JPH0719788A - Fin-tube type heat exchanger - Google Patents

Abstract

PURPOSE:To obtain a fin-tube type heat exchanger which can prevent a lubricat ing oil remaining inevitably in an assembling process of the heat exchanger from corroding by undergoing a sticking of moisture, a change in temperature and a change in an airing condition, increase the reliability and lifetime and is excellent in corrosion resistance. CONSTITUTION:In a fin-tube type heat exchanger comprising a plurality of plate-shaped fins 1 made of aluminum or an aluminum alloy and disposed in parallel and a tube 2 made of a copper alloy and brought into contact with and joined to each fin, the material of this tube 2 is the alloy which contains at least one kind of constituent selected from a group of Zn of 0.05 to 10wt.%, Mn of 0.05 to 51wt.% and Mg of 0.05 to 5wt.%, by 0.05 to 10wt.% in the total amount, and the residual part of which is constituted of Cu and unavoidable impurities. Moreover, the tube is an internally grooved tube which has a plurality of parallel grooves in the inner surface thereof and an outside diameter of 4 to 25.4 mm and of which the ratio between the depth of the grooves and the inside diameter determined by a crest part formed between the grooves and also the helix angle of the grooves to the direction of the tube axis are in prescribed ranges.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fin-tube type heat exchanger used in an air conditioner, and more particularly to a fin-tube type heat exchanger having excellent corrosion resistance against ant nest corrosion.

[0002]

2. Description of the Related Art Generally, a fin tube type heat exchanger used in an air conditioner has a plate-shaped fin made of aluminum or an aluminum alloy provided with a tube insertion hole and a cylindrical fin collar inside the insertion hole. In the state where a large number of fins are arranged in parallel, a copper tube is inserted into the fin collar so as to connect the fins, and then the tube is expanded and fixed to the fins, thereby It is assembled.
Then, a heat medium is caused to flow in the tube, and the heat is transmitted to the fins for heat dissipation.

In this fin-tube type heat exchanger, the plate-shaped fins are made of aluminum or an aluminum alloy from the viewpoint of heat conductivity and cost, and the tube is made of copper from the viewpoint of heat conductivity and corrosion resistance. Tubes are widely used. The copper tube is a pure copper tube mainly called phosphorus deoxidized copper.

[0004]

However, in these conventional fin-tube type heat exchangers, lubricating oil and organic substances such as organic solvents inevitably remain in the fin punching process and the tube expanding process. However, during storage of fins and tubes or use of this organic matter as a heat exchanger,
Repeatedly adheres and evaporates water. Further, during use as a heat exchanger, it is exposed to a peculiar temperature and humidity and a ventilation environment. Under such conditions, organic substances are decomposed to contain carboxylic acid, and peculiar corrosion which takes the form of a nest of ants locally occurs, and the tube often leaks.

Further, as described above, a lot of lubricating oil is used in the process of assembling the fin-tube heat exchanger, but due to recent environmental problems, there is a tendency to avoid degreasing cleaning with an organic solvent, and instead, volatility is reduced. The lubricating oils that they have tend to be used. Among the volatile lubricating oils, there are oils in which the base oil is volatile but the oily additive remains on the surface of the material. Therefore, as compared with the case where degreasing cleaning is performed with an organic solvent, there is a tendency that the amount of organic substances remaining on the surface of the material increases, and the risk of ant nest corrosion is higher than before.

Against this background, countermeasures against ant nest corrosion of fin-tube type heat exchangers have recently attracted attention as a major problem, and a fin tube type having excellent corrosion resistance against ant nest corrosion. Development of a heat exchanger is desired.

The present invention has been made in view of the above problems, and is a phenomenon peculiar to a fin-tube heat exchanger,
That is, the lubricating oil unavoidably left in the assembly process of the heat exchanger is repeatedly exposed to moisture and evaporated, and is exposed to an environment of unique temperature and humidity conditions and aeration conditions to contain carboxylic acid. Even so, it is an object of the present invention to provide a fin-tube heat exchanger having excellent corrosion resistance against ant nest corrosion, which can increase its reliability and life.

[0008]

A fin-tube heat exchanger according to the present invention is a copper alloy in which a plurality of plate-shaped fins made of aluminum or aluminum alloy are arranged in parallel and contact each fin to connect them. In the fin-tube heat exchanger in which tubes made of copper are arranged, the tubes made of copper alloy are made of 0.05 to 10 wt% Zn, 0.05
To 5% by weight of Mn and 0.05 to 5% by weight of Mg, and at least one component selected from the group of 0.05 to 10% by weight, with the balance being Cu and inevitable impurities. It is a copper alloy tube.

In order to improve the heat transfer performance as a heat exchanger, the copper alloy tube has a plurality of grooves parallel to the inner surface of the tube, the outer diameter of which is 4 to 25.4 mm and the groove depth. Ratio h to the pipe inner diameter Di defined by the crest of the groove
It is preferable that the inner grooved tube has a / Di of 0.01≤h / Di≤0.05 and a twist angle γ of the groove with respect to the tube axis direction of 0 ° ≤γ≤30 °.

[0010]

The present inventor has conducted various studies to obtain a fin-tube type heat exchanger having excellent corrosion resistance against ant nest corrosion, and has found the following facts.

That is, the ant nest-like corrosion is caused by the carboxylic acid produced by the decomposition of organic substances such as lubricating oil and organic solvent which are inevitably left in the assembly process of the heat exchanger. It occurs locally on both the inner and outer surfaces of the tube and often leads to leaks in the tube.

Then, the inventors of the present invention repeated various experimental studies from the viewpoint that it is necessary to improve the corrosion resistance of the material constituting the tube itself, and as a result, copper was found to contain at least one of Zn, Mn and Mg. It was found that the corrosion resistance of the fin-tube heat exchanger is remarkably improved by using a tube made of a copper alloy containing a predetermined amount of as a tube. That is, even in a corrosive environment where ant nest corrosion occurs in a fin tube type heat exchanger using a conventional phosphorous deoxidized copper tube, a copper alloy tube containing at least one of Zn, Mn and Mg. In the fin-tube type heat exchanger using, the local corrosion does not proceed and the general corrosion form is exhibited.

As described above, by adding a predetermined amount of Zn, Mn and Mg, it is possible to improve the corrosion resistance of the copper alloy tube because Zn, Mn and Mg are lower in potential than Cu, and Since it forms a solid solution in Cu and is uniformly distributed,
It is considered that this is because the surface of the material is uniformly corroded and the corrosion products are also uniformly dissolved.

If the content of Zn, Mn and Mg in the copper alloy tube is less than 0.05% by weight, the effect of improving the corrosion resistance is not sufficient. On the other hand, as the contents of these components increase, the effect of improving the corrosion resistance of the copper alloy tube increases. However, in the manufacturing process of the fin-tube heat exchanger, workability and brazing property of the tube are required, and these workability and brazing property deteriorate when the amounts of Zn, Mn and Mg increase. Therefore, in order to secure the workability and brazing property of the tube in the manufacturing process, the content of Zn is 10% by weight or less, the content of Mn and Mg is 5% by weight or less, and the total amount is 10% by weight or less. It is necessary to. Further, since all of these additive components have the same action and effect, at least one of these components may be added. Therefore, the copper alloy as the constituent material of the tube contains Zn: 0.05 to 10% by weight, Mn: 0.05 to 5% by weight and Mg: 0.05 to 5% by weight in total. The content is 0.05 to 10% by weight.

Furthermore, it is preferable to use an inner grooved tube as the copper alloy tube of the finned tube heat exchanger according to the present invention. This inner grooved tube has an outer diameter of 4-25.
4 mm, having a plurality of parallel grooves on the inner surface of the tube,
The relationship between the groove depth h and the minimum inner diameter Di (inner diameter defined by the crest) is 0.01 ≦ h / Di ≦ 0.05, and the twist angle γ in the pipe axis direction is 0 ° ≦ γ ≦ 30 °. To meet. Thereby, the heat transfer performance can be significantly improved.

When the outer diameter of the inner grooved tube is less than 4 mm,
The pressure loss of the heat medium increases, and heat transfer performance cannot be sufficiently obtained. On the other hand, when the outer diameter exceeds 25.4 mm, the heat exchanger becomes large, which is uneconomical as a fin-tube heat exchanger. Therefore, the outer diameter of the pipe needs to be 4 to 25.4 mm.

The ratio of the groove depth h to the minimum inner diameter Di, h /
When Di is less than 0.01, the heat transfer performance is not sufficiently improved, while when it exceeds 0.05, the pressure loss increases, and the heat transfer performance tends to decrease. Furthermore, if the twist angle γ in the tube axis direction exceeds 30 °, the pressure loss increases, and heat transfer performance cannot be sufficiently obtained. Therefore, the ratio h / D
i is 0.01 ≦ h / Di ≦ 0.05, and the twist angle γ
Is preferably 0 ° ≦ γ ≦ 30 °.

When the inner grooved tube having the groove of such a structure formed on the inner surface is used as a tube, as described above, the corrosion resistance against ant nest corrosion is excellent, and further, the heat transfer as a heat exchanger is performed. It is possible to obtain a high-performance fin-tube heat exchanger with excellent performance.

In addition to Zn, Mn and Mg, the copper alloy tube constituting this tube may contain P and B, which are usually used as deoxidizers, as unavoidable impurities. Even if it contains the above impurities, there is no problem in improving the corrosion resistance.

[0020]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples. Using a tube (annealing material) having the composition shown in Table 1 below, a fin-tube heat exchanger as shown in the plan view of FIG. 1 was produced, and the corrosion resistance against ant nest corrosion, heat transfer performance, and manufacturing The workability and brazing properties, which are the properties required above, were evaluated. 2 is a sectional view of the fin-tube heat exchanger in the tube tube axial direction, FIG. 3 is a lateral sectional view of the tube, and FIG. 4 is a partially enlarged view of the same.
Each plate-shaped fin 1 is substantially plate-shaped,
A plurality of tube insertion holes are formed at the center in the height direction, and a cylindrical fin collar 5 is provided on the peripheral edge of the insertion hole with its axial direction orthogonal to the fins 1. Then, the plate-shaped fins 1 are arranged so as to be parallel to each other, and the tube 2 is inserted into the fin collar 5 of each fin 1. This tube 2 has a U-shape having a hairpin bent portion 3, is inserted into a fin collar 5 and expanded to fix the tube 2 to the fin 1, and then both ends of the tube 2 and the ends of the adjacent tubes 2 By brazing and to the semicircular tubes 4, the tubes 2 are connected so as to form one tube.

The tube 2 is provided with a plurality of grooves 7 on its inner surface, and these grooves 7 extend spirally on the inner surface of the tube. The pipe inner diameter Di is defined by the crests 6 between the grooves 7, and is the minimum inner diameter.

The inner grooved tube used in the fin-tube type heat exchanger of this embodiment has an outer diameter of 7 mm, an inner diameter Di of 6.14 mm, and the number of grooves is 50 in a cross section orthogonal to the tube axis.
Individual, groove depth h is 0.18 mm, bottom wall thickness t is 0.25 m
m, the groove bottom width W is 0.23 mm, and the twist angle γ of the groove with respect to the tube axis direction is 18 °.

The composition of the copper alloy of the tube 2 is shown in Table 1 below.

[0024]

[Table 1]

Further, in manufacturing the fin-tube heat exchanger, volatile lubricating oil was used at the time of punching the fins and bending and expanding the hairpin of the tube, and the subsequent solvent degreasing step was omitted. The tube is brazed with phosphorus copper braze (BCuP-2; a type of phosphorus copper braze specified in JIS-Z3264, containing 6.8 to 7.5% P, and the balance being mainly Cu, Other elements are 0.
2% or less). The evaluation results of various characteristics are shown in Table 2 below. However, the heat transfer amount in Table 2 is the heat transfer amount when the wind speed is 1.0 m / sec.

[0026]

[Table 2]

The evaluation methods for the properties shown in Table 2 are as follows. Corrosion resistance to ant nest corrosion A fin tube type heat exchanger using tubes having the composition shown in Table 1 was operated as an indoor unit under the following conditions, and the maximum corrosion depth due to ant nest corrosion was measured. Operating environment: 30 ° C., relative humidity 80% Operating conditions: cooling operation for 5 minutes and blowing operation for 10 minutes were repeated for 6 months.

Heat Transfer Performance In a wind tunnel tester, the amount of heat transfer (evaporation / condensation) as a heat exchanger was measured. Refrigerant is R-22 (Freon HCFC
-22: The molecular formula is CHClF ₂ ) and the measurement conditions are as follows.・ Evaporation test Air side: Dry bulb temperature / wet bulb temperature 27.0 ° C
/19.0°C Refrigerant side: Heat exchanger outlet pressure 5.4 kgf / cm ² Superheat degree 5.0 deg Condensation test Air side: Dry bulb temperature / wet bulb temperature 20.0 ° C
/15.0°C Refrigerant side: Heat exchanger inlet pressure 18.8 kgf / cm ² Supercooling degree 5.0 deg

Required characteristics and workability in production (hairpin bending: radius 10.5 mm): The generation of wrinkles inside the bent portion was observed. -Brazability: An internal pressure was applied to the tube of the heat exchanger to carry out a fracture test, and the fractured portion was observed.

As is apparent from Table 2, Example 1 of the present invention
7 to 7 have extremely excellent corrosion resistance to ant nest corrosion as compared with the case of using the conventional phosphorus deoxidizing sinus (Comparative Example 8), and the heat transfer performance which is a necessary characteristic as a heat exchanger. Also, the workability and the brazing property, which are the properties required at the time of production, are not inferior to those in the case of using the conventional phosphorous deoxidized copper (Comparative Example 8).

On the other hand, in Comparative Examples 9 to 11, Zn, Mn and M were used.
Since a tube containing a large amount of g was used, heat transfer performance, workability, and brazing property were deteriorated, which is not suitable for practical use. Further, it is considered that the reason why the corrosion resistance is lowered in Comparative Example 11 is that the Mg content is too large and exceeds the solid solution amount with respect to Cu, and Mg precipitates.

[0032]

As described above, the fin-tube heat exchanger according to the present invention inevitably remains in the assembly process as compared with the conventional heat exchanger using the phosphorus-deoxidized copper tube. Corrosion resistance to ant nest corrosion that is likely to occur due to repeated adhesion and evaporation of water due to organic substances such as lubricating oil and organic solvents, and exposure to environments with unique temperature and humidity and aeration conditions Is extremely excellent and is extremely useful as a heat exchanger used in this type of environment.

The fin-tube type heat exchanger according to the present invention uses a tube containing an element which is baser than Cu, unlike the conventional heat exchanger using a phosphorus-deoxidized copper tube. Therefore, the potential difference between the tube and fins (aluminum or aluminum alloy) is reduced, and electrolytic corrosion of the fins is suppressed, so there is little deterioration in heat transfer performance during use, and the initial heat transfer performance is maintained over a long period of time. Can be maintained.

[Brief description of drawings]

FIG. 1 is a plan view showing a fin-tube heat exchanger according to an embodiment of the present invention.

FIG. 2 is a sectional view of the tube in the tube axis direction.

FIG. 3 is a cross sectional view of the tube.

FIG. 4 is a partially enlarged view of a cross section of the tube.

[Explanation of symbols]

 1; plate fin 2; tube 3; hairpin bent part 4; semi-circular tube 5; fin collar 6; mountain top 7; groove Di; minimum inner diameter h; groove depth W; groove bottom width t; bottom wall thickness

[Procedure amendment]

[Submission date] August 19, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

As is apparent from Table 2, Example 1 of the present invention
7 to 7 have extremely excellent corrosion resistance against ant nest corrosion as compared with the case of using the conventional phosphorous deoxidized copper (Comparative Example 8), and the heat transfer performance which is a necessary characteristic as a heat exchanger. Also, the workability and the brazing property, which are the properties required at the time of production, are not inferior to those in the case of using the conventional phosphorous deoxidized copper (Comparative Example 8).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motohisa Miyato 14-1 Nagafu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Works, Ltd.

Claims (2)

[Claims] 1. A fin-tube heat exchanger in which a plurality of plate-shaped fins made of aluminum or aluminum alloy are arranged in parallel, and a copper alloy tube for contacting and connecting the fins is arranged. The alloy tube has a total amount of at least one component selected from the group consisting of 0.05 to 10 wt% Zn, 0.05 to 5 wt% Mn and 0.05 to 5 wt% Mg. A fin-tube type heat exchanger, characterized in that it is a copper alloy tube containing 0.05 to 10% by weight, and the balance being Cu and inevitable impurities. 2. The copper alloy tube has a plurality of grooves parallel to the inner surface of the tube, the outer diameter of which is 4 to 25.4 mm, and the inner diameter of the tube defined by the groove depth h and the crest between the grooves. It is characterized in that the inner grooved pipe has a ratio h / Di with Di of 0.01 ≦ h / Di ≦ 0.05 and a twist angle γ of the groove with respect to the pipe axis direction of 0 ° ≦ γ ≦ 30 °. The fin-tube heat exchanger according to claim 1.