Air conditioner

Abstract

Provided is an air conditioner. Aluminum hydroxide may fly into a room. An air conditioner (1) is provided with an indoor unit (2) and an outdoor unit (3). The indoor unit (2) includes a first heat exchanger (20). The outdoor unit (3) includes a second heat exchanger (30). The first heat exchanger (20) has first flat tubes (21) and first fins (22). The first fins (22) are joined to the first flat tubes (21). The second heat exchanger (30) has second flat tubes (31) and second fins (32). The second fins (32) are joined to the second flat tubes (31). The potential difference between the first fin (22) and the first flat tube (21) is smaller than the potential difference between the second fin (32) and the second flat tube (31).

Description

Technical Field

[0001] The utility model relates to an air conditioner. Background Art

[0002] Conventionally, a heat exchanger including flat tubes and fins is known. As such a heat exchanger, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-43216) can be cited.

[0003] The heat exchanger of Patent Document 1 discloses the following technology: heat exchange tubes and fins made of aluminum and aluminum alloy are brazed together, and the potentials of the fins, the surface of the heat exchange tubes and the core of the heat exchange tubes after brazing are in the relationship of (high) heat exchange tube core > heat exchange tube surface > fins (low), and the potential differences between the core of the heat exchange tube and the surface of the heat exchange tube, and between the surface of the heat exchange tube and the fins after brazing are in the range of 40mV to 60mV respectively.

[0004] However, the present inventors have focused on the problem that, when the heat exchanger of Patent Document 1 is used in an indoor unit, aluminum hydroxide is generated as a corrosion product and may be scattered indoors.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-43216 Utility Model Content

[0006] The air conditioner of the first aspect includes an indoor unit and an outdoor unit. The indoor unit includes a first heat exchanger. The outdoor unit includes a second heat exchanger. The first heat exchanger includes a first flat tube and a first fin. The first fin is connected to the first flat tube. The second heat exchanger includes a second flat tube and a second fin. The second fin is connected to the second flat tube. The potential difference between the first fin and the first flat tube is smaller than the potential difference between the second fin and the second flat tube.

[0007] According to the air conditioner of the first aspect, the potential difference between the first fin and the first flat tube of the indoor unit is made smaller than the potential difference between the second fin and the second flat tube of the outdoor unit, so that the corrosion of the first fin and the first flat tube of the indoor unit can be effectively suppressed. Thus, the generation of aluminum hydroxide caused by the corrosion of the first fin and the first flat tube can be reduced. Therefore, the dispersion of aluminum hydroxide into the room can be suppressed.

[0008] The air conditioner according to a second aspect is the air conditioner according to the first aspect, wherein the potential of the first fin is higher than the potential of the second fin.

[0009] In the air conditioner of the second aspect, by making the potential of the first fin of the indoor unit higher than the potential of the second fin of the outdoor unit, corrosion of the first fin is suppressed, and thus scattering of aluminum hydroxide into the room can be further suppressed.

[0010] The air conditioner according to a third aspect is the air conditioner according to the first aspect or the second aspect, wherein the potential of the first fin is higher than the potential of the first flat tube.

[0011] In the air conditioner according to the third aspect, by making the potential of the first fin higher than the potential of the first flat tube, corrosion of the first fin is suppressed, and thus scattering of aluminum hydroxide into the room can be further suppressed.

[0012] An air conditioner according to a fourth aspect is the air conditioner according to any one of the first to third aspects, wherein a potential difference between the first fin and the first flat tube is 20 mV or more and 60 mV or less.

[0013] In the air conditioner of the fourth aspect, the potential difference between the first fin and the first flat tube of the indoor unit is reduced to 20 mV to 60 mV. This can further reduce the generation of aluminum hydroxide caused by corrosion of the first fin and the first flat tube.

[0014] An air conditioner according to a fifth aspect is the air conditioner according to any one of the first to fourth aspects, wherein the potential of the first fin is not less than -890 mV and not more than -750 mV.

[0015] In the air conditioner according to the fifth aspect, the first fin of the first heat exchanger of the indoor unit has a high potential of -890 mV to -750 mV, and therefore, excessive corrosion of the first fin can be suppressed.

[0016] An air conditioner according to a sixth aspect is the air conditioner according to any one of the first to fifth aspects, wherein the potential of the first fin is not less than -890 mV and not more than -800 mV.

[0017] In the air conditioner of the sixth aspect, the first fin of the first heat exchanger of the indoor unit has a very high potential of -890 mV to -800 mV, and therefore, excessive corrosion of the first fin can be further suppressed.

[0018] An air conditioner according to a seventh aspect is the air conditioner according to any one of the first to sixth aspects, and performs cooling operation and heating operation.

[0019] In the air conditioner of the seventh aspect, during cooling operation and heating operation, generation of aluminum hydroxide caused by corrosion of the first fins and the first flat tubes of the indoor unit can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic configuration diagram of an air conditioner according to one embodiment of the present disclosure.

[0021] Figure 2 This is a schematic diagram of the outdoor unit.

[0022] Figure 3is a cross-sectional view of the first flat tube and the second flat tube.

[0023] Figure 4 is a cross-sectional view of the first fin and the second fin.

[0024] Figure 5 This is a diagram for explaining the method of measuring the potential in Examples.

[0025] Figure 6 This is a diagram for explaining the method of measuring the potential in Examples.

[0026] Figure 7 This is a diagram for explaining the method of measuring the potential in Examples.

[0027] Description of symbols

[0028] 1 Air conditioner

[0029] 2Indoor unit

[0030] 3Outdoor unit

[0031] 20First heat exchanger

[0032] 21 First Flat Tube

[0033] 22 First Fin

[0034] 30 Second heat exchanger

[0035] 31 Second flat tube

[0036] 32 Second fin DETAILED DESCRIPTION

[0037] (1) Overall structure

[0038] Reference Figure 1 to Figure 4 An air conditioner 1 according to an embodiment of the present disclosure will be described. Figure 1 As shown, the air conditioner 1 is used for cooling and heating indoors of a building or the like by performing a vapor compression refrigeration cycle operation.

[0039] The air conditioner 1 mainly includes an indoor unit 2, an outdoor unit 3, and a liquid refrigerant communication pipe 4 and a gas refrigerant communication pipe 5 connecting the indoor unit 2 and the outdoor unit 3. In addition, the vapor compression refrigerant circuit 10 of the air conditioner 1 is formed by connecting the indoor unit 2 and the outdoor unit 3 via the liquid refrigerant communication pipe 4 and the gas refrigerant communication pipe 5.

[0040] (1-1) Indoor unit

[0041] The indoor unit 2 is installed indoors and mainly includes a first heat exchanger 20 and a first fan 11 .

[0042] The first heat exchanger 20 is a heat exchanger that functions as an evaporator of the refrigerant during cooling operation and as a radiator of the refrigerant during heating operation. The liquid side of the first heat exchanger 20 is connected to the liquid refrigerant communication pipe 4 , and the gas side is connected to the gas refrigerant communication pipe 5 .

[0043] The first fan 11 draws indoor air into the indoor unit 2 , supplies the indoor air to the first heat exchanger 20 , and then discharges the indoor air to the outside of the indoor unit 2 .

[0044] (1-2) Outdoor unit

[0045] The outdoor unit 3 is installed outdoors and mainly includes a compressor 12 , a flow switching mechanism 13 , a second heat exchanger 30 , and an expansion mechanism 14 .

[0046] The compressor 12 is a mechanism that compresses low-pressure refrigerant in the refrigeration cycle to a high pressure.

[0047] The flow switching mechanism 13 is a mechanism for switching the flow direction of the refrigerant when switching between cooling operation and heating operation. In cooling operation, the flow switching mechanism 13 makes the discharge side of the compressor 12 contact with the gas side of the second heat exchanger 30, and connects the gas side of the first heat exchanger 20 with the suction side of the compressor 12 via the gas refrigerant connecting pipe 5 (see Figure 1 In addition, during heating operation, the flow switching mechanism 13 connects the discharge side of the compressor 12 to the gas side of the first heat exchanger 20 via the gas refrigerant connecting pipe 5, and connects the gas side of the second heat exchanger 30 to the suction side of the compressor 12 (see Figure 1 13).

[0048] The second heat exchanger 30 is a heat exchanger that functions as a radiator of the refrigerant during cooling operation and as an evaporator of the refrigerant during heating operation. The second heat exchanger 30 is connected to the expansion mechanism 14 on its liquid side and to the flow switching mechanism 13 on its gas side.

[0049] The expansion mechanism 14 is a mechanism for decompressing the high-pressure liquid refrigerant after dissipating heat in the second heat exchanger 30 before being delivered to the first heat exchanger 20 during cooling operation, and for decompressing the high-pressure liquid refrigerant after dissipating heat in the first heat exchanger 20 before being delivered to the second heat exchanger 30 during heating operation.

[0050] In addition, the outdoor unit 3 is provided with a second fan 15 for sucking outdoor air into the outdoor unit 3 , supplying the outdoor air to the second heat exchanger 30 , and then exhausting the outdoor air to the outside of the outdoor unit 3 .

[0051] (2) Detailed structure

[0052] Reference Figure 2 to Figure 4 The first heat exchanger 20 and the second heat exchanger 30 are described. The first heat exchanger 20 and the second heat exchanger 30 are microchannel heat exchangers.

[0053] (2-1) First heat exchanger

[0054] like Figure 2 As shown, the first heat exchanger 20 has a first flat tube 21 and a first fin 22. Here, a plurality of the first flat tubes 21 and the first fin 22 are provided. The first fin 22 is joined to the first flat tube 21.

[0055] The first heat exchanger 20 performs heat exchange between the refrigerant flowing through the first flat tubes 21 and the indoor air flowing outside the first flat tubes 21. The first heat exchanger 20 performs heat exchange between the indoor air and the refrigerant without mixing with each other.

[0056] The material constituting the first flat tubes 21 and the first fins 22 is not particularly limited, and includes, for example, aluminum, copper, etc. The first flat tubes 21 and the first fins 22 of the present embodiment are made of aluminum or an aluminum alloy.

[0057] (2-1-1) First flat tube

[0058] The plurality of first flat tubes 21 are arranged in the vertical direction. The first flat tubes 21 allow the refrigerant to flow inside. Figure 2 and Figure 3 As shown, the first flat tube 21 is a heat transfer tube having a flat shape. Here, the first flat tube 21 is a flat multi-hole tube. In the first flat tube 21, a plurality of through holes 211 are formed in a predetermined direction for the refrigerant to pass through for heat exchange with the indoor air in the first heat exchanger 20. The plurality of through holes 211 penetrate along the length direction.

[0059] like Figure 3 As shown, the first flat tube 21 has a first base material 212 and a first surface layer 213 .

[0060] The first surface layer 213 is provided on the surface of the first flat tube 21. The first surface layer 213 may be provided on the entire surface of the first flat tube 21, or may be provided on a portion of the surface of the first flat tube 21 (not shown). In other words, the first surface layer 213 may be formed on the entire exposed outer surface, or may be formed on a portion of the exposed outer surface (not shown). The first surface layer 213 is formed on a portion of the first flat tube 21 in the thickness direction from the outer surface toward the inner surface for refrigerant flow, and is not formed on the entire wall thickness. In other words, in the first flat tube 21, the first surface layer 213 is not formed on at least a portion of the inner surface for refrigerant flow. In the present embodiment, the first surface layer 213 is not formed on the entire inner side surface of the first flat tube 21.

[0061] The potential of the first surface layer 213 is lower than that of the first base material 212. Therefore, in the first flat tube 21, the first surface layer 213 on the outer surface side is a sacrificial layer for preventing the first base material 212 on the inner surface side from corroding.

[0062] In order to reduce the potential, the first surface layer 213 contains a metal such as zinc. The first surface layer 213 of the present embodiment is a zinc diffusion layer formed by thermal spraying zinc.

[0063] (2-1-2) First fin

[0064] like Figure 2 As shown, the first fin 22 is joined to the plurality of first flat tubes 21. Here, the first flat tubes 21 and the first fin 22 are joined to each other by brazing. The first fin 22 may or may not be in contact with the first flat tube 21. The first fin 22 increases the heat transfer area between the first flat tube 21 and the indoor air, thereby promoting heat exchange between the refrigerant and the indoor air.

[0065] The first fins 22 are stacked in the longitudinal direction of the first flat tubes 21. Here, the plurality of first fins 22 are arranged to intersect with the first flat tubes 21 (in Figure 2 The plurality of electrodes extend in the vertical direction (in the figure, orthogonal).

[0066] The first fin 22 is a flat plate-shaped member. In addition, the first fin 22 has a notch for allowing the plurality of first flat tubes 21 to pass through. The notch is arranged in a plurality in the vertical direction. In addition, the first fin 22 may also have a clamp portion.

[0067] like Figure 4 As shown, the first fin 22 has a first main body portion 221 and a first surface layer 222 .

[0068] The first surface layer 222 is provided on the surface of the first main body portion 221. Here, the first surface layer 222 is provided on both surfaces of the first main body portion 221 extending in the length direction.

[0069] The thickness of the first surface layer 222 is smaller than the thickness of the first body portion 221. In addition, each thickness of the first fin 22 is a maximum value of a distance from the outer surface toward the inside.

[0070] The potential of the first surface layer 222 is lower than the potential of the first main body portion 221. Therefore, in the first fin 22, the first surface layer 222 on the outer surface side is a sacrificial layer that prevents the first main body portion 221 on the inner surface side from being corroded.

[0071] In order to reduce the potential, the first fin 22 contains metal such as zinc. The first surface layer 222 of the present embodiment is a zinc diffusion layer sprayed with zinc. In addition, the first fin 22 may further contain magnesium, copper, etc.

[0072] The potential of the first fin 22 may be lower than or higher than the potential of the first flat tube 21. Specifically, the potential of the first surface layer 222 of the first fin 22 may be lower than or higher than the potential of the first surface layer 213 of the first flat tube 21. In other words, the order of potential from low to high may be the first surface layer 213 of the first flat tube 21, the first fin 22, and the first base material 212 of the first flat tube 21, and the order of potential from low to high may also be the first fin 22, the first surface layer 213 of the first flat tube 21, and the first base material 212 of the first flat tube 21. However, the potential of the first fin 22 is lower than that of the first base material 212. In the present embodiment, the potential of the first fin 22 is higher than that of the first flat tube 21.

[0073] The potential of the first fin 22 of the present embodiment is greater than -890mV and less than -750mV, preferably greater than -890mV and less than -800mV, and more preferably greater than -850mV and less than -800mV. The potential of the first fin 22 is the potential of the outermost surface. Therefore, the potential of the first fin 22 is the potential of the first surface layer 222 when the first surface layer 222 is present, and is the potential of the first main body 221 when the first surface layer 222 is not present.

[0074] Such an electric potential of the first fin 22 is realized by adjusting the amount of metal such as zinc contained in order to lower the electric potential.

[0075] In addition, in the present embodiment, the potential difference between the first fin 22 and the first flat tube 21 is 20 mV or more and 60 mV or less. The potential difference is the absolute value of the difference between the potential of the first flat tube 21 and the potential of the first fin 22. Specifically, the potential difference is the absolute value of the difference between the potential of the outer surface of the first flat tube 21 and the potential of the outer surface of the first fin 22.

[0076] Such a potential difference is achieved by adjusting the amount of metal such as zinc contained in the first fins 22 and the first flat tubes 21 in order to lower the potential.

[0077] The potentials of the first flat tubes 21 and the first fins 22 are values ​​obtained by taking out a portion of the first flat tubes 21 and the first fins 22 from the first heat exchanger 20 to prepare a test piece and measuring the test piece using a three-electrode method.

[0078] (2-1-3) Brazing material

[0079] The first heat exchanger 20 further includes a brazing material (not shown) connecting the first flat tubes 21 and the first fins 22. The brazing material of the present embodiment includes aluminum.

[0080] (2-2) Second heat exchanger

[0081] like Figure 2 As shown, the second heat exchanger 30 includes a second flat tube 31 and a second fin 32. Here, a plurality of the second flat tubes 31 and the second fin 32 are provided. The second fin 32 is joined to the second flat tube 31.

[0082] The second heat exchanger 30 performs heat exchange between the refrigerant flowing through the second flat tubes 31 and the outdoor air flowing outside the second flat tubes 31. The second heat exchanger 30 performs heat exchange between the outdoor air and the refrigerant without mixing with each other.

[0083] The material constituting the second flat tubes 31 and the second fins 32 is not particularly limited, and includes, for example, aluminum, copper, etc. The second flat tubes 31 and the second fins 32 of the present embodiment are made of aluminum or an aluminum alloy.

[0084] (2-2-1) Second flat tube

[0085] The plurality of second flat tubes 31 are arranged in the vertical direction. The second flat tubes 31 allow the refrigerant to flow inside. Figure 2 and Figure 3 As shown, the second flat tube 31 is a heat transfer tube having a flat shape. Here, the second flat tube 31 is a flat multi-hole tube. In the second flat tube 31, a plurality of through holes 311 are formed in a predetermined direction for the refrigerant to pass through for heat exchange with the outdoor air in the second heat exchanger 30. The plurality of through holes 311 penetrate along the length direction.

[0086] like Figure 3 As shown, the second flat tube 31 has a second base material 312 and a second surface layer 313 .

[0087] The second surface layer 313 is provided on the surface of the second flat tube 31. The second surface layer 313 may be provided on the entire surface of the second flat tube 31, or may be provided on a portion of the surface of the second flat tube 31 (not shown). In other words, the second surface layer 313 may be formed on the entire exposed outer surface, or may be formed on a portion of the exposed outer surface (not shown). The second surface layer 313 is formed on a portion of the second flat tube 31 in the thickness direction from the outer surface toward the inner surface for refrigerant flow, and is not formed on the entire wall thickness. In other words, in the second flat tube 31, the second surface layer 313 is not formed on at least a portion of the inner surface for refrigerant flow. In the present embodiment, the second surface layer 313 is not formed on the entire inner side surface of the second flat tube 31.

[0088] The potential of the second surface layer 313 is lower than the potential of the second base material 312. Therefore, in the second flat tube 31, the second surface layer 313 on the outer surface side is a sacrificial layer that prevents the corrosion of the second base material 312 on the inner surface side.

[0089] It should be noted that the potentials of the second base material 312 and the second surface layer 313 are values ​​obtained by measuring a test piece prepared by taking out a part of the second base material 312 and the second surface layer 313 from the second heat exchanger 30 and using a three-electrode method.

[0090] In order to reduce the potential, the second surface layer 313 contains a metal such as zinc. The second surface layer 313 of the present embodiment is a zinc diffusion layer formed by thermal spraying zinc.

[0091] (2-2-2) Second fin

[0092] like Figure 2 As shown, the second fins 32 are joined to the plurality of second flat tubes 31. Here, the second flat tubes 31 and the second fins 32 are joined to each other by brazing. The second fins 32 may or may not be in contact with the second flat tubes 31. The second fins 32 increase the heat transfer area between the second flat tubes 31 and the indoor air, thereby promoting heat exchange between the refrigerant and the indoor air.

[0093] The second fins 32 are stacked in the longitudinal direction of the second flat tubes 31. Here, the plurality of second fins 32 are arranged to intersect with the second flat tubes 31 (in Figure 2 The plurality of electrodes extend in the vertical direction (in the figure, orthogonal).

[0094] The second fin 32 is a flat plate-shaped member. In addition, the second fin 32 has a notch for passing the plurality of second flat tubes 31. The notch is arranged in a plurality in the vertical direction. In addition, the second fin 32 may also have a clamp portion.

[0095] like Figure 4As shown, the second fin 32 has a second main body portion 321 and a second surface layer 322 .

[0096] The second surface layer 322 is provided on the surface of the second main body portion 321. Here, the second surface layer 322 is provided on both surfaces of the second main body portion 321 extending in the length direction.

[0097] The thickness of the second surface layer 322 is smaller than the thickness of the second body portion 321. In addition, each thickness of the second fin 32 is a maximum value of a distance from the outer surface toward the inside.

[0098] The potential of the second surface layer 322 is lower than the potential of the second main body portion 321. Therefore, in the second fin 32, the second surface layer 322 on the outer surface side is a sacrificial layer for preventing the corrosion of the second main body portion 321 on the inner surface side.

[0099] In order to reduce the potential, the second fin 32 contains metal such as zinc. The second surface layer 322 of the present embodiment is a zinc diffusion layer sprayed with zinc. In addition, the second fin 32 may further contain magnesium, copper, etc.

[0100] The potential of the second fin 32 may be lower than or higher than the potential of the second flat tube 31. Specifically, the potential of the second surface layer 322 of the second fin 32 may be lower than or higher than the potential of the second surface layer 313 of the second flat tube 31. In other words, the order of potential from low to high may be the second surface layer 313 of the second flat tube 31, the second fin 32, and the second base material 312 of the second flat tube 31, and the order of potential from low to high may also be the second fin 32, the second surface layer 313 of the second flat tube 31, and the second base material 312 of the second flat tube 31. However, the potential of the second fin 32 is lower than that of the second base material 312.

[0101] It should be noted that the potential of the second fin 32 is a value obtained by taking out a part of the second fin 32 from the second heat exchanger 30 to prepare a test piece and measuring the test piece by a three-electrode method.

[0102] (2-2-3) Brazing material

[0103] The second heat exchanger 30 further includes a brazing material (not shown) connecting the second flat tubes 31 and the second fins 32. The brazing material of the present embodiment includes aluminum.

[0104] (2-3) Relationship between the first heat exchanger and the second heat exchanger

[0105] The potential of the first fin 22 is higher than that of the second fin 32, and preferably 1.1 times or more. The potential of the first fin 22 is the potential of the outer surface of the first fin 22. The potential of the second fin 32 is the potential of the outer surface of the second fin 32.

[0106] In addition, the potential difference between the first fin 22 and the first flat tube 21 is smaller than the potential difference between the second fin 32 and the second flat tube 31, and is preferably 0.9 times or less of the potential difference between the second fin 32 and the second flat tube 31. For example, the potential difference between the first fin 22 and the first flat tube 21 is lower than the potential difference between the second fin 32 and the second flat tube 31 by 20 mV or more and 60 mV or less, and is preferably lower by 30 mV or more and 50 mV or less. Here, the potential difference between the first fin 22 and the first flat tube 21 is the absolute value of the difference between the potential of the first flat tube 21 and the potential of the first fin 22. The potential difference between the second fin 32 and the second flat tube 31 is the absolute value of the difference between the potential of the second fin 32 and the potential of the second flat tube 31. Specifically, the potential difference between the first fin 22 and the first flat tube 21 is the absolute value of the difference between the potential of the outer surface of the first flat tube 21 and the potential of the outer surface of the first fin 22. The potential difference between the second fins 32 and the second flat tubes 31 is the absolute value of the difference between the potential of the outer surfaces of the second flat tubes 31 and the potential of the outer surfaces of the second fins 32 .

[0107] Such a potential is achieved by adjusting the amount of metal such as zinc contained in the first flat tubes 21 , the first fins 22 , the second flat tubes 31 , and the second fins 32 in order to lower the potential.

[0108] (3) Action

[0109] (3-1) Refrigeration operation

[0110] When the air conditioner 1 performs cooling operation, the low-pressure refrigerant in the refrigeration cycle is sucked into the compressor 12, and is discharged after being compressed to the high pressure in the refrigeration cycle. The high-pressure refrigerant discharged from the compressor 12 is sent to the second heat exchanger 30 through the flow path switching mechanism 13. The high-pressure refrigerant sent to the second heat exchanger 30 exchanges heat with the outdoor air supplied by the second fan 15 in the second heat exchanger 30 to dissipate heat. The high-pressure refrigerant after dissipating heat in the second heat exchanger 30 is sent to the expansion mechanism 14 and is decompressed to the low pressure in the refrigeration cycle. The low-pressure refrigerant after being decompressed in the expansion mechanism 14 is sent to the first heat exchanger 20 via the liquid refrigerant communication pipe 4. The low-pressure refrigerant sent to the first heat exchanger 20 exchanges heat with the indoor air supplied by the first fan 11 in the first heat exchanger 20 and evaporates. As a result, the indoor air is cooled and blown into the room. The low-pressure refrigerant evaporated in the first heat exchanger 20 is sucked into the compressor 12 again via the gas refrigerant communication pipe 5 and the flow switching mechanism 13 .

[0111] (3-2) Heating operation

[0112] When the air conditioner 1 performs heating operation, the low-pressure refrigerant in the refrigeration cycle is sucked into the compressor 12, and is discharged after being compressed to the high pressure in the refrigeration cycle. The high-pressure refrigerant discharged from the compressor 12 is transported to the first heat exchanger 20 via the flow path switching mechanism 13 and the gas refrigerant communication pipe 5. The high-pressure refrigerant transported to the first heat exchanger 20 exchanges heat with the indoor air supplied by the first fan 11 in the first heat exchanger 20 to dissipate heat. As a result, the indoor air is heated and blown into the room. The high-pressure refrigerant after dissipating heat in the first heat exchanger 20 is transported to the expansion mechanism 14 via the liquid refrigerant communication pipe 4, and is decompressed to the low pressure in the refrigeration cycle. The low-pressure refrigerant after being decompressed in the expansion mechanism 14 is transported to the second heat exchanger 30. The low-pressure refrigerant transported to the second heat exchanger 30 exchanges heat with the outdoor air supplied by the second fan 15 in the second heat exchanger 30 and evaporates. The low-pressure refrigerant evaporated in the second heat exchanger 30 is sucked into the compressor 12 again through the flow switching mechanism 13 .

[0113] (4) Features

[0114] (4-1)

[0115] In a cross-fin heat exchanger, a technique of suppressing corrosion by forming a resin layer on the surface of the fin to insulate the fin from the heat transfer tube is considered. However, in a microchannel heat exchanger, since the fin and the heat transfer tube (flat tube) are brazed, a resin layer cannot be formed on the surface of the fin. Therefore, when a potential difference is generated between the fin and the heat transfer tube, the fin or the heat transfer tube corrodes. For example, in order to prevent the corrosion of the heat transfer tube in order to prevent the leakage of the refrigerant, the potential of the fin is sometimes made lower than that of the heat transfer tube. In this case, the fin containing aluminum corrodes preferentially, and aluminum hydroxide is generated. If the microchannel heat exchanger is set in an indoor unit, there is a problem that white powdery aluminum hydroxide may fly indoors. With this problem in mind, the inventors of the present invention came up with the air conditioner 1 disclosed in the present invention.

[0116] Specifically, the problem of powder scattering due to corrosion is not a big problem in the outdoor unit, but it becomes a problem in the indoor unit, so it is a problem unique to the indoor unit. On the other hand, the outdoor unit has a higher concentration of chloride ions in the atmosphere than the indoor unit, so there is another problem that corrosion is easily caused. In order to solve these problems, the inventors conducted intensive research and found the relationship between the potential of the fins and flat tubes of the indoor unit and the potential of the fins and flat tubes of the outdoor unit.

[0117] Therefore, the air conditioner 1 of the present embodiment includes an indoor unit 2 and an outdoor unit 3. The indoor unit 2 includes a first heat exchanger 20. The outdoor unit 3 includes a second heat exchanger 30. The first heat exchanger 20 includes a first flat tube 21 and a first fin 22. The first fin 22 is connected to the first flat tube 21. The second heat exchanger 30 includes a second flat tube 31 and a second fin 32. The second fin 32 is connected to the second flat tube 31. The potential difference between the first fin 22 and the first flat tube 21 is smaller than the potential difference between the second fin 32 and the second flat tube 31.

[0118] According to the air conditioner 1 of this embodiment, the potential difference between the first fin 22 and the first flat tube 21 of the indoor unit 2 is made smaller than the potential difference between the second fin 32 and the second flat tube 31 of the outdoor unit 3, so that the corrosion of the first fin 22 and the first flat tube 21 of the indoor unit 2 of the microchannel heat exchanger can be effectively suppressed. Therefore, the generation of aluminum hydroxide caused by the first fin 22 and the first flat tube 21 can be further reduced. Therefore, the white powdery aluminum hydroxide can be suppressed from scattering indoors.

[0119] In addition, the potential difference between the second fin 32 and the second flat tube 31 of the outdoor unit 3 can be made greater than the potential difference between the first fin 22 and the first flat tube 21 of the indoor unit 2, thereby suppressing corrosion of the second base material 312 of the second flat tube 31 of the outdoor unit 3.

[0120] In addition, the outdoor unit 3 is more susceptible to corrosion than the indoor unit 2, and therefore, it is preferable to make the potential of the second fin 32 of the outdoor unit 3 lower than the potential of the second flat tube 31. In this way, in order to suppress the corrosion of the second flat tube 31 and prevent the refrigerant from leaking, the potential design can be set to preferentially corrode the second fin 32. Even in this case, the generation of aluminum hydroxide in the outdoor unit 3 is not a big problem, and on the other hand, by reducing the potential difference between the first fin 22 and the first flat tube 21 of the indoor unit 2, the scattering of powder from the indoor unit 2 can be suppressed.

[0121] (4-2)

[0122] In the air conditioner 1 of the present embodiment, the potential of the first fins 22 is higher than the potential of the second fins 32 .

[0123] Here, by making the potential of the first fins 22 of the indoor unit 2 higher than the potential of the second fins 32 of the outdoor unit 3, corrosion of the first fins 22 is suppressed, thereby further suppressing the dispersion of aluminum hydroxide into the room.

[0124] (4-3)

[0125] In the air conditioner 1 of the present embodiment, the potential of the first fins 22 is higher than the potential of the first flat tubes 21 .

[0126] Here, by making the potential of the first fins 22 higher than the potential of the first flat tubes 21 , corrosion of the first fins 22 can be suppressed, thereby further suppressing the scattering of aluminum hydroxide into the room.

[0127] (4-4)

[0128] In the air conditioner 1 of the present embodiment, the potential difference between the first fins 22 and the first flat tubes 21 is greater than or equal to 20 mV and less than or equal to 60 mV.

[0129] Here, the potential difference between the first fins 22 and the first flat tubes 21 of the indoor unit 2 is reduced to 20 mV or more and 60 mV or less. This can further reduce the generation of aluminum hydroxide caused by corrosion of the first fins 22 and the first flat tubes 21.

[0130] (4-5)

[0131] In the air conditioner 1 of the present embodiment, the potential of the first fin 22 is greater than or equal to -890 mV and less than or equal to -750 mV.

[0132] Here, the first fin 22 of the first heat exchanger 20 of the indoor unit 2 is designed to have a high potential of -890 mV to -750 mV. This prevents the first fin 22 from being excessively corroded, and reduces the generation of aluminum hydroxide caused by corrosion of the first fin 22.

[0133] Furthermore, in the indoor unit 2 of the present embodiment, it is possible to suppress excessive corrosion of the first fin 22, and thus it is possible to suppress corrosion odor.

[0134] (4-6)

[0135] In the air conditioner 1 of the present embodiment, the potential of the first fin 22 is greater than or equal to -890 mV and less than or equal to -800 mV.

[0136] Here, the first fin 22 of the first heat exchanger 20 of the indoor unit 2 is designed to have a high potential of -890 mV or more and -800 mV or less. This prevents the first fin 22 from being excessively corroded, and can further reduce the generation of aluminum hydroxide caused by corrosion of the first fin 22.

[0137] (4-7)

[0138] The air conditioner 1 of this embodiment performs cooling operation and heating operation.

[0139] In this embodiment, even when the evaporator is operated with condensation, it is possible to suppress excessive corrosion of the first fin 22 and the first flat tube 21. Therefore, even when the air conditioner 1 is operated in cooling and heating, the generation of aluminum hydroxide caused by corrosion of the first fin 22 and the first flat tube 21 of the indoor unit 2 can be reduced.

[0140] (5) Modification

[0141] (5-1) Modification 1

[0142] In the above embodiment, the first fin 22 has the first surface layer 222 and the second fin 32 has the second surface layer 322, but the present invention is not limited thereto. Alternatively, at least one of the first fin 22 and the second fin 32 of the present disclosure may not have a surface layer.

[0143] (5-2) Modification 2

[0144] In the above embodiment, the first flat tube 21 has the first surface layer 213 and the second flat tube 31 has the second surface layer 313, but the present invention is not limited thereto. At least one of the first flat tube 21 and the second flat tube 31 of the present disclosure may not have a surface layer.

[0145] (5-3) Modification 3

[0146] In the above embodiment, the first surface layer 213 of the first flat tube 21 and the second surface layer 313 of the second flat tube 31 are described as diffusion layers sprayed with zinc, but the present invention is not limited thereto. In this modification, a cladding material is used as the base material and the surface layer.

[0147] Specifically, the first flat tube 21 is formed using a cladding material formed by laminating a metal to be the first base material 212 and a metal to be the first surface layer 213. The second flat tube 31 is formed using a cladding material formed by laminating a metal to be the second base material 312 and a metal to be the second surface layer 313.

[0148] (5-4) Modification 4

[0149] In the above embodiment, the air conditioner 1 that performs cooling operation and heating operation is described as an example, but the air conditioner of the present disclosure is not limited thereto. The air conditioner of the present disclosure may also perform dehumidification operation, or may be dedicated to cooling.

[0150] [Example]

[0151] In the present embodiment, the effect of making the potential of the first fins 22 and the first flat tubes 21 of the indoor unit 2 lower than the potential of the second fins 32 and the second flat tubes 31 of the outdoor unit 3 was investigated.

[0152] (Example 1)

[0153] In Example 1, a heat exchanger having a microchannel heat exchanger is manufactured as the first heat exchanger 20 of the indoor unit 2 and the second heat exchanger 30 of the outdoor unit 3. Figure 1 The air conditioner 1 is shown.

[0154] Specifically, as the first flat tube 21, zinc is sprayed on the surface of the first aluminum base material 212 to form the first surface layer 213. In addition, as the first fin 22, zinc is sprayed on the surface of the first aluminum main body 221 to form the first surface layer 222. The first flat tube 21 and the first fin 22 are joined using a brazing material containing aluminum to produce the first heat exchanger 20.

[0155] In addition, as the second flat tube 31, zinc is sprayed on the surface of the second base material 312 made of aluminum to form a second surface layer 313. In addition, as the second fin 32, zinc is sprayed on the surface of the second main body 321 made of aluminum to form a second surface layer 322. Such a second flat tube 31 and the second fin 32 are joined using a brazing material containing aluminum to produce a second heat exchanger 30. In Example 1, the zinc content of the first fin 22 is made lower than the zinc content of the second fin 32.

[0156] (Comparative Example 1)

[0157] Comparative Example 1 is basically the same as Example 1, but only the first fin of the first heat exchanger of the indoor unit is different. Specifically, the zinc content of the first fin of the indoor unit of Comparative Example 1 is made the same as the zinc content of the second fin of the outdoor unit.

[0158] (Measurement method and results)

[0159] The potentials of the first base material and the first surface layer of the first flat tube, the first surface layer of the first fin, the second base material and the second surface layer of the second flat tube, and the second surface layer of the second fin were measured in Example 1 and Comparative Example 1. The measurement method is as follows.

[0160] The first base material and the first surface layer of the first flat tube, the first surface layer of the first fin, the second base material and the second surface layer of the second flat tube, and a part of the second surface layer of the second fin were taken out from the first heat exchanger and the second heat exchanger to prepare test pieces, and the test pieces were measured by the three-electrode method. Figure 5 As shown in FIG. 1 , the length of the test piece S is set to 40 mm. Then, as Figure 6 As shown, epoxy resin R is pasted on the test piece S to expose the test surface S1. The length of the entire circumference of the test surface S1 is 10 mm. The test solution is a 2.67% aluminum chloride aqueous solution. The reference electrode is a saturated calomel electrode. The counter electrode is platinum. Figure 7 As shown, the test piece S was connected to the counter electrode using a lead wire. Then, in a state open to the atmosphere and at a temperature of 40° C., the pH of the test solution was adjusted, and the potential of the test surface S1 was measured by a three-electrode method.

[0161] The results of measuring the potentials of Example 1 and Comparative Example 1 are shown in Table 1 below.

[0162]

Table 1

[0163]

[0164] As shown in Table 1, in Example 1, the potential of the first fin (-800 mV) is higher than the potential of the second fin (-900 mV). In addition, in Example 1, the potential difference between the first fin and the first flat tube is 30 mV. In addition, in Example 1, the potential difference between the first fin and the first flat tube (30 mV) is smaller than the potential difference between the second fin and the second flat tube (70 mV).

[0165] (Evaluation methods and results)

[0166] The air conditioner of Example 1 and the air conditioner of Comparative Example 1 were subjected to cooling operation and heating operation, and it was visually confirmed whether aluminum hydroxide was scattered from the indoor unit.

[0167] In the air conditioner of Comparative Example 1, in which the potential of the first fin 22 and the first flat tube 21 of the indoor unit 2 is the same as the potential of the second fin 32 and the second flat tube 31 of the outdoor unit 3, aluminum hydroxide is scattered from the indoor unit. On the other hand, in the air conditioner of Example 1, in which the potential of the first fin 22 and the first flat tube 21 of the indoor unit 2 is lower than the potential of the second fin 32 and the second flat tube 31 of the outdoor unit 3, aluminum hydroxide is not scattered from the indoor unit.

[0168] From the above, it can be confirmed that by making the potential between the first fin 22 and the first flat tube 21 of the indoor unit 2 lower than the potential between the second fin 32 and the second flat tube 31 of the outdoor unit 3, the generation of aluminum hydroxide caused by the corrosion of the first fin and the first flat tube is reduced, thereby suppressing the aluminum hydroxide from scattering indoors. In addition, it can be confirmed that by making the potential of the first fin have a high potential of -890 mV or more and -750 mV or less, the generation of aluminum hydroxide caused by the corrosion of the first fin is reduced, thereby suppressing the aluminum hydroxide from scattering indoors.

[0169] As mentioned above, although embodiment of this disclosure is described, it should be understood that various changes in form and detail are possible without departing from the spirit and scope of this disclosure described in the claims.

Claims

1. An air conditioner (1), characterized in that: have: An indoor unit (2) comprising a first heat exchanger (20); and The outdoor unit (3) includes a second heat exchanger (30), The first heat exchanger has: a first flat tube (21); and a first fin (22) connected to the first flat tube, The second heat exchanger has: a second flat tube (31); and a second fin (32) engaged with the second flat tube, A potential difference between the first fin and the first flat tube is smaller than a potential difference between the second fin and the second flat tube.

2. The air conditioner according to claim 1, characterized in that: The potential of the first fin is higher than the potential of the second fin.

3. The air conditioner according to claim 1 or 2, characterized in that: The first fin has a higher potential than the first flat tube.

4. The air conditioner according to claim 1 or 2, characterized in that: A potential difference between the first fin and the first flat tube is greater than or equal to 20 mV and less than or equal to 60 mV.

5. The air conditioner according to claim 1 or 2, characterized in that: The potential of the first fin is greater than or equal to -890 mV and less than or equal to -750 mV.

6. The air conditioner according to claim 1 or 2, characterized in that: The potential of the first fin is greater than or equal to -890 mV and less than or equal to -800 mV.

7. The air conditioner according to claim 1 or 2, characterized in that: The air conditioner performs cooling operation and heating operation.

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