HEAT EXCHANGER AND HEAT EXCHANGE UNIT PROVIDED WITH SAME

Abstract

 Flat pipes (63) included in a heat exchanger (11) are divided into a plurality of heat exchange sections (60A to 601) vertically arranged side by side. Each of the heat exchange sections includes a main heat exchange section (61A to 611) and a sub heat exchange section (62A to 621) connected in series to the main heat exchange section below the main heat exchange section. The ratio of the number of flat pipes constituting the main heat exchange section (61A) to the number of flat pipes constituting the sub heat exchange section (62A) in the lowermost heat exchange section (60A) is set larger than the mean of the ratios in the other heat exchange sections (60B to 601).

Description

TECHNICAL FIELD

[0001] The present invention relates to a heat exchanger and a heat exchange unit including the heat exchanger. In particular, the present invention relates to a heat exchanger including a plurality of flat pipes vertically arrayed, each of the flat pipes including a passage for a refrigerant formed inside thereof, and a plurality of fins that partition a space between adjacent flat pipes into a plurality of air flow passages through which air flows and a heat exchange unit including the heat exchanger.

BACKGROUND ART

[0002] A heat exchanger including a plurality of flat pipes vertically arrayed and a plurality of fins that partition a space between adjacent flat pipes into a plurality of air flow passages through which air flows may be employed as a heat exchanger housed in an outdoor unit (heat exchange unit) of an air conditioner. Further, for example, such a heat exchanger includes a heat exchanger as described in Patent Literature 1 (JP 2012-163313 A) in which a plurality of flat pipes are divided into a plurality of heat exchange sections which are vertically arranged side by side, and each of the heat exchange sections includes a main heat exchange section and a sub heat exchange section which is connected in series to the main heat exchange section below the main heat exchange section.

SUMMARY OF THE INVENTION

[0003] The above conventional heat exchanger may be employed in an air conditioner that performs a heating operation and a defrosting operation in a switching manner. When the air conditioner performs the heating operation, the above conventional heat exchanger is used as an evaporator for a refrigerant. When the air conditioner performs the defrosting operation, the above conventional heat exchanger is used as a radiator for the refrigerant. Specifically, when the above conventional heat exchanger is used as the evaporator for the refrigerant, the refrigerant in a gas-liquid two-phase state is divided and flows into the sub heat exchange section included in each heat exchange section, is heated while passing through the sub heat exchange section and the main heat exchange section in that order, and flows out of the heat exchange section. Then, flows of the refrigerant merge with each other. Further, when the above conventional heat exchanger is used as the radiator for the refrigerant, the refrigerant in a gas state is divided and flows into the main heat exchange section of each heat exchange section, is cooled while passing through the main heat exchange section and the sub heat exchange section in that order, and flows out of the heat exchange section. Then, flows of the refrigerant merge with each other.

[0004] However, in the air conditioner that employs the above conventional heat exchanger, the time required for melting frost adhered to the lowermost heat exchange section tends to become longer than the time required for melting frost adhered to the heat exchange section located on the upper side relative to the lowermost heat exchange section in the defrosting operation. In particular, this tendency becomes apparent in a mode including a tall heat exchanger. Thus, frost may remain unmelted in the lowermost heat exchange section even after the defrosting operation, which may result in insufficient defrosting. Further, it is necessary to increase the time of the defrosting operation in order to suppress frost from remaining unmelted in the lowermost heat exchange section.

[0005] It is an object of the present invention to shorten the time required for melting frost adhered to the lowermost heat exchange section in a defrosting operation when a heat exchanger including a plurality of flat pipes vertically arrayed, each of the flat pipes including a passage for a refrigerant formed inside of the flat pipe, and a plurality of fins that partition a space between each adjacent two of the flat pipes into a plurality of air flow passages through which air flows is employed in an air conditioner that performs a heating operation and a defrosting operation in a switching manner.

[0006] A heat exchanger according to a first aspect includes a plurality of flat pipes vertically arrayed, each of the flat pipes including a passage for a refrigerant formed inside of the flat pipe, and a plurality of fins that partition a space between each adjacent two of the flat pipes into a plurality of air flow passages through which air flows. The flat pipes are divided into a plurality of heat exchange sections vertically arranged side by side, and each of the heat exchange sections includes a main heat exchange section which communicates with a gas-side entrance communication space and a sub heat exchange section which is connected in series to the main heat exchange section below the main heat exchange section and communicates with a liquid-side entrance communication space. Further, when a ratio of a number of the flat pipes constituting the main heat exchange section to a number of the flat pipes constituting the sub heat exchange section in each of the heat exchange sections is defined as a main-sub number ratio, the main-sub number ratio in a lowermost one of the heat exchange sections is set larger than a mean of the main-sub number ratios in the other heat exchange sections.

[0007] In the first aspect, as described above, the heat exchange sections including the main heat exchange sections and the sub heat exchange sections which are connected in series to the main heat exchange sections below the main heat exchange sections are vertically arranged side by side. When the heat exchanger having such a configuration is employed in the air conditioner that performs the heating operation and the defrosting operation in a switching manner, liquid accumulation occurs in the lowermost heat exchange section (in particular, the sub heat exchange section) due to the influence of a liquid head of the refrigerant when the refrigerant in a gas state is divided and flows into each of the heat exchange sections in the defrosting operation. Accordingly, a flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section becomes lower than those in the upper heat exchange sections, which increases the time required for melting frost adhered to the lowermost heat exchange section. In particular, in a mode in which the heat exchanger is tall, the liquid head of the refrigerant becomes large, and the flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section in the defrosting operation is further reduced. In this manner, in the heat exchanger having a configuration in which the heat exchange sections including the main heat exchange sections and the sub heat exchange sections which are connected in series to the main heat exchange sections below the main heat exchange sections are vertically arranged side by side, the occurrence of liquid accumulation in the lowermost heat exchange section due to the influence of the liquid head of the refrigerant in the defrosting operation is the reason why the time required for melting frost adhered to the lowermost heat exchange section becomes long in the defrosting operation.

[0008] Thus, in the first aspect, as described above, the main-sub number ratio in the lowermost heat exchange section is set larger than the mean of the main-sub number ratios in the other heat exchange sections. That is, in the first aspect, a channel resistance in the sub heat exchange section in the lowermost heat exchange section is larger than those in the upper heat exchange sections. Thus, in the first aspect, it is possible to make a pressure loss in the lowermost heat exchange section larger than those in the upper heat exchange sections. Accordingly, it is possible to suppress the occurrence of liquid accumulation in the lowermost heat exchange section to prevent the flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section from becoming low in the defrosting operation. As a result, in the first aspect, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section in the defrosting operation.

[0009] In this manner, in the first aspect, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section in the defrosting operation by employing the heat exchanger having the above configuration in the air conditioner that performs the heating operation and the defrosting operation in a switching manner.

[0010] A heat exchanger according to a second aspect is the heat exchanger according to the first aspect in which the main-sub number ratio in the lowermost heat exchange section is set to be maximum among the heat exchange sections.

[0011] In the second aspect, it is possible to make the channel resistance in the sub heat exchange section in the lowermost heat exchange section larger than those in all the upper heat exchange sections. Accordingly, in the second aspect, it is possible to reliably make a pressure loss in the lowermost heat exchange section larger than those in the upper heat exchange sections and reliably shorten the time required for melting frost adhered to the lowermost heat exchange section in the defrosting operation.

[0012] A heat exchanger according to a third aspect is the heat exchanger according to the first or second aspect in which each of the fins includes a plurality of cutouts into which the flat pipes are inserted, the cutouts extending from a leeward side toward a windward side in an air flow direction of the air passing through the air flow passages, a plurality of fin main parts each interposed between each adjacent two of the cutouts, and a fin windward part extending continuously with the fin main parts on the windward side in the air flow direction relative to the cutouts.

[0013] In the third aspect, as described above, each of the fins includes the cutouts into which the flat pipes are inserted. The cutouts extend from the leeward side toward the windward side in the air flow direction. Further, each of the fins includes the fin windward part which extends continuously with the fin main parts interposed between the cutouts on the windward side in the air flow direction relative to the cutouts. In the heat exchanger having such a configuration, the amount of frost adhered to the fin windward part tends to increase in the defrosting operation. Thus, there is a possibility that the time required for melting frost adhered to the lowermost heat exchange section increases.

[0014] However, as described above, the third aspect employs a configuration in which the main-sub number ratio in the lowermost heat exchange section is set larger than the mean of the main-sub number ratios in the other heat exchange sections. Thus, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section including frost adhered to the fin windward part.

[0015] A heat exchange unit according to a fourth aspect includes a casing including an inlet port for air formed on a side face and a blow-out port for the air formed on a top face; a fan disposed facing the blow-out port inside the casing; and the heat exchanger according to any one of the first to third aspects disposed below the fan inside the casing.

[0016] As described above, the fourth aspect employs the heat exchanger having a configuration in which the heat exchange sections including the main heat exchange sections and the sub heat exchange sections connected in series to the main heat exchange sections below the main heat exchange sections are vertically arranged side by side as the heat exchanger included in the top blow-out type heat exchange unit which sucks air from the side face of the casing and blows out air from the top face of the casing. In the configuration of the above heat exchange unit, the velocity of air in the heat exchange section on the lower side becomes lower than the velocity of air in the heat exchange section on the upper side. Thus, in particular, there is a possibility that the time required for melting frost adhered to the lowermost heat exchange section becomes long.

[0017] However, as described above, the fourth aspect employs the heat exchanger having a configuration in which the main-sub number ratio in the lowermost heat exchange section is set larger than the mean of the main-sub number ratios in the other heat exchange sections as the heat exchanger included in the heat exchange unit. Thus, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section in spite of the fact that the velocity of air becomes low.

[0018] A heat exchange unit according to a fifth aspect is the heat exchange unit according to the fourth aspect in which the number of the flat pipes constituting each of the heat exchange sections is set in such a manner that the number of the flat pipes of the heat exchange section corresponding to a part where a velocity of the air obtained by the fan is low is larger than the number of the flat pipes of the heat exchange section corresponding to a part where the velocity of the air obtained by the fan is high.

[0019] In a heat exchanger that exchanges heat between a refrigerant and air, there is a relationship in which the heat exchange efficiency is higher in a part where the velocity of air is higher and the heat exchange efficiency is lower in a part where the velocity of air is lower.

[0020] Thus, in the fifth aspect, the number of the flat pipes of the heat exchange section having a low air velocity is larger than the number of the flat pipes of the heat exchange section having a high air velocity taking into consideration the relationship between the air velocity distribution and the heat exchange efficiency as described above. Accordingly, it is possible to make the heat transfer area of each of the heat exchange sections correspond to the air velocity distribution. As a result, it is possible to equalize the state of the refrigerant after passing through each of the heat exchange sections.

[0021] A heat exchange unit according to a sixth aspect is the heat exchange unit according to the fifth aspect in which the number of the flat pipes constituting the sub heat exchange section in the lowermost heat exchange section is set smaller than the number of the flat pipes constituting the sub heat exchange section in a second lowermost one of the heat exchange sections.

[0022] In the sixth aspect, as described above, the main-sub number ratio in the lowermost heat exchange section is set larger than the mean of the main-sub number ratios in the other heat exchange sections by making the number of the flat pipes constituting the lowermost sub heat exchange section smaller than the number of the flat pipes constituting the second lowermost sub heat exchange section. Thus, in the sixth aspect, it is possible to reliably suppress the occurrence of liquid accumulation in the lowermost heat exchange section while employing the configuration of the heat exchange sections corresponding to the air velocity distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 

FIG. 1 is a schematic configuration diagram of an air conditioner that employs an outdoor heat exchanger as a heat exchanger according to an embodiment of the present invention and an outdoor unit as a heat exchange unit including the outdoor heat exchanger.

FIG. 2 is an external perspective view of an outdoor unit.

FIG. 3 is a front view of the outdoor unit (except refrigerant circuit constituent components other than the outdoor heat exchanger).

FIG. 4 is a schematic perspective view of the outdoor heat exchanger.

FIG. 5 is a partial enlarged perspective view of heat exchange sections of FIG. 4.

FIG. 6 is a schematic configuration diagram of the outdoor heat exchanger.

FIG. 7 is a table listing a schematic configuration of the outdoor heat exchanger.

DESCRIPTION OF EMBODIMENTS

[0024] Hereinbelow, an embodiment and modifications of a heat exchanger according to the present invention and a heat exchange unit including the heat exchanger will be described with reference to the drawings. Specific configurations of the heat exchanger according to the present invention and the heat exchange unit including the heat exchanger are not limited to the embodiment and the modifications described below, and can be changed without departing from the gist of the invention.

(1) Configuration of Air Conditioner

[0025] FIG. 1 is a schematic configuration diagram of an air conditioner 1 which employs an outdoor heat exchanger 11 as a heat exchanger according to an embodiment of the present invention and an outdoor unit 2 as a heat exchange unit including the outdoor heat exchanger 11.

[0026] The air conditioner 1 is an apparatus capable of performing cooling and heating inside a room of a building or the like by preforming a vapor compression refrigeration cycle. The air conditioner 1 mainly includes an outdoor unit 2, indoor units 3a, 3b, a liquid-refrigerant connection pipe 4 and a gas-refrigerant connection pipe 5 which connect the outdoor unit 2 to the indoor units 3a, 3b, and a control unit 23 which controls constituent devices of the outdoor unit 2 and the indoor units 3a, 3b. A vapor compression refrigerant circuit 6 of the air conditioner 1 is formed by connecting the outdoor unit 2 to the indoor units 3a, 3b through the refrigerant connection pipes 4, 5.

[0027] The outdoor unit 2 is installed outside the room (on a roof of a building, near a wall surface of a building or the like), and constitutes a part of the refrigerant circuit 6. The outdoor unit 2 mainly includes an accumulator 7, a compressor 8, a four-way switching valve 10, an outdoor heat exchanger 11, an outdoor expansion valve 12 as an expansion mechanism, a liquid-side shutoff valve 13, a gas-side shutoff valve 14, and an outdoor fan 15. These devices and valves are connected through refrigerant pipes 16 to 22.

[0028] The indoor units 3a, 3b are installed inside the room (in a living room, in a ceiling space or the like), and constitute a part of the refrigerant circuit 6. The indoor unit 3a mainly includes an indoor expansion valve 31a, an indoor heat exchanger 32a, and an indoor fan 33a. The indoor unit 3b mainly includes an indoor expansion valve 31b as an expansion mechanism, an indoor heat exchanger 32b, and an indoor fan 33b.

[0029] The refrigerant connection pipes 4, 5 are constructed in a site where the air conditioner 1 is installed in an installation place such as a building. One end of the liquid-refrigerant connection pipe 4 is connected to the liquid-side shutoff valve 13 of the indoor unit 2, and the other end of the liquid-refrigerant connection pipe 4 is connected to liquid-side ends of the indoor expansion valves 31a, 31b of the indoor units 3a, 3b. One end of the gas-refrigerant connection pipe 5 is connected to the gas-side shutoff valve 14 of the indoor unit 2, and the other end of the gas-refrigerant connection pipe 5 is connected to gas-side ends of the indoor heat exchangers 32a, 32b of the indoor units 3a, 3b.

[0030] Control unit 23 is configured by control boards or the like (not illustrated) included in the outdoor unit 2 and the indoor units 3a, 3b being communicably connected to the control unit 23. In FIG. 1, for convenience, the control unit 23 is separated from the outdoor unit 2 and the indoor units 3a, 3b. The control unit 23 controls the constituent devices 8, 10, 12, 15, 31a, 31b, 33a, 33b of the air conditioner 1 (in the present embodiment, the outdoor unit 2 and the indoor units 3a, 3b), that is, controls driving of the entire air conditioner 1.

(2) Operation of Air Conditioner

[0031] Next, the operation of the air conditioner 1 will be described with reference to FIG. 1. The air conditioner 1 performs a cooling operation which circulates a refrigerant through the compressor 8, the outdoor heat exchanger 11, the outdoor expansion valve 12, the indoor expansion valves 31a, 31b, and the indoor heat exchangers 32a, 32b in that order and a heating operation which circulates the refrigerant through the compressor 8, the indoor heat exchangers 32a, 32b, the indoor expansion valves 31a, 31b, the outdoor expansion valve 12, and the outdoor heat exchanger 11 in that order. In the heating operation, a defrosting operation for melting frost adhered to the outdoor heat exchanger 11 is performed. In the present embodiment, an inversed cycle defrosting operation which circulates the refrigerant through the compressor 8, the outdoor heat exchanger 11, the outdoor expansion valve 12, the indoor expansion valves 31a, 31b, and the indoor heat exchangers 32a, 32b in that order in a manner similar to the cooling operation is performed. The control unit 23 performs the cooling operation, the heating operation, and the defrosting operation.

[0032] In the cooling operation, the four-way switching valve 10 is switched to an outdoor heat dissipation state (a state indicated by a solid line in FIG. 1). In the refrigerant circuit 6, a low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor 8, compressed until the refrigerant becomes high pressure of the refrigeration cycle, and then discharged. The high-pressure gas refrigerant discharged from the compressor 8 is fed to the outdoor heat exchanger 11 through the four-way switching valve 10. The high-pressure gas refrigerant fed to the outdoor heat exchanger 11 dissipates heat by exchanging heat with outdoor air which is supplied as a cooling source by the outdoor fan 15 to become a high-pressure liquid refrigerant in the outdoor heat exchanger 11 which functions as a radiator for the refrigerant. The high-pressure liquid refrigerant after heat dissipation in the outdoor heat exchanger 11 is fed to the indoor expansion valves 31a, 31b through the outdoor expansion valve 12, the liquid-side shutoff valve 13, and the liquid-refrigerant connection pipe 4. The refrigerant fed to the indoor expansion valves 31a, 31b is decompressed to a low pressure of the refrigeration cycle by the indoor expansion valves 31a, 31b to become a low-pressure refrigerant in a gas-liquid two-phase state. The low-pressure refrigerant in a gas-liquid two-phase state decompressed by the indoor expansion valves 31a, 31b is fed to the indoor heat exchangers 32a, 32b. The low-pressure refrigerant in a gas-liquid two-phase state fed to the indoor heat exchangers 32a, 32b evaporates by exchanging heat with indoor air which is supplied as a heating source by the indoor fans 33a, 33b in the indoor heat exchangers 32a, 32b. Accordingly, the indoor air is cooled and then supplied into the room, thereby cooling the inside of the room. The low-pressure gas refrigerant evaporated in the indoor heat exchangers 32a, 32b is sucked into the compressor 8 again through the gas-refrigerant connection pipe 5, the gas-side shutoff valve 14, the four-way switching valve 10, and the accumulator 7.

[0033] In the heating operation, the four-way switching valve 10 is switched to an outdoor evaporation state (a state indicated by a broken line in FIG. 1). In the refrigerant circuit 6, a low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor 8, compressed until the refrigerant becomes a high pressure of the refrigeration cycle, and then discharged. The high-pressure gas refrigerant discharged from the compressor 8 is fed to the indoor heat exchangers 32a, 32b through the four-way switching valve 10, the gas-side shutoff valve 14, and the gas-refrigerant connection pipe 5. The high-pressure gas refrigerant fed to the indoor heat exchangers 32a, 32b dissipates heat by exchanging heat with indoor air which is supplied as a cooling source by the indoor fans 33a, 33b to become a high-pressure liquid refrigerant in the indoor heat exchangers 32a, 32b. Accordingly, the indoor air is heated and then supplied into the room, thereby heating the inside of the room. The high-pressure liquid refrigerant after heat dissipation in the indoor heat exchangers 32a, 32b is fed to the outdoor expansion valve 12 through the indoor expansion valves 31a, 31b, the liquid-refrigerant connection pipe 4, and the liquid-side shutoff valve 13. The refrigerant fed to the outdoor expansion valve 12 is decompressed to a low pressure of the refrigeration cycle by the outdoor expansion valve 12 to become a low-pressure refrigerant in a gas-liquid two-phase state. The low-pressure refrigerant in a gas-liquid two-phase state decompressed by the outdoor expansion valve 12 is fed to the outdoor heat exchanger 11. The low-pressure refrigerant in a gas-liquid two-phase state fed to the outdoor heat exchanger 11 evaporates by exchanging heat with outdoor air which is supplied as a heating source by the outdoor fan 15 to become a low-pressure gas refrigerant in the outdoor heat exchanger 11 which functions as an evaporator for the refrigerant. The low-pressure gas refrigerant evaporated in the outdoor heat exchanger 11 is sucked into the compressor 8 again through the four-way switching valve 10 and the accumulator 7.

[0034] When frost formation in the outdoor heat exchanger 11 is detected according to, for example, the temperature of the refrigerant in the outdoor heat exchanger 11 lower than a predetermined temperature, that is, when a condition for starting defrosting in the outdoor heat exchanger 11 is satisfied, a defrosting operation for melting frost adhered to the outdoor heat exchanger 11 is performed.

[0035] The defrosting operation is performed by switching the four-way switching valve 22 to the outdoor heat dissipation state (the state indicated by the solid line in FIG. 1) to cause the outdoor heat exchanger 11 to function as the radiator for the refrigerant in a manner similar to the cooling operation. Accordingly, frost adhered to the outdoor heat exchanger 11 can be melted. The defrosting operation is performed until a defrosting time, which is set taking into consideration a state of the heating operation before defrosting, elapses or until it is determined that defrosting in the outdoor heat exchanger 11 has been completed according to the temperature of the refrigerant in the outdoor heat exchanger 11 higher than the predetermined temperature, and the operation then returns to the heating operation. The flow of the refrigerant in the refrigerant circuit 10 in the defrosting operation is similar to that in the cooling operation. Thus, description thereof will be omitted.

(3) Configuration of Outdoor Unit

[0036] FIG. 2 is an external perspective view of the outdoor unit 2. FIG. 3 is a front view of the outdoor unit 2 (except the refrigerant circuit constituent components other than the outdoor heat exchanger 11). FIG. 4 is a schematic perspective view of the outdoor heat exchanger 11. FIG. 5 is a partial enlarged view of heat exchange sections 60A to 60I of FIG. 4. FIG. 6 is a schematic configuration diagram of the outdoor heat exchanger 11. FIG. 7 is a table listing a schematic configuration of the outdoor heat exchanger 11.

<Overall Configuration>

[0037] The outdoor unit 2 is a top blow-out type heat exchange unit that sucks air from the side face of a casing 40 and blows out air from the top face of the casing 40. The outdoor unit 2 mainly includes the casing 40 having a substantially rectangular parallelepiped box shape, the outdoor fan 15 as a fan, the devices 7, 8, 11 including the compressor and the outdoor heat exchanger, and the refrigerant circuit constituent components which include the valves 10, and 12 to 14 having the four-way switching valve and the outdoor expansion valve, and the refrigerant pipes 16 to 22 and constitute a part of the refrigerant circuit 6. In the following description, "up", "down", "left", "right", "front", "back", "front face", and "back face" indicate directions in a case where the outdoor unit 2 illustrated in FIG. 2 is viewed from the front (the diagonally left front side) unless otherwise noted.

[0038] The casing 40 mainly includes a bottom frame 42 which is put across a pair of installation legs 41 which extend in the right-left direction, supports 43 which extend in the vertical direction from corners of the bottom frame 42, a fan module 44 which is attached to the upper ends of the supports 43, and a front panel 45. The casing 40 includes inlet ports 40a, 40b, 40c for air on the side faces (in the present embodiment, the back face, and the right and left side faces) and a blow-out port 40d for air on the top face.

[0039] The bottom frame 42 forms the bottom face of the casing 40. The outdoor heat exchanger 11 is disposed on the bottom frame 42. The outdoor heat exchanger 11 is a heat exchanger which has a substantially U shape in plan view and faces the back face and the right and left side faces of the casing 40. The outdoor heat exchanger 11 substantially forms the back face and the right and left side faces of the casing 40. The bottom frame 42 is in contact with a lower end part of the outdoor heat exchanger 11, and functions as a drain pan which receives drain water generated in the outdoor heat exchanger 11 in the cooling operation and the defrosting operation.

[0040] The fan module 44 is disposed on the upper side of the outdoor heat exchanger 11 to form a part of the front face, the back face, and the right and left faces of the casing 40 above the supports 43 and the top face of the casing 40. The fan module 44 is an aggregate including a substantially rectangular parallelepiped box body whose upper and lower faces are open and the outdoor fan 15 housed in the box body. The opening on the top face of the fan module 44 corresponds to the blow-out port 40d. A blow-out grille 46 is disposed on the blow-out port 40d. The outdoor fan 15 is disposed facing the blow-out port 40d inside the casing 40. The outdoor fan 15 is a fan that takes air into the casing 40 through the inlet ports 40a, 40b, 40c and discharges air through the blow-out port 40d.

[0041] The front panel 45 is put between the supports 43 on the front face side to form the front face of the casing 40.

[0042] The refrigerant circuit constituent components other than the outdoor fan 15 and the outdoor heat exchanger 11 (FIG. 2 illustrates the accumulator 7 and the compressor 8) are also housed inside the casing 40. The compressor 8 and the accumulator 7 are disposed on the bottom frame 42.

[0043] In this manner, the outdoor unit 2 includes the casing 40 which includes the inlet ports 40a, 40b, 40c for air formed on the side faces (in the present embodiment, the back face and the right and left side faces) and the blow-out port 40d for air formed on the top face, the outdoor fan 15 (fan) which is disposed facing the blow-out port 40d inside the casing 40, and the outdoor heat exchanger 11 which is disposed below the outdoor fan 15 inside the casing 40. Further, in such a top blow-out type unit configuration, as illustrated in FIG. 3, the outdoor heat exchanger 11 is disposed below the outdoor fan 15. Thus, the velocity of air passing though the upper part of the outdoor heat exchanger 11 tends to become higher than the velocity of air passing through the lower part of the outdoor heat exchanger 11.

<Outdoor Heat Exchanger>

[0044] The outdoor heat exchanger 11 is a heat exchanger that exchanges heat between the refrigerant and outdoor air. The outdoor heat exchanger 11 mainly includes a first header collecting pipe 80, a second header collecting pipe 90, a plurality of flat pipes 63, and a plurality of fins 64. In the present embodiment, the first header collecting pipe 80, the second header collecting pipe 90, the flat pipes 63, and the fins 64 are all made of aluminum or an aluminum alloy and joined to each other by, for example, brazing.

[0045] Each of the first header collecting pipe 80 and the second header collecting pipe 90 is a vertically oriented hollow cylindrical member whose upper and lower ends are closed. The first header collecting pipe 80 stands on one end side (in the present embodiment, on the left front end side in FIG. 4 or the left end side in FIG. 6) of the outdoor heat exchanger 11. The second header collecting pipe 90 stands on the other end side (in the present embodiment, the right front end side in FIG. 4 or the right end side in FIG. 6) of the outdoor heat exchanger 11.

[0046] Each of the flat pipes 63 is a flat perforated pipe including a flat part 63a which serves as a heat transfer surface and faces in the vertical direction and a large number of small passages 63b through which the refrigerant flows, the passages 63b being formed inside the flat pipe 63. A plurality of flat pipes 63 are vertically arrayed. Both ends of each of the flat pipes 63 are connected to the first header collecting pipe 80 and the second header collecting pipe 90. The fins 64 partition a space between adjacent flat pipes 63 into a plurality of air flow passages through which air flows. Each of the fins 64 includes a plurality of cutouts 64a for inserting a plurality of flat pipes 63. In the present embodiment, the flat part 63a of the flat pipe 63 faces in the vertical direction, and the longitudinal direction of the flat pipe 63 corresponds to the horizontal direction extending along the side face (in the present embodiment, the right and left side faces) and the back face of the casing 40. Thus, an extending direction of the cutout 64a corresponds to the horizontal direction which intersects the longitudinal direction of the flat pipe 63 and also substantially coincides with an air flow direction inside the casing 40. The cutout 64a horizontally extends long so that the flat pipe 63 is inserted from the leeward side toward the windward side in the air flow direction. The shape of the cutout 64a of the fin 64 substantially coincides with the outer shape of the cross section of the flat pipe 63. The cutouts 64a of the fin 64 are formed at predetermined intervals in the vertical direction on the fin 64. The fin 64 includes a plurality of fin main parts 64c each of which is interposed between vertically adjacent cutouts 64a and a fin windward part 64d which extends continuously with the fin main parts 64c on the windward side in the air flow direction relative to the cutouts 64a.

[0047] In the outdoor heat exchanger 11, the flat pipes 63 are divided into a plurality of heat exchange sections 60A to 60I (in the present embodiment, nine heat exchange sections) which are vertically arranged side by side. Specifically, in the present embodiment, the first heat exchange section 60A which is the lowermost heat exchange section, the second heat exchange section 60B, ..., the eighth heat exchange section 60H, and the ninth heat exchange section 60I are formed in that order from bottom to top. The first heat exchange section 60A includes eleven flat pipes 63. Each of the second and third heat exchange sections 60B, 60C includes twelve flat pipes 63. The fourth heat exchange section 60D includes eleven flat pipes 63. Each of the fifth and sixth heat exchange sections 60E, 60F includes nine flat pipes 63. Each of the seventh and eighth heat exchange sections 60G, 60H includes eight flat pipes 63. The ninth heat exchange section 60I includes seven flat pipes 63.

[0048] An internal space of the first header collecting pipe 80 is vertically partitioned by partition plates 81 so that entrance communication spaces 82A to 821 respectively corresponding to the heat exchange sections 60A to 60I are formed. Further, each of the entrance communication spaces 82A to 821 is vertically partitioned into two spaces by a partition plate 83 so that upper gas-side entrance communication spaces 84A to 841 and lower liquid-side entrance communication spaces 85A to 851 are formed.

[0049] The first gas-side entrance communication space 84A communicates with top eight of the flat pipes 63 constituting the first heat exchange section 60A. The first liquid-side entrance communication space 85A communicates with the remaining three of the flat pipes 63 constituting the first heat exchange section 60A. Each of the second and third gas-side entrance communication spaces 84B, 84C communicates with top eight of the flat pipes 63 constituting each of the second and third heat exchange sections 60B, 60C. Each of the second and third liquid-side entrance communication spaces 85B, 85C communicates with the remaining four of the flat pipes 63 constituting each of the second and third heat exchange sections 60B, 60C. The fourth gas-side entrance communication space 84D communicates with top seven of the flat pipes 63 constituting the fourth heat exchange section 60D. The fourth liquid-side entrance communication space 85D communicates with the remaining four of the flat pipes 63 constituting the fourth heat exchange section 60D. Each of the fifth and sixth gas-side entrance communication spaces 84E, 84F communicates with top six of the flat pipes 63 constituting each of the fifth and sixth heat exchange sections 60E, 60F. Each of the fifth and sixth liquid-side entrance communication spaces 85E, 85F communicates with the remaining three of the flat pipes 63 constituting each of the fifth and sixth heat exchange sections 60E, 60F. Each of the seventh and eighth gas-side entrance communication spaces 84G, 84H communicates with top five of the flat pipes 63 constituting each of the seventh and eighth heat exchange sections 60G, 60H. Each of the seventh and eighth liquid-side entrance communication spaces 85G, 85H communicates with the remaining three of the flat pipes 63 constituting each of the seventh and eighth heat exchange sections 60G, 60H. The ninth gas-side entrance communication space 841 communicates with top five of the flat pipes 63 constituting the ninth heat exchange section 601. The ninth liquid-side entrance communication space 851 communicates with the remaining two of the flat pipes 63 constituting the ninth heat exchange section 601.

[0050] The flat pipes 63 communicating with the gas-side entrance communication spaces 84A to 841 are defined as main heat exchange sections 61A to 611, and the flat pipes 63 communicating with the liquid-side entrance communication spaces 85A to 851 are defined as sub heat exchange sections 62A to 621. More specifically, in the first entrance communication space 82A, the first gas-side entrance communication space 84A communicates with top eight of the flat pipes 63 constituting the first heat exchange section 60A (the first main heat exchange section 61A), and the first liquid-side entrance communication space 85A communicates with the remaining three of the flat pipes 63 constituting the first heat exchange section 60A (the first sub heat exchange section 62A). In the second entrance communication space 82B, the second gas-side entrance communication space 84B communicates with top eight of the flat pipes 63 constituting the second heat exchange section 60B (the second main heat exchange section 61B), and the second liquid-side entrance communication space 85B communicates with the remaining four of the flat pipes 63 constituting the second heat exchange section 60B (the second sub heat exchange section 62B). In the third entrance communication space 82C, the third gas-side entrance communication space 82C communicates with top eight of the flat pipes 63 constituting the third heat exchange section 60C (the third main heat exchange section 61C), and the third liquid-side entrance communication space 85C communicates with the remaining four of the flat pipes 63 constituting the third heat exchange section 60C (the third sub heat exchange section 62C). In the fourth entrance communication space 82D, the fourth gas-side entrance communication space 84D communicates with top seven of the flat pipes 63 constituting the fourth heat exchange section 60D (the fourth main heat exchange section 61D), and the fourth liquid-side entrance communication space 85D communicates with the remaining four of the flat pipes 63 constituting the fourth heat exchange section 60D (the fourth sub heat exchange section 62D). In the fifth entrance communication space 82E, the fifth gas-side entrance communication space 84E communicates with top six of the flat pipes 63 constituting the fifth heat exchange section 60E (the fifth main heat exchange section 61E), and the fifth liquid-side entrance communication space 85E communicates with the remaining three of the flat pipes 63 constituting the fifth heat exchange section 60E (the fifth sub heat exchange section 62E). In the sixth entrance communication space 82F, the sixth gas-side entrance communication space 84F communicates with top six of the flat pipes 63 constituting the sixth heat exchange section 60F (the sixth main heat exchange section 61F), and the sixth liquid-side entrance communication space 85F communicates with the remaining three of the flat pipes 63 constituting the sixth heat exchange section 60F (the sixth sub heat exchange section 60F). In the seventh entrance communication space 82G, the seventh gas-side entrance communication space 84E communicates with top five of the flat pipes 63 constituting the seventh heat exchange section 60G (the seventh main heat exchange section 61G), and the seventh liquid-side entrance communication space 85G communicates with the remaining three of the flat pipes 63 constituting the seventh heat exchange section 60G (the seventh sub heat exchange section 62G). In the eighth entrance communication space 82H, the eighth gas-side entrance communication spaces 84F communicates with top five of the flat pipes 63 constituting the eighth heat exchange section 60H (the eighth main heat exchange section 61H), and the eighth liquid-side entrance communication space 85H communicates with the remaining three of the flat pipes 63 constituting the eighth heat exchange sections 60H (the eighth sub heat exchange section 60H). In the ninth entrance communication space 821, the ninth gas-side entrance communication space 841 communicates with top five of the flat pipes 63 constituting the ninth heat exchange section 60I (the ninth main heat exchange section 611), and the ninth liquid-side entrance communication space 851 communicates with the remaining two of the flat pipes 63 constituting the ninth heat exchange section 60I (the ninth sub heat exchange section 621).

[0051] A liquid-side flow dividing member 70 which divides and feeds the refrigerant fed from the outdoor expansion valve 12 (refer to FIG. 1) into the liquid-side entrance communication spaces 85Ato 851 in the heating operation and a gas-side flow dividing member 75 which divides and feeds the refrigerant fed from the compressor 8 (refer to FIG. 1) into the gas-side entrance communication spaces 84A to 841 in the cooling operation are connected to the first header collecting pipe 80.

[0052] The liquid-side flow dividing member 70 includes a liquid-side refrigerant flow divider 71 which is connected to the refrigerant pipe 20 (refer to FIG. 1) and liquid-side refrigerant flow dividing pipes 72A to 721 which extend from the liquid-side refrigerant flow divider 71 and are connected to the liquid-side entrance communication spaces 85A to 851, respectively. Each of the liquid-side refrigerant flow dividing pipes 72A to 721 includes a capillary tube and has a length and an inner diameter corresponding to a flow dividing ratio to each of the sub heat exchange sections 62A to 621.

[0053] The gas-side flow dividing member 75 includes a gas-side refrigerant flow dividing header pipe 76 which is connected to the refrigerant pipe 19 (refer to FIG. 1) and gas-side refrigerant flow dividing branch pipes 77A to 771 which extend from the gas-side refrigerant flow dividing header pipe 76 and are connected to the gas-side entrance communication spaces 84A to 841, respectively.

[0054] An internal space of the second header collecting pipe 90 is vertically partitioned by partition plates 91 so that return communication spaces 92A to 921 respectively corresponding to the heat exchange sections 60A to 60I are formed. The internal space of the second header collecting pipe 90 is not limited to the configuration merely partitioned by the partition plates 91 as described above, and alternatively may have a configuration designed for satisfactorily maintaining a flow state of the refrigerant inside the second header collecting pipe 90.

[0055] Each of the return communication spaces 92A to 921 communicates with all the flat pipes 63 constituting the corresponding one of the heat exchange sections 60A to 601. More specifically, the first return communication space 92A communicates with all the eleven flat pipes 63 constituting the first heat exchange section 60A. Each of the second and third return communication spaces 92B, 92C communicates with all the twelve flat pipes 63 constituting each of the second and third heat exchange sections 60B, 60C. The fourth return communication space 92D communicates with all the eleven flat pipes 63 constituting the fourth heat exchange section 60D. Each of the fifth and sixth return communication spaces 92E, 92F communicates with all the nine flat pipes 63 constituting each of the fifth and sixth heat exchange sections 60E, 60F. Each of the seventh and eighth return communication spaces 92G, 92H communicates with all the eight flat pipes 63 constituting each of the seventh and eighth heat exchange sections 60G, 60H. The ninth return communication space 921 communicates with all the seven flat pipes 63 constituting the ninth heat exchange section 601.

[0056] Accordingly, the heat exchange sections 60A to 60I include the main heat exchange sections 61A to 611 and the sub heat exchange sections 62A to 621 which are connected in series to the main heat exchange sections 61A to 611 below the main heat exchange sections 61A to 611. More specifically, the first heat exchange section 60A has a configuration in which the eight flat pipes 63 constituting the first main heat exchange section 61A which communicates with the first gas-side entrance communication space 84A and the three flat pipes 63 constituting the first sub heat exchange section 62A which is located directly below the first main heat exchange section 61A and communicates with the first liquid-side entrance communication space 85A are connected in series through the first return communication space 92A. The second heat exchange section 60B has a configuration in which the eight flat pipes 63 constituting the second main heat exchange section 61B which communicates with the second gas-side entrance communication space 84B and the four flat pipes 63 constituting the second sub heat exchange section 62B which is located directly below the second main heat exchange section 61B and communicates with the second liquid-side entrance communication space 85B are connected in series through the second return communication space 92B. The third heat exchange section 60C has a configuration in which the eight flat pipes 63 constituting the third main heat exchange section 61C which communicates with the third gas-side entrance communication space 84C and the four flat pipes 63 constituting the third sub heat exchange section 62C which is located directly below the third main heat exchange section 61c and communicates with the third liquid-side entrance communication space 85C are connected in series through the third return communication space 92C. The fourth heat exchange section 60D has a configuration in which the seven flat pipes 63 constituting the fourth main heat exchange section 61D which communicates with the fourth gas-side entrance communication space 84D and the four flat pipes 63 constituting the fourth sub heat exchange section 62D which is located directly below the fourth main heat exchange section 61D and communicates with the fourth liquid-side entrance communication space 85D are connected in series through the fourth return communication space 92D. The fifth heat exchange section 60E has a configuration in which the six flat pipes 63 constituting the fifth main heat exchange section 61E which communicates with the fifth gas-side entrance communication space 84E and the three flat pipes 63 constituting the fifth sub heat exchange section 62E which is located directly below the fifth main heat exchange section 61E and communicates with the fifth liquid-side entrance communication space 85E are connected in series through the fifth return communication space 92E. The sixth heat exchange section 60F has a configuration in which the six flat pipes 63 constituting the sixth main heat exchange section 61F which communicates with the sixth gas-side entrance communication space 84F and the three flat pipes 63 constituting the sixth sub heat exchange section 62F which is located directly below the sixth main heat exchange section 61F and communicates with the sixth liquid-side entrance communication space 85F are connected in series through the sixth return communication space 92F. The seventh heat exchange section 60G has a configuration in which the five flat pipes 63 constituting the seventh main heat exchange section 61G which communicates with the seventh gas-side entrance communication space 84G and the three flat pipes 63 constituting the seventh sub heat exchange section 62G which is located directly below the seventh main heat exchange section 61G and communicates with the seventh liquid-side entrance communication space 85G are connected in series through the seventh return communication space 92G. The eighth heat exchange section 60H has a configuration in which the five flat pipes 63 constituting the eighth main heat exchange section 61H which communicates with the eighth gas-side entrance communication space 84H and the three flat pipes 63 constituting the eighth sub heat exchange section 62H which is located directly below the eighth main heat exchange section 61H and communicates with the eighth liquid-side entrance communication space 85H are connected in series through the eighth return communication space 92h. The ninth heat exchange section 60I has a configuration in which the five flat pipes 63 constituting the ninth main heat exchange section 611 which communicates with the ninth gas-side entrance communication space 841 and the two flat pipes 63 constituting the ninth sub heat exchange section 621 which communicates with the ninth liquid-side entrance communication space 851 are connected in series through the ninth return communication space 921.

[0057] In this manner, in the present embodiment, the outdoor heat exchanger 11 includes the flat pipes 63 which are vertically arrayed, each of the flat pipes 63 including the passage 63b for the refrigerant formed inside thereof, and the fins 64 which partition a space between adjacent flat pipes 63 into a plurality of air flow passages through which air flows. The flat pipes 63 are divided into the heat exchange sections 60A to 601. The heat exchange sections 60A to 60I include the main heat exchange sections 61A to 611 and the sub heat exchange sections 62A to 621 which are connected in series to the main heat exchange sections 61A to 611 below the main heat exchange sections 61A to 611. Further, when the ratio of the number of flat pipes 63 constituting each of the main heat exchange sections 61A to 611 to the number of flat pipes 63 constituting each of the sub heat exchange sections 62A to 60I in each of the heat exchange sections 60A to 60I is defined as the main-sub number ratio, the main-sub number ratio in the first heat exchange section 60A which is the lowermost heat exchange section (= 8/3 = 2.7) is set larger than the mean of the main-sub number ratio in the other heat exchange sections 60B to 60I (= 50/26 = 1.9). The main-sub number ratio in the first heat exchange section 60A is not limited to 2.7, but preferably 2.5 or higher.

[0058] Further, in the present embodiment, the main-sub number ratio in the first heat exchange section 60A (the lowermost heat exchange section) (=2.7) is set to be maximum among the heat exchange sections 60A to 601.

[0059] Further, in the present embodiment, the number of flat pipes 63 constituting each of the heat exchange sections 60A to 60I is set in such a manner that the number of flat pipes 63 of the heat exchange section corresponding to a part where the velocity of air obtained by the outdoor fan 15 (fan) is low is larger than the number of flat pipes 63 of the heat exchange section corresponding to a part where the velocity of air obtained by the outdoor fan 15 (fan) is high. Specifically, for example, the number of flat pipes 63 (eight) constituting each of the seventh and eighth heat exchange sections 60G, 60H where the velocity of air is lower than that in the ninth heat exchange section 60I is larger than the number of flat pipes 63 (seven) constituting the ninth heat exchange section 60I where the velocity of air is highest. In this manner, the heat exchange section on the lower side having a lower air velocity has a larger number of flat pipes 63.

[0060] Further, the number of flat pipes 63 (three) constituting the sub heat exchange section 62A in the first heat exchange section 60A which is the lowermost heat exchange section is set smaller than the number of flat pipes 63 (four) constituting the sub heat exchange section 62A in the second heat exchange section 60B which is the second lowermost heat exchange section. In the present embodiment, the number of flat pipes 63 constituting the lowermost sub heat exchange section 62A is smaller than the number of flat pipes 63 constituting the second lowermost sub heat exchange section 62B by one. However, the present embodiment is not limited thereto. For example, the number of flat pipes 63 constituting the lowermost sub heat exchange section 62A may be smaller than the number of flat pipes 63 constituting the second lowermost sub heat exchange section 62B by two or three.

[0061] Next, the flow of the refrigerant in the outdoor heat exchanger 11 having the above configuration will be described.

[0062] In the cooling operation, the outdoor heat exchanger 11 functions as a radiator for the refrigerant discharged from the compressor 8 (refer to FIG. 1).

[0063] The refrigerant discharged from the compressor 8 (refer to FIG. 1) is fed to the gas-side flow dividing member 75 through the refrigerant pipe 19 (refer to FIG. 1). The refrigerant fed to the gas-side flow dividing member 75 is divided into the gas-side refrigerant flow dividing branch pipes 77A to 771 from the gas-side refrigerant flow dividing header pipe 76 and fed to the gas-side entrance communication spaces 84A to 841 of the first header collecting pipe 80.

[0064] The refrigerant fed to each of the gas-side entrance communication spaces 84A to 841 is divided into the flat pipes 63 constituting the main heat exchange sections 61A to 611 of the corresponding heat exchange sections 60A to 601. The refrigerant fed to each flat pipe 63 dissipates heat by heat exchange with outdoor air while flowing through the passage 63b, and flows of the refrigerant merge with each other in each of the return communication spaces 92A to 921 of the second header collecting pipe 90. That is, the refrigerant passes through the main heat exchange sections 61A to 611. At this time, the refrigerant dissipates heat until the refrigerant becomes a gas-liquid two-phase state or a liquid state close to a saturated state from a superheated gas state.

[0065] The refrigerant merged in each of the return communication spaces 92A to 921 is divided into the flat pipes 63 constituting the sub heat exchange sections 62A to 621 of the corresponding heat exchange sections 60A to 601. The refrigerant fed to each flat pipe 63 dissipates heat by heat exchange with outdoor air while flowing through the passage 63b, and flows of the refrigerant merge with each other in each of the liquid-side entrance communication spaces 85A to 851 of the first header collecting pipe 80. That is, the refrigerant passes through the sub heat exchange sections 62A to 621. At this time, the refrigerant further dissipates heat until the refrigerant becomes a subcooled liquid state from the gas-liquid two-phase state or the liquid state close to a saturated state.

[0066] The refrigerant fed to the liquid-side entrance communication spaces 85A to 851 is fed to the liquid-side refrigerant flow dividing pipes 72A to 721 of the liquid-side refrigerant flow dividing member 70, and flows of the refrigerant merge with each other in the liquid-side refrigerant flow divider 71. The refrigerant merged in the liquid-side refrigerant flow divider 71 is fed to the outdoor expansion valve 12 (refer to FIG. 1) through the refrigerant pipe 20 (refer to FIG. 1).

[0067] In the heating operation, the outdoor heat exchanger 11 functions as an evaporator for the refrigerant decompressed by the outdoor expansion valve 12 (refer to FIG. 1).

[0068] The refrigerant decompressed by the outdoor expansion valve 12 is fed to the liquid-side refrigerant flow dividing member 70 through the refrigerant pipe 20 (refer to FIG. 1). The refrigerant fed to the liquid-side refrigerant flow dividing member 70 is divided into the liquid-side refrigerant flow dividing pipes 72A to 721 from the liquid-side refrigerant flow divider 71 and fed to the liquid-side entrance communication spaces 85A to 851 of the first header collecting pipe 80.

[0069] The refrigerant fed to each of the liquid-side entrance communication spaces 85A to 851 is divided into the flat pipes 63 constituting the sub heat exchange sections 62A to 621 of the corresponding heat exchange sections 60A to 601. The refrigerant fed to each flat pipe 63 evaporates by heat exchange with outdoor air while flowing through the passage 63b, and flows of the refrigerant merge with each other in each of the return communication spaces 92A to 921 of the second header collecting pipe 90. That is, the refrigerant passes through the sub heat exchange sections 62A to 621. At this time, the refrigerant evaporates until the refrigerant becomes a gas-liquid two-phase state having more gas components or a gas state close to a saturated state from a gas-liquid two-phase state having more liquid components.

[0070] The refrigerant merged in each of the return communication spaces 92A to 921 is divided into the flat pipes 63 constituting the main heat exchange sections 61A to 611 of the corresponding heat exchange sections 60A to 601. The refrigerant fed to each flat pipe 63 evaporates (is heated) by heat exchange with outdoor air while flowing through the passage 63b, and flows of the refrigerant merge with each other in each of the gas-side entrance communication spaces 84A to 841 of the first header collecting pipe 80. That is, the refrigerant passes through the main heat exchange sections 61A to 611. At this time, the refrigerant further evaporates (is heated) until the refrigerant becomes a superheated gas state from the gas-liquid two-phase state having more gas components or the gas state close to a saturated state.

[0071] The refrigerant fed to the gas-side entrance communication spaces 84A to 841 is fed to the gas-side refrigerant flow dividing branch pipes 77A to 771 of the gas-side refrigerant flow dividing member 75, and flows of the refrigerant merge with each other in the gas-side refrigerant flow dividing header pipe 76. The refrigerant merged in the gas-side refrigerant flow dividing header pipe 76 is fed to the suction side of the compressor 8 (refer to FIG. 1) through the refrigerant pipe 19 (refer to FIG. 1).

[0072] In the defrosting operation, the outdoor heat exchanger 11 functions as a radiator for the refrigerant discharged from the compressor 8 (refer to FIG. 1) in a manner similar to the cooling operation. The flow of the refrigerant in the outdoor heat exchanger 11 in the defrosting operation is similar to that in the cooling operation. Thus, description thereof will be omitted. However, differently from the cooling operation, the refrigerant mainly dissipates heat while melting frost adhered to the heat exchange sections 60A to 60I in the defrosting operation.

(4) Characteristics

[0073] The outdoor heat exchanger 11 (heat exchanger) of the present embodiment and the outdoor unit 2 (heat exchange unit) including the outdoor heat exchanger 11 have characteristics as described below.

<A>

[0074] In the present embodiment, as described above, a plurality of heat exchange sections 60A to 60I including the main heat exchange sections 61A to 611 which communicate with the gas-side entrance communication spaces 84A to 841 and the sub heat exchange sections 62A to 621 which are connected in series to the main heat exchange sections 61A to 611 below the main heat exchange sections 61A to 611 and communicate with the liquid-side entrance communication spaces 85A to 851 are vertically arranged side by side. When the outdoor heat exchanger 11 (heat exchanger) having such a configuration is employed in the air conditioner 1 which performs the heating operation and the defrosting operation in a switching manner, liquid accumulation occurs in the first heat exchange section 60A which is the lowermost heat exchange section (in particular, the first sub heat exchange section 62A) due to the influence of a liquid head of the refrigerant when the refrigerant in a gas state is divided and flows into each of the heat exchange sections 60A to 60I in the defrosting operation. Accordingly, a flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section 60A becomes lower than those in the upper heat exchange sections 60B to 601, which increases the time required for melting frost adhered to the lowermost heat exchange section 60A. In particular, in a mode in which the heat exchanger 11 is tall, the liquid head of the refrigerant becomes large, and the flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section 60A in the defrosting operation is further reduced. In this manner, in the heat exchanger 11 having a configuration in which the heat exchange sections 60A to 60I including the main heat exchange sections 61A to 611 and the sub heat exchange sections 62A to 621 which are connected in series to the main heat exchange sections 61A to 611 below the main heat exchange sections 61A to 611 are vertically arranged side by side, the occurrence of liquid accumulation in the lowermost heat exchange section 60A due to the influence of the liquid head of the refrigerant in the defrosting operation is the reason why the time required for melting frost adhered to the lowermost heat exchange section 60A becomes long in the defrosting operation.

[0075] Thus, in the present embodiment, as described above, the main-sub number ratio in the lowermost heat exchange section 60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections 60B to 601. That is, in the present embodiment, a channel resistance in the sub heat exchange section in the lowermost heat exchange section 60A is larger than those in the upper heat exchange sections 60B to 601. Thus, in the present embodiment, it is possible to make a pressure loss in the lowermost heat exchange section 60A larger than those in the upper heat exchange sections 60B to 601. Accordingly, it is possible to suppress the occurrence of liquid accumulation in the lowermost heat exchange section 60A to prevent the flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section 60A from becoming low in the defrosting operation. As a result, in the present embodiment, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section 60A in the defrosting operation.

<B>

[0076] Further, in the present embodiment, as described above, the main-sub number ratio in the lowermost heat exchange section 60A is set to be maximum among the heat exchange sections 60A to 601. Thus, in the present embodiment, it is possible to make the channel resistance in the sub heat exchange section in the lowermost heat exchange section 60A larger than those in all the upper heat exchange sections 60B to 601. Accordingly, in the present embodiment, it is possible to reliably make a pressure loss in the lowermost heat exchange section 60A larger than those in the upper heat exchange sections 60B to 60I and reliably shorten the time required for melting frost adhered to the lowermost heat exchange section 60A in the defrosting operation.

<C>

[0077] Further, in the present embodiment, as described above, each of the fins 64 includes the cutouts 64a into which the flat pipes 63 are inserted. The cutouts 64a extend from the leeward side toward the windward side in the air flow direction. Further, each of the fins 64 includes the fin windward part 64c which extends continuously with the fin main parts 64b interposed between the cutouts 64a on the windward side in the air flow direction relative to the cutouts 64a. In the heat exchanger 11 having such a configuration, the amount of frost adhered to the fin windward part 64c tends to increase in the defrosting operation. Thus, there is a possibility that the time required for melting frost adhered to the lowermost heat exchange section 60A increases.

[0078] However, as described in the above <A>, the present embodiment employs a configuration in which the main-sub number ratio in the lowermost heat exchange section 60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections 60B to 601. Thus, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section 60A including frost adhered to the fin windward part 64c.

<D>

[0079] Further, as described above, the present embodiment employs the heat exchanger 11 having a configuration in which the heat exchange sections 60A to 60I including the main heat exchange sections 61A to 611 and the sub heat exchange sections 62A to 621 connected in series to the main heat exchange sections 61A to 611 below the main heat exchange sections 61A to 611 are vertically arranged side by side as the heat exchanger 11 included in the top blow-out type heat exchange unit 2 which sucks air from the side face of the casing 40 and blows out air from the top face of the casing 40. In the configuration of the above heat exchange unit 2, the velocity of air in the heat exchange section on the lower side becomes lower than the velocity of air in the heat exchange section on the upper side. Thus, in particular, there is a possibility that the time required for melting frost adhered to the lowermost heat exchange section 60A becomes long.

[0080] However, as described above, the present embodiment employs the heat exchanger 11 having a configuration in which the main-sub number ratio in the lowermost heat exchange section 60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections 60B to 60I as the heat exchanger 11 included in the heat exchange unit 2. Thus, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section 60A in spite of the fact that the velocity of air becomes low.

<E>

[0081] In a heat exchanger that exchanges heat between a refrigerant and air, there is a relationship in which the heat exchange efficiency is higher in a part where the velocity of air is higher and the heat exchange efficiency is lower in a part where the velocity of air is lower.

[0082] Thus, in the present embodiment, the number of flat pipes 63 of the heat exchange section having a low air velocity is larger than the number of flat pipes 63 of the heat exchange section having a high air velocity taking into consideration the relationship between the air velocity distribution and the heat exchange efficiency as described above. Accordingly, it is possible to make the heat transfer area of each of the heat exchange sections 60A to 60I correspond to the air velocity distribution. As a result, it is possible to equalize the state of the refrigerant after passing through each of the heat exchange sections 60A to 601.

<F>

[0083] In the present embodiment, as described above, the main-sub number ratio in the lowermost heat exchange section 60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections 60B to 60I by making the number of flat pipes 63 constituting the lowermost sub heat exchange section 62A smaller than the number of flat pipes 63 constituting the second lowermost sub heat exchange section 62B. Thus, in the present embodiment, it is possible to reliably suppress the occurrence of liquid accumulation in the lowermost heat exchange section 60A while employing the configuration of the heat exchange sections 60A to 60I corresponding to the air velocity distribution.

(5) Modifications

[0084] In the above embodiment, the present invention is applied to the outdoor heat exchanger 11 including the nine heat exchange sections 60A to 601. However, the present invention is not limited thereto. The number of heat exchange sections may be less than nine or more than nine.

[0085] Further, the number of flat pipes 63 constituting each of the heat exchange sections 60A to 60I and the ratio between the number of flat pipes 63 of each of the main heat exchange sections 61A to 611 and the number of flat pipes 63 of each of the sub heat exchange sections 62A to 621 in each of the heat exchange sections 60A to 60I are not limited to the number and the ratio in the above embodiment.

INDUSTRIAL APPLICABILITY

[0086] The present invention is widely applicable to a heat exchanger including a plurality of flat pipes vertically arrayed, each of the flat pipes including a passage for a refrigerant formed inside thereof, and a plurality of fins that partition a space between adjacent flat pipes into a plurality of air flow passages through which air flows and a heat exchange unit including the heat exchanger.

REFERENCE SIGNS LIST

[0087] 

2 outdoor unit (heat exchange unit)

11 outdoor heat exchanger (heat exchanger)

15 outdoor fan (fan)

40 casing

40a, 40b, 40c inlet port

40d blow-out port

60A to 60I heat exchange section

60A first heat exchange section (lowermost heat exchange section)

60B second heat exchange section (second lowermost heat exchange section)

61A to 611 main heat exchange section

61A first main heat exchange section

62A to 621 sub heat exchange section

62A first sub heat exchange section (lowermost sub heat exchange section)

62B second sub heat exchange section (second lowermost sub heat exchange section)

63 flat pipe

63b passage

64 fin

64a cutout

64b fin main part

64c fin windward part

CITATION LIST

PATENT LITERATURE

[0088] Patent Literature 1: JP 2012-163313 A

Claims

1. A heat exchanger (11) comprising:

a plurality of flat pipes (63) vertically arrayed, each of the flat pipes including a passage (63b) for a refrigerant formed inside thereof; and

a plurality of fins (64) that partition a space between each adjacent two of the flat pipes into a plurality of air flow passages through which air flows, wherein

the flat pipes are divided into a plurality of heat exchange sections (60A to 601) vertically arranged side by side,

each of the heat exchange sections includes a main heat exchange section (61A to 611) which communicates with a gas-side entrance communication space (84A to 841) and a sub heat exchange section (62A to 621) which is connected in series to the main heat exchange section below the main heat exchange section and communicates with a liquid-side entrance communication space (85A to 851), and

when a ratio of a number of the flat pipes constituting the main heat exchange section to a number of the flat pipes constituting the sub heat exchange section in each of the heat exchange sections is defined as a main-sub number ratio, the main-sub number ratio in a lowermost one of the heat exchange sections (60A) is set larger than a mean of the main-sub number ratios in the other heat exchange sections (60B to 601).

2. The heat exchanger according to claim 1, wherein the main-sub number ratio in the lowermost heat exchange section is set to be maximum among the heat exchange sections.

3. The heat exchanger according to claim 1 or 2, wherein each of the fins includes a plurality of cutouts (64a) into which the flat pipes are inserted, the cutouts extending from a leeward side toward a windward side in an air flow direction of the air passing through the air flow passages, a plurality of fin main parts (64b) each interposed between each adjacent two of the cutouts, and a fin windward part (64c) extending continuously with the fin main parts on the windward side in the air flow direction relative to the cutouts.

4. A heat exchange unit (2) comprising:

a casing (40) including an inlet port (40a, 40b, 40c) for air formed on a side face and a blow-out port (40d) for the air formed on a top face;

a fan (15) disposed facing the blow-out port inside the casing; and

the heat exchanger according to any one of claims 1 to 3 disposed below the fan inside the casing.

5. The heat exchange unit according to claim 4, wherein the number of the flat pipes constituting each of the heat exchange sections is set in such a manner that the number of the flat pipes of the heat exchange section corresponding to a part where a velocity of the air obtained by the fan is low is larger than the number of the flat pipes of the heat exchange section corresponding to a part where the velocity of the air obtained by the fan is high.

6. The heat exchange unit according to claim 5, wherein the number of the flat pipes constituting the sub heat exchange section (62A) in the lowermost heat exchange section is set smaller than the number of the flat pipes constituting the sub heat exchange section (62B) in a second lowermost one of the heat exchange sections (60B).

Drawing