Heat exchanger and refrigeration cycle device

Abstract

A heat exchanger (100) is provided with at least one heat transfer tube (10) and a fin (20). Each of the at least one heat transfer tube has a first surface (10c). The fin has a second surface (20a). The hydrophilicity of the second surface is higher than the hydrophilicity of the first surface.

Description

Heat exchanger and refrigeration cycle device

[0001] The present disclosure relates to a heat exchanger and a refrigeration cycle device.

[0002] Japanese Patent Laid-Open Publication No. 2023-100145 (Patent Document 1) describes a heat exchanger. The heat exchanger described in Patent Document 1 has flat tubes as heat transfer tubes. The flat tubes have a sacrificial anode layer on their surfaces. The sacrificial anode layer is made of zinc. A film of an oxide of the metal material that forms the sacrificial anode layer is formed on the sacrificial anode layer.

[0003] Japanese Patent Application Laid-Open No. 2023-100145

[0004] The heat exchanger described in Patent Document 1 has room for improvement in the ability to drain water adhering to the surfaces of the heat transfer tubes (flat tubes). The present disclosure provides a heat exchanger with improved ability to drain water adhering to the surfaces of the heat transfer tubes.

[0005] The heat exchanger of the present disclosure includes at least one heat transfer tube and fins, each of the at least one heat transfer tube having a first surface, and the fin having a second surface, the second surface being more hydrophilic than the first surface.

[0006] According to the heat exchanger of the present disclosure, it is possible to improve the ability to discharge water adhering to the surface of the heat transfer tube.

[0007] FIG. 1 is a plan view of the heat exchanger 100. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a first side view of the heat exchanger 100. FIG. 4 is a second side view of the heat exchanger 100 as viewed from the opposite side to FIG. 3. FIG. 5 is a cross-sectional view of a heat transfer tube 10. FIG. 6 is an enlarged cross-sectional view of the heat transfer tube 10 in the vicinity of the surface 10c. FIG. 7 is an enlarged cross-sectional view of the fin 20 in the vicinity of the surface 20a. FIG. 8 is a model diagram illustrating the hydrophilicity of the surface of an aluminum alloy. FIG. 9 is a schematic diagram of a refrigeration cycle device 200.

[0008] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant descriptions will not be repeated.

[0009] Embodiment 1 A heat exchanger according to embodiment 1 will be described. The heat exchanger according to embodiment 1 is designated as heat exchanger 100.

[0010] (Configuration of Heat Exchanger 100) FIG. 1 is a plan view of the heat exchanger 100. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a first side view of the heat exchanger 100. FIG. 4 is a second side view of the heat exchanger 100 seen from the opposite side to that of FIG. 3. FIG. 5 is a cross-sectional view of a heat transfer tube 10. As shown in FIGS. 1, 2, 3, 4, and 5, the heat exchanger 100 has a plurality of heat transfer tubes 10 and a plurality of fins 20. The heat exchanger 100 is a heat exchanger used, for example, as a cooler. The heat exchanger 100 is a heat exchanger used, for example, in an air conditioner. However, the heat exchanger 100 may also be a heat exchanger used in a refrigeration / heating device such as a refrigerator, a freezer, a vending machine, a refrigeration system, or a water heater.

[0011] The heat transfer tubes 10 are arranged at intervals along a first direction DR1. The heat transfer tubes 10 extend along a second direction DR2. The second direction DR2 is perpendicular to the first direction DR1. A plurality of refrigerant flow paths 11 are formed inside the heat transfer tubes 10. The refrigerant flow paths 11 extend along the second direction DR2 inside the heat transfer tubes 10. In a cross-sectional view perpendicular to the second direction DR2, the shape of the refrigerant flow paths 11 is, for example, rectangular.

[0012] Each heat transfer tube 10 has a first surface 10a and a second surface 10b. The second surface 10b is the surface opposite the first surface 10a. The first surface 10a and the second surface 10b form both end surfaces in the first direction DR1. The first surface 10a of one of two adjacent heat transfer tubes 10 is disposed opposite the second surface 10b of the other of the two adjacent heat transfer tubes 10 with a gap therebetween. In a cross-sectional view perpendicular to the second direction DR2, the longitudinal direction of the heat transfer tube 10 is aligned along a third direction DR3. The third direction DR3 is perpendicular to the first direction DR1 and the second direction DR2. From another perspective, the heat transfer tube 10 has a flat portion extending along the third direction DR3 in a cross-sectional view perpendicular to the second direction DR2. The heat transfer tube 10 has, for example, an elliptical shape with its longitudinal direction aligned with the third direction DR3 in a cross-sectional view perpendicular to the second direction DR2.

[0013] The distance between two adjacent heat transfer tubes 10 is, for example, 1 mm or more and 3 mm or less. The heat transfer tubes 10 are formed, for example, by extrusion molding. However, the method for forming the heat transfer tubes 10 is not limited to this. The heat transfer tubes 10 may also be formed, for example, by roll-forming a rectangular flat plate material by bending it.

[0014] The fins 20 are arranged at intervals along the first direction DR1. One of two adjacent heat transfer tubes 10 may be referred to as the heat transfer tube 10A, and the other of the two adjacent heat transfer tubes 10 may be referred to as the heat transfer tube 10B. The fins 20 have a main body 21 and protruding portions 22 and 23. The fins 20 are formed, for example, by bending a rectangular flat plate material. However, the method of forming the fins 20 is not limited to this.

[0015] The main body 21 has a first surface 21a and a second surface 21b. The second surface 21b is the surface opposite to the first surface 21a. The first surface 21a and the second surface 21b form both end surfaces of the main body 21 in the first direction DR1. The main body 21 has bent portions 24a and base portions 25a. The number of bent portions 24a and the number of base portions 25a are, for example, plural. However, the number of bent portions 24a and the number of base portions 25a may be singular. The main body 21 and the heat transfer tubes 10 are arranged alternately in the first direction DR1.

[0016] The multiple bent portions 24a are aligned at intervals along the second direction DR2. The base portion 25a is disposed between two adjacent bent portions 24a and is continuous with both of the adjacent bent portions 24a. The bottoms of the bent portions 24a and the base portions 25a are flat. The first surface 21a of each of the multiple base portions 25a is in contact with the heat transfer tube 10B (more specifically, the first surface 10a of the heat transfer tube 10B) via a brazing material.

[0017] The main body 21 is bent in the first direction DR1 at each of the plurality of bent portions 24a such that the second surface 21b at the bottom of the bent portion 24a contacts the heat transfer tube 10A (more specifically, the second surface 10b of the heat transfer tube 10A) with the brazing material interposed therebetween. From another perspective, the main body 21 extends in the second direction DR2 while meandering between the heat transfer tube 10A and the heat transfer tube 10B in a side view along the third direction DR3.

[0018] The protrusions 22 and 23 are connected to both ends of the main body 21 in the third direction DR3 so as to protrude from the heat transfer tubes 10A and 10B along the third direction DR3, respectively. Each of the protrusions 22 and 23 has a bent portion 24b and a base portion 25b. The number of bent portions 24b and the number of base portions 25b are, for example, plural. However, the number of bent portions 24b and the number of base portions 25b may be singular.

[0019] The multiple bent portions 24b are arranged at intervals along the second direction DR2. The base portion 25b is disposed between two adjacent bent portions 24b and is connected to both of the two adjacent bent portions 24b. The bottoms of the bent portions 24b and the base portion 25b are flat. The base portion 25b is connected to the base portion 25a in the third direction DR3. From another perspective, in a side view along the third direction DR3, the position of the bent portion 24b in the second direction DR2 overlaps with the position of the bent portion 24a in the second direction DR2.

[0020] Each of the protrusions 22 and 23 is bent in the first direction DR1 at the bent portion 24b. From another perspective, each of the protrusions 22 and 23 extends in the second direction DR2 while meandering between the heat transfer tubes 10A and 10B in a side view along the third direction DR3. However, the bending direction of the bent portion 24b (leftward in FIG. 3 ) is opposite to the bending direction of the bent portion 24a (rightward in FIG. 3 ).

[0021] When the heat exchanger 100 operates as an evaporator, air from the blower flows between two adjacent heat transfer tubes 10 along the third direction DR3. At this time, a two-phase gas-liquid refrigerant supplied from the upstream side of the outdoor unit flows through the refrigerant flow path 11. This refrigerant exchanges heat with the air, becoming a low-temperature, low-pressure gas refrigerant, which is then drawn into the compressor. Due to this heat exchange, condensation may occur on the surfaces of the heat transfer tubes 10 due to the temperature difference with the air.

[0022] The heat transfer tube 10 has a surface 10c. The first surface 10a and the second surface 10b form part of the surface 10c. Fig. 6 is an enlarged cross-sectional view of the heat transfer tube 10 in the vicinity of the surface 10c. As shown in Fig. 6, the heat transfer tube 10 has a surface layer 12 and a core portion 13. The surface layer 12 is formed on the surface 10c. The core portion 13 is located inside the surface layer 12, i.e., farther from the surface 10c than the surface layer 12.

[0023] The fin 20 has a surface 20a. The first surface 21a and the second surface 21b form part of the surface 20a. Fig. 7 is an enlarged cross-sectional view of the fin 20 near the surface 20a. As shown in Fig. 7, the fin 20 has a surface layer 26 and a core portion 27. The surface layer 26 is formed on the surface 20a. The core portion 27 is located inside the surface layer 26, i.e., farther from the surface 20a than the surface layer 26.

[0024] The material potential in the surface layer 12 is lower than the material potential in the core 13. The material potential in the surface layer 26 is lower than the material potential in the core 13 and is different from the material potential in the surface layer 12. The material potential in the surface layer 26 is lower than the material potential in the surface layer 12, for example.

[0025] The material used for the heat transfer tube 10 is, for example, an aluminum alloy. Specific examples of aluminum alloys used for the heat transfer tube 10 include aluminum alloys in the A1000 series and A3000 series as specified in the JIS standard. The zinc concentration in the aluminum alloy in the surface layer 12 is higher than the zinc concentration in the aluminum alloy in the core portion 13. The material potential of the aluminum alloy decreases as the zinc concentration increases. Therefore, in the heat transfer tube 10, the material potential in the surface layer 12 is lower than the material potential in the core portion 13 due to this difference in zinc concentration in the aluminum alloy. The difference between the zinc concentration in the aluminum alloy in the surface layer 12 and the zinc concentration in the aluminum alloy in the core portion 13 is preferably 0.5 mass percent or more. Note that the core portion 13 may not contain zinc. That is, the zinc concentration in the aluminum alloy in the core portion 13 may be 0 mass percent.

[0026] The surface layer 12 is formed by, for example, a zinc thermal spraying method or a method of applying a zinc-substituted flux. In the zinc thermal spraying method, metallic zinc is sprayed onto the surface of the aluminum alloy, and high-temperature treatment is performed to diffuse the zinc component from the surface of the aluminum alloy, thereby forming the surface layer 12 from an aluminum alloy containing zinc. In the method of applying a zinc-substituted flux, zinc is diffused from the surface of the aluminum alloy by performing Nocolok brazing using a zinc-substituted flux, thereby forming the surface layer 12 from an aluminum alloy containing zinc. In addition to these methods, the surface layer 12 from an aluminum alloy containing zinc can also be formed by forming the heat transfer tube 10 using a clad material obtained by bonding an aluminum alloy containing zinc (e.g., an aluminum alloy in the A7000 series specified in the JIS standard) to a plate of another aluminum alloy and alloying it.

[0027] The material used for the fin 20 is, for example, an aluminum alloy. Specific examples of aluminum alloys used for the fin 20 include aluminum alloys in the A1000 series or A3000 series specified in the JIS standard, to which zinc has been added. The zinc concentration in the aluminum alloy in the surface layer 26 is higher than the zinc concentration in the aluminum alloy in the core portion 13 and different from the zinc concentration in the aluminum alloy in the surface layer 12. The zinc concentration in the aluminum alloy in the surface layer 26 is preferably higher than the zinc concentration in the aluminum alloy in the surface layer 12. Therefore, the material potential in the surface layer 26 is lower than the material potential in the core portion 13 and different from the material potential in the surface layer 12 (it is lower than the material potential in the surface layer 12). The difference between the zinc concentration in the aluminum alloy in the surface layer 26 and the zinc concentration in the aluminum alloy in the core portion 13 is preferably 0.5 mass percent or more. The zinc concentration in the aluminum alloy in the surface layer 26 is preferably 10 mass percent or less. As a result, the zinc concentration in the aluminum alloy in the surface layer 12 and the zinc concentration in the aluminum alloy in the core portion 13 are also preferably 10 mass percent or less. In the fin 20, the zinc concentration (material potential) in the aluminum alloy in the surface layer 26 does not need to be different from the zinc concentration (material potential) in the aluminum alloy in the core portion 27. If the material potential in the surface layer 26 is lower than the material potential in the surface layer 12 (i.e., if the zinc concentration in the aluminum alloy in the surface layer 26 is higher than the zinc concentration in the aluminum alloy in the surface layer 12), oxides are more likely to form on the surface 20a than on the surface 10c. As a result, the hydrophilicity of the surface 20c becomes higher than that of the surface 10c, and this difference in hydrophilicity generates a driving force that moves water adhering to the surface 10c toward the surface 20a, thereby improving the drainage performance of the heat exchanger 100.

[0028] For example, an aluminum alloy is used as the brazing material used to braze the heat transfer tube 10 and the fins 20. However, the melting point of the aluminum alloy used for the brazing material is lower than the melting point of the aluminum alloy used for the heat transfer tube 10 and the melting point of the aluminum alloy used for the fins 20. Specific examples of aluminum alloys used for the brazing material include aluminum-silicon alloys such as aluminum alloys in the A4000 series specified in the JIS standard.

[0029] (Effects of Heat Exchanger 100) The effects of the heat exchanger 100 will be described below.

[0030] Aluminum is an inherently active metal. However, because aluminum reacts with oxygen in the air and immediately forms a protective oxide film on its surface, it is stable in dry, room-temperature air and is considered a highly corrosion-resistant metal. On the other hand, when the air contains salt (e.g., the salt in sea salt particles), the salt locally destroys the surface oxide film, forming pits (pitting corrosion). Once pitting corrosion occurs, the active aluminum inside the oxide film is eroded, making it difficult to control and understand the corrosion process. Therefore, when heat transfer tubes are made of aluminum alloys, rust prevention treatment is required on the surface of the heat transfer tube.

[0031] In the heat exchanger 100, the material potential of the surface layer 12 is lower than the material potential of the core portion 13. That is, the surface layer 12 functions as a sacrificial anode layer for the core portion 13. As a result, the corrosion mode of the heat transfer tube 10 changes from a mode in which corrosion progresses locally toward the core portion 13 due to pitting corrosion to a mode in which corrosion occurs over the entire surface of the surface layer 12. In this way, in the heat exchanger 100, the material potential of the surface layer 12 is lower than the material potential of the core portion 13 (that is, the zinc concentration in the aluminum alloy in the surface layer 12 is higher than the zinc concentration in the aluminum alloy in the core portion 13), and therefore corrosion of the heat transfer tube 10 is suppressed.

[0032] Figure 8 is a model diagram illustrating the hydrophilicity of an aluminum alloy surface. As shown in Figure 8, an oxide film is formed on the surface of an aluminum alloy from aluminum oxide. The oxide film contains hydroxyl groups (OH groups). Although not shown, the oxide film also contains ether bonds (O bonds). These functional groups attract the hydrogen and oxygen atoms of polar water molecules, forming hydrogen bonds. In this way, the oxide film formed on the surface of an aluminum alloy exhibits hydrophilic properties. The hydrophilic properties of an oxide film increase with the number of hydroxyl groups and ether bonds, and therefore increase with the presence of more oxides on the surface of the aluminum alloy.

[0033] When the material potential of the surface layer 26 is lower than that of the surface layer 12 (i.e., when the zinc concentration in the aluminum alloy in the surface layer 26 is higher than that in the surface layer 12), oxides are more likely to form on the surface 20a than on the surface 10c. Therefore, in this case, oxide formation is promoted on the surface 20a more than on the surface 10c over time due to operation of the air conditioner, etc., which causes the hydrophilicity of the surface 20a to become higher than that of the surface 10c. This difference in hydrophilicity generates a driving force that moves water adhering to the surface 10c toward the surface 20a. More specifically, condensed water may accumulate on the surface 10c in the minute gaps between the fins 20. This driving force moves the condensed water toward the fins 20 and the outside of the heat exchanger 100, where it is discharged by the blower. In this way, the heat exchanger 100 can improve the drainage performance of the heat exchanger 100 while suppressing corrosion of the heat transfer tube 10. Furthermore, if the drainage performance of the heat exchanger 100 is improved, it is possible to suppress performance degradation due to an increase in ventilation resistance and frost formation.

[0034] The corrosion resistance of the heat transfer tube 10 having the surface layer 12 as a sacrificial anode layer is determined by the difference between the zinc concentration in the aluminum alloy in the surface layer 12 and the zinc concentration in the aluminum alloy in the core portion 13. When the difference between the zinc concentration in the aluminum alloy in the surface layer 12 and the zinc concentration in the aluminum alloy in the core portion 13 is 0.5 mass percent or more, the surface layer 12 functions sufficiently as a sacrificial anode layer, and corrosion of the core portion 13 can be sufficiently suppressed. Furthermore, the greater the difference between the zinc concentration in the aluminum alloy in the surface layer 26 and the zinc concentration in the aluminum alloy in the surface layer 12, the greater the driving force that moves water adhering to the surface 10c toward the surface 20a. Therefore, by setting the difference between the zinc concentration in the aluminum alloy in the surface layer 26 and the zinc concentration in the aluminum alloy in the surface layer 12 to be 0.5 mass percent or more, the drainage properties of the heat exchanger 100 can be sufficiently ensured.

[0035] On the other hand, if the zinc concentration in the aluminum alloy in the surface layer 12 is 10 mass percent or more, the rate of disappearance of the sacrificial anode layer (surface layer 12) becomes too fast. Therefore, by setting the zinc concentration in the aluminum alloy in the surface layer 26 to 10 mass percent or less, the zinc concentration in the aluminum alloy in the surface layer 12 becomes less than 10 mass percent, and disappearance of the sacrificial anode layer (surface layer 12) due to short-term self-corrosion can be suppressed.

[0036] In the heat exchanger 100, the protrusions 22 and 23 each have a plurality of bent portions 24b. Therefore, in the heat exchanger 100, the rigidity of the protrusions 22 and 23 is increased, and the heat transfer area of ​​the protrusions 22 and 23 is increased. Note that, by increasing the rigidity of the protrusions 22 and 23, the protrusions 22 and 23 are less likely to deform when subjected to external force. Furthermore, by connecting the base portions 25a and 25b to each other, the protrusions 22 and 23 are firmly connected to the main body portion 21, and the rigidity of the fins 20 is increased.

[0037] In the heat exchanger 100, the heat transfer tubes 10 have flat portions, and the bottoms of the bent portions 24a and the base portions 25a are flat, which facilitates the placement of jigs during manufacturing and improves the manufacturability of the heat exchanger 100. In the heat exchanger 100, only one heat transfer tube 10 is disposed between the protruding portions 22 and 23 that face each other in the third direction DR3. Therefore, even if another heat transfer tube 10 adjacent to the one heat transfer tube moves in the third direction DR3, the other heat transfer tube 10 does not come into contact with the protruding portions 22 and 23. Therefore, in the heat exchanger 100, deformation of the protruding portions 22 and 23 due to contact between the one heat transfer tube 10 located between the protruding portions 22 and 23 and the other heat transfer tube 10 adjacent to the one heat transfer tube 10 is suppressed. Furthermore, in the heat exchanger 100, the structure of the fins 20 as described above allows the spacing between adjacent heat transfer tubes 10 to be narrowed.

[0038] (Configuration of Refrigeration Cycle Apparatus 200) The configuration of the refrigeration cycle apparatus 200 using the heat exchanger 100 will be described below.

[0039] Fig. 9 is a schematic diagram of a refrigeration cycle apparatus 200. As shown in Fig. 9, the refrigeration cycle apparatus 200 has a refrigerant circuit configured with a compressor 210, a condenser 220, a throttling device 230, and an evaporator 240. The refrigerant flowing through the refrigerant circuit may be filled with any refrigerant.

[0040] The compressor 210 compresses the refrigerant. The compressor 210 may be a rotary compressor, a scroll compressor, a screw compressor, a reciprocating compressor, or the like. The condenser 220 exchanges heat between the refrigerant and air. The condenser 220 may be, for example, an outdoor heat exchanger. The throttling device 230 expands the refrigerant to reduce its pressure. The throttling device 230 may be, for example, an electric expansion valve, a mechanical expansion valve, or a capillary tube. The evaporator 240 exchanges heat between the refrigerant and air. The evaporator 240 may be, for example, an outdoor heat exchanger. The refrigeration cycle apparatus 200 further includes a blower 251 and a blower 252. The blower 251 and the blower 252 blow air to the condenser 220 and the evaporator 240, respectively. The evaporator 240 may be, for example, the heat exchanger 100.

[0041] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0042] 10, 10A, 10B heat transfer tube, 10a first surface, 10b second surface, 10c surface, 11 flow path, 12 surface layer, 13 core portion, 20 fin, 20a surface, 21 main body portion, 21a first surface, 21b second surface, 22, 23 protrusion portion, 24a, 24b bent portion, 25a, 25b base portion, 26 surface layer, 27 core portion, 100 heat exchanger, 200 refrigeration cycle device, 210 compressor, 220 condenser, 230 throttling device, 240 evaporator, 251, 252 blower, DR1 first direction, DR2 second direction, DR3 third direction.

Claims

1. A heat exchanger comprising: at least one heat transfer tube; and fins, wherein each of the at least one heat transfer tubes has a first surface; the fins have a second surface; and the second surface is more hydrophilic than the first surface.

2. A heat exchanger as described in claim 1, wherein each of the at least one heat transfer tubes has a first surface layer on the first surface and a core portion farther from the first surface than the first surface layer, the fin has a second surface layer on the second surface, the material potential of the first surface layer is lower than the material potential of the core portion, and the material potential of the second surface layer is lower than the material potential of the core portion and different from the material potential of the first surface layer.

3. The heat exchanger according to claim 2, wherein said fins and said at least one heat transfer tube are formed of an aluminum alloy.

4. A heat exchanger as described in claim 3, wherein the zinc concentration in the first surface layer is higher than the zinc concentration in the core portion, and the zinc concentration in the second surface layer is higher than the zinc concentration in the core portion and different from the zinc concentration in the first surface layer.

5. A heat exchanger according to claim 4, wherein the zinc concentration in said second surface layer is higher than the zinc concentration in said first surface layer.

6. A heat exchanger as described in claim 5, wherein the difference between the zinc concentration in the first surface layer and the zinc concentration in the core is 0.5 mass percent or more, the difference between the zinc concentration in the second surface layer and the zinc concentration in the first surface layer is 0.5 mass percent or more, and the zinc concentration in the second surface layer is 10 mass percent or less.

7. The at least one heat transfer tube includes a first flat tube and a second flat tube, the first flat tube and the second flat tube are arranged opposite each other with a gap in between along a first direction, each of the first flat tube and the second flat tube extends along a second direction perpendicular to the first direction, and in a cross-sectional view perpendicular to the second direction, the longitudinal direction is along a third direction perpendicular to the first and second directions, the fin has a main body portion, a first protrusion portion and a second protrusion portion, the main body portion has a first surface and a second surface which are end faces in the first direction, the main body portion has a plurality of first bent portions arranged with a gap in between along the second direction, the first surface is in contact with the first flat tube between two adjacent ones of the plurality of first bent portions, and each of the plurality of first bent portions is bent in the first direction so that the second surface is in contact with the second flat tube, 7. The heat exchanger of claim 1, wherein each of the first protrusions and the second protrusions is connected to both ends of the main body in the third direction so as to protrude along the third direction, each of the first protrusions and the second protrusions has a plurality of second bends arranged at intervals along the first direction, and each of the second bends is bent in the first direction to the opposite side from each of the plurality of first bends.

8. A refrigeration cycle device comprising the heat exchanger according to any one of claims 1 to 7.

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