JP7706578B2 - Air conditioning heat exchangers - Google Patents

Description

The present disclosure relates to an air-conditioning heat exchanger having a holder for storing a hairpin portion of a heat transfer tube.

A known air-conditioning heat exchanger includes a plurality of fins, a heat transfer tube with one end folded back at a hairpin section and passing through the plurality of fins, and a holder that stores the hairpin section of the heat transfer tube. For example, Patent Document 1 describes an air-conditioning heat exchanger that includes a holder that ensures strength, optimizes the air path, and prevents corrosion at the hairpin section.

Here, in an air-conditioning heat exchanger such as that described in Patent Document 1, condensation water that forms on the surface of the heat exchanger during cooling operation remains in the gap between the hairpin part and the inner surface of the holder due to surface tension, which raises concerns about corrosion in the hairpin part. Therefore, Patent Document 1 proposes to open up a sufficient gap between the hairpin part and the inner surface of the holder so that the condensation water can flow down, thereby preventing the condensation water from remaining and avoiding corrosion.

JP 2021-55953 A

However, condensation water that adheres to the hairpin portion tends to collect vertically on the hairpin portion due to gravity. Therefore, even if there is a sufficient gap between the hairpin portion and the inner surface of the holder, the condensation water may collect and remain there due to surface tension, blocking the gap. Also, condensation water that falls from the hairpin portion is received by the bottom surface of the holder. Therefore, even if condensation water falls from the hairpin portion, it may remain there blocking the gap between the heat transfer tube and the bottom surface of the holder. Therefore, if condensation water remains in the gap between the heat transfer tube and the inner surface of the holder for a long time, corrosion may occur in the hairpin portion.

The present disclosure has been made to solve the problems described above, and provides an air-conditioning heat exchanger that suppresses the occurrence of corrosion in the hairpin section of the heat transfer tube.

The air-conditioning heat exchanger according to the present disclosure includes a plurality of fins arranged at intervals in a first direction, a heat transfer tube having a hairpin portion that penetrates the plurality of fins and is folded back at an end in the first direction, and a holder having a tubular portion in which the hairpin portion is stored, the heat transfer tube having a first straight pipe portion and a second straight pipe portion that are aligned in a vertical direction, the first straight pipe portion being located above the second straight pipe portion, the hairpin portion being provided between the first straight pipe portion and the second straight pipe portion, the hairpin portion is connected to the second straight tube portion, and the outer peripheral surface of the hairpin portion has a first hydrophilic portion with a hydrophilic coating formed thereon in a portion located above the axis of the second straight tube portion in the vertical direction, the inner peripheral surface of the tubular portion has a second hydrophilic portion with a hydrophilic coating formed thereon in a portion located below the axis of the second straight tube portion, no hydrophilic coating is formed on the portion located above the axis of the second straight tube portion, and the first hydrophilic portion is not provided in the region where the second hydrophilic portion is projected onto the outer peripheral surface of the hairpin portion.

According to the present disclosure, the hairpin portion of the heat transfer tube has a first hydrophilic portion on which a hydrophilic coating is formed on the outer peripheral surface located above the axis of the second straight tube portion. Also, the tubular portion of the holder in which the hairpin portion is stored has a second hydrophilic portion on which a hydrophilic coating is formed on the inner peripheral surface of the bottom surface portion. Therefore, above the axis of the second straight tube portion, the first hydrophilic portion makes it easier for condensed water to move, and the condensed water is prevented from staying to block the gap between the outer peripheral surface of the hairpin portion and the inner peripheral surface of the tubular portion of the holder. Also, at the bottom surface portion of the holder, the second hydrophilic portion makes it easier for condensed water to move, and the condensed water is prevented from staying to block the gap between the inner peripheral surface of the holder and the outer peripheral surface of the hairpin portion. Therefore, it is possible to prevent condensed water from adhering to the hairpin portion of the heat transfer tube for a long period of time, and therefore it is possible to prevent corrosion from occurring in the hairpin portion.

1 is a circuit diagram showing an air conditioning apparatus according to a first embodiment. 1 is a perspective view showing an air-conditioning heat exchanger according to a first embodiment. FIG. 2 is a front view of the holder according to the first embodiment. 4 is a partial perspective view of a cylindrical portion of a holder and a heat transfer tube according to the first embodiment. FIG. 4 is a simplified front view showing a tube portion and a hairpin portion of the holder according to the first embodiment. FIG. 3 is a schematic diagram showing a hydrophilic portion according to the first embodiment. FIG. FIG. 4 is a schematic vertical cross-sectional view taken along line AA in FIG. 3. 10 is a schematic diagram showing a state in which condensed water remains between an outer circumferential surface of a hairpin portion and an inner circumferential surface of a tubular portion of a holder in the first embodiment. FIG. 10 is a schematic diagram showing a water-repellent portion according to a second embodiment. FIG. 11 is a schematic vertical cross-sectional view of a holder and a heat transfer tube in embodiment 2. FIG.

Hereinafter, an embodiment of the air-conditioning heat exchanger according to the present disclosure will be described with reference to the attached drawings. Note that the form of the drawings is an example and does not limit the present disclosure. Also, the same reference numerals in each drawing are the same or equivalent, and this is common throughout the entire specification. In the following description, duplicated parts will be appropriately simplified or omitted. Note that the present disclosure is not limited to the embodiments described below, and may include any combination of the configurations disclosed in the following embodiments. Also, the position, shape, and size of each component in the attached drawings may differ from the actual ones. Furthermore, hatching has been appropriately omitted in the cross-sectional views of the attached drawings in consideration of visibility.

In addition, in the following description, terms indicating directions are used as appropriate to facilitate understanding, but these terms are for explanatory purposes and do not limit the present disclosure. Examples of terms indicating directions include "up," "down," "right," "left," "front," and "rear."

Embodiment 1.
1 is a circuit diagram showing an air conditioner 1 according to embodiment 1. The air conditioner 1 is a device that adjusts indoor air, and includes an outdoor unit 2 and an indoor unit 3. The outdoor unit 2 is provided with, for example, a compressor 6, a flow path switching device 7, an outdoor heat exchanger 8, an outdoor blower 9, and an expansion section 10. The indoor unit 3 is provided with, for example, an air conditioning heat exchanger 11 and a blower 12.

The refrigerant circuit 4 is formed by connecting the compressor 6, the flow switching device 7, the outdoor heat exchanger 8, the expansion section 10, and the air conditioning heat exchanger 11 with the refrigerant piping 5. The compressor 6 draws in refrigerant in a low-temperature and low-pressure state, compresses the drawn refrigerant, and discharges it as refrigerant in a high-temperature and high-pressure state. The flow switching device 7 switches the direction in which the refrigerant flows in the refrigerant circuit 4, and is, for example, a four-way valve. The outdoor heat exchanger 8 exchanges heat between, for example, outdoor air and the refrigerant. The outdoor heat exchanger 8 acts as a condenser during cooling operation and dehumidification operation, and acts as an evaporator during heating operation. The outdoor blower 9 is a device that sends outdoor air to the outdoor heat exchanger 8.

The expansion section 10 is a pressure reducing valve or expansion valve that reduces the pressure of the refrigerant to expand it. The expansion section 10 is, for example, an electronic expansion valve whose opening degree is adjustable. The air conditioning heat exchanger 11 exchanges heat between, for example, indoor air and the refrigerant. The air conditioning heat exchanger 11 acts as an evaporator during cooling operation and dehumidification operation, and acts as a condenser during heating operation. The blower 12 is a device that sends indoor air to the air conditioning heat exchanger 11.

(Cooling and dehumidification operation)
Next, the operation of the air conditioner 1 will be described. First, the cooling operation and the dehumidification operation will be described. In the cooling operation and the dehumidification operation, the refrigerant sucked 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 state refrigerant discharged from the compressor 6 passes through the flow switching device 7 and flows into the outdoor heat exchanger 8 acting as a condenser, where it is heat exchanged with the outdoor air sent by the outdoor blower 9, and condensed and liquefied. The condensed liquid state refrigerant flows into the expansion section 10, where it is expanded and decompressed to become a low-temperature, low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flows into the air conditioning heat exchanger 11 acting as an evaporator, where it is heat exchanged with the indoor air sent by the blower 12, and evaporates and gasifies. At this time, the indoor air is cooled, and cooling or dehumidification 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 .

(Heating operation)
Next, the heating operation will be described. In the heating operation, the refrigerant sucked 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 state refrigerant discharged from the compressor 6 passes through the flow path switching device 7 and flows into the air-conditioning heat exchanger 11 acting as a condenser, where it is heat-exchanged with the indoor air sent by the blower 12, condensed and liquefied. At this time, the indoor air is warmed, and heating is performed in the room. The condensed liquid state refrigerant flows into the expansion section 10, where it is expanded and decompressed to become a low-temperature, low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant then flows into the outdoor heat exchanger 8 acting as an evaporator, where it is heat-exchanged with the outdoor air sent by the outdoor blower 9, evaporating and gasifying. The evaporated low-temperature, low-pressure gas state refrigerant passes through the flow path switching device 7 and is sucked into the compressor 6.

(Air conditioning heat exchanger 11)
Fig. 2 is a perspective view showing the air-conditioning heat exchanger 11 according to the first embodiment. In the present disclosure, as shown in Fig. 2, a first direction X indicates the width direction of the air-conditioning heat exchanger 11. A second direction Y indicates the up-down direction of the air-conditioning heat exchanger 11. A third direction Z indicates the front-rear direction of the air-conditioning heat exchanger 11. The air-conditioning heat exchanger 11 includes a plurality of fins 20, a plurality of heat transfer tubes 30, and a holder 40.

(Fin 20)
The multiple fins 20 are arranged at intervals in a first direction X, which is the width direction of the air-conditioning heat exchanger 11. Indoor air drawn into the air-conditioning heat exchanger 11 passes between the multiple fins 20.

(Heat transfer tube 30)
The heat transfer tube 30 is made of, for example, metal, and is provided to penetrate the multiple fins 20. The heat transfer tube 30 has a hairpin portion 31 that is folded back at an end in the first direction X. The hairpin portion 31 is folded 180 degrees with a predetermined curvature. When the air conditioning device 1 is in operation, the refrigerant flows inside the heat transfer tube 30. A part of the heat transfer tube 30 is exposed between the multiple fins 20 arranged in the first direction X. As a result, indoor air passing between the multiple fins 20 hits the heat transfer tube 30, and heat exchange occurs between the refrigerant flowing inside the heat transfer tube 30 and the indoor air. The heat transfer tube 30 has a cylindrical shape. At one end in the first direction X, a refrigerant pipe 5 is connected to a part of the heat transfer tube 30. The refrigerant pipe 5 is covered with a pipe cover 13. The refrigerant pipe 5 is protected by the pipe cover 13 and insulated from the outside air.

(Holder 40 and hairpin portion 31)
2, the holder 40 is provided at one end in the first direction X of a unit in which the fin 20 and the heat transfer tube 30 are combined. The end in the first direction X at which the holder 40 is provided is the end opposite to the end at which the refrigerant piping 5 is connected to the heat transfer tube 30. The holder 40 has a function of ensuring the strength of the air-conditioning heat exchanger 11 and protecting the hairpin portion 31 of the heat transfer tube 30. The holder 40 is made of, for example, resin.

The holder 40 and the hairpin portion 31 of the heat transfer tube 30 will be described with reference to Figures 3 to 7. Figure 3 is a front view of the holder 40 according to embodiment 1. Figure 4 is a partial perspective view of the tubular portion 42 of the holder 40 and the heat transfer tube 30 according to embodiment 1. Figure 4 shows a simplified outline of the holder 40, the fins 20, and the heat transfer tube 30. Figure 5 is a simplified front view showing the tubular portion 42 and the hairpin portion 31 of the holder 40 according to embodiment 1. Figure 5 shows an extracted portion of the holder 40. Figure 6 is a schematic diagram showing the hydrophilic portion 51 according to embodiment 1. Figure 7 is a schematic vertical cross-sectional view taken along line A-A in Figure 3.

As shown in Figure 3, the holder 40 has an opening 41. Also, as shown in Figure 4, the tubular portion 42 of the holder 40 protrudes from the edge of the opening 41 of the holder 40 toward the outside in the first direction X. Here, the outside in the first direction X refers to the side opposite to the side on which the fin 20 is located. The holder 40 has a tubular portion opening 43 facing the opening 41.

4 and 7, the heat transfer tube 30 has a first straight pipe section 33 and a second straight pipe section 34 aligned in the vertical direction. The first straight pipe section 33 is located above the second straight pipe section 34. The hairpin section 31 is provided between the first straight pipe section 33 and the second straight pipe section 34, and connects the first straight pipe section 33 and the second straight pipe section 34. The apex 32 of the hairpin section 31 is located midway between the first straight pipe section 33 and the second straight pipe section 34 in the vertical direction. The part of the heat transfer tube 30 that is stored in the cylindrical section 42 of the holder 40 is called the hairpin section 31. The hairpin section 31 includes a bent section and a straight pipe section.

As shown in Figure 4, the hairpin portion 31 of the heat transfer tube 30 is inserted into the opening 41 of the holder 40 and stored in the tubular portion 42 of the holder 40. A portion of the outer peripheral surface 31a of the hairpin portion 31 faces a portion of the inner peripheral surface 42a of the tubular portion 42. The tubular portion 42 has a bottom surface portion 42b. A tubular portion opening 43 is provided in the tubular portion 42. A second hydrophilic portion 51b, which will be described later, is provided on the inner peripheral surface 42a of the bottom surface portion 42b of the tubular portion 42. As shown in Figures 4 and 5, the hairpin portion 31 extending vertically can be seen from the tubular portion opening 43.

The hairpin portion 31 of the heat transfer tube 30 has an apex 32 at the end in the first direction X. The apex 32 is the apex of the bent portion of the hairpin portion 31. As shown in FIG. 4 and FIG. 7, the hairpin portion 31 is stored in the tubular portion 42 of the holder 40 without protruding from the tubular portion 42. Therefore, when the air-conditioning heat exchanger 11 is viewed in the front-rear direction, i.e., in the third direction Z, the hairpin portion 31 is covered by the tubular portion 42 and cannot be seen. By being stored in the tubular portion 42, the hairpin portion 31 is less susceptible to external influences. In other words, the tubular portion 42 of the holder 40 protects the hairpin portion 31. In FIG. 4 to FIG. 7, one hairpin portion 31 is stored in one tubular portion 42. However, although not shown, a configuration in which multiple hairpin portions 31 are stored in one tubular portion 42 may be used.

The tube portion 42 of the holder 40 optimizes the air path of the air flowing into the air-conditioning heat exchanger 11. The tube portion 42 allows the air flowing into the air-conditioning heat exchanger 11 to flow in the first direction X toward the center of the air-conditioning heat exchanger 11 where the fins 20 are arranged, rather than flowing in the third direction Z at the side of the air-conditioning heat exchanger 11 where the hairpin portion 31 is arranged. As shown in FIG. 5, there is a gap SP between the outer peripheral surface 31a of the hairpin portion 31 inserted into the tube portion 42 and the inner peripheral surface 42a of the tube portion 42. Therefore, air can flow toward the center of the air-conditioning heat exchanger 11 through this gap SP.

(Hydrophilic part 51)
Next, the hydrophilic portion 51 on the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 will be described with reference to FIGS. 6 and 7. As shown in FIGS. 6 and 7, the outer peripheral surface 31a of the hairpin portion 31 has a first hydrophilic portion 51a formed by applying a hydrophilic coating. The inner peripheral surface 42a of the tube portion 42 has a second hydrophilic portion 51b formed by applying a hydrophilic coating. In the following description, when there is no need to particularly distinguish between the first hydrophilic portion 51a and the second hydrophilic portion 51b, they will be simply referred to as "hydrophilic portion 51" as appropriate. In addition, when the term "hydrophilic portion 51" is used, it is intended to include both singular and plural portions. The hydrophilic coating of the hydrophilic portion 51 is applied to the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 by, for example, spray painting or brush painting.

6 and 7, not all of the outer peripheral surface 31a of the hairpin section 31 has the first hydrophilic portion 51a, and not all of the inner peripheral surface 42a of the tube section 42 has the second hydrophilic portion 51b. As shown in FIG. 7, when the axis AX of the second straight tube section 34 of the heat transfer tube 30 is extended to the hairpin section 31, the first hydrophilic portion 51a is provided above the axis AX on the outer peripheral surface 31a of the hairpin section 31 in the vertical direction. In other words, in the vertical direction, the first hydrophilic portion 51a is not provided on the outer peripheral surface 31a of the hairpin section 31 located below the axis AX. Also, as shown in FIG. 6, the second hydrophilic portion 51b is provided below the axis AX on the inner peripheral surface 42a of the tube section 42. In other words, in the vertical direction, the second hydrophilic portion 51b is not provided on the inner circumferential surface 42a of the tubular portion 42 located above the axis line AX.

Furthermore, the first hydrophilic portion 51a may not be provided on the outer peripheral surface 31a of the hairpin portion 31 located above the axis AX in a portion that does not face the inner peripheral surface 42a of the tube portion 42. For example, as shown in FIG. 7, the straight portion of the hairpin portion 31 connected to the first straight portion 33 of the heat transfer tube 30 may not be provided on the outer peripheral surface 31a of the bottom surface of the straight portion. Also, the straight portion of the hairpin portion 31 connected to the second straight portion 34 of the heat transfer tube 30 may not be provided on the outer peripheral surface 31a of the top surface of the straight portion. Furthermore, the first hydrophilic portion 51a may not be provided on the outer peripheral surface 31a of the bent portion between the bottom surface of the upper straight portion of the hairpin portion 31 and the upper surface of the lower straight portion.

For ease of explanation, the gap between the outer peripheral surface 31a of the hairpin portion 31 located above the axis AX and having the first hydrophilic portion 51a, and the inner peripheral surface 42a of the tubular portion 42 will be referred to as gap SP1. Also, the gap between the outer peripheral surface 31a of the hairpin portion 31 located below the axis AX and not having the first hydrophilic portion 51a, and the inner peripheral surface 42a of the tubular portion 42 will be referred to as gap SP2. Also, when there is no need to particularly distinguish between gap SP1 and gap SP2, they will be simply referred to as "gap SP" as appropriate.

The second hydrophilic portion 51b may be provided on the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42, as shown in Figures 6 and 7. More preferably, the second hydrophilic portion 51b may be provided on a portion of the inner peripheral surface 42a of the tube portion 42 that faces the outer peripheral surface 31a of the hairpin portion 31, facing a portion where the first hydrophilic portion 51a is not provided. In addition, when the second hydrophilic portion 51b is projected onto the outer peripheral surface 31a of the hairpin portion 31, the portion of the first hydrophilic portion 51a located below the axis AX does not overlap with the area where the second hydrophilic portion 51b is projected. In other words, when the second hydrophilic portion 51b is projected onto the outer peripheral surface 31a of the hairpin portion 31, the first hydrophilic portion 51a is not provided in the projected area.

The hydrophilic portion 51 prevents the condensed water 50 from remaining in the gap SP between the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 while blocking the gap. First, the state in which the condensed water 50 remains in the gap SP between the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 will be described with reference to FIG. 8. FIG. 8 is a schematic diagram showing the state in which the condensed water 50 remains between the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 of the holder 40 in the first embodiment.

When the air conditioning device 1 performs cooling or dehumidification operation and the air conditioning heat exchanger 11 acts as an evaporator, the heat transfer tube 30 is cooled by the refrigerant flowing inside the heat transfer tube 30. At this time, if the humidity around the heat transfer tube 30 is high, condensation may occur on the surface of the heat transfer tube 30. If the amount of condensed water 50 gradually increases while the cooling or dehumidification operation continues, the condensed water 50 adheres to the gap SP between the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 in a state of straddling the gap SP. In other words, the condensed water 50 blocks the gap SP. In this state, the condensed water 50 becomes difficult to move and remains in the gap SP for a long time.

In this embodiment, since the hydrophilic portion 51 is provided in a part of the portion where the gap SP contacts, the condensed water 50 moves preferentially to the hydrophilic portion 51. Therefore, the condensed water 50 is unlikely to remain in one place in the gap SP1 between the outer peripheral surface 31a of the hairpin portion 31 having the first hydrophilic portion 51a and the inner peripheral surface 42a of the tube portion 42. In addition, the condensed water 50 flows vertically along the outer peripheral surface 31a of the hairpin portion 31 due to gravity and collects. Since the heat transfer tube 30 has a cylindrical shape, the condensed water 50 is likely to collect on the outer peripheral surface 31a of the bottom surface of the straight tube portion of the hairpin portion 31. Therefore, the condensed water 50 is unlikely to remain in the gap SP1 between the outer peripheral surface 31a of the hairpin portion 31 located above the axis AX and the inner peripheral surface 42a of the tube portion 42. Furthermore, in the first hydrophilic portion 51a, since the contact angle of the condensed water 50 is small, a large amount of the condensed water 50 must gather in order to block the gap SP. However, since the condensed water 50 is unlikely to remain in the gap SP1 between the outer peripheral surface 31a of the hairpin portion 31 located above the axis AX and the inner peripheral surface 42a of the tube portion 42, blocking with the condensed water 50 is suppressed.

The condensed water 50 that has fallen from the hairpin portion 31 is received by the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42. The second hydrophilic portion 51b is provided on the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42, so the contact angle of the condensed water 50 is small. In order for the condensed water 50 to block the gap SP2, a large amount of the condensed water 50 needs to gather, but the second hydrophilic portion 51b makes it difficult for the condensed water 50 to remain in one place in large amounts. In addition, the first hydrophilic portion 51a of the hairpin portion 31 is not provided on the opposite side of the second hydrophilic portion 51b. Therefore, even if the condensed water 50 adheres to the gap SP2 between the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42 and the outer peripheral surface 31a of the hairpin portion 31 in a state of straddling it, the condensed water 50 will move preferentially to the second hydrophilic portion 51b. Therefore, between the inner circumferential surface 42 a of the bottom portion 42 b of the tube portion 42 and the outer circumferential surface 31 a of the hairpin portion 31 , the condensed water 50 is unlikely to remain blocking the gap SP<b>2 .

As described above, in this embodiment, the air-conditioning heat exchanger 11 includes a plurality of fins 20 arranged at intervals in the first direction X, a heat transfer tube 30 having a hairpin portion 31 that is provided penetrating the plurality of fins 20 and that is folded back at the end in the first direction X, and a holder 40 having a tubular portion 42 in which the hairpin portion 31 is stored. The heat transfer tube 30 has a first straight pipe portion 33 and a second straight pipe portion 34 that are aligned vertically, the first straight pipe portion 33 is located above the second straight pipe portion 34, and the hairpin portion 31 is provided between the first straight pipe portion 33 and the second straight pipe portion 34, and connects the first straight pipe portion 33 and the second straight pipe portion 34. The outer surface 31a of the hairpin portion 31 has a first hydrophilic portion 51a having a hydrophilic coating formed thereon, at a portion located above the axis AX of the second straight tube portion 34 in the vertical direction, and the inner surface 42a of the bottom portion 42b of the tube portion 42 has a second hydrophilic portion 51b having a hydrophilic coating formed thereon.

According to this configuration, the outer peripheral surface 31a of the hairpin portion 31 of the heat transfer tube 30 located above the axis AX in the vertical direction has the first hydrophilic portion 51a. On the other hand, the inner peripheral surface 42a of the tube portion 42 located above the axis AX does not have the second hydrophilic portion 51b. Therefore, in the gap SP1 between the outer peripheral surface 31a of the hairpin portion 31 and the inner peripheral surface 42a of the tube portion 42 located above the axis AX, the condensed water 50 moves preferentially to the first hydrophilic portion 51a. Therefore, above the axis AX, the condensed water 50 is less likely to remain in a blocked state in the gap SP1. In addition, the condensed water 50 flows vertically on the outer peripheral surface 31a of the hairpin portion 31 and collects, so that the condensed water 50 is more likely to fall from the outer peripheral surface 31a of the hairpin portion 31 due to gravity. In addition, the condensed water 50 that has fallen from the hairpin portion 31 is received by the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42, and moves preferentially to the second hydrophilic portion 51b. Therefore, the condensed water 50 is unlikely to remain in a state in which it blocks the gap SP2 between the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42 and the facing outer peripheral surface 31a of the hairpin portion 31. In this way, the condensed water 50 can be prevented from adhering to the outer peripheral surface 31a of the hairpin portion 31 for a long period of time, so that the occurrence of corrosion in the hairpin portion 31 can be prevented. Therefore, the corrosion of the air-conditioning heat exchanger 11 can be reduced, and a more reliable air-conditioning heat exchanger 11 can be provided. Furthermore, by reducing the corrosion of the air-conditioning heat exchanger 11, a long-life air-conditioning heat exchanger 11 can be realized.

In addition, in the air-conditioning heat exchanger 11 according to this embodiment, the first hydrophilic portion 51a is not provided in the area where the second hydrophilic portion 51b is projected onto the outer peripheral surface 31a of the hairpin portion 31. According to this configuration, the second hydrophilic portion 51b is provided on the opposite side of the outer peripheral surface 31a of the hairpin portion 31 that does not have the first hydrophilic portion 51a. The outer peripheral surface 31a of the hairpin portion 31 located below the axis AX may receive condensation water 50 that has fallen from the outer peripheral surface 31a of the hairpin portion 31 located above the axis AX. However, the outer peripheral surface 31a of the hairpin portion 31 located below the axis AX does not have a hydrophilic portion 51. Therefore, the condensation water 50 that has fallen and the condensation water 50 that was originally attached to the hairpin portion 31 gather together, and the condensation water 50 is likely to straddle and adhere to the gap SP2. However, because the inner circumferential surface 42a of the tubular portion 42 has the second hydrophilic portion 51b, the condensed water 50 moves preferentially to the second hydrophilic portion 51b. This makes it possible to prevent the condensed water 50 from remaining in a state where it blocks the gap SP2 between the outer circumferential surface 31a of the hairpin portion 31 and the inner circumferential surface 42a of the tubular portion 42 below the axis line AX. This makes it possible to prevent the condensed water 50 from adhering for a long period of time to the outer circumferential surface 31a of the hairpin portion 31 located below the axis line AX, thereby making it possible to prevent corrosion from occurring in the hairpin portion 31.

Embodiment 2.
The air-conditioning heat exchanger 11 according to the second embodiment differs from the air-conditioning heat exchanger 11 according to the first embodiment in that the outer peripheral surface 31a of the hairpin portion 31 has a water-repellent portion 52. The water-repellent portion 52 in this embodiment will be described below, focusing on the differences from the first embodiment. Except for the water-repellent portion 52, the configuration of the air-conditioning heat exchanger 11 in this embodiment is similar to the configuration of the first embodiment, and therefore a description of parts other than the water-repellent portion 52 will be omitted. Furthermore, the same components as those in the first embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

The water-repellent portion 52 in this embodiment will be described with reference to Figures 9 and 10. Figure 9 is a schematic diagram showing the water-repellent portion 52 in embodiment 2. Figure 10 is a schematic vertical cross-sectional view of the holder 40 and the heat transfer tube 30 in embodiment 2. Figure 10 shows a vertical cross-section taken along line A-A in Figure 3. In addition, in Figure 10, the water-repellent portion 52 is painted over for visibility.

9 and 10, the outer peripheral surface 31a of the hairpin portion 31 has a water-repellent portion 52 on which a water-repellent coating is formed. As shown in FIG. 10, the water-repellent portion 52 is provided on the outer peripheral surface 31a of the hairpin portion 31 at a portion located below the axis AX. More specifically, the water-repellent portion 52 is provided on the outer peripheral surface 31a of the hairpin portion 31 located below the axis AX at a portion where the first hydrophilic portion 51a is not provided. Since the water-repellent coating is formed on the water-repellent portion 52, the contact angle of the condensed water 50 becomes large, and the condensed water 50 adheres to the water-repellent portion 52 in a substantially spherical shape. For this reason, the condensed water 50 rolls on the water-repellent portion 52 and tends to collect on the outer peripheral surface 31a of the bottom surface of the straight pipe portion located below the hairpin portion 31. Therefore, the condensed water 50 is likely to adhere to the gap SP2 between the outer peripheral surface 31a of the bottom surface of the straight pipe portion of the hairpin portion 31 and the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42 in a straddling state. However, since the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42 has the second hydrophilic portion 51b, the condensed water 50 moves preferentially to the second hydrophilic portion 51b. Therefore, in the gap SP2 located below the axis AX, it is possible to prevent the condensed water 50 from remaining in a blocking state between the outer peripheral surface 31a of the bottom surface of the straight pipe portion of the hairpin portion 31 and the inner peripheral surface 42a of the bottom surface portion 42b of the tube portion 42. Therefore, it is possible to prevent the occurrence of corrosion in the hairpin portion 31, and as a result, it is possible to provide a highly reliable air-conditioning heat exchanger 11.

In addition, in the air-conditioning heat exchanger 11 according to this embodiment, the water-repellent portion 52 is provided at a position facing the second hydrophilic portion 51b. Even if the amount of condensation water 50 adhering to the water-repellent portion 52 is small, the condensation water 50 is easily brought into contact with the inner circumferential surface 42a of the tube portion 42 facing the water-repellent portion 52 because the condensation water 50 is attached in a substantially spherical shape. Since the inner circumferential surface 42a of the tube portion 42 facing the water-repellent portion 52 has the second hydrophilic portion 51b, the condensation water 50 moves preferentially to the second hydrophilic portion 51b. Therefore, even if the amount of condensation water 50 adhering to the water-repellent portion 52 is small, the condensation water 50 can move preferentially to the second hydrophilic portion 51b of the inner circumferential surface 42a of the tube portion 42. Therefore, the condensation water 50 is prevented from adhering to the hairpin portion 31 for a long time. Therefore, the occurrence of corrosion in the hairpin portion 31 can be suppressed, and as a result, a highly reliable air-conditioning heat exchanger 11 can be provided.

REFERENCE SIGNS LIST 1 Air conditioner, 2 Outdoor unit, 3 Indoor unit, 4 Refrigerant circuit, 5 Refrigerant piping, 6 Compressor, 7 Flow path switching device, 8 Outdoor heat exchanger, 9 Outdoor blower, 10 Expansion section, 11 Air conditioning heat exchanger, 12 Blower, 13 Pipe cover, 20 Fin, 30 Heat transfer tube, 31 Hairpin section, 31a Outer circumferential surface, 32 Top section, 33 First straight pipe section, 34 Second straight pipe section, 40 Holder, 41 Opening, 42 Cylinder section, 42a Inner circumferential surface, 42b Bottom section, 43 Cylinder section opening, 50 Condensed water, 51 Hydrophilic section, 51a First hydrophilic section, 51b Second hydrophilic section, 52 Water repellent section, SP Gap, SP1 Gap, SP2 Gap, AX Axis, X First direction, Y Second direction, Z Third direction.

Claims (3)

A plurality of fins spaced apart in a first direction;
a heat transfer tube having a hairpin portion that is provided through the plurality of fins and that is folded back at an end portion in the first direction;
a holder having a tubular portion in which the hairpin portion is housed;
The heat transfer tube has a first straight tube portion and a second straight tube portion aligned in a vertical direction,
The first straight pipe portion is located above the second straight pipe portion,
the hairpin portion is provided between the first straight pipe portion and the second straight pipe portion and connects the first straight pipe portion and the second straight pipe portion,
an outer circumferential surface of the hairpin portion has a first hydrophilic portion on which a hydrophilic coating is formed, the first hydrophilic portion being located above an axis of the second straight tube portion in the vertical direction;
a second hydrophilic portion on the inner circumferential surface of the cylindrical portion, the second hydrophilic portion being formed with the hydrophilic coating at a portion located below the axis of the second straight pipe portion, and the hydrophilic coating not being formed at a portion located above the axis of the second straight pipe portion;
the first hydrophilic portion is not provided in a region where the second hydrophilic portion is projected onto the outer circumferential surface of the hairpin portion. The air-conditioning heat exchanger according to claim 1 , wherein the outer circumferential surface of the hairpin portion has a water-repellent portion on which a water-repellent coating is formed, the water-repellent portion being located below the axis of the second straight pipe portion. The air-conditioning heat exchanger according to claim 2 , wherein the water-repellent portion is provided at a position facing the second hydrophilic portion.

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