JP2012102951A - Tube for heat exchanger, and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tube for a heat exchanger and the heat exchanger allowing, even when a tube surface is scraped by a fin during assembly, the tube and the fin to be surely joined without causing shortage of a composition for brazing.SOLUTION: In the tube 2 for the heat exchanger, the surface at a part contacting with the inner periphery of a channel or hole of the fin 3 at least during assembly is formed at an arithmetical mean roughness Ra of 10-100 μm, and the composition 9 for brazing is applied to the surface formed at the arithmetical mean roughness Ra.

Description

  The present invention relates to a heat exchanger tube and a heat exchanger in which fins are joined to the surface of the tube, and more particularly to a heat exchanger assembled by tightly fitting a tube into a hole or groove formed in the fin.

  Known as heat exchangers used in automotive and building air conditioners, refrigerators, freezers, etc., in which tubes formed by extrusion molding of aluminum alloys are fitted into a large number of plate-like fins. ing. There exist a thing of patent document 1 and patent document 2 as such a heat exchanger.

In the heat exchanger described in Patent Document 1, tubes (heat transfer tubes) are fitted into grooves formed in a large number of plate-like fins parallel to each other. A fin collar bent on one surface side of the fin is provided on both sides of the fin groove, and a brazing material (solder) flows into and joins between the fin collar and the tube.
The heat exchanger described in Patent Document 2 has a configuration in which a tube bent in a U-shape is inserted into a long hole formed in a large number of plate-like fins and fixed from the bent tube portion.

JP 2010-156525 A JP 11-333539 A

  By the way, in such a heat exchanger, when joining a tube and a plate-like fin by brazing, a brazing material is applied to the surface of the tube in advance, and the plate-like fin and the tube are brought into a fitted state. The brazing material is melted and solidified by heating.

  These heat exchangers described in the patent documents are all assembled by fitting the tube into the groove or hole of the fin, and a brazing material is applied to the tube in advance for brazing the tube and the fin. In such a case, the tube surface is rubbed by the fins, and the brazing material on the tube surface is peeled off. In addition, the fin may be caught by the tube during fitting and torn off. In order to prevent these, if the clearance between the fin and the tube is increased, sufficient brazing material is not supplied to these joint portions, resulting in poor joints.

  The present invention has been made in view of the above circumstances, and even when the tube surface is rubbed by fins during assembly, the heat exchanger tube and the heat exchange can reliably join them without causing a shortage of brazing material. The purpose is to provide a vessel.

  The heat exchanger tube of the present invention is a heat exchanger tube that is assembled in a state of being fitted in a groove or hole formed in a fin, and at least a surface of a portion that is in contact with an inner peripheral portion of the groove or hole of the fin is assembled. It is formed to an arithmetic average roughness Ra of 10 μm to 100 μm, and a brazing composition is applied to the surface formed to the arithmetic average roughness Ra.

  Since the surface of the tube is formed with an arithmetic average roughness Ra of 10 μm to 100 μm and has irregularities, it is assumed that the surface layer portion of the brazing composition was scraped by rubbing the surface with fins during assembly. However, the brazing composition remains in the recesses on the tube surface, and the fins and the tube can be brazed using the residual brazing composition. Therefore, the fin and the tube can be reliably brazed without causing a shortage of the brazing composition.

In this case, when the arithmetic average roughness Ra of the tube is less than 10 μm, when the brazing composition is scraped off when the fins are assembled, the remaining brazing composition is reduced and a desired effect can be obtained. However, if it exceeds 100 μm, the gap between the valley and the fin becomes large due to the presence of large irregularities, and the brazing composition may become insufficiently supplied.
As the brazing composition, any one of brazing material, flux, binder, or a mixture of two or more of them is applicable.

The flat tube for a heat exchanger according to the present invention is a heat exchanger tube assembled in a fitted state in a groove or a hole formed in a fin, wherein a brazing composition is applied to the surface, and at least the fin is assembled at the time of assembly. As a configuration in which a large number of recesses having a diameter of 0.5 mm to 10 mm and a depth of 10 μm to 50 μm are formed on a surface that is in contact with the inner peripheral portion of the groove or hole and applied with the brazing composition. Also good.
Also, a heat exchanger tube assembled in a fitted state in a groove or hole formed in a fin, wherein a brazing composition is applied to the surface, and at least the inner peripheral portion of the fin groove or hole during assembly A plurality of grooves having a width of 1 mm to 5 mm and a depth of 10 μm to 50 μm may be formed along the longitudinal direction on the surface that is in contact with the brazing composition.

  Even if the brazing composition is rubbed and scraped at the time of assembly, the brazing composition is brazed into the recess or groove because the surface of the tube to which the brazing composition is applied has a recess or groove. Remains, and the fin and the tube can be brazed reliably without causing a shortage of the brazing composition.

If the recesses or grooves on the surface of the tube are less than the lower limit of the numerical range, if the brazing composition is scraped off when the fins are assembled, the remaining brazing composition is reduced to obtain the desired effect. If the upper limit of the numerical range cannot be achieved, the presence of large irregularities increases the gap between the valley and the fin, which may lead to insufficient supply of the brazing composition.
These concave portions or grooves on the tube surface may be applied to the surface of the tube before the brazing composition is applied, with an arithmetic average roughness Ra of 10 μm to 100 μm, or the arithmetic average roughness Ra. It may be applied to a smaller smooth tube.

  The heat exchanger according to the present invention is configured by assembling the tube into a groove or hole formed in the fin in a fitted state and joining the fin and the tube by brazing.

  According to the present invention, the surface roughness of the tube surface, the concave portion or the groove suppresses the brazing composition scraped off from the tube surface when the fin and the tube are assembled, and the brazing composition remains on the tube surface. Therefore, the fin and the tube can be securely brazed without causing a shortage of the brazing composition.

It is the perspective view which abbreviate | omitted a part of heat exchanger of 1st Embodiment of this invention. It is sectional drawing of the tube surface in the heat exchanger of FIG. It is a front view of the heat exchanger of 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of the heat exchanger of FIG. It is a fragmentary sectional view which shows the state in the middle of the assembly in the heat exchanger of FIG. It is a perspective view which shows the modification of the surface shape of the tube for heat exchangers of this invention. It is a perspective view which shows the other modification of the surface shape of the tube for heat exchangers of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the heat exchanger 1 includes a plurality of tubes 2 through which a fluid as a heat medium passes, and a large number of fins 3 that contact the outer surface of the tubes 2 to dissipate heat. Heat is exchanged between a fluid as a heat medium that circulates inside and air that circulates between the fins 3. These tubes 2 and fins 3 are made of an aluminum alloy.

Further, the tube 2 has a flat shape with a small height relative to the width dimension, and a plurality of partition walls 5 are formed at intervals in the width direction inside the peripheral wall 4 forming the outer periphery thereof. This is a so-called multi-hole tube in which the inner space of the peripheral wall 4 is divided into a plurality of internal flow paths 6 parallel to each other.
Further, the outer surface of the tube 2 is formed with an arithmetic average roughness Ra of 10 μm to 100 μm. In order to obtain the tube 12 having the arithmetic average roughness Ra, a method such as pressing a wire brush against the surface of the extruded tube while rotating can be used.

On the other hand, the fins 3 are formed in a plate shape and are arranged in parallel with each other at a predetermined interval, and a groove 7 for inserting the tube 2 in the width direction is formed in one side portion in the longitudinal direction of the side portion. A plurality are formed at a predetermined interval along. In addition, on both side portions of each groove 7, a rising portion 8 that is vertically raised is integrally formed.
The tube 2 and the fin 3 are fixed by fitting the tube 2 into each groove 7 along the width direction from one side of the fins 3 arranged at regular intervals, as indicated by the arrows in FIG. ing. In this case, the tube 2 is housed in the groove 7 from the one end in the width direction to the flat surface, and the other end in the width direction is disposed in the opening of the groove 7. The raised portion 8 is in contact with the flat surface of the tube 2. A portion of the tube 2 extending from one end in the width direction to the flat surface is fixed to the fin 3 by brazing.
The gap between the groove 7 of the fin 3 and the tube 2 is preferably 10 μm or less.

A method of assembling the heat exchanger configured as described above will be described.
The tube 2 is coated with the brazing composition 9 on the surface finished to the arithmetic average roughness Ra described above. This brazing composition 9 is, for example, a brazing composition comprising a brazing powder, a flux, and a binder. As the brazing powder, Si powder, Al—Si powder, Al—Si—Zn powder or the like is used, and as the flux, K _1-3 AlF _4-6 , Cs _1-3 AlF _4-6 , Cs _{0.02 are used.} Fluoride-based fluxes such as K _1-2 AlF _4-5 , AlF ₃ , KF, KZnF ₃ , K ₂ SiF ₆ are used, and an acrylic resin is used as the binder.

The coating thickness of the brazing composition 9 is preferably 5 μm to 20 μm. In this case, the brazing composition 9 may be applied over the entire surface of the tube 2, but except for the other end portion in the width direction, the portion extending from the one end portion in the width direction contacting the fin 3 to the flat surface. The brazing composition 9 may be applied.
After fitting the tube 2 coated with the brazing composition 9 into the groove 7 of the fin 3 as shown by the arrow in FIG. 1, the whole is put in a heating furnace and heated, whereby the brazing of the surface of the tube 2 is performed. The application composition 9 is melted and then cooled and solidified to integrate the fins 3 and the tubes 2 together.

In this assembling operation, the tube 2 is fitted into the groove 7 while being rubbed against both side edges of the groove 7 of the fin 3, and is formed on both side edges of the groove 7 of the fin 3 as shown by a chain line in FIG. The raised portion 8 scrapes off a part of the brazing composition 9 applied to the surface of the tube 2, but the surface of the tube 2 is formed with an arithmetic average roughness Ra of 10 μm to 100 μm. Even if the surface layer portion of the brazing composition 9 is scraped off, the brazing composition 9 remains in the recesses in the surface irregularities. Further, the brazing composition 9 scraped off from the surface of the tube 2 adheres to the surface in the vicinity of the side edge of the groove 7 of the fin 3, and when heated during brazing, the brazing composition melts. A fillet is formed between the fin 3 and the tube 2, and the gap between the fin 3 and the tube 2 is small, so that it also enters the gap.
Accordingly, the brazing composition remaining in the recesses on the surface of the tube 2 and the brazing composition adhering to the surface of the fin 3 can be used to connect the fin 3 and the tube 2 without causing a shortage of the brazing composition. Can be brazed reliably.

  In this case, when the arithmetic average roughness Ra of the tube 2 is less than 10 μm, when the brazing composition 9 is scraped off when the fin 3 is assembled, the remaining brazing composition 9 is reduced and the desired effect is obtained. If the thickness exceeds 100 μm, the gap between the valley and the fin 3 becomes large due to the presence of large irregularities, and the brazing composition may be insufficiently supplied. For this reason, the arithmetic average roughness Ra of the tube 2 is preferably 10 μm to 100 μm, and by setting the surface roughness within this range, the tube 2 and the fin 3 can be securely fixed by brazing.

  If the gap between the tube 2 and the groove 7 of the fin 3 is 10 μm or less and the coating thickness of the brazing composition 9 is also in the range of 5 μm to 20 μm, the brazing composition flows by melting. The brazing composition can easily enter the gap between the fin 3 and the tube 2 and can be brazed reliably.

3 to 5 show a heat exchanger according to a second embodiment of the present invention.
The heat exchanger 11 includes a plurality of tubes 12 through which a fluid as a heat medium passes, and a large number of fins 13 that contact the outer surface of the tubes 12 and dissipate heat by fitting the tubes 12 in a skewered state. And a header pipe 14 that connects the tubes 12, a supply pipe 15 that supplies fluid to the tube 12 through the header pipe 14, and a recovery pipe 16 that collects fluid via the tube 12. These tubes 12, fins 13, header pipes 14, supply pipes 15 and recovery pipes 16 are made of an aluminum alloy.

Further, the tube 12 has a flat shape with a small height with respect to the width dimension, similarly to the tube of FIG. 1, and is bent in the middle of the length direction to form a U between the straight pipe portions 17. A character-shaped curved pipe portion 18 is bent and each end portion of the straight pipe portion 17 is connected to the header pipe 14. The header pipe 14 is divided into a plurality of parts, and the supply pipe 15 and the recovery pipe 16 are connected to both ends of the header pipe 14, so that each tube 12 extends from the supply pipe 15 toward the recovery pipe 16. The connection state is sequentially established through the header pipe 14, and the flow path is formed in a meandering shape.
Further, the surface of the tube 12 has an arithmetic average roughness Ra of 10 μm to 100 μm. In order to obtain the tube 12 having the arithmetic average roughness Ra, a method such as pressing a wire brush against the surface of the extruded tube while rotating can be used.

On the other hand, the fins 13 are arranged in parallel to each other at a constant interval, and a plurality of holes 19 for partially fitting the tubes 12 are formed. Further, the peripheral portion of the hole 19 is subjected to a burring process, and as shown in FIG. 5, a rising portion 20 formed by vertically rising the peripheral portion of the hole 19 is integrally formed.
The tube 12 and the fin 13 are fitted with the straight pipe portion 17 of the tube 12 in the hole 19 of the fin 13 so as to skew the fins 13 arranged at regular intervals. The fins 13 are fixed by brazing.
The gap between the hole 19 of the fin 13 and the tube 12 is preferably 10 μm or less.

A method for assembling this heat exchanger will be described.
The surface of the tube 12 is finished to the arithmetic average roughness Ra described above, and the brazing composition 9 is applied to the surface finished to the arithmetic average roughness Ra. The brazing composition 9 may be applied over the entire length of the tube 12, but it is sufficient that the brazing composition 9 is applied to the surface of the straight pipe portion 17 with which the fins 13 come into contact. The coating thickness of the brazing composition 9 is 5 μm to 20 μm.
Then, the fins 13 are fitted one by one so that the straight pipe portion 17 of the tube 12 is inserted into the hole 19 of the fin. At this time, as shown in FIG. 5, the rising portion 20 of the fin 13 is inserted so as to face the rear in the insertion direction. Then, a large number of fins 13 are sequentially fitted, and the surface of the rear fin 13 is in contact with the rising portion 20 of the front fin 13 so that each fin 13 corresponds to the length of the rising portion 20. Arranged at regular intervals. After fitting a large number of fins 13 into the tube 12 in this way, the whole is put in a heating furnace and heated to melt the brazing composition on the surface of the tube 12, and then cooled to solidify. The fin 13 and the tube 12 are integrated.

In this assembling operation, the fin 13 is fitted while rubbing the surface of the straight pipe portion 17 of the tube 12, and the fin 14 scrapes off a part of the brazing composition 9 applied to the surface of the tube 12. Since the surface of the tube 12 is formed to have an arithmetic average roughness Ra of 10 μm to 100 μm, even if the surface layer portion of the brazing composition 9 is scraped off, the brazing composition is formed in the recesses in the surface irregularities. Remains. Further, the brazing composition scraped off from the surface of the tube 12 adheres to the surface of the fin 13, and when heated at the time of brazing, the brazing composition melts so that it is between the fin 13 and the tube 12. In addition to forming a fillet, since the gap between the fin 13 and the tube 12 is small, it also enters the gap.
Therefore, the brazing composition remaining in the recesses on the surface of the tube 12 and the brazing composition adhering to the surface of the fin 13 cause the fin 13 and the tube 12 to be connected without causing a shortage of the brazing composition. Can be brazed reliably.

6 and 7 show a modification of the tube surface shape.
In the tube 21 shown in FIG. 6, the brazing composition 9 is applied to the surface, and a large number of dimple-like recesses 22 are formed. These recesses 22 have a diameter of 0.5 mm to 10 mm and a depth of 10 μm to 50 μm.
Further, the tube 23 shown in FIG. 7 has a brazing composition 9 applied on the surface, and a plurality of grooves 24 having a width of 1 mm to 5 mm and a depth of 10 μm to 50 μm are formed along the longitudinal direction. Yes.
The depths of these recesses 22 or grooves 24 are the dimensions after the brazing composition 9 is applied.

Since the surfaces of the tubes 21 and 23 to which the brazing composition 9 is applied in this way have the recesses 22 or the grooves 24, even if the brazing composition 9 is scraped and scraped during assembly, the recesses 22 or the grooves The brazing composition 9 remains in 24, and the fins and the tube can be reliably brazed without causing a shortage of the brazing composition.
In this case, in the tube 21 shown in FIG. 6, the concave portion 22 on the surface is less than 0.5 mm in diameter or less than 10 μm in depth, while in the tube 23 shown in FIG. When the depth is less than 10 μm, when the brazing composition 9 is scraped off when the fins are assembled, the remaining brazing composition 9 is reduced and a desired effect cannot be obtained. Moreover, in the tube 21 shown in FIG. 6, when the surface recess 22 exceeds 10 mm in diameter or exceeds 50 μm in depth, on the other hand, in the tube 23 shown in FIG. 7, the surface groove 24 exceeds 5 mm in width, Or when the depth exceeds 50 micrometers, there exists a possibility that the clearance gap between the trough part and a fin may become large by the presence of a large unevenness | corrugation, and the brazing composition 9 may be insufficiently supplied.
The concave portions 22 or the grooves 24 on the surfaces of the tubes 21 and 23 have an arithmetic average roughness Ra of 10 μm to 100 μm on the surface of the tube before the brazing composition shown in the first embodiment or the second embodiment is applied. You may apply to what was made, and you may apply to the smooth tube smaller than the arithmetic mean roughness Ra.

  A tube is produced by extrusion molding of an aluminum alloy, and is pressed against the surface while rotating a wire brush to give a predetermined surface roughness (shown as “rough” in Tables 1 and 2), and a plurality of dimple-shaped recesses (Indicated in Tables 1 and 2 as “dimple”) and grooves (indicated in Tables 1 and 2 as “groove”) were prepared. Further, a groove was further formed on the surface having a predetermined surface roughness with a wire brush and further having a recess (indicated as “roughening + dimple” in Table 2) and on the surface having a predetermined surface roughness with a wire brush. A thing (indicated as “roughening + groove” in Table 2) was also produced. The indication “as extruded” in Table 2 indicates that the tube has been produced by extrusion. Except for Comparative Example 15, a brazing material was applied to the surface of the tube. In Tables 1 and 2, the surface roughness is a measurement of the surface roughness of the tube before the brazing material is applied, and the dimensions of the recess or groove are those obtained by measuring the surface after the brazing material is applied. It is.

After fitting the fins of the shape shown in FIG. 5 in order to the tube thus produced, brazing was performed by heating at 590 to 600 ° C. for 5 minutes in a nitrogen gas atmosphere.
When the fins were fitted into the tube, it was confirmed that the fins were broken due to the fins being caught on the tube, or that the fin arrangement pitch was not stable. Moreover, after brazing, the joining rate was measured and the presence or absence of erosion generation | occurrence | production was confirmed.
The case where fin tearing occurred or the case where the arrangement pitch of the fins was not stable was evaluated as x, and the case where these were not observed was evaluated as ◯.

The bonding rate was determined as the ratio of the actual bonding area, which is obtained by subtracting the area of the unbonded part such as the gap from the total area to be bonded, to the total area to be bonded. . As a result, the case where the joining rate was less than 90% was rated as x, the case where it was 90% or more and less than 95% was evaluated as Δ, the case where it was 95% or more was rated as ○, and the case where it was 100% was rated as ◎.
Erosion is the erosion of the base metal caused by an excess of brazing material in part. The evaluation was conducted by embedding the brazed sample with a resin, mirror polishing the cross section, revealing the structure with Barker's solution, and observing the depth of brazing erosion (depth from the brazing filler metal surface) with an optical microscope. It was measured. Those whose erosion depth was 60 μm or more were evaluated as x, and those whose depth was less than 60 μm were evaluated as ◯.
These results are shown in Tables 1 and 2.

  As shown in Tables 1 and 2, the tube surface has an arithmetic average roughness Ra of 10 μm to 100 μm, a diameter of 0.5 mm to 10 mm, a depth of 10 μm to 50 μm, and a width of 1 mm. Those having a groove of ˜5 mm and a depth of 10 μm to 50 μm, or a combination of these surface roughness and recess or groove do not cause fin tearing, etc. when fins are fitted, has a high fin joint rate, and no erosion A good joint can be obtained.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the brazing composition is a mixture of a brazing powder, a flux, and a binder, but may be one of these, or a mixture of two or more of these.

DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Tube 3 Fin 9 Brazing composition 11 Heat exchanger 12 Tube 13 Fin 14 Hole 21 Tube 22 Recess 23 Tube 24 Groove

Claims (5)

  Arithmetic average roughness of a heat exchanger tube assembled in a fitted state in a groove or hole formed in a fin, wherein at least the surface of the part in contact with the inner periphery of the fin groove or hole at the time of assembly is 10 μm to 100 μm A heat exchanger tube, characterized in that a brazing composition is applied to a surface formed in Ra and having the arithmetic average roughness Ra.   A heat exchanger tube assembled into a groove or hole formed in a fin in a fitted state, wherein a brazing composition is applied to the surface, and at least the inner periphery of the fin groove or hole is in contact with the fin A tube for a heat exchanger, wherein a plurality of recesses having a diameter of 0.5 mm to 10 mm and a depth of 10 μm to 50 μm are formed on a surface of the part, to which the brazing composition is applied.   A heat exchanger tube assembled into a groove or hole formed in a fin in a fitted state, wherein a brazing composition is applied to the surface, and at least the inner periphery of the fin groove or hole is in contact with the fin A heat exchanger characterized in that a plurality of grooves having a width of 1 mm to 5 mm and a depth of 10 μm to 50 μm are formed along the longitudinal direction on the surface of the part and the surface to which the brazing composition is applied. tube.   The heat exchanger tube according to claim 2 or 3, wherein the surface before the brazing composition is applied is formed to have an arithmetic average roughness Ra of 10 µm to 100 µm. The heat exchanger tube according to any one of claims 1 to 4 is assembled in a fitting state in a groove or a hole formed in the fin, and the fin and the tube are joined by brazing. A heat exchanger characterized by

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