HEAT EXCHANGER AND HEAT EXCHANGE UNIT INCLUDING THE SAME

A heat exchanger includes: flat pipes vertically arrayed; and fins that partition a space between adjacent ones of the flat pipes into air flow passages. Each of the flat pipes includes a passage for a refrigerant. The flat pipes are divided into heat exchange sections vertically arranged side by side. Each of the heat exchange sections includes: a main heat exchange section that communicates with a gas-side entrance communication space, and a sub heat exchange section that 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.

TECHNICAL FIELD

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

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.

PATENT LITERATURE

Patent Literature 1: JP 2012-163313 A

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.

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.

SUMMARY

One or more embodiments of the present invention 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 includes 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.

A heat exchanger according to one or more embodiments 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.

In one or more embodiments, 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.

Thus, in one or more embodiments, 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 one or more embodiments, 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 one or more embodiments, 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 one or more embodiments, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section in the defrosting operation.

In this manner, in one or more embodiments, 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.

A heat exchanger according to one or more embodiments is the heat exchanger in which the main-sub number ratio in the lowermost heat exchange section is set to be maximum among the heat exchange sections.

In one or more embodiments, 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 one or more embodiments, 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.

A heat exchanger according to one or more embodiments is the heat exchanger 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.

In one or more embodiments, 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.

However, as described above, one or more embodiments employ 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.

A heat exchange unit according to one or more embodiments 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 disposed below the fan inside the casing.

As described above, one or more embodiments employ 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.

However, as described above, one or more embodiments employ 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.

A heat exchange unit according to one or more embodiments is the heat exchange unit 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.

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.

Thus, in one or more embodiments, 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.

A heat exchange unit according to one or more embodiments is the heat exchange unit 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.

In one or more embodiments, 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 one or more embodiments, 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.

DETAILED DESCRIPTION

Hereinbelow, embodiments 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 one or more embodiments the present invention and the heat exchange unit including the heat exchanger are not limited to the embodiments and the modifications described below, and can be changed without departing from the gist of the invention.

(1) Configuration of Air Conditioner

FIG. 1is a schematic configuration diagram of an air conditioner1which employs an outdoor heat exchanger11as a heat exchanger according to one or more embodiments of the present invention and an outdoor unit2as a heat exchange unit including the outdoor heat exchanger11.

The air conditioner1is 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 conditioner1mainly includes an outdoor unit2, indoor units3a,3b, a liquid-refrigerant connection pipe4and a gas-refrigerant connection pipe5which connect the outdoor unit2to the indoor units3a,3b, and a control unit23which controls constituent devices of the outdoor unit2and the indoor units3a,3b. A vapor compression refrigerant circuit6of the air conditioner1is formed by connecting the outdoor unit2to the indoor units3a,3bthrough the refrigerant connection pipes4,5.

The outdoor unit2is 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 circuit6. The outdoor unit2mainly includes an accumulator7, a compressor8, a four-way switching valve10, an outdoor heat exchanger11, an outdoor expansion valve12as an expansion mechanism, a liquid-side shutoff valve13, a gas-side shutoff valve14, and an outdoor fan15. These devices and valves are connected through refrigerant pipes16to22.

The indoor units3a,3bare installed inside the room (in a living room, in a ceiling space or the like), and constitute a part of the refrigerant circuit6. The indoor unit3amainly includes an indoor expansion valve31a, an indoor heat exchanger32a, and an indoor fan33a. The indoor unit3bmainly includes an indoor expansion valve31bas an expansion mechanism, an indoor heat exchanger32b, and an indoor fan33b.

The refrigerant connection pipes4,5are constructed in a site where the air conditioner1is installed in an installation place such as a building. One end of the liquid-refrigerant connection pipe4is connected to the liquid-side shutoff valve13of the indoor unit2, and the other end of the liquid-refrigerant connection pipe4is connected to liquid-side ends of the indoor expansion valves31a,31bof the indoor units3a,3b. One end of the gas-refrigerant connection pipe5is connected to the gas-side shutoff valve14of the indoor unit2, and the other end of the gas-refrigerant connection pipe5is connected to gas-side ends of the indoor heat exchangers32a,32bof the indoor units3a,3b.

Control unit23is configured by control boards or the like (not illustrated) included in the outdoor unit2and the indoor units3a,3bbeing communicably connected to the control unit23. InFIG. 1, for convenience, the control unit23is separated from the outdoor unit2and the indoor units3a,3b. The control unit23controls the constituent devices8,10,12,15,31a,31b,33a,33bof the air conditioner1(in one or more embodiments, the outdoor unit2and the indoor units3a,3b), that is, controls driving of the entire air conditioner1.

(2) Operation of Air Conditioner

Next, the operation of the air conditioner1will be described with reference toFIG. 1. The air conditioner1performs a cooling operation which circulates a refrigerant through the compressor8, the outdoor heat exchanger11, the outdoor expansion valve12, the indoor expansion valves31a,31b, and the indoor heat exchangers32a,32bin that order and a heating operation which circulates the refrigerant through the compressor8, the indoor heat exchangers32a,32b, the indoor expansion valves31a,31b, the outdoor expansion valve12, and the outdoor heat exchanger11in that order. In the heating operation, a defrosting operation for melting frost adhered to the outdoor heat exchanger11is performed. In one or more embodiments, an inversed cycle defrosting operation which circulates the refrigerant through the compressor8, the outdoor heat exchanger11, the outdoor expansion valve12, the indoor expansion valves31a,31b, and the indoor heat exchangers32a,32bin that order in a manner similar to the cooling operation is performed. The control unit23performs the cooling operation, the heating operation, and the defrosting operation.

In the cooling operation, the four-way switching valve10is switched to an outdoor heat dissipation state (a state indicated by a solid line inFIG. 1). In the refrigerant circuit6, a low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor8, compressed until the refrigerant becomes high pressure of the refrigeration cycle, and then discharged. The high-pressure gas refrigerant discharged from the compressor8is fed to the outdoor heat exchanger11through the four-way switching valve10. The high-pressure gas refrigerant fed to the outdoor heat exchanger11dissipates heat by exchanging heat with outdoor air which is supplied as a cooling source by the outdoor fan15to become a high-pressure liquid refrigerant in the outdoor heat exchanger11which functions as a radiator for the refrigerant. The high-pressure liquid refrigerant after heat dissipation in the outdoor heat exchanger11is fed to the indoor expansion valves31a,31bthrough the outdoor expansion valve12, the liquid-side shutoff valve13, and the liquid-refrigerant connection pipe4. The refrigerant fed to the indoor expansion valves31a,31bis decompressed to a low pressure of the refrigeration cycle by the indoor expansion valves31a,31bto 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 valves31a,31bis fed to the indoor heat exchangers32a,32b. The low-pressure refrigerant in a gas-liquid two-phase state fed to the indoor heat exchangers32a,32bevaporates by exchanging heat with indoor air which is supplied as a heating source by the indoor fans33a,33bin the indoor heat exchangers32a,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 exchangers32a,32bis sucked into the compressor8again through the gas-refrigerant connection pipe5, the gas-side shutoff valve14, the four-way switching valve10, and the accumulator7.

In the heating operation, the four-way switching valve10is switched to an outdoor evaporation state (a state indicated by a broken line inFIG. 1). In the refrigerant circuit6, a low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor8, compressed until the refrigerant becomes a high pressure of the refrigeration cycle, and then discharged. The high-pressure gas refrigerant discharged from the compressor8is fed to the indoor heat exchangers32a,32bthrough the four-way switching valve10, the gas-side shutoff valve14, and the gas-refrigerant connection pipe5. The high-pressure gas refrigerant fed to the indoor heat exchangers32a,32bdissipates heat by exchanging heat with indoor air which is supplied as a cooling source by the indoor fans33a,33bto become a high-pressure liquid refrigerant in the indoor heat exchangers32a,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 exchangers32a,32bis fed to the outdoor expansion valve12through the indoor expansion valves31a,31b, the liquid-refrigerant connection pipe4, and the liquid-side shutoff valve13. The refrigerant fed to the outdoor expansion valve12is decompressed to a low pressure of the refrigeration cycle by the outdoor expansion valve12to 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 valve12is fed to the outdoor heat exchanger11. The low-pressure refrigerant in a gas-liquid two-phase state fed to the outdoor heat exchanger11evaporates by exchanging heat with outdoor air which is supplied as a heating source by the outdoor fan15to become a low-pressure gas refrigerant in the outdoor heat exchanger11which functions as an evaporator for the refrigerant. The low-pressure gas refrigerant evaporated in the outdoor heat exchanger11is sucked into the compressor8again through the four-way switching valve10and the accumulator7.

When frost formation in the outdoor heat exchanger11is detected according to, for example, the temperature of the refrigerant in the outdoor heat exchanger11lower than a predetermined temperature, that is, when a condition for starting defrosting in the outdoor heat exchanger11is satisfied, a defrosting operation for melting frost adhered to the outdoor heat exchanger11is performed.

The defrosting operation is performed by switching the four-way switching valve22to the outdoor heat dissipation state (the state indicated by the solid line inFIG. 1) to cause the outdoor heat exchanger11to function as the radiator for the refrigerant in a manner similar to the cooling operation. Accordingly, frost adhered to the outdoor heat exchanger11can 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 exchanger11has been completed according to the temperature of the refrigerant in the outdoor heat exchanger11higher than the predetermined temperature, and the operation then returns to the heating operation. The flow of the refrigerant in the refrigerant circuit10in the defrosting operation is similar to that in the cooling operation. Thus, description thereof will be omitted.

(3) Configuration of Outdoor Unit

FIG. 2is an external perspective view of the outdoor unit2.FIG. 3is a front view of the outdoor unit2(except the refrigerant circuit constituent components other than the outdoor heat exchanger11).FIG. 4is a schematic perspective view of the outdoor heat exchanger11.FIG. 5is a partial enlarged view of heat exchange sections60A to60I ofFIG. 4.FIG. 6is a schematic configuration diagram of the outdoor heat exchanger11.FIG. 7is a table listing a schematic configuration of the outdoor heat exchanger11.

The outdoor unit2is a top blow-out type heat exchange unit that sucks air from the side face of a casing40and blows out air from the top face of the casing40. The outdoor unit2mainly includes the casing40having a substantially rectangular parallelepiped box shape, the outdoor fan15as a fan, the devices7,8,11including the compressor and the outdoor heat exchanger, and the refrigerant circuit constituent components which include the valves10, and12to14having the four-way switching valve and the outdoor expansion valve, and the refrigerant pipes16to22and constitute a part of the refrigerant circuit6. In the following description, “up”, “down”, “left”, “right”, “front”, “back”, “front face”, and “back face” indicate directions in a case where the outdoor unit2illustrated inFIG. 2is viewed from the front (the diagonally left front side) unless otherwise noted.

The casing40mainly includes a bottom frame42which is put across a pair of installation legs41which extend in the right-left direction, supports43which extend in the vertical direction from corners of the bottom frame42, a fan module44which is attached to the upper ends of the supports43, and a front panel45. The casing40includes inlet ports40a,40b,40cfor air on the side faces (in one or more embodiments, the back face, and the right and left side faces) and a blow-out port40dfor air on the top face.

The bottom frame42forms the bottom face of the casing40. The outdoor heat exchanger11is disposed on the bottom frame42. The outdoor heat exchanger11is 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 casing40. The outdoor heat exchanger11substantially forms the back face and the right and left side faces of the casing40. The bottom frame42is in contact with a lower end part of the outdoor heat exchanger11, and functions as a drain pan which receives drain water generated in the outdoor heat exchanger11in the cooling operation and the defrosting operation.

The fan module44is disposed on the upper side of the outdoor heat exchanger11to form a part of the front face, the back face, and the right and left faces of the casing40above the supports43and the top face of the casing40. The fan module44is an aggregate including a substantially rectangular parallelepiped box body whose upper and lower faces are open and the outdoor fan15housed in the box body. The opening on the top face of the fan module44corresponds to the blow-out port40d. A blow-out grille46is disposed on the blow-out port40d. The outdoor fan15is disposed facing the blow-out port40dinside the casing40. The outdoor fan15is a fan that takes air into the casing40through the inlet ports40a,40b,40cand discharges air through the blow-out port40d.

The front panel45is put between the supports43on the front face side to form the front face of the casing40.

The refrigerant circuit constituent components other than the outdoor fan15and the outdoor heat exchanger11(FIG. 2illustrates the accumulator7and the compressor8) are also housed inside the casing40. The compressor8and the accumulator7are disposed on the bottom frame42.

In this manner, the outdoor unit2includes the casing40which includes the inlet ports40a,40b,40cfor air formed on the side faces (in one or more embodiments, the back face and the right and left side faces) and the blow-out port40dfor air formed on the top face, the outdoor fan15(fan) which is disposed facing the blow-out port40dinside the casing40, and the outdoor heat exchanger11which is disposed below the outdoor fan15inside the casing40. Further, in such a top blow-out type unit configuration, as illustrated inFIG. 3, the outdoor heat exchanger11is disposed below the outdoor fan15. Thus, the velocity of air passing though the upper part of the outdoor heat exchanger11tends to become higher than the velocity of air passing through the lower part of the outdoor heat exchanger11.

The outdoor heat exchanger11is a heat exchanger that exchanges heat between the refrigerant and outdoor air. The outdoor heat exchanger11mainly includes a first header collecting pipe80, a second header collecting pipe90, a plurality of flat pipes63, and a plurality of fins64. In one or more embodiments, the first header collecting pipe80, the second header collecting pipe90, the flat pipes63, and the fins64are all made of aluminum or an aluminum alloy and joined to each other by, for example, brazing.

Each of the first header collecting pipe80and the second header collecting pipe90is a vertically oriented hollow cylindrical member whose upper and lower ends are closed. The first header collecting pipe80stands on one end side (in one or more embodiments, on the left front end side inFIG. 4or the left end side inFIG. 6) of the outdoor heat exchanger11. The second header collecting pipe90stands on the other end side (in one or more embodiments, the right front end side inFIG. 4or the right end side inFIG. 6) of the outdoor heat exchanger11.

Each of the flat pipes63is a flat perforated pipe including a flat part63awhich serves as a heat transfer surface and faces in the vertical direction and a large number of small passages63bthrough which the refrigerant flows, the passages63bbeing formed inside the flat pipe63. A plurality of flat pipes63are vertically arrayed. Both ends of each of the flat pipes63are connected to the first header collecting pipe80and the second header collecting pipe90. The fins64partition a space between adjacent flat pipes63into a plurality of air flow passages through which air flows. Each of the fins64includes a plurality of cutouts64afor inserting a plurality of flat pipes63. In one or more embodiments, the flat part63aof the flat pipe63faces in the vertical direction, and the longitudinal direction of the flat pipe63corresponds to the horizontal direction extending along the side face (in one or more embodiments, the right and left side faces) and the back face of the casing40. Thus, an extending direction of the cutout64acorresponds to the horizontal direction which intersects the longitudinal direction of the flat pipe63and also substantially coincides with an air flow direction inside the casing40. The cutout64ahorizontally extends long so that the flat pipe63is inserted from the leeward side toward the windward side in the air flow direction. The shape of the cutout64aof the fin64substantially coincides with the outer shape of the cross section of the flat pipe63. The cutouts64aof the fin64are formed at predetermined intervals in the vertical direction on the fin64. The fin64includes a plurality of fin main parts64ceach of which is interposed between vertically adjacent cutouts64aand a fin windward part64dwhich extends continuously with the fin main parts64con the windward side in the air flow direction relative to the cutouts64a.

In the outdoor heat exchanger11, the flat pipes63are divided into a plurality of heat exchange sections60A to60I (in one or more embodiments, nine heat exchange sections) which are vertically arranged side by side. Specifically, in one or more embodiments, the first heat exchange section60A which is the lowermost heat exchange section, the second heat exchange section60B, . . . , the eighth heat exchange section60H, and the ninth heat exchange section60I are formed in that order from bottom to top. The first heat exchange section60A includes eleven flat pipes63. Each of the second and third heat exchange sections60B,60C includes twelve flat pipes63. The fourth heat exchange section60D includes eleven flat pipes63. Each of the fifth and sixth heat exchange sections60E,60F includes nine flat pipes63. Each of the seventh and eighth heat exchange sections60G,60H includes eight flat pipes63. The ninth heat exchange section60I includes seven flat pipes63.

An internal space of the first header collecting pipe80is vertically partitioned by partition plates81so that entrance communication spaces82A to82I respectively corresponding to the heat exchange sections60A to60I are formed. Further, each of the entrance communication spaces82A to82I is vertically partitioned into two spaces by a partition plate83so that upper gas-side entrance communication spaces84A to84I and lower liquid-side entrance communication spaces85A to85I are formed.

The first gas-side entrance communication space84A communicates with top eight of the flat pipes63constituting the first heat exchange section60A. The first liquid-side entrance communication space85A communicates with the remaining three of the flat pipes63constituting the first heat exchange section60A. Each of the second and third gas-side entrance communication spaces84B,84C communicates with top eight of the flat pipes63constituting each of the second and third heat exchange sections60B,60C. Each of the second and third liquid-side entrance communication spaces85B,85C communicates with the remaining four of the flat pipes63constituting each of the second and third heat exchange sections60B,60C. The fourth gas-side entrance communication space84D communicates with top seven of the flat pipes63constituting the fourth heat exchange section60D. The fourth liquid-side entrance communication space85D communicates with the remaining four of the flat pipes63constituting the fourth heat exchange section60D. Each of the fifth and sixth gas-side entrance communication spaces84E,84F communicates with top six of the flat pipes63constituting each of the fifth and sixth heat exchange sections60E,60F. Each of the fifth and sixth liquid-side entrance communication spaces85E,85F communicates with the remaining three of the flat pipes63constituting each of the fifth and sixth heat exchange sections60E,60F. Each of the seventh and eighth gas-side entrance communication spaces84G,84H communicates with top five of the flat pipes63constituting each of the seventh and eighth heat exchange sections60G,60H. Each of the seventh and eighth liquid-side entrance communication spaces85G,85H communicates with the remaining three of the flat pipes63constituting each of the seventh and eighth heat exchange sections60G,60H. The ninth gas-side entrance communication space84I communicates with top five of the flat pipes63constituting the ninth heat exchange section60I. The ninth liquid-side entrance communication space85I communicates with the remaining two of the flat pipes63constituting the ninth heat exchange section60I.

The flat pipes63communicating with the gas-side entrance communication spaces84A to84I are defined as main heat exchange sections61A to61I, and the flat pipes63communicating with the liquid-side entrance communication spaces85A to85I are defined as sub heat exchange sections62A to62I. More specifically, in the first entrance communication space82A, the first gas-side entrance communication space84A communicates with top eight of the flat pipes63constituting the first heat exchange section60A (the first main heat exchange section61A), and the first liquid-side entrance communication space85A communicates with the remaining three of the flat pipes63constituting the first heat exchange section60A (the first sub heat exchange section62A). In the second entrance communication space82B, the second gas-side entrance communication space84B communicates with top eight of the flat pipes63constituting the second heat exchange section60B (the second main heat exchange section61B), and the second liquid-side entrance communication space85B communicates with the remaining four of the flat pipes63constituting the second heat exchange section60B (the second sub heat exchange section62B). In the third entrance communication space82C, the third gas-side entrance communication space82C communicates with top eight of the flat pipes63constituting the third heat exchange section60C (the third main heat exchange section61C), and the third liquid-side entrance communication space85C communicates with the remaining four of the flat pipes63constituting the third heat exchange section60C (the third sub heat exchange section62C). In the fourth entrance communication space82D, the fourth gas-side entrance communication space84D communicates with top seven of the flat pipes63constituting the fourth heat exchange section60D (the fourth main heat exchange section61D), and the fourth liquid-side entrance communication space85D communicates with the remaining four of the flat pipes63constituting the fourth heat exchange section60D (the fourth sub heat exchange section62D). In the fifth entrance communication space82E, the fifth gas-side entrance communication space84E communicates with top six of the flat pipes63constituting the fifth heat exchange section60E (the fifth main heat exchange section61E), and the fifth liquid-side entrance communication space85E communicates with the remaining three of the flat pipes63constituting the fifth heat exchange section60E (the fifth sub heat exchange section62E). In the sixth entrance communication space82F, the sixth gas-side entrance communication space84F communicates with top six of the flat pipes63constituting the sixth heat exchange section60F (the sixth main heat exchange section61F), and the sixth liquid-side entrance communication space85F communicates with the remaining three of the flat pipes63constituting the sixth heat exchange section60F (the sixth sub heat exchange section60F). In the seventh entrance communication space82G, the seventh gas-side entrance communication space84E communicates with top five of the flat pipes63constituting the seventh heat exchange section60G (the seventh main heat exchange section61G), and the seventh liquid-side entrance communication space85G communicates with the remaining three of the flat pipes63constituting the seventh heat exchange section60G (the seventh sub heat exchange section62G). In the eighth entrance communication space82H, the eighth gas-side entrance communication spaces84F communicates with top five of the flat pipes63constituting the eighth heat exchange section60H (the eighth main heat exchange section61H), and the eighth liquid-side entrance communication space85H communicates with the remaining three of the flat pipes63constituting the eighth heat exchange sections60H (the eighth sub heat exchange section60H). In the ninth entrance communication space82I, the ninth gas-side entrance communication space84I communicates with top five of the flat pipes63constituting the ninth heat exchange section60I (the ninth main heat exchange section61I), and the ninth liquid-side entrance communication space85I communicates with the remaining two of the flat pipes63constituting the ninth heat exchange section60I (the ninth sub heat exchange section62I).

A liquid-side flow dividing member70which divides and feeds the refrigerant fed from the outdoor expansion valve12(refer toFIG. 1) into the liquid-side entrance communication spaces85A to85I in the heating operation and a gas-side flow dividing member75which divides and feeds the refrigerant fed from the compressor8(refer toFIG. 1) into the gas-side entrance communication spaces84A to84I in the cooling operation are connected to the first header collecting pipe80.

The liquid-side flow dividing member70includes a liquid-side refrigerant flow divider71which is connected to the refrigerant pipe20(refer toFIG. 1) and liquid-side refrigerant flow dividing pipes72A to72I which extend from the liquid-side refrigerant flow divider71and are connected to the liquid-side entrance communication spaces85A to85I, respectively. Each of the liquid-side refrigerant flow dividing pipes72A to72I 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 sections62A to62I.

The gas-side flow dividing member75includes a gas-side refrigerant flow dividing header pipe76which is connected to the refrigerant pipe19(refer toFIG. 1) and gas-side refrigerant flow dividing branch pipes77A to77I which extend from the gas-side refrigerant flow dividing header pipe76and are connected to the gas-side entrance communication spaces84A to84I, respectively.

An internal space of the second header collecting pipe90is vertically partitioned by partition plates91so that return communication spaces92A to92I respectively corresponding to the heat exchange sections60A to60I are formed. The internal space of the second header collecting pipe90is not limited to the configuration merely partitioned by the partition plates91as described above, and alternatively may have a configuration designed for satisfactorily maintaining a flow state of the refrigerant inside the second header collecting pipe90.

Each of the return communication spaces92A to92I communicates with all the flat pipes63constituting the corresponding one of the heat exchange sections60A to60I. More specifically, the first return communication space92A communicates with all the eleven flat pipes63constituting the first heat exchange section60A. Each of the second and third return communication spaces92B,92C communicates with all the twelve flat pipes63constituting each of the second and third heat exchange sections60B,60C. The fourth return communication space92D communicates with all the eleven flat pipes63constituting the fourth heat exchange section60D. Each of the fifth and sixth return communication spaces92E,92F communicates with all the nine flat pipes63constituting each of the fifth and sixth heat exchange sections60E,60F. Each of the seventh and eighth return communication spaces92G,92H communicates with all the eight flat pipes63constituting each of the seventh and eighth heat exchange sections60G,60H. The ninth return communication space92I communicates with all the seven flat pipes63constituting the ninth heat exchange section60I.

Accordingly, the heat exchange sections60A to60I include the main heat exchange sections61A to61I and the sub heat exchange sections62A to62I which are connected in series to the main heat exchange sections61A to61I below the main heat exchange sections61A to61I. More specifically, the first heat exchange section60A has a configuration in which the eight flat pipes63constituting the first main heat exchange section61A which communicates with the first gas-side entrance communication space84A and the three flat pipes63constituting the first sub heat exchange section62A which is located directly below the first main heat exchange section61A and communicates with the first liquid-side entrance communication space85A are connected in series through the first return communication space92A. The second heat exchange section60B has a configuration in which the eight flat pipes63constituting the second main heat exchange section61B which communicates with the second gas-side entrance communication space84B and the four flat pipes63constituting the second sub heat exchange section62B which is located directly below the second main heat exchange section61B and communicates with the second liquid-side entrance communication space85B are connected in series through the second return communication space92B. The third heat exchange section60C has a configuration in which the eight flat pipes63constituting the third main heat exchange section61C which communicates with the third gas-side entrance communication space84C and the four flat pipes63constituting the third sub heat exchange section62C which is located directly below the third main heat exchange section61cand communicates with the third liquid-side entrance communication space85C are connected in series through the third return communication space92C. The fourth heat exchange section60D has a configuration in which the seven flat pipes63constituting the fourth main heat exchange section61D which communicates with the fourth gas-side entrance communication space84D and the four flat pipes63constituting the fourth sub heat exchange section62D which is located directly below the fourth main heat exchange section61D and communicates with the fourth liquid-side entrance communication space85D are connected in series through the fourth return communication space92D. The fifth heat exchange section60E has a configuration in which the six flat pipes63constituting the fifth main heat exchange section61E which communicates with the fifth gas-side entrance communication space84E and the three flat pipes63constituting the fifth sub heat exchange section62E which is located directly below the fifth main heat exchange section61E and communicates with the fifth liquid-side entrance communication space85E are connected in series through the fifth return communication space92E. The sixth heat exchange section60F has a configuration in which the six flat pipes63constituting the sixth main heat exchange section61F which communicates with the sixth gas-side entrance communication space84F and the three flat pipes63constituting the sixth sub heat exchange section62F which is located directly below the sixth main heat exchange section61F and communicates with the sixth liquid-side entrance communication space85F are connected in series through the sixth return communication space92F. The seventh heat exchange section60G has a configuration in which the five flat pipes63constituting the seventh main heat exchange section61G which communicates with the seventh gas-side entrance communication space84G and the three flat pipes63constituting the seventh sub heat exchange section62G which is located directly below the seventh main heat exchange section61G and communicates with the seventh liquid-side entrance communication space85G are connected in series through the seventh return communication space92G. The eighth heat exchange section60H has a configuration in which the five flat pipes63constituting the eighth main heat exchange section61H which communicates with the eighth gas-side entrance communication space84H and the three flat pipes63constituting the eighth sub heat exchange section62H which is located directly below the eighth main heat exchange section61H and communicates with the eighth liquid-side entrance communication space85H are connected in series through the eighth return communication space92h. The ninth heat exchange section60I has a configuration in which the five flat pipes63constituting the ninth main heat exchange section61I which communicates with the ninth gas-side entrance communication space84I and the two flat pipes63constituting the ninth sub heat exchange section62I which communicates with the ninth liquid-side entrance communication space85I are connected in series through the ninth return communication space92I.

In this manner, in one or more embodiments, the outdoor heat exchanger11includes the flat pipes63which are vertically arrayed, each of the flat pipes63including the passage63bfor the refrigerant formed inside thereof, and the fins64which partition a space between adjacent flat pipes63into a plurality of air flow passages through which air flows. The flat pipes63are divided into the heat exchange sections60A to60I. The heat exchange sections60A to60I include the main heat exchange sections61A to61I and the sub heat exchange sections62A to62I which are connected in series to the main heat exchange sections61A to61I below the main heat exchange sections61A to61I. Further, when the ratio of the number of flat pipes63constituting each of the main heat exchange sections61A to61I to the number of flat pipes63constituting each of the sub heat exchange sections62A to60I in each of the heat exchange sections60A to60I is defined as the main-sub number ratio, the main-sub number ratio in the first heat exchange section60A 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 sections60B to60I (=50/26=1.9). The main-sub number ratio in the first heat exchange section60A is not limited to 2.7, but may be 2.5 or higher.

Further, in one or more embodiments, the main-sub number ratio in the first heat exchange section60A (the lowermost heat exchange section) (=2.7) is set to be maximum among the heat exchange sections60A to60I.

Further, in one or more embodiments, the number of flat pipes63constituting each of the heat exchange sections60A to60I is set in such a manner that the number of flat pipes63of the heat exchange section corresponding to a part where the velocity of air obtained by the outdoor fan15(fan) is low is larger than the number of flat pipes63of the heat exchange section corresponding to a part where the velocity of air obtained by the outdoor fan15(fan) is high. Specifically, for example, the number of flat pipes63(eight) constituting each of the seventh and eighth heat exchange sections60G,60H where the velocity of air is lower than that in the ninth heat exchange section60I is larger than the number of flat pipes63(seven) constituting the ninth heat exchange section60I 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 pipes63.

Further, the number of flat pipes63(three) constituting the sub heat exchange section62A in the first heat exchange section60A which is the lowermost heat exchange section is set smaller than the number of flat pipes63(four) constituting the sub heat exchange section62A in the second heat exchange section60B which is the second lowermost heat exchange section. In one or more embodiments, the number of flat pipes63constituting the lowermost sub heat exchange section62A is smaller than the number of flat pipes63constituting the second lowermost sub heat exchange section62B by one. However, one or more embodiments are not limited thereto. For example, the number of flat pipes63constituting the lowermost sub heat exchange section62A may be smaller than the number of flat pipes63constituting the second lowermost sub heat exchange section62B by two or three.

Next, the flow of the refrigerant in the outdoor heat exchanger11having the above configuration will be described.

In the cooling operation, the outdoor heat exchanger11functions as a radiator for the refrigerant discharged from the compressor8(refer toFIG. 1).

The refrigerant discharged from the compressor8(refer toFIG. 1) is fed to the gas-side flow dividing member75through the refrigerant pipe19(refer toFIG. 1). The refrigerant fed to the gas-side flow dividing member75is divided into the gas-side refrigerant flow dividing branch pipes77A to77I from the gas-side refrigerant flow dividing header pipe76and fed to the gas-side entrance communication spaces84A to84I of the first header collecting pipe80.

The refrigerant fed to each of the gas-side entrance communication spaces84A to84I is divided into the flat pipes63constituting the main heat exchange sections61A to61I of the corresponding heat exchange sections60A to60I. The refrigerant fed to each flat pipe63dissipates heat by heat exchange with outdoor air while flowing through the passage63b, and flows of the refrigerant merge with each other in each of the return communication spaces92A to92I of the second header collecting pipe90. That is, the refrigerant passes through the main heat exchange sections61A to61I. 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.

The refrigerant merged in each of the return communication spaces92A to92I is divided into the flat pipes63constituting the sub heat exchange sections62A to62I of the corresponding heat exchange sections60A to60I. The refrigerant fed to each flat pipe63dissipates heat by heat exchange with outdoor air while flowing through the passage63b, and flows of the refrigerant merge with each other in each of the liquid-side entrance communication spaces85A to85I of the first header collecting pipe80. That is, the refrigerant passes through the sub heat exchange sections62A to62I. 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.

The refrigerant fed to the liquid-side entrance communication spaces85A to85I is fed to the liquid-side refrigerant flow dividing pipes72A to72I of the liquid-side refrigerant flow dividing member70, and flows of the refrigerant merge with each other in the liquid-side refrigerant flow divider71. The refrigerant merged in the liquid-side refrigerant flow divider71is fed to the outdoor expansion valve12(refer toFIG. 1) through the refrigerant pipe20(refer toFIG. 1).

In the heating operation, the outdoor heat exchanger11functions as an evaporator for the refrigerant decompressed by the outdoor expansion valve12(refer toFIG. 1).

The refrigerant decompressed by the outdoor expansion valve12is fed to the liquid-side refrigerant flow dividing member70through the refrigerant pipe20(refer toFIG. 1). The refrigerant fed to the liquid-side refrigerant flow dividing member70is divided into the liquid-side refrigerant flow dividing pipes72A to72I from the liquid-side refrigerant flow divider71and fed to the liquid-side entrance communication spaces85A to85I of the first header collecting pipe80.

The refrigerant fed to each of the liquid-side entrance communication spaces85A to85I is divided into the flat pipes63constituting the sub heat exchange sections62A to62I of the corresponding heat exchange sections60A to60I. The refrigerant fed to each flat pipe63evaporates by heat exchange with outdoor air while flowing through the passage63b, and flows of the refrigerant merge with each other in each of the return communication spaces92A to92I of the second header collecting pipe90. That is, the refrigerant passes through the sub heat exchange sections62A to62I. 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.

The refrigerant merged in each of the return communication spaces92A to92I is divided into the flat pipes63constituting the main heat exchange sections61A to61I of the corresponding heat exchange sections60A to60I. The refrigerant fed to each flat pipe63evaporates (is heated) by heat exchange with outdoor air while flowing through the passage63b, and flows of the refrigerant merge with each other in each of the gas-side entrance communication spaces84A to84I of the first header collecting pipe80. That is, the refrigerant passes through the main heat exchange sections61A to61I. 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.

The refrigerant fed to the gas-side entrance communication spaces84A to84I is fed to the gas-side refrigerant flow dividing branch pipes77A to77I of the gas-side refrigerant flow dividing member75, and flows of the refrigerant merge with each other in the gas-side refrigerant flow dividing header pipe76. The refrigerant merged in the gas-side refrigerant flow dividing header pipe76is fed to the suction side of the compressor8(refer toFIG. 1) through the refrigerant pipe19(refer toFIG. 1).

In the defrosting operation, the outdoor heat exchanger11functions as a radiator for the refrigerant discharged from the compressor8(refer toFIG. 1) in a manner similar to the cooling operation. The flow of the refrigerant in the outdoor heat exchanger11in 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 sections60A to60I in the defrosting operation.

The outdoor heat exchanger11(heat exchanger) of one or more embodiments and the outdoor unit2(heat exchange unit) including the outdoor heat exchanger11have characteristics as described below.

In one or more embodiments, as described above, a plurality of heat exchange sections60A to60I including the main heat exchange sections61A to61I which communicate with the gas-side entrance communication spaces84A to84I and the sub heat exchange sections62A to62I which are connected in series to the main heat exchange sections61A to61I below the main heat exchange sections61A to61I and communicate with the liquid-side entrance communication spaces85A to85I are vertically arranged side by side. When the outdoor heat exchanger11(heat exchanger) having such a configuration is employed in the air conditioner1which performs the heating operation and the defrosting operation in a switching manner, liquid accumulation occurs in the first heat exchange section60A which is the lowermost heat exchange section (in particular, the first sub heat exchange section62A) 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 sections60A to60I in the defrosting operation. Accordingly, a flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section60A becomes lower than those in the upper heat exchange sections60B to60I, which increases the time required for melting frost adhered to the lowermost heat exchange section60A. In particular, in a mode in which the heat exchanger11is 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 section60A in the defrosting operation is further reduced. In this manner, in the heat exchanger11having a configuration in which the heat exchange sections60A to60I including the main heat exchange sections61A to61I and the sub heat exchange sections62A to62I which are connected in series to the main heat exchange sections61A to61I below the main heat exchange sections61A to61I are vertically arranged side by side, the occurrence of liquid accumulation in the lowermost heat exchange section60A 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 section60A becomes long in the defrosting operation.

Thus, in one or more embodiments, as described above, the main-sub number ratio in the lowermost heat exchange section60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections60B to60I. That is, in one or more embodiments, a channel resistance in the sub heat exchange section in the lowermost heat exchange section60A is larger than those in the upper heat exchange sections60B to60I. Thus, in one or more embodiments, it is possible to make a pressure loss in the lowermost heat exchange section60A larger than those in the upper heat exchange sections60B to60I. Accordingly, it is possible to suppress the occurrence of liquid accumulation in the lowermost heat exchange section60A to prevent the flow rate of the refrigerant in a gas state flowing into the lowermost heat exchange section60A from becoming low in the defrosting operation. As a result, in one or more embodiments, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section60A in the defrosting operation.

Further, in one or more embodiments, as described above, the main-sub number ratio in the lowermost heat exchange section60A is set to be maximum among the heat exchange sections60A to60I. Thus, in one or more embodiments, it is possible to make the channel resistance in the sub heat exchange section in the lowermost heat exchange section60A larger than those in all the upper heat exchange sections60B to60I. Accordingly, in one or more embodiments, it is possible to reliably make a pressure loss in the lowermost heat exchange section60A larger than those in the upper heat exchange sections60B to60I and reliably shorten the time required for melting frost adhered to the lowermost heat exchange section60A in the defrosting operation.

Further, in one or more embodiments, as described above, each of the fins64includes the cutouts64ainto which the flat pipes63are inserted. The cutouts64aextend from the leeward side toward the windward side in the air flow direction. Further, each of the fins64includes the fin windward part64cwhich extends continuously with the fin main parts64binterposed between the cutouts64aon the windward side in the air flow direction relative to the cutouts64a. In the heat exchanger11having such a configuration, the amount of frost adhered to the fin windward part64ctends to increase in the defrosting operation. Thus, there is a possibility that the time required for melting frost adhered to the lowermost heat exchange section60A increases.

However, as described in the above <A>, one or more embodiments employ a configuration in which the main-sub number ratio in the lowermost heat exchange section60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections60B to60I. Thus, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section60A including frost adhered to the fin windward part64c.

Further, as described above, one or more embodiments employ the heat exchanger11having a configuration in which the heat exchange sections60A to60I including the main heat exchange sections61A to61I and the sub heat exchange sections62A to62I connected in series to the main heat exchange sections61A to61I below the main heat exchange sections61A to61I are vertically arranged side by side as the heat exchanger11included in the top blow-out type heat exchange unit2which sucks air from the side face of the casing40and blows out air from the top face of the casing40. In the configuration of the above heat exchange unit2, 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 section60A becomes long.

However, as described above, one or more embodiments employ the heat exchanger11having a configuration in which the main-sub number ratio in the lowermost heat exchange section60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections60B to60I as the heat exchanger11included in the heat exchange unit2. Thus, it is possible to shorten the time required for melting frost adhered to the lowermost heat exchange section60A in spite of the fact that the velocity of air becomes low.

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.

Thus, in one or more embodiments, the number of flat pipes63of the heat exchange section having a low air velocity is larger than the number of flat pipes63of 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 sections60A to60I 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 sections60A to60I.

In one or more embodiments, as described above, the main-sub number ratio in the lowermost heat exchange section60A is set larger than the mean of the main-sub number ratios in the other heat exchange sections60B to60I by making the number of flat pipes63constituting the lowermost sub heat exchange section62A smaller than the number of flat pipes63constituting the second lowermost sub heat exchange section62B. Thus, in one or more embodiments, it is possible to reliably suppress the occurrence of liquid accumulation in the lowermost heat exchange section60A while employing the configuration of the heat exchange sections60A to60I corresponding to the air velocity distribution.

In the above embodiments, the present invention is applied to the outdoor heat exchanger11including the nine heat exchange sections60A to60I. However, the present invention is not limited thereto. The number of heat exchange sections may be less than nine or more than nine.

Further, the number of flat pipes63constituting each of the heat exchange sections60A to60I and the ratio between the number of flat pipes63of each of the main heat exchange sections61A to61I and the number of flat pipes63of each of the sub heat exchange sections62A to62I in each of the heat exchange sections60A to60I are not limited to the number and the ratio in the above embodiments.

INDUSTRIAL APPLICABILITY

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

2outdoor unit (heat exchange unit)11outdoor heat exchanger (heat exchanger)15outdoor fan (fan)40casing40a,40b,40cinlet port40dblow-out port60A to60I heat exchange section60A first heat exchange section (lowermost heat exchange section)60B second heat exchange section (second lowermost heat exchange section)61A to61I main heat exchange section61A first main heat exchange section62A to62I sub heat exchange section62A first sub heat exchange section (lowermost sub heat exchange section)62B second sub heat exchange section (second lowermost sub heat exchange section)63flat pipe63bpassage64fin64acutout64bfin main part64cfin windward part