 Lg Electronics Inc. Regenerative air-conditioning apparatus and method of controlling the same
US9816739B2 (en) 2011-09-02 2017-11-14 Carrier Corporation Refrigeration system and refrigeration method providing heat recovery
CN107726667A (zh) * 2017-10-20 2018-02-23 青岛海尔空调电子有限公司 多联式空调系统
CN112682922A (zh) * 2020-12-07 2021-04-20 珠海格力电器股份有限公司 一种多联空调器的制热控制方法

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5217531B2 (ja) * 2008-03-13 2013-06-19 アイシン精機株式会社 空気調和装置及びその制御方法
JP2009293899A (ja) * 2008-06-09 2009-12-17 Daikin Ind Ltd 冷凍装置
CN103033007B (zh) * 2011-09-29 2015-11-18 杭州三花研究院有限公司 一种汽车空调系统电子膨胀阀的控制方法
JP5741512B2 (ja) * 2012-04-05 2015-07-01 ダイキン工業株式会社 空気調和機
JP6064412B2 (ja) * 2012-07-30 2017-01-25 株式会社富士通ゼネラル 空気調和装置
JP2016003848A (ja) * 2014-06-19 2016-01-12 日立アプライアンス株式会社 空気調和システムおよびその制御方法
CN111219784B (zh) * 2017-08-29 2021-05-04 珠海格力电器股份有限公司 室内机冷媒控制装置及其控制方法、室内机和空调系统
JP2019086251A (ja) * 2017-11-09 2019-06-06 三菱重工サーマルシステムズ株式会社 マルチ型空気調和装置の制御装置、マルチ型空気調和装置、マルチ型空気調和装置の制御方法及びマルチ型空気調和装置の制御プログラム

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6986259B2 (en) * 2002-04-08 2006-01-17 Daikin Industries, Ltd. Refrigerator
US7380407B2 (en) * 2004-08-04 2008-06-03 Samsung Electronics Co., Ltd. Multi air conditioning system and method for operating the same

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3057985B2 (ja) * 1993-12-01 2000-07-04 ダイキン工業株式会社 多室型空気調和装置
JP3377632B2 (ja) 1994-12-06 2003-02-17 東芝キヤリア株式会社 空気調和機
JP3424868B2 (ja) * 1994-12-19 2003-07-07 東芝キヤリア株式会社 マルチシステム空気調和機
JP4105413B2 (ja) * 2001-08-08 2008-06-25 日立アプライアンス株式会社 マルチ式空気調和機
KR100903148B1 (ko) * 2003-06-27 2009-06-16 삼성전자주식회사 다실형 공기조화기 및 그 제어방법

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6986259B2 (en) * 2002-04-08 2006-01-17 Daikin Industries, Ltd. Refrigerator
US7380407B2 (en) * 2004-08-04 2008-06-03 Samsung Electronics Co., Ltd. Multi air conditioning system and method for operating the same

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120055177A1 (en) * 2010-09-08 2012-03-08 Samsung Electronics Co., Ltd. Air conditioner and control method thereof
US20140208787A1 (en) * 2011-09-01 2014-07-31 Daikin Industries, Ltd. Refrigeration apparatus
US9803897B2 (en) * 2011-09-01 2017-10-31 Daikin Industries, Ltd. Refrigeration apparatus which injects an intermediate-gas liquid refrigerant from multi-stage expansion cycle into the compressor
US9816739B2 (en) 2011-09-02 2017-11-14 Carrier Corporation Refrigeration system and refrigeration method providing heat recovery
US20140245766A1 (en) * 2012-01-24 2014-09-04 Mitsubishi Electric Corporation Air-conditioning apparatus
US9518754B2 (en) * 2012-01-24 2016-12-13 Mitsubishi Electric Corporation Air-conditioning apparatus
US20150343365A1 (en) * 2014-05-28 2015-12-03 Ingersoll-Rand Company Compressor system and oil separation system
US9669346B2 (en) * 2014-05-28 2017-06-06 Ingersoll-Rand Company Compressor system and oil separation system
US20160003499A1 (en) * 2014-07-07 2016-01-07 Lg Electronics Inc. Regenerative air-conditioning apparatus and method of controlling the same
US9970688B2 (en) * 2014-07-07 2018-05-15 Lg Electronics Inc. Regenerative air-conditioning apparatus and method of controlling the same
CN107726667A (zh) * 2017-10-20 2018-02-23 青岛海尔空调电子有限公司 多联式空调系统
CN112682922A (zh) * 2020-12-07 2021-04-20 珠海格力电器股份有限公司 一种多联空调器的制热控制方法

Also Published As

Publication number Publication date
TW200809151A (en) 2008-02-16
CN101449117A (zh) 2009-06-03
EP2023061B1 (fr) 2017-09-27
EP2023061A4 (fr) 2014-04-02
WO2007139010A1 (fr) 2007-12-06
EP2023061A1 (fr) 2009-02-11
KR20090009315A (ko) 2009-01-22
JP2007315702A (ja) 2007-12-06
JP4069947B2 (ja) 2008-04-02
CN101449117B (zh) 2010-10-20

Similar Documents

Publication Publication Date Title
US20090282848A1 (en) Refrigeration system
US10527322B2 (en) Air conditioner
US7752864B2 (en) Refrigeration apparatus
US8307668B2 (en) Air conditioner
US8047011B2 (en) Refrigeration system
US9010135B2 (en) Refrigeration apparatus with a refrigerant collection operation between a plurality of outdoor units
US9103557B2 (en) Air conditioner and method for controlling the same based on a calculated value of a malfunctioning sensor
US8302413B2 (en) Air conditioner
US20100139312A1 (en) Refrigeration apparatus
US20080282728A1 (en) Refrigerating Apparatus
JP4704728B2 (ja) 空調機の冷媒温度制御装置及び制御方法
EP3683511B1 (fr) Dispositif de climatisation
JP2019086251A (ja) マルチ型空気調和装置の制御装置、マルチ型空気調和装置、マルチ型空気調和装置の制御方法及びマルチ型空気調和装置の制御プログラム
JP5310101B2 (ja) 空気調和装置
JP4418936B2 (ja) 空気調和装置
US9689589B2 (en) Refrigeration apparatus
KR20190005445A (ko) 멀티형 공기조화기
KR950014470B1 (ko) 공기조화기
EP2314954B1 (fr) Réfrigérateur
EP3236168B1 (fr) Dispositif de climatisation
KR101414860B1 (ko) 공기 조화기 및 그의 제어방법
KR20190005052A (ko) 멀티형 공기조화기
JPWO2018008130A1 (ja) 空気調和装置
JP7553833B2 (ja) 熱源ユニット、および冷凍装置
JP2019066088A (ja) 冷凍装置

Legal Events

Date Code Title Description
AS Assignment

Owner name: DAIKIN INDUSTRIES, LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TAKEGAMI, MASAAKI;NOMURA, KAZUYOSHI;KONDO, AZUMA;AND OTHERS;REEL/FRAME:021913/0705

Effective date: 20070625

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION