Air conditioner

Abstract

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 present application relates to an air conditioner. BACKGROUND

[0002] In the past, a heat exchanger provided with a flat tube and a fin is known. As such a heat exchanger, for example, Patent Literature 1 (Japanese Patent Application Publication No. 2013-43216) can be cited.

[0003] The heat exchanger of Patent Literature 1 discloses a technology in which an aluminum or aluminum alloy heat exchange tube is brazed with a fin, and the potential of the fin, the heat exchange tube surface, and the heat exchange tube core portion after brazing is in the relationship (high) heat exchange tube core portion > heat exchange tube surface > fin (low), and the potential difference of the heat exchange tube core portion after brazing with the heat exchange tube surface, and the heat exchange tube surface with the fin is in the range of 40 mV to 60 mV, respectively. SUMMARY

[0004] PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, the present inventors focused on the problem that if the heat exchanger of Patent Literature 1 described above is used for an indoor unit, aluminum hydroxide as a corrosion product is generated, and there is a possibility of flying into the room.

[0006] MEANS FOR SOLVING THE PROBLEMS

[0007] The air conditioner of the first aspect is provided with 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 has a first flat tube and a first fin. The first fin is joined to the first flat tube. The second heat exchanger has a second flat tube and a second fin. The second fin is joined to the second flat tube. The potential difference of the first fin and the first flat tube is smaller than the potential difference of the second fin and the second flat tube.

[0008] According to the air conditioner of the first aspect, the potential difference of the first fin and the first flat tube of the indoor unit is made smaller than the potential difference of the second fin and the second flat tube of the outdoor unit, and thus corrosion of the first fin and the first flat tube of the indoor unit can be effectively suppressed. Thereby, generation of aluminum hydroxide due to corrosion of the first fin and the first flat tube can be reduced. Therefore, flying of aluminum hydroxide into the room can be suppressed.

[0009] The air conditioner of the second aspect is the air conditioner of the first aspect in which the potential of the first fin is higher than the potential of the second fin.

[0010] 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 flying of aluminum hydroxide into the room can be further suppressed.

[0011] The air conditioner of the third aspect is the air conditioner of any one of the first aspect or the second aspect, in which the potential of the first fin is higher than the potential of the first flat tube.

[0012] In the air conditioner of the third aspect, corrosion of the first fin is suppressed by making the potential of the first fin higher than the potential of the first flat tube, so that the scattering of aluminum hydroxide into the room can be further suppressed.

[0013] The air conditioner of the fourth aspect is the air conditioner of any one of the first aspect to the third aspect, in which the potential difference between the first fin and the first flat tube is 20 mV or more and 60 mV or less.

[0014] 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 or more and 60 mV or less. Thus, the generation of aluminum hydroxide due to corrosion of the first fin and the first flat tube can be further reduced.

[0015] The air conditioner of the fifth aspect is the air conditioner of any one of the first aspect to the fourth aspect, in which the potential of the first fin is -890 mV or more and -750 mV or less.

[0016] In the air conditioner of the fifth aspect, the first fin of the first heat exchanger of the indoor unit has a high potential of -890 mV or more and -750 mV or less, so that excessive corrosion of the first fin can be suppressed.

[0017] The air conditioner of the sixth aspect is the air conditioner of any one of the first aspect to the fifth aspect, in which the potential of the first fin is -890 mV or more and -800 mV or less.

[0018] 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 or more and -800 mV or less, so that excessive corrosion of the first fin can be further suppressed.

[0019] The air conditioner of the seventh aspect is the air conditioner of any one of the first aspect to the sixth aspect, in which a cooling operation and a heating operation are performed.

[0020] In the air conditioner of the seventh aspect, the generation of aluminum hydroxide due to corrosion of the first fin and the first flat tube of the indoor unit can be reduced when the cooling operation and the heating operation are performed. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic configuration view of an air conditioner of one embodiment of the present disclosure.

[0022] Figure 2 is a schematic view of an outdoor unit.

[0023] Figure 3is a cross-sectional view of the first flat tube and the second flat tube.

[0024] Figure 4 is a cross-sectional view of the first fin and the second fin.

[0025] Figure 5 is a graph illustrating a method of measuring a potential in an example.

[0026] Figure 6 is a graph illustrating a method of measuring a potential in an example.

[0027] Figure 7 is a graph illustrating a method of measuring a potential in an example. DETAILED DESCRIPTION

[0028] (1) Overall Configuration

[0029] Reference Signs Figures 1-4 An air conditioning machine 1 according to one embodiment of the present disclosure will be described. As shown in FIG. 1, the air conditioning machine 1 functions to cool and heat an indoor room of a building or the like by operating a refrigeration cycle of a vapor compression type. Figure 1

[0030] The air conditioning machine 1 mainly has 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. Further, a refrigerant circuit 10 of the air conditioning machine 1 of the vapor compression type is configured 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.

[0031] (1-1) Indoor Unit

[0032] The indoor unit 2 is provided in an indoor room. The indoor unit 2 mainly has a first heat exchanger 20 and a first fan 11.

[0033] The first heat exchanger 20 functions as an evaporator of a 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.

[0034] The first fan 11 sucks indoor air into the indoor unit 2 and discharges the indoor air to the outside of the indoor unit 2 after supplying the indoor air to the first heat exchanger 20.

[0035] (1-2) Outdoor Unit

[0036] The outdoor unit 3 is provided outside. The outdoor unit 3 mainly has a compressor 12, a flow path switching mechanism 13, a second heat exchanger 30, and an expansion mechanism 14.

[0037] ​Compressor 12 is a mechanism that compresses the low-pressure refrigerant in the refrigeration cycle to a high-pressure state.

[0038] The flow path switching mechanism 13 is a mechanism that switches the refrigerant flow direction when switching between cooling and heating operations. During cooling operation, the flow path switching mechanism 13 brings the discharge side of the compressor 12 into contact with the gas side of the second heat exchanger 30, and connects the gas side of the first heat exchanger 20 to the suction side of the compressor 12 via the gas refrigerant connecting pipe 5 (see reference). Figure 1 (Solid line of flow path switching mechanism 13 in the diagram). Furthermore, during heating operation, flow path switching mechanism 13 connects the discharge side of compressor 12 to the gas side of first heat exchanger 20 via gas refrigerant connecting pipe 5, and connects the gas side of second heat exchanger 30 to the suction side of compressor 12 (see reference). Figure 1 (The dashed line of the flow path switching mechanism 13 in the middle).

[0039] The second heat exchanger 30 functions as a refrigerant radiator during refrigeration operation and as a refrigerant evaporator during heating operation. The liquid side of the second heat exchanger 30 is connected to the expansion mechanism 14, and the gas side is connected to the flow path switching mechanism 13.

[0040] The expansion mechanism 14 is a mechanism that reduces the pressure of the high-pressure liquid refrigerant after it has dissipated heat in the second heat exchanger 30 before it is delivered to the first heat exchanger 20 during cooling operation, and reduces the pressure of the high-pressure liquid refrigerant after it has dissipated heat in the first heat exchanger 20 before it is delivered to the second heat exchanger 30 during heating operation.

[0041] In addition, a second fan 15 is provided in the outdoor unit 3. The second fan 15 is used to draw in outdoor air into the outdoor unit 3 and exhaust it to the outside of the outdoor unit 3 after supplying outdoor air to the second heat exchanger 30.

[0042] (2) Detailed structure

[0043] Reference Figures 2-4 The first heat exchanger 20 and the second heat exchanger 30 will be described. The first heat exchanger 20 and the second heat exchanger 30 are microchannel heat exchangers.

[0044] (2-1) First heat exchanger

[0045] like Figure 2 As shown, the first heat exchanger 20 has a first flat tube 21 and first fins 22. Here, multiple first flat tubes 21 and first fins 22 are provided. The first fins 22 are engaged with the first flat tube 21.

[0046] The first heat exchanger 20 performs heat exchange between the refrigerant flowing in the first flat tube 21 and the indoor air flowing outside the first flat tube 21. The first heat exchanger 20 performs heat exchange between the indoor air and the refrigerant without mixing each other.

[0047] The material constituting the first flat tube 21 and the first fin 22 is not particularly limited, and includes, for example, aluminum, copper, or the like. The first flat tube 21 and the first fin 22 of the present embodiment are made of aluminum or an aluminum alloy.

[0048] (2-1-1) First Flat Tube

[0049] A plurality of the first flat tubes 21 are arranged in the up-and-down direction. The first flat tube 21 causes the refrigerant to flow inside. As shown in Figs. 1 and 2, the first flat tube 21 is a heat transfer tube having a flat shape. Here, the first flat tube 21 is a flat porous tube. In the first flat tube 21, a plurality of through-holes 211 through which the refrigerant exchanges heat with the indoor air in the first heat exchanger 20 are arranged in a prescribed direction. The plurality of through-holes 211 are penetrated in the length direction. Figure 2 and Figure 3 As shown in Figs. 1 and 2, the first flat tube 21 is a heat transfer tube having a flat shape. Here, the first flat tube 21 is a flat porous tube. In the first flat tube 21, a plurality of through-holes 211 through which the refrigerant exchanges heat with the indoor air in the first heat exchanger 20 are arranged in a prescribed direction. The plurality of through-holes 211 are penetrated in the length direction.

[0050] As shown in Figs. 1 and 2, the first flat tube 21 is a heat transfer tube having a flat shape. Here, the first flat tube 21 is a flat porous tube. In the first flat tube 21, a plurality of through-holes 211 through which the refrigerant exchanges heat with the indoor air in the first heat exchanger 20 are arranged in a prescribed direction. The plurality of through-holes 211 are penetrated in the length direction. Figure 3

[0051] The first surface layer 213 is provided to the surface of the first flat tube 21. The first surface layer 213 can be provided to the entire surface of the first flat tube 21, or can be provided to a part of the surface of the first flat tube 21 (not shown). In other words, the first surface layer 213 can be formed on the entire exposed outer surface, or can be formed on a part of the exposed outer surface (not shown). The first surface layer 213 is formed on a part of the thickness direction of the first flat tube 21 from the outer surface toward the inner surface through which the refrigerant flows, 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 part of the inner surface through which the refrigerant flows. In the present embodiment, the first surface layer 213 is not formed on the entire inner side surface of the first flat tube 21.

[0052] The potential of the first surface layer 213 is lower than the potential 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 that prevents corrosion of the first base material 212 on the inner surface side from proceeding.

[0053] In order to lower 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 on which zinc is sprayed.

[0054] (2-1-2) First Fin

[0055] As​Figure 2 As shown in FIG. 1, the first fins 22 are joined to the plurality of first flat tubes 21. Here, the first flat tubes 21 and the first fins 22 are joined to each other by brazing. The first fins 22 can or can not be in contact with the first flat tubes 21. The first fins 22 increase the heat transfer area of the first flat tubes 21 with respect to the indoor air, and promote heat exchange between the refrigerant and the indoor air.

[0056] The first fins 22 are stacked in the length direction in which the first flat tubes 21 extend. Here, the plurality of first fins 22 extend in the up-down direction in a manner that crosses (is orthogonal to) the first flat tubes 21. Figure 2

[0057] The first fins 22 are flat plate-shaped members. In addition, the first fins 22 have notches for the plurality of first flat tubes 21 to pass through. The notches are arranged in the up-down direction in a plurality. In addition, the first fins 22 can also have a clamp portion.

[0058] As shown in FIG. 1, the first fins 22 have a first main body portion 221 and a first surface layer 222. Figure 4

[0059] The first surface layer 222 is provided to the surfaces of the first main body portion 221. Here, the first surface layer 222 is provided to both surfaces of the first main body portion 221 that extend in the length direction.

[0060] The thickness of the first surface layer 222 is smaller than the thickness of the first main body portion 221. In addition, each thickness of the first fins 22 is the maximum value of the distance from the outer surface toward the inside.

[0061] The electric potential of the first surface layer 222 is lower than the electric potential of the first main body portion 221. Therefore, in the first fins 22, the first surface layer 222 on the outer surface side is a sacrificial layer that proceeds to prevent corrosion of the first main body portion 221 on the inner surface side.

[0062] In order to lower the electric potential, the first fins 22 contain a metal such as zinc. The first surface layer 222 of the present embodiment is a zinc diffusion layer in which zinc is sprayed. In addition, the first fins 22 can also contain magnesium, copper, or the like.

[0063] ​​The potential of the first fin 22 can be lower than the potential of the first flat tube 21, or can be higher than the potential of the first flat tube 21. In detail, the potential of the first surface layer 222 of the first fin 22 can be lower than the potential of the first surface layer 213 of the first flat tube 21, or can be higher than the potential of the first surface layer 213 of the first flat tube 21. In other words, the order of the potential from low to high can 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, or can 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 the potential of the first base material 212. In the present embodiment, the potential of the first fin 22 is higher than the potential of the first flat tube 21.

[0064] The potential of the first fin 22 of the present embodiment is -890 mV or more and -750 mV or less, preferably -890 mV or more and -800 mV or less, and more preferably -850 mV or more and -800 mV or less. 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 fin 22 has the first surface layer 222, and is the potential of the first main body portion 221 when the first fin 22 does not have the first surface layer 222.

[0065] The potential of the first fin 22 is achieved by adjusting the amount of metal such as zinc contained in order to lower the potential.

[0066] 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.

[0067] The potential difference is achieved by adjusting the amount of metal such as zinc contained in the first fin 22 and the first flat tube 21 in order to lower the potential.

[0068] Note that the potential of the first flat tube 21 and the first fin 22 is a value obtained by taking out a part of the first flat tube 21 and the first fin 22 from the first heat exchanger 20, making a test piece, and measuring the test piece by a three-electrode method.

[0069] (2-1-3) Solder

[0070] The first heat exchanger 20 also has a solder (not shown) that connects the first flat tube 21 and the first fin 22. The solder of the present embodiment includes aluminum.

[0071] (2-2) Second heat exchanger

[0072] As shown in Figure 2 , the second heat exchanger 30 has second flat tubes 31 and second fins 32. Here, the second flat tubes 31 and the second fins 32 are provided in plural. The second fins 32 are joined to the second flat tubes 31.

[0073] The second heat exchanger 30 performs heat exchange between refrigerant flowing in the second flat tubes 31 and 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 each other.

[0074] The material constituting the second flat tubes 31 and the second fins 32 is not particularly limited, and includes, for example, aluminum, copper, or the like. The second flat tubes 31 and the second fins 32 of the present embodiment are made of aluminum or an aluminum alloy.

[0075] (2-2-1) Second flat tube

[0076] The second flat tubes 31 are arranged in the up-and-down direction in plural. The second flat tubes 31 make refrigerant flow inside. As shown in Figure 2 and Figure 3 , the second flat tube 31 is a heat transfer tube having a flat shape. Here, the second flat tube 31 is a flat porous tube. In the second flat tube 31, a plurality of through-holes 311 through which refrigerant performing heat exchange with outdoor air in the second heat exchanger 30 passes are arranged in a prescribed direction. The plurality of through-holes 311 are penetrated in the length direction.

[0077] As shown in Figure 3 , the second flat tube 31 has a second base material 312 and a second surface layer 313.

[0078] The second surface layer 313 is provided to the surface of the second flat tube 31. The second surface layer 313 can be provided to the entire surface of the second flat tube 31, or can be provided to a part of the surface of the second flat tube 31 (not shown). In other words, the second surface layer 313 can be formed to the entire exposed outer surface, or can be formed to a part of the exposed outer surface (not shown). The second surface layer 313 is formed to a part of the second flat tube 31 in the thickness direction from the outer surface toward the inner surface through which refrigerant flows, and is not formed to the entire wall thickness. In other words, in the second flat tube 31, the second surface layer 313 is not formed to at least a part of the inner surface through which refrigerant flows. In the present embodiment, the second surface layer 313 is not formed to the entire inner side surface of the second flat tube 31.

[0079] The potential of the second surface layer 313 is lower than that 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 corrosion of the second base material 312 on the inner surface side.

[0080] It should be noted that the potentials of the second base material 312 and the second surface layer 313 are obtained by taking a portion of the second base material 312 and the second surface layer 313 from the second heat exchanger 30 to make a test piece and measuring the test piece using the three-electrode method.

[0081] To reduce the potential, the second surface layer 313 contains a metal such as zinc. In this embodiment, the second surface layer 313 is a zinc diffusion layer sputtered with zinc.

[0082] (2-2-2) Second fin

[0083] like Figure 2 As shown, the second fin 32 is joined to a plurality of second flat tubes 31. Here, the second flat tubes 31 and the second fin 32 are joined together by brazing. The second fin 32 may or may not be in contact with the second flat tubes 31. The second fin 32 increases the heat transfer area between the second flat tubes 31 and the indoor air, promoting heat exchange between the refrigerant and the indoor air.

[0084] The second fins 32 are stacked along the length of the second flat tube 31. Here, multiple second fins 32 are arranged to intersect with the second flat tube 31 (in... Figure 2 It extends in the vertical direction in a manner that is orthogonal to the center.

[0085] The second fin 32 is a flat plate component. Furthermore, the second fin 32 has notches for multiple second flat tubes 31 to pass through. These notches are arranged in a vertical direction. Additionally, the second fin 32 may also have clamping portions.

[0086] like Figure 4 As shown, the second fin 32 has a second main body portion 321 and a second surface layer 322.

[0087] The second surface layer 322 is disposed on the surface of the second main body portion 321. Here, the second surface layer 322 is disposed on both surfaces of the second main body portion 321 that extend along the length direction.

[0088] The thickness of the second surface layer 322 is less than the thickness of the second main body 321. Furthermore, the thickness of each of the second fins 32 is the maximum value of the distance from the outer surface toward the interior.

[0089] The potential of the second surface layer 322 is lower than that of the second main body 321. Therefore, in the second fin 32, the second surface layer 322 on the outer surface side is a sacrificial layer that prevents corrosion of the second main body 321 on the inner surface side.

[0090] In order to lower the potential, the second fin 32 contains a metal such as zinc. The second surface layer 322 of the present embodiment is a zinc diffusion layer onto which zinc is sprayed. In addition, the second fin 32 can also contain magnesium, copper, or the like.

[0091] The potential of the second fin 32 can be lower than the potential of the second flat tube 31, or can be higher than the potential of the second flat tube 31. In detail, the potential of the second surface layer 322 of the second fin 32 can be lower than the potential of the second surface layer 313 of the second flat tube 31, or can be higher than the potential of the second surface layer 313 of the second flat tube 31. In other words, in order from low to high potential, it can 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, or it can 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, in order from low to high potential. However, the potential of the second fin 32 is lower than the potential of the second base material 312.

[0092] Note that the potential of the second fin 32 is a value obtained by making a test piece by taking out a portion of the second fin 32 from the second heat exchanger 30, and measuring the test piece by the three-electrode method.

[0093] (2-2-3) Solder

[0094] The second heat exchanger 30 also has a solder (not shown) that connects the second flat tube 31 and the second fin 32. The solder of the present embodiment includes aluminum.

[0095] (2-3) Relationship between the first heat exchanger and the second heat exchanger

[0096] The potential of the first fin 22 is higher than the potential of the second fin 32, and is preferably 1.1 times or more of the potential of the second fin 32. 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.

[0097] Further, 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 20 mV or more and 60 mV or less, and preferably 30 mV or more and 50 mV or less, lower than the potential difference between the second fin 32 and the second flat tube 31. 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 fin 32 and the second flat tube 31 is the absolute value of the difference between the potential of the outer surface of the second flat tube 31 and the potential of the outer surface of the second fin 32.

[0098] Such a potential is achieved by adjusting the amount of metal such as zinc contained in the first flat tube 21, the first fin 22, the second flat tube 31, and the second fin 32 in order to lower the potential.

[0099] (3) Operation

[0100] (3-1) Cooling operation

[0101] In the case where the air conditioner 1 performs the 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 by the flow path switching mechanism 13. The high-pressure refrigerant sent to the second heat exchanger 30 is heat-exchanged with the outdoor air supplied by the second fan 15 in the second heat exchanger 30 to be radiated. The high-pressure refrigerant radiated in the second heat exchanger 30 is sent to the expansion mechanism 14 to be reduced to the low pressure in the refrigeration cycle. The low-pressure refrigerant reduced 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 is heat-exchanged with the indoor air supplied by the first fan 11 in the first heat exchanger 20 to be evaporated. Thus, the indoor air is cooled to be blown into the room. The low-pressure refrigerant evaporated in the first heat exchanger 20 is again sucked into the compressor 12 via the gas refrigerant communication pipe 5 and the flow path switching mechanism 13.

[0102] (3-2) Heating operation

[0103] In a case where the air conditioner 1 performs a heating operation, low-pressure refrigerant in the refrigeration cycle is sucked into the compressor 12, and is discharged after being compressed to 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 indoor air supplied by the first fan 11 in the first heat exchanger 20 to be radiated. Thus, the indoor air is heated to be blown into the room. The high-pressure refrigerant radiated in the first heat exchanger 20 is transported to the expansion mechanism 14 via the liquid refrigerant communication pipe 4, and is reduced in pressure to low pressure in the refrigeration cycle. The low-pressure refrigerant reduced in pressure 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 outdoor air supplied by the second fan 15 in the second heat exchanger 30 to be evaporated. The low-pressure refrigerant evaporated in the second heat exchanger 30 is again sucked into the compressor 12 through the flow path switching mechanism 13.

[0104] (4) Features

[0105] (4-1)

[0106] In a cross fin heat exchanger, a technique of forming a resin layer on the surface of a fin to insulate the fin from a heat transfer tube to suppress corrosion is considered. However, in a microchannel heat exchanger, since a fin is brazed to a heat transfer tube (flat tube), it is not possible to form a resin layer on the surface of the fin. Therefore, when a potential difference occurs between the fin and the heat transfer tube, the fin or the heat transfer tube is corroded. For example, in a case where corrosion of the heat transfer tube is prevented to prevent leakage of refrigerant, the potential of the fin is sometimes made lower than the potential of the heat transfer tube. In this case, the fin containing aluminum is preferentially corroded, and aluminum hydroxide is generated. If this microchannel heat exchanger is provided in an indoor unit, there is a problem that white powdery aluminum hydroxide can be scattered into the room. The present inventors focused on this problem, and conceived the air conditioner 1 of the present disclosure.

[0107] In detail, the problem of scattering of powder resulting from corrosion is not a large problem in an outdoor unit, but becomes a problem in an indoor unit, and thus is a problem unique to an indoor unit. On the other hand, the presence degree of chloride ions in the atmosphere is large in an outdoor unit relative to an indoor unit, and thus there is another problem that corrosion is easily caused. In order to solve these problems, the present inventors conducted intensive research, and as a result, obtained a relationship between the potential of a fin and a flat tube of an indoor unit and the potential of a fin and a flat tube of an outdoor unit.

[0108] Therefore, the air conditioner 1 of the present embodiment is provided with the indoor unit 2 and the outdoor unit 3. The indoor unit 2 includes the first heat exchanger 20. The outdoor unit 3 includes the second heat exchanger 30. The first heat exchanger 20 has the first flat tube 21 and the first fin 22. The first fin 22 is joined to the first flat tube 21. The second heat exchanger 30 has the second flat tube 31 and the second fin 32. The second fin 32 is joined to the second flat tube 31. The potential difference between the first fin 22 and the first flat tube 21 of the indoor unit 2 is smaller than the potential difference between the second fin 32 and the second flat tube 31 of the outdoor unit 3.

[0109] According to the air conditioner 1 of the present 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, and thus, 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. Thus, the white powdery aluminum hydroxide can be suppressed from flying into the room.

[0110] In addition, the potential difference between the second fin 32 and the second flat tube 31 of the outdoor unit 3 can be made larger than the potential difference between the first fin 22 and the first flat tube 21 of the indoor unit 2, and thus, the corrosion of the second base material 312 of the second flat tube 31 of the outdoor unit 3 can be suppressed.

[0111] In addition, the outdoor unit 3 is more likely to be corroded than the indoor unit 2, and thus, 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 case, in order to suppress the corrosion of the second flat tube 31 and prevent the leakage of refrigerant, the potential can be designed 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, 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 flying of powder from the indoor unit 2 can be suppressed.

[0112] (4-2)

[0113] In the air conditioner 1 of the present embodiment, the potential of the first fin 22 is higher than the potential of the second fin 32.

[0114] Here, by making the potential of the first fin 22 of the indoor unit 2 higher than the potential of the second fin 32 of the outdoor unit 3, the corrosion of the first fin 22 can be suppressed, and thus, the flying of aluminum hydroxide into the room can be further suppressed.

[0115] (4-3)

[0116] In the air conditioner 1 of the present embodiment, the potential of the first fin 22 is higher than the potential of the first flat tube 21.

[0117] Here, by making the potential of the first fin 22 higher than the potential of the first flat tube 21, corrosion of the first fin 22 is suppressed, whereby the scattering of aluminum hydroxide into the room can be further suppressed.

[0118] (4-4)

[0119] In the air conditioner 1 of 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.

[0120] Here, the potential difference between the first fin 22 and the first flat tube 21 of the indoor unit 2 is reduced to 20 mV or more and 60 mV or less. Thus, the generation of aluminum hydroxide due to corrosion of the first fin 22 and the first flat tube 21 can be further reduced.

[0121] (4-5)

[0122] In the air conditioner 1 of the present embodiment, the potential of the first fin 22 is -890 mV or more and -750 mV or less.

[0123] 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 -750 mV or less. Thus, the first fin 22 is not excessively corroded, and the generation of aluminum hydroxide due to corrosion of the first fin 22 can be reduced.

[0124] Further, in the indoor unit 2 of the present embodiment, the first fin 22 is not excessively corroded, and thus the corrosion odor can also be suppressed.

[0125] (4-6)

[0126] In the air conditioner 1 of the present embodiment, the potential of the first fin 22 is -890 mV or more and -800 mV or less.

[0127] 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. Thus, the first fin 22 is not excessively corroded, and the generation of aluminum hydroxide due to corrosion of the first fin 22 can be further reduced.

[0128] (4-7)

[0129] The air conditioner 1 of the present embodiment performs cooling operation and heating operation.

[0130] In the present embodiment, even when operation accompanied by dew condensation is performed in the evaporator, the first fin 22 and the first flat tube 21 are not excessively corroded. Thus, even when the air conditioner 1 performs cooling operation and heating operation, the generation of aluminum hydroxide due to corrosion of the first fin 22 and the first flat tube 21 of the indoor unit 2 can be reduced.

[0131] (5) Modification

[0132] (5-1) Modification 1

[0133] In the above-described embodiments, the first fin 22 has the first surface layer 222 and the second fin 32 has the second surface layer 322, but not limited thereto. Also, at least one of the first fin 22 and the second fin 32 of the present disclosure can not have a surface layer.

[0134] (5-2) Modification 2

[0135] In the above-described embodiments, the first flat tube 21 has the first surface layer 213 and the second flat tube 31 has the second surface layer 313, but not limited thereto. Also, at least one of the first flat tube 21 and the second flat tube 31 of the present disclosure can not have a surface layer.

[0136] (5-3) Modification 3

[0137] In the above-described embodiments, 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 by way of example of a diffusion layer in which zinc is spattered, but not limited thereto. In the present modification, a clad material is used as a base material and a surface layer.

[0138] Specifically, the first flat tube 21 is formed using a clad material in which a metal that becomes the first base material 212 and a metal that becomes the first surface layer 213 are bonded. The second flat tube 31 is formed using a clad material in which a metal that becomes the second base material 312 and a metal that becomes the second surface layer 313 are bonded.

[0139] (5-4) Modification 4

[0140] In the above-described embodiments, the air conditioner 1 that performs the cooling operation and the heating operation is described by way of example, but the air conditioner of the present disclosure is not limited thereto. The air conditioner of the present disclosure can also perform the dehumidifying operation, and can also be a cooling-only type.

[0141]

Example

[0142] In the present example, the effect of making the potential of the first fin 22 and the first flat tube 21 of the indoor unit 2 lower than the potential of the second fin 32 and the second flat tube 31 of the outdoor unit 3 is investigated.

[0143] (Example 1)

[0144] In Example 1, as the first heat exchanger 20 of the indoor unit 2 and the second heat exchanger 30 of the outdoor unit 3, a microchannel heat exchanger-equipped air conditioner 1 shown in FIG. 1 was manufactured. Figure 1

[0145] ​Specifically, as the first flat tube 21, a first surface layer 213 was formed by plating zinc on the surface of an aluminum first base material 212. Also, as the first fin 22, a first surface layer 222 was formed by plating zinc on the surface of an aluminum first main body portion 221. The first flat tube 21 and the first fin 22 were joined using a solder containing aluminum, and the first heat exchanger 20 was produced.

[0146] Also, as the second flat tube 31, a second surface layer 313 was formed by plating zinc on the surface of an aluminum second base material 312. Also, as the second fin 32, a second surface layer 322 was formed by plating zinc on the surface of an aluminum second main body portion 321. The second flat tube 31 and the second fin 32 were joined using a solder containing aluminum, and the second heat exchanger 30 was produced. In Example 1, the zinc content of the first fin 22 was made lower than the zinc content of the second fin 32.

[0147] (Comparative Example 1)

[0148] Comparative Example 1 was basically the same as Example 1, but only the first fin of the first heat exchanger of the indoor unit was different. Specifically, the zinc content of the first fin of the indoor unit of Comparative Example 1 was made the same as the zinc content of the second fin of the outdoor unit.

[0149] (Measurement method and results)

[0150] The potential 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 of Example 1 and Comparative Example 1 was measured. The measurement method was as follows.

[0151] A part 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 was taken out from the first heat exchanger and the second heat exchanger, and a test piece was produced, and the test piece was measured by the three-electrode method. Specifically, as shown in Figure 5 the length of the test piece S was set to 40 mm. Then, as shown in Figure 6 epoxy resin R was attached to the test piece S, and a test surface S1 was exposed. The length of the entire circumference of the test surface S1 was 10 mm. The test solution was a 2.67% aluminum chloride aqueous solution. The reference electrode was a saturated calomel electrode. The counter electrode was platinum. As shown in Figure 7 the test piece S was connected to the counter electrode using a lead. Then, in a state where the atmosphere was open and the temperature was 40°C, after adjusting the pH of the test solution, the potential of the test surface S1 was measured by the three-electrode method.

[0152] The results of measuring the potential of Example 1 and Comparative Example 1 are shown in Table 1 below.

[0153]

Table 1

[0154]

[0155] As described 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).

[0156] (Evaluation method and results)

[0157] For the air conditioner of Example 1 and the air conditioner of Comparative Example 1, cooling operation and heating operation were performed, and it was visually confirmed whether or not aluminum hydroxide flew out from the indoor unit.

[0158] 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 flew out 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 did not fly out from the indoor unit.

[0159] From the above, it can be confirmed that by making the potential of the first fin 22 and the first flat tube 21 of the indoor unit 2 lower than the potential of the second fin 32 and the second flat tube 31 of the outdoor unit 3, the generation of aluminum hydroxide due to corrosion of the first fin and the first flat tube is reduced, and thus the flying out of aluminum hydroxide into the room can be suppressed. In addition, it can also 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 due to corrosion of the first fin is reduced, and thus the flying out of aluminum hydroxide into the room can be suppressed.

[0160] The embodiments of the present disclosure have been described above, but it should be understood that various modifications of the modes and details can be made without departing from the spirit and scope of the present disclosure described in the claims.

[0161] Explanation of reference numerals

[0162] 1 Air conditioner

[0163] 2 Indoor unit

[0164] 3 Outdoor unit

[0165] 20 First heat exchanger

[0166] 21 first flat tube

[0167] 22 first fin

[0168] 30 second heat exchanger

[0169] 31 second flat tube

[0170] 32 second fin

[0171] Prior art document

[0172] Patent document

[0173] Patent document 1: Japanese Patent Application Publication No. 2013-43216

Claims

1. An air conditioner (1) comprising: an indoor unit (2) including a first heat exchanger (20); and an outdoor unit (3) including a second heat exchanger (30), the first heat exchanger having: a first flat tube (21); and a first fin (22) joined to the first flat tube, the second heat exchanger having: a second flat tube (31); and a second fin (32) joined to the second flat tube, a potential difference between the first fin and the first flat tube being smaller than a potential difference between the second fin and the second flat tube.

2. The air conditioner according to claim 1, wherein a potential of the first fin is higher than a potential of the second fin.

3. The air conditioner according to claim 1 or 2, wherein a potential of the first fin is higher than a potential of the first flat tube.

4. The air conditioner according to any one of claims 1 to 3, wherein the potential difference between the first fin and the first flat tube is 20 mV or more and 60 mV or less.

5. The air conditioner according to any one of claims 1 to 4, wherein the potential of the first fin is -890 mV or more and -750 mV or less.

6. The air conditioner according to any one of claims 1 to 5, wherein the potential of the first fin is -890 mV or more and -800 mV or less.

7. The air conditioner according to any one of claims 1 to 6, wherein the air conditioner performs a cooling operation and a heating operation. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images