JP7693095B2 - Outdoor unit of air conditioner and air conditioner - Google Patents

Description

The present disclosure relates to an outdoor unit for an air conditioning system and an air conditioning system in which a heat exchanger is formed by providing a plurality of heat exchange bodies each having a plurality of flat tubes.

Heat exchangers that use flat tubes as heat transfer tubes are known. Flat tubes have a smaller diameter than circular tubes, so when they are used as heat transfer tubes in a heat exchanger, the number of refrigerant branches increases compared to when circular tubes are used as heat transfer tubes. In order for the heat exchanger to perform efficiently, the two-phase gas-liquid refrigerant flowing through a collecting pipe such as a header needs to be appropriately distributed to each flat tube according to the amount of heat exchange in the heat exchanger.

For example, Patent Document 1 describes an outdoor unit of an air conditioner equipped with a heat exchanger that uses flattened tubes as heat transfer tubes. This outdoor unit is configured to include a heat exchanger equipped with a heat exchanger having a heat exchanger body with a plurality of flat tubes that extend vertically and are arranged horizontally at intervals. The heat exchanger is provided with a plurality of heat exchangers in the air flow direction, and a header into which hot gas refrigerant flows from the refrigerant circuit is provided at the bottom of the heat exchanger that is the most windward of the plurality of heat exchangers. In addition, a double-pipe distributor that distributes the refrigerant in a gas-liquid two-phase state when the heat exchanger functions as an evaporator is provided at the bottom of the heat exchanger that is the most downwind of the plurality of heat exchangers. By providing such a distributor, the heating capacity of the heat exchanger can be improved.

International Publication No. 2019/239446

In the outdoor unit of an air conditioner, multiple heat exchangers may be connected in series. Also, a partition may be provided inside the header of one heat exchanger, so that the single heat exchanger is used as if it were two heat exchangers connected in series.

When the heat exchangers described in Patent Document 1 are used as multiple heat exchangers connected in series and function as condensers, the refrigerant in a gas-liquid two-phase state flows into the heat exchanger located downstream of the refrigerant flow. In this case, the refrigerant is distributed in the header of the heat exchanger into which the refrigerant in a gas-liquid two-phase state flows, with more gas refrigerant present at the front near the inlet and more liquid refrigerant present at the back.

Thus, when the heat exchanger described in Patent Document 1 functions as a condenser, the refrigerant in a two-phase gas-liquid state flowing into the downstream heat exchanger is not properly distributed to each flat tube due to its distribution state, which causes a problem in that the condenser performance of the heat exchanger deteriorates.

The present disclosure has been made in consideration of the problems with the above-mentioned conventional technology, and aims to provide an outdoor unit for an air conditioner and an air conditioner that can improve refrigerant distribution and enhance heat exchange performance when multiple heat exchangers connected in series function as condensers.

The outdoor unit of an air conditioner according to the present disclosure is an outdoor unit of an air conditioner equipped with a heat exchanger having a first heat exchanger and a second heat exchanger connected in series, the first heat exchanger being connected to the downstream side of a refrigerant flow when the heat exchanger functions as a condenser relative to the second heat exchanger, and comprising: a plurality of heat exchange bodies arranged in an air flow direction, the plurality of heat exchange bodies having a vertical tube extension direction and a plurality of flat tubes arranged at intervals in the horizontal direction; a first header provided under an inlet side heat exchange body, among the plurality of heat exchange bodies, into which a refrigerant flows when the heat exchanger functions as a condenser; and a second header provided under an inlet side heat exchange body, among the plurality of heat exchange bodies, into which a refrigerant flows when the heat exchanger functions as an evaporator, the first header being connected to the downstream side of a refrigerant flow when the heat exchanger functions as an evaporator. The first header has a double-pipe structure having an inner pipe in which orifices are formed at intervals, and an outer pipe into which the inner pipe is inserted, and the orifices formed in the first header are formed in the inner pipe so as to open at a circumferential angle from a lower end of the inner pipe on a vertical line passing through the center of the inner pipe by a preset first angle. The second header has a double-pipe structure having an inner pipe in which a plurality of orifices through which the refrigerant flows are formed at intervals, and an outer pipe into which the inner pipe is inserted, and the orifices formed in the second header are formed in the inner pipe so as to open at a circumferential angle from a lower end of the inner pipe on a vertical line passing through the center of the inner pipe of the second header by a preset second angle, and the second angle is formed so as to be different from the first angle .

Furthermore, the air conditioning apparatus according to the present disclosure is equipped with the above-mentioned outdoor unit.

According to the present disclosure, in a first heat exchanger connected downstream of the refrigerant flow when the heat exchanger functions as a condenser, a first header is provided under the heat exchange body on the inlet side where the refrigerant flows in. In addition, the first header has a double-pipe structure, and a plurality of orifices through which the refrigerant flows are formed at intervals in the inner pipe. As a result, when the heat exchanger functions as a condenser, the refrigerant flowing into the first heat exchanger is uniformly distributed, thereby improving the heat exchange performance of the heat exchanger.

1 is a circuit diagram showing an example of the configuration of an air conditioning apparatus according to Embodiment 1. FIG. 2 is a perspective view showing an example of the appearance of the outdoor unit of FIG. 1 . 2 is a perspective view showing an example of the appearance of a first outdoor heat exchanger according to the first embodiment; FIG. 2 is a perspective view showing an example of the appearance of a second outdoor heat exchanger or a third outdoor heat exchanger according to the first embodiment. FIG. FIG. 4 is a perspective view showing an example of the appearance of the first header of FIG. 3 . 4 is a schematic cross-sectional view showing a cross section of the first header taken along a plane perpendicular to the extension direction. FIG. FIG. 4 is a schematic diagram for explaining an angle of an orifice. 4 is a schematic diagram for illustrating a flow of a refrigerant in the outdoor heat exchanger when the outdoor heat exchanger functions as a condenser. FIG. 4 is a schematic diagram for explaining a flow of refrigerant in the outdoor heat exchanger when the outdoor heat exchanger functions as an evaporator. FIG. 13 is a schematic diagram for explaining the angles of the orifices of the first header and the second header in accordance with the second embodiment. FIG.

Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and can be modified in various ways without departing from the spirit of the present disclosure. The present disclosure also includes all combinations of the configurations shown in the following embodiments that can be combined. In addition, in each figure, the same reference numerals are attached to the same or equivalent parts, and this is common throughout the entire specification. In addition, in the following description, the upper side in FIG. 1 will be described as the "upper side" and the lower side as the "lower side". Furthermore, the high and low of pressure and temperature are not determined in relation to absolute values, but are determined relatively in the state and operation of the device, etc. In addition, hatching has been omitted appropriately in the drawings of cross-sectional views in consideration of visibility.

Embodiment 1.
A description will be given of an air-conditioning apparatus according to the present embodiment 1. The air-conditioning apparatus according to the present embodiment 1 performs air-conditioning of a space to be air-conditioned by circulating a refrigerant in a refrigerant circuit and transferring heat between outdoor air and indoor air via the refrigerant.

[Configuration of the air conditioning device 100]
Fig. 1 is a circuit diagram showing an example of the configuration of an air conditioner according to the first embodiment. As shown in Fig. 1, the air conditioner 100 includes an outdoor unit 10 and one or more indoor units 20. The outdoor unit 10 and the indoor units 20 are connected by a refrigerant pipe through which a refrigerant flows. By connecting the outdoor unit 10 and the indoor units 20 by the refrigerant pipe, a refrigerant circuit in which the refrigerant circulates is formed. In this example, three indoor units 20 are connected, but this is not limited thereto, and the number of indoor units 20 may be one or two, or four or more.

(Outdoor unit 10)
The outdoor unit 10 includes a compressor 11 , a refrigerant flow switching device 12 , an outdoor heat exchanger 13 , an accumulator 14 , and a fan 15 .

The compressor 11 draws in low-temperature, low-pressure refrigerant, compresses it, and discharges high-temperature, high-pressure refrigerant. The compressor 11 is, for example, an inverter compressor whose capacity, which is the amount of refrigerant discharged per unit time, is controlled by changing the operating frequency.

The refrigerant flow path switching device 12 is, for example, a four-way valve, and switches between cooling and heating operation by switching the direction of the refrigerant flow. The refrigerant flow path switching device 12 is not limited to the above-mentioned four-way valve, and may be used in combination with other valves, for example.

The outdoor heat exchanger 13 exchanges heat between the refrigerant and outdoor air supplied by a fan 15, which is a blower installed nearby. Specifically, the outdoor heat exchanger 13 functions as a condenser that releases heat from the refrigerant to the outdoor air during cooling operation, condensing the refrigerant to liquefy it. The outdoor heat exchanger 13 also functions as an evaporator that evaporates the refrigerant to gasify it during heating operation, and absorbs heat from the outdoor air as heat of vaporization.

In this example, the outdoor heat exchanger 13 is configured such that the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c are connected in parallel to each other, and the first outdoor heat exchanger 13a is connected in series to the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c connected in parallel. Here, when the outdoor heat exchanger 13 functions as a condenser, the first outdoor heat exchanger 13a is connected downstream of the refrigerant flow relative to the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c. Note that the "first outdoor heat exchanger 13a", "second outdoor heat exchanger 13b", and "third outdoor heat exchanger 13c" may be referred to as the "first heat exchanger 13a", "second heat exchanger 13b", and "third heat exchanger 13c", respectively.

Furthermore, the configuration of the outdoor heat exchanger 13 is not limited to this example, and in the air-conditioning apparatus 100 according to the first embodiment, it is sufficient that at least two outdoor heat exchangers 13 are connected in series.
Specifically, the outdoor heat exchanger 13 may be, for example, a first outdoor heat exchanger 13a and a second outdoor heat exchanger 13b connected in series. When the outdoor heat exchanger 13 functions as a condenser, the first outdoor heat exchanger 13a is connected downstream of the second outdoor heat exchanger 13b in the refrigerant flow direction.

The fan 15 is a blower for supplying outdoor air to the outdoor heat exchanger 13. The rotation speed of the fan 15 is controlled by a control device (not shown). This controls the condensation capacity or evaporation capacity of the outdoor heat exchanger 13.

The accumulator 14 is provided on the suction side of the compressor 11. The accumulator 14 stores surplus refrigerant caused by the difference in the operating state between cooling operation and heating operation, and surplus refrigerant due to transient changes in operation. Note that the accumulator 14 does not necessarily have to be provided.

(Indoor unit 20)
Each indoor unit 20 has a throttling device 21 and an indoor heat exchanger 22. The throttling device 21 is, for example, an expansion valve, and reduces the pressure of the refrigerant to expand it. The throttling device 21 is, for example, a valve that can control the opening degree, such as an electronic expansion valve.

The indoor heat exchanger 22 exchanges heat between the refrigerant and indoor air supplied by a blower such as a fan (not shown). This generates heating air or cooling air, which is conditioned air supplied to the space to be air-conditioned. The indoor heat exchanger 22 functions as an evaporator during cooling operation. The indoor heat exchanger 22 also functions as a condenser during heating operation.

[Structure of outdoor unit 10]
Fig. 2 is a perspective view showing an example of the appearance of the outdoor unit of Fig. 1. Note that Fig. 2 illustrates the arrangement of the outdoor heat exchanger 13 inside the outdoor unit 10 so as to be clearly understood.

As shown in FIG. 2, the outdoor unit 10 according to the first embodiment is formed in a rectangular parallelepiped shape that is rectangular when viewed from above. In the outdoor unit 10, the first outdoor heat exchanger 13a, the second outdoor heat exchanger 13b, and the third outdoor heat exchanger 13c are arranged in a C-shape along three of the four side surfaces. In addition, a fan 15 is provided at the top of the outdoor unit 10 to blow air upward. In this way, the outdoor unit 10 according to the first embodiment is a top-flow type in which the fan 15 that blows air upward is arranged above the outdoor heat exchanger 13, which is composed of multiple heat exchangers.

(First outdoor heat exchanger 13a)
Fig. 3 is a perspective view showing an example of the appearance of the first outdoor heat exchanger according to the embodiment 1. The white arrows in Fig. 3 indicate the flow of air generated by the fan 15. Moreover, the dotted arrows indicate the flow of the refrigerant when the outdoor heat exchanger 13 functions as a condenser.

As shown in Fig. 3, the first outdoor heat exchanger 13a has a plurality of heat exchange bodies 50 arranged side by side in the air flow direction. In this example, two heat exchange bodies 50 are the same size and arranged side by side in the air flow direction.

The heat exchange body 50 has a plurality of flat tubes 51 arranged horizontally at intervals with the tube extension direction being the vertical direction. The flat tubes 51 are arranged in parallel in the horizontal direction at intervals so that the wind generated by the fan 15 can flow, and the refrigerant flows vertically in the tubes extending in the vertical direction.

In addition, fins 52 are provided between adjacent flat tubes 51 and joined to the flat tubes 51 to transfer heat to the flat tubes 51. The fins 52 improve the efficiency of heat exchange between the air and the refrigerant. For example, corrugated fins are used as the fins 52. Note that, if sufficient heat exchange between the air and the refrigerant can be performed on the surface of the flat tubes 51, the fins 52 do not need to be provided.

A first header 53 is provided at the bottom of the heat exchange body 50 located furthest downwind among the multiple heat exchange bodies 50. The first header 53 extends in the arrangement direction of the multiple flat tubes 51, and the lower ends of the flat tubes 51 of the heat exchange body 50 located furthest downwind are directly inserted into the first header 53. The first header 53 is connected to the refrigerant circuit of the air conditioning device 100 via a refrigerant piping 56.

When the air conditioning device 100 performs cooling operation so that the outdoor heat exchanger 13 functions as a condenser, the two-phase refrigerant flowing out from the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c flows into the first header 53 via the refrigerant piping 56. When the air conditioning device 100 performs heating operation so that the outdoor heat exchanger 13 functions as an evaporator, the first header 53 allows the two-phase refrigerant that has been heat exchanged in the heat exchange body 50 on the most downwind side to flow out via the refrigerant piping 56.

A second header 54 is provided at the bottom of the heat exchange body 50 that is the windwardest of the multiple heat exchange bodies 50. The second header 54 extends in the arrangement direction of the multiple flat tubes 51 and is arranged in parallel to the first header 53. The lower end of the flat tube 51 of the heat exchange body 50 that is arranged the windwardest is directly inserted into the second header 54. The second header 54 is connected to the refrigerant circuit of the air conditioning device 100 via a refrigerant piping 57.

When the outdoor heat exchanger 13 functions as a condenser, the second header 54 allows the liquid refrigerant that has been heat exchanged in the windward-most heat exchange body 50 to flow out through the refrigerant piping 57. When the outdoor heat exchanger 13 functions as an evaporator, the two-phase refrigerant that flows out from the throttling device 21 of the indoor unit 20 flows into the second header 54 through the refrigerant piping 57.

A third header 55 is provided above the heat exchange bodies 50, into which the upper ends of the flat tubes 51 inserted into the first header 53 and the second header 54 are inserted. When the outdoor heat exchanger 13 functions as a condenser, the third header 55 causes the refrigerant flowing in from the flat tubes 51 on the leeward side to flow back into the flat tubes 51 on the windward side. When the outdoor heat exchanger 13 functions as an evaporator, the third header 55 causes the refrigerant flowing in from the flat tubes 51 on the windward side to flow back into the flat tubes 51 on the leeward side.

The multiple flat tubes 51, fins 52, first header 53, second header 54, third header 55, and refrigerant pipes 56 and 57 are each made of, for example, aluminum and are joined by brazing.

(Second outdoor heat exchanger 13b and third outdoor heat exchanger 13c)
Fig. 4 is a perspective view showing an example of the appearance of the second outdoor heat exchanger or the third outdoor heat exchanger according to the embodiment 1. The white arrows in Fig. 4 indicate the flow of air generated by the fan 15. Note that the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c have the same configuration, and therefore, the second outdoor heat exchanger 13b will be described as an example here.

As shown in Fig. 4, the second outdoor heat exchanger 13b, like the first outdoor heat exchanger 13a, has multiple heat exchange bodies 50. In this example, two heat exchange bodies 50 are the same size and are arranged side by side in the air flow direction.

The heat exchange body 50 is provided with a plurality of flat tubes 51 and fins 52, similar to the first outdoor heat exchanger 13a. The fins 52 may not be provided.

A fourth header 63 is provided at the bottom of the heat exchange body 50 located furthest downwind among the multiple heat exchange bodies 50. The fourth header 63 extends in the arrangement direction of the multiple flat tubes 51, and the lower end of the flat tube 51 of the heat exchange body 50 located furthest downwind is directly inserted into this fourth header 63. The fourth header 63 is connected to the refrigerant circuit of the air conditioning device 100 via refrigerant piping 66, and allows hot gas refrigerant to flow in from the refrigerant circuit.

When the air conditioning device 100 performs cooling operation so that the outdoor heat exchanger 13 functions as a condenser, high-temperature, high-pressure gas refrigerant from the compressor 1 flows into the fourth header 63 via the refrigerant piping 66. When the air conditioning device 100 performs heating operation so that the outdoor heat exchanger 13 functions as an evaporator, the fourth header 63 allows the gas refrigerant that has been heat exchanged in the heat exchange body 50 on the most downwind side to flow out via the refrigerant piping 66.

A fifth header 64 is provided at the bottom of the heat exchange body 50 that is the windwardest of the multiple heat exchange bodies 50. The fifth header 64 extends in the arrangement direction of the multiple flat tubes 51 and is arranged in parallel to the fourth header 63. The lower end of the flat tube 51 of the heat exchange body 50 that is arranged the windwardest is directly inserted into the fifth header 64. The fifth header 64 is connected to the refrigerant circuit of the air conditioning device 100 via a refrigerant piping 67.

When the outdoor heat exchanger 13 functions as a condenser, the fifth header 64 allows the two-phase refrigerant that has been heat exchanged in the windward-most heat exchange body 50 to flow out through the refrigerant piping 67. When the outdoor heat exchanger 13 functions as an evaporator, the two-phase refrigerant that has flowed out from the first outdoor heat exchanger 13a flows into the fifth header 64 through the refrigerant piping 67.

A sixth header 65 is provided above the heat exchange bodies 50, into which the upper ends of the flat tubes 51 inserted into the fourth header 63 and the fifth header 64 are inserted. When the outdoor heat exchanger 13 functions as a condenser, the sixth header 65 causes the refrigerant flowing in from the flat tubes 51 on the downwind side to flow back into the flat tubes 51 on the upwind side. When the outdoor heat exchanger 13 functions as an evaporator, the sixth header 65 causes the refrigerant flowing in from the flat tubes 51 on the upwind side to flow back into the flat tubes 51 on the downwind side.

The flat tubes 51, fins 52, fourth header 63, fifth header 64, sixth header 65, and refrigerant pipes 66 and 67 are each made of, for example, aluminum and are joined by brazing.

[Structures of the first header 53, the second header 54 and the fifth header 64]
The structures of the first header 53 and the second header 54 provided in the first outdoor heat exchanger 13a, and the fifth header 64 provided in the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c will be described. Note that the first header 53, the second header 54, and the fifth header 64 have the same structure, and therefore the first header 53 will be described here as an example. Also, the "first header 53," the "second header 54," and the "fifth header 64" in the present embodiment 1 correspond to the "first header," the "second header," and the "third header" in the present disclosure, respectively.

Figure 5 is a perspective view showing an example of the appearance of the first header in Figure 3. Figure 6 is a schematic cross-sectional view showing a cross section of the first header cut along a plane perpendicular to the extension direction. In Figure 5, the internal structure of the first header 53 is shown by dotted lines to make it easier to understand the internal structure of the first header 53.

The first header 53 has a double-tube structure having an inner tube 71 and an outer tube 72. The inner tube 71 and the outer tube 72 extend linearly in the tube extension direction. The inner tube 71 is inserted inside the outer tube 72. The inner tube 71 and the outer tube 72 are joined by brazing.

The inner pipe 71 is, for example, a circular pipe, and is connected to the refrigerant piping 56. The inner pipe 71 has a plurality of orifices 73 formed at intervals in the extension direction through which the refrigerant flows. By forming a plurality of orifices 73 in this way in the inner pipe 71, when the outdoor heat exchanger 13 functions as a condenser, the refrigerant that flows into the inner pipe 71 of the first header 53 via the refrigerant piping 56 flows into the outer pipe 72 via the plurality of orifices 73.

The outer pipe 72 is a pipe with a U-shaped cross section formed in an arc shape at the bottom. The U-shaped cross section of the outer pipe 72 smoothly changes the refrigerant flowing out of the inner pipe 71 through the orifice 73 along the arc.

(Orifice 73)
The multiple orifices 73 are formed to open at a preset angle φ _opt in the circumferential direction from the lower end of the inner pipe 71 on a vertical line passing through the center of the inner pipe 71. By forming the orifices 73 to be inclined at the set angle φ _opt in this manner, the liquid refrigerant and gas refrigerant in the two-phase refrigerant flowing into the inner pipe 71 are distributed uniformly regardless of the distance from the refrigerant inlet side of the first header 53.

Figure 7 is a schematic diagram for explaining the angle of the orifice. In the present embodiment 1, in which the refrigerant in the inner tube 71 exists in two states, liquid and gas, the orifice 73 is provided at a position where the refrigerant in both liquid and gas phases present in the inner tube 71 can pass through appropriately.

Specifically, if the liquid level angle, which is the angle when the slip ratio of the refrigerant gas and liquid is assumed to be 1 and the gas-liquid interface is assumed to be flat and horizontal, is defined as "φ ₀ ", and the wet boundary angle, which is the angle in the circumferential direction of the pipe taking into account the slip ratio of the refrigerant gas and liquid and the inertial force, is defined as "φ _S ", the angle φ _opt is expressed by equation (1).
φ ₀ < φ _opt < φ _S ...(1)

More specifically, the liquid level angle _φ0 is the angle seen from the center of the inner pipe 71 from the lower end of the inner pipe 71 on a vertical line passing through the center of the inner pipe 71 to the liquid level AL that touches the inner pipe 71. Also, the wet boundary angle _φS is the angle seen from the center of the inner pipe 71 from the lower end of the inner pipe 71 on a vertical line passing through the center of the inner pipe 71 to a position reached while touching the inner pipe 71 due to inertial force or the like.

In addition, when the flow path cross-sectional area of the inner tube 71 is defined as "AS [mm ² ]", the liquid level angle φ ₀ is expressed by formula (2), and the wet boundary angle φ _S is expressed by formula (3). Note that formulas (2) and (3) were obtained through studies by the inventors in the document "International Publication No. 2021/235463".
φ ₀ = (-0.0408×AS+74.124)×0.62
... (2)
φ _S = (-0.0408×AS+74.124)×1.2
...(3)

Therefore, the orifices 73 are provided at equal intervals at positions that satisfy formulas (1) to (3). As a result, the two-phase refrigerant that flows into the first header 53 is uniformly distributed to the flat tubes 51 regardless of its position inside the header.

[Refrigerant Operation of the Air Conditioning Device 100]
Next, the operation of the air conditioning device 100 configured in this manner will be described with reference to Fig. 1. Here, as an example, the flow of refrigerant when the air conditioning device 100 performs cooling operation and heating operation will be described. Note that the air conditioning device 100 is not limited to this example, and can also perform various operations that general air conditioning devices are capable of, such as a fan operation and a defrosting operation.

(Cooling operation)
When the air-conditioning apparatus 100 performs cooling operation, first, the refrigerant flow switching device 12 is switched to the state shown by the solid line in Fig. 1. That is, the refrigerant flow switching device 12 is switched so that the discharge side of the compressor 11 is connected to the outdoor heat exchanger 13 and the suction side of the compressor 11 is connected to the indoor heat exchanger 22.

When the compressor 11 is driven, a high-temperature, high-pressure gas refrigerant is discharged from the compressor 11. The high-temperature, high-pressure gas refrigerant discharged from the compressor 11 flows into the outdoor heat exchanger 13, which functions as a condenser, via the refrigerant flow switching device 12. In the outdoor heat exchanger 13, heat exchange takes place between the high-temperature, high-pressure gas refrigerant that has flowed in and the outdoor air supplied by the fan 15. As a result, the high-temperature, high-pressure gas refrigerant condenses into a low-temperature, high-pressure liquid refrigerant, which flows out of the outdoor heat exchanger 13. The low-temperature, high-pressure liquid refrigerant that has flowed out of the outdoor heat exchanger 13 flows out of the outdoor unit 10.

The low-temperature, high-pressure liquid refrigerant flowing out from the outdoor unit 10 flows into each indoor unit 20. In each indoor unit 20, the low-temperature, high-pressure liquid refrigerant expands in the throttling device 21 and becomes a two-phase refrigerant in which the low-temperature, low-pressure gas refrigerant and the liquid refrigerant are mixed. The low-temperature, low-pressure two-phase refrigerant flows into the indoor heat exchanger 22, which functions as an evaporator. In the indoor heat exchanger 22, heat is exchanged between the low-temperature, low-pressure two-phase refrigerant that has flowed in and the indoor air supplied by a blower (not shown). As a result, the liquid refrigerant in the two-phase refrigerant evaporates and becomes a high-temperature, low-pressure gas refrigerant, which flows out from the indoor heat exchanger 22. Then, the high-temperature, low-pressure gas refrigerant that has flowed out from each indoor heat exchanger 22 flows out from the indoor unit 20, merges, and flows into the outdoor unit 10.

The high-temperature, low-pressure gas refrigerant that flows into the outdoor unit 10 flows into the compressor 11 via the refrigerant flow switching device 12 and the accumulator 14. This cycle is then repeated, causing the refrigerant to circulate through the refrigerant circuit.

Figure 8 is a schematic diagram to explain the flow of refrigerant in the outdoor heat exchanger when the outdoor heat exchanger functions as a condenser. In Figure 8, the arrows shown in solid lines indicate the flow of refrigerant in the first to third outdoor heat exchangers 13a to 13c that make up the outdoor heat exchanger 13. Also, the dotted lines indicate the connection state of the first to third outdoor heat exchangers 13a to 13c.

When the outdoor heat exchanger 13 functions as a condenser, such as during cooling operation, the gas refrigerant discharged from the compressor 11 flows into the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c. At this time, the gas refrigerant flows through the refrigerant piping 66 into the fourth header 63, which is located most downstream of the air flow in the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c.

The gas refrigerant that flows into the fourth header 63 condenses as it passes through the connected flat tubes 51 and sixth header 65, becoming a two-phase refrigerant that flows into the outer tube 72 of the fifth header 64. The two-phase refrigerant that flows into the outer tube 72 of the fifth header 64 then flows out of the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c via the inner tube 71 and the refrigerant piping 66.

The two-phase refrigerant flowing out of the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c join together and flow into the first outdoor heat exchanger 13a. The two-phase refrigerant that flowed into the first outdoor heat exchanger 13a flows through the refrigerant piping 56 into the inner pipe 71 of the first header 53, which is located on the most downwind side of the air flow. The two-phase refrigerant that flowed into the inner pipe 71 of the first header 53 flows into the outer pipe 72 through multiple orifices 73.

The two-phase refrigerant that flows into the outer tube 72 of the first header 53 condenses as it passes through the connected flat tubes 51 and the third header 55, and becomes liquid refrigerant and flows into the outer tube 72 of the second header 54. The liquid refrigerant that flows into the outer tube 72 of the second header 54 then flows out of the first outdoor heat exchanger 13a via the inner tube 71 and the refrigerant piping 57.

(Heating operation)
Returning to Fig. 1 , when the air-conditioning apparatus 100 performs heating operation, first, the refrigerant flow switching device 12 is switched to the state shown by the dashed line in Fig. 1. That is, the refrigerant flow switching device 12 is switched so that the discharge side of the compressor 11 is connected to the indoor heat exchanger 22 and the suction side of the compressor 11 is connected to the outdoor heat exchanger 13.

When the compressor 11 is driven, a high-temperature, high-pressure gas refrigerant is discharged from the compressor 11. The high-temperature, high-pressure gas refrigerant discharged from the compressor 11 flows out of the outdoor unit 10 via the refrigerant flow switching device 12. The high-temperature, high-pressure gas refrigerant flowing out of the outdoor unit 10 branches and flows into each indoor unit 20. In each indoor unit 20, the high-temperature, high-pressure gas refrigerant flows into the indoor heat exchanger 22, which functions as a condenser. In the indoor heat exchanger 22, heat exchange occurs between the high-temperature, high-pressure gas refrigerant that has flowed in and the indoor air supplied by a blower (not shown). As a result, the high-temperature, high-pressure gas refrigerant condenses to become a low-temperature, high-pressure liquid refrigerant.

The low-temperature, high-pressure liquid refrigerant flowing out of the indoor heat exchanger 22 expands in the throttling device 21, becoming a two-phase refrigerant in which the low-temperature, low-pressure gas refrigerant and liquid refrigerant are mixed. The low-temperature, low-pressure two-phase refrigerant flows out of each indoor unit 20, merges, and flows into the outdoor unit 10. The low-temperature, low-pressure two-phase refrigerant that flows into the outdoor unit 10 flows into the outdoor heat exchanger 13, which functions as an evaporator. In the outdoor heat exchanger 13, heat exchange occurs between the low-temperature, low-pressure two-phase refrigerant that has flowed in and the outdoor air supplied by the fan 15. As a result, the liquid refrigerant in the two-phase refrigerant evaporates and becomes a high-temperature, low-pressure gas refrigerant. The high-temperature, low-pressure gas refrigerant then flows out of the outdoor heat exchanger 13.

The high-temperature, low-pressure gas refrigerant that flows out of the outdoor heat exchanger 13 flows into the compressor 11 via the refrigerant flow switching device 12 and the accumulator 14. This cycle is then repeated, causing the refrigerant to circulate through the refrigerant circuit.

Figure 9 is a schematic diagram to explain the flow of refrigerant in the outdoor heat exchanger when the outdoor heat exchanger functions as an evaporator. In Figure 9, the arrows shown in solid lines indicate the flow of refrigerant in the first to third outdoor heat exchangers 13a to 13c that make up the outdoor heat exchanger 13. Also, the dotted lines indicate the connection state of the first to third outdoor heat exchangers 13a to 13c.

When the outdoor heat exchanger 13 functions as an evaporator, such as during heating operation, the two-phase refrigerant flowing out of the throttling device 21 of the indoor unit 20 flows into the first outdoor heat exchanger 13a. The two-phase refrigerant that has flowed into the first outdoor heat exchanger 13a flows through the refrigerant piping 57 into the inner pipe 71 of the second header 54, which is located on the windward side of the air flow.

The two-phase refrigerant that flows into the inner tube 71 of the second header 54 flows into the outer tube 72 through a plurality of orifices 73. The two-phase refrigerant that flows into the outer tube 72 of the second header 54 evaporates as it passes through the connected flat tubes 51 and the third header 55, and flows into the outer tube 72 of the first header 53. The two-phase refrigerant that flows into the outer tube 72 of the first header 53 then flows out of the first outdoor heat exchanger 13a through the inner tube 71 and the refrigerant piping 56.

The two-phase refrigerant flowing out of the first outdoor heat exchanger 13a branches and flows into the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c. At this time, the two-phase refrigerant flows through the refrigerant piping 67 into the inner pipe 71 of the fifth header 64, which is located on the windward side of the air flow in the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c.

The two-phase refrigerant that flows into the inner tube 71 of the fifth header 64 flows into the outer tube 72 through a plurality of orifices 73. The two-phase refrigerant that flows into the outer tube 72 of the fifth header 64 evaporates as it passes through the connected flat tubes 51 and the sixth header 65, and becomes a gas refrigerant and flows into the fourth header 63. The gas refrigerant that flows into the fourth header 63 then flows out of the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c through the refrigerant piping 66.

As described above, in the outdoor unit 10 of the air conditioning apparatus 100 according to the first embodiment, the first outdoor heat exchanger 13a is connected in series with the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c on the downstream side of the refrigerant flow when the first outdoor heat exchanger 13a functions as a condenser. In addition, of the multiple heat exchange bodies 50 of the first outdoor heat exchanger 13a, the first header 53 is provided at the bottom of the inlet side heat exchange body into which the refrigerant flows when the first outdoor heat exchanger 13a functions as a condenser. The first header 53 has a double pipe structure having an inner pipe 71 and an outer pipe 72, and the inner pipe 71 has multiple orifices 73 formed at intervals.

Because the outdoor unit 10 has such a configuration, when the outdoor heat exchanger 13 functions as a condenser, the two-phase refrigerant flowing into the first outdoor heat exchanger 13a is uniformly distributed to the flat tubes 51 that constitute the heat exchange body 50. This improves the heat exchange performance of the outdoor heat exchanger 13.

In the outdoor unit 10, the orifice 73 formed in the first header 53 is formed in the inner tube 71 so as to open at a set angle φ _opt in the circumferential direction from the lower end of the inner tube 71 on a vertical line passing through the center of the inner tube 71. The angle φ _opt at this time is set to be larger than the liquid level angle φ ₀ and smaller than the wet boundary angle φ _S. This allows the inflowing two-phase refrigerant to be distributed to the flat tubes 51 more appropriately.

Embodiment 2.
Next, a description will be given of the present embodiment 2. The present embodiment 2 differs from the embodiment 1 in that the angles of the orifices 73 provided in the inner pipes 71 of the first header 53 and the second header 54 are different. In the present embodiment 2, the parts common to the embodiment 1 are given the same reference numerals and detailed description will be omitted.

When the outdoor heat exchanger 13 functions as an evaporator, the two-phase refrigerant flowing out from the throttling device 21 of the indoor unit 20 flows into the second header 54 of the first outdoor heat exchanger 13a. On the other hand, when the outdoor heat exchanger 13 functions as a condenser, the two-phase refrigerant flowing out from the second outdoor heat exchanger 13b and the third outdoor heat exchanger 13c flows into the first header 53 of the first outdoor heat exchanger 13a.

At this time, the dryness fraction at the inlet of the second header 54 when functioning as an evaporator is less than about 0.2, and the dryness fraction at the inlet of the first header 53 when functioning as a condenser is about 0.2 to 0.6. In other words, the ratio of liquid refrigerant differs between the two-phase refrigerant flowing into the second header 54 when functioning as an evaporator and the two-phase refrigerant flowing into the first header 53 when functioning as a condenser. Therefore, if the angle of the orifice 73 in each header is the same, the refrigerant may not be distributed appropriately depending on the operating state of the outdoor heat exchanger 13.

Therefore, in this embodiment 2, the position of the orifice 73 in each of the first header 53 and the second header 54 is made different, and the orifice 73 is arranged in a position appropriate for the operating conditions.

10 is a schematic diagram for explaining the angles of the orifices of the first header and the second header according to the second embodiment. The dryness fraction at the inlet of the first header 53 when the outdoor heat exchanger 13 functions as a condenser is higher than the dryness fraction at the inlet of the second header 54 when the outdoor heat exchanger 13 functions as an evaporator. Therefore, in the second embodiment, when the angle of the orifice 73b of the second header 54 is "φ _opt2 " and the angle of the orifice 73a of the first header 53 is "φ _opt1 ", the relationship between the angles of the orifices 73 is expressed by Equation (4).
φ _opt2 ≦φ _opt1 ...(4)

In this manner, in the second embodiment, the angle of the orifice 73a of the first header 53 is made different from the angle of the orifice 73b of the second header 54. This allows the refrigerant flowing into the first outdoor heat exchanger 13a to be appropriately distributed whether the outdoor heat exchanger 13 functions as a condenser or an evaporator.

Although the above describes embodiments 1 and 2, the present disclosure is not limited to the above-mentioned embodiments 1 and 2, and various modifications and applications are possible without departing from the gist of the present disclosure.

10 Outdoor unit, 11 Compressor, 12 Refrigerant flow switching device, 13 Outdoor heat exchanger, 13a First outdoor heat exchanger, 13b Second outdoor heat exchanger, 13c Third outdoor heat exchanger, 14 Accumulator, 15 Fan, 20 Indoor unit, 21 Throttle device, 22 Indoor heat exchanger, 50 Heat exchange body, 51 Flat tube, 52 Fin, 53 First header, 54 Second header, 55 Third header, 56, 57 Refrigerant piping, 63 Fourth header, 64 Fifth header, 65 Sixth header, 66, 67 Refrigerant piping, 71 Inner tube, 72 Outer tube, 73, 73a, 73b Orifice, 100 Air conditioning device.

Claims (8)

An outdoor unit of an air conditioner including a heat exchanger having a first heat exchanger and a second heat exchanger connected in series,
The first heat exchanger is
the second heat exchanger is connected to a downstream side of a refrigerant flow when the heat exchanger functions as a condenser;
A plurality of heat exchange bodies having a plurality of flat tubes arranged at intervals in a horizontal direction with a tube extension direction in a vertical direction, and arranged in an air flow direction;
a first header provided under an inlet side heat exchanger into which a refrigerant flows when the heat exchanger functions as a condenser, among the plurality of heat exchangers ;
a second header provided under an inlet side heat exchanger into which a refrigerant flows when the heat exchanger functions as an evaporator, among the plurality of heat exchangers;
Equipped with
The first header comprises:
The cooling medium has a double-pipe structure including an inner pipe having a plurality of orifices formed at intervals through which the refrigerant flows, and an outer pipe into which the inner pipe is inserted .
The orifice formed in the first header is
the inner pipe is formed so as to open at a first angle inclined in a circumferential direction from a lower end of the inner pipe on a vertical line passing through a center of the inner pipe,
The second header comprises:
The cooling medium has a double-pipe structure including an inner pipe having a plurality of orifices formed at intervals through which the refrigerant flows, and an outer pipe into which the inner pipe is inserted.
The orifice formed in the second header is
the inner pipe is formed so as to open at a second angle in the circumferential direction from a lower end of the inner pipe on a vertical line passing through a center of the inner pipe of the second header,
The second angle is formed to be different from the first angle.
An outdoor unit for an air conditioning system. The first angle is:
2. The outdoor unit for an air conditioner according to claim 1 , wherein the angle is greater than a liquid level angle of the refrigerant present in the inner tube and smaller than a wet boundary angle of the refrigerant. The second angle is
3. The outdoor unit for an air conditioner according to claim 1, wherein the angle is equal to or less than the first angle. The heat exchange element including the second header,
4. The outdoor unit of an air conditioner according to claim 1 , wherein the outdoor unit is disposed on the most windward side in the flow direction of air carrying out heat exchange. The heat exchange element including the first header,
The outdoor unit for an air conditioner according to any one of claims 1 to 4 , which is disposed on the most downwind side in the flow direction of air carrying out heat exchange. The second heat exchanger is
A plurality of heat exchange bodies having a plurality of flat tubes arranged at intervals in a horizontal direction with a tube extension direction in a vertical direction, and arranged in an air flow direction;
a third header provided under an inlet-side heat exchanger, into which a refrigerant flows when the heat exchanger functions as an evaporator, among the plurality of heat exchangers;
The third header comprises:
The outdoor unit of an air-conditioning apparatus according to any one of claims 1 to 5 , which has a double-pipe structure including an inner pipe in which a plurality of orifices through which the refrigerant flows are formed at intervals, and an outer pipe into which the inner pipe is inserted. The heat exchange element including the third header,
7. The outdoor unit of an air conditioner according to claim 6 , wherein the outdoor unit is disposed on the most windward side in the flow direction of air carrying out heat exchange. An air conditioner comprising the outdoor unit according to any one of claims 1 to 7 .

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