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CN113646597A - Refrigeration cycle device - Google Patents

Refrigeration cycle device Download PDF

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Publication number
CN113646597A
CN113646597A CN201980094530.8A CN201980094530A CN113646597A CN 113646597 A CN113646597 A CN 113646597A CN 201980094530 A CN201980094530 A CN 201980094530A CN 113646597 A CN113646597 A CN 113646597A
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CN
China
Prior art keywords
refrigerant
heat exchanger
heat
refrigeration cycle
expansion device
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.)
Granted
Application number
CN201980094530.8A
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Chinese (zh)
Other versions
CN113646597B (en
Inventor
中村伸
前田刚志
八柳晓
森田敦
永田龙一
东井上真哉
石桥晃
松井繁佳
高桥笃史
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.)
Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Filing date
Publication date
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Publication of CN113646597A publication Critical patent/CN113646597A/en
Application granted granted Critical
Publication of CN113646597B publication Critical patent/CN113646597B/en
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Classifications

    • 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
    • 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
    • F25B6/00—Compression machines, plants or systems, with several condenser circuits
    • F25B6/04—Compression machines, plants or systems, with several condenser circuits arranged in series
    • 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
    • F25B39/00—Evaporators; Condensers
    • F25B39/04—Condensers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/385—Dispositions with two or more expansion means arranged in parallel on a refrigerant line leading to the same evaporator
    • 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
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/02—Defrosting cycles
    • F25B47/022—Defrosting cycles hot gas defrosting
    • F25B47/025—Defrosting cycles hot gas defrosting by reversing the cycle
    • 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
    • F25B2313/025—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple outdoor units
    • F25B2313/0252—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple outdoor units with bypasses
    • 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
    • F25B2313/025—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple outdoor units
    • F25B2313/0254—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple outdoor units in series 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
    • 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
    • F25B2400/04—Refrigeration circuit bypassing means
    • F25B2400/0417—Refrigeration circuit bypassing means for the subcooler
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00—Problems to be solved
    • F25B2500/31—Low ambient temperatures

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
  • Details Of Heat-Exchange And Heat-Transfer (AREA)

Abstract

A refrigeration cycle device in which freezing of the lower portion of a heat exchanger, in which drain water is likely to accumulate, is suppressed, and the amount of refrigerant in a refrigerant circuit can be reduced. A refrigeration cycle device is provided with a refrigerant circuit (1), wherein a compressor, a1 st expansion device and a1 st heat exchanger functioning as an evaporator during heating operation are connected to the refrigerant circuit (1) by refrigerant pipes. The 1 st heat exchanger includes a1 st heat exchanging unit and a2 nd heat exchanging unit, and the 2 nd heat exchanging unit is connected in series with the 1 st heat exchanging unit in the refrigerant circuit. The 1 st expansion device is connected in parallel to the 2 nd heat exchanging unit in the refrigerant circuit, and the 2 nd heat exchanging unit is located below the 1 st heat exchanging unit.

Description

Refrigeration cycle device
Technical Field
The present invention relates to a refrigeration cycle apparatus, and more particularly to connection between a heat exchanger functioning as an evaporator and an expansion device.
Background
An air conditioner, which is one type of refrigeration cycle apparatus, cools a high-temperature and high-pressure gas refrigerant discharged by a compressor by exchanging heat with indoor air in an indoor heat exchanger functioning as a condenser during a heating operation, and changes its phase into a low-temperature and high-pressure liquid refrigerant. Then, the low-temperature high-pressure liquid refrigerant is phase-changed into a low-temperature low-pressure two-phase refrigerant in the expansion device. The two-phase refrigerant is heated by heat exchange with air in an outdoor heat exchanger functioning as an evaporator, is phase-changed into a low-temperature and low-pressure gas refrigerant, and is sucked into the compressor. Subsequently, the low-temperature low-pressure gas refrigerant is compressed in the compressor and discharged again as a high-temperature high-pressure gas refrigerant.
Here, when the temperature of the outside air in which the outdoor heat exchanger is installed is close to minus when the air conditioner is operated to perform heating operation, the surface temperature of the outdoor heat exchanger is decreased to be lower than minus in order to maintain the heat exchange performance. In this case, frost may be deposited on the outdoor heat exchanger. When frost attached to the outdoor heat exchanger increases, defrosting is required. For example, in defrosting of an outdoor heat exchanger, a defrosting operation is performed by a method of allowing hot gas to flow into the outdoor heat exchanger. In general, drain water generated by defrosting drips onto a drain pan and is drained. However, water may accumulate at the lower end of the heat exchanger due to the influence of drainage pressure or surface tension of the drain pan. In a state where water is retained in the heat exchanger, during heating operation, the retained drain water freezes, and may damage the outdoor heat exchanger. Then, a method of preventing freezing of the outdoor heat exchanger by providing a heater on the drain pan is known.
For example, in the air conditioner disclosed in patent document 1, the refrigerant having a higher pressure (temperature) than the upper portion of the heat exchanger flows through the lower portion of the heat exchanger, thereby suppressing the frost formation and freezing of the drain pan and the lower portion of the heat exchanger.
Documents of the prior art
Patent document
Patent document 1: japanese examined patent publication (Kokoku) No. 5-44653
Disclosure of Invention
Problems to be solved by the invention
However, in the air conditioner disclosed in patent document 1, the cross-sectional area of the heat transfer pipe may be reduced in order to further improve the heat transfer performance of the heat exchanger or reduce the amount of refrigerant flowing through the heat transfer pipe constituting the heat exchanger, for example. For example, in a heat transfer pipe formed of a circular pipe, it is conceivable to reduce the outer diameter or to make the flow path inside the pipe small and porous by making the pipe flat in cross section. In the air conditioner of the patent document, when the cross-sectional area of the flow path of the heat transfer pipe constituting the heat exchanger is reduced, there is a problem that the flow path resistance at the lower portion of the heat exchanger where the number of branches of the refrigerant flow path is small is increased.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigeration cycle apparatus capable of suppressing freezing of a lower portion of a heat exchanger, in which retention of drain water is likely to occur, even when a heat transfer pipe is made smaller.
Means for solving the problems
A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, a1 st expansion device, and a1 st heat exchanger functioning as an evaporator during heating operation are connected by refrigerant pipes, the 1 st heat exchanger includes the 1 st heat exchanging portion and a2 nd heat exchanging portion, the 2 nd heat exchanging portion is connected in series with the 1 st heat exchanging portion in the refrigerant circuit, the 1 st expansion device is connected in parallel with the 2 nd heat exchanging portion in the refrigerant circuit, and the 2 nd heat exchanging portion is located below the 1 st heat exchanging portion.
Effects of the invention
With the above configuration, the present invention can reduce the cross-sectional area of the refrigerant flow path of the heat transfer pipe of the heat exchanger, thereby reducing the amount of refrigerant flowing through the refrigerant circuit and suppressing freezing of the drain pan and the lower portion of the heat exchanger.
Drawings
Fig. 1 is a circuit diagram of a refrigerant circuit 1 of a refrigeration cycle apparatus 100 according to embodiment 1.
Fig. 2 is a perspective view of the 1 st heat exchanger 10 of the refrigeration cycle apparatus 100 according to embodiment 1.
Fig. 3 is an explanatory diagram of a sectional configuration of the 1 st heat exchanger 10 of fig. 2.
Fig. 4 is an explanatory view of a structure of the 1 st heat exchanger 10 according to embodiment 1 as viewed from the front.
Fig. 5 is a cross-sectional view showing a flat tube as an example of the heat transfer tube 20 used in the 1 st heat exchanger 10 according to embodiment 1.
Fig. 6 is a circuit diagram of the refrigerant circuit 101 of the refrigeration cycle apparatus 1100 as a comparative example of the refrigeration cycle apparatus 100 according to embodiment 1.
Fig. 7 is a perspective view of the 1 st heat exchanger 110 of the refrigeration cycle apparatus 1100 of the comparative example.
Fig. 8 is a diagram showing characteristics of the refrigeration cycle apparatus 1100 of the comparative example during the heating operation.
Fig. 9 is a diagram showing characteristics of the refrigeration cycle apparatus 100 according to embodiment 1 during the heating operation.
Fig. 10 is an enlarged view of a portion a of fig. 9.
Fig. 11 is a circuit diagram of a refrigerant circuit 201 of the refrigeration cycle apparatus 200 according to embodiment 2.
Fig. 12 is a perspective view of the 1 st heat exchanger 210 of the refrigeration cycle apparatus 200 according to embodiment 2.
Fig. 13 is a diagram showing characteristics of the refrigeration cycle apparatus 200 according to embodiment 2 during the heating operation.
Fig. 14 is a diagram showing characteristics of the refrigeration cycle apparatus 200 according to embodiment 2 during the heating operation.
Fig. 15 is a circuit diagram of a refrigerant circuit 301 of a refrigeration cycle apparatus 300 according to embodiment 3.
Fig. 16 is a perspective view of the 1 st heat exchanger 310 of the refrigeration cycle apparatus 300 according to embodiment 3.
Fig. 17 is a diagram showing characteristics of the refrigeration cycle apparatus 300 according to embodiment 3 during the heating operation.
Fig. 18 is a diagram showing characteristics of the refrigeration cycle apparatus 300 according to embodiment 3 during the heating operation.
Fig. 19 is a circuit diagram of a refrigerant circuit 401 of a refrigeration cycle apparatus 400 according to embodiment 4.
Fig. 20 is a perspective view of the 1 st heat exchanger 410 of the refrigeration cycle apparatus 400 according to embodiment 4.
Fig. 21 is a diagram showing characteristics of the refrigeration cycle apparatus 400 according to embodiment 4 during the heating operation.
Detailed Description
Hereinafter, embodiments of the refrigeration cycle apparatus will be described. The form of the drawings is an example, and the present invention is not limited thereto. In addition, the members denoted by the same reference numerals in the drawings are the same or correspond to the same members, and this is common throughout the specification. In the following drawings, the relationship between the sizes of the respective constituent members may be different from the actual one.
Embodiment 1.
Fig. 1 is a circuit diagram of a refrigerant circuit 1 of a refrigeration cycle apparatus 100 according to embodiment 1. The refrigeration cycle apparatus 100 shown in fig. 1 is, for example, an air conditioner. As shown in fig. 1, the refrigeration cycle apparatus 100 includes a refrigerant circuit 1 formed by connecting a compressor 2, a four-way valve 7, a1 st heat exchanger 10, a1 st expansion device 5, and a2 nd heat exchanger 3 by refrigerant pipes. For example, when the refrigeration cycle apparatus 100 is an air conditioner, the refrigerant flows through the refrigerant piping, and the flow of the refrigerant is switched by the four-way valve 7, whereby the heating operation, the cooling operation, or the defrosting operation can be switched. In embodiment 1, an air conditioner is exemplified as the refrigeration cycle apparatus 100, but the refrigeration cycle apparatus 100 can be used for refrigeration applications or air conditioning applications such as a refrigerator, a freezer, a vending machine, an air conditioner, a freezer, and a water heater, for example.
The compressor 2, the 2 nd heat exchanger 3, the 1 st expansion device 5, the 1 st heat exchanger 10, and the four-way valve 7 constitute a refrigerant circuit 1 in which a refrigerant can circulate. In the refrigeration cycle apparatus 100, a refrigeration cycle is performed in which a refrigerant is circulated while changing phase in the refrigerant circuit 1. The compressor 2 compresses a refrigerant. The compressor 2 is, for example, a rotary compressor, a scroll compressor, a screw compressor, a reciprocating compressor, or the like.
The 1 st heat exchanger 10 functions as an evaporator when the refrigeration cycle apparatus 100 performs a heating operation, and the 1 st heat exchanger 10 functions as a condenser when the refrigeration cycle apparatus 100 performs a cooling operation. The 1 st heat exchanger 10 is composed of a1 st heat exchanging part 11 and a2 nd heat exchanging part 12. The 2 nd heat exchanging part 12 is positioned below the 1 st heat exchanging part 11.
The 2 nd heat exchanger 3 functions as a condenser when the refrigeration cycle apparatus 100 performs a heating operation, and the 2 nd heat exchanger 3 functions as an evaporator when the refrigeration cycle apparatus 100 performs a cooling operation. However, in the 2 nd heat exchanger 3, during the heating operation, the refrigerant temperature may be lowered by the pressure loss in the pipe, and a part of the refrigerant may function as an evaporator. The 1 st heat exchanger 10 and the 2 nd heat exchanger 3 are, for example, fin-tube type heat exchangers, microchannel heat exchangers, finless heat exchangers, shell-and-tube type heat exchangers, heat pipe type heat exchangers, double-tube type heat exchangers, fin-fin type heat exchangers, or the like.
The 1 st expansion device 5 expands and decompresses the refrigerant. The 1 st expansion device 5 is, for example, an electric expansion valve or the like capable of adjusting the flow rate of the refrigerant. The expansion device 1 may be not only an electric expansion valve but also a mechanical expansion valve using a diaphragm in a pressure receiving portion, a capillary tube, or the like.
The four-way valve 7 changes the direction of circulation of the refrigerant in the refrigerant circuit 1 by switching the flow path of the refrigerant in the refrigeration cycle apparatus 100. During the heating operation, the four-way valve 7 is switched to connect the discharge port of the compressor 2 and the 2 nd heat exchanger 3 and to connect the suction port of the compressor 2 and the 1 st heat exchanger 10. In the cooling operation and the dehumidifying operation, the four-way valve 7 is switched to connect the discharge port of the compressor 2 to the 1 st heat exchanger 10 and to connect the suction port of the compressor 2 to the 2 nd heat exchanger 3.
A blower 6 is disposed in the vicinity of the 1 st heat exchanger 10. Further, the 2 nd heat exchanger 3 is provided with a blower 4 in the vicinity thereof. Here, the 1 st heat exchanger 10 is an outdoor heat exchanger mounted on an outdoor unit, and the blower 6 sends outside air into the 1 st heat exchanger 10 to perform heat exchange between the outside air and the refrigerant. The 2 nd heat exchanger 3 is an indoor heat exchanger mounted on an indoor unit, and the blower 4 introduces indoor air into a casing of the indoor unit, sends the indoor air into the indoor heat exchanger, and exchanges heat between the indoor air and the refrigerant to adjust the temperature of the indoor air.
The configuration of the refrigerant circuit 1 of the refrigeration cycle apparatus 100 according to embodiment 1 will be described based on the flows of the refrigerant in the cooling and heating operation states. In the cooling operation, the refrigerant discharged from the compressor 2 flows into the 1 st heat exchanging portion 11 of the 1 st heat exchanger 10 through the four-way valve 7. The refrigerant flowing out of the 1 st heat exchanger 11 is branched into two refrigerant paths, one refrigerant path passes through the 1 st expansion device 5, and the other refrigerant path passes through the 2 nd heat exchanger 12. Then, the refrigerant having passed through the 1 st expansion device 5 and the refrigerant having passed through the 2 nd heat exchanging portion 12 merge, pass through the 2 nd heat exchanger 3 and the four-way valve 7 in this order, and are sucked into the compressor 2.
On the other hand, in the heating operation, the refrigerant discharged from the compressor 2 flows into the 2 nd heat exchanger 3 through the four-way valve 7. The refrigerant flowing out of the 2 nd heat exchanger 3 is branched into two refrigerant paths, one of which passes through the 1 st expansion device 5, and the other of which passes through the 2 nd heat exchanging portion 12 of the 1 st heat exchanger 10. The refrigerant having passed through the 1 st expansion device 5 and the refrigerant having passed through the 2 nd heat exchanging portion 12 merge together, and are sequentially passed through the 1 st heat exchanging portion 11 and the four-way valve 7 to be sucked into the compressor 2.
The refrigerant circuit 1 of the refrigeration cycle apparatus 100 includes a branch portion 90 that branches off refrigerant piping between the 2 nd heat exchanger 3 and the 1 st heat exchanger 10 and between the 1 st expansion device 5. That is, no other expansion device is provided between the 2 nd heat exchanger 3 and the branch portion 90.
1 st Heat exchanger 10 construction
Fig. 2 is a perspective view of the 1 st heat exchanger 10 of the refrigeration cycle apparatus 100 according to embodiment 1. Fig. 2 is a partially schematic view showing refrigerant pipes connected to the 1 st heat exchanger 10. As shown in fig. 2, the 1 st heat exchanger 10 includes a1 st heat exchanging portion 11 and a2 nd heat exchanging portion 12. The 2 nd heat exchanging part 12 is positioned below the 1 st heat exchanging part 11.
Each of the 1 st heat exchanging portion 11 and the 2 nd heat exchanging portion 12 includes two heat exchanging portions arranged in series in the flow direction of the air flowing into the 1 st heat exchanger 10. The 1 st heat exchanging unit 11 includes a1 st upwind-side heat exchanging unit 11a as a heat exchanging unit located on the upwind side, and a1 st downwind-side heat exchanging unit 11b as a heat exchanging unit located on the downwind side. The 1 st upstream heat exchanger 11a and the 1 st downstream heat exchanger 11b are connected at their ends by a header 14. When the 1 st heat exchanger 10 functions as an evaporator, the refrigerant flowing out of the 1 st leeward heat exchanging portion 11b flows into the 1 st windward heat exchanging portion 11 a.
The 2 nd heat exchange unit 12 includes a2 nd upstream side heat exchange unit 12a as a heat exchange unit located on the upstream side, and a2 nd downstream side heat exchange unit 12b as a heat exchange unit located on the downstream side. The 2 nd upstream heat exchanger 12a and the 2 nd downstream heat exchanger 12b are connected at their ends by a header 14. When the 1 st heat exchanger 10 functions as an evaporator, the refrigerant flowing out of the 2 nd upwind heat exchanging portion 12a flows into the 2 nd downwind heat exchanging portion 12 b.
The 1 st heat exchanger portion 11 and the 2 nd heat exchanger portion 12 constituting the 1 st heat exchanger 10 each include a heat transfer pipe 20. The heat transfer pipes 20 are juxtaposed in the z direction shown in fig. 2. In embodiment 1, the z-axis is along the direction of gravity. However, the 1 st heat exchanger 10 is not limited to be provided so that the z direction is along the gravitational direction, and the 1 st heat exchanger 10 may be provided so that the z direction is inclined, for example. That is, the plurality of heat transfer pipes 20 may be arranged in parallel in the vertical direction.
The header 14 includes an upper header 14a connecting the 1 st upstream heat exchanger 11a and the 1 st downstream heat exchanger 11b, and a lower header 14b connecting the 2 nd upstream heat exchanger 12a and the 2 nd downstream heat exchanger 12 b. The upper header 14a and the lower header 14b of the header 14 are integrally formed, but the interior of the header 14 is partitioned into a plurality of spaces so as not to mix at least the refrigerant of the 1 st heat exchanging part 11 and the refrigerant of the 2 nd heat exchanging part 12.
Further, the 1 st upstream heat exchanger 11a and the 1 st downstream heat exchanger 11b may not be connected by the header 14. For example, the end portions of the heat transfer tubes 20 in the 1 st upstream-side heat exchanger 11a and the end portions of the heat transfer tubes 20 in the 1 st downstream-side heat exchanger 11b may be connected by U-shaped tubes. Similarly, instead of the structure in which the 2 nd upwind heat exchanger 12a and the 2 nd downwind heat exchanger 12b are connected by the header 14, the end portions of the heat transfer tubes 20 may be connected by U-shaped tubes.
In fig. 2, the 1 st heat exchanging portion 11 includes a plurality of heat transfer pipes 20. The 1 st upstream heat exchanger 11a and the 1 st downstream heat exchanger 11b each include a plurality of heat transfer tubes 20 of the same number and are connected by a header 14. The plurality of heat transfer pipes 20 are arranged in parallel in the z direction. Further, the plurality of heat transfer tubes 20 of the 1 st upstream heat exchanger 11a are connected to the upstream manifold 13a at the end in the y direction. The plurality of heat transfer tubes 20 of the 1 st leeward heat exchanger portion 11b are also connected to the leeward collecting tube 13b at the end in the y direction. The collecting pipes 13a and 13b are connected to refrigerant pipes constituting the refrigerant circuit 1, and serve as an inflow portion into which the refrigerant flows into the 1 st heat exchanging unit 11 or an outflow portion from the 1 st heat exchanging unit 11. The manifolds 13a and 13b may be divided into a plurality of parts. For example, the upper 3 heat transfer tubes 20, the middle 3 heat transfer tubes 20, and the lower 3 heat transfer tubes 20 of the plurality of heat transfer tubes 20 of the 1 st leeward heat exchanger portion 11b may be connected to different manifolds.
In fig. 2, the 2 nd upwind side heat exchanger 12a and the 2 nd downwind side heat exchanger 12b constituting the 2 nd heat exchanger 12 each have 1 heat transfer pipe 20. However, the 2 nd upwind heat exchanger 12a and the 2 nd downwind heat exchanger 12b may have a plurality of heat transfer pipes 20.
In embodiment 1, the 1 st heat exchanger unit 11 has 9 heat transfer tubes 20 arranged in the z direction, and the 2 nd heat exchanger unit 12 has 1 heat transfer tube 20 in the z direction. That is, the number of the heat transfer tubes 20 arranged in parallel in the 1 st heat exchanger unit 11 is larger than the number of the heat transfer tubes 20 arranged in parallel in the 2 nd heat exchanger unit 12. The number of heat transfer tubes 20 is not limited to this. The number of refrigerant flow paths in each of the 1 st heat exchanging portion 11 and the 2 nd heat exchanging portion 12 can be set as appropriate. However, the number of refrigerant flow paths in the 1 st heat exchanging unit 11 located at the upper portion is greater than the number of refrigerant flow paths in the 2 nd heat exchanging unit 12.
Here, the operation of the 1 st heat exchanger 10 when the refrigeration cycle apparatus 100 performs the heating operation will be described. In the refrigeration cycle apparatus 100, the high-pressure liquid refrigerant condensed by the 2 nd heat exchanger 3, at least a part of which functions as a condenser, branches into two flow paths at the branch portion 90 of the refrigerant pipe, and flows in a circuit connected to the 1 st expansion device 5 and a bypass 95 connected to the 2 nd windward heat exchanging portion 12a while branching in parallel. The refrigerant flowing into the 1 st expansion device 5 expands, i.e., decompresses, to become a low-temperature gas-liquid two-phase refrigerant. The refrigerant flowing out of the 1 st expansion device 5 merges with the refrigerant having passed through the 2 nd leeward heat exchanging portion 12 b. Generally, when a refrigerant passes through a device such as the 1 st expansion device 5, a predetermined flow resistance is generated depending on the flow path shape of the 1 st expansion device 5, the circulation amount of the refrigerant in the refrigerant circuit 1, and the flow state (Japanese: flow phase) of the refrigerant. The flow state of the refrigerant is the physical property of the refrigerant, and changes depending on whether the refrigerant is in a gas phase, a liquid phase, or a gas-liquid two-phase state. In addition, the flow resistance of the 1 st expansion device 5 causes a pressure loss in the flow of the refrigerant passing through the 1 st expansion device 5. That is, the pressure of the refrigerant passing through the 1 st expansion device 5 is decreased.
On the other hand, the refrigerant flowing into the 2 nd upwind heat exchanger 12a flows through the heat transfer tubes 20, and flows into the header 14 for moving the refrigerant from the 2 nd upwind heat exchanger 12a to the 2 nd downwind heat exchanger 12 b. The space inside the header 14 is divided, corresponding to the positions of the plurality of heat transfer tubes 20 juxtaposed in the z direction. The inner space of the header 14 is divided, and a lower header 14b is formed at a lower portion of the header 14. The lower header 14b connects the heat transfer tubes 20 of the 2 nd upwind heat exchanger 12a and the heat transfer tubes 20 of the 2 nd downwind heat exchanger 12 b. The refrigerant having passed through the lower header 14b flows into the 2 nd downstream heat exchanger 12b, flows through the heat transfer tubes 20, and then merges with the refrigerant having passed through the 1 st expansion device 5.
Here, similarly to the first expansion device 5 described above, when the refrigerant flows through the heat transfer tubes 20, the heat transfer tubes 20 also have a predetermined flow resistance. Flow resistance is generated depending on the shape of the flow path in the heat transfer pipe 20, the circulation amount of the refrigerant in the refrigerant circuit 1, and the flow state of the refrigerant, and pressure loss is generated in the flow of the refrigerant. The refrigerant that has passed through the 2 nd heat exchange unit 12 merges with the refrigerant that has passed through the 1 st expansion device 5, and flows into the 1 st heat exchange unit 11. The 1 st heat exchanging portion 11 has a plurality of heat transfer pipes 20. For example, the refrigerant is distributed to the plurality of heat transfer tubes 20 in the leeward collecting tube 13b, and the refrigerant flows into the heat transfer tubes 20 in parallel. The refrigerant flowing into the heat transfer tubes 20 in parallel passes through the 1 st leeward heat exchanger portion 11b, passes through the upper header 14a, and flows into the 1 st windward heat exchanger portion 11 a. The refrigerant that has passed through the plurality of heat transfer tubes 20 of the 1 st upstream heat exchanger 11a merges into the upstream collecting tube 13 a. That is, the refrigerant branched into the plurality of refrigerant flow paths by the 1 st heat exchanger portion 11 merges into the upstream-side collecting pipe 13a and flows out of the 1 st heat exchanger 10. The refrigerant flowing out of the 1 st heat exchanger 10 is sucked into the compressor 2 through the four-way valve 7.
Here, the circulation amount ratio of the refrigerant branched to each of the 1 st expansion device 5 and the 2 nd heat exchange unit 12 is such a ratio that the pressure loss generated in the 1 st expansion device 5 is equal to the pressure loss generated in the 2 nd heat exchange unit 12. That is, the circulation amount ratio of the refrigerant varies depending on the flow path shapes of the 1 st expansion device 5 and the 2 nd heat exchanging portion 12, and the change in flow state caused by the pressure reduction and the heat balance of the refrigerant. For example, when the flow state of the refrigerant is a single-phase state of liquid or gas, the pressure loss Δ P is expressed by the following equation.
Expression 1
Figure BDA0003273979600000091
Here,. DELTA.P is a pressure loss [ Pa ]]λ is the coefficient of friction loss, L is the flow path length [ m ]]And d is the equivalent diameter [ m ] of the flow path]G is the mass velocity [ kg/(m)2·s)]Rho is working fluid density [ kg/m ]3]Re is Reynolds number-]. In addition, depending on the range of values taken by the Reynolds number Re
λ＝64/Re(Re<2300)
Or
λ＝0.3164·Re-0.25(2300<Re)
The coefficient of friction loss λ is expressed.
The equivalent diameter d of the flow path is the diameter of the refrigerant flow path when the cross-sectional shape of the refrigerant flow path is circular. When the refrigerant flow path has a shape other than a circle, the equivalent diameter d is represented by d 4A/l based on the cross-sectional area of the refrigerant flow path and the length of the edge of the cross-sectional shape of the refrigerant flow path. In this case, A is a flow path cross-sectional area [ Pa ], and l is a length [ m ] of a flow path edge. The equivalent diameter d is a diameter of a refrigerant flow passage having a circular cross-sectional shape equivalent to a refrigerant flow passage having a non-circular cross-sectional shape.
As can be seen from the above-described equation expressing the pressure loss Δ P, the pressure loss increases in the narrow refrigerant flow path and the long refrigerant flow path.
Further, when the refrigerant has a two-phase gas-liquid state as a flow state, the liquid and the gas are mixed in a complicated state, and the pressure loss increases. On the other hand, in the case of the form in which the pressure is rapidly reduced by passing through the flow portion which is locally narrow, such as the 1 st expansion device 5, the pressure loss Δ P is basically expressed as a value of the capacity coefficient Cv which is unique to the shape of the 1 st expansion device 5. For example, the inlet of the first expansion device 5 is in a gas-liquid two-phase state as described below.
Expression 2
Figure BDA0003273979600000101
Here,. DELTA.P is a pressure loss [ Pa ]]Rho is the workflowBulk density [ kg/m ]3]，ρwaterIs the density of water [ kg/m3](fixed value), Q is the volume flow [ m ]3/min]Cv is the capacity coefficient-]. Strictly speaking, the pressure loss Δ P is also considered in consideration of other influences, but the ratio of the circulating amounts of the refrigerants in the parallel refrigerant passages including the refrigerant passage provided with the 1 st expansion device 5 and the bypass passage 95 provided with the 2 nd heat exchanging portion 12 is determined approximately by the above-described equation.
Fig. 3 is an explanatory diagram showing a cross-sectional structure of the 1 st heat exchanging portion 11 and the 2 nd heat exchanging portion 12 of the 1 st heat exchanger 10 according to embodiment 1. A portion of the cross-sectional configuration of the 1 st heat exchanger 10 on a cross-section through point a1, point a2, point A3, and point a4 shown in fig. 2 is shown. A cross-section through point A1, point A2, point A3, and point A4 is a cross-section parallel to the x-z plane. Fig. 3 shows a state as viewed from the direction of arrow Y1 shown in fig. 2. That is, fig. 3 shows a cross section perpendicular to the tube axis of the heat transfer tube 20. As shown in fig. 3, the heat transfer pipe 20 is inserted into each of the plurality of notches 31 of the fin 30 extending in the z direction in the longitudinal direction, thereby forming the 1 st heat exchanger 10. The cross-sectional shape of the heat transfer tube 20 is a flat shape, and the long axis of the cross-sectional shape of the heat transfer tube 20 is oriented in the x direction and the short axis is oriented in the z direction. The air flows into the 1 st heat exchanger 10 in the x direction, passes between the fins 30 and the heat transfer tubes 20, and exchanges heat between the air and the refrigerant flowing through the heat transfer tubes 20.
Fig. 4 is an explanatory view of a structure of the 1 st heat exchanger 10 according to embodiment 1 as viewed from the front. As shown in fig. 4, the airflow flowing into the 1 st heat exchanger 10 during the heating operation flows in a direction from the near side to the far side in the drawing. The 1 st heat exchanger 10 is configured by arranging a plurality of heat transfer tubes 20 in parallel in the z direction with the tube axes of the plurality of heat transfer tubes 20 oriented in the y direction. The plurality of heat transfer tubes 20 are, for example, flat tubes. The plurality of flat tubes are configured in a flat shape having a major axis and a minor axis in a cross section perpendicular to the tube axis. The long axes of the plurality of flat tubes are oriented in the x direction.
Fig. 5 is a cross-sectional view of a flat tube as an example of a heat transfer tube 20 used in the 1 st heat exchanger 10 according to embodiment 1. The flat tubes are made of a metal material having thermal conductivity. As a material constituting the flat tube, for example, aluminum, an aluminum alloy, copper, or a copper alloy is used. The flat tube is manufactured by extrusion processing in which the heated material is extruded from the hole of the die to form the internal flow path 21 shown in fig. 5. The flat tube may be manufactured by drawing a material from a hole of a die to form a cross section shown in fig. 5. The method of manufacturing the heat transfer pipe 20 can be appropriately selected depending on the cross-sectional shape of the heat transfer pipe 20. The heat transfer tubes 20 are not limited to flat tubes, and may be, for example, heat transfer tubes having a circular or elliptical cross-sectional shape.
Refrigeration cycle apparatus 1100 of comparative example
Fig. 6 is a circuit diagram of the refrigerant circuit 101 of the refrigeration cycle apparatus 1100 as a comparative example of the refrigeration cycle apparatus 100 according to embodiment 1. Fig. 7 is a perspective view of the 1 st heat exchanger 110 of the refrigeration cycle apparatus 1100 of the comparative example. Fig. 7 partially schematically shows refrigerant piping connected to the 1 st heat exchanger 110. The refrigeration cycle apparatus 100 according to embodiment 1 and the refrigeration cycle apparatus 1100 according to the comparative example differ in the refrigerant circuit configuration on the downstream side of the 2 nd heat exchanger 3 in the refrigerant flow direction during the heating operation.
As shown in fig. 1, the refrigeration cycle apparatus 100 according to embodiment 1 branches off the refrigerant pipe downstream of the 2 nd heat exchanger 3, the 1 st expansion device 5 is disposed in parallel with the 2 nd heat exchanging portion 12, and the refrigerant flows into the 1 st heat exchanging portion 11 after passing through the 1 st expansion device 5 and the 2 nd heat exchanging portion 12 and merging.
In contrast, as shown in fig. 6, the refrigeration cycle apparatus 1100 according to the comparative example connects the 1 st expansion device 5 and the 2 nd heat exchanging portion 112 in series on the downstream side of the 2 nd heat exchanger 3, and the refrigerant flows into the 1 st heat exchanging portion 111 after passing through the 1 st expansion device 5 and the 2 nd heat exchanging portion 112 in this order. As shown in fig. 7, the number of refrigerant flow paths in the 1 st heat exchanger portion 111 and the number of refrigerant flow paths in the 2 nd heat exchanger portion 112 in the comparative example are set in the same manner as in the 1 st heat exchanger 10 in embodiment 1.
Fig. 8 is a diagram showing characteristics of the refrigeration cycle apparatus 1100 of the comparative example during the heating operation. Fig. 8 shows changes in pressure and enthalpy of the refrigerant when the refrigeration cycle apparatus 1100 is subjected to the heating operationP-h line graph of (a). In the refrigeration cycle apparatus 1100 of the comparative example, a high-pressure gas refrigerant (P) discharged from the compressor 201) After passing through the four-way valve 7, the refrigerant flows into the 2 nd heat exchanger 3 as an indoor heat exchanger. In addition, the term [ P ] shown in parentheses]The symbols shown with the subscripts are the symbols shown on the P-h line graph of fig. 8. The refrigerant is the enthalpy and pressure at the point indicated by the symbol shown in parentheses.
The refrigerant flowing into the 2 nd heat exchanger 3 exchanges heat with the indoor air in the 2 nd heat exchanger 3, and is cooled (condensed). At this time, the temperature of the refrigerant is higher than that of the indoor air. The refrigerant is cooled by the indoor air in the 2 nd heat exchanger 3, and becomes a high-pressure liquid-phase refrigerant at the outlet of the 2 nd heat exchanger 3.
High-pressure liquid refrigerant (P) having passed through the 2 nd heat exchanger 311) The first expansion device 5 is depressurized. The refrigerant (P) in a gas-liquid two-phase state having passed through the 1 st expansion device 521) Flows into the 2 nd heat exchanging portion 112, and the refrigerant (P) is caused to flow through the flow path in the heat transfer pipe 2021) And (4) decompressing. In the diagram shown in fig. 8, the refrigerant (P) having passed through the 1 st expansion device 521) The refrigerant is in a gas-liquid two-phase state, but may be a medium-pressure single-phase liquid refrigerant due to the pressure reduction in the 1 st expansion device 5.
The refrigerant (P) in a gas-liquid two-phase state having passed through the 1 st expansion device 521) Flows into the heat transfer pipe 20 of the 2 nd heat exchanging part 112. As shown in fig. 7, the 2 nd heat exchanging portion 112 has a refrigerant flow path formed by 1 heat transfer tube 20. Therefore, according to the above equation (1), the refrigerant in the gas-liquid two-phase state passing through the 2 nd heat exchanging portion 112 causes the pressure loss Δ P. That is, the refrigerant in the gas-liquid two-phase state passing through the 2 nd heat exchanging portion 112 is decompressed.
When the refrigerant is decompressed and changes phase from a liquid single-phase state to a gas-liquid two-phase state, the temperature of the refrigerant is determined according to the pressure. The temperature of the refrigerant becomes a saturation temperature at a predetermined pressure. That is, the temperature of the gas-liquid two-phase refrigerant is also decreased by the pressure reduction. At this time, heat exchange is performed according to the temperature of the working fluid outside the heat transfer pipe 20. In the case where the refrigerant temperature is higher than the temperature of the working fluid outside the tubes, the refrigerant is cooled (condensed), and the working fluid outside the tubes is heated. In the case where the refrigerant temperature is lower than the temperature of the working fluid outside the tubes, the refrigerant is heated (evaporated), and the working fluid outside the tubes is cooled. In embodiment 1, the working fluid outside the pipe is an outside gas.
The low-pressure two-phase refrigerant (P) having passed through the 1 st expansion device 5 and the 2 nd heat exchanging portion 11231) Is lower than the temperature of the working fluid outside the tube, so that the two-phase refrigerant (P)31) Flows into the 1 st heat exchanging portion 111 and is heated (evaporated). The refrigerant flowing into the 1 st heat exchanging unit 111 evaporates in the 1 st heat exchanging unit 111, and a low-pressure gas refrigerant (P)41) Is sucked into the compressor 2 through the four-way valve 7.
Problem of refrigeration cycle apparatus 1100 of comparative example
In the 1 st heat exchanger 110 of the refrigeration cycle apparatus 1100 of the comparative example, when the flow resistance in the heat transfer tubes 20 is large, the pressure loss Δ P in the 2 nd heat exchange portion 112 increases, and P is21The pressure of the refrigerant therein decreases. The case where the flow resistance of the heat transfer tube 20 is large refers to the case where the refrigerant flow path formed inside the heat transfer tube 20 is thin and the refrigerant flow path is long, or the case where the refrigerant flow path is thin and long. For example, when the internal flow path 21 shown in fig. 5 is narrow, the pressure loss Δ P in the heat transfer pipe 20 increases. As shown in the above equation 1, when the equivalent diameter d of the flow path is reduced and the flow path length L is increased, the pressure loss Δ P increases.
At this time, as shown in fig. 8, when the opening degree of the 1 st expansion device 5 is insufficient and the pressure loss of the 2 nd heat exchanging portion 112 is large, the refrigerant (P) flowing into the 1 st heat exchanging portion 11131) The pressure of (2) may be lower than the ideal state. That is, as shown in fig. 8, the pressure of the refrigerant flowing into the 1 st heat exchanging portion 111 of the 1 st heat exchanger 110 functioning as an evaporator may be lower than the appropriate evaporator pressure P0. Such a state is likely to occur when the number of refrigerant flow paths of the 2 nd heat exchanging portion 112 is small, the refrigerant flow paths inside the heat transfer tubes 20 are thin, and the refrigerant flow paths are long.
As described above, in the refrigeration cycle apparatus 1100 of the comparative example1 Heat exchanger 110, suction part (P) of compressor 241) And a discharge part (P)01) The pressure difference of (2) increases, and there is a problem that the work of the compressor 2 increases and the power consumption also increases. This reduces the efficiency of the refrigeration cycle apparatus 1100, and affects energy saving. Alternatively, when the temperature of the refrigerant flowing through the 1 st heat exchanging portion 111 decreases with a decrease in pressure and the 1 st heat exchanger 110 serving as an outdoor heat exchanger is operated at a low outside air temperature, the amount of frost formation may increase and heat exchange performance may deteriorate.
On the other hand, when different heat transfer tubes 20 are used in the lower portion and the upper portion of the 1 st heat exchanger 110 and a heat transfer tube 20 having a large cross-sectional area of the flow path is used in the lower portion, there is a problem that the manufacturability of the 1 st heat exchanger 110 is deteriorated.
In fig. 8, if it is desired to operate the 1 st heat exchanger 110 at an appropriate value P0, the opening degree of the 1 st expansion device 5 needs to be further increased. Since the pressure loss Δ P in the 2 nd heat exchanging portion 112 depends on the shape of the heat transfer pipe 20 of the 2 nd heat exchanging portion 112, it is difficult to use only the 2 nd heat exchanging portion 112 to set point P in fig. 821Point P31The pressure difference of the refrigerant therebetween is adjusted to decrease. Thus, to further improve the efficiency at point P in FIG. 831The pressure of the refrigerant (1) needs to be increased by increasing the opening degree of the 1 st expansion device 5 to increase the refrigerant flowing in the 1 st expansion device 5. That is, it is necessary to increase the opening degree of the 1 st expansion device 5 and decrease the point P of fig. 811Point P21The amount of reduced pressure therebetween. However, there are problems as follows: the adjustment range of the opening degree of the electric expansion valve, the mechanical expansion valve, the capillary tube, or the like used as the 1 st expansion device 5 is limited, and it is difficult to set an appropriate opening degree adjustment range in the 1 st expansion device 5 in consideration of the control of the refrigerating capacity of the refrigeration cycle apparatus 1100. That is, there are problems as follows: if the flow path resistance in the lower portion of the 1 st heat exchanger 110 increases, the required refrigerant flow rate may not be adjusted even if the 1 st expansion device 5 is at the maximum opening degree, and the controllability of the refrigeration cycle apparatus 1100 may deteriorate.
Operation of refrigeration cycle apparatus 100 according to embodiment 1
Fig. 9 is a diagram showing characteristics of the refrigeration cycle apparatus 100 according to embodiment 1 during the heating operation. Fig. 10 is an enlarged view of a portion a of fig. 9. Fig. 9 is a P-h diagram showing changes in pressure and enthalpy of the refrigerant when the refrigeration cycle apparatus 100 is subjected to the heating operation. In the refrigeration cycle apparatus 100, a high-pressure gas refrigerant (P) discharged from the compressor 201) Flows into the 2 nd heat exchanger 3 as an indoor heat exchanger through the four-way valve 7. The refrigerant is cooled (condensed) by heat exchange with the indoor air. At this time, the temperature of the refrigerant is higher than that of the indoor air. The refrigerant is cooled by the indoor air in the 2 nd heat exchanger 3, and becomes a high-pressure liquid-phase refrigerant at the outlet of the 2 nd heat exchanger 3.
High-pressure liquid refrigerant (P) having passed through the 2 nd heat exchanger 311) The refrigerant is branched into two flow paths, distributed to the 2 nd heat exchanger 12 and the 1 st expansion device 5, and expanded, i.e., decompressed. Like the refrigerant flowing into the 2 nd heat exchanging unit 112 in the comparative example, the refrigerant flowing into the 2 nd heat exchanging unit 12 is decompressed by the refrigerant flow paths in the heat transfer tubes 20. When the refrigerant is depressurized in the heat transfer tubes 20 and changes its phase from a liquid single-phase state to a gas-liquid two-phase state, the temperature of the refrigerant is determined according to the pressure. That is, as the pressure of the refrigerant is reduced, the temperature also decreases. At this time, heat is exchanged between the outside air and the refrigerant flowing through the heat transfer tubes 20, depending on the temperature of the outside air, which is the working fluid outside the heat transfer tubes 20. In the case where the refrigerant temperature is higher than the working fluid temperature outside the tubes, the refrigerant is cooled (condensed), and the working fluid outside the tubes is heated. In the case where the refrigerant temperature is lower than the temperature of the working fluid outside the tube, the refrigerant is heated (evaporated), and the working fluid outside the tube is cooled. As a result, the refrigerant flowing through the 2 nd heat exchanging portion 12 becomes a low-pressure gas-liquid two-phase refrigerant (P)22)。
The refrigerant flowing into the 1 st expansion device 5 is expanded (decompressed) into a low-pressure gas-liquid two-phase refrigerant (P)21). At this time, the first expansion device 5 is adiabatic expansion without heat exchange of the refrigerant, and therefore the gas-liquid two-phase refrigerant (P) is generated21) Enthalpy value and state before expansion (P)11) The same is true.
Here, the ratio of the refrigerant circulation amounts distributed to the 2 nd heat exchanging portion 12 and the 1 st expansion device 5 is determined in accordance with the difference between the magnitude of the flow resistance in the heat transfer pipe 20 of the 2 nd heat exchanging portion 12 and the magnitude of the flow resistance caused by the expansion and contraction of the 1 st expansion device 5.
The pressure loss Δ P of the heat transfer tube 20 is obtained from the above equation (1). The friction loss coefficient λ, the flow path length L, and the equivalent diameter d of the flow path in the equation (1) are determined by the shape of the heat transfer tubes 20 and the number of heat transfer tubes 20 included in the 2 nd heat exchanging portion 12. On the other hand, in the formula (1), the mass velocity G is determined according to the amount of the refrigerant flowing into the 2 nd heat exchanging portion 12, and the working fluid density ρ varies depending on whether the refrigerant is in a single phase or a gas-liquid two-phase. On the other hand, the pressure loss Δ P of the 1 st expansion device 5 is determined according to equation 2. When the opening degree is small (when Cv is small), the flow rate decreases and the pressure loss Δ P increases. When the opening degree is large (when Cv is large), the flow rate increases and the pressure loss Δ P is small.
Thus, in the refrigerant circuit 1, the opening degree of the 1 st expansion device 5 can be used to control the pressure reduction of the refrigerant, that is, P, in the section where the 2 nd heat exchange unit 12 and the 1 st expansion device 5 are connected in parallel11～P31The pressure of the refrigerant in the section (2) is reduced.
The low-pressure gas-liquid two-phase refrigerant (P) having passed through the 2 nd heat exchanging portion 1222) And a low-pressure gas-liquid two-phase refrigerant (P) having passed through the 1 st expansion device 521) Merging to form a low-pressure two-phase refrigerant (P) corresponding to the ratio of the refrigerant circulation amounts and the respective enthalpies31) And flows into the 1 st heat exchanging portion 11 to be heated (evaporated). The low-pressure gas refrigerant (P) evaporated in the 1 st heat exchanging portion 1141) Is sucked into the compressor 2 through the four-way valve 7.
Effect of embodiment 1
The refrigeration cycle apparatus 100 according to embodiment 1 forms the bypass 95 in parallel with the refrigerant flow path in which the 1 st expansion device 5 is provided, even when the in-tube flow resistance of the heat transfer tubes 20 of the 2 nd heat exchanging portion 12 is large. Therefore, the flow resistance of the refrigerant flow paths in the parallel portions of the refrigerant circuit 1 is reduced as compared with the case where the 2 nd heat exchanging portion 12 or the 1 st expansion device 5 is individually provided in series. Thus, the opening degree of the 1 st expansion device 5 does not need to be increased, and the opening degree of the 1 st expansion device 5 does not become insufficient. Then, the liquid refrigerant having a high pressure and a temperature higher than that of the indoor air can be made to flow into the 2 nd heat exchange unit 12 including the lowermost stage of the 1 st heat exchanger 10. Therefore, the drain water retained in the lower portion of the 1 st heat exchanger 10 can be suppressed from freezing.
The refrigeration cycle apparatus 100 according to embodiment 1 includes a refrigerant circuit 1, and a compressor 2, a1 st heat exchanger 10, and a1 st expansion device 5 are connected to the refrigerant circuit 1 by refrigerant pipes. The 1 st heat exchanger 10 includes a1 st heat exchanging unit 11 and a2 nd heat exchanging unit 12, and the 2 nd heat exchanging unit 12 is connected in series to the 1 st heat exchanging unit 11 in the refrigerant circuit 1. The 1 st expansion device 5 is connected in parallel to the 2 nd heat exchanging unit 12 in the refrigerant circuit 1, and the 2 nd heat exchanging unit 12 is located below the 1 st heat exchanging unit 11.
When the 1 st heat exchanger 10 functions as an evaporator, the refrigerant flowing out of the 2 nd heat exchanger 3 is first distributed to the 1 st expansion device 5 and the 2 nd heat exchanging portion 12. Therefore, the 2 nd heat exchanging portion 12 causes the refrigerant to flow in a range of saturation temperature based on the pressure difference between the upstream side and the downstream side of the 1 st expansion device 5 of the conventional refrigerant circuit 101. That is, since the temperature of the refrigerant in the 2 nd heat exchanger 12 of embodiment 1 is higher than the inlet of the 1 st heat exchanger 110 serving as an evaporator in the refrigerant circuit 101 of the comparative example, it is possible to suppress the occurrence of freezing of the water retained in the lowermost portion of the 1 st heat exchanger 10 serving as an evaporator.
The 2 nd heat exchange unit 12 is a bypass 95 with respect to the 1 st expansion device 5. By adding the 2 nd heat exchanging portion 12 to the 1 st expansion device 5 in parallel, the maximum opening degree of the 1 st expansion device 5 can be reduced as compared with the refrigerant circuit 101 in which the 1 st expansion device 5 and the 2 nd heat exchanging portion 12 are connected in series as in the comparative example. Accordingly, when the pressure loss Δ P of the refrigerant passing through the 2 nd heat exchange unit 12 is large, the 1 st expansion device 5 is less likely to be short of opening degree, and the range in which the pressure of the refrigerant in the evaporator can be controlled is widened.
In particular, when flat tubes are used as the heat transfer tubes 20 of the 1 st heat exchanger 10, the pressure loss may increase when the refrigerant flow paths are narrow and the refrigerant flows therethrough. In order to reduce the amount of refrigerant in the 1 st heat exchanger 10 and the refrigerant circuit 1, the heat transfer tubes 20 are preferably formed to have a small refrigerant flow path, and for example, flat tubes having a thickness in the minor axis direction of 1mm or less, more preferably 0.8mm or less are preferably used. At this time, when the refrigerant pressure of the 1 st heat exchanger 10 functioning as an evaporator is to be increased, that is, when the operation is to be performed in a state where the heat exchange capacity of the evaporator is low, the pressure loss Δ P in the 2 nd heat exchanging portion 112 located at the lower portion of the 1 st heat exchanger 10 is high in the refrigerant circuit 101 of the comparative example. Therefore, the following problems are present: if the opening degree of the 1 st expansion device 5 is not increased, the pressure in the 1 st heat exchanging portion 111 becomes lower than the appropriate evaporator pressure P0. On the other hand, in the refrigerant circuit 1 of the refrigeration cycle apparatus 100 according to embodiment 1, the 2 nd heat exchange unit 12 having a large pressure loss is disposed in parallel with the 1 st expansion device 5, and therefore the pressure in the evaporator can be appropriately controlled without widening the opening range of the 1 st expansion device 5.
In addition, since the 1 st heat exchanging part 11 and the 2 nd heat exchanging part 12 of the 1 st heat exchanger 10 are integrally formed, there is an advantage that the assembling property is improved when the 1 st heat exchanger 10 is manufactured.
In the refrigeration cycle apparatus 100 according to embodiment 1, the number of refrigerant flow paths in the 1 st heat exchange unit 11 is greater than the number of refrigerant flow paths in the 2 nd heat exchange unit 12. The 1 st heat exchanger 10 is configured by two elements, i.e., the 1 st heat exchanging unit 11 and the 2 nd heat exchanging unit 12, and the 1 st heat exchanging unit 11 and the 2 nd heat exchanging unit 12 are connected in series, so that the pressure loss Δ P of the 1 st heat exchanger 10 can be increased. In particular, when the evaporator is used, the pressure loss Δ P in the 2 nd heat exchanging unit 12 can be increased by making the number of refrigerant bypass branches of the 2 nd heat exchanging unit 12 on the upstream side of the 1 st heat exchanging unit 11 in the refrigerant flow smaller than the number of refrigerant bypass branches of the 1 st heat exchanging unit 11. Therefore, the freezing of the water retained in the lowermost portion of the 1 st heat exchanger 10 can be suppressed, and the pressure of the refrigerant flowing into the 1 st heat exchanging unit 11 can be reduced without providing an additional expansion device on the downstream side of the 2 nd heat exchanging unit 12.
In the refrigeration cycle apparatus 100 according to embodiment 1, the heat transfer pipe 20 included in the 1 st heat exchanging unit 11 and the heat transfer pipe 20 included in the 2 nd heat exchanging unit 12 are arranged in parallel. As a result, the 1 st heat exchanger 10 allows the refrigerant having a high temperature to flow through the heat transfer tubes 20 disposed below, in which water droplets flowing down from the heat transfer tubes 20 disposed above are likely to accumulate. This can suppress the occurrence of freezing of the stagnant water accumulated on the upper surface of the heat transfer tubes 20.
In the refrigeration cycle apparatus 100 according to embodiment 1, the heat transfer tubes 20 are flat tubes. The heat transfer tubes 20 included in the 2 nd heat exchange portion 12 located below the 1 st heat exchanger 10 are flat tubes, and therefore the pressure of the refrigerant passing through the 2 nd heat exchange portion 12 is likely to decrease. Therefore, the pressure of the refrigerant can be reduced by the 2 nd heat exchange portion 12 disposed not in the bypass 95 of the 1 st expansion device 5, and the refrigerant having a high temperature can be circulated in the lower portion of the 1 st heat exchanger 10, so that freezing of the lower portion of the 1 st heat exchanger 10 can be suppressed. Further, since the heat transfer tubes 20 are flat tubes, the refrigerant capacity of the 1 st heat exchanger 10 can be reduced while maintaining or improving the heat exchange capacity, and the amount of refrigerant flowing through the refrigerant circuit 1 can be reduced.
Embodiment 2.
The refrigeration cycle apparatus 100 according to embodiment 2 is further provided with an expansion device in addition to the refrigerant circuit 1 of the refrigeration cycle apparatus 100 according to embodiment 1. The refrigeration cycle apparatus 200 according to embodiment 2 will be described mainly with respect to modifications to embodiment 1. Components of the refrigeration cycle apparatus 200 according to embodiment 2 having the same functions as those in the drawings described in embodiment 1 are denoted by the same reference numerals as those in the drawings.
Fig. 11 is a circuit diagram of a refrigerant circuit 201 of the refrigeration cycle apparatus 200 according to embodiment 2. Fig. 12 is a perspective view of the 1 st heat exchanger 210 of the refrigeration cycle apparatus 200 according to embodiment 2. The refrigerant circuit 201 of the refrigeration cycle apparatus 200 according to embodiment 2 is provided with a2 nd expansion device 51 added between the 2 nd heat exchange unit 12 and the 1 st heat exchange unit 11 of the 1 st heat exchanger 10 of the refrigeration cycle apparatus 100 according to embodiment 1. The 2 nd expansion device 51 is disposed closer to the 2 nd heat exchanging portion 12 side than the merging portion 91, and the merging portion 91 merges the flow path branched at the branching portion 90 and in which the 1 st expansion device 5 is disposed with the flow path in which the 2 nd heat exchanging portion 12 is disposed. In other words, the bypass 295 connecting the 2 nd heat exchanging part 12 and the 2 nd expansion device 51 in series is connected in parallel to the 1 st expansion device 5.
Fig. 13 is a diagram showing characteristics of the refrigeration cycle apparatus 200 according to embodiment 2 during the heating operation. Fig. 13 is a P-h diagram showing changes in pressure and enthalpy around a low-temperature and low-pressure region of the refrigeration cycle apparatus 200. Depending on the specifications of the 2 nd heat exchanger 12, the refrigeration cycle apparatus 100 according to embodiment 1 may have a small pressure loss Δ P in the 2 nd heat exchanger 12 and a high pressure of the refrigerant immediately after flowing out of the 2 nd heat exchanger 12. That is, sometimes as point P in FIG. 1323In this way, the temperature of the refrigerant flowing out of the 2 nd heat exchanging portion 12 is higher than that of the outdoor air. As a result, the refrigerant flowing out of the 2 nd heat exchanger 12 is further decompressed by the 2 nd expansion device 51, and the refrigerant is lowered to a pressure lower than the pressure corresponding to the outdoor air temperature. With such a configuration, the refrigeration cycle apparatus 200 can appropriately set or control the pressure of the 1 st heat exchanger 210 serving as an evaporator. At this time, since the temperature of the refrigerant flowing out of the 2 nd heat exchange unit 12 is higher than the outdoor air temperature, even in a low outdoor air temperature environment in which the outdoor air temperature is in the vicinity of the freezing point of water, frost formation and freezing can be suppressed by flowing the refrigerant having a high temperature through the 2 nd heat exchange unit 12.
Fig. 14 is a diagram showing characteristics of the refrigeration cycle apparatus 200 according to embodiment 2 during the heating operation. Fig. 14 is a P-h diagram showing changes in pressure and enthalpy around a low-temperature and low-pressure region of the refrigeration cycle apparatus 200. Fig. 14 is a diagram of a case where the pressure loss Δ P in the 2 nd heat exchanging portion 12 is larger than that in fig. 13. At this time, the temperature of the refrigerant flowing out of the 2 nd heat exchanging portion 12 is lower than that of the outdoor air. Therefore, since the temperature of the portion immediately before the heat exchanger unit 2 flows out of the heat exchanger unit 12 is lower than the outdoor air, it is considered that frost formation or freezing of stagnant water occurs around the outlet of the heat exchanger tubes 20 of the heat exchanger unit 2. However, the refrigeration cycle apparatus 200 of embodiment 2 includes the 2 nd expansion device 51, the opening degree of the 2 nd expansion device 51 can be set or controlled so as to be at the point P in accordance with the outdoor air temperature23The temperature of (a) is not lower than the freezing point of water. This can suppress the formation of frost and ice only in a part of the periphery of the outlet of the 2 nd heat exchanger 12.
The 1 st expansion device 5 and the 2 nd expansion device 51 are not limited to the configurations in which the opening degrees can be changed, and may be configurations in which the opening degrees are fixed. In addition, at least one of the 1 st expansion device 5 and the 2 nd expansion device 51 may be configured to be capable of changing the opening degree.
In the refrigeration cycle apparatus 200 according to embodiment 2, the 2 nd expansion device 51 is connected in parallel with the 1 st expansion device 5 in the refrigerant circuit 201, and is connected in series with the 2 nd heat exchanger 12.
Since the refrigerant having passed through the 2 nd heat exchanging portion 12 is decompressed in the 2 nd expansion device 51, the refrigerant pressure and the refrigerant temperature also increase on the upstream side of the 2 nd expansion device 51, that is, on the outlet side of the 2 nd heat exchanging portion 12. This can maintain the refrigerant temperature high throughout the 2 nd heat exchanger 12. Therefore, the 1 st heat exchanger 210 is easier to suppress freezing of the water retained in the lower portion of the 1 st heat exchanger 210 than the 1 st heat exchanger 10 of embodiment 1.
In addition, for example, in an operation state in which the refrigerant circulation amount needs to be reduced, such as when the refrigeration cycle device 200 performs a low load capacity operation, the operation needs to be performed with the opening degree of the 1 st expansion device 5 closed. However, when the flow path resistance of the 2 nd heat exchanger 12 is small, the amount of the refrigerant flowing into the 2 nd heat exchanger 12 increases. Alternatively, the pressure of the refrigerant flowing into the 1 st heat exchanging portion 11 may not be appropriately set in consideration of the insufficient resolution of the opening degree setting of the 1 st expansion device 5, and the refrigeration cycle apparatus 200 may not be set or controlled to the target low load capacity. The case where the flow path resistance of the 2 nd heat exchanger 12 is small means, for example, the case where the pressure loss Δ P of the heat transfer tubes 20 in the 2 nd heat exchanger 12 is small.
In the refrigeration cycle apparatus 200 according to embodiment 2, by providing the bypass 295 to which the 2 nd heat exchange unit 12 and the 2 nd expansion device 51 are connected in series, the flow path resistance can be applied also to the bypass 295 on the 2 nd heat exchange unit 12 side. That is, the pressure of the refrigerant flowing into the 1 st heat exchanging part 11 can be controlled using not only the 1 st expansion device 5 but also the 2 nd expansion device 51 provided in the bypass 295. Therefore, the refrigeration cycle apparatus 200 can improve the performance of controlling the pressure of the 1 st heat exchanger 10 functioning as an evaporator when operating in the low load capacity state, compared to the refrigeration cycle apparatus 100 according to embodiment 1.
Embodiment 3.
The refrigeration cycle apparatus 300 according to embodiment 3 is obtained by adding an expansion device to the refrigerant circuit 1 of the refrigeration cycle apparatus 100 according to embodiment 1. The refrigeration cycle apparatus 300 according to embodiment 3 will be described mainly with respect to modifications to embodiment 1. In the refrigeration cycle apparatus 300 according to embodiment 3, components having the same functions in the respective drawings are denoted by the same reference numerals as those used in the description of embodiment 1.
Fig. 15 is a circuit diagram of a refrigerant circuit 301 of a refrigeration cycle apparatus 300 according to embodiment 3. Fig. 16 is a perspective view of the 1 st heat exchanger 310 of the refrigeration cycle apparatus 300 according to embodiment 3. The refrigerant circuit 301 of the refrigeration cycle apparatus 300 according to embodiment 3 is obtained by adding the 2 nd expansion device 52 between the 2 nd heat exchange unit 12 and the 1 st heat exchange unit 11 of the 1 st heat exchanger 10 of the refrigeration cycle apparatus 100 according to embodiment 1. The 2 nd expansion device 52 is disposed closer to the 1 st heat exchanging portion 11 side than the merging portion 91, and the merging portion 91 merges the flow path branched at the branching portion 90 and in which the 1 st expansion device 5 is disposed with the flow path in which the 2 nd heat exchanging portion 12 is disposed. In other words, the 1 st expansion device 5 and the 2 nd heat exchanging portion 12 are connected in series to the 2 nd expansion device 52.
Fig. 17 is a diagram showing characteristics of the refrigeration cycle apparatus 300 according to embodiment 3 during the heating operation. Fig. 17 is a P-h diagram showing changes in pressure and enthalpy around a low-temperature and low-pressure region of the refrigeration cycle apparatus 300. Depending on the specifications of the 2 nd heat exchanger 12, the refrigeration cycle apparatus 100 according to embodiment 1 may have a small pressure loss Δ P in the 2 nd heat exchanger 12 and a high pressure of the refrigerant immediately after flowing out of the 2 nd heat exchanger 12. That is, sometimes as point P in FIG. 1722In this way, the temperature ratio of the refrigerant flowing out of the 2 nd heat exchanging portion 12The outdoor air is high.
It is also considered that the pressure of the refrigerant flowing out of the 1 st expansion device 5, that is, the point P cannot be set according to the resolution of the capacity or the opening degree of the 1 st expansion device 521The pressure of the refrigerant is sufficiently lowered. As a result, the refrigerant that has flowed out of the 2 nd heat exchange unit 12 and the 1 st expansion device 5 and merged together is further decompressed by the 2 nd expansion device 52, and the refrigerant is lowered to a pressure lower than the pressure corresponding to the outdoor air temperature. With such a configuration, the refrigeration cycle apparatus 300 according to embodiment 3 can appropriately set or control the pressure of the 1 st heat exchanger 310 serving as an evaporator.
In the characteristics of the refrigeration cycle apparatus 300 shown in fig. 17 during the heating operation, the refrigerant pressure and the refrigerant temperature on the outlet side of the 2 nd heat exchanging unit 12 can be kept high, and therefore a high refrigerant temperature can be maintained throughout the entire area of the 2 nd heat exchanging unit 12. Therefore, similarly to the 1 st heat exchanger 210 of embodiment 2, there is an advantage that freezing of the water retained in the lowermost portion of the 1 st heat exchanger 10 is easily suppressed.
Fig. 18 is a diagram showing characteristics of the refrigeration cycle apparatus 300 according to embodiment 3 during the heating operation. Fig. 18 is a P-h diagram showing changes in pressure and enthalpy around a low-temperature and low-pressure region of the refrigeration cycle apparatus 200. Fig. 18 is a diagram of a case where the pressure loss Δ P in the 2 nd heat exchanging portion 12 is larger than that in fig. 17. At this time, the temperature of the refrigerant flowing out of the 2 nd heat exchanging portion 12 is lower than that of the outdoor air. Therefore, since the temperature of the portion immediately before the portion flows out of the 2 nd heat exchanging portion 12 is lower than the outdoor air, it is considered that frost formation or freezing of stagnant water occurs around the outlet of the heat transfer pipe 20 of the 2 nd heat exchanging portion 12. However, since the refrigeration cycle apparatus 300 according to embodiment 3 includes the 2 nd expansion device 52, the opening degree of the 2 nd expansion device 52 can be set or controlled so as to be at the point P in accordance with the outdoor air temperature32The temperature of (a) is not lower than the freezing point of water. This can suppress the formation of frost and ice only in a part of the periphery of the outlet of the 2 nd heat exchanger 12.
In embodiment 3, the opening degree of the 1 st expansion device 5 and the 2 nd expansion device 52 may be variable or fixed. In addition, at least one of the 1 st expansion device 5 and the 2 nd expansion device 52 may be configured to be capable of changing the opening degree.
Embodiment 4.
The refrigeration cycle apparatus 400 according to embodiment 4 is obtained by changing the structure of the 1 st heat exchanger 10 of the refrigeration cycle apparatus 100 according to embodiment 1. The refrigeration cycle apparatus 400 according to embodiment 4 will be described mainly with respect to modifications to embodiment 1. Components of the refrigeration cycle apparatus 400 according to embodiment 4 having the same functions as those in the drawings described in embodiment 1 are denoted by the same reference numerals as those in the drawings.
Fig. 19 is a circuit diagram of a refrigerant circuit 401 of a refrigeration cycle apparatus 400 according to embodiment 4. Fig. 20 is a perspective view of the 1 st heat exchanger 410 of the refrigeration cycle apparatus 400 according to embodiment 4. The refrigerant circuit 401 of the refrigeration cycle apparatus 400 according to embodiment 4 is configured to separate the 1 st heat exchanging portion 11 of the 1 st heat exchanger 10 of the refrigeration cycle apparatus 100 according to embodiment 1. The heat transfer tubes 20 of the 1 st heat exchanging unit 11 according to embodiment 1 are all arranged in parallel, and the refrigerant flows into all of the heat transfer tubes 20 at the same time. On the other hand, the 1 st heat exchanging unit 11 according to embodiment 4 connects in series the plurality of heat transfer pipes 20 located in the lower portion 16 of the 1 st heat exchanging unit 11 and the plurality of heat transfer pipes 20 located in the upper portion 15 of the 1 st heat exchanging unit 11.
Fig. 21 is a diagram showing characteristics of the refrigeration cycle apparatus 400 according to embodiment 4 during the heating operation. Fig. 21 is a P-h diagram showing changes in pressure and enthalpy around a low-temperature and low-pressure region of the refrigeration cycle apparatus 400. Depending on the specifications of the 2 nd heat exchanger 12, the refrigeration cycle apparatus 100 according to embodiment 1 may have a small pressure loss Δ P in the 2 nd heat exchanger 12 and a high pressure of the refrigerant immediately after flowing out of the 2 nd heat exchanger 12. That is, sometimes as point P in FIG. 2122In this way, the temperature of the refrigerant flowing out of the 2 nd heat exchanging portion 12 is higher than that of the outdoor air.
It is also considered that the point P cannot be set according to the capacity or the opening degree resolution of the 1 st expansion device 521The pressure of the refrigerant is sufficiently lowered. Thereby, the outflow is further changed by the 2 nd heat exchanger by the lower portion 16 of the 1 st heat exchanger 11The refrigerant merged in the hot section 12 and the 1 st expansion device 5 needs to be decompressed and reduced to a pressure lower than a pressure corresponding to the outdoor air temperature. With such a configuration, the refrigeration cycle apparatus 400 can appropriately set or control the pressure of the 1 st heat exchanger 410 serving as an evaporator.
With this configuration, when the outside air temperature around the 1 st heat exchanger 410 serving as an evaporator is near the freezing point of water or below, it is possible to supply a refrigerant having a high temperature not only to the 2 nd heat exchange unit 12 but also to the lower portion 16 of the 1 st heat exchange unit 11.
The present invention has been described above based on the embodiments, but the present invention is not limited to the configurations of the above-described embodiments. For example, the 1 st heat exchanger 10, 210, 310 according to embodiments 1 to 3 has been described as a structure in which the 1 st heat exchanging unit 11 and the 2 nd heat exchanging unit 12 are divided into two parts, but the respective heat exchanging units may be appropriately divided. For example, the 1 st heat exchanging unit 11 and the 2 nd heat exchanging unit 12 may be divided into the same number, and the divided heat exchanging units may be connected in series. The present invention may be configured by combining the embodiments. In short, the accompanying description also includes, for the sake of caution, various modifications, applications, and ranges of use that can be made as necessary by those skilled in the art within the spirit (scope of claims) of the present invention.
Description of the reference numerals
1. A refrigerant circuit; 2. a compressor; 3. a2 nd heat exchanger; 4. a blower; 5. a1 st expansion device; 6. a blower; 7. a four-way valve; 10. a1 st heat exchanger; 11. the 1 st heat exchanging part; 11a, a1 st upwind side heat exchange part; 11b, the 1 st downwind side heat exchange part; 12. the 2 nd heat exchanging part; 12a, a2 nd upstream side heat exchange part; 12b, a2 nd downwind side heat exchange part; 13a, (windward) manifold; 13b, (leeward) collecting pipes; 14. a header; 14a, an upper header; 14b, a lower header; 15. an upper portion; 16. a lower portion; 20. a heat transfer tube; 21. an internal flow path; 30. a fin; 31. a notch portion; 51. a2 nd expansion device; 52. a2 nd expansion device; 80. a refrigerant pipe; 90. a branching section; 91. a confluence section; 95. a bypass; 100. a refrigeration cycle device; 101. a refrigerant circuit; 110. a1 st heat exchanger; 111. the 1 st heat exchanging part; 112. the 2 nd heat exchanging part; 200. a refrigeration cycle device; 201. a refrigerant circuit; 210. a1 st heat exchanger; 295. a bypass; 300. a refrigeration cycle device; 301. a refrigerant circuit; 310. a1 st heat exchanger; 400. a refrigeration cycle device; 401. a refrigerant circuit; 410. a1 st heat exchanger; 1100. a refrigeration cycle device; G. mass velocity; p0, evaporator pressure; re, Reynolds number; y1, arrow; d. an equivalent diameter; Δ P, pressure loss; λ, coefficient of friction loss; ρ, working fluid density.

Claims (7)

1. A refrigerating cycle apparatus, wherein,
the refrigeration cycle device is provided with a refrigerant circuit, wherein a compressor, a1 st expansion device and a1 st heat exchanger which functions as an evaporator during heating operation are connected by refrigerant pipes,
the 1 st heat exchanger is provided with a1 st heat exchanging part and a2 nd heat exchanging part,
the 2 nd heat exchanging portion is connected in series with the 1 st heat exchanging portion in the refrigerant circuit,
the 1 st expansion device is connected in parallel with the 2 nd heat exchange portion within the refrigerant circuit,
the 2 nd heat exchange part is positioned below the 1 st heat exchange part.
2. The refrigeration cycle apparatus according to claim 1,
a2 nd expansion device is provided between the 1 st heat exchange unit and the 2 nd heat exchange unit.
3. The refrigeration cycle apparatus according to claim 2,
the 2 nd expansion device is connected in parallel with the 1 st expansion device in the refrigerant circuit, and is connected in series with the 2 nd heat exchange portion.
4. The refrigeration cycle apparatus according to claim 2,
the 2 nd expansion device is connected in series with the 1 st expansion device and the 2 nd heat exchange portion within the refrigerant circuit.
5. The refrigeration cycle apparatus according to any one of claims 1 to 4,
the number of refrigerant passages of the 1 st heat exchanging portion is greater than the number of refrigerant passages of the 2 nd heat exchanging portion.
6. The refrigeration cycle apparatus according to any one of claims 1 to 5,
the 1 st heat exchanger includes a plurality of heat transfer tubes arranged in parallel in the vertical direction,
the plurality of heat transfer pipes are flat pipes, respectively.
7. The refrigeration cycle apparatus according to any one of claims 1 to 6,
the refrigerant circuit is provided with a2 nd heat exchanger at least a part of which functions as a condenser during a heating operation,
a branching portion that branches the refrigerant pipe is provided between the 2 nd heat exchanger and the 1 st expansion device.
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