JPS60216148A - Solar heat collector - Google Patents

Abstract

PURPOSE:To efficiently absorb the reflected light incident on the outer peripheral surface of an collector pipe from the back side and consequently contrive to enhance the heat collecting efficiency by a structure wherein selective adsorption film is formed on both the surface and back of an absorber plate and over the whole region of the outer peripheral surface of the collector pipe. CONSTITUTION:Selective absorption film 7 is coatingly formed over the whole surface region on the outer peripheral surface of a collector pipe 2 and both the surface and back of an absorber plate 3. Abutting portions W of the collector pipe 2 against the absorber plate 3 are seam-welded in order to integrally join each other. Due to the selective absorption film 7, which is also coatingly formed on the outer peripheral surface of the collector pipe 2, the reflected light incident from the underside of a solar heat collector is efficiently absorbed. resulting in enabling to effectively collect heat and consequently to enhance the heat collecting efficiency. The selective absorption film is preferably formed by heat treatment after applying the electroless plating of nickel and phosphorus.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention is constructed by integrally joining a heat collecting plate whose plate surface is a solar heat absorption surface and a heat collecting pipe through which a heat medium flows, and is incorporated into a collector pipe of a vacuum glass tube type solar heat collector, for example. Regarding solar heat collectors.

[Prior art and its problems]

As is well known, the evacuated tube collector for solar heat collectors consists of a heat collecting tube through which a heating medium flows, and a heat collecting plate thermally connected to the heat collecting tube in a vacuum glass outer tube. It is configured to incorporate a heat collecting body consisting of a heat collecting plate and to transmit solar heat absorbed by the heat collecting plate to a heat medium flowing in the heat collecting pipe. Its basic structure is as shown in Figs. 1 and 2. L is a long translucent glass outer tube with a length of 2 to 3 m, and inside it is a heat collecting tube 2 and a heat collecting plate. A solar heat collector 4 is housed therein, which is a thermally conductive combination of solar heat collectors 3 and 3. The open end surface of the glass outer tube l is closed with an end plate 5, and the inside is evacuated.
In addition, the solar heat collector 4 is supported within the glass outer tube via a support plate 6 made of a material with low thermal conductivity. Further, the heat collecting tube 2 has, for example, a double-vib structure, and water as a heat medium flows through the outgoing path and the returning path within the tube. Here, the structure of the conventional solar heat collector 4 is as shown in FIG. 7 is formed on the back side thereof, and a heat collecting tube 2 made of, for example, copper is fitted into the recess of the heat collecting plate and closely joined by, for example, a caulking method. Note that although an iron pipe may be used as the heat collecting tube 2, its surface is generally copper-plated in order to prevent rust from forming on the iron vibrator from the viewpoint of parts storage management. By the way, a solar heat collector constructed by arranging a plurality of vacuum glass tube collectors in parallel as shown in FIG. 4 has a minimum gap of about 15 to 20 fins between the glass outer tubes 1. When a solar heat collector is installed on the ground or on the roof of a building, in addition to the direct sunlight that illuminates the top surface of the heat collector plate 3, the sunlight that shines through the gap or is scattered in the sky and is used once installed. Some of the light that reaches the surface 8 is reflected and enters the back surface of the heat collecting plate 3 and the outer peripheral surface of the heat collecting tube 2. Although the amount of reflected incident light varies depending on the reflectance of the installation surface, it reaches a maximum of 8 to 30% of the direct sunlight. On the other hand, the area covered by the heat collecting tubes 2 on the back side of the heat plate 3 is about 15%, and if the reflectance of the installation surface 8 is 30%, the amount of light that is incident on the circumference of the heat collecting tubes 2 is approximately 15%. The ratio of light intensity is 4 of the total solar radiation, which is the sum of direct solar radiation and reflected light.
．． It can be as high as 3%. Further, if the reflectance is 8%, the ratio is 1.2%. However, in the past, no particular consideration was given to the amount of solar radiation that enters the outer peripheral surface of the heat collecting tube 2 from the back side of the solar heat collector, and as mentioned above, the heat collecting tube 2 is left as a steel pipe or copper-plated. None had actively taken steps to absorb heat.

[Purpose of the invention]

This invention has been made in consideration of the above points, and aims to provide a solar heat collector that efficiently absorbs sunlight incident on the back side of the solar heat collector and improves heat collection efficiency. .

[Key points of the invention]

In order to achieve the above object, the present invention forms a selective absorption film on both the front and back surfaces of the heat collecting plate and the entire outer circumferential surface of the heat collecting tube, thereby blocking light reflected from the back surface side that enters the outer circumferential surface of the heat collecting tube. It is designed to efficiently absorb heat and improve the heat collection efficiency of the solar heat collector as a whole.

[Embodiments of the invention]

FIG. 5 and FIG. 6 show an embodiment of the present invention, in which the outer circumferential surface of the heat collecting tube 2 and both the front and back surfaces of the heat collecting plate 3,
A selective absorption film 7 is coated over the entire surface area, and the heat collecting tube 2 and the heat collecting plate 3 are joined together by seam welding at the abutting portions shown by the symbol W. The selective absorption film 7 is formed by subjecting the base materials of the heat collecting tubes 2 and the heat collecting plate 3 to, for example, electroless nickel-phosphorus plating, and then heat-treating and oxidizing and coloring this in the atmosphere. The selective absorption film 7 may be formed separately to cover the heat collecting tube 2 and the heat collecting plate 3 before seam welding, or
After the heat collecting plate 3 and the heat collecting plate 3 are integrated by seam welding, the covering is formed all at once. In this case, since the selective absorption membrane 7 itself has a rust prevention function, the heat collecting tube 2. Heat collecting plate 3
When making the heat collecting pipe 2. from cheap iron, heat collecting pipe 2. Heat collecting plate 3
By separately forming a selective absorption film on the parts, it becomes easier to store and manage the parts from the standpoint of rust prevention. Further, when the selective absorption film is formed to cover the heat collecting tube 2 and the heat collecting plate 3 after seam welding, there is an advantage that the selective absorption film can be processed only once. In addition, by adopting the seam welding method for joining the heat collecting pipe 2 and the heat collecting plate 3, selective absorption! Even if the heat collecting tube 2 and the heat collecting plate 3 are joined together after I7 is coated, there is little thermal influence on areas other than the welded parts, so there is almost no deterioration of the selective absorption film, and it is even better than conventional Compared to the caulking connection method, higher heat transfer properties can be obtained between the heat collecting plate 3 and the heat collecting tube 2. On the other hand, regarding solar heat collection efficiency, by coating the outer peripheral surface of the heat collecting tube 2 with selective absorption 1l17, it efficiently absorbs reflected light from the lower surface side of the solar heat collector, as well as the fat tuna effect of the parts. This enabled the heat collection efficiency of the collector tube to be improved by 1 to 4%.

【Effect of the invention】

As described above, according to the present invention, selective absorption coatings are formed on both the front and back surfaces of the heat collecting plates constituting the solar heat collector and the entire outer circumferential surface of the heat collecting tubes, thereby improving the outer circumferential surface of the heat collecting tubes. It is actively used as a solar heat absorption surface, and when in use, it reflects on the installation surface and effectively absorbs the sunlight that enters the circumferential surface of the heat collection tube from the back side of the solar heat collector, increasing the overall heat collection efficiency. Furthermore, even when inexpensive iron pipes are used as heat collecting pipes, the anti-corrosion effect of the selective absorption membrane itself can prevent parts from rusting and facilitate storage management. is obtained.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view showing the basic structure of the collector tube of a vacuum glass tube type solar heat collector, and Figure 2 is taken from the arrow nn in Figure 1.
A sectional view, FIG. 3 is a partial perspective view showing the structure of a conventional solar heat collector, FIG. 4 is a diagram showing the state of sunlight incident on the solar heat collector during use, and FIGS. 5 and 6 are respectively 1 is a partial external perspective view and an enlarged sectional view showing the structure of an embodiment of the present invention. FIG. 100. Vacuum glass outer tube, 201. Heat collecting pipe, 31. . heat collecting plate, 410. Solar heat collector, 7019 selective absorption membrane,
W16. seam welds. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1) In a solar heat collector formed by integrally bonding a heat collecting tube through which a heat medium flows to the back surface of a heat collecting plate whose plate surface serves as a solar radiation absorbing surface, the front and back sides of the heat collecting plate A solar heat collector characterized in that a selective absorption film is formed on both sides and the entire outer peripheral surface of the heat collector tube. 2. The solar heat collector according to claim 1, wherein the heat collecting plate and the heat collecting tube are joined by seam welding. 3) The solar heat collector according to claim 1, wherein the selective absorption film is formed by subjecting an electroless nickel-phosphorus plating film to heat treatment.