JP2015078789A - Heat exchanger and air conditioning device including heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger in which aluminum heat transfer pipes and refrigerant pipes can be simply connected and that has excellent corrosion resistance.SOLUTION: A heat exchanger comprises: fins 12 stacked at regular intervals; and heat transfer pipes 14 and 15 that penetrate through the respective stacked fins 12 and are fixed and in which aluminum refrigerant pipes 19 are connected to both end parts 14a and 14b. The heat transfer pipes 14 and 15 and the refrigerant pipes 19 are connected by a low melting point brazing material 17 mixed with noncorrosive flux, and surfaces of the low melting point brazing material 17 in contact with air are covered by coating members 18.

Description

  The present invention relates to an aluminum heat exchanger to which, for example, an aluminum refrigerant pipe is brazed, and an air conditioner including the heat exchanger.

  As a method for joining aluminum pipes (hereinafter referred to as “aluminum pipes”), brazing using a brazing material of an aluminum-silicon alloy is common. However, since the melting point of the aluminum-silicon alloy is about 600 ° C. and the melting point of the aluminum pipe is about 660 ° C., the melting point difference between the brazing material and the aluminum pipe is small. For this reason, when brazing, the aluminum piping is not melted, and the heat is weakened by the melting of the aluminum piping, so that there is no shortage of brazing material around the brazing. The current situation is that the burden on the brazing worker is heavy to maintain the characteristics.

  In order to reduce the burden on the operator, as a method for easily connecting aluminum piping, for example, a non-corrosive flux containing CsF and a low melting point brazing material made of zinc or a zinc-aluminum alloy mainly composed of zinc are used. There is a method of brazing at a low temperature using a mixture (see, for example, Patent Document 1).

JP 2005-111527 A (summary)

  However, when brazing is performed by the method according to Patent Document 1, the brazed portion becomes lower in terms of potential, so that corrosion between different metals occurs at the joint between the brazing and the aluminum piping, and the corrosion resistance of the brazed portion is reduced. It will be inferior. Therefore, corrosion progresses from the joining point of the low melting point brazing material, and there is a possibility that a substance (refrigerant) flowing inside the pipe leaks to the outside.

  The present invention has been made to solve the above-described problems, and is capable of simply joining an aluminum heat transfer tube and a refrigerant pipe, and having excellent corrosion resistance and heat. It aims at obtaining the air conditioning apparatus provided with the exchanger.

  The heat exchanger according to the present invention includes fins stacked at regular intervals, and aluminum heat transfer tubes that are fixed through the stacked fins and joined to both ends with aluminum refrigerant pipes. The heat transfer pipe and the refrigerant pipe are joined with a low melting point brazing material mixed with a non-corrosive flux, and the surface of the low melting point brazing material in contact with the atmosphere is covered with a coating member.

  In the present invention, the heat transfer tube and the refrigerant pipe are joined with a low melting point brazing material mixed with a non-corrosive flux, and the surface of the low melting point brazing material that comes into contact with the atmosphere is covered with a coating member. With this configuration, the melting point difference between the low melting point brazing filler metal, the aluminum heat transfer tube, and the refrigerant piping is increased. For this reason, it becomes possible to perform easier joining, and furthermore, since the low melting point brazing material having a low potential is covered with a coating member, corrosion between different kinds of metals can be prevented and the reliability of joining is also improved. To do.

It is a refrigerant circuit figure showing a schematic structure of an air harmony device concerning an embodiment of the invention. It is an expansion perspective view of the outdoor heat exchanger shown in FIG. It is sectional drawing which expands and shows the A section and B section in FIG. It is a figure which shows the measurement result of the electrode potential of aluminum piping, a common brazing material (aluminum-silicon alloy), and a low melting point brazing material.

Hereinafter, an embodiment of an air-conditioning apparatus including a heat exchanger according to the present invention will be described.
FIG. 1 is a refrigerant circuit diagram showing a schematic configuration of an air-conditioning apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, an air conditioner 100 according to an embodiment includes a compressor 1, a muffler 2, a four-way valve 3, an outdoor heat exchanger 4 that is a heat exchanger according to the present invention, and a capillary tube 5. And a strainer 6, an electronically controlled expansion valve 7, stop valves 8 a and 8 b, an indoor heat exchanger 9, and an auxiliary muffler 10 are connected to each other through a refrigerant pipe 19. .

  The indoor heat exchanger 9 of the air conditioner 100 is provided with a control unit 11 that controls the actuators such as the compressor 1 and the electronically controlled expansion valve 7 based on the temperatures of the outside air, the room, the refrigerant, and the like. It has been. The aforementioned four-way valve 3 is a valve for switching between the cooling and heating refrigerant cycles, and is controlled by the control unit 11.

  When the four-way valve 3 is switched to cooling by the control unit 11, the refrigerant is compressed by the compressor 1 to become a high-temperature and high-pressure gas refrigerant and flows into the outdoor heat exchanger 4 through the four-way valve 3. The high-temperature and high-pressure gas refrigerant that has flowed into the outdoor heat exchanger 4 undergoes heat exchange (heat radiation) with outdoor air that passes through the outdoor heat exchanger 4 and flows out as high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the outdoor heat exchanger 4 is depressurized by the capillary 5 and the electronically controlled expansion valve 7, becomes a low-pressure gas-liquid two-phase refrigerant, and flows into the indoor heat exchanger 9. The gas-liquid two-phase refrigerant flowing into the indoor heat exchanger 9 is heat-exchanged with the indoor air passing through the indoor heat exchanger 9, and is drawn into the compressor 1 as a low-temperature and low-pressure gas refrigerant.

  When the control unit 11 switches the four-way valve 3 to heating, the refrigerant is compressed by the compressor 1 to become a high-temperature and high-pressure gas refrigerant in the same manner as described above, and enters the indoor heat exchanger 9 via the four-way valve 3. Inflow. The high-temperature and high-pressure gas refrigerant that has flowed into the indoor heat exchanger 9 is heat-exchanged with indoor air that passes through the indoor heat exchanger 9 and becomes high-pressure liquid refrigerant. The high-pressure liquid refrigerant flowing out of the indoor heat exchanger 9 is depressurized by the electronically controlled expansion valve 7 and the capillary tube 5 to become a low-pressure gas-liquid two-phase refrigerant and flows into the outdoor heat exchanger 4. The low-pressure gas-liquid two-phase refrigerant that has flowed into the outdoor heat exchanger 4 is heat-exchanged with outdoor air that passes through the outdoor heat exchanger 4 and is sucked into the compressor 1 as a low-temperature low-pressure gas refrigerant.

Next, the configuration of the outdoor heat exchanger 4 will be described with reference to FIG. FIG. 2 is an enlarged perspective view of the outdoor heat exchanger shown in FIG.
The outdoor heat exchanger 4 shown in FIG. 2 is, for example, a fin-and-tube heat exchanger, and is arranged outside the plurality of fins 12 stacked in parallel at regular intervals and the plurality of fins 12 in the stacking direction. A fixed plate 13, a plurality of laminated fins 12, a plurality of U-shaped hairpin tubes 14 inserted perpendicularly to the fixed plate 13, and a U-shaped bend communicating the ends of adjacent hairpin tubes 14 15. The hairpin tube 14 and the bend 15 constitute a heat transfer tube.

  The fin 12, the fixing plate 13, the hairpin tube 14, and the bend 15 are formed of an aluminum material. The hairpin tube 14 is inserted into a hole provided in each fin 12 and then expanded to be fixed to each fin 12. The hairpin tube 14 and the bend 15 are joined by an aluminum-silicon alloy brazing material 16 on the production line. The fixing plate 13 is a member for fixing the outdoor heat exchanger 4 described above in a box-shaped casing that forms the outline of the outdoor unit. Of the plurality of hairpin tubes 14, end portions 14 a and 14 b of the hairpin tubes 14 positioned at both ends are joined to an aluminum refrigerant pipe 19 by a low melting point brazing material 17. The joints A and B are covered with a coating member 18.

Here, the configuration of the joints A and B will be described in detail with reference to FIG. FIG. 3 is an enlarged cross-sectional view showing a portion A and a portion B in FIG.
The ends 14 a and 14 b of the hairpin tube 14 are expanded larger than the outer diameter of the refrigerant pipe 19. Due to the expansion of the end portions 14 a and 14 b, a cylindrical gap Wa is formed between the inner peripheral surface of the end portions 14 a and 14 b and the outer peripheral surface of the refrigerant pipe 19. The gap Wa is filled with a low melting point brazing material 17. Further, the outer peripheral surfaces of the end portions 14 a and 14 b and the surface of the low melting point brazing material 17 that comes into contact with the atmosphere are covered with the coating member 18. The low melting point brazing material 17 is made of a mixture of non-corrosive flux containing CsF and zinc or a zinc-aluminum alloy containing zinc as a main component, and has a melting point of 560 ° C. or lower.

Next, the joining of the end portions 14a and 14b of the hairpin tube 14 and the refrigerant pipe 19 will be described.
The refrigerant pipe 19 is inserted into the end portions 14 a and 14 b of the hairpin tube 14, and the low melting point brazing material 17 is filled in the gap Wa between the end portions 14 a and 14 b and the refrigerant pipe 19. In this state, the low melting point brazing material 17 is melted while heating the ends 14a and 14b of the hairpin tube 14 with heating means such as a torch, and the ends 14a and 14b of the hairpin tube 14 and the refrigerant pipe 19 are joined. .

  Thus, by using the low melting point brazing material 17 having a melting point of 560 ° C. or less for joining the end portions 14a, 14b of the aluminum hairpin tube 14 and the aluminum refrigerant pipe 19, the low melting point brazing material 17 and The melting point difference from the aluminum piping (hairpin tube 14 and refrigerant piping 19) having a melting point of 660 ° C. is 100 ° C. or more. For this reason, it is possible to perform easier and more reliable bonding.

  However, since the low melting point brazing material 17 is mainly composed of zinc, the electrode potential is lower than that of the aluminum material, that is, it is “base”. Is more susceptible to corrosion. The corrosion between different metals is corrosion that occurs when two types of metals having different potentials come into contact with each other in the electrolyte. In other words, when a potential difference occurs between two types of metals that come into contact with each other and an electrolyte is contacted, a local battery is formed, and from a “noble” metal (aluminum material) with a high potential to a “base” metal (zinc with a low potential) ), And corrosion occurs in the “base” metal (low melting point brazing material 17) having a low potential.

FIG. 4 is a diagram showing measurement results of electrode potentials of aluminum piping, a general brazing material (aluminum-silicon alloy), and a low melting point brazing material.
The measurement was performed in a 5% NaCl solution, and a silver-silver chloride electrode was used as a reference electrode. As shown in FIG. 4, the potential difference between aluminum pipes, that is, the hairpin pipe 14 and the refrigerant pipe 19, and the general brazing material is about 130 mV, whereas the hairpin pipe 14 and the refrigerant pipe 19 and the low melting point brazing material. The potential difference from 17 is about 200 mV. In general, when the potential difference is 200 mV or more, corrosion between different types of metals becomes prominent. Therefore, when the low melting point brazing material 17 is used for joining the aluminum hairpin tube 14 and the refrigerant piping 19, the corrosion should be prevented. Is essential.

  In order to prevent corrosion between dissimilar metals in the low melting point brazing material 17, it is important that the electrolyte does not adhere to the contact portion between the hairpin tube 14 and the refrigerant pipe 19 and the low melting point brazing material 17. The electrolytic solution is a liquid that conducts electricity, and includes tap water, rain water, and water droplets due to condensation.

  Therefore, in the present embodiment, as shown in FIG. 3, the contact portion between the hairpin tube 14 and the low melting point brazing material 17 and the contact between the refrigerant pipe 19 and the low melting point brazing material 17 to which the electrolytic solution may adhere. And the surface of the low melting point brazing material 17 in contact with the atmosphere is covered with the coating member 18. A heat shrinkable tube is used as the coating member 18. This heat-shrinkable tube shrinks and cures with hot air, and as shown in FIG. cover.

As described above, according to the embodiment, the low melting point brazing solder having a melting point difference of 100 ° C. or more at the joining between the ends 14a and 14b of the aluminum hairpin tube 14 and the aluminum refrigerant pipe 19 is 100 ° C. The material 17 is used. For this reason, joining with edge part 14a, 14b of the hairpin pipe | tube 14 and the refrigerant | coolant piping 19 can be performed more easily and highly reliable.
Further, the surface of the low melting point brazing material 17 that comes into contact with the atmosphere is covered with a heat shrinkable tube as the coating member 18, and the contact portion between the hairpin tube 14 and the low melting point brazing material 17, and the contact between the refrigerant pipe 19 and the low melting point brazing material 17. This prevents electrolytes such as rainwater and water droplets from condensing from entering. For this reason, it is possible to prevent the corrosion of the “base” low melting point brazing material 17 having a lower potential than the aluminum material.

  In the embodiment, the surface of the low melting point brazing material 17 that comes into contact with the atmosphere is covered with a heat shrinkable tube, but a heat shrinkable tube coated with an adhesive on the inside may be used. If a gap is formed when the heat-shrinkable tube covers the surface of the low melting point brazing material 17 that comes into contact with the atmosphere, the electrolyte may enter through the gap. In that case, since the electrolyte solution in the gap is held by the heat-shrinkable tube, erosion due to corrosion between different metals may be accelerated. In order to prevent this, as described above, the surface of the low melting point brazing material 17 that is in contact with the atmosphere is covered with a heat shrinkable tube coated with an adhesive on the inside, and the portion is brought into close contact with the adhesive so that there is no gap. Like that. The adhesion of the heat shrinkable tube with the adhesive can completely prevent the electrolyte from entering.

  Further, instead of the heat shrinkable tube, a room temperature curable paint containing zinc powder may cover the surface of the low melting point brazing material 17 in contact with the atmosphere. By using a room temperature curable coating, a heating step is not required, the intrusion of the electrolytic solution can be prevented, and corrosion protection by the sacrificial anode layer can be performed. Furthermore, sacrificial corrosion protection can be performed by containing zinc powder in the paint. In the case of anticorrosion with a paint, it is necessary to always contain zinc or zinc alloy powder whose electrode potential is “base” than the low melting point brazing material 17.

  In the embodiment, the coating member 18 prevents corrosion between different metals of aluminum and zinc alloy (or zinc). However, this is an example, and “base” metal and “noble” It may be made to cover with the coating member 18 as long as it is a joining of different metals.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 Muffler, 3 Four way valve, 4 Outdoor heat exchanger, 5 Capillary, 6 Strainer, 7 Electronically controlled expansion valve, 8a, 8b Stop valve, 9 Indoor heat exchanger, 10 Auxiliary muffler, 11 Control part, 12 Aluminum fin plate, 13 Aluminum fixing plate, 14 Aluminum hairpin tube, 14a, 14b End of hairpin tube, 15 Aluminum bend, 16 Brazing material, 17 Low melting point brazing material, 18 Coating member, 19 Aluminum refrigerant piping, 100 air conditioner.

Claims (6)

Fins stacked at regular intervals;
An aluminum heat transfer tube, which is fixed by penetrating each laminated fin and joined with an aluminum refrigerant pipe at both ends,
The heat transfer pipe and the refrigerant pipe are joined with a low melting point brazing material mixed with a non-corrosive flux, and the surface of the low melting point brazing material that contacts the atmosphere is covered with a coating member. vessel.   The heat exchanger according to claim 1, wherein the coating member is a heat shrinkable tube that is cured by heat.   The heat exchanger according to claim 2, wherein an adhesive is applied to the inside of the heat shrinkable tube.   2. The heat exchanger according to claim 1, wherein the coating member is a room temperature curable coating material containing zinc powder.   5. The heat exchanger according to claim 1, wherein the low melting point brazing material is made of zinc or a zinc-aluminum alloy containing zinc as a main component, and has a melting point of 560 ° C. or less. .   An air conditioner comprising the heat exchanger according to any one of claims 1 to 5 as an outdoor heat exchanger.

Images