JP2014077600A - Heat exchanger and method for making the same, and air conditioner with heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger which has a heat exchanger applicable flattened refrigerant pipe and a heat exchanger applicable fins that are joined together by brazing, and drains dew condensation water generated in the heat exchanger to suppress increase of air flow resistance and progress of corrosion which can be caused by remaining of the dew condensation water.SOLUTION: On a heat transfer surface of a heat exchanger, metal oxide having a density greater than that of brazing filler metal is added to a brazing filler metal layer and brazing is performed, thereby providing a heat exchanger with a density gradient region in which the density of the metal oxide increases toward the downstream of air flow in operation of an air conditioner.

Description

  The present invention relates to a method for draining condensed water, in particular, in a heat exchanger in an air conditioner or the like.

  A fin tube type heat exchanger combining a plate-like fin and a heat transfer tube is generally used as a heat exchanger for an air conditioner. In the manufacture of fin-tube heat exchangers, a large number of plate-like fins stacked at appropriate intervals are fixed with a jig, and a heat transfer tube is inserted into the insertion hole of each plate-like fin so that the plate-like fin and the circular tube Then, they are joined or fixed by expanding the circular tube, brazing material, adhesive or the like.

  The finned tube heat exchanger is suitable for use only with a condenser, but when used as an evaporator, the temperature of the refrigerant flowing in the heat transfer tube when exchanging heat with air falls below the dew point of the air. Moisture in the air condenses on the surface of the heat exchanger, and condensed water (drain water) is generated. The generated condensed water is not a problem if it is quickly drained from the fin end face or the heat transfer tube surface, but if it accumulates on the surface, the ventilation resistance of the heat exchanger increases and the amount of air passing therethrough decreases. As a result, if the evaporating temperature decreases, the condensed water grows into frost, and if it falls into a vicious circle where the ventilation resistance increases and the air volume decreases, the heat exchange efficiency may be significantly impaired. .

  In addition, when a corrosive factor of outside air such as sea salt particles dissolves in the condensed water, there is a problem that the condensed condensed water corrodes the metal material constituting the heat exchanger. Therefore, in order to suppress a decrease in heat exchange efficiency and material corrosion, it is necessary to ensure drainage of the fins and heat transfer tube surfaces.

  On the other hand, there is a finned tube heat exchanger that combines a flat heat transfer tube (hereinafter referred to as a flat tube) having a flat cross-sectional shape and a flat portion on the outer shell and having a plurality of refrigerant channels inside and a fin material. Sometimes used. By using a flat tube as the heat transfer tube of the heat exchanger, there is an advantage that the area inside the tube in contact with the refrigerant can be increased and the ventilation resistance can be further reduced as compared with a heat exchanger using a circular tube. .

  However, fin tube heat exchangers that use flat tubes have the disadvantage of drainage that condensate tends to accumulate between plate fins or on the upper surface of the flat tubes. Fin tube heat exchangers that use circular tubes Compared to the vessel, there were restrictions on the use conditions.

In a conventional fin tube heat exchanger, fine irregularities are formed by plasma irradiation on a hydrophilic or water-repellent polyamide resin coating layer on the fin surface to obtain a desired hydrophilic property. (For example, refer to Patent Document 1.)
In addition, a brazing material layer, a flux layer, and a sol layer having zirconium dioxide nanoparticles are used on an aluminum substrate, and a semi-ceramic oxide layer is formed in a brazing process to adjust hydrophilicity. (For example, refer to Patent Document 2.)

Japanese Patent Laid-Open No. 2002-90084 Special table 2009-502509

  In the conventional fin tube heat exchanger, the surface of the fin or heat transfer tube is coated or processed to adjust the hydrophilicity. However, the fin made of metal such as aluminum and the coating material have a thermal expansion coefficient. Different. For this reason, a very thin fin with a plate thickness of 0.3 mm or less may cause a problem of warpage. In addition, there is a problem that the coating is cracked or peeled off due to a temperature cycle caused by a temperature difference between operation and stop and a temperature difference between day and night.

  Furthermore, when using an organic polymer resin such as a polyamide resin, it cannot withstand the high temperature of about 600 ° C. at the time of brazing, so it is necessary to perform coating after brazing, and there are restrictions on the method for forming the hydrophilic layer. It was. Furthermore, since the hydrophilic treatment by surface processing requires complicated processes and equipment for production, it has been difficult to apply from the viewpoint of production.

  The present invention has been made to solve the above-described problems. Even in a finned tube heat exchanger manufactured by brazing involving high-temperature treatment, the condensed water generated on the surface of the heat exchanger is efficiently removed. An object of the present invention is to obtain a heat exchanger that has been subjected to a hydrophilization treatment for stably draining to the outside.

  The finned tube heat exchanger of the present invention includes a plurality of fins arranged in parallel at a predetermined interval, and a heat transfer tube that vertically penetrates the surfaces of the plurality of fins and is joined to the plurality of fins. The air contact surface of the air passage surrounded by the plurality of fins and the heat transfer tubes has a hydrophilic gradient region in which the hydrophilicity monotonously increases along the air flow direction.

  Since the heat exchanger of the present invention has a hydrophilic gradient region in which the hydrophilicity improves toward the downstream side of the air passage, dew condensation water flows between the fins or on the flat tube during operation toward the downstream side of the air passage. Flow and dew condensation water can be discharged out of the heat exchanger efficiently and stably.

It is a schematic perspective view which shows the positional relationship of the finned-tube type heat exchanger which concerns on Embodiment 1 of this invention, and a ventilation fan. It is a perspective view which shows the structural example of the heat exchanger comprised with the flat tube and fin which concern on Embodiment 1 of this invention. It is a figure which shows the positional relationship of the fin and flat tube at the time of brazing which concerns on Embodiment 1 of this invention. It is an enlarged view of the junction part of the fin and flat tube after brazing which concerns on Embodiment 1 of this invention. It is a perspective view which shows the structure of the clad fin which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the metal oxide density | concentration distribution of the fin surface which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the state which combined the clad fin and flat tube which concern on Embodiment 1 of this invention. It is a schematic diagram which shows the flow of the dew condensation water in the heat exchanger which concerns on Embodiment 1 of this invention. It is an enlarged view of the junction part of the fin and flat tube after brazing which concerns on Embodiment 1 of this invention. It is a flowchart which shows the test conditions of a combined cycle test. It is a figure which shows the example of arrangement | positioning of the brazing material at the time of brazing which concerns on the modification of Embodiment 1 of this invention. It is a schematic diagram which shows the flow of the dew condensation water in the heat exchanger which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the inclination-angle of the flat tube which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic perspective view showing the positional relationship between the finned tube heat exchanger and the blower fan according to Embodiment 1, and corresponds to, for example, an outdoor unit for an air conditioner. The blower fan 1 and the heat exchanger 3 face each other in the housing 2, and the air flow 4 is generated by the wind sent from the blower fan 1 toward the heat exchanger 3 during operation. Indicates the direction of passage. In addition to the heat exchanger and the blower fan 1, the outdoor unit for the air conditioner includes a machine room, a control board, a compressor, and the like in the air conditioner configuration. Omitted because it is not directly related to the flow and movement of condensed water. Moreover, what attached | subjected the same code | symbol in another figure is the same or it corresponds, and this is common in the whole text of this specification.

  FIG. 2 is a perspective view showing a structural example of the core portion of the heat exchanger 3 configured by combining a flat tube and fins vertically and horizontally, and a cross section of the flat tube 5 is shown to show the internal structure of the flat tube 5. Has been. In an actual heat exchanger, the flat tube 5 in the core portion is connected by piping to form a refrigerant circuit. The heat exchanger 3 is a flat plate in which plate-like fins 6 having a plurality of U-shaped cutouts are arranged in parallel at a predetermined interval, and the surfaces of the plurality of fins 6 are vertically penetrated and joined to the fins 6. A tube 5 is provided. When the heat exchanger 3 is used, the fins 6 are normally arranged so as to stand in a vertical direction with respect to the ground as shown in FIG. A space defined by the fins 6 and the flat tubes 5 forms an air path of the heat exchanger 3. Further, the inside of the flat tube 5 has a partition, and each partitioned space serves as a refrigerant flow path.

  In the blower fan and heat exchanger of the arrangement shown in FIG. 1, the blower fan 1 side of the flat tube 5 shown in FIG. 2 is the upstream side of the air flow, and the opposite side of the blower fan 1 is the downstream side. In FIG. 2, the portion where the curved surface serving as the side surface portion of the flat tube 5 is exposed from the U-shaped cutout may be the upstream side. The flat tube 5 and the fin 6 are joined by a brazing material at the fitting portion and thermally connected. As will be described later, the plurality of fins 6 and the flat tube 5 are joined by a brazing material in which metal oxide particles are dispersed, and the brazing filler metal layer after joining is joined from the upstream side to the downstream side of the air flow. As the density of the particles increases monotonously, it has a hydrophilic gradient region in which the hydrophilicity increases monotonously from the upstream side toward the downstream side. In addition, hydrophilicity can generally be evaluated by the contact angle of water droplets, and it can be defined that the lower the contact angle, the higher the hydrophilicity. In addition, an evaluation method such as a drop speed from the surface may be used.

  Next, a method for manufacturing the heat exchanger 3 shown in FIG. 2 will be described. FIG. 3 is a diagram showing the positional relationship between the fins and the flat tube during brazing, and shows how the respective members are arranged for assembly. The arrow of the air flow 4 indicates the direction in which the wind flows when the heat exchanger 3 is used after completion of the heat exchanger 3, and indicates the lower direction in FIG. The specific manufacturing procedure of the core part is that the plate-like fins 6 are arranged parallel to each other at a predetermined interval, the flat tube 5 is inserted into the U-shaped notch part of the fin 6 and the whole is heated and brazed. To do. Since the U-shaped notch end face of the fin 6 and the flat tube 5 are inserted with a predetermined clearance, the clearance is almost filled with the brazing material by welding with the brazing material.

  FIG. 4 is an enlarged view of the joint portion between the fin 6 and the flat tube 5 after brazing. The flat tube 5 is inserted into the U-shaped notch, and the brazing material enters the clearance between the two. Is shown without gaps. As a material of the flat tube 5, for example, an aluminum alloy or copper of JIS A1000 series or JIS A3000 series is used. Further, as the material of the fin 6, an aluminum material of JIS A1000 series is used.

  FIG. 5 is a perspective view showing the structure of the clad fin before the fin 6 is assembled. The clad fin has a two-layer structure including a core material layer 7 of aluminum alloy and a brazing material layer 8. As the brazing material used for the brazing material layer 8, an Al material that is a core material layer of the flat tube 5 and the fin 6 or an Al alloy having a lower melting point than the Al alloy, such as a JIS A4000 series made of an Al—Si based alloy, is used. . The brazing material layer 8 is mixed with metal oxide particles in addition to the brazing material.

The metal oxide has a carbonyl group (═O group) or a hydroxyl group (—OH group) on its surface, and these have hydrophilicity because they attract water molecules. In the state of the clad fin, the metal oxide particles are uniformly dispersed in the brazing material layer 8. In the first embodiment, the core portion of the heat exchanger 3 is manufactured by brazing a clad fin in which iron oxide (Fe 2 O ₃ , Fe (OH) ₃ ) is dispersed in the brazing material layer 8 in combination with the flat tube 5. By using this method, the metal oxide particles carried on the molten brazing material layer after the brazing step are exposed on the surfaces of the fins and the joints, thereby imparting a hydrophilic function to the heat exchanger 3. The density of the iron oxide is 5.24 g / cm ^3, the density of aluminum is 2.38 g / cm ³ (during melting), wax in a state of combining the flat tubes 5 and fins 6 as shown in FIG. 3 When attaching, the brazing filler metal layer 8 in the clad fin melts and the iron oxide particles having a hydrophilic function move downward due to gravity. That is, particles having a hydrophilic function, which has a higher density than the brazing material used for bonding, are dispersed inside the brazing material, and when the brazing material is melted, the particles are moved downward by the action of gravity, so that the surface of the heat exchanger It is a feature of the production method of the present invention that the particle has a particle density gradient. That is, in the brazing process, the metal oxide particles in the molten brazing material move downward by sedimentation, and a gradient occurs in the distribution state of the metal oxide particles, so that the surface of the fin 6 has a hydrophilic gradient. A region arises.

  FIG. 6 is a schematic diagram showing the concentration distribution of the metal oxide particles on the surface of the fin 6, and the region where the metal oxide density is high is expressed in dark gray. In addition, in FIG. 6, the flat tube 5 is abbreviate | omitted and the periphery of the U-shaped notch part 9 in which one flat tube 5 is installed is shown. As shown in FIG. 6, on the fin surface, the more the metal oxide particles are contained toward the leeward side when the heat exchanger is used, and as a result, the hydrophilicity gradient becomes higher as the leeward side is reached. A region is formed. Needless to say, the particles dispersed in the brazing material are not limited to iron oxide particles as long as the material has heat resistance and hydrophilicity.

FIG. 7 is a cross-sectional view showing a state in which the clad fin and the flat tube are combined, and the clad fin provided with the fin collar 10 is arranged around one flat tube 5 installed in the U-shaped notch. The part is shown enlarged. The fin collar 10 has a rising shape formed on the end face of the U-shaped notch, and can be produced by performing burring when forming the U-shaped notch.
The fins 6 constituting the heat exchanger are arranged so that the interval (fin pitch) is about 2 mm, and the surface of the flat tube 5 is a fin collar 10 that becomes a fin-flat tube joint surface during brazing. Covered. Even in the portion not covered with the fin collar, the surplus brazing material at the time of brazing spreads and is covered, so that a hydrophilic function is also given to the flat tube surface after brazing.

  Next, loading of the metal oxide having a hydrophilic function on the fin 6 and movement of the metal oxide by brazing will be described. About the iron oxide particle added to the brazing material before brazing, brazing property will fall, if the amount increases, and a hydrophilic function will fall if it decreases. In the present invention, the amount of iron oxide added relative to the amount of brazing material is preferably within the range of 10 to 30% by weight. It is desirable that some iron oxide particles remain on the upstream side of the air flow on the surface of the fin 6, and the brazing time corresponding to each addition amount of oxide is controlled so that iron oxide remains on the upstream side. It is necessary.

  Moreover, it is necessary to control also about the particle size of the iron oxide particle to add. When the average particle size of the iron oxide particles is large, uniform dispersion in the brazing material layer 8 becomes difficult. However, when the average particle size is too small, sedimentation hardly occurs in the brazing process. Therefore, the average particle diameter of the iron oxide particles is suitably 0.5 to 10 μm. From the viewpoint of the above-described deterioration of brazing and mold wear, the range of the thickness of the brazing material layer 8 is preferably 5% or more and 15% or less with respect to the thickness of the core material layer 7 of the fin.

Next, the flow of the dew condensation water generated on the fin surface when an air conditioner configured by a heat exchanger having a gradient in hydrophilicity is actually operated will be described. FIG. 8 is a schematic diagram showing the flow of condensed water on the flat tube of the heat exchanger and on the fin surface. The plate-like fins 6 are arranged vertically, and the flat surface of the flat tube 5 is arranged horizontally. The state which is blowing in the heat exchanger is shown. A bottom plate 11 that receives condensed water is disposed below the heat exchanger. The flow of air 4a blown from the fan and the flow of air 4b that has passed through the air passage in the heat exchanger are indicated by arrows, and the broken arrow schematically indicates the direction in which the condensed water flows. .
As described above, a hydrophilic gradient region is formed on the surface of the fin 6 of the heat exchanger 3, and when air flows from the blower fan to the outside of the outdoor unit, Air flows from the upstream side having low hydrophilicity toward the downstream side having high hydrophilicity.

  The fin for a heat exchanger according to the present invention has an affinity to take condensed water on the surface of particles having hydrophilicity, that is, the surface of iron oxide particles, so that the condensed water is attracted to a region where the distribution density of iron oxide is high. . That is, when the condensed water moves from the upstream side of the air path on the surface of the fin 6 to the downstream side of the air path, it passes through the hydrophilic gradient region where the hydrophilicity gradually increases, thereby generating a driving force for moving the condensed water to the downstream side. Therefore, in the present invention, even in a state where there is no air flow, the dew condensation water has a driving force that moves to the high density region side of iron oxide, that is, the highly hydrophilic side. Therefore, it can be considered that the air flow by the air blown from the blower fan assists the driving force for moving the condensed water simultaneously with the heat exchange action.

The fins 6 are arranged perpendicular to the bottom plate 11, and are basically connected from the upper part of the heat exchanger to above the bottom plate 11. When the outdoor unit is operated, an air flow is generated by the blower fan 1, and the dew condensation water generated on the surface of the heat exchanger by the operation of the compressor moves from the air flow upstream side of the fins to the air flow downstream side and collects on the downstream side. The condensed water flows down the fins and flows down toward the bottom of the heat exchanger. The condensed water that has flowed down is collected on the bottom plate 11 and discharged from a drain hole (not shown), so that the condensed water does not stay between the heat exchanger and the bottom plate 11. As a result, the progress of dissimilar metal contact corrosion of the heat exchanger by the bottom plate 11 made of a steel plate or the like is not promoted.
A hydrophilic gradient region is also formed on the surface of the flat tube 5 due to the precipitation phenomenon of iron oxide particles contained in the brazing material that flows from the fins to the fin-flat tube junction during brazing. Accordingly, the condensed water generated on the surface of the flat tube 5 is also drained using the driving force of the hydrophilic gradient region.

  Moreover, in Embodiment 1, the structure which provides the brazing filler metal layer 8 which has a hydrophilic function to the fin piece side as shown in FIG. 5 is taken. This is because the fin pitch of the heat exchanger is very narrow, about 1.5 to 2.5 mm, and the dew condensation water is generated while forming a bridge in the gap between the fins, so it is downstream by the hydrophilic function given to one side. This is because it can be moved to the side. On the other hand, when the brazing material layer is provided on both surfaces, the Al—Si alloy in the brazing material layer is harder than the core material layer 7, which raises a problem that the hardness of the fin material increases. When the fin material becomes hard, the mold used in the production of the fins wears, so forming the brazing material layer on both sides is disadvantageous in the production of the fins.

  FIG. 9 is an enlarged view of the joint portion between the fin 6 and the flat tube 5 after brazing. The distance d between the portions where the flat tube 5 fits into the U-shaped bottom portion of the U-shaped notch 9 of the fin 6 is shown in FIG. It has expanded a little compared with, and has shown the state by which the brazing material was filled with the space and the brazing part S was formed. The distance d between the short side of the flat tube 5 and the U-shaped notch portion of the fin 6 may be wider than the distance between the long side (flat portion side) of the flat tube 5 and the fin 6. , A gap may be generated due to insufficient filling of the brazing material. In this heat exchanger, even in the gap due to the unfilling of the brazing material, the dew condensation water wets and spreads due to the action of the metal oxide particles having a hydrophilic function, thereby preventing stagnation. Since there is no retention of condensed water, even when a corrosion factor such as sea salt particles is taken in during actual operation, the progress of corrosion in the gap between the short side of the flat tube 5 and the fin U-shaped notch 9 is suppressed.

  As described above, in the present invention, by using a heat exchanger having a hydrophilic gradient region and a blower fan in an outdoor unit, condensed water is efficiently removed from the heat exchanger to the outside of the outdoor unit. It is possible.

Next, a method for demonstrating the above actions and effects and the results will be described.
In order to evaluate the influence of a hydrophilized surface with a gradient on the movement of condensed water, the following experiment was conducted. First, a fin having a hydrophilic function added in advance by applying an organic solvent on the surface was prepared, and bonded to a flat tube by an adhesive method to produce a heat exchanger T1. In this case, it is considered that the fin surface of the heat exchanger T1 has a uniform hydrophilic performance and has no distribution. For comparison, a heat exchanger R having fins not adding a hydrophilic function was also produced.
As a result of installing the heat exchanger T1 in the outdoor unit for an air conditioner and operating the blower fan, compared with the heat exchanger R, an effect of suppressing the retention of condensed water was recognized, but the fin surface Condensed water stayed in the area, and increase in ventilation resistance and decrease in heat exchange performance were observed.
On the other hand, when a heat exchanger T2 using fins whose hydrophilic functions were changed stepwise was prepared and tested in the same manner, the retention of dew condensation water was reduced, and ventilation resistance was increased and heat exchange performance was decreased. It was confirmed that it can be suppressed.

  As described above, when aluminum material is used for the fins 6 and the flat tubes 5, if the drainage of the heat exchanger surface is not sufficient, the condensed water staying on the aluminum material surface takes in corrosion factors such as sea salt particles. , May accelerate the corrosion of aluminum material. In addition, when a noble metal than aluminum adheres to the surface thereof, there is a possibility that the different metal contact corrosion of aluminum by the attached metal proceeds. Since many metal oxides for adding hydrophilic functions are more noble than aluminum materials, it is necessary to grasp the influence of these on the corrosion of aluminum materials. Here, in order to confirm the drainage effect by adding metal oxide to the heat exchange surface and evaluate the influence on the corrosion of the aluminum fin, the time-dependent change of the surface condition of the heat exchanger by the acceleration test was investigated.

  In an outdoor unit equipped with a heat exchanger combining fins and flat tubes, a combined cycle test, which is an accelerated test of actual machine operation, was carried out with the blower fan in operation, and the corrosion state of the heat exchanger was evaluated. FIG. 10 is a flowchart showing test conditions for the combined cycle test. An aqueous solution having a salt concentration of 5% by weight was used as the spray solution. The test time was 2000 h.

  In the test, a heat exchanger A manufactured by applying a fin provided with a hydrophilic gradient region by adding iron oxide to a brazing filler metal layer and a fin having a brazing filler metal layer not added with iron oxide were applied. Comparison with manufactured heat exchanger B was performed. In order to confirm the improvement of the hydrophilic function, the fin material of each heat exchanger was cut out and the contact angle was investigated. As a result, the contact angle at the fin of the heat exchanger A was 50 ° as a minimum, and the heat exchanger B The contact angle at the fin was 90 °. It was confirmed that the contact angle was reduced by adding iron oxide to the brazing filler metal layer, and the hydrophilicity was improved.

  After the heat exchanger A was subjected to the combined cycle test, the aluminum material constituting the heat exchanger was investigated, and although white rust was generated due to overall corrosion, local corrosion leading to refrigerant gas leakage and fin dropout was observed. Confirmed that there is no. It is considered that the sprayed salt water did not stay on the surface of the heat exchanger and was quickly removed outside the outdoor unit because the drainage function due to the hydrophilic gradient worked on the surface of the heat exchanger. In addition, in the region between the short side of the flat tube and the fin U-shaped notch, where the gap is likely to occur, the condensed water that incorporates corrosion factors such as sea salt particles does not stay due to the hydrophilic function. It was confirmed that the progress of corrosion was suppressed.

In addition, when iron oxide (Fe ₂ O ₃ , Fe (OH) ₃ ) and an aluminum material are in contact with each other, there is a concern that iron oxide promotes corrosion of the aluminum material because of its higher potential than aluminum metal. Later, no local corrosion progressed starting from iron oxide. This is because, although iron oxide itself has a higher potential than aluminum, the surface of the iron oxide in contact with aluminum is highly polarized, so the corrosion current flowing between the iron oxide and aluminum material is reduced, resulting in corrosion of the aluminum material. It is thought that progression was suppressed. That is, in the heat exchanger using iron oxide particles, it was confirmed that the hydrophilic function does not change even when the operation is performed for a long time, and the effect of removing the dew condensation water from the heat exchanger is not affected.

  Similarly, the combined cycle test described above was performed in a state where the blower fan was operated in an outdoor unit equipped with the heat exchanger B, and the corrosion state of the heat exchanger was evaluated. After the test, when the aluminum material constituting the heat exchanger was investigated, it was confirmed that white rust was generated due to overall corrosion on the surface of the aluminum material and that pitting corrosion had occurred under the traces of salt water retention. . When the depth of pitting corrosion was examined by cross-sectional observation, it was about 150 μm. Pitting corrosion known as a form of local corrosion is difficult to suppress the progress of corrosion in the depth direction, and as a result, there is a possibility of forming through holes. It was confirmed that pitting corrosion leading to gas leakage can be suppressed by applying the heat exchanger according to the present invention.

  In the present invention, by using the fin 6 having a hydrophilic gradient region where the density of the metal oxide monotonously changes on the surface, even if the flat tube 5 is used as the heat transfer tube, the dew condensation water is removed from the heat exchanger 3. Therefore, corrosion of the aluminum material can be suppressed even after long-term operation.

  In the first embodiment, the brazing process is performed using the clad fin in which the brazing material layer 8 containing metal oxide particles is bonded to the core material layer 7. However, the brazing material is applied to the aluminum core material layer 7. As another means for providing the layer 8, a method of applying a paste wax to the surface can also be used. Here, a method of providing the brazing filler metal layer 8 on the fin and a fin tube heat exchanger to which the fin is applied will be described.

Paste brazing is based on a binder made of an organic resin such as polyvinylidene fluoride (PVDF) as a binder, and a fine powder of Al-Si alloy and a metal oxide such as iron oxide are added to form a paste. Apply to the fin surface. By assembling and brazing the fin and the flat tube in the same manner as in the first embodiment, the paste wax applied to the fin surface is melted, and the fin and the flat tube are joined while flowing between the fin and the flat tube. The At this time, the binder is decomposed and the brazing material is melted. Similarly, a large amount of iron oxide flows toward the downstream side of the air passage due to the influence of gravity, thereby forming a density gradient region of the metal oxide particles. The effect of preventing condensation water from moving on the heat transfer surface surface toward the downstream side of the air passage during air conditioner operation and preventing condensation from accumulating in the heat exchanger can be obtained. Progress is suppressed.

Embodiment 2.
In the first embodiment, a brazing filler metal layer is provided in the fin core material layer, and a metal oxide having a hydrophilic function is dispersed in the brazing filler metal layer. As it flows, it is possible to incorporate the brazing material alone with fins and flat tubes in the brazing process. FIG. 11 shows an arrangement example of the brazing material at the time of brazing in the second embodiment, in which the brazing material 12 containing metal oxide particles is arranged at the same pitch as the flat tube 5. The brazing material 12 in FIG. 11 has a bar shape with an elliptical cross section, but may have a plate shape.

  In the brazing step, the brazing material is arranged on the end of the fin with the upstream side of the air passage when used as a heat exchanger facing upward, and the brazing material 12 is melted in the gap between the fin 6 and the flat tube 5. The brazing filler metal 12 flows into the capillarity and flows downward. In the molten brazing filler metal, iron oxide is dispersed toward the lower side, that is, the downstream side of the air passage when used as a heat exchanger due to the influence of gravity. As described above, the metal oxide particles such as iron oxide are dispersed downward in the brazing material, and a hydrophilic gradient region having a high density is formed on the lower side to join the fin 6 and the flat tube 5. Further, a part flows on the surface of the fin 6 to form a brazing material layer on the surface of the fin 6. The joining portion is similar to the brazing portion S of FIG. 9, and the supported metal oxide particles are exposed on the surface and have hydrophilicity.

Therefore, the dew condensation water moves toward the downstream side of the air passage at the joint portion with the fin 6 on the flat tube 5 where the dew condensation water accumulates during the operation of the air conditioner, and is removed from the heat exchanger and is condensed in the heat exchanger. Does not stay. Furthermore, since the brazing material containing a metal oxide having a hydrophilic function also flows between the short side of the flat tube where the gap is likely to be formed and the fin U-shaped notch, the sea salt particles and the like are also operated during operation in this gap. Condensation water incorporating the corrosion factor does not stay, and the progress of corrosion in the gap between the short side of the flat tube 5 and the U-shaped notch 9 of the fin 6 is suppressed.

Embodiment 3.
FIG. 14 is a schematic diagram showing the structure of the heat exchanger and the flow of condensed water on the heat exchanger in the third embodiment, and shows a flat tube 15 that vertically penetrates the surface of the fin 16. In the first embodiment, the flat portion of the flat tube 5 is arranged so as to be horizontal as shown in FIG. 8, whereas in FIG. 12, the flat tube 15 is constant in the direction in which the downstream side 14b of the air flow is lowered. It is fixed to the vertically arranged fins 16 so as to be inclined at an angle. That is, the direction of the U-shaped notch for inserting the flat tube 15 into the fin 16 is different. When brazing, the flat surface of the flat tube 15 is arranged so as to be perpendicular to the ground, so that the metal oxide particles dispersed in the brazing material flow downward to form a hydrophilic gradient region. To do.

  By adopting this structure, the condensed water on the surface of the flat tube 15 is affected by gravity, and therefore it is possible to more efficiently remove the condensed water from the heat exchanger. Since the upstream air flow 14a is in the horizontal direction as in FIG. 8, in the third embodiment, the direction of the air flow is changed downward in the air path in the heat exchanger.

  Note that by increasing the inclination angle of the flat tube 15, the condensed water on the surface of the flat tube is more easily moved to the downstream side of the air passage, but at the same time, the ventilation resistance of the heat exchanger is also increased. When the ventilation resistance increases, the flow rate of air passing through the heat exchanger decreases, so the heat exchange efficiency decreases. Therefore, the angle with respect to the air flow sent from the blower fan 1 in the heat exchanger needs to be considered with respect to the ventilation resistance.

  FIG. 15 is a cross-sectional view showing the inclination angle θ of the flat tube 15. The inclination angle θ is an angle with respect to the horizontal direction. Normally, when the blower fan 1 is tilted, the installation area of the housing 2 increases. Therefore, the rotation axis of the blower fan 1 and the air flow 14a are assumed to be horizontal. Yes. As a result of the experiment, when the effective height h1 seen from the horizontal direction of the inclined flat tube 15 is larger than 120% of h0 with respect to the thickness h0 of the flat tube 15, the heat transfer performance of the heat exchanger is significantly deteriorated. I found out that Therefore, as for inclination | tilt angle (theta) with respect to the air flow 14a sent from the ventilation fan 1 in a heat exchanger, it is desirable that h1 is 120% or less of h0. Further, if the air blowing fan side is installed at an angle so as to be the same angle as the flat tube, and the air blowing direction of the air blowing fan 1 and the flat surface on the long side of the flat tube are arranged in parallel, the ventilation resistance is reduced. Needless to say, it is reduced.

  Therefore, the dew condensation water moves toward the downstream side of the air passage on the flat tube 15 where the dew condensation water accumulates during the operation of the air conditioner and is not efficiently removed from the heat exchanger and stays there. Furthermore, since there exists a brazing material containing a metal oxide having a hydrophilic function between the short side of the flat tube 15 where the gap is likely to be formed and the fin U-shaped notch, the corrosion factor is also taken into this gap. Condensation water does not stay and corrosion progress is suppressed.

In Embodiments 1 to 3, the description has been made on the assumption that the heat exchanger is applied to an outdoor unit for an air conditioner. However, the present invention can also be applied to a heat exchanger used for an indoor unit.

DESCRIPTION OF SYMBOLS 1 Blower fan 2 Housing | casing 3 Heat exchanger 4 Air flow 5 Flat tube 6 Fin 7 Core material layer 8 Brazing material layer 9 U-shaped notch 10 Fin collar 11 Bottom plate 12 Brazing material S Brazing part

Claims (10)

A plurality of fins arranged in parallel at predetermined intervals;
A heat transfer tube that penetrates the surfaces of the plurality of fins and is joined to the plurality of fins,
The heat exchanger which has the hydrophilicity gradient area | region where hydrophilicity increases monotonously along the air flow direction in the air contact surface of the air path enclosed by the said several fin and the said heat exchanger tube. The plurality of fins and the heat transfer tube are bonded with a bonding material in which hydrophilic metal oxide particles are dispersed to form an air passage,
The heat exchanger according to claim 1, wherein the air contact surface in the air passage has a hydrophilic gradient region in which the density of the metal oxide particles monotonously increases along the air flow direction. The material of the plurality of fins is a metal mainly composed of aluminum,
The metal oxide particles are iron oxide particles;
The bonding material is an aluminum alloy,
The heat exchanger according to claim 2. The heat transfer tube is a flat tube having a flat cross-sectional shape,
The plurality of fins are arranged in a direction in which the surface of the fin is vertical,
The flat surface of the flat tube is arranged in a horizontal direction,
The heat exchanger as described in any one of Claims 1-3. The heat transfer tube is a flat tube having a flat cross-sectional shape,
The plurality of fins are arranged in a direction in which the surface of the fin is vertical,
The flat surface of the flat tube is disposed to be inclined at a predetermined angle with respect to the direction of air flow,
The heat exchanger as described in any one of Claims 1-3. The heat exchanger according to any one of claims 1 to 5,
A fan for blowing air toward the heat exchanger,
The air conditioner in which the hydrophilic gradient region of the heat exchanger has higher hydrophilicity from the upstream side to the downstream side of the wind sent from the fan. Insert the heat transfer tube into the opening or notch of the fin member,
Melting the bonding material layer containing the bonding material and the metal oxide particles in a state in which the end portion on the downstream side of the air flow of the fin member faces downward,
After the metal oxide particles settle down downward to form a density gradient region,
The manufacturing method of the fin tube type heat exchanger which joins the said fin member and the said heat exchanger tube. Inserting the heat transfer tube into the opening or notch of the fin member on which the bonding material layer is formed on one side;
The manufacturing method of the heat exchanger of Claim 7 which joins the said fin member and the said heat exchanger tube. The specific gravity of the metal oxide particles is greater than the specific gravity of the bonding material,
The manufacturing method of the fin tube type heat exchanger of Claim 7 or 8. The metal oxide particles are iron oxide particles having an average particle size of 0.5 μm to 10 μm,
The thickness of the bonding material layer is 5% to 15% with respect to the thickness of the core member of the fin member.
The manufacturing method of the finned-tube type heat exchanger of Claim 9.