JPS6080055A - Heat exchanger - Google Patents

Abstract

PURPOSE:To improve the durability of the heat exchanger, prevent incomplete combustion or deterioration of heat exchanging efficiency and improve a reliability as an instrument by preventing the corrosion of the heat exchanger due to acidic dew water in which the exhaust gas of combustion is dissolved. CONSTITUTION:Layer of plating 5, constituted of a metal consisting of the principal constituent of either one kind of nickel, lead and aluminum, is formed on the surface of a heat tranfer member of copper by a means either one of non- electrolyte, electrolyte and fusion, then, a coating, obtained by dispersing and mixing the binder of organic silicon polymer, consisting of the principal constituent of polyborosiloxane, inorganic filler of mica powder 6b, glass powder 6c and silicon carbide powder 6d and a solvent such as toluene or the like, is coated thereon, thereafter, the coating is hardened by heating and thereby forming the layer of coating 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchanger made of a copper heat transfer member used in instantaneous water heaters, water heaters, heating equipment, and the like.

The structure of the conventional example and its problems The first heat exchanger used in the conventional gas instantaneous water heater
As shown in the figure. As shown in the figure, the heat exchanger consists of a drum 1 having a combustion chamber inside, a heat exchange tube 2 through which water to be heat exchanged passes, and heat absorption fins 3 provided on the upper part of the drum 1. It is composed of a copper heat transfer member, and its surface is further plated with a molten metal whose main component is lead.

In this configuration, in the parts where the combustion exhaust gas comes into contact, especially in the low-temperature parts of the contact parts between the drum 1 and the heat exchanger 2 and the contact parts between the heat exchanger fins 2 and the heat-absorbing fins 3, the amount of water contained in the combustion exhaust gas is Nox, sox.

A problem has arisen in that CO, CO2, water vapor, etc. condense to produce acidic condensation/water, which severely corrodes the molten metal plating and the base material copper.

When such corrosion occurs, a large amount of corrosion products such as lead carbonate, lead nitrate, and patina are generated, which accumulate on the heat absorption fins 3 and the drum 1, obstructing the flow of exhaust gas and causing incomplete combustion. In addition, the heat exchange efficiency is significantly reduced due to poor heat conduction to the water passing through the heat exchange tube 2, and the corrosion products peel off into powder and stain the surrounding area. It was not favorable from a safety and health standpoint.

Further, as the corrosion progresses, problems such as holes are created in members such as the drum 1 and the heat absorbing fins 3, resulting in a lack of durability as a device.

In addition, attempts have been made to coat the molten metal plating with organic and inorganic paints to improve its corrosion resistance, but organic paints with binders such as silicone resin and polyamide resin have low heat resistance. However, inorganic paints such as silicate-based and phosphate-based paints have poor corrosion resistance due to the presence of many pinholes in the coating layer, and have not been able to solve the above problems.

OBJECTS OF THE INVENTION The present invention solves these conventional drawbacks, and improves the durability of the heat exchanger by preventing corrosion of the heat exchanger due to acidic condensation water in which combustion exhaust gas is dissolved.
The purpose is to prevent incomplete combustion and a decrease in heat exchange efficiency, and to improve the reliability of the device.

Structure of the Invention In order to achieve this object, the present invention forms a plating layer made of metal on the surface of a copper heat transfer member, and further forms an organosilicon polymer containing polyborosiloxane as a binder on the plating layer. , a coating layer is formed with a paint in which inorganic fillers such as mica powder, glass powder, and silicon carbide powder are dispersed and mixed in the binder, and the coating layer has excellent heat resistance and is a dense film. There is no deterioration of the coating layer due to heat, and even if condensed water is generated by dissolving combustion exhaust gas, it is possible to prevent the condensed water from entering the coating layer, and corrosion of the copper heat transfer member and the plating layer is eliminated. It is possible to prevent incomplete combustion caused by accumulation of corrosion products, contamination of the surrounding area due to scattering and falling of corrosion products, and reduction in heat exchange efficiency.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

In the figure, 4 is a copper heat transfer member which is a cross-section of the main part of a heat exchanger consisting of a drum 5 with a combustion chamber formed therein, heat absorption fins, and heat exchanger tubes.
A plating layer 5 made of a metal whose main component is one of nickel, lead, and aluminum is formed by melting, and an organosilicon polymer 6a whose main component is polyborosiloxane is further formed on this plating layer 5. as a binder,
A coating layer 6 is formed by adding inorganic fillers such as mica powder 6b, glass powder 6c, and silicon carbide powder 6d to this, dispersing and mixing the resulting paint with a solvent such as toluene, and heating and curing. .

As shown in FIG. 2, this coating layer 6 is a coating film in which mica powder 6b is arranged parallel to the plating layer 5, with many of the mica powders overlapping like leaves near the surface, and glass powder 6c and silicon carbide powder 6d are uniformly dispersed. It becomes.

In this configuration, when the burner disposed at the bottom of the combustion chamber in the drum 1 of the heat exchanger shown in FIG. The NOx in the combustion exhaust gas is cooled by condensation of water vapor to produce dew water.

SOX, CO2, etc. are dissolved in the dew condensation water and concentrated to become a highly corrosive acid with a pH of 3 to 4, and the tip of the heat absorbing fin 3 reaches a high temperature of 250''C or more, creating an extremely harsh environment.

The binder used in the coating layer 6 of the present invention is an organosilicon polymer whose main component is polyborosiloxane with silicon, carbon, boron, and oxygen skeletons, so it has excellent heat resistance of 300°C or higher, and has excellent heat resistance as described above. It can sufficiently withstand the operating temperature of the heat exchanger. However, when the coating layer 6 is heated and cured, some of the organic components of the binder decompose, resulting in a porous film with many pinholes. Acidic condensation water enters and corrodes the plating layer 5 and the copper heat transfer member 4.

In the present invention, by applying mica powder 6b to coating layer 6, the above-mentioned corrosion problem could be solved. That is, since a large amount of mica powder 6b having a flake-like particle shape is present in the vicinity of the surface of the coating layer 6, overlapping each other in a leaf-like manner, the barrier properties of the surface of the coating layer 6 are high, and the mica powder 6b has the effect of closing the pinholes existing in the coating layer 6, so that the acidic condensation water does not enter, preventing corrosion of the plating layer 5 and the copper heat transfer member 4, and the mica powder 6b has excellent acid resistance. Since it is a durable material, it can achieve excellent corrosion resistance over a long period of time. Therefore, unlike the conventional heat absorbing fins 3 and drum 1,
This eliminates the accumulation of corrosion products on the surface of the combustion equipment, prevents incomplete combustion and contamination of the surrounding area, and greatly improves the safety of combustion equipment.

Furthermore, by uniformly dispersing the glass powder 6C containing silicon dioxide as the main component in the coating layer 6, the coating layer 6 becomes extremely hard and resistant to mechanical shock, making it difficult to transport and install the heat exchanger. Even if the coating layer 6 is dropped or comes into contact with a tool such as a screwdriver, the coating layer 6 can be prevented from peeling off or being scratched.

JP-A-Sho Go-80055 (3) Furthermore, since silicon carbide powder 6d with excellent thermal conductivity is dispersed in the coating layer 6, the coating layer 6
Even if there is, there is no difference in heat exchange efficiency from conventional heat exchangers,
Furthermore, since there is no reduction in heat exchange efficiency due to corrosion as in the past, excellent heat exchange efficiency can be maintained over a long period of time.

Furthermore, if the total amount of mica powder 6b, glass powder 6c, and silicon carbide powder 6d is 10% or less by weight relative to the heating residue (solid content) of organosilicon polymer 6a, which is the binder, organosilicon polymer 6a Since the surface of the coating layer 6 is porous and has many pinholes, its corrosion resistance deteriorates, and when it exceeds 40%, there is too much filler, which reduces the adhesive strength of the organosilicon polymer 6a. However, since the adhesion of the coating layer 6a deteriorates, it is preferably in the range of 10 to 40%.

On the other hand, the organosilicon polymer 6a mainly composed of polyborosiloxane has extremely poor adhesion to copper, which is a heat transfer member.
Although it was not possible to directly form the vegetating layer 6 on the surface of the copper heat transfer member 4, this is because the surface of the copper heat transfer member 4 was coated with nickel, lead, or aluminum, which has excellent oxidation resistance. It has been found that excellent adhesion with the coating layer 6 can be achieved by providing the plating layer 5 made of a metal containing one type of metal as the main component.

Next, experimental results showing the effects of this embodiment will be explained.

A plating layer shown in Table 1 was formed on the heat exchanger made of the copper heat transfer member shown in FIG. A coating layer was formed by spray painting to a film thickness of 10 to 20 μm and baking at 300° C. for 1 hour.

10" 11 Purge The heat exchangers A to C, which are implementation products of the present invention described above, were incorporated into a gas instantaneous water heater (No. 5 type), and a repeated combustion experiment of burning for 2 minutes and extinguishing for 2 minutes was conducted. For comparison, a test under the same conditions was also conducted on a conventional heat exchanger (with hot-dip lead plating on the surface of a copper heat transfer member).

The results are shown in Table 2.

As seen in Table 2, repeated combustion test results, severe corrosion occurred in the conventional heat exchanger, but the heat exchanger A-
C is JP-A-Sho GO-8005 with no corrosion and excellent resistance.
5(4) Showed eating habits.

Furthermore, it was confirmed that the heat exchange efficiency of the heat exchanger A-C of the present invention was equivalent to that of a conventional heat exchanger, and that there was almost no decrease in thermal conductivity due to the provision of the coating layer.

Effects of the Invention As explained above, the present invention provides a coating layer with excellent oxidation resistance and adhesion on the surface of a copper heat transfer member consisting of a drum in which a combustion chamber is formed, heat absorption fins, and heat exchanger tubes. Since a coating layer with excellent corrosion resistance, heat resistance, and thermal conductivity is formed, 0) corrosion of the copper heat transfer member is eliminated, and the durability of the heat exchanger is greatly improved.

(2) Accumulation of corrosion products on the drum and heat-absorbing fins is eliminated, making it possible to prevent incomplete combustion and eliminating contamination of the surrounding area.

(3) The initial excellent heat exchange efficiency can be maintained over a long period of time.

It has the following effects and has extremely high practical value.

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[Brief explanation of drawings]

FIG. 1 is an external perspective view showing a heat exchanger for a conventional instantaneous water heater, and FIG. 2 is a sectional view of a main part of a heat exchanger according to an embodiment of the present invention. 4... Copper heat transfer member, 5... Plating layer, 6... Coating layer, 6a... Organosilicon polymer, 6b...
- Mica powder, 6c...Glass powder, 6d...Silicon carbide powder. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] A plating layer made of a metal mainly composed of one of nickel, lead, and aluminum is formed on the surface of the copper heat transfer member, and an organosilicon polymer mainly composed of polyborosiloxane is further applied as a binder on the plating layer. A heat exchanger in which a coating layer is formed with a paint obtained by dispersing and mixing inorganic fillers such as mica powder, glass powder, and silicon carbide powder into the binder.