JPS5855648A - Solar heat collector - Google Patents

Abstract

PURPOSE:To obtain the titled heat collector which is anticorrosive, excellent in heat collecting efficiency and light in weight by a method wherein a metallic fin is bonded to a plastic pipe with a heat conductive bond and a selective adsorption film is coated on the surface of the fin. CONSTITUTION:The solar heat collector comprises the plastic pipe 1 and the metallic fin 2 which are bonded together with the heat conductive bond 3. Further, the selective adsorption film 4 is coated on the surface of the metallic fin 2. In this case, the plastic pipe 1 is made of a heat resistant resin and the bond 3 consists of a silicon type bond dispersed with a metal oxide, carbon and metallic powder. As the selective adsorption film 4, a film consisting of a pigment containing more than one of metal oxides selected from iron manganese, copper, chromium, cobalt and nickel and a binder mainly consisting of a silicon resin or an acrylic resin is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar heat collector, and aims to improve heat collection performance and reduce costs.

In recent years, solar energy has attracted attention from the viewpoint of energy conservation and oil alternative energy, and its practical use in home water heaters and the like is being promoted. Solar heat collectors are being developed as the core of solar heat utilization systems, and are available in flat plate type, tubular type,
Various types have been proposed, such as a vacuum-insulated tubular type, a heat-vib type, and a condensing type.

Home solar water heating systems are pump-type.

Although it is broadly divided into natural circulation type and forced circulation type, the natural circulation type is currently becoming mainstream, and it is predicted that the forced circulation type will also increase in the future.

However, when it comes to the use of solar energy, economic comparisons are made with other forms of energy, and solar thermal equipment is always required to have high performance, long life, and an economically viable price. It has been.

Solar heat collectors currently in practical use include those made of metals such as stainless steel and copper, and those made of blow-molded plastics such as polyethylene.

Comparing both metal and plastic, there are advantages and disadvantages, but plastic is attractive because it is lightweight, does not have the problem of corrosion on the water circuit side, and is inexpensive. In addition, in the case of metals, it is relatively easy to impart selective absorption properties through surface treatment, and high performance has been achieved, but with plastics, it is almost impossible to impart selective absorption properties. However, there are also drawbacks regarding heat resistance.

Solar heat collectors composed of fins and pipes have already been put into practical use, both of which use metal. In most cases, copper pipes are used in combination with copper fins, aluminum fins, etc.

Copper pipes are excellent in terms of pressure resistance and corrosion resistance, but depending on the water quality, copper ions may flow out, resulting in so-called "blue water".
There is a concern that this may cause problems.

The "blue water" problem is a phenomenon in which minute amounts of copper ions react with fatty acid salts in soap, producing a blue-colored slurry when hot water is supplied to a bath. It is often seen in cases where

The present invention utilizes a plastic pipe and forms the pipe and metal fins by bonding them with a thermally conductive incubator ali, thereby bringing out the advantages of metal and plastic and making up for their disadvantages.

Hereinafter, the present invention will be explained based on drawings showing one embodiment thereof. Figure 1 is a cross-sectional view of the main parts of the solar heat collector. In Figure 1, 1 is a plastic pipe, 2 is a metal fin, and this metal fin 2 is the plastic pipe IK thermally conductive adhesive. It is glued with adhesive 3.

Further, a selectively absorptive coating film 4 is formed on the surface of the metal fin 2.

In the above configuration, sunlight a is received by the selectively absorbing coating film 4, and this heat is transferred from the metal fins to the plastic pipe 1 via the thermally conductive adhesive 3, and the medium inside the plastic pipe 1 is heated. heat up. Thermal radiation C from the surface of the metal fin 2 whose temperature has increased is suppressed by the selective absorption properties of the selectively absorbent coating film 4.

In addition, the material of the plastic pipe 1 needs to be a heat-resistant resin, and since hot water passes through the inner surface and is used for hot water supply, it should be made of a material that does not have the risk of leaking harmful heavy metals or plasticizers. It is necessary to use A suitable example is a thermosetting silicone resin. This resin has the disadvantage of low tear strength, so
It is better to coat the outer surface with a resin such as nylon at 1°C. Examples of thermally conductive adhesives include metal oxides and carbon in silicone adhesives.

It is preferable to use an adhesive in which metal powder or the like is dispersed (1.degree. 11-+) For the metal fin 2, it is preferable to use a thin aluminum plate or foil from the viewpoints of thermal conductivity, light weight, corrosion resistance, etc.

Further, the selectively absorbing coating film 4 on the metal fin 2 may be formed not only on the front surface, which is the heat receiving surface of sunlight, but also on the back surface. The selectively absorbent coating film 4 may be formed by pre-coating it on the metal surface and then processing it afterward, but since it may cause scratches, after bonding the metal fins 2 and the plastic pipe 1, A preferable and preferable selective absorbing coating 4 is iron.

Examples include a coating film made of a pigment made of one or more metal oxides selected from the group of manganese, copper, chromium, cobalt, and nickel, and a binder whose main component is a silicone resin or an acrylic resin.

The selectively absorbing coating film 4 ideally absorbs light of 2 μm or less in the wavelength range of sunlight and is as transparent as possible to infrared rays of 2 μm or more corresponding to radiation from the surface. Examples of the pigment include one or more metal oxides selected from the group consisting of iron, manganese, copper, chromium, cobalt, and nickel. On the other hand, as a binder,
This is particularly difficult in terms of infrared transparency, and this is due to the emissivity ε
Therefore, it is necessary to make the coating film as thin as possible. From the viewpoint of overall performance as a binder, a binder containing an acrylic resin or a silicone resin as a main component is preferable. As the selectively absorbent coating film 4, a combination of the above-mentioned pigment and binder is suitable.

Next, an example of a method for forming the selectively absorbent coating film 4 will be described.

27 parts by weight of Dipyroxide Color≠9550J (trade name), a Fe20Fe205II/CuO pigment from Dainichiseika Co., Ltd., and 1 dianal SIC-653, a silicone-modified acrylic resin from Mitsubishi Rayon Co., Ltd.
A paint was prepared by mixing 100 parts by weight of (trade name) and 200 parts by weight of xylene using Attritor (trade name) for 6 hours. Then, the coating material was applied onto an aluminum plate and baked at 200°C for 10 minutes. FIG. 2 shows the relationship between the film thickness, absorption rate, and emissivity of the coating film thus obtained.

The above selectively absorbing coating film has a relatively high emissivity ε when compared to selectively absorbing films such as metal black, but has a high absorption rate α, so it is excellent for hot water supply applications where heat collection efficiency is high. .

Although the solar heat collector in one embodiment of the present invention can sufficiently withstand dry baking at about 200°C, the selectively absorbing coating film 4
Because it uses , it has a larger radiation loss compared to metal black, etc., and contributes to keeping the temperature of the plastic part from becoming too high.

Compared to conventional solar heat collectors made of metal pipes and metal fins, since the pipe 1 is made of plastic, there is no problem of corrosion. Also especially copper pipes,
Unlike aluminum fins, there is no fear of corrosion due to battery action at the contact parts.

Furthermore, since the pipe 1 is made of plastic, there are advantages such as the hot water supply being always hygienic even when used in a single water circuit.

It is also lighter overall compared to conventional metal solar collectors.

Furthermore, compared to conventional blow-molded flat plate plastic solar heat collectors, it has overwhelmingly superior heat collection performance centered on selective absorption, and is also superior in terms of reliability such as heat resistance during dry firing. , which is absolutely superior.

As described above, according to the present invention, a plastic pipe and a metal fin are bonded together using a thermally conductive adhesive, and a selectively absorbing coating film is formed on the surface of the metal fin, and the pipe is made of plastic. As a result, the inner walls of the pipes are no longer corroded by hot water, and as a result, hot water is always hygienic, and the overall weight is also light. Since a selectively absorbing coating film is formed on the surface of the metal fins, the heat collection performance is quite excellent, and the cost is low and various excellent effects are achieved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main parts of a solar heat collector showing an embodiment of the present invention, and Fig. 2 shows the thickness and absorption rate of the selectively absorbing coating formed on the surface of the metal fins of the heat collector. It is a graph showing the relationship with emissivity. 1...Plastic pipe, 2...Metal fin, 3...Thermal conductive adhesive, 4...
...Selective absorbent coating. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
@ No. 2 Figure 01'1J4j67811θ Membrane 4 (P)

Claims (2)

[Claims] (1) A solar heat collector in which a plastic pipe and metal fins are bonded together using a thermally conductive adhesive, and a selectively absorbing coating film is formed on the surface of the metal fins. (2) The selectively absorbent coating film is made of iron, manganese, or copper. Claims that form a coating film consisting of a pigment made of one or more metal oxides selected from the group consisting of nickel, cobalt, and nickel, and a binder whose main component is a silicone resin or an acrylic resin. The solar heat collector according to item 1.