JPH01142394A - Heat exchanger - Google Patents

Abstract

PURPOSE:To prevent corrosion due to condensed water or the like without loosing heat transfer characteristics by a method wherein a first layer, consisting of a metal inferior electrochemically to an anti-corrosion body, is formed on the anti-corrosion body and a second layer, consisting of another metal inferior electrochemically to the anti-corrosion body and the first layer, is formed on the first layer. CONSTITUTION:First layers 2a, 2b, consisting of a metal (aluminum, for example) interior electrochemically to an anti-corrosion material 1, is formed on the anti- corrosion material 1 or the heat transfer wall of a heat exchanger and second layers 3a, 3b, consisting of another metal (tin plating, for example) inferior electrochemically to the first layers 2a, 2b are formed on the first layers 2a, 2b. Accordingly to this method, the corrosion of the anti-corrosion material 1 may be prevented by the existence of the first layer 2a even when a pin hole 4 is produced on the second layer 3a. Further, even when a pin hole 5, penetrating through the second layer 3a and the first layer 2a, is generated, the first layer 2a is eluted as a sacrificed anode, whereby the corrosion of the second layer and the anti-corrosion material 1 may be prevented. The corrosion of the anti-corrosion material 1 can be prevented without impairing the heat transfer characteristics of the heat exchanger in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a heat exchanger that is less likely to be corroded by condensed water or the like.

BACKGROUND ART In a conventional heat exchanger, as shown in FIG. 7, a heat transfer wall 21 to be protected against corrosion is protected by a tin plating layer 23 which is electrochemically nobler than the corrosion resistant material. If there is a pinhole 24 in the fi plating coating layer 23, the corrosion protection material 21 will corrode and elute.

In another prior art example shown in FIG. 8, a material to be protected 21 is protected against corrosion by a coating layer 22 made of a metal that is electrochemically more base than the material to be protected. is easily corroded by condensed water.

In some cases, corrosion can be prevented by coating with synthetic resin, etc.
In this case, the heat exchange efficiency will be reduced.

Problems to be Solved by the Invention In such prior art, sufficient durability cannot be obtained in harsh usage environments.On the other hand, steel materials widely used as heat transfer walls of heat exchangers have poor heat transfer properties. Because of this characteristic, even if the coating layer has a high anticorrosive effect, materials with high heat transfer resistance such as synthetic resins cannot be used because they impair this characteristic.

An object of the present invention is to provide a heat exchanger having an anticorrosion layer that does not impair the heat transfer characteristics of the heat exchanger and has an excellent anticorrosion effect.

Means for Solving the Problems The present invention forms a first layer made of a metal that is electrochemically more base on a wave protector, and a layer to be protected and a first layer are formed on the first layer. This heat exchanger is characterized in that a second layer is formed of a metal that is electrochemically more noble than the second layer.

Function According to the present invention, on the first layer and the eleventh layer, which are made of a metal that is electrochemically less noble than the corrosive body, there is a layer that is electrochemically more noble than the body to be corroded and the first layer. The second part made of metal
form a layer. Therefore, the first layer protects the object to be corrosion protected as a sacrificial anode. For example, even if there is local wear or pinholes in the first layer, the object to be protected against corrosion will be sufficiently protected from corrosion due to the presence of the first layer. Also, even if a pinhole penetrates the second layer and the first layer, the first layer
Corrosion protection of the layer at the same time. Therefore, corrosion of the object to be protected is less likely to occur.

Example FIG. 1 is a cross-sectional □ view of one embodiment of the present invention.

The material to be protected 1, which is the heat transfer wall of the heat exchanger, is made of copper, and the first layers 2a and 2b formed on the material to be protected 1 are made of a metal that is electrochemically more base than the material to be protected, for example. It is made of magnesium, aluminum, zinc, or an alloy containing at least one of these.

A second layer 3a is formed on the first layers 2a and 2b.

3b is made of a metal that is electrochemically more noble than the metals of the corrosion protection target 1 and the first layers 2a and 2b, such as tin plating.

FIG. 2 is a cross-sectional view of the embodiment shown in FIG. 1 in which a pinhole is formed in the second N 3 a. In this case, since the first layer 2a exists, the material to be protected 1 is protected from corrosion.

FIG. 3 is a cross-sectional view of a state in which a pinhole 5 penetrating the second layer 3a and the first layer 2a is formed.

In this case, the magnesium in the first layer 2a is eluted as a sacrificial anode and protects the second layer and the corrosion-protected material.

FIG. 4 shows an example in which the pinhole 6 is found in an airtight space in the first layer 2a, and the pinhole 7 is found in the second layer 3a. Even if the metal of the second layer 2a is exposed after being consumed, the metal magnesium of the first layer 2a is eluted and the material to be protected 1 is protected from corrosion. The latter 7 brings about the elution of the first N 2 a metal, but the rIi of the 5-wave protective material 1 is caused by the sacrificial anode action of the first layer 2a.
No eclipse occurs.

FIG. 5 is a plan view of a heat exchanger according to an embodiment of the present invention having the configuration shown in FIG. A heat transfer tube 12 having a large number of fins 11 formed on its outer circumferential surface is arranged in a bent manner in a housing 10 of the gas water heater. A liquid to be heated, for example water, is supplied from one end 13 of the heat transfer tube 12, and a heated liquid, for example hot water, is discharged from the other end 14. A burner is provided below the heat exchanger tube 12, and the liquid flowing inside the heat exchanger tube 12, such as water, is heated by the high-temperature exhaust gas, and heat exchange is performed.

Water vapor in the exhaust gas condenses and adheres to the surfaces of the fins 11 and heat exchanger tubes 12, and the surfaces of the fins 11 and heat exchanger tubes 12 tend to corrode easily. The present invention is implemented to protect the fins 11 and heat transfer tubes 12 from corrosion.

FIG. 6 is an enlarged sectional view of section (2) in FIG. 5.

The fins 11 and the heat exchanger tubes 12 are made of copper, and a first layer 15 made of a metal baser than copper is formed on the surface of the fins 11 to prevent corrosion, as in the previous embodiment. A second layer 16 made of a metal more noble than the metal of layer 15 is formed.

Specifically, a copper plate-fin type heat exchanger is subjected to pre-treatments such as degreasing, pickling, water washing, and flag treatment, then immersed in magnesium or magnesium alloy at approximately 650°C for 1 to 2 minutes, and then pulled out. Cool afterwards. In this way, the first layer 15 is formed. Thereafter, after performing the same pretreatment as above, it is immersed in tin or tin alloy at about 400° C. for 1 to 2 minutes, pulled out, and cooled to complete the coating and form the second layer 16.

Effects According to the present invention, since corrosion caused by condensed water, etc. can be prevented, durability is extremely high, and since a metal anti-corrosion layer is applied, thermal conductivity is not impaired in any way by anti-corrosion treatment. A heat exchanger with good heat conductivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and FIGS. 2, 3, and 4 show pinholes 4 to 7 in the embodiment of FIG.
5 is a plan view of a heat exchanger that is an embodiment of the present invention, FIG. 6 is an enlarged sectional view of section Cross-sectional view of the technology, FIG. 8 is a cross-sectional view of another prior art. 1... Material to be protected, 2a, 2b, 15-first layer, 3a,
3b, 16-2nd layer, 4,5,6.7-...pinhole, 11...fin, 12...heat exchanger tube agent patent attorney Number of strokes Keiichi fA1 figure M4 figure 5 figure payment 7th Prisoner Figure 8

Claims (1)

[Claims] A first layer made of a metal that is electrochemically more noble than the corrosive protection body is formed on the corrosion protection body, and a first layer made of a metal that is electrochemically more noble than the corrosion protection body and the first layer is formed on the first layer. A heat exchanger characterized by forming a second layer.