JPH0328672B2 - - Google Patents

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 solar water heaters, electric water heaters, and the like.

BACKGROUND TECHNOLOGY Copper, which is a heat transfer member of a heat exchanger, corrodes in water environments such as groundwater where the pH (hydrogen ion concentration) is 7 or less and there are large amounts of free carbonate and anions. When water containing copper ions eluted due to this corrosion is used in a bath, etc., the copper ions react with fatty acids such as soap to form blue complex salts, which are then adsorbed to towels and bathtub walls, causing a blue discoloration. Ta.

Conventionally, as a means to solve this problem, (1) a metal plating layer of nickel, tin, etc. is provided on the surface of a copper heat transfer member.

(2) Provide a coating layer using organic or inorganic paint.

(3) A rust preventive agent such as a silicate or phosphate polymer is added to water to form a protective film of the rust preventive component on the surface of the copper heat transfer member.

There is such a thing.

Problems to be Solved by the Invention The above-mentioned nickel and tin plating layer has only a short-term corrosion protection effect because the metal plating corrodes in a short period of time in an environment with poor water quality, and the copper is exposed as the plating layer wears out. Corrosion factors enter through the existing pinholes and gaps in the molecular structure of the paint coating layer and corrode the copper, which impairs the adhesion of the coating layer and causes phenomena such as peeling. There was a problem that the anti-corrosion effect was only for a short period of time.

Furthermore, since the protective film formed by the rust preventive agent deteriorates and peels off in a short period of time, it is necessary to add the rust preventive agent periodically, which is difficult to manage in general households.

The present invention solves such conventional problems,
The aim is to prevent corrosion of heat exchangers made of copper heat transfer members over a long period of time, significantly improving their durability and reliability.

Means for Solving the Problems In order to solve the above problems, the heat exchanger of the present invention has an organic paint (lower layer) formed so that a part of the copper heat transfer member on the side that comes into contact with water is exposed. The structure includes a heat exchange part having two coating layers consisting of a top layer and an organic resin binder (upper layer), and a water treatment agent made of alkali glass disposed at a position completely immersed in the water inside the hot water storage tank.

Effect The above configuration allows the heat exchanger to function like underground water.
Even when used in a highly corrosive water environment with low pH, alkaline content elutes from the alkaline glass, which is a water treatment agent installed in the hot water storage tank, and due to the neutralizing effect of the water.
Because the pH increases, the corrosive nature of water can be eliminated. On the other hand, even if the alkaline content of the alkali glass is completely eluted and the neutralization function is lost, two coating layers are formed on the copper heat transfer member of the heat exchanger so that a portion of it is exposed. Corrosion occurs only in the exposed portions (uncoated portions) mentioned above, and the corroded area becomes extremely small, making it possible to significantly suppress the amount of copper eluted. Further, even if there are pinholes in the coating layer, most of the corrosion factors in the water width are consumed by the corrosion reaction at the exposed copper portion, so that corrosion through the pinholes is eliminated.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

FIG. 2 is a sectional view of a heat pipe type solar water heater applied as an example of the present invention. In the figure, 1 is a solar heat collecting plate, 2 is a heat exchanger made of a copper heat transfer member, 3 is a heat medium such as fluorocarbon gas, and 4 is a hot water storage tank made of polyethylene for storing water. The present invention is applied to this hot water storage tank 4.

FIG. 1 is a sectional view of a main part of a heat pipe type solar water heater showing an embodiment of the present invention. In the figure, 5 is a coating layer made of organic paint; 6 is a coating layer made of organic paint;
is a coating layer made only of an organic resin binder, and these coating layers 5 and 6 are formed so that an exposed portion 2' of the heat exchanger exists on the surface of the heat exchanger 2 made of a copper heat transfer member. 7 is a water treatment agent made of alkali glass, and this water treatment agent 7 is placed inside the hot water storage tank 4 so as to be completely submerged in water. Although the means for fixing the water treatment agent 7 is not particularly limited, the water treatment agent 7 is housed in a nonwoven fabric 8 made of polyethylene and attached to the wall surface of the hot water tank 4, for example. Furthermore, the shape and dimensions of the water treatment agent 7 are not particularly limited, and may be rod-shaped or granular in size of several mm.

On the other hand, the organic resin binder applied to the coating layers 5 and 6 may be a mixture of acrylic resin, melamine resin, and epoxy resin from the viewpoints of hot water resistance, corrosion resistance, and adhesion to copper. If there is only one coating layer, pinholes will occur frequently, and if the coating layer is made of multiple layers, the coating will be thick and the heat conduction will be poor. In the present invention, first, on the surface of the heat exchanger 2, a fine powder filler such as alumina, titania, silicon carbide, etc., which has good thermal conductivity and excellent dispersibility with the above-mentioned resin binder, is added to the above-mentioned organic resin binder. A coating layer 5 is formed by applying the dispersed and mixed paint and hardening it by heating, and then only the above-mentioned organic resin binder is further applied onto this coating layer 5, and it is hardened by heating to form a coating layer 6. As a result, a coating layer with extremely few pinholes and excellent thermal conductivity can be realized.

In this configuration, even if the solar water heater shown in FIG. 2 is used in water with a low pH and strong corrosivity, such as underground water, the alkali content is gradually removed by the alkali glass of the water treatment agent 7 placed in the hot water storage tank 4. Since the water is eluted, the water is neutralized and the corrosive properties are eliminated.
Corrosion of the heat exchanger 2 is prevented until the alkaline content of the water treatment agent 7 is completely eliminated and the neutralization function of the water is lost, so there is no elution of copper, and the corrosion of towels and bathtub walls caused by copper ions does not occur. The problem of blue coloring can be solved.

On the other hand, when the neutralization function of the water treatment agent 7 deteriorates, the corrosive factors in the water start a corrosive reaction with the heat exchanger 2, but the heat exchanger 2 exchanges heat with the parts where the coating layers 5 and 6 are formed. Exposed part 2' (uncoated part)
Since the heat exchanger is configured to have such a structure, corrosion occurs only in the exposed portion 2' of the heat exchanger. Therefore, the corrosion area of the heat exchanger 2 is extremely small, and furthermore, a chemically stable green rust film is formed on the surface of the exposed portion 2' of the heat exchanger due to the corrosion reaction. The concentration of copper ions can be suppressed to below the level required to turn towels and bathtub walls blue.

In addition, since the coating layers 5 and 6 have extremely few pinholes, corrosion through the pinholes is difficult to occur, and corrosion factors are consumed in the exposed portion 2' of the heat exchanger, so corrosion from the pinholes in the coating layer is less likely to occur. Corrosion is suppressed and peeling of coating layers 5 and 6 can be prevented. Therefore, corrosion of the heat exchanger 2 can be prevented for a long period of time, and durability and reliability can be significantly improved.

Further, since the coating layer 5 contains fine powders of alumina, titania, silicon carbide, etc., which have excellent thermal conductivity, the thermal conductivity is good, and it is possible to prevent a decrease in the thermal efficiency of the device.

Effects of the Invention As described above, according to the heat exchanger of the present invention, the following effects can be obtained.

(1) Corrosion of heat exchangers made of copper heat transfer members can be significantly suppressed, and the elution of copper ions can be prevented, thereby preventing bluing of towels and bathtub walls caused by copper ions.

(2) Since it has two anti-corrosion functions: a water treatment agent and a coating layer, the anti-corrosion effect of the heat exchanger can be maintained over a long period of time.

(3) Corrosion of the heat exchanger can be prevented, and since the coating layer has excellent heat conduction, it is possible to prevent a decrease in the thermal efficiency of the equipment.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a heat pipe type solar water heater showing an embodiment of the present invention, and FIG. 2 is a sectional view of a heat pipe type solar water heater applied as an example of the present invention. 2...Heat exchanger, 2'...Exposed part of heat exchanger, 4
...Hot water tank, 5...Coating layer, 6...Coating layer, 7...Water treatment agent.

Claims (1)

[Scope of Claims] 1 Two layers consisting of a hot water tank and an organic paint as a lower layer and an organic resin binder as an upper layer formed so that a part of the copper heat transfer member on the side that comes into contact with water is exposed. a heat exchange section having a coating layer of;
A heat exchanger comprising a water treatment agent made of alkaline glass disposed at a position completely immersed in water inside the hot water storage tank. 2. The heat exchanger according to claim 1, wherein the coating layer made of organic paint is a mixture of an organic resin binder and at least one kind of fine powder selected from the group of alumina, titania, and silicon carbide.