JPH0118343B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a heat collector that utilizes solar heat, for example, for air conditioning, hot water supply, power generation, etc., and a method for manufacturing the same. (Prior art) In general, as shown in Figure 1, a heat collector formed by forming a selective absorption film on the surface associated with the optical interference method of solar heat energy has a wavelength of 0.5μ to 2.0μ, which is considered to be the most intense solar thermal energy. In order to measure the effective transmittance for wavelengths, it is considered most effective to use a selective absorption film that is extremely thin, especially one-fourth of the wavelength range. As a selective absorption film in a conventional heat collector, for example, a black paint film or a black chromium plating film by electroplating has been formed and used for that purpose. (Problem to be Solved by the Invention) However, in the case of the former, it is extremely difficult to form the coating film itself in the ultra-thin range as described above, and at the same time, it is difficult to form the coating film itself in the extremely thin range as described above, and at the same time, it generally has a high emissivity and is difficult to use over a long period of time. In general, the maximum possible heat storage temperature is only 80℃, and in the case of the latter, it is easy to form an extremely thin film, and the heat collection effect is reduced due to the deterioration of the coating film due to Although the former has a reasonable heat collecting effect, as with the former, the heat collecting effect at high temperatures decreases due to deterioration of weather resistance including rust due to long-term use, and the maximum possible heat storage temperature is generally around 400°C. In any case, it is still not fully satisfactory as a selective absorption membrane, and improvements are desired. (Means for Solving the Problems) The present invention extremely effectively solves the above-mentioned problems, and provides a solar heat collector having good weather resistance and heat resistance, and excellent performance, and an efficient method thereof. The purpose of this invention is to provide a manufacturing method, and the present invention will be described in detail below with reference to FIGS. 2 and 3. copper materials and copper alloy materials,
Alternatively, a single layer of chromium oxide or complex chromate may be applied to the surface of the metal member 1, which is a plate, tube, or strip material having a desired shape, which is formed by plating these metals with nickel or chromium, or by chemical conversion treatment. The solution or the solution contains one or more metal oxides such as iron oxide, manganese dioxide, or copper oxide.
A concentrated solution with a specific gravity in the range of 1.6 to 1.8 made by mixing fine powder with a grain size of 2.0μ or more is applied, and then heat treatment is performed at a high temperature in a heating furnace such as an electric furnace. . Heat treatment is performed stepwise over a range of 170°C to 670°C, for example, to increase the thickness of a film of chromium oxide, complex chromium oxide, or a mixture of these compounds and metal oxide. A relatively thick black ceramic film 3 of μ is deposited. Next, on the surface of the ceramic membrane, a dilute solution similar to the one described above, having a specific gravity in the range of 1.0 to 1.4 and having a dilute concentration compared to the concentrated solution, is applied again, and the temperature is again heated to 170°C to 670°C. A thin black ceramic film 4 with a thickness ranging from 0.125μ to 0.5μ having the same composition as described above is deposited and polymerized by performing stepwise heat treatment over a temperature range of A black color consisting of a pair of thick and thin films containing individual solutions of different concentrations, with a thick film made of a concentrated solution located on the lower layer, and a thin film obtained from a diluted solution placed on the upper layer of the surface of the thick film. Ceramic membrane 3, 4
A selective absorption film is formed by depositing and polymerizing a desired number of thick and thin films alternately as shown in FIG. 3 as required. The stepwise heating in several stages in the heat treatment of the coating solution described above causes the chromic acid or complex chromium oxide salts contained in the solution, or the metal oxides contained together with these compounds, to form strong chemical bonds with each other. The black ceramic film thus obtained can be uniformly densified and the heat collector of the present invention can be used stably at high temperatures for a long period of time. However, it is desirable that the heating temperature at the initial stage of this stepwise heat treatment be 180°C or lower, and the heating temperature at the final stage be 650°C or higher. Note that the first
Reference numeral 2 in the figures and FIG. 2 is a plating film layer or a chemically formed film layer applied to the surface of the metal material as necessary. (Function) As described above, in the present invention, when forming the selective absorption film constituting the heat collector, two types of chromic acid, a simple solution of complex chromate, or a concentrated solution containing fine metal oxide powder mixed therewith are used. By first applying a concentrated solution to the surface of a metal material and then heat-treating it in stages, it is finally turned into a ceramic, producing a thick black ceramic film mainly composed of chromium oxide or chromium oxide-based compounds. A film is applied, a diluted solution is applied on top of this, and the same treatment is applied to deposit and polymerize the thin film of black ceramic, so it is only necessary to adjust the concentration of the solution (or adjust the specific gravity). The process control is extremely easy and efficient because the upper ceramic film can be formed thin and the lower ceramic film thick by applying the solution at approximately the same thickness and using approximately the same heating operation. In particular, according to the present invention, the thickness of the upper ceramic film, which is extremely difficult to achieve with conventional coating film methods, must be kept within the range of 0.125μ to 0.5μ, which indicates the most effective solar energy transmission efficiency. It is extremely effective. The selective absorption film according to the present invention thus formed is composed of a thick and thin double-layered film of a uniformly dense black ceramic film with strong chemical bonds mainly composed of a chromium oxide composition. It has been confirmed that the material has extremely excellent heat and moisture resistance, and does not cause any problems such as deterioration even if kept at high temperatures around 800℃ for a long time, and the thick ceramic that forms the lower layer can withstand high temperatures. Since it exhibits an extremely low emissivity up to , it can be said to be suitable as a solar heat collector. (Example) Examples of the present invention will be described in detail below. Example 1 Metal parts/Material S45C, dimensions 1000mm in height and 1000mm in width.
A 2 mm thick plate was subjected to the usual degreasing and rust removal treatments as pretreatment. Simple concentrated solution of chromium oxide - 500 g of chromic anhydride to 500 c.c. of water.
were mixed and stirred to form a concentrated solution with a specific gravity of 1.66. 100 c.c. of the concentrated solution was applied uniformly to the surface of the metal member by coating and brushing. Heat treatment/Electric furnace at 170℃ for 10 minutes → 390℃
Heat treatment was carried out in three stages: 10 minutes → 10 minutes at 670° C., and a thick film made of a concentrated solution having a thickness of 3 μm was deposited. Simple dilute solution of chromium oxide - 60 g of chromic anhydride to 500 c.c. of water.
were mixed and stirred to form a dilute solution with a specific gravity of 1.07. 100 c.c. of the diluted solution was uniformly applied to the surface of the metal member covered with the thick film by coating treatment/brushing. Heat treatment/Electric furnace at 170℃ for 10 minutes → 390℃
Heat treatment was carried out in three stages: 10 minutes → 10 minutes at 670° C., and a thin film of the dilute solution having a film thickness of 0.2 μm was formed by polymerization. Repeated lamination processing - The above processing was considered as one cycle, and two cycles of processing were performed by repeating it again under exactly the same conditions. Example 2 Metal member - Same as Example 1. (However, the surface was treated with a black iron oxide film of 4 μm.) Mixed solution of complex chromate and metal oxide - Specific gravity 1.72 made by mixing 500 g of chromic acid anhydride with 15 g of carbon powder and 500 g of water.
2.5 g of iron oxide powder with a particle size of about 0.5 μm or less was added to the solution and mixed with stirring. Coating treatment: Same as Example 1. Heat treatment: Same as Example 1. (However, the thickness of the deposited film is
It was 4μ. ) Simple dilute solution of chromium oxide - Same as Example 1. Coating treatment: Same as Example 1. Heat treatment: Same as Example 1. (However, the thickness of the deposited film is
It was 0.5μ. ) Repeated lamination processing ・The above processing is considered as one cycle, and two cycles are performed by repeating processing under exactly the same conditions.
The cycle was processed. The results of a comparative performance test between the heat collector of the present invention obtained above and a conventional product are as follows. (b) Selective absorption performance

[Table] As can be seen from the results in Table 1, the product of the present invention has a high absorption rate and a low emissivity, and even when kept at a high temperature of 700°C, it still maintains a sufficiently low emissivity state. On the other hand, the conventional black-coated product is inferior to the inventive product in both absorption rate and emissivity, and furthermore, when the temperature exceeds 250°C, the coating film deteriorates and loses its function as a selective absorption film. (by chromium plating), the absorption rate is almost comparable to the product of the present invention, and the emissivity is a low value that even exceeds the product of the present invention at low temperatures. It can no longer be used as an absorbent membrane. The absorption rate and emissivity in the above table were measured using a reflectance meter and an emissivity meter manufactured by D&S, respectively, and the spectral distribution of sunlight was measured using AM2. (b) Weather resistance test The above-mentioned samples of the present invention and the conventional product were heated and held in the atmosphere at 600°C for 8 hours, then allowed to cool to room temperature, and then held at 40°C and saturated humidity for 6 hours. As a result of visual inspection after 7 cycles of repeating this, Example 1 was found.
No abnormalities were observed in either the product or the two products in Example 2, whereas the coating film of the conventional black-painted product was completely burnt out, and the plating film of the black chrome-plated product deteriorated. Numerous spots of rust were observed based on (Effects) As described above, the solar heat collector of the present invention maintains excellent heat absorption efficiency up to high temperatures, and can reach up to 800℃.
It is possible to continuously achieve a heat storage temperature of up to 100% without any hindrance, and its production is extremely easy and efficient, so it has excellent industrial effects.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between solar thermal energy and wavelength, and FIGS. 2 and 3 are enlarged sectional views showing each embodiment of the heat collector according to the present invention. 1... Metal member, 3, 3'... Thick black ceramic film, 4, 4'... Thin black ceramic film.

Claims (1)

[Scope of Claims] 1. A simple solution of chromium oxide or complex chromate, or a solution containing 1 chromium oxide of a metal oxide on the surface of a metal member.
A thick film made of a concentrated solution obtained by heat-treating individual solutions containing seeds or a mixture of one or more types of fine powder with different solution concentrations is placed in the lower layer, and a thin film made of a thin solution is placed in the upper layer. At least one pair or more of black ceramic films made of chromium oxide or a chromium oxide-based compound and strongly chemically bonded to form a pair of thick and thin films are formed by laminating and polymerizing them. A solar heat collector characterized by: 2. Applying a simple solution of chromium oxide or complex chromate to the surface of the metal member, or adding one of the metal oxides to the solution.
Chromium oxide or chromium oxide-based compounds, or these compounds and metal oxides, are strongly chemically bonded by applying a concentrated solution containing seeds or one or more fine powders and then heat-treated. A black ceramic film made of a composition comprising: By applying the coating and heat-treating it again, a thin black ceramic film having the same composition as described above is polymerized and deposited.In this way, a black ceramic film with a thick film in the lower layer and a thin film in the upper layer is formed. A method for producing a solar heat collector, which comprises forming a pair of thick and thin films and polymerizing and depositing thick and thin films of black ceramic in a layered manner by repeating polymerization treatment as necessary.