US20240240845A1 - Refrigeration cycle apparatus - Google Patents

Refrigeration cycle apparatus Download PDF

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Publication number
US20240240845A1
US20240240845A1 US18/558,923 US202118558923A US2024240845A1 US 20240240845 A1 US20240240845 A1 US 20240240845A1 US 202118558923 A US202118558923 A US 202118558923A US 2024240845 A1 US2024240845 A1 US 2024240845A1
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Prior art keywords
refrigerant
refrigeration cycle
cycle apparatus
evaporator
temperature
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US18/558,923
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English (en)
Inventor
Shunya GYOTOKU
Kimitaka Kadowaki
Masahiro Ito
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Assigned to MITSUBISHI ELECTRIC CORPORATION reassignment MITSUBISHI ELECTRIC CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ITO, MASAHIRO, GYOTOKU, Shunya, KADOWAKI, Kimitaka
Publication of US20240240845A1 publication Critical patent/US20240240845A1/en
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    • 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
    • F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
    • F24F11/41—Defrosting; Preventing freezing
    • F24F11/42—Defrosting; Preventing freezing of outdoor 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
    • F25B39/00—Evaporators; Condensers
    • F25B39/02—Evaporators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/006—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass for preventing frost
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/006—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant containing more than one component
    • 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
    • F25B2313/02741—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using one four-way valve
    • 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
    • F25B2313/029—Control issues
    • F25B2313/0292—Control issues related to reversing 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
    • F25B2400/12—Inflammable refrigerants
    • 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
    • F25B2600/25—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
    • F25B2700/11—Sensor to detect if defrost is necessary
    • 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
    • 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
    • F25B2700/2117—Temperatures of an evaporator

Definitions

  • the present disclosure relates to a refrigeration cycle apparatus.
  • Japanese Patent Laying-Open No. 2018-21721 discloses a refrigeration cycle apparatus for which a non-azeotropic refrigerant mixture is used, with a reduced deviation of the temperature distribution for the entire evaporator.
  • the system is designed such that the maximum capacity that can be exhibited in a non-frosted state under a low-temperature high-humidity condition is sufficient.
  • the operating frequency of the compressor is increased so as to increase the amount of circulating refrigerant, thereby avoiding deterioration of the heating capacity due to frosting.
  • Defrosting operation is performed when the compressor frequency reaches the maximum frequency and the capacity is deteriorated due to frosting.
  • this operation there is a problem that low-temperature refrigerant flows into the load side to lower the temperature, which impairs comfort of the load side.
  • defrosting period which is the sum of the time of a single heating operation and a subsequent defrosting time, results in deterioration of the integrated heating capacity and reduction of the average coefficient of performance (COP).
  • defrosting period which is the sum of the time of a single heating operation and a subsequent defrosting time
  • An object of the present disclosure is to provide a refrigeration cycle apparatus that enables extension of the defrosting period while suppressing frosting.
  • the present disclosure relates to a refrigeration cycle apparatus.
  • the refrigeration cycle apparatus comprises: a refrigerant circuit in which a compressor, a condenser, a first expansion valve, and an evaporator are connected by a refrigerant pipe; and a non-azeotropic refrigerant that flows through the refrigerant pipe.
  • a temperature difference occurs between an inlet and an outlet of the evaporator.
  • the evaporator comprises: a group of fins that are stacked at intervals; and a heat transfer tube that extends through the group of fins in a stacking direction of the group of fins and allows the non-azeotropic refrigerant to flow inside the heat transfer tube.
  • the group of fins comprises: a first fin part to which frost can adhere in a humid environment; and a second fin part to which no frost adheres to ensure ventilation.
  • the refrigeration cycle apparatus of the present disclosure enables suppression of frosting and extension of the defrosting period during low-temperature high-humidity heating operation, to thereby enable improvement in the comfort of the load side.
  • FIG. 1 is shows a configuration of a refrigeration cycle apparatus according to Embodiment 1.
  • FIG. 2 is a p-h diagram of a refrigeration cycle apparatus in a reference example using an azeotropic refrigerant.
  • FIG. 3 shows a frost region of an outdoor heat exchanger in a reference example using an azeotropic refrigerant.
  • FIG. 4 is a p-h diagram of the refrigeration cycle apparatus of the present embodiment using a non-azeotropic refrigerant.
  • FIG. 5 shows a configuration of an outdoor heat exchanger and a frost region of the present embodiment using a non-azeotropic refrigerant.
  • FIG. 6 is a front view of the outdoor heat exchanger shown in FIG. 5 .
  • FIG. 7 illustrates a difference in defrosting period between a refrigeration cycle apparatus in a reference example and the refrigeration cycle apparatus of the present embodiment.
  • FIG. 8 shows a configuration of a refrigeration cycle apparatus according to Embodiment 2.
  • FIG. 9 illustrates arrangement of a temperature sensor 111 .
  • FIG. 10 illustrates how the position where temperature sensor 111 is to be attached is determined.
  • FIG. 11 is a flowchart for illustrating a process performed by a controller according to Embodiment 2.
  • FIG. 12 is a p-h diagram for illustrating a change in refrigeration cycle according to Embodiment 2.
  • FIG. 13 shows a configuration of a refrigeration cycle apparatus according to Embodiment 3.
  • FIG. 14 is a flowchart for illustrating a process performed by a controller according to Embodiment 3.
  • FIG. 15 is a p-h diagram for illustrating a change in refrigeration cycle according to Embodiment 3.
  • FIG. 16 shows a configuration of a refrigeration cycle apparatus according to Embodiment 4.
  • FIG. 17 is a flowchart for illustrating a process performed by a controller according to Embodiment 4.
  • FIG. 18 is a p-h diagram for illustrating a change in refrigeration cycle according to Embodiment 4.
  • FIG. 19 shows a configuration of a refrigeration cycle apparatus according to Embodiment 5.
  • FIG. 20 is a flowchart for illustrating a process performed by a controller according to Embodiment 5.
  • FIG. 21 is a p-h diagram for illustrating a change in refrigeration cycle according to Embodiment 5.
  • FIG. 22 shows a configuration of a refrigeration cycle apparatus according to Embodiment 6.
  • FIG. 23 is a flowchart for illustrating a process performed by a controller according to Embodiment 6.
  • FIG. 24 is a p-h diagram for illustrating a change in refrigeration cycle according to Embodiment 6.
  • FIG. 1 shows a configuration of a refrigeration cycle apparatus according to Embodiment 1.
  • Refrigeration cycle apparatus 100 includes a refrigerant circuit 80 including a compressor 10 , an indoor heat exchanger 20 , an expansion valve LEV 1 , an outdoor heat exchanger 40 , pipes 51 to 56 , and a four-way valve 50 .
  • Four-way valve 50 has ports P 1 to P 4 .
  • Pipe 51 is connected between a discharge outlet of compressor 10 and port P 1 of four-way valve 50 .
  • Pipe 52 is connected between port P 3 of four-way valve 50 and port P 1 of indoor heat exchanger 20 .
  • Pipe 53 is connected between indoor heat exchanger 20 and expansion valve LEV 1 .
  • Pipe 54 is connected between LEV 1 and outdoor heat exchanger 40 .
  • Pipe 55 is connected between port P 2 of outdoor heat exchanger 40 and port P 4 of four-way valve 50 .
  • Pipe 56 is connected between a suction inlet of compressor 10 and port P 2 of four-way valve 50 .
  • Compressor 10 is configured to change the operating frequency based on a control signal received from a controller (not shown). Specifically, compressor 10 has a drive motor incorporated therein, the rotational speed of the drive motor is a variable under inverter control, and changing of the operating frequency causes the rotational speed of the drive motor to change. The output of compressor 10 is adjusted by changing the operating frequency of compressor 10 . Any of various types of compressors, such as rotary type, reciprocating type, scroll type, screw type and like may be employed as compressor 10 .
  • Four-way valve 50 is controlled to be set in either a cooling operation state or a heating operation state by a control signal received from a controller (not shown).
  • a control signal received from a controller (not shown).
  • port P 1 communicates with port P 3 and port P 2 communicates with port P 4 , as shown by a solid line.
  • ports P 1 and P 4 communicate with each other and ports P 2 and P 3 communicate with each other, as shown by a broken line.
  • compressor 10 In the heating operation state, compressor 10 is operated to cause refrigerant to circulate in the refrigerant circuit in the order of compressor 10 , indoor heat exchanger 20 , LEV 1 , outdoor heat exchanger 40 , and compressor 10 .
  • compressor 10 In the cooling operation state, compressor 10 is operated to cause refrigerant to circulate in the refrigerant circuit in the order of compressor 10 , outdoor heat exchanger 40 , LEV 1 , indoor heat exchanger 20 , and compressor 10 .
  • FIG. 2 is a p-h line diagram of a refrigeration cycle apparatus in a reference example using an azeotropic refrigerant.
  • FIG. 3 shows a frost region of an outdoor heat exchanger in a reference example using an azeotropic refrigerant.
  • FIG. 4 is a p-h diagram of the refrigeration cycle apparatus of the present embodiment using a non-azeotropic refrigerant.
  • FIG. 5 shows a configuration of an outdoor heat exchanger and a frost region of the present embodiment using a non-azeotropic refrigerant.
  • FIG. 6 is a front view of the outdoor heat exchanger shown in FIG. 5 .
  • the temperature of a refrigerant outlet of outdoor heat exchanger 40 can be set to 0.5° C. during heating operation even when the temperature of a refrigerant inlet of outdoor heat exchanger 40 is ⁇ 5° C.
  • the temperature of a part of outdoor heat exchanger 40 can be set to 0° C. or more.
  • the refrigeration cycle apparatus is operated so as to have a temperature distribution as shown in FIG. 4 during low-temperature high-humidity heating operation performed at an outside air temperature of around 2° C.
  • the refrigerant flows from pipe 54 into outdoor heat exchanger 40 , and the refrigerant flows from outdoor heat exchanger 40 into pipe 55 .
  • a group of fins L 1 in the first row is disposed on the front side and a group of fins L 2 in the second row is disposed on the rear side.
  • a pipe serving as a refrigerant flow path and made up of six pipes is arranged for each of respective groups of fins L 1 and L 2 , and these pipes are arranged in parallel and connected together on each lateral side.
  • the six pipes for fin group L 1 are herein referred to as heat transfer tubes R 1 to R 6 in order from the top
  • the six pipes for fin group L 2 are herein referred to as heat transfer tubes R 7 to R 12 in order from the bottom.
  • refrigerant flows from the right side of heat transfer tube R 1 which is the top one in fin group L 1 in the first row, flows from right to left through heat transfer tube R 1 , then flows through a connection pipe C 12 , and the refrigerant flows from left to right through heat transfer tube R 2 , thus completing a single go-and-return passage.
  • the refrigerant flowing out from heat transfer tube R 2 flows through a connection pipe C 23 , and flows from right to left through heat transfer tube R 3 . Then, the refrigerant flows through a connection pipe C 34 , and flows from left to right through heat transfer tube R 4 , thus completing a further single go-and-return passage.
  • refrigerant flowing out from heat transfer tube R 4 flows through a connection pipe C 45 , and flows from right to left through heat transfer tube R 5 . Then, the refrigerant flows through a connection pipe C 56 , and flows from left to right through heat transfer tube R 6 , thus completing a further single go-and-return passage.
  • refrigerant flowing out from heat transfer tube R 4 flows through a connection pipe C 45 , and flows from right to left through heat transfer tube R 5 . Then, the refrigerant flows through a connection pipe C 56 , and flows from left to right through heat transfer tube R 6 , thus completing a further single go-and-return passage.
  • refrigerant flowing out from heat transfer tube R 4 flows through a connection pipe C 45 , and flows from right to left through heat transfer tube R 5 . Then, the refrigerant flows through a connection pipe C 56 , and flows from left to right through heat transfer tube R 6 , thus completing a further single go-and-return passage.
  • Heat transfer tubes R 7 to R 12 similarly flows through three go-and-return passages in the left-right direction in FIG. 6 .
  • Heat transfer tubes R 7 to R 12 differ from heat transfer tubes R 1 to R 6 in that the refrigerant flows in order from the lower stage toward the upper stage.
  • refrigerant flowing out from heat transfer tube R 6 flows through a connection pipe C 67 , and flows through heat transfer tube R 7 from right to left in FIG. 6 . Then, the refrigerant flows through a connection pipe, and flows from left to right through heat transfer tube R 8 , thus completing a further single go-and-return passage.
  • the refrigerant flowing out from heat transfer tube R 8 flows through a connection pipe C 89 , and flows through heat transfer tube R 9 from right to left in FIG. 6 . Then, the refrigerant flows through a connection pipe, and flows from left to right through heat transfer tube R 10 , thus completing a further single go-and-return passage.
  • the refrigerant flowing out from heat transfer tube R 10 flows through a connection pipe C 1011 , and flows through heat transfer tube R 11 from right to left in
  • FIG. 6 the refrigerant flows through a connection pipe, flows from left to right through heat transfer tube R 12 , thus completing a further single go-and-return passage, and flows to pipe 55 .
  • FIG. 7 illustrates a difference in defrosting period between a reference example and the refrigeration cycle apparatus of the present embodiment.
  • FIG. 7 shows capacity J 0 , compressor frequency F 0 , and amount of frost G 0 of the refrigeration cycle apparatus in the comparative example shown in FIGS. 2 and 3 , and capacity J 1 , compressor frequency F 1 , and amount of frost G 1 of the refrigeration cycle apparatus in the present embodiment shown in FIGS. 4 to 6 .
  • the amount of frost if formed on the entire surface, satisfies G 0 >G 1 for time t 0 to t 1 .
  • compressor frequency F 0 reaches the maximum frequency (upper limit frequency) at time t 1 . Therefore, for time t 1 to t 3 , with the increase of amount of frost G 0 , capacity J 0 decreases earlier and defrosting becomes necessary and started at time t 3 .
  • amount of frost G 1 is smaller than amount of frost G 0 , and compressor frequency F 1 reaches the upper limit at time t 2 later than time t 1 . Therefore, capacity J 1 has decreased to reach a value at which start of defrosting is required at time t 4 later than time t 3 .
  • the subsequent defrosting time is substantially constant in both the comparative example and the present embodiment, and therefore, the defrosting period of the present embodiment, in which the heating operation time is longer, is longer than that of the comparative example. Therefore, the refrigeration cycle apparatus of the present embodiment has the extended defrosting period, which provides improvement in the comfort for the load, as well as improvement in the average COP.
  • FIG. 8 shows a configuration of a refrigeration cycle apparatus according to Embodiment 2.
  • Refrigeration cycle apparatus 110 shown in FIG. 8 further includes a controller 90 and a temperature sensor 111 , in addition to the components of refrigeration cycle apparatus 100 in FIG. 1 .
  • the description of the other components is given above in connection with FIG. 1 , and therefore, the description thereof is not herein repeated.
  • Controller 90 includes a CPU (Central Processing Unit) 91 , a memory 92 (ROM (Read Only Memory) and RAM (Random Access Memory)), and an input/output buffer (not shown), for example.
  • CPU 91 deploys and executes, on the RAM for example, a program stored in the ROM.
  • the program stored in the ROM is a program in which a processing procedure for controller 90 is specified.
  • Controller 90 controls each device in refrigeration cycle apparatus 110 in accordance with these programs. This control is not limited to processing by software, but may also be performed by dedicated hardware (electronic circuit).
  • controller 90 is configured to control LEV 1 based on an output of temperature sensor 111 .
  • FIG. 9 illustrates arrangement of temperature sensor 111 .
  • FIG. 9 shows temperature sensor 111 disposed in outdoor heat exchanger 40 shown in FIG. 5 .
  • the description of outdoor heat exchanger 40 is given above in connection with FIGS. 4 to 6 , and therefore, the description thereof is not herein repeated.
  • Temperature sensor 111 is disposed at the boundary between a portion intended to serve as frost region A 1 of outdoor heat exchanger 40 and a portion intended to serve as non-frost region A 2 thereof.
  • the refrigeration cycle apparatus is controlled in such a manner that the temperature detected by temperature sensor 111 is 0° C., so that frost is formed in frost region A 1 and no frost is formed in non-frost region A 2 during low-temperature high-humidity heating operation, so that ventilation in non-frost region A 2 can be ensured and the defrosting period can be extended appropriately.
  • the boundary between frost region A 1 and non-frost region A 2 can be determined experimentally in advance so as to be appropriate for performing low-load heating under a low-temperature low-humidity condition.
  • FIG. 10 illustrates how the position where temperature sensor 111 is to be attached is determined. As shown by the solid line in FIG. 10 , the relation between the area of frost and the capacity at the maximum frequency under a low-temperature high-humidity operating condition is determined in advance. The position where temperature sensor 111 is to be attached is determined, such that the area of frost region A 1 is equal to an area of frost S (A 1 ) with which the capacity required during low-temperature high-humidity operation is exhibited.
  • FIG. 11 is a flowchart for illustrating a process performed by the controller according to Embodiment 2.
  • Controller 90 determines whether or not temperature Tsen detected by temperature sensor 111 attached to outdoor heat exchanger 40 is lower than frosting temperature Tfro (step S 1 ).
  • Frosting temperature Tfro may for example be set to 0° C.
  • controller 90 While Tsen ⁇ Tfro is not satisfied (NO in S 1 ), controller 90 repeats the process in step S 1 .
  • controller 90 increases the degree of opening of LEV 1 such that Tsen ⁇ Tfro is satisfied (S 2 ).
  • FIG. 12 is a p-h diagram for illustrating a change in a refrigeration cycle according to Embodiment 2.
  • the degree of opening of LEV 1 is increased in step S 2 , the degree of subcooling at the outlet of the load-side heat exchanger decreases, so that the refrigeration cycle changes from the state indicated by solid line CY 1 to the state indicated by broken line CY 2 on the p-h diagram.
  • controller 90 adjusts compressor frequency F such that heating capacity Q reaches target heating capacity Qtar (S 5 ), and then performs the process from step S 1 again.
  • controller 90 determines whether or not defrosting is necessary. Whether or not defrosting is necessary can be determined based on the time for which heating operation is continued, and/or an allowable ratio of decrease in capacity during heating (decrease of refrigerant pressure in low-pressure portion), for example.
  • controller 90 When defrosting is unnecessary (NO in S 4 ), controller 90 performs the process again from step S 1 . When defrosting is necessary (YES in S 4 ), controller 90 starts defrosting operation.
  • the refrigeration cycle apparatus increases, during low-temperature high-humidity heating operation, the enthalpy at the refrigerant inlet of outdoor heat exchanger 40 and increases the temperature using the temperature gradient of non-azeotropic refrigerant. In this way, only a partial region of outdoor heat exchanger 40 is frosted, and the defrosting period is extended.
  • temperature sensor 111 is disposed at the boundary between the frost region and the non-frost region of outdoor heat exchanger 40 , and therefore, the frost region can be controlled accurately.
  • FIG. 13 shows a configuration of a refrigeration cycle apparatus according to Embodiment 3.
  • refrigerant circuit 80 further includes an internal heat exchanger 121 and an expansion valve LEV 2 , in addition to the components of refrigeration cycle apparatus 110 in FIG. 8 .
  • a part of refrigerant flowing through pipe 53 is branched into a bypass flow path 61 , reduced in pressure by expansion valve LEV 2 , and returned to compressor 10 . While the refrigerant is returned to an intermediate pressure port of compressor 10 in FIG. 13 , the bypass flow path may be formed to cause the refrigerant to be returned to a suction inlet of compressor 10 .
  • Internal heat exchanger 121 is configured to exchange heat between the refrigerant flowing out from indoor heat exchanger 20 and the refrigerant after being reduced in pressure by expansion valve LEV 2 in bypass flow path 61 .
  • the description of the other components is given above in connection with FIG. 8 , and therefore, the description thereof is not herein repeated.
  • FIG. 14 is a flowchart for illustrating a process performed by a controller according to Embodiment 3.
  • the process in the flowchart of FIG. 14 includes step S 12 instead of step S 2 of the process in the flowchart shown in FIG. 11 .
  • step S 12 is described here.
  • FIG. 15 is a p-h diagram for illustrating a change in refrigeration cycle according to Embodiment 3.
  • the degree of opening of LEV 2 is decreased in step S 12 , the degree of subcooling at the outlet of internal heat exchanger 121 decreases, so that the refrigeration cycle changes from the state indicated by solid line CY 11 to the state indicated by broken line CY 12 on the p-h diagram.
  • Embodiment 3 changes the degree of opening of LEV 2 so as to keep, at around 0° ° C., the portion where temperature sensor 111 is disposed, and keep the boundary as intended between frost region A 1 and non-frost region A 2 .
  • FIG. 16 shows a configuration of a refrigeration cycle apparatus according to Embodiment 4.
  • refrigerant circuit 80 further includes a bypass flow path 62 and an expansion valve LEV 3 , in addition to the components of refrigeration cycle apparatus 110 in FIG. 8 .
  • a part of discharged gas refrigerant flowing through pipe 51 is branched into bypass flow path 62 at a branch point BP 2 , adjusted in flow rate by expansion valve LEV 3 , and merged into refrigerant in pipe 54 at a merging point MP 2 .
  • the description of the other components is given above in connection with FIG. 8 , and therefore, the description thereof is not be herein repeated.
  • FIG. 17 is a flowchart for illustrating a process performed by a controller according to Embodiment 4.
  • the process in the flowchart of FIG. 17 includes step S 22 instead of step S 2 of the process in the flowchart shown in FIG. 11 .
  • step S 22 is described here.
  • FIG. 18 is a p-h diagram for illustrating a change in the refrigeration cycle according to Embodiment 4.
  • step S 22 the degree of opening of LEV 3 is increased, which increases refrigerant in bypass flow path 62 that merges into two-phase refrigerant flowing into outdoor heat exchanger 40 , so that the temperature at the inlet of outdoor heat exchanger 40 increases.
  • a part of the discharged gas merges into the refrigerant, and accordingly, the specific enthalpy of the refrigerant at the inlet of outdoor heat exchanger 40 also increases.
  • Embodiment 4 changes the degree of opening of LEV 3 so as to keep, at around 0° C., the portion where temperature sensor 111 is disposed, and keep the boundary as intended between frost region A 1 and non-frost region A 2 .
  • FIG. 19 shows a configuration of a refrigeration cycle apparatus according to Embodiment 5.
  • refrigerant circuit 80 further includes a heater 141 , in addition to the components of refrigeration cycle apparatus 110 in FIG. 8 .
  • Heater 141 is capable of heating refrigerant flowing in pipe 54 .
  • the description of the other components is given above in connection with FIG. 8 , and therefore, the description thereof is not be herein repeated.
  • FIG. 20 is a flowchart for illustrating a process performed by a controller according to Embodiment 5.
  • the process in the flowchart of FIG. 20 includes step S 32 instead of step S 2 of the process in the flowchart shown in FIG. 11 .
  • step S 32 is described here.
  • FIG. 21 is a p-h diagram for illustrating a change in the refrigeration cycle according to Embodiment 5.
  • step S 32 the amount of heat generated by heater 141 is increased, which raises the temperature of refrigerant flowing into outdoor heat exchanger 40 , so that the temperature at the inlet of outdoor heat exchanger 40 increases.
  • the refrigeration cycle changes from CY 31 to CY 32 on the p-h diagram shown in FIG. 21 , and the specific enthalpy of refrigerant at the inlet of outdoor heat exchanger 40 also increases as shown by an arrow in the drawing.
  • Embodiment 5 changes the amount of heat generated by heater 141 , so as to keep, at around 0° C., the portion where temperature sensor 111 is disposed, and keep the boundary as intended between frost region A 1 and non-frost region A 2 .
  • FIG. 22 shows a configuration of a refrigeration cycle apparatus according to Embodiment 6.
  • refrigerant circuit 80 further includes, in addition to the components of refrigeration cycle apparatus 110 in FIG. 8 , a three-way valve 152 and an internal heat exchanger 151 .
  • Three-way valve 152 is a flow-path switching device that is provided on pipe 51 and switches, in accordance with a control signal from controller 90 , the flow path to convey refrigerant discharged from compressor 10 directly to port P 1 of the four-way valve, or to convey the refrigerant through internal heat exchanger 151 to port P 1 .
  • Internal heat exchanger 151 is configured to exchange heat between refrigerant flowing through pipe 54 and refrigerant conveyed from compressor 10 through three-way valve 152 .
  • the description of the other components is given above in connection with FIG. 8 , and therefore, the description thereof is not be herein repeated.
  • FIG. 23 is a flowchart for illustrating a process performed by a controller according to Embodiment 6.
  • the process in the flowchart of FIG. 23 includes step S 42 instead of step S 2 of the process in the flowchart shown in FIG. 11 .
  • step S 42 is described here.
  • FIG. 24 is a p-h diagram for illustrating a change in the refrigeration cycle according to Embodiment 6.
  • step S 42 three-way valve 152 is switched so as to introduce the discharged refrigerant into internal heat exchanger 151 , and then, the refrigeration cycle changes from CY 41 to CY 42 on the p-h diagram shown in FIG. 24 .
  • CY 42 refrigerant discharged from compressor 10 releases heat as shown by arrow CY 42 A until the refrigerant flows into indoor heat exchanger 20 .
  • the refrigerant having passed through LEV 1 receives heat as indicated by arrow CY 42 B, and therefore, the temperature of the refrigerant flowing into outdoor heat exchanger 40 increases.
  • Embodiment 6 changes the destination of the discharged refrigerant so as to cause the refrigerant to flow through internal heat exchanger 151 so as to keep, at around 0° C., the portion where temperature sensor 111 is disposed, and keep the boundary as intended between frost region A 1 and non-frost region A 2 .
  • Refrigeration cycle apparatus 100 shown in FIG. 1 includes: refrigerant circuit 80 in which compressor 10 , indoor heat exchanger 20 (condenser), first expansion valve LEV 1 , and outdoor heat exchanger 40 (evaporator) are connected by refrigerant pipes 51 to 56 ; and a non-azeotropic refrigerant that flows through refrigerant pipes 51 to 56 .
  • refrigerant circuit 80 in which compressor 10 , indoor heat exchanger 20 (condenser), first expansion valve LEV 1 , and outdoor heat exchanger 40 (evaporator) are connected by refrigerant pipes 51 to 56 ; and a non-azeotropic refrigerant that flows through refrigerant pipes 51 to 56 .
  • a temperature difference occurs between the inlet and the outlet of outdoor heat exchanger 40 (evaporator).
  • outdoor heat exchanger 40 (evaporator) includes: groups of fins L 1 , L 2 that are stacked at intervals; and heat transfer tubes R 1 to R 12 that extend through groups of fins L 1 , L 2 in a stacking direction of groups of fins L 1 , L 2 and allow the non-azeotropic refrigerant to flow inside the heat transfer tubes.
  • Groups of fins L 1 , L 2 each include: a first fin part (frost region A 1 ) to which frost can adhere in a humid environment; and a second fin part (non-frost region A 2 ) to which no frost adhere to ensure ventilation.
  • refrigeration cycle apparatus 100 further includes controller 90 configured to control refrigerant circuit 80 .
  • controller 90 is configured to control refrigerant circuit 80 such that the non-azeotropic refrigerant flowing in the heat transfer tubes (heat transfer tubes R 1 to R 3 ) extending through the first fin part has a temperature of 0° C. or lower and the non-azeotropic refrigerant flowing in the heat transfer tubes (heat transfer tubes R 4 to R 12 ) extending through the second fin part has a temperature of 0° C. or higher.
  • the first fin part is disposed in predetermined frost region A 1 in outdoor heat exchanger 40 (evaporator).
  • the second fin part is disposed in predetermined non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Refrigeration cycle apparatus 110 further includes temperature sensor 111 disposed at a boundary between frost region A 1 and non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Controller 90 is configured to control the degree of opening of first expansion valve LEV 1 based on an output of temperature sensor 111 such that the temperature of the boundary between frost region A 1 and non-frost region A 2 is 0° C.
  • refrigerant circuit 80 further includes: bypass flow path 61 that branches at branching point BP 1 from refrigerant pipe 53 connecting indoor heat exchanger 20 (condenser) to first expansion valve LEV 1 , to return refrigerant to compressor 10 ; second expansion valve LEV 2 disposed in bypass flow path 61 ; and internal heat exchanger 121 configured to exchange heat between refrigerant flowing from indoor heat exchanger 20 (condenser) toward branching point BP 1 and refrigerant having passed through second expansion valve LEV 2 .
  • the first fin part is disposed in predetermined frost region A 1 in outdoor heat exchanger 40 (evaporator).
  • the second fin part is disposed in predetermined non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Refrigeration cycle apparatus 120 shown in FIG. 13 further includes temperature sensor 111 disposed at a boundary between frost region A 1 and non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Controller 90 is configured to control the degree of opening of second expansion valve LEV 2 based on an output of temperature sensor 111 , as shown in FIG. 14 , such that the temperature of the boundary between frost region A 1 and non-frost region A 2 is 0° C.
  • refrigerant circuit 80 further includes: bypass flow path 62 that branches from the refrigerant pipe between a discharge outlet of compressor 10 and indoor heat exchanger 20 (condenser) and merges into the refrigerant pipe connecting first expansion valve LEV 1 to outdoor heat exchanger 40 (evaporator); and expansion valve LEV 3 serving as a flow rate adjustment valve disposed in bypass flow path 62 .
  • the first fin part is disposed in predetermined frost region A 1 in outdoor heat exchanger 40 (evaporator).
  • the second fin part is disposed in predetermined non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Refrigeration cycle apparatus 130 shown in FIG. 16 further includes temperature sensor 111 disposed at a boundary between frost region A 1 and non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Controller 90 is configured to control the degree of opening of LEV 3 based on an output of temperature sensor 111 , as shown in FIG. 17 , such that the temperature of the boundary between frost region A 1 and non-frost region A 2 is 0° C.
  • refrigerant circuit 80 further includes heater 141 configured to heat refrigerant flowing in refrigerant pipe 54 connecting first expansion valve LEV 1 to outdoor heat exchanger 40 (evaporator).
  • the first fin part is disposed in predetermined frost region A 1 in outdoor heat exchanger 40 (evaporator).
  • the second fin part is disposed in predetermined non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Refrigeration cycle apparatus 140 shown in FIG. 19 further includes temperature sensor 111 disposed at a boundary between frost region A 1 and non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Controller 90 is configured to control the amount of heat generated by heater 141 based on an output of temperature sensor 111 , as shown in FIG. 20 , such that the temperature of the boundary between frost region A 1 and non-frost region A 2 is 0° C.
  • refrigerant pipe 51 which is a part of the refrigerant pipe connecting the discharge outlet of compressor 10 to indoor heat exchanger 20 (condenser), includes a first flow path 51 A and a second flow path 51 B disposed in parallel with first flow path 51 A.
  • Refrigerant circuit 80 further includes: internal heat exchanger 151 configured to exchange heat between refrigerant flowing from first expansion valve LEV 1 toward outdoor heat exchanger 40 (evaporator), and refrigerant flowing in second flow path 51 B; and three-way valve 152 configured to switch to allow refrigerant discharged from compressor 10 to flow in first flow path 51 A or flow in second flow path 51 B.
  • the first fin part is disposed in predetermined frost region A 1 in outdoor heat exchanger 40 (evaporator).
  • the second fin part is disposed in predetermined non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Refrigeration cycle apparatus 150 shown in FIG. 22 further includes temperature sensor 111 disposed at a boundary between frost region A 1 and non-frost region A 2 in outdoor heat exchanger 40 (evaporator).
  • Controller 90 is configured to control three-way valve 152 based on an output of temperature sensor 111 as shown in FIG. 23 , such that the temperature of the boundary between frost region A 1 and non-frost region A 2 is 0° C.
  • refrigeration cycle apparatus 100 further includes a four-way valve 50 capable of interchanging the discharge outlet and the suction inlet of compressor 10 to connect the discharge outlet and the suction inlet to refrigerant circuit 80 .
  • Four-way valve 50 is capable of switching to allow refrigerant to flow through refrigerant circuit 80 in a first direction in which refrigerant flows in the order of compressor 10 , indoor heat exchanger 20 (condenser), first expansion valve LEV 1 , and outdoor heat exchanger 40 (evaporator), or a second direction in which refrigerant flows in the order of compressor 10 , outdoor heat exchanger 40 (evaporator), first expansion valve LEV 1 , and indoor heat exchanger 20 (condenser).
  • the above configuration provide unbalanced frosting to enable extension of the defrosting period, which also provides improvement in comfort for the load. Further, the integrated heating capacity increases, which improves the average COP.

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