JPS5924768B2 - Treatment method for heat collecting surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for treating a solar heat collecting surface that has excellent spectral characteristics and durability.

The rise of the consumer economy over the past few years has encouraged the overspending of large amounts of natural resources, while also producing a huge amount of industrial and household waste, and the various resources that have been used in the past as if they were inexhaustible are far from being depleted. In the future, environmental pollution caused by waste emissions gradually deteriorated the living environment and caused many problems, including the outbreak of pollution-related diseases.

For this reason, not only in Japan but also in other countries around the world, the ideal form and methods of industrial structures that conserve resources, conserve energy, and provide clean energy are being seriously studied, and the use of solar energy has been taken up as a central research topic.

However, solar energy has a low energy density, so in order to make full-scale use of it, it is necessary to develop a so-called collector that efficiently collects energy in some way.
Research and development of the heat collecting surface, which plays the central role of the collector, is the most decisive factor in realizing the effective use of solar energy.

The properties required for this heat collecting surface include general things such as economical, long life, and ease of handling. It is necessary to have good performance (2) excellent spectral characteristics such as low radiation loss in the infrared region (2.5 to 30 μ).

Currently, the heat transfer surfaces developed for this purpose have the following surface treatments, but none have been found that are both efficient and economical, and this remains an issue for the future.

Method〉 Disadvantage〉 (ω Chemical conversion treatment of metal → poor thermal efficiency.

Durability means turning black.

Poor. (b) Silicon particles are made of metal → high cost.

Paste it on the surface you want to paste it on.

I don't have a good binder.

(C) Black due to electroplating → poor efficiency.

Formation of colored film.

(d) Black by vapor deposition method → cost.

Mass production and film production.

do not have. Difficult to process large items.

(θ Painting with black paint r is inefficient.

Poor durability.

Especially recently, there is a strong tendency to place emphasis on durability and use the black chemical conversion treated surface of stainless steel as a heat collecting surface, but this treated surface has lower absorption performance and radiation loss compared to copper treated surfaces. The deterioration of large cases such as f]'i-, cannot be criticized.

In view of these circumstances, the present invention has developed spectral characteristics (good absorption performance in the visible range, low radiation loss in the infrared range,
Of course, it has excellent spectral characteristics (hereinafter referred to simply as spectral characteristics),
The purpose of this is to provide a method for treating a heat collecting surface for a collector that is durable, easy to manufacture, and exhibits little performance deterioration even under high temperature conditions. When performing the chemical conversion treatment, copper ions are added to the chemical conversion treatment liquid and applied to the heat collecting surface, and the heat collecting surface is blackened and at the same time, fine metallic copper is deposited on the heat collecting surface. A method for treating a heat collecting surface is provided.

The method of the present invention blackens iron-based metal materials such as mild steel, chromium steel, or chromium-nickel steel by chemical conversion treatment, and when used as a heat collecting surface, the spectral characteristics are improved by adding copper ions to the treatment solution. It is something that improves.

In other words, in conventional black chemical conversion treatment surfaces, iron and the chromium and nickel contained therein exist in an oxidized state, but in the method of the present invention, copper ions are added to the treatment solution, so the treatment ion exchange (e.g. iron dissolves,
Copper ions precipitate), resulting in fine metal particles adhering to the chemical conversion treated surface.

For this reason, the black chemical conversion treated surface tends to change from pure black to slightly reddish, but this actually results in an improvement in the spectral characteristics.

Conventional jet-black treated surfaces have good absorption characteristics, but have large radiation losses in the infrared region.

In contrast, the method of the present invention is characterized by comparable absorption characteristics and small radiation loss.

Next, examples of the method of the present invention will be described.

1. Test materials (a) mild steel, (c) 18% chromium 10% nickel austenitic stainless steel were each cut into 5cm length and width (thickness 1mm) as test pieces.

2. Composition of chemical conversion treatment liquid (indicates weight ratio) (→ Potassium dichromate (50%), Sodium dichromate (50%)
0%) is melted at 450℃ (υ A solution prepared by adding 10% chromic acid to sulfuric acid (70%) and heated to 90℃. In the method of the present invention, copper sulfate is Two parts of copper sulfate were added to 2% (b) and immersed for 3 to 15 minutes to perform a chemical conversion treatment, and then the treatment solution remaining on the surface of the test piece was removed by washing with water.

3. Evaluation The spectral characteristics of the treated surface were compared and examined by measuring the absorption performance in the visible range and the radiation loss in the infrared range using a spectrometer.

4. Results The evaluation results of the spectral characteristics are shown in Table 1, and from these results the following can be seen regarding the heat collecting surface obtained by the method of the present invention.

(1) Although it has little effect on absorption characteristics in the visible region (wavelength 0.2 to 2.5μ), it has a considerable effect on mild steel.

(2) Radiation loss in the infrared region (wavelength 2.5 to 30μ) is very small, and high heat collection efficiency can be expected as a whole.

In other words, radiation loss is large in the conventional method, but since fine particles of copper are precipitated on the treated surface and this is further blackened, a state in which a chemically formed copper surface and a chemically formed surface of an iron-based material coexist is created. Therefore, the situation is such that the chemically formed surface of copper compensates for the drawbacks of iron-based materials.

In addition, the surface treated by the method of the present invention was lightly polished with emery paper.
Afterwards, observation using an optical microscope confirmed that fine copper particles were attached to the entire surface.

Next, as a method for adding copper ions, in addition to using salts such as copper sulfate, a method of immersing a metal copper plate in a chemical solution was used, but the same effect was observed.

This is because the copper plate is immersed in a chemical solution, and copper ions are generated in the solution.The purpose is achieved by making copper ions exist in the solution in some way, even without adding salts. Is possible.

In the case of mild steel materials and chromium steel, it is pre-immersed in a solution containing 2% copper sulfate in V-sulfuric acid to precipitate copper on its surface, and then chemical conversion treatment is performed using the method described above. However, a considerable effect was observed.

As described above, the heat collecting surface produced by the method of the present invention has excellent spectral characteristics and durability, is easy to manufacture, and exhibits little performance deterioration even at high temperatures, and can be used, for example, as a collector for hot water supply equipment or as a heat source for small absorption refrigerators. It is useful because it can be applied to a wide range of applications such as collectors.

Claims (1)

[Claims] 1 When blackening a heat collecting surface made of iron-based metal materials, copper ions are added to the chemical conversion treatment liquid and applied to the heat collecting surface, and at the same time as the heat collecting surface is blackened, the heat collecting surface is blackened. A heat collecting surface treatment method characterized by depositing fine metallic copper.