Heat exchanger and air conditioner

Abstract

This heat exchanger includes: a main heat exchanger group including a plurality of main fins arranged at intervals and transmitting heat, and a plurality of main heat transfer tubes penetrating the main fins, having a refrigerant flowing inside and arranged in the vertical direction; an auxiliary heat exchanger group that is arranged below the main heat exchanger group and has a plurality of auxiliary fins arranged at intervals and transmitting heat, and a plurality of auxiliary heat transfer tubes penetrating the auxiliary fins, having the refrigerant flowing inside and arranged in the vertical direction; a main primary-side header that is connected to the plurality of main heat transfer tubes and through which the sucked refrigerant flows into the plurality of main heat transfer tubes; an auxiliary primary-side header that is connected to the plurality of auxiliary heat transfer tubes and through which the refrigerant flows out from the plurality of auxiliary heat transfer tubes; a main secondary-side header that is connected to the plurality of main heat transfer tubes on the opposite side to the main primary-side header and through which the refrigerant flows out from the plurality of main heat transfer tubes; and an auxiliary secondary-side header that is connected to the plurality of auxiliary heat transfer tubes on the opposite side to the auxiliary primary-side header and into which the refrigerant flowing from the main secondary-side header flows, the inside of the auxiliary secondary-side header being partitioned into a plurality of auxiliary compartments, the number of auxiliary heat transfer tubes connected to the lowest auxiliary compartment being less than the number of auxiliary heat transfer tubes connected to the auxiliary compartments above the lowest.

Description

Heat exchanger and air conditioning device

[0001] The present disclosure relates to a heat exchanger that exchanges heat between air and a refrigerant, and an air conditioner.

[0002] Fin-and-tube heat exchangers are known as heat exchangers used in air conditioners and the like. A fin-and-tube heat exchanger is a heat exchanger in which a heat transfer tube through which a refrigerant flows is inserted between a plurality of fins arranged at intervals. In a fin-and-tube heat exchanger, air flows between the fins, and heat is exchanged between the refrigerant flowing in the heat transfer tube and the air, thereby performing cooling or heating operation.

[0003] Patent Document 1 discloses an example of such a fin-and-tube heat exchanger, which includes a plurality of flat tubes arranged vertically and extending horizontally, and fins joined to the flat tubes. When functioning as a condenser, the heat exchanger of Patent Document 1 includes a main heat exchanger group consisting of a plurality of flat tubes and fins, through which refrigerant discharged from a compressor flows, and an auxiliary heat exchanger group consisting of a smaller number of flat tubes and fins than the main heat exchanger group, into which refrigerant that has passed through the main heat exchanger group flows. In the heat exchanger of Patent Document 1, an upper section of the main heat exchanger group is connected to an upper section of the auxiliary heat exchanger group, and a lower section of the main heat exchanger group is connected to a lower section of the auxiliary heat exchanger group.

[0004] Patent No. 5679084

[0005] For example, when the outside air temperature is low and heating operation is performed, frost is likely to form on the heat exchanger. When the frost is removed, meltwater is generated. Once the meltwater is generated, even if a high-temperature refrigerant flows through, the meltwater exchanges heat with the meltwater, causing the temperature of the meltwater to rise. That is, the meltwater generated by defrosting in the upper stages of the heat exchanger exchanges heat with the high-temperature refrigerant, causing the refrigerant temperature to decrease toward the lower stages of the heat exchanger, making it more difficult to melt the frost. Furthermore, due to the influence of head difference, the refrigerant flow rate tends to decrease toward the lower stages of the heat exchanger, which can easily result in a lack of heat for defrosting.

[0006] However, in the heat exchanger disclosed in Patent Document 1, the lower section of the auxiliary heat exchanger group, which is the most difficult to defrost, is connected to the lower section of the main heat exchanger group, which is the most difficult to defrost among the main heat exchangers. As a result, the defrosting capacity of the lower section of the auxiliary heat exchanger group is insufficient, which may cause freezing and damage to the heat exchanger.

[0007] The present disclosure has been made in light of the above-mentioned problems, and provides a heat exchanger and an air conditioner that ensure defrosting capacity in the lower stage of an auxiliary heat exchanger group.

[0008] A heat exchanger according to the present disclosure includes a main heat exchanger group having a plurality of main fins arranged at intervals to transfer heat and a plurality of main heat transfer tubes that penetrate the main fins and are aligned in the vertical direction and through which a refrigerant flows; an auxiliary heat exchanger group having a plurality of auxiliary fins arranged at intervals to transfer heat and a plurality of auxiliary heat transfer tubes that penetrate the auxiliary fins and are aligned in the vertical direction and through which a refrigerant flows, the auxiliary heat exchanger group being arranged below the main heat exchanger group; a main primary side header connected to the plurality of main heat transfer tubes and through which drawn refrigerant flows into the plurality of main heat transfer tubes; and a plurality of auxiliary heat transfer tubes connected to the plurality of auxiliary heat transfer tubes and arranged below the main heat exchanger group. a main secondary header connected to the plurality of main heat transfer tubes on the opposite side from the main primary header and through which the refrigerant flows out from the plurality of main heat transfer tubes; and an auxiliary secondary header connected to the plurality of auxiliary heat transfer tubes on the opposite side from the auxiliary primary header and into which the refrigerant flowing from the main secondary header flows, the interior of which is partitioned into a plurality of auxiliary compartments, and the number of auxiliary heat transfer tubes connected to the lowest auxiliary compartment is fewer than the number of auxiliary heat transfer tubes connected to the auxiliary compartments above the lowest.

[0009] According to the present disclosure, in an auxiliary secondary header, the number of auxiliary heat transfer tubes connected to the lowest auxiliary compartment is smaller than the number of auxiliary heat transfer tubes connected to the auxiliary compartments above the lowest. Therefore, the flow rate of refrigerant flowing through the auxiliary heat transfer tubes in the lowest compartment is relatively higher than the flow rate of refrigerant flowing through the auxiliary heat transfer tubes above the lowest compartment. The higher the refrigerant flow rate, the better the defrosting capacity. Therefore, the defrosting capacity can be ensured in the lower compartments of the auxiliary heat exchanger group.

[0010] Fig. 1 is a circuit diagram showing an air conditioning apparatus according to embodiment 1. Fig. 2 is a perspective view showing a heat exchanger according to embodiment 1. Fig. 3 is a side view showing a heat exchanger according to embodiment 1. Fig. 4 is a schematic diagram showing a flow of refrigerant when the heat exchanger according to embodiment 1 acts as a condenser. Fig. 5 is a schematic diagram showing a heat exchanger according to embodiment 2. Fig. 6 is a schematic diagram showing a flow of refrigerant when the heat exchanger according to embodiment 3 acts as a condenser. Fig. 7 is a schematic diagram showing a heat exchanger and a blower according to embodiment 4.

[0011] Hereinafter, embodiments of a heat exchanger and an air conditioning apparatus according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, in the following drawings, including FIG. 1, the dimensional relationships between components may differ from the actual relationships. Furthermore, in the following description, terms indicating directions are used as appropriate to facilitate understanding of the present disclosure, but these terms are used only to explain the present disclosure and do not limit the present disclosure. Examples of terms indicating directions include "up," "down," "right," "left," "front," and "rear."

[0012] Embodiment 1. Figure 1 is a circuit diagram showing an air conditioner 1 pertaining to embodiment 1. The air conditioner 1 is a device that conditions the air in an indoor space, and as shown in Figure 1, is equipped with a heat source side unit 2 and a user side unit 3. The heat source side unit 2 is equipped with, for example, a compressor 6, a flow path switching device 7, a heat exchanger 8, a blower 9, and an expansion section 10. The user side unit 3 is equipped with, for example, a user side heat exchanger 11 and a user side blower 12.

[0013] The refrigerant circuit 4 is configured by connecting a compressor 6, a flow switching device 7, a heat exchanger 8, an expansion unit 10, and a user-side heat exchanger 11 via refrigerant piping 5. The compressor 6 draws in a low-temperature, low-pressure refrigerant, compresses it, and discharges it as a high-temperature, high-pressure refrigerant. The compressor 6 is, for example, a capacity-controllable inverter compressor. The flow switching device 7 switches the flow direction of the refrigerant in the refrigerant circuit 4 and is, for example, a four-way valve. The heat exchanger 8 exchanges heat between, for example, outdoor air 1a and the refrigerant. The heat exchanger 8 functions as a condenser during cooling operation and as an evaporator during heating operation. The blower 9 is a device that sends indoor air to the user-side heat exchanger 11. The expansion unit 10 is a pressure-reducing valve or expansion valve that reduces the pressure of the refrigerant to expand it. The expansion unit 10 is, for example, an electronic expansion valve whose opening is adjustable.

[0014] The user-side heat exchanger 11 exchanges heat between, for example, indoor air and a refrigerant. The user-side heat exchanger 11 acts as an evaporator during cooling operation and as a condenser during heating operation. The user-side blower 12 is a device that sends indoor air to the user-side heat exchanger 11.

[0015] (Operation Modes, Cooling Operation) Next, the operation modes of the air conditioner 1 will be described. First, cooling operation will be described. In cooling operation, the refrigerant drawn into the compressor 6 is compressed by the compressor 6 and discharged in a high-temperature, high-pressure gas state. The high-temperature, high-pressure gas refrigerant discharged from the compressor 6 passes through the flow switching device 7 and flows into the heat exchanger 8, which functions as a condenser. In the heat exchanger 8, the refrigerant exchanges heat with the outdoor air 1a sent by the blower 9, condensing and liquefying. The condensed liquid refrigerant flows into the expansion section 10, where it expands and is decompressed to become a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant then flows into the user-side heat exchanger 11, which functions as an evaporator. In the user-side heat exchanger 11, the refrigerant exchanges heat with the indoor air sent by the user-side blower 12, evaporating and gasifying. At this time, the indoor air is cooled, and cooling is performed in the room. The evaporated refrigerant in a low-temperature, low-pressure gas state passes through the flow switching device 7 and is sucked into the compressor 6 .

[0016] (Operation Mode, Heating Operation) Next, the heating operation will be described. In the heating operation, the refrigerant drawn into the compressor 6 is compressed by the compressor 6 and discharged in a high-temperature, high-pressure gas state. The high-temperature, high-pressure gas refrigerant discharged from the compressor 6 passes through the flow path switching device 7 and flows into the user-side heat exchanger 11, which functions as a condenser. In the user-side heat exchanger 11, the refrigerant exchanges heat with the indoor air sent by the user-side blower 12, condensing and liquefying. At this time, the indoor air is heated, and heating is performed in the room. The condensed liquid refrigerant flows into the expansion section 10, where it expands and decompresses to become a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant then flows into the heat exchanger 8, which functions as an evaporator. In the heat exchanger 8, the refrigerant exchanges heat with the outdoor air 1a sent by the blower 9, evaporating and gasifying. The evaporated low-temperature, low-pressure gas refrigerant passes through the flow path switching device 7 and is drawn into the compressor 6.

[0017] (Operation Mode, Defrosting Operation) Next, the defrosting operation will be described. In the defrosting operation, the refrigerant drawn into the compressor 6 is compressed by the compressor 6 and discharged in a high-temperature, high-pressure gas state. The high-temperature, high-pressure gas refrigerant discharged from the compressor 6 passes through the flow switching device 7 and flows into the heat exchanger 8, which functions as a condenser. In the heat exchanger 8, the refrigerant exchanges heat with the outdoor air 1a and condenses to become a liquid. At this time, the flow of the high-temperature, high-pressure refrigerant removes frost adhering to the heat exchanger 8. The condensed liquid refrigerant flows into the expansion section 10, where it expands and is decompressed to become a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant then flows into the user-side heat exchanger 11, which functions as an evaporator. In the user-side heat exchanger 11, the refrigerant exchanges heat with the indoor air and evaporates to become a gas. The evaporated low-temperature, low-pressure gas refrigerant passes through the flow switching device 7 and is drawn into the compressor 6.

[0018] The air conditioner 1 does not have to have the flow path switching device 7. In this case, the air conditioner 1 becomes a dedicated cooling machine or a dedicated heating machine.

[0019] Fig. 2 is a perspective view showing the heat exchanger 8 according to the first embodiment. Next, the heat exchanger 8 will be described in detail. As shown in Fig. 2, the heat exchanger 8 includes a main heat exchanger group 20 and an auxiliary heat exchanger group 30 having a plurality of auxiliary fins 31 and a plurality of auxiliary heat transfer tubes 32. The heat exchanger 8 also includes a main primary-side header 40, an auxiliary primary-side header 50, a main secondary-side header 60, an auxiliary secondary-side header 70, and a communication portion 80.

[0020] (Main heat exchanger group 20) The main heat exchanger group 20 constitutes the upper part of the heat exchanger 8. When the heat exchanger 8 functions as an evaporator, the refrigerant that has flowed through the auxiliary heat exchanger group 30 flows into the main heat exchanger group 20. On the other hand, when the heat exchanger 8 functions as a condenser, the refrigerant discharged from the compressor 6 flows into the main heat exchanger group 20. The main heat exchanger group 20 has a plurality of main fins 21 and a plurality of main heat transfer tubes 22.

[0021] (Main fins 21) A plurality of main fins 21 are provided, and are arranged at intervals in a direction perpendicular to the flow direction of the outdoor air 1a (direction of arrow X). The intervals are, for example, equal intervals. The main fins 21 are, for example, rectangular aluminum plates. The outdoor air 1a passes between the main fins 21. Note that the multiple main fins 21 are arranged in a row in a row direction (direction of arrow Y) parallel to the flow direction of the outdoor air 1a, but they may be arranged in two or more rows.

[0022] (Main Heat Transfer Tubes 22) The main heat transfer tubes 22, through which the refrigerant flows, penetrate the main fins 21 in the thickness direction (arrow X direction). The main heat transfer tubes 22 are, for example, aluminum heat transfer tubes with a flat cross section. The interior of the main heat transfer tubes 22 is divided by partition walls, forming multiple main flow paths. It is sufficient that at least one main flow path is formed. The main heat transfer tubes 22 are arranged in a row direction (arrow Z direction) parallel to the direction of gravity. The main heat transfer tubes 22 penetrate the main fins 21 so that their longitudinal axes are aligned in a row direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a. Although the first embodiment illustrates a case in which the main heat transfer tubes 22 are arranged in a single row in the row direction, they may be arranged in two or more rows.

[0023] (Auxiliary Heat Exchanger Group 30) The auxiliary heat exchanger group 30 constitutes the lower part of the heat exchanger 8. When the heat exchanger 8 functions as an evaporator, the refrigerant discharged from the compressor 6 flows into the auxiliary heat exchanger group 30. On the other hand, when the heat exchanger 8 functions as a condenser, the refrigerant that has flowed through the main heat exchanger group 20 flows into the auxiliary heat exchanger group 30 and subcools the refrigerant. The auxiliary heat exchanger group 30 has a smaller heat exchange area than the main heat exchanger group 20. The main heat exchanger group 20 and the auxiliary heat exchanger group 30 each use different main fins 21 and auxiliary fins 31, but the main fins 21 and auxiliary fins 31 may be formed integrally. The auxiliary heat exchanger group 30 has a plurality of auxiliary fins 31 and a plurality of auxiliary heat transfer tubes 32.

[0024] (Auxiliary fins 31) A plurality of auxiliary fins 31 are provided, and are arranged at intervals in a direction perpendicular to the flow direction of the outdoor air 1a (direction of arrow X). The intervals are, for example, equal intervals. The auxiliary fins 31 are, for example, rectangular aluminum plates. The outdoor air 1a passes between the auxiliary fins 31. Note that the multiple auxiliary fins 31 are arranged in a row in a row direction (direction of arrow Y) parallel to the flow direction of the outdoor air 1a, but they may be arranged in two or more rows.

[0025] (Auxiliary Heat Transfer Tube 32) The auxiliary heat transfer tube 32, through which the refrigerant flows, penetrates the auxiliary fin 31 in the thickness direction (arrow X direction). The auxiliary heat transfer tube 32 is, for example, an aluminum heat transfer tube with a flat cross section. The interior of the auxiliary heat transfer tube 32 is divided by partition walls to form multiple sub-flow paths. It is sufficient that at least one sub-flow path is formed. The auxiliary heat transfer tubes 32 are arranged in a row direction (arrow Z direction) parallel to the direction of gravity. The auxiliary heat transfer tubes 32 penetrate the auxiliary fin 31 so that their longitudinal axes are aligned in a row direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a. Although the first embodiment illustrates a case in which the auxiliary heat transfer tubes 32 are arranged in a single row in the row direction, two or more rows may be arranged. Although the main heat transfer tube 22 and the auxiliary heat transfer tube 32 have the same shape in the first embodiment, they may also have different shapes.

[0026] (Main Primary Side Header 40) The main primary side header 40 is connected to the plurality of main heat transfer tubes 22 and collects and distributes the refrigerant. The main primary side header 40 is, for example, a rectangular parallelepiped member. The main primary side headers 40 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a. A gas pipe 41 is connected to the main primary side header 40, and when the heat exchanger 8 functions as a condenser, high-temperature, high-pressure gaseous refrigerant flows in from the gas pipe 41. At this time, the refrigerant is distributed from the main primary side header 40 to the plurality of main heat transfer tubes 22. Note that the main primary side headers 40 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a, but two or more rows may be arranged.

[0027] (Auxiliary Primary Header 50) The auxiliary primary header 50 is connected to the plurality of auxiliary heat transfer tubes 32 and collects and distributes the refrigerant. The auxiliary primary header 50 is, for example, a rectangular parallelepiped member. The auxiliary primary headers 50 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a. A liquid pipe 51 is connected to the auxiliary primary header 50, and when the heat exchanger 8 functions as a condenser, liquid refrigerant flows into the liquid pipe 51. At this time, the refrigerant flows out of the plurality of auxiliary heat transfer tubes 32 and merges in the auxiliary primary header 50. Note that the auxiliary primary headers 50 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a, but two or more rows may be arranged. Furthermore, in the first embodiment, the main primary header 40 and the auxiliary primary header 50 are configured as an integrated unit, but they may also be configured as separate units.

[0028] (Main Secondary Side Header 60) The main secondary side header 60 is connected to the multiple main heat transfer tubes 22 on the opposite side from the main primary side header 40 and collects and distributes the refrigerant. The main secondary side header 60 is, for example, a rectangular parallelepiped member. The main secondary side headers 60 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a. A communication part 80 is connected to the main secondary side header 60. When the heat exchanger 8 functions as a condenser, the refrigerant flowing out of the multiple main heat transfer tubes 22 joins in the main secondary side header 60 and then passes through the communication part 80 to reach the auxiliary secondary side header 70. Note that the main secondary side headers 60 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a, but two or more rows may be arranged.

[0029] Fig. 3 is a side view showing the heat exchanger 8 according to the first embodiment. Next, the main compartments 61 of the main secondary header 60 will be described. As shown in Fig. 3, the main secondary header 60 is internally divided into a plurality of main compartments 61. The main compartments 61 of the main secondary header 60 are each connected to the same number of main heat transfer tubes 22. However, the main compartments 61 of the main secondary header 60 may be connected to a different number of main heat transfer tubes 22.

[0030] (Auxiliary Secondary Header 70) As shown in FIG. 2 , the auxiliary secondary header 70 is connected to the multiple auxiliary heat transfer tubes 32 on the opposite side to the auxiliary primary header 50 and collects and distributes the refrigerant. The auxiliary secondary header 70 is, for example, a rectangular parallelepiped member. The auxiliary secondary headers 70 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a. A communication portion 80 is connected to the auxiliary secondary header 70. When the heat exchanger 8 functions as a condenser, the refrigerant flowing from the main secondary header 60 and through the communication portion 80 joins in the auxiliary secondary header 70 and is distributed to the multiple auxiliary heat transfer tubes 32. Note that the auxiliary secondary headers 70 are arranged in a row in a column direction (arrow Y direction) parallel to the flow direction of the outdoor air 1a, but two or more rows may be arranged. Furthermore, in the first embodiment, the main secondary header 60 and the auxiliary secondary header 70 are configured as an integrated unit, but they may also be configured as separate units.

[0031] Next, the auxiliary partitions 71 of the auxiliary secondary header 70 will be described. As shown in FIG. 3 , the interior of the auxiliary secondary header 70 is partitioned into a plurality of auxiliary partitions 71. Some of the auxiliary partitions 71 of the auxiliary secondary header 70 are connected to different numbers of auxiliary heat transfer tubes 32. Specifically, three auxiliary heat transfer tubes 32 are connected to the upper and middle auxiliary partitions 71, and two auxiliary heat transfer tubes 32 are connected to the lowermost auxiliary partition 71. In this manner, the number of auxiliary heat transfer tubes 32 connected to the lowermost auxiliary partition 71 is fewer than the number of auxiliary heat transfer tubes 32 connected to the auxiliary partitions 71 above the lowermost. Note that all of the auxiliary partitions 71 of the auxiliary secondary header 70 may be connected to different numbers of auxiliary heat transfer tubes 32.

[0032] (Communicating section 80) The communicating section 80 connects the main secondary header 60 and the auxiliary secondary header 70. The communicating section 80 is, for example, a hollow pipe, and a plurality of communicating sections 80 are provided. The communicating section 80 communicates between the uppermost main compartment 61 of the main secondary header 60 and the lowermost auxiliary compartment 71 of the auxiliary secondary header 70. The communicating section 80 also communicates between the middle main compartment 61 of the main secondary header 60 and the middle auxiliary compartment 71 of the auxiliary secondary header 70. The communicating section 80 also communicates between the lower main compartment 61 of the main secondary header 60 and the upper auxiliary compartment 71 of the auxiliary secondary header 70. In this way, each communication section 80 connects the upper side of the main compartment section 61 of the main secondary side header 60 to the lower side of the auxiliary compartment section 71 of the auxiliary secondary side header 70, and connects the lower side of the main compartment section 61 of the main secondary side header 60 to the upper side of the auxiliary compartment section 71 of the auxiliary secondary side header 70.

[0033] (Refrigerant Flow in Heat Exchanger 8) FIG. 4 is a schematic diagram showing the flow of refrigerant when the heat exchanger 8 according to the first embodiment functions as a condenser. Next, the flow of refrigerant in the heat exchanger 8 will be described. As shown in FIG. 4 , when the heat exchanger 8 functions as a condenser, high-temperature, high-pressure refrigerant discharged from the compressor 6 flows from the gas pipe 41 into the main primary header 40. The refrigerant is distributed to the multiple main heat transfer tubes 22 in the main primary header 40. The refrigerant flowing through the multiple main heat transfer tubes 22 flows into the main compartments 61 of the main secondary header 60 and merges. The refrigerant that merges in the main compartments 61 flows into the communication sections 80 and reaches the auxiliary compartments 71 of the auxiliary secondary header 70. The refrigerant is distributed to the multiple auxiliary heat transfer tubes 32 in the auxiliary compartments 71. The refrigerant flowing through the multiple auxiliary heat transfer tubes 32 merges in the auxiliary primary header 50. The refrigerant that has joined in the auxiliary primary header 50 flows out from the liquid pipe 51 and into the expansion section 10 .

[0034] When the air conditioner 1 performs cooling operation and defrosting operation, the heat exchanger 8 functions as a condenser.

[0035] According to the first embodiment, in the auxiliary secondary header 70, the number of auxiliary heat transfer tubes 32 connected to the lowest auxiliary partition 71 is smaller than the number of auxiliary heat transfer tubes 32 connected to the auxiliary partitions 71 above the lowest. Therefore, the flow rate of refrigerant flowing through the auxiliary heat transfer tubes 32 in the lowest stage is relatively higher than the flow rate of refrigerant flowing through the auxiliary heat transfer tubes 32 above the lowest stage. The higher the refrigerant flow rate, the better the defrosting capacity. Therefore, the defrosting capacity can be ensured in the lower stages of the auxiliary heat exchanger group 30.

[0036] As shown in FIG. 4 , in the main heat exchanger group 20, the closer to the main primary header 40 and the higher up, the easier it is to defrost. In FIG. 4 , the areas where frost remains are indicated by hatched areas. As described above, in the first embodiment, the flow rate of refrigerant flowing through the auxiliary heat transfer tubes 32 in the lowest stage is relatively greater than the flow rate of refrigerant flowing through the auxiliary heat transfer tubes 32 in stages above the lowest stage. Therefore, the auxiliary heat transfer tubes 32 of the auxiliary heat exchanger group 30 are defrosted evenly in the vertical direction. Since the main heat transfer tubes 22 in the main heat exchanger group 20 are more defrosted as they are closer to the main primary header 40 and higher up, the auxiliary heat transfer tubes 32 of the auxiliary heat exchanger group 30 are more easily defrosted as they are closer to the auxiliary primary header 50. In this way, the auxiliary heat exchanger group 30 is efficiently defrosted.

[0037] The communication section 80 also connects the uppermost main compartment 61 of the main secondary header 60 with the lowermost auxiliary compartment 71 of the auxiliary secondary header 70. When frost formed in the heat exchanger 8 is removed during heating operation, meltwater is generated. When meltwater is generated, even if a high-temperature refrigerant flows through, the meltwater exchanges heat with the meltwater, increasing its temperature. That is, the meltwater generated by defrosting in the upper sections of the heat exchanger 8 exchanges heat with the high-temperature refrigerant, increasing its temperature. Therefore, the refrigerant temperature decreases toward the lower sections of the heat exchanger 8, making it more difficult to melt the frost. Furthermore, due to the influence of head difference, the refrigerant flow rate tends to decrease in the lower sections of the heat exchanger 8, which can easily result in a lack of heat for defrosting.

[0038] In contrast, the communication section 80 in the first embodiment communicates the uppermost main compartment 61 of the main secondary header 60 with the lowermost auxiliary compartment 71 of the auxiliary secondary header 70. This makes it possible to prevent a shortage of defrosting capacity in the lower compartment of the auxiliary heat exchanger group 30.

[0039] Second Embodiment Fig. 5 is a schematic diagram showing a heat exchanger 108 according to a second embodiment. The second embodiment differs from the first embodiment in the number of auxiliary heat transfer tubes 32 connected to the auxiliary partition section 71 of the auxiliary secondary header 70. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and their description will be omitted, and the following description will focus on the differences from the first embodiment.

[0040] 5, the number of auxiliary heat transfer tubes 32 connected to the lowest auxiliary compartment of the auxiliary secondary header 70 is one. The number of auxiliary heat transfer tubes 32 connected to the middle auxiliary compartment of the auxiliary secondary header 70 is two. The number of auxiliary heat transfer tubes 32 connected to the upper auxiliary compartment of the auxiliary secondary header 70 is three.

[0041] According to the second embodiment, the number of auxiliary heat transfer tubes 32 connected to the lowest auxiliary compartment of the auxiliary secondary header 70 is one. Therefore, the refrigerant flows through the region that is most difficult to defrost during defrosting without deterioration of refrigerant distribution due to head difference. This further enhances the defrosting effect of the auxiliary heat exchanger group 30.

[0042] Embodiment 3. Figure 6 is a schematic diagram showing the flow of refrigerant when heat exchanger 208 according to embodiment 3 functions as a condenser. This embodiment 3 differs from embodiments 1 and 2 in that the pressure loss of communication part 80 is adjusted. In this embodiment 3, parts common to embodiments 1 and 2 are assigned the same reference numerals and description thereof will be omitted, and the following description will focus on the differences from embodiments 1 and 2.

[0043] The pressure loss in the communicating portion 80 is greater than the pressure loss in the main heat transfer tube 22 and the auxiliary heat transfer tube 32. Here, the refrigerant flow rate in the communicating portion 80 that communicates the uppermost main compartment 61 of the main secondary header 60 with the lowermost auxiliary compartment 71 of the auxiliary secondary header 70 is defined as G1. The refrigerant flow rate in the communicating portion 80 that communicates the middle main compartment 61 of the main secondary header 60 with the middle auxiliary compartment 71 of the auxiliary secondary header 70 is defined as G2. The refrigerant flow rate in the communicating portion 80 that communicates the lower main compartment 61 of the main secondary header 60 with the upper auxiliary compartment 71 of the auxiliary secondary header 70 is defined as G3.

[0044] As shown in FIG. 6 , the pressure loss in the communication portion 80 is greater than the pressure loss in the main heat transfer tube 22 and the auxiliary heat transfer tube 32, which tends to result in G1≒G2≒G3. In this case, the flow rate of refrigerant flowing through the three auxiliary heat transfer tubes 32 connected to the upper auxiliary compartments of the auxiliary secondary header 70 is (1 / 3)×G1 per tube. Furthermore, the flow rate of refrigerant flowing through the single auxiliary heat transfer tube 32 connected to the lowermost auxiliary compartment of the auxiliary secondary header 70 is G3 per tube. Since G3 > (1 / 3)×G1, a large amount of refrigerant flows through the auxiliary heat transfer tube 32 connected to the lowermost auxiliary compartment of the auxiliary secondary header 70. Therefore, a lack of defrosting capacity in the lower compartments of the auxiliary heat exchanger group 30 can be suppressed.

[0045] 7 is a schematic diagram showing a heat exchanger 308 and a blower 309 according to a fourth embodiment. In this fourth embodiment, the configuration of the blower 309 differs from that of the first to third embodiments. In this fourth embodiment, the same parts as those in the first to third embodiments are denoted by the same reference numerals and their description is omitted, and the following description will focus on the differences from the first to third embodiments.

[0046] The blower 309 is configured so that the amount of air blown by it decreases radially from its axial center in the axial direction normal to the heat exchanger 308. That is, the blower 309 is a side flow fan. In FIG. 7 , the horizontal axis represents air speed, and the vertical axis represents the axial position of the blower 309. As shown in FIG. 7 , the axial center of the blower 309 faces a position of the main heat exchanger group 20 on the auxiliary heat exchanger group 30 side. The portion of the blower 309 facing the heat exchanger 308 moves farther from the axial center of the blower 309 in the radial direction. This reduces the amount of heat exchange at the topmost main heat transfer tube 22 and the bottommost auxiliary heat transfer tube 32, which are farthest from the position facing the axis of the blower 309. This reduces the amount of frost that forms on the topmost main heat transfer tube 22 and the bottommost auxiliary heat transfer tube 32.

[0047] In the above-described first to fourth embodiments, the heat exchanger 8 is exemplified, but the use-side heat exchanger 11 may have the above configuration, or both the heat exchanger 8 and the use-side heat exchanger 11 may have the above configuration. In addition, in the above-described first to fourth embodiments, the air conditioning device 1 is exemplified, but the present invention is not limited to this and may also be applied to a refrigeration device or a heat pump device that constitutes a refrigerant circuit 4 and has a heat exchanger 8 that acts as an evaporator or a condenser.

[0048] 1 Air conditioning device, 1a Outdoor air, 2 Heat source side unit, 3 User side unit, 4 Refrigerant circuit, 5 Refrigerant piping, 6 Compressor, 7 Flow path switching device, 8 Heat exchanger, 9 Fan, 10 Expansion section, 11 User side heat exchanger, 12 User side fan, 20 Main heat exchanger group, 21 Main fin, 22 Main heat transfer pipe, 30 Auxiliary heat exchanger group, 31 Auxiliary fin, 32 Auxiliary heat transfer pipe, 40 Main primary side header, 41 Gas pipe, 50 Auxiliary primary side header, 51 Liquid pipe, 60 Main secondary side header, 61 Main compartment, 70 Auxiliary secondary side header, 71 Auxiliary compartment, 80 Communication section, 108 Heat exchanger, 208 Heat exchanger, 308 Heat exchanger, 309 Fan.

Claims

1. A main heat exchanger group having a plurality of main fins arranged at intervals to transfer heat, and a plurality of main heat transfer tubes that penetrate the main fins and have a refrigerant flowing through them and are aligned in a vertical direction; an auxiliary heat exchanger group arranged below the main heat exchanger group, having a plurality of auxiliary fins arranged at intervals to transfer heat, and a plurality of auxiliary heat transfer tubes that penetrate the auxiliary fins and have a refrigerant flowing through them and are aligned in a vertical direction; a main primary side header connected to a plurality of the main heat transfer tubes and through which the sucked refrigerant flows into the plurality of main heat transfer tubes; an auxiliary primary side header connected to a plurality of the auxiliary heat transfer tubes and through which the refrigerant flows out from the plurality of auxiliary heat transfer tubes; and a main secondary side header connected to the side of the plurality of main heat transfer tubes opposite to the main primary side header and through which the refrigerant flows out from the plurality of main heat transfer tubes. an auxiliary secondary header connected to the opposite side of the auxiliary heat transfer tubes from the auxiliary primary header, into which refrigerant flowing from the main secondary header flows, the interior of which is partitioned into a plurality of auxiliary compartments, and the number of the auxiliary heat transfer tubes connected to the lowest auxiliary compartment is fewer than the number of the auxiliary heat transfer tubes connected to the auxiliary compartments above the lowest compartment.

2. The heat exchanger according to claim 1, further comprising a communication portion connecting said main secondary header and said auxiliary secondary header.

3. A heat exchanger as described in claim 2, wherein the main secondary header is internally divided into a plurality of main compartments, and the communication section connects the uppermost main compartment of the main secondary header with the lowermost auxiliary compartment of the auxiliary secondary header.

4. A heat exchanger according to claim 2 or 3, wherein the pressure loss in the communication section is greater than the pressure loss in the main heat transfer tube and the auxiliary heat transfer tube.

5. A heat exchanger according to any one of claims 1 to 4, wherein the number of the auxiliary heat transfer tubes connected to the auxiliary compartment section at the lowest stage of the auxiliary secondary header is one.

6. An air conditioner comprising a compressor, a flow switching device, a refrigerant circuit in which a heat exchanger according to any one of claims 1 to 5, an expansion section, and a utilization side heat exchanger are connected by piping.

7. The air conditioning apparatus according to claim 6, further comprising a blower which blows air to the heat exchanger in a radial direction away from the heat exchanger from an axial center in an axial direction along a normal direction of the heat exchanger.

8. The air conditioner according to claim 6 or 7, wherein cooling operation, heating operation and defrosting operation are performed by switching the flow path switching device.

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