WO2023166708A1

WO2023166708A1 - Air conditioner

Info

Publication number: WO2023166708A1
Application number: PCT/JP2022/009409
Authority: WO
Inventors: 俊光鎌田; 純平 ▲高▼木
Original assignee: 三菱電機株式会社
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2023-09-07
Also published as: JPWO2023166708A1; JP7114011B1

Abstract

This air conditioner performs both a space heating operation and a defrosting operation, and comprises a heat exchanger and a flow passage switching device. The heat exchanger causes heat to be exchanged between outdoor air and a refrigerant. The heat exchanger has a plurality of units arranged in a vertical direction. Each unit includes one or more heat transfer pipes that form a forked refrigerant flow passage in which a single passage comprising one refrigerant flow passage and a multiple passage comprising a plurality of refrigerant flow passages are connected together. During the defrosting operation, the flow passage switching device causes the refrigerant to flow from the multiple passage to the single passage, and during the space heating operation, the flow passage switching device causes the refrigerant to flow from the single passage to the multiple passage. The multiple passage of the lowermost unit disposed lowest among the plurality of units includes a first flow passage, being the refrigerant flow passage, in the forked refrigerant flow passage, of which an inlet for the refrigerant during the defrosting operation is positioned on the most upstream side in a flow direction of air. The inlet of the first flow passage is in a position that is lowest in the forked refrigerant flow passage.

Description

air conditioner

The present disclosure relates to an air conditioner that air-conditions a room.

Conventionally, as an outdoor heat exchanger for an air conditioner, a sub-cooler was used at the bottom for the purpose of securing condensation capacity during cooling operation, preventing frost formation during heating operation, and improving evaporation capacity. A configuration has been proposed in which the coolant is not circulated in the lowermost portion (see, for example, Patent Literature 1).

Japanese Patent No. 2923166

However, in the heat exchanger with the above configuration, the heat transfer area of the subcooler cannot be used as an evaporator during heating operation, so the required heat exchange amount may not be obtained. Here, if the evaporation temperature is lowered in order to secure the heat exchange amount of the heat exchanger, even if the outside air temperature is higher than 0 [° C.], the surface temperature of the heat transfer tube in the heat exchanger will be below the freezing point and frost will form. may occur. As a result, the heating capacity of the air conditioner is reduced, and there is a possibility that the operation desired by the user cannot be obtained.

The present disclosure has been made to solve the above problems, and aims to provide an air conditioner that achieves both suppression of frost formation on the heat exchanger and improvement of the performance of the heat exchanger.

An air conditioner according to the present disclosure is an air conditioner that performs both a heating operation and a defrosting operation, and includes a heat exchanger that exchanges heat between outdoor air and a refrigerant, and a direction in which the refrigerant flows. and a flow path switching device for switching the heat exchanger, wherein the heat exchanger has a plurality of units arranged along the vertical direction, and each of the plurality of units is a single refrigerant flow path. and one or more heat transfer tubes forming a crotch-shaped refrigerant flow path connected to a plurality of double paths that are refrigerant flow paths, and the flow path switching device, during the defrosting operation, the refrigerant is circulated from the double path to the single path, and during the heating operation, the refrigerant is circulated from the single path to the double path, and the double path of the lowest unit arranged at the lowest among the plurality of units includes a first flow path which is a refrigerant flow path in which the inlet of the refrigerant during the defrosting operation is located on the most upstream side in the flow direction of the air in the crotch-shaped refrigerant flow path, and the first flow The inlet of the channel is the lowest in the forked coolant channel.

According to the air conditioner according to the present disclosure, during heating operation, the double path of each unit of the heat exchanger is on the downstream side of the refrigerant. As a result, the dry refrigerant in the double path slows down, allowing it to receive more heat from the air. In addition, the deceleration of the refrigerant reduces the friction between the refrigerant and the heat transfer tubes, thereby reducing the pressure loss. Therefore, the capacity of the heat exchanger is improved. Further, according to the air conditioner, the inlet of the refrigerant during the defrosting operation of the first flow path included in the double path of the lowermost unit is the most upstream side in the flow direction of the air in the crotch-shaped refrigerant flow path. , and the lowest position. Therefore, among the one or more heat transfer tubes, the windward side where more frost occurs during heating operation and the lowest portion where melted water flows during defrosting operation are in an overheated state during defrosting operation. gaseous refrigerant flows into the Therefore, the amount of frost formed in the heat exchanger can be reduced. Therefore, the air conditioner can achieve both suppression of frost formation on the heat exchanger and improvement of the performance of the heat exchanger.

1 is a refrigerant circuit diagram schematically showing a configuration example of an air conditioner according to Embodiment 1. FIG. FIG. 2 is a diagram schematically illustrating the inside of the outdoor heat exchanger according to Embodiment 1; FIG. 3 is a diagram schematically exemplifying refrigerant flow paths in the outdoor heat exchanger according to Embodiment 1; FIG. 4 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 2; FIG. 10 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 3; FIG. 11 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 4; FIG. 11 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 5; FIG. 21 is a perspective view illustrating a specific configuration of part of an outdoor heat exchanger according to Embodiment 6;

Hereinafter, the air conditioner according to the embodiment will be described in detail with reference to the drawings.

Embodiment 1.
FIG. 1 is a refrigerant circuit diagram schematically showing a configuration example of an air conditioner according to Embodiment 1. FIG. The air conditioner 100 according to Embodiment 1 performs each of a cooling operation, a heating operation, and a defrosting operation. The air conditioner 100 has an outdoor unit 1 and an indoor unit 3 . The outdoor unit 1 is installed outside the air-conditioned space, for example outdoors, and the indoor unit 3 is installed in the air-conditioned space. The outdoor unit 1 and the indoor unit 3 are connected via a refrigerant pipe 4 , and a refrigerant circuit 5 is formed by the outdoor unit 1 , the indoor unit 3 and the refrigerant pipe 4 .

The outdoor unit 1 includes a compressor 10, a flow path switching device 11, an outdoor fan 12, an outdoor heat exchanger 13, an expansion valve 14, and an accumulator 15 inside a housing indicated by a dashed-dotted square in FIG. . The accumulator 15 , the compressor 10 , the flow switching device 11 , the outdoor heat exchanger 13 and the expansion valve 14 are sequentially connected by the refrigerant pipes 4 .

The compressor 10 sucks refrigerant from the refrigerant pipe 4 , compresses the sucked refrigerant, and discharges the compressed refrigerant to the refrigerant pipe 4 . The compressor 10 is, for example, an inverter compressor whose capacity can be controlled by an inverter.

The channel switching device 11 is, for example, a four-way valve that switches the direction of refrigerant flow. The air conditioner 100 can switch from the heating operation to the cooling operation or the defrosting operation by switching processing by the flow path switching device 11, and switches from the cooling operation or the defrosting operation to the heating operation. be able to. The solid line portion in the flow switching device 11 shown in FIG. 1 indicates the refrigerant flow path during the cooling operation and the defrosting operation, and the broken line portion indicates the refrigerant flow path during the heating operation. In FIG. 1 , solid arrows indicate the direction of refrigerant flow during cooling operation and defrosting operation, and broken arrows indicate the direction of refrigerant flow during heating operation.

The outdoor blower 12 includes an outdoor drive source 12A such as a fan motor, and an outdoor fan 12B such as a propeller fan, turbo fan, or sirocco fan. The outdoor fan 12 operates during the cooling operation and during the heating operation, and guides the air in the space other than the air-conditioned space to the outdoor heat exchanger 13 .

The outdoor heat exchanger 13 causes heat exchange between refrigerant and air. The outdoor heat exchanger 13 is an example of a heat exchanger.

The outdoor blower 12 sends the air after heat exchange in the outdoor heat exchanger 13 to a space other than the air-conditioned space during the cooling operation and the heating operation.

The expansion valve 14 decompresses and expands the refrigerant. The expansion valve 14 is, for example, an electric expansion valve capable of adjusting the flow rate of refrigerant. The accumulator 15 stores refrigerant.

The indoor unit 3 includes an indoor fan 30 and an indoor heat exchanger 31 inside a housing indicated by a two-dot chain line square in FIG. Indoor fan 30 includes an indoor drive source 30A such as a fan motor, and an indoor fan 30B such as a propeller fan, turbo fan, or sirocco fan. The indoor fan 30 operates during the cooling operation and during the heating operation, and guides the air in the air-conditioned space to the indoor heat exchanger 31 .

The indoor heat exchanger 31 causes heat exchange between refrigerant and air. The indoor blower 30 sends out the air after heat exchange in the indoor heat exchanger 31 to the air-conditioned space during the cooling operation and the heating operation.

The following describes the refrigerant flow and state changes during cooling operation. In cooling operation, refrigerant discharged from the compressor 10 flows into the outdoor heat exchanger 13 . The outdoor heat exchanger 13 functions as a condenser, and the refrigerant flowing into the outdoor heat exchanger 13 exchanges heat with the air supplied to the outdoor heat exchanger 13 by the outdoor fan 12 and is condensed. The refrigerant that has flowed out of the outdoor heat exchanger 13 flows into the indoor heat exchanger 31 after being decompressed when passing through the expansion valve 14 . The indoor heat exchanger 31 functions as an evaporator, and the refrigerant flowing into the indoor heat exchanger 31 exchanges heat with the air supplied to the indoor heat exchanger 31 by the indoor blower 30 and evaporates. The air cooled by heat exchange in the indoor heat exchanger 31 is sent out to the air-conditioned space by the indoor blower 30 . The refrigerant that has flowed out of the indoor heat exchanger 31 is sucked into the compressor 10 via the accumulator 15 and compressed.

Next, the refrigerant flow and state changes during heating operation will be explained. In heating operation, the refrigerant discharged from the compressor 10 flows into the indoor heat exchanger 31 . The indoor heat exchanger 31 functions as a condenser, and the refrigerant flowing into the indoor heat exchanger 31 exchanges heat with the air supplied to the indoor heat exchanger 31 by the indoor blower 30 and is condensed. The air heated by heat exchange in the indoor heat exchanger 31 is sent out to the air-conditioned space by the indoor blower 30 . The refrigerant that has flowed out of the indoor heat exchanger 31 flows into the outdoor heat exchanger 13 after being decompressed when passing through the expansion valve 14 . The outdoor heat exchanger 13 functions as an evaporator, and the refrigerant that has flowed into the outdoor heat exchanger 13 exchanges heat with the air supplied to the outdoor heat exchanger 13 by the outdoor blower 12 and evaporates. The refrigerant that has flowed out of the outdoor heat exchanger 13 is sucked into the compressor 10 via the accumulator 15 and compressed.

Furthermore, the refrigerant flow and state changes during defrosting operation will be explained. The defrosting operation is started when it is detected that the heat transfer performance of the outdoor heat exchanger 13 has deteriorated due to frost generated in the outdoor heat exchanger 13 during the heating operation. A decrease in the heat transfer performance of the outdoor heat exchanger 13 is detected based on a physical quantity such as the surface temperature of the heat transfer tubes 21, which will be described later, in the outdoor heat exchanger 13, for example. In the defrosting operation, the refrigerant flows in the same direction as in the cooling operation, the outdoor heat exchanger 13 functions as a condenser, and the indoor heat exchanger 31 functions as an evaporator. Here, the outdoor fan 12 does not operate during the defrosting operation. As a result, in the outdoor heat exchanger 13 , the air heated by the refrigerant that is in a superheated state and is in a gaseous state is prevented from flowing out of the outdoor heat exchanger 13 . Therefore, the outflow of heat from the outdoor heat exchanger 13 is suppressed, and quick defrosting becomes possible. Also, the indoor fan 30 does not operate during the defrosting operation. This suppresses the outflow of the air cooled by the refrigerant in the indoor heat exchanger 31 to the air-conditioned space. Therefore, the temperature drop in the air-conditioned space is suppressed. The air conditioner 100 performs a defrosting operation intermittently during heating operation under a low outdoor air condition where the outdoor temperature is, for example, 5 [° C.] or less, thereby recovering the heat transfer performance of the outdoor heat exchanger 13. do. As a result, it becomes possible to maintain the operating efficiency of the heating operation for a long period of time.

Next, the configuration of the outdoor heat exchanger 13 in Embodiment 1 will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a diagram schematically illustrating the inside of the outdoor heat exchanger according to Embodiment 1. FIG. FIG. 3 is a diagram schematically illustrating refrigerant flow paths in the outdoor heat exchanger according to Embodiment 1. FIG. The outdoor heat exchanger 13 illustrated in FIG. 2 is a cross-fin tube type heat exchanger. The white arrows in FIG. 2 indicate the direction of air flow.

The outdoor heat exchanger 13 in Embodiment 1 has a plurality of units 20, and each of the plurality of units 20 is arranged along the vertical direction. Note that the lowest unit 20 among the plurality of units 20 may be referred to as the lowest unit 20A, and the units 20 other than the lowest unit 20A may be referred to as the upper unit 20B.

Each unit 20 includes one or more heat transfer tubes 21 through which the refrigerant flows. In FIG. 2, one or more heat transfer tubes 21 are indicated by hatched areas. One or more heat transfer tubes 21 pass through a plurality of heat transfer fins 22 included in the outdoor heat exchanger 13 . Each of the plurality of heat transfer fins 22 is arranged along the air flow direction. The plurality of heat transfer fins 22 are arranged at predetermined intervals.

One or more heat transfer tubes 21 of each unit 20 in Embodiment 1 form a forked refrigerant flow path 23M such as a two-forked or three-forked shape. 2 and 3 illustrate a bifurcated coolant channel 23M as the forked coolant channel 23M formed by one or more heat transfer tubes 21. FIG. Note that in FIG. 2 , the circle pointed by the solid line arrow indicates the entrance when the refrigerant flows into the one or more heat transfer tubes 21 during the defrosting operation. In addition, the circle located at the starting point of the solid line arrow indicates the outlet when the refrigerant flows out from the one or more heat transfer tubes 21 during the defrosting operation. The crotch-shaped coolant channel 23M is indicated by a hatched area indicating the heat transfer tube 21 and dashed lines connecting a plurality of the areas. Solid arrows in FIGS. 2 and 3 indicate the direction in which the refrigerant flows during the defrosting operation.

The crotch-shaped coolant channel 23M is formed by connecting a single channel 23A, which is one coolant channel 23, and a double channel 23B, which is a plurality of coolant channels 23. The forked refrigerant channel 23M may be formed by a plurality of heat transfer tubes 21, and each unit 20 includes a heat transfer tube 21 forming a single path 23A and a plurality of heat transfer tubes 21 forming a double path 23B. It may include a connection such as a branch pipe that connects the It should be noted that the number of refrigerant flow paths 23 included in the double path 23B of each unit 20 in Embodiment 1 is equal to each other.

In each unit 20, of the one or more heat transfer tubes 21, the part forming the double path 23B is connected to the gas side flow divider 16, and the part forming the single path 23A is connected to the liquid side flow divider 17. there is During cooling operation, that is, when the outdoor heat exchanger 13 functions as a condenser, the refrigerant that has flowed into the gas side flow divider 16 flows through multiple outlets of the gas side flow divider 16 into the double path 23B. do. The refrigerant flowing into the gas side flow divider 16 is gaseous and high-temperature superheated gas refrigerant. The refrigerant that has flowed into the double path 23B flows into the single path 23A and joins. Thereafter, the refrigerant flows from the single path 23</b>A to the liquid side flow divider 17 and flows out to the refrigerant pipe 4 via the liquid side flow divider 17 . When the refrigerant flows through one or more heat transfer tubes 21 during cooling operation, the refrigerant gives heat to the air, becomes a gas-liquid two-phase state in which a part of the refrigerant phase changes to a liquid phase, and after all becomes a saturated liquid state. , the temperature drops and becomes a supercooled liquid state.

During heating operation, that is, when the outdoor heat exchanger 13 operates as an evaporator, the gas-liquid two-phase refrigerant that has flowed into the liquid side flow divider 17 flows into the single path 23A. Refrigerant flowing through the single path 23A flows into the double path 23B. After that, the refrigerant flows from the double path 23B to the gas side flow divider 16 and flows out to the refrigerant pipe 4 via the gas side flow divider 16 . When the refrigerant flows through one or more heat transfer tubes 21 during heating operation, the refrigerant takes heat from the air and enters a gas-liquid two-phase state in which a part of the refrigerant undergoes a phase change to a gas phase, and all of them are in a saturated gas state. After that, the temperature rises and becomes a superheated gas state.

According to the above configuration, the refrigerant flows from the double path 23B to the single path 23A during cooling operation, thereby increasing the average flow velocity of the refrigerant in the single path 23A. During cooling operation, a supercooled liquid refrigerant having a low heat transfer coefficient flows downstream of the single passage 23A, but the flow velocity of the refrigerant increases in the single passage 23A, thereby promoting convective heat transfer and improving the heat transfer coefficient. Therefore, the effect of reducing the amount of refrigerant required for air conditioning can be obtained.

On the other hand, during heating operation, the dryness increases from upstream to downstream of the refrigerant flow path 23 . Therefore, conventionally, the average flow velocity of the refrigerant increases downstream of the refrigerant flow path 23, thereby increasing the friction acting on the refrigerant and increasing the pressure loss. In Embodiment 1, since the refrigerant flows from the single path 23A to the double path 23B during heating operation, an increase in the average flow velocity of the refrigerant in the double path 23B on the downstream side is suppressed, or the average flow velocity is reduced. . Therefore, the friction acting between the refrigerant and the inner wall surface of the part forming the double path 23B among the one or more heat transfer tubes 21 is reduced. As a result, pressure loss can be reduced. Therefore, it is possible to reduce the change in the saturation temperature of the refrigerant due to the pressure loss and ensure the temperature difference between the refrigerant and the air.

In Embodiment 1, one refrigerant passage 23 of the double paths 23B in the lowermost unit 20A has a refrigerant inlet during the defrosting operation in the forked refrigerant passage 23M in the air flow direction. Arranged on the most upstream side. In the following description, the one refrigerant passage 23 in which the inlet of the refrigerant during the defrosting operation is arranged on the most upstream side in the air flow direction in the crotch-shaped refrigerant passage 23M is referred to as the first passage 24. It may be described. Further, the most upstream side in the air flow direction in the outdoor heat exchanger 13 may be referred to as the windward side. The most downstream side in the air flow direction in the outdoor heat exchanger 13 may also be referred to as the leeward side. Furthermore, the inlet of the refrigerant to the double path 23B of each unit 20 during the defrosting operation may be referred to as the first inlet 25 in some cases. In Embodiment 1, the first inlet 25 of the first channel 24 is arranged at the bottom. That is, the first inlet 25 of the first channel 24 is arranged at the bottom of the crotch-shaped coolant channel 23M in the lowest unit 20A.

The effects of the air conditioner 100 according to Embodiment 1 will be described below. Air conditioner 100 performs each of heating operation and defrosting operation. The air conditioner 100 includes an outdoor heat exchanger 13 and a channel switching device 11 . The outdoor heat exchanger 13 exchanges heat between the outdoor air and the refrigerant. The channel switching device 11 switches the direction in which the coolant flows. The outdoor heat exchanger 13 has a plurality of units 20 arranged along the vertical direction. Each unit 20 includes one or more coolant flow paths 23M that form a crotch-shaped coolant flow path 23M, in which a single flow path 23A that is one flow path 23 and a double flow path 23B that is a plurality of flow paths 23 are connected. A heat transfer tube 21 is included. The flow switching device 11 circulates the refrigerant from the double path 23B to the single path 23A during the defrosting operation, and circulates the refrigerant from the single path 23A to the double path 23B during the heating operation. The double path 23B of the lowermost unit 20A arranged at the bottom among the plurality of units 20 includes the first flow path 24 . The first flow path 24 is the refrigerant flow path 23 in which the first inlet 25, which is the inlet of the refrigerant during the defrosting operation, is located on the most upstream side in the air flow direction in the crotch-shaped refrigerant flow path 23M. The first inlet 25 of the first channel 24 is located at the lowest position in the crotch-shaped coolant channel 23M.

According to the above configuration, it is possible to achieve both an improvement in heating capacity and suppression of frost formation. This will be described in detail below. During heating operation, the double path 23B of each unit 20 of the outdoor heat exchanger 13 is on the downstream side of the refrigerant. Therefore, the dry refrigerant in double path 23B is decelerated, and the refrigerant can receive more heat from the air. In addition, the deceleration of the refrigerant reduces the friction between the refrigerant and the heat transfer tubes 21, thereby reducing the pressure loss. Therefore, the heating capacity of the outdoor heat exchanger 13 is improved.

Further, according to the air conditioner 100, the first inlet 25 of the first flow path 24 included in the double path 23B of the lowermost unit 20A is located on the most upstream side in the air flow direction in the crotch-shaped refrigerant flow path 23M. Located in Furthermore, the first inlet 25 of the first flow path 24 is positioned at the bottom in the crotch-shaped coolant flow path 23M.

Here, the heat transfer coefficient between the air and the refrigerant is often higher on the windward side than on the leeward side. Specifically, a temperature boundary layer occurs between two substances having different temperatures, and the thinner the temperature boundary layer, the higher the heat transfer coefficient. On the windward side of the outdoor heat exchanger 13, the temperature boundary layer between the air and the surfaces of the heat transfer tubes 21 in which the refrigerant flows is thinner than on the leeward side. Therefore, the heat transfer coefficient between the air and the refrigerant on the windward side of the outdoor heat exchanger 13 is higher than the heat transfer coefficient between the air and the refrigerant on the leeward side of the outdoor heat exchanger 13 . Also, during heating operation, the air on the windward side of the outdoor heat exchanger 13 has a higher absolute humidity than the air on the leeward side. Therefore, during heating operation, a large amount of frost is generated on the windward end of the heat transfer fins 22 .

On the other hand, during the defrosting operation, melted water produced by melting the frost formed on the surfaces of the heat transfer fins 22 in the upper unit 20B flows downward along the surfaces of the heat transfer fins 22 according to gravity. The melted water further flows down along the heat transfer fins 22 in the lowest unit 20A, flows below the refrigerant flow path 23 located at the lowest position, and is discharged from the outdoor heat exchanger 13 .

As described above, during heating operation, more frost occurs on the windward side, and during defrosting operation, melted water flows downward. Most of the meltwater flows around the lowest part of the High-temperature refrigerant flows into the first flow path 24 from the first inlet 25 during the defrosting operation. By arranging the first inlet 25 of the first flow path 24 on the windward side and at the lowest position in the outdoor heat exchanger 13, the temperature of a portion serving as a route for many melted water increases. , re-occurrence of frost at the location is suppressed, and smooth discharge of the melt water becomes possible. Therefore, the amount of frost formed in the outdoor heat exchanger 13 can be reduced. Therefore, the air conditioner 100 can achieve both suppression of frost formation on the outdoor heat exchanger 13 and improvement of the heating capacity of the outdoor heat exchanger 13 .

The number of refrigerant flow paths 23 included in the double path 23B of each unit 20 in Embodiment 1 is the same. As a result, the pressure loss of the refrigerant in each unit 20 is equalized, and the distribution ratio of the flow rate of the refrigerant is equalized.

A plurality of units 20 in Embodiment 1 include an upper unit 20B arranged above a lowermost unit 20A. The first inlets 25 of all the refrigerant flow paths 23 included in the double path 23B of the upper unit 20B are located on the most downstream side in the air flow direction in the forked refrigerant flow path 23M of the upper unit 20B. Thereby, the air conditioner 100 can maintain the cooling capacity. This will be described in detail below.

When the first inlet 25 into which the high-temperature refrigerant flows during cooling operation is arranged on the windward side, the air is heated on the windward side, so that the temperature difference between the air and the refrigerant on the leeward side becomes small, and heat transfer occurs. The performance is reduced and the cooling of the refrigerant is hindered. In the upper unit 20B of Embodiment 1, the first inlet 25 into which the high-temperature refrigerant flows during the cooling operation is arranged on the leeward side. The outlet portion of the single path 23A, through which the refrigerant flows out during the cooling operation, is arranged on the windward side. As a result, the temperature difference between the air and the refrigerant in the outdoor heat exchanger 13 is maintained, thereby maintaining the cooling capacity.

Embodiment 2.
FIG. 4 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 2. FIG. In Embodiment 2, the same code|symbol shall be attached|subjected to the component similar to the component in Embodiment 1. FIG. Further, in the second embodiment, descriptions of the same configurations as those in the first embodiment and the same functions as the functions in the first embodiment will be omitted unless there are special circumstances.

The configuration of the upper unit 20B in the second embodiment is the same as in the first embodiment. In the lowest unit 20A in Embodiment 2, all the first inlets 25 are arranged at the lowest position in the crotch-shaped coolant channel 23M.

The effects of the air conditioner 100 according to Embodiment 2 will be described below. The first inlets 25 of all the refrigerant flow paths 23 included in the double path 23B of the lowermost unit 20A in the second embodiment are located at the lowest position in the crotch-shaped refrigerant flow path 23M. According to this configuration, when the melted water generated during the defrosting operation flows to a drainage mechanism (not shown) disposed further below the bottom of the outdoor heat exchanger 13, each of all the first inlets 25 heated by the superheated gas refrigerant flowing from the Therefore, refreezing of the melted water is suppressed. Therefore, it is possible to smoothly discharge the melted water during the defrosting operation.

Embodiment 3.
FIG. 5 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 3. FIG. In the third embodiment, the same reference numerals are given to the same constituent elements as those in the first and second embodiments. Further, in Embodiment 3, there are no special circumstances regarding the same configuration as the configuration in Embodiments 1 and 2, and the same function as the function in Embodiments 1 and 2. The explanation is omitted as much as possible.

The configuration of the bottom unit 20A in the third embodiment is the same as in the first embodiment. In Embodiment 3, the outdoor heat exchanger 13 has a plurality of upper units 20B. In Embodiment 3, the shape of the crotch-like coolant flow path 23M in each of the plurality of upper units 20B is the same. This makes it possible to reduce the number of types of shapes of the heat transfer tubes 21 in the upper unit 20B. In addition, it is possible to reduce the number of types of shapes of pipes connecting heat transfer pipes 21 to gas side flow dividers 16 and liquid side flow dividers 17 . Therefore, the production process of the outdoor heat exchanger 13 can be simplified.

Embodiment 4.
FIG. 6 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 4. FIG. In the fourth embodiment, the same reference numerals are given to the same components as those in the first to third embodiments. In addition, in the fourth embodiment, there are no particular circumstances regarding the same configuration as the configurations in the first to third embodiments and the same functions as the functions in the first to third embodiments. The explanation is omitted as much as possible.

The configuration of the bottom unit 20A in the fourth embodiment is the same as in the second embodiment. The outdoor heat exchanger 13 of the fourth embodiment has a plurality of upper units 20B, and the configuration of the plurality of upper units 20B is the same as that of the third embodiment. That is, the shapes of the crotch-like refrigerant flow paths 23M obtained by the one or more heat transfer tubes 21 of each upper unit 20B are the same. Therefore, in Embodiment 4, smooth discharge of melted water in the lowest unit 20A during defrosting operation and simplification of the production process of the outdoor heat exchanger 13 are possible.

Embodiment 5.
FIG. 7 is a diagram schematically illustrating the inside of an outdoor heat exchanger according to Embodiment 5. FIG. In the fifth embodiment, the same reference numerals are given to the same components as those in the first to fourth embodiments. Further, in the fifth embodiment, there are no special circumstances regarding the same configuration as the configurations in the first to fourth embodiments and the same functions as the functions in the first to fourth embodiments. The explanation is omitted as much as possible.

The configuration of the upper unit 20B in the fifth embodiment is the same as in the first to fourth embodiments. In the lowest unit 20A of Embodiment 5, the length of the first channel 24 is the shortest among all the coolant channels 23 included in the double channel 23B.

According to the above configuration, in the lowermost unit 20A, the distribution ratio of the refrigerant flowing into the first flow path 24 is greater than the distribution ratio of the refrigerant flowing into the other refrigerant flow paths 23 of the multiple paths 23B. The refrigerant flowing into the double path 23B during the defrosting operation is a gas single-phase refrigerant, and the heat transfer coefficient monotonously increases according to the flow rate. That is, in the lowest unit 20A during the defrosting operation, the inner-pipe heat transfer coefficient in the first passage 24 becomes larger than the inner-pipe heat transfer coefficient in the other refrigerant passages 23 of the double passages 23B. As a result, the area around the first inlet 25 located on the windward side can be quickly heated during the defrosting operation, and the melted water can be discharged more smoothly.

Embodiment 6.
FIG. 8 is a perspective view illustrating a specific configuration of part of the outdoor heat exchanger according to Embodiment 6. FIG. In the sixth embodiment, the same reference numerals are given to the same components as those in the first to fifth embodiments. In addition, in Embodiment 6, there are no particular circumstances with regard to the same configuration as in Embodiments 1 to 5, and the same functions as in Embodiments 1 to 5. The explanation is omitted as much as possible.

The configuration of the outdoor heat exchanger 13 in Embodiment 6 is the same as in Embodiments 1 to 5. In FIG. 8, white arrows indicate the direction of air flow, and solid arrows indicate the direction of refrigerant flow during the defrosting operation. As shown in FIG. 8 , the outdoor heat exchanger 13 is provided with a gas side flow divider 16 and a liquid side flow divider 17 . The gas side flow divider 16 has a main pipe 16A and a plurality of branch pipes 16B branched from the main pipe 16A. 16 A of trunk pipes are arrange|positioned so that a longitudinal direction may turn into a vertical direction. The outer diameter of the trunk pipe 16A is larger than the outer diameter of the heat transfer tube 21 . On the other hand, the outer diameter of the branch pipe 16B is equal to or less than the diameter of the first inlet 25 . The tip of the branch pipe 16B is connected to the end corresponding to the first inlet 25 among the one or more heat transfer tubes 21 . With such a configuration, the pressure loss of the refrigerant in the gas side flow divider 16 can be suppressed. Moreover, since the piping processing can be simplified, the production cost can be suppressed.

The liquid side flow divider 17 has a main body 17A and a plurality of flow division pipes 17B. The main body 17A is cylindrical and arranged so that the height direction of the cylinder is the vertical direction. The outer diameter of main body 17A is larger than the outer diameter of heat transfer tube 21 . The flow dividing tube 17B has an outer diameter smaller than that of the heat transfer tube 21 and an inner diameter of 3.0 [mm] or less. One end of each of the plurality of branch pipes 17B is connected to the main body 17A so as to be positioned at regular intervals along the circumference of the bottom surface of the main body 17A. The other end of the branch tube 17B is connected to a portion of the one or more heat transfer tubes 21 that forms an outlet in the single path 23A through which the refrigerant flows out of the unit 20 during the defrosting operation. According to such a configuration, during heating operation, the two-phase flow of the refrigerant passing through the main body 17A while forming an annular flow is directed to the branch pipes 17B connected at equal intervals along the circumference of the bottom surface of the main body 17A. On the other hand, it becomes possible to distribute the liquid refrigerant and the gas refrigerant so that the ratio becomes equal. In addition, by selecting the length and inner diameter of the branch pipe 17B, the distribution ratio of the refrigerant to each refrigerant flow path 23 in the outdoor heat exchanger 13 can be adjusted to each refrigerant flow path 23 due to the wind speed distribution generated in the outdoor heat exchanger 13. It can be according to the heat load distribution of Thereby, the heat transfer loss due to the mismatch of the distribution ratio between the heat load and the flow rate of the refrigerant can be reduced. In addition, during cooling operation, pressure loss caused by friction caused by accelerating the supercooled liquid refrigerant flowing out of the single path 23A by the branch pipe 17B having a small inner diameter causes the single path 23A of each unit 20 stacked in the vertical direction. It is possible to reduce the influence of deterioration in flow distribution due to head differences caused by height differences.

Embodiments 1 to 6 describe the air conditioner 100 that performs the cooling operation, the heating operation, and the defrosting operation, but the air conditioner 100 performs only the heating operation and the defrosting operation. may

Although the embodiment has been described above, the content of the present disclosure is not limited to the embodiment, and includes a conceivable equivalent range.

1 Outdoor unit, 3 Indoor unit, 4 Refrigerant piping, 5 Refrigerant circuit, 10 Compressor, 11 Flow switching device, 12 Outdoor fan, 12A Outdoor drive source, 12B Outdoor fan, 13 Outdoor heat exchanger, 14 Expansion valve, 15 Accumulator, 16 gas side flow divider, 16A trunk pipe, 16B branch pipe, 17 liquid side flow divider, 17A main body, 17B branch pipe, 20 unit, 20A bottom unit, 20B upper unit, 21 heat transfer tube, 22 heat transfer fin, 23 refrigerant passage, 23A single passage, 23B double passage, 23M forked refrigerant passage, 24 first passage, 25 first inlet, 30 indoor blower, 30A indoor drive source, 30B indoor fan, 31 indoor heat exchanger , 100 air conditioner.

Claims

An air conditioner that performs each of heating operation and defrosting operation,
a heat exchanger for exchanging heat between the outdoor air and the refrigerant;
a channel switching device for switching the direction of flow of the coolant;
with
The heat exchanger is
having a plurality of units arranged along the vertical direction,
each of the plurality of units,
One or more heat transfer tubes forming a crotch-shaped refrigerant flow path in which a single refrigerant flow path and a plurality of double refrigerant flow paths are connected,
The flow path switching device is
During the defrosting operation, the refrigerant is circulated from the double path to the single path, and during the heating operation, the refrigerant is circulated from the single path to the double path,
The double path of the lowest unit arranged at the lowest among the plurality of units,
The inlet of the refrigerant during the defrosting operation includes a first flow path which is the refrigerant flow path located most upstream in the flow direction of the air in the crotch-shaped refrigerant flow path,
the inlet of the first flow path,
An air conditioner located at the lowest position in the crotch-shaped refrigerant channel.
The air conditioner according to claim 1, wherein the number of refrigerant passages included in each of said double paths of said plurality of units is the same.
The air conditioner according to claim 1 or 2, wherein the inlet of each of all refrigerant flow paths included in the double path of the lowermost unit is located at the lowest position in the crotch-shaped refrigerant flow path.
The plurality of units are
an upper unit positioned above the lowermost unit;
2. The entrance of each of all the refrigerant passages included in the double path of the upper unit is positioned most downstream in the flow direction of the air in the crotch-shaped refrigerant passage of the upper unit. The air conditioner according to any one of claims 3 to 4.
The plurality of units are
including a plurality of said upper units;
The air conditioner according to claim 4, wherein the forked refrigerant circuits in each of the plurality of upper units have the same shape.
The air conditioner according to any one of claims 1 to 5, wherein the first flow path is the shortest of all refrigerant flow paths included in the double path in the lowermost unit.